微波暗室内静区大小的计算

微波暗室对电磁兼容性的检测具有重要的意义．目前，国内外对一定形状微波暗室中静区大小的计算还没有成熟的方案．依据电磁场的几何绕射理论、反射理论推导出微波暗室中场强分布与材料性质和材料形状的函数关系，并依此设计出计算程序，为设计求解微波暗室提供了理论参考．     

A Low‐Cost Method to Evaluate Absorber Reflectivity Using an Antenna with a Small Radiating Aperture and Frequency‐Domain Instrument

We propose a way to measure the absorber reflectivity at a low cost. Only one simple antenna with a small radiating aperture and a frequency‐domain instrument are utilized. The previously used equation for calculating the reflectivity of an absorber is inaccurate, and, therefore, a new equation is derived based on multiple reflection analysis and three test models. Notably, the reflection coefficient of the antenna is included in the derived equation. The accuracy of the proposed method is proven through simulation and measurements. It can be easily applied to a product examination by absorber manufacturers and customers owing to its advantages of simplicity, cost effectiveness, and non‐cutting examination.     

小湾水电站枢纽区工程地质条件

小湾工程枢纽区地震地质条件复杂，地震基本烈度为Ⅷ度。坝址区地层呈单斜构造。横河展布。陡倾上游，岩性主要为黑云花岗片麻岩、角闪斜长片麻岩。两岸山体雄厚，地下水丰富，埋藏较浅；崩塌作用普遍；卸荷作用强烈，边坡稳定条件较差。岩体中高岭土化蚀变现象较普遍，陡倾角破裂结构面发育，且分布有顺坡中缓倾角节理，存在坝基(肩)抗滑和变形稳定问题。工程区属中高地应力区，地下洞室埋藏深度大，围岩以微风化一新鲜岩体为主，总体稳定条件较好。     

DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation: (1)The low frequency resonances introduced into the system; (2)Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke; (3) Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation (MFRC) are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions: one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.     

标准声源声功率级的半消声室检测法

本文介绍了半消声法检测标准声源声功率级的方法,并对用半消声室法检测标准声源声功率级的测量结果进行了不确定度的评定分析。     

测试平台对自由场影响的初步实验研究

消声室内放置声源的平台对自由声场的影响与频率有关。采用实验方法研究有限大平台对自由声场的影响,并提出改进方法。     

20MPa高压消声水池系统设计

随着我国深海探测活动的不断增多,适用于深海声学传感、声学通讯的各种换能器、传感器以及相关产品需求不断增加,同时对声学测试平台的要求也越来越高.该文提出了一种20 MPa高压消声水池设计方案,可以满足2000 m水深以内的静压力测试,同时配以声学计量系统可实现不同水深条件下的声学性能测试.耐压舱采用圆柱形外壳,两端端盖为...     

Electromagnetic modeling of 2D electronic mode‐stirred reverberating chambers for electromagnetic compatibility and interference analysis and design

This research concentrates on developing a complete theoretical tool to analyze the electronic mode‐stirred reverberating chamber. A 2D modeling of the EM fields is performed, which can then readily be extended to a 3D analysis of the cavity. The finite‐difference time‐domain (FDTD) method is implemented to discretize the Maxwell's equations. With our newly proposed method, the electromagnetic‐field characteristics can be easily studied inside the reverberating chamber under a realistic circumstance, thus opening doors to the analysis of a large spectrum of problems related to both commercial and military applications. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

消声水池中弹性球回声的测量与标定

在消声水池中对直径范围为2cm～5cm的钢球进行了回声测量。对长脉冲和短脉冲入射声信号的回声信号进行了分析比较。研究了目标的弹性作用在这两种情况下对回声的影响。通过对标准钢球回声测量结果与解析计算结果的比较,检验了消声水池目标回声测量的精度,并为其他非标准目标回声测量提供对比标定的依据。     

新型隔离开关的设计

介绍新一代负荷隔离开关产品的用途、适用范围、结构特点、性能指标、产品结构及工作原理等,由于采用双断点、双灭弧室结构,具有接通分断能力高、隔离距离大;直接显示触头合分状态;结构紧凑等优点,故新型隔离开关必将在低压负荷隔离线路中得到广泛应用.