软开关技术在SRD系统中的应用研究

介绍了软开关技术的基本原理、基本的软开关电路拓扑,提出一种开关磁阻电机功率变换器的软开关方案,该方案在直流电源与相绕组控制电路间插入一种准谐振直流环节电路,并给每个相开关并联电容器后实现了开关磁阻电机功率电路中所有器件的软开关操作.对主电路工作模式进行了分析,并通过仿真验证了所提电路的软开关性能.     

普通电感式荧光灯电路的改进

综合分析了普通电感式荧光灯电路的改进方法，指出若将二灯并联起来，组成双管荧光灯电路，则可以大大提高电路的功率因数。     

分户计量住宅采暖户内系统形式对比分析

分户计量住宅采暖技术规程一般推荐:双管放射式系统、双管并联式系统、水平串联单管跨越式系统3种方案。在工程实际项目中,一种新的双管放射式与水平串联单管跨越式相结合的系统得到越来越广泛的应用。针对4种设计方案,结合工程实例,从散热器片数、管长和管径等方面对各系统作了计算对比,说明了4种方案的等效性。     

双管串联的功率变换器控制电路研究

结合一高频高压开关电源实际课题，针对高压输出情况下功率管的耐压问题，提出了在功率变换级采用双管串联反激组态电路解决功率管耐压这一有效措施，并对功率变换级采用双管串联反激组态的开关电源控制电路进行了实验研究。     

功率器件IGBT串联的移相控制技术

IGBT器件在电力装置中得到广泛应用，用IGBT串联提高装置对超单管耐压电源的控制是切实可行的，关键问题要解决IGBT串联的静态均压和动态过压问题。提出用并联电阻的办法解决静态均压问题；用移相控制技术，通过对主电源分级，对各级电源移相控制，实现主电源的分级接入和撤离，解决主控电路中IGBT的动态过压问题。文中讨论了IGBT串联电路的耐压、移相角度等参数的确定办法，分析了该技术对开关极限频率、输出波形的影响以及存在的问题。该技术已在大功率激电发送机产品中得到成功应用。     

双管板换热器的特点及应用

本文结合化工生产工艺条件，对双管板换热器的应用场合，常见的双管板换热器的类型以及双管板换热器与单管板换热器的区别进行了相关阐述。     

单位恒压源与恒流源串并联激励时功率问题的讨论

以澄清电路分析中关于功率发出与功率吸收的概念为基本出发点，对单位恒压源和恒流源串、并联激励时的功率问题做了定量分析。并由此得出，单位恒压源和恒流源串联激励时，恒流源既不产生功率也不吸收功率；单位恒压源和恒流源并联激励时，恒压源既不产生功率也不吸收功率。     

单相并联型有源滤波器的研究

给出了具有自适应谐波检测电路的单相并联型有源滤波器。设计和实现的有源滤波器采用了电压型脉宽调制（ＰＷＭ）功率逆变电路，定频开关电流跟随方式和基于干扰对消原理实现的模拟自适应谐波及无功检测电路。给出了电压型ＰＷＭ功率逆变器的数学模型和自适应谐波检测电路原理及硬件实现。详细讨论了限流电感及逆变器电容电压对补偿特性的影响，并给出了限流电感和储能电容器的选取条件。最后给出了并联型有源滤波器对感性及容性负载补偿的实验波形及分析。实验结果证实所提方案的正确性和实用性     

铁磁谐振式稳压器谐振状态的理论分析

铁磁谐振问题是一个典型的非线性磁路问题,在电路磁路理论中已对它进行多次探讨.但一般文献多限于研究它的应用及计算方法(这当然是极为重要的),纯理论的分析则不多见.本文针对并联铁磁谐振稳压器的谐振状态进行了新的研究,分析了磁路的工作情况,在此基础上给出了并联铁磁谐振稳压器中发生串联和并联谐振的条件,并绘制了由理论分析得到的各谐振曲线.这些谐振曲线与实验结果几乎完全一致,证明理论分析的正确性.     

三相单管Boost型功率因数校正电路的仿真研究

本文对三相单管升压型功率因数校正器的运行原理进行了分析，并提出了这种电路工作于电流心界连续模式下的调频控制方案。然后根据主电路运行原理和控制方案，建立主电路和控制电路的仿真模型，最后对仿真结果进行了分析并证实控制方案可行性。     

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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