X再生码:一类适用于云存储的准确修复编码

通过将(n,k)-RS编码和X编码结合,为云存储系统设计一类新的准确修复编码——X再生码。它具有容忍n-k个节点故障的可靠性,并且当系统中单个或者两个节点出现故障时,仅需从少量的节点下载数据块,使用简单的异或运算即可修复。对X再生码的存储代价、修复带宽、修复局部性(修复过程中需要连接的节点数)和编码率进行分析,并与RS编码、SRC以及LRC进行对比。结果显示,X再生码在一个或者两个节点故障时,修复局部性以及修复带宽上都具有显著的优势,并能达到任意高的编码率。     

变长检错码

本文提出变长错误模型和变长错误检错码的概念，具体给出两类变长检错码，分析了其检测变长错误的能力，并介绍了其在计算机病毒防治中的实际应用．     

CONVOLUTIONAL CODES FOR PHASE-MODULATED CHANNELS

Abstract

The use of Lee-metric makes it possible to construct convolutional codes which utilize the fact that in a nonbinary phase-modulation scheme certain symbol errors are less probable than others. In this paper the use of the Lee-metric in constructing convolutional codes is studied, a class of optimal convolutional codes is defined and the results of a computer search for finding memory length two optimal codes is presented.     

PHASED ERROR CORRECTING PERFECT CODES

Abstract

Random errors increase with the increase in word length. The random errors which are spread over the word in blocks of suitable lengths are defined as phased errors. Correction of phased errors is considered, and special types of codes correcting double phased errors that are perfect in the sense that they correct all single and double phased errors and no others ate systematically defined and studied. Decoding algorithms, nonbinary extensions, modifications, weight enumerators and generalizations for correcting more than two phased errors are also investigated.     

ADJACENT-ERROR CORRECTING BINARY PERFECT CODES

Abstract

A new type of codes that correct only a given number of adjacent errors in the binary case have been introduced in this paper. These codes are adjacent-error correcting perfect and form a doubly infinite class, i.e., for a given number of adjacent errors these exist for different lengths as also for different number of adjacent errors these can be developed for specific lengths.     

LINEAR CODES HAVING A SUB-BLOCK STRUCTURE

Linear codes having a sub-block structure are discussed. A substitute method of constructing codes capable of detecting and correcting combinations of error patterns in various sub-blocks is given. Codes where error-correction capabilities are determined in terms of various sub-blocks of the word length are introduced.     

并发代码的继承问题

文献[1]提出了一种新的刻划并发行为的方法.本文继续讨论这种方法在面向对象的程序设计中是如何解决并发代码在继承过程中的冲突问题的.     

ERROR-CORRECTING CODES AND CRYPTOGRAPHY PART I

Charles L. Dodgson, better known as Lewis Carroll, invented several polyal-phabetic ciphers by 1868. The two that he published are put into historical perspective in this paper. His Alphabet Cipher produces a Vigenère enciphered text, while his Telegraph Cipher is equivalent to a Beaufort cipher. In constructing the Telegraph Cipher, Dodgson used two sliding alphabets, similar to the St. Cyr slide invented by Auguste Ker-ckhoff fifteen years later. A program is available to explore these ciphers and another, the Variant Beaufort.     

几类SAB码的不可检测错误概率

SAB码是一种为控制ASCⅡ型数据的传输误差而设计的高效率线性码.目前已知的SAB码共有四大类.前人已对第一类SAB码在ARQ系统中的不可检测错误概率的近似值作了研究.在本文中首次利用布尔函数去研究SAB码并精确地计算出了第二、三类SAB码的不可检错误概率.文中方法对第四类SAB码仍然有效,但限于篇幅在此略去.     

RLL码的计算机辅助设计

本文着重讨论计算机辅助设计RLL码的具体实现问题.该过程首先根据RLL码两个参数d,k确定一个编码率p/q,然后构造出RLL码的高阶状态转换-输出符号矩阵并求相应的近似特征向量.最后通过状态分裂和状态归并过程,即可得到一个满足d,k约束的编码输出表.其中状态转换-输出符号矩阵为实现计算机辅助设计RLL码提供了有效的数据结构,而且要优化RLL码编码器,就必须有选择地进行状态分裂.     

AMERICAN CODES: A BOOK REVIEW

The auto-correlation function of a shift register sequence as used in cryptology does not correspond to the classical statistical definition. The aim of this paper is to point out the differences and some relations between those twin concepts.     

实用的并行程序性能分析方法

Firstly, with the discusses of main ingredients to exert the peak floatperformance for currently high performance mirco-processors in detail,this paper analyzed the principal motivations for the speedup ofparallel applied codes under the parallel computers consisted of thethese micro-processors. Secondly, this paper presented a suite ofperformance evaluations rules for parallel codes, which can reveal theoverall numerical and parallel performance with respect to the serialcodes, pose the performance improving strategies, explain exactly thereasons for super-linear Speedup. The numerical experimential results oftwo realistic applied codes under two parallel computer are also givenin this paper     

误码校正码在信息隐藏中的应用

在信息隐藏技术不断发展的过程中,隐藏分析技术也在不断地进步,信息隐藏的分析和攻击者们发现:在对某个载体对象嵌入秘密信息后,载体对象的某些特征会发生改变,当这种改变达到某种程度时就可以确定某个载体对象中含有秘密信息.因此,在设计一个信息隐藏算法时应尽量考虑减少由于秘密信息的嵌入而带来的载体对象某种特征的改变程度.简要介绍了误码校正码及信息隐藏的概念,并提出了一种在信息隐藏的过程中引入误码校正码来减小载体对象在隐藏信息前后差异的方法.     

非奇H-矩阵细分迭代判定准则

非奇H-矩阵在科学和工程实际中有着广泛的应用,因此研究其判定问题是很有必要的.根据α-对角占优矩阵与非奇H-矩阵的关系,通过构造递进系数和细分区间的方法,给出了非奇H-矩阵的细分迭代判定准则,该判定准则改进了近期的一些结果,数值算例说明了该判定准则的有效性.     

THE LOCATION OF FIGURES IN ALPHA-NUMERIC CODES

In designing a six-character alpha-numeric code, a combination of operational and scientific factors required two characters to be figures and four to be letters. It was predicted that when the figures were located in the fourth and fifth positions, immediate recall of the codes would be better than, when the figures were in any other positions.

An experiment was carried out which tested recall with the pair of figures in each of the five possible locations. The prediction was found to have been correct, and the underlying reasons for making it to have been substantially supported.     

SE-SYSTEMS,TIMING MECHANISMS,AND TIME-VARYING CODES

We show that synchronized extension systems [17] can be successfully used to simulate timing mechanisms incorporated into grammars and automata [3, v 7-9, v 12]. Further, we introduce the concept of a time-varying code as a natural generalization of L-codes, and the relationship with classical codes, gsm codes and SE-codes is established. Finally, an algorithm for testing the time-varying code property in case of periodicity is given.     

面向卫星导航系统的多进制LDPC码的构造

面向卫星导航系统应用,设计一种性能优越且编码复杂度低的多进制低密度奇偶校验(LDPC)码。结合渐进边增长(PEG)算法与准循环扩展的半随机构造法,并优化非零元素的选择,构造与新一代卫星导航系统IS-GPS-800接口标准中参数一致的多进制LDPC码。进一步,通过将校验矩阵转换为重复累加码(RA)码的校验矩阵结构,实现低复杂度编码。仿真结果表明,与卫星导航系统IS-GPS-800接口标准中码长码率相同的二进制LDPC码相比,多进制LDPC码有明显的编码增益,且其编码复杂度较低。     

Adler滑动窗译码算法的改进

Ａｄｌｅｒ等人的滑动窗译码算法能保持滑动窗译码，但对状态的归并重视不够，根据状态分裂原理，文中提出了改进Ａｄｌｅｒ等人算法的想法，以及朝前看译码方式下的改进规则，文章以２／３（１，７）码为例，说明对Ａｄｌｅｒ算法改进的操作步骤，所得结果比Ａｌｄｅｒ等人算法的结果少用一个编码状态。