Reduction of alternating current loss in a high-TC superconducting transmission cable by means of helical pitch adjustment

We have reported that the alternating current (ac) losses in a 66 kV_rms 3-core high-T_C superconducting (HTS) transmission cable fabricated by Tokyo Electric Power Company and Sumitomo Electric Industries Ltd. are calculated correctly by using an electric-circuit model. According to the calculated results, the circumferential field losses are dominant in the total ac losses in compared with the self-field losses and the axial-field losses. The helical pitches of each layer in the HTS cable are designed to obtain almost same layer currents, which gives the minimum self-field losses. We think that the optimum helical pitches giving the minimum total losses are different from the helical pitches designed by the companies and calculate the optimum values in the condition of the same helical direction of each layer in the cable. As a result, for example, it is found that the ac loss of 2.1 W m⁻¹ cc⁻¹ at transporting 1 kA_rms can be reduced to 1.8 W m⁻¹ cc⁻¹ (about 14% reductions) after redesigning the cable with the optimum helical pitches. The optimum helical pitches are obtained for each given transport current. After redesigning, the distribution of layer currents is not uniform and the circumferential fields are reduced.     

采煤技术及采煤方法的选择

介绍采煤技术的发展、采煤工作的现状及目前采煤工作中存在的一些问题，然后，对我国单一走向长壁采煤法采煤工艺、普通机械化采煤工艺、倾斜分层走向长壁下行垮落采煤法、倾斜长壁采煤法以及放项煤采煤法做了简要论述，最后，指出了采煤方法选择的原则以及具体措施。     

钴溶液除铁的工艺改进

对钴渣溶解后液原使用的中和法除铁的情况和采用黄钠铁矾法除铁后的现状进行了对比分析，介绍了采用黄钠铁矾法除铁后，金属回收率、辅材消耗量等项指标有明显改善，提高了经济效益。     

输电损耗的分摊原则

在分析现有输电网损耗分配方法的基础上，针对损耗分配中的主要问题，从公平公正、快速高效、收支平衡、过程透明、经济信号、潮流基础和网络拓扑几个方面，分析并提出了输电损耗分配应该满足的主要原则，为进一步研究输电损耗的公正有效分配方法奠定了基础。     

Compomer的摩擦磨损特性

采用Compoglass，F2000，Elan，Dyract AP4种牙科用复合体材料(Compomer)，对其玻璃颗粒含量和表面硬度进行了测量，并在球一盘往复摩擦磨损试验机上考察了它们的摩擦磨损特性。结果表明：F2000的摩擦系数最高，Elan的摩擦系数次之，Compoglass和DyractAP的摩擦系数分别为第三和第四．摩擦系数随玻璃颗粒含量的增加而增加．在同样试验条件下，低摩擦系数的DyractAP和Compoglass与高摩擦系数的F2000和Elan相比具有较好的耐磨性．磨损机理主要表现为由玻璃颗粒脆性断裂引起的玻璃颗粒脱落和磨粒磨损。     

电机中几个概念性问题的深入分析

分析了电机中铁心损耗的形成机理及其本质,讨论了直流电机电枢反应的去磁机理,明确了同步发电机准同期并列的含义,从而深刻理解有关基本概念。     

串行通讯中的波特率设置和误差分析

波特率设置的误差是串行通讯中一个非常重要的参数。本文作者首先介绍了MCS 51单片机串行通讯中波特率的设置方法,然后分析了波特率的误差来源,并着重介绍了几种波特率误差的消除方法。     

岩土热-流-固耦合理论及在采矿工程中的应用

比较系统地介绍了煤炭工业中遇到的不可忽略的渗流-温度-应力耦合问题，而且对各领域的主要研究方法、研究结果等进行了报道，总结了岩土渗流-温度-应力耦合的研究方法和宏观方程，并提出了若干前沿研究方向。     

基于文本挖掘的搭配词典自动架构探讨

研究词语搭配的关系对于自然语言处理有很大的帮助。目前对计算机用的搭配词典是用人工方法实现的，它由人工进行维护，有更新慢、收藏的词少等缺点。为此，利用文本挖掘技术对大规模语料库进行分析，挖掘词语搭配的深层关系，在此基础上自动建立词语搭配词典，实验结果显示该方法是有效的。     

Improvement of Heater Surface Flatness and Uniformity of TiN Film Deposition

The deposition rate and the thickness uniformity of chemical vapor deposition (CVD) titanium nitride films depend on wafer temperatures. The heater surface conditions, such as flatness, roughness, and surface imperfections, can greatly affect heat transfer efficiency from the heater surface to the wafer, and the process performance. Because heater surface imperfections or “hot spots” that caused poor uniformity had to be eliminated, the origin of “hot spots” was identified by a detailed study of heater surface profiles. A better visualization of “hot spots” could be obtained by comparing wafer-chucking patterns with deposition patterns. Thus, the time needed to locate “hot spots” could be shortened. The manufacturing process was revised to prevent “hot spots” and improve heater performance.