Construction of universal one-way hash functions: Tree hashing revisited

We present a binary tree based parallel algorithm for extending the domain of a universal one-way hash function (UOWHF). For t?2, our algorithm extends the domain from the set of all n-bit strings to the set of all ((2^t-1)(n-m)+m)-bit strings, where m is the length of the message digest. The associated increase in key length is 2m bits for t=2; m(t+1) bits for 3?t?6 and m×(t+⌊log₂(t-1)⌋) bits for t?7.     

使用确定应力模型研究离心压气机叶片相互作用

离心压气机叶轮和扩压器叶片间空隙很小,在无叶区和半有叶区的流动非定常特性十分明显。特别是离心叶轮出口通常的射流／尾迹流动使得有叶扩压器进口在时间、空间两个尺度上都存在十分强烈的不均匀性。叶轮和扩压器叶片间的相互作用,历来都被认为是影响离心压气机效率和稳定工作范围的重要因素。本文引入确定应力模型和改进的计算域延伸方法,计算了Ｋｒａｉｎ离心压气机组的流场,着重分析了叶轮出口无叶区、半无叶区等叶片间相互作用最强烈的区域的复杂流动现象。     

Integrability Aspects and Soliton Solutions for a System Describing Ultrashort Pulse Propagation in an Inhomogeneous Multi-Component Medium

For the propagation of the ultrashort pulses in an inhomogeneousmulti-component nonlinear medium, a system of coupled equations isanalytically studied in this paper. Painlevé analysis shows thatthis system admits the Painlevé property under some constraints.By means of the Ablowitz-Kaup-Newell-Segur procedure, the Lax pairof this system is derived, and the Darboux transformation (DT) isconstructed with the help of the obtained Lax pair. With symboliccomputation, the soliton solutions are obtained by virtue of the DTalgorithm. Figures are plotted to illustrate the dynamical featuresof the soliton solutions. Characteristics of the solitonspropagating in an inhomogeneous multi-component nonlinear medium arediscussed: (i) Propagation of one soliton and two-peak soliton; (ii) Elastic interactions of the parabolic two solitons; (iii) Overlapphenomenon between two solitons; (iv) Collision of two head-onsolitons and two head-on two-peak solitons; (v) Two different typesof interactions of the three solitons; (vi) Decomposition phenomenonof one soliton into two solitons. The results might be useful in thestudy on the ultrashort-pulse propagation in the inhomogeneousmulti-component nonlinear media.     

接触热阻的蒙特卡罗法模拟

 用蒙特卡罗随机模拟法计算了固体接触界面间的接触热阻。取服从高斯分布的随机数作为粗糙峰高度，分别对每个粗糙峰计算出单点接触热阻，再并联所有单点接触热阻得到总的接触热阻。修正了“积分法”的理论结果且与发表的文献数据相符。     

激光衍射微粒测量中的独立模式反演算法

在用激光衍射法测量微粒直径及其分布时得到的矩阵方程组是一组病态方程 ,无法直接求解。目前大多数求解方法是采用已知模式的拟合算法。但由于在实际中的微粒直径的分布是多种多样的 ,因此难以用一种或几种分布函数去近似描述。试图从微粒衍射的特征着手提出一种未知分布的独立模式的求解方法     

VADERMONDE-TYPE ODD-SOLITON SOLUTIONS FOR THE WHITHAM–BROER–KAUP MODEL IN THE SHALLOW WATER SMALL-AMPLITUDE REGIME

Under investigation in this paper, with symbolic computation, is the Whitham–Broer–Kaup (WBK) system for the dispersive long waves in the shallow water small-amplitude regime. N-fold Darboux transformation (DT) for a spectral problem associated with the WBK system is constructed. Odd-soliton solutions in terms of the Vandermonde-like determinant for the WBK system are presented via the N-fold DT and evolution of the three-soliton solutions is graphically studied. Our results could be used to illustrate the bidirectional propagation of the waves in the shallow water small-amplitude regime.     

时间和相位混合编码的量子密钥分发方案

提出了一种在双马赫-曾德尔干涉仪量子保密通信系统上同时实现时间编码和相位编码的混合量子密钥分发方案.提出的方案将原来相位编码方案中丢弃的脉冲进行时间编码,因此成码率是原方案的二倍.系统同时获得时间编码密钥和相位编码密钥,既可以一组用于通信,另一组用于监视窃听,又可以将两组密钥组合成新密钥.系统具有良好的应用前景. 关键词： 量子保密通信 量子密钥分发 相位编码 时间编码     

Quantum phase estimation algorithm in presence of static imperfections

We study numerically the effects of static imperfections and residual couplings between qubits for the quantum phase estimation algorithm with two qubits. We show that the success probability of the algorithm is affected significantly more by static imperfections than by random noise errors in quantum gates. An improvement of the algorithm accuracy can be reached by application of the Pauli-random-error-correction method (PAREC).     

量子安全直接通信研究进展

简要地介绍了量子安全直接通信的必要条件,初步介绍了两个量子安全直接通信模型,即Two-Step和Quantum-One-Time-Pad模型。 The requirements of quantum secure direct communication （QSDC） are briefly introduced. Two QSDC schemes i. e. , the Two-Step QSDC scheme and the Quantum-One-Time-Pad QSDC scheme, are discussed in brief.     

Statistical modeling of inductances in high-Tc superconductor electronic structures

In the design of electronic applications, e.g. rapid single flux quantum (RSFQ) circuits, with high-T_c superconductors there is an obvious necessity of having precise knowledge of loop inductances. In general, these inductances have to be computed numerically due to the small sizes of the structures and the large contribution of the kinetic inductance. The present work is based on the analysis of a large number of inductances which have been calculated numerically for several high-T_c superconducting loop configurations. By means of statistical modeling, analytical formulae, which are customized for the considered type of structure, are derived. They can efficiently be used to simplify and accelerate the process of layout design in high-T_c RSFQ electronics.