Authorship：Corresponding author   Language：Japanese  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Visualization Society of Japan  

Due to the influence of the COVID-19, great damage has occurred all over the world. Not only health and medical problems, but also the effects of the decline in quality of life and economic activity due to the suspension of social activities cannot be ignored. It is thought that the main cause of virus infection is coughing and sneezing, but in recent it has become a topic that there is a possibility of airborne infection by aerosols containing viruses scattered in the air. In the case of airborne infection, the risk of infection is considered to increase when the mucous membrane is exposed to exhaled aerosol for a long time. Therefore, in this study, we actually visualized human breath by using the smoke of electronic cigarettes as tracer particles. For 4 patterns of the human posture, exhaled breath was visualized. As a result, it was clarified that the exhaled breath is affected by the body wall temperature and rises when it stays in the boundary layer, falls when it leaves, or diffuses randomly. This finding is effective in reducing the risk of infection during face-to-face customer service, and is considered to be the first discussion of the characteristics of human exhalation affected by temperature.

DOI： 10.3154/tvsj.41.21

CiNii Research

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Because of the COVID-19, the world has been affected significantly. Not only health and medical problems but also the decline in life quality and economic activity due to the suspension of social activities cannot be disregarded. It is assumed that the virus is transmitted through coughing and sneezing; however, the possibility of airborne infection by aerosols containing viruses scattered in the air has become a popular topic recently. In airborne infections, the risk of infection increases when the mucous membrane is exposed to exhaled aerosols for a significant amount of time. Therefore, in this study, we visualize human breath using the smoke of electronic cigarettes as tracer particles. Exhalation when speaking was visualized for four human posture patterns. The result shows that the exhaled breath is affected by the body wall temperature; it rises when it remains in the boundary layer by wearing a mask. On the other hand, without a mask, it initially flows downward due to the structure of the nose and mouth, so it flows downward due to inertia and diffuses randomly. This finding is effective in reducing the risk of infection during face-to-face customer service.

DOI： 10.1063/5.0038380

PubMed

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Last author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

The present study focused on the rise time and decay times of mechanoluminescence (ML) during cyclic elastic deformation of SrAl2O4:Eu2+. The time constants during compression and decompression, tau(up) and tau(down), respectively, did not change from the 2nd to the 5th cycle. Both tau(up) and tau(down) were expressed by a linear function of the maximum load and the inverse of the loading rate. tup depended only on the loading time, whereas tdown was affected by the loading time and the rate of change of the strain energy. Measuring tau(down) may enable evaluation of the loading conditions even under cyclic loading and may enhance the practicality of a ML phosphor. (C) 2014 Optical Society of America

DOI： 10.1364/OE.22.021991

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)  

The stress and loading rate on disks of SrAl2O4:Eu mixed epoxy resin were measured by a lifetime-based method. The concentration of the mechanoluminescence (ML) phosphor and the excitation power did not affect the measured lifetime. The lifetime was proportional to the stress and was inversely proportional to the loading rate. The concentration, the excitation power, the stress, and the loading rate affected the peak intensity of ML, while previous work estimated the stress using the absolute intensity under well-controlled excitation and concentration conditions. The method used here can shorten the measurement time and enhance the practicality of a ML phosphor. © 2013 Optical Society of America.

DOI： 10.1364/OL.38.001095

Scopus

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Authorship：Lead author   Language：Japanese  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Mechanoluminescence (ML) intensity is proportional to magnitude of load and loading rate in elastic region. However, ML intensity is affected by initial excitation level, concentration of ML materials and so on, resulting in difficulties to evaluate the stress quantitatively. Controlling the initial conditions for the quantitative measurement requires a long stand-by time. In this study, we evaluated relations between increasing/decreasing stress and the response characteristics of ML. The transient ML intensity was measured by a photomultiplier tube. The rise time of ML, τup, and decay time, τdown, were proportional to maximum load and inversely proportional to loading rate. Furthermore, τup and τdown were not affected by initial excitation level, concentration of ML materials. Investigating responses to the cyclic load, τ was not affected by cycle stress. In order to confirm whether external force affects the value of τ, same loading time and various magnitude of external force were added to the sample and calculated τ. Results show τup was affected only by loading time. On the other hand, τdown was affected by loading time and rate of time variation of strain energy. Appling to two-dimensional measurement, qualitatively correct results were obtained in each area. The above results indicate τ would be a useful parameter to visualize stress field in elastic body arbitrary and sequentially. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaic.79.3721

Scopus

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

This paper proposes a combined method for two-dimensional temperature and velocity measurements in liquid and gas flows using temperature-sensitive particles (TSPs), a pulsed ultraviolet laser, and a high-speed camera. TSPs respond to temperature changes in the flow and can also serve as tracers for the velocity field. The luminescence from the TSPs was recorded at 15,000 frames per second as sequential images for a lifetime-based temperature analysis. These images were also used for the particle image velocimetry calculations. The temperature field was estimated using several images, based on the lifetime method. The decay curves for various temperature conditions fit well to exponential functions, and from these the decay constants at each temperature were obtained. The proposed technique was applied to measure the temperature and velocity fields in natural convection driven by a Marangoni force and buoyancy in a rectangular tank. The accuracy of the temperature measurement of the proposed technique was +/- 0.35-0.40A degrees C.

DOI： 10.1007/s00348-010-0894-0

Web of Science

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Anodized-aluminum pressure-sensitive paint (AA-PSP) uses the dipping deposition method to apply a luminophore on a porous anodized-aluminum surface. We study the dipping duration, one of the parameters of the dipping deposition related to the characterization of AA-PSP. The dipping duration was varied from 1 to 100,000 s. The properties characterized are the pressure sensitivity, temperature dependency, and signal level. The maximum pressure sensitivity of 65% is obtained at the dipping duration of 100 s, the minimum temperature dependency is obtained at the duration of 1 s, and the maximum signal level is obtained at the duration of 1,000 s, respectively. Among the characteristics, the dipping duration most influences the signal level. The change in the signal level is a factor of 8.4. By introducing a weight coefficient, an optimum dipping duration can be determined. Among all the dipping parameters, such as the dipping duration, dipping solvent, and luminophore concentration, the pressure sensitivity and signal level are most influenced by the dipping solvent.

DOI： 10.3390/s101109799

Web of Science

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Anodized-aluminum pressure-sensitive paint (AA-PSP) has been used as a global pressure sensor for unsteady flow measurements. We use a dipping deposition method to apply a luminophore on a porous anodized-aluminum surface, controlling the luminophore concentration of the dipping method to optimize AA-PSP characteristics. The concentration is varied from 0.001 to 10 mM. Characterizations include the pressure sensitivity, the temperature dependency, and the signal level. The pressure sensitivity shows around 60 % at a lower concentration up to 0.1 mM. Above this concentration, the sensitivity reduces to a half. The temperature dependency becomes more than a half by setting the luminophore concentration from 0.001 to 10 mM. There is 3.6-fold change in the signal level by varying the concentration. To discuss an optimum concentration, a weight coefficient is introduced. We can arbitrarily change the coefficients to create an optimized AA-PSP for our sensing purposes.

DOI： 10.3390/s100706836

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

This paper proposes a combined method for two-dimensional temperature and velocity measurements using temperature sensitive particles (TSParticles), a pulsed ultraviolet (UV) laser and a single high-speed camera. TSParticles were synthesized using ion-exchange particles and Eu(TTA) luminescent dye. The size and material of the particles for synthesizing TSParticles are selectable. TSParticles respond to temperature changes in a flow and can also serve as tracers for the velocity field. TSParticles were seeded into a heated water flow in a complex-shaped channel constructed of MEXFLON resin, which has a refractive index exactly equal to that of water. Particle images of flow beyond the structure can be recorded without any distortion. The TSParticles were excited by the UV pulsed laser and the luminescence from the TSParticles were recorded at 40,000 frames per second as sequential images for a lifetime-based temperature analysis. Another advantage of our approach is that high time-resolved PIV can be carried out without a high-frequency laser. The recorded images were also used for the particle image velocimetry (PIV) calculation.

DOI： 10.1007/s00340-010-3926-9

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)  

A surface temperature inside an optical engine with or without heating the intake gas was measured using the phosphor thermometry (PT) in view of a combined measurement of the velocity and temperature map. The temperature distribution was measured by the PT using only 3 or 10 images, which were recorded by the non-intensi- fied high-speed CMOS camera, by taking into account the local pixel nonlinearity. The temporal standard deviation of the decay constant was 0.17-0.33% and it changed 0.15% by the position, indicating that the nonuniformity of the pixel nonlinearity was large. With the local calibration, the spatial fluctuation of the measured temperature was 0.10-0.53°C. This technique was applied to temperature measurement in the optical engine, resulting in reasonable temperature maps. © 2010 by Begell House, Inc.

DOI： 10.1615/JFlowVisImageProc.v17.i2.30

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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Language：Japanese   Publisher：社団法人 可視化情報学会  

DOI： 10.3154/jvs.32.125_8

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Language：Japanese  

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Language：Japanese   Presentation type：Symposium, workshop panel (public)  

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Event date： 2023.8 　 　

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Event date： 2022.10 　 　

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Event date： 2022.8 　 　

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Event date： 2020.11 　 　

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Event date： 2019.12 　 　

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Author：Other 

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