Principle Of Flux Conservation Research Articles

Investigations on a Passive Real-Time Magnetic Flux Density Amplifier Made From Eight-Shaped HTS Loops

The superconducting devices made by high temperature superconducting (HTS) tapes attract great significance in high magnetic fields and at low temperature. A configuration of the magnetic flux density amplifier (MFDA) composed of rare earth-Ba-Cu-O (REBCO) HTS tapes with one central slit and twisted to form an “eight-shaped” loop with two different sizes of “closed-loops” is reported by our group in recent years. However, it can only achieve the fixed amplified function of magnetic flux density. This article proposes a passive dynamic MFDA made by the same HTS tape as an “eight-shaped” loop, which abides by the principle of flux conservation. An experimental setup is established to investigate the real-time amplification of magnetic flux density, and numerical method is used to simulate the process of dynamic magnetic flux density. Five kinds of multipulse excitation amplitudes are utilized in the experiment and a real-time process of magnetic flux density is displayed within a period. The feasibility of amplified magnetic flux density in the HTS loop is separately verified by experiment and simulation in 77 K. In order to improve the accuracy of ac loss calculation, analytical method and finite element method are compared with each other. Temperature distribution of the real-time MFDA is obtained and thermal stability is also analyzed by comparing the effects of different transmission currents and frequencies to the HTS loop. The results show that REBCO loops achieve the real-time amplified function of magnetic flux density and it has the ability of passive long-term stable operation, which is potential for sensor of flux density.

On the Transmittance of Metallic Superlattices in the Optical Regime and the True Refraction Angle

Transmission of electromagnetic fields through (dielectric/metallic)n superlattices, for frequencies below the plasma frequency ωp, is a subtle and important topic that is reviewed and further developed here. Recently, an approach for metallic superlattices based on the theory of finite periodic systems was published. Unlike most, if not all, of the published approaches that are valid in the n→∞ limit, the finite periodic systems approach is valid for any value of n, allows one to determine analytical expressions for scattering amplitudes and dispersion relations. It was shown that, for frequencies below ωp, large metallic-layer thickness, and electromagnetic fields moving along the so-called “true” angle, anomalous results with an apparent parity effect appear. We show here that these results are related to the lack of unitarity and the underlying phenomena of absorption and loss of energy. To solve this problem we present two compatible approaches, both based on the theory of finite periodic systems, which is not only more accurate, but has also the ability to reveal and predict the intra-subband resonances. In the first approach we show that by keeping complex angles, above and below ωp, the principle of flux conservation is fully satisfied. The results above ωp remain the same as in Pereyra (2020). This approach, free of assumptions, where all the information of the scattering process is preserved, gives us insight to improve the formalism where the assumption of electromagnetic fields moving along the real angles is made. In fact, we show that by taking into account the induced currents and the requirement of flux conservation, we end up with an improved approach, with new Fresnel and transmission coefficients, fully compatible with those of the complex-angle approach. The improved approach also allows one to evaluate the magnitude of the induced currents and the absorbed energy, as functions of the frequency and the superlattice parameters. We show that the resonant frequencies of intra-subband plasmons, which may be of interest for applications, in particular for biosensors, can be accurately determined. We also apply the approach for the transmission of electromagnetic wave packets, defined in the optical domain, and show that the predicted space-time positions agree extremely well with the actual positions of the wave packet centroids.

The Application of Group Theory in Communication Operation Pipeline System

To resolve the “pipeline” crisis for telecom operators, this study pioneers the application of Group theory in communication operation pipeline system. The pipeline entity group model was built for information transmission in the pipeline system to analyze operation of pipeline entities. The equations of pipeline system network traffic were established according to the flux conservation principle and matrix of pipeline network. Based on pipeline entity group model, dimensionality of the matrix was reduced. The solution scheme of the flow state transition relationship of the pipeline system is obtained, which will be very useful for the telecom operators to construct high-level mobile e-commerce application model and architecture.

The Study of Residual Voltage of Induction Motor and the Influence of Various Parameters on the Residual Voltage

The majority important load of industrial area is mainly composed of induction motor, it is more common that induction motor becomes sluggishness and even tripping due to the lose of power supply or other malfunction in the practical work. In this paper, space vector method is used to establish a reduced order model of induction motor, and then study the changes of motor electromagnetic after losing electricity. Based on motion equations of the rotor and magnetic flux conservation principle, it uses mathematical methods to deduce the expression of rotor current, rotor flux, the stator flux and the residual voltage of stator side. In addition, relying on thermal power plants, it uses the actual data of power plants, takes DIgsilent software to simulate the residual voltage of motor after losing electricity. analyses the influence on the residual voltage with the changes of the moment of inertia, load ratio, initial size of slip and the load characteristic of induction motor. By analysis of these, it has a more detailed understanding about the changes of residual voltage in practical application, in additional, it is more beneficial to put into standby power supply safely and effectively, moreover, reduce the influence of the input process to the whole system.

Flux conservation principle on construction of residual restriction operators for multigrid method

Multigrid method is one of the most efficient iterative algorithms to accelerate the convergence rate of both linear and non-linear algebraic equations. It has been indicated by many researches that the actual performance of multigrid method is influenced by various factors, among which the most important one is the implementation of residual restriction. For different discretized forms of the same partial differential governing equation, it is proposed in the present paper that the multigrid method could behave most effectively only in the case that the implementation of residual restriction satisfies the flux conservation principle of the finite volume method. Taking the correction scheme (CS scheme) of the multigrid method into consideration, when the flux conservation principle is well satisfied, residual restriction operators for different algebraic equations are derived. Corresponding numerical studies are made via four cases of pure diffusion and convective-diffusion problems. It is found that the acceleration of the convergence rate of the multigrid method is most desirable when the residual restriction satisfies the flux conservation principle.

Structure and the Reflectionless/Refractionless Nature of Parabolic Diffusion-Wave Fields

We show the impossibility of reflection and refraction phenomena at linear diffusion-wave-field (DWF) interfaces. Instead, interfacial flux expressions are derived which involve coherent accumulation or depletion phenomena subject to an interface flux conservation principle. The conditions for reflectionless and refractionless interfaces are the parabolic nature and the concomitant Fickian constitutive relations satisfied by DWFs. Simulations show that the reflection and Snell's laws can be adequate approximations only under near-normal incidence conditions, in agreement with published experimental evidence in wide areas of biomedical, electronic, and materials physics.

Effective parameters of surface energy balance in heterogeneous landscape

This paper addresses the problem of estimating surface fluxes at large scale over heterogeneous terrain, and the corresponding determination of effective surface parameters. Two kinds of formulation are used to calculate the fluxes of sensible and latent heat: the basic diffusion equations (Ohm's law type) and the Penman-Monteith equations. The strategy explored is based upon the principle of flux conservation, which stipulates that the average flux over a large area is simply the area-weighted mean of the contributions from the different patches making up the area. We show that the application of this strategy leads to different averaging schemes for the surface parameters, depending on the type of flux (latent heat, sensible heat) and on the type of formulation used to express the flux. It appears that the effective value of a given parameter must be appraised for each individual application, because it is not unique, but differs according to the magnitude being conserved and the equation used to express this magnitude. Numerical simulations are carried out to test over contrasted areas the aggregation procedures obtained. The areal fluxes estimated from these effective parameters, together with the areal fluxes calculated by means of a simple areal averaging of the parameters, are compared to the “true’ average fluxes, calculated as area-weighted means of the elementary fluxes. The aggregation procedures obtained prove to be much more accurate for estimating areal fluxes and for closing the energy balance equation than those based upon simple areal averaging of the parameters.

Comparison of two cell‐centered multigrid schemes for problems with discontinuous coefficients

AbstractTwo different schemes for constructing coarse‐grid operators are implemented in a linear multigrid code. In the first scheme, the construction of the coarse‐grid operators is done using a variational approach. Certain conservation properties of the fine‐grid matrices are shown to be preserved on the coarser grids by the variational construction. In the second scheme, the diffusion coefficients for the coarse grids are calculated by a simple restriction of the coefficient from the fine grid, using a flux conservation principle. The multigrid codes are then applied to solve the linear equations from an IMPES formulation of a two‐phase porous‐media flow model. A standard elliptic model problem with jump discontinuous coefficients is also solved using the two multigrid schemes. In simple cases of particular elliptic equations these two schemes are identical. However, in more general cases, such as in reservoir problems, these schemes differ. It is shown that multigrid efficiency typical of the constant coefficient cases is obtained for these problems involving discontinuous coefficients. © 1993 John Wiley & Sons, Inc.

Observation of magneto-thermoelectric effects in high-T c superconducting Tl 2Ba 2CaCu 2O x single crystals

The anomalous peaks in the temperature dependences of the magnetic moment and the transverse Nernst voltage were observed in Tl 2Ba 2CaCu 2O x single crystals, when a perpendicularly directed temperature gradient and transport current were applied. The effects observed have been discussed within the context of the fluctuation vortex dynamics and vortex-antivortex imbalance in the Berezinskii-Kosterlitz-Thouless temperature regime. A model for the magnetic moment and the Nernst voltage in zero magnetic field was proposed corresponding to the principle of flux conservation. The model accounts for the results obtained.

Sources of magnetic fields in recurrent interplanetary streams

We examined the sources of magnetic fields in recurrent streams observed by the Imp 8 and Heos spacecraft at 1 AU and by Mariner 10 en route to Mercury between October 31, 1973, and February 9, 1974, during Carrington rotations 1607–1610. Most fields and plasmas at 1 AU were related to coronal holes, and the magnetic field lines were open in those holes. However, some of the magnetic fields and plasmas at 1 AU were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines may be more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes, estimated by projecting the measured interplanetary magnetic fields back to the sun by using the principle of flux conservation, ranged from 2 to 18 G with an average of 9 G. Average measured photospheric magnetic fields along the footprints of the corresponding unipolar fields on circular equatorial arcs at 2.5 RS had a similar range and average, but in two cases the intensities were approximately 3 times higher than the projected intensities. The coronal footprints of the sector boundaries on the source surface at 2.5 RS, determined by a potential field extrapolation of the measured photospheric fields, meandered between −45° and +45° latitude, and their inclination with respect to the solar equator ranged from near 0° at some longitudes to near 90° at others. It is possible that sector boundaries are related to convergence surfaces of the flow near the sun. The high densities observed near sector boundaries between streams might be due in part to the convergence of flows from adjacent coronal holes.

Analysis of a Distributed Superconductive Energy Converter

An equivalent circuit for a distributed superconductive energy converter, the operation of which is based on the principle of flux conservation in superconducting loops, is presented. The Laplace transformation is used to analyze the circuit, and the solutions are examined in order to optimize the operation of the device. While previously only dc operation of such a device has been realized, it is shown herein that under certain conditions a low frequency ac mode can be achieved.