We developed an interactive and menu-driven computer program to help investigators design and analyze phase II cancer clinical trials with a group sequential method, namely the sequential probability ratio test or the triangular test. Based on the values selected for the parameters of the trial, the
Two-phase coexistence analysis of the bellows control mechanism for a J–T cryocooler
✍ Scribed by S.B. Chien; L.T. Chen
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 292 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0011-2275
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✦ Synopsis
The bellows control mechanism is one of the most critical control elements in the Joule-Thomson cryocooler. In the cool-down process, the interior gas of the bellows may reach liquefaction temperature, cause vapour-liquid two phase coexistence phenomena, and achieve the quick open/close control function of a J-T valve. This paper establishes a transient model of a simplified bellows mechanism, investigates the variation of the state properties of nitrogen inside the bellows, and its effects on the performance with different bellows stiffness in the cool-down process. According to the real shape and dimension, the two-phase model is put into a J-T cryocooler integrated model to accomplish the J-T cryocooler system simulation. To adopt the benefit of two-phase coexistence behavior effectively, a revised initial J-T valve design is also proposed in this work.
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