@techreport{oai:jaxa.repo.nii.ac.jp:00006226,
 author = {大西, 充 and 吉原, 正一 and 桜井, 誠人 and Onishi, Mitsuru and Yoshihara, Shoichi and Sakurai, Masato},
 month = {Jan},
 note = {Thermal energy applied to a pure fluid 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 our study, an ultra-sensitive and high-speed density measurement system was developed to conduct a quantitative measurement of the 'Piston Effect'. By using the system, we succeeded to directly 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. Using the FFT method to the experimental results, 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 profile should have the scale universality. However, the profile from the experimental results obeys another scale universality if T-T(sub c) is less than 0.1 K. These indicate that our experimental system enables us to quantitatively discuss the critical phenomena., 資料番号: AA0049057017, レポート番号: JAXA-SP-05-011},
 title = {臨界点近傍流体のピストン効果の直接観察},
 year = {2006}
}