Finite Resistance Research Articles

Transverse thermal instability of partially ionized radiative plasma with impact of neutral collisions and finite electron inertia effect in ISM

The impact of neutral friction, finite electron inertia and radiative heat-loss function on the thermal instability of viscous, partially-ionized plasma has been explored integrating the impacts of finite electrical resistivity and thermal conductivity. Normal mode analysis scheme is used to derive universal dispersion relation by means of the related linearized perturbation equations of the difficulty and a tailored thermal situation of instability is explored. It is finding that the thermal condition of instability is modified owing the occurrence of radiative heat-loss function, thermal conductivity, finite electron inertia and neutral particle. For transverse mode of propagation, we discover that the condition of thermal instability depends on the finite electron inertia, magnetic field strength, radiative heat-loss function, thermal conductivity, neutral particle and finite electrical resistivity, but independent viscosity of two-components. From the graphs, we explored that the temperature dependent heat-loss function, thermal conductivity, neutral collision frequency and viscosity of two-components demonstrates stabilizing effect, while finite electron inertia and finite electrical resistivity demonstrates destabilizing effect. Our results help’s to understand the process of molecular cloud formation in ISM.

Theoretical study of effect of hyper-resistivity on linear stability of ballooning mode

The coupling of ballooning mode and peeling mode forms the so-called peeling-ballooning mode, which is widely used in the physical explanation of the edge localized mode (ELM). The nonlinear platform simulation based on the non-ideal peeling-ballooning mode model successfully explained the ELM experimental results. Therefore, exploring the influences of various non-ideal effects on the ballooning mode in the edge transport barrier is very important in controlling the ELM in the future fusion reactors. Among the reports on non-ideal effects, there are few reports involving the effect of hyper-resistivity caused by anomalous electron viscosity on ballooning mode. It has been found that the hyper-resistivity has a destabilizing effect on the ballooning mode, but the associated physical mechanism is still unclear. Therefore, it is necessary to systematically explore the influence of hyper-resistivity on the ballooning mode theoretically by introducing hyper-resistivity into the ballooning mode model. The linear growth rate of ideal and non-ideal ballooning mode are solved by the shooting method for the derived eigenvalue equation of non-ideal ballooning mode containing hyper-resistivity, finite resistivity and diamagnetic drift effects, and the dependence of ballooning mode on hyper-resistivity is also explored under different conditions. The results show that the hyper-resistivity may destabilize the ballooning mode, and the physical mechanism is that the current diffusion effect caused by the hyper-resistivity weakens the stabilizing effect of the magnetic field line bending on the ballooning mode. When both the resistivity and hyper-resistivity are considered, they are in a competitive relationship. When the ratio of hyper-resistivity to resistivity is relatively high, hyper-resistivity plays a dominant role, and the destabilizing effect of resistivity will be shielded by hyper-resistivity, and vice versa. The destabilization effect of hyper-resistivity on ballooning modes is enhanced with the increase of the toroidal mode number. The hyper-resistivity will destabilize the original stable modes once the toroidal mode number exceeds a certain threshold. Further studies show that the threshold is inversely proportional to the ratio of hyper-resistivity to resistivity. The research results have important reference value for the control of edge localized modes in low-collisionality edge plasma in future fusion reactors.

The role of electron inertia on jeans instability of radiative quantum plasma with the impact of rotation and resistivity

With the use of the Quantum Magnetohydrodynamic (QMHD) model, we took into account the Jeans instability of rotating magnetized radiative quantum plasma under the impact of finite electron inertia and resistivity. The issue is set up and using the linearization method and normal mode technique, we can get the general dispersion relation, which is then described in terms of various modes of propagation. Within the prescribed boundaries, we also get the Jeans instability criteria. Plotting the curves between the system's growth rate and wave number for the investigation of the stability analysis of the system, which is then thoroughly explained.

Online Control Strategy for Tolerating Resistance Asymmetry With Minimum Copper Loss in the Full Torque Range for Symmetrical Six-Phase AC Drives

Multiphase drives exhibit remarkable advantages (e.g., fault tolerance) over three-phase ones. Six-phase drives are particularly attractive, given their moderate complexity and suitability for off-the-shelf three-phase converters. Regarding the stator winding arrangement, the symmetrical one offers superior postfault capabilities in most scenarios. On the other hand, resistance asymmetry in the stator phases or connections may arise due to different causes. The conventional full-range minimum-loss strategy (FRMLS) generates stator-current references under open-phase (infinite resistance) faults so that torque ripple is prevented while minimizing the losses for each torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{d}$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{q}$</tex-math></inline-formula> current) value and maximizing the torque range; however, this method is unsuitable for unequal resistances of finite value. This article proposes an FRMLS for setting the current references to reach these goals in symmetrical six-phase drives with any resistance asymmetry. The optimum references are found online depending on the resistances, without lookup tables. The phase currents are individually limited by an iterative algorithm, so that minimum stator copper loss (SCL) is achieved over the maximum admissible torque range. In this manner, unlike the conventional FRMLS, minimum SCL and maximum torque range are attained even for finite resistance imbalance. The currents in phases affected by high resistances are suitably reduced. Experimental results are provided.

A rigorous surface renewal model for transient gas absorption with first-order chemical reaction in a stirred liquid

This work presents a rigorous surface renewal model for unsteady-state gas absorption in a stirred batch cell in which the dissolved gas undergoes a first-order chemical reaction with a liquid-phase reagent for the cases of zero and finite gas-phase mass-transfer resistance, with the concentration of dissolved gas in the bulk liquid being a function of time. For oxygen absorption in water containing a reagent (e.g., sodium sulfite), the model predicts that the rates of absorption and dissolved-gas transfer to the bulk liquid have an inverse behavior during the initial moments of absorption after which they level out as steady state is approached, with the former being higher than the latter due to the consumption of dissolved gas by the reaction occurring in the surface elements. In general, predictions of the dissolved oxygen concentration made with the rigorous model compare quite well with those of a much simpler pseudo steady-state model. However, the rigorous surface renewal model gives a finer grained picture of the phenomenon of absorption, i.e., of the rates of absorption and dissolved-gas transfer, especially during the initial moments of absorption. A hybrid model, which uses both the pseudo steady-state and rigorous surface renewal models, is proposed for performing unsteady-state gas absorption calculations.

Viscous flow through a finite-width slit: Boundary conditions and dissipation

We study the hydrodynamic viscous electronic transport in a two-dimensional sample separated into two semi-infinite planes by a one-dimensional infinite barrier. The semi-infinite planes are electrically connected via the finite-size slit in the barrier. We calculate the current through the slit assuming finite voltage drop between the planes and neglecting disorder-induced Ohmic resistance, so dissipation and resistance are purely viscosity induced. We find that the only solution to the Stokes equation in this geometry, which yields a finite dissipation at finite resistance (and, hence, is not self-contradictory), is the one that fulfills both the no-stress and no-slip boundary conditions simultaneously. As a remarkable consequence, the obtained velocity profile satisfies the so-called partial-slip (Maxwell) boundary condition for any value of the slip length, which drops out from all final results. We also calculate the electronic temperature profile for the small and large heat conductivity and find asymmetric (with respect to the barrier) temperature patterns in the former case.

CAPACITIVE INFLUENCE OF HIGH VOLTAGE OVERHEAD TRANSMISSION LINES ON THE MEASUREMENT OF SOIL RESISTIVITY

In this article, an analysis is presented of the impact of high voltage overhead transmission lines on the measurement of soil resistivity. Through analysis, the measurement noise level due to the vicinity of the phase conductors of a high voltage overhead transmission line is determined. The soil is modeled as an anisotropic homogeneous half-space of finite resistivity. In order for the article to be of practical use to engineers, simple mathematical instrumentation has been used. Detailed expressions and the physically objective hypotheses under which the cited model is valid have been derived. For the simplicity and generality of the presentation, analysis was performed using a practical example of the measurement of soil resistivity by the Wenner method. The example refers to a single system high voltage transmission line with a steel tower. The results obtained by the theory presented are compared to the results obtained with the software package CDEGS (Current Distribution, Electromagnetic Fields, Grounding and Soil Structure Analysis). The results obtained are presented analytically, graphically and are discussed.

Non-ideal instabilities in sinusoidal shear flows with a streamwise magnetic field

We investigate the linear stability of a sinusoidal shear flow with an initially uniform streamwise magnetic field in the framework of incompressible magnetohydrodynamics (MHD) with finite resistivity and viscosity. This flow is known to be unstable to the Kelvin–Helmholtz instability in the hydrodynamic case. The same is true in ideal MHD, where dissipation is neglected, provided the magnetic field strength does not exceed a critical threshold beyond which magnetic tension stabilizes the flow. Here, we demonstrate that including viscosity and resistivity introduces two new modes of instability. One of these modes, which we refer to as an Alfvénic Dubrulle–Frisch instability, exists for any non-zero magnetic field strength as long as the magnetic Prandtl number ${{{Pm}}} &lt; 1$ . We present a reduced model for this instability that reveals its excitation mechanism to be the negative eddy viscosity of periodic shear flows described by Dubrulle &amp; Frisch (Phys. Rev. A, vol. 43, 1991, pp. 5355–5364). Finally, we demonstrate numerically that this mode saturates in a quasi-stationary state dominated by counter-propagating solitons.

An intuitive form of the energy functional for resistive plasma perturbations

The energy functional of ideal magnetohydrodynamics (MHD) is extended to the regime of finite resistivity and transformed into an intuitive form, which separates pressure-gradient, current-density drive and stabilising phenomena, analogously to the ideal version of the functional derived by Greene and Johnson (Plasma Phys., vol. 10, issue 8, 1968, pp. 729–745). The resulting resistive energy functional is not in the form of a solvable eigenvalue problem but is intended to analyse the energetic composition of eigenfunctions which were calculated in advance by solving the MHD equations. The new resistive energy functional provides information on the different energetic drives and stabilising phenomena of an eigenfunction. The new energy functional has been implemented in the CASTOR3D code in general 3D curvilinear coordinates and successfully validated across three different coordinate systems for a numerical test case.

Fill Factor Losses and Deviations from the Superposition Principle in Lead Halide Perovskite Solar Cells

The enhancement of the fill factor in the current generation of perovskite solar cells is the key for further efficiency improvement. Thus, methods to quantify the fill factor losses are urgently needed. Two methods are presented to quantify losses due to the finite resistance of the semiconducting layers of the solar cell as well as its contacts. The first method is based on the comparison between the voltage in the dark and under illumination analyzed at equal recombination current density and results in a voltage‐dependent series resistance. Furthermore, the method reveals the existence of a strong photoshunt under illumination. The second method is based on measuring the photoluminescence of perovskite solar cells as a function of applied voltage. Thereby, the recombination current is determined as a function of voltage from short circuit to open circuit, and the presence of the photoshunt is explained with a high resistance of the electron and/or hole transport layers combined with field screening in the absorber.

Reliability analysis-based investigation of the historical Széchenyi Chain Bridge deck system

Before the recent reconstruction, significant corrosion damages were observed on the deck system of the ∼170-year-old Széchenyi Chain Bridge. Therefore, an advanced reliability analysis-based study is executed to assess the risk of failure of the structure in its situation until the refurbishment starts. The current paper has the aim to introduce the applied assessment method for the risk analysis and damage grade determination of the historical structure. The novel method combines the following techniques: (i) input data coming from on-site measurements implemented into state-of-the-art corrosion models, (ii) advanced finite element model-based resistance calculation (GMNI analysis) implemented into (iii) Monte Carlo simulation-based stochastic reliability assessment method to determine the risk of the bridge deck system failure. It is concluded that the introduced method is a powerful tool for risk assessment of existing aging structures.

Electromagnetic, Gravitational, and Plasma-Related Perturbations of Locally Rotationally Symmetric Class II Spacetimes

We investigate electromagnetic, gravitational, and plasma-related perturbations to the first order on homogeneous and hypersurface orthogonal locally rotationally symmetric (LRS) class II spacetimes. Due to the anisotropic nature of the studied backgrounds, we are able to include a non-zero magnetic field to the zeroth order. As a result of this inclusion, we find interesting interactions between the electromagnetic and gravitational variables already of the first order in the perturbations. The equations governing these perturbations are found by using the Ricci identities, the Bianchi identities, Einstein’s field equations, Maxwell’s equations, particle conservation, and a form of energy-momentum conservation for the plasma components. Using a 1+1+2 covariant split of spacetime, the studied quantities and equations are decomposed with respect to the preferred directions on the background spacetimes. After linearizing the decomposed equations around an LRS background, performing a harmonic decomposition, and imposing the cold magnetohydrodynamic (MHD) limit with a finite electrical resistivity, the system is then reduced to a set of ordinary differential equations in time and some constraints. On solving for some of the harmonic coefficients in terms of the others, the system is found to decouple into two closed and independent subsectors. Through numerical calculations, we then observe some mechanisms for generating magnetic field perturbations, showing some traits similar to previous works using Friedmann–Lemaître–Robertson–Walker (FLRW) backgrounds. Furthermore, beat-like patterns are observed in the short wave length limit due to interference between gravitational waves and plasmonic modes.

Wave reflections in counter-current separation processes with unequal mass transfer coefficients

In this paper, the influence of finite mass transfer resistance on the steady state and dynamic behavior of spatially distributed counter-current separation processes is analyzed. Special attention is given to the pinch states, at which thermodynamic equilibrium between the phases prevails. In a classical paper, Sundaresan et al. (1987) have shown that these pinch states may depend on the mass transfer coefficients. It is shown that this apparent contradiction can be explained by means of wave reflections at the system boundaries, which are reported here to the best of our knowledge for the first time. As an application example, a counter-current adsorption process as introduced in the above reference is considered, and it is shown how these wave solutions can be constructed in the concentration phase space by using the characteristic curves of equilibrium theory in combination with the wave trajectories generated with a non-equilibrium model.

Instabilities in a current sheet with plasma jet

We study the stability problem of a magnetohydrodynamic current sheet with the presence of a plasma jet. The flow direction is perpendicular to the normal of the current sheet and we analyse two cases: (1) the flow is along the antiparallel component of the magnetic field; (2) the flow is perpendicular to the antiparallel component of the magnetic field. A generalized equation set with the condition of incompressibility is derived and solved as a boundary value problem. For the first case we show that the streaming kink mode is stabilized by the magnetic field at $V_0/B_0 \lesssim 2$ , where $V_0$ and $B_0$ are the jet speed and upstream Alfvén speed, and it is not affected by resistivity significantly. The streaming sausage mode is stabilized at $V_0/B_0 \lesssim 1$ , and it can transit to the streaming tearing mode with a finite resistivity. The streaming tearing mode has larger growth rate than the pure tearing mode, though the scaling relation between the maximum growth rate and the Lundquist number remains unchanged. When the jet is perpendicular to the antiparallel component of the magnetic field, the most unstable sausage mode is usually perpendicular (wavevector along the jet) without a guide field. But with a finite guide field, the most unstable sausage mode can be oblique, depending on the jet speed and guide field strength.

Effective Time Constants at 4.2 to 70 K inReBCO Pancake Coils With Different Inter-Turn Resistances

For future <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Re</i> BCO tape based accelerator magnets it is proposed to use no- or partial inter-turn insulation to deal with quench detection and protection. In a non-insulated coil the turns are separated by a finite electrical resistance, providing a bypass for the current at hot-spots, improving thermal stability and quench detection time. However, such coils show different dynamic electromagnetic behavior compared to insulated coils under normal charging and transient quench conditions. To study such coils in detail two pancake coils, one dry-wound and one with solder in between turns, are prepared and tested in a variable temperature cryostat between 4.2 and 70 K. Properties of the coils that are studied are charge and discharge time behavior, turn-to-turn resistance, response to current stepping, and operational stability. In this paper, the first results are presented and compared to a simplified network model in order to gain further understanding into the underlying physics.

Observations of Current Sheet Heating in X-Ray during a Solar Flare

In the solar corona, magnetic reconnection occurs due to the finite resistivity of the plasma. At the same time, this resistivity leads to ohmic heating. Therefore, the reconnecting current sheet should heat the surrounding plasma. This paper presents experimental evidence of such plasma heating being caused by magnetic reconnection. We observed the effect during a C1.4 solar flare on 2003 February 16 at the active region NOAA 10278, near the solar limb. Thanks to such a location, we successfully identified all the principal elements of the flare: the flare arcade, the flux rope, and, most importantly, the presumed position of the current sheet. By analyzing the monochromatic X-ray images of the Sun obtained by the CORONAS-F/SPIRIT instrument in the Mg xii 8.42 Å spectral line, we detected a high-temperature (T ≥ 4 MK) emission at the predicted location of the current sheet. The high-temperature emission appeared during the CME’s impulsive acceleration phase. We believe that this additionally confirms that the plasma heating around the current sheet and the magnetic reconnection inside the current sheet are strongly connected.

Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect.

The prospect of controlling the electronic properties of materials via the vacuum fields of cavity electromagnetic resonators is emerging as one of the frontiers of condensed matter physics. We found that the enhancement of vacuum field fluctuations in subwavelength split-ring resonators strongly affects one of the most paradigmatic quantum protectorates, the quantum Hall electron transport in high-mobility two-dimensional electron gases. The observed breakdown of the topological protection of the integer quantum Hall effect is interpreted in terms of a long-range cavity-mediated electron hopping where the anti-resonant terms of the light-matter coupling Hamiltonian develop into a finite resistivity induced by the vacuum fluctuations. Our experimental platform can be used for any two-dimensional material and provides a route to manipulate electron phases in matter by means of vacuum-field engineering.

Nonlinear magnetoresistivity in two-dimensional systems induced by Berry curvature

The band geometric properties of quantum materials play an elemental role in the linear and nonlinear transport of electrons. In this paper, we propose that the interplay of the Berry curvature, the orbital magnetic moment and the Lorentz force can induce a finite nonlinear resistivity in two dimensional systems in presence of a perpendicular magnetic field. The induced nonlinear magnetoresistivity scales linearly with the magnetic field and is purely quantum mechanical in origin. This novel transport signature can be used as an additional experimental probe for the geometric quantities in intrinsically time reversal symmetric systems.

L-Glutamic acid (i.e. L-amino acid) based molecular junction as rectifiers

Dissimilar metal electrodes in molecular junction play significant role in exploring the intriguing properties of biomolecules. One such property is rectification ratio, which ensures the candidature of different biomolecules as nanoelectronics devices. Protein based nanoelectronics devices are gaining enduring attention among researchers working in the field of bio nanotechnology. The alluring properties of proteins can be predicted if the subunit i.e. amino acids be explored individually. With the aim of exploring amino acid based nanoelectronics devices, we consider the negatively charged amino acid (i.e., L-Glutamic acid, (C5H9NO4)) with dissimilar metal electrodes on either side, forming Au-Glutamic-Ag, Au-Glutamic-Cu and Ag-Glutamic-Cu molecular junctions. The first-principle calculations are performed using Density functional theory in local density approximations (DFT-LDA). The molecule with dissimilar electrodes offers dissimilar rectification ratio and finite negative differential resistance. The Au-Glutamic-Cu molecular device exhibits highest while Ag-Glutamic-Cu exhibits the lowest zero bias conductance values. Higher rectification ratio and lower Homo-Lumo gap is observed with Au-Glutamic-Cu and Au-Glutamic-Ag molecular devices. Such investigation highlights the prospect of L-Glutamic acid like biomolecules for future nanoelectronic devices.

Constructal design of a circular micro-channel Stirling regenerator based on exergy destruction minimization

Regenerator is a key component in Stirling engines, and its characteristics have a significant influence on engine performance. Herein, subjected to the global constraints of the fixed total volume and porosity, constructal design of a circular micro-channel regenerator was conducted to achieve its optimal structures. The total exergy destruction rate in the irreversible regenerative process, which includes three types of individual exergy destruction contributions caused by the heat transfer with a finite temperature difference, flow resistance, and axial heat conduction of the solid matrix, was adopted as the optimization objective. The optimal channel diameter was obtained, and the effects of the regenerator inner radius, total volume of regenerators, regenerator porosity, engine speed, piston phase angle, hot part temperature, charge pressure, and thermal conductivity ratio due to the segmentation of regenerators on the optimization results were analyzed. The results show that the total exergy destruction rate offers a minimum at a relatively low channel diameter of around 0.5 mm under the given parameter values. All the parameters studied have an obvious effect on the minimum total exergy destruction rate, and the regenerator inner radius, total volume and porosity of regenerators, and engine speed also have an evident influence on the optimal structure of the regenerator. These indicate that the regenerator performance can be further improved by selecting appropriate global geometric parameter values of regenerators and operating parameter values of engines. The findings of this study can provide some guidelines for the optimal design of micro-channel regenerators and the performance improvement of Stirling engines.