Analysis of a secure conference scheme for mobile communication

Dynamic participation is a feature of the secure conference schemes that allows new conferees to join and the old conferees to leave. The conferees who have left should not be able to decrypt the secure conference communication anymore. A secure conference scheme with dynamic participation was proposed in M.S. Hwang and W.P. Yang (1995) and later it was modified with the self-encryption mechanism in K.F. Hwang and C.C. Chang (2003) for a better performance. In this paper we analyze both the original scheme and the modified version. We show that both of them are subject to the active and passive attacks presented in this paper. Our active attack works in the way that a colluding group of attackers can still obtain the conference key even after they all leave the conference. The passive attack does not need any attacker to ever participate the conference. The conference key can be compromised with a large probability as long as the number of conferees is large.     

一种新型半绝缘键合SOI结构

报道了一种新型半绝缘键合SOI结构,采用化学气相淀积加外延生长键合过渡多晶硅层的方法实现了该结构.研制出的这种新结构,完整率大于85%,Si-Si键合界面接触比电阻小于5×10-4Ω·cm2.这种新结构可以广泛用于高低压功率集成电路、高可靠集成电路、MEMS、硅基光电集成等新器件和电路中.     

平面型RTD及其MOBILE的设计与研制

鉴于已报道的平面共振遂穿二极管(PRTD)存在的缺点,文中提出了一种新的平面RTD器件结构.以n+ GaAs代替半绝缘GaAs衬底,利用硼离子注入产生的非晶化作为RTD器件的电隔离,成功设计研制平面型RTD和由其构成的单-双稳转换逻辑单元,此种结构可适用于以输出端作为公用端的所有电路.     

微型柔性红外传感器的制作研究

利用微机电系统(MEMS)技术,制作了一种128×1元柔性红外传感器阵列;首先在硅片衬底上生长一层PDMS柔性材料,然后再在柔性材料上利用MEMS技术制作红外传感器阵列.采用六轴微小器件试验台进行扭弯试验.在传感器的两端施加一定的力使其弯曲,然后测传感器不同单元的电阻.试验结果表明:所制作的柔性传感器阵列能经受多次弯扭,电阻值基本没有变化,柔性传感器在经过弯扭3 300次后,传感器本身的柔性材料并没有断.     

Terahertz Semiconductor Quantum Well Devices

For eventually providing terahertz science with compact and convenient devices,terahertz (1～10THz) quantum-well photodetectors and quantum-cascade lasers are investigated. The design and projected detector performance are presented together with experimental results for several test devices,all working at photon energies below and around optical phonons. Background limited infrared performance (BLIP) operations are observed for all samples (three in total) ,designed for different wavelengths. BLIP temperatures of 17,13, and 12K are achieved for peak detection frequencies of 9.7THz(31μm) ,5.4THz(56μm) ,and 3.2THz(93μm) ,respectively. A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is studied. The δ-doping density for each period varies from 3.2 × 1010 to 4. 8 × 1010cm-2. We observe that the lasing threshold current density increases monotonically with doping concentration. Moreover, the measurements for devices with different cavity lengths provide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically. Interestingly the observed maximum lasing temperature is best at a doping density of 3.6 × 1010cm-2.     

The transistor laser

A research team at the University of Illinois at Urbana-Champaign has developed a new, more powerful kind of device, called the transistor laser. The transistor puts out both electrical signals and a laser beam, which can be directly modulated to send optical signals at the rate of 10 billion bits per second. With some further modification, the transistor laser will eventually send a staggering 100 billion bits per second or more. Instead of using relatively slow wires to connect chips stacked together in packages, transistor lasers can be used as optical interconnects, which would let data flow instantaneously to and from memory chips, graphics processors, and microprocessors. There is much work ahead, but unlike the host of self-assembling, blue-sky nanotechnologies currently being touted as the next big thing in optoelectronics, transistor lasers do not need an entirely new fabrication infrastructure for further development or even to go into production.     

DSP最小应用系统的设计

介绍了基于DSP(数字信号处理)的最小应用系统的整体设计过程。系统采用TMS320VC5402作为主控芯片;ADC0809完成数据的采样及A/D转换,通过TMS320VC5402处理后,由DAC0832完成D/A转换并输出;外部存储器采用通用EPROM,TMS320VC5402采用8位并行EPROM引导方式;并加入了标准的14针JTAG接口,便于系统的调试与仿真。     

逆热传导方程的一类正则化算法

考虑了标准的一维逆热传导方程,问题是不适定的,即解不连续地依赖于数据.通过Fourier逼近的方法进行正则化处理,提出了一类新的算法并且与已有的正则化算法进行了比较,理论分析和数值实验均表明该算法是稳定的,且具有相同的精度和计算复杂性,同时也具有灵活性和广泛性.     

基于CORBA实现电网联合反事故演习

联合反事故演习是保证电网安全稳定运行的关键。随着电力系统仿真技术的发展,文中提出利用分布式仿真技术来实现电网联合反事故演习。在此方案中基于CORBA的分布式面向对象的体系结构,提出一种多层的C/S的数据服务模型,从而提高了分布式仿真系统中数据的可用性和实时性,并且大大地减少了网络传输中的冗余信息。     

用磁控溅射和退火方法制备AlSb多晶薄膜

采用磁控溅射法在玻璃衬底上制备Al/Sb预制多层薄膜,然后将Al/Sb预制多层薄膜在退火炉中退火得到AlSb多晶薄膜.用X射线衍射(XRD)法测薄膜结构;用扫描电镜(SEM)测薄膜Al/Sb成分比,结果表明AlSb多晶薄膜具有单一的晶相、均匀的结构,以及粒径大约20nm的晶粒.根据电导率(lnσ)与温度(T)的关系得到电导激活能为0.21和0.321eV,为制备出适用于太阳电池的AlSb多晶薄膜奠定了一定的技术基础.