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.     

等离子点火装置在1913T／H超临界锅炉上的应用

介绍了等离子点火装置的原理和系统，通过对等离子点火技术控制、运行的研究和完善，成功地实现了无油点火启动，节约了大量燃油，产生了较大的经济效益和社会效益．     

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。     

基于小波子带模型匹配的同水域下目标探测

针对水下声呐目标搜寻过程中环境复杂、成像分别率低、人工识别目标困难等实际问题,提出基于双树双密度复小波子带模型匹配的方法自动判别水下目标有无。首先利用双树双密度复小波对所传回待测声图进行分解得到不同方向子带,接着采用三参数广义Γ函数对不同方向子带系数分布拟合作为特征项,最后利用含有目标声图与背景声图在分布特征上存在差异性,根据计算两者间KL距离进行相似度匹配并通过设定最优门限对声图目标有无自动判别。实验证明,利用所提出方法对含有多目标声呐图像判别,其检测品质因子达97.2%,并在不同噪声水平下其检测品质因子对比其他方式平均高出10%,具有较高的检出率和一定鲁棒性。     

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。     

西门子PCS7在600T/H CFB锅炉中的应用

研讨西门子DCS过程控制系统PCS7的热电厂解决方案,给出硬件软件和网络的应用解析。     

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.     

高压硅堆中电压分布规律的研究

生产高压硅堆时,经常在元件之间不采取均压措施,认为各元件会自动按照拐弯电压值的比例关系来分担电压,或者认为硅堆内部足够自我保护。根据大量试验论证,作者认为这种观点是错误的,是高压硅堆工作不可靠的根源。最后提出了改进办法。     

Analysis and simulation of distributed T/H with averaging technique in folding and interpolating A/D converters

Distributed track‐and‐hold (T/H) circuit is widely used in folding and interpolating analog‐to‐digital (A/D) converters as a good candidate of single T/H circuits for an optimum overall system performance. But, rigorous analysis and method for design do not exist. This paper brings averaging network to suppress the random offset voltages of the differential difference pre‐amplifiers (DDPAs), which locate before T/H circuit featuring two differential inputs for the requirement of fully differential A/D converters. The first contribution of this work is to present the exact expressions for the output voltage and gain in S‐domain, the integral nonlinearity (INL) and differential nonlinearity (DNL) in DDPAs through the further insight into this architecture. Furthermore, distortion resulting from settling time limitation, interpolation error, folder offset, and all sources of mismatch in averaged DDPAs is considered. In addition, the figure of merit for INL and DNL is proposed to quantify the effectiveness of averaging and be served as the guideline for the optimum design. Finally, these theoretical results were verified against Hspice simulations from a design example of distributed T/H circuits for 8‐bit 250 MHz folding and interpolating A/D converter, which confirmed the accurate and exhaustive analysis and exhibited a good agreement. Copyright © 2009 John Wiley & Sons, Ltd.     

考虑天然气混氢的园区综合能源系统电制氢优化配置

电制氢和天然气混氢技术在促进可再生能源消纳、降低系统碳排放量方面具有良好的理论研究和工程应用前景。面向含高比例可再生能源的园区综合能源系统,提出一种计及天然气混氢及跨季节存储的电制氢优化配置方法。首先梳理了含氢园区综合能源系统的运行框架和能量流动关系,建立园区内部能源生产、转换与存储设备的数学模型,其次以设备的年化投资成本、园区综合能源系统的年度运行成本和碳交易成本最优为目标,提出电制氢优化配置模型。最后通过算例分析表明电制氢及天然气混氢技术的引入可提升可再生能源的消纳能力,降低系统的整体经济成本和碳排放量,并分析了电解槽投资成本、混氢体积分数上限以及经济性和低碳性成本权重系数变化对规划运行结果的影响。关键词：园区综合能源系统;电制氢;天然气混氢;碳交易;跨季节储氢;优化配置 中图分类号：TM732     

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.