An iterative method is presented for solving the problem of a uniformly rotating, selfgravitating ring without a central body in Newtonian gravity by expanding about the thin ring limit. Using this method, a simple formula relating mass to the integrated pressure is derived to the leading order for a general equation of state. For polytropes with the index n = 1, analytic coefficients of the it...

We complete previous investigations on the thermodynamics of self-gravitating systems by studying the grand canonical, grand microcanonical and isobaric ensembles. We also discuss the stability of polytropic spheres in connexion with a generalized thermodynamical approach proposed by Tsallis. We determine in each case the onset of gravitational instability by analytical methods and graphical co...

We study the evolution (expansion or oscillation) of cylindrically symmetric magnetic flux ropes when the energy dissipation is due to a drag force proportional to the product of the plasma density and the radial speed of expansion. The problem is reduced to a single, second-order, ordinary differential equation for a damped, non-linear oscillator. Motivated by recent work on the interplanetary...

A computer model of a single screw oil-flooded low pressure air compressor was developed which predicts the internal conditions based on certain empirical values. A characteristic thread technique is used for steady state operation. A polytropic process is used and the model will iterate for the polytropic coefficient to best correlate internal predictions with empirical values. The geometric v...

Resonant oscillations in warped disks are examined in order to explain highfrequency QPOs and horizontal-branch QPOs in low-mass X-ray binaries. Different from our previous work, addressed to the same subjects, we relax in this paper the assumption that the disks are isothermal in the vertical direction. That is, the pressure, density, and temperature are assumed to be distributed in the vertic...

An approximate strategy for studying the evolution of binary systems of extended objects is introduced. The stars are assumed to be polytropic ellipsoids. The surfaces of constant density maintain their ellipsoidal shape during the time evolution. The equations of hydrodynamics then reduce to a system of ordinary differential equations for the internal velocities, the principal axes of the star...

Abstract Existing models of bulk modulus for aerated hydraulic fluids primarily focus on the effects pressure and air fraction, whereas effect temperature is disregarded. Based lumped parameter method full cavitation model, combined with improved Henry’s law polytropic course equation, a theoretical model dynamic an fluid derived. The system pressure, are investigated using controlled variable ...

We develop a cosmological model based on a quadratic equation of state p/c = −(α + 1)ρ/ρP + αρ− (α + 1)ρΛ, where ρP is the Planck density and ρΛ the cosmological density, “unifying” vacuum energy and dark energy in the spirit of a generalized Chaplygin gas model. For ρ → ρP , it reduces to p = −ρP c leading to a phase of early accelerating expansion (early inflation) with a constant density equ...

In this work, a generalized expression of the photoacoustic ~PA! effect in a multilayer material is derived. This expression takes thermal and optical properties and geometry of a multilayer structure, as well as the thermal contact resistances between layers into consideration. In addition, a composite piston model consisting of a thermal piston and a mechanical piston of the PA effect is deve...

The problems of equilibrium structures and periods of oscillations of rotationally and/or tidally distorted polytropic models of stars in binary systems have been studied previously. In the studies, only the effects of gravitational and centrifugal forces while obtaining the Roche equipotential of such stars were considered. The Coriolis force were not considered. In the present study, we have ...