脉冲磁场测量系统的研制和标定

为了评估雷击建筑物或其附近室内的脉冲磁场水平,研制了一套由自制磁场探测线圈与光纤传输系统集成的脉冲磁场测量系统.光纤传输系统的灵敏度系数通过正弦波发生器进行标定.8/20μs冲击电流发生器输出端连接直径为0.3 m的单匝线圈组成磁场发生器,磁场探测线圈通过固定在单匝线圈的中心进行标定.试验结果表明,该系统能够有效地测量脉冲磁场,磁场探测线圈的B/U标定系数误差小于3%.     

时谐磁场中的金属微粒磁化及电阻脉冲检测方法

为进一步提高电感式金属微粒检测芯片的灵敏度,提出一种基于电阻脉冲的微粒探测方法.理论分析了金属微粒在探测线圈时谐磁场中的磁化,同时,在微粒流速恒定的情况下,实验研究了不同微粒粒度、磁场变化频率下的电阻正向脉冲.实验结果表明,采用电阻脉冲方法可以提高非铁磁微粒检测的信噪比,并由此进一步提高了非铁磁微粒的探测灵敏度.     

用脉冲移动指零法测量磁场强度的方法

用音频发生器使坡莫合金片探头激磁,在外磁场为零时,从示波器观察探头测量线圈中感应电动势正脉冲波形的位置.再将探头放到被测磁场处,则见正脉冲已移动某一距离.然后在补偿线圈中通入一电流使正脉冲回到原来位置,从补偿线圈常数和电流即可确定被测磁场的大小,这便是脉冲移动指零法的原理.本文对探头的结构、测量线路及其工作原理加以说明,并用实验数据来验证.最后对此法的测量范围和准确度加以估计.     

单边核磁共振磁体梯度磁场设计的Gram-Schmidt正交化拟合方法

针对传统圆形Halbach磁体结构封闭难以应用于开放式核磁共振中的缺点,提出一种半椭圆形分布的开放式Halbach磁体结构.调节各磁体模块中心点所在椭圆曲线的长轴长度,计算YOZ平面内不同高度上磁场的平坦程度,使用Gram-Schmidt数据拟合方法,得到一种平坦程度最优的磁体结构.优化结果表明:该结构磁体可在YOZ平面上50 mm×50 mm范围内产生水平方向平坦,垂直方向近似梯度变化的磁场,梯度值为2 mT/mm,且获得一个面积为4 mm×4 mm,均匀度为1.3×10-3,场强为0.073 9 T的均匀磁场区域.根据优化设计结果,搭建了实际磁体系统,并对该磁体系统的磁场进行测量,测量结果与设计结果一致.该开放式磁体优点在于垂直方向的梯度磁场由永磁体结构自然形成,不需额外的梯度线圈,从而简化了梯度编码系统的设计.     

亥姆霍兹线圈磁场均匀性的研究

为了探究亥姆霍兹线圈空间磁场均匀区域的大小、形状及范围,利用FD-HM-I型亥姆霍兹磁场测定仪及其所配备的高灵敏度毫特斯拉计传感器探头,探测了亥姆霍兹线圈轴截面上有限元磁场的大小,以两线圈中心连线的中点为坐标原点,建立坐标系,根据线圈的对称性,得到了亥姆霍兹线圈空间磁场均匀区域的大小、形状及范围.由于毫特斯拉计传感器探头的体积小、分辨率高,因此,该传感器适用于物理实验中弱磁场的测量,用它探测磁场准确度较高,误差较小。     

空心电抗器匝间短路在线检测的改进技术探究

基于场路结合方法,采用MATLAB软件编程,对空心电抗器匝间短路前后的电流与磁场分布情况进行了研究,为通过感应线圈检测电抗器匝间短路故障的磁场探测法提供了理论依据,并将2010-10217935. 7号专利提出的两组测试线圈的磁场探测法改进为多路测试线圈探测法。以一台干式空心电抗器试验样机为例,采用FPGA进行了信号采集和短路信号检测。由实验结果可知,该检测系统可以迅速及时地获取匝间短路信号并发出报警,验证了改进型磁场探测法的有效性。     

基于Ansoft的磁处理线圈的电磁场分析

为了解中频脉冲磁场去应力样机中磁处理线圈磁场的分布情况,应用Ansoft对样机中线圈产生的电磁场进行分析,分析了线圈内部无工件状况下电磁场的分布,及线圈内部不同位置存放轴承外圈工件后电磁场的分布,其分析结果与实际测量结果吻合较好。对于中频脉冲磁场去应力样机中线圈的优化设计具有较好的指导价值。     

共振驱动的类轴子粒子探测实验设计与优化

为了进一步提高类轴子粒子传播的与自旋速度相关的新相互作用的实验灵敏度,本文研究了极化³He作为探针的共振驱动方法来探测其与非极化物质间的新相互作用.首次将核磁共振Bloch方程中驱动磁场看作微扰,使用微扰法求解出Bloch方程的解析解,并计算出共振时有效磁场的放大倍数.其次分析了玻璃气室参数对有效磁场放大倍数的影响,优化设计后半径为1-2 mm的特种玻璃气室可使有效磁场放大倍数达到10⁷.依托我们的特种玻璃气室制备设施和工艺,可使现有的实验探测灵敏度提高5个数量级.     

基于心脏刺激的强脉冲磁场刺激器的设计

提出了一种强脉冲刺激器的设计方案,应用此方案设计了一台基于心脏刺激的强脉冲磁场刺激装置.该装置的充电电压达到1200V时,在刺激线圈中心可以获得磁感应强度为10.6 T的磁场.阐述了该磁场刺激装置的具体设计思想和磁感应强度的计算方法.应用刺激线圈中心磁感应强度为2.7 T,周期为0.2Hz的脉冲磁场刺激开胸蛙的心脏,结论是脉冲磁场直接刺激蛙的心脏可以改变蛙的心率.     

基于COMSOL软件的半线圈电磁远探测响应特性分析

传统电法测井仪器探测深度仅数米,无法满足井周数十米水平井地层边界识别的需求.传统的电磁远探测方法都是基于磁场进行计算的,本文利用半线圈所具有的远探测能力,同时测量电场强度和磁场强度,计算了仪器旋转角度、工作频率、线圈系源距、仪器距边界距离等因素对半线圈响应特性的影响.研究表明:半线圈对旋转角度反应敏感;半线圈接收的信号...     

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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