170 research outputs found
Entropy Identity and Material-Independent Equilibrium Conditions in Relativistic Thermodynamics
On the basis of the balance equations for energy-momentum, spin, particle and
entropy density, an approach is considered which represents a comparatively
general framework for special- and general-relativistic continuum
thermodynamics. In the first part of the paper, a general entropy density
4-vector, containing particle, energy-momentum, and spin density contributions,
is introduced which makes it possible, firstly, to judge special assumptions
for the entropy density 4-vector made by other authors with respect to their
generality and validity and, secondly, to determine entropy supply and entropy
production. Using this entropy density 4-vector, in the second part,
material-independent equilibrium conditions are discussed. While in literature,
at least if one works in the theory of irreversible thermodynamics assuming a
Riemann space-time structure, generally thermodynamic equilibrium is determined
by introducing a variety of conditions by hand, the present approach proceeds
as follows: For a comparatively wide class of space-time geometries the
necessary equilibrium conditions of vanishing entropy supply and entropy
production are exploited and, afterwards, supplementary conditions are assumed
which are motivated by the requirement that thermodynamic equilibrium
quantities have to be determined uniquely.Comment: Research Paper, 30 page
Mesoscopic continuum mechanics applied to liquid crystals
Beyond the usual 5-field theory (basic fields: mass density, velocity, internal energy), additional variables are needed for the unique description of complex media. Beside the conventional method of introducing additional fields by their balances, an other procedure, the mesoscopic theory, is here discussed and applied to liquid crystals
Variational Principles in Thermodynamics
Instead of equations of motion, variational principles are often used for describing the dynamical behavior of a system. If the equations of motion are variational self-adjoint, the variational principle is equivalent to the equations of motion, because those are given by the Euler-Lagrange equations which belong to the variational principle. If the equations of motion are not variational self-adjoint -as it is the general case in thermodynamics- procedures are discussed to obtain also in these cases a variational problem. Because of lack of variational self-adjointness these variational problems cannot be true ones, they are non-Hamiltonian. By presupposing suflicient conditions an evolution criterion can be derived from the Second Law which results in a Hamiltonian variational principle, also in thermodynamics
Bildung atmosphärischer gasförmiger Schwefelsäure in Natur und Technik: elektrische Entladungen und Dieselkraftfahrzeuge
Several procedures in nature and technology generate gaseous sulfuric acid, being the most important aerosol precursor gas. This was detected for the first time in atmospheric high voltage discharges. Moreover, comparative measurements of gaseous sulfuric acid and further trace gases emerging in high voltage atmospheric discharges were undertaken. Particularly the formation of the trace gases sulfuric and nitric acid was compared here. Another part of this work deals with the formation of gaseous sulfuric acid in the exhaust of a modern truck diesel engine with exhaust aftertreatment. For the measurement of gaseous sulfuric acid the chemical Ionization Mass Spectrometry that was developed by our group was applied in both cases
Deterministic quantum teleportation between distant atomic objects
Quantum teleportation is a key ingredient of quantum networks and a building
block for quantum computation. Teleportation between distant material objects
using light as the quantum information carrier has been a particularly exciting
goal. Here we demonstrate a new element of the quantum teleportation landscape,
the deterministic continuous variable (cv) teleportation between distant
material objects. The objects are macroscopic atomic ensembles at room
temperature. Entanglement required for teleportation is distributed by light
propagating from one ensemble to the other. Quantum states encoded in a
collective spin state of one ensemble are teleported onto another ensemble
using this entanglement and homodyne measurements on light. By implementing
process tomography, we demonstrate that the experimental fidelity of the
quantum teleportation is higher than that achievable by any classical process.
Furthermore, we demonstrate the benefits of deterministic teleportation by
teleporting a dynamically changing sequence of spin states from one distant
object onto another
- …