Possible Routes to Obtain Enhanced Magnetoresistance in a Driven Quantum Heterostructure with a Quasi-Periodic Spacer

In this work, we perform a numerical study of magnetoresistance in a one-dimensional quantum heterostructure, where the change in electrical resistance is measured between parallel and antiparallel configurations of magnetic layers. This layered structure also incorporates a non-magnetic spacer, subjected to quasi-periodic potentials, which is centrally clamped between two ferromagnetic layers. The efficiency of the magnetoresistance is further tuned by injecting unpolarized light on top of the two sided magnetic layers. Modulating the characteristic properties of different layers, the value of magnetoresistance can be enhanced significantly. The site energies of the spacer is modified through the well-known Aubry–André and Harper (AAH) potential, and the hopping parameter of magnetic layers is renormalized due to light irradiation. We describe the Hamiltonian of the layered structure within a tight-binding (TB) framework and investigate the transport properties through this nanojunction following Green’s function formalism. The Floquet–Bloch (FB) anstaz within the minimal coupling scheme is introduced to incorporate the effect of light irradiation in TB Hamiltonian. Several interesting features of magnetotransport properties are represented considering the interplay between cosine modulated site energies of the central region and the hopping integral of the magnetic regions that are subjected to light irradiation. Finally, the effect of temperature on magnetoresistance is also investigated to make the model more realistic and suitable for device designing. Our analysis is purely a numerical one, and it leads to some fundamental prescriptions of obtaining enhanced magnetoresistance in multilayered systems.

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NUMERICAL STUDY ON LIQUEFACTION USING DISCRETE ELEMENT METHOD WITH MICROSCOPIC FLUID COUPLING SCHEME

Doboku Gakkai Ronbunshuu C ◽

10.2208/jscejc.66.800 ◽

2010 ◽

Vol 66 (4) ◽

pp. 800-813

Author(s):

Yoshiyuki SHIMIZU ◽

Yusen INAGAWA

Keyword(s):

Discrete Element Method ◽

Numerical Study ◽

Discrete Element ◽

Coupling Scheme ◽

Fluid Coupling ◽

Element Method

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Cardiac Spiral Wave Drifting Due to Spatial Temperature Gradients – a Numerical Study

10.1101/362913 ◽

2018 ◽

Cited By ~ 1

Author(s):

Guy Malki ◽

Sharon Zlochiver

Keyword(s):

Numerical Simulations ◽

Single Cell ◽

Numerical Study ◽

Spiral Wave ◽

Spiral Waves ◽

Temperature Gradients ◽

Effect Of Temperature ◽

Local Perturbation ◽

Marginal Effect ◽

Spatial Temperature

ABSTRACTCardiac rotors are believed to be a major driver source of persistent atrial fibrillation (AF), and their spatiotemporal characterization is essential for successful ablation procedures. However, electrograms guided ablation have not been proven to have benefit over empirical ablation thus far, and there is a strong need of improving the localization of cardiac arrhythmogenic targets for ablation. A new approach for characterize rotors is proposed that is based on induced spatial temperature gradients (STGs), and investigated by theoretical study using numerical simulations. We hypothesize that such gradients will cause rotor drifting due to induced spatial heterogeneity in excitability, so that rotors could be driven towards the ablating probe. Numerical simulations were conducted in single cell and 2D atrial models using AF remodeled kinetics. STGs were applied either linearly on the entire tissue or as a small local perturbation, and the major ion channel rate constants were adjusted following Arrhenius equation. In the AF-remodeled single cell, recovery time increased exponentially with decreasing temperatures, despite the marginal effect of temperature on the action potential duration. In 2D models, spiral waves drifted with drifting velocity components affected by both temperature gradient direction and the spiral wave rotation direction. Overall, spiral waves drifted towards the colder tissue region associated with global minimum of excitability. A local perturbation with a temperature of T=28°C was found optimal for spiral wave attraction for the studied conditions. This work provides a preliminary proof-of-concept for a potential prospective technique for rotor attraction. We envision that the insights from this study will be utilize in the future in the design of a new methodology for AF characterization and termination during ablation procedures.

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Numerical study on the fluid flow pass a square cylinder: The temperature-viscosity dependence

International Journal of Modern Physics C ◽

10.1142/s0129183113501015 ◽

2014 ◽

Vol 25 (03) ◽

pp. 1350101

Author(s):

Jianhua Lu ◽

Sheng Li ◽

Zhaoli Guo ◽

Baochang Shi

Keyword(s):

Fluid Flow ◽

Free Stream ◽

Numerical Study ◽

Effect Of Temperature ◽

Square Cylinder ◽

Efficient Tool ◽

Multiple Relaxation Time ◽

Upward Velocity ◽

Drag And Lift ◽

Viscosity Dependence

In this paper, the 2D fluid flow pass a heated/cooled square cylinder exposed to a constant free-stream upward velocity is simulated via a multiple relaxation time (MRT) lattice-Boltzmann (LB) method. The buoyancy effect on the drag and lift coefficients as well as Nusselt number related is compared with the results in the existing literatures to validate the code used. The effect of temperature-viscosity dependence is then investigated to test whether the effect can be neglected or not for the mixed convection case. It is shown that the effect cannot be ignored when |Ri| > 0.15. Fortunately, the effect can be captured by using an effective temperature formula [J. M. Shi, D. Ferlach, M. Breuer, G. Biswas and F. Durst, Phys. Fluids16, 4331 (2004)] in a rather large range of Ri. All the numerical results, from another angle, also demonstrate that the MRT method is an efficient tool in simulating the problems such as the present one.

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Experimental and numerical study of chip formation during straight turning of hardened AISI 4340 steel

Proceedings of the Institution of Mechanical Engineers Part B Journal of Engineering Manufacture ◽

10.1243/095440505x32445 ◽

2005 ◽

Vol 219 (7) ◽

pp. 515-524 ◽

Cited By ~ 41

Author(s):

S Belhadi ◽

T Mabrouki ◽

J-F Rigal ◽

L Boulanouar

Keyword(s):

Chip Formation ◽

Numerical Study ◽

Chip Morphology ◽

Effect Of Temperature ◽

Serrated Chip ◽

Aisi 4340 Steel ◽

4340 Steel ◽

Sawtooth Chip ◽

Coated Carbide ◽

Aisi 4340

The present paper is a contribution to the investigation of physical phenomena accompanying sawtooth chip formation in the case of hard turning. The study concerns the machining with coated carbide of tempered AISI 4340 steel with a Rockwell C hardness of 47 HRC. The main idea in this paper deals with the establishment of a direct relationship between serrated-chip morphology simultaneously with force component signals derived from acquisition at high frequency and with the width of facets detected on a workpiece machined surface. This experimental work was supported by a numerical simulation based on Abaqus/ Explicit software. Numerical results dealing with effect of temperature evolution on the chip morphology show that the beginning of the sawtooth chip initiation is due to an adiabatic shear at the tool tip with propagation pathway towards the free surface. In addition, computed results have a good corroboration with those obtained experimentally.

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Synthesis of High Purity Layered Structure Sn3O4 and Its Photocatalytic Performance for Hydrogen Evolution Reaction Under Visible-Light Irradiation

ECS Meeting Abstracts ◽

10.1149/ma2016-01/41/2091 ◽

2016 ◽

Keyword(s):

Visible Light ◽

Hydrogen Evolution ◽

Hydrogen Evolution Reaction ◽

Visible Light Irradiation ◽

Layered Structure ◽

High Purity ◽

Photocatalytic Performance ◽

Light Irradiation

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Numerical Study of Stability and Accuracy of the Immersed Boundary Method Coupled to the Lattice Boltzmann BGK Model

Communications in Computational Physics ◽

10.4208/cicp.260313.291113a ◽

2014 ◽

Vol 16 (1) ◽

pp. 136-168 ◽

Cited By ~ 18

Author(s):

Yongguang Cheng ◽

Luoding Zhu ◽

Chunze Zhang

Keyword(s):

Lattice Boltzmann ◽

Numerical Study ◽

Rigid Wall ◽

Segment Length ◽

Immersed Boundary ◽

Coupling Scheme ◽

Circular Membrane ◽

Shearing Flow ◽

Dirac Delta ◽

Forcing Term

AbstractThis paper aims to study the numerical features of a coupling scheme between the immersed boundary (IB) method and the lattice Boltzmann BGK (LBGK) model by four typical test problems: the relaxation of a circular membrane, the shearing flow induced by a moving fiber in the middle of a channel, the shearing flow near a non-slip rigid wall, and the circular Couette flow between two inversely rotating cylinders. The accuracy and robustness of the IB-LBGK coupling scheme, the performances of different discrete Dirac delta functions, the effect of iteration on the coupling scheme, the importance of the external forcing term treatment, the sensitivity of the coupling scheme to flow and boundary parameters, the velocity slip near non-slip rigid wall, and the origination of numerical instabilities are investigated in detail via the four test cases. It is found that the iteration in the coupling cycle can effectively improve stability, the introduction of a second-order forcing term in LBGK model is crucial, the discrete fiber segment length and the orientation of the fiber boundary obviously affect accuracy and stability, and the emergence of both temporal and spatial fluctuations of boundary parameters seems to be the indication of numerical instability. These elaborate results shed light on the nature of the coupling scheme and may benefit those who wish to use or improve the method.

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Giant Magnetoresistance Induced by Ultrathin Magnetic Layers

MRS Proceedings ◽

10.1557/proc-475-99 ◽

1997 ◽

Vol 475 ◽

Author(s):

G.J. Strijkers ◽

H.J.M. Swagten ◽

A.H.M. Mettler ◽

M.M.H. Willekens ◽

W.J.M. De Jonge

Keyword(s):

Giant Magnetoresistance ◽

Spin Valve ◽

Short Length ◽

Spin Valves ◽

Length Scale ◽

Magnetic Layers ◽

Ferromagnetic Layers ◽

Experimental Tool ◽

Spin Dependent Scattering

ABSTRACTWe introduce an interface selective structure, composed of a spin-valve on top of which a thick nonmagnetic back layer is deposited as a straightforward experimental tool to measure the GMR induced by ultrathin magnetic layers. The interface selectivity of spin-dependent scattering is evidenced by calculations and illustrated in both Co/Cu/Co and Ni80Fe20/Cu/Ni80Fe20 spin-valves by an almost discontinuous behavior in the GMR ratio. The temperture dependence of the extremely short length scale associated with this discontinuity is discussed in relation to the structure of ultrathin ferromagnetic layers.

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Thermo-optics of Luminescent Solar Concentrators

MRS Proceedings ◽

10.1557/opl.2012.1062 ◽

2012 ◽

Vol 1447 ◽

Author(s):

Ahmadreza Hajiaboli ◽

Mark P. Andrews

Keyword(s):

Numerical Study ◽

Detailed Balance ◽

Effect Of Temperature ◽

Device Performance ◽

Solar Concentrators ◽

Polymer Waveguide ◽

Luminescent Solar Concentrators ◽

Luminescent Solar Concentrator ◽

Ray Tracing Simulation ◽

Balance Treatment

ABSTRACTWe present a numerical study on effect of temperature on the performance of a waveguide luminescent solar concentrator (LSC). The purpose is to determine how changes in temperature of the ambient environment of an LSC affect device performance. The thermo-optical coefficient of the polymer waveguide is modeled using the well known Prod’homme formulation and applied in a forward Monte Carlo ray-tracing simulation. We show that the number of collected photons decreases almost linearly as the ambient temperature increases from -50 ºC to +50ºC. This behavior is associated with several competing loss mechanisms in the waveguide. For example, increases in optical confinement due to increased refractive index at low temperature are opposed by increases in cone loss (escape loss) of photons. Other competing mechanisms that exhibit temperature dependence are explained in terms of a detailed balance treatment of the LSC as a function of temperature.

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