2,169 research outputs found
Development of three dimensional constitutive theories based on lower dimensional experimental data
Most three dimensional constitutive relations that have been developed to
describe the behavior of bodies are correlated against one dimensional and two
dimensional experiments. What is usually lost sight of is the fact that
infinity of such three dimensional models may be able to explain these
experiments that are lower dimensional. Recently, the notion of maximization of
the rate of entropy production has been used to obtain constitutive relations
based on the choice of the stored energy and rate of entropy production, etc.
In this paper we show different choices for the manner in which the body stores
energy and dissipates energy and satisfies the requirement of maximization of
the rate of entropy production that leads to many three dimensional models. All
of these models, in one dimension, reduce to the model proposed by Burgers to
describe the viscoelastic behavior of bodies.Comment: 23 pages, 6 figure
Broken-symmetry-adapted Green function theory of condensed matter systems:towards a vector spin-density-functional theory
The group theory framework developed by Fukutome for a systematic analysis of
the various broken symmetry types of Hartree-Fock solutions exhibiting spin
structures is here extended to the general many body context using spinor-Green
function formalism for describing magnetic systems. Consequences of this theory
are discussed for examining the magnetism of itinerant electrons in nanometric
systems of current interest as well as bulk systems where a vector spin-density
form is required, by specializing our work to spin-density-functional
formalism. We also formulate the linear response theory for such a system and
compare and contrast them with the recent results obtained for localized
electron systems. The various phenomenological treatments of itinerant magnetic
systems are here unified in this group-theoretical description.Comment: 17 page
A thermodynamic framework to develop rate-type models for fluids without instantaneous elasticity
In this paper, we apply the thermodynamic framework recently put into place
by Rajagopal and co-workers, to develop rate-type models for viscoelastic
fluids which do not possess instantaneous elasticity. To illustrate the
capabilities of such models we make a specific choice for the specific
Helmholtz potential and the rate of dissipation and consider the creep and
stress relaxation response associated with the model. Given specific forms for
the Helmholtz potential and the rate of dissipation, the rate of dissipation is
maximized with the constraint that the difference between the stress power and
the rate of change of Helmholtz potential is equal to the rate of dissipation
and any other constraint that may be applicable such as incompressibility. We
show that the model that is developed exhibits fluid-like characteristics and
is incapable of instantaneous elastic response. It also includes Maxwell-like
and Kelvin-Voigt-like viscoelastic materials (when certain material moduli take
special values).Comment: 18 pages, 5 figure
Quantitative Risk Assessment in Process Plant
This paper outlines quantitative assessment of a critical event in the sub-section of a process plant where in a key ingredient required for the manufacture of propellants is produced. This sub-section is identified as possessing a fire hazard by qualitative HAZAN techniques. Fault tree and safety. tree analyses have been used to identify basic equipment and the operational failures which could lead to top event occurrence and to calculate its probability. Consequence analysis of one of the probable scenarios has lead to an estimation of risk in terms of fatality and injury . These results form basic inputs for risk management decisions
Hazard Assessment of a Nitration Plant using Fault Tree Analysis
Hazard assessment techniques, namely, fault tree analysis and safety analysis, have been applied to the nitration section of a plant producing explosives in the defence sector. Critical components and operations, the failure of which could lead to the occurrence of an unwanted event, have been identified and their effects quantitatively assessed. Some remedial measures have been suggested to minimise potential hazards and the effect of incorporating these measures on the system safety has been examined by means of specific case studies
The nature of the long time decay at a second order transition point
We show that at a second order phase transition, of \phi^4 like system, a
necessary condition for streched exponential decay of the time structure factor
is obeyed. Using the ideas presented in this proof a crude estimate of the
decay of the structure factor is obtained and shown to yield stretched
exponential decay under very reasonable conditions.Comment: 7 page
Implications of Form Invariance to the Structure of Nonextensive Entropies
The form invariance of the statement of the maximum entropy principle and the
metric structure in quantum density matrix theory, when generalized to
nonextensive situations, is shown here to determine the structure of the
nonextensive entropies. This limits the range of the nonextensivity parameter
to so as to preserve the concavity of the entropies. The Tsallis entropy is
thereby found to be appropriately renormalized.Comment: 8 page
Photons in gapless color-flavor-locked quark matter
We calculate the Debye and Meissner masses of a gauge boson in a material
consisting of two species of massless fermions that form a condensate of Cooper
pairs. We perform the calculation as a function of temperature, for the cases
of neutral Cooper pairs and charged Cooper pairs, and for a range of parameters
including gapped quaisparticles, and ungapped quasiparticles with both
quadratic and linear dispersion relations at low energy.
Our results are relevant to the behavior of photons and gluons in the gapless
color-flavor-locked phase of quark matter. We find that the photon's Meissner
mass vanishes, and the Debye mass shows a non-monotonic temperature dependence,
and at temperatures of order the pairing gap it drops to a minimum value of
order sqrt(alpha) times the quark chemical potential. We confirm previous
claims that at zero temperature an imaginary Meissner mass can arise from a
charged gapless condensate, and we find that at finite temperature this can
also occur for a gapped condensate.Comment: 22 pages, LaTeX; expanded discussion of temperature dependenc
Effect of friction on disoriented chiral condensate formation
We have investigated the effect of friction on the DCC domain formation. We
solve the Newton equation of motion for the O(4) fields, with quenched initial
condition. The initial fields are randomly distributed in a Gaussian form. In
one dimensional expansion, on the average, large DCC domains can not be formed.
However, in some particular orbits, large instabilities may occur. This
possibility also greatly diminishes with the introduction of friction. But, if
the friction is large, the system may be overdamped and then, there is a
possibility of large DCC domain formation in some events.Comment: 9 pages, including figure
- …