基于遥测信号的测距技术及其发展趋势

基于遥测信号的测距技术可以有效解决深空测距下行链路同时传输遥测、测距信号时出现的遥测数据传输速率受限、频谱带宽增加等问题，应用前景广阔。介绍了基于遥测信号的测距技术发展历程，重点总结了其中的关键技术，包括上行测距码的选择、遥测帧的设计和传输、PN码相位估计算法，最后探讨了其发展趋势。基于遥测信号的测距技术适应未来深空测距的发展需求，是深空测距的重要发展方向之一。     

一种动态加权的LDPC译码方法

为了加快低密度奇偶校验（LDPC）码的译码速度，有效改善LDPC码的译码性能，针对校验节点更新过程中的对数似然比（LLR）值的大小，设计了一种LDPC码的动态加权译码方法。以IEEE 802.16e标准的奇偶校验矩阵为例，根据LLR值的变化规律，利用增长因子和抑制因子对和积译码算法和最小和译码算法进行动态加权。仿真结果显示，基于动态加权的译码方法相对于传统译码方法误码率都有明显改进，译码复杂度也有所降低。     

一种混合多边缘型LDPC码密度进化算法

在二进制输入加性高斯白噪声信道下，研究了基于多边缘型低密度奇偶校验码（Multi-edge Low Density Parity Check，MET-LDPC）的密度进化算法。针对高斯近似算法在前期迭代中的不准确问题，提出了一种改进算法。在分析MET-LDPC码的密度进化的基础上，将全密度进化与高斯近似算法结合，通过设置切换限制条件，弥补早期迭代的不准确，提高编码阈值估计的准确性。仿真结果表明,与MET-LDPC全密度进化算法相比，所提算法可以有效提高编码阈值估计的准确性，对LDPC编码的设计有一定的参考价值。     

一种带辅助译码比特的Polar码译码方法

在传统的Polar码译码的基础上，引入辅助译码比特，构造了一个辅助的Polar码字以提高译码性能。辅助比特由信道选择辅助窗口内的信息位决定。接收端如译码失败，将进行二次译码尝试。译码方案分两阶段进行：基于相同结构的扩展生成矩阵，将辅助译码比特译出；结合译出的辅助比特，对原码字进行译码，提高译码成功率。仿真结果显示，使用所提方法进行译码，其译码性能明显优于普通串行抵消译码方法；与两种传统的自动重传请求方案相比，能分别获得1 dB和1.9 dB的性能增益。     

利用ACE值构造QC-LDPC码

为进一步提升中短码长下准循环低密度奇偶校验(Quasi-cyclic Low-density Parity-check,QC-LDPC) 码的纠错性能，提出了一种综合短环数目和环连通性的QC-LDPC码构造方法。首先，采用Golomb规则构造QC-LDPC码，对基矩阵中的部分元素进行替换预处理，初步降低短环数目；其次，采用所提的利用近似环外信息度（Approximate Cycle Extrinsic message degree，ACE）的消环掩模算法来优化QC-LDPC码，使得掩模后的校验矩阵具有较大的ACE平均值，最终完成QC-LDPC码的构造。该构造方法简单、通用性强，在短环数目和连通性间进行了平衡。与只考虑减少短环数目、增大围长等方法相比，该方法构造的QC-LDPC码有更加优异的纠错性能。     

一种适用于遥测测距信号的新型码跟踪环

遥测测距技术采用再生伪码作为上行链路信号。针对飞行器现有码跟踪环结构复杂、低信噪比条件下环路跟踪性能差的问题，提出了一种新的基于锁相环的码跟踪环结构，推导了环路的信号处理流程。该结构降低了环路实现的复杂度，改善了低信噪比条件下的相位测量精度，仿真进一步验证了方法的有效性和稳定性，较现有方法在信噪比为-10 dB时能提高1.5×10－3个码片的精度，适合遥测测距技术。     

Ethical Exemplification and the AICPA Code of Professional Conduct: An Empirical Investigation of Auditor and Public Perceptions

This research applies the impression management theory of exemplification in an accounting study by identifying and measuring differences in both auditor and public perceptions of exemplary behaviors. The auditors were divided into two groups, one of which reported self-perceptions (A-S) while the other group reported their perceptions of a typical auditor (A-O). There were two separate public groups, which gave their perceptions of a typical auditor and were divided based on their levels of accounting sophistication. The more sophisticated public group was comprised of bank loan officers (LO) while the less sophisticated public group consisted of investment club members (IC). Comparisons were made on 30 behaviors contained in the AICPA Code of Professional Conduct, which served as the basis for the research instrument. Profile analysis, a special form of MANOVA technique, was used to analyze the results. A-S perceptions were the highest of the four treatment levels and were significantly higher (i.e., more exemplary) than the perceptions of both the A-O and LO groups. The more sophisticated user group (LO) provided the lowest perceptions of the four treatment levels. For at least four of the six measures, the LO treatment group perceived the typical auditor to be less exemplary than both the IC and A-O treatments. There were no differences in perceptions between the A-O group and IC. Additional analysis revealed that auditors overrated the degree to which the public relied on financial statements. However, both public groups reported a reasonably high level of reliance on financial statements when making decisions. Philip A. Brown is an Associate Professor and Directtor of the Accounting Program at Harding University in Searcy, Arkansas. He has a bachelor's degree from Harding University, an MBA from West Virginia University and a Ph.D. from the University of Mississippi. His research interests are in accounting ethics and in accounting education. He has published in Advances in Accounting, The Journal of Accounting and Finance Research, and others. He is a CPA in the State of Arkansas. Morris H. Stocks serves as the Dean of the Patterson School of Accountancy at the Universtiy of Mississippi. He received his undergraduate degree in accounting from Trevecca Nazarene University, his Masters degree from Middle Tennessee State University and his Ph.D. from the University of South Carolina. He is a Certified Public Accountant in the State of Mississippi. He is a behavioral accounting researcher and has published in Accounting, Organizations and Society, Accounting Horizons, Behavioural Research in Accounting, Decision Sciences Journal, Advances in Accounting, Advances in Accounting Information Systems, Advances in Behavioral Accounting Research, Accounting, Auditing and Accountability Journal, Advances in Taxation and others. W. Mark Wilder is KPMG Lecturer and Associate Professor of Accountancy at The University of Mississippi. His educational background includes a bachelor's degree in mathematics from The University of Alabama, an MBA from the University of South Alabama, and a Ph.D. in Accounting from Florida State University. He is a CPA in the State of Mississippi. Mark has published in Accounting Horizons, Advances in Taxation, the Journal of Applied Corporate Finance, the Journal of Computer and Information Systems, the CPA Journal, and others. In the past 2 years he has received several awards, including the top two campus-wide faculty awards at Ole Miss and also the MSCPA Outstanding Educator Award. In 2004 he was inducted into the Alabama Tennis Hall of Fame.     

发射分集系统在空间相关莱斯快衰落信道下的性能

我国加入WTO以后,对于上海的发展是一个千栽难逢的机遇,同时也给上海的发展带来新的挑战。本文通过详实的资料分析了上海经济发展的现状和制约上海进一步发展的问题,并运用市场营销新理论,提出构建上海现代化大都市的营销战略。     

信道估计偏差对空时编码的OFDM系统性能的影响

本文研究了采用空时编码的OFDM系统的性能，通过Monte Carlo仿真分析了系统性能和信道估计偏差对系统的影响。