一种有限元模型动力缩聚移频迭代法

提出了一种基于矩阵广义逆的有限元模型动力缩聚移频迭代方法,该方法首先直接从原系统特征方程出发,导出反映系统主,副自由度之间位移关系的动力缩聚矩阵的控制方程,然后给出了相应的迭代求解方法和收敛准则。为了减少求矩阵广义逆的计算工作量,本文给出了一种替代方法,把对一个高阶满阵求逆转化为对一个同阶高度稀疏矩阵求逆。与已有的动力缩聚迭代法相比,本文提出的方法具有两个显著的优点：其一是迭代收敛速度高,其二是通     

AISI 4340钢干滑动摩擦磨损特性研究

室温条件下,采用CFT-Ⅰ型多功能材料表面综合性能测试仪对AISI 4340钢进行了往复干摩擦磨损试验,研究了其摩擦磨损特性.采用扫描电子显微镜(SEM)和能谱仪(EDS)对磨痕和亚表层进行了观察和检测,分析了磨损表面微观形貌、亚表层塑性变形和碳氧元素含量演化.结果表明:磨损形式以磨粒磨损为主,并伴随轻微黏着磨损和剥落磨损;磨损表面分布着长度、宽度、深度不一的划痕以及鳞片状和颗粒状磨屑;磨损表面出现轻微氧化,磨屑呈现不同程度的碳富集和氧化;亚表层出现明显摩擦影响层,距表层越近,塑性变形越明显,晶界角逐渐汇聚于表面,在表面处趋于平行;往复运动导致塑性变形方向不一致,磨痕中部,塑性变形向某位置聚集.     

Model for processive movement of myosin V and myosin VI

Myosin V and myosin VI are two classes of two-headed molecular motors of the myosin superfamily that move processively along helical actin filaments in opposite directions. Here we present a hand-over-hand model for their processive movements. In the model, the moving direction of a dimeric molecular motor is automatically determined by the relative orientation between its two heads at free state and its head‘s binding orientation on track filament.This determines that myosin V moves toward the barbed end and myosin VI moves toward the pointed end of actin.During the moving period in one step, one head remains bound to actin for myosin V whereas two heads are detached for myosin VI: the moving manner is determined by the length of neck domain. This naturally explains the similar dynamic behaviours but opposite moving directions of myosin VI and mutant myosin V (the neck of which is truncated to only one-sixth of the native length). Because of different moving manners, myosin VI and mutant myosin V exhibit significantly broader step-size distribution than native myosin V. However, all the three motors give the same mean step size of -36nm (the pseudo-repeat of actin helix). All these theoretical results are in agreement with previous experimental ones.     

直觉不确定语言PROMETHEEP多属性决策方法

针对直觉不确定语言群决策问题,提出一种基于级别高于关系思想的决策方法.首先对个体决策矩阵利用直觉不确定语言算子集结,得到群体决策矩阵;然后,基于群体决策矩阵离差最大化思想构建属性权重目标模型,从而获得属性权重;进一步,将群体决策矩阵转化为区间决策矩阵,通过区间可能度函数计算备选方案的综合优序值,进而确定方案排序.最后利...     

多解法MULTAN失败原因的探讨

本文从三相角结构不变量的概率分布出发,分析了多解法的根本缺点——小起始套是如何影响相角的推导和修正的,从而说明程序系统MULTAN和SHELX中多解法失败的原因及其克服这一缺点的途径。并简要说明随机多解法RANTAN的原理,优点及其应用,在四个结构实例中加以比较。 关键词：     

退化矩阵Liouville,Beta,Dirichlet分布

该文引进和讨论了退化矩阵Liouville分布，由此导出退化矩阵Beta分布、退化矩阵Dirichlet分布．推广了文献［1］关于退化Wishart分布和秩为1的退化矩阵Beta分布的结果。     

Influences of Hard Donor on Cation Selectivities Closing to Soft Selenium Donor in Tweezer-like Calix[4]arene Receptors

Three novel 25,27-dihydroxy-26,28-bis(3-benzylselenopropoxy)-5,11,17,23-tetra-tert-butylcalix[4]-arene (2),25,27-dihydroxy-26,28-bis[3-(2-hydroxyethylseleno)propoxy]-5,11,17,23-tetra-tert-butyl-calix[4]arene (3) and 25,27-dihydroxy-26,28-bis(3-propylselenoproppxy)-5,11,17,23-tetra-tert-butyl-calix[4]arene (4) were synthesized for the comparison of their ion-selectivity in ion-selective electrodes (ISE). X-ray structure of the CH/π complex of 4.CH2Cl2 was elucidated. ISEs based on 2-4 as neutral ionophores were prepared, and their selectivity coefficients for Ag (logKAg,M^pot) were investigated against some main group metal ions and transition metal ones using the fixed interference method (FIM). These ISEs showed excellent Ag^ selectivity over most of the interfering cations examined. It is evident that the stronger Hg^2 interference may not be produced while hard donors (hydroxy) are close to the soft selenium donors.     

超支化极性官能团化烯烃齐聚物的合成及表征

设计、合成并表征了两种不同烷基链长取代的大位阻二芳基甲基吡啶亚胺配体及其相应的钯配合物。这些钯催化剂在乙烯与丙烯齐聚中表现出高活性（高达1.6×10⁵g·mol^-1h^-1）和能够生成低分子量的超支化（BD=112~238/1000C）乙烯与丙烯齐聚物（M_HNMR=258~478 g·mol^-1）。最为重要的是,通过利用这些吡啶亚胺钯催化剂催化乙烯或丙烯与丙烯酸甲酯共齐聚,能够得到超支化高插入率（高达24.3 mol%）的极性官能团化的乙烯与丙烯齐聚物。这些极性官能团位于齐聚物支链的末端。这类新型的钯催化剂为解决超支化极性官能团化烯烃齐聚物制备过程中稳定性差和插入率低等问题提供了可能。      

基于柔性MXenes/石墨烯纤维直接电沉积NiS构建非酶葡萄糖传感器

使用一步电沉积法在二维过渡金属碳(氮)化物(MXenes)/石墨烯纤维(GF)上直接合成NiS,制备非酶葡萄糖传感器。在最佳条件下,NiS/MXenes/GF微电极传感器检测葡萄糖,在葡萄糖浓度2.5～5000μmol/L范围内呈良好的线性关系,检出限为1.64μmol/L,灵敏度3951.35μA·L/(mmol·cm²)。结果表明,制备的NiS/MXenes/GF柔性纤维状微电极可作为生物传感器的电极材料。