21 research outputs found
A Discrete Four Stroke Quantum Heat Engine Exploring the Origin of Friction
The optimal power performance of a first principle quantum heat engine model
shows friction-like phenomena when the internal fluid Hamiltonian does not
commute with the external control field. The model is based on interacting
two-level-systems where the external magnetic field serves as a control
variable.Comment: 4 pages 3 figure
Quantum thermodynamic processes: A control theory for machine cycles
The minimal set of thermodynamic control parameters consists of a statistical
(thermal) and a mechanical one. These suffice to introduce all the pertinent
thermodynamic variables; thermodynamic processes can then be defined as paths
on this 2-dimensional control plane. Putting aside coherence we show that for a
large class of quantum objects with discrete spectra and for the cycles
considered the Carnot efficiency applies as a universal upper bound. In the
dynamic (finite time) regime renormalized thermodynamic variables allow to
include non-equilibrium phenomena in a systematic way. The machine function
ceases to exist in the large speed limit; the way, in which this limit is
reached, depends on the type of cycle considered.Comment: 14 pages, 12 figures, Replaced by version accepted for publication in
European Physical Journal
Bounds and phase diagram of efficiency at maximum power for tight-coupling molecular motors
The efficiency at maximum power (EMP) for tight-coupling molecular motors is
investigated within the framework of irreversible thermodynamics. It is found
that the EMP depends merely on the constitutive relation between the
thermodynamic current and force. The motors are classified into four generic
types (linear, superlinear, sublinear, and mixed types) according to the
characteristics of the constitutive relation, and then the corresponding ranges
of the EMP for these four types of molecular motors are obtained. The exact
bounds of the EMP are derived and expressed as the explicit functions of the
free energy released by the fuel in each motor step. A phase diagram is
constructed which clearly shows how the region where the parameters (the load
distribution factor and the free energy released by the fuel in each motor
step) are located can determine whether the value of the EMP is larger or
smaller than 1/2. This phase diagram reveals that motors using ATP as fuel
under physiological conditions can work at maximum power with higher efficiency
() for a small load distribution factor ().Comment: 5 pages, 4 figure
Modeling and Simulation of Power Yield in Thermal, Chemical and Electrochemical Systems: Fuel Cell Case
A rapid-scan device for the determination of spectral line profiles in pulsed discharges
Adult education, community development and rural regeneration Synopsis report of the Rural Development and Regeneration Project
An Interreg Project funded by the European UnionAvailable from British Library Document Supply Centre- DSC:q95/16766 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo