数控稳压稳流直流电源的设计

本文主要论述了一种基于Atmega16单片机为核心控制器的数控稳压稳流电源的设计原理和实现方法。该电源可通过键盘设置电源的输出电压电流,设置步进电压等级为0.1V,输出电压范围0～25V连续可调;步进电流等级为0.1A,输出电流范围0～2.5A连续可调,电压稳定度小于1%,纹波电压小于l0mV。并设有温度传感器,报警器,所有参数由液晶屏实时显示。     

一种数控直流电源的设计

本文介绍一种基于单片机的数控直流电源的设计。该系统主要由单片机、D/A转换器、功率放大电路及键盘显示电路等构成。该电源能够提供-9.9-~＋9.9V,步进为01V的直流电压,电压的预期值和实测值均可由LED显示。具有结构简单合理的优点。     

直流电源数字化调节的实现

本文介绍一种新的实现电源电压或电流的调节方法。该方法摈弃了传统的利用模拟电位器进行电压或电流的调节方法,利用数字化的手段进行电压或电流的调节。该方法的特点为：首先将待调节的电压或电流通过模数转换器转换为数字量,然后设置好调节的步进值,将该步进数值与通过模数转换器转换而获得的数字量相加或相减,将所得结果通过数模转换器转换为模拟量,即实现了电源的数字化调节。     

步进电机控制器在智能脚线机上的应用

为了提高生产力需要，采用AT89C51和L298组成的步进通过软件节省了L297芯片，实现了对多台步进电机的同时控制，降低成本，提高性能；并配有细分恒流电源，通过程序调整，对电机做到平滑启动、停止和失调角度补偿保证电机精确运行；用户可以通过键盘和LED显示器任意调节电机的旋转速度、方向和周期，从而得出实现智能脚线机的方法。     

步进电机高低压电源驱动电路设计

步进电机的驱动电路有单一电压型和单电压恒流斩波型,但这2种驱动方式都存在一定的缺陷,在应用中有一定的局限性,重点介绍了一种步进电机高低压电源切换型驱动电路的构成及工作原理,并且通过实验证明,高低压电源驱动方式在多方面性能都优于传统的单一电压型和单电压恒流斩波型驱动方式.     

高精度直流稳压电源的设计

直流稳压电源在生活应用比较广泛,但是现代科技的进步,使得各行业对它有了更高要求,即精度更高、调节范围更广、输出功率更大、性能更稳定。该设计主要采用单片机AT89S52为控制核心,利用数码管显示达到精准显示电压值,通过键盘设定和步进调整,同时具有过流和过压保护的作用。通过系统设计,可使最大输出电流、输出电压范围、电压调整率、纹波电压峰峰值、负载调整率、DC—DC变换器效率和动作电流的指标均能达到题目要求。     

反应式步进电机单电压驱动方式的改进设计

传统的反应式步进电机单电压驱动方式电源效率低、运转噪音大，仅适用于小功率步进电机。针对单电压驱动存在的问题，从分析反应式步进电动机绕组中的电流入手，提出了基于单电压驱动方式的改进方案。谈方案通过改变单电压驱动的通电方式，有效提高电源的使用效率，降低电机运转嗓音。实际使用效果表明，此方法切实有效。     

基于MAX038的函数信号发生器设计

详细介绍了一种基于MAX038,以STC89C52为主控部件的函数信号发生器的设计.通过键盘设置输出波形、波形的频率和步进值,使其输出规定的波形.波形频率在10 Hz～1 MHz范围内步进可调、幅度在0～5 V范围内步进可调,输出波形稳定,失真度很小.     

一种新型信号发生器设计与实现

本文主要探讨了由DDS芯片、键盘设备，和LCD显示等模块组成。AT89S52对DDS芯片内部进行控制，使之产生标准正弦波、方波，通过RC积分电路生成三角波。利用编程实现频率的预置，电压输出幅度可步进调整。     

步进电动机调频调压电源

一、引言 步进电动机控制系统一般由逻辑控制、功率放大、直流驱动电源等几个部分组成。其作用是控制步进电动机相应绕组依次通电。其中,直流驱动电源一般是由电网电压经隔离变压器降压、整流、滤波而得到的非稳定直流电压。该电压通过功率开关、克服步进电动机绕组阻抗压降和旋转电势,建立起一定的绕组电流。这种直流驱动电     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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