Degradation Uniformity of RF-Power GaAs PHEMTs Under Electrical Stress

We have studied the electrical degradation of RF-power PHEMTs by means of in situ 2-D light-emission measurements. Electroluminescence originates in the recombination of holes that have been generated by impact ionization. The local light intensity, thus, maps the electric-field distribution at the drain side of the device. This allows us to probe the uniformity of electrical degradation due to electric-field-driven mechanisms. We find that electrical degradation proceeds in a highly nonuniform manner across the width of the device. In an initial phase, degradation takes place preferentially toward the center of the gate finger. In advanced stages of degradation, the edges of the device degrade at a preferential rate. We identify the origin of this behavior as a small systematic nonuniformity in the recess geometry that impacts the magnitude of the electric field on the drain of the device. Our research suggests that a close examination of the width distribution of electric field in RF-power PHEMTs (and FETs in general) is essential to enhance their long-term reliability.     

Selective Area Metal–Organic Vapor Phase Epitaxy of Nitride Semiconductors for Multicolor Emission

Selective area metal–organic vapor phase epitaxy (SA-MOVPE) allows in-plane control of emission wavelength by tailored width of masks. For InGaN/GaN multiple quantum wells (MQWs), modulation of luminescence wavelength was achieved based on a balance between vapor-phase diffusion of group-III precursors and their surface incorporation. For the basic understanding of the SA-MOVPE of nitride semiconductors, thickness profiles of GaN, InN, AlN, and InGaN layers around relatively wide (≫ $10, mu$m) masks were investigated. The effective lateral diffusion length $D/k_{s}$, which is the ratio of the vapor-phase mass diffusivity of a precursor to its surface incorporation rate constant, was extracted for GaN and InN. The value was much larger for InN due to smaller surface incorporation rate. In the SA-MOVPE of InGaN bulk layer at around $800^circ$C, indium incorporation rate seems to be limited by the surface flux of a gallium precursor, resulting in no variation in the indium content. Varied width of the InGaN wells by the existence of masks seems to govern the shift in the luminescence wavelength from InGaN/GaN MQWs. Therefore, design of the thickness distribution of GaN based on the quantitative model is essential to the controlled in-plane color modulation of solid-state lighting devices using SA-MOVPE.      

G&W金属应力锥电缆终端故障原理分析及对策

GW金属应力锥电缆终端为美国GW电气公司制造主要应用于110 kV及以上电压等级的产品,在我国电力行业内应用范围较广。而从近两年来北京电网故障分析可以看出,GW型高压电缆终端接头故障率有明显上升趋势,为此从华北地区电缆终端故障原因进行分析,结合作者所在国华北京热电分公司GIS电缆出线终端老化分析经验及应对措施,提出了一套高压电缆终端维护和反事故对策,以期对相关电力单位所属高压电缆终端维护工作提供借鉴与帮助。     

TLM‐based solutions of the Klein–Gordon equation (Part I)

The transmission line matrix (TLM) method has become well established as a numerical solution scheme for wave problems in electromagnetics and, to a lesser extent, in acoustics and mechanics. It has also been applied to diffusion/heat‐conduction problems. Here the technique is extended to solving the Klein–Gordon equation that arises in Quantum Mechanics and in the dynamics of an elastically anchored vibrating string. In Part I, two novel, TLM‐based algorithms are presented and verified. By considering them as solving a special case of the more general ‘forced’ wave equation, they illustrate how, with care, the TLM algorithm can be adapted to model a wide range of effects. Copyright © 2001 John Wiley & Sons, Ltd.     

TLM‐based solutions of the Klein–Gordon equation (Part II)

In Part I, two TLM‐based solutions were presented for the Klein–Gordon Equation in its basic form, with the TLM pulses representing the primary variable. In Part II, two further approaches are presented in which the TLM pulses now represent derivatives of the primary variable, with respect to either space or time. As in Part I, the two solution schemes were verified symbolically and numerically. They illustrate further ways to extend the power of TLM beyond its traditional application areas. Some of these areas are discussed briefly. Copyright © 2002 John Wiley & Sons, Ltd.     

Dynamic mixed serial–parallel content addressable memory (DMSP CAM)

A novel dynamic mixed serial–parallel content addressable memory (DMSP CAM) is proposed to achieve both low‐power consumption and high performance. The replica circuits provide optimal timings to enable and disable the matchline charge transistor, which maximizes performance and minimizes leakage current, respectively. The DMSP CAM does not suffer from charge sharing in the serial stage and achieves high performance by removing the predischarge or precharge operation of the matchline before every comparison. To guarantee the robustness of the proposed scheme, a statistical design methodology is also applied. Using the 45‐nm technology, the DMSP CAM achieves both energy saving and performance improvement, and thus over 53% energy‐delay product reduction compared with the other serial–parallel mixed CAMs. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigation of the nonlinearity properties of the DC I-V characteristics of metal-insulator-metal (MIM) tunnel diodes with double-layer insulators

The DC I-V characteristics of metal-insulator-metal (MIM) tunnel diodes with double insulator layer is investigated by means of computer simulations. Simulation results on the properties of the diode characteristics such as resistance and quality factor are presented in various diagrams and the dependences on the different diode parameters are discussed. The simulations algorithm applied is also described in brief.     

浅谈小功率金卤灯色温(下)

<正>(续上期)4金卤灯色温的控制事实告诉我们,填充某标准色温金属填充物的金卤灯在制作完成后色温存在较大偏差。如何更好地控制金卤灯的色温,已经成为同行业一致追求的目标。金卤灯制作过程中的每一道工序都与色温有着密切的关系。笔者曾对70W石英金卤灯的色温做过     

An analytical model of triple‐material double‐gate metal–oxide–semiconductor field‐effect transistor to suppress short‐channel effects

This paper presents an analytical subthreshold model for surface potential and threshold voltage of a triple‐material double‐gate (DG) metal–oxide–semiconductor field‐effect transistor. The model is developed by using a rectangular Gaussian box in the channel depletion region with the required boundary conditions at the source and drain end. The model is used to study the effect of triple‐material gate structure on the electrical performance of the device in terms of changes in potential and electric field. The device immunity against short‐channel effects is evaluated by comparing the relative performance parameters such as drain‐induced barrier lowering, threshold voltage roll‐off, and subthreshold swing with its counterparts in the single‐material DG and double‐material DG metal–oxide–semiconductor field‐effect transistors. The developed surface potential model not only provides device physics insight but is also computationally efficient because of its simple compact form that can be utilized to study and characterize the gate‐engineered devices. Furthermore, the effects of quantum confinement are analyzed with the development of a quantum‐mechanical correction term for threshold voltage. The results obtained from the model are in close agreement with the data extracted from numerical Technology Computer Aided Design device simulation. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of Water Tree Degradation in Dry‐Cured and Extruded Three‐Layer (E‐E Type) 6.6‐kV Removed XLPE Cables

Dry‐cured and extruded three‐layer (E‐E type) 6.6‐kV cross‐linked polyethylene (XLPE) cables were introduced into electric power systems more than 30 years ago, but they do not experience failures because of water tree degradation. Also, the degradation index of water treeing for these cables has not been established. Therefore, investigating results of residual breakdown voltage and water tree degradation of these cables will help us plan for cable replacement and determine water tree degradation diagnosis scheduling, and will be fundamental data for cable lifetime evaluation. In this study, the authors measured the ac breakdown voltages of dry‐cured and E‐E type 6.6‐kV XLPE cables removed after 18 to 25 years of operation and observed the water trees in their XLPE insulation. As a result, it was observed that breakdown voltages were larger than the maximum operating voltage (6.9 kV) and the ac voltage for the dielectric withstanding test (10.3 kV). Water trees were mainly bow‐tie water trees and their maximum length was approximately 1 mm. Although the number of measured cables was limited, the lifetime of this type of cable was estimated to be approximately 40 years, even experiencing water immersion.     

一起串补MOV的故障分析

对一起串补MOV设备在运行过程中发生的故障进行了分析。对串补MOV进行外观检查、电气试验,分析了MOV的设计要求,分析了故障录波,开展了故障仿真分析,发现某支MOV在区外故障时发生故障,导致了电容器组对故障MOV放电,MOV过电流保护动作,而GAP拒触发保护动作。针对此次故障提出不可随意更换单支MOV,及早整组更换运行年限久、性能裂化的MOV设备,以提高设备的运行可靠性。     

金属氧化锌避雷器(MOA)的在线监测及故障诊断

MOA 阀片温度上升,严重时将导致MOA 损坏或爆炸, 引发大面积停电事故。因此, 监测其运行状态非常重要。MOA 的在线监测方法中全电流法、三次谐波法、谐波补偿法和基波法各有弊益, 同时需重视2 个干扰源: 电压波动的影响和间谐波的影响。在诊断中, MOA 泄漏电流的阻性分量是其运行状况的良好指标, 利用模拟信号法时, 交流电网中即使不需要任何电压信号也可以进行测量, 此方法值得推荐监测现有避雷器的劣化; 阀片温度能精确地显示避雷器的运行参数, 能为避雷器的电气老化、工作电压和暂态过电压下的功耗提供详细信息, 避免发生热崩溃, 及时释放避雷器能量。温度监测有望成为避雷器监测的标准方法。     

Evaluation of the degree of deterioration of circuit‐breaker insulators using chemical analysis and the Mahalanobis–Taguchi (MT) method

We have developed a novel evaluation technique of the deterioration degree of insulators for breakers using a chemical analysis and the Mahalanobis–Taguchi (MT) method. It is possible to evaluate the deterioration degree with great accuracy and nondestructively on‐site by this technique without the effect of humidity and external noise such as electromagnetic waves. The mechanism of the insulator's surface resistivity reduction was clarified, and it was found that the deterioration degree of insulators could be evaluated by this technique because a linear relationship existed between the results judged by the MT method and the actual measurement results for the surface resistivity. In comparison to electrical methods, such as partial electric discharge and megohmmeters, the evaluation accuracy has been improved by three digits and the range of the deterioration degree that could be evaluated was expanded by seven digits. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 11–20, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20849     

An adaptive controller–observer scheme for temperature control of non‐chain reactions in batch reactors

In this paper an adaptive controller–observer temperature control scheme is developed for a class of irreversible non‐chain reactions taking place in batch reactors. The scheme is based on a nonlinear observer for the estimation of the heat released by the reaction, where the heat transfer coefficient is adaptively estimated. Tracking of the desired reactor temperature is achieved via a two‐loop control scheme, where an independent adaptive estimate of the heat transfer coefficient is used as well. Remarkably, the observer and the controller can be designed and tuned separately. The convergence of both the nonlinear observer and of the overall controller–observer scheme is analyzed by resorting to a Lyapunov‐like argument. A comparative simulation case study is developed to test the performance of the proposed scheme and compare it with other approaches already known in the literature. Copyright © 2007 John Wiley & Sons, Ltd.     

Behavior of MV Insulators Under Lightning-Induced Overvoltages: Experimental Results and Reproduction of Volt–Time Characteristics by Disruptive Effect Models

This paper presents the results of experimental tests performed with an impulse voltage of short tail (STLI: 1.2/4 ?s), similar to lightning-induced overvoltages, on composite insulators used in the electric traction lines. The characteristics of volt-time breakdown under STLI waves are shown and compared with the characteristics obtained under standard lightning impulse (LI:1.2/50 ?s). Models based on the disruptive effect, as proposed by Kind and Chowdhuri, are considered and applied in order to reproduce the volt-time characteristics under standard and nonstandard lightning voltages. The application viability of these models to tested insulators is considered and discussed and the accuracy in their reproduction is evaluated. It is demonstrated that the Kind model, calibrated with a suitable selection of the parameters using standard flashover data (LI), is able to estimate the response of the insulators to the short tail lightning impulses (STLI) with satisfactory accuracy.     

An accurate power delivery system (PDS) design methodology for high‐speed digital systems

The trend in high‐speed digital circuits is to increase speed and density and to operate at lower voltage. This fast increase in the switching speed combined with the decrease of the operating voltage causes the allowable absolute voltage variations to decrease, which makes the PDS design a more challenging task than ever. Moreover, the complex 3D nature of the modern PDS causes it to be more sensitive to capacitors' placement as well as capacitance value. In this paper, we introduce an efficient complete solution for the design of high‐speed digital PDS. This solution (a) takes the effects of the decoupling capacitor placement into consideration through a 3D electromagnetic simulation of the PDS, (b) defines a more‐realistic PDS design target, and (c) presents a clear capacitor value selection methodology. Finally, we applied our methodology to an industrial test case, compared its results with that of industrial design, and showed its advantages. Copyright © 2010 John Wiley & Sons, Ltd.