基于 RIE 的自适应窄带干扰抑制算法

针对直接序列扩频(direct sequence spread spectrum,DSSS)通信系统中窄带干扰(narrow-band interference,NBI)抑制问题,将窄带干扰存在性识别技术(recognition of interference existence,RIE)和变换域窄带干扰抑制算法相结合,提出了一种自适应窄带干扰抑制算法.该算法能根据接收到的信号,利用基于能限因子的RIE算法判断接收信号中是否含有窄带干扰信号,从而决定是否需要对其进行干扰抑制处理.理论分析表明,当接收信号中不合窄带干扰或干扰信号较小时,既可减少由于窄带干扰抑制算法对有用信号造成的损伤,提高误码率性能,又能降低系统处理的复杂度.仿真结果表明,自适应窄带干扰抑制方案抑制干扰误码率性能明显优于非自适应窄带干扰抑制方案.     

应用于同频带全双工中的宽带自干扰射频抵消技术

针对同频带全双工通信系统存在的自干扰问题,设计完成了一款可集成的单天线同频带全双工自干扰射频抵消系统。同频带全双工系统最关键的问题是:收发机内部发射信号经过不同的路径反射后,通过天线耦合到接收端给接收机带来的强自干扰。由于干扰信号和接收信号位于同一频带内,传统的滤波技术无法将干扰信号滤除,基于正交矢量合成原理,所提可集成自干扰射频抵消技术采用单天线模式,通过自适应控制从发射机获取的两路正交参考信号幅值,合成与自干扰信号幅值相同、相位相同的抵消信号,最后在接收机的射频前端进行相减从而实现自干扰射频抵消。该方法摒弃了限制带宽的相移元件,使得抵消带宽不再严格受限,而且结构简单,易于片上集成,并且采用了自适应控制算法,使得系统工作的适应性更广。系统仿真结果表明,在60 MHz频带内,自干扰射频抵消比均大于41dB。     

直接序列扩频通信中基于循环累积量的自适应干扰对消技术

在可以获得与干扰强相关的参考信号的扩频通信系统中，自适应干扰对消器是常用的抗干扰技术．为在保证对消器性能的同时，减少运算量，提出了一种基于二阶循环累积量(SOCS)自适应干扰对消器(AIC-SOCS)，利用源信号和参考信号的循环二阶累积量，自适应调整对消器中滤波器系数．与基于四阶累积量的自适应干扰对消器(AIC-FOS)相比，乘法次数减少50％，加法次数减少60％．仿真实验表明，AIC-SOCS的性能和AIC-FOS的干扰抑制性能相当，表现出比基于二阶累积量的自适应干扰对消器(AIC-SOS)更优良的干扰抑制性能．     

超宽带通信中干扰抑制方法

针对修改接收模板信号的方法(MRTW)在抑制随机窄带干扰上的不足,提出了一种超宽带通信系统(UWB)干扰抑制的新方法—自适应修改接收模板信号(AMRTW)方法,该方法通过增加的自适应频谱估计器和自适应接收模板信号分解单元,准确的将干扰信号分量从UWB接收模板信号中恰当的去除,从而提高了UWB接收机的抗干扰能力,仿真结果表明,在UWB系统处于随机用户干扰的条件下,AMRTW方法对UWB系统误码率的改善明显优于MRTW方法。     

非高斯噪声背景下的自适应信号提取方法研究

为实现对非高斯背景噪声干扰条件下用信号的提取,将BP神经网络作为自适应噪声对消滤波器,以与干扰噪声强相关的噪声源作为参考噪声,实现对背景噪声的抑制,达到了有用信号提取的目的。BP神经网络自适应噪声对消技术不仅适用于线性相关参考噪声,同时也适用于非线性相关参考噪声,可以有效提高信号传递和接收的信噪比。     

直扩通信中窄带干扰的自适应抑制技术研究

针对直接序列扩频通信系统中存在窄带干扰影响信号接收的问题,给出了几种自适应抑制窄带干扰的方法,针对各种抑制方法给出了结论和分析,比较了各自的性能。     

基于LMS算法的混合干扰对消模块的设计与分析

为了解决无线通信中多类型混合干扰问题,利用LMS算法设计和仿真了混合干扰对消模块;首先对LMS自适应噪声干扰对消原理和周期性干扰分离原理进行了阐述和分析,通过分析可知自适应对消器的对消效果与LMS自适应算法阶数、步长的选取密切相关,而输入信号的自相关矩阵直接决定LMS参数的设置,不同类型的干扰差异较大;然后对混合干扰对消模块进行了建模,证明了所设计模块的可行性和有效性;最后,在不同信干噪比(SINR)下分析了所设计模块的性能,得出混合干扰对消模块在低信干噪比时性能好于高信干噪比时的结论。     

考虑天线极化特性的ASLC系统性能分析

交叉极化响应使得雷达的天线方向图具有复杂的极化结构,为了研究雷达天线极化特性对天线自适应旁瓣对消系统性能的影响,在干扰为任意极化的情况下,从主辅通道幅相特性出发,分析了天线极化特性对自适应旁瓣对消系统主辅通道幅相特性的影响,进而研究了极化干扰条件下的自适应旁瓣对消系统工作性能.仿真分析表明,由于主辅天线极化特性的不一致,最终将导致自适应旁瓣对消系统通道幅相不一致,特别是当干扰方实施交叉极化干扰时,主辅通道幅相不一致最严重,系统工作性能显著下降,干扰对消比最差.因此,为了得到较好的旁瓣对消效果,除了对自适应旁瓣对消系统通道幅相特性有一定的要求以外,对于雷达天线的极化特性也应有所要求.     

面向空间复用系统的抗干扰空频自适应均衡方法

针对多天线空间复用系统中各天线发射信号互相干扰,进而降低系统通信质量的问题,提出了一种抗干扰空频自适应均衡方法。首先,在发射端将待发射信号以空间复用的形式发送至接收端;然后,基于最小均方误差(MMSE)准则,利用各接收天线接收到的导频信息进行自适应均衡器的参数估计;最后,利用估计所得参数,进一步通过迭代优化的方法实现数据检测。在参数估计的过程中,通过引入相关移位矢量集的方法对抗多天线发射信号间的相互干扰,从而降低这种内部干扰对系统性能的影响。与传统针对空间复用结构的自适应空时、空频均衡方法相比,所提自适应均衡方法在性能上有显著提升。仿真结果表明:相较传统针对空间复用结构的自适应空时、空频均衡方法,在误比特率为10~(-5)时,所提自适应均衡方法有约2.5 dB的性能提升;在外界干扰影响下,传统针对空间复用结构的自适应空时、空频均衡方法具有明显误比特率平台,而所提自适应均衡方法表现出了更强的抗干扰能力,没有明显的性能平台。     

一种抑制周期性干扰的二级自适应时间延迟估计方法

当接收信号中伴有周期性干扰时，相关时延估计方法会受到严重的影响而不能有效工作，采用二级自适应时间延迟估计方法，可以有效地去除周期性干扰对时延估计的影响，在较强的干扰下仍可得到准确的时延估值，其中第一级为干扰对消器，第二级为ＬＭＳ自适应时延估计器。     

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.     

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.     

A computer generator for randomly layered structures

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

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。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

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     

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

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.