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Although high-temperature superconducting induction motors have a simple structure, they are distinguished by their high efficiency and high power density. However, an accurate theoretical model that defines the primary electrical characteristics controlling the motor has not been established because of the nonlinear characteristics of high-temperature superconducting squirrel-cage rotor winding. As part of establishing such a model, an experiment was conducted to analyze the relationship between the induced voltage of the rotor bar in a high-temperature superconducting squirrel-cage rotor winding and stator-side quantities (voltage and transport current), as well as its rotation characteristics. A subject was a 1.5 kW class induction motor using Bi–Sr–Ca–Cu–O high-temperature superconducting rotor bars and the experiment was performed at a temperature and a frequency of 77 K and 60 Hz, respectively. The induced voltages of the rotor bars were measured by applying a rotating magnetic field and exhibited a distorted waveform characterized by a third-order harmonic in a magnetic flux flow state. Despite the distorted voltage waveform of the rotor bar, the stator transport current responsible for driving the induction motor remained unaffected and the motor initiated rotation in a slip rotation mode. From the above results, it was experimentally clarified that a stator voltage exceeding the critical current of the rotor bar must be applied when starting the induction motor. It was also shown that the rotor bar can be regarded as a constant resistance for a constant effective value of the stator current when transitioning the motor into a slip rotation state. [ABSTRACT FROM AUTHOR]

In this paper, we extract distinctive determination for quasi magnetic flux of the quasi binormal magnetic flows of magnetic quasi $ \mathbf {b}^{\mathbf {q}} $ b q -particle by considering directional frame in 3D ordinary space. Also, we construct some advanced optical qualifications for magnetic quasi Lorentz flux for magnetic quasi- $ \mathbf {b}^{\mathbf {q}} $ b q particle along with the quasi directional frame fields. Then, we calculate quasi magnetic Lorentz flux with directional-quasi magnetic fields. Besides, we obtain original simulations with regard to directional potentials for directional-quasi magnetic binormal flows with Heisenberg optical ferromagnetic model. Magnetic optical flux surfaces are demonstrated in a homogeneous optical flux surface by fractional numerical and applied developments. By using above models, we get new fractional model with q-homotopy analysis transform method (qHATM) and its illustrative presentation to consider magnetic optical flux surface. [ABSTRACT FROM AUTHOR]

Over the last decade, industrial applications and promising research domains including robotics and automotive engineering have adopted the rotary switched reluctance actuator (SRA). SRA's fault tolerance, simple, strong structure, and high-frequency operation make it popular. However, the SRA's nonlinear magnetic flux flow and saturation operation negate its benefits. Several control systems have been developed; however, they often need extensive mechanism models and advanced control theory, making them impracticable. This paper proposes a modified proportional integral derivative (PID) controller to evaluate the control performance, which comprises of PID controller with an anti-windup, a linearizer unit, and switching mechanism to activate the SRA phases. The linearizer unit aids to compensate for the nonlinear current-displacement relationship. The anti-windup element helps to halt the integral action during the starting motion. At the fully aligned position, 60°, the modified PID reduced positioning steady-state error by 4.3 times at 76.9%, overshoot by 48.8%, and settling time by 25.3%. Both the modified PID and conventional PID showed zero steady-state error at intermediate position, 70°, however the modified PID controller depicted an improved percentage overshoot by 54.5% and settling time by 74.5%. The results show that the modified PID outperforms conventional PID in transient response, steady-state error, overshoot, and settling time. [ABSTRACT FROM AUTHOR]

Matter transport is a fundamental process in nature. Understanding and manipulating flow in a synthetic media often have rich implications for modern device design. Here we experimentally demonstrate directional transport of photons in a two-dimensional quantum walk, where the light propagation is highly tunable through dissipation and synthetic magnetic flux. The directional flow hereof underlies the emergence of the non-Hermitian skin effect, with its orientation continuously adjustable through the photon-loss parameters. By contrast, the synthetic magnetic flux originates from an engineered geometric phase, which, by inducing localized cyclotron orbits, suppresses the bulk flow through magnetic confinement. We further demonstrate how the directional flow and synthetic flux impact the dynamics of the Floquet topological edge modes along an engineered boundary. Our results exemplify an intriguing strategy for engineering directed light transport, highlighting the interplay of non-Hermiticity and gauge fields in synthetic systems of higher dimensions. Non-Hermitian phenomena such as non-Hermitian skin effect have a strong impact on open system dynamics. Here, the authors use a photonic quantum walk including a synthetic gauge field to show that the interplay of synthetic flux and dissipation enables the full control over the directional transport. [ABSTRACT FROM AUTHOR]

This paper proposes a novel cubic WPT system for an enclosed sensor scenario, and its transmission characteristics in a metal environment have been analyzed. In addition, stable and high transmission efficiency can be normally achieved in all positions. The proposed quasi‐double D coil structure is composed of two pairs of transmitting coils; each transmitting coil pair is placed face to face and connected serially. Through current amplitude modulation, magnetic flux can flow towards the centre of the receiving coil and keep the system high efficiency when the rotation angle of the receiving coil changes. However, the installation position of the receiving coil is not fixed in the switch cabinet application, and an irregular iron wall and the metal shell of sensors could also lead to inconsistent iron loss of multiple transmitters. To overcome the resulting disturbances in efficiency, the improved current amplitude control method and the optimal load have been theoretically deduced in the case of the position variation of the receiving coil in a metal environment. Finally, experimental results in two‐dimensional space verify the omnidirectional transmission capability of the proposed quasi‐double D coil, and efficiency disturbances are effectively alleviated. [ABSTRACT FROM AUTHOR]

Using fractional differential geometry, we define different types of conformable magnetic curves to discuss some geometric features of the motion of the charged particle when its geometry is induced by the conformable fractional derivative. We obtain the non-stretching motions and the inextensibility conditions of the conformable curves to focus on their evolutions. Then, as a special case, we obtain the time evolution of the Frenet–Serret vectors of the conformable curves with respect to the optical ferromagnetic and antiferromagnetic cases. Finally, we focus on the time evolution of conformable curves under the case of the optical ferromagnetic and antiferromagnetic conditions to investigate how the anholonomy density is associated with the magnetic flux flow. [ABSTRACT FROM AUTHOR]

This paper presents the results of experiments using the eddy current system designated for nondestructive inspection of carbon fiber-reinforced composites. For this purpose, the eddy current testing system with a differential transducer with two pairs of excitation coils oriented perpendicularly and a central pick-up coil was utilized. The transducer measures the magnetic flux difference flowing through the pick-up coil. The transducer of this design has already been successfully utilized to inspect isotropic metal structures. However, the anisotropy of the composites and their lower conductivity compared to metal components made the transducer parameters adjustment essential. Thus, various excitation frequencies were considered and investigated. The system was evaluated using a sample made of orthogonally woven carbon fiber-reinforced composites with two artificial flaws (the notches with a maximum relative depth of 30% and 70%, respectively, thickness of 0.4 mm, and a length of 5 mm). The main goal was to find a configuration suitable for detecting hidden flaws in such materials. [ABSTRACT FROM AUTHOR]

This article proposes a new hybrid analytical model combining subdomain model and equivalent magnetic network for permanent magnet vernier machines, which are easy to get saturated due to the air-gap field modulation effect. The key is representing saturation effect by iterating equivalent surface current as part of interface conditions in the proposed subdomain model. First, five subdomains are divided to calculate magnetic field distribution. The equivalent surface current is utilized as the boundary constraint between subdomains and iron core. Second, the equivalent magnetic network is established based on stator structure, and the fluxes flowing into flux modulation poles are equivalent as the magnetic flux sources. Node magnetic potentials can be achieved with the application of Kirchhoff's law of current. Then, the equivalent surface current is updated for convergence by node magnetic potential to accurately predict saturated performance. Finally, a prototype is manufactured, and the effectiveness of the proposed hybrid model is verified by the finite-element analysis (FEA) and experimental results. The hybrid model combines the subdomain model and the equivalent magnetic network model to complement each other and it is demonstrated to be more efficient than the FEA model while maintaining high accuracy. [ABSTRACT FROM AUTHOR]

Regularly used in power transformers, grain-oriented (GO) steels are also usually chosen for the manufacturing of the stator cores of hydro generator and turbogenerator. These steels are renowned for their high magnetic performances in the rolling direction (RD) (high permeability and low magnetic losses). Nevertheless, in a turbogenerator where GO steels are employed to reduce the size of the stator core, the magnetic flux flows through several successive directions within the plane of the steel. So, the anisotropic behavior of the GO steel has to be considered in the design step of the related devices in order to improve their energy efficiency as well as their diagnosis based on modeling. In this article, an anisotropic phenomenological iron loss model, quite recently developed, has been studied and successfully implemented in a finite element method (FEM) simulation environment. The implementation has been validated against experimental data achieved on an industrial conventional GO grade typically used in turbogenerators. The results show a good agreement of the computational results with the experiments for both quasi-static and dynamic regimes. [ABSTRACT FROM AUTHOR]

In the actual operation of the high temperature superconducting (HTSC) maglev, due to the irregularity of the permanent magnetic guideway (PMG), the superconducting bulk always fluctuates in a small range. In order to explore this influence on the levitation force and guidance force, this paper considers that the superconducting bulk drops from the field cooling height (FCH) to the working height (WH), then maintains for a while and returns to the FCH, during the whole process of which the PMG has been subjected to the stochastic lateral and vertical excitations. Two E-J's constitutive relations are used in COMSOL Multiphysics 5.6, and compared with the model without excitations. The results show that for the levitation force, the lateral excitation mainly affects its amplitude, while the vertical excitation mainly affects its overall trend and position of the peak value. The more intense the excitation's fluctuation, the weaker the effect of the magnetic flux flow. For the guidance force, the lateral excitation mainly affects its amplitude and fluctuation's intensity, while the vertical excitation's influence is so small that can be neglected. When the superconducting bulk moves near the peak value, the effect of magnetic flux flow is particularly obvious, while near the equilibrium position, the effect is weak. On the whole, the magnetic flux flow has a distinct impact on the vertical excitation than on the lateral excitation. When without excitations, the magnetic flux flow is relatively obvious. These results reveal the rules providing the reference for the design of the HTSC maglev. [ABSTRACT FROM AUTHOR]

In the framework of the microscopic Bogoliubov–de Gennes theory, we investigate the vortex and skyrmionic states as well as phase transitions between them in mesoscopic superconducting squares with coexisted spin-triplet (p-wave) and spin-singlet (s-wave and d-wave) pairing symmetries. By choosing different chemical potential μ , the influence of next-nearest-neighbor hopping t ′ on the evolution of mixed pairing orders is mainly discussed. For the case of small | μ | in which the triplet p x ± i p y -wave symmetry is dominant, the skyrmionic structures containing the vortex-antivortex pair become stable at appropriate external magnetic flux. The transitions between different coreless skyrmionic modes can take place with tuning t ′ . For further enlarged | μ | , the singlet s-wave component is gradually enhanced in the present mescoscopic sample. We can obtain the transitions between different multivortex states and between the multivortex and skyrmionic states when t ′ is varied. The corresponding zero-energy local density of states and the relative phase differences are provided to display different topological defects. [ABSTRACT FROM AUTHOR]

The magnetic flux distribution in the transformer core, and particularly at the joints, has a considerable influence on the efficiency of the core. This paper considers a more realistic scenario of magnetic flux transfer, combining the effects of air gaps and the anisotropic characteristics of transformer core laminations. Based on the anisotropic magnetization characteristics of modern graded grain-oriented electrical steels, the magnetic flux distribution in the core joint region as a function of the operating flux density and the joint configuration is investigated using the finite element method up to high flux densities. 2D results illustrate the benefits of using multi-step lapped joints versus single-step lapped (SSL) joints at various flux densities. Thin low-permeability gaps are introduced in the 3D model with SSL 45° mitred overlapped joint configuration, which successfully addresses computation challenges of the large number of mesh elements for the air. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) bulks act as magnets with trapped magnetic flux and potentially exhibit high magnetic field performance, superior to that of permanent magnets. In the fourth industrial revolution, HTS magnets could potentially facilitate the development of highly efficient and lightweight motors and generators for propulsion. To evaluate and verify the durability of HTS rotating machines, we developed a radial-gap-type rotating machine whose field-pole modules comprised HTS bulks. We examined the stability of the trapped magnetic flux of the field poles during the machine's operation. The rotating machine was operated with different loads, and the magnetic field associated with the trapped flux of the HTS bulks was analyzed. The analysis was performed for different loads and revolution speeds, and the long-term operation for a constant load was investigated. The trapped flux of the bulk field poles and the output power were observed to be almost constant for over 360 h, and the HTS bulk magnet's surface temperature hardly changed below 40 K during the machine's operation. Furthermore, the magnetic flux decay determined from magnetic flux measurements before and after a load test was less than 1%. An analysis of the magnetic field distribution around the HTS bulk revealed that the transverse magnetic flux flowed through the magnetic guide of the rotor core. These results indicate the potential synchronous machine application of the high trapped magnetic flux of the field-pole modules accumulated by the appropriate positioning the HTS bulks three-dimensionally. [ABSTRACT FROM AUTHOR]

Since the discovery of high temperature superconducting (HTS) material, HTS maglev with the characteristics of self-stabilization and zero magnetic drag, has shown excellent potential for future transportation applications. However, this stability characteristic of HTS maglev is difficult to fully ensure in a spatial position, because of the magnetic flux flow and creep of the HTS bulk. Hence, to study the drift phenomenon of the HTS maglev vehicle excited by this unguaranteed stability characteristic, the linear superconducting magnetic bearing system, composed of a ring permanent magnetic guideway line (double track) and a HTS maglev vehicle, the 'Super-Maglev', was utilized. This system aims to explore the drift phenomenon in the vertical and lateral directions of the whole maglev vehicle under various operating conditions: different running speeds, unbalanced loading and cyclic loading situations. As an illustration induced by the experimental results, the lateral drift (LD) at a faster running speed (15 km h−1) is twice than that at 10 km h−1. Also, compared to the constant load condition, the vertical drift (VD) under cyclic load is larger. Moreover, with time going by, both LD and VD tend to be stable. Specifically, for the LD curve, it can be fitted by an exponential function. Finally, all the above experimental results support references for the future design and study of linear SMB systems. [ABSTRACT FROM AUTHOR]

In order to obtain experimental evidence for the influence of flux focusing effect on the characteristics of planar grain boundary (GB) Josephson junctions, we measured the current–voltage characteristics and magnetic-field-dependent current–voltage steps of integrated YBa2Cu3O7-δ bicrystal GB Junctions with different junction widths. Under the self-magnetic field, the critical current of the GB junction is proportional to the square root of the junction width, which is different from the traditional linear relationship between the critical current and the junction width. When a vertical magnetic field is applied, the flux flow current–voltage step could be observed, and the step voltage increases monotonously with an increase in the junction width. When a magnetic field rotating in the bc plane is applied, the voltage value of the flux flow step decreases slowly as the magnetic field inclined angle increases when the field inclined angle is relatively large. Based on these results, we demonstrate the presence of the magnetic flux focusing effect on YBa2Cu3O7-δ GB Josephson junctions. The size of flux focusing in the GB is closely associated with the width of the junctions and the orientation of the magnetic field. [ABSTRACT FROM AUTHOR]

Large fault direct current with fast rising speed has always been a significant threat to high voltage direct current systems. Fault current limiters (FCLs) are one of the most promising solutions. However, the biased permanent magnets (PM)s in traditional FCLs have large magnetic reluctance that causes FCLs to have small inductance changing ratios when a fault occurs. In this study, a novel three-limb topology of a saturated iron core-type fault current limiter (TSFCL) is proposed and a central PM bias limb is inserted to force flux flow through this limb. Therefore, the inductance changing ratio is greatly enhanced and the steep rising trend of fault current will be restrained effectively. The operating principles and characteristics of the TSFCL are analyzed to verify the deductions. Moreover, different lengths and cross-sectional areas of the inserted PM are tested and optimization study is carried out. The results show that the clipping inductance has a 55% increase compared with a traditional two-limb model. Moreover, compared with the existing smoothing reactor and traditional two-limb model, proposed topology can decrease the fault current by 45% and 16% within 5 ms, respectively. Finally, a typical HVDC system was built and the effectiveness of proposed TSFCL was verified. [ABSTRACT FROM AUTHOR]

The high-Tc superconductor of Ba2CaCu2O4(O,F)2 (F-0212) is an appealing material for application as it has a simple crystal structure with a highest Tc of 108 K. We have derived the intragrain critical current density (Jc), irreversibility field (Birr), flux pinning properties, etc., for the polycrystalline samples from under doping (Tc=82 K) to slightly-over doping (Tc=106 K) from the dc magnetization hysteresis loops. The Jc and Birr properties were found to improve rapidly as the doping state changes from under doping to slightly-over doping. Here we show that property of the spacing is crucial to enhance Birr as well as its thickness. An anisotropy factor for under doped Ba2CaCu2O4F2 was reckoned to 118 from a three-dimensional-two-dimensional crossover field of about 0.28 T. The double logarithmic plot of irreversibility field versus [1-(T/Tc)] analysis hints that the flux line melting model is adopted. Analysis of the normalized pinning force reveals that a surface pinning mechanism is dominant and reduced magnetic field bmax=0.2 agree with surface pinning mechanism with closely spaced pins. [ABSTRACT FROM AUTHOR]

The orientation flow of paths of real skew-adjoint Fredholm operators with invertible endpoints was studied by Carey, Phillips and Schulz-Baldes. For paths of real skew-adjoint Fredholm operators with odd-dimensional kernel the orientation flow is defined with respect to a real one-dimensional reference projection. It is homotopy invariant and fulfills a concatenation property. When applied to closed paths it is independent of the reference projection and provides an isomorphism of the fundamental group of the space of real skew-adjoint Fredholm operators with odd-dimensional kernel to Z 2. As an example the orientation flow of the magnetic flux inserted in a half-sided Kitaev chain is studied. [ABSTRACT FROM AUTHOR]

Following some prehistory, we discuss the steps leading to the Abrikosov vortex lattice and type-II superconductivity. Dissipation due to flux flow and flux creep represented an important discovery and leads to the strong interest in magnetic flux pinning. High-temperature superconductors and pancake vortices started the new concepts of vortex matter. Nonlinear effects at high vortex velocities, flux-flow instabilities, and some resulting open questions are discussed. [ABSTRACT FROM AUTHOR]

An electrovortex flow of gallium alloy generated in a cylindrical cell by two electrodes localized at the side walls is studied experimentally. It is shown that the electrovortex flow in this geometry appears in the entire considered range of the electric current. The flow velocity is low (the maximum bulk velocity is 40mm/s), but the flow itself is non-stationary at all considered parameters. Even at the lowest current, the flow is not symmetric and its pattern differs from that expected from the channel geometry and location of the electrodes. Application of an external magnetic field, being coaxial to the electrodes, significantly alters the intensity and pattern of the flow. [ABSTRACT FROM AUTHOR]

A third-order accurate gas-kinetic scheme based on the correction procedure via reconstruction (CPR) framework is developed for the Euler and Navier–Stokes equations on triangular meshes. The scheme combines the accuracy and efficiency of the CPR formulation with the multidimensional characteristics and robustness of the gas-kinetic flux solver. Comparing with high-order finite volume gas-kinetic methods, the current scheme is more compact and efficient by avoiding wide stencils on unstructured meshes. Unlike the traditional CPR method where the inviscid and viscous terms are treated differently, the inviscid and viscous fluxes in the current scheme are coupled and computed uniformly through the kinetic evolution model. In addition, the present scheme adopts a fully coupled spatial and temporal gas distribution function for the flux evaluation, achieving high-order accuracy in both space and time within a single step. Numerical tests with a wide range of flow problems, from nearly incompressible to supersonic flows with strong shocks, for both inviscid and viscous problems, demonstrate the high accuracy and efficiency of the present scheme. [ABSTRACT FROM AUTHOR]

In this study, Fe77P6B10Si4Nb2Cr1 amorphous powder in the particle size range below 75 µm was synthesized using industrial raw materials by water atomization. Then the amorphous magnetic powder cores (AMPCs) were prepared from the mixture of the amorphous alloy powder with different contents of epoxy resin as insulation/bonding materials by cold pressing. After annealed at 673 K for 1 h, the evolution of the high-frequency properties for the FePBSiNbCr AMPCs with the epoxy resin contents was studied. The AMPCs showed excellent magnetic properties, including high effective permeability of 62-82 with a high frequency stability up to 10 MHz, low core loss of 308-500 mW/cm3 at 100 kHz under the maximum magnetic flux density of 0.05 T, and superior DC-bias permeability of 62-72% at a bias field of 100 Oe. The development of Fe-based AMPCs with excellent soft magnetic properties is encouraging for future applications as functional materials. [ABSTRACT FROM AUTHOR]

First, we give a gauge-independent definition of chromomagnetic monopoles in Yang-Mills theory which is derived through a non-Abelian Stokes theorem for the Wilson loop operator. Then we discuss how such magnetic monopoles can give a nontrivial contribution to the Wilson loop operator for understanding the area law of the Wilson loop average. Next, we discuss how the magnetic monopole condensation picture are compatible with the vortex condensation picture as another promising scenario for quark confinement. We analyze the profile function of the magnetic flux tube as the non-Abelian vortex solution of gauge-Higgs model, which is to be compared with numerical simulations of the Yang-Mills theory on a lattice. This analysis gives an estimate of the string tension based on the vortex condensation picture, and possible interactions between two non-Abelian vortices. [ABSTRACT FROM AUTHOR]

In view of their excellent combination of strength and toughness, maraging steels (18Ni 250 grade) are widely used for the fabrication of large sized solid rocket motor casings. Gas tungsten arc welding is commonly employed to fabricate these thin walled metallic casings, as the technique is not only simple but also provides the desired mechanical properties. However, sometimes, radiographic examination of welds reveals typical unacceptable indications requiring weld repair. As a consequence, there is a significant drop in weld efficiency and productivity. In this work, the nature and the cause of the occurrence of these defects have been investigated and an attempt is made to overcome the problem. It has been found that weld has a tendency to form typical Ca and Al oxide inclusions leading to the observed defects. The use of calcium fluoride flux has been found to produce a defect free weld with visible effect on weld bead finish. The flux promotes the separation of inclusions, refines the grain size and leads to significant improvement in mechanical properties of the weldment. [ABSTRACT FROM AUTHOR]

In this work, an immersed boundary-simplified sphere function-based gas kinetic scheme (SGKS) is presented for the simulation of 3D incompressible flows with curved and moving boundaries. At first, the SGKS [Yang et al., "A three-dimensional explicit sphere function-based gas-kinetic flux solver for simulation of inviscid compressible flows," J. Comput. Phys. 295, 322 (2015) and Yang et al., "Development of discrete gas kinetic scheme for simulation of 3D viscous incompressible and compressible flows," J. Comput. Phys. 319, 129 (2016)], which is often applied for the simulation of compressible flows, is simplified to improve the computational efficiency for the simulation of incompressible flows. In the original SGKS, the integral domain along the spherical surface for computing conservative variables and numerical fluxes is usually not symmetric at the cell interface. This leads the expression of numerical fluxes at the cell interface to be relatively complicated. For incompressible flows, the sphere at the cell interface can be approximately considered to be symmetric as shown in this work. Besides that, the energy equation is usually not needed for the simulation of incompressible isothermal flows. With all these simplifications, the simple and explicit formulations for the conservative variables and numerical fluxes at the cell interface can be obtained. Second, to effectively implement the no-slip boundary condition for fluid flow problems with complex geometry as well as moving boundary, the implicit boundary condition-enforced immersed boundary method [Wu and Shu, "Implicit velocity correction-based immersed boundary-lattice Boltzmann method and its applications," J. Comput. Phys. 228, 1963 (2009)] is introduced into the simplified SGKS. That is, the flow field is solved by the simplified SGKS without considering the presence of an immersed body and the no-slip boundary condition is implemented by the immersed boundary method. The accuracy and efficiency of the present scheme are validated by simulating the decaying vortex flow, flow past a stationary and rotating sphere, flow past a stationary torus, and flows over dragonfly flight. [ABSTRACT FROM AUTHOR]

The study of vortex flows around solid obstacles is of considerable interest from both a theoretical and practical perspective. One geometry that has attracted renewed attention recently is that of vortex flows past a circular cylinder placed above a plane wall, where a stationary recirculating eddy can form in front of the cylinder, in contradistinction to the usual case (without the plane boundary) for which a vortex pair appears behind the cylinder. Here we analyze the problem of vortex flows past a cylinder near a wall through the lenses of the point-vortex model. By conformally mapping the fluid domain onto an annular region in an auxiliary complex plane, we compute the vortex Hamiltonian analytically in terms of certain special functions related to elliptic theta functions. A detailed analysis of the equilibria of the model is then presented. The location of the equilibrium in front of the cylinder is shown to be in qualitative agreement with recent experimental findings. We also show that a topological transition occurs in phase space as the parameters of the systems are varied. [ABSTRACT FROM AUTHOR]

The understanding of energy and magnetic flux losses in a magnetized plasma medium confined by a cold wall is of great interest in the success of magnetized liner inertial fusion (MagLIF). In a MagLIF scheme, the fuel is magnetized and subsonically compressed by a cylindrical liner. Magnetic flux conservation is degraded by the presence of gradient-driven transport processes such as thermoelectric effects (Nernst) and magnetic field diffusion. In previous publications [Velikovich et al., Phys. Plasmas 22, 042702 (2015)], the evolution of a hot magnetized plasma in contact with a cold solid wall (liner) was studied using the classical collisional Braginskii's plasma transport equations in one dimension. The Nernst term degraded the magnetic flux conservation, while both thermal energy and magnetic flux losses were reduced with the electron Hall parameter ωeτe with a power-law asymptotic scaling (ωeτe)-1/2. In the analysis made in the present paper, we consider a similar situation, but with the liner being treated differently. Instead of a cold solid wall acting as a heat sink, we model the liner as a cold dense plasma with low thermal conduction (that could represent the cryogenic fuel layer added on the inner surface of the liner in a high-gain MagLIF configuration). Mass ablation comes into play, which adds notably differences to the previous analysis. The direction of the plasma motion is inverted, but the Nernst term still convects the magnetic field towards the liner. Magnetization suppresses the Nernst velocity and improves the magnetic flux conservation. Thermal energy in the hot plasma is lost in heating the ablated material. When the electron Hall parameter is large, mass ablation scales as (ωeτe)-3/10, while both the energy and magnetic flux losses are reduced with a power-law asymptotic scaling (ωeτe)-7/10. [ABSTRACT FROM AUTHOR]

It is reported that in National Ignition Facility's shock timing campaign, there is a 2 μm layer of residual air condensation on the cold laser entrance hole window, and residual gas level of ∼5 x 10-6 Torr (∼6:6 x 10-4Pa) in the chamber [Robey et al., Phys. Plasmas 19, 042706 (2012)]. On Shenguang (SG) II and III laser facilities, a nominal residual gas level in the chamber is ∼10-2 Pa in experiment. In this work, the residual Carbon (C) level in the SG II chamber is investigated experimentally using a transmission grating spectrometer (TGS). The experimental result shows that there is a clear C K edge (280-300 eV), which implies that there is residual C condensation on the charge-coupled device (CCD) silicon oxide layer. The effect of the C condensation on the CCD response is studied with a condensed-C-foil model. With the modified CCD responses, the unfolded spectra by TGS are shown and the significant C K edge decreases as the C foil thickness increases. Compared to the simulated C K edge depth, the measured spectrum presents that the condensed C foil thickness is 27nm in the SG II chamber. The correction ratio for the TGS measured flux is 1.165, and there is an insignificant effect on the M band (>1800 eV) fraction measurement in SG II. [ABSTRACT FROM AUTHOR]

Three issues related to the physics of divertor detachment are analyzed in detail: the criteria for the onset of complete divertor detachment, the role of neutrals in "symmetryzation" of detachment in the inner and outer divertors, and the transition to divertor detachment. The results of comprehensive 2D numerical simulations with the SOLPS4.3 package are compared with some experimental data and predictions based on simplified analytical models. It is shown that it is the ratio of the upstream plasma pressure to the specific power flux entering the recycling region that controls the local onset of detachment on a specific flux tube. Pup/qreclycl ⩾ (Pup/qreclycl)crit remains the valid criterion also in the presence of seeded impurity, if the impurity radiation and hydrogen recycling regions are spatially separated. Detailed analysis indicates that the reverse plasma flow forming on the most heat loaded flux tubes in the outer divertor under the influence of the neutrals coming from the deeply detached inner divertor plays the key role in the detachment "symmetryzation" and allows the outer divertor to reach the detached regime. Finally, it is demonstrated that a gradual increase of the perpendicular heat transport in the edge plasma during transition to the detached regime can make this transition bifurcation-like. [ABSTRACT FROM AUTHOR]

A region of steep plasma gradients, the so-called "narrow-feature," has been found in the near scrape-off layer (SOL) of inner-wall limited (IWL) discharges. Dedicated IWL discharges were carried out in Alcator C-Mod [Marmar et al., Nucl. Fusion 55, 104020 (2015)] to study this phenomenon, allowing detailed observations of the plasma profiles and fluctuations. Langmuir probe (LP) measurements show a clear two-decay length ne and Te profile structure at the outer midplane. The Gas-Puff Imaging (GPI) diagnostic shows large turbulent fluctuations across the last closed flux-surface, hence supporting the hypothesis that turbulent phenomena play a role in setting the profile steepness. Flux-driven non-linear turbulence simulations of two C-Mod discharges have been carried out, allowing a three-way comparison between LP, GPI and simulation data. Observations and simulations correlate the steep gradient region characterizing the narrow feature with sheared poloidal flows and a deviation of the plasma potential from its floating value. The ExB shear rate exceeds the linear ballooning growth rate, indicating that the narrow feature could result from the effects of sheared flows, although causality could not be established. The fluctuation level in the narrow feature remains of order unity across the entire SOL, indicating that the transport reduction in the near-SOL cannot result from a simple quench rule. [ABSTRACT FROM AUTHOR]

Two kink unstable magnetic flux ropes are produced in a carefully diagnosed laboratory experiment. Using probes, the time varying magnetic field, plasma potential, plasma flow, temperature and density were measured at over 42 000 spatial locations. These were used to derive all the terms in Ohm's law to calculate the plasma resistivity. The resistivity calculated by this method was negative in some spatial regions and times. Ohm's law was shown to be non-local. Instead, the Kubo resistivity at the flux rope kink frequency was calculated using the fluctuation dissipation theorem. The resistivity parallel to the magnetic field was as large as 40 times the classical value and peaked where magnetic field line reconnection occurred as well as in the regions of large flux rope current. [ABSTRACT FROM AUTHOR]

Magnetic helicity has become a useful tool in the analysis of astrophysical plasmas. Its conservation in the magnetohydrodynamic limit (and other fluid approaches) constrains the global behavior of large plasma structures. One such astrophysical structure is a magnetic flux rope: a tube-like, current-carrying plasma embedded in an external magnetic field. Bundles of these ropes are commonly observed in the near-earth environment and solar atmosphere. In this well-diagnosed experiment (three-dimensional measurements of ne, Te, Vp, B, J, E, and uflow), two magnetic flux ropes are generated in the Large Plasma Device at UCLA. These ropes are driven kink-unstable to trigger complex motion. As they interact, helicity conservation is examined in regions of reconnection. We examine (1) the transport of helicity and (2) the dissipation of the helicity. As the ropes move and the topology of the field lines diverge, a quasi-separatrix layer (QSL) is formed. As the QSL forms, magnetic helicity is dissipated within this region. At the same time, there is an influx of canonical helicity into the region such that the temporal derivative of magnetic helicity is zero. [ABSTRACT FROM AUTHOR]

From the perspective of circuit theoretical integrity, it can be predicted that there is a fourth passive basic element, and this missing circuit element is named as memristor. Memristor is a two-terminal device whose value depends on the history of the magnetic flux or charge flowing through it. As a fourth basic element, it is considered a promising device in many analog and digital applications. However, the cost and difficulty of making nanodevices limit the commercialization of memristor. To better study memristor, researchers have proposed the use of circuits composed of different components to simulate memristor characteristics, also known as memristor emulator circuits. This paper presents the current research status of memristor emulator circuits, and analyses the design ideas, circuit composition, advantages and disadvantages of emulator circuits implemented by different schemes, then introduces the application of some emulators in real circuits. [ABSTRACT FROM AUTHOR]

Ansys Maxwell software, which is FEM-based software, was utilized to run the simulations for various operation conditions. The FEM technique enabled software to simulate and analyze various electromagnetic parameters including flux lines, flux density, losses, etc., under varying solutions very accurately. This paper investigates the behavior of three-phase three-leg in power transformer core type design under sinusoidal and non-sinusoidal operating conditions. Three types of cold-rolled grain-oriented core materials grades(M4,M5,M6) have been chosen to compare the core losses in steady-state and transient operation condition. The influence of magnetic hysteresis, flux couplings in the core-structure and material performance in three-phase transformers has been simulated. Simulation results of core loss behaviour based on the different materials are presented and discussed. [ABSTRACT FROM AUTHOR]

This paper proposes two high-performance switched flux hybrid magnet memory machines (SF-HMMMs) based on the design concepts of E-core and C-core SF permanent magnet (PM) machine topologies. Since two kinds of PMs (i.e., NdFeB and low coercive force magnets) are employed, the proposed machines can offer the merits of high torque capability, excellent flux adjustability, and high efficiency across a wide speed range. In this paper, the PM arrangement and dimensions, stator/rotor pole number combination, as well as the major design parameters are optimized first. Then, the electromagnetic characteristics of the proposed machines are investigated and compared with their conventional 12-stator pole SF-HMMM. It is found that compared with their conventional 12-stator pole counterpart, the proposed machines offer improved torque density and flux adjustability, even with the reduced PM usage. Finally, two machine prototypes are manufactured and tested to validate the analyses. [ABSTRACT FROM PUBLISHER]

A demagnetization fault in a permanent-magnet synchronous machine (PMSM) degrades performance and energy efficiency. The demagnetization fault causes flux-density difference and changes the PMSM inductances. Such varying parameters make it difficult to detect and diagnose the exact severity of a demagnetization fault. In this paper, we suggest a use of structural analysis of the PMSMs to diagnose the demagnetization fault. We can calculate varying inductances and consider the magnetic saturation effect with varying flux linkages of the machine. Combination of the proposed technique with the least-square (LS) method shows better results than the conventional methods in the estimation of flux linkages in the PMSMs with the demagnetization fault. Experimental results demonstrate that the proposed method works well both in the tracking of varying inductances and the diagnosis of the demagnetization fault. [ABSTRACT FROM PUBLISHER]

In this paper, an analytical model is proposed to predict magnetic flux leakage (MFL) signals from the surface defects in ferromagnetic tubes. The analytical expression consists of elliptic integrals of first kind based on the magnetic dipole model. The radial (Bz) component of leakage fields is computed from the cylindrical holes in ferromagnetic tubes. The effectiveness of the model has been studied by analyzing MFL signals as a function of the defect parameters and lift-off. The model predicted results are verified with experimental results and a good agreement is observed between the analytical and the experimental results. This analytical expression could be used for quick prediction of MFL signals and also input data for defect reconstructions in inverse MFL problem. [ABSTRACT FROM AUTHOR]

Multifilament Bi-2223/Ag tapes with different Pb contents in precursor powders were fabricated by powder in tube (PIT) method. The influence of Pb contents on the phase formation, microstructure and critical current density of Bi-2223/Ag tapes were systematically investigated. X-ray photoelectron spectroscopy (XPS) demonstrated that the content and oxidation states change of Pb ions can influence the carrier concentration of superconducting phase. Scanning electron microscopy (SEM) revealed that the variation of Pb content can lead to the difference in microstructure due to the change of thermodynamic properties. The results showed that with the Pb content of x =0.35 in the nominal composition of Bi 2− x Pb x Sr 2 Ca 2 Cu 3 O y , proper content of liquid phase can be formed during the sintering process, thus maximum critical current ( I c ) was obtained. The correlation between the transport property, carrier concentration and Pb content was discussed. [ABSTRACT FROM AUTHOR]

Aims. Here we report evidence of a large solar filament eruption on 2013, September 29. This smooth eruption, which passed without any previous flare, formed after a two-ribbon flare and a coronal mass ejection towards Earth. The coronal mass ejection generated a moderate geomagnetic storm on 2013, October 2 with very serious localized effects. The whole event passed unnoticed to flarewarning systems. Methods. We have conducted multi-wavelength analyses of the Solar Dynamics Observatory through Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) data. The AIA data on 304, 193, 211, and 94 Å sample the transition region and the corona, respectively, while HMI provides photospheric magnetograms, continuum, and linear polarization data, in addition to the fully inverted data provided by HMI. Results. This flux emergence happened very close to a filament barb that was very active in mass motion, as seen in 304 Å images. The observed flux emergence exhibited hectogauss values. The flux emergence extent appeared just beneath the filament, and the filament rose during the following hours. The emergence acquired a size of 33" in ~12 h, about ~0.16 km s-1. The rate of signed magnetic flux is around 2 × 1017 Mx min-1 for each polarity. We have also studied the eruption speed, size, and dynamics. The mean velocity of the rising filament during the ~40 min previous to the flare is 115±5 kms-1, and the subsequent acceleration in this period is 0.049 ± 0.001 km s-2. Conclusions. We have observed a supergranular-sized emergence close to a large filament in the boundary of the active region NOAA11850. Filament dynamics and magnetogram results suggest that the magnetic flux emergence takes place in the photospheric level below the filament. Reconnection occurs underneath the filament between the dipped lines that support the filament and the supergranular emergence. The very smooth ascent is probably caused by this emergence and torus instability may play a fundamental role, which is helped by the emergence. [ABSTRACT FROM AUTHOR]

Several experiments in fundamental physics demand an environment of very low, homogeneous, and stable magnetic fields. For the magnetic characterization of such environments, we present a portable SQUID system that measures the absolute magnetic flux density vector and the gradient tensor. This vector-tensor system contains 13 integrated low-critical temperature (LTc) superconducting quantum interference devices (SQUIDs) inside a small cylindrical liquid helium Dewar with a height of 31 cm and 37 cm in diameter. The achievable resolution depends on the flux density of the field under investigation and its temporal drift. Inside a seven-layer mu-metal shield, an accuracy better than ±23 pT for the components of the static magnetic field vector and ±2 pT/cm for each of the nine components of the gradient tensor is reached by using the shifting method. [ABSTRACT FROM AUTHOR]

Depending on the Ginzburg-Landau parameter κ, superconductors can either be fully diamagnetic if (type I superconductors) or allow magnetic flux to penetrate through Abrikosov vortices if (type II superconductors; refs , ). At the Bogomolny critical point, , a state that is infinitely degenerate with respect to vortex spatial configurations arises. Despite in-depth investigations of conventional type I and type II superconductors, a thorough understanding of the magnetic behaviour in the near-Bogomolny critical regime at κ  κc remains lacking. Here we report that in confined systems the critical regime expands over a finite interval of κ forming a critical superconducting state. We show that in this state, in a sample with dimensions comparable to the vortex core size, vortices merge into a multi-quanta droplet, which undergoes Rayleigh instability on increasing κ and decays by emitting single vortices. Superconducting vortices realize Nielsen-Olesen singular solutions of the Abelian Higgs model, which is pervasive in phenomena ranging from quantum electrodynamics to cosmology. Our study of the transient dynamics of Abrikosov-Nielsen-Olesen vortices in systems with boundaries promises access to non-trivial effects in quantum field theory by means of bench-top laboratory experiments. [ABSTRACT FROM AUTHOR]

The doping dependence of the critical current density Jc was measured in a series of high quality oaxis-oriented Bi2Sr2CaCu2O8+δ thin films. For each doping level we measured the temperature dependence of Jc. We find that all samples have the same temperature dependence, but the critical current at zero temperature Jc(0) has a nontrivial doping dependence with a maximum at a unique doping level in the overdoped side of the superconducting dome. [ABSTRACT FROM AUTHOR]