Random discrete PWM method for DC-DC power converters

A random discrete pulse-width modulation (RDPWM) scheme is examined and compared with the randomised pulse-position modulation (RPPM) method for DC-DC power conversion. The RDPWM method has no switching harmonics while the RPPM method has significant switching harmonics. Power spectral characteristics of the two methods are presented and discussed     

专家系统在化工中的应用进展

本文综述了近年来专家系统在化工领域的应用状况，并指出今后的发展趋势。     

石膏制品防水防潮剂的研制与开发

本文提出采用高分子有机材料配合，生产石膏制品防水防潮剂的生产方法和工艺。该剂还可以应用到氧化镁系列板材，同时提出开发珠光或彩色防水防潮剂，能达到满足的装饰效果，值提开发推广。     

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��Consulting the relevant documents at home and abroad,the author finisheid the derivation of quations about critical flow quantity,critical flow rate,contrast flow quantity,contrast flow rate which are necessary to the continuous water withdrawal through the flow string with different diameters and the rational flow string formula that should be selected when the contrust parameter1.The author also works out the solving programme for TI-59 computer and designs and draws up the nomograrn of mathematical mode.The evident economical results have been obtained from practice of optimizing the flow string for water withdrawal in gas production in Southern Sichuan and from studying the gas-water two-phase flow characteristics through vertical pipe.     

北京核电站模拟器硬件的功能和特点

本文介绍北京核电站模拟器硬件构成并分析其功能和特点。     

Designing the MPC105 PCI bridge/memory controller

The MPC105 peripheral component interconnection bridge/memory controller provides a platform-specification-compliant bridge between Power PC microprocessors and the PCI bus. With it, designers can create systems using peripherals already designed for a variety of standard PC interfaces. This bridge chip also integrates a secondary cache controller and high-performance memory controller that supports DRAM or synchronous DRAM and ROM or flash ROM     

Application of the Taguchi Method to the Optimization of the Submerged Arc Welding Process

Application of the Taguchi method to the optimization of the submerged arc welding process is reported. The Taguchi method is used to formulate the experimental layout, to analyze the effect of each welding parameter on welding performance, and to predict the optimal setting for each welding parameter. Experimental results are provided to confirm the effectiveness of this approach.     

ELEVATED TEMPERATURE FRACTURE OF PARTICULATE-REINFORCED ALUMINUM PART I: FRACTURE TOUGHNESS

Abstract—The plane-strain initiation and growth fracture toughnesses of powder-metallurgy-processed, SiC particulate-reinforced 2009 plate were measured at temperatures from 25°C to 316°C. Initiation toughness from electrical potential monitoring ( K _JICi) is 18 MPa°m at 25°C, and is nearly constant to 220°C before decreasing sharply to 6 MPa°m at 316°C. Growth toughness, given by the tearing modulus ( T _R), is less than 3 from 25°C to 125°C, and increases dramatically above 200°C. The magnitude and temperature dependence of initiation toughness depend on detection of the critical fracture event. Standard measures of toughness K _IC and K _JIC exceed K _JICi and increase to a plateau with increasing temperature. The fracture mode for the composite is microvoid nucleation, growth and coalescence at all temperatures. Void nucleation is associated with SiC; such particles both crack and create stress and plastic strain concentrations that rupture the interface or adjacent matrix, particularly at corners. Matrix plasticity and cavitation increase with increasing temperature. Void growth is regular at all temperatures, but limited by adjacent SiC particles. Both K _JICi and T _R are governed by the temperature-dependent crack-tip plastic stress and strain fields, and the intrinsic damage resistance of the composite microstructure.     

一种新型无突变自动高压电源

本文介绍一种新型高压直流电源，它的输出高压的提升、下降均自动、无级、缓慢地变化，无突变现象，尤其在电网供电突然中断时，也能使用高压自动、缓慢地下降到０。它用于半导体放射性射线探测器，可以避免由于操作的粗心或电网供电突然中继引起高压快速变化或而产生的对该类昂贵探测器及其附件的损害，使探测器的优良性能得以保持。