[en] The effect of Bond-dilution on the magnetic properties of a quantum transverse spin-1 Blume-Emery-Griffiths model is investigated within an expansion technique for cluster identities of a spin-1 localized spin system. The longitudinal and transverse magnetizations and quadrupolar moments are studied for several values of the bond concentration. A general formula, applicable to structures with arbitrary coordination number N, are given. (author). 41 refs, 6 figs

[en] Using an expansion technique for cluster identities of spin-1 localized spin systems, we study the magnetic properties of a quantum transverse spin-1 Blume-Emery-Griffiths model. The longitudinal and transverse magnetizations and the quadrupolar moments are calculated. General formula applicable to structures with arbitrary coordination number are given. (author). 38 refs, 6 figs

[en] The magnetic order-disorder layering transitions of a spin-1 Ising model are investigated, under the effect of a variable surface crystal field Δ_s, using the mean-field theory. Each layer k, of the film formed with N layers, disorders at a finite surface crystal field distributed according to the law Δ_k=Δ_s/k^α, k=1,2,...,N and α being a positive constant. We have established the temperature-crystal field phase diagrams and found a constant tricritical point and a reentrant phenomenon for the first k₀ layers. This reentrant phenomenon is absent for the remaining N-k₀ layers, but the cricritical points subsist and depend not only on the film thickness but also on the exponent α. On the other hand, the thermal behaviour of the surface magnetisation for a fixed value of the surface crystal field Δ_s and selected values of the parameter α are established

[en] The effect of a variable surface transverse magnetic field Ω_s, on the order-disorder layering transitions of an Ising spin-((1)/(2)) model is investigated using mean field theory (MF) and finite cluster approximation (FC). For a film with finite thickness formed with N layers, each layer z transits at a fixed temperature from the ordered to the disordered phase, under the effect of the transverse magnetic field Ω(z)=Ω_s/z^α, (z=1, triple dot, N). These order-disorder layering transitions are absent for α=0 even if increasing the temperature and/or the surface transverse magnetic field. On the other hand, the dependency of longitudinal and transverse magnetisations on temperature and surface transverse magnetic field are illustrated for a fixed value of the exponent α

[en] In this paper, we propose a stochastic Cellular Automata (CA) model to study traffic flow at a single-lane urban roundabout (resp. traffic circle) of N entry points (resp. exit points), the entry points are controlled by rates α_1 and α_2 while the removal rates from the exit points are denoted by β. The traffic is controlled by a self-organized scheme. Based on computer simulation, density profiles, global density and current are calculated in terms of rates. Furthermore, the phase diagrams for roundabout as well as traffic circle are constructed. It has turned out that the phase diagrams consist essentially of two phases namely free flow and jamming. It is noted that the typology of the phase diagrams of the roundabout is not similar to it in the traffic circle. Furthermore, we have compared the performance of the two systems in terms of the geometrical properties and the number of entry points. - Highlights: • Simulations are conducted to study traffic flow at a single-lane urban roundabout as well as traffic circle. • Phase diagrams for roundabout as well as traffic circle are constructed. • The performance of the two systems are compared in terms of the geometrical properties and the number of entry points

[en] We study the phase diagram and magnetic properties of a transverse spin-1 Ising model with random longitudinal crystal field interactions within an expansion technique for cluster identities of spin-1 localized spin systems. The partially ordered phases appear for a particular two valued distribution P(D_i) = 1/2[δ(D_i-(1+α)D)+δ(D_i-(1-α)D)], and for sufficiently small transverse field Ω. The longitudinal and transverse magnetizations, the quadrupolar moments are calculated. General formulae applicable to structures with arbitrary coordination number, are given. (author). 19 refs, 3 figs

[en] The effects of alternating transverse fields Ω_a and Ω_b on the critical behavior of an alternating spin-1 Ising superlattice are studied within an effective field theory with a probability distribution technique that accounts for the single-site spin correlation. Critical temperatures are calculated as a function of the thickness of the superlattice and the strength of the transverse field. Depending on the values of the transverse fields Ω_a and Ω_b, the critical temperature can increase or decrease with increasing the thickness of the film, such result is not obtained in the uniform transverse field case (Ω_a = Ω_b). Furthermore, for each thickness L of the film, a long range ordered phase persist at low temperature for selected values of the transverse field Ω_a and arbitrary values of Ω_b. The effects of interlayer and intralayer exchange interactions are also examined

[en] Phase diagram of the q state antiferromagnetic Potts model on a square lattice is investigated in a neighborhood of the critical point h = 4, T = 0. Using a constructive criterion of uniqueness introduced by Dobrushin, Kolafa, and Shlosman, for the antiferromagnetic Ising model, we show that the activity, a_c(q) > 1/(q - 1) and the slope increases from zero (q = 2) to infinity (q = is proportional). The phase diagram bulges near the mentioned critical point for 2 < q < is proportional. (author). 5 refs, 6 figs

[en] The three dimensional spin-1 Ising model with crystal field interactions exhibit tri-critical behaviour. Using an expansion technique for cluster identities of spin-1 localized spin systems, we study the influence of transverse magnetic field on this behaviour. Temperature-crystal-field phase diagrams is investigated for different values of transverse field. The longitudinal and transverse magnetizations, the quadrupolar moments are calculated. General formulae, applicable to structures with arbitrary coordination number N, are given. (author). 19 refs, 5 figs

[en] Using numerical simulations we study the effect of the jumping rate on the density, current and phase diagram in the open boundaries case, and on the velocities of particles in the case of one and two species of particles on a ring, of one dimensional asymmetric exclusion model. However, on the one hand, a passage from discontinuous to continuous transition occurs by decreasing the jumping rate in the open boundaries, on the other hand, for two species of particles on a ring the velocity of particle 1 increases while the velocity of particle 2 decreases as the jumping rate increases. (author)