横向磁场开关磁阻电机永磁屏蔽技术研究

首先阐述了横向磁场开关磁阻电机转矩提升原理，着重分析了漏磁通产生原因以及对电机性能产生的影响，在此基础上研究了一种具有双边永磁屏蔽外转子低速横向磁场开关磁阻电机，介绍了样机的结构特点，并采用三维等效磁网络法对样机进行了磁场计算，研究表明利用装设在定、转子极间的永磁体能有效屏蔽漏磁通，增加磁通变化率，提高输出转矩。样机的计算结果和试验结果基本吻合。     

盾构隧道漏泥砂后结构响应分析

天津地铁津滨轻轨漏泥砂事故致使软土盾构隧道产生了不均匀沉降,导致隧道结构产生了次生变形和结构内力.依据弹性地基理论,对高斯地基纵向沉降曲线进行了修正,得到了此次事故后隧道结构纵向沉降拟合曲线,进一步得到隧道结构次生内力分布.结果显示,此次事故造成的最大次生弯矩为6 000kN·m、剪力为1.4kN,位于漏泥砂处;现场调查发现,漏点前后7 ～12环处,拱顶管片内侧裂损严重,且为受压破坏.对比现场调查,沉降曲线反映的事故后的结构响应是可靠的,同时分析了粘钢法加固后的稳定性.     

盾构隧道通用管片排版设计与纠偏研究

通用楔形管片作为一种较先进的隧道衬砌形式,在盾构法施工中能够较好地控制隧道掘进轴线和管片成环质量.以宁波地铁2号线机场站-栎社新村站区间工程为背景,结合现场实际施工经验,针对通用管片的特点,对通用管片排版设计进行了研究.对通用管片在不同点位拼装时上、下、左、右各方向的超差和轴线偏差进行了计算,分析了通用管片排版设计时应当考虑的影响因素.研究结果表明,按照设计的排版方案对通用管片进行成组使用,可以较好地拟合直线段、圆曲线段以及缓和曲线段的设计路线,在管片排版中应重点考虑线路拟合、盾构姿态、油缸行程差、盾尾间隙等因素.     

弱电设备屏蔽体接地点的选择

屏蔽是抑制干扰的重要措施,屏蔽体屏蔽效能的高低与屏蔽体的接地又有密切的关系.重点分析了板型屏蔽体、电缆屏蔽层、信号电路屏蔽盒等3种有代表性的屏蔽体.通过选择不同接地点,运用等效电路进行分析、比较,从而选定了最佳接地点,进而总结了屏蔽体接地点总的选择原则.     

小曲线半径隧道无铰接盾构施工技术

通过理论分析证明了采用无铰接盾构施工小曲线隧道存在可能性.根据无铰接盾构施工小曲线隧道的特点,结合实际工程,介绍了在曲线段始发、隧道推进过程中的轴线控制、管片偏移等方面采取的针对性控制措施.工程实践表明,采用无铰接盾构施工小曲线半径隧道取得良好效果.     

A method for preparation of a high-quality high temperature superconducting ceramics

An improved method for hot pressing of high temperature superconducting (HTSC) powders prepared by conventional solid phase synthesis of the initial BaCO₃, CuO and Ln₂O₃ allows one to obtain HTSC targets and magnetic shields possessing a high degree of homogeneity. By sputtering such targets HTSC films with critical current density of 3.3·10⁶ A/cm² have been deposited. Shields, prepared according to this method, show a shielding coefficient of 10⁵ andH _c of 79 Öe in the constant magnetic field and in the alternating magnetic field the amplitude is 90 Öe in the frequency range of 70–3000 Hz.     

Mechanically aspirated radiation shields: A CFD and neural network design analysis

Accurate air temperature measurements made by surface meteorological stations are demanded by climate research programs for various uses. Heating of the temperature sensor due to coupling with the environment can lead to significant errors. Therefore, accurate in situ temperature measurements require shielding the sensor from exposure to direct and reflected solar radiation, while also allowing the sensor to be brought into contact with atmospheric air at the ambient temperature. The difficulty in designing a radiation shield for such a temperature sensor lies in satisfying these two conditions simultaneously. In this paper, we perform a computational fluid dynamics analysis of mechanically aspirated radiation shields (MARS) to study the effect of geometry, wind speed, and interplay of multiple heat transfer processes. Finally, an artificial neural network model is developed to learn the relationship between the temperature error and specified input variables. The model is then used to perform a sensitivity analysis and design optimization.     

Geometrical aspects of cylindric magnetic shields in strong static fields

Motivated by rrER (the International Thermonuclear Experimental Reactor),research on a magnetic shield against a strong field has been carried out.In this paper,a cylindric magnetic shield is studied by using the finite element method with a nonlinear magnetization curve.The geometrical aspects of shielding performance are identified and corresponding suggestions for application are provided.Among them,the effects of the edge and cover thickness have not been mentioned elsewhere to our knowledge.     

The Void and Hole Effect in D2 Moderated Reactor

The reactivity cbange due to increase in the radius of empty hole was measured in a D₂O moderated reactor and some results differing from experiments with ZEEP were obtained. It can be concluded that the streaming in a hole is not so effective for reactivity. In measuring neutron flux in a void, a flat thermal neutron flux distribution was obtained and it has been concluded that the neutrons leaking through the empty hole or the void do not consist of thermal neutrons but fast neutrons for the most part. The experimental result of reactivity change due to the void location in the core indicates that the relation between the void location and the reactivity change is independent of the neutron flux distribution.     

Albedo Component of Gamma-Ray Streaming through Straight Cylindrical Ducts

An experimental study was performed to investigate the effect of γ-ray streaming through cylindrical steel and lead ducts having various lengths and radii. In the experiment, ⁶⁰Co and ¹³⁷Cs point sources, and small sized detector (pulse dosimeter with plastic scintillator) was adopted, source and detector being located at the centers of opposite duct mouths. The albedo-to-direct component ratio is about 30% for steel ducts and 10% for lead at γ-ray energies of 1.25 and 0.661 MeV, with L/R ₀~10.

The measured results were compared with those calculated by the Monte Carlo method; they showed a good agreement. Consequently, the prediction of doses for straight cylindrical ducts having various length-to-radius ratios can be made by the procedures based on the Monte Carlo calculations.