THERMOELECTRIC POWER COEFFICIENT IN A QUANTUM WELL

2002 ◽  
Vol 09 (05n06) ◽  
pp. 1765-1768 ◽  
Author(s):  
B. A. PAEZ ◽  
H. MÉNDEZ ◽  
J. C. GIRALDO
Keyword(s):  
Boltzmann Equation ◽  
Quantum Well ◽  
Variational Methods ◽  
Thermoelectric Power ◽  
Computer Code ◽  
Power Coefficient ◽  
Dimensional System ◽  
Scattering Mechanism ◽  
Transport Approximation ◽  
Low Dimensional

Based on the solution of the quantum Boltzmann equation, in the linear transport approximation for an isotropic low-dimensional system, the thermoelectric power coefficient, Q, in a quantum well structure was determined. These calculations are based on variational methods, taking into account especial functions which include important parameters being varied at the time of evaluating the thermoelectric power, e.g. height and width barrier. Values of Q are carried out by using a computer code written in Mathematica, which allows one to depict them easily and in this way to compare different behaviors of Q against temperature according to the scattering mechanism (phonons).

Thermoelectric Power in Quantum Confined Bismuth Under Classically Large Magnetic Field

1990 ◽  
Vol 216 ◽  
Author(s):  
Kamakhya P. Ghatak ◽  
S. N. Biswas
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Quantum Well ◽  
Film Thickness ◽  
Quantum Wells ◽  
Thermoelectric Power ◽  
Large Magnetic Field ◽  
Quantum Well Wires ◽  
Electron Dispersion ◽  
Theoretical Results

ABSTRACTIn this paper we studied the thermoelectric power under classically large magnetic field (TPM) in quantum wells (QWs), quantum well wires (QWWS) and quantum dots (QDs) of Bi by formulating the respective electron dispersion laws. The TPM increases with increasing film thickness in an oscillatory manner in all the cases. The TPM in QD is greatest and the least for quantum wells respectively. The theoretical results are in agreement with the experimental observations as reported elsewhere.

scholarly journals Evidence accumulation and change rate inference in dynamic environments

2016 ◽  
Author(s):  
Adrian E Radillo ◽  
Alan Veliz-Cuba ◽  
Kresimir Josic ◽  
Zachary Kilpatrick
Keyword(s):  
Rate Of Change ◽  
Ideal Observer ◽  
Moment Closure ◽  
Dimensional System ◽  
Change Rate ◽  
Observer Model ◽  
Low Dimensional ◽  
State Of The Environment ◽  
Rate Correlation ◽  
Moment Closure Approximation

In a constantly changing world, animals must account for environmental volatility when making decisions. To appropriately discount older, irrelevant information, they need to learn the rate at which the environment changes. We develop an ideal observer model capable of inferring the present state of the environment along with its rate of change. Key to this computation is updating the posterior probability of all possible changepoint counts. This computation can be challenging, as the number of possibilities grows rapidly with time. However, we show how the computations can be simplified in the continuum limit by a moment closure approximation. The resulting low-dimensional system can be used to infer the environmental state and change rate with accuracy comparable to the ideal observer. The approximate computations can be performed by a neural network model via a rate-correlation based plasticity rule. We thus show how optimal observers accumulates evidence in changing environments, and map this computation to reduced models which perform inference using plausible neural mechanisms.

Non-Standard Reduction of Noisy Structural Systems: Shallow Arches

2000 ◽  
Author(s):  
Lalit Vedula ◽  
N. Sri Namachchivaya
Keyword(s):  
Markov Process ◽  
Random Perturbation ◽  
Exit Time ◽  
Stochastic Averaging ◽  
Dimensional System ◽  
Shallow Arches ◽  
Higher Dimensional ◽  
Mean Exit Time ◽  
Stationary Probability Density Function ◽  
Low Dimensional

Abstract The dynamics of a shallow arch subjected to small random external and parametric excitation is invegistated in this work. We develop rigorous methods to replace, in some limiting regime, the original higher dimensional system of equations by a simpler, constructive and rational approximation – a low-dimensional model of the dynamical system. To this end, we study the equations as a random perturbation of a two-dimensional Hamiltonian system. We achieve the model-reduction through stochastic averaging and the reduced Markov process takes its values on a graph with certain glueing conditions at the vertex of the graph. Examination of the reduced Markov process on the graph yields many important results such as mean exit time, stationary probability density function.

scholarly journals Observable for a Large System of Globally Coupled Excitable Units

2019 ◽  
Vol 24 (2) ◽  
pp. 37 ◽  
Author(s):  
Santiago Boari ◽  
Gonzalo Uribarri ◽  
Ana Amador ◽  
Gabriel Mindlin
Keyword(s):  
Order Parameter ◽  
Field Potential ◽  
Dimensional System ◽  
System Of Equations ◽  
In Vivo Electrophysiology ◽  
Excitable Systems ◽  
Global Variable ◽  
Good Proxy ◽  
Low Dimensional

The study of large arrays of coupled excitable systems has largely benefited from a technique proposed by Ott and Antonsen, which results in a low dimensional system of equations for the system’s order parameter. In this work, we show how to explicitly introduce a variable describing the global synaptic activation of the network into these family of models. This global variable is built by adding realistic synaptic time traces. We propose that this variable can, under certain conditions, be a good proxy for the local field potential of the network. We report experimental, in vivo, electrophysiology data supporting this claim.

scholarly journals Thermoelectric Properties of InA Nanowires from Full-Band Atomistic Simulations

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5350
Author(s):  
Damiano Archetti ◽  
Neophytos Neophytou
Keyword(s):  
Surface Roughness ◽  
Thermoelectric Power ◽  
Power Factor ◽  
Large Scale ◽  
Large Diameter ◽  
Computational Method ◽  
Thermoelectric Power Factor ◽  
Full Band ◽  
Low Dimensional ◽  
Power Factor Improvement

In this work we theoretically explore the effect of dimensionality on the thermoelectric power factor of indium arsenide (InA) nanowires by coupling atomistic tight-binding calculations to the Linearized Boltzmann transport formalism. We consider nanowires with diameters from 40 nm (bulk-like) down to 3 nm close to one-dimensional (1D), which allows for the proper exploration of the power factor within a unified large-scale atomistic description across a large diameter range. We find that as the diameter of the nanowires is reduced below d < 10 nm, the Seebeck coefficient increases substantially, as a consequence of strong subband quantization. Under phonon-limited scattering conditions, a considerable improvement of ~6× in the power factor is observed around d = 10 nm. The introduction of surface roughness scattering in the calculation reduces this power factor improvement to ~2×. As the diameter is decreased to d = 3 nm, the power factor is diminished. Our results show that, although low effective mass materials such as InAs can reach low-dimensional behavior at larger diameters and demonstrate significant thermoelectric power factor improvements, surface roughness is also stronger at larger diameters, which takes most of the anticipated power factor advantages away. However, the power factor improvement that can be observed around d = 10 nm could prove to be beneficial as both the Lorenz number and the phonon thermal conductivity are reduced at that diameter. Thus, this work, by using large-scale full-band simulations that span the corresponding length scales, clarifies properly the reasons behind power factor improvements (or degradations) in low-dimensional materials. The elaborate computational method presented can serve as a platform to develop similar schemes for two-dimensional (2D) and three-dimensional (3D) material electronic structures.

Hopf Bifurcation Analysis and Stability for a Ratio-Dependent Predator–Prey Diffusive System with Time Delay

2020 ◽  
Vol 30 (03) ◽  
pp. 2050037
Author(s):  
Longyue Li ◽  
Yingying Mei ◽  
Jianzhi Cao
Keyword(s):  
Hopf Bifurcation ◽  
Time Delay ◽  
Periodic Solutions ◽  
Positive Equilibrium ◽  
Dimensional System ◽  
Normal Form Theory ◽  
Center Manifold Reduction ◽  
Predator Prey ◽  
Ratio Dependent ◽  
Low Dimensional

In this paper, we are focused on a new ratio-dependent predator–prey system that introduced the diffusive and time delay effect simultaneously. By analyzing the characteristic equations and the distribution of eigenvalues, we examine the stability and boundary of positive equilibrium states, and the existence of spatially homogeneous and spatially inhomogeneous bifurcating periodic solutions, respectively. Further, we prove that when [Formula: see text], the system has Hopf bifurcation at the positive equilibrium state. By using the center manifold reduction, we simplify the system so that we can convert an infinite-dimensional system into a low-dimensional finite-dimensional system. By using the normal form theory, we obtain explicit expressions for the direction, stability and period of Hopf bifurcation periodic solutions. Finally, we have illustrated the main results in this thesis by numerical examples, our work may provide some useful measures to save time or cost and to control the ecosystem.

Synthetic Control over Quantum Well Width Distribution and Carrier Migration in Low-Dimensional Perovskite Photovoltaics

2018 ◽  
Vol 140 (8) ◽  
pp. 2890-2896 ◽  
Author(s):  
Andrew H. Proppe ◽  
Rafael Quintero-Bermudez ◽  
Hairen Tan ◽  
Oleksandr Voznyy ◽  
Shana O. Kelley ◽  
...  
Keyword(s):  
Quantum Well ◽  
Synthetic Control ◽  
Width Distribution ◽  
Quantum Well Width ◽  
Low Dimensional

Phonon drag and carrier diffusion contribution to heat transport of superconductor MgB2

2017 ◽  
Vol 06 (01) ◽  
pp. 1750008 ◽  
Author(s):  
Roopam Sharma ◽  
Namita Singh ◽  
Khurshid Akhtar ◽  
R. Khenata ◽  
Dinesh Varshney
Keyword(s):  
Heat Transfer ◽  
Relaxation Time ◽  
Thermoelectric Power ◽  
Linear Temperature Dependence ◽  
Phonon Drag ◽  
Scattering Mechanism ◽  
Linear Temperature ◽  
Carrier Diffusion ◽  
Time Approximation ◽  
Relaxation Time Approximation

The temperature variation of phonon drag thermoelectric power [Formula: see text] is computed within the relaxation time approximation for high temperature MgB2 superconductors. The phonon drag thermoelectric power ([Formula: see text] in normal state of MgB2 superconductors dominates and is an artifact of strong phonon-impurity and phonon scattering mechanism. The carrier diffusive thermoelectric power is explored when heat transfer is limited by the scattering of phonons from defects, grain boundaries, phonons and charge carriers. The carrier diffusion contribution to the thermoelectric power ([Formula: see text] is analyzed keeping in mind the inherent two energy gaps. The conductivity within the relaxation time approximation for [Formula: see text] and [Formula: see text] band carriers has been taken into account ignoring a possible energy dependence of the scattering rates. Such an estimate sets an upperbound on [Formula: see text] and is about 50% of total heat transfer at room temperature. Both these channels for heat transfer are added and [Formula: see text] starts departing from linear temperature dependence at about 150[Formula: see text]K, before increasing at higher temperatures weakly. It is shown that the behavior of the [Formula: see text] is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions. The numerical analysis of thermoelectric power in the metallic phase of MgB2 shows similar results as those revealed from experiments. The anomalies reported experimentally are well accounted in terms of the scattering mechanism by phonon drag and carrier scattering with impurities.

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