A Study on Spatial Growth of Beijing's Central Urban Area from 1950s to 2005 Supported by Spatial Information Technology

1. Introduction According to the National Bureau of Statistics of China, the urban population and urbanization rate of China have increased very rapidly in recent years (see Fig. 1). In     

黄土区特高压输电线路杆塔全掏挖基础抗拔分析

全掏挖基础是人工在地基中直接掏挖出基础形状,插入钢筋笼,灌入混凝土形成基础的一种施工方法。采用规范中给出的土重法和剪切法,计算了输电线路杆塔基础的抗拔承载力,并与有限元计算结果做了对比,分析了土重法和剪切法计算的极限抗拔力对应的基础周围土体状态。土重法和剪切法计算的极限抗拔力均小于有限元计算的极限抗拔力,3种方法极限抗拔力土体均处于弹性状态。剪切法计算结果大于土重法,且有相应的安全度,基础设计中可以采用剪切法。     

中国国际贸易中心三期A主塔楼结构设计

位于北京的中国国际贸易中心三期主塔楼高330m,包括一座五星级酒店和甲级写字楼。结构设计的主要难点是在北京这一高烈度地区建设超高层大楼,如何能综合考虑结构的安全性与经济性的要求,在结构设计过程中,各种结构类型及不同材料的使用都经过讨论研究。最终的结构体系是一个组合支撑框架核心筒和组合周边刚性框架筒,在机电层再辅以伸臂桁架连接内外筒。由于塔楼外立面宽度逐渐收小,结构上采用了3层腰桁架,而在腰桁架之间柱子的数量逐渐减少。塔楼的底部是8层高带转换桁架的V型柱,既符合建筑上对五星级酒店和甲级写字楼首层宏大的主入口的要求,同时又可平缓地过渡到上部的抗弯刚架。结构体系中根据不同的部位相对采用了各种类型的组合构件来满足刚度,延性以及冗余度的要求,并达到最好的性能价格比。工程大规模应用了组合钢板墙(C-SPW)这一新型结构体系,以增加剪力墙的抗剪承载力和刚度,并改善延性。结构设计中运用了有限元分析及非线性弹塑性时程分析来评估结构的     

Thirty Years' Reform and Development in China's Refractories Industry

1 Development of Refractories Industry Since the People's Republic of China FoundedRefractories is mainly used in high temperature industries,such as metallurgy,building materials,nonferrous,chemical,mechanical,electric power industries,which is the important fundamental material for high temperature industries.China began to manufacture refractories and had it firstly applied in ceramics industry in Shang Dynasty lasting more than 3 000 years. However,China's refractories industry was in a backward stat...     

Effect of Chromium Powder on Sintering Property of Chrome Oxide Materials

The specimens were prepared using Cr2O3 micropowder, TiO2 micropowder and chromium powder as starting materials, PVA as binder, after spraying granulation and cold isostatic pressing, firing at 1 450 ℃ for 3 h in standard nitrogen and oxygen control atmosphere (oxygen partial pressure was 1 010 Pa and 10.1 Pa, respectively). Effects of chromium powder (mass percent were 0, 0.5%, 1.0%, 1.5% and 2.0%, respectively) on sintering behaviors of Cr2O3 materials were researched. The results show that: adding 0.5% c...     

Situation of China's Refractories Industry in Last Sixty Years

The annual output of China's refractories in 1949 was 74 thousand tons,and was 29.11 million tons in 2007,which was 65% of the world total refractories output.The export of China's refractory products and raw materials in 2008 was 6.18 million tons,which were exported to hundreds of countries and regions in the world.China is a big country in the field of refractories production and refractories export,which has devoted a lot to relative high temperature industry.     

High-temperature Reaction of Silica Fume-Si_3N_4 System

The specimens were prepared by molding the mixture of silica fume(w(SiO2)=94.5%;average particle size:0.08 μm) and silicon nitride(≤0.074 mm) with a mass ratio of 11,carbon embedded firing at 1 300 ℃,1 450 ℃,1 500 ℃,1 550 ℃ and 1 600 ℃ for 3 h in air,and then water-cooling,respectively.The microstructure and phase composition of the specimens were analyzed.The results show that:(1) silica fume reacts obviously with Si3N4 forming Si2N2O above 1 550 ℃.The edges and corners of Si3N4 grains become smooth and th...     

钢包透气砖在精炼条件下的应力场分布研究

利用ANSYS有限元分析软件对钢包透气砖在精炼奈件下(不同吹氩压力、精炼温度)的应力场分布进行了计算研究.结果认为,铝镁质透气材料结构应力与其热膨胀系数成正比变化;透气砖工作面狭缝尖端处应力最大,是其非工作底面的6.62倍,并且从非工作底面到工作面狭缝尖端应力增加最快;吹氩压力对透气材料应力的影响可忽略不计;精炼温度提高50℃,工作面狭缝各部位应力相应增加1%～2%.     

大型高炉用非氧化物复合耐火材料的演变及性能

系统分析了大型高炉用3代非氧化物复合耐火材料的演变及其性能.从材料演变的角度阐述了近年来中国耐火材料行业技术进步的快速发展,并提出了不同材料未来需要改进和完善的方向.探讨了我国大型高炉用长寿型氧化物-非氧化物复合材料发展中存在及需要解决的问题.     

Si_3N_4-Al_2O_3-SiO_2体系高温还原条件下的物相变化

以闪速燃烧合成的Si3N4(w(Si3N4)≥95%,粒度≤0.044 mm)、α-Al2O3微粉(w(Al2O3)≥99%,d50=1.2μm)及SiO2微粉(w(SiO2)≥92%,粒度≤μm)为原料,按照m(Si3N4):m(Al2O3):m(SiO2)=4:4:2比例混合,液压成型为φ20 mm×20 mm试样在埋炭(不接触焦炭)条件下分别于1 300、1 400、1 500、1 600℃保温6 h处理后进行XRD分析.结果表明:1 300 ℃的新生物相主要为Si2N2O和方石英,SiO2微粉方石英化明显;1 400 ℃的新生物相主要为Si2N2O、方石英和O'-SiAlON;1 500 ℃的新生物相为Si2N2O、方石英、O'-SiAlON、X相及莫来石;与1 500 ℃相比,1 600 ℃的新生物相没有变化,但是Si2N2O、O'-SiAlON、X相及莫来石的生成量增加明显,方石英生成量显著减少.