SLIM revisited

SLIM (spectroscopic localization by imaging), a tool for in vivo magnetic resonance spectroscopy that provides compartmental spectra from relatively few phase-encoded data, is limited by the inhomogeneities within each compartment. It is shown that the SLIM-derived spectra approach the average compartmental spectra as the number of phase encoded data approaches infinity, and the convergent rate of the error for each compartment is proportional to the size of the compartment. Numerical simulation studies are conducted to confirm the convergence property. A detailed discussion of the result is provided.     

活塞加工的计算机辅助工艺过程设计

本文介绍一个在微机上实现的活塞CAPP系统,它具有适合于活塞结构与工艺特点的分段层次式混合编码输入系统和嵌入式知识基形式的工艺决策系统,可自动生成包括工艺规程、工序卡、相应刀、夹、量、辅具的全套完整工艺文件。在工序图自动绘制方面,本文还提出了一种“半参数化”自动生成技术。     

梯形波脉冲筛板萃取柱传质性能

本文以UO_2(NO_3)_2—30％TBP(KO)为实验体系,进行了梯形波脉冲筛板柱传质性能的研究。实验中测量了两组分的两相稳态浓度剖面共13组,以扩散模型为基础,求得了梯形波脉冲柱的“真实”传质单元高度HTU_(ox),分散单元高度HDU及表观传质单元高度HTU_(oxp)。通过对实验结果进行分析,选择出了适于本实验体系的较好的操作条件。     

Effects of hydrogen on mechanical properties and fracture mechanism of 8090 Al-Li alloy

The effects of hydrogen and strain rate on the mechanical properties and fracture mechanism of 8090 Al-Li alloy under electrochemical charging conditions have been studied. Experimental results demonstrate that the tensile strength [ultimate tensile strength (UTS) and yield strength (YS)] and plasticity [reduction of area (RA) and elongation (EL)] drop linearly with the decrease of strain rate. The charged hydrogen increases the tensile strength but markedly impair the plasticity. The susceptibility of hydrogen embrittlement increases with the decreases of strain rate, and the susceptibility of the charged specimens was larger than that of the uncharged ones over the strain-rate range. Observation by scanning electron microscope (SEM) reveals that the charged hydrogen enhances intergranular delamination cracking on the fracture surface. The fracture model of charged specimens at low strain rates is grain boundary brittle fracture (GBBF), while that of other conditions is grain boundary ductile fracture (GBDF). Secondary ion mass spectroscopy (SIMS) study shows that the atomic binding energy of Al and Li in the alloy decreased after hydrogen charging, and the atomic binding energy drop of the former is more than the latter. In this article, the hydrogen transport through the mobile dislocation mechanism of hydrogen-induced fracture and the hydrogen effect on atomic binding energy were also discussed in detail.     

分布式多媒体系统中音频和视频实时传输

本文在分析了分布式多媒体实时传输系统的基础上 ,并说明了 RTP/ RTCP协议和 IP Multicast在单频和视频传输及控制中的应用。     

A MODIFIED METHOD FOR SUPERVISOR SPECIFICATION AND SYNTHESIS OF A CLASS OF DISCRETE EVENT SYSTEMS

In this paper, a model‐refining method is proposed to alleviate the complexity involved in specification interpretation of DES control problems. The legal constraint language is defined in terms of illegal states and events in contrast with constructing the automaton of the specification language. This method could provide a more intuitive view of the DES control problem and would be suitable for practical implementation. Two examples, which have commonly been used in the literature, are employed to show the efficiency of the proposed method. Further, under this framework, it is shown that the supremal controllable sublanguage can take a simpler form based on the concept of an illegal state set. A state‐based supervisor synthesis procedure is presented, and a simple example is provided.     

Exact solution of a fountain-like texture for 3He-A in a half-space

The exact solution is presented of a fountain-like texture for ³He-A in a half-space, representing the simplest member of a class of textures discussed by Mermin which is singular on the surface only. The present texture may be regarded as the final stable configuration when a topologically unstable point singularity in the bulk of ³He-A is attracted to the surface. For this texture the orbital or anisotropy axis % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% GabmiBayaajaaaaa!3C6D!\[\hat l\] distributes itself in space much like half of a dipole field, and a ring supercurrent flows near the point singularity on the surface, contributing to a total angular momentum of the order of (_s/) per particle.Work supported in part by the National Science Foundation under Grant #DMR76-81328.     

湿法相分离不对称超滤膜形成机理

本文选择了憎水的极怀非普质子性聚砜和亲水的极性质子怀聚砜酰胺两种膜材料，从铸膜液组成和凝胶过程两方面，用气相色谱和高效液相色谱研究了表征膜材料－溶剂－添加剂－水作用力的混合自由焓，平衡分配常数，及其与膜性能，不同溶剂特性粘度，雾点值和溶解度参数的关系，提出了铸膜液中有机溶剂的作用机理，及不对称超滤膜形成的一些规律。     

RP—HPLC流动相组成优化方法的研究及其专家系统的建造

本文提出了一种既便于自动求值,又不致产生歧义的色谱分离优化目标函数。对于反相高效液相色谱RP-HPLC流动相组成优化问题,提出了新的高效迭代方法,并建立了组成优化专家系统。该系统包括优化搜索区域确定、实验谱图辨识、保留特性关系的自适应回归和最优目标预测等功能。经实验验证,该系统具有较高的迭代搜索效率。     

不同肟类N－甲基氨基甲酸酯的杀虫活性和离体胆碱酯酶抑制作用的研究

文中测定了一系列α－氰基甲酮肟和三氟甲基苯基甲酮肟类Ｎ－甲基氨基甲酸酯的杀虫活性和抑制胆碱酯酶活性。α－氰基烷基甲酮肟类Ｎ－甲基氨基甲酸酯具有极好的杀虫活性和抑制胆碱酯酶活性，而α－氰基苯基甲酮肟类衍生物仅仅呈现抑制胆碱酯酶活性。三氟甲基苯基甲酮肟类Ｎ－甲基氨基甲酸酯具有有力的杀虫活性和胆碱酯酶抑制活性。