117 research outputs found
Segmentation algorithms of biomedical images: development and quantitative evaluation
The article presents the comparative analysis of the biomedical image segmentation methods. The work discusses segmentation methods on the basis of previous labeling and spatial moments. The experimental results show that the developed methods have higher accuracy by signal-noise ratio compared to the nowadays known. Moreover the authors have developed the quantitative evaluation of the segmentation algorithms based on the metrical approach.У статті представлений порівняльний аналіз методів сегментації біомедичних зображень. У роботі досліджуються методи сегментації на основі попередньої розмітки та просторових моментів. Експериментальні результати показують, що розроблені методи мають більш високу точність за співвідношенням сигнал-шум у порівнянні з відомими. Крім того, автори розробили алгоритм кількісної оцінки алгоритмів сегментації на основі метричного підходу.The proposed research has been developed within the state budget project "Hybrid Intelligent Information Technology Diagnosing of Precancerous Breast Cancer Based on Image Analysis" (state registration number 1016U002500)
Ratio of shear viscosity to entropy density in multifragmentation of Au + Au
The ratio of the shear viscosity () to entropy density () for the
intermediate energy heavy-ion collisions has been calculated by using the
Green-Kubo method in the framework of the quantum molecular dynamics model. The
theoretical curve of as a function of the incident energy for the
head-on Au+Au collisions displays that a minimum region of has been
approached at higher incident energies, where the minimum value is
about 7 times Kovtun-Son- Starinets (KSS) bound (1/4). We argue that the
onset of minimum region at higher incident energies corresponds to the
nuclear liquid gas phase transition in nuclear multifragmentation.Comment: 6 pages, 8 figure
Liquid-Drop Model and Quantum Resistance Against Noncompact Nuclear Geometries
The importance of quantum effects for exotic nuclear shapes is demonstrated.
Based on the example of a sheet of nuclear matter of infinite lateral
dimensions but finite thickness, it is shown that the quantization of states in
momentum space, resulting from the confinement of the nucleonic motion in the
conjugate geometrical space, generates a strong resistance against such a
confinement and generates restoring forces driving the system towards compact
geometries. In the liquid-drop model, these quantum effects are implicitly
included in the surface energy term, via a choice of interaction parameters, an
approximation that has been found valid for compact shapes, but has not yet
been scrutinized for exotic shapes.Comment: 9 pages with 3 figure
Mass independence and asymmetry of the reaction: Multi-fragmentation as an example
We present our recent results on the fragmentation by varying the mass
asymmetry of the reaction between 0.2 and 0.7 at an incident energy of 250
MeV/nucleon. For the present study, the total mass of the system is kept
constant (ATOT = 152) and mass asymmetry of the reaction is defined by the
asymmetry parameter (? = | (AT - AP)/(AT + AP) |). The measured distributions
are shown as a function of the total charge of all projectile fragments,
Zbound. We see an interesting outcome for rise and fall in the production of
intermediate mass fragments (IMFs) for large asymmetric colliding nuclei. This
trend, however, is completely missing for large asymmetric nuclei. Therefore,
experiments are needed to verify this prediction
Antibaryons in massive heavy ion reactions: Importance of potentials
In the framework of RQMD we investigate antiproton observables in massive
heavy ion collisions at AGS energies and compare to preliminary results of the
E878 collaboration. We focus here on the considerable influence of the *real*
part of an antinucleon--nucleus optical potential on the antiproton momentum
spectra
Consequences of a covariant Description of Heavy Ion Reactions at intermediate Energies
Heavy ion collisions at intermediate energies are studied by using a new RQMD
code, which is a covariant generalization of the QMD approach. We show that
this new implementation is able to produce the same results in the
nonrelativistic limit (i.e. 50MeV/nucl.) as the non-covariant QMD. Such a
comparison is not available in the literature. At higher energies (i.e. 1.5
GeV/nucl. and 2 GeV/nucl.) RQMD and QMD give different results in respect to
the time evolution of the phase space, for example for the directed transverse
flow. These differences show that consequences of a covariant description of
heavy ion reactions within the framework of RQMD are existing even at
intermediate energies.Comment: LaTex-file, 28 pages, 8 figures (available upon request), accepted
for publication in Physical Review
Subthreshold antiproton production in proton-carbon reactions
Data from KEK on subthreshold antiproton as well as on pi(+-) and K(+-)
production in proton-nucleus reactions are described at projectile energies
between 3.5 and 12.0 GeV. We use a model which considers a hadron-nucleus
reaction as an incoherent sum over collisions of the projectile with a varying
number of target nucleons. It samples complete events and allows thus for the
simultaneous consideration of all particle species measured. The overall
reproduction of the data is quite satisfactory. It is shown that the
contributions from the interaction of the projectile with groups of several
target nucleons are decisive for the description of subthreshold production.
Since the collective features of subthreshold production become especially
significant far below the threshold, the results are extrapolated down to COSY
energies. It is concluded that an antiproton measurement at ANKE-COSY should be
feasible, if the high background of other particles can be efficiently
suppressed.Comment: 15 pages, 5 figures, gzipped tar file, submitted to J. Phys. G v2:
Modification of text due to demands of referee
Medium effects in high energy heavy-ion collisions
The change of hadron properties in dense matter based on various theoretical
approaches are reviewed. Incorporating these medium effects in the relativistic
transport model, which treats consistently the change of hadron masses and
energies in dense matter via the scalar and vector fields, heavy-ion collisions
at energies available from SIS/GSI, AGS/BNL, and SPS/CERN are studied. This
model is seen to provide satisfactory explanations for the observed enhancement
of kaon, antikaon, and antiproton yields as well as soft pions in the
transverse direction from the SIS experiments. In the AGS heavy-ion
experiments, it can account for the enhanced ratio, the difference
in the slope parameters of the and transverse kinetic energy
spectra, and the lower apparent temperature of antiprotons than that of
protons. This model also provides possible explanations for the observed
enhancement of low-mass dileptons, phi mesons, and antilambdas in heavy-ion
collisions at SPS energies. Furthermore, the change of hadron properties in hot
dense matter leads to new signatures of the quark-gluon plasma to hadronic
matter transition in future ultrarelativistic heavy-ion collisions at RHIC/BNL.Comment: RevTeX, 65 pages, including 25 postscript figures, invited topical
review for Journal of Physics G: Nuclear and Particle Physic
Rapidity distribution as a probe for elliptical flow at intermediate energies
Interplay between the spectator and participant matter in heavy-ion
collisions is investigated within isospin dependent quantum molecular dynamics
(IQMD) model in term of rapidity distribution of light charged particles. The
effect of different types and size rapidity distributions is studied in
elliptical flow. The elliptical flow patterns show important role of the nearby
spectator matter on the participant zone. This role is further explained on the
basis of passing time of the spectator and expansion time of the participant
zone. The transition from the in-plane to out-of-plane is observed only when
the mid-rapidity region is included in the rapidity bin, otherwise no
transition occurs. The transition energy is found to be highly sensitive
towards the size of the rapidity bin, while weakly on the type of the rapidity
distribution. The theoretical results are also compared with the experimental
findings and are found in good agreement.Comment: 8 figure
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