基于PN序列的短波3G-ALE信号识别研究

在非协作通信中,对短波3G-ALE(第三代短波自动链路建立)协议信号,传统的识别方法是利用信号的探测报头,但其持续时间短,接收时容易丢失,无法准确识别;针对此问题,在结合滑动相关FFT法的基础上,提出了利用PN(伪随机噪声)扰码识别信号,并进行了理论推导及试验验证。PN扰码识别仿真结果表明,在低信噪比的情况下,不仅峰均比高,而且识别信号的准确率也高。研究表明,PN扰码识别是非常有效的短波协议信号识别方法之一。     

Galileo脉冲伪卫星信号接收方法比较

研究一种Galileo伪卫星信号格式.针对脉冲伪卫星信号的接收,提出两种脉冲同步方法,即分段FFT方法和脉冲图案匹配法.分段FFT方法利用伪卫星脉冲与接收机本地伪码间的分段相关特性,使用分段FFT相关算法获取脉冲时序信息;脉冲图案匹配法则利用伪卫星脉冲图案的伪随机特性,通过将接收脉冲图案与本地图案进行匹配操作实现脉冲同步.仿真分析显示,对于Galileo E1信号,脉冲图案匹配法的虚警特性最佳;而分段FFT方法平均捕获时间最短.两种方法都可极大地提高伪卫星接收机的同步性能.     

利用微分电路减小PCB上串扰的方法

基于印刷电路板(PCB)上总线串扰的微分传输特性,提出了一种利用RC微分电路来减小传输线间串扰的方法.即在分析串扰抵消原理的基础上,在传输线终端利用RC微分电路对干扰线上接收到的信号进行微分,获得与受扰线上的远端串扰信号幅度相近、相位相反的微分信号;然后用微分信号抵消受扰线上的串扰信号,从而减小串扰.同时给出了串扰抵消微分电路中参数取值的近似计算公式.仿真与实验结果表明:文中方法能够使串扰峰值衰减10 dB以上,与传统的从物理结构角度来减小串扰的方法相比,串扰减小的效果明显改善,且电路易于实现,代价较低.     

脉冲干扰时TH-PAM-UWB信号抗截获方法研究

设计低截获概率超宽带信号在战时通信中具有重要的现实意义。在抗截获性能指标分析的基础上,构建脉冲干扰模型,针对脉冲幅度调制超宽带系统,运用随机过程、信号统计理论和实验仿真,对信号脉冲参数、跳时码参数与抗截获性能之间的关系进行研究。仿真和分析表明增大跳时码周期和减小单位发射脉冲时延两种方法能很好地提高抗截获性能;而减低信号脉冲宽度虽能提高隐蔽性能,但在脉冲干扰实时改变时误码率会大大增加。新的研究结果为系统的参数选择策略提供有价值的参考。     

GPS军码信号的带限高斯噪声干扰参数选择分析

为了提高带限高斯噪声对GPS军码信号的干扰效率,以GPS接收机的码跟踪误差作为干扰效果评估指标,对其特定干信比下的干扰频偏和干扰带宽进行优化确定。在分析GPS P(Y)码和M码信号功率谱特点的基础上,根据非相干超前减滞后处理码跟踪环路工作原理,理论推导得到干扰频偏和干扰带宽与码跟踪误差的解析式。基于实际情况设置接收机码环参数,分别定量地仿真计算出不同干信比下针对P(Y)码和M码信号的高效干扰频偏和干扰带宽。以造成码环失锁所需干信比最小为主要评判准则,同时考虑干扰易实施性和频域滤波等因素的影响,通过综合比较得出:当干信比在50~60dB范围内时,针对P(Y)码信号的干扰频偏和干扰带宽分别设置为0和8.8MHz,针对正弦BOC和余弦BOC调制的M码信号的干扰频偏分别设置为9.833 MHz和10.9 MHz,干扰带宽统一设置为10 MHz。     

神经元中的随机共振及含噪周期方波脉冲信号的最优检测

理论研究表明 ,神经元用于含噪周期方波脉冲信号传输时存在随机共振现象 ,信号的占空比和神经元的阈值对随机共振的影响有一定的规律 .同时 ,可获得大于 1的信噪比增益 ,这是线性系统不能实现的 ,因而可将神经元的应用推广到非线性信号处理领域 .在此基础上 ,对应用神经元实现含噪周期方波脉冲信号检测的最优条件和最优特性进行了分析 .最后 ,通过仿真实验验证了理论分析的正确性     

欠驱动智能水下机器人的自抗扰路径跟踪控制

为削弱欠驱动智能水下机器人(AUV)在路径跟踪过程中遇到的外界环境干扰和载体内部信号传输干扰的影响,以某欠驱动AUV为研究目标,基于自抗扰控制技术以及在Serret-Frenet坐标系下建立的路径跟踪误差方程,结合水下机器人相关运动学及动力学方程,建立了二阶自抗扰路径跟踪控制器,并进行了与传统PID控制器的对比仿真实验.仿真实验包括水平面随机干扰下的圆路径跟踪和渐变干扰下的空间螺旋线跟踪.仿真结果表明,基于自抗扰控制技术的欠驱动AUV路径跟踪控制器能够实现相应的参考路径跟踪任务,同时,相比于传统PID控制器,自抗扰路径跟踪控制器能够更有效地抑制干扰造成的颤抖、超调等现象,具有更优的控制效果.     

非合作直扩信号伪码及信息序列联合盲估计

研究了短码直接序列扩频信号扩频序列及信息序列联合盲估计问题。在已知码片速率和扩频码周期的前提下,对接收信号以2倍伪码周期进行分段构造信号矩阵,然后对其进行奇异值分解,对最大和次大左奇异向量进行线性变换,得到信息序列;利用自相关函数从最大和次大右奇异向量中得到扩频码序列。该算法在失步时间未知的情况下能够同时估计出伪码序列及信息码序列,避免了传统特征值分解盲估计算法利用2个矢量空间组合扩频序列时存在的相位模糊问题。同时,在引入了矩阵的线性变换后,避免了不同时延估计结果存在模糊的问题,提高了盲估计性能。通过理论分析和计算机仿真结果表明：该算法能够有效估计扩频序列,并且具有精确度高、性能不受时延大小影响等优点。     

频带传输的码间串扰

针对通信中信号传输发生错误的问题进行研究,指出了造成判决错误的主要原因是噪声和由于传输特性不良引起的码间串扰,给出频带传输通信系统的模型,分析了无码间串扰的情况下,它的系统函数应满足的关系式,并指出了最高码元速率与系统带宽之间的关系。对于带通系统而言,最高码元速率为2W Baud,此时可获得的最高频带利用率为2Baud/Hz。     

钻杆声波传输对可调脉宽驱动的敏感性研究

设计了一种占空比可调的激振器驱动电路,并对短距离钻杆进行声波传输试验,研究占空比可调的脉冲驱动信号对单钻杆声波传输特性的影响。脉冲信号频率不同时,调节驱动信号的占空比从10%到90%变化,利用压电传感器接收传输信号。测试数据分析表明:所设计的电路可以输出占空比任意调节的驱动信号,且占空比在20%~30%时钻杆声波信号传输效果较好。     

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)

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).     

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.