107,042 research outputs found
Long-Time Evolution of Gas-Free Disc Galaxies in Binary Systems
We present the results of several detailed numerical N-body simulations of
the dynamical interactions of two equal mass disc galaxies. Both galaxies are
embedded in spherical halos of dark matter and contain central bulges. Our
analysis of the dynamical evolution of the binary system focuses on the
morphological evolution of the stellar distribution of the discs. The satellite
galaxy has coplanar or polar disc orientation in relation to the disc of the
primary galaxy and their initial orbits are prograde eccentric (,
or ). Both galaxies have mass and size comparable to the Milky
Way. We show that the merger of the two disc galaxies, depending on the
relative orientation of the discs, can yield either a disc or lenticular
remnant, instead of an elliptical one. These are the first simulations in the
literature to show the formation of S0-like galaxies from protracted binary
galaxy interactions. Additionally, we demonstrate that the time to merger
increases linearly with the initial apocentric distance between the galaxies,
and decreases with the initial orbital eccentricity. We also show that the
tidal forces of the discs excite transient and wave modes, i.e.,
lopsidedness, spiral arms, and bars. However, after the merging of the discs,
such instabilities fade completely, and the remnant is thicker and bigger than
the original discs. The maximum relative amplitude of these waves is at most
about 15 times greater compared to the control case. of these two wave modes.
Finally, the disc settles down quickly, after the merger, in less than one
outer disc rotation period.Comment: 23 pages, 3 tables and 16 figures. Accepted for publication in A&
Physics of heat pipe rewetting
Although several studies have been made to determine the rewetting characteristics of liquid films on heated rods, tubes, and flat plates, no solutions are yet available to describe the rewetting process of a hot plate subjected to a uniform heating. A model is presented to analyze the rewetting process of such plates with and without grooves. Approximate analytical solutions are presented for the prediction of the rewetting velocity and the transient temperature profiles of the plates. It is shown that the present rewetting velocity solution reduces correctly to the existing solution for the rewetting of an initially hot isothermal plate without heating from beneath the plate. Numerical solutions have also been obtained to validate the analytical solutions
Graphical method for analyzing digital computer efficiency
Analysis method utilizes graph-theoretic approach for evaluating computation cost and makes logical distinction between linear graph of a computation and linear graph of a program. It applies equally well to other processes which depend on quatitative edge nomenclature and precedence relationships between edges
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Heating experiments of the Tagish Lake meteorite: Investigation of the effects of short-term heating on chondritic organics
We present in this study the effects of short-term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body’s heating extent with common cosmothermometers. The kinetics of short-term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites—potential analogues of the target asteroid Ryugu of the Hayabusa2 mission—which had experienced posthydration, short-duration local heating. In an attempt to understand the effects of short-term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X-ray microscopy utilizing X-ray absorption near edge structure spectroscopy, and ultraperformance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 °C for 96 h, as the OM maturity trend was influenced by the heating conditions, kinetics, and the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long-term internal heating
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