Evaluation of performance enhancing proxies in internet over satellite

Performance enhancing proxies (PEPs) are widely used to improve the performance of TCP over high delay‐bandwidth product links and links with high error probability. In this paper we analyse the performance of using TCP connection splitting in combination with web caching via traces obtained from a commercial satellite system. We examine the resulting performance gain under different scenarios, including the effect of caching, congestion, random loss and file sizes. We show, via analysing our measurements, that the performance gain from using splitting is highly sensitive to random losses and the number of simultaneous connections, and that such sensitivity is alleviated by caching. On the other hand, the use of a splitting proxy enhances the value of web caching in that cache hits result in much more significant performance improvement over cache misses when TCP splitting is used. We also compare the performance of using different versions of HTTP in such a system. Copyright © 2003 John Wiley & Sons, Ltd.     

CFH-Ⅱ型翻车机传动齿轮轴承座的座脚螺栓联接失效分析与改进

分析了CFH-Ⅱ型翻车机传动齿轮轴承座的座脚螺栓组联接失效(松动)的原因，得出控制和保证合适的螺栓组联接预紧力是防止螺栓联接失效(松动)的关键；依据现场条件，对座脚螺栓进行了设计改进；提出了一种适合现场使用的螺栓预热伸长的装配方法，经实践验证此法是简单可靠的装配方法。     

测井新技术在四川油气勘探开发中的应用

综述随着四川盆地油气勘探深入所面临的油气领域复杂和困难的技术问题，介绍应用测井新技术为四川油气开发解决了大量的技术难题，特别是在复杂缝，洞型储层的评价，井旁地质构造形态精细分析和地质，测井，地震多学科结合储层横向预测等3个方面所取得的良好应用效果。     

A direct stiffness analysis of a composite beam with partial interaction

The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd.     

广州中城广场主体工程施工技术

广州中城广场工程结构形式复杂，平面曲折多角。施工中在应用多种模板体系、泵送混凝土、无粘结预应力楼板及核心筒部分小平台滑模等方面，采用了多项新技术，保证了工程质量，加快了工程进度。     

一起二次回路接线错误引发的事故分析

通过一起由二次回路接线错误引发的事故分析,阐述二次回路的重要性。从设计、安装、调试和管理上对二次回路进行探讨,提出反事故措施和对策,以防止类似事故的发生。     

一种分布式的洋葱路由新机制

洋葱路由技术在公网上提供双向、实时的匿名通信，其面向连接和严格的源路由方式导致效率低、扩展性差。利用分布式的概念，采用分段连接技术思想提出了一种安全、高效的分布式洋葱路由机制(DORS)，给出了DORS路由实现算法，并从方案实现效率、安全性方面对DORS进行了分析。分析结果表明DORS具有良好的扩展性、鲁棒性、简单性和有效性。     

电子直线加速器中计入纵向与横向耦合效应的束流包络线方程组

一、引言从束流动力学的观点出发,对于粒子束在直线加速器中的运动,有两种主要的分析方法,也即粒子轨迹跟踪法及考察束流包络运动的方法。前者是通过解单粒子运动方程,跟踪大量的单粒子运动轨迹而后进行分析;后者则是通过解束流的包络线方程,根据束流包络的变化来进     

Analysis of adhesive bonded composite lap joints with transverse stitching

The effect of transverse stitching on the stresses in the adhesive is investigated using an adhesive sandwich model with nonlinear adhesive properties and a transverse stitching model for adhesive bonded composite single-lap and double-lap joints. Numerical results indicate that, among all stitching parameters, thread pretension and stitch density have significant effect on the peel stresses in the adhesive; increase in the thread pretension and the stitch density leads to a decrease in peel stress in the adhesive, while an increase in other parameters generally results in a negligible reduction in peel stress. The effect of stitching was found to be negligible on the shear stresses in the adhesive. Thus it is concluded that stitching is effective for the joints where peel stresses are critical and ineffective for those where shear stresses are critical.     

化学结构式的拓扑描述

化学结构式的拓扑描述,是化学信息计算机化的手段之一。这里系统地建立了一整套的连接表(三类:紧缩连接表、冗余连接表、和连接方阵),用来进行结构式中原子之间连接关系的拓扑描述,对分子结构进行数值化。同时,阐述了连接表唯一化的方法,并介绍了不同类型连接表之间的转换关系和还原为平面结构式图形的绘图程序。