Utilizing a recently derived extension of the Maxwell-Boltzmann distribution to low occupation numbers (Simons 1994) this investigation discusses the structure of stellar dynamical isothermal spheres. The resulting models, which resemble King models, constitute a new sequence of physically well-motivated spherical equilibrium configurations of finite mass, and give nice fits to pre-core collaps...

We consider the problem of lensing by binary galaxies idealized as two isothermal spheres. This is a natural extension of the problem of lensing by binary point masses first studied by Schneider & Weiss (1986). In a wide binary, each galaxy possesses individual tangential, nearly astroidal, caustics and roundish radial caustics. As the separation of the binary is made smaller, the caustics unde...

We performed N-body/SPH simulations of merging gas rich disk-galaxies with a mass ratio of 3:1. A stellar disk and bulge component and a dark halo is realized with collisionless particles, the gas is simulated using SPH particles. In this paper we focus on the gas dynamics in mergers and its influence on the structure of the final merger remnant, neglecting star formation. During the merger aro...

We consider a space-homogeneous gas of inelastic hard spheres, with a diffusive term representing a random background forcing (in the framework of so-called constant normal restitution coefficients α ∈ [0, 1] for the inelasticity). In the physical regime of a small inelasticity (that is α ∈ [α∗, 1) for some constructive α∗ ∈ [0, 1)) we prove uniqueness of the stationary solution for given value...

Isothermal melt crystallization kinetics of PVDF was investigated by differential scanning calorimetry. Thin PVDF film has been fabricated by the solvent casting technique using dimethylformamide (DMF). Then, the samples were melted and subsequently crystallized in the range of the crystallization temperature (Tc) between 138 and 145 °C. The crystallization kinetics was derived from Avrami equa...

Dilute gas-particle flows can be described by a kinetic equation containing terms for spatial transport, gravity, fluid drag, and particle-particle collisions. However, the direct numerical solution of the kinetic equation is intractable for most applications due to the large number of independent variables. A useful alternative is to reformulate the problem in terms of the moments of the veloc...

the present work is the successful extension of an improved equation of state (eos) to refrigerant fluids. the objective is the prediction of isothermal and saturated liquid densities of refrigerants. two temperature-independent parameters appearing in the modified eos are closely related to critical point properties of refrigerant fluids. our results showed that, the proposed eos can predict w...

Polytropic models play a very important role in galactic dynamics and in the theory of stellar structure and evolution. However, in general, the solution of the Lane-Emden equation can not be given analytically but only numerically. In this paper we give a good analytic approximate solution of the Lane-Emden equation. This approximation is very good for any finite polytropic index n and for the...

We consider the spatially homogeneous Boltzmann equation for inelastic hard spheres, in the framework of so-called constant normal restitution coefficients. We prove the existence of self-similar solutions, and we give pointwise estimates on their tail. We also give general estimates on the tail and the regularity of generic solutions. In particular we prove Haff’s law on the rate of decay of t...

We develop the Cauchy theory of the spatially homogeneous inelastic Boltzmann equation for hard spheres, for a general form of collision rate which includes in particular variable restitution coefficients depending on the kinetic energy and the relative velocity. It covers physically realistic models for granular materials. We prove (local in time) non-concentration estimates in Orlicz spaces, ...