Peak-power reduction by the lattice-reduction-aided closest point search for MIMO broadcast channels

In this letter, we present a modified vector-perturbation precoding scheme for the multiple-input multiple-output broadcast channel, where a perturbation vector is chosen to take into account both the instantaneous power and the instantaneous peak power of the transmitted signal. This perturbation vector is obtained by using the closest point search, with the aid of the lattice-reduction algorithm. Simulation results show that the proposed scheme yields a tradeoff among power efficiency, peak-to-average power ratio reduction, and complexity.     

Applying sub-band energy extraction to noise cancellation of ultrasonic NDT signal

In ultrasonic non-destructive tests, the echo signal at the flaw is highly complex due to the interference of multiple echoes with random amplitudes and phases, and is disturbed by all kinds of noises, such as thermal noise, digitalization noise, and structure noise. In this paper, the ultrasonic signal was decomposed by empirical mode decomposition （EMD） to obtain the intrinsic mode function （IMF） components according to ultrasonic defect echo signals occuring at the corresponding time, and the energy of the ultrasonic signal was concentrated. The IMF component selection criterion based on sub-band energy extraction was proposed to extract the ultrasonic signal component accurately and automatically from IMF components. When the selected IMF components were filtered by a band pass filter, the signal-to-noise ratio （SNR） was enhanced greatly.     

知识检索与信息检索的检索效率比较

本文在对知识检索与信息检索的检索机制分析的基础上，对知识检索与信息检索的检全率、检准率进行了比较，认为知识检索的检索效率优于传统信息检索，同时对影响知识检索效率的因素进行了讨论，指出信息检索要向知识检索过渡和发展，并针对目前网络检索的现状，提出了一些改进措施。     

学术社交网络中iSchool成员用户结构与利用差异分析

[目的/意义]学术社交网络是开展知识交流与学术合作的重要平台，对iSchool成员用户的研究有助于图情学科研究人员合理利用学术社交网络。[方法/过程]本文以ResearchGate （RG）为例，采集61所iSchool成员机构的用户行为数据，依据被关注—关注比例指标进行用户细分，并从地区与层级角度对用户结构及利用差异进行比较分析。[结果/结论]地区角度，北美机构拥有较多明星型用户且注重展现与互动，亚太机构用户则更倾向于搜寻信息；层级角度，iCaucus机构用户更偏好学术资源分享，低层级机构用户跟踪获取学术资源的需求则更普遍。此外，iSchool成员机构能被RG指标进行良好的层级区分，学术影响力和层级领先的机构表现出更大的学术影响，因此应进一步合理拓展对学术社交网络的利用。     

基于资金限制的Sharp-ARIMA期货套期保值决策模型

通过ARIMA时间序列预测期货套期保值的资金需求量,以Sharp套期比模型为目标函数,以套保者的手头资金大于套保资金需求量为约束,建立基于资金限制的Sharp-ARIMA期货套期保值决策模型,解决基于资金限制的单品种期货套期比的确定问题。并利用WS411合约的历史数据实证分析了该模型。本模型的创新与特色一是决策模型确定了套期保值的资金需求,避免了因资金短缺导致的套保失败。二是提出了能够反映期货价格一阶平稳和季节性变化的套期保值资金需求量预测的研究思路,这就改变了现有研究仅对历史数据进行简单平均预测的现状,更加符合期货价格的波动规律。三是揭示出套期保值者手头持有的资金与套保比之间关系。     

核型不对称性的一种定量测定法及其在进化研究中的应用

本文提出了一种测定核型不对称性的定量方法。决定核型不对称性的两变量是染色体臂比和相 对长度。核型全部染色体臂比等于1，且长度彼此相等时，称该核型为理想对称核型。任一实际观测核型与理想对称核型的差异用臂比不对称系数Dc和长度不对称系数Dt度量。以Dc和Dl作座标可以绘制二维平面图。不同居群或分类群依其核型不对称性在平面图中有其确切的相对位置，进而反映出其间在细胞学上的关系及核型变异趋势。     

单调似然比族双侧假设可以不存在UMPU检验

举例证明了：存在这样的单调似然比分布放｛f（x,θ）dμ（x），θ∈Θ｝），其双侧假设H（θ_1≤θ≤θ_2）没有一致最优无偏（UMPU）检验，也存在这样的非指数族的单调似然比族，其假设的UMPU检验存在。     

中国的M2/GDP水平与趋势的国际比较、影响因素:1978～2002

本文对1978—2002年期间我国M2／GDP的长期趋势和周期性趋势进行了实证分析和国际比较。我国M2／GDP较高的原因在于：M2的货币乘数和准货币所占比重上升，经济货币化进程深入，融投资体制效率低下，金融体系不发达。并提出相应建议。     

Automatic building of new Field Association word candidates using search engine

With increasing popularity of the Internet and tremendous amount of on-line text, automatic document classification is important for organizing huge amounts of data. Readers can know the subject of many document fields by reading only some specific Field Association (FA) words. Document fields can be decided efficiently if there are many FA words and if the frequency rate is high. This paper proposes a method for automatically building new FA words. A WWW search engine is used to extract FA word candidates from document corpora. New FA word candidates in each field are automatically compared with previously determined FA words. Then new FA words are appended to an FA word dictionary. From the experiential results, our new system can automatically appended around 44% of new FA words to the existence FA word dictionary. Moreover, the concentration ratio 0.9 is also effective for extracting relevant FA words that needed for the system design to build FA words automatically.     

具有几何分布统计特征的在线租赁竞争分析

近年来,在线算法的兴起为金融领域的研究提供了新的视角,但传统的竞争分析方法有意规避概率分布假设。在金融领域中,似乎有时忽略这些极有价值的信息而只运用标准的竞争比方法分析显然是一个极大浪费。在本文中,我们首次结合输入结构的分布信息研究了离散型在线租赁问题,建立了最优的离散型在线租赁决策模型,并给出了最优的竞争策略及其竞争比。相比较Karp和El Yaniv的研究结果,由于本文引进了输入的分布信息使得竞争比改善;而相对于Fujiwara的研究结果,由于本文研究了离散型情形,给出了实际问题的精确解。