基于PROFIBUS-DP的西门子变频器控制系统

介绍了现场总线变频器控制系统的构成和特点,在汽车总装生产线线上组建基于PROFIBUS-DP的变频器控制系统,分析了可编程序控制器与变频器之间的通讯协议,并详细说明了变频器PROFIBUS-DP控制系统的参数设置及编程方法。     

基于PROFIBUS-DP的压力传感器设计

根据PROFIBUS-DP现场总线协议，采用支持该协议的专用芯片SPC3，设计了带有现场总线PROFIBUS-DP通讯接口的压力传感器的硬件电路和控制软件．传感器选用了带有温度补偿功能的高精度硅压阻式压力传感器MPX2100GP，从而提高了测量精度．该传感器具有信号采集和处理、数字通信等功能，可作为从站方便地接入PROFIBUS-DP现场总线控制系统．     

Profibus-DP通讯在PLCS7—300和变频器6SE70上的应用

本文通过介绍PROFIBUS-DP通讯的特性和举例阐述PROFIBUS-DP现场总线在生产现场的具体应用,详细介绍了西门子PLC S7-300与变频器6SE70通过PROFIBUS-DP通讯的硬件组态、软件编程及变频器的相关参数设置。     

现场总线Profibus—DP在火炬回收控制系统中的应用

本文描述现场总线PROFIBUS—DP在丘东天然气处理厂天然气火炬回收控制系统中的具体应用。通过现场总线PROFIBUS-DP,西门子S7—300、S7—200PLC实现对远程I／O、MM440变频器的控制,并实现与DehaV—DCS系统的数据通信。     

PROFIBUS-DP和MPI 在造纸生产通信网络中的应用

针对某造纸厂生产线改造项目,文章介绍一种基于MPI和PROFIBUS-DP通信网络控制系统,该通信网络控制系统包括监控级和现场级,监控级采用MPI通信总线,现场级采用PROFIBUS-DP通信总线,系统可靠性高、开放性好.文中介绍了通信网络的整体结构,详细阐述了上位机中WinCC监控系统的实现方式和现场级网络中DP主站...     

平面长距离转弯胶带机自动化控制

本研究通过S7-200、ET200M,分布式I/O作为控制系统的分站,采用PROFIBUS-DP现场总线实现单机10公里长距离水平转弯胶带机自动化控制。     

基于PROFIBUS-DP的变频器网络控制

磁悬浮列车的运行原理和结构特点形成了其特殊的牵引控制方式——长定子换流技术．为研究这种牵引控制方式对于解决列车在相邻的两个长定子间的切换过程中推力损失最小问题，以实际磁悬浮列车的牵引控制系统为基础，组建了基于PROFIBUS-DP现场总线的变频器网络控制系统．在STEP7编程环境下，利用系统所提供的各类功能函数完成主站与从站间的数据通信及系统监控，并初步实现了对于长定子换流过程的模拟。     

PROFIBUS-DP在钢厂压平机控制系统中的应用

本文介绍了PROFIBUS-DP现场总线技术的特点及其在压平机控制系统中的应用以及在运行过程中表现出来的优越性.     

基于PROFIBUS-DP的智能电动执行机构关键技术研究

现场总线技术（FCS）是现代工业发展的必然趋势，电动执行机构作为工业过程控制系统不可缺少的部分，实现总线化功能是其目前主要研究方向．本文主要研究了基于PROFIBUS-DP总线智能化接口芯片SPC3实现电动执行机构的总线通讯功能，着重介绍电动执行结构PROFIBUS-DP通信接口的设计与实现，实验结果表明，所提出的方案正确可行并具有良好的性能．     

变频器在开放式工业控制现场总线中的应用

介绍了开放式工业控制现场总线的特点以及SIEMEMS变频器连入分布式外围设备PROFIBUS-DP(简称DP协议)的硬件和软件结构,研究了在DP协议网络环境下用参数过程数据PPO型1或PPO型3对变频器进行实时或一般要求下的监控方法。     

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-