Electrical characteristics of AlInN/GaN HEMTs under cryogenic operation

Electrical properties of an AlInN/GaN high-electron mobility transistor (HEMT) on a sapphire substrate are investi-gated in a cryogenic temperature range from 295 K down to 50 K. It is shown that drain saturation current and conductance increase as transistor operation temperature decreases. A self-heating effect is observed over the entire range of temperature under high power consumption. The dependence of channel electron mobility on electron density is investigated in detail. It is found that aside from Coulomb scattering, electrons that have been pushed away from the AlInN/GaN interface into the bulk GaN substrate at a large reverse gate voltage are also responsible for the electron mobility drop with the decrease of electron density.     

8～10轮AES-128的biclique攻击

高级加密标准(AES)是信息安全中实现数据加密、认证和密钥管理的核心分组密码算法,其安全性分析是密码学的重要课题之一.本文利用AES独立的相关密钥差分,构造了3轮biclique;基于该biclique,使用重计算技术,针对8~10轮AES-128给出新攻击.研究结果表明,攻击8轮AES-128所需的数据复杂度为264选择密文,时间复杂度为2125.29次加密;攻击9轮AES-128所需的数据复杂度为264选择密文,时间复杂度为2125.80次加密;攻击10轮AES-128所需的数据复杂度为264选择密文,时间复杂度为2126.25次加密.与已有的同轮攻击结果相比,新分析所需要的时间复杂度或数据复杂度降低.     

Effect of interface-roughness scattering on mobility degradation in SiGe p-MOSFETs with a high-k dielectric/SiO2 gate stack＊

A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer （SiO2） thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping alow equivalent oxide thickness. Simulated results agree reasonably with experimental data.     

单压状态下保护层对埋置式光纤传感器的影响

由于光纤制造工艺的因素,埋置式光纤传感器的应变量测受到光纤构造的影响,该文主要分析保护层对测量精度的影响。由于光纤保护层材料的特殊力学性质,采用理论分析具有诸多的局限性,且分析结果难以应用于大应变区间,该文将模型在理想化的假设条件下,采用有限元数值计算方法(FEM)进行分析,并且将数值计算结果和实验结果相比较。结果表明两者吻合得较好,证实保护层对大范围应变影响较大,影响系数在被测量材料的应变的变化全过程可以确定。     

Modelling of an obliquely deposited thin film in three dimensions by kinetic Monte Carlo method

A simulation of the growth of an obliquely deposited thin film in a three-dimensional lattice was made using kinetic Monte Carlo method. Cu growth in three dimensions on a (001) substrate with high deposition rates has been simulated in this model. We mainly investigated the variation of three-dimensional morphology and microstructure offilms with incidence angle of sputtered flux. The relation of roughness and densities of films with incidence angle was also investigated. The simulation results show that the surface roughness increases and the relative density of thin film decreases with increasing incidence angle, respectively; the columnar structures were separated by void regions for large incidence angle and high deposition rate. The simulation results are in good agreement with experimental results.However, the orientation angle of columns is not completely consistent with the classical tangent rule.     

改进的无证书聚合签名方案

聚合签名是近年被关注的一个热点。基于无证书密码体制,构造了一个改进的无证书聚合签名方案,较之于已有的方案,本方案的对运算是常量的,只需3次对运算,提高了签名验证时的效率。改进的方案可以抵抗无证书攻击模型中类型Ⅰ敌手与类型Ⅱ敌手的攻击,在计算性Diffie Hellman困难问题假设下,该方案是存在性不可伪造的,并在随机预言机模型中给出了方案的安全性证明。     

一种新的分段非线性混沌映射及其性能分析

研究了logistic混沌映射的相关性质,指出当系统参数取值改变时,产生的混沌序列在相空间不具有遍历性.基于以上分析,构造了一种分段logistic混沌映射,对logistic映射和定义的分段logistic映射的分岔图和Lyapunov指数进行了研究,同时通过实验对这二种映射生成序列的随机性、相关系数、功率谱等性能进行了比较分析.在此基础上,定义了一种新的混沌系统性能评价指标——分岔迭代次数.结果表明,定义的分段logistic映射不仅具有良好的遍历性,而且对应的混沌系统相关评价指标的性能良好. 关键词： 混沌系统 相关系数 Lyapunov指数 功率谱     

一种新的分段非线性混沌映射及其性能分析

结合线性反馈移位寄存器（LFSR）和混沌理论各自的优点,采用循环迭代结构,给出一种将LFSR和混沌理论相结合的伪随机序列生成方法.首先根据LFSR的计算结果产生相应的选择函数,通过选择函数确定当前迭代计算使用的混沌系统,应用选择的混沌系统进行迭代计算产生相应的混沌序列;然后把生成的混沌序列进行数制转换,在将得到的二进制序列作为产生的伪随机序列输出的同时将其作为反馈值与LFSR的反馈值进行相应的运算,运算结果作为LFSR的最终反馈值,实现对LFSR生成序列的随机扰动.该方法既可生成二值伪随机序列,也可生成实值伪随机序列.通过实验对生成的伪随机序列进行了分析,结果表明,产生的序列具有良好的随机性和安全性.     

电控离子选择渗透膜分离过程传质模型的构建（英文）

【目的】电控离子选择渗透(electrochemically switched ion permselectivity, ESIP)是一种新型的离子选择性膜分离技术,已成功应用于低浓度目标离子的高效、连续、选择性分离。然而,离子在膜内传质不符合Nernst-Planck理论,建立ESIP离子传质模型有助于人们理解ESIP分离过程。【方法】在ESIP膜分离系统中,为研究离子在膜上双脉冲电势与极室槽电压耦合动态场中的传质行为,提出了修正的Nernst-Planck模型。根据唐南(Donnan)平衡以及电中性假设等,建立了ESIP膜分离过程的离子传递稳态模型。通过数值模拟考察了电流密度、膜厚、膜内离子活性位点浓度对膜分离系统中离子浓度和电阻分布的影响。【结果】在原料侧扩散层和膜相内,膜厚和离子活性位点浓度对离子浓度分布影响较大,降低膜厚、提高离子活性位点浓度是提高离子传质的主要方式。在高电流密度、低膜厚和高离子活性位点浓度下,原料侧扩散层电阻在整体电阻中占主导作用,通过增加流体流速或减小腔室厚度以提高离子传质速率。在低电流密度、较高膜厚下,Donnan层电阻占主导作用,通过增加膜的离子活性位...