正压冲固基础海洋平台冰激振动动力响应

正压冲固基础海洋平台是一种新型平台桩基结构形式。采用三维有限元的数值分析方法,建立了正压冲固平台的三维有限元模型。基于冰激强迫振动理论提出动冰载荷的计算方法,根据海冰破碎长度和冰速确定冰载周期,冰强度限制的水平冰力作为冰力峰值,得到的动冰载荷用于正压冲固平台的动力响应分析,并依照规范计算了6倍桩径处刚性固定时的动力响应。三维有限元方法计算得到的动力响应大于6倍桩径刚性固定时的计算结果,结构安全性评估偏于安全。     

贯流式水轮发电机集电环短路原因分析及改善措施

白石窑水电厂1～4号发电机组在投运初期,集电环曾多次出现绝缘降低甚至短路的非正常现象。通过分析,引发故障的原因主要是碳刷架、集电环绝缘结构设计欠妥、运行环境恶劣以及机组的振动过大。针对上述原因,改进了绝缘结构设计上的不足,加强巡视和维护检查,装设工业电视监控,加装碳粉回收装置,对受油器进行防漏油或喷油技术处理,加强清污力度、提高发电水头以便减少机组振动,从内外因加以防范和改善后,问题得到了标本兼治,取得了理想的效果。     

小浪底水库坝前漏斗区泥沙测验分析

小浪底水库坝前漏斗区的形成和发展,直接影响到枢纽建筑物的安全运行。为了保持塔前“门前清,”掌握坝前漏斗区的形成和发展,保证水库进入拦沙后期和正常运用期的正常运用,对坝前漏斗区进行了泥沙测验分析。结果表明:目前漏斗区范围内纵向坡度较缓,尚没有明显的漏斗形成,仅在坝前和塔前200m×1000m范围形成了漏斗雏形。     

数据挖掘技术在有线电视领域的应用

数据挖掘是近年来在数据库技术、统计学、人工智能、神经网络等学科的基础上发展起来的一门交叉学科，数据挖掘技术已经成功地应用于商业领域，随之又迅速地扩展到社会保险、医学、电信等领域，探讨和分析数据挖掘技术在有线电视领域的应用，并给出了系统体系结构和挖掘算法。     

Boundary knot method for 2D and 3D Helmholtz and convection–diffusion problems under complicated geometry

The boundary knot method (BKM) of very recent origin is an inherently meshless, integration‐free, boundary‐type, radial basis function collocation technique for the numerical discretization of general partial differential equation systems. Unlike the method of fundamental solutions, the use of non‐singular general solution in the BKM avoids the unnecessary requirement of constructing a controversial artificial boundary outside the physical domain. The purpose of this paper is to extend the BKM to solve 2D Helmholtz and convection–diffusion problems under rather complicated irregular geometry. The method is also first applied to 3D problems. Numerical experiments validate that the BKM can produce highly accurate solutions using a relatively small number of knots. For inhomogeneous cases, some inner knots are found necessary to guarantee accuracy and stability. The stability and convergence of the BKM are numerically illustrated and the completeness issue is also discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Criteria and methodology for the evaluation of conservation interventions on treated porous stone susceptible to salt decay

Susceptibility of stone to salt decay is directly related to its microstructural and mechanical characteristics. In the present work, a porous stone from a quarry in Cyprus was examined. Samples of this stone were consolidated and protected with certain conservation materials. The modification of microstructural characteristics of the stone was evaluated by mercury intrusion porosimetry, while its mechanical characteristics were measured by compressive and bending strength tests. From these data, the susceptibility of Cyprus stone to salt (NaCl) decay was estimated. The values of crystallization pressure of NaCl were calculated and compared to the experimentally measured compressive and tensile strength of the stone, in order to examine the probability of stone disruption due to salt crystallization. The development of the phenomenon after coarse pores’ filling with crystals, i.e. crystallization of salts in capillaries or mechanical failure of the stone, was determined by thermodynamic analysis. Additionally, artificial weathering tests of marine salt spray were performed for the evaluation of stone’s durability after the conservation. The treated stone proved to be resistant to salt decay, as it presented ameliorated microstructural and mechanical characteristics, concerning decay due to soluble salt crystallization. The most possible thermodynamic scenario was small pores repletion with crystals, avoiding mechanical failure of the stone.     

根据过采样和求均值理论提高ADC 测量分辨率

8bit嵌入式单片机系统A／D变换的两个关键指标是有效分辨率和信噪比(SNR)。通过对过采样(Over sample)和求均值(Average)理论的分析，得出“对噪声源的特性为白噪声的信号，每增加一位分辨率可以通过用4倍的过采样频率进行采样来达到。而分辨率每增加一位将使SNR增加6dB”的结论。进而采用8bit徽处理器内嵌12bit ADC成功实现了16bit ADC的精度,即小数点后两位(25．99℃)的温度测量，和小数点后四位(2．4299 V)的直流电压测量．     

Drying of Uncoated Paper with Gas-Fired Infrared Emitters—Optimum Emitters' Location Within a Paper Machine Drying Section

This article theoretically investigates the drying of uncoated paper with gas-fired infrared (IR) emitters installed within the drying section of a given commercial paper machine. Specifically, it presents the ideal location of two opposing IR emitters within the drying section. The ideal location of the two opposing IR emitters corresponds to the highest machine speed with specified average moisture content of paper sheet at the end of the drying section. This article also presents the average evaporation rate, temperature, and moisture content of the paper sheet as it travels through the drying section with the two opposing IR emitters operating at the optimum location. In addition, the temperature and moisture profiles in the sheet thickness direction, before and after the IR emitters, are provided. This article is not concerned with the potential effects of drying with IR emitters on paper sheet properties and machine runnability issues.     

我国突发性水资源污染事故应急机制的若干问题评述

基于突发性水资源污染事故应急处理现状的分析,对目前我国突发性水资源污染事故防范和应急机制的建立进行探讨,指出当前工作中的三大缺陷,并有针对性地提出如何加快防范突发性水资源污染事故以及建立相关应急机制的进程的若干措施,包括突发污染事故的隐患调查、脆弱性评价、水质预报、动态监测以及应急组织机构等方面,以期能为我国减少突发性水资源污染事故及其损失提供一定的理论分析依据。     

土工植草网在城防工程中的应用

文章以双辽市城防工程建设为例,介绍土工植草网新材料在护坡工程中的应用方法.