OFDM系统载波小数频偏与子载波间干扰分析

在OFDM通信系统中，由于发射端和接收端之间的载波同步误差带来了载波小数频偏，导致了ICI的产生，直接影响到OFDM通信系统性能。该文从数学角度定量分析了0FDM通信系统载波小数频偏，及其引入的ICI对0FDM通信系统的影响，其有实用的参考价值。     

岩石破裂失稳的前兆规律研究

提出用“两体作用”模型来研究自然界的岩体破裂换稳现象。具体分析了两冉体作用系统的失稳过程，运用微机差分计算获得了它的变形和声发射前兆规律。最后在文献［１］的声发射序列关系中引入了距离因子和随机因子，发现有些序列中出现的声发射活动相对平静是由于在两岩体相互作用过程中某一岩体弹性恢复所致。     

非线性对OFDM符号误码率的影响

研究了非线性效应对OFDM符号吗率的影响。在发射机，为了提高发射效率，放大器有时工作于非线性区域，因而带业非线性的影响。对于多载波系统，由于非线性的影响，会使各个子载波之间产生干扰，从而影响所传输的数字信号。本文研究了这种非线性效应的影响，并给出二阶，三阶非线性对系统误吗率影响的具体情况。     

Fourier变换重建超声图像的研究

基于有限衍射波理论的高帧率(high frame rate，HFR)超声成像系统是通过发射平面波成像的．由于采用平面波，故成像区域为矩形．为了得到扇形成像，提出了一种更一般化的Fourier重建图像的方法，它同样基于一次发射就可重建超声图像．与原HFR方法不同的是发射声场可以是非平面波．在非平面波声场中进行了计算机仿真．由于采用了由零阶汉克尔函数所定义的圆柱场，获得了具有扇形形状的超声图像，仿真结果显示了新方法的有效和更具有一般性的特点．     

一波三折：美国航天飞机重返太空

在停飞2年多之后，美国发现号航天飞机终于在2005年7月26日再次成功发射，由于它担当着航天飞机重返太空的重任，因此吸引了全世界的目光。为确保发射安全，这次发射承受了巨大的压力，曾多次推迟发射日期，可谓一波三折。     

声发射岩屑检测系统设计及实验室评价

随着石油勘探开发的需要,大位移井技术及PDC钻头使用日益广泛。由于易产生岩屑床、造成岩屑颗粒细碎等问题,给钻井带来一定困难。为此,研制开发了声发射岩屑检测系统,并进行室内评价试验。该装置利用声发射传感器采集岩屑撞击产生的声发射信号,并通过专门的计算机软件对岩屑声发射信号进行时频分析。在实验室条件下模拟一定黏度钻井液在不同岩屑含量和粒度条件下的声发射信号特征。     

由双模场驱动的级联三能级原子发射谱

给出了与双模光场相互作用的级联三能级原子发射谱的一般表达式,讨论了系统初态对级联三能级原子发射谱的影响,证明了在适当的条件下,由于原子不同跃迁通道的干涉,原子发射谱呈现相位敏感性.     

工程石墨声发射行为及其与结构性能的相关性

通过对多种工程石墨材料声发射行为的系统研究，探讨了石墨材料声发射行为的特征，发现并提出了石墨材料声射数随载指数增加以及声发射振幅服从指数分布的规律，并从其微观结构的角度对发射进行作了解释，在此基础上，对石墨声发射行为与结构性能的相关性首次进行了较为系统的定量分析研究。结果表明，石墨的声发射行为与晶粒尺寸，抗折强度，非线性程度等有着显著的相关性，因此，对在石墨材料生产检测中应用声发射技术具有一定的指     

基于声发射的活塞环缸套系统的摩擦润滑特性

由于活塞环-缸套系统摩擦润滑特性与缸套表面的声发射信号的关联性尚不明确。通过建立活塞环缸套润滑模型,对比研究摩擦力数值仿真结果与试验采集对发动机缸体表面声发射信号。根据冲程中部黏滞摩擦力、声发射信号和活塞速度的相关性,设计阈值-小波包降噪方法提取冲程中部声发射信号特征值。结果表明,冲程中部的声发射信号与系统黏滞摩擦力具有相关性,随发动机转速和润滑油动黏度的增大而增大。     

无线遥控系统在火灾报警方面的应用

介绍了以8051单片机为核心芯片，配合新型的发射芯片U2741B和接收芯片U3741BM构成的无线遥控火灾报警系统，由于U2741B和U3741BM自身的功能特点，使该系统具有较高的性能价格比和实用价值。     

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