scholarly journals STOCHASTIC ENERGETICS OF A BROWNIAN MOTOR AND REFRIGERATOR DRIVEN BY NONUNIFORM TEMPERATURE

2014 ◽  
Vol 28 (08) ◽  
pp. 1450055 ◽  
Author(s):  
RONALD BENJAMIN
Keyword(s):  
Heat Pump ◽  
Linear Response ◽  
Heat Engine ◽  
Temperature Profiles ◽  
Nonuniform Temperature ◽  
Brownian Motor ◽  
Linear Response Regime ◽  
Stochastic Energetics ◽  
Parameter Values

The energetics of a Brownian heat engine and heat pump driven by position dependent temperature, known as the Büttiker–Landauer heat engine and heat pump, is investigated by numerical simulations of the inertial Langevin equation. We identify parameter values for optimal performance of the heat engine and heat pump. Our results qualitatively differ from approaches based on the overdamped model. The behavior of the heat engine and heat pump, in the linear response regime is examined under finite time conditions and we find that the efficiency is lower than that of an endoreversible engine working under the same condition. Finally, we investigate the role of different potential and temperature profiles to enhance the efficiency of the system. Our simulations show that optimizing the potential and temperature profile leads only to a marginal enhancement of the system performance due to the large entropy production via the Brownian particle's kinetic energy.

The effect of adding side group and changing contact geometry in single pyrene molecular devices

2018 ◽  
Vol 32 (07) ◽  
pp. 1850078
Author(s):  
M. F. Jamali ◽  
H. Rahimpour Soleimani ◽  
M. Bagheri Tagani
Keyword(s):  
Density Functional Theory ◽  
Linear Response ◽  
Density Functional ◽  
Molecular Devices ◽  
Side Group ◽  
Functional Theory ◽  
Linear Response Regime ◽  
P Type ◽  
Type Conduction

In this study, the thermopower of pyrene molecule in both symmetric and asymmetric junctions to gold electrodes and the role of adding side group have been studied using density functional theory and Green’s function formalism in the linear response regime. We have considered four different configurations and investigated the thermopower property of them. Calculations show that adding electron donating side groups to both symmetrical and anti-symmetrical junction will increase the thermopower. However, the increase is more evident in asymmetric junction. Additionally, the Seebeck coefficient sign is positive which indicates p-type conduction.

RADIATING COLLAPSE WITH VANISHING WEYL STRESSES

2005 ◽  
Vol 14 (03n04) ◽  
pp. 667-676 ◽  
Author(s):  
S. D. MAHARAJ ◽  
M. GOVENDER
Keyword(s):  
Irreversible Thermodynamics ◽  
Temperature Profiles ◽  
Junction Conditions ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Extended Irreversible Thermodynamics ◽  
Recent Approach ◽  
Dust Solution ◽  
Limiting Case

In a recent approach in modeling a radiating relativistic star undergoing gravitational collapse the role of the Weyl stresses was emphasized. It is possible to generate a model which is physically reasonable by approximately solving the junction conditions at the boundary of the star. In this paper we demonstrate that it is possible to solve the Einstein field equations and the junction conditions exactly. This exact solution contains the Friedmann dust solution as a limiting case. We briefly consider the radiative transfer within the framework of extended irreversible thermodynamics and show that relaxational effects significantly alter the temperature profiles.

Second language acquisition: Theoretical and experimental issues in contemporary research

1996 ◽  
Vol 19 (4) ◽  
pp. 677-714 ◽  
Author(s):  
Samuel David Epstein ◽  
Suzanne Flynn ◽  
Gita Martohardjono
Keyword(s):  
Second Language ◽  
Second Language Acquisition ◽  
Universal Grammar ◽  
Functional Categories ◽  
L2 Acquisition ◽  
Psycholinguistic Research ◽  
Explanatory Theory ◽  
Parameter Values ◽  
Theoretical Issues

AbstractTo what extent, if any, does Universal Grammar (UG) constrain second language (L2) acquisition? This is not only an empirical question, but one which is currently investigable. In this context, L2 acquisition is emerging as an important new domain of psycholinguistic research. Three logical possibilities have been articulated regarding the role of UG in L2 acquisition: The first is the “no access” hypothesis that claims that no aspect of UG is available to the L2 learner. The second is the “partial access” hypothesis that claims that only LI instantiated principles and LI instantiated parameter-values of UG are available to the learner. The third, called the “full access” hypothesis, asserts that UG in its entirety constrains L2 acquisition.In this paper we argue that there is no compelling evidence to support either of the first two hypotheses. Moreover, we provide evidence concerning functional categories in L2 acquisition consistent with the claim that UG is fully available to the L2 learner (see also Flynn 1987; Li 1993; Martohardjono 1992; Schwartz & Sprouse 1991; Thomas 1991; White 1989). In addition, we will attempt to clarify some of currently unclear theoretical issues that arise with respect to positing UG as an explanatory theory of L2 acquisition. We will also investigate in some detail certain crucial methodological questions involved in experimentally testing the role of UG in L2 acquisition and finally, we will present a set of experimental results of our own supporting the “Full Access” hypothesis.

scholarly journals Optimization and Stability of Heat Engines: The Role of Entropy Evolution

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 865 ◽  
Author(s):  
Julian Gonzalez-Ayala ◽  
Moises Santillán ◽  
Maria Santos ◽  
Antonio Calvo Hernández ◽  
José Mateos Roco
Keyword(s):  
Local Stability ◽  
Production Efficiency ◽  
Basin Of Attraction ◽  
Heat Engine ◽  
Time Constraints ◽  
Thermal Gradients ◽  
Heat Engines ◽  
Low Dissipation ◽  
The Basin Of Attraction

Local stability of maximum power and maximum compromise (Omega) operation regimes dynamic evolution for a low-dissipation heat engine is analyzed. The thermodynamic behavior of trajectories to the stationary state, after perturbing the operation regime, display a trade-off between stability, entropy production, efficiency and power output. This allows considering stability and optimization as connected pieces of a single phenomenon. Trajectories inside the basin of attraction display the smallest entropy drops. Additionally, it was found that time constraints, related with irreversible and endoreversible behaviors, influence the thermodynamic evolution of relaxation trajectories. The behavior of the evolution in terms of the symmetries of the model and the applied thermal gradients was analyzed.

scholarly journals Transport in one-dimensional integrable quantum systems

2020 ◽  
Author(s):  
Jesko Sirker
Keyword(s):  
Transport Properties ◽  
Spin Chain ◽  
Linear Response ◽  
Summer School ◽  
Condensed Matter ◽  
Quantum Systems ◽  
Integrable Models ◽  
One Dimensional ◽  
Integrable Quantum ◽  
Linear Response Regime

These notes are based on a series of three lectures given at the Les Houches summer school on ’Integrability in Atomic and Condensed Matter Physics’ in August 2018. They provide an introduction into the unusual transport properties of integrable models in the linear response regime focussing, in particular, on the spin-1/21/2 XXZ spin chain.

scholarly journals Chart for Thermoelectric Systems Operation Based on a Ternary Diagram for Bithermal Systems

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 666
Author(s):  
Julien Ramousse ◽  
Christophe Goupil
Keyword(s):  
Heat Pump ◽  
Heat Engine ◽  
Ternary Diagram ◽  
Operating Conditions ◽  
Thermal Dissipation ◽  
Maximum Efficiency ◽  
Joule Effect ◽  
Parametric Curve ◽  
Thermoelectric Systems ◽  
The Impact

Thermoelectric system’s operation needs careful attention to ensure optimal power conversion depending on the application aims. As a ternary diagram of bithermal systems allows a synthetic graphical analysis of the performance attainable by any work-heat conversion system, thermoelectric systems operation is plotted as a parametric curve function of the operating conditions (electric current and reservoirs’ temperature), based on the standard model of Ioffe. The threshold of each operating mode (heat engine, heat pump, thermal dissipation, and forced thermal transfer), along with the optimal efficiencies and powers of the heat pump and heat engine modes, are characterized graphically and analytically as a function of the material properties and the operating conditions. The sensibility of the performance aims (maximum efficiency vs. maximum power) with the operating conditions is, thus, highlighted. In addition, the specific contributions of each phenomenon involved in the semiconductor (reversible Seebeck effect, irreversible heat leakage by conduction and irreversible thermal dissipation by Joule effect) are discussed in terms of entropy generation. Finally, the impact of the exo-irreversibilities on the performance is analyzed by taking the external thermal resistances into account.

Sign in / Sign up

Export Citation Format

Share Document