基于结构强震记录的结构时变模态参数识别

为研究结构在地震过程中动力特性变化和损伤过程,为结构地震损伤评估提供可靠依据,采用递归式在线系统辨识算法RARX模型,利用结构强震记录识别了结构时变模态参数。以一座6层钢筋混凝土框架结构为例,识别了其时变自振频率、阻尼比和等效刚度。结果发现：在小地震动作用下,结构自振频率随时间几乎不发生改变;在大地震动作用的整个时间过程中,结构自振频率随时间逐渐降低,降低到一定程度到达最低点后,频率开始回升,直至地震结束,但最后不能回升到初始值,说明经历大震发生损伤的结构在震后性能会有所恢复;结构等效刚度变化趋势和自振频率相同,但在大震中下降比频率下降大的多;结构阻尼比在经历大震发生损伤后增大。结果可供结构地震损伤预测及结构震后安全鉴定参考。     

The trend in current and near future energy consumption from a statistical perspective

Energy consumption has increased remarkably over the past half century mainly due to increasing population and economic development. The influences of these two factors are considered. In most developed countries, such as Japan, France, Germany and Korea, the growth rate of energy consumption is due to economic development. The effects of population in Germany and Japan will substantially decline. In the USA, it is due to both factors as well as in the developing countries, such as China, India, Indonesia and Latin America. Economic success is more effective than increasing population in China, India and Indonesia, while both factors are roughly equal in Latin America. In Africa, though the growth rate depends on the effect of increasing population, its contribution to world energy consumption is small. On a worldwide scale, the growth rate of energy consumption will be affected by improving standards of living.     

3D reconstruction considering calculation time reduction for linear trajectory shooting and accuracy verification with simulator

Artificial Life and Robotics - Photogrammetry is a three-dimensional (3D) reconstruction from images. In photogrammetry, when each image captures the features of the target object for 3D...     

A linear-time algorithm for finding a sparsek-connected spanning subgraph of ak-connected graph

We show that anyk-connected graphG = (V, E) has a sparsek-connected spanning subgraphG′ = (V, E′) with ¦E′¦ =O(k¦V¦) by presenting anO(¦E¦)-time algorithm to find one such subgraph, where connectivity stands for either edge-connectivity or node-connectivity. By using this algorithm as preprocessing, the time complexities of some graph problems related to connectivity can be improved. For example, the current best time boundO(max{k ²¦V¦^1/2,k¦V¦}¦E¦) to determine whether node-connectivityK(G) of a graphG = (V, E) is larger than a given integerk or not can be reduced toO(max{k ³¦V¦^3/2,k ²¦V¦²}).     

Inelastic behaviour of 214Cr-1Mo steel under plasticity-creep interaction condition: An interim report of the Bench Mark project by the subcommittee on inelastic analysis and life prediction of high temperature materials,JSMS

Some of the interim results of the Bench Mark Project by the Subcommittee on the Inelastic Analysis and Life Prediction of High Temperature Materials, JSMS, is presented. The purpose of the present bench mark study is to review and evaluate the inelastic constitutive models relevant to material response under the plasticity-creep interaction.By specifying normalized and tempered $\text{2}\text{1}\text{4}\text{Cr-1Mo}$ steel at 600°C, sixteen bench mark problems of four categories are first established: (I) tensile stress-strain relations and creep curves, (II) material response under mixed modes of plastic and creep loading, (III) ratcheting and deformation under program loads, and (IV) cyclic deformation behaviour under the combination of different strain rates. Then, the outline of seventeen inelastic constitutive models of nine types discussed in this project is presented. Finally, the interim results of these bench mark tests are compared with the corresponding predictions of the constitutive models to evaluate their accuracy in simulating the actual behaviour of the material.     

New wear tests of tool materials for metal forming

Tribological phenomena, i.e. friction, tool wear and material pick-up to the tool, in metal forming processes are influenced by various factors. Therefore, in friction tests in the laboratory, these factors should be varied widely and independently and they should be measured easily. A new test method which has these features is described; the test parameters are the tool pressure, sliding speed, enlargement of the workpiece surface, length of contact between the tool and workpiece, sliding distance, contact angle and viscosity of the lubricant. Some results of the tests on tool wear are presented and discussed.     

Metal cation–acidic proton bifunctional catalyst for methane activation: conversion of CH4 in the presence of ethylene over metal cations-loaded H-ZSM-5

It has been investigated that ¹³CH₄ reacts with ethylene over metal cations such as indium cations-loaded H-ZSM-5 to form singly ¹³C-labeled propylene (¹³C¹²C₂H₆) and hydrogen at 673 K. The heterolytic dissociation of C---H bond in methane presumably proceeds by the reaction of methane with metal cations for the formation of CH₃^δ+ and metal hydride species, thus allowing the reaction of CH₃^δ+ with ethylene to form propylene and acidic protons. Metal cations are regenerated by the reaction of silver-hydride species with acidic protons, and hydrogen is simultaneously formed. Thus, bifunctionality of metal cations and acidic protons is essential for the activation of methane.     

Effect of atmosphere on pyrolysis of Nicalon

The pyrolytic behaviour of Nicalon under a N₂ atmosphere was investigated at temperatures from 1673 to 1973 K, and was compared with that under an Ar atmosphere. The pyrolytic rate was measured by thermogravimetry, and heat-treated Nicalon was examined by X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy and tensile testing. The pyrolytic rate was smaller in N₂ than in Ar. The nitrided case retarded the crystallization into -SiC and retained its high strength. The effectiveness of the nitrided case disappeared on heating in Ar. The strength was related to the size of the -SiC crystal in Nicalon.     

Relations between the molecular aggregation state and ionic conductivity in photopolymerized crosslinking polymers with oligo(oxyethylene) chains

A mixture of a vinyl monomer and a crosslinking agent was photopolymerized to form a crosslinked polymer film. Methacrylate with pendant oligo(oxyethylene) chain and poly(ethylene glycol) dimethacrylate were used as the vinyl monomer and crosslinking agent, respectively. The ionic conductivity of the film increased with an increasing concentration of LiClO₄ and then decreased. The size of the quasicrystalline aggregation phase composed of pendant and crosslinking chains in the film decreased with an increasing concentration of LiClO₄. The amorphous pendant and crosslinking oxyethylene chains gave rise to increased segmental motion and conductivity. The dissolution was depressed for a decrease in the ionic conductivity at a high LiClO₄ concentration at which the interactions among ions became stronger and the crystal phase of LiClO₄ was formed. The amount of the dissolution of the aggregation phase increased with an increasing crosslinking agent concentration. The quasicrystalline aggregation phase became larger with an increasing length of the pendant chains, and an increase in the size of the aggregation phase resulted in a decrease in the ionic conductivity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1272–1277, 2002