The statistics of NBTI-induced V/sub T/ and /spl beta/ mismatch shifts in pMOSFETs

Negative bias temperature instability (NBTI) is a pFET degradation mechanism that can result in threshold voltage shifts up to 100 mV or more, even in very thin oxide devices. Since analog circuits that utilize matched pairs of devices, such as current mirrors and differential pairs, generally depend on V/sub T/ matching considerably better than this, NBTI-induced V/sub T/ mismatch shift may represent a serious reliability concern for CMOS analog applications. Furthermore, induced /spl beta/ mismatch shift (affecting drain current level at a fixed gate overdrive voltage) may also impact drain current and transconductance mismatch. In this paper, experimental results of the statistics and scaling properties of NBTI-induced V/sub T/ and /spl beta/ mismatch shifts in saturation, and models describing these results, are presented.     

A theoretical investigation of the characteristic temperature T/sub 0/ for semiconductor lasers

The temperature dependence of the characteristic temperature T/sub 0/ of semiconductor quantum-well lasers is investigated using detailed simulations. The critical-temperature-dependent processes are the optical gain and the nonradiative recombination. The gain model is based on k /spl middot/ p theory with the multiple quantum wells in the active layer represented by a superlattice. The Auger process is assumed to be thermally activated. It is shown that, with inclusion of the continuum state filling and interband mixing, the most important features experimentally observed in the temperature dependence of the T/sub 0/ value can be explained. The continuum state filling and band nonparabolicity cause a significant deviation from the ideal linear carrier density versus temperature relation for quantum wells. The results are compared to experiment for broad area devices lasing at 980 nm and 1.3, and 1.55 /spl mu/m, and show good agreement over a broad range of temperature.     

Gas-flow Simulation with contact moving in GCB considering high-pressure and high-temperature transport properties of SF/sub 6/ gas

This paper addresses a thermal gas-flow simulation in gas circuit-breaker (GCB) chambers, introducing SF/sub 6/ gas constants up to a pressure of 10 MPa and to a temperature of 30 000 K. In the simulation, moving parts, such as nozzle, movable arcing contact, and operating rod, are moved with the opening motion of GCB to see if different results are produced from the conventional simulation method, in which fixed parts in the real GCB are moved. As a result, as far as the pressure profile in the puffer chamber is concerned, it is confirmed that this simulation method can produce better results than the conventional method for the hybrid-puffer-type chamber.     

Comparative study on the spectroscopic properties of Nd:GdVO/sub 4/ and Nd:YVO/sub 4/ with hybrid process

We have proposed a hybrid procedure for determining spectroscopic parameters for uniaxial solid-state laser crystals. Using our procedure, the spectroscopic properties of Nd:GdVO/sub 4/ were evaluated and compared to those of Nd:YVO/sub 4/. As a result, the peaks of absorption and stimulated emission cross sections of Nd:GdVO/sub 4/ in /spl pi/-polarization were determined to be 2.6 and 10.3/spl times/10/sup -19/ cm/sup 2/, respectively, and were smaller than those of Nd:YVO/sub 4/. On the other hand, the fluorescence lifetime of 1 at% Nd:GdVO/sub 4/ was evaluated to be 83.4 /spl mu/s, and was similar to 84.1 /spl mu/s of 1 at% Nd:YVO/sub 4/. Therefore, the product of stimulated emission cross section and fluorescence lifetime (/spl sigma//sub em//spl tau//sub f/ product) of Nd:GdVO/sub 4/ was smaller than that of Nd:YVO/sub 4/ under 1 at% of Nd/sup 3+/ doping concentration. The radiative lifetime of spontaneous emission of Nd:GdVO/sub 4/ was 168 /spl mu/s and was 1.9 times longer than that of Nd:YVO/sub 4/. Because of the low value of radiative quantum efficiency of Nd:GdVO/sub 4/ (50%), careful cavity design is required for creating a well performing solid-state laser with Nd:GdVO/sub 4/, based on the larger /spl sigma//sub em//spl tau//sub f/ product rather than the /spl sigma//sub em//spl tau//sub f/ product of Nd:YAG.     

An integrated model for the study of flicker compensation in electrical networks

This paper presents an integrated model for the simulation of the voltage flicker introduced to a power system due to an arc furnace operation. The model was developed for power system planning purpose in the ATP computational environment. It can be adjusted to the desired operation conditions so as to correctly simulate the furnace operation stages (melting or refining stage) and the expected furnace's degree of flicker severity, for each particular arc furnace and power system combination. Chua's oscillator circuit is used to achieve the chaotic nature behavior of the arc voltage and a Static Var Compensator (SVC) is used for flicker compensation. Modeling and simulation of the full package, including an IEC flickermeter used to evaluate flicker severity, are presented.     

浓淡燃烧器在220T/H锅炉上的应用

太原第二热电厂3＃炉在低负荷下稳燃能力较差,后采用浓淡燃烧器进行了改造。由于该燃烧器稳燃效果好,增强了煤种和负荷的适应性,经济效果显著。     

650T/H直流锅炉稳参数启动分析

捷制650T／H直流锅炉每次启动在投第一套制粉系统时，屏过壁温难以控制，摆动幅度很大。为此制定出新的启动方案，从而加以稳定启动参数。     

DG420t/h锅炉高温过热器结渣原因分析

针对广东某电厂锅炉过热器段严重结焦的现状,采用FLUENT数值模拟和现场实验的方法进行研究,通过对燃烧的煤种、脱硫剂的投用等方面进行分析,认为脱硫剂的大量连续使用和燃用劣质煤是造成过热器段严重结渣的原因,从而提出减弱结焦的对策,使锅炉结焦现象得到一定缓解。     

High-power continuous-wave intracavity frequency-doubled Nd:GdVO/sub 4/-LBO laser under diode pumping into the emitting level

The continuous-wave high power laser emission of Nd:GdVO/sub 4/ at the fundamental wavelength of 1.06 /spl mu/m and its 531-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 808 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 5/2/ transition) and 879 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 3/2/ transition). It is shown that, in spite of a lower absorption at 879 nm, the infrared emission is comparable under these two wavelengths of pump. The green emission performances were, however, improved by the 879 nm pump: 5.1 W at 531 nm with M/sup 2/=1.46 and 0.31 overall optical-to-optical efficiency was obtained from a 3-mm-thick 1-at.% Nd:GdVO/sub 4/ laser medium and a 10-mm-long LBO nonlinear crystal in a Z-type cavity for 16.5 W pump power. In similar conditions, the maximum green power for the 808 nm pump was 4.4 W, with 0.26 overall optical-to-optical efficiency and M/sup 2/=3.40 beam quality; at this pump wavelength the green emission shows evident saturation for pump power in excess of 9.9 W. This behavior is connected with the enhanced heat generation under 809-nm pumping, as evidenced by the increased thermal lensing of the fundamental emission. A careful alignment of the laser enables emission almost free of chaotic intensity fluctuations.     

Influence of doping concentration on the power performance of diode-pumped continuous-wave Tm/sup 3+/:YAlO/sub 3/ lasers

We investigated the effect of thulium ion concentration on the continuous-wave (CW) power performance of diode single-end-pumped thulium-doped YAlO/sub 3/ (Tm:YAP) lasers. Three samples with 1.5%, 3%, and 4% Tm/sup 3+/ concentration were examined at 18/spl deg/C. Lifetime and fluorescence measurements were further performed to assess the strength of cross relaxation and nonradiative decay. Our results showed that in single-end-pumped configurations, the best CW power performance was obtained with the 1.5% Tm:YAP sample, and laser performance of the samples degraded monotonically with increasing Tm/sup 3+/ concentration. By using 9.5 W of incident pump power at 797 nm, a maximum of 1430 mW of output power was obtained with the 1.5% Tm:YAP sample and 2% output coupler. We discuss how the effects of cross relaxation, reabsorption, nonradiative decay, and internal heating vary with increasing concentration. Spectroscopic measurements and rate-equation analysis suggest that cross relaxation should already be effective in samples with 1.5% Tm/sup 3+/ ion concentration and doping concentrations larger than 4% will lead to degradation in power performance due to higher nonradiative decay rates and larger reabsorption losses.     

In vivo localized1 H spectroscopy of the rat eye at 7 T: preliminary studies

Preliminaryin vivo proton spectroscopic studies of the posterior chamber of the rat eye have been undertaken at 7 T. The Spatial and Chemical shift encoded Excitation (SPACE) localization sequence was used to acquire signals from 10-µl voxels and demonstrate the presence of metabolites associated with the vitreous humor, lens, retina, and the optic nerve. LocalizedT ₂ andT ₁ measurements of water in the vitreous humor indicate a relatively fluid environment. Susceptibility maps are used to demonstrate the difficulties ofin vivo spectroscopic investigations in the anterior regions of the eye. Comments are made concerning the implications for spectral resolution in these regions.     

System of closing relations of a two-fluid model for the HYDRA-IBRAE/LM/V1 code for calculation of sodium boiling in channels of power equipment

The system of equations from a two-fluid model is widely used in modeling thermohydraulic processes during accidents in nuclear reactors. The model includes conservation equations governing the balance of mass, momentum, and energy in each phase of the coolant. The features of heat and mass transfer, as well as of mechanical interaction between phases or with the channel wall, are described by a system of closing relations. Properly verified foreign and Russian codes with a comprehensive system of closing relations are available to predict processes in water coolant. As to the sodium coolant, only a few open publications on this subject are known. A complete system of closing relations used in the HYDRA-IBRAE/LM/V1 thermohydraulic code for calculation of sodium boiling in channels of power equipment is presented. The selection of these relations is corroborated on the basis of results of analysis of available publications with an account taken of the processes occurring in liquid sodium. A comparison with approaches outlined in foreign publications is presented. Particular attention has been given to the calculation of the sodium two-phase flow boiling. The flow regime map and a procedure for the calculation of interfacial friction and heat transfer in a sodium flow with account taken of high conductivity of sodium are described in sufficient detail. Correlations are presented for calculation of heat transfer for a single-phase sodium flow, sodium flow boiling, and sodium flow boiling crisis. A method is proposed for prediction of flow boiling crisis initiation.     

BEVs/PHEVs动态V2B技术在智能电网中的应用

电动汽车向楼字反向服务(vehicle-to-building,简称V2B)为使用电动汽车自身电池的储能供应电网负荷提供了一个选择.国内外很多研究人员已经证明,电动汽车向电网反向服务(Vehicl-to-grid,简称V2G)有很多潜在的好处.但由于各种实践原因,这一概念被预测在将来5～10年的时间广泛应用.而V2B作为一个新提出的概念,在实践上比V2G要更容易实现,预计3～5年的时间就可实现.提出利用纯电动汽车(BEVs)和可插电混合动力汽车(PHEVs)所携带的电池,作为动态配置的分散储能系统,将交通系统和电力系统通过“智能车库”有机地结合起来,以实现V2B技术.根据智能车库提供的数据,基于BEVs和PHEVs车载电池储能充放电的V2B技术可实现智能电网里的需求侧管理(DSM),并用仿真结果验证了V2B的可行性.     

台山1750MW发电机定子绕组绝缘耐压放电问题分析

台山核电1号主发电机在东方电机厂进行定子下线后,在104k V直流耐压试验时,绕组端部相间引线绝缘发生放电,虽经修复及临时绝缘加固处理,仍未能通过试验。综合考虑1号机生产进度及绝缘安全性,确定加固绝缘,并通过1.5Un(40.5k V)交流耐压试验,以满足型式试验对绝缘耐压考核的要求,将端部绝缘修复及104k V直流耐压试验调整至型式试验结束后处理。修复完成的端部绝缘,顺利通过了104k V直流耐压试验及55k V交流出厂耐压试验考核,验证了定子的绝缘性能满足设计要求。本文通过介绍台山1750MW发电机的端部结构及绝缘操作工艺探讨耐压试验产生放电的原因,并制定最终的绝缘修复方案。     

T/P91钢焊接问题探讨

对T/P 91钢焊接中存在的问题进行了探讨。由于对焊接规范掌握不当、对焊接热处理工艺的理解存在误区影响了T/P 91钢的焊接质量,大电流加慢焊速的操作手法使T/P 91钢焊接接头性能劣化,预热温度太高,降低了该钢材焊接接头在室温时的冲击韧性。焊接热处理工艺中对温度的监控必须准确,否则就达不到要求的回火性能。DL/T 869-2004《火力发电厂焊接技术规程》对T/P 91钢焊后的组织和硬度的规定不够详细,需进一步完善。     

电厂用高压大型异步电机变频调速经济效益和技术问题分析

本文在广泛调研的基础上，综述了国内外电厂用变频调速装置开发生产状况和技术特点及所取得的技术经济效果。分析了我国研制开发适合电厂使用的高压大型变频调速装置的技术经济意义和社会经济效益以及需解决的主要技术问题。     

Transmit/receive headcoil for optimal <Superscript>1</Superscript>H MR spectroscopy of the brain in paediatric patients at 3 T

¹H magnetic resonance (MR) spectroscopy is a useful tool to obtain metabolic information from the brain in paediatric patients. To detect signals of metabolites at low concentrations or from small volumes, the signal-to-noise ratio (SNR) has to be optimized. The SNR can be increased by going to higher field strengths. However, this leads to higher spectral bandwidths, which increases the chemical shift artefact. Here we present a transmit/receive headcoil which is adapted to the dimensions of the paediatric head and enables PRESS localization with high radio-frequency (RF) bandwidths that minimize the chemical shift displacement to only 5%. In addition, since the pulse lengths are shorter with higher RF bandwidths, the echo time can be reduced to 10 ms improving SNR as well.Parts of this work have been presented at the European Society for Magnetic Resonance in Medicine and Biology in Rotterdam in 2003     

新疆高温差地区750kV电抗器用金属波纹式储油柜选型及T/H曲线矫正计算

在介绍750kV金属波纹管内油式储油柜结构和原理的基础上,分析了新疆地区某750kV变电站高压并联电抗器所使用的金属波纹式储油柜在高温差环境下油位变化规律和加补充油工作存在的问题,论证了储油柜选型的正确性,矫正了储油柜油位温度曲线,并提出了运行维护建议。     

新型光电光热系统的封装工艺及经济性研究

用一种热阻小、散热快的5052型铝合金代替常规光伏组件背板材料,将这种背板材料的光伏组件与不锈钢扁合流道用导热硅胶粘接成新型光伏光热一体化(PV/T)系统,并对该系统封装工艺及环境效益进行了探讨。此外,比较分析了新型PV/T系统、独立光伏系统及独立平板集热器的经济性,得出新型PV/T系统在投资上较其它两个系统具有费用少、占地面积减半、回收年限介于二者之间等优势,能为今后PV/T系统规模化生产及市场推广提供一定参考。