浅析远程监控技术

远程监控系统是指利用计算机通过网络实现对生产过程控制系统的监视和控制,突破了地域上的制约而实现异地监视和控制生产过程现场设备。传统的工业控制网络是基于现场总线的,由于现场总线的通讯标准尚未统一,使得现场总线的标准各种各样,这使设备在不同的现场总线监控系统中难以兼容。此外,现场总线目前尚处于低速阶段,难以满足数据高速传输的需要。因此本论文通过和现场总线的对比,分析了在工控领域中,以太网技术的优势。     

现场总线技术的发展及应用选择浅析

介绍了现场总线技术的优点，发展过程及多协议标准的形成，分析了当今几种典型现场总线的技术特点及优势。面对多协议标准并存的现实及统一标准形成的不可预期性，就国内现场总线技术应用开发的技术与经济环境，提出了国内现场总线技术应用开发的道路及不同应用领域现场总线协议的择优选型。     

现场总线技术及其发展趋势

１现场总线的产生传统的工业自动化测控系统一般是基于ＤＯＳ（分散式控制系统）和ＰＬＣ（可编程逻辑控制器）的，属于封闭式的控制系统。一个系统不经过网关等接口无法实现和其他系统的通信。由于控制器与现场设备的连接是点对点的，即一个Ｉ／Ｏ点对现场设备的一个测控点，这种连接需要铺设大量的线缆，成本高，结构复杂，可靠性差，维护不方便。而且由于ＤＣＳ不是开放系统，互操作性差，难以实现数据共享。为了解决这些问题，现场总线（Ｆｉｅｌｄｂｕｓ）技术应运而生。现场总线技术是计算机技术、通信技术和控制技术发展的产物；是连接智能现场设备和自动化系统的数字式、双向传输、多分枝结构的通信网络，它的关键标志是支持全数字通信。它可以把所有的现场设备（仪表、传感器与执行器）与控制器通过一根线缆相连，形成现场设备级、车间级的数字化通信网络，可完成现场状态监测、控制、远传等功能。现场总线技术使企业网（Ｉｎｔｒａｎｅｔ）的信息采集延伸到了工业现场。它代表了当今自动化的发展方向，是工业现场级设备通信的一场数字化革命。由于现场总线技术明显的优越性，在国际上成为一个研究开发的热点。各大公司都开发出了自己的现场总线产品，形成了自己的标准。目前常见的标准有数十种...     

现场总线技术及其发展趋势

１现场总线的产生传统的工业自动化测控系统一般是基于ＤＯＳ（分散式控制系统）和ＰＬＣ（可编程逻辑控制器）的，属于封闭式的控制系统。一个系统不经过网关等接口无法实现和其他系统的通信。由于控制器与现场设备的连接是点对点的，即一个Ｉ／Ｏ点对现场设备的一个测控点，这种连接需要铺设大量的线缆，成本高，结构复杂，可靠性差，维护不方便。而且由于ＤＣＳ不是开放系统，互操作性差，难以实现数据共享。为了解决这些问题，现场总线（Ｆｉｅｌｄｂｕｓ）技术应运而生。现场总线技术是计算机技术、通信技术和控制技术发展的产物；是连接智能现场设备和自动化系统的数字式、双向传输、多分枝结构的通信网络，它的关键标志是支持全数字通信。它可以把所有的现场设备（仪表、传感器与执行器）与控制器通过一根线缆相连，形成现场设备级、车间级的数字化通信网络，可完成现场状态监测、控制、远传等功能。现场总线技术使企业网（Ｉｎｔｒａｎｅｔ）的信息采集延伸到了工业现场。它代表了当今自动化的发展方向，是工业现场级设备通信的一场数字化革命。由于现场总线技术明显的优越性，在国际上成为一个研究开发的热点。各大公司都开发出了自己的现场总线产品，形成了自己的标准。目前常见的标准有数十种...     

基于现场总线的网络故障分析

现场总线是用于过程控制现场仪表与控制室之间的一个标准的、开放的、双向的多站数字通信系统。本文介绍了变电站综合自动化系统中常用的两种现场总线：CAN（Controller Area Network控制器局域网）、LonWorks（Local Operation Network局部操作网）。。详细分析了基于RS-485现场总线网络的故障查找与排除方法。     

现场总线控制系统的现状与发展

本文介绍了现场总线所具有的全数字化通信、分散控制、开放互连性等优点，以及当前有代表性的几个现场总线标准，分析了现场总线控制系统的可靠性问题，并对现场总线的府用前景及我国应用FCS的现状做了介绍。     

浅析FF基金会现场总线

说明基金会现场总线的特点及标准,详细介绍FF总线所挂接仪表数量和连接电缆长度的算法,阐述FF总线本质安全防爆的方法。通过列举应用实例,说明该总线系统有着广阔的发展前景。     

CAN总线在发动机测试系统中的应用

现场的总线控制系统（FCS）将是新世纪自动控制系统发展的主流，是继DCS后新一代的控制系统。现场总线是综合自动化发展的需要，同时智能仪器仪表则为现场总线的出现奠定了基础。     

INTERBUS在自动化控制中的应用及意义

由于生产机电设备经常出现信号干扰大、系统稳定性差、控制经常失灵的问题，而采用当前国际先进的现场总线技术，进行信号传输和现场控制，因其开放性和可互操作的网络，能够高可靠性的保障正常生产，降低安装成本和维护费用。现场总线通过将现场各控制器及仪表设备互连，构成现场总线控制系统，并且INTERA3US现场总线快速检测、定位故障的功能，为系统快速的排除故障提供了有力保障，对自动化控制发展具有重大意义。     

浅析现场总线在电厂辅助车间的应用

随着控制，计算机．通信．网络．信息等技术的飞速发展，产生了现场总线技术，并且其在人们的生产生活中发挥着越来越大的作用。该文主要介绍了现场总线控制系统的特点，以及其较与DCS的优点；对在过程控制领域中应用广泛的基金会现场总线和过程现场总线作了简要介绍。继而讨论了现场总线在电厂中的适用范围。并结合平顶山鲁阳发电厂2X1000MW机组主厂房外水系统的工程应用实例，提出了目前现场总线在电厂应用中需要注意的一些问题，展望了现场总线的发展。     

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-