12bit 800MSPS电流舵结构的高速DAC设计

本文设计了一个分辨率为12位，采样频率为800MHz的高速电流舵结构DAC。该设计基于TSMC0．18umCMOS工艺，采用了二进制码控制和温度计码译码控制相结合的方式，从而在降低DNL误差和减小毛刺的同时，又能实现较小的芯片面积和功耗。为达到高的精度和高的转换速度，该设计在系统结构、电路结构以及芯片版图等方面都做了优化。     

大容量整流变压器送电冲击跳闸分析及防范措施

通过实例,分析变压器冲击跳闸故障的原因,并介绍故障处理程序及解决办法.     

Two guaranteed equilibrated error estimators for Harmonic formulations in eddy current problems

In this paper a guaranteed equilibrated error estimator is developed for the 3D harmonic magnetodynamic problem of Maxwell’s system. This system is recasted in the classical $\mathbf{A}?\phi$ potential formulation and solved by the Finite Element method. The error estimator is built starting from the $\mathbf{A}?\phi$ numerical solution by a local flux reconstruction technique. Its equivalence with the error in the energy norm is established. A comparison of this estimator with an equilibrated error estimator already developed through a complementary problem points out the advantages and drawbacks of these two estimators. In particular, an analytical benchmark test illustrates the obtained theoretical results and a physical benchmark test shows the efficiency of these two estimators.     

基于VB与PCI-1712采集卡的电流监视系统设计与实现

在分析了目前船载雷达天线伺服系统电机电流监视中存在不足的基础上,提出了基于VB与PCI-1712采集卡的电机电流监视系统设计方案,详细说明了PCI-1712数据采集卡的主要驱动函数和特征,搭建了硬件平台并对监视系统的数据采集、数据处理、图形输出、故障报警、数据库、记录输出进行了详细的介绍.     

Current Awareness Using PubMed

ABSTRACT

Current awareness is something that librarians do, at least informally, passing on relevant current information to their patrons on a regular basis. The type of current awareness service considered here entails running preselected searches against electronic databases. The availability of these electronic bibliographic databases allows automating much of the current awareness process. Any successful current awareness service will have three key attributes: speed, ease of use, and relevance. The flexibility and accessibility of the National Library of Medicine's PubMed make it ideal as the basis for a current awareness service. Six freely available services are evaluated according to uniform criteria with notes made of special features. Four services use PubMed as the source for data, and the other two use MEDLINE. Recommendations are made for modifying one of the services to embody the key attributes of a successful service. Particular attention is given to local needs. Such a service can be run from a single desktop machine with a dial-up connection to the Internet.     

Characteristics of flow field near sea bottom in a combined wave and current motion

Abstract

A reasonable time‐invariant eddy viscosity model is proposed to describe turbulent flow over a rough sea bottom in a combined wave‐current system. The linearized governing equations are solved for the wave and current kinematics both inside and outside the wave boundary layer. The results of velocity profile, friction factor and apparent roughness in a wave‐current motion are presented. The friction factors are shown to be consistent with previous theoretical results for the limiting cases of pure wave and pure current motions. Present results are compared favorably with the available data.     

Characteristics of the Arc Voltage of a High‐Current Air Arc in a Sealed Chamber

The effect of the arc voltage on various factors of design and control was investigated for high currents in order to develop design guidelines for circuit breakers. In this study, the dependence on such factors, namely, the current, arc length, electrode surface area, and internal pressure of the arc voltage, was evaluated quantitatively. As a result of the evaluations, it was estimated that the arc voltage near the electrode surface rises linearly with the arc current and the power ?0.8 of the surface area, and that the voltage in the arc column rises as the 0.3 power of the pressure increase. We confirmed the validity of the estimated voltage characteristics by comparison with the generated voltage in an actual arc‐extinction chamber. The characteristics of the estimated voltage can provide effective guidelines for the design of arc extinguishing chambers. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(1): 34–42, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22487     

Evaluation of the lift-off robustness of eddy current imaging techniques

The development of lift-off invariant strategies is one of the main goals in Eddy Current Non-Destructive Testing research. In the present work, from the analysis of amplitude and phase signals of magnetic field sensors under Multi-Frequency Eddy Current excitation, two imaging procedures are analyzed and compared with respect to their ability to retrieve reliable results even in presence of huge changes of lift-off. A figure of merit based on the Signal to Noise Ratio evaluated on the 2D reconstructed images allows the comparison of the different strategies in terms of the quality of the image to show the defect. The numerical and the experimental tests realized show that the imaging procedure relying on the analysis of the phase-lag is quite insensitive to changes in the lift-off with respect to that based on the amplitude analysis. In detail the former guarantees good results even when the probe lift-off is randomly changed during the test with variations up to 3 mm, while the latter is able to tolerate only lift-off fluctuation lower than 1 mm.     

液氮传导冷却型高温超导电流引线研制

80 A和200 A液氮传导冷却型高温超导(HTS)电流引线由铜引线段、中间过渡段和高温超导段组成,HTS热端采用液氮传导冷却,HTS冷端采用液氦传导冷却。铜引线段工作在室温到中间温度(~80 K),高温超导段工作温区6—80 K。介绍该传导冷却型电流引线的结构设计和低温性能测试。实验结果表明,中间过渡段温度~78 K,高温超导热端温度77 K;80 A、200 A电流引线液氦下稳态测试电流分别为100 A和250 A。