考虑三轴约束时孔洞的聚合机理及有效能量准则

通过体胞分析方法,对不同状孔洞在从光滑试样到裂纹试样的三轴应力场中的聚合机理进行了较精解的有限元分析,计算结果表明：（１）孔洞的相互靠近和横向扩展是导致相邻孔洞发生内颈缩聚合的两种基本机制,在应力三维度Ｒσ等于１．２５附近,这两种机制发生较明显的变化。（２）单纯以孔洞体积分数ｆＣ概念为基础的材料破坏参数一般敏感于应力三维度,不能很好地预报不同三轴应力场中材料的破坏,在此基础上,提出了描述孔洞聚合的     

Delay systems and optimal control

0. IntroductionIt is well known that evolution systems are an important class of distributed parametersystems and the optimal control of infinite dimensional systems is a remarkable subjectin control theory. Some authors including us investigated the existence of solutions orperiodic solutions (see [l--4] or [5,6] ). To the knowledge of the authors, optimal controls fordistributed parameter delay systems have not been extensively studied. Li and Yao obtaina maximum principle (see [7]). Here w…     

芽胞杆菌全细胞热裂解气相色谱聚类分析

通过热裂解气相色谱对１４ 个芽胞杆菌模式菌株全细胞进行分析, 确定芽胞杆菌不同属间特征性谱峰;利用ＳＴＡＴＩＳＴＩＣＡ 系统对热裂解气相色谱图中３０ 个主要谱峰进行聚类分析, 绘制出的树状谱清楚地表明各菌株间的亲缘关系。     

（2R,3S）—2甲基—3—羟基戊酸甲酯的手性合成

１引言烟草甲ＬａｊｓｔｏｄｅｒｍａｓｅｒｒｉｃｏｒｎｅＦａｂｒ。ｉｎｓ是一种主要危害烟草、香烟、干燥植物以及谷物、面粉的农业害虫。这种害虫在我国主要分布在淮河以南地区以及世界各地的温暖地带［‘］。（２,３Ｓ）－２一甲基一３一羟基成酸甲酯是我们设计的合成烟草甲性信息素的一个重要中间体。我们以丙快醇为基本原料合成了该化合物。丙炔醇参照文献ｌ’］方法制得２一戊炔一ｌ一醇２,催化还原条件下,炔键可被部分加氢得到（Ｑ－２一戊烯一卜醇３。在四异丙氧基钛、Ｄ－（）一酒石酸＄［Ｊ４Ａ分于筛催化条件下,顺式烯丙醇…     

WIMPs search by scintillators: possible strategy for annual modulation search with large-mass highly-radiopure NaI(TI)

The DAMA experiments are running deep underground in the Gran Sasso National Laboratory. Several interesting results have been achieved so far. Here a maximum likelihood method to search for the WIMP annual modulation signature is discussed and applied to a set of preliminary test data collected with large mass highly radiopure NaI(Tl) detectors. Various related technical arguments are briefly addressed.     

Einstein-Maxwell Spacetime with Two Commuting Spacelike Killing Vector Fields and Newman-Penrose Formalism

Einstein-Maxwell spacetimes endowed with twocommuting spacelike Killing vector fields areconsidered. Subject to the hypotheses that one of thetwo null geodesic congruence orthogonal to thetwo-surface generated by the two commuting spacelikeKilling vector fields is shearfree and theelectromagnetic field is non null, it is shown that,with a specific choice of null tetrad, theNewman-Penrose equations together with the Maxwell equations for theclass of spacetime considered may be reduced to asecond-order ode of Sturm-Liouville type, from whichexact solutions of the class of spacetimes consideredmay be constructed. Examples of exact solutions arethen given. Exact solutions with distribution-valuedWeyl curvature describing the scattering ofelectromagnetic shock wave with gravitational impulsiveor shock wave of variable polarisation are also constructed.     

Thermal stresses in box-type laser packages

The effect of Au coating on thermally induced stresses in box-type semiconductor laser packages was investigated by a finite-element method (FEM). The simulated results showed that Invar–Invar joints with Au coating have maximum stresses two times higher than joints without Au coating. This is due to the different coefficients of the thermal expansion (CTE) between dissimilar materials of Invar and Au, resulting in higher stresses. Maximum stresses were also found to be increased as the Au thickness increased. This effect is attributed to the increase in the thermal gradient in the welded region provided by the increased thermal conduction of the thicker Au coating layer. These results suggest that both the difference in CTE between dissimilar materials and higher thermal conduction of Au coating layer have an important impact on thermally induced stresses for optoelectronic packages having laser-welded Au coated materials.     

C(3P)与H2S反应的反应机理

The mechanisms of the C(3P)+H 2S→HCS+H and C(3P)+H 2S → HSC+H reactions have been studied at the UMP2/6-31G(d,p),UMP2/6-311G(d,p),and G2 levels, and six transition states and three intermediates have been located along the reaction paths. The predicted path for the C(3P)+H2S→HCS+H reaction is: C(3P)+H2S→IM1→TS1→IM2→TS4→HCS+H, in line with the reaction process suggested by Lee et al. [1] in which only the intermediates were given. Our energetic results indicate that the C(3P)+H2S→HCS+H reaction is more favorable than the C(3P)+H 2S→HSC+H reaction, in agreement with experiment.     

跨国公司与化学

跨国公司是现代企业发展到国际化生产的产物 ,是世界商品的重要生产者 ,它在激烈的世界性竞争中 ,不断地进行科学研究及技术开发 ,大大推动了世界科技革命进程。在化工领域 ,跨国公司利用自身的经济实力及技术力量为化学基础理论、化学工业的发展作出了巨大的贡献。     

钌(Ⅲ)-二安替比林对氯苯甲烷-高碘酸钾体系催化分光光度法测定痕量钉

在磷酸介质中及加热条件下,钌（Ⅲ）对高锰酸钾氧化二安替比林对氯苯基甲烷（ＤＡｐＣＭ）显色反应有强烈的催化作用,由此建立了测定痕量钉的方法。体系的最大吸收波长为 ５００ ｎｍ,钌的含量在 ０．０～４．０μｇ／Ｌ范围内具有线性关系,检测限为 １．９４×１０－１０ｇ／ｍＬ,反应的表观活化能为 ８８．２０ ｋＪ／ｍｏｌ,反应表现速率常数为 ７．７ ０×１０－４／ｓ。本方法用于矿样中痕量钌的测定得到了满意的结果