62 research outputs found
Generalized Kinetic Theory of Electrons and Phonons: Models, Equilibrium, Stability
In the present paper our aim is to introduce some models for the
generalization of the kinetic theory of electrons and phonons (KTEP), as well
as to study equilibrium solutions and their stability for the generalized KTEP
(GKTEP) equations. We consider a couple of models, relevant to non standard
quantum statistics, which give rise to inverse power law decays of the
distribution function with respect to energy. In the case of electrons in a
phonon background, equilibrium and stability are investigated by means of
Lyapounov theory. Connections with thermodynamics are pointed out.Comment: 10 pages, 2 figures, (RevTeX4), to appear in Physica B (2003
Bose-Einstein Condensation in the Framework of -Statistics
In the present work we study the main physical properties of a gas of
-deformed bosons described through the statistical distribution
function . The
deformed -exponential , recently proposed in Ref.
[G.Kaniadakis, Physica A {\bf 296}, 405, (2001)], reduces to the standard
exponential as the deformation parameter , so that
reproduces the Bose-Einstein distribution. The condensation temperature
of this gas decreases with increasing value, and
approaches the transition temperature
, improving the result obtained in the standard case
(). The heat capacity is a continuous function and
behaves as for , in
contrast with the standard case , it is always increasing.
Pacs: 05.30.Jp, 05.70.-a Keywords: Generalized entropy; Boson gas; Phase
transition.Comment: To appear in Physica B. Two fig.p
CONVERGENT AND DIVERGENT ANGLES OF A SOLID-FUEL ROCKET NOZZLE AND ITS INFLUENCES ON THE MOTOR’S THRUST CURVE
The main goal of this work is to investigate how the angles of a convergent-divergent rocket nozzle influence the thrust curve of a solid-propulsion rocket. The work has been conducted within an academic rocketry team. As there is not clear reasoning on how to define these angles, the present research provides insights on how these geometrical parameters influence the performance of a rocket motor. A 2D-axisymmetric CFD domain is considered, comprising the fluid domain inside and outside the nozzle, to give room for the shock waves to happen and also accommodate the flow. The study comprises a baseline geometry and twelve modified designs, varying the convergent and the divergent angles of the nozzle. Since the convergent diameter must match the chamber diameter, it is fixed. For the divergent diameter, there is no such restriction; therefore, there are two possibilities: a divergent section with the same divergent diameter or with the same length as the baseline. The benchmark thrust curve is generated with a MATLAB code based on solid-fuel modeling and the De Laval theory. The curve is divided into six steady-state simulations, using boundary conditions of mass flow, pressure and temperature at the inlet and pressure and temperature at the outlet. The baseline geometry is simulated in Ansys Fluent and normalized by the MATLAB benchmark. A mesh study selects which mesh and turbulence model to use based on this normalization. The modified geometries are then compared to the baseline. The main quantity of interest is the thrust but quantities such as static pressure and average velocity at the nozzle exit aid the understanding of the changes in thrust
Physiological processes of inflammation and edema initiated by sustained mechanical loading in subcutaneous tissues : a scoping review
Deep tissue injuries are pressure ulcers which initiate in the subcutaneous tissues and extend through a bottom-up pathway. Once deep tissue injuries are visual at skin level, serious irreversible tissue damage has already occurred. In pressure ulcer development, inflammation and edema are coupled physiological processes associated with tissue damage arising due to sustained mechanical loading. This study aimed to provide an in-depth overview of the physiological processes of inflammation and edema initiated by sustained mechanical loading in subcutaneous tissues, in the context of pressure ulceration. A scoping review was performed according to the framework by Arksey and O'Malley. The databases MEDLINE, EMBASE, Web of Science, and Scopus, and the reference lists of included studies were searched for in vivo (animal, human), and in vitro studies matching the study objectives (from inception to 28 May 2018). No restrictions for inclusion were applied for study design, setting, participants, and year of publication. A total of 12 studies were included, varying in study design, sample characteristics, amount and duration of mechanical loads that were applied, follow-up time, and assessment methods. Neutrophil infiltration and edema occur in the subcutaneous tissues nearly immediately after the application of load on soft tissues. The amount of neutrophils and edema increase in the first days after the mechanical insult and decrease once healing has been initiated and no supplementary mechanical load was applied. One study indicated that edema may extend up to the level of the dermo-epidermal junction. Further research should focus on how deep tissue inflammation and edema are reflected into unique tissue changes at skin level, and how abnormal inflammatory responses manifest (e.g. when the nervous system is not functioning normally)
Characterization of amorphous In2O3: an ab initio molecular dynamics study
In this work, we report on the structural and electronic properties of amorphous In2O3 obtained with ab initio molecular dynamics. Our results show crystal-like short range InO6 polyhedra having average In-O distance consistent with x-ray spectroscopy data. Structural disorder yields band tailing and localized states, which are responsible of a strong reduction of the electronic gap. Most importantly, the appearance of a peculiar O-O bond imparts n-type character to the amorphous compound and provides contribution for interpreting spectroscopic measurements on indium based oxidized systems. Our findings portray characteristic features to attribute transparent semiconductive properties to amorphous In2O3
Maxwell-Jüttner distributions in relativistic molecular dynamics
In relativistic kinetic theory, which underlies relativistic
hydrodynamics, the molecular chaos hypothesis stands at the basis of
the equilibrium Maxwell-J\ddot{\mbox{u}}ttner probability
distribution for the four-momentum pα. We investigate the
possibility of validating this hypothesis by means of microscopic
relativistic dynamics. We do this by introducing a model of
relativistic colliding particles, and studying its dynamics. We
verify the validity of the molecular chaos hypothesis, and of the
Maxwell-J\ddot{\mbox{u}}ttner distributions for our model. Two
linear relations between temperature and average kinetic energy are
obtained in classical and ultrarelativistic regimes
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