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951.
The spallation yield of neutrons and other mass fragments produced in 800 MeV proton induced reaction on208Pb have been calculated in the framework of quantum molecular dynamics (QMD) model. The energy spectra and angular distribution
have been calculated. Also, multiplicity distributions of the emitted neutrons and kinetic energy carried away by them have
been estimated and compared with the available experimental data. The agreement is satisfactory. A major contribution to the
neutron emission comes from statistical decay of the fragments. For mass and charge distributions of spallation products the
QMD process gives rise to target-like and projectile-like fragments only. 相似文献
952.
C. Y. Ryu C. H. Hyun S. W. Hong B. K. Jennings 《The European Physical Journal A - Hadrons and Nuclei》2005,24(1):149-157
We investigate the properties of the neutron star with relativistic mean-field models. We incorporate in the quantum hadrodynamics and in the quark-meson coupling models a possible reduction of meson masses in nuclear matter. The equation of state for neutron star matter is obtained and is employed in Oppenheimer-Volkov equation to extract the maximum mass of the stable neutron star. We find that the equation of state, the composition and the properties of the neutron stars are sensitive to the values of the meson masses in medium. 相似文献
953.
Neutron stars with isovector scalar correlations 总被引:1,自引:0,他引:1
B.?Liu H.?Guo M.?Di ToroEmail author V.?Greco 《The European Physical Journal A - Hadrons and Nuclei》2005,25(2):293-298
Neutron stars with the isovector scalar δ-field are studied in the framework of the relativistic mean-field (RMF) approach in a pure-nucleon-plus-lepton scheme. The δ-field leads to a larger repulsion in dense neutron-rich matter and to a definite splitting of proton and neutron effective masses. Both features are influencing the stability conditions of the neutron stars. Two parametrizations for the effective nonlinear Lagrangian density are used to calculate the nuclear equation of state (EOS) and the neutron star properties, and compared to correlated Dirac-Brueckner results. We conclude that in order to reproduce reasonable nuclear structure and neutron star properties within a RMF approach, a density dependence of the coupling constants is required. 相似文献
954.
In this work,the neutron radiation field at Heavy Ion Research Facility in Lanzhou (HIRFL) was investigated.Total neutron yields,spectra and angular distributions in the bombardment of various thick targets by 12C and 18O ions with energies up to 75 MeV/u were obtained using the activation method.The neutron dose equivalent rates of 60 MeV/u 18O on various thick targets at different angles were measured with a modified A-B remmeter.Our results are compared with those of other reports. 相似文献
955.
Using the isospin- and momentum-dependent hadronic transport model IBUU04, we have in-vestigated the influence of the entrance-channel isospin asymmetry on the sensitivity of the pre-equilibrium neutron/proton ratio to symmetry energy in central heavy-ion collisions induced by high-energy radioactive beams. Our analysis and discussion are based on the dynamical simulations of the three isotopic reaction systems 132Sn+124Sn, 124Sn+112Sn and 112Sn+112Sn which are of the same total proton number but different isospin asymmetry. We find that the kinetic-energy distributions of the pre-equilibrium neutron/proton ratio are quite sensitive to the density-dependence of symmetry energy at incident beam energy E/A = 400 MeV,and the sensitivity increases as the isospin asymmetry of the reaction system increases. 相似文献
956.
K. Oda Y. Imasaka K. Tsukahara T. Yamauchi Y. Nakane Y. Yamaguchi 《Radiation measurements》2003,36(1-6):119-124
The effect of radiators supplying charged particles to plastic nuclear track detectors has been investigated both experimentally and theoretically in order to apply them to personal dosimeters for high-energy neutrons. Performance of four types of radiator materials, CH2, CD2 (deuterized hydrocarbon), LiF (lithium fluoride) and C (graphite), was checked in a quasi-monoenergetic neutron field generated by p-Li reactions. The efficiency has been numerically calculated based on a model with a special attention to the angular dependence of cross sections and data of characteristic response to light ions. The effect of respective radiator candidates has been evaluated as a function of the neutron energy. A two-layer radiator has also been proposed to adjust the energy dependence of the relative sensitivity to conversion factor for dose-equivalent. 相似文献
957.
The microemulsions formed in the 4-component system water-potassium oleate-hexanol-dodecane have been investigated by time-average light scattering and small angle neutron scattering. A constant volume fraction ratio water: potassium oleate of 1.44 was used and at this constant composition, which gave a pseudo 3-component system, a wide region of the microemulsion domain was examined. In order to interpret the scattering data at finite volume fractions of the dispersed phase, water, allowance had to be made for interactions between the water-in-oil microemulsion droplets. This was carried out using a hard sphere model for the interaction. It is shown that using this model self-consistent results are obtained by light scattering and neutron scattering and an estimate can be made of the size of the particles in concentrated colloidal dispersions. 相似文献
958.
Fred Brauer 《Natural Resource Modeling》1987,2(2):259-278
We formulate a Volterra integral equation which contains as special cases the differential-difference equation model of Blythe, Gurney and Nisbet for populations with delayed recruitment and a differential-difference equation with two delays related to the epidemic model of Wilson and Burke. We establish upper and lower bounds for positive solutions and give a classification of equilibria with conditions to determine whether an equilibrium is stable for all delays (absolutely stable), unstable for all delays, or switches from stable to unstable as the delay increases. 相似文献
959.
M. C. A. Donkersloot 《Journal of solution chemistry》1979,8(4):293-307
With the help of the Kirkwood-Buff theory of liquid mixtures it is demonstrated that there is a close relationship between, on the one hand, x-ray and neutron scattering intensities from liquid mixtures and, on the other hand, certain thermodynamic properties of the systems considered. This relationship can be utilized without having to specify the intermolecular interaction potential and without having to perform computer simulation calculations. In the present paper the Kirkwood-Buff theory is applied to liquid water and to the binary systems H2O/MeOH, H2O/EtOH, and cyclohexane/2,3-dimethyl-butane. On the basis of these examples it is explained that, from the thermodynamic quantities used, the detailed shape of the various molecular radial distribution functions cannot be established. However, in principle this information could well be obtained from the x-ray and neutron scattering intensities of the liquids that are being studied, provided an acceptable procedure could be found to isolate the different radial distribution functions. In this respect the information extracted from thermodynamic data would be essential since, in the first place, it provides a valuable way of normalization of the scattered intensity, and, in the second place, for multicomponent liquids it puts forward specific conditions to be satisfied by the various radial distribution functions. 相似文献
960.
Neutron scattering of cold neutrons from liquid silane at 137° K and 98°K is explained on the basis of a simple model. The
rotational diffusion constant,D
r, and the delay time,τ
0, after which rotational diffusion may be said to occur are derived on the basis of this model. At 137° K we getD
r=0.22×1013 sec−1 andτ
0=0.68×10−13 sec. At 98°KD
r (=0.06×1013 sec−1) is down by a factor of more than three butτ
0=(0.54×10−13 sec) shows only a small change. By comparison with data on liquid CH4 it is concluded that the law of corresponding states is not applicable for describing rotational dynamics of CH4 and SiH4. Rotational motions in SiH4 are more hindered than in CH4 at the same reduced temperature. 相似文献