基于变量节点串行消息传递的LDPC码译码研究

针对标准LDPC码译码中洪水消息传递机制的不足,提出以串行机制进行消息传递,按照变量节点的顺序进行消息处理和传递,对每个变量节点同时接收校验消息和发送变量消息。该方法使更新的消息能够很快进入当前迭代计算,改善了LDPC迭代译码的收敛性能。通过对几种常用译码算法的仿真比较,验证了在复杂度不增加的情况下,该方法性能优于其它几种最大后验概率准则的译码方法,且算法收敛快,是一种能较好兼顾性能与实现复杂度的译码方法。     

一种与连续相位调制相适应的信道编码技术

以Rimoldi提出的分解方法为基础,文中介绍了一种与连续相位调制CPM(Continuous PhaseModulation)相适应的环卷积编码技术,该编码与CPM内在编码具有相同的代数结构,文中给出了两者结合后的常用研究方法。通过计算机搜索,以最小欧氏距离最大为目标,得到了一些典型参数下最优的编码方案。仿真结果表明,采用环编码后CPM信号的误比特性能有很大的提升。     

Investigating optimal replacement of aging air force systems

An availability‐oriented approach has been developed to decide when to replace an aging system. For an existing system, it is optimal to operate another year if and only if the incremental cost per available year is less than the lifetime average cost per available year of a new aircraft. We illustrate our approach using United States Air Force KC‐135 tanker data. In demonstrating our approach, we find it will be optimal to replace the KC‐135 by the end of the decade.     

Military Spending and Income Inequality:Evidence on Cointegration and Causality for Turkey,1963–2007

This paper investigates a series of unit root, cointegration and causality tests to ascertain the direction of causality between the growth of GNP and defence expenditure in Turkey for the years 1955–2000. The main conclusion is that there is a long‐run equilibrium relationship between GNP and defence expenditures. Furthermore, the short run causality test indicates that there is a unidirectional causality between variables, from defence expenditure to economic growth. In order to see the effect of a shock, we employed impulse response analyses. The results show that GNP decreased during the period then output finally recovered from the initial shock to defence expenditures.     

小波域非加性失真函数设计

在最小化嵌入失真隐写算法框架的基础上,提出了一种基于小波域的非加性失真函数图像隐写算法。首先在离散小波域设计了加性失真函数,主要考虑了亮度、频率和纹理掩蔽因子对载体失真的影响;然后结合模型矫正的方法对设计的加性失真函数进行了非加性矫正;最后结合网格码设计了隐写算法,将嵌入信息对载体的修改最小化,并且集中在人眼不敏感区域。实验结果显示,方案具有良好的视觉不可见性,且能抵抗空域SPAM特征隐写分析的攻击。     

基于纠错编码理论的计算机故障诊断研究

故障诊断技术是提高计算机可靠性的措施之一,本文在研究检错和纠错编码理论的基础上,论述了用于计算机故障诊断的奇偶编码、纠一检二编码和纠字节错编码技术,并给出了总体逻辑设计框图。     

低错误平层数列分割移位LDPC码构造算法研究

为降低LDPC码错误平层,提出一种基于环分类搜索的数列分割移位LDPC码构造算法。该算法具有码长、码率和列重的任意可设性,同时该类码的Tanner图围长至少为8。循环移位因子可以通过简单的代数表达式描述,从而降低内存需求。仿真结果表明,当误码率达到10-5时,数列分割移位LDPC(496,248)码相对于PEG-LDPC码获得了约1.9dB的性能提升;且随着信噪比的升高,两条译码性能曲线之间的差距将更为增大。此外,列重为3的数列分割移位LDPC码(6144,5376)在信噪比4.6dB以后并未出现明显的错误平层。该构造算法与PS-LDPC码相比在误码率达到10-8时大约获得0.25dB增益,特别在错误平层区域其译码性能优于围长为4和6的PEG构造算法,其构造复杂度和耗时也相较于PS-LDPC码和PEG-LDPC码构造算法展现出一定优势。通过基于Tanner图的诱捕集分析方法,统计(496,248)APPS-LDPC码中由8环组成的部分小型诱捕集并不存在,从而证明了其错误平层降低的原因。     

基于重要性采样的空时分组码快速仿真系统设计

高效的仿真技术对研究提高军事通信的性能具有重要意义。针对传统的蒙特卡罗仿真时间长的问题,提出了基于重要性采样的空时分组码高效仿真方法,给出了仿真模型和实现流程。仿真和分析结果表明本方法在运行较少的时间内能够获得较好的误码性能。采用该高效仿真方法可以加快军事通信技术研究的进程。     

Human conflict and universal ethics (part 2)

This second part of the review article begins with a definition of military power, when and how it should be used. From a large number of authors, “moral forces” are linked to “codes of conduct”, and the fundamental understandings about the “profession of arms”, based on “fiduciary trust”, “covenanted” service and professional and personal “conscience”. The article covers what authors have written about “culture” and the ethics of “technology” devices and systems, including “cyber” warfare. It concludes with recognition of the increase in ethical sensitivity in this century which is characterized by a phenomenon, the crises of “identity”, personal, national and global.     

本原BCH码的维数与周期分布

本文给出了求分圆陪集首集中元素个数新的计算公式，确定了长度为ｋ的分圆陪集的个数。给出了ｑ元域上狭义本原ＢＣＨ码的维数的计算公式，确定了狭义本原ＢＣＨ码的周期分布。