898 research outputs found
Cooling Effect of the Richtmyer-Meshkov Instability
We provide numerical evidence that the Richtmyer-Meshkov (RM) instability
contributes to the cooling of a relativistic fluid. Due to the presence of jet
particles traveling throughout the medium, shock waves are generated in the
form of Mach cones. The interaction of multiple shock waves can trigger the RM
instability, and we have found that this process leads to a down-cooling of the
relativistic fluid. To confirm the cooling effect of the instability, shock
tube Richtmyer-Meshkov instability simulations are performed. Additionally, in
order to provide an experimental observable of the RM instability resulting
from the Mach cone interaction, we measure the two particle correlation
function and highlight the effects of the interaction. The simulations have
been performed with an improved version of the relativistic lattice Boltzmann
model, including general equations of state and external forces.Comment: 10 pages, 6 figure
Derivation subalgebras of Lie algebras
Let be a Lie algebra and be two ideals of . If \Der_J^I(L) denotes the set of all derivations of whose images are in and send to zero, then we give necessary and sufficient conditions under which \Der_J^I(L) is equal to some special subalgebras of the derivation algebra of . We also consider finite dimensional Lie algebra for which the center of the set of inner derivations, Z(\IDer(L)), is equal to the set of central derivations of , \Der_z(L), and give a characterisation of such Lie algebras
On the motion of spinning test particles in plane gravitational waves
The Mathisson-Papapetrou-Dixon equations for a massive spinning test particle
in plane gravitational waves are analysed and explicit solutions constructed in
terms of solutions of certain linear ordinary differential equations. For
harmonic waves this system reduces to a single equation of Mathieu-Hill type.
In this case spinning particles may exhibit parametric excitation by
gravitational fields. For a spinning test particle scattered by a gravitational
wave pulse, the final energy-momentum of the particle may be related to the
width, height, polarisation of the wave and spin orientation of the particle.Comment: 11 page
Analysis of flood impact on reinforced concrete(Pre-stressed) girder bridges – a case study
In recent years, frequencies of flood events in Australia have increased. It is noted that flood events cause the most damage to infrastructure compared to any other natural hazards in the world. Bridge structures located over waterways are prone to failure under flood events. Failure of a bridge can impact on the community significantly by reducing the evacuation capability and recovery operations during and after a disaster. A recent research project commenced at RMIT University aims to examine failure of road bridges under flood events. The paper has reviewed different bridge design codes used over several years in Australia for designing the bridges. Various failure mechanisms of bridges due to flood events have been investigated and the most common failure mechanisms of the bridges in Queensland have been identified by examining bridge inspections conducted after the 2011 and 2013 flood events. A case study bridge, which failed under flood loading, has been modeled and the effects of different flood scenarios have been investigated. The impacts of different types of debris, urban and regional, have also been studied. Damage indices have been derived for a concrete girder bridge to demonstrate the methodology for vulnerability modeling of bridge structures
An investigation on Vibrionaceae family of bacteria as probiotic factors in shrimp culture
We investigated the effects of Vibrionaceae family of bacteria as probiotics in the process of growth and survival rate of shrimp during propagation stages. Bacterial flora were extracted from seawater, culture farms, shrimp culture farms and sludge of private propagation farms. Different bacteria such as Vibrio alginolyticus (serotype 1-4), Vibrio splendidus I, Vibrio fluvialis II, Vibrio anguillarum I, Vibrio costicul, Vibrio vulnificaus, Vibrio nereis, Vibrio camplbelli, Vibrio natriegens, Vibrio proteolyticus, Vibrio plegius II ,Vibrio fischeri, Aeromonas hydrophila, Aeromonas schuberti, Aeromonas salmonisida, Aeromonas veronii were isolated, identified and lyophilized. These bacteria were used in different experiments on shrimp life cycle stages while the shrimps were being fed on live food such as Chaetoceros, Skeletonema and Tetraselmis algae. Vibrio alginolyticus (serotype 1) with 107 cells/ml increased proliferation of Tetraselmis sp to 71 % in 6 days compared to the control experiment. Also Vibrio alginolyticus (serotype 4) with 105 cells/in' increased Tetraselmis sp. production to 389% in 6 days compared to control. Vibrio splendidus I was also found to be able to increase shrimp fork length in postlarvae stage 3 up to 23% as compared to control. Vibrio alginolyticus and Vibrio fischeri increased survival, fork lenght and body weight of green tiger shrimp in postlarvae stage significantly (P<0.05)
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