查询词典 impedance

A new conception of power per unit impedance is defined and the basic equation to express the variation of load voltage magnitude with the variation of its dynamic equivalent impedance and that of power per unit impedance is derived.

定义了单位阻抗功率的新概念，推导了电压幅值随其等值阻抗和单位阻抗功率变化而变化的基本方程式。

In the paper, an algebraic reconstruction algorithm based on magnetic resonance electrical impedance tomography was presented for 3-dimensional (3D) electrical impedance tomography, especially to image the 3D continuous impedance distribution of the head tissues.

文章给出了一种基于核磁共振技术的三维阻抗成像重构算法，并将该方法应用于人体头部组织电导率分布重构上。

A new method relying on the Stroh formulism and the theory of the surface impedance tensor was developed to investigate the dynamic instability of interfacial slip waves.The concept of the surface impedance tensor was extended to the case where the wave speed is of a complex value,and the boundary conditions at the frictionally contacting interface were expressed by the surface impedance tensor.Then the boundary value problem was transformed to searching for zeroes of a complex polynomial in the unit circle...

基于Stroh公式和表面阻抗张量理论，提出了研究界面滑移波动态失稳问题的一种新的方法·该方法将表面阻抗张量概念推广到复波速域，并将摩擦接触界面上的边界条件以表面阻抗张量表示·最终将边值问题化归为求解一个复多项式在单位圆内的根·以弹性半空间与刚体平面相对稳态摩擦滑移为例进行了详细的分析，导出了一个4次复特征方程并讨论了方程在单位圆内解的特性，给出了滑移界面波失稳条件的显式解析表达式

According to the studied results at present, the studied objects are mainly thin plate and beam about sound radiation mode, a method computed sound radiation mode of complex structure is presented in this dissertation, according to the results of the previous two chapter, a theoretical method to solve acoustical radiation mode and acoustical radiation efficiency of complex structure by boundary element method and acoustical radiation theory is posed, the acoustical radiation power is expressed as a Hermitian quadratic form, while the radiation modes is determined by general eigenvalue decomposing, and then the radiation efficiency is computed via the orthodoxy of radiation modes with regard to impedance matrix and average velocity matrix; lastly, the validity of the method is proved by pulsating sphere and radiating cube with analytical results. According to results of the form three chapter, the structure sound radiation sensitivity is studied in detail, the sound radiation power of structure can be expressed as positive Hermitian quadratic form, the sound radiation sensitivity can be expressed as two parts by partial differential with respect to design variable, which are sensitivity of boundary velocity and impedance matrix, combined with the theory of FEM and BEM, the structure sound radiation can be translated to the analysis of structure dynamic sensitivity and impedance matrix sensitivity. The theory posted in this dissertation is tested by the FEM software ANSYS and the software AAS programmed by author.

在前几章的基础上，通过结构声辐射的模态理论对结构的声辐射的机理进行了深入地探讨，针对目前声辐射模态的研究对象主要是简单的板和梁类结构，提出了一种计算复杂结构声辐射模态的方法，利用前两章研究所得的结论，将边界元方法与广义特征值的理论结合起来研究了复杂结构的声辐射模态与声辐射效率，先将结构的声辐射功率表示为一个正定的厄米特二(来源：ABb7C论文0909网www.abclunwen.com)次型，运用广义特征值分解求解了复杂结构的声辐射模态，然后利用声辐射模态关于阻抗矩阵与均方速度耦合矩阵的正交性，求解了复杂结构的声辐射效率，最后用具有解析解的脉动球与辐射立方体验证了该方法的有效性。

Different biases can result in the opposite phase shifts of the impedance with respect to the applied signal. Neutral gas pressure affects the magnitude of the impedance, but does not change the shape of the frequency response curve. In addition, the position of the grid inside the vacuum chamber has little effect on the impedance.

结果显示栅网上的直流偏压对阻抗的影响很大，不同偏压可以使阻抗的频率响应反位相，气压对阻抗的大小有明显影响，但一般不改变频率响应曲线的形状，栅网的位置对阻抗几乎无影响。

The design for impedance converting circuit of input current,transistor amplifying circuit and converting circuit of output current is presented.The telegrapher equations are adopted to determine the impedance of transmission-line transformer,which is used to convert circuit impedance between signal source and transistor.

讨论了放大器输入回路阻抗变换电路、晶体管放大电路以及输出回路阻抗变换电路的设计思想，运用电报方程从理论上推导出用于信号源和晶体管之间阻抗变换的传输线变压器输入输出阻抗计算公式，由此设计出模拟信号处理电路中非常重要的AB类高功率放大器。

These antennas can cover GSM900/DCS/PCS/UMTS operation. In the chapter 2, the antenna is designed based on the concept of monopole antenna. Furthermore, the antenna structure have two radiant paths and coupled each other at tail end to do impedance matching. In addition, to raise distance between radiation plane and ground will avoid capacitative effect effectually. In the chapter 3, the antenna is designed based on the concept of planar inverted-F antenna. Furthermore, that the antenna structure have two radiant paths and coupled each other at tail end to do impedance matching is similar to chapter 2. But there is a difference in them. We can choose the short position to change input impedance at this structure. In the chapter 4, the antenna is designed based on the concept of planar inverted-F antenna which takes coupled-fed. It will produce the first mode and high-order mode near the frequency, 900MHz. The feature of this type is to reduce the volume effectually. This antenna can not only cover GSM900/DCS/PCS/UMTS operation but maintain good radiation efficiency. Finally, we will compare three antennas, and develop procedure with industrial view, and propose the prospect of the GSM/GPRS antenna in PND, as a conclusion.

在第二章中，我们使用单极天线设计概念，使用双路径架构并於末端耦合来对天线阻抗做匹配，产生涵盖GSM900/DCS/PCS/UMTS四频操作频带，并提高与接地面的辐射高度，以避免电容效应，使天线具有良好的辐射特性；在第三章中，使用倒F形天线设计概念，使用双路径架构於末端耦合，并於辐射臂上采取适当接地点电感效应作输入阻抗匹配，达成涵盖GSM900/DCS/PCS/UMTS系统的四个操作频带；在第四章中，采用倒F形架构并使用耦合馈入方式，使得长辐射金属臂在低频900 MHz附近产生共振，产生低频基频模态及高阶模态，以达成宽频及频宽涵盖GSM900/DCS/PCS/UMTS频带操作，并有效缩减使用体积；最后，分别比较此三种架构的优缺点，再加以业界角度来思考，研发产品天线的流程及思考方向，以及天线应用於可携式导航装置中未来的展望作为本论文的总结。

Geophysical characteristics of Ordovician carbonate rock were studied using drilling data. Impedance is affected mostly by material properties and reservoirs types, to a negligibly extent by lithology and flow. Compact layers and minor\|fracture reservoirs of Ordovician carbonate rock have characteristics of high density, high velocity and high impedance, and the prediction of minor fractures reservoir is difficult by the general seismic ways. Big fractures and fractured\|vuggy and vuggy and cavity reservoirs of Ordovician carbonate rock have characteristics of minor density and low velocity and low impedance in central Tarim basin, which obviously different from the surrounding rock and produce obvious characteristics in seismic data, so reservoirs can be predicted by applying general seismic data.

根据已钻井资料，对塔中地区上奥陶统良里塔格组岩石地球物理特征进行了研究，结果表明：物性、储层类型对波阻抗影响最大，岩性、流体对波阻抗影响较小；奥陶系碳酸盐岩致密层和小裂缝型储层具有密度大、速度高、波阻抗值大的特点，利用地震常规预测手段较难预测出小裂缝型储层，而塔中地区奥陶系碳酸盐岩大裂缝型、裂缝-孔洞型、孔洞型、洞穴型储层具有密度小、速度低、波阻抗值小的特点，与围岩具有较为明显的差异，在地震上可以产生明显的响应，可利用常规地震资料来预测这种类型储层。

Taking the development platform of HVDC power transmission for example, the calculation result of impedance-frequency characteristic of traditional line commutated converter and that of FCC are compared. Simulation results show that the impact of impedance-frequency characteristic of converter on the resonance frequency of AC system is not negligible, and FCC can enhance the strength of AC system in a certain extent, improve system stability and effectively reduce AC equivalent impedance under resonance frequency, thus the harmonic instability of HVDC power transmission system can be avoided.

以直流输电开发平台为例，对传统电网换相换流器(line commutated converter，LCC)与FCC的阻抗频率特性计算结果进行对比，仿真结果表明换流器的阻抗频率特性对交流系统的谐振频率有着不可忽略的作用，FCC在一定程度上提高了交流系统强度，改善了系统稳定性，有效降低了系统谐振频率下的交流等值阻抗，从而更好避免直流输电系统谐波不稳定现象的发生。

This research adopts the impedance marching method, by varying duty cycle in a DC-DC converter to make the apparent load impedance matching with current system impedance, and reach the mpp operation.

控制电路的部分由单晶片PIC18F452为中心，重点为如何有效的取得太阳电池的开路电压及短路电流，以便正确计算出太阳电池的内部阻抗。

Now she was hungry and angry.She began to smoulder.

现在她又饿又气，她开始流露难以抑制的怒火。

You have placed our iniquities before You, Our secret sins in the light of Your presence.

诗90：8 你将我们的罪孽摆在你面前、将我们的隐恶摆在你面光之中。