Finite element assessment of the temperature field couple under joule heat and friction heat between a third rail and collector shoe

Based on the finite element software COMSOL Multiphysics 4.3b, a temperature field model for an aluminium/stainless steel composite third rail and a copper impregnated carbon collector shoe contact with coupling of joule heat and friction heat was established. A method of coupling the two kinds of heat was developed, the temperature fields were calculated, and the maximum coupled temperature change under different electric current, normal forces, sliding velocities and sliding distances were studied. The results show that the temperature distribution expands around the contact area in a descending tendency at positions closer to the electric contact area and the temperature gradients are higher; the maximum coupled temperature increases with an increase of electric current; with an increase of normal force, the maximum coupled temperature initially decreases then increases; the maximum coupled temperature increases initially then gradually becomes stable with an increase of sliding distance; an optimal normal force range exists in frictional sliding with an electric current, at which the maximum coupled temperature is at its lowest; joule heat and friction heat are competitive with each other. When normal force is lower, the joule heat becomes the main heat source, but when normal force is greater, mechanical friction heat becomes the main heat source

Effects of oxygen adsorption on carbon nanotube field emitters

Effects of oxygen adsorption on the field emission of carbon nanotubes are studied through first-principles calculations. Calculated emission currents are significantly enhanced when oxygen is adsorbed at the tip and the underlying physics is explained in terms of the change in the electronic structure by oxidation and the local field increase at the adsorption site. The issue of the current degradation accompanied by the oxidative etching is also addressed. The field-emission-microscopy images on the phosphor screen are simulated, displaying various patterns characteristic of each adsorption configuration.open546

Exploration of hyperfine interaction between constituent quarks via eta productions

In this work, the different exchange freedom, one gluon, one pion or Goldstone boson, in constituent quark model is investigated, which is responsible to the hyperfine interaction between constituent quarks, via the combined analysis of the eta production processes, $\pi^{-}p\rightarrow\eta n$ and $\gamma p\rightarrow\eta p$. With the Goldstone-boson exchange, as well as the one-gluon or one-pion exchange, both the spectrum and observables, such as, the differential cross section and polarized beam asymmetry, are fitted to the suggested values of Particle Data Group and the experimental data. The first two types of exchange freedoms give acceptable description of the spectrum and observables while the one pion exchange can not describe the observables and spectrum simultaneously, so can be excluded. The experimental data for the two processes considered here strongly support the mixing angles for two lowest S11 sates and D13 states as about -30 and 6 degree respectively.Comment: 7 pages, 4 figures, 4 table

Experimental study of neutron-rich nuclei 89Rb and 91Rb

Neutron-rich 89,91Rb nuclei populated as fission products in heavy-ion reactions have been studied with the Gammasphere array. The previously known level schemes have been extended to higher excitation energies and spins. Spin and parity assignments were based on angular correlation analyses. A value of T1/2 = 8(2) ns was extracted for the isomeric g9/2 state in 89Rb

Measurements of the Mass and Full-Width of the ηc\eta_c Meson

In a sample of 58 million $J/\psi$ events collected with the BES II detector, the process J/$\psi\to\gamma\eta_c$ is observed in five different decay channels: $\gamma K^+K^-\pi^+\pi^-$, $\gamma\pi^+\pi^-\pi^+\pi^-$, $\gamma K^\pm K^0_S \pi^\mp$ (with $K^0_S\to\pi^+\pi^-$), $\gamma \phi\phi$ (with $\phi\to K^+K^-$) and $\gamma p\bar{p}$. From a combined fit of all five channels, we determine the mass and full-width of $\eta_c$ to be $m_{\eta_c}=2977.5\pm1.0 ({stat.})\pm1.2 ({syst.})$ MeV/$c^2$ and $\Gamma_{\eta_c} = 17.0\pm3.7 ({stat.})\pm7.4 ({syst.})$ MeV/$c^2$.Comment: 9 pages, 2 figures and 4 table. Submitted to Phys. Lett.

Revised B(E3) transition rate and structure of the 3− level in 96Zr

The B(E3) transition strength from the 1897-keV, 3− level in 96Zr has been reevaluated from six high-statistics, independent data sets. The measured value of 42(3) W.u. is significantly lower than that adopted in recent compilations. It is, however, in line with the global systematics of collective B(E3) rates found throughout the periodic table. Thus, the “exceptional” character of this transition, that challenged theory, no longer applies. Monte Carlo shell-model calculations indicate that the collectivity of the octupole vibration arises from both proton and neutron excitations involving a large number of orbitals

Revised B(E3) transition rate and structure of the 3− level in 96Zr

The B(E3) transition strength from the 1897-keV, 3− level in 96Zr has been reevaluated from six high-statistics, independent data sets. The measured value of 42(3) W.u. is significantly lower than that adopted in recent compilations. It is, however, in line with the global systematics of collective B(E3) rates found throughout the periodic table. Thus, the “exceptional” character of this transition, that challenged theory, no longer applies. Monte Carlo shell-model calculations indicate that the collectivity of the octupole vibration arises from both proton and neutron excitations involving a large number of orbitals

A Measurement of Psi(2S) Resonance Parameters

Cross sections for e+e- to hadons, pi+pi- J/Psi, and mu+mu- have been measured in the vicinity of the Psi(2S) resonance using the BESII detector operated at the BEPC. The Psi(2S) total width; partial widths to hadrons, pi+pi- J/Psi, muons; and corresponding branching fractions have been determined to be Gamma(total)= (264+-27) keV; Gamma(hadron)= (258+-26) keV, Gamma(mu)= (2.44+-0.21) keV, and Gamma(pi+pi- J/Psi)= (85+-8.7) keV; and Br(hadron)= (97.79+-0.15)%, Br(pi+pi- J/Psi)= (32+-1.4)%, Br(mu)= (0.93+-0.08)%, respectively.Comment: 8 pages, 6 figure

Shape coexistence from lifetime and branching-ratio measurements in 68,70Ni

© 2016 The Author(s) Shape coexistence near closed-shell nuclei, whereby states associated with deformed shapes appear at relatively low excitation energy alongside spherical ones, is indicative of the rapid change in structure that can occur with the addition or removal of a few protons or neutrons. Near 68Ni (Z=28, N=40), the identification of shape coexistence hinges on hitherto undetermined transition rates to and from low-energy 0+ states. In 68,70Ni, new lifetimes and branching ratios have been measured. These data enable quantitative descriptions of the 0+ states through the deduced transition rates and serve as sensitive probes for characterizing their nuclear wave functions. The results are compared to, and consistent with, large-scale shell-model calculations which predict shape coexistence. With the firm identification of this phenomenon near 68Ni, shape coexistence is now observed in all currently accessible regions of the nuclear chart with closed proton shells and mid-shell neutrons

Multinucleon transfer in the interaction of 977 MeV and 1143 MeV Hg 204 with Pb 208

A previous study of symmetric collisions of massive nuclei has shown that current models of multinucleon transfer (MNT) reactions do not adequately describe the transfer product yields. To gain further insight into this problem, we have measured the yields of MNT products in the interaction of 977 (E/A=4.79 MeV) and 1143 MeV (E/A=5.60 MeV) Hg204 with Pb208. We find that the yield of multinucleon transfer products are similar in these two reactions and are substantially lower than those observed in the reaction of 1257 MeV (E/A=6.16 MeV) Hg204+Pt198. We compare our measurements with the predictions of the GRAZING-F, dinuclear systems (DNS), and improved quantum molecular dynamics (ImQMD) models. For the observed isotopes of the elements Au, Hg, Tl, Pb, and Bi, the measured values of the MNT cross sections are orders of magnitude larger than the predicted values. Furthermore, the various models predict the formation of nuclides near the N=126 shell, which are not observed