血管无造影剂X射线定量相衬成像

为克服血管造影术的缺点并提高分辨率,采用X射线定量相衬成像方法进行了血管成像研究.结果表明,采用该方法进行血管成像不存在造影剂对样品的危害,有效提高了成像分辨率,可获得微血管的精确尺度.     

基于复合成像的电力设备故障检测

提出一种基于复合成像检测的电力设备故障检测方法.在故障条件下,采用复合成像技术对电力设备进行图像采集,对采集的电力设备复合成像进行角点匹配和边缘轮廓特征提取,采用三维区域轮廓扫描方法进行电力设备故障部位的信息增强和分段融合检测处理,实现电力设备故障复合成像检测.仿真结果表明,该方法的检测准确度高,成像输出质量好,提高了电力设备故障检测的测准性.     

虚物经薄透镜成像的规律研究

采用作图法和解析法对虚物经薄透镜的成像规律进行研究,给出虚物经薄透镜成像的典型,指出虚物经薄透镜成像规律与实物经薄透镜成像的规律类同,并总结出两者的成像规律.     

复合材料层合板损伤的延迟累加成像算法

由于复合材料结构的各向异性,导致难以准确获得导波的波速和传播时间。因此在使用传统的延迟累加成像算法对复合材料结构进行损伤识别过程中,会造成损伤定位精度的降低。考虑到复合材料的各向异性导致导波在各个方向的波速并不相同,提出了一种改进的延迟累加损伤成像算法。该方法通过利用激励器与成像点以及成像点与传感器之间的方向角,在成像过程中选取了不同的方向波速进行损伤识别。通过一复合材料层合板冲击损伤的监测实验,将所提算法与采用不同方向波速的传统延迟累加成像算法进行对比,对所提方法的有效性进行了验证。实验结果表明:相比于采用单一速度的延迟累加成像算法,该方法的损伤监测误差控制在4%以内。     

基于物理实验的超广角光栅直透镜成像研究

传统方法中,超广角光栅直透镜成像在受到红外模拟强噪声干扰下,成像清晰度不高。本文提出一种基于矢量细节边缘保留压缩的超广角光栅直透镜成像方法。分析了超广角光栅直透镜成像机理,提出超广角光栅直透镜光束传播理论,采用强边缘保留压缩,确定超广角光栅直透镜成像的网格顶点,通过拓扑连接结构并连接为三角网格,进行矢量细节边缘保留压缩,得到成像输出。实验结果表明,采用该方法进行超广角光栅直透镜的成像,清晰度和保真度较高,抗干扰性能较强,光线发散程度明显减小。     

复合材料层合板损伤的椭圆环定位损伤概率成像

因复合材料结构的各向异性特性导致导波沿各个方向的传播群波速并不相同,因此传统的采用单一波速的椭圆定位成像算法,对复合材料结构损伤的定位监测具有一定的监测误差。为了提高损伤的定位精度,提出了一种改进的椭圆环定位损伤概率成像算法。该方法首先获得导波在复合材料结构中的传播波速带宽,进一步得到各监测通道的损伤散射峰值时刻,最终基于椭圆环定位损伤概率成像算法,进行损伤的定位监测。通过对复合材料层合板的冲击损伤进行定位监测,将所提成像算法的监测结果与采用不同方向群波速的椭圆定位算法的监测结果进行了对比,对所提方法的有效性进行了验证。实验结果表明：相比于采用单一波速的椭圆定位成像算法,所提成像算法的损伤定位误差小于6.5%。     

电容层析成像系统中未知介电常数时测量数据的归一化处理

电容层析成像系统重建图像前要对电容测量值进行归一化处理.对于已知介电常数的成像对象,电容测量值采用0-1校验法进行归一化处理;对于未知介电常数的成像对象,电容测量值采用仿真校验法进行归一化处理,仿真结果表明,可获得很好的重建图像质量.     

利用复合型介质透镜的毫米波成像研究

毫米波焦平面成像技术有广泛的应用前景.本文采用一种复合型介质透镜,将其用于主动式毫米波成像系统,测量了透镜材料的折射率,对金属板进行成像,得到了轮廓较为清晰的图像.     

一种改进的太赫兹主动成像系统

利用卡塞格伦反射镜组自行搭建了一套反射式太赫兹主动成像系统,以商用肖特基二极管探测太赫兹信号,进行室温下的太赫兹快速成像.系统采用二维旋转式扫描,相较于光栅扫描,其扫描速度得到了大幅提高.通过大量实验发现该太赫兹成像系统,仅对铜柱成像效果较好,对其他物体成像效果不佳,甚至无法成像.通过对其可能存在的问题进行分析,利用数学建模的方法重新构建系统扫描轨迹,解决了成像物体形变的问题.此外,采用狄洛尼三角剖分算法对采集的数据点进行插值运算,进一步改善了系统的成像质量.实验结果表明,改进后的太赫兹主动成像系统不仅成像结果形变小,而且对一些复杂结构的物体,仍能获得较好的成像效果,对于促进该系统应用于安检等领域有着重要的意义.     

基于成像算子优化的微震逆时定位方法

针对目前微震逆时定位成像存在的问题,提出一种优化后的成像算子,对模型数据进行抗噪性、误差速度以及检波器分布和数量进行测试,并提出采用峰度值作为定位成像结果的评价标准.结果表明,优化后的成像条件在定位能量聚焦程度和成像分辨率上都得到了提升,对含速度误差和含噪微震数据都有较好的成像结果,并且对检波器的分布和数量有较好的适应...     

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.     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has