基于网络的工程制图读图系统的研究与实现

基于网络的工程制图读图系统的设计和开发本着易用和实用的原则,系统中使用了多种技术手段,并将具有可交互的、适时显示的虚拟模型引入其中;网页的设计将4个模块：习题原题、习题答案、解题思路、虚拟模型同屏显示,完全符合工程制图课程的教学、实验特点和学生的学习实际.整个系统由具有丰富教学和实践经验的教师亲手完成,具有很强的实用性和推广性.系统实现的关键技术可用于工程制图其他助学系统,也可供其他课程的教学和实验系统所借鉴.     

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.     

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。     

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.     

评论以美元为中心的国际货币体系

基于对现今世界以美元为中心运行的国际货币体系的考察,包括其形成的历史原因,运行的各种规则,以及对现实世界经济发展产生的种种促进作用和一些不利的影响,对以美元为中心的国际货币体系的未来进行了探讨。     

浅谈造价管理与控制方法

从预算标底编制、评标定标、工程设计变更、竣工决算审计等关键环节,就加强工程造价管理的方法进行探讨。     

略论影响技校学生制图课学习因素及对策

本文从学生的学习动机、智力因素、教学方法、学业评价、教学环境,就业前景等方面进行了影响学生学习机械制图课程因素分析,探讨了现状对学生学习主动性、积极性的制约,针对各个现状提出了解决的思路办法以及对策.     

单音节持具类手部动词初步研究

单音节手部动词指需要用手参与才能完成的具体动作的动词。持具类手部动词是手部动词的一个小类,其特点是在完成动作时必须使用身体器官以外的工具。持具类手部动词的两个典型句式:含使用工具的句式为"NP1+用+GN+V+C+NP2",不含使用工具的句式为"NP1+V+C+NP2"。     

多功能车刀几何角度测量仪的研制

针对工科院校车刀几何角度测量实验中存在的问题,从教学目标出发分析了车刀几何角度测量仪应具有的目标功能,在此基础上研制了多功能车刀几何角度测量仪,并进行了实验验证。该测量仪具有参考坐标系的建立、车刀几何角度测量和车刀纵横方向进给等多种功能,便于学生对金属切削刀具知识的学习、理解和掌握。