Pulsed magnetic field losses of two 15000 A test superconductors designed for the swiss fusion research LCT coil

Pulsed magnetic field losses have been investigated on two different NbTi superconductors designed for direct cooling with supercritical He and for Itr= 15000 A. The loss measurements were performed with perpendicular and parallel pulsed field components. The influence of the dc field component on the pulsed field hysteresis losses was measured up to 7 Tesla.     

Calculation of the magnetic field of a coil

An approximate method is given for calculating the magnetic field of a coil of circular cross section with continuous coil windings.     

Trigonometric Integrals for the magnetic field of the coil of rectangular cross section

Formulas are derived giving the vector potential and the magnetic field components of a general coil of rectangular cross section and constant winding density. The solution is given in a cylindrical coordinate system in terms of trigonometric integrals. The formulas presented have been cross-checked and validated against alternative expressions giving the various field components as integrals of expressions containing Bessel and Struve functions. The trigonometric integrals for the fields can be evaluated easily to several hundred significant figures using mathematical packages such as Maple or Mathematica. Alternatively, they can be evaluated with a small FORTRAN program. Sample results and field line plots obtained with the method are given, and the field of a coil of rectangular cross section is examined in some detail. A comparison with the results of a finite-element method is also given.     

Oval test coil for examining mechanical effects in superconducting coils

A method of investigating mechanical effects in superconducting coils has been demonstrated using an oval magnet constructed to produce high mechanical stress in a portion of a small test coil. The oval shape is maintained by an internal longitudinal strut which may be used to prestress the winding and control the longitudinal deformation. Lateral and longitudinal deflections during energization are monitored by linear variable differential transformers. Initial results show very complex deflection patterns, particularly at low field. There are indications of diamagnetic behaviour of the composite twisted multifilamentary conductor below Hc₁ and of possible conductor slippage but much remains unexplained.     

大型风冷冷水机组工况试验室声学设计

以实际工程为例,介绍了在大型风冷冷水机组性能试验室中如何进行试验室声学设计,在满足大型风冷机组性能试验的基础上,在兼顾工况试验所需要的温度变化、湿度变化以及气流组织需要的同时,考虑噪声测试的特殊需要,采取合理组织气流走向等技术措施,保证大型空调冷冻设备性能试验室内的声场效果达到预期要求。     

A high speed drive coil for a large capacity bubble memory

We calculated an eddy current loss in a wire as a function of an applied ac field. Estimating the field at an actual coil wire and summing the losses in all points of wires we obtained a formula representing a coil loss. Based on the calculated results, we designed coils which drive thirty-two 64 kb chips. The observed loss of the coils was in good accord with the calculated one. This 2 Mb module was operated at 40 Oe rotation field of 500 kHz with the coil loss of 8 W.     

Pulsed electric field assisted assembly of polyaniline

Assembling conducting polyaniline (PANi) on pre-patterned nano-structures by a high rate, commercially viable route offers an opportunity for manufacturing devices with nanoscale features. In this work we report for the first time the use of pulsed electric field to assist electrophoresis for the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g.,?17.4?s, assembly resolution of 100?nm). Moreover, the area coverage increases with the increase in number of pulses. A similar trend was observed with the deposition height and the increase in deposition height followed a linear trend with a correlation coefficient of 0.95. When the experimental mass deposited was compared with Hamaker's theoretical model, the two were found to be very close. The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process.     

大型高度-温度试验舱分布式送风流场仿真及分析

针对大型高度-温度试验舱在低气压环境下试验空间内温度场均匀性下降的问题,通过对大型高度-温度试验舱分布式送风流场进行数值仿真及分析,研究了两种不同送风方式下低气压试验舱内的温度场变化规律。结果表明,试验舱内温度场均匀性随着环境压力的降低而下降;增加试验舱内壁辐射换热、提高流场风速,均可以提高试验舱内的温度均匀性;同样环境压力下,采用双侧送风方式比单侧送风方式的试验舱内温度场均匀性更好,但平均风速较高。在进行高度-温度试验舱设计时,需根据不同的试验需求选择不同的送风方式。     

电磁兼容试验中亥姆霍兹线圈的设计及验证

主要研究电磁兼容中亥姆霍兹线圈低频磁场抗扰度试验技术,给出了亥姆霍兹线圈的设计研制思路。根据国际标准和实际使用情况的要求,对其结构、性能及均匀性等分别进行分析、研究和验证,并对实际使用的磁场强度根据具体标准进行了举例验证。研究成果能为电磁兼容低频磁场的测试方法与测试线圈的研制提供技术指导。     

Analysis of a novel laminated coil using eddy currents for AC highmagnetic field

The analysis and performance of an eddy current type laminated coil for a high AC magnetic fields are described. It is usually difficult to obtain a high AC magnetic field using an air-gap coil because of eddy currents. The present coil circumvents this limitation by making use of the magnetic shielding effect of eddy currents. Two different realizations of the coil are proposed to provide design flexibility. The field distributions are analyzed by the two-dimensional finite-element method. The coils can also be applied to an induction electromagnetic pump     

大型飞机地面空调现场测试方法的探讨

大型飞机地面空调往往体积很大,难以实现试验室内的性能测试。本文主要提出一种现场测试方法,供业内人士参考。     

大型双机双级压缩机性能测试方法

目前,我国尚无双机双级压缩机的测试标准,本文参照国家标准GB/T5773—2004《容积式制冷剂压缩机性能试验方法》制定一套测试方案,以解决双机双级压缩机的测试难题。     

The method of the field of thermal characteristics for determining the temperature field in disperse systems

A concept is described from which it is possible to formulate an effective heat conduction equation in which the parameters are functions of the properties and the state of the material. A method is proposed for the solution of similar problems, noting the difficulties which occur at each stage of the similar approaches.Translated from Inzhenerno-Fizieheskii Zhurnal, Vol. 19, No. 5, pp. 886–892, November, 1970.     

Fabrication and characterization of giant magnetoresistive elementswith an integrated test coil

Magnetoresistive elements (MREs) containing exchange-biased spin valve multilayers as the magnetoresistive material have been fabricated. Their electrical response has been measured using an integrated test coil. Both parallel and crossed arrangements of the easy axes of the free and biased layers have been studied. Output voltage levels of these elements in response to an ac magnetic field are typically a factor of 7-10 higher than those obtained in similar elements based on a conventional, 30 nm thick anisotropic magnetoresistive (AMR) Ni₈₀ Fe₂₀ film linearized by the “barber-pole” method. The parallel arrangement is found to result in a switching behavior which is characteristic of domain wall movement and contains hysteresis, Barkhausen noise, and strong harmonic distortion. The arrangement with crossed anisotropies is found to display a behavior characteristic of switching by magnetization rotation as evidenced by a strong reduction of hysteresis, Barkhausen noise, and harmonic distortion. Demagnetization effects are calculated in order to quantitatively explain the shape of the response curve and the difference in output voltage when compared to AMR-based MREs     

Integral analysis of a magnetic field for an arbitrary geometry coil with rectangular cross section

The integral method can effectively analyze magnetic fields, but the traditional integral method can analyze only coils with regular geometries. Therefore, a new integral method was developed to calculate the three-dimensional (3-D) magnetic field created by an arbitrary geometry coil with a rectangular cross section using the local coordinate method and a 3-D coordinate transformation. However, when the field points are on the surface of the coil or the basic segment is the right angle trapezoidal prism, singularities occur that make the numerical analysis of the magnetic field more difficult. Thus, we present here some mathematical methods to eliminate the singularities to allow accurate numerical analysis of the magnetic field. We validate the integral method by comparing it with the analytical solutions for regular geometry coils.     

Effect of twist on the longitudinal field loss for an in situ superconductor

The effect of twist on the full penetration loss of an in situ superconductor is calculated for the case of a longitudinal applied magnetic field. An increase in hysteresis with increasing twist is predicted due to a large anisotropy in the critical current density. The anisotropy results from the fact that the critical current density along the length of a filament in the in situ material is determined by the filament, while along the thickness it is determined by the proximity effect in the matrix surrounding the filament. From the measurements of Braginski and Wagner the ratio of these critical current densities is calculated to be about 70, which is in order of magnitude agreement with the value previously found from transverse field measurement.