面向虚拟样机的一种机构运动仿真算法

文中就虚拟样机四连杆机构的运动分析提出一种新的运动仿真算法，在基于场景图的虚拟样机产品模型中实现产品四连杆机构的运动仿真．其算法特点是：利用空间矢量运算原理和四连杆机构特性直接求出四连杆机构从动件的变换矩阵，再通过四连杆机构特征点构造的三角形面积变化求出从动件变换矩阵的偏离角，用偏离角补偿法校正从动件变换矩阵，实现四连杆机构的运动仿真．其算法简单，运算效率高，实现容易．     

搜寻平面机构中虚约束的拆杆组法

本文根据机构的组成原理,提出一种搜寻机构中虚约束的新方法一拆杆组法,用该方法能方便地判断出机构中所含的虚约束,同时能迅速排除含有特定几何条件而实际上并不存在虚约束的机构.     

构建城市危机管理联动机制提高城市危机防范能力

介绍了城市危机和城市危机管理联动机制的概念,并探讨了构建政府各危机管理主体之间、政府与市民及民间组织之间和政府与媒体之间的联动机制问题。     

ARP欺骗攻击的整网解决方案研究

随着各种病毒与木马程序的泛滥,ARP欺骗攻击在校园网中已经成为危害网络正常稳定运行的主要问题.本文在对ARP协议进行深入分析的基础上,提出一种全网设备联动实现整体防御ARP欺骗的可行方案.     

天门冬糖蛋白AG-b的研究

ＡＧ＿ｂ为４０％丙酮沉淀的天门冬糖蛋白级份,它的β－消去反应产物在２４３ｎｍ有紫外吸收峰,表明其糖和蛋白质连接键为０－型糖肽键。凝胶层析测定ＡＧ－ｂ中多糖部分ＰＡ－Ｉ分子量为２．１９×１０６。１３ＣＮＭＲ波谱显示,ＰＡ－Ｉ具有α１→２、α１→４和α１→６三种糖苷键,不含有糖醛酸组份。ＩＲ光谱显示,ＡＧ－ｂ在１２５０ｃｍ－１和１７３０ｃｍ－１处有吸收峰,说明其含乙酰基团。     

The drawing behavior of Y-Ba-Cu-O sol from non-aqueous solution by a complexing process

A complexing process is developed to prepare Y-Ba-Cu-O superconducting fibers. The process is not identical to typical sol-gel processes; here the resulting gel network is built up by hydrogen bonding linkage among complexing species in non-aqueous solution. Cu acetate, [Cu(OAC)₂], Ba methoxyethoxide [Ba(ORE)₂] and Y acetate [Y(OAC)₃] are used as precursors for preparing homogeneous gels while -methacrylic acid (HOAA) and diethylenetriamine (DETA) as complexing agents, and methoxyethanol (REOH) as solvent. Fibers drawn from a sol obtained through reduced pressure present no or little deformation at 80°MoC via adjusting the amount of DETA and HOAA. Cu(OAC)₂, Ba(ORE)₂ and Y(OAC)₃ in the complexing process have been demonstrated to form gels without hydrolysis and condensation at ambient atmosphere. The relationships between the drawing behavior of sols and gel structure with different amounts of DETA and HOAA are suggested. The concentration region of drawing the gel fibers with no or little deformation heated at 80°MoC is also found.     

Synthesis and Characterization of Novel Organosoluble Methyl Substituted Poly(aryl Ether Ketone)s Containing Sulfone Linkage

Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosities of 0.62–0.84 dL/g have been prepared from 4,4′‐bis(2‐methylphenoxy)diphenylsulfone and 4,4′‐bis(3‐methylphenoxy)diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic Friedel‐Crafts acylation in the presence of DMF with anhydrous AlCl₃ as a catalyst in 1,2‐dichloroethane, respectively. These polymers having weight‐average molecular weight in the range of 71,000–49,000 are all amorphous and show high glass transition temperatures ranging from 167 °C to 191 °C, excellent thermal stability at temperatures over 400 °C in air or nitrogen, high char yields of 51–58% in nitrogen and good solubility in CHCl₃ and polar solvents such as DMF, DMSO and NMP at room temperature.     

Synthesis and properties of new soluble aromatic polyamides and polyimides on the basis of N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine

A new N‐phenylated amide (N‐phenylamide) unit containing aromatic diamine, N,N′‐bis(3‐aminobenzoyl)‐N,N′‐diphenyl‐1,4‐phenylenediamine, was prepared by the condensation of N,N′‐diphenyl‐1,4‐phenylenediamine with 3‐nitrobenzoyl chloride, followed by catalytic reduction. Two series of organosoluble aromatic poly(N‐phenylamide‐imide)s and poly(N‐phenylamide‐amide)s with inherent viscosities of 0.58–0.82 and 0.56–1.21 dL/g were prepared by a conventional two‐stage method and the direct phosphorylation polycondensation, respectively, from the diamine with various aromatic dianhydrides and aromatic dicarboxylic acids. All polyimides and polyamides are amorphous and readily soluble in many organic solvents such as N,N‐dimethylacetamide and N‐methyl‐2‐pyrrolidone. These polymers could be solution cast into transparent, tough, and flexible films with high tensile strengths. These polyimides and polyamides had glass‐transition temperatures in the ranges of 230–258 and 196–229 °C, respectively. Decomposition temperatures of the polyimides for 10% weight loss all occurred above 500 °C in both nitrogen and air atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2564–2574, 2002     

Mass spectrometric determination of selenenylsulfide linkages in rat selenoprotein P

The reversible formation of a selenenylsulfide linkage in mammalian thioredoxin reductase was identified as having a key role in its activity. Identification of selenenylsulfide and/or diselenide linkages is therefore critical to the determination of the structure and function of selenoproteins. A selenopeptide, (298)SGSAITUQCAENLPSLCSUQGLFAEEK(324) (U=selenocysteine), was isolated from a tryptic digest of rat selenoprotein P. Its two cysteine residues and two selenocysteine (Sec) residues were determined to be present in oxidized form by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The selenopeptide was subjected to partial reduction by dithiothreitol with immediate alkylation by iodoacetamide. This process was monitored by MALDI-TOFMS to determine the number of alkylations that had taken place. The partially reduced and alkylated peptides were then analyzed by nano-electrospray ionization tandem mass spectrometry and the results indicated that selenenylsulfide linkages Sec304-Cys314 and Cys306-Sec316 were present. It is concluded that selenoprotein P contains these two selenenylsulfide bonds.     

火灾自动报警系统与消防设备的联动

火灾自动报警系统的设计与各种消防设备的联动密不可分。从自动喷水灭火系统、气体灭火系统，防排烟系统、电梯、防火卷帘等方面，探讨了当前火灾自动报警系统与消防设备的联动配合。