On cyclically time-varying autoregressive digital filters

A first-order autoregressive filter is altered by changing the constant gain to two or more gains that cyclically alternate in time. The advantages of this system are shown, and the relation to linear autoregressive moving average difference equations of higher order is derived.     

Generating cyclically permutable codes (Corresp.)

Large sets of cyclically permutable (or cyclically inequivalent) codewords can be created by interleaving the cyclic shifts of several shorter words and selecting a cyclically inequivalent subset from the resulting set, This correspondence presents an efficient algorithm for generating the cyclically inequivalent subset directly.     

New constructions of optimal cyclically permutable constant weightcodes

Three new constructions for families of cyclic constant weight codes are presented. All are asymptotically optimum in the sense that in each case, as the length of the sequences within the family approaches infinity, the ratio of family size to the maximum possible under the Johnson upper bound, approaches unity     

On a class of cyclically permutable error-correcting codes

Cyclically permutable codes have error-correcting properties which are invariant under arbitrary cyclic permutation of any of their code words. This paper summarizes the results of an empirical investigation of certain of these codes, which have parameters not covered by a previous paper of E. N. Gilbert.^{1}These codes are thought to be nearly optimal. Estimates of the obtainable number of code words are given. The codes may be suitable for use in certain asynchronous multiplex communication systems.     

Reduced State Enumeration?Another Algorithm for Reliability Evaluation

This new algorithm for reliability evaluation is a refinement of the state enumeration method. The set of enumerated states is different for different parts of the fault tree, in particular the number of enumerated states does not necessarily increase towards the top event. This method makes it feasible to treat some large fault trees analytically rather than by Monte Carlo simulation. A lot of research remains to be done, like programming and evaluating the algorithm, and finding intrinsic measures of difficulty for fault trees.     

非退化相关免疫函数的构造与计数

本文给出了非退化一阶相关免疫函数的一个构造方法，得到了这类函数的一个新的下界，并且给出了阶数大于１的相关免疫函数非退化的一个充分条件及实例。     

对8轮ARIA算法的差分枚举攻击

给出了ARIA算法4轮差分性质,提出了对ARIA算法的差分枚举攻击。攻击了7轮和8轮ARIA-256算法,攻击的数据复杂度是256,攻击7轮时预计算的复杂度为2238.2次加密7轮ARIA算法,恢复密钥的计算复杂度是2124.2次加密7轮ARIA算法;攻击8轮时预计算的复杂度为2238次加密8轮ARIA算法,恢复密钥的计算复杂度是2253.6次加密8轮ARIA算法。     

密码体制中的布尔置换的构造与计数

布尔置换在密码体制设计中有重要的应用。本文研究了构造布尔置换的一般方法，并得到了目前最好的计数下界。     

m阶相关免疫函数的构造和计数

若布尔函数的输出不泄漏其输入值的有关信息,则称该函数是相关免疫的.这类函数在计算机保密应用中用途广泛.本文研究了m阶相关免疫函数的构造和计数问题,给出了两种新的构造方法.进一步,将这两种新构造方法与Seigenthaler,杨义先,Camion,Seberry以及温巧燕等人的构造方法进行了比较,证明了本文中的构造方法实际上推广了这些文献中的结论.利用本文中的构造方法,既可直接构造任意阶的相关免疫函数,又可根据已知的相关免疫函数来构造新的相关免疫函数.另外,基于新的构造方法,改进了m阶相关免疫的平衡函数的计数下界.     

仿射全向置换的构造和计数

利用仿射全向置换的结构,给出了仿射全向置换的一种构造方法,同时给出了仿射全向置换的计数公式,从而部分解决了全向置换的计数问题。     

Enumeration of Hamiltonian circuits in digraphs

A simple procedure for the enumeration of Hamiltonian circuits of a directed graph is presented. The new method is based on an efficient technique of subset generation. The method can be easily implemented on a computer.     

Stability criteria for multivariable polynomials

Algebraic criteria are proposed for testing stability properties of multivariable polynomials. The tests are recursive and can be executed in finite number of steps.     

Stability criteria for negative-resistance oscillators

The stability criterion for a free-running negative-resistance oscillator is shown to be invariant to transformation through a wide class of 2-port networks connecting the device terminals to a convenient reference plane in the external circuit. In this way, the experimental application of the criterion to a given circuit is greatly simplified.     

Some criteria for reliability growth

The sequence of failures of a system is assumed to be modelled by a stochastic point process. Criteria for the reliability growth of such a system are introduced. The relationships between the criteria are deduced and preservation of the criteria under the formation of series systems is discussed.     

Design criteria for surface-acoustic-wave convolvers

The effect of acoustic dispersion and attenuation on the performance of surface acoustic wave convolvers is shown to be equivalent to an ideal convolver in cascade with a linear time-invariant filter. Using this result calculations of the implementation loss due to acoustic dispersion and attenuation, transducer bandpass response, and input/output matching networks are given showing the effects of phase and amplitude responses which are representative of typical convolver designs.     

Simple construction of multiple interleavers: cyclically shifting a single interleaver

Utilizing multiple interleavers recently attracted increasing attention in many research areas. Interleaver generation should be simple in order to avoid huge memory requirements for storing interleaving patterns. We propose to derive multiple interleavers by cyclically shifting and self-interleaving a common mother interleaver in a few steps. Our focus is on the good user separation in interleave division multiple access systems. The proposed method may also find other application areas such as multi-dimensional concatenated codes.     

Frequency-domain instability criteria for time-varying and nonlinear systems

Recent research has produced a number of frequency-domain stability criteria applicable to linear systems having nonlinear and/or time-varying feedback. One of the more interesting of these stability criteria is the so-called Circle Criterion which represents a generalization of the familiar result of Nyquist. The present paper provides a basis for generating instability counterparts of most of the available frequency-domain stability criteria. The procedure is described in detail for the Circle Criterion. Once the general pattern is established it becomes a simple matter to generate instability counterparts of other similar stability criteria. Several worked examples are included to illustrate the theory. The paper has been written with both the general reader and the specialist in mind; it is hoped that both will find something of interest.