116 research outputs found
Radial flow of kaon mesons in heavy ion reactions
This work investigates the collective motion of kaons in heavy ion reactions
at SIS energies (about 1-2 GeV/nucleon). A radial collective flow of
mesons is predicted to exist in central Au + Au collisions, which manifests in
a characteristic "shoulder-arm" shape of the transverse mass spectrum of the
midrapidity mesons. The radial flow arises from the repulsive
mean field in nuclear matter. In spite of a strong reabsorption and
rescattering the attractive mean field leads as well to a collective
radial flow of mesons. The radial flow, however, is different from
that of mesons and can be observed by a characteristic "concave"
structure of the transverse mass spectrum of the mesons emitted at
midrapidity. The kaon radial flows can therefore serve as a novel tool for the
investigation of kaon properties in dense nuclear matter.Comment: 30 pages RevTex, 5 PS figures, accepted for publication in Phys. Rev.
In-medium dependence and Coulomb effects of the pion production in heavy ion collisions
The properties of the high energy pions observed in heavy ion collisions, in
particular in the system Au on Au at 1 GeV/nucleon are investigated. The
reaction dynamics is described within the Quantum Molecular Dynamics (QMD)
approach. It is shown that high energy pions freeze out early and originate
from the hot, compressed matter. --resonances are found to give an
important contribution toward the high energy tail of the pion. Further the
role of in-medium effects in the description of charged pion yields and spectra
is investigated using a microscopic potential derived from the Brueckner
G-matrix which is obtained with the Reid soft-core potential. It is seen that
the high energy part of the spectra is relatively more suppressed due to
in-medium effects as compared to the low energy part. A comparision to
experiments further demonstrates that the present calculations describe
reasonably well the neutral (TAPS) and charged (FOPI) pion spectra. The
observed energy dependence of the ratio, i.e. deviations from the
isobar model prediction, is due to Coulomb effects and again indicate that high
energy pions probe the hot and dense phase of the reaction. These findings are
confirmed independently by a simple phase space analysis.Comment: 28 pages Latex, prepared with elsevier-style, 13 PS-figure
Painlev\'e Analysis, Prelle-Singer Approach, Symmetries and Integrability of Damped H\'enon-Heiles System
We consider a modified damped version of H\'enon-Heiles system and
investigate its integrability. By extending the Painlev\'e analysis of ordinary
differential equations we find that the modified H\'enon-Heiles system
possesses the Painlev\'e property for three distinct parametric restrictions.
For each of the identified cases, we construct two independent integrals of
motion using the well known Prelle-Singer method. We then derive a set of
nontrivial non-point symmetries for each of the identified integrable cases of
the modified H\'enon-Heiles system. We infer that the modified H\'enon-Heiles
system is integrable for three distinct parametric restrictions. Exact
solutions are given explicitly for two integrable cases.Comment: Accepted for publication in Journal of Mathematical Physic
Effect of chemicals treatment and fiber loading on mechanical properties of borassus (Toddy palm) fiber/epoxy composites
Abstract: The aim of the present study was to investigate and compare the mechanical properties of untreated and chemically modified Borassus fiber reinforced epoxy composites. Composites were prepared by hand lay-up process by reinforcing Borassus fibers with epoxy matrix. To improve the fiber-matrix adhesion properties, alkali (NaOH), and alkali combined with silane (3- aminopropyltriethoxysilane) treatments on the fibers surface were carried out. Examinations through Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were conducted to investigate the structural and physical properties of the Borassus fibers. Tensile properties such as modulus and strength of the composites made by chemically modified and untreated Borassus fibers were studied using a Universal Testing Machine (UTM). Based on the experimental results, it was found that the tensile properties of the Borassus reinforced epoxy composites were significantly improved, as compared with the neat epoxy. It was also found that the fiber treated with combination of alkali and silane exhibited superior mechanical properties as compared with alkali and untreated fiber composites. The nature of fiber/matrix interface was examined through SEM of cryo-fractured samples. Chemical resistance of composites was also found to be improved with chemically modified fiber composites
Preparation and properties of biodegradable spent tea leaf powder/poly(propylene carbonate) composite films
Abstract: The aim of the present work is to develop novel biobased lightweight material with improved tensile and thermal properties. Spent tea leaf powder (STLP) is used as a filler to improve the tensile and thermal properties of polypropylene carbonate (PPC). Tea is an important material of hotels and household and spent tea leaf forms a conjugal solid waste. Composite films are obtained by solution casting method. These films are characterized by Optical microscopy, scanning electron microscopy, Fourier transforms infrared spectroscopy, thermogravimetric analysis and tensile testing to examine the effect of filler content on the properties of the composites. The results have shown that composite films are having increased tensile strength due to enhanced interfacial adhesion between the filler and the matrix. In addition, the composite films have also exhibited higher thermal degradation temperatures compared to pure polypropylene carbonate. The morphology results indicate that there is a good interface interaction between STLP and PPC. Results of the study reveal STLP to be a promising green filler for polymer plastics
D' Production in Heavy Ion Collisions
The production of d' dibaryons in heavy ion collisions due to the elementary
process NN -> d' + pion is considered. The cross section NN -> d' + pion is
estimated using the vacuum d' width = 0.5 MeV extracted from data on the double
charge exchange reactions on nuclei. The d' production rate per single
collision of heavy ions is estimated at an incident beam energy of 1 A GeV
within the framework of the Quantum Molecular Dynamics transport model. We
suggest to analyse the invariant mass spectrum of the NN + pion system in order
to search for an abundance of events with the invariant mass of the d'
dibaryon. The d' peak is found to exceed the statistical fluctuations of the
background at a level of 6 standard deviations for 2 10^5 A central collisions
of heavy ions with the atomic number A.Comment: 29 pages including 7 figures, REVTe
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