改进异步电机直接转矩控制系统的仿真研究

本文介绍了直接转矩控制系统的控制原理,并针对基于直接转矩控制的异步电动机运行时存在较大的电流及转矩脉动问题,提出一种新的控制方案,并基于Matlab 6.5对这种新方法进行仿真,仿真结果表明该方案能有效的解决电流及转矩脉动的问题.     

高炉富氧鼓风的现状及机前供氧

阐述了高炉生产采用富氧大喷煤的必要性，国内高炉富氧鼓风的现状，以及机前富氧的优点和应采取的安全措施。     

The Region 1 & 3 Broadcasting‐Satellite Service Plan after WRC‐03

The 1977 Broadcasting‐Satellite Service (BSS) Plan for Region 1 & 3 had been widely acknowledged to be out‐of‐date by the late 1980s. Development of digital modulation in the early 1990s provided an opportunity to update the technical provisions of the Plan to make it more economically viable. After a decade of work and three World Radiocommunication Conferences (WRCs), the revision of Region 1 & 3 BSS Plan was finally completed in 2003. The new Plan increased channel assignments from 5 to 10 analog‐equivalent channels for each country in Region 1, and from 4 to 12 channels for each country in Region 3. Yet, despite the increase in capacity, the new Plan is surprisingly similar to the original one in terms of the technical parameters. It is still based on national coverage, and the channel plan, orbital location, orbital spacing, and polarization are also the same. As a result, the new Plan is no more economically viable to implement than the old. To create economically viable BSS systems would most likely require modifications to the assignment in the Plan. Yet, modification procedures were made more difficult to apply after replanning. Less future implementation of BSS networks than would otherwise have occurred can be expected, and an inefficient usage of these frequency bands will likely result. On the other hand, less implemented systems will mean more capacity set aside for future use. This is important for countries that currently do not have satellite operations. In the end, BSS replanning reflects the eternal conflict between efficient usage and guaranteed future access. Copyright © 2005 John Wiley & Sons, Ltd.     

“四低一高”工艺在85kA预焙槽的应用与优化

本文介绍了“四低一高”(低电解温度、低分子比、低氧化铝浓度、低阳极效应系数、高工作电压)工艺技术条件在85kA预焙槽上的应用与优化,实验证明“四低一高”工艺需要针对具体槽型进行优化设计,适宜的技术条件对提高电流效率、降低直流电耗,节能效果显著。     

阳平关砂金矿精选厂尾矿综合回收的研究

本文详细的介绍了陕西省阳平关砂金矿精选厂尾矿金和其他可利用的矿物综合回收方法和最佳分选流程。     

我国清洁代用燃料汽车发展状况

随着汽车数量的迅速增加，汽车排放的有害废气也急剧增加，人们的健康受到威胁，解决这一问题的最好办法是发展清洁代用燃料汽车。介绍了天然气汽车和液化石油气汽车的主要优点，分析了目前我国清洁代用燃料汽车的发展现状，阐述了近期适宜发展我国清洁代用燃料汽车的机遇和面临的困难。最后就提高人们的环保意识、修改和完善汽车尾气污染控制法及排放标准、清洁代用燃料汽车的有关标准和安全措施。对发展这种汽车应给予优惠政策以及零部件生产和车辆改装企业的管理等方面，提出了建议。     

LZW压缩算法解析及应用设计

ＬＺＷ压缩算法是一种无限压缩算法，它主要是用一种代码来表示数据流中出现的重复串，以达到压缩的目的。     

起重机吊钩拖动绕线电动机他励双高调速系统

本文提出励磁电流可自动控制的他励式双高调速系统设计方案。系统在提升特别是在下放重物时，具有较硬的机械性；在负载１０－１００％的变化范围内，可实现最大偏差Δｎｍａｘ／ｎｍｉｎ１００％≤１０％，调速范围Ｄ≥１０；在满载运行条件下，可节约电能８０％以上。     

Superconductivity and magnetism in niobium doped YBa2Cu3O7 Related high Tc ceramics

Magnetic characterization has been performed on the members of the cuprateniobate RBa₂Cu₂NbO₈ (R = Pr, Nd, and La) series and R_1.5Ce_0.5Sr₂Cu₂NbO₁₀ (R = Pr, Eu, Nd, and Sm) series. The PrBCNO samples show a signature in the magnetization of a magnetic ordering at 12K. The PrCSCNO sample is nonsuperconducting and shows two distinct orderings at 17K and 53K. No such magnetic phase transition is observed down to 2K in the Nd and La based RBCNO materials or the Nd, Sm, and Eu based RCSCNO materials. Measurements of the lower critical field curve, dc irreversibility line, and critical curent densities are reported for each of the superconducting NdCSCNO, SmCSCNO, and EuCSCNO compounds.     

碱性氰化物防渗碳光亮镀铜工艺的研究

本文介绍了一种高效率，高韧性，防渗碳底铜工艺，可以大辐度提高镀层的沉积速度，降低铜层孔隙率，提高产品合格率，具有显著的经济效益和社会效益。