基于湿度控制技术的岩心电阻率测量研究

针对油田岩心室内试验中工作气体湿度控制现状，提出对在室内以气体为工作介质的试验流程中引用双压法气体湿度发生装置，从而获得已知湿度的工作气体进行岩心的常规试验．岩心电阻率测量的实验数据表明，控制工作气体的湿度，可提高试验结果的准确性．     

基于SVPWM的异步电机矢量控制系统仿真

介绍了电压空间矢量脉宽调制(SVPWM)的基本原理,基本感应电机理论和坐标变换关系,给出转子磁场定向控制确定定向磁场在两相静止坐标系中位置角的算法,分析了基于SVPWM的感应电机转子磁场定向控制系统原理,并实现了SVPWM算法。通过MATLAB仿真软件对系统进行了仿真,给出了仿真结果。     

Mathematical methods for modelling price fluctuations of financial times series

Statistical and Fourier analysis methods of time series representing fluctuations of stock market in general and Indian stock markets in particular are well known. This work is motivated by a recent paper by Guharay [Operations Research and Financial Engineering, Princeton University, Princeton, NJ, preprint, 2002] where he has studied trends in the S & P 500 for various time periods using wavelet tools. Our paper deals with a few Indian and Saudi stock prices and return fluctuation for a certain period of time. The main objective of the analysis is to understand the dynamics of the Indian and Saudi stock markets. We look for similarities, point of abrupt changes, normalized data, return, volatility, graph, pure and noise part, correlation lengths, and signal-to-noise ratio.     

基于Vb和Flash的电力电子技术实验教学系统的设计

针对电力电子技术可控整流部分的内容,设计了基于Vb和Flash的实验教学系统,通过Flash实现各电路工作原理的动态演示,通过Vb的编程作图功能实现对可控整流电路的实验控制,并实现了2种软件的有机融合.在实际实验教学中,有效地改善了教学手段,激发了学生的学习兴趣,提高了教学质量,锻炼了学生的动手能力.     

变频器在切削力测量实验中的应用

切削力是金属切削中的重要参数之一,与切削速度呈驼峰曲线关系。为了使车削中的切削速度不受工件直径变化的影响而得到清晰完整的驼峰曲线,采用变频器对机床主电机进行无级调速,从而使主轴转速由主电机工作频率和调速手柄共同决定。实验结果表明无级调速可得到较理想的驼峰曲线。     

基于云计算的数据中心虚拟机管理平台的设计

随着数字化校园和绿色校园的深入开展,校园网各项业务逐渐自动化和集成化。大连理工大学基于VMware虚拟化技术构建了安全高效的数据中心,并对校内各部门提供虚拟机服务。然而在虚拟机申请和管理维护过程中涉及大量人工操作,这构成了数据中心管理瓶颈。基于云计算思想设计了虚拟机管理平台,并以Web服务虚拟机申请为例介绍了该平台的功能。该管理平台对提高虚拟机管理效率有重要意义。     

拉瓦尔大学医学研究中心运营及管理模式

介绍加拿大拉瓦尔大学医学研究中心的运营和管理模式,从仪器设备管理和受控试剂管理2个方面分享该中心在管理上的先进经验;探讨提高大型仪器设备使用效率和建立合理废物回收制度的改革内容;提出信息导航、资源共享,加强合作、互惠双赢的理念;强调废物回收管理的重要性,将环境保护和可持续发展作为高校试剂管理的重点.     

浅析“人肉搜索”的实质、利弊及引导策略

＂人肉搜索＂在当前已成为热门的社会话题,从一种单纯的网络文化现象逐渐到对现实社会生活产生越来越大的影响。鉴于人们对于＂人肉搜索＂的实质存在诸多误解,文章将对其相关的一些概念、内容进行厘定,分析此现象的利弊并提出可能的规范和引导措施。     

Development of integrated precision vibration-assisted micro-engraving system

A novel precision vibration-assisted micro-engraving system was developed by the integration of fast tool servo and ultrasonic elliptical vibration system, in which the flexure hinge was designed to avoid backlash and PID control algorithm was established to guarantee specific precision. Apart from experimental validation of the performance of the system, various micro-V-grooves cutting experiments on aluminum alloy, ferrous material and hard cutting material were performed, in which Kistler force sensor was used to measure cutting force. Through experiments, it was clear that the vibration-assisted micro-engraving system can ensure good quality of micro-V-grooves and reduce cutting force by about 60% compared with traditional removal process without ultrasonic vibration.     

Experimental and FEM Study of Coated and Uncoated Tools Used for Dry Milling of Compacted Graphite Cast Iron

Compacted graphite cast iron (CGI) has been the material for high-power diesel engines recently, but its increased strength causes poor machinability. In this study, coated and uncoated carbide tools were used in dry milling experiment and FEM simulation to study the machinability of CGI and wear behaviour of tools. The experimental and FEM simulation results show that coated tool has great advantage in dry milling of CGI. SEM and EDS analysis of tool wear indicate the wear morphology and wear mechanism. Adhesive wear is the main mechanism to cause un-coated tool wear, while abrasive wear and delamination wear are the main mechanism to cause coated tool wear. Stress and temperature distribution in FEM simulation help to understand the wear mechanism including the reason for coating peeled off.