Search results for "Shock wave"
showing 10 items of 194 documents
Metastable oxygen atom velocity and temperature in supersonic CO2plasma expansions
2008
Radial and axial velocity distribution functions of metastable oxygen atoms were obtained by way of resonant laser induced fluorescence spectroscopy at 777.19 nm in rarefied supersonic plasma jets produced from pure CO2 and CO2–N2 gas mixtures. The N2 seeded fraction is 3% in volume in order to mimic the Martian atmosphere composition. The measured lineshapes allow computation of the mean radial velocity and the perpendicular temperature, with respect to the jet axis, as well as the mean axial velocity and the parallel temperature. With an arcjet plasma source input power of 6.5 kW, the metastable O(5S) atom axial velocity is around 4500 m s−1 and the atom perpendicular temperature reaches …
X-ray emission from the Vela SNR shock region: Spectral fitting with a non-equilibrium ionization model
1994
We report on the 5′ scale spectral analysis of the X‐ray emission from a region near the edge of the Vela SNR with a Non‐Equilibrium Ionization (NEI) model. We have found significant variations of temperature, density, ionization time and interstellar absorption. We have identified an overdense region with higher density and lower temperature than the surrounding medium. That can be interpreted as an ISM cloudlet recently shocked by the blast wave, not yet in thermal equilibrium. Our independent determination of the Vela SNR distance is in agreement with the most recent results based on ROSAT All‐Sky Survey data. Our analysis indicates the occurrence of fast electron‐ion energy equipartitio…
Spectral long-range interaction of temporal incoherent solitons.
2014
We study the interaction of temporal incoherent solitons sustained by a highly noninstantaneous (Raman-like) nonlinear response. The incoherent solitons exhibit a nonmutual interaction, which can be either attractive or repulsive depending on their relative initial distance. The analysis reveals that incoherent solitons exhibit a long-range interaction in frequency space, which is in contrast with the expected spectral short-range interaction described by the usual approach based on the Raman-like spectral gain curve. Both phenomena of anomalous interaction and spectral long-range behavior of incoherent solitons are described in detail by a long-range Vlasov equation.
Recollimation shocks in relativistic jets
2018
Recollimation shocks (RS) appear associated with relativistic flows propagating through pressure mismatched atmospheres. Astrophysical scenarios invoking the presence of such shocks include jets from AGNs and X-ray binaries and GRBs. We shall start reviewing the theoretical background behind the structure of RS in overpressured jets. Next, basing on numerical simulations, we will focus on the properties of RS in relativistic steady jets threaded by helical magnetic fields depending on the dominant type of energy. Synthetic radio maps from the simulation of the synchrotron emission for a selection of models in the context of parsec-scale extragalactic jets will also be discussed.© 2018 World…
Analysis of laser shock waves and resulting surface deformations in an Al-Cu-Li aluminium alloy
2012
Abstract Laser shock processing is now a recognized surface treatment for improving fatigue or corrosion behaviour of metallic materials through the generation of a compressive stress field. In turn, the analysis of shock wave propagation is of primary importance to predict numerically morphological and mechanical surface modifications. Considering experimental and numerical analyses of shock wave propagation, and surface deformations induced by single impacts, a 2050 aluminum alloy having different microstructures was investigated under laser-shock loading. In a first step, the evolution of shock wave attenuation and elastic precursor amplitude was correctly reproduced by finite element si…
Überprüfung der Läsionsgefahr des N. ischiadicus des Kaninchens durch die Applikation niedrig- und mittelenergetischer extrakorporaler Stoßwellen
2008
Aim The aim of the study was to evaluate the likeliness for peripheral nerve lesions following extracorporeal shock wave application. Material and method 82 rabbit sciatic nerves were randomized to undergo low-energetic (0.08 mJ/mm2), middle-energetic (0.28 mJ/mm2) or no (controls) shock wave therapy. After 1 to 28 days an independent neuropathologist checked the specimen for signs of neural lesions. Results Only after 14 and 28 days vacuolic swelling of the axons was noted, somewhat pronounced in the middle-energetic group. In no case was there any disruption of the nerve's continuity. We did not observe any neurapraxia. Conclusion Shock wave application does not threaten peripheral nerve …
Electromagnetically generated extracorporeal shock waves for gallstone lithotripsy: in vitro experiments and clinical relevance.
1989
. First generation shock wave sources have been proved to disintegrate gallstones effectively, but they require the immersion of the patient's body in a tank of water. A recently developed second generation shock wave source (Siemens-Lithostar, Erlangen, FRG) generates shock waves electromagnetically. It presents several novel features. In particular the waterbath can be omitted and due to lower shock wave pressure general anaesthesia is not required. In vitro studies showed that 36 out of 38 gallstones (11–30 mm in diameter) could be disintegrated. Two concrements resisting lithotripsy were pure white cholesterol stones. Independent of shape, size, and composition (cholesterol or pigment) …
Extracorporeal Shock Wave Lithotripsy of Ureteral Stones: Clinical Experience and Experimental Findings
1986
AbstractESWL of impacted ureteral or caliceal stones is not as successful as expected. To study this problem a model for extracorporeal shock wave lithotripsy of ureteral stones has been designed. After initial fragmentation of the outer shell of impacted stones during the first series of shock wave application those fragments are kept in place by external mucosal contact, creating a lot of new interfaces.Absorption or reflection of shock wave energy within this fragmented shell seems to be responsible for the poor success rate in these cases. In regard to our experimental and clinical results we advise pushing ureteral stones back into the renal collecting system by means of a ureteral cat…
High-order regularization in lattice-Boltzmann equations
2017
A lattice-Boltzmann equation (LBE) is the discrete counterpart of a continuous kinetic model. It can be derived using a Hermite polynomial expansion for the velocity distribution function. Since LBEs are characterized by discrete, finite representations of the microscopic velocity space, the expansion must be truncated and the appropriate order of truncation depends on the hydrodynamic problem under investigation. Here we consider a particular truncation where the non-equilibrium distribution is expanded on a par with the equilibrium distribution, except that the diffusive parts of high-order nonequilibrium moments are filtered, i.e., only the corresponding advective parts are retained afte…
Post-adiabatic supernova remnants in an interstellar magnetic field: oblique shocks and non-uniform environment
2018
Monthly notices of the Royal Astronomical Society 479(3), 4253 - 4270 (2018). doi:10.1093/mnras/sty1750