A method to determine direct‐ and quadrature‐axis inductances of permanent magnet synchronous motors

The equivalent circuit constants of permanent magnet synchronous motors are needed in the calculation of operation characteristics, construction of a control system, etc. These constants can be computed from the data on structural form and materials. However, measurements are necessary to obtain highly precise values. Methods for measurement of the d‐ and q‐axis inductances can be roughly divided into rotational and standstill methods. The standstill methods have the advantage that they are easy to carry out. However, it is difficult to consider magnetic saturation and distortion of the change in the armature winding inductance. The accuracy of the standstill method can be improved if these effects can be readily taken into account. This paper describes a standstill method for measuring accurate d‐ and q‐axis synchronous inductances of permanent magnet synchronous motors. By utilizing the fact that the EMF interference terms in the motor voltage equation considering the distortion of the inductance change are equal to zero when the rotor is in a specific position, the proposed method determines the inductances considering both magnetic saturation and inductance distortion effects from simple off‐line standstill testing. In addition, this method is capable of taking cross‐magnetic saturation into account when used with the necessary testing equipment. The proposed method was implemented on a 0.4‐kW interior permanent magnet synchronous motor with concentrated stator winding. The validity of the proposed method was demonstrated by comparing the measured and calculated results of the no‐load and on‐load characteristics. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 41–50, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20969     

Low temperature fabrication of high strength porous calcium phosphate and the evaluation of the osteoconductivity

Porous NaO₂–MgO–CaO–P₂O₅ bioglass doped beta-tri-calcium phosphate (β-TCP) bioceramic possessing high mechanical properties and well pore structure with high porosity and high pore connectivity has been prepared through dipping method with the porous polyurethane as the pore forming template. The sintering mechanism and the mechanical properties of the bioglass doped β-TCP scaffold have been investigated by the X-ray diffraction (XRD) analysis, Scanning electron microscope (SEM) and thermal differential analysis (DTA). The scaffold’s in vivo osteoconductivity has been evaluated by implantation of scaffolds into the femurs of New Zealand rabbits. The results show that the porous structure can achieve the densification process at a low temperature about 950°C by a solid solution sintering mechanism and hence dense macropore scaffold with a compressive strength of 4.32 MPa when the porosity is 75% has been obtained. The in vivo test shows that the Na₂O–MgO–CaO–P₂O₅ bioglass doped porous β-TCP bioceramic has a relatively fast bone formation after implantation; after 1 month implantation new deposited bone tissue has been detected on the strut of the porous scaffold and degraded particles also has been found on the surface of the new formed bone. After 6 months implantation the porous scaffold has been thoroughly covered with new formed bone. Results show that the Na₂O–MgO–CaO–P₂O₅ bioglass doped porous β-TCP bioceramic is potential bone tissue engineering scaffold for orthopedic use.     

石油贸易计价货币的国际政治经济博弈

石油贸易不是简单的商品贸易,它体现出更多的政治属性和金融属性,这也是世界大国在国际石油贸易计价货币上博弈的重要原因。美国在二战后,凭借经济实力的增长和布雷顿森林体系的建立,确立了"石油美元"的地位,并从中获得了大量好处。然而随着美元的持续贬值、"双赤字"问题以及"新特里芬悖论"等原因,"石油美元"体制日渐衰落。欧元、卢布、日元等欲成为新的石油贸易计价垄断货币。国际石油贸易的多元货币计价体制必将变为现实,其未来发展有几种可能,一是以多个大国货币作为计价基准,构建石油贸易的"多元混合货币"计价体制;二是以"国际石油货币"为基准;三是以特别提款权(SDR)作为计价基准。面对石油定价和交易货币的激烈争夺,中国应充分利用当前世界市场上大量的石油贸易盈余,既要创造有利于投资的金融和法律环境,又要避免给我国金融市场和国家经济安全造成负面影响。同时,应寻求建立自己的能源期货交易机构,以更有效地参与国际能源期货交易。     

关于县级检验检测机构改革与发展的思考

县级检验检测机构存在设立部门多、主管部门多,重复建设情况严重,检验检测业务覆盖范围窄、水平参差不齐,在编在岗人员少,检验检测设备陈旧等情况,笔者就县级检验检测机构存在的问题、改革与发展、前景展望等方面进行了思考和阐述,为县级检验检测机构改革方向提供参考。     

衡——浅谈建筑与结构的关系

建筑与结构是相互关联、相互依存不可分割的整体。建筑作为凝固的艺术．它一直处于不断创新和发展之中．始终与城市发展的脉搏相呼应。建筑是一门综合艺术．是各项技术运用的产物。要让建筑作品成为艺术，需要建筑师与工程师共同来进行创造．倾注热情和智慧。     

Degradation of hexahydro‐1,3,5‐trinitro‐1,3, 5‐triazine (RDX) by anaerobic mesophilic granular sludge from a UASB reactor

BACKGROUND: This study investigated the performance of anaerobic mesophilic granular sludge for the degradation of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX). Batch tests were conducted to investigate the effects of different supplements on the RDX degradation ability of anaerobic granular sludge, as well as the contributions of both physicochemical and biological processes involved in RDX removal from aqueous solution. RESULTS: Anaerobic granular sludge exhibited good performance in treating RDX as the sole substrate. Biodegradation was the main mechanism responsible for RDX removal. Ammonium had no significant promoting effect on the degradation process. The presence of glucose was found to enhance the degradation of RDX by anaerobic granular sludge, while the addition of sulfate and nitrate had adverse effects on the reductive transformation of RDX. CONCLUSIONS: Anaerobic granular sludge is capable of removing RDX from aqueous solution with high efficiency. This study showed good prospects for high‐rate anaerobic processes in the treatment of munition wastewater. The results can be used for the design and optimization of high rate anaerobic systems for the elimination of RDX. Copyright © 2010 Society of Chemical Industry     

Synthesis,characterization and thermal properties of novel epoxy/expandable graphite composites

Epoxy resins are widely used as coatings, adhesives and primers and in semiconductor encapsulation. A requirement that has recently gained importance is that of flame resistance, and imparting flame retardancy to epoxy resins has attracted much attention. Expandable graphite (EG) can improve flame‐retardant properties of polymers. Due to poor compatibility between polymer matrix and EG, flame‐retardant performance will be impaired. EG can be functionalized using a coupling agent. This gives rise to covalent bonding between organic and inorganic phases. This will improve the compatibility between filler and polymer to enhance the thermal stability of composites. X‐ray photoelectron spectroscopy was used to characterize the functionalizing reaction between coupling agent and EG. Thermogravimetric analysis (TGA) and integral procedural decomposition temperature (IPDT) were used to calculate the thermal stability of composites. The results show that functionalized EG can improve the thermal stability of the composites. TGA/mass spectroscopy (MS) shows that the amount of toxic gases liberated from the composites is less than that from pure epoxy. Novel epoxy/EG composites were prepared successfully via the sol–gel method. The results of TGA, IPDT and TGA/MS showed that functionalized EG can enhance the thermal stability of composites and can suppress the production of toxic gases. The composite materials could provide a safer choice. Copyright © 2009 Society of Chemical Industry     

太阳能供热采暖系统研究现状及思考

太阳能供热采暖系统是以太阳能作为热源,供给建筑物冬季采暖和全年其他用热的系统。本文介绍了太阳能供热采暖系统国内外现状,在此基础上分析了存在的问题及改进的措施。     

盐水工段的技改措施及其效果

我厂是一个小型氯碱企业，年产烧碱1．5万t，由原来石墨阳极改为金属阳极电解槽，原来盐水工段设计基本能满足工艺要求，但在生产中仍存在缺陷，盐水质量不稳定，纯碱消耗高，经不断地生产实践和经济的积累，我们对工艺中不合理部分做了大胆地改进，收到了很好的效果，生产出高质量的精盐水，保障了金属阳极在高电流效率下平衡运行，保证了阳极片的使用寿命。     

UEA混凝土在重庆世界贸易中心工程中的应用

分析了大体积混凝土结构早期开裂的原因，提出了防裂技术思路与对策。并应用ＵＥＡ混凝土微膨胀剂于“重庆世界贸易中心”工程，将混凝土早期收缩变为限制性膨胀，取得了有效防止混凝土早期开裂，保证强度的工程实践经验。