用8098单片机的PWM波进行步进电机细分驱动

步进电机的控制精度直接影响到数控设备的控制精度，本文提出的步进电机细分驱动将能有效地提高步进电机的控制精度，使数控精度大大提高。     

多通道虚拟超声检测系统研究

多通道虚拟超声检测系统由计算机、３块ＰＣ插卡（多通道超声发射／接收卡、超声图像卡与步进电机驱动卡）、聚焦探头和机械系统组成,能够实现,Ａ、Ｂ、Ｃ扫描成像,数据处理,缺陷定位,定性和定量分析,将计算机技术,虚拟仪器技术,信号和图像处理技术引入超声无损检测领域,拓宽了传统超声检测的应用范围。     

一种计算机数控的医用呼吸模拟平台设计

为了给呼吸补偿方法的验证提供数据,设计了一种计算机数字化控制的医用呼吸模拟平台.本文将拟合的呼吸运动曲线映射成三维运动坐标数据,以ATmega2560单片机为核心,采用42BYGH34两相步进电机设计了一种模拟人体呼吸运动的三维运动平台.该平台利用单片机解析来自上位机发送的三维运动曲线数据,然后转换成驱动信号并结合驱动芯片对两相步进电机进行驱动,进而带动与皮带相连夹具上体模的周期运动,从而模拟人体器官的运动.经测试,该运动平台性能稳定,可以为模拟呼吸运动数据的采集提供硬件平台.     

基于ARM的步进电机细分控制

本文设计的步进电机细分控制系统,基于ARM7芯片LPC2214和专用驱动芯片LMD18245,采用“线性＋正弦”波形驱动方法和电流矢量恒幅均匀旋转算法,通过ARM控制器产生波形数据,经D／A芯片MAX526转换成对应的控制电压,经过驱动芯片LMD18245放大,驱动两相步进电机．通过键盘输入控制信号,利用液晶显示电机的频率和细分倍数,利用uCLinux和MiniGUI平台进行程序设计．该系统实现了步进电机的多功能控制,得到4096细分的精确步进效果．     

步进电机细分驱动中绕组电流的修正

在步进电机细分驱动系统中，由于步进电机绕组电流与磁场幅值之间的非线性关系，以及步进电机转子的磁滞效应等因素，细分后得不到均匀的步距角，因此必须对细分电流的大小进行修正，讨论了修正的方法，并给出了修正后的实验数据。     

无线控制原子力显微镜系统

无线控制的原子力显微镜系统,一方面可以排除各种连线对操作原子力带来的不方便;另一方面,可以很好的排除外界噪声对操作结果带来的不利影响;同时有利于非工作人员了解实验状况。无线发射端通过电脑连接无线发射模块收发射操作指令及数据,无线接收模块接收到数据进行处理后驱动步进电机移动。同时数据采集卡采集AFM微悬臂梁的偏转信号,通过无线收发模块传送给计算机进行分析,实时监测探针与样品之间的作用力,最终实现探针的逼近,及对操作样品的观察。该系统不仅操作灵活,而且工作稳定。     

无线控制原子力显微镜系统简

无线控制的原子力量微镜系统,一方面可以排除各种连线对操作原子力带来的不方便;另一方面,可以很好的排除外界噪声对操作结果带来的不利影响;同时有利于非工作人员了解实验状况.无线发射端通过电脑连接无线发射模块收发射操作指令及数据,无线接收模块接收到数据进行处理后驱动步进电机移动.同时数据采集卡采集AFM微悬臂梁的偏转信号,通过无线收发模块传送给计算机进行分析,实时监测探针与样品之间的作用力,最终实现探针的逼近,及对操作样品的观察.该系统不仅操作灵活,而且工作稳定.     

基于经济型数控机床的步进电机选用原则研究

步进电机是开环步进驱动系统中的关键部件,电机选择的优劣直接影响机床的加工精度和快速反应性,本文探讨了步进电机的选用原则及方法。     

步进电机驱动系统的相平面法计算机设计

本文推导几种步进电机驱动方式的数学模型,并借助于计算机作图。文中使用相平面法来分析研究驱动方式及系统参数对步进电机性能的影响。使得在设计步进电机驱动系统时,可正确选择参数,避免失步。     

显微镜坐标自动定位系统

本设计采用ATMEL公司的单片机AT89S51对步进电机进行控制．通过I／O口输出的具有时序的方波作为步进电机的控制信号。信号经过4个差分器驱动步进电机;同时,用8个键来对电机的状态进行控制。     

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