Design of low-density parity check codes for MIMO systems with doubly-iterative receivers

In this paper, the Multiple Input Multiple Output (MIMO) doubly-iterative receiver which consists of the Probabilistic Data Association detector (PDA) and Low-Density Parity-Check Code (LDPC) decoder is developed. The receiver performs two iterative decoding loops. In the outer loop, the soft information is exchanged between the PDA detector and the LDPC decoder. In the inner loop, it is exchanged between variable node and check node decoders inside the LDPC decoder. On the light of the Extrinsic Information Transfer (EXIT) chart technique, an LDPC code degree profile optimization algorithm is developed for the doubly-iterative receiver. Simulation results show the doubly-receiver with optimized irregular LDPC code can have a better performance than the one with the regular one.     

不完全信道状态信息条件下多用户Turbo-BLAST迭代检测算法

该文将空时多用户检测技术和Turbo-BLAST方案相结合,构造了基于CDMA技术的多用户Turbo- BLAST系统模型,提出了不完全信道状态信息条件下的解相关算法和迭代检测算法。在发送端将V-BLAST结构与CDMA技术相结合实现多路复用,在接收端利用空时多用户检测算法去除用户间干扰,得到期望用户的接收信号,然后采用考虑信道估计误差的软干扰抵消迭代检测算法,对期望用户的接收信号进行检测以去除天线间干扰。仿真结果说明,所提算法对于多用户Turbo-BLAST系统是有效的,可在不增加复杂度的条件下达到良好的迭代效果。     

中频通信信号信噪比的快速盲估计

信噪比是通信信号处理中的一个重要参数,许多算法都以它作为先验信息来获取最佳性能。该论文通过确定中频通信信号的频谱范围来计算信号能量,进而根据定义估计信噪比,由此提出了一种中频通信信号的信噪比快速盲估计方法。对BPSK,QPSK,16QAM等常用线性调制通信信号的仿真表明：该方法性能稳定,在数据样点长度为4096且信噪比变化范围为-5 dB到25 dB时,估计值的偏差和均方根误差基本都小于0.5 dB。与基于特征值分解的方法相比,在得到精确估计结果的同时具有计算复杂度小、适应动态范围广等优点。     

"信息"到底是什么?--限于无生命、物质和科学领域的讨论

本文在无生命、物质和科学三个限制的前提下讨论“信息”到底是什么.依次论证：（1）自然科学没有能力度量信息的“质”,只能讨论信息的“量”;（2）“信息熵”只是度量信息“量”的概念;（3）在无生命的物质科学领域内,信息熵完全等价于Boltzmann熵,对应于实验中的热熵;（4）运用Occam剃刀原理,信息熵和Boltzmann熵两个名词只能留下其中的任意一个;（5）“熵”取决于体系的微观状态总数,即最终取决于热运动引起的分子核骨架的动态变化.于是,在无生命、物质和科学三个限制的领域内“信息”只是望文生义的产物.     

均匀设计在蚕蛹虫草和冬虫夏草活性成分分析中的应用

采用均匀实验设计方法快速找到蚕蛹虫草活性成分的高效液相色谱最优分离条件;将该优化条件用于蚕蛹虫草和冬虫夏草的水溶性成分的分离取得满意结果,并对部分组分进行了定性定量分析;均匀实验设计方法可较快找到复杂未知或半未知体系的色谱分离条件。     

用Hirshfeld电荷定量标度亲电性和亲核性:含氮体系(英文)

准确预测化学过程中分子内各原子提供或接受电子的能力以及化学反应可能的位点,即定量确定亲电性、亲核性和区域选择性,是一个十分重要却仍然亟待解决的课题.此前,基于我们新近提出的信息守恒原理,曾建议使用Hirshfeld电荷和信息增益作为两个等价的描述符用于此目的.我们的这个想法已经被成功地应用于两个系列的分子体系,且其有效性得到了充分的验证.然而,先前我们只考察了碳元素的这些性质,所以其结论的普遍性仍存在疑问.我们尚不清楚它是否适用于其他元素,而且对于同一元素的不同价态该结论是否适用也不清楚.为此,本文将考察含氮体系.对5个不同类别的含氮体系共计40个分子进行了研究,其中包括重氮苯、偶氮、重氮、一级和二级胺体系.结果表明,对所有五个含氮体系其Hirshfeld电荷与实验得到的亲电性和亲核性标度之间仍然存在着较强的线性关联.然而,这些相关性却依赖于氮元素的化合价类型和键合环境.该线性关系只能在同一类型中成立.我们对其可能的原因进行了讨论.     

Estimation of the limit of detection using information theory measures

Definitions of the limit of detection (LOD) based on the probability of false positive and/or false negative errors have been proposed over the past years. Although such definitions are straightforward and valid for any kind of analytical system, proposed methodologies to estimate the LOD are usually simplified to signals with Gaussian noise. Additionally, there is a general misconception that two systems with the same LOD provide the same amount of information on the source regardless of the prior probability of presenting a blank/analyte sample. Based upon an analogy between an analytical system and a binary communication channel, in this paper we show that the amount of information that can be extracted from an analytical system depends on the probability of presenting the two different possible states. We propose a new definition of LOD utilizing information theory tools that deals with noise of any kind and allows the introduction of prior knowledge easily. Unlike most traditional LOD estimation approaches, the proposed definition is based on the amount of information that the chemical instrumentation system provides on the chemical information source. Our findings indicate that the benchmark of analytical systems based on the ability to provide information about the presence/absence of the analyte (our proposed approach) is a more general and proper framework, while converging to the usual values when dealing with Gaussian noise.     

Privacy and pricing personal information

The issues we address here are – How should a firm (e.g. Internet service provider (ISP)) that is capable of collecting personal information (browsing information, purchase history, etc.) about consumers, price its service, given that consumers vary in their valuation for privacy, and also vary in terms of the value of their personal information to a third party (firms that need consumer information)? Should the firm have a blanket policy of never collecting, or a policy of always collecting and revealing information? Surprisingly we find that in some cases the collector of information may be no worse off in the asymmetric information case than in the full information case. The paper provides a justification for the strategy of some firms such as ISP’s which never collect information and also for the strategy of other firms, like grocery stores that do. We also find that it is non-optimal for the firm to design contracts where the consumer can choose an intermediate level of privacy.     

基于GIS的露天矿车辆运输监控系统

车辆运输监控是露天矿车辆管理的主要内容，也是影响露天矿企业生产效率的重要因素之一。阐述了露天矿车辆运输监控系统的开发技术、系统功能以及实现GIS的关键技术，在某钼矿的应用中，系统运行状况良好，实现了对露天矿车辆的实时监控和调度。     

Possibilistic networks for information retrieval

This paper proposes an information retrieval (IR) model based on possibilistic directed networks. The relevance of a document w.r.t a query is interpreted by two degrees: the necessity and the possibility. The necessity degree evaluates the extent to which a given document is relevant to a query, whereas the possibility degree evaluates the reasons of eliminating irrelevant documents. This new interpretation of relevance led us to revisit the term weighting scheme by explicitly distinguishing between informative and non-informative terms in a document. Experiments carried out on three standard TREC collections show the effectiveness of the model.