Energy dissipation in the Nagel-Schreckenberg model with open boundary condition

In this paper, we numerically investigate energy dissipation caused by traffic in the Nagel-Schreckenberg (NaSch) model with open boundary conditions (OBC). Boundary results in excess energy dissipation. The effects of the stochastic boundary conditions on energy dissipation are discussed. The behaviors of energy dissipation in different traffic phase are distinct. As an order parameter, energy dissipation rate E _d characterizes the phase transition behaviors well. It is shown that there is no true free-flow state in nondeterministic NaSch model with OBC. We refer to this non-true free-flow state as quasi-free-flow (QFF) phase in which there are interactions between vehicles caused by stochastic braking but no backward moving jam exists. In the maximum current phase, E _d is minimal thus the social payoff is maximal. Energy dissipation profiles in QFF, jammed and maximum current phase are presented. Theoretical analyses are in good agreement with numerical results for the case v _max = 1.     

The relations of “go and stop” wave to car accidents in a cellular automaton with velocity-dependent randomization

In this paper we numerically study the probability P_ac of the occurrence of traffic accidents in the Nagel-Schreckenberg (NS) model with velocity-dependent randomization (VDR). Numerical results show that there is a critical density over which car accidents occur, but below which no car accidents happen. Different from the accident probability in the NS model, the accident probability in the VDR model monotonously decreases with increase of car density above the critical density. The value of the accident probability is only determined by the stochastic noise and the number of cars on road. In the stochastic VDR model with the speed limit v_max=1, no critical density exists and car accidents happen in the whole density region. The braking probabilities of standing cars and moving cars have different influences on the accident probability. A mean-field theory reveals that the accident probability is proportional to the mean density of “go and stop” wave per time step. Theoretical analyses give excellent agreement with numerical results in the VDR model.     

Secondary electron emission yield behaviour of polymers

The secondary electron emission yields of highly-insulating, thin polymer foils have been measured for incident primary beam energies, 50 ? E_p ? 2500 eV. The results follow closely a ‘universal’ reduced yield curve determined by the energy loss law, dE_p/dx = -A/E_p^n-1, where n = 2 and A is a constant proportional to the density of the solid, as predicted by the elementary theory of Lye and Dekker (1957). This behaviour remains true up to high primary beam energies and, as such, is unique to these low density solids.     

Temperature dependence of the energy separation between Γ and L minima in n-type GaSb

Energy separation ΔE_c between Λ and L minima of GaSb conduction band is deduced from temperature dependence of tunneling current in p−n junctions. ΔE_c is found to inceasing vx. temperature with a coefficient d(ΔE_c/dT) of about - 2.10^-4eV/dgK.     

Energy spectra of cosmic pions and nucleons at the top of the atmosphere

The production spectra of cosmic pions and their primaries have been derived from the experimental muon spectrum by using the theories of Barrettet al. and Feynman. The calculated pion production spectrum takes the formI(E _π)d E _π = 0.206E _π ^{? 2.65} d E _πper cm² sec str GeV in the energy range 3<E _π<1500 GeV and the nucleon spectrum follows the relationN(E _p)d E _p = 2.7 × 10⁴ (E _p/GeV)^2.65 d E _pper m² sec str GeV in the range 5 <E _p <3000 Gev.     

Intense deuteron beam investigation by activation yield-ratio technique

In this work, the intense deuteron beam from a plasma focus device is investigated by the activation yield-ratio technique. It is shown that boron-carbide (B₄C) and boron-nitride (BN) are complimentary targets for high energy deuteron beam studies. For deuteron spectra of the form dNd/dE∝E−n, when deuteron spectra decrease relatively gradually (n<6) BN is a better choice, while for the case of very rapidly decreasing deuteron spectra (n>6), B₄C is more suitable.     

Isothermal adsorption kinetics on heterogeneous surfaces

Adsorption kinetics on energetically heterogeneous surfaces under isothermal conditions is analyzed using the uniform energy distribution model. Considering the quasi-equilibrium of surface diffusion between the adsorption sites with different energy, the kinetic equations dΘ/dt=(k_ap−A_dK_diff)(1−Θ) for first-order adsorption and dΘ/dt=k_ap(1−Θ)²−A_dK_diffΘ(1−Θ) for dissociative adsorption are obtained, where K_diff is a coefficient describing the surface diffusion equilibrium, which depends on the coverage and the energy distribution. Under isochoric conditions with p decreasing due to adsorption, surface diffusion accelerates the rate towards equilibrium significantly, as observed in static calorimetric adsorption experiments. An approximate solution in Lagergren form is derived for this condition.     

Spin-0 and spin-1/2 particles in a constant scalar-curvature background

We study the Klein-Gordon and Dirac equations in the presence of a background metric ds²=−dt²+dx²+e^−2gx(dy²+dz²) in a semi-infinite lab (x>0). This metric has a constant scalar-curvature R=6g² and is produced by a perfect fluid with equation of state p=−ρ/3. The eigenfunctions of spin-0 and spin-1/2 particles are obtained exactly, and the quantized energy eigenvalues are compared. It is shown that both of these particles must have nonzero transverse momentum in this background. We show that there is a minimum energy E²_min=m²c⁴+g²c²?² for bosons (E_KG>E_min), while the fermions have no specific ground state (E_Dirac>mc²).     

Evidence for a deep acceptor level in p-InSb from the variation of hole density with uniaxial stress

The hole density of Cd doped p-InSb has been studied as a function of uniaxial compressive stress along [001] at T = 77 K. Analysis implies the presence of a deep acceptor level whose activation energy decreases with compressive stress, dE_A/dχ = ?3.9 meV/kbar.     

Hybridization and electron interaction in nickel compounds

The bare Coulomb interaction, defined by the reaction 2dⁿ = d^n?1 + d^{n + 1} ? U is determined for some Ni compounds. It is found that U is larger than the 3d bandwidth even for metallic compounds. More relevant to the metal nonmetal transition is the optical gap energy E_G = U ? (E(3d^n?1) ? E(L)) where E(3d^n?1) and E(L) are the d-electron and ligand electron ionization potentials respectively.     

Final state effect for Au 4f line from gold-nano-particles grown on oxides and HOPG supports

The effect of a positive charge left to a small metal particle immediately after photoemission, so called the final state effect is studied for Au 4f binding energy (E_B) shifts. The size and shape of Au nano-particles were determined by high-resolution medium energy ion scattering combined with scanning electron microscopy of a field emission type. The shape of Au nano-particles is well approximated by a partial sphere with diameter d and height h. It is found that the E_B shift is well expressed as number of atoms per particle (n_A) and independent of support species. The E_B shift changes dramatically at a critical n_A value of ∼70 atoms, where metal-nonmetal transition takes place. In the nonmetal region, the E_B shift increases steeply almost exponentially with decreasing n_A and in contrast, gradually decreases with increasing n_A in the metallic region. The effect of the positive charge of an Au 4f vacancy created by photoemission is expressed by the relaxation time τ and the effective charge +αe when the photoelectron just leaves the Au particle surface (e: electron charge, α < 1).     

Landau quantization of a two-dimensional electron with the nonparabolic dispersion law, pseudospin components and chirality terms

The Landau quantization of a two-dimensional electron in a perpendicular magnetic field on the basis of a Hamiltonian with two pseudospin components is considered. The diagonal elements of the Hamiltonian have non-parabolic but circular symmetric dispersion laws, whereas the off diagonal elements contain the chirality terms of different degrees. The solution of the matrix form Schrödinger equation was found following the method proposed by Rashba in his theory of spin-orbit coupling, taking into account different degrees of chirality and deviations on the parabolic dispersion law. The Landau quantization Hamiltonians were obtained by substituting the canonical momentum operators by the kinetic momentum operators. Two concrete examples were discussed. One of them concerns the Mexican hatlike dispersion law in the biased bilayer graphene with second order chirality, when the Landau quantization levels except two are characterized by two quantum numbers (n−2) and n for n≥2, corresponding to different pseudospin projections. They differ by 2 as the degree of chirality is. There are two energy levels E^±(n−2,n) with the same numbers (n−2) and n. The lower energy levels E⁻(n−2,n) have a linear decreasing behavior with dependence on the magnetic field strength H with different slopes and minima for different values of n≥2. At the intersection point H_th, two energy levels E⁻(1,3) and E⁻(0,2) have the same energy forming two degenerate LLLs. Touching the minima at different values of H, the energy branches gradually transform in the increasing quadratic dependences proportional to (2n+1)²H². The similar results were obtained in the case of cosine-type dispersion law in the frame of one-band model.     

Low-Spin Ferriheme Models of the Cytochromes: Correlation of Molecular Structure with EPR and Mössbauer Spectral Parameters

The electronic properties of the intermetallic compound HfCo₃B₂ were investigated using combined TDPAC measurements and first principles LAPW calculations. The V _zz value at the hafnium site is determined from dominant positive p–p contribution, with less than 20%, negative s–d and d–d contributions. Based on the calculated density of state (DOS) at 0 K, a band contribution (γ _band) of 7.26 (mJ/mol/K²) to the value of the electronic specific heat coefficient (γ) was obtained. This relatively low γ _band value is attributed to the hybridization between hafnium d-states, boron 2p-states and cobalt 3d-states, formed at the energy interval below E _Fermi. This hybridization, together with the dip in the DOS around E _Fermi, implies a possible reduction of the low temperature magnetic moment in this compound.     

Electroreflectance in GeSi alloys under hydrostatic pressure

From the electroreflectance spectra measured under hydrostatic pressure to 7 kbar we have determined the pressure coefficients for germanium (dE₁/dP = 7.8 ± 0.4⁻⁶eV/bar, dP = 1.4 ± 0.8 10⁻⁶eV/bar), for Si (dE′_o/dP = 1 ± 1 10⁻⁶eV/bar, dE₁dP = 6.2 ± 0.4 10⁻⁶eV/bar) and for GeSi alloys in the entire composition region. For the composition 80–100% of Si which is widely discussed in the literature, we could distinguish two maxima with substantially different pressure coefficients. The absolute experimental values of dE/dP agree rather well with theoretical values which, together with composition shift of electroreflectance peaks, enable us to connect the peak E₁ predominantly with λ and L and E′_o with Г and Δ transitions in the entire composition region.     

The energy dependence of single particle spectra in e+e− annihilation

We present explicit predictions of the statistical bootstrap model for inclusive single particle spectra in e⁺e^? annihilation. The distribution (ω/σ_tot·E) (dσ/p² dp) is found to become, for E ? 3 GeV, a function only of the secondary energy ω, independent of the incident e⁺d^? energy E.     

Disordered cellular automaton traffic flow model: phase separated state, density waves and self organized criticality

We suggest a disordered traffic flow model that captures many features of traffic flow. It is an extension of the Nagel-Schreckenberg (NaSch) stochastic cellular automata for single line vehicular traffic model. It incorporates random acceleration and deceleration terms that may be greater than one unit. Our model leads under its intrinsic dynamics, for high values of braking probability p_r, to a constant flow at intermediate densities without introducing any spatial inhomogeneities. For a system of fast drivers p_r→0, the model exhibits a density wave behavior that was observed in car following models with optimal velocity. The gap of the disordered model we present exhibits, for high values of p_r and random deceleration, at a critical density, a power law distribution which is a hall mark of a self organized criticality phenomena.     

Fluorescence Quenching Studies of 1,3‐Diphenyl Benzene

Fluorescence quenching of 1,3‐diphenyl benzene (m‐terphenyl) by carbon tetrachloride (CCl₄) at steady state in different solvents, namely n‐hexane, n‐heptane, cyclohexane, toluene, benzene acetonitrile, 1,4‐dioxane, and with a transient method in benzene has been done at room temperature to understand the role of quenching mechanisms. The Stern–Volmer plot was found to be linear for all the solvents studied. The probability of quenching per encounter p was determined in all the solvents and was found to be less than unity. Further, from the studies of rate parameters and lifetime measurements in benzene at different temperatures (30–60°C), it was shown that the phenomenon of quenching is generally governed by the well‐known Stern–Volmer (S‐V) plot. The activation energy E _a (E′_a) of quenching was determined using literature values of activation energy of diffusion E _d, and it was found to be greater than E _d, which confirms the fact that the quenching mechanism is not solely due to material diffusion but there is also contribution from activation energy.     

Formation of the space charge region in diffusion p-n junctions under high-density current interruption

The recovery of diodes with diffusion p-n junctions in the case of high reverse current density j is analyzed. A condition for quasi-neutrality breaking in the diffusion layers with allowance for the dependence of charge carrier mobility μ on electric field strength E is obtained that is valid for a wide range of j. The problem of formation of the space charge region in a circuit with inductance L and resistance R is reduced to a system of two ordinary differential equations. Approximation of a numerical solution to this system makes it possible to derive crude analytical relationships between interrupted current density {ie88-1}, circuit parameters, diode parameters, and parameters of a forming voltage pulse (with amplitude V _m and pulse rise time t _p). The limiting parameters of a pulser with an inductive energy storage and current interrupter based on diffusion diodes are studied. The critical density of interrupted current {ie88-2} is determined at which the field in the space charge region near the anode reaches breakdown value E _b and intense impact ionization by holes begins. The impact ionization decreases the rates of current decay and voltage increase in the space charge region. As a result, at {ie88-3}, t _p starts increasing and the overvoltage factor of the pulser decreases. The value of V _m corresponding to {ie88-4} is roughly given by {ie88-5}, where m is the number of diodes in the interrupter, ? is the permittivity of the semiconductor, {ie88-6} is the saturated drift velocity of holes, and l _p is the depth of the p-n junction (diffusion depth). Theoretical predictions are confirmed by exact numerical simulation of the recovery process and qualitatively agree with the available experimental data.     

On pattern formation in a class of traffic models

We consider a simple microscopic follow-the-leader model of N identical cars on a circular road. In the classical setting, a car is not allowed to reach its leader. If it happens at a particular time t_E, we propose to extend the model beyond this time t_E: The idea is to define a physically reasonable leader for each car. Mathematically, the resulting model is a kind of Filippov system. The objective is to study a long time behavior of the model. In case N=3, we observed several invariant patterns which apparently exhibit spatial-temporal symmetries. We managed to classify and identify two kinds of rotating waves. The classification exploits symbolic dynamical notions.