Results of the ASTM field test of tristimulus weighting functions

In 1993, the American Society for Testing and Materials carried out a field test of newly calculated tristimulus weighting factors. These weighting factors had been calculated by a method proposed by Venable. the test also included a method of correction for bandpass dependence put forth by Stearns. the purpose of the trial was to assess the possible reduction in bandpass dependence introduced by each of these sets of weights. A large number of sets of spectral data were gathered from the cooperators in the field test. Results of integration by the various sets of tristimulus weighting factors were calculated. A total of 15 120 color differences were calculated and statistics were derived to test the probable error resulting from each method of correction. Errors attributable to bandpass dependence were on the order of a few tenths to as much as one CIELAB unit when uncorrected weight sets were used. These errors could be reduced to a few hundreths of a CIELAB unit, and in some cases to a few thousandths of a unit, by employing one correcting strategy or the other. an overall mix of strategies was ultimately chosen to minimize the bandpass dependence over the entire range of weight sets. Utilizing this mixed strategy, the median error introduced into 10-nm integration by bandpass dependence was only 0.004 CIELAB units. © 1995 John Wiley & Sons, Inc.     

一种制做三维牙——颌骨光弹性模型的新方法

本文提出一种用“整体浇注法”制做三维牙——颌骨光弹性模型的新方法,即用价格便宜的石膏做阴模,先制出与真实牙几何相似的牙光弹性模型和模拟牙周膜的乳胶套,将它们粘接好,然后将其放入颌骨石膏阴模的适当位置,浇入环氧树脂混合液,用“二次固化法”进行固化,即可制成三维牙——颌骨整体光弹性模型。此法能保证模型与实物的严格几何相似和牙周的边界条件相似,使实验精度大大提高且工艺简单、成本低。     

改进煤气含苯分析的校正系数

随着焦炉煤种及配比的改变,煤气含苯分析的谱图发生了变化。为了能更好地指导生产,我们从实际出发,改进了煤气含苯分析校正系数,减小了煤气含苯分析误差,大大提高了分析准确度。     

浅谈SN388采集站维修

SN388采集站器件的高度集成化给维修工作带来了一定的困难,本文列举了SN388采集站及其测试设备的一些常见故障,并介绍了使用测试设备TMS388排除相应故障的方法。     

A novel approach of reference current generation for power quality improvement in three-phase, three-wire distribution system using DSTATCOM

This paper presents a novel approach based on an improved instantaneous active and reactive current component theory for generating reference currents for distribution static compensator (DSTATCOM). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the DSTATCOM using the proposed control strategy has been evaluated under various source and load conditions. The performance of the proposed control strategy has been evaluated in terms of load balancing, reactive power compensation, compensator rating and harmonic mitigation. A three-phase, three-wire distribution system supplying star connected linear as well as non-linear unbalanced load is considered for simulation study. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy.     

5KW全数字控制单级隔离型功率因数校正变换器的研究

针对当前工业界某些应用场合对高功率等级、严格的谐波标准以及输入输出隔离等要求,本文提出了一种新的结合主电路拓扑和全数字控制技术的解决方案。文章采用单级隔离型全桥结构结合传统BOOST型PFC的输入电感和RCD钳位作为主电路,并融合数字控制方案,对中大功率单级隔离型PFC进行研究。分析了主电路工作原理,建立了小信号动态模型,并详细分析了基于该模型的数字控制设计方法。提供输入输出电气隔离的变压器,允许输出可以在较大范围内调整,既可以高于输出电压也可以低于输出电压,此外允许多路输出方案。因此,变压器的加主大大拓展了此类PFC变换器的使用场合。采用的数字控制方案,同时具有良好的动态响应特性和稳态调节特性。优异的动态调节特性可成功解决模拟控制引入的变压器偏磁现象。基于本文所提出的拓扑以及控制方案,制作了5kW输出功率且开关频率为55kHz的样机,验证了该变换器的优良性能,满载功率因数达到0．994,效率超过92％。     

光纤传输电视伴音的二次调制技术

本文简述光纤传输电视伴音的二次调制技术的基本原理,并对实现二次调制的实际电路进行了详细分析。     

油气两相文丘里流量计测量灵敏度分析

油气两相文丘里流量计对气液两相流的流型有很好的调整作用,测量结果准确,且能适应苛刻的操作环境。然而关于流量计测量灵敏度的研究却很少。为此,在介绍文丘里流量计工作原理的基础上,建立了文丘里流量计流场数值计算模型,分析了流速、压力、收缩锥角、直径比和喉部取压位置对压差比和虚高修正系数的影响;借助正交试验综合分析了结构参数对文丘里流量计灵敏度的影响,得出了流量计的最优结构参数。分析结果表明:流体在文丘里管的入口直管段静压值缓慢降低;进入收缩段后静压值迅速下降,在喉管末端压力最低;流经出口直管段后压力趋于稳定;流速不影响流量计的测量灵敏度,其他参数对压差比与液相质量分数关系式中的斜率影响显著,从而影响流量计的测量灵敏度。所得结论可为文丘里流量计的结构优化提供参考。     

多微机联控在大型三面翻广告牌中的应用

多微机联控系统应用不同类型的单片机,构成一个主控制器和多个现场控制器,充分发挥不同类型单片机的长处以提高系统的实用性和性价比。主控制器和多个现场控制器之间采用异步串口通信或“软串口”按照“通信协议”实现分支通信,组成多微机联控的“集散式控制”系统,按三面翻牌面翻转的控制要求分段驱动电机,实现大型三面翻牌面的定画面、定时间、可选翻转方式、出错牌面的“自动纠错翻转”等驱动要求。多微机联控系统极大地简化了控制电路的连线,简化了电气控制安装工艺与施工,在降低工程费用和后期维修费用的同时,可大幅提高控制系统工程的可靠性、稳定性、性价比。     

运用遗传算法结合FFT进行多单元失效阵列校准

提出了利用遗传算法（GA）结合快速傅立叶变换（FFT）方法来进行阵列失效的校准,通过引入傅立叶变换的变换域和角域的映射,在变换域中利用FFT计算个体阵列的阵因子,减少了GA评估个体的时间,从而大大提高了失效校准的速度。以一个-35分贝副瓣电平的32单元阵列为例,校准一单元失效和二单元失效的时间都减少了至少一个数量级,算法也可应用于两个以上单元失效的情况。