Nodal sensitivities as error estimates in computational mechanics

Summary This paper proposes the use of special sensitivities, called nodal sensitivities, as error indicators and estimators for numerical analysis in mechanics. Nodal sensitivities are defined as rates of change of response quantities with respect to nodal positions. Direct analytical differentiation is used to obtain the sensitivities, and the infinitesimal perturbations of the nodes are forced to lie along the elements. The idea proposed here can be used in conjunction with general purpose computational methods such as the Finite Element Method (FEM), the Boundary Element Method (BEM) or the Finite Difference Method (FDM); however, the BEM is the method of choice in this paper. The performance of the error indicators is evaluated through two numerical examples in linear elasticity.     

SOPHO—S的结构分析与线路传输技术

ＳＯＰＨＯ－Ｓ系列数字程控交换机是由飞利蒲公司生产的。本文分析了该系列交换机的总体结构，并了它的线路传输技术。     

DGPSL：A DISTRIBUTED GRAPHICS LIBRARY

ＤＧＰＳＬ：ＡＤＩＳＴＲＩＢＵＴＥＤＧＲＡＰＨＩＣＳＬＩＢＲＡＲＹＳｈｉＪｉａｏｙｉｎｇ；ＰａｎＺｈｉｇｅｎｇ；ＺｈｅｎｇＷｅｎｔｉｎｇＤＧＰＳＬ：ＡＤＩＳＴＲＩＢＵＴＥＤＧＲＡＰＨＩＣＳＬＩＢＲＡＲＹ￥ＳｈｉＪｉａｏｙｉｎｇ；ＰａｎＺｈｉｇｅｎｇ；...     

程序可视化系统ProVS的设计和实现

本文研究程序代码可视化技术，即从现存的程序生成某种可视化表示，增强程序的易读性、易理解性和易维护性。首先介绍ＰｒｏＶＳ的设计思想和实现技术，然后给出输出例子。     

给水流量控制系统仿真辅助设计

本文将给水流量系统规范化，给出静、动态数学模型，通过计算机仿真计算建立起设计参数Ｓ与系统特性间关系数据库，这些数据可用于控制系统辅助设计。本文还介绍了在Ｓ较小时自动补偿系统增益和时间常数的自适应控制方法并给出仿真结果。     

Optical bistability in reflective fiber gratings

Optical bistability in a nonlinearly reflective fiber grating through the mode coupling between the LP₀₁ and counter propagation LP₀₂ modes (i,e., the reflective LP₀₁&rlhar2;LP₀₂ mode converter) is investigated by using the coupled-mode theory. Both the transmissive and the reflective properties of this nonlinear device are analyzed, which show that the output-versus-input relation exhibits the optical bistability. The switching power and the bistable hysteresis performances are also discussed. In addition, the comparison between the nonlinearly reflective mode converter (LP₀₁&rlhar2;LP₀₂) and the nonlinear fiber Bragg grating reflector (i,e., the LP₀₁ and counter-propagation LP₀₁ modes) is also presented. It is shown that the former has much lower switching power than the latter     

A Linear Cross-Coupled Control System for High-Speed Machining

We present a linear cross-coupled controller to improve highspeed contouring accuracy independently of tracking accuracy in a biaxial machine tool feed drive servomechanism. Unlike conventional cross-coupled controllers, the cross-coupled controller presented here is a linear system, so it is very easy to perform the stability and steady-state error analysis, and to optimise the controller parameters. The proposed controller is evaluated experimentally on a CNC LOM machine and compared to an uncoupled controller and a conventional cross-coupled controller. Controller performance is evaluated for a circular contour at a feedrate of 30 m min _1 . The experimental results show that the proposed controller can greatly reduce the contour error at large feedrates. The linear cross-coupled controller is simple to implement and is practical.     

既有钢筋混凝土框架结构抗震加固若干问题探讨

针对钢筋混凝土框架结构抗震加固问题的复杂性 ,本文深入分析了抗震加固结构的受力特征 ,探讨了卸荷对加固构件承载力的影响 ,并针对抗震加固后的“隐含危险转移”问题提出了相应的对策。最后 ,提出了抗震加固的基本原则 ,可供结构抗震加固时参考     

点阴极电场辅助阳极连接中的紧密接触面积和电流

用等效电路的方法研究了点阴极情况下的电场辅助阳极连接效应，计算了连接电流，连接孕育期和紧密接触面积，本文结果表明，连接初期电流迅速衰减，随后缓慢变小，直至某一稳定值，孕育期随温度上升指数下降，连接温度高时，孕育期将难以观察到；待连接表面之间紧密接触面积随时间延长而非线性扩展，紧密接触区域增大时，其边界向外推进速度渐小，而接触面积增加渐快。