Topic
Total pressure
About: Total pressure is a research topic. Over the lifetime, 5199 publications have been published within this topic receiving 66658 citations.
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TL;DR: In this article, a global magnetohydrodynamic (MHD) simulation of a nonradiative accretion flow originating in a pressure supported torus is presented, which is controlled by the magnetorotational instability which produces turbulence.
Abstract: We present a global magnetohydrodynamic (MHD) three dimensional simulation of a nonradiative accretion flow originating in a pressure supported torus. The evolution is controlled by the magnetorotational instability which produces turbulence. The flow forms a nearly Keplerian disk. The total pressure scale height in this disk is comparable to the vertical size of the initial torus. Gas pressure dominates only near the equator; magnetic pressure is more important in the surrounding atmosphere. A magnetically dominated bound outflow is driven from the disk. The accretion rate through the disk exceeds the final rate into the hole, and a hot torus forms inside 10 r_g. Hot gas, pushed up against the centrifugal barrier and confined by magnetic pressure, is ejected in a narrow, unbound, conical outflow. The dynamics are controlled by magnetic turbulence, not thermal convection, and a hydrodynamic alpha model is inadequate to describe the flow. The limitations of two dimensional MHD simulations are also discussed.
116 citations
TL;DR: In this paper, the adsorption of H2 molecules on the [100] MoS2 surfaces was investigated theoretically, by quantum DFT calculations, considering various edge sulfur stoichiometries.
Abstract: We investigate theoretically, by quantum DFT calculations, the adsorption of H2 molecules on the [100] MoS2 surfaces, considering various edge sulfur stoichiometries. Depending on the nature of the...
115 citations
TL;DR: In this article, the controllable growth of vertically aligned ZnO nanowires using a simple vapour deposition method system was reported, and the growth properties were studied as a function of the thickness of the Au catalyst layer, total pressure, deposition temperature and oxygen partial pressure.
Abstract: The controllable growth of vertically aligned ZnO nanowires using a simple vapour deposition method system is reported. The growth properties are studied as a function of the thickness of the Au catalyst layer, total pressure, deposition temperature and oxygen partial pressure. The experiments indicate the existence of five main zones of growth. The zone in which the aligned wires grow varies according to the pressure, temperature and oxygen partial pressure. A specific level of low supersaturation of Zn and oxygen vapour are both necessary to ensure the correct rate of growth, which then leads to having thin and densely aligned wires. The growth kinetics are discussed in terms of the interdependent variables. It was found that the diameter and density of the nanowires is controlled mostly by the growth temperature and pressure. The zone with the most aligned nanowires with the highest aspect ratio was found to be at 5?mbar in a temperature range of 860?800??C with a flow of 27?sccm of a N2/O2 mixture.
112 citations
TL;DR: In this article, the authors formulate a theory appropriate to the conditions of a magma chamber and calculate the increased pressure using realistic physical parameters, and show that the excess pressure from rectified diffusion is between 0.4 and 4 MPa for a regional M≥8 earthquake.
Abstract: Rectified diffusion is a mechanism by which a strain wave can rapidly pump volatiles into a bubble and therefore increase the pressure in a closed system. The dynamic strain of either distant regional tectonic earthquakes or local volcanic tremor can be translated to static strain inside a magma chamber via this process. We formulate a theory appropriate to the conditions of a magma chamber and calculate the increased pressure using realistic physical parameters. For a basaltic system initially at 130 MPa pressure, the excess pressure from rectified diffusion is between 0.4 and 4 MPa for a regional M≥8 earthquake. The pressure from rectified diffusion is often significantly above the static stress caused by deformation for documented cases of triggered eruptions and thus presents a more viable mechanism for triggering. Prolonged tremor can have a similar effect since the total pressure added increases linearly with the duration of the excitation.
111 citations
01 Jan 2009
TL;DR: In this paper, two kinds of sample wires, made by nickel-chrome (NiCr) and iron (Fe) as core metal, are used in the experiment to study the electric fire spread along a single wire harness in sub-atmospheric pressure.
Abstract: Flame spread along the single wire harness (thin-metal wire with coating of polyethylene film) in sub-atmospheric pressure has been examined experimentally to gain better understandings of the electric fire in the aircraft and space habitats. Two kinds of sample wires, made by nickel-chrome (NiCr) and iron (Fe) as core metal, are used in this study. Ambient gas is fixed as air and total pressure is varied from atmospheric to sub-atmospheric (100–20 kPa). As the pressure decreases, flame shape changes from typical “teardrop” to “oval” and flame becomes less-luminous irrespective of the materials of the wire. It turns out that the dependence of the spread rate on pressure varies with the materials of the wire; when the pressure decreases, the spread rate of NiCr-harness monotonically increases, whereas that of Fe-harness mostly remains as constant. From the simple thermal-length analysis, it is proposed that there are two modes in the spread depending on the controlling factor; one is “wire-driven mode” (the spread is mainly governed by the thermal input through the wire) and the other is “flame-driven mode” (the spread is mainly governed by the thermal input from the flame). Observed two cases (NiCr- and Fe-harness) would be categorized to the latter and former modes, respectively.
110 citations