基于低压电力线载波的远程电能抄表系统的设计

本文设计了一种基于低压电力线通讯技术的远程电能抄表系统,该系统采用低压电力线作为通信信道,不必另外架设通信电缆,能够大大节省投资。叙述了系统的结构和功能,以及软、硬件设计方案,并给出了部分原理框图。该系统成本低,可靠性高,稳定性好,应用前景较好。     

基于MSK的低压电力线通信

由于低压电力线的信道特性是复杂多变的，如何利用低压电力线实现可靠且具有较高通信速率的通信，一直是电力线通信领域的热点问题。笔者把MSK应用于低压电力线通信，分析了MSK的应用原理，构建了基于MSK的低压电力线通信系统模型。仿真结果表明：MSK调制技术较好地满足了电力线通信信道有效带宽窄、对信号振幅的衰减具有时变性和频率选择性的特点，实现了较好的频谱利用率。     

扩频通信在低压电力载波通信系统中的抗干扰性分析

简要介绍低压电力线载波通信的发展前景和技术难点,在阐述扩频通信的基本原理的基础上,将通信理论中的直接序列扩频技术（DSSS）用于解决低压电力线通信的干扰问题,采用SC1128加之辅助外围电路,设计出低压电力线载波通信系统,并对该系统进行仿真,验证DSSS技术对干扰信号的抑制作用。     

基于PL3201的电力线扩频载波技术应用

设计了以PL3201为核心的载波通信功能模块,针对该芯片提出一种符合我国低压电力线载波信道传输特性的通信调制方法,采用QPSK调制等技术自制了一个低压电力线载波通信系统,其抗衰减和抗干扰的性能具有较大的优势,实验结果表明利用220V低压电力线进行数字信号的传输是切实可行的。     

基于差分算法的低压载波通信信道模型多参数辨识

低压电力线载波通信是通过低压电力线网络传输模拟和数字信号的一种通信方式。本文在已有的传输模型结构上,将差分算法应用到低压载波通信信道模型的多参数辨识上,取得了不错的参数辨识效果,为电力线系统的研究和设计提供了依据。     

一种基于OFDM的低压窄带电力线通信基带系统

通过对低压电力线的信道模型和电力线噪声的分析,提出了基于正交频分复用(OFDM)的低压电力线(LV-PLC)基带系统方案,采用差分正交相移键控(DQPSK)调制和改良的同步方式以适应电力线通信,并在Matlab平台上完成OFDM的3~500 kHz通信系统建模和系统仿真,在NI仪器上完成现场可编程门阵列(FPGA)硬件实现,并结合实际信道进行测试,测试结果表示,系统使用应用于LV-PLC,可以实现高速稳定的通信,传输速率峰值可达300 kb/s.     

LPLC自适应速率传输技术的实现

针对低压电力线信道复杂多变的特点,提出了根据信道环境实时改变数据传输速率的通信方式。其中,包括CRC检错码技术、ARQ重传技术、混合型ARQ自适应速率传输协议以及数据合并判决等方面的应用。最后,采用TMS320F2812DSP作为处理器,以FSK调制解调为通信方式,搭建电力线载波通信系统,实现自适应速率传输的低压电力线载波通信方案。     

一种基于SC1128的扩频通信电路

介绍一种基于SC1 1 2 8的扩频通信电路 .论述了SC1 1 2 8的特点 ,详细阐述了该通信系统的硬件组成及其功能 ,同时介绍了该系统中的主要软件功能模块并进行了测试分析 .该通信系统可实现干扰较强的低压电力线载波通信 ,成本较低 ,具有一定的应用前景     

基于正交频分复用技术的低压电力线载波宽带通信的研究与实现

本文介绍了电力线通信的发展和优势,研究分析了低压电力线信道特性及其模型的建立,研究了正交频分复用（OFDM-orthogonalfrequency division multiplexing）的系统组成与原理。并以芯片组INT5500CS为核心,设计了一个电力线调制解调器,实现了宽带电力线载波通信。     

基于正交频分复用的宽带电力线MODEM的设计与实现

本文介绍了电力线通信的发展和优势,研究分析了低压电力线信道特性及其模型的建立,研究了正交频分复用（OFDM-orthogonalfrequency division multiplexing）的系统组成与原理,并以芯片组INT5500CS为核心,设计了一个电力线调制解调器,实现了宽带电力线载波通信。     

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