椭圆曲线密码体制

本文对椭圆曲线密码体制进行了概述与研究,并对椭圆曲线的原理、群的构成、对数问题、“倍点”公式以及城上元素运算的实现等一系列问题进行了讨论。最后,介绍了在椭圆曲线支持下的公开密钥密码体制。     

时域有限差分法分析数字信号传输线的耦合

超大规模数字电路的信号开关速度和集成度的提高，导致了信号波形变异和信号耦合问题，并要求用全波分析法才能给出准确结果。文中用时域有限差分法（FD－TD）分析了高速数字信号传输线的耦合特性，给出了经介质补偿后的结果。FD－TD方法中采用了完全匹配层（PML）吸收边界和电流源激励等最新研究结果。研究表明FD－TD方法是计算高速数字电路的有力工具。     

Anisotropic Crystal Plasticity Finite Element Modeling of the Effect of Crystal Orientation and Solder Joint Geometry on Deformation after Temperature Change

The crystal orientation of the tin phase in a Pb-free Sn solder joint has a significant effect on the stress state, and hence on the reliability of the solder joint. A set of crystal plasticity analyses was used to evaluate stress and strain resulting from a 165°C temperature change in a single-crystal joint using two simplified geometries used in practical solder joints. Phenomenological flow models for ten slip systems were estimated based upon semiquantitative information available in the literature, along with known anisotropic elastic property information. The results show that the internal energy of the system is a strong function of the tin crystal orientation and geometry of the solder joint. The internal energy (and presumably the likelihood of damage) is highest when the crystal c-axis lies in the plane of the substrate, leading to significant plastic deformation. When the a-axis is in the plane of the interface, deformation due to a 165°C temperature change is predominantly elastic. The texture of the copper substrate using isotropic Cu elastic properties, or anisotropic elastic properties with [001] substrate normal direction, does␣not have a significant effect on the stress or strain in the Sn phase of the joint.     

二维圆柱在高超声速气流中的耦合传热计算

高超声速飞行器热结构和热防护设计离不开对飞行器表面的气动热载荷和固体内温度的准确预测,两者之间的耦合作用对此有着重要影响.开展高超声速流场与结构温度场的耦合数值计算,流场部分求解了二维非定常全N-S方程,空间差分采用Harten-Yee的TVD格式,时间离散采用双时间步推进.固体结构传热部分求解了二维非稳态的热传导方程.通过流固交界面,流体从固体部分得到温度边界条件,固体从流体部分得到热流边界条件,从而实现流场和固体温度场的紧耦合计算.将这套算法成功应用于绕无限长圆柱的气动加热计算中,对圆柱在气动加热过程中的温度变化做了详细的分析.     

潜射导弹筒盖系统弹性缓冲支撑方案研究

提出了两套筒盖系统弹性缓冲支撑方案,利用有限元技术分别对两套方案的筒盖系统进行了瞬态动力学仿真,分析提取了轴承基座支反力和弹性器件的变形状况,通过对比刚性固支形式的计算结果得出:双向缓冲方案中,如缓冲件刚度较小,则轴承基座的支反力能得到明显改善;但缓冲件的变形量较大;如缓冲件刚度增大,轴承基座的支反力改善并不明显.而单向缓冲方案能明显改善轴承基座的支反力特性.     

Novel Approach for Modeling Wireless Fading Channels Using a Finite State Markov Chain

Empirical modeling of wireless fading channels using common schemes such as autoregression and the finite state Markov chain (FSMC) is investigated. The conceptual background of both channel structures and the establishment of their mutual dependence in a confined manner are presented. The novel contribution lies in the proposal of a new approach for deriving the state transition probabilities borrowed from economic disciplines, which has not been studied so far with respect to the modeling of FSMC wireless fading channels. The proposed approach is based on equal portioning of the received signal‐to‐noise ratio, realized by using an alternative probability construction that was initially highlighted by Tauchen. The associated statistical procedure shows that a first‐order FSMC with a limited number of channel states can satisfactorily approximate fading. The computational overheads of the proposed technique are analyzed and proven to be less demanding compared to the conventional FSMC approach based on the level crossing rate. Simulations confirm the analytical results and promising performance of the new channel model based on the Tauchen approach without extra complexity costs.     

Quantum states of a hydrogenic donor impurity in a cubic quantum dot by the finite difference method

The problem of a hydrogenic donor impurity in a cubic quantum dot with finite confinement potential is solved by the finite difference method. The discretized matrix equation needs to be solved for its eigenvalues and eigenfunctions. An algorithm of nonlinear programming is utilized for this problem. The results match references qualitatively in the weak regime, but introduce new problems in the strong and intermediate regimes.     

FDTD方法及其在多注电子光学系统研究中的应用

采用时域有限差分(FDTD)方法对L波段100 kW多注速调管的单个电子枪进行三维模拟计算,通过设置最小网格尺寸和发射时间间隔,得出的电流和导流系数与采用EGUN等软件计算的结果相一致,通过从MAFIA中导入三维磁场数据,模拟了位于径向不同位置处电子注通道的电子轨迹,研究发现在磁场均匀性较好的情况下,位于径向不同位置处的电子轨迹相差很小,同时讨论了如何减少模拟时间的问题.本文最后计算了多个注的电子枪,求得了电流值和导流系数,从中导入数据可以分段模拟多注速调管高频互作用段的注波互作用,以及收集极区域的电子发散.     

基于共前缀连续长度码的测试数据的压缩和解压方法

为减少测试数据存储量。提出了一种省略FDR码前缀的变一变长度压缩码．称之为共前缀连续长度码CPRL（Co—Prefixal Run Length）。压缩过程分两步，先对测试集差分运算．然后采用CPRL码编码差分向量。它的解压体系结构由一个解码器和循环扫描寄存器CSR（Cyclical Scan Register）组成。针对ISCAS-89基准电路硬故障集的实验结果表明，该方法是一种非常高效的压缩方法。