Conductive Slab Research Articles

Investigation of de-icing of roads with conductive concrete pavement containing carbon fibre-reinforced polymer (CFRP)

ABSTRACTIn this article, an electrically conductive concrete slab was made using carbon fibre-reinforced polymer (CFRP) and adding it to the concrete matrix. The purpose of making these conductive concrete slabs was evaluating the potential of de-icing the conductive concrete slabs due to electrical heating generated and also, investigating the mechanical strength of concrete samples. In this experiment, two direct and alternating electric current of 3.75 V were used. Using digital thermocouples, the slab surface temperatures were measured and recorded over time. The increase in the compressive strength of cubic concrete samples with the dimensions of 100 mm and 1 and 2% of CFRP, as compared with plain concrete specimens, was 8.39 and 21.43%, respectively. Also, increase in the flexural strength of beam concrete samples with the dimensions of 100 mm × 100 mm × 500 mm and 1 and 2% of CFRP, as compared with plain concrete specimens, was 5.62 and 5.34%, respectively. The temperature of concrete slabs containing 1% and 2% of CFRP in a 3.75-V alternating current at the time of 200 min was increased from −10 to 10.5 °C and 11.7 °C, respectively. The temperature of the slabs under the direct current of 3.75 V at the same time was increased to 5.5 and 6.4 °C, respectively. The results indicated that concrete slabs containing CFRPs, besides having proper mechanical properties, had a superior ability in de-icing.

Effective Nonlinear Surface Impedance of Conductive Magnetic Slabs

A new formula is developed for the surface impedance of a nonlinear magnetic conductive semi-infinite slab. The impedance expression allows for proper incorporation of the nonlinear characteristic of the magnetic material, also using an analytical expression. Thus, the usual step representation of the $B$ – $H$ curve is superseded. Normal and tangential magnetic components may simultaneously exist, avoiding the classical premise that only the tangential component exists. This way, it is possible to represent highly magnetic permeable materials where the normal component of the magnetic field is the main one. Our analytical formulation and solution can be for example used for calculation of losses in electrical machines or along with FE software code to avoid meshing of magnetic conductive regions.

Equivalent Circuit Model for the Frequency-Selective Surface Embedded in a Layer With Constant Conductivity

In this paper, an equivalent circuit model for a frequency-selective surface (FSS) embedded in a layer with constant conductivity is proposed and investigated. Because the medium surrounding the FSS is lossy, the equivalent model consists of not only inductance and capacitance elements but also resistive elements. The reflection response of a square patch FSS embedded in the conductive slab is simulated in a wideband of frequency. Then, all circuit elements are extracted by genetic algorithm optimization, when the reflection coefficient achieved from the equivalent circuit model is the same as the one obtained by numerical simulation. It is also found that the behavior of the model is consistent with that of the simulated one with a good accuracy. Values of the model elements are plotted by the variation of the conductivity and permittivity of layer, and the effects of these parameters are studied on the values of circuit elements. Moreover, it is shown that the obtained model can be applied to determine the model of FSS used in practical absorbers.

Oscillatory Motion of Permanent Magnets Above a Conducting Slab

This paper provides the 3-D time-dependent analytical solution of the electromagnetic fields and forces emerging if a coil or a permanent magnet moves with a sinusoidal velocity profile relative to a conducting slab of finite thickness. The results can be readily used in application scenarios related to electromagnetic damping, eddy current braking, energy harvesting, or nondestructive testing in order to efficiently analyze diffusion and advection processes in case of harmonic motion. This paper is performed for rectangular and circular coils as well as for cuboidal and cylindrical permanent magnets. The back reaction of the conductor and therewith associated inductive effects are considered. The solutions of the governing equations and the integral expressions for the time-dependent drag and lift force are provided. The analytical results are verified by a comparison with numerical simulations obtained by the finite-element method. The relative difference between the analytically and numerically evaluated force profiles was $v_{0}$ , the magnitude of the velocity oscillation amplitude $v_{1}$ , and the underlying oscillation frequency $f_{v}$ .

Proterozoic orogenic belts and rifting of Indian cratons: Geophysical constraints

The Aravalli–Delhi and Satpura Mobile Belts (ADMB and SMB) and the Eastern Ghat Mobile Belt (EGMB) in India form major Proterozoic mobile belts with adjoining cratons and contemporary basins. The most convincing features of the ADMB and the SMB have been the crustal layers dipping from both sides in opposite directions, crustal thickening (∼45 km) and high density and high conductivity rocks in upper/lower crust associated with faults/thrusts. These observations indicate convergence while domal type reflectors in the lower crust suggest an extensional rifting phase. In case of the SMB, even the remnant of the subducting slab characterized by high conductive and low density slab in lithospheric mantle up to ∼120 km across the Purna–Godavari river faults has been traced which may be caused by fluids due to metamorphism. Subduction related intrusives of the SMB south of it and the ADMB west of it suggest N–S and E–W directed convergence and subduction during Meso–Neoproterozoic convergence. The simultaneous E–W convergence between the Bundelkhand craton and Marwar craton (Western Rajasthan) across the ADMB and the N–S convergence between the Bundelkhand craton and the Bhandara and Dharwar cratons across the SMB suggest that the forces of convergence might have been in a NE–SW direction with E–W and N–S components in the two cases, respectively. This explains the arcuate shaped collision zone of the ADMB and the SMB which are connected in their western part. The Eastern Ghat Mobile Belt (EGMB) also shows signatures of E–W directed Meso–Neoproterozoic convergence with East Antarctica similar to ADMB in north India. Foreland basins such as Vindhyan (ADMB–SMB), and Kurnool (EGMB) Supergroups of rocks were formed during this convergence. Older rocks such as Aravalli (ADMB), Mahakoshal–Bijawar (SMB), and Cuddapah (EGMB) Supergroups of rocks with several basic/ultrabasic intrusives along these mobile belts, plausibly formed during an earlier episode of rifting during Paleo–Mesoproterozoic period. They are highly disturbed and deformed due to subsequent Meso–Neoproterozoic convergence. As these Paleoproterozoic basins are characterized by large scale basic/ultrabasic intrusives that are considerably wide spread, it is suggested that a plume/superplume might have existed under the Indian cratons at that time which was responsible for the breakup of these cratons. Further, the presence of older intrusives in these mobile belts suggests that there might have been some form of convergence also during Paleoproterozoic period.

Skin effect of alternating electric current on laminated CFRP

When an alternating current is applied to a conductive slab, the induced current impedes the electric current and causes a skin effect. This effect is found in all conductive materials. For laminated carbon fiber reinforced plastics (CFRP), however, the depth of the skin effect has not previously been evaluated. In the present study, therefore, we analytically solve Maxwell’s equations to derive the skin effect depth of unidirectional CFRP. Using this result, the skin effect is analyzed for laminated CFRP, and its depth is then derived. The effect is then compared with a newly defined skin effect of anisotropic conductance. For highly toughened CFRP that have resin rich layers, the skin effect of anisotropic conductance is found to be more important than that of the alternating current.

Stability of rolls in finite-amplitude Rayleigh–Bénard convection in a high-Prandtl-number fluid between a perfectly conducting boundary and a slab of finite thickness and finite conductivity

Non-linear solutions in the form of two-dimensional rolls are investigated for Rayleigh–Bénard convection in the limit of an infinite Prandtl number fluid in an infinitely wide horizontal fluid layer. The temperature is kept constant at the upper boundary of a slab of finite thickness and thermal conductivity placed on top of the fluid layer. The convection is driven by the temperature difference between this upper boundary and a higher temperature kept constant at the rigid lower fluid boundary. The dependency of the heat transfer on the thickness and conductivity of the slab is reported. Similar to the classical case of two perfectly heat conducting, rigid boundaries the stability region of the rolls is restricted by the cross-roll instability and the zigzag instability. Stability regions relevant for experimental conditions are presented for upper slabs covering a wide range of thicknesses and thermal conductivities. It is shown, how the uppermost Rayleigh number within the stability region varies as a function of the slab properties.

Magnetotelluric survey for undercover structural mapping, Central Victoria

Over 2% of total world gold production has come from the Victorian gold fields; however, most of the shallow deposits have now been discovered, and new methods are required for exploration beneath the thick sedimentary cover of the Murray Basin. Consequently, as part of the GeoScience Victoria Gold Undercover Initiative, new magnetotelluric (MT) data have now been obtained to provide a greater understanding of potential gold bearing structures extending to mid-crustal and greater depths. Coinciding with part of the 2006 Central Victorian Seismic Survey, a 170 km long MT transect lies within the Bendigo and Melbourne Zones, two of the fault bounded subdivisions of the western Lachlan Fold Belt. Additional transient electromagnetic (TEM) data have now been obtained at each of the MT sites allowing further processing, including compensation for static shifts that are significant in this area. The revised MT section provides an image consistent with the seismic section. The major fault zones align with several dipping conductive slabs supporting the orientation and depth extent revealed by the seismic profile. There is some evidence in the MT data that near-surface geological structures can be extrapolated to mantle depths.

The electromagnetic field in conductive slabs and cylinders submitted to a harmonic longitudinal magnetic field

The analysis of the induced current distribution in conducting wires subjected to a harmonic axial voltage is important in designing many electrical devices such as transformers and transmission lines. The azimuthal magnetic field induces axial electric currents and therefore the impedance of the wire depends on the excitation frequency. The current density is increasingly confined to a thin layer at the boundary of the wire as the frequency increases. To minimize this effect at higher frequencies it is necessary to enhance the surface-to-volume ratio by using thin high-conductivity wires. The study of induction phenomena in conducting samples subjected to a harmonic longitudinal magnetic field has attracted less attention. The time-varying magnetic flux induces eddy currents, which flow perpendicularly to the axis of the sample. We study the electromagnetic field in samples of simple geometry, making the usual approximations in good conductors. The validity of our calculations extends to several GHz and allows us to propose a method for determining the electrical conductivity by measuring the phase angle of the complex mutual inductance between a primary coil, responsible for the external magnetic field, and a secondary winding around the sample.

Inductance of Coil in Nonhomogenous Surrounding

The paper introduces the concept of the complex inductance as a parameter of a coil loaded by sinusoidal current and placed near an electrically well conductive body in which the magnetic field of the coil induces eddy currents. Studied will be only axi-symmetric cylindrical coils and the paper shows how easily their complex inductances can be determined by means of professional programs for electromagnetic field analysis. The suggested methodology is illustrated on computation of the inductance of a ring coil placed near a conductive slab. Investigated is also dependence of the complex inductance on frequency.

Assessment of homotopy analysis method and homotopy perturbation method in non-linear heat transfer equation

Two new analytical methods to solve nonlinear heat transfer equations are homotopy perturbation method and homotopy analysis method. Here, homotopy analysis method, which gives us a vast freedom to choose the answer type, is applied to solve nonlinear heat transfer differential equations and analytical results are compared with those of HPM and the numerical results. In this study, the procedure of HAM is applied to two cases in different ways according to the physics of the target problem. Comparing the two methods, our attention is focused on the results accuracy; and applicability of different methods in many cases with different limitation is studied. In the two examples of this paper, the effect of small parameter increaser on the accuracy of the analytical results of two methods also has been studied. The first differential equation is the modeling equation of a cooling lumped system with combined convection and radiation. The second one is the modeling equation of heat transfer with conduction in a slab of thermal dependent conductivity.

Analysis of the performance of a combined coil-rail launcher

An electromagnetic system that operates both as a rail and as a coil launcher is proposed, and its performance is analyzed. The device has a composite stator that consists of two rails properly slotted in order to allow the presence of a system of coils. The armature consists of a conductive slab sliding between the rails. Another system of slots is present in the armature where a system of short-circuited coils is placed. A source of constant voltage is connected to the rails and the current flowing in the armature through the sliding contacts produces a thrust force on it. If a proper system of currents able to produce a traveling wave of flux density in the region between the rails is used to feed the barrels, the induced currents that flow in the armature's short-circuited coils produce a further thrust force on the armature itself. The analysis of the behavior of this launcher is performed via a computer code based on an integral formulation and a tool that analyzes the phenomena related to the velocity skin effect; the interactions between the two systems of currents on the armature and the currents on the stator (rails and barrels) are investigated. The thermal behavior of the device has been taken into account by a simple adiabatic model since the short operating time allows one to neglect heat diffusion in the conductive parts of the system. A comparison between the velocities, respectively obtained by separately feeding rails and coils and the system with the combined feeding, has been performed. Preliminary results of the analysis show that this device, because of the presence of two systems of thrust forces acting on the armature, can be successfully used in the acceleration of heavy masses at relatively high velocities, the maximum achievable speed being limited by thermal and mechanical stresses.

Sensitivity studies applied to a two-dimensional resistivity model from the Central Andes

SUMMARY Long-period magnetotelluric (MT) data have been collected along an E‐W profile across the Central Andes in Northern Chile and Southern Bolivia. A 2-D resistivity model explaining these data was found by inverse modelling. The model includes a prominent conductivity anomaly in the backarc of the South American subduction zone below the Bolivian Altiplano. Another, comparatively localized anomaly occurs beneath the Precordillera in the forearc. The enhanced conductivity in the backarc correlates with reflective zones, low seismic velocities and high seismic attenuation. In contrast, no correlation can be found in the forearc. A strong seismic reflector in context with the down-going slab, and another reflector in the middle crust below the Pre- and Western Cordillera do not coincide with anomalous conductivity. Other 2-D models may also be consistent with the data. We applied different techniques to find the range of relevant models. One simple but useful approach is the direct use of the sensitivity matrix containing the partial derivatives of the data with respect to the model parameters. The sensitivity of the model parameters to the data or data subsets can be visualized by calculating columnwise sums from the sensitivity matrix. These sensitivities may be used to indicate model parameters that are less resolved by the data and thus should not form part of an interpretation. Another approach is to perform systematic studies to establish the validity of geologically important features of the model. These studies comprise forward modelling and the use of a priori information. Combining all approaches generates a more complete assessment of the principal model features. We conclude that a minimum depth extent of the Altiplano conductor can be specified as approximately 50 km. Low sensitivity in the forearc beneath the Longitudinal Valley indicates a limited structure resolution, and therefore may explain the absence of a conductive slab in the model. The existence of the localized conductor below the Precordillera can be established by high sensitivity. Finally, we included the two seismic reflectors in the forearc as a priori information in the inversion process. As a result the absence of a conductive slab in the model is probably a result of low sensitivity, but cannot be totally excluded. A conductive zone coinciding with the strong reflector below the Pre- and Western Cordillera is not manifested by the MT data.

Interpretation of long-offset transient electromagnetic data from the Odenwald area, Germany, using two-dimensional modelling

SUMMARY The standard 1-D inversion approach for the interpretation of transient electromagnetic (TEM) data usually fails in the presence of near-surface conductivity anomalies. Since multidimensional inversion codes are not routinely available, the only alternative to discarding the data may be trial-and-error forward modelling. We interpret data from a long-oVset transient electromagnetic (LOTEM) survey which was carried out in 1995 in the Odenwald area, using 2-D finite-diVerence modelling. We focus on a subsegment of the LOTEM profile, which was shot with two diVerent electric dipole transmitters. A model is found which consistently explains the electric and magnetic field data at eight locations for both transmitters. First, we introduce a conductive dyke under the receiver spread to explain sign reversals in the magnetic field transients. A conductive slab under one of the transmitters is required to obtain a reasonable quantitative fit for that transmitter. Consideration of the electric field data then requires a modification of the layered earth background. Finally, we study the response of a crustal conductor, which was the original target of the survey. The data are sensitive to the conductor, and for the investigated subset of the data the fits are slightly better without the conductive layer.

Influence of viscosity variation on the stationary B�nard-Marangoni instability with a boundary slab of finite conductivity

The onset of stationary Benard-Marangoni instability in a variable-viscosity fluid layer with a boundary slab of finite conductivity is studied. The relations of the viscosity and surface tension of the fluid with the temperature are exponential and linear, respectively. The asymptotic solutions of the long wavelength, for small values of the conductivity and thickness of the solid, are achieved and are very well compared with the numerical results. As the viscosity ratio increases, the validity of the asymptotical solutions is extended for cases of larger values of the thermal conductivity and thickness ratios.

Conjugate natural convection from a vertical heated slab

Conjugate natural convection heat transfer from a vertical plate has been investigated analytically and experimentally. Assuming the existence of vertically averaged interfacial temperature between plate and fluid, it is shown that there is a unique nondimensional parameter to characterize the problem. The interfacial temperature is obtained as a root of 5th order polynomial for laminar natural convection, and it is presented as a function of the conjugate parameter. For turbulent convection it is also shown that the polynomial becomes 4th order. A simple expression for the average heat transfer is given as a function of conjugate parameter and the apparent Rayleigh number defined by an overall temperature difference. An experiment, using a water vessel with a heating plate on a side wall, was carried out in order to test a proposed theory for the heat transfer. Three different materials, copper, stainless steel and ceramics, were used as a conductive slab. The measured average heat transfer rates are in good agreement with the theory.

Electronic band structures of and ionic conduction in β-alumina-type superionic conductors

The electronic band structures of β-alumina-type superionic conductors (SIC) are proposed and discussed using experimental results for the reflection and absorption spectra in the ultraviolet and vacuum-ultraviolet regions and photoemission spectra. The measurements were performed using beam lines with synchrotron radiation. The valence bands of all β-alumina-type SIC are constructed from the 2p orbital of oxygen (O 2p). In the case of alkali β″-aluminas, the lowest conduction band is due to the s orbitals of alkali ions. It is concluded from this result that all conduction ions are not perfectly free, but construct bonds, giving rise to an ordered structure existing in a limited region. On the other hand, in the case of alkali β-aluminas, this is due to the 3s orbital of aluminum. The low lying exciton bands due to the orbitals of Ag ions and due to the orbitals of Tl ions are observed in Ag β- and Ag β″-aluminas, and in Tl β- and Tl β″-aluminas, respectively. In these cases, there are also ordered regions in the conduction plane or slab. It is therefore suggested that an ordered structure of the conduction plane or slab should be considered in order to understand the ionic conduction in β-alumina-type SIC.

A three-dimensional finite element method for computing magnetically induced currents in tissues

Time-varying magnetic fields used both in nerve stimulation and in magnetic resonance imaging induce electric fields and currents in conducting tissues. Knowledge of the spatial distributions of these induced electric fields and currents in the tissues is very limited because of the complex geometry and inhomogeneous, anisotropic conductivities of the tissues, as well as the spatial nonuniformity of the applied magnetic fields. In this paper, we present a finite element solution method that can be used to compute the induced electric field and current density distributions in tissues when the time rate of change of the applied magnetic field is low enough that the propagation time and magnetic diffusion time in the conductive tissues are negligible, and when the conduction current in the tissues is substantially larger than the displacement current. This finite element implementation is tested for some simple conductive models with both spatially uniform and nonuniform magnetic fields. Our solutions for a homogeneous isotropic conductive slab and a homogeneous anisotropic conductive slab exposed to a uniform magnetic field are in good agreement with analytical results. The finite element approach enables us to include conductive inhomogeneity and anisotropy. I allows us to closely model the complex geometry of the tissues. Therefore, it is well suited for realistic models of the conductive anatomy of biological tissues.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Comparison of Dipole-Dipole and Gradient Arrays

In exploration practice in the Western U.S., the two most commonly used IP/resistivity electrode configurations are the dipole-dipole and gradient arrays. Differences in the relative responses between the two electrode configurations have been noted and the relative merits debated, but published data are limited. A suite of dipole-dipole and gradient-array profiles have been computed for direct comparison of both conductive and resistive bodies. Profiles for thin vertical and thin horizontal tabular bodies (dykes and slabs respectively), are the primary basis for comparison. The anomalies at a typical resistivity and chargeability contrast are normalized by determining the ratio of amplitude to the background response. Plots of resistivity and chargeability illustrate the differences with depth for the two types of bodies.For thin conductive dykes, dipole data give a strong characteristic response on both resistivity and chargeability parameters; gradient profiles, however, show a weak resistivity and nil chargeability response. Conductive slabs show excellent anomalous response for both arrays. Resistive dykes produce better relative resistivity and chargeability responses on the gradient array than the low amplitude, peculiar characteristics, responses of the dipole array. The resistive slab produces almost no chargeability response on the gradient array.Overburden effects, multiple bodies, dip and several case histories are also examined to show the differences in interpretation potential.An eventual recommendation for use of either array depends upon the interpretation required, geological assumptions of the target size, shape, and physical property contrast, and the cost differential of data acquisition.

Frequency and transient analysis of a thin conductive slab in lossy Earth due to a uniform magnetic line source

In this paper we present frequency and transient analysis of a thin tabular conductive slab in lossy Earth due to a uniform magnetic line source excitation. The line source is parallel to the slab, and thus the problem is two dimensional. Under these conditions the frequency domain solution can be expressed in the form of a series which has an exact time domain representation. Our results are checked against two well‐known limiting cases. This problem can model ore slabs and fluid‐filled cracks in geophysical applications. The analytical and numerical results give a diagnosis of the thickness and conductivity of the slab and provide physical insight in the interpretation of actual field data.