超导磁通流晶体管的研究进展

对超导磁通流晶体管的结构、原理、特性及与高Ｔｃ材料的适应性和应用状况作了简要的评述。

磁通流阻型高温超导限流器模型研究

磁通流阻型高温超导限流器利用磁通流动电阻来限制短路电流,具有失超恢复迅速的优点,能够满足电力系统重合闸要求。采用多根Bi2223超导管材设计了1台磁通流阻型高温超导限流器模型机,并对其进行了交流电力系统的正常运行和失超限流运行的动模实验。分析了在不同预期短路电流下,超导材料过流失超后的限流效果。给出了Bi2223管材串联后的磁通流阻特性曲线,分析了管材电阻率与短路电流的关系,并对超导管材的失超一致性进行了研究。

高压直流电流测量装置的应用现状与研究进展

高压直流电流测量装置为高压直流输电系统的线路控制和保护提供输入信号。随着我国直流输电系统电压等级的不断升高,系统中的直流电流的测量已成为一个新课题。文章首先综述了已在国内外直流输电工程中运行的高压直流电流测量装置的结构和工作原理,指出各自存在的问题。然后介绍了我国在高压直流电流测量技术领域的研究进展,主要涵盖零磁通直流电流互感器、有源式直流电流互感器、全光纤式直流电流互感器、基于巨磁电阻效应的直流电流互感器和基于光纤光栅器件的直流电流互感器,希望能为未来高压直流电流测量装置的设计、实施与运行维护提供有益的参考。

JFFT控制特性的近似解析分析

由高Ｔｃ超导材料制备的Ｊｏｓｅｐｈｓｏｎ磁通流晶体管（ＪＦＦＴ）的控制特性中呈现了很强的非对称性。笔者分析了ＪＦＦＴ的控制场分布，并在电流－相位线性近似条件下，获得了这种非对称控制特性的近似解析描述。解析分析结果揭示了由控制线产生的不均匀外磁场是控制特性中非对称性产生的原因。其解析分析与实验结果之间符合较好。文中还讨论了各结构参数对ＪＦＦＴ的最大电流放大倍数的影响。

Numerical simulation on magnetohydrodynamic power generation channel of scramjet

The reverse magnetohydrodynamic(MHD)energy bypass technology is a promising energy redis⁃tribution technology in the scramjet system,in augmented with a power generation equipment to supply the neces⁃sary long-distance flight airframe power.In this paper,a computational model of the scramjet magnetohydrody⁃namic channel is developed and verified by using the commercial software Fluent.It is found that when the mag⁃netic induction intensity is 1,2,3,4 T,the power generation efficiency is 22.5%,22.3%,22.0%,21.5%,and decreases with the increase of the magnetic induction intensity,and the enthalpy extraction rate is 0.026%,0.1%,0.21%,0.34%,and increases with the increase of the magnetic induction intensity.The deceleration ef⁃fect of electromagnetic action on the airflow in the power channel increases with the increase of magnetic induc⁃tion intensity.The stronger the magnetic field intensity,the more obvious the decreasing effect of fluid Mach num⁃ber in the channel.The power generation efficiency decreases as the magnetic induction intensity increases and the enthalpy extraction rate is reversed.As the local currents gathering at inlet and outlet of the power generation area,total temperature and enthalpy along the flow direction do not vary linearly,and there are maximum and minimum values at inlet and outlet.Increasing the number of electrodes can effectively regulate the percentage of Joule heat dissipation,which can improve the power generation efficiency.

高温超导融熔织构材料中单颗粒边界结的制备和测量

研究了从高温超导ＹＢＣＯ融熔织构材料中分离出单颗粒边界的工艺。采用聚酰亚胺材料作为绝缘层，从单颗粒上引出了电压测量引线，实现了对单颗粒边界传输特性的测量。实验观察到这类样品中的颗粒边界有不同的传输特性，包括磁通流类型和Ｊｏｓｅｐｈｓｏｎ弱连接类型。文中还对样品的成分和结构进行了分析，并讨论了出现弱连接行为的原因。对具有弱连接特性的样品的成分分析表明，在颗粒边界上金属元素的成分有一些偏离，Ｘ－衍射分析观察到除（００Ｌ）峰之外，还有（２００）峰，表明样品中有ａ轴取向的颗粒。而颗粒边界上的成分偏离以及颗粒间大角度的取向错位均可能导致弱连接行为的出现．

Study of macroscopic fundamental diagram on Shanghai urban expressway network in China

The macroscopic fundamental diagram（ MFD） is studied to obtain the aggregate behavior of traffic in cities. This paper investigates the existence and the characteristics of different types of daily MFD for the Shanghai urban expressway network. The existence of MFD in the Shanghai urban expressway network is proved based on two weeks＇ data.Moreover, the hysteresis phenomena is present in most days and the network exhibits different hysteresis loops under different traffic situations. The relationship between the hysteresis phenomena and the inhomogeneity of traffic distribution is verified. The MFDs in the years of 2009 and 2012 are compared. The hysteresis loop still exists in 2012, which further verifies the existence of the hysteresis phenomenon. The direct relationship between the length of the hysteresis loop（ ΔO） and the congestion is proved based on sufficient data. The width of the hysteresis loop, i. e., the drop in network flow（ ΔQ） has no relationship with the congestion, and it varies from day to day under different traffic situations.

电力电缆绝缘在线监测装置设计

高压电力电缆在区域间传输大量电能,对它的监测非常重视,已经做了很多研究。本文叙述了一种装置的设计方法,其可在线监测电力电缆绝缘介质损耗程度,同时测量绝缘泄露电流。使用双向过零比较,用微控制器边沿触发捕捉计时,取中间值的方式测量介质损耗角,以有效地消除谐波和直流分量的干扰。将电源、信号处理、人机交互等电路集集成设计,并制作了样机达到了预期设计指标。

NiFe alloy particles doping effect of Gd-Ba-Cu-O bulks processed by a new cold-seeding technology

The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.

Optimal design of auxiliary-teeth to solve circulation current reduction of permanent magnet linear synchronous motor

A discontinuity of magnetic circuits according to the end effect is generated in the permanent magnet linear synchronous motor （PMLSM）. Due to the unbalanced back electro-motive force （EMF） and impedance produced, unbalanced current is generated. The cireulatin8 current, which is caused by a decrease in the thrust, is generated by the unbalanced current. The optimal design of auxiliary-teeth at the end of the mover was carried out to solve the unbalance of phase by using design of experiment （DOE）, and compared with the basic model through finite element analysis （FEA）. As a result, the auxiliary-teeth model compensates for the decrease of thrust caused by the unbalanced phase. Also, this model is proven to reduce the detent force by the vibration and noise of the PMLSM and copper loss caused by the circulating current.

Pinning Characteristics in a Single Crystal Nd-123 Superconductors at Low, Intermediate and High Temperatures Using Flux Creep-Flow Model

The pinning characteristics of a single crystal NdBaaCu3Oy superconductor at low （40 K）, intermediate （77.3 K） and high （88 K） temperatures were investigated. The experimental results of the critical current density dc and the apparent pinning potential u o which estimated from magnetic relaxation measurements are compared with the theoretical analysis based on the flux creep-flow model, taking the distribution of the flux pinning strength into account. The number of flux lines in the flux bundle （g2）, the most probable value of pinning strength （Am）, distribution width of pinning strength （σ-2） and other pinning parameters such as m, γ,δ are determined so that a good fit is obtained between the experimental and theoretical results. The behavior of these parameters is discussed in correspondence to the pinning characteristics of low, intermediate and high temperatures. The observed results are approximately consistent with the theoretical predictions of Brandt et al. model of the order-disorder transition.

Continuous on-line adaptation of the rotor time constant in FOC induction machine system

Rotor time constant is an important parameter for the indirect lleld oraentateO control of mauc- tion motor. Incorrect rotor tittle constant value will cause the flux observer generating a wrong angu- lar orientation of the rotor field. A new approach serves for rotor time constant on-line adaptation by setting the stator current to be zero for a short period. A smooth eorrector is designed to prevent ab- normal detection result from making adaptation. Impact of zero current duration on detection error and rotor speed is analyzed by experiments.

Delta-shocks and vacuums in zero-pressure gas dynamics by the flux approximation

In this paper,firstly,by solving the Riemann problem of the zero-pressure flow in gas dynamics with a flux approximation,we construct parameterized delta-shock and constant density solutions,then we show that,as the flux perturbation vanishes,they converge to the delta-shock and vacuum state solutions of the zero-pressure flow,respectively.Secondly,we solve the Riemann problem of the Euler equations of isentropic gas dynamics with a double parameter flux approximation including pressure.Furthermore,we rigorously prove that,as the two-parameter flux perturbation vanishes,any Riemann solution containing two shock waves tends to a delta-shock solution to the zero-pressure flow;any Riemann solution containing two rarefaction waves tends to a two-contact-discontinuity solution to the zero-pressure flow and the nonvacuum intermediate state in between tends to a vacuum state.Finally,numerical results are given to present the formation processes of delta shock waves and vacuum states.

New method for determining central axial orientation of flux rope embedded within current sheet using multipoint measurements

A new method for determining the central axial orientation of a two-dimensional coherent magnetic flux rope(MFR)via multipoint analysis of the magnetic-field structure is developed. The method is devised under the following geometrical assumptions:(1) on its cross section, the structure is left-right symmetric;(2) the projected structure velocity is vertical to the line of symmetry. The two conditions can be naturally satisfied for cylindrical MFRs and are expected to be satisfied for MFRs that are flattened within current sheets. The model test demonstrates that, for determining the axial orientation of such structures, the new method is more efficient and reliable than traditional techniques such as minimum-variance analysis of the magnetic field,Grad-Shafranov(GS) reconstruction, and the more recent method based on the cylindrically symmetric assumption. A total of five flux transfer events observed by Cluster are studied using the proposed approach, and the application results indicate that the observed structures, regardless of their actual physical properties, fit the assumed geometrical model well. For these events, the inferred axial orientations are all in excellent agreement with those obtained using the multi-GS reconstruction technique.

Numerical calculation for circulating current in stator transposition bars of large water-cooled turbo-generators

Accurate calculation of circulating current is one of the key problems for stator transposition bars in the design of turbo-generators. Aimed at limitation that analytical algorithm of circulating current could not reflect the local electromagnetic field distribution and difficulty that overlaps easily exist in solid modeling process of stator transposition bars, a simplified physical model of transposition bars is established. A three-dimensional(3-D) numerical method for circulating current in stator transposition bars of large water-cooled turbo-generators is investigated, which is combined with field-circuit coupling method. Taking stator bars less than 540° transposition with void model of a 600-MW water-cooled turbo-generator as the research object, the magnetic flux density distribution, current density distribution and circulating current distribution of transposition strands are obtained by numerical calculation. Compared with calculation results of the improved analytical algorithm, the correctness of the numerical calculation for circulating current is demonstrated, the calculation value difference for the maximum current of strands is obtained. The numerical calculation for circulating current will provide an appropriate basis for the reasonable calculation of local overheating of stator transposition bars and the design of safety margin for turbo-generators.

Hydromagnetic Blood Flow of Sisko Fluid in a Non-uniform Channel Induced by Peristaltic Wave

In this paper, a smooth repetitive osciflating wave traveling down the elastic walls of a non-uniform two- dimensional channels is considered. It is assumed that the fluid is electrically conducting and a uniform magnetic field is perpendicular to flow. The Sisko fluid is grease thick non-Newtonian fluid can be considered equivalent to blood. Taking long wavelength and low Reynolds number, the equations are reduced. The analytical solution of the emerging non-linear differential equation is obtained by employing Homotopy Perturbation Method （HPM）. The outcomes for dimensionless flow rate and dimensionless pressure rise have been computed numerically with respect to sundry concerning parameters amplitude ratio , Hartmann number M, and Sisko fluid parameter bl. The behaviors for pressure rise and average friction have been discussed in details and displayed graphically. Numerical and graphical comparison of Newtonian and non-Newtonian has also been evaluated for velocity and pressure rise. It is observed that the magnitude of pressure rise is maximum in the middle of the channel whereas for higher values of fluid parameter it increases. Further, it is also found that the velocity profile shows converse behavior along the walls of the channel against multiple values of fluid parameter.

The causal sequence investigation of the ring current ion-flux increasing and the magnetotail ion injection during a major storm

Comprehensive records are available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm （which incorporated a series of substorms）. Ion fluxes at 4-min temporal resolution derived from ENA data in the energy ranges 50-81 and 81-158 keV are compared with in situ particle fluxes measured by the LANL-SOPA instruments aboard LANL-01, LANL-02, LANL-97, and LANL-84 （a series of geostationary satellites that encircle the equatorial plane at -6.6 RE）. Also, magnetic fields measured simultaneously by the magetometers aboard GOES-10 and GOES-12 （which are also geostationary satellites） are compared with the particle data. It is demonstrated that ion fluxes in the ring current were enhanced during geomagnetic field tailward stretching in the growth phases of substorms rather than after Earthward directed dipolarization events. This observation, which challenges the existing concept that ring current particles are injected Earthward from the magnetotail following dipolarization events, requires further investigation using a large number of magnetic storm events.

Entropy Generation Analysis in Convective Ferromagnetic Nano Blood Flow Through a Composite Stenosed Arteries with Permeable Wall

The study of heat transfer is of significant importance in many biological and biomedical industry problems.This investigation comprises of the study of entropy generation analysis of the blood flow in the arteries with permeable walls. The convection through the flow is studied with compliments to the entropy generation. Governing problem is formulized and solved for low Reynold's number and long wavelength approximations. Exact analytical solutions have been obtained and are analyzed graphically. It is seen that temperature for pure water is lower as compared to the copper water. It gains magnitude with an increase in the slip parameter.

Peristaltic flow of Williamson fluid in a convected walls channel with Soret and Dufour effects

Peristaltic flow of magnetohydrodynamic （MHD） Williamson fluid in a symmetric chan- nel is addressed. Modeling is given with Sorer and Dufour effects. Channel walls have compliant properties. Analysis has been carried out through long wavelength and low Reynolds number approach. The obtained series solutions for small Weissenberg number are developed. Impact of variables reflecting the salient features of wall properties, Blot numbers and Soret and Dufour on the velocity, temperature and concentration has been point out. Trapping phenomenon is also analyzed.

The Blood Flow of Prandtl Fluid Through a Tapered Stenosed Arteries in Permeable Walls with Magnetic Field

This Communication deals with the blood flow of Prandtl fluid through a tapered stenosed arteries having permeable walls.The governing equations of two-dimensional Prandtl fluid model are modelled in cylindrical coordinates.The highly nonlinear equations are simplified with the help of non-dimensional variables under the assumption of mild stenosis.The solution of reduced nonlinear equation subject to boundary condition of porous walls having the effects of Darcy's number and slip parameter are computed analytically with the help of perturbation method.Effects of emerging parameters such as impedance A,slip parameter a,stenosis height 6,magnetic parameter and stress component Srz on velocity are illustrated graphically.The streamlines have also been presented to discuss the trapping bolus discipline.