Properties of strong hydrogen-bonded systems: The formation of hydrogen-bonded ion pair in amine·HCL systems

The hydrogen-bonded complexes between CH₃NH₂ and (CH₃)₂NH with HCl have been studied by the ab initio molecular orbital method using the 4–31G basis set. Calculations show that the proton potential curve has a single minimum near to the nitrogen atom in both complexes. This means that the proton has been transferred from HCl to the amine. ΔE and the dipole moment of the complexes studied are as follows: ?18.2 kcal mol^?1, 10.3 D for methylamine ·HCl, and ?21.7 kcal mol^?1 11.1 D for the corresponding dimethylamine complex. Other properties of the hydrogen-bonded ion pairs are discussed.     

A theoretical approach to substituent effects: Stabilities and conformational preferences in β-substituted ethyl radicals

Ab initio molecular orbital theory is used to study substituent effects in a series of β-substituted Et radicals XCH₂CH₂. For X = BH₂ (plan.), CH₃, NH₂, OH and F, only slight conformational preferences and weak stabilizations are indicated. Such behaviour may be rationalized, using a PMO model, in terms of opposing changes, accompanying variation in X, in positive and negative hyperconjugation between the XCH₂ group and the CH₂ centre. On the other hand, for groups containing an appropriately oriented, low-lying vacant orbital, viz. X = Li, BeH and BH₂ (perp.), there is a pronounced preference for the perpendicular conformation of the radical. This is attributed to 1,3-interaction between the singly-occupied 2p(C) orbital and the vacant 2p(X) orbital.     

Trace element determinations in shale oil products by neutron activation

Neutron activation offers some important advantages for the determination of selected trace elements in shale oil products. This paper gives techniques and results of a study of crude shale oil and naphtha, heavy distillate, and wax products of shale oil. The elements determined were Al, As, Au, Br, Ce, Cl, Co, Cr, Fe, Hg, I, K, Mn. Mo, Na, S, Sb, Se, V, and Zn. Some elements (Mn, Na, As) tend to accumulate in heavier fractions, whereas chlorine and iodine are concentrated in the more volatile fractions. The volatility of sulphur compounds in the shale oil products appears to be essentially uniform, with some tendency toward accumulation in distillation residues. The tendency for the trace elements to accumulate in the waxes that precipitated from cooled heavy distillates was very low.     

On the character of local electric fields in amorphous semiconductors

On the basis of the agreement of calculated and measured parameters of some amorphous semiconductors, an argument is stated in favour of the central-symmetric type of random local electric fields. A possible mechanism of the transport of electrons is discussed.     

桥接网络模式下多虚拟机初始参数冲突的解决方法

针对网络对拷后在桥接网络模式下多虚拟机之间的MAC地址冲突及计算机重名问题,提出了虚拟机初始参数的自动配置方法(VPIAAC).该方法预先定义了宿主主机与虚拟机系统初始参数的对应关系,利用VmwareTools映射网络路径,确保在无IP条件下虚拟机仍可完成对宿主主机参数的读取访问,并通过VBS脚本实现虚拟机MAC地址与计算机名的自动配置.实验结果表明,该方法可有效地避免网络对拷后虚拟机之间初始参数冲突,确保虚拟机参数在网络中的唯一性.     

IP与MAC绑定技术的应用

论述了网络安全的重要性，分析了造成网络不安全的主要原因是IP和MAC地址以及账号的被盗用，提出了解决的策略．指出在交换机端口上绑定MAC地址、绑定MAC地址的扩展访问列表、绑定主机的MAC-IP地址以及IP—MAC绑定与行为控制软件相结合等技术的应用，对维护网络安全都是行之有效的方法．     

模态置信标准（MAC）在环锭细纱机机架模态识别中的应用

应用模态置信标准（ＭＡＣ）的概念对细纱机机架的模态进行了辨识。实验和分析计算表明，ＭＡＣ可以弥补常用模态识别方法的不足，使模态参数的评估定量化。     

NOVELL网络用户自动上网方法

本文叙述了如何编写程序和设置网络以适应不同类型上机的需要．     

基于IEEE802．11e MAC的联合无线资源管理

联合无线资源管理（JRRM）是针对耦舍多种无线接入技术的异构网络进行无线资源管理的一种新型机制，其目的是基于重配置技术和业务分流来整体优化异构网络的资源利用率。这种资源管理机制对其管理的各个接入网提出了QoS保证机制的要求。IEEE 802．11e的提出为WLAN提供了MAC层的QoS保证机制，从而促使IRRM能够高效工作。对基于IEEE 802．11e MAC的JRRM进行介绍，并分析了在联合会话允许控制和联合资源调度方面，基于IEEE802．11e MAC的方式能够改善异构无线环境中的网络性能。