The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
C Pfrommer - One of the best experts on this subject based on the ideXlab platform.
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detecting Shock Waves in cosmological smoothed particle hydrodynamics simulations
Monthly Notices of the Royal Astronomical Society, 2006Co-Authors: C Pfrommer, Volker Springel, T A Enslin, Martin JubelgasAbstract:We develop a formalism for the identification and accurate estimation of the strength of structure formation Shocks during cosmological smoothed particle hydrodynamics simulations. Shocks play a decisive role not only for the thermalization of gas in virializing structures but also for the acceleration of relativistic cosmic rays (CRs) through diffusive Shock acceleration. Our formalism is applicable both to ordinary non-relativistic thermal gas, and to plasmas composed of CRs and thermal gas. To this end, we derive an analytic solution to the one-dimensional Riemann Shock tube problem for a composite plasma of CRs and thermal gas. We apply our methods to study the properties of structure formation Shocks in high-resolution hydrodynamic simulations of the Lambda cold dark matter (� CDM) model. We find that most of the energy is dissipated in weak internal Shocks with Mach numbers M ∼ 2 which are predominantly central flow Shocks or merger Shock Waves traversing halo centres. Collapsed cosmological structures are surrounded by external Shocks with much higher Mach numbers up to M ∼ 1000, but they play only a minor role in the energy balance of thermalization. This is because of the higher pre-Shock gas densities within non-linear structures, and the significant increase of the mean Shock speed as the characteristic halo mass grows with cosmic time. We show that after the epoch of cosmic reionization the Mach number distribution is significantly modified by an efficient suppression of strong external Shock Waves due to the associated increase of the sound speed of the diffuse gas. Invoking a model for CR acceleration in Shock Waves, we find that the average strength of Shock Waves responsible for CR energy injection is higher than that for Shocks that dominate the thermalization of the gas. This implies that the dynamical importance of Shock-injected CRs is comparatively large in the low-density, peripheral halo infalling regions, but is less important for the weaker flow Shocks occurring in central highdensity regions of haloes. When combined with radiative dissipation and star formation, our formalism can also be used to study CR injection by supernova Shocks, or to construct models for Shock-induced star formation in the interstellar medium.
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detecting Shock Waves in cosmological smoothed particle hydrodynamics simulations
arXiv: Astrophysics, 2006Co-Authors: C Pfrommer, Volker Springel, T A Ensslin, Martin JubelgasAbstract:We develop a formalism for the identification and accurate estimation of the strength of structure formation Shocks during cosmological smoothed particle hydrodynamics simulations. Shocks not only play a decisive role for the thermalization of gas in virialising structures but also for the acceleration of relativistic cosmic rays (CRs) through diffusive Shock acceleration. Our formalism is applicable both to ordinary non-relativistic thermal gas, and to plasmas composed of CRs and thermal gas. To this end, we derive an analytical solution to the one-dimensional Riemann Shock tube problem for a composite plasma of CRs and thermal gas. We apply our methods to study the properties of structure formation Shocks in high-resolution hydrodynamic simulations of the LCDM model. We find that most of the energy is dissipated in weak internal Shocks with Mach numbers M~2 which are predominantly central flow Shocks or merger Shock Waves traversing halo centres. Collapsed cosmological structures are surrounded by external Shocks with much higher Mach numbers up to M~1000, but they play only a minor role in the energy balance of thermalization. We show that after the epoch of cosmic reionisation the Mach number distribution is significantly modified by an efficient suppression of strong external Shock Waves due to the associated increase of the sound speed of the diffuse gas. Invoking a model for CR acceleration in Shock Waves, we find that the average strength of Shock Waves responsible for CR energy injection is higher than that for Shocks that dominate the thermalization of the gas. When combined with radiative dissipation and star formation, our formalism can also be used to study CR injection by supernova Shocks, or to construct models for Shock-induced star formation in the interstellar medium. (abridged)
François Coulouvrat - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of 3D Shock Waves on nonlinear acoustical vortices
Physics Procedia, 2010Co-Authors: Thomas Brunet, Jean-louis Thomas, Régis Marchiano, François CoulouvratAbstract:We report experimental results about the 3D structure of Shock Waves on nonlinear acoustical vortices (AV). We will investigate classical Shock Waves (in the direction of propagation) and the azimuthal ones (in the transverse plane). At last, both quasi-monochromatic and transient regimes will be considered.
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Experimental observation of azimuthal Shock Waves on nonlinear acoustical vortices
New Journal of Physics, 2009Co-Authors: Thomas Brunet, Jean-louis Thomas, Régis Marchiano, François CoulouvratAbstract:Thanks to a new focused array of piezoelectric transducers, experimental results are reported here to evidence helical acoustical Shock Waves resulting from the nonlinear propagation of acoustical vortices (AVs). These Shock Waves have a three-dimensional spiral shape, from which both the longitudinal and azimuthal components are studied. The inverse filter technique used to synthesize AVs allows various parameters to be varied, especially the topological charge which is the key parameter describing screw dislocations. Firstly, an analysis of the longitudinal modes in the frequency domain reveals a wide cascade of harmonics (up to the 60th order) leading to the formation of the Shock Waves. Then, an original measurement in the transverse plane exhibits azimuthal behaviour which has never been observed until now for acoustical Shock Waves. Finally, these new experimental results suggest interesting potential applications of nonlinear effects in terms of acoustics spanners in order to manipulate small objects.
Dirk H Rischke - One of the best experts on this subject based on the ideXlab platform.
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relativistic Shock Waves in viscous gluon matter
Physical Review Letters, 2009Co-Authors: I Bouras, E Molnar, H Niemi, Oliver Fochler, Carsten Greiner, Dirk H RischkeAbstract:We solve the relativistic Riemann problem in viscous gluon matter employing a microscopic parton cascade. We demonstrate the transition from ideal to viscous Shock Waves by varying the shear viscosity to entropy density ratio eta/s from zero to infinity. We show that an eta/s ratio larger than 0.2 prevents the development of well-defined Shock Waves on time scales typical for ultrarelativistic heavy-ion collisions. Comparisons with viscous hydrodynamic calculations confirm our findings.
Martin Jubelgas - One of the best experts on this subject based on the ideXlab platform.
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detecting Shock Waves in cosmological smoothed particle hydrodynamics simulations
Monthly Notices of the Royal Astronomical Society, 2006Co-Authors: C Pfrommer, Volker Springel, T A Enslin, Martin JubelgasAbstract:We develop a formalism for the identification and accurate estimation of the strength of structure formation Shocks during cosmological smoothed particle hydrodynamics simulations. Shocks play a decisive role not only for the thermalization of gas in virializing structures but also for the acceleration of relativistic cosmic rays (CRs) through diffusive Shock acceleration. Our formalism is applicable both to ordinary non-relativistic thermal gas, and to plasmas composed of CRs and thermal gas. To this end, we derive an analytic solution to the one-dimensional Riemann Shock tube problem for a composite plasma of CRs and thermal gas. We apply our methods to study the properties of structure formation Shocks in high-resolution hydrodynamic simulations of the Lambda cold dark matter (� CDM) model. We find that most of the energy is dissipated in weak internal Shocks with Mach numbers M ∼ 2 which are predominantly central flow Shocks or merger Shock Waves traversing halo centres. Collapsed cosmological structures are surrounded by external Shocks with much higher Mach numbers up to M ∼ 1000, but they play only a minor role in the energy balance of thermalization. This is because of the higher pre-Shock gas densities within non-linear structures, and the significant increase of the mean Shock speed as the characteristic halo mass grows with cosmic time. We show that after the epoch of cosmic reionization the Mach number distribution is significantly modified by an efficient suppression of strong external Shock Waves due to the associated increase of the sound speed of the diffuse gas. Invoking a model for CR acceleration in Shock Waves, we find that the average strength of Shock Waves responsible for CR energy injection is higher than that for Shocks that dominate the thermalization of the gas. This implies that the dynamical importance of Shock-injected CRs is comparatively large in the low-density, peripheral halo infalling regions, but is less important for the weaker flow Shocks occurring in central highdensity regions of haloes. When combined with radiative dissipation and star formation, our formalism can also be used to study CR injection by supernova Shocks, or to construct models for Shock-induced star formation in the interstellar medium.
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detecting Shock Waves in cosmological smoothed particle hydrodynamics simulations
arXiv: Astrophysics, 2006Co-Authors: C Pfrommer, Volker Springel, T A Ensslin, Martin JubelgasAbstract:We develop a formalism for the identification and accurate estimation of the strength of structure formation Shocks during cosmological smoothed particle hydrodynamics simulations. Shocks not only play a decisive role for the thermalization of gas in virialising structures but also for the acceleration of relativistic cosmic rays (CRs) through diffusive Shock acceleration. Our formalism is applicable both to ordinary non-relativistic thermal gas, and to plasmas composed of CRs and thermal gas. To this end, we derive an analytical solution to the one-dimensional Riemann Shock tube problem for a composite plasma of CRs and thermal gas. We apply our methods to study the properties of structure formation Shocks in high-resolution hydrodynamic simulations of the LCDM model. We find that most of the energy is dissipated in weak internal Shocks with Mach numbers M~2 which are predominantly central flow Shocks or merger Shock Waves traversing halo centres. Collapsed cosmological structures are surrounded by external Shocks with much higher Mach numbers up to M~1000, but they play only a minor role in the energy balance of thermalization. We show that after the epoch of cosmic reionisation the Mach number distribution is significantly modified by an efficient suppression of strong external Shock Waves due to the associated increase of the sound speed of the diffuse gas. Invoking a model for CR acceleration in Shock Waves, we find that the average strength of Shock Waves responsible for CR energy injection is higher than that for Shocks that dominate the thermalization of the gas. When combined with radiative dissipation and star formation, our formalism can also be used to study CR injection by supernova Shocks, or to construct models for Shock-induced star formation in the interstellar medium. (abridged)
G Haupt - One of the best experts on this subject based on the ideXlab platform.
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Extracorporeal Shock Waves in the Treatment of Pseudarthrosis, Tendinosis Calcarea of the Shoulder, and Calcaneal Spur
Extracorporeal Shock Waves in Orthopaedics, 1998Co-Authors: R. Diesch, G HauptAbstract:The introduction of extracorporeal Shock Waves for the treatment of urolithiasis revolutionized urinary stone therapy [1, 2]. Further applications have included stones elsewhere in the body, such as gall bladder, pancreas, and salivary glands [3–5]. We have evaluated the effect on Shock Waves on wound and fracture healing in experimental models since 1986 and confirmed for the first time the osteogenetic potential of Shock Waves [6–8].
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use of extracorporeal Shock Waves in the treatment of pseudarthrosis tendinopathy and other orthopedic diseases
The Journal of Urology, 1997Co-Authors: G HauptAbstract:AbstractPurpose: The use of Shock Waves in orthopedic diseases was reviewed with special regard to the clinical applications.Materials and Methods: Findings in the literature and results from our own studies were analyzed and summarized.Results: Extracorporeal Shock Waves induced osteoneogenesis in animal models with intact and fractured bones. Based on these findings Shock Waves were used for the treatment of pseudarthrosis in humans. Most patients had at least 1 unsuccessful operation before Shock wave therapy. Complete reunion was noted in 62 to 91% of cases and Shock Waves are recommended by some as the first choice of treatment for hypertrophic pseudarthrosis.After failed nonoperative therapy Shock Waves were used for the treatment of patients with various diseases as secondary treatment. The success rate for treatment of tendinopathies, such as tennis elbow, periarthritis humeroscapularis or calcaneal spur, was approximately 80%. For calcific tendinitis Shock wave therapy seems to be superior to all...
