导管反循环成槽法在长江干堤的应用

介绍了导管反循环法在长江干堤加固中的应用,从工艺原理、流程和浇筑要点等几方面作了阐述.     

跨导线性环电流放大器

在应用TL回路的原理分析跨导线性环电流放大器的基础上,以电压模电路的分析方法,推导了跨导线性环电流放大器频率特性的表达式,证实了跨导线性原理关于增益表述的正确性,以及该电流放大器具有较高上限截止频率的论述。在推演过程中说明了该放大器为理想电流放大器,其输出电流iod≈ion,从而克服了电压模电路中的密勒效应。输入为电流源激励,即输入端呈现低阻特性。正因为跨导线性环电流放大器具备这些特性,才使得它在高速、宽带集成电路中得到广泛的应用。     

直流控制电动机的电子稳速与限流控制

直流控制电机的限流与稳速控制方式适用于转矩控制与扭矩测量。它具有控制简便、允许电机堵转，并能在扭矩测量时减少因转速变化引起的附加误差。文中给出了基本控制电路。并可以此为基础设计出新颖、实用的教学实践课题。     

城区堤防工程防渗墙施工工法的选用

结合汉口沿河堤防渗工程，对液压抓斗、深层搅拌和高压旋喷三种防渗墙施工工法在城区堤防防渗工程中的应用进行分析和评价。     

Validity of Alternative Cut-Off Scores for the Back-Saver Sit and Reach Test

The purpose of the study was to determine if currently used FITNESSGRAM® cut-off scores for the Back Saver Sit and Reach Test had the best criterion-referenced validity evidence for 6–12 year old children. Secondary analyses of an existing data set focused on the passive straight leg raise and Back Saver Sit and Reach Test flexibility scores of 87 boys and 91 girls. The reliability and validity evidence was determined for Back Saver Sit and Reach Test cut-off scores of 7, 8, 9, and 10 inches for the boys and girls separately. Reliability evidence for passive straight leg raise and all Back Saver Sit and Reach Test cut-off scores was good to excellent. The most valid cut-off scores had the highest proportion of correct decisions associated with sensitivity ≥.67, and false-positive rate ≤.24. Based on moderate validity evidence, the best Back Saver Sit and Reach Test cut-off scores for 6–12 year olds are 8 and 9 inches for boys and girls, respectively. These findings should be cross-validated with other samples.     

列车对半椭圆形隧道中电磁波截止频率的影响

将隧道看成波导,列车的存在改变了隧道的截面形状和尺寸,从而影响了电磁波的截止频率.在对列车—隧道导波问题进行物理建模的基础上,应用有限元法研究了列车的高度、宽度和位置以及半椭圆形隧道椭圆的偏心率的变化对半椭圆形隧道电磁波截止频率的影响.