最优外插Jacobi信号检测算法

针对大规模多输入多输出(multiple input multiple output,简称MIMO)系统中最小均方误差(minimum mean square error,简称MMSE)信号检测算法复杂度过高及传统Jacobi信号检测算法收敛较慢的问题,提出最优外插Jacobi(optimal extrapolation Jacobi,简称OEJ)信号检测算法.在Jacobi迭代计算中,通过最优外插因子将当前解与下次迭代解进行组合,以加快迭代收敛速度.OEJ信号检测算法的复杂度比MMSE信号检测算法的复杂度低一个数量级.仿真实验结果表明：相对于传统Jacobi及阻尼Jacobi信号检测算法,OEJ信号检测算法的误码率最低,随迭代次数的增加误码率减小最明显、收敛最快.     

大规模MIMO系统中软输出信号检测方法

为解决在上行多用户大规模多输入多输出(MIMO)系统中,迫零(ZF)检测算法可取得近似最优性能,但ZF检测算法涉及复杂度高达O(K3)的矩阵求逆运算(其中K为用户数)的问题,基于Lanczos算法提出一种软输出信号检测方法,避免了高阶矩阵求逆运算,使复杂度由O(K3)降为O(K2).该方法为了计算软输出信息——对数似然比(LLR),通过对基于Lanczos算法的迭代计算解向量的过程进行分析,给出了一种低复杂度的LLR近似计算方法.仿真结果表明:提出的软输出信号检测方法的误比特率(BER)性能与计算复杂度均优于基于Neumann级数近似的信号检测算法,同时,最多仅需5次迭代就可取得逼近于ZF检测算法的性能.     

基于改进梯度投影法的MIMO-NOMA系统迭代信号检测算法

针对多输入多输出-非正交多址(multiple-input multiple-output non-orthogonal multiple access,MIMO-NOMA)系统信号检测问题,基于改进梯度投影(improved gradient projection,IGP)方法,提出一种适用于多用户MIMO-NOMA系统的上行链路的迭代信号检测算法。在该算法中,利用MIMO-NOMA系统中活跃用户的稀疏特性,基于IGP方法实现对发送信号的迭代恢复;在每次迭代后,先对所得估计解向量进行预处理,以得到更为接近真实值的估计值,接着再对活跃用户支撑集进行更新,以便于下次迭代操作。仿真结果表明,与经典的基于压缩感知的信号检测算法相比,基于IGP的迭代算法具有更低的误比特率(bit error rate,BER),在计算复杂度基本相同的条件下,可取得更佳的BER性能。     

MIMO系统中基于条件数阈值的格基约减信号检测算法

在多输入多输出系统中,最大似然(maximum likelihood,ML)检测算法性能最优但复杂度很高,最小均方误差(minimum mean-square error,MMSE)检测算法复杂度低但其性能较差.较高的信道矩阵条件数会给信号检测算法的误码率性能带来不利影响.针对这些问题,提出一种基于信道矩阵条件数阈值的信号检测算法来提升高条件数下传统检测算法的性能.该算法通过比较信道矩阵的条件数与预先设定的条件数阈值,选取相应的检测算法:当条件数低于阈值时,采用复杂度较低的LLL(lenstra-lenstra-lovasz)约减的MMSE(LLL-MMSE)算法来减少计算量;当条件数高于阈值时,采用基于排序分组的ML与LLL-MMSE联合的检测算法,通过增加一定的计算量来保证检测性能.对不同阂值下的误码率性能进行了仿真,结果表明算法的性能明显优于传统的LLL-MMSE检测算法,并且通过预先设定条件数阈值可以使得算法在性能和复杂度之间获得较好的平衡,最终达到优化检测算法性能的目的.     

不完全信道信息下基于信号特征的MIMO检测算法研究

针对接收端信道信息不全的情况提出一种基于信号特征利用的多输入多输出(multiple input multiple output,MIMO)接收机算法,该算法通过利用非循环信号的特征,扩展了接收机的处理维数以更好地抑制噪声.理论证明和数字仿真均表明,与传统的迫零(zero-forcing,ZF)和最小均方误(minimum mean square error,MMSE)接收机相比,提出的算法可以将噪声和信道估计错误的影响减少一半以上,而提出算法的复杂度却几乎保持不变.结合排序串行干扰消除(ordered successive interference canceling,OSIC)法,提出算法可以达到和最大似然法相当的误码率性能.     

基于迭代QR分解的MMSE V-BLAST算法

针对采用最小均方误差(minimum mean square error,MMSE)检测算法在MIMO系统接收端进行检测时,需要进行大量伪逆运算导致检测复杂度增加的问题,提出了用一种基于迭代QR分解的MMSE V-BLAST算法,避免了伪逆运算,有效地降低了检测算法的复杂度,使系统检测性能得到了明显改善.在多散射物无线通信环境下进行仿真实验,结果表明,与传统的算法相比,提案算法在保证相同信噪比,误码率没有显著变化的前提下,系统检测复杂度明显改善.理论分析证明,系统中有效天线数目越多,所提出的算法优越性越明显.     

低复杂度的正交空间调制检测算法

正交空间调制(quadrature spatial modulation,QSM)系统通过增加空间维来提高传统空间调制(spatial modulation,SM)的频谱利用率(频谱效率), 这在传统的多输入多输出 (multiple-input multiple-output,MIMO)技术中引起了极大的关注。虽然最大似然(maximum likelihood,ML)检测算法能够实现最优性能,但其穷尽搜索带来了极高的计算复杂度。而经典的线性检测算法最小均方误差(minimum mean square error,MMSE)和迫零(zero forcing,ZF) ,虽然在复杂度方面较最大似然ML最优检测低,但其误比特性能却比最大似然ML检测算法差很多。为了更好实现系统在计算复杂度和误比特性能之间的均衡,提出一种基于迫零的线性检测算法——增强型迫零(enhance zero forcing,EZF)。仿真结果表明,提出的检测算法不仅能够实现比传统检测算法(如迫零和最小均方误差)更好的性能,而且在复杂度方面较ML有明显的降低。     

基于MMAS的MIMO-OFDM系统上行多用户检测

在多输入多输出-正交频分复用(multiple input multiple output-orthogonal frequency division multiplexing,MIMO-OFDM)系统上行多用户检测(multi-user detection,MUD)中,针对基本蚁群算法(ant colony optimization,ACO)在搜索过程中易出现过早停滞及收敛于局部最优解等问题,提出一种基于最大最小蚁群系统(max-min ant system,MMAS)的MUD新算法.该算法在蚁群每次循环结束后,仅处于最优路径上的单只蚂蚁释放信息素;同时,通过限制每条路径上信息素的取值范围,避免路径间信息素的差值过大,从而使蚂蚁在每次循环时尽可能地选择不同的路径,提高算法的搜索能力.仿真结果表明,MMAS算法能够有效降低蚁群陷入局部最优解的概率,进而提高了检测性能;同时,随用户数的增加,该算法的计算复杂度却远低于最大似然(maximum likelihood,ML)检测算法,因此,该算法能够在检测性能与计算复杂度之间取得较好的折中.     

基于增强蚁群优化算法与排序的 MIMO 检测算法

基于最大似然比的多输入多输出(multiple input multiple output,MIMO)检测算法的计算复杂度随着天线阵的规模呈指数级增加,提出一种计算复杂度较优的MIMO检测算法.采用基于对数似然比的排序QR分解技术将信道矩阵分解为正交矩阵与上三角矩阵,相应地修改信号的发射顺序,降低错误判断引起的错误传播效应;为传统人工蚁群优化算法的信息素更新策略引入负信息素概念,有效地控制系统的拥塞;根据优化路径的距离积累了信息素.该方法设计了基于负信息素的信息素更新策略,增加MIMO系统的拥塞控制能力,考虑信道的衰落本性,基于路径的距离积累信息素.为了测试该算法的性能,进行了多组对比实验,结果表明,误码率性能优于其他智能优化算法,且对于64×64等大规模天线阵,该算法的计算复杂度随天线规模增长较小.     

基于简化信号模型的多用户检测算法

针对UWB系统的两种多用户检测算法复杂度较高的问题进行了分析,提出了基于改进的离散接收信号模型下的低复杂度解相关检测算法和最小均方误差检测算法(MMSE).仿真结果表明,在不影响性能的情况下复杂度大大降低.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to