978 research outputs found
Linear and non-linear thermodynamics of a kinetic heat engine with fast transformations
We investigate a kinetic heat engine model constituted by particles enclosed
in a box where one side acts as a thermostat and the opposite side is a piston
exerting a given pressure. Pressure and temperature are varied in a cyclical
protocol of period : their relative excursions, and
respectively, constitute the thermodynamic forces dragging the system
out-of-equilibrium. The analysis of the entropy production of the system allows
to define the conjugated fluxes, which are proportional to the extracted work
and the consumed heat. In the limit of small and the fluxes
are linear in the forces through a -dependent Onsager matrix whose
off-diagonal elements satisfy a reciprocal relation. The dynamics of the piston
can be approximated, through a coarse-graining procedure, by a Klein-Kramers
equation which - in the linear regime - yields analytic expressions for the
Onsager coefficients and the entropy production. A study of the efficiency at
maximum power shows that the Curzon-Ahlborn formula is always an upper limit
which is approached at increasing values of the thermodynamic forces, i.e.
outside of the linear regime. In all our analysis the adiabatic limit and the the small force limit are not directly
related.Comment: 10 pages, 9 figure
A kinetic model for the finite-time thermodynamics of small heat engines
We study a molecular engine constituted by a gas of molecules
enclosed between a massive piston and a thermostat. The force acting on the
piston and the temperature of the thermostat are cyclically changed with a
finite period . In the adiabatic limit , even for finite
size , the average work and heats reproduce the thermodynamic values,
recovering the Carnot result for the efficiency. The system exhibits a stall
time where net work is zero: for it consumes work
instead of producing it, acting as a refrigerator or as a heat sink. At
the efficiency at maximum power is close to the Curzorn-Ahlborn
limit. The fluctuations of work and heat display approximatively a Gaussian
behavior. Based upon kinetic theory, we develop a three-variables Langevin
model where the piston's position and velocity are linearly coupled together
with the internal energy of the gas. The model reproduces many of the system's
features, such as the inversion of the work's sign, the efficiency at maximum
power and the approximate shape of fluctuations. A further simplification in
the model allows to compute analytically the average work, explaining its
non-trivial dependence on .Comment: 8 pages, 6 figures, accepted for publication on Physical Review
Fourier's Law in a Generalized Piston Model
A simplified, but non trivial, mechanical model -- gas of particles of
mass in a box partitioned by mobile adiabatic walls of mass --
interacting with two thermal baths at different temperatures, is discussed in
the framework of kinetic theory. Following an approach due to Smoluchowski,
from an analysis of the collisions particles/walls, we derive the values of the
main thermodynamic quantities for the stationary non-equilibrium states. The
results are compared with extensive numerical simulations; in the limit of
large , and , we find a good approximation of
Fourier's law.Comment: 14 pages, 5 figure
Development and growth of hatchery-reared larval Florida pompano (Trachinotus carolinus)
Although the Florida pompano (Trachinotus carolinus) is
a prime candidate for aquaculture, the problematic production of juveniles remains a major impediment to
commercial culture of this species. In order to improve the understanding of larval development and to refine hatchery production techniques, this study was conducted to characterize development and growth of Florida pompano from hatching through metamorphosis by using digital photography
and image analysis. Newly hatched larvae were transparent and had a large, elongate yolk sac and single oil globule. The lower and upper jaws as well as the digestive tract
were not fully developed at hatching. Rotifers were observed in the stomach of larvae at three days after hatching (DAH), and Artemia spp. were observed in the stomach of larvae at 14 DAH. Growth rates calculated
from total length measurements were 0.22 ±0.04, 0.23 ±0.12, and 0.35 ±0.09 mm/d for each of the larval rearing trials. The mouth gape of larvae was 0.266 ±0.075 mm at first feeding and increased with a growth rate of 0.13 ± 0.04 mm/d. Predicted values for optimal prey sizes ranged from 80
to 130 μm at 3 DAH, 160 to 267 μm at 5 DAH, and 454 to 757 μm at 10 DAH. Based on the findings of this study, a refined feeding regime was developed to provide stage- and size-specific guidelines for feeding Florida pompano larvae reared under hatchery co
Door Barricade
My senior capstone project will be a door barricade. The main idea for the use of the door barricade is for schools in the case of an intruder. The barricade that I will be designing is a solution to the inefficient barricades that I saw at my high school. It could also be used at businesses and homes. My design would be easy to use and have a fail-safe option. The two areas of mechanical engineering technology that my capstone project will focus on are stress analysis and electronics. Every part for my door barricade is drawn in SolidWorks. All of the parts are assembled in a drawing. I did a statics analysis on two of my parts. There are also wiring diagrams for the toggle switch, photo eye and other electronics in my door barricade. Every detail of the project was documented. This report gives details of my senior capstone project for Mechanical Engineering Technology along with the drawings and calculations
Strumenti informatici per indici dei nomi. Come creare un indice analitico con MS-WORD
[Computer tools for indexes of names. How to realize an analytical index with MS-WORD]. The article proposes computer tools useful to set up indexes of names for texts of any measure, in an automatic or semi-automatic way. Macros for Microsoft Word successfully experimented by the ISPF in dealing with philosophical journals and books are submitted. The article includes listings that can be copied for implementation
The role of the number of degrees of freedom and chaos in macroscopic irreversibility
This article aims at revisiting, with the aid of simple and neat numerical
examples, some of the basic features of macroscopic irreversibility, and, thus,
of the mechanical foundation of the second principle of thermodynamics as drawn
by Boltzmann. Emphasis will be put on the fact that, in systems characterized
by a very large number of degrees of freedom, irreversibility is already
manifest at a single-trajectory level for the vast majority of the
far-from-equilibrium initial conditions - a property often referred to as
typicality. We also discuss the importance of the interaction among the
microscopic constituents of the system and the irrelevance of chaos to
irreversibility, showing that the same irreversible behaviours can be observed
both in chaotic and non-chaotic systems.Comment: 21 pages, 6 figures, accepted for publication in Physica
Review of Fault Mitigation Approaches for Deep Neural Networks for Computer Vision in Autonomous Driving
The aim of this work is to identify and present challenges and risks related to the employment of DNNs in Computer Vision for Autonomous Driving. Nowadays one of the major technological challenges is to choose the right technology among the abundance that is available on the market.
Specifically, in this thesis it is collected a synopsis of the state-of-the-art architectures, techniques and methodologies adopted for building fault-tolerant hardware and ensuring robustness in DNNs-based Computer Vision applications for Autonomous Driving
Fluctuations in partitioning systems with few degrees of freedom
We study the behavior of a moving wall in contact with a particle gas and
subjected to an external force. We compare the fluctuations of the system
observed in the microcanonical and canonical ensembles, at varying the number
of particles. Static and dynamic correlations signal significant differences
between the two ensembles. Furthermore, velocity-velocity correlations of the
moving wall present a complex two-time relaxation which cannot be reproduced by
a standard Langevin-like description. Quite remarkably, increasing the number
of gas particles in an elongated geometry, we find a typical timescale, related
to the interaction between the partitioning wall and the particles, which grows
macroscopically.Comment: 10 pages, 12 figure
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