基于MATLAB/Simulink的交流伺服系统的仿真

交流伺服系统是一种复杂的非线性时变系统。文中介绍了应用MATLAB/SIMULINK可视化动态仿真平台进行软件伺服的系统仿真方法。该方法采用易扩展的模块化设计,可在线修改和观察所有参数以及参数变化对系统控制效果的影响,从而能方便地验证各种控制策略,并据此选出高效的快速设计方案,缩短了研制周期,对系统设计和调试起到了很大的作用。     

论给水变频控制系统在100MW机组中的应用

引用某热电厂100MW机组给水系统的变频改造实际运行和测试结果，证明在电厂给水系统中应用给水变频控制系统进行改造是切实可行的。不仅可以有效改善系统自动化水平和控制品质，而且可以取得良好的经济效益。     

PRO——一种新的地震资料处理方法

PRO(影像的参数展开)技术是由俄罗斯地球物理学家开发的一种崭新的地震资料处理技术。本文从PRO基本原理入手,简单介绍了PRO的速度分析原理。PRO速度分析和成像均以信号的椭圆展开和参数展开为基础,其中参数展开方法考虑波型转换、介质的横向不均匀造成传播速度的变化。该技术抛开了传统共中心点叠加的思想,从根本上解决了以CMP方法为基础的传统地震处理技术遇到的困难。通过模型与实例分析对比,PRO比传统CMP方法更优越。     

Determination of polymer–polymer interaction parameters using inverse gas chromatography

A modified method is discussed that is based on Farooque and Deshpande's method to obtain polymer–polymer interaction parameters using inverse gas chromatography (IGC) data. In the Farooque and Deshpande method, the ratio of the difference of probe–polymer interaction parameters between two polymers and the probe volume [(χ₁₂ ? χ₁₃)/V₁] is used as the abscissa. In the modified method, the ratio [(?₂χ₁₂ + ?₃χ₁₃)/V₁] is used as the abscissa. Experimental data previously reported for a poly(?‐caprolactone)‐polyepichlorohydrin (PCL/PECH) blend and a poly(ethyl acrylate)‐poly(vinyl propionate) (PEA/PVPr) blend are analyzed. It is found that the slopes obtained by the new method had smaller deviations from the theoretical values than the Farooque and Deshpande method. The standard deviations of both slopes and intercepts obtained from the new method are also smaller. Using the new method, the polymer–polymer interaction parameters obtained from the intercept are negative numbers for the PCL/PECH system and very small positive numbers for PEA/PVPr. Explanations are given for the probe and concentration dependency of the polymer–polymer interaction parameters that are generally observed in IGC studies. A new method for selecting the best probe for calculating the interaction parameter is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 671–680, 2003     

An Area Optimization Method for Digital Filter Design

In this paper, we propose an efficient design method for area optimization in a digital filter. The conventional methods to reduce the number of adders in a filter have the problem of a long critical path delay caused by the deep logic depth of the filter due to adder sharing. Furthermore, there is such a disadvantage that they use the transposed direct form (TDF) filter which needs more registers than those of the direct form (DF) filter. In this paper, we present a hybrid structure of a TDF and DF based on the flattened coefficients method so that it can reduce the number of flip‐flops and full‐adders without additional critical path delay. We also propose a resource sharing method and sharing‐pattern searching algorithm to reduce the number of adders without deepening the logic depth. Simulation results show that the proposed structure can save the number of adders and registers by 22 and 26%, respectively, compared to the best one used in the past.     

铁通资源管理系统的设计和实现

在分析铁路通信资源结构的基础上,利用地理信息系统技术、数据库技术和客户/服务器(C/S)模式,为铁通(ChinaTietong)各级分公司和运营部门提供一套较为完善的资源管理信息系统。文中分析了铁通资源的结构与资源之间的关联,介绍了系统功能、物理结构及体系结构,详细分析了数据库设计、地理信息系统和系统安全性所采用的关键技术。这套系统的应用对铁通网络管理的现代化将起到重要的推动作用。     

Chemical compositions and optical properties of HfOxNy thin films at different substrate temperatures

High-k HfO_xN_y thin films have been grown by radio frequency (rf) reactive sputtering of metal Hf target in N₂/Ar/O₂ ambient at different substrate temperatures. The chemical compositions of the films have been investigated as a function of substrate temperature by X-ray photoelectron spectroscopy (XPS). XPS measurements showed that nitrogen concentration increases with an increase in substrate temperature. Room-temperature spectroscopic ellipsometry (SE) with photon energy 0.75–6.5 eV was used to investigate the optical properties of the films. SE results demonstrated that refractive index n increases with an increase in substrate temperature. Based on TL parameters which were obtained from the best fit results used in a simulation of the measured spectra, meanwhile, we conclude that the energy band gap (E_g) decreases with an increase in substrate temperature.     

有限元数值试井解释技术在复杂断块油气藏评价中的应用

有限元数值模拟试井技术,可通过描述不同网格的瞬变压力对测试范围内各个小单元进行精细描述.综合运用解析试井、数值试井联带分析方法,将测试动态成果与地质静态成果有机结合、相互补充,可实现对复杂断块油气藏的精细描述,达到一口井搞清一个小型复杂断块油气藏的目的.     

针对混合应用业务的ARQ改进方案

在高速无线通信中,自动请求重传(ARQ)是链路层不可缺少的技术,它通过重传向上层屏蔽无线链路上包的丢失。随着无线网络的发展,无线传输速率不断提高,应用的业务类型也越来越广泛。目前,众多ARQ技术的研究都集中在如何提高该技术的确认效率,以适应更高的传输速率,但鲜有研究着手于如何使ARQ能够更好地应用于混合业务环境。针对混合业务环境下的ARQ改进提出了2种方案,并给出其中1种在实际应用中的改善效果。     

The flame retardant mechanism of polyolefins modified with chalk and silicone elastomer

This paper presents the current understanding of the flame retardant mechanism of Casico?. The study includes the flame retardant effect of each individual component: ethylene–acrylate copolymer, chalk and silicone elastomer, as well as the formation of an intumescent structure during heating. The flame retardant properties were investigated by cone calorimetry and oxygen index tests. To obtain insight into the flame retardant mechanism, heat treatment under different conditions has also been performed. The results indicate that the flame retardant mechanism of Casico is complex and is related to a number of reactions, e.g. ester pyrolysis of acrylate groups, formation of carbon dioxide by reaction between carboxylic acid and chalk, ionomer formation and formation of an intumescent structure stabilized by a protecting char. Special emphasis is given to the formation of the intumescent structure and its molecular structure as evaluated from ¹³C MAS‐NMR and ²⁹Si MAS‐NMR, ESCA and XRD analysis. After treatment at 500°C the intumescent structure consists mainly of silicon oxides and calcium carbonate and after treatment at 1000°C the intumescent structure consists of calcium silicate, calcium oxide and calcium hydroxide. Copyright © 2003 John Wiley & Sons, Ltd.