The synthesis and mesomorphic properties of ferroelectric liquid crystals with a fluorinated asymmetric frame

A novel series of ferroelectric liquid crystals with a fluorinated asymmetric frame were synthesized by utilizing optically active (S)-2-, (S)-3-, (S)-4- and (S)-5-fluoroalkanols prepared from corresponding (R)-1,2-epoxyalkanes. Their mesomorphic and physical properties, such as spontaneous polarization, optic tilt angle and response time, were investigated systematically in a series of homologous compounds having the chiral centre at different positions on tails of various lengths. All the compounds exhibited the chiral smectic C phase in a wide range of temperatures and were found to possess a fast response time in spite of the small magnitude of the spontaneous polarization.     

叶轮机械内部不稳定流动现象的研究

叶轮机械的内部流动的不稳定现象-喘振与失速,不但影响了叶轮机械的性能,而且限制了叶轮机械的运行范围．本文采用了混沌理论的SVD(Singular Value Decomposition)方法,通过构造相空间的轨迹图(Phase Portrait),分析了离心压气机的失速和诱导轮(Inducer)的气化过程的不稳定现象．结果表明．SVD方法可以用来分析叶轮机械的不稳定现象．