水下机器人数字光纤传输系统的研究与设计

针对某探坝遥控式水下机器人(ROV,remotely operated vehicles)在水下作业时需要与岸基之间完成导航、动力控制和探测信息收集等大量的数据交换的问题,文中设计了一种在1根光纤中传输所有信息的数字光纤传输系统,整个系统的设计核心是基于一片FPGA芯片的高速串行收发器.在高速串行收发器的设计过程中,分别介绍了发送器与接收器的整体结构和功能,利用QuartusII和Modelsim等仿真软件分别对高速串行收发器的各功能模块进行仿真验证,并将该模块应用于整个传输系统中,完成了系统数据传输的要求.该FPGA芯片在系统中的应用不但可以降低系统板级的体积和复杂度,而且实验证明,系统的抗干扰性得到了很大的提高.     

沿航向运动误差对SAR回波特性的影响

分析了合成孔径雷达(SAR)平台沿航向运动误差对回波信号时域及频域特性的影响.建立了带有沿航向运动误差的时域回波信号模型,得到了回波时域误差的计算公式;利用级数反转原理,推导了回波频域误差的表达式,为SAR系统分析及成像算法设计提供了理论依据.理论分析和计算机仿真表明,回波频域特征对沿航向运动误差更为敏感.     

RS-485总线的高速串行远距离数据传输

为实现工业参数的高速远距离长线传输,应用FPGA技术,设计并实现了一种基于RS-485总线的高速串行数据传输方法。分析RS-485数据传输的影响因素,阐述系统总体结构,由时钟脉冲传输测试确定了外围接口。利用串行信号的跳变沿作为高速时钟采样检测的起点以实现位同步,采用8B/10B的链路编码方案,支持高速时钟恢复和数据帧同步,并以双绞线作为传输介质进行了数据传输实验。结果表明:系统在20Mb/s传输速率下实现了串行编码数据流沿220m双绞线电缆的高速远距离数据传输,误码率可达10-11,为现场原始数据监测提供了高效的传输方法。     

RS-485总线的高速串行远距离数据传输方法

为实现工业参数的高速远距离长线传输,应用FPGA技术,设计并实现了一种基于RS-485总线的高速串行数据传输方法。分析RS-485数据传输的影响因素,阐述系统总体结构,由时钟脉冲传输测试确定了外围接口。利用串行信号的跳变沿作为高速时钟采样检测的起点以实现位同步,采用8B/10B的链路编码方案,支持高速时钟恢复和数据帧同步,并以双绞线作为传输介质进行了数据传输实验。结果表明:系统在20Mb/s传输速率下实现了串行编码数据流沿220m双绞线电缆的高速远距离数据传输,误码率可达10-11,为现场原始数据监测提供了高效的传输方法。     

基于Optisystem的DD-OFDM传输性能仿真研究

本文介绍了光正交频分复用(OOFDM)技术及其系统的构造,并展示了Optisystem软件的光路仿真功能.以此为基础,给出了DD-OFDM基于Optisystem的光发送,光链路和光接收模块的仿真模型,模拟了直接检测(direct detection)结构下不同传输距离的系统性能.对接收到的信号进行处理,对传输性能SNR及误码率,星座图等参数进行分析,验证了DD-OFDM传输系统方案的可行性.     

四路视频和音频信号的光纤传输系统设计

利用可编程式逻辑器件、并串转换器和串并转换器及光收发器,设计一个专用的数字光纤传输系统.将多路模拟基带信号的视频和音频进行数字化,形成高速数字流;然后,在现场可编程门阵列(FPGA)上对高速数字流进行时分复用,并通过并串转换器转换为串行数字流,送到光发射器;最后,通过光发射器发射耦合进入光纤传输.接收端则进行相反的操作...     

铰接式高速列车车间悬挂参数优化

以列车为研究对象 ,采用面向对象的建模技术 ,建立了三车铰接垂向及横向非线性动力学模型 ,进行了时域和频域仿真计算 .对铰接式高速列车的车间悬挂参数对列车的垂向和横向运行平稳性的影响进行了研究 ,并得出了结论     

基于光载无线电技术的超宽带脉冲信号产生方法

提出了一种利用光纤色散特性产生超宽带脉冲信号的光学方法.对12.5G b/s伪随机序列的传输特性进行了仿真,结果表明:高斯脉冲通过光纤传输系统后,时域上获得的脉冲信号接近于FCC的超宽带脉冲波形模板,频域上获得的信号频谱接近于FCC的频谱规范.     

基于FPGA的高速数据传输方案设计与实现

为解决目前信号处理系统中数据传输的瓶颈问题,设计并实现了一种基于可编程门阵列(field programma-ble gate array,FPGA)的高速实时数据传输方案.该方案借助Xilinx FPGA的ChipSync技术,稳定地完成了数据的串化/解串,以及通信链路相对延迟的精确测量和调整.同时,利用提出的数据传输同步方法一系统同步和串行低压差分信号(low-voltage differential signaling,LVDS)总线技术实现板卡间大量数据的高速传送,有效地保证了多通道传输的同步性和可靠性,并大大降低了系统互联的复杂度和系统成本.     

基于高速PCB传输线建模的仿真

在高速印刷电路板(PCB)设计中,逻辑门元器件速度的提高,使得PCB传输线效应成了电路正常工作的制约因素.对传输线做计算机仿真,可以找出影响信号传输性能的各种因素,优化信号的传输特性.采用全电荷格林函数法结合矩量法提取高速PCB传输线分布参数并建立等效时域网络模型,应用端接I/O缓冲器IBIS瞬态行为模型,对实际PCB布线进行电气特性仿真,其结果与Cadence公司的SPECCTRAQUEST软件仿真结果一致,且仿真效率得到提高.     

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