蒸汽发生器管头焊缝撕裂的失效分析和解决办法

分析了蒸汽发生器管头焊缝发生撕裂事故的原因,提出了有针对性的改进措施,取得了明显的改进效果。     

Preparation of amorphous poly(ethylene terephthalate) from U‐polymer via a copolymerization process

U‐Polymer, a kind of polyarylate, was synthesized by interfacial polycondensation method with terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), and bisphenol A (BPA) as raw materials. The structure of the U‐Polymer was characterized by IR and ¹H–NMR spectra. Then, an amorphous poly(ethylene terephthalate) (APET) was prepared with the introduction of the U‐Polymer to the PET sequence to improve thermal and mechanical behaviors of PET via the polymerization process. The structure and property of the APET were characterized by DSC and DMA. The results showed that the APET exhibits amorphism, transparency, higher glass‐transition temperature (T_g), and higher storage modulus than that of PET. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1653–1657, 2001     

无须常规维修的长输液氨管道的设计和管理

长输液氨管道的维修，由于受多种因素的制约，其困难非同一般。采用现代技术和科学管理相结合的办法，通过精心设计、严格施工、法制化管理，可保证管道在使用年限内（10～30年）长期不维修或大修，秦皇岛长输液氨管道运行10年的经验，值得借鉴。     

DDC在建筑电气设计中的应用研究

探讨DDC在建筑电气设计中的应用,以DDC为核心设计变风量空调末端(VAV BOX)控制器,介绍控制算法设计,工程实验运行和数据分析证明能够满足现场运行要求。     

围岩松动圈与锚杆支护参数设计的关系

叙述了松动圈的形成及机理,并对锚杆支护参数进行了设定。     

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。