水及水蒸气对YBa_2Cu_3O_(7-x)相结构及超导电性的影响

以热重分析(TGA)、X 射线衍射及电阻-温度关系测定等方法,研究了水及水蒸气于285-1223K 间对 YBa_2Cu_3O_(7-x)超导材料的超导电性退化、水解及热重变化等过程的影响.YBa_2Cu_3O_(7-x)试样在水及水蒸气冷凝于试样表面的水膜的作用下,将逐渐水解为 BaCO_3、CuO 及 Y_2O_3等产物.当试样或水蒸气的温度高于373K 时,水蒸气对YBa_2Cu_3O_(7-x)的晶体结构与超导电性无明显影响.在20%H_2O+80%O_2的气体介质中,YBa_2Cu_3O_(7-x)于373-1223K 问的 TGA 曲线与在常压大气中相似,其放-吸氧及相变过程是完全可逆的.自1223K 降温至373K,YBa_2Cu_3O_(7-x)恢复原来结构与性能.     

相控电力机车整流装置桥段数的选择

本文从我国相控机车的发展现状,分析了整流装置桥段数的发展过程,阐明了经济4段桥和2段桥加滤波器(PFC)形成的合理性,并提出根据运输量和用电指标在变电所或机车上合理配置PFC的建议。     

SVC和STATCOM在电气化铁道中的应用

针对目前国际上电气化铁道主要采用的供电方式，相应的负荷不平衡的特点，以及传统的通过提高电气化铁道变电所接人系统的短路容量来减小负序电流等做法的局限性进行了讨论。较为详细地介绍了SVC和STATCOM在电气化铁道中的具体应用，并进行了比较，指出适合中国当前国情的应用方式。     

Study on the Formation of η Phase During TIG Welding

The paper studied the effect of Ni-Fe-C filler materials on the η phase formation during TIG welding of WC-30Co and 45 steel. ηphase's morphology and forming condition were discussed using BEI method. The properties of the weld joints were also measured using microhardness measurement and four-point bending measurement. The results show that the weld joints of WC-30Co/45 steel can be obtained by TIG welding using different Ni-Fe-C materials as filler materials, and ηphase formed in the joints is M6C, M12C type carbides. The poor carbon content of the W-Co-C system resulted from the C diffusion and the high ingredient Fe are the two vital factors inducing to ηphase formation. It can be restricted by the addition of C element into Ni-Fe material. When carbon content is 0.01 % in filler material, bend strength σbb of weld joint is 908 MPa. However, when carbon content increases to 0. 41% in filler material, bend strength σbb is 1 260 MPa.     

连续梁桥减震性能中阻尼影响的试验研究

阻尼是桥梁的重要动力参数之一 ,研究阻尼在减震中的作用对抗震设计很有指导价值 .通过有机玻璃连续梁桥模型振动台试验 ,分析了阻尼对模型桥梁和墩减震性能的影响 .试验表明 ,阻尼的大小对减震性能有着重要的作用 .适当的增加阻尼会降低振动幅值 ,扰乱振动过程中规则的相位 ,从而得到良好的减震效果     

VFT PHASE VOLTAGE MEASUREMENT IN THREE-PHASE ENCLOSED GIS

Ｇａｓｉｎｓｕｌａｔｅｄｓｕｂｓｔａｔｉｏｎ (ＧＩＳ)ｈａｖｅｂｅｅｎｕｓｅｄｉｎａｗｉｄｅｒａｎｇｅｏｆｖｏｌｔａｇｅｌｅｖｅｌｆｒｏｍ 12 3ｋＶｔｏ765ｋＶｏｒａｂｏｖｅ .Ａｓｖｏｌｔａｇｅｌｅｖｅｌｓｅｘｃｅｅｄ 30 0ｋＶ ,ｆａｉｌｕｒｅｓｃａｕｓｅｄｂｙｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｔｒａｎｓｉｅｎｔｐｈｅｎｏｍ ｅｎａｂｅｇｉｎｔｏａｐｐｅａｒ .Ｔｈｅｓｅｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｔｒａｎ ｓｉｅｎｔｓａｒｅｃａｕｓｅｄｂｙｄｉｓｃｏｎｎｅｃｔｓｗｉｔｃｈｉｎｇｉｎｔｈｅＧＩＳ .Ｔｈｉｓ…     

浅谈房地产开发设计阶段成本管理

随着我国房地产开发的不断发展,越来越多的房地产商意识到了设计阶段成本管理的重要性.但如何进行设计阶段成本管理,如何改善和提高设计阶段成本管理水平,大多数房地产商还处于摸索阶段.本文通过对一些具体案例的分析,来阐述设计阶段成本管理的一些办法和思路.     

IL-1α和MMP-9在中耳胆脂瘤上皮中的表达

目的研究白介素-1α(interleukin-1α,IL-1α)和基质金属蛋白酶-9(matrix metalloproteinase-9,MMP-9)的表达,探讨二者与胆脂瘤侵袭破坏能力的关系。方法采用免疫组织化学SP法检测了IL-1α、MMP-9在21例后天继发性胆脂瘤上皮与10例胆脂瘤患者外耳道皮肤表皮中的表达。结果IL-1α和MMP-9在胆脂瘤上皮的阳性表达率明显高于外耳道皮肤表皮,差异具显著性(P<0.01,P<0.01);胆脂瘤上皮IL-1α、MMP-9表达均与胆脂瘤的侵袭破坏程度正相关(P<0.05,P<0.05);胆脂瘤上皮中IL-1α、MMP-9表达存在正相关性。结论IL-1α、MMP-9是介导胆脂瘤侵袭破坏行为的重要细胞因子。在体内IL-1α可能对MMP-9表达具有上调作用。     

Statistical Features and Phase Identification of Traffic Flow on Urban Freeway

At present, researches on traffic flow theory mainly focus on highway traffic, which is significantly different from urban freeway. Because traffic science is an “empirical science”, it is based on actual traffic flow data of urban freeway, the statistical features of velocity distribution at different densities have been investigated in this paper. Moreover, four steady phases: free flow, coherent-moving flow, synchronized flow, and jams are identified in the flow rate-density plane of the traffic flow. Finally, features of the four phases as well as functional forms of phase boundaries are discussed in detail.