記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

DOI： 10.1109/iecon49645.2022.9968594

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：情報処理学会  

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人日本統計学会  

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

DOI： 10.1109/itsc45102.2020.9294592

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：統計数理研究所  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1371/journal.pone.0205889

PubMed

researchmap

記述言語：日本語  

DOI： 10.14954/jste.3.2_A_76

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

Cellular structures are hydrodynamically interconnected, such that force generation in one location can move distal structures. One example of this phenomenon is cytoplasmic streaming, whereby active forces at the cell cortex induce streaming of the entire cytoplasm. However, it is not known how the spatial distribution and magnitude of these forces move distant objects within the cell. To address this issue, we developed a computational method that used cytoplasm hydrodynamics to infer the spatial distribution of shear stress at the cell cortex induced by active force generators from experimentally obtained flow field of cytoplasmic streaming. By applying this method, we determined the shear-stress distribution that quantitatively reproduces in vivo flow fields in Caenorhabditis elegans embryos and mouse oocytes during meiosis II. Shear stress in mouse oocytes were predicted to localize to a narrower cortical region than that with a high cortical flow velocity and corresponded with the localization of the cortical actin cap. The predicted patterns of pressure gradient in both species were consistent with species-specific cytoplasmic streaming functions. The shear-stress distribution inferred by our method can contribute to the characterization of active force generation driving biological streaming.

DOI： 10.1371/journal.pone.0159917

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

researchmap

記述言語：日本語   掲載種別：研究論文（研究会，シンポジウム資料等）  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：COPERNICUS GESELLSCHAFT MBH  

A technique for estimating the age-depth relationship in an ice core and evaluating its uncertainty is presented. The age-depth relationship is determined by the accumulation of snow at the site of the ice core and the thinning process as a result of the deformation of ice layers. However, since neither the accumulation rate nor the thinning process is fully known, it is essential to incorporate observational information into a model that describes the accumulation and thinning processes. In the proposed technique, the age as a function of depth is estimated by making use of age markers and delta O-18 data. The age markers provide reliable age information at several depths. The data of delta O-18 are used as a proxy of the temperature for estimating the accumulation rate. The estimation is achieved using the particle Markov chain Monte Carlo (PMCMC) method, which is a combination of the sequential Monte Carlo (SMC) method and the Markov chain Monte Carlo method. In this hybrid method, the posterior distributions for the parameters in the models for the accumulation and thinning process are computed using the Metropolis method, in which the likelihood is obtained with the SMC method, and the posterior distribution for the age as a function of depth is obtained by collecting the samples generated by the SMC method with Metropolis iterations. The use of this PMCMC method enables us to estimate the age-depth relationship without assuming either linearity or Gaussianity. The performance of the proposed technique is demonstrated by applying it to ice core data from Dome Fuji in Antarctica.

DOI： 10.5194/npg-23-31-2016

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ASSOC COMPUTING MACHINERY  

Real-time estimation of human mobility following a massive disaster will play a crucial role in disaster relief. Because human mobility in massive disasters is quite different from their usual mobility, real-time human location data is necessary for precise estimation. Due to privacy concerns, real-time data is anonymized and a popular form of anonymization is population distribution. In this paper, we aim to estimate human mobility following an unprecedented disaster using such population distribution data. To overcome technical obstacles including high dimensionality, we propose novel particle filter by devising proposal distribution. Our proposal distribution provides states considering both prediction model and acquired observation. Therefore, particles maintain high likelihood. In the experiments, our methods realized more accurate estimation than the baselines, and its estimated mobility was consistent with the survey researches. The computational cost is significantly low enough for real-time operations. The GPS data collected on the day of the Great East Japan Earthquake is used for the evaluation.

DOI： 10.1145/2996913.2997000

Web of Science

researchmap

記述言語：英語  

DOI： 10.1038/srep13076

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Industrial Management Association  

Japan needs to develop data analytics talent quickly in order to catch up with the trend of using data for making business decisions. The Ministry of Education, Culture, Sports, Science and Technology started a three-year project to develop so-called data scientists. This paper reviews the findings of the first year of the project, and discusses future challenges.

DOI： 10.11221/jima.65.334

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

The development of the so-called intelligent tire has changed the role of the tire. Here we discuss a real-time road condition classification system that employs monitoring tire acceleration. Because the tire acceleration is non-stationary and is warped non-linearly in the time domain, we applied the time alignment algorithm to it similarly to speech recognition. High accuracy classification systems robust against tire-size range variations have been achieved in previous studies, in which the same pattern tires with prescribed pressure and several vehicles were used. However, there is no discussion on the execution speed of such a system. Therefore, we validated the algorithm and improved it for use in real-time applications. Specially, the calculation time was reduced by limiting the path of the global alignment kernel, which handles a sequence with time warping. Furthermore, we used SVM with L1 norm regularization instead of L2 norm regularization. We succeeded in achieving a real-time road condition classification system, which was verified in a vehicle test.

DOI： 10.1109/MLSP.2015.7324381

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER CHEMICAL SOC  

The measurement of molecular similarity is an essential part of various machine learning tasks in chemical informatics. Graph kernels provide good similarity measures between molecules. Conventional graph kernels are based on counting common subgraphs of specific types in the molecular graphs. This approach has two primary limitations: (i) only exact subgraph matching is considered in the counting operation, and (ii) most of the subgraphs will be less relevant to a given task. In order to address the above-mentioned limitations, we propose a new graph kernel as an extension of the subtree kernel initially proposed by Ramon and Gartner (2003). The proposed kernel tolerates an inexact match between subgraphs by allowing matching between atoms with similar local environments. In addition, the proposed kernel provides a method to assign an importance weight to each subgraph according to the relevance to the task, which is predetermined by a statistical test. These extensions are evaluated for classification and regression tasks of predicting a wide range of pharmaceutical properties from molecular structures, with promising results.

DOI： 10.1021/ci400403w

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

We have developed a technique for estimating the temporal evolution of the plasmaspheric helium ion density based on a sequence of extreme ultraviolet (EUV) data obtained from the IMAGE satellite. In the proposed technique, the estimation is obtained by incorporating EUV images from IMAGE into a two-dimensional fluid model of the plasmasphere using a data assimilation approach based on the ensemble transform Kalman filter. Since the motion and the spatial structure of the helium plasmasphere is strongly controlled by the electric field in the inner magnetosphere, the electric field around the plasmapause can also be estimated using the ensemble transform Kalman filter. We performed an experiment using synthetic images that were generated from the same numerical model under a certain condition. It was confirmed that the condition that generated the synthetic images was successfully reproduced. We also present some results obtained using real EUV imaging data. Finally, we discuss the possibility of estimating the density profile along a magnetic field line. Since each EUV image was taken from a different direction due to the motion of the IMAGE satellite, we could obtain the information on the density profile along a field line by combining multiple images.

DOI： 10.1002/2013JA019734

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

We have developed a technique by which to estimate the spatial distribution of plasmaspheric helium ions based on extreme ultraviolet (EUV) data obtained from the IMAGE satellite. The estimation is performed using a linear inversion method based on the Bayesian approach. The global imaging data from the IMAGE satellite enable us to estimate a global two-dimensional distribution of the helium ions in the plasmasphere. We applied this technique to a synthetic EUV image generated from a numerical model. This technique was confirmed to successfully reproduce the helium ion density that generated the synthetic EUV data. We also demonstrate how the proposed technique works for real data using two real EUV images.

DOI： 10.1002/2013JA019733

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The solar minimum between solar cycles 23 and 24 was unusually long and deep. The upward region-1 (R1) field-aligned current (FAC) response to this extreme solar minimum was investigated using Defense Meteorological Satellite Program observations. The solar cycle responses on the dayside are different than those on the nightside. The field-aligned current density (J(//)) on the dayside, at 12-17 magnetic local time (MLT), peaks in the declining phase of the solar cycle, in 2003, when the solar wind speed also peaks, whereas J(//) on the nightside, at 18-23 MLT, appears insensitive to the solar cycle. In 1995-2010, J(//) at 15-17 MLT reaches the lowest value during the extreme solar minimum in 2009, when the solar wind speed also reaches the lowest value. At 12-17 MLT, R1 is located mostly on open field lines or at the boundary layer, where the current is driven mostly by the velocity shear at the magnetopause boundary. However, on the nightside, R1 is located mostly on the closed field lines where J(//) is not driven directly and immediately by the solar wind. The nightside current width () exhibits a solar cycle effect such that is smaller at the solar minimum and smallest in 2009. However, the dayside exhibits little solar cycle effect. As a result, the FAC intensity (latitudinally integrated J(//)) exhibits a solar cycle variation at all local times and the FAC intensity is lower during the extreme solar minimum than that of the previous solar minimum.

DOI： 10.1002/2013JA019452

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

In the present study we observationally address the role of ionospheric conductivity in the solar wind-magnetosphere coupling in terms of global field-aligned currents (FACs). Solar EUV irradiance changes during a solar cycle and so does its contribution to the ionospheric conductivity. We statistically examine how, under fixed external conditions, the intensities of the R1 and R2 currents and their demarcation latitude depend on solar activity (F-10.7). An emphasis is placed on nightside FACs in the dark hemisphere. The result shows that for fixed ranges of interplanetary electric field, the nightside FACs are more intense for higher solar activity irrespective of their polarities or local times. It is also found that the R1-R2 pair, therefore the auroral oval, moves equatorward as the solar activity increases. For both current intensity and latitude, the dependence on F-10.7 is more sensitive at smaller F-10.7 and it levels off with increasing F-10.7. The intensities of dayside FACs reveal similar F-10.7 dependence as expected from the enhancement of the local ionospheric conductance. Interestingly, they also move equatorward with increasing F-10.7. It is expected from force balance that as the dayside R1 current becomes more intense with increasing solar activity, the magnetosphere shrinks on the day side and expands on the night side. This configurational change of the magnetosphere presumably affects the energy transport from the solar wind to the magnetosphere, although its details still remain to be understood. We conclude that the ionospheric conductivity plays an active role in the solar wind-magnetosphere-ionosphere coupling.

DOI： 10.1002/2013JA019410

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

Sentinel observations of influenza epidemic in each prefecture indicates basically unimodal trend but with irregular shocks, which are synchronous among prefectures. In this study, we have confirmed that the the strength of inter-regional connection and local probabilistic fluctuation are separately identifiable in a multi-compartment SIR model.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

In the present study we observationally address the role of ionospheric conductivity in the solar wind-magnetosphere coupling in terms of global field-aligned currents (FACs). Solar EUV irradiance changes during a solar cycle and so does its contribution to the ionospheric conductivity. We statistically examine how, under fixed external conditions, the intensities of the R1 and R2 currents and their demarcation latitude depend on solar activity (F 10.7). An emphasis is placed on nightside FACs in the dark hemisphere. The result shows that for fixed ranges of interplanetary electric field, the nightside FACs are more intense for higher solar activity irrespective of their polarities or local times. It is also found that the R1-R2 pair, therefore the auroral oval, moves equatorward as the solar activity increases. For both current intensity and latitude, the dependence on F 10.7 is more sensitive at smaller F10.7 and it levels off with increasing F10.7. The intensities of dayside FACs reveal similar F10.7 dependence as expected from the enhancement of the local ionospheric conductance. Interestingly, they also move equatorward with increasing F10.7. It is expected from force balance that as the dayside R1 current becomes more intense with increasing solar activity, the magnetosphere shrinks on the day side and expands on the night side. This configurational change of the magnetosphere presumably affects the energy transport from the solar wind to the magnetosphere, although its details still remain to be understood. We conclude that the ionospheric conductivity plays an active role in the solar wind-magnetosphere-ionosphere coupling. Key Points Nightside R1 and R2 currents become more intense with increasing solar activity The auroral oval moves equatorward as solar activity increases The dayside conductivity affects the SW-M-I coupling through the R1 system. ©2013. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013JA019410

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

We have developed a technique for estimating the temporal evolution of the plasmaspheric helium ion density based on a sequence of extreme ultraviolet (EUV) data obtained from the IMAGE satellite. In the proposed technique, the estimation is obtained by incorporating EUV images from IMAGE into a two-dimensional fluid model of the plasmasphere using a data assimilation approach based on the ensemble transform Kalman filter. Since the motion and the spatial structure of the helium plasmasphere is strongly controlled by the electric field in the inner magnetosphere, the electric field around the plasmapause can also be estimated using the ensemble transform Kalman filter. We performed an experiment using synthetic images that were generated from the same numerical model under a certain condition. It was confirmed that the condition that generated the synthetic images was successfully reproduced. We also present some results obtained using real EUV imaging data. Finally, we discuss the possibility of estimating the density profile along a magnetic field line. Since each EUV image was taken from a different direction due to the motion of the IMAGE satellite, we could obtain the information on the density profile along a field line by combining multiple images. Key Points A data assimilation approach is applied for modeling the plasmasphere The proposed technique allows us to estimate the evolution of He+ distribution The parameter for the profile along a field line could also be estimated ©2014. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013JA019734

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

We have developed a technique by which to estimate the spatial distribution of plasmaspheric helium ions based on extreme ultraviolet (EUV) data obtained from the IMAGE satellite. The estimation is performed using a linear inversion method based on the Bayesian approach. The global imaging data from the IMAGE satellite enable us to estimate a global two-dimensional distribution of the helium ions in the plasmasphere. We applied this technique to a synthetic EUV image generated from a numerical model. This technique was confirmed to successfully reproduce the helium ion density that generated the synthetic EUV data. We also demonstrate how the proposed technique works for real data using two real EUV images. Key Points A technique to estimate the plasmaspheric He+ density distribution is proposed The estimation is based on EUV data from the IMAGE satellite The uncertainty and sensitivity of the estimate are also evaluated ©2014. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013JA019733

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The solar minimum between solar cycles 23 and 24 was unusually long and deep. The upward region-1 (R1) field-aligned current (FAC) response to this extreme solar minimum was investigated using Defense Meteorological Satellite Program observations. The solar cycle responses on the dayside are different than those on the nightside. The field-aligned current density (J//) on the dayside, at 12-17 magnetic local time (MLT), peaks in the declining phase of the solar cycle, in 2003, when the solar wind speed also peaks, whereas J// on the nightside, at 18-23 MLT, appears insensitive to the solar cycle. In 1995-2010, J// at 15-17 MLT reaches the lowest value during the extreme solar minimum in 2009, when the solar wind speed also reaches the lowest value. At 12-17 MLT, R1 is located mostly on open field lines or at the boundary layer, where the current is driven mostly by the velocity shear at the magnetopause boundary. However, on the nightside, R1 is located mostly on the closed field lines where J// is not driven directly and immediately by the solar wind. The nightside current width (Λ) exhibits a solar cycle effect such that Λ is smaller at the solar minimum and smallest in 2009. However, the dayside Λ exhibits little solar cycle effect. As a result, the FAC intensity (latitudinally integrated J//) exhibits a solar cycle variation at all local times and the FAC intensity is lower during the extreme solar minimum than that of the previous solar minimum. Key Points Upward R1 responds to solar cycle differently in the closed than open field line Dayside R1 J// has a strong solar cycle variation which can be attributed to Vsw R1 FAC intensity exhibits a solar cycle variation at 1200-2300 MLT ©2014. American Geophysical Union. All Rights Reserved.

DOI： 10.1002/2013JA019452

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：統計数理研究所  

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

In order to understand the evolution of the 2009 influenza A (H1N1) pandemic within local regions of Japan, we studied the significance of regional migration between these regions. For this purpose, we have employed an extended SEIR model to describe the immigration of infected people and the stochastic variation of the infectious efficiency. We then applied a data assimilation technique in order to study how the agreement of the simulation results with the observed data depends on the presence/absence of immigration and the degree of variation of the infectious efficiency. Reproducibility is evaluated by log-likelihood values. The log-likelihood does not indicate the significance of immigration. Although there are multiple waves in the time course of the number of reported infected individuals, these waves could be explained by the stochastic nature of infectious events. (C) 2013 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.mbs.2013.08.009

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

Vaccination is a preventive measure against influenza that does not require placing restrictions on social activities. However, since the stockpile of vaccine that can be prepared before the arrival of an emerging pandemic strain is generally quite limited, one has to select priority target groups to which the first stockpile is distributed. In this paper, we study a simulation-based priority target selection method with the goal of enhancing the collective immunity of the whole population. To model the region in which the disease spreads, we consider an urban area composed of suburbs and central areas connected by a single commuter train line. Human activity is modelled following an agent-based approach. The degree to which collective immunity is enhanced is judged by the attack rate in unvaccinated people. The simulation results show that if students and office workers are given exclusive priority in the first three months, the attack rate can be reduced from 30% in the baseline case down to 1-2%. In contrast, random vaccination only slightly reduces the attack rate. It should be noted that giving preference to active social groups does not mean sacrificing those at high risk, which corresponds to the elderly in our simulation model. Compared with the random administration of vaccine to all social groups, this design successfully reduces the attack rate across all age groups.

DOI： 10.1371/journal.pone.0072866

Web of Science

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本マーケティング・サイエンス学会  

DOI： 10.11295/marketingscience.210103

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：国立研究開発法人 科学技術振興機構  

ビッグデータの活用によりイノベーションを引き起こすことが産業界からアカデミアまで幅広く期待されている一方，その成功の鍵となる人材の不足についてはあまり真剣に議論されていない。データ・サイエンティストと呼ぶ，統計学や機械学習の高度な知識と，ビッグデータの取り扱いに関する十分なスキルを持った人材の養成は焦眉の急である。すでに産業界においては優秀な人材の争奪戦が相当激しいものとなっている。国際的競争力の維持の観点から日本の人材育成上の問題点を指摘するとともに，アメリカで始まった新しいポスドク・インターンシップ制度を紹介し，データ・サイエンティストを増やす方策を考えてみる。

DOI： 10.1241/johokanri.56.2

CiNii Books

researchmap

その他リンク： https://jlc.jst.go.jp/DN/JALC/10016665773?from=CiNii

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Tide gauge observations along the coastline of Japan have recorded the land sinking due to the continuous subduction of the oceanic plates, indicating that stress and strain energies have been accumulating at the plate boundary, which would eventually cause large oceanic trench earthquakes like the 2011 Great East Japan Earthquake. The proposed method extracts such long-term activities of the Earth's crust together with rapid displacements related to earthquakes, even before the establishment of the global positioning system, from monthly mean data of the sea levels. A state space model decomposes the tide gauge time series into trend, seasonal, autoregressive and observation noise components, each of which are estimated using the particle filter algorithm. The spatial and temporal distributions of the extracted trend component clearly indicate high-risk regions, near which giant earthquakes have occurred or are predicted to occur. A multivariate analysis of the observatories located at the northeast coast of Japan successfully determines the past crustal displacement in the case of the 1978 Off-Miyagi Earthquake. The proposed method has the potential application for monitoring crustal activities related to the accumulation of earthquake energy. © 2012 The Author 2012.

DOI： 10.1093/comjnl/bxs139

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Japanese Association for Petroleum Technology  

A tracer test is a powerful experiment to identify fractures in underground reservoirs, which significantly affect fluid flow in a porous medium. The complex variable boundary element method (CVBEM) is capable of simulating time-series of the tracer concentration at a producer when the physical properties of the medium and the tracer injection plan are given. Several studies have proposed inversion procedures to identify physical parameters of a fracture in a homogeneous porous medium, using such as the genetic algorithm (GA) or the ensemble Kalman filter (EnKF) combined with iterative computations of CVBEM. The present paper proposes, for this inversion problem, a Markov chain Monte Carlo (MCMC) algorithm, which enables us to obtain a posterior probability density function (PDF) as well as an optimum value for each model parameter that characterizes the fracture. The proposed algorithm is performed to twin experiments that confirm whether properties of a synthetically-assumed fracture are reproduced from time-series of tracer concentration at a producer, which CVBEM has computed in advance. A clustering result of the K-means, which is applied to the samples obtained by MCMC, provides candidate solutions corresponding to local maximums of the posterior PDF. The candidate solutions are ranked by the posterior PDF at the centroid of each cluster. Especially in the case of the two-directional tracer test, in which two pairs of injector and producer are located, the optimum parameter set that maximizes the posterior PDF successfully reproduces both the fracture properties and the concentration curves.

DOI： 10.3720/japt.78.197

CiNii Books

researchmap

その他リンク： https://jlc.jst.go.jp/DN/JALC/10019782927?from=CiNii

researchmap

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

Sentinel observations of influenza epidemic in each prefecture indicates basically unimodal trend but with irregular shocks, which are synchronous among prefectures. In this study, we have examined the possibility that the observed treads can be modeled by SIR with stochastic outer force added. The result shows that this is formally possible but large outer forces are needed in some prefecture.

Web of Science

researchmap

記述言語：日本語   出版者・発行元：化学工学会  

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：公益社団法人日本オペレーションズ・リサーチ学会  

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本統計学会  

日本列島の沿岸部では,140か所に及ぶ験潮所において潮位観測が実施されている.古い験潮所では,100年以上前から連続記録が残されているため,2011年3月11日の東北地方太平洋沖地震(東日本大震災)のようなプレート境界型の巨大地震を惹き起こす数十年周期の地殻変動を知る上で,非常に貴重な観測データとなっている.潮位月平均値データから地殻変動を抽出することを目的に開発した粒子フィルタアルゴリズムを,実際の潮位データに適用したところ,特に西日本の太平洋側に面した験潮所において,地殻の沈降量が非常に大きいことが分かった.この結果は,南海トラフにおいて大きな地震エネルギーが蓄積され続けており,東海・東南海・南海地震がいつ起こってもおかしくない状況であることを示すものであると考えられる.

CiNii Books

researchmap

その他リンク： http://dl.ndl.go.jp/info:ndljp/pid/10823273

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

Purpose: To identify stage I lung adenocarcinoma patients with a poor prognosis who will benefit from adjuvant therapy.
Patients and Methods: Whole gene expression profiles were obtained at 19 time points over a 48-hour time course from human primary lung epithelial cells that were stimulated with epidermal growth factor (EGF) in the presence or absence of a clinically used EGF receptor tyrosine kinase (RTK)-specific inhibitor, gefitinib. The data were subjected to a mathematical simulation using the State Space Model (SSM). "Gefitinib-sensitive" genes, the expressional dynamics of which were altered by addition of gefitinib, were identified. A risk scoring model was constructed to classify high- or low-risk patients based on expression signatures of 139 gefitinib-sensitive genes in lung cancer using a training data set of 253 lung adenocarcinomas of North American cohort. The predictive ability of the risk scoring model was examined in independent cohorts of surgical specimens of lung cancer.
Results: The risk scoring model enabled the identification of high-risk stage IA and IB cases in another North American cohort for overall survival (OS) with a hazard ratio (HR) of 7.16 (P = 0.029) and 3.26 (P = 0.0072), respectively. It also enabled the identification of high-risk stage I cases without bronchioalveolar carcinoma (BAC) histology in a Japanese cohort for OS and recurrence-free survival (RFS) with HRs of 8.79 (P = 0.001) and 3.72 (P = 0.0049), respectively.
Conclusion: The set of 139 gefitinib-sensitive genes includes many genes known to be involved in biological aspects of cancer phenotypes, but not known to be involved in EGF signaling. The present result strongly re-emphasizes that EGF signaling status in cancer cells underlies an aggressive phenotype of cancer cells, which is useful for the selection of early-stage lung adenocarcinoma patients with a poor prognosis.

DOI： 10.1371/journal.pone.0043923

Web of Science

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人電子情報通信学会  

近年の計測技術の向上によって,高速で回転するタイヤから振動などの物理量を計測することが可能になり,それら物理量の特徴が路面状態変化の影響を受け変化することが明らかになってきた.本論文ではその逆問題として,タイヤ内面に取り付けた加速度センサの出力から,走行している路面状態をリアルタイムに判別する方法を提案する.タイヤ振動は非定常性の強い波形を示し,その特徴は車輪速やタイヤサイズによって時間伸縮する.この時間伸縮に対応するため,本方法ではHMMでタイヤ振動波形をモデル化する.路面状態の変化に伴う特徴が含まれる接地面付近の波形を,路面状態ごとにHMMでモデル化するとともに,接地面外の波形もHMMでモデル化しておき,接地面近傍の波形のHMMが,接地面外のHMMに挟まれた構造をもつHMMのネットワークを構成する.そして未知データが入力されたときに,そのゆう度が最も高いモデルに対応する路面状態に判別する.異なる四つの路面状態を,4種のタイヤで走行したデータを用いて行った実験結果から,車輪速やタイヤサイズの情報なしに精度良く路面状態判別ができる可能性を示す.

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PUBLIC LIBRARY SCIENCE  

Different models for animal cell cytokinesis posit that the stiffness of the equatorial cortex is either increased or decreased relative to the stiffness of the polar cortex. A recent work has suggested that the critical cytokinesis signaling complex centralspindlin may reduce the stiffness of the equatorial cortex by inactivating the small GTPase Rac. To determine if such a reduction occurs and if it depends on centralspindlin, we devised a method to estimate cortical bending stiffness with high spatio-temporal resolution from in vivo cell shapes. Using the early Caenorhabditis elegans embryo as a model, we show that the stiffness of the equatorial cell surface is reduced during cytokinesis, whereas the stiffness of the polar cell surface remains stiff. The equatorial reduction of stiffness was compromised in cells with a mutation in the gene encoding the ZEN-4/kinesin-6 subunit of centralspindlin. Theoretical modeling showed that the absence of the equatorial reduction of stiffness could explain the arrest of furrow ingression in the mutant. By contrast, the equatorial reduction of stiffness was sufficient to generate a cleavage furrow even without the constriction force of the contractile ring. In this regime, the contractile ring had a supportive contribution to furrow ingression. We conclude that stiffness is reduced around the equator in a centralspindlin-dependent manner. In addition, computational modeling suggests that proper regulation of stiffness could be sufficient for cleavage furrow ingression.

DOI： 10.1371/journal.pone.0031607

Web of Science

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPRINGER-VERLAG BERLIN  

We have developed a parallel agent-based influenza pandemic simulator, in order to study the influenza spread in a city. In the simulator, the city consists of several towns connected tightly by trains. Residents of the towns walk around places such as corporations and schools using trains by need, following to own schedulers. The influenza spread in these congested places is simulated as stochastic processes. We have demonstrated simulations with a realistic scale of population (an order of million) and showed that one simulation run is completed around one hour.

DOI： 10.1007/978-3-642-27216-5_27

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

We consider the problem of generating 3D facial animation of characters. An efficient procedure is realized by using the motion capture data (MoCap data), which is obtained by tracking the facial markers from an actor/actress. In some cases of artistic animation, the MoCap actor/actress and the 3D character facial animation show different expressions. For example, from the original facial MoCap data of speaking, a user would like to create the character facial animation of speaking with a smirk. In this paper, we propose a new easy-to-use system for making character facial animation via MoCap data. Our system is based on the interpolation: once the character facial expressions of the starting and the ending frames are given, the intermediate frames are automatically generated by information from the MoCap data. The interpolation procedure consists of three stages. First, the time axis of animation is divided into several intervals by the fused lasso signal approximator. In the second stage, we use the kernel k-means clustering to obtain control points. Finally, the interpolation is realized by using the control points. The user can easily create a wide variety of 3D character facial expressions by changing the control points.

DOI： 10.1080/02664763.2012.724391

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：COPERNICUS GESELLSCHAFT MBH  

The D-st index has a long-term variation that is not associated with magnetic storms. We estimated the long-term non-storm component of the D-st variation by removing the short-term variation related to magnetic storms. The results indicate that the variation of the non-storm component includes not only a seasonal variation but also an irregular variation. The irregular long-term variation is likely to be due to an anti-correlation with the long-term variation of solar-wind activity. In particular, a clear anti-correlation is observed between the non-storm component of D-st and the long-term variation of the solar-wind dynamic pressure. This means that in the long term, the D-st index tends to increase when the solar-wind dynamic pressure decreases. We interpret this anti-correlation as an indication that the long-term non-storm variation of D-st is influenced by the tail current variation. The long-term variation of the solar-wind dynamic pressure controls the plasma sheet thermal pressure, and the change of the plasma sheet thermal pressure would cause the non-storm tail current variation, resulting in the non-storm variation of D-st.

DOI： 10.5194/angeo-30-153-2012

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SPRINGER-VERLAG BERLIN  

In recent years. the importance of environment is widely recognized and various kinds of environmental policies have been implemented. However. when one establishes a policy, there are few cases that the contents and the period of the policy are evaluated by using prediction method for its effect. In this study, we aim to predict the effects of a policy in micro-level by using agent simulations and estimate the optimal period of the policy implementation by totally evaluating its effect. For sugarcane farmer of an area in Japan. we performed 200 thousand patterns of simulations in order to optimize the subsidy of green manure and its implementation period. In particular, when the values of the parameters in the simulation model are not clearly defined, we are able to show various futures caused by the policy implementation of interest based on large-scale simulations with a huge variety of the parameter values.

DOI： 10.1007/978-3-642-27216-5_25

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

To predict an occurrence of extraordinary phenomena, such as earthquakes, failures of engineering systems and financial market crushes, it is important to identify precursory events in time series. However, existing methods are limited in their applicability for real world precursor detections. Recently, Ide and Inoue [1] have developed an SSA-based change-point detection method, called singular spectrum transformation (SST). SST is suitable for detecting various types of change-points, but real world precursor detections can be far more difficult than expected. In general, precursory events are observed as minute and less-visible fluctuations preceding an onset of massive fluctuations of extraordinary phenomena and therefore they are easily over-looked. To overcome this point, we extend the conventional SST to the multivariable SST. The originality of our strategy is in focusing on synchronism detections of precursory events in multiple sequences of univariate time series. We performed some experiments by using artificial data and showed the superiority of multivariable SST in detecting onset of precursory events. Furthermore, the superiority is also shown statistically in determi

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

Variations in the dayside field-aligned current (FAC) density (J(//)), field-aligned parallel potential drop (Delta phi(//)), peak precipitating electron energy (peak E(e)), and precipitating electron energy flux (epsilon) as functions of solar wind (SW) and interplanetary magnetic field (IMF) are investigated with Defense Meteorological Satellite Program observations and a quasi-stationary low-latitude boundary layer (LLBL)-FAC coupling model. Region 1 (R1) J(//) responses to variations in SW velocity (V(sw)) and density (n(sw)) at 8-16 magnetic local time (MLT) suggest that R1 at these local times is frequently open while R1 at 6-08 and 17-18 MLT is frequently closed. R2 is located mostly on closed field lines. In the afternoon open R1 at 12-16 MLT, an increase in n(sw) increases J(//), decreases maximum peak Ee (proxy for Delta phi(//)), but has little effect on maximum epsilon. In the same R1 region, an increase in V(sw) increases J(//), maximum peak E(e), and maximum epsilon. The dependencies of J(//), maximum peak E(e), and maximum epsilon are consistent with the Knight relation and the voltage generator at the magnetopause boundary in the afternoon open R1. In the midmorning and midafternoon, the response of J(//) to V(sw) is higher for southward than for northward IMF. This can be attributed to the higher-velocity shear at the magnetopause boundary due to higher sunward convection in the LLBL inside the magnetopause. R1 in the closed-field lines near dawn and dusk appears to be more sensitive to merging rate (d Phi/dt = V(4/3)(sw) B(T)(2/3) sin(8/3)(theta(c)/2)) than to SW dynamic pressure.

DOI： 10.1029/2011JA016579

Web of Science

researchmap

掲載種別：研究論文（学術雑誌）  

CiNii Research

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：食農資源経済学会  

CiNii Books

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

We reproduce a magnetospheric reconfiguration under southward interplanetary magnetic field (IMF) conditions using numerical magnetohydrodynamic simulations. To investigate the relative displacements of the geomagnetic conjugate points, we trace both footprints of the geomagnetic field lines during the magnetospheric reconfiguration under positive and negative IMF B-y conditions. Several substormlike features, namely, the formation of a near-Earth neutral line, a fast earthward flow, and tailward releases of the plasmoid, occur about 1 h after a southward turning of the IMF. The surveyed field line traced from the near-Earth magnetotail was strongly distorted duskward in the north and south after the substorm onset for positive and negative IMF B-y, respectively. The maximum of the relative longitudinal displacement of both footprints is 4.5 and 5.5 h in magnetic local time for positive and negative IMF B-y, respectively. While observational studies have indicated that the IMF orientation is the main factor controlling the relative displacement of the conjugate points, the present simulation-based study with a constant IMF orientation shows for the first time that the combined effects of plasma pressure, magnetic field intensity, and the field-aligned current density distribution along the field line are likely to be major factors controlling the relative displacement of conjugate points.

DOI： 10.1029/2010JA016155

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：SIAM International Workshop on Data Mining for Marketing  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

We reproduce a magnetospheric reconfiguration under southward interplanetary magnetic field (IMF) conditions using numerical magnetohydrodynamic simulations. To investigate the relative displacements of the geomagnetic conjugate points, we trace both footprints of the geomagnetic field lines during the magnetospheric reconfiguration under positive and negative IMF By conditions. Several substormlike features, namely, the formation of a near-Earth neutral line, a fast earthward flow, and tailward releases of the plasmoid, occur about 1 h after a southward turning of the IMF. The surveyed field line traced from the near-Earth magnetotail was strongly distorted duskward in the north and south after the substorm onset for positive and negative IMF By, respectively. The maximum of the relative longitudinal displacement of both footprints is 4.5 and 5.5 h in magnetic local time for positive and negative IMF By, respectively. While observational studies have indicated that the IMF orientation is the main factor controlling the relative displacement of the conjugate points, the present simulation-based study with a constant IMF orientation shows for the first time that the combined effects of plasma pressure, magnetic field intensity, and the field-aligned current density distribution along the field line are likely to be major factors controlling the relative displacement of conjugate points. Copyright 2011 by the American Geophysical Union.

DOI： 10.1029/2010JA016155

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

Variations in the dayside field-aligned current (FAC) density (J //), field-aligned parallel potential drop (δφ //), peak precipitating electron energy (peak Ee), and precipitating electron energy flux (ε) as functions of solar wind (SW) and interplanetary magnetic field (IMF) are investigated with Defense Meteorological Satellite Program observations and a quasi-stationary low-latitude boundary layer (LLBL)-FAC coupling model. Region 1 (R1) J// responses to variations in SW velocity (Vsw) and density (nsw) at 8-16 magnetic local time (MLT) suggest that R1 at these local times is frequently open while R1 at 6-08 and 17-18 MLT is frequently closed. R2 is located mostly on closed field lines. In the afternoon open R1 at 12-16 MLT, an increase in nsw increases J//, decreases maximum peak Ee (δφ//), but has little effect on maximum ε. In the same R1 region, an increase in Vsw increases J//, maximum peak Ee, and maximum ε. The dependencies of J//, maximum peak Ee, and maximum ε are consistent with the Knight relation and the voltage generator at the magnetopause boundary in the afternoon open R1. In the midmorning and midafternoon, the response of J// to Vsw is higher for southward than for northward IMF. This can be attributed to the higher-velocity shear at the magnetopause boundary due to higher sunward convection in the LLBL inside the magnetopause. R1 in the closed-field lines near dawn and dusk appears to be more sensitive to merging rate (dΦ/dt = Vsw4/3 BT2/3 sin8/3(θc/2)) than to SW dynamic pressure. Copyright 2011 by the American Geophysical Union.

DOI： 10.1029/2011JA016579

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The source regions of region-0 (R0), region-1 (R1), and region-2 (R2) field-aligned currents (FACs) were statistically determined using DMSP particle precipitation and magnetometer data. Each FAC sheet originates from more than one region in the magnetosphere, depending on the latitude and the magnetic local time (MLT). R2 originates mostly from the central plasma sheet (CPS) and boundary plasma sheet (BPS) in the morning and from the CPS, BPS, and inner magnetosphere in the afternoon, all of which are on closed field lines. Near noon, some R2 may originate from the low-latitude boundary layer (LLBL), which is located near the magnetopause and can be open or closed. R1 mostly maps to the BPS, hence on closed field lines, in morning and afternoon, but near noon, it maps mostly to the LLBL. The LLBL source region can be found more frequently in the dawn-noon sector than in the noon-dusk sector. On the other hand, R0 is located mostly on open field lines and is associated mostly with mantle precipitation. However, the mantle precipitation has a dependency on the polarity of R0. Within up-flowing R0, sometimes an upward field-aligned electric field, which accelerates electron downward and retards ion precipitation, modifies mantle distribution to look more like those of polar rain or BPS. This electric field has the opposite polarity to the background electric field that maintains charge-quasi-neutrality and that limits some solar wind electrons from entering the magnetosphere in the mantle and polar rain regions. Implications to current generation mechanisms are discussed.

DOI： 10.1029/2010JA015837

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The present study statistically examines the location of various precipitation boundaries introduced by Newell et al. (1996) relative to R2 and R1 currents on the night side. Results are summarized as follows: (1) The electron and ion zero-energy boundaries, b1e and b1i, are located mostly inside the R2 current at dusk-to-midnight and near the equatorward boundary of the R2 current or farther equatorward at midnight-to-dawn. (2) The maximum energy flux of ion precipitation (b2i) occurs inside the R2 current irrespective of magnetic local time. (3) The occurrence distributions of the most equatorward (b3a) and poleward (b3b) electron acceleration events indicate that mono-energetic electron precipitation is mostly confined in the upward R1 current at dusk-to-midnight, whereas at midnight-to-dawn, it is more widely distributed including the downward R1 current. (4) The transition between structured and unstructured electron precipitation (b4s) tends to occur around the R2/R1 demarcation, but its occurrence distribution has extending tails. (5) The distributions of the poleward boundaries of the electron and ion auroral ovals, b5e and b5i, are centered around the poleward boundary of the R1 current but have extending tails especially at midnight-to-dawn. Result 1 suggests that the overlap between the ring current and the plasmasphere is more significant at dusk than at dawn. Result 2 indicates that the b2i boundary can be used as an identifier of the R2 current. Results 3-5 suggest that the R1 current is more structured than the R2 current and that the field-aligned current structure is more complex at midnight-to-dawn than at dusk-to-midnight.

DOI： 10.1029/2010JA015444

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：INST ENGINEERING TECHNOLOGY-IET  

The present study describes a frequency spectrum classification method for fault detection of the LP gas pressure regulator using support vector machines (SVMs). Conventional diagnosis methods are inefficient because of problems such as significant noise and non-linearity of the detection mechanism. In order to address these problems, a machine learning method with a divergence-based kernel is introduced into spectrum classification. The authors use the normalised frequency spectrum directly as input with the divergence-based kernel. The proposed method is applied to the vibration spectrum classification of the rubber diaphragm in a pressure regulator. As a result, the classification performance using the divergence-based kernel is shown to be better than when using common kernels such as the Gaussian kernel or the polynomial kernel. The high classification performance is achieved by using an inexpensive sensor system and the machine learning method. The proposed method is widely applicable to other spectrum classification applications without limitation on the generality if the spectra are normalised.

DOI： 10.1049/iet-spr.2008.0195

Web of Science

researchmap

掲載種別：研究論文（学術雑誌）  

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Motivation Biochemical reactions in cells are made of several types of biological circuits. In current systems biology, making differential equation ( DE) models simulatable in silico has been an appealing, general approach to uncover a complex world of biochemical reaction dynamics. Despite of a need for simulation-aided studies, our research field has yet provided no clear answers: how to specify kinetic values in models that are difficult to measure from experimental/theoretical analyses on biochemical kinetics.
Results: We present a novel non-parametric Bayesian approach to this problem. The key idea lies in the development of a Dirichlet process (DP) prior distribution, called Bayesian experts, which reflects substantive knowledge on reaction mechanisms inherent in given models and experimentally observable kinetic evidences to the subsequent parameter search. The DP prior identifies significant local regions of unknown parameter space before proceeding to the posterior analyses. This article reports that a Bayesian expert-inducing stochastic search can effectively explore unknown parameters of in silico transcription circuits such that solutions of DEs reproduce transcriptomic time course profiles.

DOI： 10.1093/bioinformatics/btq389

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Motivation Biochemical reactions in cells are made of several types of biological circuits. In current systems biology, making differential equation ( DE) models simulatable in silico has been an appealing, general approach to uncover a complex world of biochemical reaction dynamics. Despite of a need for simulation-aided studies, our research field has yet provided no clear answers: how to specify kinetic values in models that are difficult to measure from experimental/theoretical analyses on biochemical kinetics.
Results: We present a novel non-parametric Bayesian approach to this problem. The key idea lies in the development of a Dirichlet process (DP) prior distribution, called Bayesian experts, which reflects substantive knowledge on reaction mechanisms inherent in given models and experimentally observable kinetic evidences to the subsequent parameter search. The DP prior identifies significant local regions of unknown parameter space before proceeding to the posterior analyses. This article reports that a Bayesian expert-inducing stochastic search can effectively explore unknown parameters of in silico transcription circuits such that solutions of DEs reproduce transcriptomic time course profiles.

DOI： 10.1093/bioinformatics/btq389

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Any sensor for detecting a certain physical variable is more or less influenced by other physical variables, which are designated as "noise." The objective in conventional sensor design has been to minimize the noise. In this paper, however, we make use of sensing devices that are easily influenced by multiple physical variables andmake full use of their multisensing characteristic. We consider such devices as multiple-input-single-output sensors. First, the output signal derived from multiple input signals must be dissociated. The input signals resulting from physical phenomena have inherent characteristics and can mathematically be modeled. Application of a Kalman filter realized by such models can provide estimates of the state variables of all input models, and thus, the input signals are dissociated. As an example, a novel sensor based on a microphone is presented. This sensor can detect various variables such as pressure and acceleration in the frequency range of 0.1 Hz to 10 kHz, temperature, and even light emission. We apply the sensor to monitor the symptoms of fire, earthquake, and break-in by an intruder from within a house.

DOI： 10.1109/TIM.2009.2030716

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1109/ICIF.2010.5712015

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/qj.654

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The present study statistically examines the location of various precipitation boundaries introduced by Newell et al. (1996) relative to R2 and R1 currents on the night side. Results are summarized as follows: (1) The electron and ion zero-energy boundaries, b1e and b1i, are located mostly inside the R2 current at dusk-to-midnight and near the equatorward boundary of the R2 current or farther equatorward at midnight-to-dawn. (2) The maximum energy flux of ion precipitation (b2i) occurs inside the R2 current irrespective of magnetic local time. (3) The occurrence distributions of the most equatorward (b3a) and poleward (b3b) electron acceleration events indicate that mono-energetic electron precipitation is mostly confined in the upward R1 current at dusk-to-midnight, whereas at midnight-to-dawn, it is more widely distributed including the downward R1 current. (4) The transition between structured and unstructured electron precipitation (b4s) tends to occur around the R2/R1 demarcation, but its occurrence distribution has extending tails. (5) The distributions of the poleward boundaries of the electron and ion auroral ovals, b5e and b5i, are centered around the poleward boundary of the R1 current but have extending tails especially at midnight-to-dawn. Result 1 suggests that the overlap between the ring current and the plasmasphere is more significant at dusk than at dawn. Result 2 indicates that the b2i boundary can be used as an identifier of the R2 current. Results 3-5 suggest that the R1 current is more structured than the R2 current and that the field-aligned current structure is more complex at midnight-to-dawn than at dusk-to-midnight. Copyright 2010 by the American Geophysical Union.

DOI： 10.1029/2010JA015444

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The source regions of region-0 (R0), region-1 (R1), and region-2 (R2) field-aligned currents (FACs) were statistically determined using DMSP particle precipitation and magnetometer data. Each FAC sheet originates from more than one region in the magnetosphere, depending on the latitude and the magnetic local time (MLT). R2 originates mostly from the central plasma sheet (CPS) and boundary plasma sheet (BPS) in the morning and from the CPS, BPS, and inner magnetosphere in the afternoon, all of which are on closed field lines. Near noon, some R2 may originate from the low-latitude boundary layer (LLBL), which is located near the magnetopause and can be open or closed. R1 mostly maps to the BPS, hence on closed field lines, in morning and afternoon, but near noon, it maps mostly to the LLBL. The LLBL source region can be found more frequently in the dawn-noon sector than in the noon-dusk sector. On the other hand, R0 is located mostly on open field lines and is associated mostly with mantle precipitation. However, the mantle precipitation has a dependency on the polarity of R0. Within up-flowing R0, sometimes an upward field-aligned electric field, which accelerates electron downward and retards ion precipitation, modifies mantle distribution to look more like those of polar rain or BPS. This electric field has the opposite polarity to the background electric field that maintains charge-quasi-neutrality and that limits some solar wind electrons from entering the magnetosphere in the mantle and polar rain regions. Implications to current generation mechanisms are discussed. Copyright 2010 by the American Geophysical Union.

DOI： 10.1029/2010JA015837

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.1109/ICIF.2010.5712049

researchmap

掲載種別：研究論文（学術雑誌）  

DOI： 10.1504/IJKESDP.2010.037492

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WORLD SCIENTIFIC AND ENGINEERING ACAD AND SOC  

To predict an occurrence of extraordinary phenomena, such as earthquakes, failures of engineering system and financial market crushes, it is important to identify precursory events in time series. However, existing methods are limited in their applicability for real world precursor detections. Recently, Ide and Inoue [1] have developed an SSA-based change-point detection method, called singular spectrum transformation (SST). In this paper, we extend the SST so that it is applicable for real world precursor detections, focusing on the wide applicability of the conventional SST. Although the SST is suitable for detecting various types of change-points, detecting precursors can be far more difficult than expected because, in general, real world time series contains measurement noise and non-stationary trends. Furthermore, precursory events are usually observed as minute and less-visible fluctuations preceding an onset of massive fluctuations of extraordinary phenomena and therefore they are easily over-looked. To overcome this, we extend the conventional SST to the multivariable SST, focusing on the synchronism detection of precursory events in multiple sequences of univariate time series. First, we would like to define the problem setting of real world precursory detections and consider its difficulties. Second, the multivariable SST is introduced. Third, we apply SST to geomagnetic time series data and show the multivariable SST is more suitable than the conventional SST for real world precursor detections. Finally, we show further experimental results using artificial data to evaluate the reliability of SST-based precursor detections.

Web of Science

researchmap

掲載種別：研究論文（学術雑誌）  

DOI： 10.11345/nctam.58.101

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE Computer Society  

The estimation of many unknown parameters is carried out using a simplified Sequential Importance Sampling (SIS) algorithm which is implemented in a graphic processing unit (GPU). The aim of the present work is to show technical points to bring out the performance of GPU. Using the implemented code, two numerical experiments are demonstrated. In the first demonstration, it is shown that a parameter estimation involving 109 Monte Carlo samples is completed within eight hours. In the second demonstration, accuracy-guaranteed evaluation of the likelihood is carried out.

DOI： 10.1109/icif.2010.5712017

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The present study statistically addresses the dependence of large-scale field-aligned currents (R1/R2) and particle precipitation in the premidnight sector on solar illumination at the ionosphere. The energy flux and average energy of precipitating electrons and ions are examined for downward R2 and upward R1 currents. Results are summarized as follows: (1) The R1 current density is larger in the dark hemisphere, whereas the dependence of R2 density on solar illumination is unclear. (2) For R1 currents the electron energy flux is larger and the average electron energy is higher in the dark hemisphere. (3) For R2 currents, a similar preference for the dark hemisphere is found for the electron energy flux, which, however, is significantly lower than for R1 currents. The average electron energy is similar between the two hemispheres. (4) For both R1 and R2 currents, ion precipitation is more intense and energetic in the dark hemisphere. (5) For a given field-aligned current density, whether R1 or R2 currents, both electron and ion precipitation is more intense and energetic in the dark hemisphere. The Pedersen conductivity is estimated from electron precipitation and solar illumination. The result suggests that in the dark hemisphere the absence of solar illumination is often overcompensated by more intense and energetic electron precipitation. The interhemispheric difference in electron acceleration may be interpreted in terms of plasma density in the acceleration region, which is known to be significantly lower in the dark hemisphere, and therefore electrons need to be more accelerated along the field line to carry imposed currents.

DOI： 10.1029/2009JA014115

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The D(st) index is the most popular measure of a scale of magnetic storms, and it is widely used as a monitor of the conditions of the Earth's magnetosphere. Since the D(st) index contains contributions from multiple magnetospheric phenomena, it is important to distinguish each of the contributions in order to obtain meaningful information about the conditions of the magnetosphere. There have been several efforts which modeled temporal evolution of the D(st) index empirically. and these empirical models considers some contributions separately. However, they take only short-term varations into accout, and contributions from phenomena which show long-term variations are neglected. In the present study, we have developed a technique for estimating the component of long-term variations of the D(st) index using solar wind data and a nonlinear empirical model. The newly-developed technique adopts an algorithm which is similar to the particle filter. This algorithm allows an on-line processing of a long sequence of D(st) data, which would enable a real-time estimation of system variables in a nonlinear system model. The estimates of the long-term variations can be used for accurate estimation of other contributions to the D(st) index, which would provide credible information about the conditions of the magnetosphere. The framework proposed in the present study could be applied for the purpose of continuous real-time monitoring of the environment of the magnetosphere.

DOI： 10.1587/transinf.E92.D.1382

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

An accurate prediction of ocean tides in southeast Alaska is developed using a regional, barotropic ocean model with a finite difference scheme. The model skill is verified by the observational tidal harmonics in southeast Alaska including Glacier Bay. The result is particularly improved in Glacier Bay compared to the previous model described by Foreman et al. (2000). The model bathymetry dominates the model skill. We re-estimate tidal energy dissipation in the Alaska Panhandle and suggest a value for tidal energy dissipation of 3.4 GW associated with the M(2) constituent which is 1.5 times the estimation of Foreman et al. (2000). A large portion of the M(2) energy budget entering through Chatham Strait is dissipated in the vicinity of Glacier Bay. Moreover, it is shown that the developed model has the potential to correct the ocean tide loading effect in geodetic data more efficiently than the model of Foreman et al. (2000), especially around Glacier Bay.

DOI： 10.1007/s10872-009-0031-y

Web of Science

researchmap

掲載種別：研究論文（その他学術会議資料等）  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The relationship between the Region 2 field-aligned currents and the solar wind dynamic pressure is investigated using magnetic field data from Defense Meteorological Satellite Program-F13 (DMSP-F13). The generation of the Region 2 currents is associated with the direction of the magnetic pressure gradient in the magnetosphere, in relation to that of the thermal pressure gradient. Past spacecraft observations have suggested that the spatial distribution of the magnetic pressure in the magnetosphere varies with the solar wind dynamic pressure. Therefore, we can expect that the Region 2 currents would depend on the solar wind dynamic pressure. We compared the Region 2 field-aligned current intensity at the altitude of the ionosphere, as derived using magnetic field data from DMSP-F13, with the solar wind dynamic pressure derived from 0MNI2 hourly data. It was confirmed that the Region 2 current intensity depends on the solar wind dynamic pressure during magnetic storms. During nonstorm times, however, the correlation between the Region 2 currents and the solar wind dynamic pressure is weak. The weak correlation during nonstorm times suggests that the plasma pressure in the ring current region is also essential for the effect of the solar wind dynamic pressure on the Region 2 currents. © 2009.

DOI： 10.1029/2008JA013674

Scopus

researchmap

掲載種別：研究論文（その他学術会議資料等）  

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The relationship between the Region 2 field-aligned currents and the solar wind dynamic pressure is investigated using magnetic field data from Defense Meteorological Satellite Program-F13 (DMSP-F13). The generation of the Region 2 currents is associated with the direction of the magnetic pressure gradient in the magnetosphere, in relation to that of the thermal pressure gradient. Past spacecraft observations have suggested that the spatial distribution of the magnetic pressure in the magnetosphere varies with the solar wind dynamic pressure. Therefore, we can expect that the Region 2 currents would depend on the solar wind dynamic pressure. We compared the Region 2 field-aligned current intensity at the altitude of the ionosphere, as derived using magnetic field data from DMSP-F13, with the solar wind dynamic pressure derived from OMNI2 hourly data. It was confirmed that the Region 2 current intensity depends on the solar wind dynamic pressure during magnetic storms. During nonstorm times, however, the correlation between the Region 2 currents and the solar wind dynamic pressure is weak. The weak correlation during nonstorm times suggests that the plasma pressure in the ring current region is also essential for the effect of the solar wind dynamic pressure on the Region 2 currents.

DOI： 10.1029/2008JA013674

Web of Science

researchmap

掲載種別：研究論文（その他学術会議資料等）  

researchmap

掲載種別：研究論文（その他学術会議資料等）   出版者・発行元：Springer  

researchmap

掲載種別：研究論文（学術雑誌）  

DOI： 10.1109/ICASSP.2008.4517999

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD  

The aim of this paper is to demonstrate the potential power of large-scale particle filtering for the parameter estimations of in silico biological pathways where time course measurements of biochemical reactions are observable. The method of particle filtering has been a popular technique in the field of statistical science, which approximates posterior distributions of model parameters of dynamic system by using sequentially-generated Monte Carlo samples. In order to apply the particle filtering to system identifications of biological pathways, it is often needed to explore the posterior distributions which are defined over an exceedingly high-dimensional parameter space. It is then essential to use a fairly large amount of Monte Carlo samples to obtain an approximation with a high-degree of accuracy. In this paper, we address some implementation issues on large-scale particle filtering, and then, indicate the importance of large-scale computing for parameter learning of in silico biological pathways. We have tested the ability of the particle filtering with 10(8) Monte Carlo samples on the transcription circuit of circadian clock that contains 45 unknown kinetic parameters. The proposed approach could reveal clearly the shape of the posterior distributions over the 45 dimensional parameter space.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD  

The aim of this paper is to demonstrate the potential power of large-scale particle filtering for the parameter estimations of in silico biological pathways where time course measurements of biochemical reactions are observable. The method of particle filtering has been a popular technique in the field of statistical science, which approximates posterior distributions of model parameters of dynamic system by using sequentially-generated Monte Carlo samples. In order to apply the particle filtering to system identifications of biological pathways, it is often needed to explore the posterior distributions which are defined over an exceedingly high-dimensional parameter space. It is then essential to use a fairly large amount of Monte Carlo samples to obtain an approximation with a high-degree of accuracy. In this paper, we address some implementation issues on large-scale particle filtering, and then, indicate the importance of large-scale computing for parameter learning of in silico biological pathways. We have tested the ability of the particle filtering with 10(8) Monte Carlo samples on the transcription circuit of circadian clock that contains 45 unknown kinetic parameters. The proposed approach could reveal clearly the shape of the posterior distributions over the 45 dimensional parameter space.

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The present study statistically addresses the dependence of large-scale field-aligned currents (R1/R2) and particle precipitation in the premidnight sector on solar illumination at the ionosphere. The energy flux and average energy of precipitating electrons and ions are examined for downward R2 and upward Rl currents. Results are summarized as follows: (1) The Rl current density is larger in the dark hemisphere, whereas the dependence of R2 density on solar illumination is unclear. (2) For Rl currents the electron energy flux is larger and the average electron energy is higher in the dark hemisphere. (3) For R2 currents, a similar preference for the dark hemisphere is found for the electron energy flux, which, however, is significantly lower than for Rl currents. The average electron energy is similar between the two hemispheres. (4) For both Rl and R2 currents, ion precipitation is more intense and energetic in the dark hemisphere. (5) For a given field-aligned current density, whether Rl or R2 currents, both electron and ion precipitation is more intense and energetic in the dark hemisphere. The Pedersen conductivity is estimated from electron precipitation and solar illumination. The result suggests that in the dark hemisphere the absence of solar illumination is often overcompensated by more intense and energetic electron precipitation. The interhemispheric difference in electron acceleration may be interpreted in terms of plasma density in the acceleration region, which is known to be significantly lower in the dark hemisphere, and therefore electrons need to be more accelerated along the field line to carry imposed currents. Copyright 2009 by the American Geophysical Union.

DOI： 10.1029/2009JA014115

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：統計数理研究所  

要旨ありデータマイニングと統計数理研究ノート

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Motivation: Mathematical modeling and simulation, based on biochemical rate equations, provide us a rigorous tool for unraveling complex mechanisms of biological pathways. To proceed to simulation experiments, it is an essential. first step to. find effective values of model parameters, which are difficult to measure from in vivo and in vitro experiments. Furthermore, once a set of hypothetical models has been created, any statistical criterion is needed to test the ability of the constructed models and to proceed to model revision.
Results: The aim of our research is to present a new statistical technology towards data-driven construction of in silico biological pathways. The method starts with a knowledge-based modeling with hybrid functional Petri net. It then proceeds to the Bayesian learning of model parameters for which experimental data are available. This process exploits quantitative measurements of evolving biochemical reactions, e. g. gene expression data. Another important issue that we consider is statistical evaluation and comparison of the constructed hypothetical pathways. For this purpose, we have developed a new Bayesian information-theoretic measure that assesses the predictability and the biological robustness of in silico pathways.

DOI： 10.1093/bioinformatics/btn483

Web of Science

PubMed

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本統計学会  

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本統計学会  

現在,マーケティング分野ではCRMやOne to Oneマーケティングと呼ばれる活動が,その有効性から注目を浴びている.それらの活動は,顧客1人1人の好みや価値観,状況の違いを把握・認識し,それぞれのニーズに合わせて異なったアプローチを行おうというマーケティング・コンセプトに基づいている.統計的モデリングの観点からこれらの現象を的確に捉えるためには,"消費者異質性"や"消費者の動的変化"を評価しうるモデルの開発が必要になる.本研究でモデル化するマーケティングの現象は消費者の来店行動である.消費者の来店は,トレンドや週周期などの時系列成分及び天気やチラシ等の回帰成分などが作用して規定されると考えられる.本研究ではそれらを動的かつ個人単位で解析するためのモデルの提案及び解析事例を提示した.モデル化は一般状態空間モデルの枠組みで行い,そのモデルの推定は粒子フィルタ/平滑化のアルゴリズムで行った.モデルに基づく解析の結果,個人毎の来店の有無を高い精度で判別できることが示された.

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

We present a technique for estimating ring current ion distributions and electric potential in the inner magnetosphere by incorporating data from the High-Energy Neutral Atom (HENA) imager on the IMAGE satellite into a kinetic ring current model in the context of data assimilation. Data assimilation is an approach which adjusts a physicsbased model according to differences with observations. We perform the data assimilation using the particle filter (PF) which is applicable to high-dimensional systems and observations with relatively low computational cost. In the present technique, the magnetospheric electric potential distribution is represented by the sum of a Volland-Stern field and a deviation, and the deviation is improved in the assimilation process. The ring current ion distribution is then determined from the electric potential distribution. The method is tested by assimilating artificial data generated by another simulation. The results demonstrate that the ring current ion distribution is successfully reconstructed by the proposed algorithm and that the distorted structures of the electric potential distribution are also well reproduced. An example to illustrate how the present technique could be applied for assimilating a real IMAGE/HENA data set is also demonstrated. This technique provides a useful tool for investigating the global dynamic structure of ring current and electric potential. Copyright 2008 by the American Geophysical Union.

DOI： 10.1029/2006JA011853

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：計測自動制御学会  

DOI： 10.9746/ve.sicetr1965.44.444

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

We present a technique for estimating ring current ion distributions and electric potential in the inner magnetosphere by incorporating data from the High-Energy Neutral Atom (HENA) imager on the IMAGE satellite into a kinetic ring current model in the context of data assimilation. Data assimilation is an approach which adjusts a physics-based model according to differences with observations. We perform the data assimilation using the particle filter (PF) which is applicable to high-dimensional systems and observations with relatively low computational cost. In the present technique, the magnetospheric electric potential distribution is represented by the sum of a Volland-Stern field and a deviation, and the deviation is improved in the assimilation process. The ring current ion distribution is then determined from the electric potential distribution. The method is tested by assimilating artificial data generated by another simulation. The results demonstrate that the ring current ion distribution is successfully reconstructed by the proposed algorithm and that the distorted structures of the electric potential distribution are also well reproduced. An example to illustrate how the present technique could be applied for assimilating a real IMAGE/HENA data set is also demonstrated. This technique provides a useful tool for investigating the global dynamic structure of ring current and electric potential.

DOI： 10.1029/2006JA011853

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

We have developed a new geodetic inversion method for space-time distribution of fault slip velocity with time-varying smoothing regularization in order to reconstruct accurate time histories of aseismic fault slip transients. We introduce a temporal smoothing regularization on slip and slip velocity through a Bayesian state space approach in which the strength of regularization (temporal smoothness of slip velocity) is controlled by a hyperparameter. The time-varying smoothing regularization is realized by treating the hyperparameter as a time-dependent stochastic variable and adopting a hierarchical Bayesian state space model, in which a prior distribution on the hyperparameter is introduced in addition to a conventional Bayesian state space model. We have tested this inversion method on two synthetic data sets generated by simulated aseismic slip transients. Results show that our method reproduces well both rapid changes of slip velocity and steady-state velocity without significant oversmoothing and undersmoothing, which has been hard to overcome by the conventional Bayesian approach with time-independent smoothing regularization. Application of this method to transient deformation in 2002 caused by a silent earthquake off the Boso peninsula, Japan, also shows similar advantages of this method over the conventional approach.

DOI： 10.1111/j.1365-246X.2007.03722.x

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Motivation: Statistical inference of gene networks by using time-course microarray gene expression profiles is an essential step towards understanding the temporal structure of gene regulatory mechanisms. Unfortunately, most of the current studies have been limited to analysing a small number of genes because the length of time-course gene expression profiles is fairly short. One promising approach to overcome such a limitation is to infer gene networks by exploring the potential transcriptional modules which are sets of genes sharing a common function or involved in the same pathway.
Results: In this article, we present a novel approach based on the state space model to identify the transcriptional modules and module-based gene networks simultaneously. The state space model has the potential to infer large-scale gene networks, e.g. of order 10(3), from time-course gene expression profiles. Particularly, we succeeded in the identification of a cell cycle system by using the gene expression profiles of Saccharomyces cerevisiae in which the length of the time-course and number of genes were 24 and 4382, respectively. However, when analysing shorter time-course data, e.g. of length 10 or less, the parameter estimations of the state space model often fail due to overfitting. To extend the applicability of the state space model, we provide an approach to use the technical replicates of gene expression profiles, which are often measured in duplicate or triplicate. The use of technical replicates is important for achieving highly-efficient inferences of gene networks with short time-course data. The potential of the proposed method has been demonstrated through the time-course analysis of the gene expression profiles of human umbilical vein endothelial cells (HUVECs) undergoing growth factor deprivation-induced apoptosis.

DOI： 10.1093/bioinformatics/btm639

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Fusion of a simulation model and observation data has been investigated extensively for the purpose of data assimilation in geophysics. The inaccuracy of the parameters, initial conditions, or boundary conditions causes a discrepancy in the simulation results and the actual phenomenon. The present paper describes the parameter identification of a pressure regulator with a nonlinear structure by sequential Bayes estimation in the framework of data assimilation. A damping coefficient of feedback system in the pressure regulator that cannot be observed directly is estimated using a particle filter and a nonlinear state space model. The data assimilation concept is demonstrated using a pressure regulator as an engineering application.

DOI： 10.1109/ICIF.2008.4632304

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

In the kernel method, the appropriate selection or design of the kernel function is important for the construction of a high-performance classifier. The present paper describes a dynamic spectrum classification method using kernel classifiers with the divergence-based kernel and its application to the detection of worn-out banknotes. We introduce the divergence-based kernel that was proposed as a measure between two probability distributions into the dynamic spectrum classification. The present method is applied to the detection of worn-out banknotes by using acoustic signals for the facilitation of identifying counterfeit banknotes. As a result, the classification performance using the divergence-based kernel is shown to have better performance than those using common kernels such as the Gaussian kernel or the polynomial kernel.

DOI： 10.1109/ICASSP.2008.4517999

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IMPERIAL COLL PRESS  

We propose a statistical strategy to predict differentially regulated genes of case and control samples from time-course gene expression data by leveraging unpredictability of the expression patterns from the underlying regulatory system inferred by a state space model. The proposed method can screen out genes that show different patterns but generated by the same regulations in both samples, since these patterns can be predicted by the same model. Our strategy consists of three steps. Firstly, a gene regulatory system is inferred from the control data by a state space model. Then the obtained model for the underlying regulatory system of the control sample is used to predict the case data. Finally, by assessing the significance of the difference between case and predicted-case time-course data of each gene, we are able to detect the unpredictable genes that are the candidate as the key differences between the regulatory systems of case and control cells. We illustrate the whole process of the strategy by an actual example, where human small airway epithelial cell gene regulatory systems were generated from novel time courses of gene expressions following treatment with (case)/without(control) the drug gefitinib, an inhibitor for the epidermal growth factor receptor tyrosine kinase. Finally, in gefitinib response data we succeeded in finding unpredictable genes that are candidates of the specific targets of gefitinib. We also discussed differences in regulatory systems for the unpredictable genes. The proposed method would be a promising tool for identifying biomarkers and drug target genes.

DOI： 10.11234/gi1990.21.101

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IMPERIAL COLL PRESS  

We propose a statistical strategy to predict differentially regulated genes of case and control samples from time-course gene expression data by leveraging unpredictability of the expression patterns from the underlying regulatory system inferred by a state space model. The proposed method can screen out genes that show different patterns but generated by the same regulations in both samples, since these patterns can be predicted by the same model. Our strategy consists of three steps. Firstly, a gene regulatory system is inferred from the control data by a state space model. Then the obtained model for the underlying regulatory system of the control sample is used to predict the case data. Finally, by assessing the significance of the difference between case and predicted-case time-course data of each gene, we are able to detect the unpredictable genes that are the candidate as the key differences between the regulatory systems of case and control cells. We illustrate the whole process of the strategy by an actual example, where human small airway epithelial cell gene regulatory systems were generated from novel time courses of gene expressions following treatment with (case)/without(control) the drug gefitinib, an inhibitor for the epidermal growth factor receptor tyrosine kinase. Finally, in gefitinib response data we succeeded in finding unpredictable genes that are candidates of the specific targets of gefitinib. We also discussed differences in regulatory systems for the unpredictable genes. The proposed method would be a promising tool for identifying biomarkers and drug target genes.

DOI： 10.11234/gi1990.21.101

Web of Science

researchmap

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

In order to estimate accurate gene networks from time course gene expression data, replicated time course data are useful. However, existing methods do not clearly distinguish between biological and technical replicates, while these two kinds of replicates have different features. In this paper, we propose a statistical model based on state space models to use biologically and technically replicated time course data and show an algorithm to estimate a gene network that is a graphical representation of gene-gene regulation. To our knowledge, for estimating gene networks, the proposed model is the first model that can simultaneously use two types of replicated time course data. We show the effectiveness of the proposed method through the analysis of the microarray human T-cell data. © 2008 IEEE.

DOI： 10.1109/AMS.2008.150

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人電子情報通信学会  

線形判別学習機械であるサポートベクタマシン(SVM)は,非線形判別を可能とするカーネル法との組合せにより,今世紀に入り目覚ましい成功を収め今なお発展し続けている.しかしながら,能力の高い判別器の構成のためにはパラメータのチューニングに加え,適切なカーネル関数の設計が不可欠である.本研究では,正規化周波数スペクトル判別問題に対し,確率分布間の近さを測る指標であるKullback-Leiblerダイバージェンスをもとに作成されたカーネル関数を使用することで,より判別能力の高い非線形SVMの構成を目指す.また,その方法を高圧ガス圧力調整器のゴム膜劣化の診断に応用する.その結果として,本応用事例に対しては多項式カーネル,ガウシアンカーネルなどの一般によく使用されるカーネル関数を使用するよりも,高い判別性能をもつことを実験的に示す.

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

We study the statistical characteristics of four-sheet structures of large scale field-aligned currents (FACs) with an emphasis on particle precipitation collocated with each FAC sheet observed in dayside using magnetic field and particle precipitation data from the Defense Meteorological Satellite Program (DMSP). A total of 3247 four-sheet events were identified by applying an automatic procedure to the magnetic field data. The occurrence frequency of the events was less than 10% in each magnetic local time (MLT) sector for both hemispheres. The selected events were classified into two groups (type W and type M) with respect to the polarity of FACs. The polarity of the most equatorward type W (type M) FAC sheet is upward (downward). Type W (type M) events are observed predominantly in the morning (evening) sector and display a clear interplanetary magnetic field (IMF) BY dependence. Type W (type M) events appear for negative (positive) IMF BY in the Northern Hemisphere with the opposite dependence in the Southern Hemisphere. For each FAC sheet for type W events, we examined the occurrence of different precipitation regions identified with another automatic procedure. The most equatorward FAC sheet is collocated predominantly with central plasma sheet precipitation except for the prenoon sector, where boundary plasma sheet (BPS) precipitation has the highest occurrence. For the second and the third equatorward sheets, boundary layer-like precipitation, BPS near dawn and low-latitude boundary layer near noon, is dominant. In the most poleward sheet, mantle precipitation was observed frequently near noon, while BPS precipitation was dominant at earlier MLTs. These results, especially precipitation characteristics near noon, are consistent with our interpretation of the four-sheet structures, which is based on IMF BY dependence of convection patterns consisting of lobe, merging, and viscous cells. Copyright 2007 by the American Geophysical Union.

DOI： 10.1029/2006JA012036

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

We study the statistical characteristics of four-sheet structures of large scale field-aligned currents (FACs) with an emphasis on particle precipitation collocated with each FAC sheet observed in dayside using magnetic field and particle precipitation data from the Defense Meteorological Satellite Program (DMSP). A total of 3247 four-sheet events were identified by applying an automatic procedure to the magnetic field data. The occurrence frequency of the events was less than 10% in each magnetic local time (MLT) sector for both hemispheres. The selected events were classified into two groups (type Wand type M) with respect to the polarity of FACs. The polarity of the most equatorward type W (type M) FAC sheet is upward (downward). Type W (type M) events are observed predominantly in the morning (evening) sector and display a clear interplanetary magnetic field (IMF) B-Y dependence. Type W (type M) events appear for negative (positive) IMF B-Y in the Northern Hemisphere with the opposite dependence in the Southern Hemisphere. For each FAC sheet for type W events, we examined the occurrence of different precipitation regions identified with another automatic procedure. The most equatorward FAC sheet is collocated predominantly with central plasma sheet precipitation except for the prenoon sector, where boundary plasma sheet (BPS) precipitation has the highest occurrence. For the second and the third equatorward sheets, boundary layer-like precipitation, BPS near dawn and low-latitude boundary layer near noon, is dominant. In the most poleward sheet, mantle precipitation was observed frequently near noon, while BPS precipitation was dominant at earlier MLTs. These results, especially precipitation characteristics near noon, are consistent with our interpretation of the four-sheet structures, which is based on IMF B-Y dependence of convection patterns consisting of lobe, merging, and viscous cells.

DOI： 10.1029/2006JA012036

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In the framework of sensor fusion, multiple sensors corresponding to the number of physical variables that must be measured are used. In this paper, we propose a novel sensing approach that simultaneously deals with heterogeneous physical variables with a sensor. It is fundamentally different from sensor fusion. The proposed approach takes into consideration the fact that any sensor that detects a certain physical variable is influenced to a degree by other physical variables, which are designated as noise. The objective in conventional sensor design has been the minimization of noise. In contrast, the proposed approach takes advantage of sensors that are easily influenced by many physical variables and makes full use of the multisensing characteristics of these sensors. The system designed using this concept has advantages in terms of cost performance and system simplification compared to existing approaches. This concept can be realized by developing a novel multiple-input/single-output sensor that can detect various variables, including pressure, acceleration, temperature and incandescent light emission, by a single device. We apply the sensor to monitor the symptoms of fire, earthquakes, and break-ins for the purpose of home security. The proposed security system is realized through statistical signal processing and machine learning techniques.

DOI： 10.1109/JSEN.2007.894887

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：COPERNICUS PUBLICATIONS  

A new filtering technique for sequential data assimilation, the merging particle filter (MPF), is proposed. The MPF is devised to avoid the degeneration problem, which is inevitable in the particle filter (PF), without prohibitive computational cost. In addition, it is applicable to cases in which a nonlinear relationship exists between a state and observed data where the application of the ensemble Kalman filter (EnKF) is not effectual. In the MPF, the filtering procedure is performed based on sampling of a forecast ensemble as in the PF. However, unlike the PF, each member of a filtered ensemble is generated by merging multiple samples from the forecast ensemble such that the mean and covariance of the filtered distribution are approximately preserved. This merging of multiple samples allows the degeneration problem to be avoided. In the present study, the newly proposed MPF technique is introduced, and its performance is demonstrated experimentally.

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1527/tjsai.22.200

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

The present paper describes a frequency spectrum classification method for fault diagnosis of the LP gas pressure regulator using Support Vector Machines. Conventional diagnosis methods are not efficient because of problems such as significant noise and nonlinearity of the detection mechanism. In order to solve these problems, a machine learning method with the Kullback-Leibler (KL) kernel based on the KL divergence is introduced into spectrum classification. We use the normalized frequency spectrum directly as input with the KL kernel. The proposed method demonstrates a higher accuracy than popular kernels, such as polynomial or Gaussian kernels, or the conventional fault diagnosis method and Gaussian Mixture Model with the KL kernel for the examined problem. The high classification performance is achieved by using an inexpensive sensor system and the machine learning method. This method is widely applicable to other spectrum classification applications without limitation on the generality if the spectrums are normalized.

DOI： 10.1109/MLSP.2006.275593

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：METEOROLOGICAL SOC JAPAN  

We report an application of the ensemble Kalman filter (EnKF) and smoother (EnKS) to an intermediate coupled atmosphere-ocean model of Zebiak and Cane, into which the sea surface height (SSH) anomaly observations by TOPEX/POSEIDON (T/P) altimetry are assimilated. Smoothed estimates of the 54,403 dimensional state are obtained from 1,981 observational points with 2,048 ensemble members. While assimilated data are SSH anomalies alone, the estimated sea surface temperature (SST) anomalies reproduce primary temporal characteristics of the actual SST. The smoothed estimate of the zonal wind anomalies is also consistent with the observation except for the westerly anomalies in the western Pacific.

DOI： 10.2151/sola.2007-002

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IMPERIAL COLL PRESS  

We propose a novel method to classify samples where each sample is characterized by a time course gene expression profile. By exploiting the mixture of state space model, the proposed method addresses the following tasks: (1) clustering samples according to temporal patterns of gene expressions, (2) automatic detection of genes that discriminate identified clusters, (3) estimation of a restricted autoregressive coefficient for each cluster. We demonstrate the proposed method along with the cluster analysis of 53 multiple sclerosis patients under recombinant interferon beta therapy with the longitudinal time course expression profiles.

DOI： 10.11234/gi1990.18.258

Web of Science

PubMed

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人 人工知能学会  

The number of competing-brands changes by new products entry. The new product introduction is endemic among consumer packaged goods firm and is an integral component of their marketing strategy. As a new products entry affects markets, there is a pressing need to develop market response model that can adapt to such changes. In this paper, we develop a dynamic model that capture the underlying evolution of the buying behavior associated with the new product. This extends an application of a dynamic linear model, which is used by a number of time series analyses, by allowing the observed dime...

DOI： 10.1527/tjsai.22.200

researchmap

記述言語：日本語   出版者・発行元：統計数理研究所  

要旨あり予測と発見総合報告

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：電子情報通信学会情報・システムソサイエティ  

従来,センサ設計の目標はノイズの影響を可能な限り減少させ,対象とする物理量を高精度・高分解能・高信頼性で計測することである.しかし本論文では,従来のセンサ設計目標とは反対に多くの物理量から影響を受けるように設計されたセンサの使用による,安価でスマートなホームセキュリティシステムの開発について述べる.使用したセンサは一つのデバイスで圧力変動,加速度,温度変化,白熱光の四つの物理量をとらえ,各々の物理量の重み付き線形和で近似できるスカラ時系列を出力とする.そのため,ホームセキュリティの対象である火災,侵入(ドアの開閉,夜間の照明のオンオフ,ドアのこじ開け),地震を一つのセンサで検出することが可能である.しかし,その問題設定からオンラインで災害の検知・判別を行う必要がある.そこで,ARモデルによる確率的外れ値検出により災害発生を検知し,状態空間モデル上でのカルマンフィルタを用いた特徴抽出後,サポートベクタマシンを用い発生災害の判別を行った.この結果,従来は五つのセンサが必要であったホームセキュリテイの対象を一つのセンサにより監視できるシステムの可能性を示した.

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

One of the significant challenges in gene expression analysis is to find unknown subtypes of several diseases at the molecular levels. This task can be addressed by grouping gene expression patterns of the collected samples on the basis of a large number of genes. Application of commonly used clustering methods to such a dataset however are likely to fail owing to over-learning, because the number of samples to be grouped is much smaller than the data dimension which is equal to the number of genes involved in the dataset. To overcome such difficulty, we developed a novel model-based clustering method, referred to as the mixed factors analysis. The ArrayCluster is a freely available software to perform the mixed factors analysis. It provides us some analytic tools for clustering DNA microarray experiments, data visualization and an automatic detector for module transcriptional of genes that are relevant to the calibrated molecular subtypes and so on.

DOI： 10.1093/bioinformatics/btl129

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A track inspection car, which measures the shape of railway tracks (hereafter, rail geometry) while it is running on rails, discretizes the measurement results at nearly fixed spatial intervals. However, the distance between the discretized locations (spatial sampling intervals) may shorten or lengthen locally due to slipping or sliding of the car wheel, and this prevents the sampling locations from aligning with those of a dataset obtained with another measuring run. The authors developed an algorithm for approximately aligning the sampling locations of the measurement datasets obtained with different runs. First, they considered this problem as the selection of the series of data corresponding to each supervised data from a training dataset, which was constructed by interpolation in order to minimize the evaluation function of a number sequence representing data points. Next, they used the maximum likelihood method to identify the unknown parameters contained in the evaluation function. This problem uses two features of the evaluation function. The first is that the evaluation function is minimized by dynamic programming, and the obtained optimum sequence is equivalent to a maximum a posteriori (MAP) estimate in the Bayesian framework. The second is that by converting the evaluation function to a general state space representation, the log likelihood of the model that includes the parameters is obtained by a nonlinear filtering method. Also, to simplify the search for the identification, they devised a parameter search procedure for the parameters in the autoregressive (AR) model. © 2005 Wiley Periodicals, Inc.

DOI： 10.1002/scj.20313

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We propose a novel statistical method for estimating gene networks based on microarray gene expression data together with information from biological knowledge databases. Although a large amount of gene regulation information has already been stored in some biological databases, there are still errors and missing facts due to experimental problems and human errors. Therefore, we cannot blindly use them for understanding gene regulation and a robust procedure with a statistical model for using such database information is required. By using gene expression data, we provide a probabilistic framework of a joint learning model for repairing database information and for estimating a gene network based on dynamic Bayesian networks, simultaneously. To show the effectiveness of the proposed method, we analyze Saccharomyces cerevisiae cell-cycle gene expression data together with KEGG information. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.stamet.2005.09.013

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

We report the first application of the ensemble Kalman filter (EnKF) to an intermediate coupled atmosphere-ocean model by [1], into which the sea surface height (SSH) anomaly observations by TOPEX/POSEIDON (T/P) altimetry are assimilated. Smoothed estimates of the 54,403 dimensional state are obtained from 1981 observational points with 2048 ensemble members. While data assimilated are SSH anomalies alone, an ensemble experiment of 2002/03 El Ni (n) over tildeo event based on the EnKF can predict consistent Ni (n) over tildeo 3 sea surface temperature (SST) anomalies about 5 months in advance.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：INDERSCIENCE ENTERPRISES LTD  

We use linear Gaussian state-space models to analyse time-course gene expression data of yeast. They are modelled to be generated from hidden state variables in a system. To identify the system, we estimate parameters of the model by EM algorithm and determine the dimension of the state variable by BIC.

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Data assimilation is a method of combining an imperfect simulation model and a number of incomplete observation data. Sequential data assimilation is a data assimilation in which simulation variables are corrected at every time step of observation. The ensemble Kalman filter is developed for a sequential data assimilation and frequently used in geophysics. On the other hand, the particle filter developed and used in statistics is similar in view of ensemble-based method, but it has different properties. In this paper, these two ensemble based filters are compared and characterized through matrix representation. An application of sequential data assimilation to tsunami simulation model with a numerical experiment is also shown. The particle filter is employed for this application. An erroneous bottom topography is corrected in the numerical experiment, which demonstrates that the particle filter is useful tool as the sequential data assimilation method.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

Any sensor to detect a certain physical variable is influenced to some degree by other physical variables designated as "noise". The objective in conventional sensor design is to minimize such noise. In this study, conversely we welcome sensing devices that are easily influenced by many physical variables and make full use of their multi-sensing characteristic. We consider such devices as multiple-inputs and single-output sensors. The output signal derived from multiple input signals must be dissociated. The input signals resulting from physical realities have inherent characteristics and can be mathematically modeled. Application of a Kalman filter realized by such models can provide estimates of state variables of all input models, and thus the input signals can be dissociated. As an example, a novel sensor based on a microphone is presented. It can detect various variables such as pressure and acceleration in the frequency range of 0.1 Hz to 10 kHz, temperature, and even light emission. We use the sensor to monitor the symptoms of fire, earthquake and break-in by intruders from within a house.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE  

Conventional sensors have been designed to minimize noise effects. Any sensor that is designed to detect a certain physical variable is influenced to a certain degree by other physical variables. This suggests that any sensor is potentially capable of detecting multiple physical variables. In the present study, we consider sensing devices that are easily influenced by several physical variables and make full use of their multi-sensing characteristics through statistical signal processing and machine learning techniques with a wide variety of prior information. The proposed sensor design approach is completely different from the conventional approach with respect to system design and has advantages in terms of cost and system simplification compared to existing approaches. This new idea can be realized by developing a novel multiple-input/single-output sensor that can detect various variables such as pressure, acceleration, temperature and light emission by a single device. The sensor is applied to monitor the symptoms of fire, earthquake and break-in for the purpose of home security. The proposed security system consists of the following three steps: (1) Detection of disaster by a probabilistic outlier detection procedure using an auto-regressive model, (2) Disaster feature extraction by Kaiman filter on a state space model, and (3) Disaster classification by multiclass support vector machine.

Web of Science

researchmap

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：1  

DOI： 10.11234/gi1990.17.46

Scopus

researchmap

掲載種別：研究論文（学術雑誌）   出版者・発行元：2  

Scopus

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Institute of Electrical and Electronics Engineers Inc.  

Conventional sensors have been designed to minimize noise effects. Any sensor that is designed to detect a certain physical variable is influenced to a certain degree by other physical variables. This suggests that any sensor is potentially capable of detecting multiple physical variables. In the present study, we consider sensing devices that are easily influenced by several physical variables and make full use of their multi-sensing characteristics through statistical signal processing and machine learning techniques with a wide variety of prior Information. The proposed sensor design approach is completely different from the conventional approach with respect to system design and has advantages in terms of cost and system simplification compared to existing approaches. This new idea can be realized by developing a novel multiple-input/single-output sensor that can detect various variables such as pressure, acceleration, temperature and light emission by a single device. The sensor is applied to monitor the symptoms of fire, earthquake and break-in for the purpose of home security. The proposed security system consists of the following three steps: (1) Detection of disaster by a probabilistic outlier detection procedure using an auto-regressive model, (2) Disaster feature extraction by Kaiman filter on a state space model, and (3) Disaster classification by multiclass support vector machine. © 2006 IEEE.

DOI： 10.1109/ijcnn.2006.247296

Scopus

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本応用数理学会  

It is known that an execution of price and/or a non-price promotion has a strong influence on the sales of a brand sold in a supermarket. Usually, we can easily obtain information on a price promotion from a POS data. On the other hand, unless investigator collects information on an execution of non-price promotion in every retail store, we can not obtain such information. In this paper, we consider a problem to identify whether or not non-price promotion is conducted. We treat a non-price promotion execution/non-execution as a state variable. An unknown stationary probability matrix is ass...

DOI： 10.11540/jsiamt.15.4_537

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人電子情報通信学会  

非線形・非ガウス型時系列データを記述する広範囲の時系列モデルが, 状態空間モデルの一般化版である一般状態空間モデルで表現できる.カオス時系列, 隠れマルコフモデルもこのモデルの特殊ケースに当たる.一般状態空間モデルにおける高次元の状態ベクトルの推定手法として10年ほど前に提案され, 実装の容易さから様々な応用分野へ急速に普及しつつあるのが粒子フィルタである.この計算手法は, どのような非線形・非ガウスモデルも取り扱うことができるという点で原理的に万能であるばかりか, アルゴリズムの著しい簡単さから具体的応用問題に即適用可能である.本稿では一般状態空間モデルと粒子フィルタの概説及び遺伝的アルゴリズムとの類似性の解説のみを行い, 各方面での多様な応用成果については割愛する.

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：応用統計学会  

データ観測領域において何らかの事情により,ある領域でデータが観測できない状況がある.本論文は,まずデータの欠損数が未知と既知の2つの状況を2種類の統計モデルで提示し,これらが同値なモデルであることを示す.また複数の母集団分布が仮定される欠損領域を含む観測データがあり,意味のある成分分布に分ける必要がある.この目的のために,欠損状況を考慮した欠損混合分布モデルを提案し,パラメータの推定方法や欠損領域で観測されたと思われるデータ数を推定する方法を提案する.提案する統計モデルの有効性を数値実験を通して検証するとともに,プラズマ速度データへの適用を行う.

DOI： 10.5023/jappstat.34.57

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

[1] The present study statistically compares large-scale field-aligned currents (FACs) under sunlit and dark ionospheric conditions. A total of similar to 74,000 auroral oval crossings are selected from magnetic field measurements from the DMSP F7 and F12 to F15 satellites. For the dayside FAC it is reconfirmed that both current intensity and density are statistically larger in the illuminated events than in the unilluminated events. As for the nightside FAC, in contrast, a few important features become clear for the first time, which can be summarized as follows: ( 1) At 20 <= MLT < 02 both R1 and R2 intensities tend to be larger when the ionosphere is dark than when it is sunlit. ( 2) Although dependence on the ionospheric condition is less clear for the FAC density, a systematic preference of the occurrence of strong FACs for the dark ionosphere can be found for both R1 and R2 currents in the dusk-to-premidnight ( 16 <= MLT < 22) sector and for the R1 current in the postmidnight sector ( 00 <= MLT < 02). ( 3) For both FAC intensity and density the difference between the illuminated and unilluminated events tends to increase with increasing geomagnetic activity as measured by the IMF B-Z component. Result 1 can be partially explained in terms of the interhemispheric asymmetry of the magnetospheric configuration, which, however, should not affect the FAC density. Therefore result 2 strongly suggests that the solar-induced conductivity controls the M-I coupling in a different way in certain nightside MLT sectors than in dayside sectors.

DOI： 10.1029/2005JA011057

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

[ 1] The present study examines seasonal variations of large- scale field- aligned current ( FAC) systems in terms of the dipole tilt and clock angles. Magnetic field measurements from the DMSP F7 and F12- F15 satellites are used. This data set consists of a total of similar to 185,000 auroral oval crossings, out of which similar to 121,000 crossings were selected for the present analysis. Focus is placed on the latitude at the demarcation between the region 2 ( R2) and region 1 ( R1) currents and the intensities of these currents. It is found that the dayside FAC moves poleward and equatorward in the summer and winter hemispheres, respectively, and the nightside FAC has the opposite seasonal dependence. In the midday sector the peak- to- peak variation of the FAC latitude over the entire range of the dipole tilt is similar to5degrees, whereas it is similar to4degrees around midnight. In the flank sectors the average FAC latitude is higher around the solstices than around the equinoxes irrespective of hemisphere. The corresponding dependence on the dipole clock angle can actually be found for almost all local time sectors, although the peak- to- peak variation of the expected semiannual variation, 2 degrees around noon and < 1 ° in other local time sectors, is smaller than that of the annual variation except for the flank sectors. A comparison with a model magnetic field strongly suggests that the dipole tilt effect on the magnetospheric configuration is the primary cause of the annual variation, whereas the semiannual variation is inferred to reflect the fact that geomagnetic activity tends to be higher around the equinoxes. The average dayside FAC intensity is larger in the summer hemisphere than in the winter hemisphere, which can be explained in terms of the seasonal variation of the ionospheric conductivity. The dayside R1 current intensity depends more strongly on the dipole tilt than the dayside R2 current intensity, and it changes by a factor of 2 - 3 over the entire range of the dipole tilt angle. In contrast, the annual variation of the nightside FAC intensity is more complicated, and the nightside R2 current seems to be more intense in the winter hemisphere than in the summer hemisphere. The dependence of the FAC intensity on the dipole clock angle is less significant especially for the R1 system. Nevertheless, the result suggests that the FAC tends to be more intense around the equinoxes, which is consistent with the semiannual variation of geomagnetic activity.

DOI： 10.1029/2004JA010634

Web of Science

researchmap

記述言語：日本語   出版者・発行元：統計数理研究所  

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The present study statistically compares large-scale field-aligned currents (FACs) under sunlit and dark ionospheric conditions. A total of ∼74,000 auroral oval crossings are selected from magnetic field measurements from the DMSP F7 and F12 to F15 satellites. For the dayside FAC it is reconfirmed that both current intensity and density are statistically larger in the illuminated events than in the unilluminated events. As for the nightside FAC, in contrast, a few important features become clear for the first time, which can be summarized as follows: (1) At 20 ≤ MLT &lt
02 both R1 and R2 intensities tend to be larger when the ionosphere is dark than when it is sunlit. (2) Although dependence on the ionospheric condition is less clear for the FAC density, a systematic preference of the occurrence of strong FACs for the dark ionosphere can be found for both R1 and R2 currents in the dusk-to-premidnight (16 ≤ MLT &lt
22) sector and for the R1 current in the postmidnight sector (00 ≤ MLT &lt
02). (3) For both FAC intensity and density the difference between the illuminated and unilluminated events tends to increase with increasing geomagnetic activity as measured by the IMF BZ component. Result I can be partially explained in terms of the interhemispheric asymmetry of the magnetospheric configuration, which, however, should not affect the FAC density. Therefore result 2 strongly suggests that the solar-induced conductivity controls the M-I coupling in a different way in certain nightside MLT sectors than in dayside sectors. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2005JA011057

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE COMPUTER SOC  

In gene network, estimation from time series microarray data, dynamic models such as differential equations and dynamic Bayesian networks assume that the network structure is stable through all time points, while the real network might changes its structure depending on time, affection of some shocks and so on. If the true network structure underlying the data changes at certain points, the fitting of the usual dynamic linear models fails to estimate the structure of gene network and we cannot obtain efficient information from data. To solve this problem, we propose a dynamic linear model with Markov switching for estimating time-dependent network-struture from time series gene expression data. Using our proposed method, the network structure between genes and its change points are autoniatically estimated We demonstrate the effectiveness of the proposed method through the analysis of Saccharomyces cerevisiae cell cycle time series data.

DOI： 10.1109/CSB.2005.32

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE COMPUTER SOC  

In gene network, estimation from time series microarray data, dynamic models such as differential equations and dynamic Bayesian networks assume that the network structure is stable through all time points, while the real network might changes its structure depending on time, affection of some shocks and so on. If the true network structure underlying the data changes at certain points, the fitting of the usual dynamic linear models fails to estimate the structure of gene network and we cannot obtain efficient information from data. To solve this problem, we propose a dynamic linear model with Markov switching for estimating time-dependent network-struture from time series gene expression data. Using our proposed method, the network structure between genes and its change points are autoniatically estimated We demonstrate the effectiveness of the proposed method through the analysis of Saccharomyces cerevisiae cell cycle time series data.

DOI： 10.1109/CSB.2005.32

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Blackwell Publishing Ltd  

The present study examines seasonal variations of large-scale field-aligned current(FAC) Systems in terms of the dipole tilt and clock angles. Magnetic field measurements from the DMSP F7 and F12-F15 satellites are used. This data set consists of a total of ∼185,000 auroral oval crossings, out of which ∼121,000 crossings were selected for the present analysis. Focus is placed on the latitude at the demarcation between the region 2 (R2) and region 1 (R1) currents and the intensities of these currents. It is found that the dayside FAC moves poleward and equatorward in the summer and winter hemispheres, respectively, and the nightside FAC has the opposite seasonal dependence. In the midday sector the peak-to-peak variation of the FAC latitude over the entire range of the dipole tilt is ∼5°, whereas it is ∼4° around midnight. In the flank sectors the average FAC latitude is higher around the solstices than around the equinoxes irrespective of hemisphere. The corresponding dependence on the dipole clock angle can actually be found for almost all local time sectors, although the peak-to-peak variation of the expected semiannual variation, 2° around noon and &lt
1° in other local time sectors, is smaller than that of the annual variation except for the flank sectors. A comparison with a model magnetic field strongly suggests that the dipole tilt effect on the magnetospheric configuration is the primary cause of the annual variation, whereas the semiannual variation is inferred to reflect the fact that geomagnetic activity tends to be higher around the equinoxes. The average dayside FAC intensity is larger in the summer hemisphere than in the winter hemisphere, which can be explained in terms of the seasonal variation of the ionospheric conductivity. The dayside R1 current intensity depends more strongly on the dipole tilt than the dayside R2 current intensity, and it changes by a factor of 2-3 over the entire range of the dipole tilt angle. In contrast, the annual variation of the nightside FAC intensity is more complicated, and the nightside R2 current seems to be more intense in the winter hemisphere than in the summer hemisphere. The dependence of the FAC intensity on the dipole clock angle is less significant especially for the R1 system. Nevertheless, the result suggests that the FAC tends to be more intense around the equinoxes, which is consistent with the semiannual variation of geomagnetic activity. Copyright 2005 by the American Geophysical Union.

DOI： 10.1029/2004JA010634

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG BERLIN  

In this paper, we propose a new clustering procedure for high dimensional microarray data. Major difficulty in cluster analysis of microarray data is that the number of samples to be clustered is much smaller than the dimension of data which is equal to the number of genes used in an analysis. In such a case, the applicability of conventional model-based clustering is limited by the occurence of overlearning. A key idea of the proposed method is to seek a linear mapping of data onto the low-dimensional subspace before proceeding to cluster analysis. The linear mapping is constructed such that the transformed data successfully reveal clusters existed in the original data space. A clustering rule is applied to the transformed data rather than the original data. We also establish a link between this method and a probabilistic framework, that is, a penalized likelihood estimation of the mixed factors model. The effectiveness of the proposed method is demonstrated through the real application.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG BERLIN  

We propose a robust estimation method of gene networks based on microarray gene expression data. It is well-known that microarray data contain a large amount of noise and some outliers that interrupt the estimation of accurate gene networks. In addition, some relationships between genes are nonlinear, and linear models thus are not enough for capturing such a complex structure. In this paper, we utilize the moving boxcel median filter and the residual bootstrap for constructing a Bayesian network in order to attain robust estimation of gene networks. We conduct Monte Carlo simulations to examine the properties of the proposed method. We also analyze Saccharomyces cerevisiae cell cycle data as a real data example.

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人電子情報通信学会  

Pi2型地磁気脈動とは地球磁気圏内で観測される波形が不規則な周期40〜150秒の準周期的脈動で,初動部分が緩慢な変動をする特徴をもつ.地上磁場変動中で確認されるこの現象は,いまだにその開始時刻(オンセットタイム)の有効な決定法が確立していない.そこで本論文では,これまでの決定法の問題点を克服し,客観的かつ定量的にPi2のオンセットタイムを決定するために最ゆう法とベイズ推定を用いて構築した2種類の手法について述べる.一つ目の手法は,Pi2を準周期的波動成分を近似する確率差分方程式で表し,その成分を含むモデルと含まないモデルの最適分岐点,つまり波動成分(=Pi2)の開始点を情報量規準を用いて求めるものである.二つ目は,中・低緯度で観測された地上磁場変動のデータについてその値が急激に増加する点をオンセットタイムとみなすもので,磁場変動データの差分値に傾きをもった直線をあてはめ情報量規準で評価していき,最初に正の変動を示す点を決定した.この2種類の手法から求まるそれぞれのオンセットタイムの時間差からヒストグラムを作ったところ,Pi2には初助成分が存在することが確認された.

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL PUBLISHING LTD  

In the last decade, continuous Global Positioning System (GPS) networks have observed transient crustal deformation associated with various types of aseismic fault-slip event in many subduction zones. It is important to precisely clarify the entire time history of these events to understand the physical process of earthquake generation. For this purpose, we have developed a new time-dependent inversion method for imaging transient fault slips from geodetic data. Segall & Matthews (1997) presented a time-dependent inversion method to infer the spatiotemporal distribution of fault slip from geodetic data. They modelled a transient crustal deformation associated with fault-slip events using a linear Gaussian state space model and employed a Kalman filter. They introduced a scaling parameter that represents the temporal smoothness of the fault slip, and assumed that the scaling parameter is constant over the observation period. Under this assumption, abrupt changes of slip have been overly smoothed, whereas estimated slips in a 'quiet' steady-state period have been oscillatory. To improve the method, we developed a new filtering technique, a Monte Carlo mixture Kalman filter (MCMKF), and apply it to time-dependent inversion. The MCMKF allows variations of the temporal smoothness of slips by regarding it as a stochastic variable. The MCMKF is based on a Monte Carlo method in which conditional probability density functions of the stochastic variable are estimated recursively. We examine the validity of the introduced MCMKF-based inversion scheme through numerical experiments using simulated displacement time-series. Then, the results are compared with those obtained by a conventional Kalman filter-based scheme. In all cases, MCMKF gives a significantly smaller Akaike information criterion (AIC) values than the Kalman filter. This indicates that MCMKF yields better state estimates than the Kalman filter. We also find that MCMKF is capable of imaging the initiation process of transient slip events in cases with a high signal-to-noise ratio, while the Kalman filter is not. Furthermore, MCMKF is superior to the Kalman filter in detecting small signals from noisy data sets. From all of the results above, we conclude that the new filtering approach introduced here may provide a powerful tool for imaging the time history of fault slips.

DOI： 10.1111/j.1365-246X.2004.02383.x

Web of Science

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人電子情報通信学会  

軌道検測車は鉄道線路の形状を走行しながら測定し,得られる測定結果は,ほぼ一定の空間距離ごとに離散化されている.しかし,車輪の空転・滑走に伴って離散間隔が局所的に伸縮することがあり,異なる走行で得たデータセットとの測定位置をそろえる妨げになる.筆者らは,このようにして得られた測定データセットの測定位置を,近似的にそろえるアルゴリズムを開発した.まずこの問題を,補間により構成した学習データセットからの,教師データ一つひとつに対応するデータの選択とみなすことで,データポイントを表す数列の評価関数の最小化問題とした.次に,評価関数に含まれる未知のパラメータを最ゆう法によって推定した.本問題は,目的関数の二つの特徴を利用している.一つ目は,目的関数が動的計画法によって最小化でき,それがベイズ統計の枠組みにおけるMAP推定値(事後分布を最大化する推定値)と等価であること.二つ目は,目的関数を一般状態空間表現に変換できることにより,パラメータを含むモデルの対数ゆう度が非線形フィルタ演算で得られることである.また,最ゆう法における探索を簡略化するため,未知であるARモデルのパラメータ探索を工夫した.

CiNii Books

researchmap

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人日本オペレーションズ・リサーチ学会  

CiNii Books

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：1  

We propose a statistical method for estimating a gene network based on Bayesian networks from microarray gene expression data together with biological knowledge including protein-protein interactions, protein-DNA interactions, binding site information, existing literature and so on. Microarray data do not contain enough information for constructing gene networks accurately in many cases. Our method adds biological knowledge to the estimation method of gene networks under a Bayesian statistical framework, and also controls the trade-off between microarray information and biological knowledge automatically. We conduct Monte Carlo simulations to show the effectiveness of the proposed method. We analyze Saccharomyces cerevisiae gene expression data as an application. © Imperial College Press.

DOI： 10.1142/S021972000400048X

Scopus

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：KLUWER ACADEMIC PUBL  

The execution of price and/or display promotion has a significant effect on the sales of a brand sold in a supermarket. Information on price and/or sales is available from POS data. However, unless an investigator collects information on the execution of display promotions from every retail store, such information is unavailable. This paper presents a method of identifying whether display promotion has been executed without having to visit individual stores. We treat the execution/non-execution of a display promotion as a state variable. An unknown stationary probability matrix is assumed to describe the probability of a transition between states. Each state is characterized by a different stationary time series model with unknown parameters. The objective of the analysis is to identify the model and to assign a probability model for each state at each time instant. Finally, we provide a high precision estimator of a past execution/non-execution of a display promotion based on the proposed model.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE COMPUTER SOC  

When we cluster tissue samples on the basis of genes, the number of observations to be grouped is much smaller than the dimension of feature vector In such a case, the applicability of conventional model-based clustering is limited since the high dimensionality of feature vector leads to overfitting during the density estimation process. To overcome such difficulty, we attempt a methodological extension of the factor analysis. Our approach enables us not only to prevent from the occurrence of overfitting, but also to handle the issues of clustering, data compression and extracting a set of genes to be relevant to explain the group structure. The potential usefulness are demonstrated with the application to the leukemia dataset.

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE COMPUTER SOC  

When we cluster tissue samples on the basis of genes, the number of observations to be grouped is much smaller than the dimension of feature vector In such a case, the applicability of conventional model-based clustering is limited since the high dimensionality of feature vector leads to overfitting during the density estimation process. To overcome such difficulty, we attempt a methodological extension of the factor analysis. Our approach enables us not only to prevent from the occurrence of overfitting, but also to handle the issues of clustering, data compression and extracting a set of genes to be relevant to explain the group structure. The potential usefulness are demonstrated with the application to the leukemia dataset.

Web of Science

researchmap

記述言語：英語  

J-GLOBAL

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

[1] The occurrence epochs and duration periods of the 1969, 1978, and 1991 geomagnetic jerks are estimated for 65 geomagnetic observatories by applying a statistical time series model to monthly means of the geomagnetic eastward component. It is found for every jerk that the occurrence epochs around South Africa and South Pacific Ocean are delayed several years from those in other regions. Moreover, it is found for the 1969 and 1978 jerks that the duration times around South Africa, which are defined as the lengths of the duration periods, are longer than those in other regions. The distribution of these anomalous regions of the jerks (i.e., South Africa and South Pacific Ocean) may imply the existence of higher conductivities in the lower mantle beneath these regions, which possibly relates to the fact that the velocity of a seismic S wave in the D" layer beneath these regions is slower than that in other regions. The mantle conductivities beneath South Africa, South Pacific Ocean, and other regions are estimated through a numerical simulation; the magnetic diffusion equation in the mantle is solved for an abrupt magnetic change generated at the core-mantle boundary. Comparing the results obtained by the simulation with those obtained by the data analysis, it is plausible that the mantle conductivities beneath South Africa and South Pacific Ocean are higher than that beneath other regions, although there is an ambiguity in the estimated magnitudes of the mantle conductivity.

DOI： 10.1029/2002JB001786

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

This article is addressed to the problem of modeling and exploring mean value structure of large-scale time series data and time-space data. A smoothness prior modeling approach (Smoothness Prior Analysis of Time Series, Lecture Notes in Statistics, vol. 116, Springer, New York, 1996.) is taken. In this approach, the observed series are decomposed into several components each of which are expressed by smoothness priors models. In the analysis of POS and GPS data, various useful information were extracted by this decomposition, and result in discoveries in these areas. (C) 2002 Elsevier Science B.V. All rights reserved.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：IEEE COMPUTER SOC  

We propose a statistical method for estimating a gene network based on Bayesian networks from microarray gene expression data together with biological knowledge including protein-protein interactions, protein-DNA interactions, binding site information, existing literature and so on. Unfortunately, microarray data do not contain enough information for constructing gene networks accurately in many cases. Our method adds biological knowledge to the estimation method of gene networks under a Bayesian statistical framework; and also controls the trade-off between microarray information and biological knowledge automatically. We conduct Monte Carlo simulations to show the effectiveness of the proposed method We analyze Saccharomyces cerevisiae gene expression data as an application.

DOI： 10.1109/CSB.2003.1227309

Web of Science

PubMed

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TERRA SCIENTIFIC PUBL CO  

The geomagnetic jerk amplitudes, which are defined as abruptness of changes in the trends of geomagnetic time series, are investigated with geomagnetic monthly means computed from hourly mean values at each local time. A statistical time series model in which the trend component is expressed by a second order spline function with variable knots is constructed for each time series. The optimum parameter values of the model including positions of knots are estimated by the maximum likelihood method, and the optimum number of parameters including the number of knots are determined based on the Akaike Information Criterion (AIC). The jerks are detected objectively and automatically by regarding the optimized positions of knots as the occurrence epochs. This analysis reveals that the spatial distributions of jerk amplitudes essentially do not depend on the local time, which indicates that the jerks cannot be explained by abrupt changes in intensities of latitudinally flowing external currents such as the field-aligned currents. Longitudinally flowing currents, on the other hand, such as the ring current could explain the distributions. The abrupt changes of the ring current intensity are estimated from the distributions of jerk amplitudes in the eastward component in 1969, 1978, and 1991 supposing that an abrupt change in the ring current intensity causes a jerk. However those estimated changes cannot consistently explain the distributions of the jerks in the northward and downward components. Therefore it is plausible that the jerks which occur-red in 1969, 1978, and 1991 are not caused by external sources but internal ones. It is also confirmed that the occurrence epochs of jerks in the southern hemisphere are a few years after those of the 1969 and 1978 jerks in the northern hemisphere. and it is also found that the jerk in the southern hemisphere occurred a few years after the occurrence of the 1991 jerk in Europe. Taking these time tags in occurrence epochs into account, it can be said that the 1969, 1978, and 1991 jerks are global phenomena.

DOI： 10.1186/BF03351712

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：PHYSICA-VERLAG GMBH & CO  

Tracking problem of maneuvering target is treated with assumption that the maneuver is unknown and its acceleration has abrupt changes sometimes. To cope with unknown maneuver, Bayesian switching structure model, which includes a set of possible models and switches among them, is used. It can be formalized into general (nonlinear, non-Gaussian) state space model where system model describes the target dynamics and observation model represents a process to observe the target position. Heavy-tailed uni-modal distribution, e.g. Cauchy distribution, is used for the system noise to accomplish good performance of tracking both for constant period and abrupt changing time point of acceleration. Monte Carlo filter, which is a kind of particle filter that approximates state distribution by many particles in state space, is used for the state estimation of the model. A simulation study shows the efficiency of the proposed model by comparing with Gaussian case of Bayesian switching structure model.

Web of Science

researchmap

記述言語：日本語   出版者・発行元：一般社団法人 日本応用数理学会  

DOI： 10.11540/bjsiam.12.2_216

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：PHYSICA-VERLAG GMBH & CO  

By the progress of fast computing facilities and various computing technologies, it becomes realistic to apply computer intensive methods to statistical analysis. In time series analysis, sequential Monte Carlo methods was developed for general state space models which enables to consider very complex nonlinear non-Gaussian models.
In this paper, we show algorithms, implementations and parameter estimation for Monte Carlo filter and smoother. Various ways of the use of parallel computer. are also discussed. The usefulness of the general state space modeling is illustrated with several examples.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

SGURP

DOI： 10.1007/3-540-45884-0_27

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/3-540-45884-0_26

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

Recent space plasma observations have provided us with three-dimensional velocity distributions having multiple peaks. We propose a method for analyzing such velocity distributions via a multivariate Maxwellian mixture model where each component of the model represents each of the multiple peaks. The parameters of the model are determined through an iterative nonlinear optimization technique, specifically the expectation-maximization (EM) algorithm. For the automatic judgment of the preferable number of components in the mixture model, we introduce a method of examining the number of extrema of a resulting mixture model. We show applications of our method to ion observations in the plasma sheet boundary layer (PSBL) and in the central plasma sheet (CPS) of the Earth's magnetotail. From an analysis of the PSBL and CPS, low-energy ions that have properties similar to those of lobe ions were detected also in the PSBL and CPS. In the PSBL, middle-energy ion component which is flowing dawnward and directed the neutral sheet was extracted. We suggested that magnetic field fluctuations in the PSBL can be explained only when the two ion components were properly treated.

DOI： 10.1029/2001JA900079

DOI： 10.1029/2001ja900079

Web of Science

researchmap

In this study,we consider a time series model which combines the partial nonGaussian state space model and self-organizing state space model (SOSSM), where the SOSSM has been proposed to an extension of the generalized state space model. The competing different system/observation models for the state vector can be simultaneously dealt in this model as introducing a switching structure, and appropriate system/observation models among them is automatically determined as a function of time. As a result, we are free from a procedure of selecting models among competing models. Of course, this model allows us to consider an inclusion of two system/observation models which conflicts each other in some sense. Namely,we need not havewell-organized knowledge about modeling of the time series. We therefore call this model the evolutionary time series model. We regard the approach based on the evolutionary time series model as one of the machine learning approaches. The evolutionary time series model can be formulated within a framework of an extension of SOSSM whichtakes a convenient form from a computational point of view.

researchmap

掲載種別：研究論文（国際会議プロシーディングス）  

Abstract. Electron velocity distribution obtained by direct spacecraft observation in space is contaminated by photoelectrons. The photoelectrons are generated due to the solar ultraviolet ray, and are regarded as artificial noise from a viewpoint of scientific research. We propose a method for separating photoelectron component from ambient electron component. Our method uses multivariate normal mixture model, whose parameters are determined via the Expectation-Maximization (EM) algorithm. Initial parameters of the EM algorithm are computed through the classification of the velocity space by a spherical surface of some arbitrary radius. 1

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The study of large-scale field-aligned currents (LSFACs) has depended on visual inspection of data plots, which is often subjective and time-consuming, and therefore limits the efficiency of analyses. The present paper reports a new procedure to automatically identify the spatial structure of LSFACs from satellite magnetic field measurements. The procedure is based on the concept of the first-order B spline fitting with variable node positions, which may be envisioned as fitting line segments to a line plot. The fitting is made for the maximum variance component of magnetic variations in the plane perpendicular to the background magnetic field. If the distribution of LSFACs can be approximated as an infinite sheet, each slope of the plot corresponds to the crossing of a FAC sheet. The number of node points, which determines the number of FAC sheets, is one of the fitting parameters and is optimized for each orbit so that the Akaike information criterion (AIC) is minimized. Whereas other methods, such as a spherical harmonic fitting, seek to obtain two-dimensional distributions of FACs from assembled data, the present method is basically the automation of the way we visually examine a plot of satellite magnetic field data, and it can be applied even to a single satellite pass. Therefore the procedure can be implemented to real-time data processing and now-casting. The procedure should also provide a powerful tool for data mining. Magnetic field data from the Defense Meteorological Satellite Program-F7 (DMSP-F7) were used for demonstration, and the present paper reports the initial results.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

The present study investigates the statistical characteristics of four-sheet structures of large-scale field aligned currents (FACs) observed by the Defense Meteorological Satellite Program-F7 (DMSP-F7) satellite in the dayside high-latitude region. A total of 495 four-FAG-sheet events were selected from the entire set of DMSP-F7 magnetometer data. With respect to the polarity of FACs, the selected events are classified into two groups, which are named type M and type W after the shape of a plot of the azimuthal magnetic component. The polarity of the equatorward most FAC is downward for the type M structure, whereas it is upward for the type W structure. Type W and type M events tend to take place in the prenoon and postnoon sectors, respectively, but the transition takes place slightly before noon. The type W structure tends to be observed for negative and positive interplanetary magnetic field (IMF) B-y,in the Northern and Southern Hemispheres, respectively. For a given hemisphere, the favorable sign of IMF B-Y, for the type M structure is opposite to that for the type W structure. It is also found that both types occur more often when the IMF B-Z, is northward than when it is southward. The four-sheet structure can be interpreted in terms of two zonal ionospheric convection flows separated in latitude. The equatorward one is a part of the viscous cell and, possibly, also the merging cell, whereas the poleward one is a part of the lobe cell. The direction (of the major cell) of the lobe convection is determined by the sign of IMF By and is different in different hemispheres, explaining the discovered IMF B-Y dependence. The preference for northward IMF B-Z, is consistent with the required development of the lobe convection. It is inferred from the expected polar distribution of FACs that the four-sheet structure is a superposition of a pair of midday region 0 and region 1 currents and a pair of conventional region 1 and region 2 currents.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

SGURP

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：AMER GEOPHYSICAL UNION  

The present paper reports a newly developed procedure to automatically identify : a spatial structure of large-scale field-aligned currents (FACs) from satellite magnetic field measurements. The procedure is based on the concept of the first-order B-spline fitting with variable (i.e., movable) node positions, which may be envisioned as fitting line segments to a,plot of a magnetic field component. The number of node points is optimized for each current sheet crossing so that a certain information criterion is minimized. The properties of a FAC system such as its location and intensity can be easily calculated from the information of node points. The procedure is applied to the entire set of nightside magnetic field measurements (1339 days) made by the DMSP-F7 satellite and for demonstration, the intensity of nightside region-1 FACs is examined as a function of magnetic latitude. The results not only confirm the general expectation that intense region 1 currents tend to be observed at lower latitudes but also quantify the relationship between the current intensity and latitude. The capability of such quantification should be useful for future studies including practical applications such as space weather forecast.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：AMER GEOPHYSICAL UNION  

Large-scale field-aligned current (FAC) systems occasionally disappear in the midday sector (9 < MLT < 13), even though this is the local time sector where FACs tend to be most intense. The present study investigates 26 such events observed by the DMSP-F7 satellite. It is found that the events tend to occur in the winter hemisphere in a certain UT range when the dipole axis was inclined most antisunward and therefore the contribution of solar illumination to the ionospheric conductivity is minimum. Before most events, IMF B(Z) was positive, and the solar wind bulk flow momentum was below the average. Although one might expect to see such events when the sign of B(X) was unfavorable for merging at the high-latitude tail magnetopause in the winter hemisphere, no clear preference for IMF B(X) was found. It was also found that the asymmetry of the ionospheric conductivity between the summer and winter hemispheres suppresses the IMF-dependent characteristics of particle precipitation in the polar cap. These results suggest that ionospheric conductivity not only determines the intensity of FACs for the convection electric field imposed by the solar wind-magnetosphere interaction, but also affects how the magnetosphere interacts with the solar wind.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG BERLIN  

DOI： 10.1007/3-540-46846-3_51

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG BERLIN  

This article is addressed to the problem of modeling and exploring time series with mean value structure of large scale time series data and time-space data. A smoothness priors modeling approach [11] is taken and applied to POS and GPS data. In this approach, the observed series are decomposed into several components each of which are expressed by smoothness priors models. In the analysis of POS and GPS data, various useful information were extracted by this decomposition, and result in some discoveries in these areas.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER-VERLAG BERLIN  

The statistical information processing can be characterized by using the Likelihood function defined by giving an explicit form for an approximation to the true distribution from which the data are generated. This mathematical representation as an approximation, which is usually called a model, is built based on not only the current data but also prior knowledge on the object and the objective of the analysis. Akaike ([2] and [3]) showed that the log-likelihood can be considered as an estimate of the Kullback-Leibler information which defines the similarity between the predictive distribution of the model and the true distribution and proposed the Akaike information criterion (AIC). By the use of this AIC, it becomes possible to evaluate and compare the goodness of many models objectively and it enables us to select the best model among many candidates. In consequence, the minimum AIC procedure allows us to develop automatic modeling and signal extraction procedures. In this study, we give a simple explanation of statistical modeling based on the AIC and demonstrate four examples of applying the minimum AIC procedure to an automatic transaction of signals observed in the earth sciences. In each case, the AIC plays an important role in making the procedure automatic and objective, and promises to realize a detail examination of a large amount of data sets, which provides us with an opportunity to discover new information.

Web of Science

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：European Geosciences Union  

In order to determine the normal direction of the magnetopause, the minimum variance analysis technique is frequently used: it is applied to the magnetic field data of a magnetopause crossing observed by a satellite, and provides the direction along which the magnetic field variation is minimum. In this study we propose a method to extend naturally the framework of the minimum variance analysis so that it includes all continuity conditions across a planar magnetopause, so that we could use all physical quantities observed by the spacecraft. We first extend it to the electric field: we discuss how to determine the normal direction and the speed of the magnetopause along the normal by using both the magnetic and electric field data. We next discuss the full extension to all continuity conditions across the magnetopause. Finally, we discuss how to extend our method further so that it can deal with the magnetopause which is accelerating. A discussion of application to observations will appear separately.

DOI： 10.1007/s00585-996-1019-1

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The minimum variance analysis technique introduced by Sonnerup and Cahill (1967) is a useful tool in space physics. However the statistical errors appearing in this method are difficult to estimate accurately because of the complicated form of the eigenvalue decomposition. To deal with this problem, this paper introduces the bootstrap method (Efron, 1979) which replaces analytical solutions with repeated simple calculations. We apply this method to the estimation of the statistical errors in the minimum variance direction and the average component in the minimum variance direction, and show that this method accurately estimates the errors. Copyright 1995 by the American Geophysical Union.

DOI： 10.1029/94GL02969

Scopus

researchmap

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Springer Verlag  

The statistical information processing can be characterized by using the likelihood function defined by giving an explicit form for an approximation to the true distribution from which the data are generated. This mathematical representation as an approximation, which is usually called a model, is built based on not only the current data but also prior knowledge on the object and the objective of the analysis. Akaike ([2] and [3]) showed that the log-likelihood can be considered as an estimate of the Kullback-Leibler information which defines the similarity between the predictive distribution of the model and the true distribution and proposed the Akaike information criterion (AIC). By the use of this AIC, it becomes possible to evaluate and compare the goodness of many models objectively and it enables us to select the best model among many candidates. In consequence, the minimum AIC procedure allows us to develop automatic modeling and signal extraction procedures. In this study, we give a simple explanation of statistical modeling based on the AIC and demonstrate four examples of applying the minimum AIC procedure to an automatic transaction of signals observed in the earth sciences. In each case, the AIC plays an important role in making the procedure automatic and objective, and promises to realize a detail examination of a large amount of data sets, which provides us with an opportunity to discover new information.

Scopus

researchmap

1.1 Generalized state space model The generalized state space model (GSSM) that we deal with in this study is de ned by a set of two equations system model xt = f(xt;1 � vt) � and (1.1)

researchmap

総ページ数：203   担当ページ：pp145-168  

ASIN

researchmap

総ページ数：209  

ASIN

researchmap

総ページ数：xii, 204p   記述言語：日本語  

researchmap

総ページ数：xvii, 349p   記述言語：日本語   著書種別：学術書

ASIN

researchmap

総ページ数：xiii, 433p   記述言語：日本語   著書種別：学術書

ASIN

researchmap

総ページ数：256  

ASIN

researchmap

総ページ数：158  

ASIN

researchmap

総ページ数：x, 323p, 図版 [2] p   記述言語：日本語  

researchmap

researchmap

総ページ数：136  

ASIN

researchmap

総ページ数：210  

ASIN

researchmap

総ページ数：vii, 262p   記述言語：日本語  

researchmap

担当ページ：pp429-444   記述言語：英語  

researchmap

researchmap

総ページ数：2冊   記述言語：日本語  

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

researchmap

記述言語：日本語  

researchmap

記述言語：日本語  

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

researchmap

記述言語：日本語  

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）   出版者・発行元：国立研究開発法人 科学技術振興機構  

DOI： 10.1241/johokanri.59.629

CiNii Books

researchmap

その他リンク： http://search.jamas.or.jp/link/ui/2017054109

記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）  

DOI： 10.1241/johokanri.59.331

researchmap

記述言語：日本語   出版者・発行元：ダイヤモンド社  

CiNii Books

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）   出版者・発行元：国立研究開発法人 科学技術振興機構  

DOI： 10.1241/johokanri.59.53

CiNii Books

researchmap

その他リンク： https://jlc.jst.go.jp/DN/JLC/20022241236?from=CiNii

記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）   出版者・発行元：日本統計協会  

CiNii Books

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）   出版者・発行元：電子情報通信学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：交通工学研究会  

CiNii Books

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：(公社)日本生化学会  

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

researchmap

記述言語：日本語   出版者・発行元：日本分子腫瘍マーカー研究会  

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）  

DOI： 10.7210/jrsj.33.68

researchmap

記述言語：日本語   出版者・発行元：日本分子腫瘍マーカー研究会  

DOI： 10.11241/jsmtmr.31.46

researchmap

記述言語：日本語   出版者・発行元：公益社団法人 日本雪氷学会／日本雪工学会  

DOI： 10.14851/jcsir.2015.0_63

J-GLOBAL

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）   出版者・発行元：一般社団法人電子情報通信学会  

地球大気などのような大規模な非線形システムの振舞いを計算機上で再現するには,シミュレーションモデルの中に様々な観測データの情報を取り入れるデータ同化と呼ばれる手続きが重要となる.気象モデルに同化される衛星観測データなどの様々なデータは,それ自体が膨大な量であるが,データ同化によって得られる計算結果は,空間全体を網羅した更に膨大なデータとなる.そして,これを気象や気候などの将来予測に役立てるためには,この膨大なデータに不確実性の情報も付加する必要がある.そこで,データ同化において以前から用いられている不確実性の計算方法を概観するとともに,エミュレーションと呼ばれるシミュレーションを模倣したモデルによる不確実性の評価方法についても議論する.

CiNii Books

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：日本放送協会放送技術研究所  

CiNii Books

researchmap

記述言語：英語   出版者・発行元：American Geophysical Union  

CiNii Books

researchmap

記述言語：英語   出版者・発行元：American Geophysical Union  

CiNii Books

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）   出版者・発行元：特定非営利活動法人 横断型基幹科学技術研究団体連合  

This document gives a brief explanation for what is "Statistical Mathematics," and describeshow its notion has been expanding to a wide variety of research fields. The recent interests ofstatistical mathematics are focused on generating more flexible mathematical models for describingcomplex phenomena in terms of data generation mechanism and/or its function. Such efforts demandcollaborative works with the machine learning community in a big data era which we are now facedwith.

DOI： 10.11487/trafst.8.1_14

CiNii Books

researchmap

その他リンク： https://jlc.jst.go.jp/DN/JALC/10035139040?from=CiNii

掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）  

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：日本シミュレーション学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本シミュレーション学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：小宮山印刷工業  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：公益社団法人 日本雪氷学会／日本雪工学会  

DOI： 10.14851/jcsir.2013.0_153

J-GLOBAL

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：ダイヤモンド社  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

CiNii Books

researchmap

記述言語：英語  

J-GLOBAL

researchmap

掲載種別：記事・総説・解説・論説等（学術雑誌）  

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：日本気象学会  

CiNii Books

J-GLOBAL

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）   出版者・発行元：日本流体力学学会  

CiNii Books

researchmap

その他リンク： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=377136

記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：AMER ASSOC CANCER RESEARCH  

DOI： 10.1158/1538-7445.AM2012-LB-99

Web of Science

researchmap

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

researchmap

記述言語：日本語   出版者・発行元：日本評論社  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：一般社団法人電子情報通信学会  

本研究では,3Dモーションキャプチャーデータ(MoCapデータ)を用いて,キャラクターのアニメーション生成を行う.MoCapデータは,ビデオカメラと全く同じ動きをキャラクターに取り込むことを可能にするが,アニメーションの制作にあたっては,生理学的な基本的な動きに,制作者独自のアーティスティックな部分を加味することが重要である.そこで,編集機能をより柔軟にして,MoCapデータでは得られなかった高品質のアニメーションを作成できる方法を提案する.

CiNii Books

researchmap

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：情報処理学会  

一般に，前兆現象は突発現象にそのものに比べて非常に目立ちにくく，その開始時刻は曖昧である．従来よく用いられてきた変化点検出法を適用した場合，このような微小で緩慢な変化は見逃されやすい．Tokunaga et al.1) では，Ide and Inoue2) の提案した特異スペクトル分析を応用した変化点検出法 (SST) を，多次元データを用いたアルゴリズム (MSST) へと拡張することで，鋭敏に前兆現象の開始時刻を推定出来ることを示した．MSST は，緩慢な変化も検出できる鋭敏な手法であるが，実データへの適用では誤検出が問題になる．本稿では，突発現象の大まかな開始時刻を予め検出し，さらに検出された時刻の前後で前兆現象の開始時刻と終了時刻を個別に探索することで，誤検出を劇的に減少させることができることを示す．

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：東京 : 岩波書店  

CiNii Books

CiNii Research

researchmap

その他リンク： http://id.ndl.go.jp/bib/10887823

記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

Data Assimilation (DA) is a technique for a synthesis of information from a dynamic numerical model and observation data. In statistical methodology, DA can be formulated in the generalized state space model. We briefly explain a recent advancement in the ensemble-based sequential DA (EnSDA), and discuss on how EnSDA is employed in combining CFD and EFD.

CiNii Books

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：AMER ASSOC CANCER RESEARCH  

DOI： 10.1158/1538-7445.AM10-LB-132

Web of Science

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：宇宙航空研究開発機構  

第6回宇宙環境シンポジウム (2009年2月29日-30日. 北九州国際会議場)
6th Spacecraft Enivironment Symposium (February 29-30, 2009. Kitakyushu International Conference Center)
形態: カラー図版あり
Physical characteristics: Original contains color illustrations
資料番号: AA0064542030
レポート番号: JAXA-SP-09-006

CiNii Books

CiNii Research

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：情報処理学会  

バイオロジカルパスウェイモデルのパラメータ推定は探査空間が高次元空間となり、モデルの非線形性もあいまって困難な問題となりうる。近年話題に上ることが多い GPGPU の並列計算機能を活かした粒子フィルタを実装した。SIS 粒子フィルタを用いて各ノードで行う処理は非同期かつ独立であり、初期データの転送、処理結果の集計以外に通信は発生しない。試計算の結果、67 倍の高速化が得られた。The parameter estimation of biological pathway models is a difficult problem. The difficulty comes from the high dimensionality and the nonlinearity make of models. We combat this problem by means of an parallelised particle filter algorithm dedicated to parallel environment, particular GPGPU. Our algorithm is based on SIS (Sequential Importance Sampling) and hence no communication occurs during the simulation. We have increased the computation speed 67 times, compared to a computation with a single CPU core.

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1001/00067005/

記述言語：日本語   出版者・発行元：日本統計学会  

生化学物質の測定データを利用して,生化学反応ネットワークの数理モデルをいかに構築・再構築していくかという課題は,システム生物学における重要不可避な問題となりつつある.ここでいう「ネットワーク」とは,細胞内外で起こる様々な化学反応の連鎖を表す多義的な用語である.具体例として,転写制御(mRNAの合成)に関わる一連の生化学反応群,タンパク質間相互作用,代謝反応ネットワークなどが挙げられる.モデリングの過程は概ね次のプロトコルから成る:(1)文献やデータベースの情報にもとづく仮説モデルの作成,(2)計測データ(例えば,遺伝子発現データ)にもとづく反応速度パラメータの推定,(3)推定モデルの性能評価,(4)リモデリング.本稿では,生化学反応ネットワークの推測手法確立へ向けたバイオインフォマティクスの世界的動向について紹介すると同時に,ここ数年に渡って我々が推進してきた研究開発の成果および現状について報告する.また,研究領域に課された諸問題に対して統計科学的観点から整理を行い,予想される今後の研究動向について述べる.

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：一般社団法人情報処理学会  

進化アルゴリズムを用い，領域海洋潮汐モデルの境界条件および物理パラメータを最適化した．水深は海洋モデルの境界条件であり，人工衛星による重力観測に基づいて推定された全球水深データから与えることが多い．しかし，人工衛星起源の水深データの精度は，海洋潮汐のシミュレーションにとってしばしば不十分である．我々は進化アルゴリズムを用い，アラスカ多島海の複数の特定の海域の平均水深を最適化した．最適化された平均水深は，船舶からの音波観測に基づく水深データに比較的忠実であった．一般的に，音波観測起源の水深データは，重力観測起源のデータに比べ正確であるが，データはまばらにしか存在しない．一方，最適化の結果，重力観測起源の水深データの誤差が非常に大きい場所を特定することができた．このように，進化アルゴリズムを用いる最適化手法は，海洋モデルの境界条件の修正を行う有効な手立てとなると期待される．An evolutionary algorithm (EA) is applied to a regional ocean tide model to optimize a boundary condition and a physical parameter in the model. The bathymetry is one of the boundary conditions in ocean models and is frequently given by global sea depth data based on estimation derived from the satellite gravity observation. Accuracy of the satellite-derived depth data is often insufficient for accurate ocean tide simulations. We apply the EA to modify the mean depth in specific regions in the Alaska Panhandle, U.S. The mean depth in those regions is optimized to be close to the multibeam-derived depth data which is generally accurate further more than the satellite-derived data but its spatial coverage is sparse. Also, a region with large errors of the satellite-derived data is successfully found through the optimization. The EA has a prospect of correction of erroneous boundary conditions for accurate ocean modeling.

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1001/00061902/

記述言語：日本語   出版者・発行元：社団法人電子情報通信学会  

CiNii Books

researchmap

J-GLOBAL

researchmap

記述言語：日本語  

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：統計数理研究所  

要旨なしデータマイニングと統計数理その他・前書き特集前書き

CiNii Books

researchmap

記述言語：英語   出版者・発行元：SPRINGER HEIDELBERG  

DOI： 10.1007/s10463-008-0208-y

Web of Science

researchmap

記述言語：日本語   出版者・発行元：(公社)日本生化学会  

researchmap

記述言語：日本語   出版者・発行元：日本行動計量学会  

CiNii Books

researchmap

researchmap

記述言語：日本語   出版者・発行元：社団法人情報処理学会  

遺伝子発現情報を利用して生体内分子ネットワークを推測するための統計解析理論について議論する.生体内分子ネットワークとは,細胞内で起こる様々な化学反応の連鎖を表す多義的な用語である.具体例としては,転写制御(mRNAの合成),タンパク質相互作用ネットワーク,代謝ネットワークなどが挙げられる.ネットワークの統計的推測の過程は次のように要約される: (1)生体内分子ネットワークの(インシリコ)モデリング (2)観測データ(例えば遺伝子発現データ)にもとづくモデルパラメータの推定 (4)推定モデルの性能評価 (5)リモデリング. 本研究の目標は,これら一連の過程に関わる方法論を整備することである.ここでは,時系列遺伝子発現データを利用した転写制御ネットワークの推測を例に,提案手法について概説する.

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本知能情報ファジィ学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：社団法人電子情報通信学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本マーケティング・サイエンス学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本評論社  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：総合研究大学院大学  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本行動計量学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：統計数理研究所  

要旨なし予測と発見その他・前書き特集前書き

CiNii Books

researchmap

記述言語：英語   出版者・発行元：人工知能学会  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：一般社団法人 人工知能学会  

本研究ではバイオインフォマティクスのデータから飽和頻出木をマイニングすることを試みる。対象データの構造はDAGなので、我々のツリーマイニングアルゴリズムDryadeをＤＡＧに適用可能なように改良した。実験でこの効果を確かめる。

DOI： 10.11517/pjsai.JSAI06.0.7.0

researchmap

researchmap

記述言語：日本語   出版者・発行元：社団法人情報処理学会  

当研究では, マイクロアレイにより得られた細胞周期に伴い変動するイースト菌(Saccharomyces cerevisiae)の遺伝子発現量データに状態空間モデルを適用する.EMアルゴリズムによるパラメータ推定と, 情報量規準による評価により, 細胞周期を表す少数の潜在変数の次元を自動同定し, 他の手法による既存研究の結果との比較も行う.

CiNii Books

researchmap

J-GLOBAL

researchmap

記述言語：日本語   出版者・発行元：社団法人電子情報通信学会  

飲食店の日々の売上は,曜日,祝日,天気,近所での催し物への人出等の様々な要因に左右される.またその要因の売上への寄与の仕方は店舗ごとに異なる.そこで各店舗の売上時系列データをこれら各要因成分に分解するモデルを構成し,そのモデルによって得られる各店舗固有の情報に基づいて将来の売上を精度良く予測することは,仕入れ,人員配置,新規出店計画等,様々なレベルにおける経営戦略立案上有益であることは疑いようもない.我々は,状態空間モデルの柔軟な表現力と情報量規準によるモデル評価を利用した売上予測手法を提案し,実際に,ある大規模催事場及びビジネス街に隣接した飲食店の二年間分の日々売上データに応用した.なお本発表は,私と山口及び土屋との共同研究の成果を概括しながら,状態空間モデルによるマイクロマーケティングヘの接近法を紹介する.

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本知能情報ファジィ学会  

CiNii Books

researchmap

記述言語：英語   出版者・発行元：COPERNICUS GESELLSCHAFT MBH  

The present study statistically examines the dependence of the intensities of dayside (MLT = 8-12 h) large-scale field-aligned currents (FACs) on the ionospheric conductance using the summary data of DMSP-F7 constructed by the procedure of Higuchi and Ohtani (2000). We have found that, in the dayside region, R1 and R0 have a higher correlation between ionospheric conductivity and FAC intensity than R2, suggesting that R0 and R1 are driven by a more voltage-like source than R2. This result is consistent with the idea that R1 and R0 are driven by the interaction between the solar wind and the open magnetospheric magnetic field. We have also found that dayside FAC intensities are latitudinally well balanced when they have a three sheet structure (R0, R1 and R2); on the other hand, for a two sheet structure (R1 and R2), the intensity of R1 is larger than that of R2, so that the net current has the polarity of R1.

Web of Science

researchmap

記述言語：日本語   出版者・発行元：統計数理研究所  

CiNii Books

researchmap

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：宇宙航空研究開発機構  

本研究の目的は,雲移動ベクトルを見積もる作業で誤差の本質的要因となる雲の形の変化や空間分解能の影響を見積もることである.過去の研究では雲移動ベクトルの誤差は周囲のベクトルとの比較から求めていたため,解析対象とする物理現象の空間的・時間的スケールが誤差に含まれて物理現象より誤差が大きくなっていた.本研究では,統計モデルを作ることで限られた情報からより詳細な情報を統計的に推測する手法を用いて,雲の形の変化や空間分解能の影響を評価する方法を考えた.この方法をテストパターンを使った計算に適応して誤差評価の適切さを調査した.また,金星の雲画像にも適応して過去の誤差評価方法によって見積もられた値よりも4分の1程度小さい値が得られ,解析対象とする物理現象の大きさを誤差が下回ることができた.この誤差評価方法は雲惑星の気象を詳細に理解する上で重要な方法である.

CiNii Books

researchmap

その他リンク： http://repository.tksc.jaxa.jp/pl/dr/IS0200054000

記述言語：日本語   出版者・発行元：日本統計学会  

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1141/00024500/

記述言語：日本語   出版者・発行元：CA研究グループ  

CiNii Books

researchmap

記述言語：日本語   出版者・発行元：日本統計学会  

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1141/00024580/

記述言語：日本語   出版者・発行元：日本統計学会  

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1141/00024583/

記述言語：日本語   出版者・発行元：日本統計学会  

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1141/00024405/

記述言語：日本語   出版者・発行元：日本統計学会  

CiNii Books

researchmap

その他リンク： http://id.nii.ac.jp/1141/00024411/