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In this study, a conductivity-regulated barrel-type permanent magnet eddy current governor is proposed, and a conductor barrel structure scheme consisting of four sections of materials with different conductivities is presented. The torque equation of the barrel-type permanent magnet eddy current governor with the equivalent conductivity as the covariate was established using the separation variable method based on the subdomain model. The equivalent conductivity function was established to obtain the speed regulation characteristics of the governor under a constant torque load, and the calculation method for the governor’s transmission efficiency was provided. The influence of the conductivity parameters of the conductor barrel on the speed regulation characteristics was studied by numerical simulation, the influence of the conductivity values of each Section of the material on the conductivity function was investigated, the torque equation and conductivity function were verified by three-dimensional electromagnetic finite element simulation, and the direction and distribution of eddy current in conductor layer under different working conditions were simulated. The results show that the structural scheme of the four-segment combined conductor barrel can realize a continuous change in conductivity with the displacement of the magnet disk, thus realizing continuous speed regulation of the constant torque load, and the speed regulation characteristic of the governor is segmented linearly. Compared with the air gap-regulated disk-type permanent magnet eddy current governor, the conductivity-regulated barrel-type permanent magnet eddy current governor has a wider speed regulation range, a lower unloading torque after overload protection, and can start with its maximum torque, thus enabling heavy-load starting of constant torque loads, speed regulation operation, and unloading overload protection of equipment.

Steady well‐type flow was monitored in an aquifer that was artificially packed in order to reproduce a given, highly heterogeneous, statistical distribution of the log‐conductivity Y. In particular, we focus on pumping tests carried out at 10 volumetric flow rates. The experimental arrangement was composed by a pumping well and several surrounding observation piezometers. The unique feature of this experimental study is that the high heterogeneity structure of Y is known fairly well. Thus, the study lends itself as a valuable tool to corroborate theoretical findings about flows driven by sources through porous formations, where the variance σY2 ${\sigma }_{Y}^{2}$ (in the present study equal to 3.79) of Y is large. Besides discussing experimental findings, we tackle the crucial issue of upscaling the hydraulic conductivity in a well‐flow configuration. In particular, we deal with the equivalent conductivity (EC) as that pertaining to a homogeneous (fictitious) medium which conveys the same volumetric flow rate of the real one, under the same boundary conditions. Hence, the EC can be identified straightforwardly by means of head measurements. Even if we show that the EC is a proper parameter to reproduce measurements, it is experimentally shown (in line with the theoretical results) to be position‐dependent, and therefore, it cannot be regarded (unlike groundwater‐type flow) as a formation's property. This implies that the EC applies only to the configuration at stake. Then, we show that the EC, combined with a recent model of effective conductivity in well‐flows through highly heterogeneous porous formation, leads to a reasonably reliable estimate of σY2 ${\sigma }_{Y}^{2}$, some limitations and approximations, notwithstanding. It is hoped that the present experimental study will be useful for other researchers who are engaged with similar research‐topics. Key Points: Steady well‐flow through a strongly heterogeneous formation is investigated by means of an experimental studyThe formation was artificially packed to reproduce a given, statistical distribution of the hydraulic conductivityThe equivalent conductivity is proved to be a proper parameter to simulate the average flow [ABSTRACT FROM AUTHOR]

The influence of rare earth Y on the microstructure and mechanical properties of Al-Zr alloy produced by dynamic ECAE was studied by OLYMPUS-BX51M optical microscope (OM), S4800 energy disperse spectroscopy (EDS) and SANS CMT5105 electronic universal material testing machine, and the corresponding equivalent conductivity was also investigated by using QJ48 DC electric bridge. The results show that the tensile strength of Al-Zr conductor first increases and then decreases with the increase of the aging time and temperature, and the highest tensile value can be obtained under the aging temperature of 160 °C for 4 h. The ductility and the resistivity of the Al-Zr alloy have inverse proportion to the aging time. The rare earth Y has significantly improved the electrical and mechanical properties of Al-0.3%Zr heat-resistant alloy. In this study, the tensile strength and the elongation of the Al-0.3%Zr-0.2%Y alloy, after aging treatment at 220 °C for 14 h, are about 278.49 MPa and 6.7%, respectively, and the equivalent conductivity is about 59.6 IACS. Hence the synthetical properties of the Y-containing alloy are significantly improved compared with traditional Al-0.3%Zr alloy. [ABSTRACT FROM AUTHOR]

A quasi-three-dimensional (3-D) analytic method is presented for calculating the performance of single-sided linear induction motor with the ladder secondary. To simplify the analytic model, the ladder aluminum plate is equivalent to the flat-solid one, and the equivalent conductivity is derived and given. In the direction of the motion, the finite primary length and end effect are considered by the method of the Fourier transform and Residue theorem. In the transverse direction, considering finite width of the primary core and the region between the overhang of the primary windings and the secondary, the equivalent integral length is given. Finally, the thrust, vertical force and secondary efficiency are calculated and compared with the results of the 3-D finite-element method and experiment, it is shown that the method presented in the paper is much simpler and the accuracy of the analytic method is verified. [ABSTRACT FROM AUTHOR]

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In order to accurately design microwave, millimeter-wave components and circuits, a simple and accurate method for extracting extremely wideband characteristics of the printed circuit board (PCB), including relative dielectric constant, dielectric loss tangent, and equivalent copper conductivity, is proposed and validated in this paper. By properly selecting wideband distribution of multiple TMmn0 modes in the designed circular substrate integrated waveguide (CSIW) cavities, extremely broadband properties of PCB can theoretically be extracted with only one pair of CSIW cavities. The proposed method overcomes the limitations of conventional methods that only support narrowband applications, require a large number of cavities, and have relatively large errors. The experiments show that the proposed method is able to extract, accurately and efficiently, 8-110 GHz characteristics of a TLY-5Z substrate-based PCB and the extracted results are verified by designing and measuring the fourth-order Chebyshev filter at X-band.

• Flow toward a drain through heterogeneous porous media is solved by a perturbation method. • The mean Green function for bounded heterogeneous domains is computed. • The mean head field for a drain-type flow is computed. • The equivalent conductivity concept is applied for the first time to a drain-type flow. We consider the problem of steady pumping of water from a line drain on the surface of a wet ground. Unlike the classical formulation, which regards the conductivity parameter K as uniformly distributed in the domain, the problem here is solved within a stochastic framework in order to account for the irregular (random), and more realistic, spatial variability of K. Due to the linearity of the problem at stake, we focus on the derivation of the mean Green function G. This is computed by means of an asymptotic expansion. The fundamental result is an analytical (closed form) expression of G which generalizes the classical solution. Based on this, we develop an equivalent conductivity K eq which enables one to tackle the problem similarly to the classical one. In particular, it is shown that the equivalent conductivity grows monotonically with the radial distance r from the drain, and it lies within the range K eq(0) ≤ K eq(r) ≤ K eq(∞) < ∞. [ABSTRACT FROM AUTHOR]

The comparison of three field methods for homogenization of the laminated cores has been presented in this work. As a result, the equivalent electrical conductivity and magnetic permeability for the geometry of the core entire body were obtained for magnetic field 3D modelling. The first method is an iterative homogenization method (IHM) connected with the field solution, whereas the two others are based on analytical expressions arising from the Maxwell's equations. For 3D field solution, Finite Element numerical model including eddy currents under various frequency values was used in IHM. The model is based on a combination of the total and the reduced magnetic potentials. For comparison to our IHM, the two analytical approaches for core homogenization were used, as well. To calculate the stray losses in the homogenized laminated C-core these three approaches have been executed, as a case study. Applying suitable simplifications, according the methods of analytical homogenization, between the analytically calculated and measured values of the core losses high differences have been obtained. For the cores from amorphous strip, the analytical methods are inappropriate and our method, though iteratively implicit, gives significantly better equivalent parameters for the laminated C-core. [ABSTRACT FROM AUTHOR]

With an increase in the usage of LNG, there is a heightened interest about its safety aspects regarding the explosion of LNG carrier tank. The need for a cryogenic explosion-proof camera has increased. The camera has to work in cryogenic environment (below −160 °C) in LNG carrier. This study conducted design and heat transfer analysis of cryogenic camera to secure working time in limitation of heat source. The design with gap width of double pane windows was conducted based on simple vertical cavity model to insulate from cryogenic environment. The optimal gap width was 12.5 mm. For effective analysis considering convection within the camera, equivalent thermal conductivity method was adopted with ABAQUS. The working time of the camera predicted was over 10 h at warm-start condition. In cold-start condition, it required about 5 h of pre-warming time to work. The results of analysis were compared with the ones of the actual cryogenic test.

Copyright of Österreichische Wasser- und Abfallwirtschaft is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this study is to characterize the features of magnetic flux density perturbation as a result of the variation of conductivity in an equivalent model of the stress-corrosion crack (SCC). By using numerical computation of A-𝜙 method, the magnetic field nearby the inspection target was simulated for an eddy current probe of large rectangular excitation coil and a conductor plate with a modeled SCC. A conductive notch was set in the center of the conductor plate as an equivalent crack model of a real SCC. Different conductivities and crack depths were varied into the equivalent SCC model for analyzing their influences to the distribution of magnetic flux density perturbation above the model plate. Numerical results showed that the distributions of magnetic flux density were suitable to distinguish the difference of the conductivities of the SCC between 0% and 20% of the base material for normal testing frequencies. In addition, it was also found that the profile of distributed conductivity along the crack length can be better represented with the field induced by the excitation current laterally to the crack length. [ABSTRACT FROM AUTHOR]

Abstract Expanded PolyStyrene (EPS) foams are very widely used as thermal insulators, especially for the Building insulation. Therefore, the heat transfer in these materials has been extensively studied and optimised. Nevertheless, due to their very low density, the IR thermal radiation propagating through their porous structure still contributes significantly to the total heat transfer. In order to increase their insulation performances even more, the addition of particles strongly interacting with IR radiation in the polymer matrix is very promising. We have investigated this solution from the theoretical and experimental points of view. The influences of the presence of particles on both the conductive and radiative properties of the opacified foams have been modelled. A parametric study allows us to highlight the key properties required to make the opacifying particles efficient and to evaluate the corresponding potential savings. Alongside, several powders have been tested experimentally by incorporating them into polystyrene thin films. Spectrometric measurements conducted on these films allow us to identify their radiative properties, evaluate the reduction of equivalent conductivity and confirm the efficiency of the solution. This investigation then constitutes a useful tool for selecting appropriate opacifiers. [ABSTRACT FROM AUTHOR]

The aim of the article is to present the method for modeling transformer winding inductance, taking into account the complex magnetic permeability and equivalent electric conductivity of the magnetic core. In the first stage of the research, a physical model of a 24-turn coil wound on the distribution transformer core was prepared. The Frequency Response Analysis (FRA) measurements of the coil were taken; then, the inductance of the coil as a function of frequency was calculated from the received frequency response curves. In the second stage, two-dimensional (2D) and three-dimensional (3D) computer models of the coil based on the finite element method (FEM) were established. In order to obtain the equivalent inductance characteristics of the winding modeled in 2D and 3D in a wide frequency range, the equality of the reluctance of the limbs and yokes in both models was assured. In the next stage of the research, utilization of the equivalent properties for the laminated magnetic material simulations was proposed. This outcome can be used to calculate the frequency response of the winding of the power transformer. The other obtained result is the method for modeling the resonance slope, which is visible on the inductance curve received from the FRA measurement.

Electrodialysis desalination plants, for brackish water, are designed based on different parameters such as feed concentration, current density, and stack construction. Among the various model assumptions, the constancy of the equivalent conductivity of the diluate and concentrate streams is considered a prominent one. In this paper, this assumption is relaxed at different levels and closed-form solutions are obtained to ascertain its effects. It is shown that previously published results can be replicated. Also, a comparison between the lumped and staged model shows that using the inlet flow rate in the lumped model instead of the product flow rate provides more accurate results. Further analysis reveals a non-dimensional number, termed the electrodialytic Biot number, which is the ratio of the total to exit concentration based average cell pair volume resistance. It was found to be physically equivalent to the number of stacks. This provided a clear criterion as to when the lumped model should be used. Specifically, as long as the electrodialytic Biot number is (less than or) equal to 1, the lumped model should be used, otherwise the staged model is a more appropriate choice. It also provides direction for future research. A design chart is also developed to facilitate the calculation procedure. [ABSTRACT FROM AUTHOR]

Electromagnetically induced transparency (EIT) is a fascinating phenomenon in optical physics and has been employed in slow light technology. In this work, we use terahertz (THz) metamaterials to mimic EIT phenomenon and study their spectral dependence on the coupling strength between bright and dark resonators. In these metamaterials, two kinds of resonators are located on two different layers separated by a 10-µm-thick polyimide (PI) film. The whole sample is supported by a 5-µm-thick flexible PI film, so the Fabry-Perot resonance at THz can be avoided. The coupling strength is tuned by the translational offset of symmetry axes between two different kinds of resonators, resulting in the change of EIT-like spectra. [ABSTRACT FROM AUTHOR]

A hybrid radial magnetic bearing (HRMB) with permanent magnet creating bias flux is used to reduce the power consumption. Laminated cores are widely used in HRMB to reduce eddy currents. Nevertheless, when the frequencies of rotation and control currents are extremely high, eddy-current effects in laminated iron cores still have a significant influence on the behavior and performance of magnetic bearings. In order to predict performance and guide design of the HRMB system in high frequency, an analytical method based on equivalent circuit model whose parameters are frequency-dependent is used in this paper. The analytical results show that, the eddy currents induced due to rotor movement and dynamically changing control currents will result in considerable magnitude decrease and phase lag of bearing stiffness. Furthermore, the eddy current effect on HRMB can be reduced by increasing the air gap, decreasing the laminations thickness and decreasing the laminations conductivity. Finally, a prototype is designed and fabricated; the experimental results demonstrate the validity of the analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] Simultaneous parameter, initial, and boundary condition estimation for transient flow. [•] Local approximate solution imposes physical flow constraints on inversion. [•] Highly parameterized conductivities and equivalent parameters can be estimated. [ABSTRACT FROM AUTHOR]

Highlights: [•] The impact of topology and geometry on the equivalent conductivity is investigated. [•] The Euler number is not a good measure of connectivity of a binary medium. [•] The area of influence on flow of each inclusion is related to its convex hull. [•] A new algorithm for the estimation of the equivalent conductivity is proposed. [•] The new algorithm gives accurate estimations on isotropic complex heterogeneities. [ABSTRACT FROM AUTHOR]

The eddy current fields in a laminated iron core and a single lamination, where the fields are considered as the 2-D and the 1-D problems, respectively, are analyzed. Then a new and simple formulation of equivalent conductivity in the direction normal to the laminations is derived by equating the eddy current loss expressions obtained from the above two problems. The validity of the formulation is verified by comparing the eddy current losses, calculated with the finite-element method using the proposed conductivity formulation and a long known formula, in an analyzed model. [ABSTRACT FROM PUBLISHER]

Based on a three-dimensional heterogeneous aquifer model exhibiting non-stationary, statistically anisotropic correlation, three hydrostratigraphic models (HSMs) are created within a sedimentary hierarchy. A geostatistical analysis of natural log conductivity (ln K) is conducted for the units of the HSMs. Hydraulic conductivity is then upscaled using numerical and analytical methods. Increasing ln K variances are evaluated. Results suggest that for the aquifer model tested: (1) the numerical method is capable of upscaling irregular domains with reasonable accuracy for a ln K variance up to 7.0. (2) Accuracy of the upscaled equivalent conductivities ( K*) and associated performance of the HSMs are sensitive to homogenization level, heterogeneity variance, and boundary condition. Variance is found to be the most significant factor impacting the accuracy of the HSMs. (3) Diagonal tensor appears a good approximation for the full-tensor K*. (4) For the HSM units, when the variance is low (less than 1.0), all analytical methods are nearly equally accurate; however, when variance becomes higher, analytical methods generally are less accurate. [ABSTRACT FROM AUTHOR]

Summary: A critical issue facing large scale numerical simulation models is the estimation of representative hydraulic conductivity to account for the unresolved sub-grid-scale heterogeneity. In this study, two experiment-based hydraulic conductivity models offer a test case to evaluate this parameter. Each model contains a different heterogeneity pattern with connectivity characteristics that cannot be captured by univariate and bivariate statistics. A three-dimensional numerical upscaling method was developed to compute an equivalent conductivity full tensor for each model. The equivalent conductivities were compared to direct averages of local conductivities and to an effective conductivity predicted by several analytical methods. For each model, ln K variances up to 16 were evaluated. The impact of variance on both upscaled conductivity and three fluid flow connectivity factors was assessed. Results suggest: (1) the upscaling method gave reliable results comparable to an established method which only gives the diagonal components, (2) for both aquifer models, when ln K variances are low (less than 1.0), all analytical methods evaluated are nearly equally accurate; however, when variance becomes higher, the analytical methods of were found to provide robust estimates of equivalent conductivities, despite possible violation of the multiGaussian assumption, (3) fluid flow characteristics in each model were significantly impacted by increasing variance, which can result in flow channeling in the lateral direction and increasing global anisotropy ratios of the equivalent conductivity, and (4) geometric connectivity, as analyzed by a percolation cluster analysis, indicates the importance of such features in focusing flow, in addition to the effects of high variance. [Copyright &y& Elsevier]

This paper deals with the computation of eddy-current losses in laminated cores. In the first part we recall some approximate formulas existing in the literature and implemented in many electromagnetic computer packages. Then we assess their accuracy by making comparisons with the exact loss values obtained by numerical solution of the quasi-static Maxwell equations. In the second part we introduce a definition of an equivalent electric conductivity allowing us to replace the laminated core with a homogeneous isotropic or anisotropic medium. We compare the values of this equivalent conductivity with those obtained from some approximate formulas. [ABSTRACT FROM AUTHOR]

Average steady source flow in heterogeneous porous formations is modelled by regarding the hydraulic conductivity K( x) as a stationary random space function (RSF). As a consequence, the flow variables become RSFs as well, and we are interested into calculating their moments. This problem has been intensively studied in the case of a Neumann type boundary condition at the source. However, there are many applications (such as well-type flows) for which the required boundary condition is that of Dirichlet. In order to fulfill such a requirement the strength of the source must be proportional to K( x), and therefore the source itself results a RSF. To solve flows driven by sources whose strength is spatially variable, we have used a perturbation procedure similar to that developed by Indelman and Abramovich (Water Resour Res 30:3385–3393, ) to analyze flows generated by sources of deterministic strength. Due to the linearity of the mathematical problem, we have focused on the explicit derivation of the mean head distribution G d ( x) generated by a unit pulse. Such a distribution represents the fundamental solution to the average flow equations, and it is termed as mean Green function. The function G d ( x) is derived here at the second order of approximation in the variance σ2 of the fluctuation $$\varepsilon \left({{\mathbf{x}}}\right) = 1- \frac{K{\left({{\mathbf{x}}}\right)}}{K_{A}}$$ (where K A is the mean value of K( x)), for arbitrary correlation function ρ( x), and any dimensionality d of the flow domain. We represent G d ( x) as product between the homogeneous Green function G ( x) valid in a domain with constant K A , and a distortion term Ψ d ( x) = 1 + σ2ψ d ( x) which modifies G ( x) to account for the medium heterogeneity. In the case of isotropic formations ψ d ( x) is expressed via one quadrature. This quadrature can be analytically calculated after adopting specific (e.g.. exponential and Gaussian) shape for ρ( x). These general results are subsequently used to investigate flow toward a partially-penetrating well in a semi-infinite domain. Indeed, we construct a σ2-order approximation to the mean as well as variance of the head by replacing the well with a singular segment. It is shown how the well-length combined with the medium heterogeneity affects the head distribution. We have introduced the concept of equivalent conductivity K eq( r, z). The main result is the relationship $$\frac{K^{\rm eq}\left(r,z\right)} {K_{A}} = 1-\sigma^{2}\psi^{\left(w\right)}\left(r,z\right)$$ where the characteristic function ψ( w)( r, z) adjusts the homogeneous conductivity K A to account for the impact of the heterogeneity. In this way, a procedure can be developed to identify the aquifer hydraulic properties by means of field-scale head measurements. Finally, in the case of a fully penetrating well we have expressed the equivalent conductivity in analytical form, and we have shown that $$K^{({\rm efu})}\leq K^{\rm eq}\left(r\right) \leq K_{A}$$ (being $$K^{({\rm efu})}$$ the effective conductivity for mean uniform flow), in agreement with the numerical simulations of Firmani et al. (Water Resour Res 42:W03422, ). [ABSTRACT FROM AUTHOR]

The conductivities of aqueous solutions of sodium sulphate and sodium tetraborate at different concentrations were measured. Using a novel method, these data were used to determine the limiting equivalent ionic conductivity and ionic radius of tetraborate ion. It was found that the limiting equivalent ionic conductivity of tetraborate ion is 34.58 ohm-1 cm2 and the ionic radius of tetraborate is 3.507±0.076 Å. [ABSTRACT FROM AUTHOR]

Summary: A critical issue facing groundwater flow models is the estimation of representative hydraulic conductivity assigned to the model units. In this study, an experiment-based, high-resolution hydraulic conductivity map offers a test case to evaluate this parameter. Various hydrogeological units are distinguished, each is of irregular shape with distinct heterogeneity pattern created by physical sedimentation. Extending a previous study which used numerical upscaling to compute equivalent conductivities for these units (at two upscaling scales) [Zhang, Y., Gable, C.W., Person, M., 2006. Equivalent hydraulic conductivity of an experimental stratigraphy – implications for basin-scale flow simulations. Water Resources Research 42, W05404. doi:10.1029/2005WR004720], this study compares them with local statistics and effective conductivities predicted by a stochastic theory. Results suggest that for a system with moderate lnK variance (4.07) and low topographic slope (∼1°), the arithmetic mean (K A) provides a good estimate for the maximum principal component (K max) of the equivalent conductivity. The minimum principal component (K min) lies between the harmonic and geometric means: its closeness to the geometric mean is affected by heterogeneity pattern and upscaling scale. Using K max (alternatively, the arithmetic mean), geometric mean, and ln(K) variance, the stochastic theory predicts a K min that is consistent with the up-scaled value. Similarly, knowing K min, K max predicted by theory is also consistent with the up-scaled value. For most deposits (some with variance greater than 1), a low-variance version of the theory is more accurate than a high-variance version. However, the increase of topographic slope (to ∼4°) and total lnK variance (to 16) result in increased deviation of K max from K A. High variance also results in significantly larger anisotropy ratio, possibly due to the dominance of preferential flow. Finally, for select units, equivalent conductivity exhibits scale effect. Field scale representative elementary volume thus does not exist and upscaling the full unit is necessary to obtain the representative conductivity. [Copyright &y& Elsevier]

Abstract: LiMF6 (M=Ta, Nb) was prepared by the reaction between LiF and MF5 (M=Ta, Nb) in F2 gas. Pure LiMF6 (M=Ta, Nb) salts were obtained by using the reaction at temperatures higher than 473K under 80kPa (F2) for 24h. The x values in LiMF x (M=Ta, Nb) were confirmed as 5.7–6.0 by XRD–Rietveld analysis. Results showed that LiMF6 (M=Ta, Nb) has a trigonal structure (, Z =3). The respective lattice parameters of LiTaF6 and LiNbF6 are a 0 =0.533nm, c 0 =1.362 and a 0 =0.532nm, c 0 =1.360. The equivalent conductivities of both LiMF6 (M=Ta, Nb) in propylene carbonate (PC) are equal at 15.2Ω−1 cm2 mol−1 at 0.01moldm−3. The electrochemical potential window of TaF6 − is 7.0V, which is 0.4 and 0.2V wider, respectively, than those of BF4 − and PF6 −. [Copyright &y& Elsevier]

This paper deals with the definition of an equivalent thermal conductivity for particulate foods. An homogenized thermal model is used to asses the effect of particulate spatial distribution and differences in thermal conductivities. We prove that the spatial average of the conductivity can be used in an homogenized heat transfer model if the conductivity differences among the food components are not very large, usually the highest conductivity ratio between the foods components is lower than 5. In the general case we propose to use a standard spatial homogenisation procedure. Although the heterogeneity give rise to an anisotropic heat transfer behaviour, this effect is negligible when the food particles are randomly distributed. When we use pre-mixed particulate foods a statistical average can be defined from a small number of possible particle arrangements. [Copyright &y& Elsevier]

Solute transport through highly heterogeneous geologic environments with connected pathways through high-conductivity material and lenses of low permeability often is not described well by a macroscopic advection-dispersion equation. An upscaled advection-dispersion model with a uniform velocity and dispersion coefficient does not predict the significant plume asymmetry and extended tailing often observed over finite distances in such environments. We investigate the hydrogeologic conditions under which an upscaled model must incorporate another mechanism to describe the extended tailing arising from slow advection through and diffusion into and out of low-permeability inclusions. We use high-resolution simulations to determine ground truth transport results for 84 hydrogeologic scenarios comprising distinct low-permeability lenses set into an otherwise homogeneous background. We compare the ability of two one-dimensional, fitted, upscaled models to reproduce the arrival time curves from the fully resolved simulations. The first model uses a macrodispersion coefficient to describe the spreading due to the low-permeability inclusions. The second model accounts for the effect of the geologic heterogeneity with a nonequilibrium mass transfer component. When the equivalent conductivity of a domain is less than or equal to the geometric mean conductivity, a macroscopic advection-dispersion model matches the results well. When the equivalent conductivity is greater than the geometric mean, however, another model may be needed to describe the solute tailing. [ABSTRACT FROM AUTHOR]

A numerical code for the electromagnetic analysis of high T/sub c/ superconductors by finite element method has been developed. The E-j characteristics of superconductor are represented with the n-value. The equivalent conductivity of superconductor is determined as a function of electric field, and Ohm's law is used as the constitutive equation. First, the current and magnetic flux distributions in the infinite slabs of superconductor exposed to a parallel external magnetic field are analyzed. The influence of n-value on AC loss and the frequency dependence of AC loss are studied. The AC loss in the infinitely-long superconductor tapes exposed to the external magnetic field is calculated numerically to study the influence of n-value. [ABSTRACT FROM PUBLISHER]

The aim of the article is to present the method for modeling transformer winding inductance, taking into account the complex magnetic permeability and equivalent electric conductivity of the magnetic core. In the first stage of the research, a physical model of a 24-turn coil wound on the distribution transformer core was prepared. The Frequency Response Analysis (FRA) measurements of the coil were taken; then, the inductance of the coil as a function of frequency was calculated from the received frequency response curves. In the second stage, two-dimensional (2D) and three-dimensional (3D) computer models of the coil based on the finite element method (FEM) were established. In order to obtain the equivalent inductance characteristics of the winding modeled in 2D and 3D in a wide frequency range, the equality of the reluctance of the limbs and yokes in both models was assured. In the next stage of the research, utilization of the equivalent properties for the laminated magnetic material simulations was proposed. This outcome can be used to calculate the frequency response of the winding of the power transformer. The other obtained result is the method for modeling the resonance slope, which is visible on the inductance curve received from the FRA measurement. [ABSTRACT FROM AUTHOR]