2,577 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
Theory of ferromagnetism in (A,Mn)B semiconductors
A brief review of theory of ferromagnetism of dilute magnetic semiconductors
of the form (A,Mn)B based on the double exchange model is first given. A
systematic investigation of the phenomena extending the current theory is
outlined. We begin with an investigation of the regions of instability of the
nonmagnetic towards the ferromagnetic state of a system of Mn-atoms doped in
AB-type semiconductor. A self-consistent many-body theory of the ferromagnetic
state is then developed, going beyond the mean field approaches by including
fluctuations of the Mn-spins and the itinerant hole-gas. A functional theory
suitable for computation of system properties such as Curie temperature as a
function of hole and the Mn-concentration, spin-current, etc. is formulated.Comment: 16 page
Rocketdyne PSAM: In-house enhancement/application
The development was initiated of the Probabilistic Design Analysis (PDA) Process for rocket engines. This will enable engineers a quantitative assessment of calculated reliability during the design process. The PDA will help choose better designs, make them more robust, and help decide on critical tests to help demonstrate key reliability issues to aid in improving the confidence of the engine capabilities. Rockedyne's involvement with the Composite Loads Spectra (CLS) and Probabilistic Structural Analysis Methodology (PSAM) contracts started this effort and are key elements in the on-going developments. Internal development efforts and hardware applications complement and extend the CLS and PSAM efforts. The completion of the CLS option work and the follow-on PSAM developments will also be integral parts of this methodology. A brief summary of these efforts is presented
Overview of event-by-event analysis of high energy nuclear collisions
The event-by-event analysis of high energy nuclear collisions aims at
revealing the richness of the underlying event structures and provide unique
measures of dynamical fluctuations associated with QGP phase transition. The
major challenge in these studies is to separate the dynamical fluctuations from
the many other sources which contribute to the measured values. We present the
fluctuations in terms of event multiplicity, mean transverse momentum, elliptic
flow, source sizes, particle ratios and net charge distributions. In addition,
we discuss the effect of long range correlations, disoriented chiral
condensates and presence of jets. A brief review of various probes used for
fluctuation studies and available experimental results are presented.Comment: Invited talk at the "XIth International Workshop on Correlation and
Fluctuation in Multiparticle Production", Nov 21-24, 2006, Hangzhou, China
(19 pages
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
Probabilistic evaluation of SSME structural components
The application is described of Composite Load Spectra (CLS) and Numerical Evaluation of Stochastic Structures Under Stress (NESSUS) family of computer codes to the probabilistic structural analysis of four Space Shuttle Main Engine (SSME) space propulsion system components. These components are subjected to environments that are influenced by many random variables. The applications consider a wide breadth of uncertainties encountered in practice, while simultaneously covering a wide area of structural mechanics. This has been done consistent with the primary design requirement for each component. The probabilistic application studies are discussed using finite element models that have been typically used in the past in deterministic analysis studies
Quantum reading of digital memory with non-Gaussian entangled light
It has been shown recently (Phys. Rev. Lett. 106, 090504 (2011)) that
entangled light with Einstein-Podolsky-Rosen (EPR) correlations retrieves
information from digital memory better than any classical light. In identifying
this, a model of digital memory with each cell consisting of reflecting medium
with two reflectivities (each memory cell encoding the binary numbers 0 or 1)
is employed. The readout of binary memory essentially corresponds to
discrimination of two Bosonic attenuator channels characterized by different
reflectivities. The model requires an entire mathematical paraphernalia of
continuous variable Gaussian setting for its analysis, when arbitrary values of
reflectivities are considered. Here we restrict to a basic quantum read-out
mechanism with non-Gaussian entangled states of light, with the binary channels
to be discriminated being ideal memory characterized by reflectivity one i.e.,
an identity channel and thermal noise channel, where the signal light
illuminating the memory location gets completely lost (zero reflectivity) and
only a white thermal noise hitting the upper side of the memory reaches the
decoder. We compare the quantum reading efficiency of entangled light with any
classical source of light in this model. We show that entangled transmitters
offer better reading performance than any classical transmitters of light in
the regime of low signal intensity.Comment: 7 pages, 6 figures, To appear in Phys. Rev.
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