Along with the development of space science and technology,miniature liquid helium temperature long life cryocooler is a focus subject in cryogenic study.Since it is the precondition of space detection researches,inst...Along with the development of space science and technology,miniature liquid helium temperature long life cryocooler is a focus subject in cryogenic study.Since it is the precondition of space detection researches,institutions of space in many countries do the research on it.In this article,we designed a compound cooling system.A three-stage high frequency thermal coupled pulse tube cryocooler was used to precool a Joule-Thomson(JT)cryocooler.This system has no moving parts at low temperatures and is hence suitable for space operation.Liquid helium temperature was successfully achieved in both open loop and closed cycle experiments.In the closed cycle experiment,when 473 W electric power was inputted,the cooling system reached a no-load temperature of 4.4 K,and a cooling capacity of 11.6 mW was provided at 4.54 K.It is the first miniature liquid helium temperature JT cryocooler in China and the research achievement paves a way for the space application of ultra-long wave infrared detection and THz technologies.展开更多
This research tends to make the experimental study on the mathematics teaching model of“situated creation and problem-based instruction”(SCPBI),namely,the teaching process of“creating situations—posing problems—s...This research tends to make the experimental study on the mathematics teaching model of“situated creation and problem-based instruction”(SCPBI),namely,the teaching process of“creating situations—posing problems—solving problems—applying mathematics”.It is aimed at changing the situation where students generally lack problem-based learning experience and problem awareness.Result shows that this teaching model plays a vital role in arousing students’interest in mathematics,improving their ability to pose problems and upgrading their mathematics learning ability as well.展开更多
基金supported by the Strategic Pioneer Program on Space Science,Chinese Academy of Sciences(Grant No.XDA04074100)the National Natural Science Foundation of China(Grant No.51306196)
文摘Along with the development of space science and technology,miniature liquid helium temperature long life cryocooler is a focus subject in cryogenic study.Since it is the precondition of space detection researches,institutions of space in many countries do the research on it.In this article,we designed a compound cooling system.A three-stage high frequency thermal coupled pulse tube cryocooler was used to precool a Joule-Thomson(JT)cryocooler.This system has no moving parts at low temperatures and is hence suitable for space operation.Liquid helium temperature was successfully achieved in both open loop and closed cycle experiments.In the closed cycle experiment,when 473 W electric power was inputted,the cooling system reached a no-load temperature of 4.4 K,and a cooling capacity of 11.6 mW was provided at 4.54 K.It is the first miniature liquid helium temperature JT cryocooler in China and the research achievement paves a way for the space application of ultra-long wave infrared detection and THz technologies.
文摘This research tends to make the experimental study on the mathematics teaching model of“situated creation and problem-based instruction”(SCPBI),namely,the teaching process of“creating situations—posing problems—solving problems—applying mathematics”.It is aimed at changing the situation where students generally lack problem-based learning experience and problem awareness.Result shows that this teaching model plays a vital role in arousing students’interest in mathematics,improving their ability to pose problems and upgrading their mathematics learning ability as well.
