Maxwell strata in the Euler elastic problem

The classical Euler problem on stationary configurations of elastic rod in the plane is studied in detail by geometric control techniques as a left-invariant optimal control problem on the group of motions of a two-dimensional plane E(2). The attainable set is described, the existence and boundedness of optimal controls are proved. Extremals are parametrized by the Jacobi elliptic functions of natural coordinates induced by the flow of the mathematical pendulum on fibers of the cotangent bundle of E(2). The group of discrete symmetries of the Euler problem generated by reflections in the phase space of the pendulum is studied. The corresponding Maxwell points are completely described via the study of fixed points of this group. As a consequence, an upper bound on cut points in the Euler problem is obtained. This work was partially supported by the Russian Foundation for Basic Research, project No. 05-01-00703-a.     

基于USB2.0的193nm极紫外光强检测系统设计

介绍一种以USB2.0为接口的实时极紫外光强检测系统。光敏二极管输出电压经模拟放大器OP07放大后,再经模数转换器ADS8322转换得到与光强成线性的数字量,用VC++6.0编程对CY7C68013A芯片I/O端口控制实现对转换后的数字量的实时采集,从而实现对193nm光刻照明系统光强的实时检测。     

耐湿硫化氢腐蚀07Cr2AlMo无缝钢管研制

对研制的耐湿硫化氢腐蚀 0 7Cr2AlMo无缝钢管进行多项性能试验 ,结果表明 :该钢性能优良 ,各种试验数据均达到设计要求 ,能够满足在湿硫化氢环境下设备的安全使用     

Renewable Types and the Urban Plan

The notion of designing according to building type for some might imply constraint, or even a reversion to convention. In Diploma Unit 6 at the AA in London, Christopher Lee and Sam Jacoby have proved typology can be used to liberating effect, producing series that harness ‘the cumulative intelligence’ of type, while ‘surpassing both its idea and its deep structure’. Copyright © 2008 John Wiley & Sons, Ltd.     

Convoluted Flesh: A Synthetic Approach to Analogue and Digital Architecture

Marcos Cruz and Marjan Colletti advocate their own distinct design approach that is intuitive and blissful in its opulence, evoking the sublime.Here they discuss the potential of opening up ‘new spatial, or material possibilities’ that are liberated from the self-imposed restrictions of their more technologically driven contemporaries. Copyright © 2008 John Wiley & Sons, Ltd.     

Hamiltonian structures in optimal control theory

The concept of a piecewise smooth Hamiltonian system, motivated by optimal control theory, is introduced and developed. It is proved that the Poisson bracket of two integrals of such a system is globally continuous. Integrable piecewise smooth systems are proved to be equivalent to smooth integrable systems.This research was partially supported by the Russian Foundation for Fundamental Research, grant No. 93-012-470     

Zr-rich layers electrodeposited onto stainless steel cladding during the electrorefining of EBR-II fuel

Argonne National Laboratory is developing an electrometallurgical treatment for spent nuclear fuels. The initial demonstration of this process is being conducted on U–Zr alloy fuel elements irradiated in the Experimental Breeder Reactor II (EBR-II). We report the first metallographic characterization of cladding hull remains for the electrometallurgical treatment of spent metallic fuel. During the electrorefining process, Zr-rich layers, with some U, deposit on all exposed surfaces of irradiated cladding segments (hulls) that originally contained the fuel alloy that was being treated. In some cases, not only was residual Zr (and U) found inside the cladding hulls, but a Zr-rind was also observed near the interior cladding hull surface. The Zr-rind was originally formed during the fuel casting process on the fuel slug. The observation of Zr deposits on all exposed cladding surfaces is explained with thermodynamic principles, when two conditions are met. These conditions are partial oxidation of Zr and the presence of residual uranium in the hulls when the electrorefining experiment is terminated. Comparisons are made between the structure of the initial irradiated fuel before electrorefining and the morphology of the material remaining in the cladding hulls after electrorefining.     

07MnCrMoVR水电钢的生产工艺及组织性能

采用激光共聚焦扫描显微镜对07MnCrMoR水电钢奥氏体晶粒长大的动态过程进行了原位观察,并对其静态CCT曲线进行了测定,利用淬火机和热处理炉对38 mm厚的试验钢进行了淬火和回火试验。结果表明:试验钢在1200℃以下加热时奥氏体晶粒长大趋势不明显;当冷却速率为0.05~0.25℃/s时,试验钢的组织转变为多边形铁素体+珠光体,冷却速率为0.5~20℃/s时转变为贝氏体组织,冷却速率为20~50℃/s时转变为马氏体组织;930℃淬火后,试验钢的组织转变为板条贝氏体+马氏体,600℃回火后转变为铁素体+回火贝氏体,大量的碳化物在铁素体基体上析出,其屈服强度为602 MPa,抗拉强度为713 MPa,-20℃低温冲击吸收能量为259 J,力学性能高于国家标准的要求,为最佳的调质生产工艺。     

某水电站07MnCrMoVR钢岔管焊缝裂纹成因分析

07MnCrMoVR是一种常用在大型构件上的低合金高强度钢,具有优良的焊接性能和低温韧性.但某水电站在现场安装此种钢材的压力钢岔管时却在制造焊缝上发现了大量裂纹.通过分析,确定裂纹是由于焊接工艺不当产生的延迟裂纹,并提出了避免此类焊接裂纹的建议及处理方法.