检索结果-内蒙古大学图书馆

IEEE Industry Applications Society Annual Meeting (IAS)

作者： Markus Zahn Lori Antis Jorge Mescua Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science Laboratory for Electromagnetic and Electronic Systems High Voltage Research Laboratory Cambridge MA 02139 M.I.T. Visiting Scientist (1984-85 academic year) from the University of North Carolina Charlotte

Kerr electro-optic field mapping measurements have shown strong space charge effects in high voltage stressed dielectrics, where the magnitude and sign of injected charge depends on electrode material. with appropriate choice of electrode material combinations and voltage polarity, it is possible to have uncharged, unipolar charged positive or negative, or bipolar charged dielectric. The bipolar homocharge case lowers the electric field at both electrodes due to space charge shielding and thus allows a higher voltage without breakdown. Charge transport analysis considers the general case of charge injection from both electrodes and solves for the time and space dependences of the electric field and charge distributions and the time dependences of the terminal voltage and current. This analysis extends earlier work by including non-equilibrium charge dissociation and recombination so that the effective ohmic conductivity is not constant but rather varies with time and position due to local net charge density. Specific cases discussed are the open circuit voltage decay of an initially charged capacitor, the charging and discharging by a Marx generator, and alternating voltage excitations.

关键词： Electrodes Trajectory Conductivity Electric fields Dielectrics Space charge Electric breakdown

来源：评论

学校读者我要写书评

暂无评论

Kere Electro-Optic Field and Space Charge Mapping Measurements in High Voltage Stressed Gas, Liquid and Solid Dielectrics

Kere Electro-Optic Field and Space Charge Mapping Measuremen...

引用

IEEE Industry Applications Society Annual Meeting (IAS)

作者： M. Zahn J. Brennan R. Carreras C. M. Cooke M. Hikita M. Masui H. Reyes K. Rhoads S. Shepard G. Sun T. Wang K. A. Wright Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science Laboratory for Electromagnetic and Electronic Systems High Voltage Research Laboratory Cambridge MA 02139 MIT Visiting Scientist from Nagoya University Japan MIT Visiting Scientist from Ibaraki University Japan MIT Visiting Scientist from Academia Sinica China

Preliminary Kerr electro-optic field and space charge mapping measurements are reported in weakly birefringent materials typically used in high voltage insulation applications. Measurements are reported in mineral transformer oil with and without creped paper and glue typically used in power transformers, silicone oil used as a retro-fill fluid for PCB contaminated transformers, liquid and gaseous sulfur hexafluoride used as high voltage insulation in compact power apparatus, and polymethylmethacrylate, both high voltage stressed and electron beam irradiated to high fields.

关键词： Electric fields Electrodes Voltage measurement Oils Oil insulation Power transformer insulation Dielectric measurement

来源：评论

学校读者我要写书评

暂无评论

Streamer propagation times along insulator surfaces in transformer oil

Streamer propagation times along insulator surfaces in trans...

引用

Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Chathan M. Cooke Hiroshi Yamada Massachusetts Institute of Techology Department of Electrical Engineering and Computer Science High Voltage Research Laboratory Laboratory for Electromagnetic and Electronic Systems Cambridge MA 02139

The electrical failure of practical oil insulated apparatus often develops as a surface flashover along the interface of a solid dielectric support and the oil. While there is substantial reported information about breakdown and streamer propagation in plain oil gaps, there is little comparable information about the surface flashover case. The studies reported here concern measured surface flashover characteristics and mechanisms of a point-to-plane gap with a solid dielectric surface perpendicular to the plane bridging the gap. A nanosecond risetime step voltage was applied, and the currents and time to breakdown were determined by an electro-optic coupling method.

关键词： Oils Dielectrics Electrodes Delays Electric breakdown Oil insulation Needles

来源：评论

学校读者我要写书评

暂无评论

Kerr electro-optic field mapping measurements in highly purified water between coaxial electrodes

Kerr electro-optic field mapping measurements in highly puri...

引用

Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Michael J. LaGasse Markus Zahn Jim Huang Massachusetts Institute of Techology Department of Electrical Engineering and Computer Science High Voltage Research Laboratory Laboratory for Electromagnetic and Electronic Systems Cambridge MA 02139

Highly purified water is being investigated for use as a high voltage dielectric due to its high permittivity, ε≈80ε ο , and relatively high resistivity, ρ≈60MΩ-cm at 6°C. Previous Kerr electro-optic field mapping measurements using parallel plate electrodes have shown significant space charge distortion of the electric field in the dielectric. The sign and magnitude of the space charge injected into the dielectric was shown to be a function of the electrode materials and voltage polarity. For example, aluminum always injects negative space charge, while stainless steel generally injects positive charge but under some conditions has injected negative charge [1].

关键词： Electrodes Aluminum Space charge Steel Electric breakdown Dielectrics Electric fields

来源：评论

学校读者我要写书评

暂无评论

Bipolar charge transport analysis in high voltage stressed dielectrics

Bipolar charge transport analysis in high voltage stressed d...

引用

Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Markus Zahn Jorge Mescua Massachusetts Institute of Techology Department of Electrical Engineering and Computer Science High Voltage Research Laboratory Laboratory for Electromagnetic and Electronic Systems Cambridge MA 02139

Modern pulse power machines commonly use deionized water in intermediate energy storage capacitors. Recent work has shown that charge injection phenomena can play an important role in determining the limits of performance of the dielectric [1]. For unipolar conduction, this anomalous behavior was shown to be due to injected charge that increases the effective ohmic conductivity σ to σ+qμ, where q was the time and space dependent charge density with mobility μ of the single charge carrier.

关键词： Electrodes Generators Space charge Capacitors Conductivity Mathematical model

来源：评论

学校读者我要写书评

暂无评论

Adaptive vector quantization by progressive codevector replacement

Adaptive vector quantization by progressive codevector repla...

引用

International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： A. Gersho M. Yano Department of Electrical & Computer Engineering University of California Santa Barbara CA USA C & C Systems Research Laboratory NEC Corporation Limited Kawasaki Japan

This paper presents a new class of adaptive vector quantizers in which a codebook is gradually changed to track time-varying source statistics by dynamically updating some of the codevectors. The partial distortion of a codevector, defined as the product of the average distortion when a particular codevector is selected and the probability that selection occurs, is used as a measure to determine which codevectors are updated. Codevectors with small partial distortion are deleted from the codebook, and those with large partial distortion are shifted or split so that the input vectors that are mapped into those codevectors are quantized more finely to give smaller partial distortions. Experimental results illustrate the application of this adaptive vector quantizer to image coding.

关键词： Vector quantization Statistics Distortion measurement Buffer storage Block codes Size measurement Probability Particle measurements Books Image coding

来源：评论

学校读者我要写书评

暂无评论

Pulsed electro-acoustic method for the measurement of volume charges in E-beam irradiated PMMA

Pulsed electro-acoustic method for the measurement of volume...

引用

Conference on electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： T. Maeno H. Kushibe T. Takada C. M. Cooke Tokyo Toshi Daigaku - Yokohama Campus Yokohama Kanagawa JP Massachusetts Institute of Techology Department of Electrical Engineering and Computer Science High Voltage Research Laboratory Laboratory for Electromagnetic and Electronic Systems Cambridge MA 02139

The measurement of volume charges within insulators has been attempted by various methods, including thermal, optical, mechanical, and electrical stimulation of the sample. A new method incorporating pulse electrical stimulation and pulsed acoustic detection is reported here. This technique is an extension of a previously reported [1] high frequency AC steady state electro-acoustic measurements in which electric fields at an electrode surface are determined by measuring the AC high frequency vibration of the electrode in response to a DC plus high frequency AC excitation. The use of pulse operation allows the measurements of time domain delay information which yields the spatial distribution of the volume charge.

关键词： Electrodes Electric fields Radiation effects Acoustics Acoustic measurements Frequency measurement Mathematical model

来源：评论

学校读者我要写书评

暂无评论

Optically Controlled Microwave Devices and Circuits

Optically Controlled Microwave Devices and Circuits

引用

Microwave, MTT-S International Symposium

作者： P.R. Herczfield A.S. Daryoush V.M. Contarino A. Rosen Z. Turski A.P.S. Khana Department of Electrical and Computer Engineering Drexel University Philadelphia PA USA David SanOff Research Laboratory RCA Advanced Technology Laboratories Princeton NJ USA LORAL ATL Lanham MD USA

There is a growing interest in optically controlled microwave devices and systems. This paper is concerned with two experiments in this emerging area. The first describes the design, fabrication and application of optically controlled microwave PIN diodes. The utilization of these devices for phase-shifting and switching at X-band was demonstrated. The second experiment involved the optical tuning and indirect optical injection locking of a X-band dielectric resonator oscillator. A locking range of 400 KHz was achieved utilizing a third harmonic.

关键词： Optical devices Optical control Microwave devices Microwave circuits Optical resonators Injection-locked oscillators Control systems Optical design Optical device fabrication Optical tuning

来源：评论

学校读者我要写书评

暂无评论

A Practical Robustness Theorem for Adaptive Control

A Practical Robustness Theorem for Adaptive Control

引用

American Control Conference (ACC)

作者： Charles E. Rohrs Gunter Stein Karl J. Astrom TelLaboratories Research Laboratory South Bend IN and Department of Electrical Engineering University of Notre Dame Notre Dame IN USA Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA Systems and Research Center Honeywell Inc. Minneapolis MN USA Department of Automatic Control Lund Institute of Technology Lund Sweden

In this paper, two theorems are quoted which, when applied together, provide much information about the robustness of adaptive control schemes. From these two theorems, another theorem is developed which can explain why adaptive controllers can perform robustly in certain practical situations, while possibly failing in other situations. In particular, if the bandwidth constraints on a control systems are lenient enough to allow the use of a sampling frequency which is smaller than the frequency at which unstructured uncertainty becomes significant, an adaptive controller can behave robustly. Many, if not all, of the applications of adaptive control which have been successful employ relatively slow sampling of the process. Thus, the results of this paper provide a theoretical explanation of how certain adaptive controllers are performing robustly in practice. In addition, the final theorem is of a form which provides insight into what a priori knowledge is required to achieve robust adaptive control and how this knowledge say be used.

关键词： Robust control Adaptive control Uncertainty Frequency Sampling methods Programmable control Control systems Transfer functions Automatic control Bandwidth

来源：评论

学校读者我要写书评

暂无评论

A REDUCED STRUCTURE OF THE FREQUENCY-DOMAIN BLOCK LMS ADAPTIVE DIGITAL-FILTER

引用

PROCEEDINGS OF THE IEEE 1984年第12期72卷 1816-1818页

作者： LEE, JC UN, CK Department of Electrical Engineering and Computer Science and Electronics Research Laboratory Korea Advanced Institute of Science and Technology Seoul South Korea

In this letter, it is shown that the frequency-domain block LMS (FBLMS) adaptive digital filter (ADF) for the block length of one reduces to the frequency-domain LMS (FLMS) ADF. Using the relation between the two convergence factors of the FBLMS and FLMS ADFs, it is possible to predict the steady-state performance of the former from that of the latter.

关键词： Least squares approximation Digital filters Frequency estimation Probability Sensor arrays Multiple signal classification Signal processing algorithms Entropy Adaptive signal processing Array signal processing

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：