电流连续性方程离散技术优劣判据

本文提出了一套判断电流连续性方程离散技术优劣的基本判据,为选择合适的离散方法提供了依据,并根据这套判据,提出了一种新的有限差分方法。误差分析和数值实验结果都表明,该方法优于不完全满足基本判据的SG方法和SUPG方法。     

电流连续性方程离散技术优劣判据

本文提出了一套断电流连续性方程离散技术优劣的基本判据，为选择合适的离散方法提供了依据，并根据这套判据，提出了一种新的有限差分方法，误差分析和数值实验结果都表明，该方法优于不完全满足基本判据的ＳＧ方法和ＳＵＰＧ方法。     

气体回热式制冷机的数值分析方法

气体回热式制冷机的数值分析方法中科院低温技术实验中心王超，周远本文发展了一种具有通用性的气体回热式制冷机的数值分析方法，建立了数值模拟的控制方程组，提出制冷机空间离散方法和控制方程组离散以及求解方法。文中以斯特林、脉冲管和Ｇ—Ｍ制冷机为例，给出不同机...     

具有高容量稳定存贮的加权神经网络

根据离散神经网络动力学过程中的系统能量演化的趋势，提出利用汉明距离构造高容量离散联想神经网络的设想，并用计算机进行数值模拟，给出了一些结果。     

室温下Si/Si1-xGex共振隧穿二极管的数值模拟

采用量子水动力学(QHD)模型模拟了35nm Si/Si1-xGex空穴型共振隧穿二极管(RTD)在室温下的I-V特性.模拟过程中,引入second upwind,Schafetter-Gummel(SG)和二阶中心差分法相结合的离散方法对方程组进行离散,保证了结果的收敛性.还模拟了不同的器件结构,对结果的分析表明器件的势垒厚度和载流子有效质量都会对RTD的负阻效应产生影响.在室温下(T=293K),当x=0.23时,模拟结果的峰谷电流比为1.14,与实验结果相吻合.     

室温下Si/Si1-xGex共振隧穿二极管的数值模拟

采用量子水动力学(QHD)模型模拟了35nm Si/Si1-xGex空穴型共振隧穿二极管(RTD)在室温下的I-V特性.模拟过程中,引入second upwind,Schafetter-Gummel(SG)和二阶中心差分法相结合的离散方法对方程组进行离散,保证了结果的收敛性.还模拟了不同的器件结构,对结果的分析表明器件的势垒厚度和载流子有效质量都会对RTD的负阻效应产生影响.在室温下(T=293K),当x=0.23时,模拟结果的峰谷电流比为1.14,与实验结果相吻合.     

总变分图像复原方程的离散化方法

基于总变分的图像重建和复原导致一类最小化问题,它归结为解一个非线性椭圆型偏微分方程。为了得到数值解,必须将问题线性化和离散化。C.R.Vogel和M.E.Oman等人(1996)的定点迭代是一个良好的线性化方法。然而文献中已报道的离散化方法需要微分方程数值解的工具,比较繁杂。该文提出一种新的离散化方法,它只需要图像处理中的常规技术。图像反降晰和噪声抑制的实验结果表明该文的结果不亚于文献中报道的结果。     

赋形波纹喇叭模转换的数值计算

本文提出用三次样条函数来逼近赋形波纹喇叭模转换计算公式中模转换系数的数值方法，导出了喇叭辐射口多模透射系数和喇叭输入口多模反射波系数的离散化计算公式，较好地解决了这种喇叭模转换计算的难题，并得到了与实测值吻合一致的数值结果。     

基于天然气组分红外光谱图的数据预处理方法研究

利用红外光谱分析仪对天然气组分进行组分分析时所获得光谱信号往往会受杂散光、噪声、基线漂移等因素的干扰,从而影响最终定量分析结果,故需要在建模前对原始光谱进行预处理。为解决仪器测量光谱图的噪声干扰问题,本文提出一种Savitzky-Golay平滑法结合sym6小波函数软阈值去噪法对光谱图进行预处理。将传统的预处理方法与SG平滑法结合小波函数法进行对比分析。结果表明,以SG平滑法结合sym6小波函数软阈值去噪法对光谱图进行预处理,其拟合优度数值最高为0.98652,残差平方和数值最低为5.50694,证明使用该方法后的函数分峰拟合效果最佳,处理效果优于传统方法。     

LED产生局域空心光束的数值分析与实验

首次使用了离散傅里叶方法数值分析局域空心光束。用离散傅里叶方法描述单色平面波产生局域空心光束（bottle beam）的光强分布,引入色散公式使得一定频谱宽度的LED光源同样适用。讨论抽样要求并对变量进行离散化,导出LED产生bottle beam的离散化傅里叶公式。最后代入相关参数并用MATLAB进行数值模拟,得到了在不同距离处光束的强度分布。设计实验进行验证,实验结果表明:使用LED也能够产生高质量的bottle beam。数值模拟与实验结果基本吻合,证明了采用傅里叶方法可以精确地分析非相干光源产生bottle beam,并且相较于传统的标量衍射理论,它更加简洁、快速,是研究bottle beam的一种全新又可靠的方法。     

侧风效应和SG方法

本文分析了SG方法存在侧风效应的起因及其对SG方法的影响,为SG方法的应用提供了依据。     

Privacy-preserving data aggregation scheme against internal attackers in smart grids

With fast advancements of communication, systems and information technologies, a smart grid (SG) could bring much convenience to users because it could provide a reliable and efficient energy service. The data aggregation (DA) scheme for the SG plays an important role in evaluating information about current energy usage. To achieve the goal of preserving users’ privacy, many DA schemes for the SG have been proposed in last decade. However, how to withstand attacks of internal adversaries is not considered in those schemes. To enhance preservation of privacy, Fan et al. proposed a DA scheme for the SG against internal adversaries. In Fan et al.’s DA scheme, blinding factors are used in evaluating information about current energy usage and the aggregator cannot get the consumption information of any individual user. Fan et al. demonstrated that their scheme was secure against various attacks. However, we find that their scheme suffers from the key leakage problem, i.e., the adversary could extract the user’s private key through the public information. To overcome such serious weakness, this paper proposes an efficient and privacy-preserving DA scheme for the SG against internal attacks. Analysis shows that the proposed DA scheme not only overcome the key leakage problem in Fan et al.’s DA scheme, but also has better performance.     

大口径倒腔式等离子体开关

大口径倒腔式等离子体开关是神光Ⅱ升级装置倒腔式多程放大方案的关键单元,该方案要求等离子体开关能够在极短的时间内完成工作状态的转换。采用正负开关脉冲驱动的等离子体开关响应时间较长,无法满足装置的使用要求。基于Blumlein脉冲形成线结构的高压低阻抗开关脉冲发生器能够实现倍压输出,使单一脉冲驱动等离子体开关成为可能,从而大幅减小开关响应时间。单一脉冲驱动的350mm×350mm口径倒腔式等离子体开关理论充电时间约为54ns,其开关响应时间可做到小于90ns。实验测得的等离子体开关全口径开关效率大于99.7%,静态消光比大于381,时间窗口顶宽大于160ns,底宽小于400ns,上述指标均满足神光II升级装置的使用要求。     

基于SG3525的电机刹车系统电源设计

针对目前刹车系统电源存在的缺陷,介绍了一种以SG3525控制器为核心的刹车系统电源设计方案。采用SG3525芯片内部的主要结构,分析了其特性和工作原理。给出了该电源的设计方法及原理,并对系统进行了仿真测试。仿真结果表明,该系统具有较高的可靠性且输出电压稳定,在未来具有广泛的应用前景。     

一种太阳能电动车用开关电源的设计

设计了一种供太阳能电动车无刷直流电机控制模块使用的半桥型开关电源电路,在实现输出采样反馈的同时,利用SG3525芯片的关闭功能设计了过流检测电路,有效防止过电流或过电压对控制系统的危害。实验结果表明,该电路具有响应快、稳定性好、输出电压精度高等优点,很好地满足了太阳能电动车无刷直流电机控制模块的供电需求。     

GaAs MESFET旁栅效应与旁栅距的关系研究

旁栅效应是影响 Ga As器件及电路性能的有害寄生效应。本文研究了旁栅阈值电压 Vth SG与旁栅距 LSG的关系 ,发现 Vth SG的大小与 LSG成正比关系 ,并理论探讨了产生这一现象的机制 ,从而验证了旁栅阈值电压与旁栅距关系的有关理论。     

Dynamics modeling and deviation control of the composites winding system

During the composites winding process, running speed, tension fluctuation and other factors often lead to the tape deviation. To improve the winding precision and eliminate the running deviation, lateral dynamics of the tape winding is analyzed and mathematical model of the rectifying system is established. Then, a novel adaptive sliding mode controller (ASMC) is proposed, and principle of this control scheme is employing two fuzzy systems to approximate the nonlinear functions and utilizing another two fuzzy systems to adjust the feedback gain (FG) and switching gain (SG). Stability and convergence of the control system can be guaranteed by the Lyapunov theory and Barbalat Lemma. Simulation and experimental results show that the designed ASMC has highest control precision and much smaller input chattering when compared with other controllers.     

A consistent nonisothermal extension of the Scharfetter—Gummel stable difference approximation

Computer simulation is becoming an increasingly important aspect of device analysis and design, and it is well known that stability of the associated numerical solution procedures is enhanced by use of the Scharfetter-Gummel (SG) approximation. Accurate transport models utilizing carrier temperature as a crucial parameter are emerging, however the SG expression is valid only for isothermal analyses. In this letter, a consistent nonisothermal extension of the SG stable difference approximation is presented. Simplifications of the new expression are shown to agree with previous results.     

Full-VDD and near-threshold performance of 8T FinFET SRAM cells

We evaluate full-V_DD and near-threshold operation of nine novel eight-transistor (8T) FinFET SRAM cell schemes using shorted gate (SG) and low power FinFET configurations for 32-bit by 1024-word SRAMs. 8T SRAM schemes outperform six-transistor schemes since SG-configured read FinFETs minimize delay and reverse-biased inverter FinFETs’ back gates reduce leakage current by up to 97%. At near-threshold, 8T FinFET cell delay increases by 56%, but leakage current and energy-delay product (EDP) decrease by up to 16% and 77%, respectively. 8T Low-Power Inverters scheme uses these configurations and reduces EDP by 60% (79% at near-threshold) versus the conventional SG 8T FinFET SRAM.