The mathematical formulation of numerous physical problems a results in differential
equations actually partial or ordinary differential equations.In our study we are
interested in solutions of partial differential equations.The aim of this work is
to calculate the concentrations of the pollution, by solving the atmospheric diffusion
equation(ADE) using different mathematical methods of solution. It is difficult to
solve the general form of ADE analytically, so we use some assumptions to get its
solution.The solutions of it depend on the eddy diffusivity profiles(k) and the wind
speed u. We use some physical assumptions to simplify its formula and solve it. In
the present work, we solve the ADE analytically in three dimensions using Green's
function method, Laplace transform method, normal mode method and these separation
of variables method. Also, we use ADM as a numerical method. Finally, comparisons
are made with the results predicted by the previous methods and the observed data.$$$$
The paper looks at problems concerning the recovery of operators from noisy information
in non-Euclidean metrics. A number of general theorems are proved and applied
to recovery problems for functions and their derivatives from the noisy Fourier transform.
In some cases, a family of optimal methods is found, from which the methods requiring
the least amount of original information are singled out. Bibliography: 25 titles$$$$
We present an evolutionary computational approach for the solution of nonlinear ordinary
differential equations (NLODEs). The mathematical modeling is performed by a feed-forward
artificial neural network that defines an unsupervised error. The training of these
networks is achieved by a hybrid intelligent algorithm, a combination of global search
with genetic algorithm and local search by pattern search technique. The applicability
of this approach ranges from single order NLODEs, to systems of coupled differential
equations. We illustrate the method by solving a variety of model problems and present
comparisons with solutions obtained by exact methods and classical numerical methods.
The solution is provided on a continuous finite time interval unlike the other numerical
techniques with comparable accuracy. With the advent of neuroprocessors and digital
signal processors the method becomes particularly interesting due to the expected
essential gains in the execution speed. (authors)$$$$
The paper is concerned with the topological analysis of the Chaplygin integrable case
in the dynamics of a rigid body in a fluid. A full list of the topological
types of Chaplygin systems in their dependence on the energy level is compiled on
the basis of the Fomenko-Zieschang theory. An effective description of the topology
of the Liouville foliation in terms of natural coordinate variables is also presented,
which opens a direct way to calculating topological invariants. It turns out
that on all nonsingular energy levels Chaplygin systems are Liouville equivalent to
the well-known Euler case in the dynamics of a rigid body with fixed point. Bibliography:
23 titles$$$$
Methods used to address protection issues in graphite-gas reactors 11 MB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/46/034/46034786.pdf - Text Version by Brisbois, Jacques; Commissariat a l'Energie Atomique - CEA, Centre d'Etudes Nucleaires de Fontenay-aux-Roses,
Direction des Piles Atomiques, Departement des Etudes de Piles, Service d'Etudes de
Protections de Piles (France) Read MoreCollapse
[en]
Protection issues are problems related to the presence of neutron and gamma radiations:
biological dose, material heating, Wigner effect, gas ionization. The objective is
then to determine the biological doses which are predictable in some reactor areas,
and to assess the effects of irradiation on materials during the reactor lifetime.
For these purposes, problems of particle propagation are addressed, and the effects
of radiations related to one phenomenon or another are studied with respect to radiation
energy. The author first describes methods used to compute general propagation. These
are mainly codes using Monte Carlo or multi-group scattering methods. These methods
are experimentally controlled on a sub-critical graphite-natural uranium set. In a
second part, the author presents the different radiation sources which are to be taken
into account in calculations. Then he indicates the nuclear constants to be used in
the different codes, as well as the response functions to be used to calculate a specific
phenomenon (steel, graphite Wigner effect, so on) from the particle spectrum. In the
fourth part, the author describes the different methods which can be used to solve
problems which are specific to graphite reactors. In the last part, obtained calculated
results are compared with experimental measurements performed on power reactors$$$$
The ray-tracing code Zgoubi has been used in a number of projects, in the frame of
high energy and nuclear physics R and D, since it was last documented in review articles.
Its library of optical elements and its accelerator simulation tools have been further
developed in these contexts. Its use covers design studies regarding large colliders
such as LHC and RHIC, synchrotron radiation, short lived beams, acceleration of polarized
lepton and hadron beams. This report gives an overview of the present state of the
code and of its evolution, illustrated with examples aimed at highlighting its capabilities$$$$
Fullerenes and disk-fullerenes http://dx.doi.org/10.1070/RM2013v068n04ABEH004850 by Deza, M (Ecole Normale Superieure, Paris (France)); Dutour Sikirić, M (Rudjer
Boškovic Institute, Zagreb (Croatia)); Shtogrin, M I (P.G.Demidov Yaroslavl State
University (Russian Federation)) Read MoreCollapse
[en]
A geometric fullerene, or simply a fullerene, is the surface of a simple closed convex
3-dimensional polyhedron with only 5- and 6-gonal faces. Fullerenes are
geometric models for chemical fullerenes, which form an important class of organic
molecules. These molecules have been studied intensively in chemistry, physics, crystallography,
and so on, and their study has led to the appearance of a vast literature on fullerenes
in mathematical chemistry and combinatorial and applied geometry. In particular, several
generalizations of the notion of a fullerene have been given, aiming at various
applications. Here a new generalization of this notion is proposed: an n-disk-fullerene.
It is obtained from the surface of a closed convex 3-dimensional polyhedron which
has one n-gonal face and all other faces 5- and 6-gonal, by removing the n-gonal face.
Only 5- and 6-disk-fullerenes correspond to geometric fullerenes. The notion
of a geometric fullerene is therefore generalized from spheres to compact simply
connected two-dimensional manifolds with boundary. A two-dimensional surface is said
to be unshrinkable if it does not contain belts, that is, simple cycles consisting
of 6-gons each of which has two neighbours adjacent at a pair of opposite edges.
Shrinkability of fullerenes and n-disk-fullerenes is investigated. Bibliography: 87
titles$$$$
Heavy steel reflector evaluation using diffusion theory 242 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/45/091/45091439.pdf - Text Version by Piovezan, Pamela; Carluccio, Thiago (Centro Tecnologico da Marinha (CTMSP), Sao Paulo,
SP (Brazil). Dept. de Neutronica e Blindagem); Abe, Alfredo; Santos, Adimir dos (Instituto
de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)), E-mail:
pamela.piovezan@ctmsp.mar.mil.br, E-mail: thiago.carluccio@ctmsp.mar.mil, E-mail:
alfredo@ctmsp.mar.mil.br, E-mail: asantos@ipen.br; Associacao Brasileira de Energia Nuclear (ABEN), Rio de Janeiro, RJ (Brazil) Read MoreCollapse
[en]
A new component named heavy reflector that did not exist in actual nuclear power plants
was introduced recently by the EPR reactor. The component was designed to partially
reflect neutrons inside the core to increase fuel efficiency and protect the vessel
during its 60-year operational life. Recently, an experiment was designed and performed
to address the real neutron reflector contribution due to the stainless steel in the
IPEN/MB-01 research reactor. The experiment consisted of several plates of stainless
steel which were conveniently positioned at water reflector region of the reactor
core. The main experimental results were the critical control bank positions and reactivity
as a function of the number of stainless steel plates. The main outcome of the experimental
results showed a quite clear effect on neutron absorption and neutron reflection due
to the stainless steel plates. The objective of this preliminary work is to address
theoretically this experiment using the diffusion theory code CITATION, besides existing
evaluation using Monte Carlo (MCNP and Tripoli) and transport (TORT) codes, in order
to verify the performance of diffusion theory for the reflector region. (author)$$$$
A GPU-based Monte Carlo dose calculation code for photon transport in a voxel phantom 360 KB - http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/45/089/45089780.pdf - Text Version by Bellezzo, M.; Do Nascimento, E.; Yoriyaz, H. (Instituto de Pesquisas Energeticas e
Nucleares / CNEN, Av. Lineu Prestes 2242, Cidade Universitaria, 05508-000 Sao Paulo
(Brazil)), E-mail: mbellezzo@gmail.br; Sociedad Peruana de Radioproteccion, Lima (Peru); Sociedad Mexicana de Irradiacion
y Dosimetria, Mexico D. F. (Mexico). Funding organisation: Organizacion Panamericana
de la Salud, Washington D. C. (United States); Universidad Nacional de San Antonio
de Abad del Cusco, Cusco (Peru); Instituto Peruano de Energia Nuclear, Lima (Peru);
Elekta AB (Sweden); RadPro International GmbH (Germany); ThermoFisher Scientific,
Inc. (United States); Varian Medical Systems (United States) Read MoreCollapse
[en]
As the most accurate method to estimate absorbed dose in radiotherapy, Monte Carlo
method has been widely used in radiotherapy treatment planning. Nevertheless, its
efficiency can be improved for clinical routine applications. In this paper, we present
the CUBMC code, a GPU-based Mc photon transport algorithm for dose calculation under
the Compute Unified Device Architecture platform. The simulation of physical events
is based on the algorithm used in Penelope, and the cross section table used is the
one generated by the Material routine, als present in Penelope code. Photons are transported
in voxel-based geometries with different compositions. To demonstrate the capabilities
of the algorithm developed in the present work four 128 x 128 x 128 voxel phantoms
have been considered. One of them is composed by a homogeneous water-based media,
the second is composed by bone, the third is composed by lung and the fourth is composed
by a heterogeneous bone and vacuum geometry. Simulations were done considering a 6
MeV monoenergetic photon point source. There are two distinct approaches that were
used for transport simulation. The first of them forces the photon to stop at every
voxel frontier, the second one is the Woodcock method, where the photon stop in the
frontier will be considered depending on the material changing across the photon travel
line. Dose calculations using these methods are compared for validation with Penelope
and MCNP5 codes. Speed-up factors are compared using a NVidia GTX 560-Ti GPU card
against a 2.27 GHz Intel Xeon CPU processor. (Author)$$$$