小型制冷机替代工质的研究(下)

３替代工质在中国的研究历史３．１ 早期的研究 在８０年代中期,我国的学术界就开始注意到制冷剂的替代工作。１９８３年天津大学开始了制冷剂的基础研究工作,建立了制冷剂的ＰＶＴ试验装置［１０］,制冷剂的比热实验台［１１］。针对国产制冷剂进行其热物性测量,建立有关的关联式进行替代工质的模拟计算研究［１２］［１３］［１４］［１５］［１６］［１７］;并且在实验中第一次观测到国产Ｒ２２的临界乳光现象［１８］。相关的研究工作在清华大学、西安交通大学、哈尔滨工业大学也在开展枉家用电器的应用试验相继也在国内各大学展开…     

m－相依随机截断下K－M估计的强相合一致收敛速度

对一维和二维情形，讨论了强平稳ｍ－相依随机截断下Ｋａｐｌａｎ－Ｍｅｉｅｒ估计的强相合一致收敛速度，得到了与［２］和［４］ｉ．ｉ．ｄ．截断下相同的结果     

双基本图形的度量方程及应用

本文从理论上将［２］中的度量方程推广到Ｅｎ中的一个双Ｎ元基本图形的度量方程．在此基础上推广了［３］中的高维余弦定理;并将［３］中的一类几何不等式推广到对Ｅｎ中基本图形为点的双基本图形仍然成立。     

论圆柱度(二)

6圆柱度的最小区域评定法圆柱度的最小区域评定法目前有两大类，一类是用各种优化法进行逐步逼近计算~［13］［15］［16］［17］另一类则是按照统一的形状误差最小区域判别准则找出满足该准则的特征占~［20］－［27］。关于前者本文不想多加评述，关于后者各文虽有不同，但他们的一个共同点是建立在文献~［7］的作者提出的“凸分析理论”~［26］基础上。6．1应用“凸理论”评定最小区域圆柱度~［20］～［27］［22］指出形状误差都可用下式表示F（v;ω）＝f（v）＋ω~tk（v）（17）式中：V为形成变量，表示形成各种表面形状所需的独立变量；…     

PbO－Bi_2O_3－B_2O_3－SiO_2系重金属氧化物玻璃的结构与光学性

通过密度、可见光光谱、红外吸收光谱、Ｃｏ－６０辐照损伤试验及荧光光谱的测试，研究了ＰｂＯ－Ｂｉ２Ｏ３－Ｂ２Ｏ３－ＳｉＯ２玻璃系的光学性能与结构．密度最高可达８．４６４ｇ／ｃｍ３其紫外吸收达截止波长随Ｐｂ２＋及Ｂｉ３＋含量升高而红移．玻璃熔化温度低达８５０℃．在ＰｂＯ－Ｂｉ２Ｏ３－Ｂ２Ｏ３系玻璃中加人ＳｉＯ２可使玻璃结构更致密．室温下该系统玻璃在３６０ｎｍ有一个宽的激发峰，能产生４１８ｕｍ及４３８ｕｍ两个弱的发射峰．该系统玻璃的结构是由［ＳｉＯ４］４－、［ＢＯ３］３－、［ＢＯ４］５－、［ＰｂＯ４］６－及［ＢｉＯ６］９－构成．其中部分Ｐｂ２＋及Ｂｉ３＋以网络外体进入玻璃．     

一类Lazer－Mckenna吊桥型方程周期解的存在性

本文研究如下吊桥型方程的周期解问题这个方程可以看成来自于Ａ．Ｃ．Ｌａｚｅｒ和Ｐ．Ｊ．Ｍｃｋｅｎｎａ在文［１］中提出的简单吊桥非线性振动模型［２］［３］研究了当ｃ＝０时问题（２）的周期解，并公开提出δ≠０时，什么条件能保证解存在。本文借助Ｌ－Ｓ不动点定理，在δ≠０的基本假定下研究问题（１），得到了两个存在性结果：定理１和定理２。对非线性项ｆ所加的条件，当把ｆ看成特殊的－ｋｕ￣＋＋Ｗ＿０时与文［２］对δ＝０时的结果完全类似。     

光色玻璃结构因子[Ψ]与材料改性的研究

本文研究了Ｒ２Ｏ（ＲＯ）－Ａｌ２Ｏ３－Ｂ２Ｏ３－ＳｉＯ２系光色玻璃基础组成、结构因子［Ψ］与光色玻璃饱和变暗透射率（ＴＤ）的温度系数ｆ（ＴＤ）（简称温度系数）的相互关系。研究结果表明，光色玻璃的温度系数ｆ（ＴＤ）随结构因子［Ψ］的变化具有一定的规律性。随着结构因子［Ψ］的增大，即当［Ψ］＝０．２８￣０．３５时，光色玻璃的温度系数ｆ（ＴＤ）出现了较小值。根据以上结构，探索并研制出了具有较好光色性能即     

线性赋范空间中非线性优化的若干注记

设Ｅ是线性赋范空间．Ｇ是Ｅ中子集，是Ｅ上实值连续凸泛函，本文讨论非线性优化问题：　得到关于强唯一性的若干结果．当　即Ｇ对Ｘ的最佳逼近问题，作为我们结果的推论，得到了文献［１］－［６］中关于非线性逼近的许多结果．     

快速凝固Al—Li─Cu—Mg—Zr合金中H相和Z相的TEM研究

用ＨＲＴＥＭ、ＴＥＭ及ＥＤＡＸ分析研究了Ａｌ─Ｌｉ—Ｃｕ—Ｍｇ—Ｚｒ合金中的一种新相（暂名Ｈ相）和六角Ｚ相的结构，确定Ｈ相具有四方点阵，点阵参数为α＝２．８ｎｍ，ｃ＝２．４ｎｍ，ＥＤＡＸ分析表明Ｈ相和Ｚ相均含Ａｌ、Ｍｇ、Ｃｕ发现Ｈ相与Ｚ相的共存取向关系为［１００］‖［１１２０］Ｚ，［１０１０］Ｈ‖［０００１］Ｚ。还观察到Ｚ相中一种特有的旋转畴结构     

镍钴离子浓度比对化学镀Co-Ni-P合金工艺的影响

讨论了［Ni2＋］／［Co2＋］的比值、镀液组成和操作条件对化学镀Co－Ni－P合金沉积速度的影响。［Ni2＋］／［Co2＋］的比值越大，沉积速度越快。［Ni2＋］／［Co2＋］的比值对镀液组成和沉积速度之间的关系有明显的影响。当镀液的温度和pH值较低时，［Ni2＋］／［Co2＋］的比值对沉积速度的影响也较小。     

随机信号AR频谱模型的本质研究

本文对期望为准周期函数的随机信号AR频谱模型进行了深入研究,将AR模型从平稳随机信号扩展到非平稳随机信号,研究了该AR模型的基本原理,成立条件,模型参数求解等问题,并利用该模型对一实际随机信号进行了频谱分析。     

基于随机振动的拱圈结构动力机会约束规划设计

针对地震振动作用的随机性,建立了带有随机参数的结构动力机会约束规划设计模型,在拱圈结构的动力优化设计中,采用随机模拟技术,利用上述模型对工程实例进行了分析计算,优化结果充分显示动力机会约束束规划设计可有降低拱圈结构受地震振动袭击时的系统风险。     

An Application of Majorization to Comparison of Variances

Empirical comparisons of variances of estimators of the population mean in a two-stage nested design, random effects model are given by Koch [3]. He uses the methods in [Z] to obtain a new estimator and then conjectures that its variance is intermediate with respect to better known estimators. His conjecture is proved by using theorems from [4]. All three estimators are compared with the expression that maximizes the likelihood function.     

In-plane shear properties of unidirectional glass fiber (U)/random glass fiber (R)/epoxy hybrid and non-hybrid composites

The in-plane shear properties (shear strength τ_xy and shear modulus G_xy) of unidirectional glass fiber (U)/random glass fiber (R)/epoxy hybrid and non-hybrid composites have been investigated experimentally and theoretically. The effect of stacking sequence and random fiber relative volume fraction (V_fR/V_fT) in hybrid composites were reported. Laminates were fabricated by hand lay-up technique with a total of 5 plies, by varying the number and position of random glass layers so as to obtain four different hybrid laminates; i.e. [0.5R/U/U]_S, [U/0.5R/U]_S, [U/U/0.5R]_S, and [U/R/U/R/U]. All unidirectional fiber laminate [U]₅ and another of all random fiber laminate [R]₅ were also fabricated for comparison purpose. The average thickness of the manufactured laminates is 5.5 ± 0.2 mm and the total fiber volume fraction (V_fT) is 37%. Failure modes of all specimens were investigated. Results indicated that the in-plane shear properties (shear strength τ_xy and shear modulus G_xy) of unidirectional fiber composite can be considerably improved by incorporation of random glass fiber and forming hybrid composites.     

New developments on FRAMs: [3D] structures and all-perovskite FETs

A discussion is presented of new directions in ferroelectric random access memories (FRAMs) and ferroelectric capacitors for dynamic random access memories (DRAMs), emphasizing [3D] structures and new materials, as well as ferroelectric gates and new mechanisms of domain wall motion in nano-scale geometries.     

Epitaxy of copper on muscovite mica

The vapour deposition of copper onto air-cleaved mica (001) has been studied by reflection high energy electron diffraction in ultrahigh vacuum. At room temperature, crystallites with random orientation and crystallites with Cu(111)mica (001) and Cu[1$\text{1}$0]mica [100] (orientation I) or Cu[1$\text{1}$0]mica [010] (orientation II) are observed. On annealing, either orientation I or orientation II dominates. Also at room temperature, good epitaxy of copper on Cu(111) occurs. Deposition at 570 K always leads to a single-crystal film in orientation I. During early growth, however, crystallites in both orientations appears to have comparable importance, but those with orientation I grow at the expense of those with orientation II during coalescence.     

具扰动的极大单调算子非线性随机方程

本文证明极大单调算子与一个单调算子的和是广义伪单调的;利用此结果与多值映射的可测选择理论,得出具扰动的极大单调算子非线性随机方程的解,把Browder[2,§7]的几个主要结果推广到随机情形。     

A mechanistic approach to damage in short-fiber composites based on micromechanical and continuum damage mechanics descriptions

A micro-macro mechanistic approach to matrix cracking in randomly oriented short-fiber composites is developed in this paper. At the micro-scale, the virgin and reduced elastic properties of the reference aligned fiber composite are determined using micromechanical models [Proc. Roy Soc. Lond. A241 (1957) 376; Acta Metall. 21 (1973) 571; Mech. Mater. 2 (1983) 123], and are then distributed over all possible orientations in order to compute the stiffness of the random fiber composite containing random matrix microcracks. After that the macroscopic response is obtained by means of a continuum damage mechanics formulation, which extends the thermodynamics based approach in [Comp. Sci. Technol. 46 (1993) 29] to randomly oriented short-fiber composites. Damage accumulations leading to initiation and propagation of a macroscopic crack are modeled using a vanishing element technique. The model is validated against the published experimental data and results [Comp. Sci. Technol 55 (1995) 171]. Finally, its practical application is illustrated through the damage analysis of a random glass/epoxy composite plate containing a central hole and under tensile loading.     

Morphology and texture evolution of nanostructured CaF2 films on amorphous substrates under oblique incidence flux

The morphology and biaxial texture of vacuum evaporated CaF(2) films on amorphous substrates as a function of vapour incident angle, substrate temperature and film thickness were investigated by scanning electron microscopy, x-ray pole figure and reflection high energy electron diffraction surface pole figure analyses. Results show that an anomalous [220] out-of-plane texture was preferred in CaF(2) films deposited on Si substrates at < 200?°C with normal vapour incidence. With an increase of the vapour incident angle, the out-of-plane orientation changed from [220] to [111] at a substrate temperature of 100?°C. In films deposited with normal vapour incidence, the out-of-plane orientation changed from [220] at 100?°C to [111] at 400?°C. In films deposited with an oblique vapour incidence at 100?°C, the texture changed from random at small thickness (5 nm) to biaxial at larger thickness (20 nm or more). Using first principles density functional theory calculation, it was shown that [220] texture formation is a consequence of energetically favourable adsorption of CaF(2) molecules onto the CaF(2)(110) facet.     

Stochastic simulation method for a 2D elasticity problem with random loads

We develop a stochastic simulation method for a numerical solution of the Lamé equation with random loads. To treat the general case of large intensity of random loads, we use the Random Walk on Fixed Spheres (RWFS) method described in our paper [Sabelfeld KK, Shalimova IA, Levykin AI. Discrete random walk over large spherical grids generated by spherical means for PDEs. Monte Carlo Methods and Applications 2006; 12(1): 55–93]. The vector random field of loads which stands on the right-hand side of the system of elasticity equations is simulated by the Randomization Spectral method presented in [Sabelfeld KK. Monte Carlo methods in boundary value problems. Berlin (Heidelberg, New York): Springer-Verlag; 1991] and recently revised and generalized in [Kurbanmuradov O, Sabelfeld KK. Stochastic spectral and Fourier-wavelet methods for vector Gaussian random field. Monte Carlo Methods and Applications 2006; 12(5–6): 395–445]. Comparative analysis of the RWFS method and an alternative direct evaluation of the correlation tensor of the solution is made. We derive also a closed boundary value problem for the correlation tensor of the solution which is applicable in the case of inhomogeneous random loads. Calculations of the longitudinal and transverse correlations are presented for a domain which is a union of two arbitrarily overlapped discs. We also discuss a possibility to solve an inverse problem of the determination of the elastic constants from the known longitudinal and transverse correlations of the loads, and give some relevant numerical illustrations.