短波信道下直扩信号检测与载频盲估计

针对通信侦察识别中广泛遇到的短波信道下直接序列扩频信号(DSSS)的检测与参数估计问题,提出了一种利用广度优先搜索邻居(BFSN)聚类分析提取未知信号高阶循环累积量循环频率的算法。该算法通过聚类比较截获信号的各类峰值,剔除干扰和奇异类信号,克服了短波信道中常见的多径效应引起的码间串扰(ISI)影响,从而实现了在低信噪比条件下,对直扩信号进行检测和载频的盲估计。对算法进行了理论分析,并通过计算机仿真验证了该算法在低信噪比下具有较好的稳健性。     

针对短波3G-ALE信号的改进脉冲干扰性能研究

针对美军新一代短波3G-ALE信号为提高其协议信息传输可靠性而在通信链路层进行的多重数据编码,提出一种改进脉冲干扰方法。首先利用公开的伪随机扰码,建立对周期脉冲信号进行伪随机预加扰的干扰模型;之后推导信号接收处理公式,在此基础上分析脉冲占空比、脉冲周期等干扰参数,以及扰码失步、干扰频偏等因素对于干扰性能的影响;最后仿真干扰实验并得到相关结论。实验结果验证改进脉冲干扰对于3G-ALE信号协议信息可靠传输的干扰有效性,在设置脉冲占空比75%、脉冲周期使得脉冲持续时间等于整数倍符号长度TB时的干扰效果最佳;2TB以内的扰码失步、80 Hz以内的干扰频偏导致的干扰效果下降,则可以通过提高干信比较好地予以克服。     

基于谱范数和CPAST算法的周期长码直扩信号PN序列估计

针对周期长码直接序列扩频(DSSS)信号的伪噪声(PN)序列盲估计问题,提出一种新的谱范数和约束投影逼近子空间跟踪(CAPST)算法相结合的PN序列估计算法。算法首先根据最大化分段协方差矩阵的谱范数法,估计出PN序列的同步点;然后利用CPAST算法,分别估计各子段的PN码序列;最后按照一定顺序拼接成完整的周期长码PN序列。算法具有运算量小、复杂度低、实时处理及硬件实现的优点。仿真结果表明,在较低的信噪比情况,该算法能够有效地估计出同步点和PN码序列。     

低信噪比直扩信号PN序列参数估计

在直接序列扩频信号侦察过程中,针对信噪比低,参数未知的特点,本文提出了一种PN序列参数估计的方法.首先,利用的二次谱方法对PN码周期进行估计,然后根据基带信号能量累积最大化的原理,运用二位搜索算法估计PN码同步起始点,最后,将信号按照PN周期分成多个时段,利用多重互相关方法估计PN码序列.计算机仿真结果表明,在极低的信噪比条件下仍能良好地工作.     

结合跳频的二重频率分集四相差分移相组合编码调制

提出了一种适于在短波电离层反射信道上传输数据信号的新方案——结合跳频的二重频率分集四相差分移相组合编码(2FD4DPSK/FH)体制。针对短波信道的特点,采用组合编码、跳频和频率分集技术构造出这种编码,解释了这种编码体制抗击短波电离层反射信道上存在的多径时延引起的码间串扰和减小衰落对信号影响的原理。最后确定了该编码体制主要参数的选择范围,分析了采用这种编码体制的短波传输数据系统的整体性能。     

基于MCC-PAST算法的直扩信号PN码序列盲估计

针对在脉冲噪声环境下的直接序列扩频信号的伪随机(PN)码盲估计问题,提出了一种利用最大熵准则投影逼近子空间(MCC-PAST)算法和滑窗技术相结合的PN码盲估计方法。该方法利用最大熵准则,实现了在脉冲噪声背景下对扩频信号的特征进行稳定快速的追踪。通过对迭代过程中的特征子空间进行梯度估计,实现了可变遗忘因子(VFF)的自适应更新,使得权值的收敛精度和收敛速度得到了同时的优化。算法数据存储量小,复杂度低,易于硬件实现和实时数据处理。仿真结果表明,在脉冲噪声环境下该方法对PN序列估计的正确率和稳定性优于传统方法。     

卫星混合载波混沌相位扰码安全传输方案

针对卫星通信信号在传输过程中易被截获的问题,提出一种混合载波混沌相位扰码(HCLogistic)传输方案。首先将信号源在基带上进行QPSK映射,映射所得信号经过加权类分数阶傅里叶变换处理后,再将该信号与Logistic映射产生的混沌相位扰码结合,得到最终的基带加密信号;最后将信号经数模转换和上变频过程后送入卫星信道。仿真结果表明,信号经HC-Logistic方案加密,星座图的特征难以识别,且由于Logistic映射具有初值敏感性,截获该方案所需的计算代价是传统加权类分数阶傅里叶变换的10~(20)倍。     

小波与多分辨分析用于PN码捕获时刻的检测

DS－SS技术在CDMA系统中应用最为广泛，因此基于DS－SS方面的PN码捕获方法研究很多。传统的PN码捕获的判定是通过能量检测的办法进行的。基于PN码已被捕获时信号(被高斯白噪声污染的BPSK或QPSK信号）及未捕获信号（高斯白噪声）的特征，介绍了PN码捕获时刻的小波检测方法，并且研究了小波门限的性能。最后，对本检测方法的参数进行了统计，结果表明在这样的信号处理中，小波的多分辨分析具有优越的实用价值。     

Costas序列短波MFSK通信时频联合同步方法

针对低信噪比与强多径传播导致短波MFSK信号捕获困难、同步精度低的问题，提出一种基于Costas序列的短波MFSK信号时频联合同步方法。利用Costas序列二维图案优异的自相关特性进行信号检测与同步，将传统的滑动窗口法由时域扩展到时频域，同步获得时间和频率的估计值;为了降低计算量，给出了频偏与时延的精估计方法。仿真结果表明，与传统伪随机码(PN码)同步方法相比，提出的方法具有更好的抗噪声和抗频偏性能。在信号带宽为50 Hz、同步序列长度为1.28 s的ITU-R中纬度短波信道上，该同步方法能够达到98%的捕获率，虚警概率低于10^-2;时间同步误差低于12 ms;频率估计误差低于1 Hz。     

基于弧形修正滤波的柱面AR码识别算法

AR码在增强现实系统、空间视觉定位系统中应用广泛,正确识别AR码是增强现实系统和空间视觉定位系统中实现物体识别和定位的关键技术,经典的AR码识别方法对于平面上的AR码有较高识别率,粘贴于柱面上的码由于在空间中发生畸变,经典的识别方法无法准确识别AR码所携带的信息,为此提出一种针对产生柱面畸变的AR码的识别方法.首先采用一种通过添加定位标志位的改进的AR码编码方法对AR码进行编码,利用弧形修正滤波算法对产生柱面畸变的AR码图像进行二维与三维空间校正,在获得校正后的AR码图像后,再利用AR码的行数与每个数据位之间长度的非线性关系对AR码进行划线分割,最后利用像素值统计法实现AR码的识别,并给出了相应的实验结果.实验结果表明,该方法对产生一定程度的柱面畸变的AR码具有鲁棒的识别效果.     

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.     

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)

正~~     

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).     

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.     

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.