394 research outputs found
Efficiency Analysis of Hybrid Fuzzy C-Means Clustering Algorithms and their Application to Compute the Severity of Disease in Plant Leaves
Data clustering has a wide range of application varying from medical image analysis, social network analysis, market segmentation, search engines, recommender systems and image processing. A clustering algorithm should be fast as well accurate. Some applications give priority to the speed of the clustering algorithms while some emphasize more on the accuracy rather than speed. A number of clustering algorithms have been proposed in the literature. Some of these include Fuzzy C-Means (FCM), Intuitionistic Fuzzy C-Means (IFCM), Rough Fuzzy C-Means (RFCM) and Rough Intuitionistic Fuzzy C-Means (RIFCM). In this paper, we compare the accuracy and execution time of the fuzzy based clustering algorithms. The clustering algorithms are applied on an image dataset and their running time as well as accuracy is compared by varying the number of clusters. Our results show that there is a clear trade-off between execution time and accuracy of these clustering algorithms. Also, we apply these algorithms on two different diseased leaf images and compute the severity of the disease of the leaves
SPA+RPA approach to canonical and grandcanonical treatments of nuclear level densities
Using an exactly solvable pairing model Hamiltonian in the static path
approximation together with small-amplitude quantal fluctuation corrections in
random phase approximation (SPA+RPA), we have analyzed the behaviour of
canonical (number projected) and grandcanonical treatments of nuclear level
densities as a function of temperature and number of particles. For small
particle numbers at a low temperature, we find that though the grandcanonical
partition function in SPA+RPA approach is quite close to its exact value, the
small errors in its estimation causes significant suppression of level density
obtained using number projected partition function. The results are also
compared with the smoothed out exact values of level density. Within this model
study, it appears that due to saddle point approximation to multiple
Laplace-back transform, the grandcanonical treatment of level density at low
temperature may be reliable only for relatively large number of particles.Comment: 11 pages(LaTex), figure available by the author, accepted for
publication in Physics Letters
Temperature dependence of volume and surface symmetry energy coefficients of nuclei
AbstractThe thermal evolution of the energies and free energies of a set of spherical and near-spherical nuclei spanning the whole periodic table are calculated in the subtracted finite-temperature ThomasâFermi framework with the zero-range Skyrme-type KDE0 and the finite-range modified SeylerâBlanchard interaction. The calculated energies are subjected to a global fit in the spirit of the liquid-drop model. The extracted parameters in this model reflect the temperature dependence of the volume symmetry and surface symmetry coefficients of finite nuclei, in addition to that of the volume and surface energy coefficients. The temperature dependence of the surface symmetry energy is found to be very substantial whereas that of the volume symmetry energy turns out to be comparatively mild
Anatomy of nuclear shape transition in the relativistic mean field theory
A detailed microscopic study of the temperature dependence of the shapes of
some rare-earth nuclei is made in the relativistic mean field theory. Analyses
of the thermal evolution of the single-particle orbitals and their occupancies
leading to the collapse of the deformation are presented. The role of the
non-linear field on the shape transition in different nuclei is also
investigated; in its absence the shape transition is found to be sharper.Comment: REVTEX file (13pages), 12 figures, Phys. Rev. C(in press),
\documentstyle[aps,preprint]{revtex
On the angular momentum dependence of nuclear level densities
Angular momentum dependence of nuclear level densities at finite temperatures
are investigated in the static path approximation(SPA) to the partition
function using a cranked quadrupole interaction Hamiltonian in the following
three schemes: (i) cranking about x-axis, (ii) cranking about z-axis and (iii)
cranking about z-axis but correcting for the orientation fluctuation of the
axis. Performing numerical computations for an and a shell nucleus,
we find that the x-axis cranking results are satisfactory for reasonably heavy
nuclei and this offers a computationally faster method to include the angular
momentum dependence at high temperatures in the SPA approach. It also appears
that at high spins inclusion of orientation fluctuation correction would be
important.Comment: 19 Latex pages, 9 figures(available upon request
Thermal shape fluctuation effects in the description of hot nuclei
The behavior of several nuclear properties with temperature is analyzed
within the framework of the Finite Temperature Hartree-Fock-Bogoliubov (FTHFB)
theory with the Gogny force and large configuration spaces. Thermal shape
fluctuations in the quadrupole degree of freedom, around the mean field
solution, are taken into account with the Landau prescription. As
representative examples the nuclei Er, Dy and Hg are
studied. Numerical results for the superfluid to normal and deformed to
spherical shape transitions are presented. We found a substantial effect of the
fluctuations on the average value of several observables. In particular, we get
a decrease in the critical temperature () for the shape transition as
compared with the plain FTHFB prediction as well as a washing out of the shape
transition signatures. The new values of are closer to the ones found in
Strutinsky calculations and with the Pairing Plus Quadrupole model Hamiltonian.Comment: 17 pages, 8 Figure
Optimization of relativistic mean field model for finite nuclei to neutron star matter
We have optimized the parameters of extended relativistic mean-field model
using a selected set of global observables which includes binding energies and
charge radii for nuclei along several isotopic and isotonic chains and the
iso-scalar giant monopole resonance energies for the Zr and Pb
nuclei. The model parameters are further constrained by the available
informations on the energy per neutron for the dilute neutron matter and bounds
on the equations of state of the symmetric and asymmetric nuclear matter at
supra-nuclear densities. Two new parameter sets BSP and IUFSU* are obtained,
later one being the variant of recently proposed IUFSU parameter set. The BSP
parametrization uses the contributions from the quartic order cross-coupling
between and mesons to model the high density behaviour of the
equation of state instead of the meson self-coupling as in the case of
IUFSU* or IUFSU. Our parameter sets yield appreciable improvements in the
binding energy systematics and the equation of state for the dilute neutron
matter. The importance of the quartic order cross coupling term
of the extended RMF model, as often ignored, is realized.Comment: 22 pages, 11 figures, Nucl. Phys. A (in press
Nuclear matter incompressibility coefficient in relativistic and nonrelativistic microscopic models
We systematically analyze the recent claim that nonrelativistic and
relativistic mean field (RMF) based random phase approximation (RPA)
calculations for the centroid energy E_0 of the isoscalar giant monopole
resonance yield for the nuclear matter incompressibility coefficient, K_{nm},
values which differ by about 20%. For an appropriate comparison with the RMF
based RPA calculations, we obtain the parameters for the Skyrme force used in
the nonrelativistic model by adopting the same procedure as employed in the
determination of the NL3 parameter set of an effective Lagrangian used in the
RMF model. Our investigation suggest that the discrepancy between the values of
K_{nm} predicted by the relativistic and nonrelativistic models is
significantly less than 20%.Comment: Revtex file (13 pages), appearing in PRC-Rapid Com
Heat capacity and pairing transition in nuclei
A simple model based on the canonical-ensemble theory is outlined for hot
nuclei. The properties of the model are discussed with respect to the Fermi gas
model and the breaking of Cooper pairs. The model describes well the
experimental level density of deformed nuclei in various mass regions. The
origin of the so-called S-shape of the heat capacity curve Cv(T) is discussed.Comment: 6 pages + 8 figure
Mirror displacement energies and neutron skins
A gross estimate of the neutron skin [0.80(5) fm] is extracted from
experimental proton radii, represented by a four parameter fit, and observed
mirror displacement energies (CDE). The calculation of the latter relies on an
accurately derived Coulomb energy and smooth averages of the charge symmetry
breaking potentials constrained to state of the art values. The only free
parameter is the neutron skin itself. The Nolen Schiffer anomaly is reduced to
small deviations (rms=127 keV) that exhibit a secular trend. It is argued that
with state of the art shell model calculations the anomaly should disappear.
Highly accurate fits to proton radii emerge as a fringe benefit.Comment: 4 pages 3 figures, superseeds first part of nucl-th/0104048 Present
is new extended version: 5 pages 4 figures. Explains more clearly the
achievements of the previous on
- âŠ