电流正反馈自动调速系统设计

在电压负反馈的基础上,给发电机、电动机换向绕组两端并联电阻R1,用以检测主回路电流I,从R,取出它的一部分电压作为电流正反馈信号加到扩大机控制绕组CII上．当电压负反馈系数αV增大时,电流正反馈系数α1也要增大,从而提高了发电机的端电压,补偿了电动机因负载变化而造成的转速降,保证了系统具有较硬的静特性．     

一种改进的带冗余项的LCD多行选址算法及其实现

提出了一种带有冗余项的多行选址驱动算法及电路实现方案,其适用于液晶显示驱动芯片。算法通过在行调制矩阵中增加冗余行,在显示数据矩阵中增加冗余数据,从而减少了列驱动电平数。此外,还提出了本算法的实现电路。实验结果表明,在液晶显示驱动芯片中,该算法能降低30%的驱动功耗。     

基于Multisim的恒流源式差分放大电路分析

以Multisim为平台分析恒流源式差分放大电路。使用虚拟电压表、电流表、示波器、函数发生器等虚拟元件,仿真分析恒流源式差分放大电路的工作特性,并演示Multisim中虚拟仪器及各种分析方法的使用。对差分放大器中各三极管的静态工作点和差模电压放大倍数的仿真分析结果与理论计算相符。     

一种低压直流LED照明分级供电系统

随着半导体照明技术的快速发展,LED照明已得到广泛的应用。本文提出一种采用低压直流分级的供电方式,系统集中提供AC/DC的转换,而对单个的LED照明单元直接通过DC直流供电驱动。本系统因其具有高效率、低成本、高可靠性等特点,可在家庭、小区以及今后城市供电中进行推广、应用。     

Different durations within the method of best practice affect the parameters of the speed–duration relationship

The aim of the study was to determine whether estimates of the speed–duration relationship are affected using different time-trial (TT) field-based testing protocols, where exhaustive times were located within the generally recommended durations of 2–15?min. Ten triathletes (mean?±?SD age: 31.0?±?5.7?years; height: 1.81?±?0.05?m; body mass: 76.5?±?6.8?kg) performed two randomly assigned field tests to determine critical speed (CS) and the total distance covered above CS (D?). CS and D? were obtained using two different protocols comprising three TT that were interspersed by 60?min passive rest. The TTs were 12, 7, and 3?min in Protocol I and 10, 5, and 2?min in Protocol II. A linear relationship of speed vs. the inverse of time (s?=?D??×?1/t?+?CS) was used to determine parameter estimates. Significant differences were found for CS (p?=?0.026), but not for D? (p?=?0.123). The effect size for CS (d?=?0.305) was considered small, while that for D? was considered moderate (d?=?0.742). CS was significantly correlated between protocols (r?=?0.934; p?D? (r?=?0.053; p?=?0.884). The 95% limits of agreement were ±0.28m?s^?1 and ±73.9?m for CS and D?, respectively. These findings demonstrate that the choice of exhaustive times within commonly accepted durations results in different estimates of CS and D?, and thus protocols cannot be used interchangeably. The use of a consistent protocol is therefore recommended, when investigating or monitoring the speed–duration relationship estimates in well-trained athletes.     

二复变量整函数在多极集上的性质

引入多极集的定义,并将二复变量整函数与多极集结合起来,运用极大值原理研究了二复变量次调和整函数在多极集中的性质。     

时频信息融合的电弧故障识别及仿真实验北大核心

为保证实验室用电安全,针对实验室电弧故障,提出一种时频信息融合的电弧故障识别方法并模拟验证。首先分别搭建模型模拟并联与串联电弧,然后在PSCAD/EMTDC中搭建三相五线制实验室用电系统模拟实验室用电电弧,最后针对难以辨识的串联电弧故障,依据突变理论融合时频信息,与阈值进行比较判断故障,并依据多类型负载实验室用电仿真系统进行验证。结果表明该方法可行性高且故障识别率达90%以上。将电弧故障辨识方法以及仿真实验用于教学有助于增强学生实验室安全用电意识,加深学生对相关电路原理、信号处理和故障辨识相关知识的理解,培养学生分析和解决实际电气问题的能力。