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。     

基于Givens旋转多用户多径DS-CDMA信号伪码盲估计

针对多径多用户低信噪比下的伪码估计,提出一种基于Givens旋转多用户多径DS-CDMA信号伪码盲估计的算法.该算法在同步接收扩频信号的基础上,利用特征值分解法获得用户特征向量子空间,通过2维Givens矩阵对子空间特征向量组成的2维载荷矩阵进行旋转,当定义的载荷矩阵总方差达到极小值时停止旋转,得到伪码序列的最佳估计.该算法克服了传统特征分解法估计多用户伪码序列时的缺陷,解决了多用户多径低信噪比情况下伪码序列的盲估计问题.仿真结果表明该算法是有效的,且具有抗多径干扰的能力.     

基于聚类的多进制扩频伪码序列盲估计方法*

针对多进制扩频系统伪码序列估计的问题,借鉴无监督聚类分析的思想,提出了一种基于K均值聚类算法的多进制扩频系统伪码序列估计方法。该方法首先将多进制扩频信号分段成不重叠的信号向量构造数据集合,利用数据集合的自相关矩阵的检测统计量完成信号的盲同步;其次通过搜索基于K均值聚类的代价函数来估计伪码集合规模,代价函数曲线的拐点位置为伪码集合规模的估计值;最后利用数据集合的聚类特征完成伪码序列的估计。理论分析和计算机仿真表明,该方法可以准确估计多进制扩频系统伪码时延和伪码序列值。     

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。     

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。     

阵列天线MC-CDMA系统用户波达方向估计

提出了一种阵列天线MC-CDMA系统用户波达方向估计算法.该算法首先利用MC-CDMA系统用户扩频码的正交性、子载波频域分集性,进行用户信号的分离、多址干扰的抑制和用户信号的增强,然后再通过传统波达方向估计的子空间算法实现用户信号波达方向的估计.仿真结果显示所提出算法在估计阵列天线MC-CDMA系统用户波达方向时,波达角估计误差很小,表明了算法的有效性.     

基于矩阵变换法的DSSS信号盲估计

提出一种基于矩阵变换法的简便盲估计算法.此算法在已知PN码速率及PN码周期已知的情况下,对基带扩频信号进行分段处理和累加运算以消除噪声的影响,进而实现PN码的盲估计,并在此基础上分析了使用不同m序列作扩频序列时的系统性能.Matlab仿真结果表明此算法可以在SNR低于-18dB的环境下正常工作.     

基于压缩循环谱的mW复合序列参数估计

针对m W(m-Walsh)复合序列扩频信号的参数估计问题,根据循环谱理论推导了m W复合序列扩频信号的循环谱表达式,并结合Walsh序列的频谱特征分析了m W复合序列扩频信号的循环谱特征,提出了基于循环谱的参数估计算法.针对m W复合序列循环谱的获取所需采样率较高的问题,引入压缩循环谱技术,通过信号的压缩采样值来重构循环谱.实验结果表明,利用压缩采样理论能有效地重构出信号循环谱,并实现对Walsh序列序号、m序列码片速率和载频等参数的有效估计.     

基于SCS算法的盲自适应多用户检测器

提出了一种基于SCS(Soft-Constraint-Satisfaction)算法的盲自适应多用户检测器。基于SCS算法的盲自适应多用户检测器只需知道期望用户的扩频码及定时信息,而且通过自动选择用来估计期望信号的非线性函数,可以调节算法的收敛速度和估计误差。仿真实验表明该方法具有较好的抗多址干扰的能力。     

多通道直扩信号并行捕获算法

为了缩短多通道直接序列扩频信号的捕获时间,提出了一种新的多通道并行捕获算法.该算法将多个通道的伪码序列进行叠加,形成一个新的伪码序列,由新的伪码序列和多通道直扩信号进行相关,检测到信号后再判决具体通道.分析和仿真结果均表明,提出的算法在不增加实现资源的情况下,以少量降低相关信噪比为代价缩短了捕获时间,适用于多通道直扩信号的快速捕获.     

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.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that