13,959 research outputs found
Non-Linear Affine Embedding of the Dirac Field from the Multiplicity-Free SL(4,R) Unirreps
The correspondence between the linear multiplicity-free unirreps of SL(4, R)
studied by Ne'eman and {\~{S}}ija{\~{c}}ki and the non-linear realizations of
the affine group is worked out. The results obtained clarify the inclusion of
spinorial fields in a non-linear affine gauge theory of gravitation.Comment: 13 pages, plain TeX, macros include
Understanding chemical evolution in resolved galaxies -- I The local star fraction-metallicity relation
This work studies the relation between gas-phase oxygen abundance and
stellar-to-gas fraction in nearby galaxies. We first derive the theoretical
prediction, and argue that this relation is fundamental, in the sense that it
must be verified regardless of the details of the gas accretion and star
formation histories. Moreover, it should hold on "local" scales, i.e. in
regions of the order of 1 kpc. These predictions are then compared with a set
of spectroscopic observations, including both integrated and resolved data.
Although the results depend somewhat on the adopted metallicity calibration,
observed galaxies are consistent with the predicted relation, imposing tight
constraints on the mass-loading factor of (enriched) galactic winds. The
proposed parametrization of the star fraction-metallicity relation is able to
describe the observed dependence of the oxygen abundance on gas mass at fixed
stellar mass. However, the "local" mass-metallicity relation also depends on
the relation between stellar and gas surface densities.Comment: 10 pages, 4 figures. Matches accepted version (significant typo
corrected
A Novel Hybrid CNN-AIS Visual Pattern Recognition Engine
Machine learning methods are used today for most recognition problems.
Convolutional Neural Networks (CNN) have time and again proved successful for
many image processing tasks primarily for their architecture. In this paper we
propose to apply CNN to small data sets like for example, personal albums or
other similar environs where the size of training dataset is a limitation,
within the framework of a proposed hybrid CNN-AIS model. We use Artificial
Immune System Principles to enhance small size of training data set. A layer of
Clonal Selection is added to the local filtering and max pooling of CNN
Architecture. The proposed Architecture is evaluated using the standard MNIST
dataset by limiting the data size and also with a small personal data sample
belonging to two different classes. Experimental results show that the proposed
hybrid CNN-AIS based recognition engine works well when the size of training
data is limited in siz
The motion of two masses coupled to a massive spring
We discuss the classical motion of a spring of arbitrary mass coupled to two
arbitrary massive blocks attached at its ends. A general approach to the
problem is presented and some general results are obtained. Examples for which
a simple elastic function can be inferred are discussed and the normal modes
and normal frequencies obtained. An approximation procedure to the evaluation
of the normel frequencies in the case of uniform elastic function and mass
density is also discussed.Comment: Standard Latex file plus three eps figure
Effective Potential and Thermodynamics for a Coupled Two-Field Bose Gas Model
We study the thermodynamics of a two-species homogeneous and dilute Bose gas
that is self-interacting and quadratically coupled to each other. We make use
of field theoretical functional integral techniques and evaluate the one-loop
finite temperature effective potential for this system considering the
resummation of the leading order temperature dependent as well as infrared
contributions. The symmetry breaking pattern associated to the model is then
studied by considering different values of self and inter-species couplings. We
pay special attention to the eventual appearance of reentrant phases and/or
shifts in the observed critical temperatures as compared to the monoatomic
(one-field Bose) case.Comment: 21 pages, 4 eps figure
Integrated Planning of Industrial Gas Supply Chains
In this work, we propose a Mixed Integer Linear Programming (MILP) model for optimal planning of industrial gas supply chain, which integrates supply contracts, production scheduling, truck and rail-car scheduling, as well as inventory management under the Vendor Managed Inventory (VMI) paradigm. The objective used here is minimisation of the total operating cost consisting of purchasing of raw material, production, and transportation costs by trucks/rail-cars so as to satisfy customer demands over a given time horizon. The key decisions for production sites include production schedule and purchase schedule of raw material, while the distribution decisions involve customer to plant/depot allocation, quantity transported through rail network, truck delivery amounts, and times. In addition, a relaxation approach is proposed to solve the problem efficiently. An industrial case study is evaluated to illustrate the applicability of the integrated optimisation framework
Gaussian superpositions in scalar-tensor quantum cosmological models
A free scalar field minimally coupled to gravity model is quantized and the
Wheeler-DeWitt equation in minisuperspace is solved analytically, exhibiting
positive and negative frequency modes. The analysis is performed for positive,
negative and zero values of the curvature of the spatial section. Gaussian
superpositions of the modes are constructed, and the quantum bohmian
trajectories are determined in the framework of the Bohm-de Broglie
interpretation of quantum cosmology. Oscillating universes appear in all cases,
but with a characteristic scale of the order of the Planck scale. Bouncing
regular solutions emerge for the flat curvature case. They contract classically
from infinity until a minimum size, where quantum effects become important
acting as repulsive forces avoiding the singularity and creating an
inflationary phase, expanding afterwards to an infinite size, approaching the
classical expansion as long as the scale factor increases. These are
non-singular solutions which are viable models to describe the early Universe.Comment: 14 pages, LaTeX, 3 Postscript figures, uses graficx.st
A general treatment of geometric phases and dynamical invariants
Based only on the parallel transport condition, we present a general method
to compute Abelian or non-Abelian geometric phases acquired by the basis states
of pure or mixed density operators, which also holds for nonadiabatic and
noncyclic evolution. Two interesting features of the non-Abelian geometric
phase obtained by our method stand out: i) it is a generalization of Wilczek
and Zee's non-Abelian holonomy, in that it describes nonadiabatic evolution
where the basis states are parallelly transported between distinct degenerate
subspaces, and ii) the non-Abelian character of our geometric phase relies on
the transitional evolution of the basis states, even in the nondegenerate case.
We apply our formalism to a two-level system evolving nonadiabatically under
spontaneous decay to emphasize the non-Abelian nature of the geometric phase
induced by the reservoir. We also show, through the generalized invariant
theory, that our general approach encompasses previous results in the
literature
Hierarchical Approach to Integrated Planning of Industrial Gas Supply Chains
In this article, an optimization-based framework is proposed for integrated production and distribution planning of industrial gas supply chains. The main goal is to minimize the overall cost, which is composed of raw material, product sourced from external suppliers, production, truck, and rail-car costs, while satisfying customer demands. The overall problem is formulated as a mixed-integer linear programming (MILP) model while a two-phase hierarchical solution strategy is developed to solve the resulting optimization problem efficiently. The first phase relies on truck scheduling decisions being relaxed, whereas the second phase solves the original model at reduced space by fixing product allocation as determined by phase one. Finally, an industrial-size case study is used to illustrate the applicability and efficiency of the proposed optimization framework
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