轧机油膜轴承实验台轧制力精确控制方法研究

装有油膜轴承轧机的轧制力的稳定性是轧钢产品的纵向尺寸精度的重要参数之一。油膜轴承实验台采用闭环控制方法,上位机对PLC通讯发送控制指令,PLC控制电液比例控制器的输出电流的大小,来控制比例阀的开度,同时压力传感器检测液压缸的压力,上位机的设定值减去检测值得到偏差值,通过比例与积分运算得到反馈值,偏差值和反馈值的差值作为进一步调整比例阀开度的依据.反复重复以上步骤,直到偏差值和反馈值的差值趋于零,达到稳定控制设定压力的目的。同时上位机软件Win CC进行在线监控。     

基于模糊PID控制的螺杆空压机温度控制系统

为了改善传统螺杆空压机温度控制系统中的PID控制器参数设定的准确性不高,提高控制器初始参数设置的及时性和准确性,提出一种基于模糊控制理论的并采用齐格勒·尼克尔斯第一法确定PID控制器参数的初值的方法,并运用于新的控制器中,通过运用模糊控制理论实现对PID控制器参数的修正,从而得到满足控制要求的PID控制器参数。并通过仿真实验,实现PID控制器的参数满足控制要求,验证了该控制器的可行性和有效性。     

蚁群算法PID控制器在磁轴承控制系统中的应用

磁悬浮轴承是磁悬浮转轴系统的重要组成部分.由于磁轴承具有较大的非线性,难于控制,采用常规的参数整定方法很难达到较好的控制效果.因此,采用不完全微分PID控制算法,利用蚁群算法根据设定的系统性能指标实时优化控制器参数.仿真结果证明,这种控制器能够很好地满足系统性能指标的要求.     

基于S7-200 PLC自整定PID控制系统的设计与仿真

为了改善常规PID控制效果,增强系统的稳定性,将S7-200 PLC自整定PID算法引入到闭环控制系统中,在STEP7-Micro/Win编程软件下进行测试,实验结果表明：该方法很好地实现了对PID控制器参数的整定,具有整定过程简单、方便,动态性能优等特点,对实际工程的应用具有一定的指导意义。     

基于参数自整定模糊PID算法的平地机行走速度优化控制系统设计

针对平地机作业时行进速度精度的滞后问题及控制参数,提出了基于参数自整定模糊PID算法的平地机行走速度优化控制系统,协调解决行进速度的滞后问题,并完成了将该算法应用在平地机的控制系统中.系统采用单片机作为行走速度的控制中心,为验证参数自整定模糊PID算法的有效性和可靠性,对平地机的行进速度控制进行了设定干扰信号的测试.通过Matlab软件的Simulink仿真,分析了不加PID的常规控制、PID控制、参数自整定模糊PID控制进行速度稳定控制的效果,测试显示响应时间短、响应速度较快,能够满足设计的要求.     

基于WinCC组态的锅炉废气余热回收监控系统

该文介绍了基于Win CC组态的锅炉废气余热回收监控系统,余热利用的现状,系统的总体设计思路,结合控制要求介绍了系统的组成、硬件配置、程序设计、组态界面的组成及开发过程,通过采用西门子PLC设备与Win CC组态实现对废气余热回收系统的监控。     

轴承动态测量仪神经网络控制系统设计

轴承摩擦转矩的测量是一种动态测量,需要轴承在转动条件下获得数据.轴承型号及承载条件的改变,影响电机转速的控制规律.针对经典PID控制器的结构参数不能在线修改的问题,提出利用BP神经网络的自学习能力,对PID控制器进行结构参数调整,实现对电机速度规律的优化控制方法.仿真结果表明,经神经网络修正过的PID控制器,动态性能优于未修正的PID控制器.     

基于PLC和WinCC的电热锅炉压力监控系统开发

实验室电热锅炉设备开发了以S7-300 PLC为控制器、以Win CC为组态软件的锅炉压力监控系统,作为PLC控制技术课程实践教学的案例。该文构建了PLC控制系统硬件回路,编写了锅炉压力闭环控制PLC程序,完成了上位机监控界面组态。通过实验调试表明,该系统能够将锅炉压力控制在设定值,上位机具有控制系统启停、设置PID参数和锅炉压力、实时显示压力曲线等功能。     

PID在轴承模拟试验加载系统中的应用

将小二元回归数学模型与PID控制算法相结合，对轴承模拟试验加载系统的智能控制进行了试验研究。由于微机控制系统的计算机程序具有很高的灵活性，可以方便地修改PID控制算式，使得这种控制方式有很高的控制精度。实践也表明PID参数的调整使力加载过程更加准确，经实际运行得到了理想的控制效果。     

基于模糊RBF神经网络的双电机驱动伺服系统研究

双电机驱动伺服系统中存在齿隙和摩擦等非线性,常规PID控制不能满足其控制要求.针对常规PID控制器参数固定而导致在控制中效果差的缺陷,提出一种基于模糊RBF神经网络整定的PID控制方法.该方法结合了模糊控制的推理能力强与神经网络学习能力强的特点,可以在线调整得到一组适合于控制对象的PID控制参数.最后在双电机驱动伺服系统中进行仿真试验结果表明所提出的控制策略是有效的.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the