Probing the Dissipation Mechanism in Ternary Reactions of ^197Au＋^197Au by Mean Free Path of Nucleons

the collision of very heavy nuclei ^197Au＋^197Au at 15AMeV has been studied within the improved quantum molecular dynamics model. A class of ternary events satisfying nearly complete balance of mass numbers is selected. The experimental mass distributions for the system ^197Au＋^197Au ternary fission fragments, the heaviest（A1）, the intermediate （A2） and the lightest （A3）, are reproduced well. The mean free path of nucleons in the reaction system is studied and the shorter mean free path is responsible for the ternary fission with three mass comparable fragments, in which the two-body dissipation mechanism plays a dominant role.     

Approach to Phonon Relaxation Time and Mean Free Path in Nonlinear Lattices

Based on the self-consistent phonon theory,the spectral energy density is calculated by the canonical transformation and the Fourier transformation.Through fitting the spectral energy density by the Lorentzian profile,the phonon frequency as well as the phonon relaxation time is obtained in one-dimensional nonlinear lattices,which is validated in the Fermi-Pasta-Ulam-β(FPU-β) and φ~4 lattices at different temperatures.The phonon mean free path is then evaluated in terms of the phonon relaxation time and phonon group velocity.The results show that,in the FPU-β lattice,the phonon mean free path as well as the phonon relaxation time displays divergent power-law behavior.The divergent exponent coincides well with that derived from the Peierls-Boltzmann theory at weak anharmonic nonlinearity.The value of the divergent exponent expects a power-law divergent heat conductivity with system size,which violates Fourier's law.For the φ~4 lattice,both the phonon relaxation time and mean free path are finite,which ensures normal heat conduction.     

Determination of Inelastic Mean Free Path by Electron Holography Along with Electron Dynamic Calculation

Off-axis electron holography in a field emission gun transmission-electron microscope and electron dynamic calculation are used to determine the absorption coefficient and inelastic mean free path(IMFP) of copper. Dependence of the phase shift of the exit electron wave on the specimen thickness is established by electron dynamic simulation. The established relationship makes it possible to determine the specimeu thickness with the calculated phase shift by match of the phase shift measured in the reconstructed phase image. Based on the measured amplitudes in reconstructed exit electron wave and reference wave in the vacuum, the examined IMFP of electron with energy of 200kV in Cu is obtained to be 96nm.     

Studying Validity of Single-Fluid Model in Inertial Confinement Fusion

The validity of single-fluid model in inertial confinement fusion simulations is studied by comparing the results of the multi- and single-fluid models. The multi-fluid model includes the effects of collision and interpenetration between fluid species. By simulating the collision of fluid species, steady-state shock propagation into the thin DT gas and expansion of hohlraum Au wall heated by lasers, the results show that the validity of single-fluid model is strongly dependent on the ratio of the characteristic length of the simulated system to the particle mean free path. When the characteristic length L is one order larger than the mean free path A, the single-fluid model＇s results are found to be in good agreement with the multi-fluid model＇s simulations, and the modeling of single-fluid remains valid. If the value of L/A is lower than 10, the interpenetration between fluid species is significant, and the single-fluid simulations show some unphysical results; while the multi-fluid model can describe well the interpenetration and mix phenomena, and give more reasonable results.     

Rarefied Gas Flow in Rough Microchannels by Molecular Dynamics Simulation

The molecular dynamics simulation method is applied to investigate the rarefied gas flow in a submicron channel with surface roughness which is modelled by an array of triangle modules. The boundary conditions are found to be determined not only by the Knudsen number but also the roughness, which implies that the breakdown of the Maxwell slip model under the conditions that the surface roughness is comparable to the molecular mean free path. The effects of the rarefaction and the surface roughness on the boundary conditions and the flow characteristics are strongly coupled. The flow friction increases with increasing roughness and with decreasing Knudsen number.     

Can a Higgs boson be produced at the LHC?

A simple model is designed to simulate, by using the mean free path method, the probability of Higgs boson production at the Large Hadron Collider (LHC). The probability that the colliding particles could get close to a given distance with different colliding energies is discussed in this model. Calculated results imply that the probability of producing a Higgs boson is near zero according to the existing theoretical mechanism for Higgs boson production.     

Microscopic calculation of the magnetic field of neutron stars

Based on the Dirac equation describing an electron moving in a uniform and cylindrically symmetric magnetic field which may be the result of the self-consistent mean field of the electrons themselves in a neutron star, we have obtained the eigen solutions and the orbital magnetic moments of electrons in which each eigen orbital can be calculated. From the eigen energy spectrum we find that the lowest energy level is the highly degenerate orbitals with the quantum numbers pz = 0, n = 0, and m ≥0. At the ground state, the electrons fill the lowest eigen states to form many Landau magnetic cells and each cell is a circular disk with the radius λfree and the thickness λe, where λfree is the electron mean free path determined by Coulomb cross section and electron density and λe is the electron Compton wavelength. The magnetic moment of each cell and the number of cells in the neutron star are calculated, from which the total magnetic moment and magnetic field of the neutron star can be calculated. The results are compared with the observational data and the agreement is reasonable.     

Bow shocks formed by a high-speed laser-driven plasma cloud interacting with a cylinder obstacle

A bow shock is formed in the interaction of a high-speed laser-driven plasma cloud with a cylinder obstacle. Its temporal and spatial structures are observed by shadowgraphy and interferometry. The width of the shock transition region is ～ 50 μm, comparable to the ion–ion collision mean free path, which indicates that collision is dominated in the shock probably. The Mach-number of the ablating plasma cloud is ～ 15 at first, and decreases with time resulting in a changing shock structure. A two-dimension hydrodynamics code, USim, is used to simulate the interaction process. The simulated shocks can well reproduce the observed.     

Effect of surface morphology on the electron mobility of epitaxial graphene grown on 0° and 8° Si-terminated 4H-SiC substrates

Graphene with different surface morphologies were fabricated on 8° -off-axis and on-axis 4H-SiC(0001) substrates by high-temperature thermal decompositions. Graphene grown on Si-terminated 8° -off-axis 4H-SiC(0001) shows lower Hall mobility than the counterpart of on-axis SiC substrates. The terrace width is not responsible for the different electron mobility of graphene grown on different substrates, as the terrace width is much larger than the mean free path of the electrons. The electron mobility of graphene remains unchanged with an increasing terrace width on Siterminated on-axis SiC. Interface scattering and short-range scattering are the main factors affecting the mobility of epitaxial graphene. After the optimization of the growth process, the Hall mobility of the graphene reaches 1770 cm 2 /V·s at a carrier density of 9.8.×10 12 cm 2 . Wafer-size graphene was successfully achieved with an excellent double-layer thickness uniformity of 89.7% on a 3-inch SiC substrate.     

A Simple Systematical Law of E2＋ Values for Heavy Nuclei in the NpNn Scheme and the Evolution of the Z=64 Shell Gap

A systematics of excitation energy of the first 2^＋ state E2＋ in even-even heavy nuclei （A ≥ 120） is studied in the NpNn scheme. It is found that a simple exponential function describes the dependence of E2＋ values on NpNn values very well. In addition, the Z = 64 shell gap is reexamined by investigating the systematics of the 52 ≤ Z ≤66 region. It is found that the Z = 64 shell gap is largest at N = 82 and becomes smMler with either increasing or decreasing of neutron numbers. The effects of this shell gap become negligible for counting the valence proton numbers when N ≥ 92 or N ≤ 72.     

Experimental Investigation on MHD Instabilities of Free Surface Jet and Film Flow for Liquid Metal Divertor/Limiter Options

1 Introduction Recently, it is rising of the study of liquid metal free surface as the divertor, limiter and the first wall in a fusion device. Many special facilities are employed to investigate MHD-related issues of free surface jet and film flow, and many results are carried out on theory and experiments . But, there are still not enough experimental data to well understand magneto- hydrodynamics （MHD） instability. For theory, the greatest challenge is how to develop a modeling to expect and understand free surface MHD phenomenon, and for experiments is how to diagnose the flow state of liquid metal free surface flow in magnetic field.     

Electromagnetic dissociation of 3.7 A GeV^16O in nuclear emulsion

The electromagnetic dissociation (ED) of 3.7 A GeV {}^{16}O in nuclear emulsion is investigated with high statistics. It is found that the electromagnetically dissociated cross section increases with increasing beam energy, the charge distribution of projectile fragments is the same as the results at 60 and 200 A GeV, and the production probability of projectile fragments with charge 3≤Z≤5 is less than that of the other projectile fragments. These results can be well explained by use of Weizsacker and Williams method for calculating the ED contributions. The percentile abundance of various decay modes for ED at 3.7 A GeV is close to the result at 60 and 200 A GeV, but it is different from the result at 14.6 A GeV. The ED of 3.7 A GeV is mainly caused by the giant dipole and quadrupole resonance of E1 and E2, which can be qualitatively explained by the multiplicity distribution of projectile proton in ED. The multiplicity distribution of the α fragments in ED and nuclear events have different functional forms. This difference may be a consequence of the different reaction mechanism involved.     

Performance analysis of FXLMS algorithm with secondary path modeling error

Performance analysis of filtered-X LMS(FXLMS) algorithm with secondary path modeling error is carried out in both time and frequency domain.It is shown firstly that the effects of secondary path modeling error on the performance of FXLMS algorithm are determined by the distribution of the relative error of secondary path model along with frequency.In case of that the distribution of relative error is uniform the modeling error of secondary path will have no effects on the performance of the algorithm.In addition,a limitation property of FXLMS algorithm is proved,which implies that the negative effects of secondary path modeling error can be compensated by increasing the adaptive filter length.At last,some insights into the “spillover“ phenomenon of FXLMS algorithm are given.     

Asymmetric diffusion model for oblique-incidence reflectometry

A diffusion theory model induced by a line source distribution is presented for oblique-incidence reflectometry.By fitting to this asymmetric diffusion model,the absorption and reduced scattering coefficients μa and μ’s of the turbid medium can both be determined with accuracy of 10% from the absolute profile of the diffuse reflectance in the incident plane at the negative position-1.5 transport mean free path(mfp’) away from the incident point;particularly,μs’ can be estimated from the data at positive positions within 0-1.0 mfp’ with 10% accuracy.The method is verified by Monte Carlo simulations and experimentally tested on a phantom.     

Optical and electrical characterizations of nanoparticle Cu2S thin films

Copper sulfide thin films are deposited onto different substrates at room temperature using the thermal evaporation technique. X-ray diffraction spectra show that the film has an orthorhombicchalcocite （7-Cu2S） phase. The atomic force microscopy images indicate that the film exhibits nanoparticles with an average size of nearly 44 nm. Specrtophotometric measurements for the transmittance and reflectance are carried out at normal incidence in a spectral wavelength range of 450 nm-2500 nm. The refractive index, n, as well as the absorption index, k is calculated. Some dispersion parameters are determined. The analyses of el and e2 reveal several absorption peaks. The analysis of the spectral behavior of the absorption coefficient, c~, in the absorption region reveals direct and indirect allowed transitions. The dark electrical resistivity is studied as a function of film thickness and temperature. Tellier＇s model is adopted for determining the mean free path and bulk resistance.     

A Solution of the DGLAP Equation for Gluon Distribution as a Function of F2 and dF2/dlnQ^2 at Low x： the Next-to-Leading Order Analysis

We obtain a solution of the DGLAP equation to extract the gluon distribution function from the deep inelastic structure function F2 and its derivative with respect to In Q^2 at low x in the next-to-leading order of perturbation theory. The values of the gluon distribution are found in the range 10^- 4 ≤ x ≤ 10^-2 at Q^2 = 20 GeV^2, We test its validity by comparing it with that of Glueck, Reya and Vogt. The detailed analysis is given for the HERA data.     

Electron inelastic mean free paths in solids: A theoretical approach

In the present paper, the inelastic mean free path (IMFP) of incident electrons is calculated as a function of energy for silicon (Si), oxides of silicon (SiO2 ), SiO, and Al2O3 in bulk form by employing atomic/molecular inelastic cross sections derived by using a semi-empirical quantum mechanical method developed earlier. A general agreement of the present results is found with most of the available data. It is of great importance that we have been able to estimate the minimum IMFP, which corresponds to the peak of inelastic interactions of incident electrons in each solid investigated. New results are presented for SiO, for which no comparison is available. The present work is important in view of the lack of experimental data on the IMFP in solids.     

POWER EMISSION OF A MONOPOLE IN REVERBERATION CHAMBERS

An exact sound power emission formula of a simple source in a reverberation chamber is derived fromnormal mode theory as a function of its position in the room,and important properties of the emission arefound from simple analyses.For example,the average emission of the source in the room is not equal to thefree space emission but greater,on the contrary to the common notion.A smooth statistical formula is alsoderived for the variation of average sound power in an axial direction,which holds even at low frequency atwhich the wave length approaches the mean free path in the room.The sound power is found to havenumerous peaks in the room forming a three-dimensional lattice structure with high power barriers aroundthe boundary walls.The space factor in an axial direction is essentially exact,but the general formula of poweremission formed with the product of space factors in three axial directions might have some error.Numericalexamples are presented to check this.The variability of sound power emission in     

Poloidal rotation of main ions in the CT-6B tokamak

The poloidal rotation velocity of neutral hydrogen atoms is measured using the Doppler shift of the Hα spectral line emitted in the CT-6B tokamak. The poloidal rotation of hydrogen atoms is generated through the collisions and charge-exchanges with main ions (protons). Therefore, the rotation direction of main ions can be deduced from that of neutral hydrogen atoms. The experimental results show that the main ions rotate in the electron diamagnetic drift direction, the same as the impurity ions, in the plasma core. The neutral hydrogen atoms rotate also in the electron diamagnetic drift direction in the edge region of the plasma. However, the rotation direction of main ions in the edge region cannot be judged from the experimental result due to the long mean free path of hydrogen atoms in the edge region. An inward diffusion flux of hydrogen atoms toward the torus inside with a velocity of the same order of magnitude as their poloidal rotation is also observed.     

Elastic wave scattering from rough free surfaces of solids

Elastic wave scattering by a rough free surface of solids is analyzed. The analysis is based on the concept of scattering amplitude (SA) and perturbation approximation. The SA method is very convenient for rough surface scattering problems. By solving the boundary equations, the first and the second order solutions of approximate scattering amplitude are obtained. The general solutions are used for, as an example, the wave scattering by rough surfaces with Gaussian distribution. The mean field and variance are given. Finally, an experiment is designed to verifv the theoretical predications.