@techreport{oai:jaxa.repo.nii.ac.jp:00002690,
 author = {大西, 充 and 吉原, 正一 and 桜井, 誠人 and Onishi, Mitsuru and Yoshihara, Shoichi and Sakurai, Masato},
 month = {Oct},
 note = {Thermal energy applied to a pure material near its critical point immediately makes a strong expansion. This causes an adiabatic compression in the front of the expansion and a large density difference is formed there. The difference with adiabatic energy is transported as an acoustic wave. This rapid heat transportation is called Piston Effect. In the present study, an ultra-sensitive and high-speed density measurement system was developed to observe the elementary process of Piston Effect. To demonstrate the performance of the system, the measurement of sound velocity in a critical fluid was conducted. Numerical simulations were also made to confirm the experimental results. Using the FFT method to both of the experiment and the simulation, the sound velocity could be precisely evaluated. The velocity profile versus temperature from the experimental results shows a good agreement with the simulation results and theoretical prediction, that is, the velocity rapidly decreases as the fluid approaches its critical point. This indicates that the present experiments and simulations complementally enable quantitative discussion of the critical phenomena., 資料番号: AA0048129026, レポート番号: JAXA-RM-04-011},
 title = {臨界流体のピストン効果直接観察},
 year = {2004}
}