流形上随机流的渐近平坦性

本文的目的是讨论流形上由随机微分方程确定的扩散过程的体积零化性质。令X_t(x)是描述流形M上的微分同胚流x→X_t(x)的扩散过程,K是M中具有正有限Hausdorff测度的紧致曲面,我们给出X_t(K)的面积在t→∞时几乎必然趋于零的条件,特别地,随机流X_t(·)的渐近零化定向可求长弧r:[0,1]→M的弧长。     

聚苯硫醚／石墨基双极板复合材料性能的研究

以聚苯硫醚树脂和人造石墨为原料一次模压成型制备双极板复合材料.研究了模压成型过程中加压时机、冷却方式及人造石墨原料对复合材料电导率和弯曲强度的影响.结果表明,制备聚苯硫醚/石墨基双极板材料宜选用石墨化程度较高且结构密实的石墨粉料;采用保温后加压及空气中冷却方式制备的复合材料的综合性能较优.     

氘代聚合物膜靶制备技术与性能研究

 氘代聚合物膜是快点火基础物理实验的一种重要靶型。通过氘代苯乙烯单体的本体自由基聚合反应制备氘代聚苯乙烯，并利用流延法和浇铸法制备出厚度从几十nm到数百μm的膜靶。溶剂挥发过程中的随机扰动对膜厚均匀性造成影响，采用清洁的基片和在涂沫基片或模具外加防护罩可以降低这种影响。采用PVA作脱膜剂有利于获得较薄的聚合物薄膜。DSC分析表明薄膜的玻璃化转变温度与热处理过程有关，缓慢退火有利于提高Ｔ-g和储能模量。     

Measurements of Boundary Plasma in Synergy Discharges of IBW and LHCD on the HT-7 Tokamak

By applying ion Bernstein wave (IBW) heating into the lower hybrid current drive (LHCD) plasma, improved confinements have been obtained in the HT-7 tokamak. The central electron temperature was doubled and the storage energy was increased significantly. The core electron density and temperature were broadened and ther profiles near the edge were steepened. A transport barrier has been formed in the vicinity of the limlter radial location. An enhanced shear in poloidal phase velocity was found in the same region with reduction of the fluctuation levels and the coherences between fluctuations. The results suggest that the improved confinement in the IBW and LHCD plasma is at least partially due to the modification of shear in poloidal velocity and then the suppression of fluctuations and fluctuation induced fluxes via de-correlation effect.     

Control Method of Cooling a Charged Particle Pair in a Paul Trap

We propose a simple feedback cooling method, including both the component feedback and the velocity feedback,for cooling a charged particle pair in a Paul trap. It is found that the system can be cooled to periodic orbits;and if control intensity is strong, the system can be cooled to a one-periodic orbit, which is only in a horizontalplane. The result shows that the cooled system is also robust for noise.     

半流及其逆极限的混沌

该文对连续动力系统研究了Devaney意义下的混沌的不变性质．证明了：（1）半流是混沌的（resP，ω混沌的）当且仅当它的逆极限是混沌的（resp,ω混沌的）；（2）自映射是混沌的（resp.ω混沌的）当且仅当它的扭扩半流是混沌的（resp．ω混沌的）；（3）自映射逆极限的扭扩流拓扑共轭于其扭扩半流的逆极限．从（2）和（3）可知，结论（1）是对自映射的推广．     

Effect of Magnetic Field and Equilibrium Flow on Rayleigh-Taylor Instability

We investigate the effect of a finite equilibrium flow and magnetic field on the Rayleigh-Taylor instability. It is found that the equilibrium flow only makes a frequency shift of perturbation and the growth rate of the Rayleigh-Taylor instability remains unchanged. However, the magnetic field can change the growth rate and, in particular,a very strong magnetic field suppresses the growth rate.     

一种简单易行的农用反光膜技术

农用反光膜技术是一种直接利用太阳光的简单易行的办法.两年前,河北省阜平县西刘庄大队的农民在河北省科协派来的老专家汤长廉、刘文重、张秋利等人的指导下推广了果树修剪、疏花疏果、浇水施肥、病虫害防治、套袋等整套技术.在此基础上,又推广了一项地表铺覆反光膜技术.他们的     

双组元姿控发动机反流特性的DSMC模拟

为准确获得双组元姿控发动机的羽流及其反流特性,采用直接模拟蒙特卡罗(DSMC)方法结合可变软球(VSS)模型数值模拟以N2O4/MMH为推进剂的真空羽流。喷口参数由喷管流动的DSMC法计算得到。与文献比较表明本文计算程序可信。模拟结果表明,分子质量越小的气体越容易进入反流区;本文的计算条件下,在偏离X轴正向116°~140°范围内,组分数密度和质量流率以及温度均出现了最大值。