大跨连续梁桥纵向减震机理和减震效果分析

基于一座实际大跨度连续梁桥,分析比较了采用动力锁定装置、黏滞阻尼器和双曲面减隔震支座的减震机理和减震效果,讨论了这些减震装置的适用范围.结果表明:动力锁定装置不耗散地震能量,在活动墩处设置该装置,可以合理分配梁体的地震惯性力,但同时结构周期减小,可能增加梁体总的惯性力;黏滞阻尼器不改变结构的周期、振型等动力特性,主要通过阻尼力消耗地震能量,减小结构动力反应;采用双曲面减隔震支座后结构的周期延长,阻尼耗能能力增加,相对于基准模型,显著减小了固定墩的内力,但同时增加了活动墩墩梁相对位移.     

单面增大截面加固剪力墙的偏压仿真试验研究

增大截面加固法是加固钢筋混凝土结构常用而有效的方法,其中双面增大截面加固法在剪力墙结构加固工程中采用较多,但是会因为建筑立面、使用功能及施工条件的限制而无法使用,单面增大截面加固法往往可以解决以上问题.为探究单面增大截面法的加固性能,配合后期的实体模型试验研究,将实际工程普通一字型剪力墙按1∶3比例缩尺建立未加固剪力墙、双面增大截面加固剪力墙、单面增大截面加固剪力墙3组模型,采用大型有限元分析软件ABAQUS对3组剪力墙模型进行偏心受压静力仿真试验,对比研究其从弹性阶段到破坏全过程的破坏特征、应力应变规律及受压承载能力.仿真试验结果表明:单面和双面增大截面加固法均能大幅提高剪力墙的正截面承载能力(提高系数分别为2.8,3.5)、刚度、延性等受力性能,其中单面加固剪力墙的正截面承载力约为双面加固的77%,建议根据剪力墙加固工程实际条件进行选用.该结果可为合理地进行剪力墙的加固设计提供理论依据.     

Variation in retained austenite content and mechanical properties of 0.2C–7Mn steel after intercritical annealing

The effects of annealing time and temperature on the retained austenite content and mechanical properties of 0.2C–7Mn steel were studied. The retained austenite content of 0.2C–7Mn steel was compared with that of 0.2C–5Mn steel. It is found that 0.2C–7Mn steel exhibits a similar variation trend of retained austenite content as 0.2C–5Mn steel. However, in detail, these trends are different. 0.2C–7Mn steel contains approximately 7.5vol% retained austenite after austenitization and quenching. The stability of the reversed austenite in 0.2C–7Mn steel is lower than that in 0.2C–5Mn steel; in contrast, the equilibrium reversed austenite fraction of 0.2C–7Mn steel is substantially greater than that of 0.2C–5Mn steel. Therefore, the retained austenite content in 0.2C–7Mn steel reaches 53.1vol%. The tensile results show that long annealing time and high annealing temperature may not favor the enhancement of mechanical properties of 0.2C–7Mn steel. The effect of retained austenite on the tensile strength of the steel depends on the content of retained austenite; in contrast, the 0.2% yield strength linearly decreases with increasing retained austenite content.     

Preparation and tensile properties of DD5 single crystal castings

The preparation procedure of DD5 single crystal castings was optimized. The microstructure characteristics of DD5 single crystal superalloy were investigated by microstructure observation and segregation behavior examination. The results show that the grain orientation is optimized by constraining the spiral crystallizer in [001] orientation and spatial scale. Also, the γ’ phase of inter-dendrites is larger and more irregular than that in dendrite arms. High temperature tensile tests of DD5 single crystal castings exhibit that the peak stress increases with increasing temperature, while the area reduction shows an opposite trend, when the temperature is below 800℃; meanwhile, when the temperature is between 800℃ and 1000℃, the fracture stress of the alloy is the same as the peak stress. The fracture mode changes from shear to ductile with increasing temperature from 600℃ and 1000℃.     

环形光束中双层球的光俘获

基于光镊的几何光学模型建立了内层折射率小于外层折射率和周围介质折射率的双层球形微粒在环形光束中的光俘获力的模型.以空心球壳为例,对其在TEM01>模式的环形高斯光束中受到的光俘获力进行了数值模拟.通过数值模拟的结果,分析了俘获低折射率双层球的三维条件.发现低折射率双层球形微粒在光轴上的稳定俘获位置较之高折射率双层球形微粒的稳定俘获位置逆着光束传播方向移动.另外,在一定条件下在光轴以外的位置低折射率双层球形微粒也能被稳定俘获.     

黄缘闭壳龟人工养殖技术初步研究

根据野生黄缘闭壳龟的生活习性,创造其人工养殖环境,利用人工合成饲料,经过１１０天的饲养试验,使幼龟体重增加１０４％,成龟体重增加２６．１％,亲龟体重增加２４．２％,亲龟的产卵率为１００％,人工养殖效果良好。     

计算机多用户XENIX操作系统中终端故障的处理

介绍了XENIX操作系统下几种终端故障的处理方法。     

金属氮化物的球磨制备方法

采用自制的可充一定压力气体的球磨装置,在抽真空后,对装有一定量的纯金属Ｚｒ,Ｎｂ的球磨罐内充入０．３ＭＰａ的氮气,并进行球磨氮化反应ＸＲＤ,ＴＥＭ结果表明,在室温下,纯金属均发生氮化反应,并生成相应稳定的氮化物,对生成物的颗粒尺度及相结构进行了表征,并对其反应机理给出了相应的讨论。     

Investigation on Porosity and In - plane Water Permeability of Nonwoven Geotextiles

Nonwoven geotextiles have been widely used as drains orfilters in many civil engineerings.The hydraulic charac-teristics of geotextiles are the basic function in these ap-plications.The in-plane permeability of nonwoven geo-textiles was discussed in this paper.The results of in-plane permeability coefficient of nonwoven geotextilesfrom measurement were analyzed.     

Effect of Fabric Elongation on the Making Up of Pressure Garments

Pressure garments are widely used in Hong Kong andmany other countries for burn rehabilitation.Thesegarments are mainly made of elastic Lycra fabrics andtailor-made to individual patient's measurement toprovide an appropriate amount of skin-garment in-terface pressure for medical treatment.However,thefabric tension would be reduced due to fabric elonga-tion under prolonged period of stress,and thus theskin-garment interface pressure cannot be main-tained after repeated use of the garment.This paperaims to study the behaviour of fabric elongation of thefabrics commonly used for making pressure garmentsin U.K.and/or Hong Kong.Attempts to correct theexisting practice of drafting the pressure garments forproviding a more effective clinical treatment.