基于稀疏字典分解的窄带雷达自旋目标干涉三维成像

空间微动目标干涉三维成像技术研究中,最关键的是对各散射点进行保相分离。当脉冲重复频率（PRF）不满足奈奎斯特采样定律时,基于图像处理的成像方法无法有效分离目标各散射点。提出了一种基于稀疏字典分解的窄带雷达自旋目标干涉三维成像方法,该方法能够直接从回波数据中分离出各散射点。首先,根据自旋目标回波信号特性构建稀疏字典,利用稀疏分解算法分解回波,得到各散射点子回波,其次通过时频分析并利用其保相性,获得各散射点的微动曲线,并提取出它们在时频平面上经过位置的干涉相位差,最后根据干涉相位差与坐标之间的关系重构散射点坐标,对空间自旋目标进行三维成像。仿真结果表明,在PRF不小于0.25倍奈奎斯特频率时,所提方法均能有效实现自旋目标三维成像。     

利用多通道联合稀疏重建的干涉逆合成孔径雷达三维成像算法

针对单通道超分辨成像算法重建的超分辨图像间散射点的位置出现偏差的问题,提出了一种利用多通道联合稀疏重建的干涉逆合成孔径雷达(MCJSR-InISAR)三维成像算法。首先利用联合包络对齐算法校正目标平动对应的包络时延,再利用联合自聚焦算法实现平动补偿的初相校正,对来自不同天线的回波信号的距离差进行补偿,然后利用MCJSR进行超分辨成像,同时利用快速傅里叶变换提高运算效率,最后利用水平及俯仰干涉相位信息实现机动目标的InISAR三维成像。MCJSR-InISAR算法具有更高的强散射中心重建精度,能够对通道间的相对相位信息进行有效的保持。实测数据表明,与单通道超分辨成像算法相比,MCJSR-InISAR算法成像结果的熵值降低了约0.17,且运算复杂度降低了O(105)。     

调频连续波雷达自旋目标干涉三维成像方法

相比脉冲体制雷达,调频连续波雷达具有功耗低、成本低、重量轻等优点,发展前景广阔,同时雷达三维成像技术可为目标的分类识别提供重要的特征信息。但是自旋目标在调频连续波信号条件下会产生一维距离走动以及回波相位的改变,这对干涉三维成像产生了影响。针对自旋目标在线性调频连续波雷达中的干涉三维成像技术进行了研究,分析了自旋产生的回波调制效应与相位变化,结合分析所得的调制前后目标在距离 慢时间像上微动特征的变化关系与扩展Hough变换提取的微动参数,解决了干涉三维成像中由于回波调制效应导致的目标坐标畸变问题,提出了基于调频连续波雷达的自旋目标干涉三维成像的具体处理方法。仿真实验证明,所提方法有效提高了自旋目标的干涉三维成像质量。     

大角度旋转目标微波成像

增大转台转角可提高目标成像时的横向分辨率,传统成像算法大转角会引起雷达像模糊,采用一种插值办法在频率空间的直角坐标系中计算出雷达回波数据,用二维快速傅里叶变换对回波数据进行处理,从而获得转台目标的雷达像。经过对仿真数据进行验证,用该方法获得的二维雷达像,其质量高于用极坐标回波数据所成的像。     

基于散射电场的飞机旋翼多普勒回波模拟

旋翼飞机飞行过程中会产生具有独特多普勒特征的雷达回波,通过对旋翼回波的准确模拟,可为不同类型飞机的精确识别提供重要依据.针对现有散射点叠加算法的假设缺陷,从目标高频电磁散射理论出发,提出了基于散射电场的飞机旋翼回波模拟方法.依据电磁散射场与雷达回波方程间的数学关系,发现目标回波的基带信号与目标后向散射电场的复振幅矢量具有一致性,基于此采用物理光学—矩量混合算法,求解飞机旋翼的散射电场;并通过短时傅里叶变换模拟得到旋翼的时频回波.最后,通过与传统散射点积分算法进行仿真对比,同时分析了不同桨叶角对旋翼回波信号的影响规律,验证了所提方法的正确性和优越性,实现了散射电场下飞机旋翼多普勒回波的准确获取,为后续研究飞机的精确识别奠定了理论基础.     

发射天线固定的点频毫米波全息成像雷达系统

基于Fresnel衍射理论分别对固定发射天线的点频毫米波全息成像雷达系统和PNNL设计的移动收发天线的点频毫米波全息成像系统建立了数学模型,确定了目标反演成像质量与发射天线增益方向图、传输空间距离、散射目标形状和接收天线增益方向图之间的关系.同时基于Fourier光学角谱理论和快速傅里叶变换算法,采用Matlab程序编...     

距离扩展目标回波序列的慢时间谱积累检测器

针对目标高速运动引起宽带雷达回波间包络平移使得距离扩展目标的检测率降低的问题,提出了一种距离扩展目标回波序列的慢时间谱积累(STSI)检测器.采用频率-慢时间模型描述距离扩展目标信号,将宽带雷达回波脉压后变换到距离频率域,然后对回波序列各频率单元沿着慢时间作傅里叶变换,最后将各频率向量的最大值累加与检测门限比较进行检测判决.STSI检测器不需要目标运动的先验信息,具有恒虚警检测性能,对目标运动引起的散射点跨距离单元走动不敏感.仿真试验表明,与不依赖散射点分布信息的广义似然比检测器相比,STSI检测器在检测率90％处有5 dB的性能改善.     

一种完全数据驱动的高精度机载L-SAR成像处理方法

雷达机载平台运动误差严重影响成像质量．为了在缺乏高精度运动补偿系统下,实现完全数据驱动的L波段合成孔径雷达（L—SAR）高精度数字重聚焦成像,进行了基于相位梯度自动聚焦的高分辨率机载L-SAR成像处理方法试验．整个方法可分为以下步骤：SAR复图像生成;最强点目标的中心循环移位;加窗;方位向的快速傅里叶变换;相位误差估计;相位矫正;傅里叶逆变换返回复图像域．机载L-SAR信号数据成像处理试验表明：该重聚焦成像方法无须机载平台运动补偿系统提供飞机的运动信息,能够有效地估计和补偿相位误差．相位误差补偿后,信噪比显著改善,可获得方位向分辨率明显提高的机载L—SAR图像,是一种可以满足仅靠数据驱动实现高精度机载L—SAR成像处理的有效方法．     

典型目标逆合成孔径雷达成像仿真

逆合成孔径雷达成像电磁仿真研究在目标识别、隐身与反隐身、目标成像诊断等领域很有实际意义和研究价值。本文采用电磁计算的方法分别模拟了几类典型目标逆合成孔径雷达成像所需的回波矩阵,并应用二维快速傅里叶变换对回波数据进行处理,仿真得到了几类典型目标的逆合成孔径雷达像。仿真结果表明,采用的方法可简单有效地计算出导弹目标的散射回波并对其进行逆合成孔径雷达成像。     

机动目标的时频变换ISAR成像仿真

针对机动飞行目标的成像难点,实施了基于时频变换的逆合成孔径雷达(ISAR)成像处理方案.与传统的点目标模型的回波模拟方法不同,该方案采用全波数值方法计算目标在飞行过程中瞬时位置、姿态下的散射场数据,再依据延时顺序将离散时刻的散射场数据叠加,最终获得雷达的回波数据.数值仿真结果验证了该方案的可行性.     

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.     

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.     

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.     

A computer generator for randomly layered structures

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

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-