Conductor design with high-Tc superconducting Bi(Pb)—2223/Ag multifilamentary tapes

With high upper critical fields, high temperature superconductors (HTSC) have been recognised as candidate materials for coil and magnet applications. High field devices, at one time or another, when operated close to their rated limits are often faced with instability problems which normally are electrical, magnetic or mechanical in nature. The determination of stability parameters, therefore, is of interest to the conductor designer which very much assists in the processing aspect of long length production of wires and tapes. Due to the morphology of the superconductor most HTSC devices made with Bi(Pb)—2223 precursor exist in tape form. Here the determination of stability parameters (for flux-jump and cryogenic stability) for multifilamentary Bi(Pb)—2223/Ag tapes are presented. Processing parameters such as intermediate deformation and filling factors have been found to play a crucial role, not only on the critical current density of the tapes but on the stability aspect in conductor design as well.     

Distributed Context Retrieval and Consistency Control in Pervasive Computing

The challenge of saturating all phases of pervasive service provision with context-aware functionality lies in coping with the complexity of maintaining, retrieving and distributing context information. To efficiently represent and query context information a sophisticated modelling scheme should exist. To distribute and synchronise context knowledge in various context repositories across a multitude of administrative domains, streamlined mechanisms are needed. This paper elaborates on an innovative context management framework that has been designed to cope with free-text and location based context retrieval and efficient context consistency control. The proposed framework has been incorporated in a multi-functional pervasive services platform, while most of the mechanisms it employs have been empirically evaluated.     

K202A压缩机电机轴瓦超温的原因及对策

K202A压缩机的电机轴瓦采用的是动压轴承,经常持续升温。其主要原因是由于滑动轴承和轴之间是半液体摩擦,润滑油在轴颈及轴瓦之间没有形成具有足够压力的油膜,造成滑动轴承和轴局部形成半液体摩擦而产生大量的热量,又无法被带走引起的。文章通过验算K202压缩机电机滑动轴承温度,分析影响滑动轴承运行温度的因素,提出在原滑动轴承上开油楔及加装一台齿轮油泵为滑动轴承强制润滑,并且通过联轴器把电机和压缩机连接起来,用压缩机轴瓦托起电机轴,使电机轴颈和轴瓦之间处于液体摩擦状态,可有效地降低滑动轴承的运行温度。     

3D model retrieval using principal plane analysis and dynamic programming

Three dimensional models play an important role in many applications; the problem is how to select the appropriate models from a 3D database rapidly and accurately. In recent years, a variety of shape representations, statistical methods, and geometric algorithms have been proposed for matching 3D shapes or models. In this paper, we propose a 3D shape representation scheme based on a combination of principal plane analysis and dynamic programming. The proposed 3D shape representation scheme consists of three steps. First, a 3D model is transformed into a 2D image by projecting the vertices of the model onto its principal plane. Second, the convex hall of the 2D shape of the model is further segmented into multiple disjoint triangles using dynamic programming. Finally, for each triangle, a projection score histogram and moments are extracted as the feature vectors for similarity searching. Experimental results showed the robustness of the proposed scheme, which resists translation, rotation, scaling, noise, and destructive attacks. The proposed 3D model retrieval method performs fairly well in retrieving models having similar characteristics from a database of 3D models.     

CNC机床结构动态设计方法研究

提出机床结构动态设计基本原则。以某数控弧齿铣齿机为研究对象,应用相关的动态设计原则,通过变量化设计与有限元分析,对该机床进行结构动态设计。结果表明,应用该方法设计的机床结构具有良好的动静态特性。     

变频调速节能改造方案的经济性评价和比较

本文详细介绍了变频调速节能改造方案的经济性评价方法。静态分析法包括投资回收期法、抵偿年限法和年计算费用法；动态分析法则包括净现值法、内部回收率法、总费用现值法和最小年费用法。     

Climate-related electricity demand-side management in oil-exporting countries—the case of the United Arab Emirates

The oil crisis of the 1970s has increased the concern about the continuity of oil imports flow to major oil-importing developed countries. Numerous policy measures including electricity demand-side management (DSM) programs have been adopted in such countries. These measures aim at reducing the growing need for electricity power that increases the dependency on imported foreign oil and damages the environment. On the other hand, the perception that energy can be obtained at very low cost in oil-rich countries led to less attention being paid to the potential of DSM policies in these countries. This paper discusses such potential using the case of the United Arab Emirates (UAE). Since air conditioning is a major source of electric energy consumption, the relationship between climate conditions and electric energy consumption is considered. An electricity demand model is constructed using time series techniques. The fitted model seems to represent these relationships rather well. Forecasts for electricity consumption using the estimated model indicate that a small reduction in cooling degrees requirement might induce a significant reduction in electric energy demand. Hence, a DSM program is proposed with policy actions to include, among others, measures to reduce cooling degrees requirement.     

Criteria of dynamic buckling estimation of thin-walled structures

The paper deals with dynamic buckling of thin-walled structures (plates and beam-columns with open cross-section) subjected to compressive rectangular pulse loading. The local, global and interactive dynamic buckling was analysed. Author proposes the new criterion for critical amplitude of pulse loading leading to stability loss. The proposed criterion is a modification of quasi-bifurcation criterion formulated by Kleiber, Kotula and Saran. Results obtained using proposed criterion were compared with other well-known criteria (Volmir (V) and Budiansky–Hutchinson (B–H) criterion).     

碳钢高温变形后的静态软化行为

在形变温度为1133K、形变速率为2×10~(-3)s~(-1)的试验条件下,采用两段加载拉伸试验方法研究了0.4%C-1.5%Mn钢高温变形后的静态软化行为.调查了由两次加载拉伸变形时的屈服应力求得的静态软化率以及相对峰值应力比和峰值应变比随等温保持时间的变化.详细讨论了动态回复组织和动态再结晶组织对高温变形后的静态软化过程的影响.     

条形药包爆炸应力场试验研究

应用动态光弹性模型试验方法研究了条形药包的爆炸应力场分布特性。研究结果表明：起爆方式和位置影响着条形药包爆炸应力场的分布形态，并首次成功地记录了条形药包瞬间爆炸应力场的动光弹条纹，得到了理想成力场的分布形式。