Hydrostatic equilibrium

About: Hydrostatic equilibrium is a research topic. Over the lifetime, 2451 publications have been published within this topic receiving 62172 citations.

I. The computational method and the inhibiting effect of the µ-gradient

Abstract: We study the effects of rotation on the structure and evolution of massive stars. The method of Kippenhahn & Thomas (1970) to incorporate the hydrostatic effects of rotation in one dimensional stellar evolutionary codes is strictly valid only in case the angular velocity distribution has a cylindrical symmetry. We demonstrate how this method can be applied (cf. Appendix) in the case where the angular velocity is constant on isobars ("shellular rotation law", cf. Zahn 1992). We also investigate the structural effects of rotation on the stellar atmo- sphere. The effects of rotational mixing are considered with the theory of Zahn (1992) for the circulation and turbulence in ro- tating stars. We suppose that the angular momentum in a given shell remains constant with time (asymptotic regime). The sub- sequent developments brought to the Richardson criterion by Maeder (1995a) and Maeder and Meynet (1996) to account for thermal effects on the shear instability are also applied. Evolutionary tracks are calculated for initial masses of 9, 20, 40 and 60 Mwith account of the above hydrostatic and mixing effects. The main results are the following ones: 1) The hydrostatic effects alone are quite modest: when the initial angular velocity () increases from 0 to 90% of the sur- facecriticalvelocity(crit),thelifetimesofmassivestarmodels (40to60M�)areincreasedby1to2%.Theevolutionarytracks are shifted towards lower luminosities, making them appear as theonesresultingfromslightlylowerinitialmassstars,typically 0.5 to 2.5 Msmaller.

Pressure dependence of the electric field gradient at Cd impurities in antimony

Abstract: The electric field gradient at111Cd in Antimony was studied at hydrostatic pressures up to 7 kbar at 150 K, 293 K and 473 K. The logarithmic pressure derivatives, dlnq/dP, were found to be −67, −37 and −26 Mbar−1 respectively. The isotropic volume dependence derived from these values was found to be positive and largely responsible for the anomalous temperature dependence, previously observed.

Hydrostatic system and hydrostatic actuator having said hydrostatic system

Abstract: The invention relates to a hydrostatic system (1.1) and to a hydrostatic actuator having said hydrostatic system. Said hydrostatic system comprises: a master cylinder (5) having a linearly displaceable master-cylinder piston (18) that variably delimits a pressure chamber (A.1) of the master cylinder; a slave cylinder (22) having a slave-cylinder piston that bounds a pressure chamber of the slave cylinder; a hydrostatic line (24) between the pressure chambers, which hydrostatic line is filled with pressure medium; a compensation tank (3) filled with pressure medium; and an extraction bore (5.8), which is arranged between the hydrostatic line and the compensation tank and which is controlled in dependence on a position of the master-cylinder piston. In order to reduce the installation space of the hydrostatic system and of the hydrostatic actuator or to at least make said installation space more compact, control of the extraction bore outside of the pressure chamber (A.1) of the master cylinder is provided.

Critical Latitude in Tidal Dynamics Using the Kara Sea as an Example

Abstract: It is well known that, within the linear nonviscous equations of tidal dynamics, the amplitudes of oscillations of the barotropic and baroclinic tidal velocity components unlimitedly increase when approaching the critical latitude. It is also known that the linear equations of tidal dynamics with a constant and specified vertical eddy viscosity indicate the occurrence of significant tidal velocity shears in the near-bottom layer, which are responsible for increasing the baroclinic tidal energy dissipation, the turbulent kinetic energy, and the thickness of the bottom boundary layer. The first circumstance—the growth of the amplitudes of oscillations of the barotropic and baroclinic tidal velocity components—is due to the elimination in the original equations of small terms, which are small everywhere except for the critical latitude zone. The second circumstance—the occurrence of significant tidal velocity shears—is due to the fact that internal tidal waves, which induce the dissipation of the baroclinic tidal energy and the diapycnal diffusion, are either not taken into account or described inadequately. It is suggested that diapycnal diffusion can lead to the degeneration (complete or partial) of tidal velocity shears, with all the ensuing consequences. The aforesaid is confirmed by simulation results obtained using the QUODDY-4 high-resolution three-dimensional finite-element hydrostatic model along the 66.25° E section, which passes in the Kara Sea across the critical latitude.