Articoli di riviste: "Shock profiles"

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ASAKURA, FUMIOKI, e MITSURU YAMAZAKI. "VISCOUS SHOCK PROFILES FOR 2 × 2 SYSTEMS OF HYPERBOLIC CONSERVATION LAWS WITH AN UMBILIC POINT". Journal of Hyperbolic Differential Equations 06, n. 03 (settembre 2009): 483–524. http://dx.doi.org/10.1142/s0219891609001903.

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This article analyzes the existence of viscous shock profiles joining two states satisfying the Rankine–Hugoniot condition that comes from hyperbolic 2 × 2 systems of conservation laws having quadratic flux functions with an isolated umbilic point: the point where the characteristic speeds coincide and the Jacobian matrix of the flux functions is diagonalizable. The systems studied in this note are particularly in Schaeffer and Shearer's cases I and II which are relevant to the three-phase Buckley–Leverett model for oil reservoir flow. It is shown that any compressive and overcompressive shocks have a viscous shock profile provided that there are no undercompressive shock with viscous profile having the same propagation speed. The idea of the proof is a generalization of the first theorem of Morse to noncompact level sets. It is also shown that there exists a shock satisfying the Liu–Oleĭnik condition but having no viscous shock profile. In this case, there is an undercompressive shock with viscous shock profile.

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Smith, M. D., e P. W. J. L. Brand. "H2 profiles of C-type bow shocks". Monthly Notices of the Royal Astronomical Society 245, n. 1 (1 luglio 1990): 108. http://dx.doi.org/10.1093/mnras/245.1.108.

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Summary We present emission-line profiles of molecular hydrogen from curved C-shocks within molecular clouds. Shock configurations arising from the supersonic motion of jets and bullets within a dense cloud are chosen. Bow shock speeds in the range vw = 40-200 km s-1 are investigated. Breakdown through dissociation and selfionization restricts the C-shock section to the bow tail. We find that profiles ire essentially single-peaked and narrow with full widths (at 10 per cent maximum intensity, deconvolved) of up to about 50,40 and 30 km s-1 for cones, hemispherical caps and paraboloids, respectively. Exceptional field alignments can produce lines as wide as 75 km s-1 in the conical shock model. Line asymmetry is critically dependent on the orientation to the observer and, for low-velocity bows, the magnetic field direction. The peak is never significantly shifted away from the radial component of the pre-shock velocity. These results are consistent with observed profiles from H2 peaks associated with Herbig-Haro objects but not with the particularly broad H2 lines in OMC-1 and DR2 1

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Barker, Blake, e Kevin Zumbrun. "Numerical proof of stability of viscous shock profiles". Mathematical Models and Methods in Applied Sciences 26, n. 13 (4 dicembre 2016): 2451–69. http://dx.doi.org/10.1142/s0218202516500585.

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We carry out the first rigorous numerical proof based on Evans function computations of stability of viscous shock profiles, for the system of isentropic gas dynamics with monatomic equation of state. We treat a selection of shock strengths ranging from the lower stability boundary of Mach number [Formula: see text], below which profiles are known by energy estimates to be stable, to the upper stability boundary of [Formula: see text], above which profiles are expected to be provable by rigorous asymptotic analysis to be stable. These results open the possibilities of: (i) automatic rigorous verification of stability or instability of individual shocks of general systems, and (ii) rigorous proof of stability of all shocks of particular systems.

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BEN ABDALLAH, NAOUFEL, HEDIA CHAKER e CHRISTIAN SCHMEISER. "THE HIGH FIELD ASYMPTOTICS FOR A FERMIONIC BOLTZMANN EQUATION: ENTROPY SOLUTIONS AND KINETIC SHOCK PROFILES". Journal of Hyperbolic Differential Equations 04, n. 04 (dicembre 2007): 679–704. http://dx.doi.org/10.1142/s0219891607001318.

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The high field approximation of a fermionic Boltzmann equation of semiconductors is performed after the formation of shocks. By employing a new entropy, whose dissipation measures the departure from the high field equilibrium, convergence towards the entropic solution of the limiting conservation law is proven. The entropy is also used to construct kinetic shock profiles for entropic shocks and to prove non-existence of non-entropic shock profiles.

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Fuda, Nguyen, Le Ngoc Tram e William T. Reach. "Modeling CO Line Profiles in Shocks of W28 and IC 443". Astrophysical Journal 944, n. 1 (1 febbraio 2023): 17. http://dx.doi.org/10.3847/1538-4357/acb259.

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Abstract Molecular emission arising from the interactions of supernova remnant (SNR) shock waves and molecular clouds provide a tool for studying the dispersion and compression that might kick-start star formation as well as understanding cosmic-ray production. Purely rotational CO emission created by magnetohydrodynamic shock in the SNR–molecular cloud interaction is an effective shock tracer, particularly for slow-moving, continuous shocks into cold inner clumps of the molecular cloud. In this work, we present a new theoretical radiative transfer framework for predicting the line profile of CO with the Paris–Durham 1D shock model. We generated line profile predictions for CO emission produced by slow, magnetized C shocks into gas of density ∼104 cm−3 with shock speeds of 35 and 50 km s−1. The numerical framework to reproduce the CO line profile utilizes the large velocity gradient (LVG) approximation and the omission of optically thick plane-parallel slabs. With this framework, we generated predictions for various CO spectroscopic observations up to J = 16 in SNRs W28 and IC 443, obtained with SOFIA, IRAM-30 m, APEX, and KPNO. We found that CO line profile prediction offers constraints on the shock velocity and pre-shock density independent of the absolute line brightness and requires fewer CO lines than diagnostics using a rotational excitation diagram.

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Jadhav, Ravi Sudam, e Amit Agrawal. "Shock Structures Using the OBurnett Equations in Combination with the Holian Conjecture". Fluids 6, n. 12 (26 novembre 2021): 427. http://dx.doi.org/10.3390/fluids6120427.

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In the present work, we study the normal shock wave flow problem using a combination of the OBurnett equations and the Holian conjecture. The numerical results of the OBurnett equations for normal shocks established several fundamental aspects of the equations such as the thermodynamic consistency of the equations, and the existence of the heteroclinic trajectory and smooth shock structures at all Mach numbers. The shock profiles for the hydrodynamic field variables were found to be in quantitative agreement with the direct simulation Monte Carlo (DSMC) results in the upstream region, whereas further improvement was desirable in the downstream region of the shock. For the discrepancy in the downstream region, we conjecture that the viscosity–temperature relation (μ∝Tφ) needs to be modified in order to achieve increased dissipation and thereby achieve better agreement with the benchmark results in the downstream region. In this respect, we examine the Holian conjecture (HC), wherein transport coefficients (absolute viscosity and thermal conductivity) are evaluated using the temperature in the direction of shock propagation rather than the average temperature. The results of the modified theory (OBurnett + HC) are compared against the benchmark results and we find that the modified theory improves upon the OBurnett results, especially in the case of the heat flux shock profile. We find that the accuracy gain is marginal at lower Mach numbers, while the shock profiles are described better using the modified theory for the case of strong shocks.

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Zhu, Z., A. Simionescu, H. Akamatsu, X. Zhang, J. S. Kaastra, J. de Plaa, O. Urban, S. W. Allen e N. Werner. "A shock near the virial radius of the Perseus Cluster". Astronomy & Astrophysics 652 (agosto 2021): A147. http://dx.doi.org/10.1051/0004-6361/202140673.

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Context. Previous X-ray studies of the Perseus Cluster, consisting of 85 Suzaku pointings along eight azimuthal directions, revealed a particularly steep decrease in the projected temperature profile near the virial radius (∼r200) towards the northwest (NW). Aims. To further explore this shock candidate, another 4 Suzaku observations on the NW edge of the Perseus Cluster have been obtained. These deeper data were designed to provide the best possible control of systematic uncertainties in the spectral analysis. Methods. Using the combined Suzaku observations, we have carefully investigated this interesting region by analyzing the spectra of various annuli and extracting projected thermodynamic profiles. Results. We find that the projected temperature profile shows a break near r200, indicating a shock with ℳ = 1.9 ± 0.3. Corresponding discontinuities are also found in the projected emission measure and the density profiles at the same location. This evidence of a shock front so far away from the cluster center is unprecedented, and may provide a first insight into the properties of large-scale virial shocks which shape the process of galaxy cluster growth.

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M., Gowtham, Sreenivasaraja N. e Kasmir Anthireyan. "MATHEMATICAL DERIVATION OF DIFFERENT NOSE ANGLES TO REDUCE DRAG FORCE ON ROCKET". International Journal of Innovative Research in Advanced Engineering 9, n. 12 (31 dicembre 2022): 471–82. http://dx.doi.org/10.26562/ijirae.2022.v0912.03.

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This article elaborates on the study of the mathematical expressions for the different nose profiles and their dimensions. The chosen nose profiles are Conical, Bi-conic, Parabolic, Elliptical, and Ogive. And order to improve the study of the pressure coefficient, shock wave angle, shock location, and drag characteristics of nose profiles to select which profile is preferable for a rocket under the aerodynamic forces.

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Howard, Peter, e Kevin Zumbrun. "Stability of undercompressive shock profiles". Journal of Differential Equations 225, n. 1 (giugno 2006): 308–60. http://dx.doi.org/10.1016/j.jde.2005.09.001.

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Yang, Zhao, e Kevin Zumbrun. "Stability of Hydraulic Shock Profiles". Archive for Rational Mechanics and Analysis 235, n. 1 (29 luglio 2019): 195–285. http://dx.doi.org/10.1007/s00205-019-01422-4.

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Held, Manfred. "Shock Profiles Along a Specimen". Propellants, Explosives, Pyrotechnics 24, n. 6 (dicembre 1999): 360–65. http://dx.doi.org/10.1002/(sici)1521-4087(199912)24:6<360::aid-prep360>3.0.co;2-t.

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Ge, Changfeng, Kyle Dunno, Mukul Anand Singh, Long Yuan e Li-Xin Lu. "Development of a Drone’s Vibration, Shock, and Atmospheric Profiles". Applied Sciences 11, n. 11 (2 giugno 2021): 5176. http://dx.doi.org/10.3390/app11115176.

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Technological advances in unmanned aerial vehicles (UAVs) have made it possible to employ drone deliveries for packaged products, but currently no standards of practice are available to qualify packaged products traveling through this distribution channel. This research proposes a methodology to collect field data from a UAV to develop simulation techniques for use with package testing equipment. This project utilized data recorders to measure the vibration, shock, and atmospheric field data on two models of the DJI drones. The root mean square G value (Grms), the power spectral density (PSD), maximum G-values and shock response spectrum, and atmospheric data were reported in this study. The study found that the general shape of the PSD profile of the drones differed from the PSD air profiles of the aircraft. The overall recorded Grms levels of the drones were also significantly higher than those of the published air profile of the aircraft. Moreover, the study found that the drone’s in-flight vibration intensities in the horizontal level were consistently higher than those in the vertical direction. The major sources of vibration and shock in both drones’ models originated from the two-propeller rotations. Shocks recorded during the flight reached 14 G, took place in the horizontal plane with the drone accelerating as opposed to the vertical plane where the drone is landing.

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GOODMAN, JEREMY, e ANDREW MACFADYEN. "Ultra-relativistic geometrical shock dynamics and vorticity". Journal of Fluid Mechanics 604 (14 maggio 2008): 325–38. http://dx.doi.org/10.1017/s0022112008001249.

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Geometrical shock dynamics, also called CCW theory, yields approximate equations for shock propagation in which only the conditions at the shock appear explicitly; the post-shock flow is presumed approximately uniform and enters implicitly via a Riemann invariant. The non-relativistic theory, formulated by G. B. Whitham and others, matches many experimental results surprisingly well. Motivated by astrophysical applications, we adapt the theory to ultra-relativistic shocks advancing into an ideal fluid whose pressure is negligible ahead of the shock, but is one third of its proper energy density behind the shock. Exact results are recovered for some self-similar cylindrical and spherical shocks with power-law pre-shock density profiles. Comparison is made with numerical solutions of the full hydrodynamic equations. We review relativistic vorticity and circulation. In an ultra-relativistic ideal fluid, circulation can be defined so that it changes only at shocks, notwithstanding entropy gradients in smooth parts of the flow.

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Slivka, M., K. Kudela, M. Borodkova e G. Zastenker. "Energetic Protons Associated with Interplanetary Shocks". International Astronomical Union Colloquium 144 (1994): 491–94. http://dx.doi.org/10.1017/s0252921100025872.

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AbstractDuring the period March - May 1981, nine interplanetary shocks passing through the position of the Prognoz-8 s/c influenced the flux of energetic protons (Ep≥ 12 keV). The temporal profiles of two of them agree with the model of diffusional acceleration. They have the greatest shock strength (among the nine observed), which corresponds to a maximum energy gain in the individual interactions of the protons with the shock front. Both are most probably associated with quasiparallel shocks initiated by the flares with the eastern heliolongitudes(> 30° E).Two events with the profile expected for the drift acceleration are caused by the flares at the western longitudes(> 30° W).The peak flux for the flares with the high importance (3B) is higher than that for low importance flares (IN) if all “intermediate” flares (position 30° E - 30° W) are combined. For those events the flux profile is more complicated and signatures of both acceleration mechanisms are apparent.

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Kahler, S. W., V. G. Stolpovskii e E. I. Daibog. "Coronal Mass Ejections and the Rise Profiles of 0.3 MeV Electron Events". International Astronomical Union Colloquium 144 (1994): 479–82. http://dx.doi.org/10.1017/s0252921100025847.

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AbstractThere is some evidence to suggest that relativistic electrons observed in interplanetary space may be produced in coronal shocks. If so, the rise phases of such events may be longer than those not arising in shocks. To test this possibility, we examined the rise profiles ofE< 0.3MeVelectron events observed on the Helios spacecraft. First we compared rise times of electron events associated with short-duration X-ray flares to events with long-duration X-ray flares. The latter events are more likely than the former to be associated with coronal shocks and coronal mass ejections (CMEs). For a smaller group of electron events we determined the rise times as a function of the speed of the CME observed with the NRL Solwind coronagraph to see whether higher shock speeds resulted in longer event rise times. The data show a weak indication that event rise times increase with CME presence and with CME speed, thus suggesting a role for shock acceleration.

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Lattanzio, Corrado, Corrado Mascia, Toan Nguyen, Ramón G. Plaza e Kevin Zumbrun. "Stability of Scalar Radiative Shock Profiles". SIAM Journal on Mathematical Analysis 41, n. 6 (gennaio 2010): 2165–206. http://dx.doi.org/10.1137/09076026x.

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Sukhtayev, Alim, Zhao Yang e Kevin Zumbrun. "Spectral stability of hydraulic shock profiles". Physica D: Nonlinear Phenomena 405 (aprile 2020): 132360. http://dx.doi.org/10.1016/j.physd.2020.132360.

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Karni, S. "Viscous Shock Profiles and Primitive Formulations". SIAM Journal on Numerical Analysis 29, n. 6 (dicembre 1992): 1592–609. http://dx.doi.org/10.1137/0729092.

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Margolin, L. G., J. M. Reisner e P. M. Jordan. "Entropy in self-similar shock profiles". International Journal of Non-Linear Mechanics 95 (ottobre 2017): 333–46. http://dx.doi.org/10.1016/j.ijnonlinmec.2017.07.003.

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Zhang, Y., J. M. Stewart, B. Morosin, R. A. Graham e C. R. Hubbard. "X-Ray Line Broadening Study on Shock-Modified Hematite". Advances in X-ray Analysis 31 (1987): 287–94. http://dx.doi.org/10.1154/s0376030800022096.

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AbstractHematite (α-Fe2O3) powder compacts have been subjected to controlled, quantitative high pressure shock loading at peak pressures from 8-27 GPa and preserved for post shook analysis. The broadened x-ray diffraction peak profiles have been analyzed to determine the residual lattice strain and the coherent crystallite sizes. Maximum modification effects are observed near 17 GPa with strain values near 3 x 10-3 and size values near 200 Å suggesting annealing at higher shock pressure, resulting from the higher shock temperature.

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Thölken, Sophia, Thomas H. Reiprich, Martin W. Sommer e Naomi Ota. "Discovery of large scale shock fronts correlated with the radio halo and radio relic in the A2163 galaxy cluster". Astronomy & Astrophysics 619 (novembre 2018): A68. http://dx.doi.org/10.1051/0004-6361/201834053.

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Context. Galaxy clusters form at the intersections of the filamentary large scale structure in merging events and by the accretion of matter along these filaments. Imprints of these formation processes should be visible in the intracluster medium and can arise in shock fronts, which are detectable via discontinuities in, for example, the gas temperature and density profiles. However, relatively few observational examples of prominent shocks have been detected in X-rays so far. Aims. In this study, we investigate the X-ray properties of the intracluster gas and the radio morphology of the extraordinary cluster A2163. This cluster shows an irregular morphology in various wavelengths and has one of the most luminous and extended radio halos known. Additionally, it is one of the hottest clusters known. We aim to measure the temperature and density profiles in two azimuthal directions to search for the presence of shock fronts. Methods. We performed a spectral analysis of data from two Suzaku observations, one in the north-east (NE) and one in the southwest (SW) direction of A2163, and used archival XMM-Newton data to remove point sources in the field of view. We deprojected the temperature and density profiles and accounted for the Suzaku point spread function. From the detected discontinuities in the density and temperature profiles, we estimated the Mach numbers and velocities of the shock fronts. To compare our findings in the X-ray regime with the radio emission, we obtained radio images of the cluster from an archival Very Large Array (VLA) observation at 20 cm. Results. We identify three shock fronts in A2163 in our spectral X-ray study. A clear shock front lies in the NE direction at a distance of 1.4 Mpc from the center, with a Mach number of M = 1.7+0.3−0.2, estimated from the temperature discontinuity. This shock coincides with the position of a known radio relic. We identify two additional shocks in the SW direction, one with M = 1.5+0.5−0.3 at a distance of 0.7 Mpc, which is likely related to a cool core remnant, and a strong shock with M = 3.2+0.6−0.7 at a distance of 1.3 Mpc, which also closely matches the radio contours. The complex structure of A2163 as well as the different Mach numbers and shock velocities suggest a merging scenario with two unequal merging constituents, where two shock fronts emerged at an early stage of the merger and traveled outwards while an additional shock front developed in front of the merging cluster cores.

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Chang, Ling Chiao, S. J. Tsai, Jia Sheng Wei e Pin Ching Chen. "Manufacturing of Cycloid Tooth Profile for RV and Cyclo Drives by Threaded Wheel Hobbing and Grinding". Key Engineering Materials 825 (ottobre 2019): 106–13. http://dx.doi.org/10.4028/www.scientific.net/kem.825.106.

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Cycloid planetary gear drives are widely used in power and precision motion transmission because of high gear-ratio and good shock absorbability. The aim of the paper is to propose a synthesis approach to generate necessary profiles for manufacturing with thread-wheel type tools based on a given cycloid tooth profile. Two different cases are illustrated in the paper to calculate these profiles, the profiles of thread wheel on normal or axial section, the equivalent rack profile, as well as the profile of dressing or grinding wheel for grinding or hobbing.

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Oh, Jong-Seok, Tae-Hoon Lee e Seung-Bok Choi. "Design and Analysis of a New Magnetorheological Damper for Generation of Tunable Shock-Wave Profiles". Shock and Vibration 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/8963491.

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A new impact testing system with an integrated magnetorheological (MR) damper is proposed, and its dynamic characteristics are analyzed. The testing system consists of a velocity generator, impact mass, test mass, spring, and MR damper. In order to tune the dual shock-wave profile, a dynamic model was constructed, and the appropriate design parameters of the MR damper were then determined to produce the required damping force. Following this, an impact testing system was constructed to evaluate the design analysis and field-dependent dual shock-wave profiles. The experimental results of impact test showed that the dual shock-wave profile can be altered by changing the intensity of the magnetic field.

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Krantz, Marcus, Bodil Nordlander, Hadi Valadi, Mikael Johansson, Lena Gustafsson e Stefan Hohmann. "Anaerobicity Prepares Saccharomyces cerevisiae Cells for Faster Adaptation to Osmotic Shock". Eukaryotic Cell 3, n. 6 (dicembre 2004): 1381–90. http://dx.doi.org/10.1128/ec.3.6.1381-1390.2004.

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ABSTRACT Yeast cells adapt to hyperosmotic shock by accumulating glycerol and altering expression of hundreds of genes. This transcriptional response of Saccharomyces cerevisiae to osmotic shock encompasses genes whose products are implicated in protection from oxidative damage. We addressed the question of whether osmotic shock caused oxidative stress. Osmotic shock did not result in the generation of detectable levels of reactive oxygen species (ROS). To preclude any generation of ROS, osmotic shock treatments were performed in anaerobic cultures. Global gene expression response profiles were compared by employing a novel two-dimensional cluster analysis. The transcriptional profiles following osmotic shock under anaerobic and aerobic conditions were qualitatively very similar. In particular, it appeared that expression of the oxidative stress genes was stimulated upon osmotic shock even if there was no apparent need for their function. Interestingly, cells adapted to osmotic shock much more rapidly under anaerobiosis, and the signaling as well as the transcriptional response was clearly attenuated under these conditions. This more rapid adaptation is due to an enhanced glycerol production capacity in anaerobic cells, which is caused by the need for glycerol production in redox balancing. Artificially enhanced glycerol production led to an attenuated response even under aerobic conditions. These observations demonstrate the crucial role of glycerol accumulation and turgor recovery in determining the period of osmotic shock-induced signaling and the profile of cellular adaptation to osmotic shock.

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Thooft, Aurélie, Raphaël Conotte, Jean-Marie Colet, Karim Zouaoui Boudjeltia, Patrick Biston e Michaël Piagnerelli. "Serum Metabolomic Profiles in Critically Ill Patients with Shock on Admission to the Intensive Care Unit". Metabolites 13, n. 4 (5 aprile 2023): 523. http://dx.doi.org/10.3390/metabo13040523.

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Inflammatory processes are common in intensive care (ICU) patients and can induce multiple changes in metabolism, leading to increased risks of morbidity and mortality. Metabolomics enables these modifications to be studied and identifies a patient’s metabolic profile. The objective is to precise if the use of metabolomics at ICU admission can help in prognostication. This is a prospective ex-vivo study, realized in a university laboratory and a medico-surgical ICU. Metabolic profiles were analyzed by proton nuclear magnetic resonance. Using multivariable analysis, we compared metabolic profiles of volunteers and ICU patients divided into predefined subgroups: sepsis, septic shock, other shock and ICU controls. We also assessed possible correlations between metabolites and mortality. One hundred and eleven patients were included within 24 h of ICU admission, and 19 healthy volunteers. The ICU mortality rate was 15%. Metabolic profiles were different in ICU patients compared to healthy volunteers (p < 0.001). Among the ICU patients, only the subgroup of patients with septic shock had significant differences compared to the ICU control patients in several metabolites: pyruvate, lactate, carnitine, phenylalanine, urea, creatine, creatinine and myo-inositol. However, there was no correlation between these metabolite profiles and mortality. On the first day of ICU admission, we observed changes in some metabolic products in patients with septic shock, suggesting increased anaerobic glycolysis, proteolysis, lipolysis and gluconeogenesis. These changes were not correlated with prognosis.

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Guan, Jian, e Ji’ang Han. "Numerical Investigation of Blade-to-Blade Surface Layout in the Ram-rotor". Journal of Physics: Conference Series 2569, n. 1 (1 agosto 2023): 012073. http://dx.doi.org/10.1088/1742-6596/2569/1/012073.

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Abstract A numerical investigation has been conducted on the ram-rotor with various blade-to-blade profiles to achieve potential benefits in enhancing their performance. The blade-to-blade profile is changed by adjusting the strake camber line to enable the formation of expansive and contractive flow paths. Results indicate that the expansive flow path can significantly improve the total pressure ratio of the ram-rotor by altering the position of shock trains. Subsonic airflow after the shock train is decelerated and pressurized, which further contributes to the pressure rising capacity. The leakage flow is suppressed as the flow path is contractive in the blade-to-blade view. This, in turn, leads to a significant reduction of both tip leakage loss and the interference effect between the leakage and the shocks.

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Zhang, Congyao, Eugene Churazov, William R. Forman e Natalia Lyskova. "Runaway merger shocks in galaxy cluster outskirts and radio relics". Monthly Notices of the Royal Astronomical Society 488, n. 4 (5 agosto 2019): 5259–66. http://dx.doi.org/10.1093/mnras/stz2135.

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ABSTRACT Moderately strong shocks arise naturally when two subclusters merge. For instance, when a smaller subcluster falls into the gravitational potential of a more massive cluster, a bow shock is formed and moves together with the subcluster. After pericentre passage, however, the subcluster is decelerated by the gravity of the main cluster, while the shock continues moving away from the cluster centre. These shocks are considered as promising candidates for powering radio relics found in many clusters. The aim of this paper is to explore the fate of such shocks when they travel to the cluster outskirts, far from the place where the shocks were initiated. In a uniform medium, such a ‘runaway’ shock should weaken with distance. However, as shocks move to large radii in galaxy clusters, the shock is moving down a steep density gradient that helps the shock to maintain its strength over a large distance. Observations and numerical simulations show that, beyond R500, gas density profiles are as steep as, or steeper than, ∼r−3, suggesting that there exists a ‘habitable zone’ for moderately strong shocks in cluster outskirts where the shock strength can be maintained or even amplified. A characteristic feature of runaway shocks is that the strong compression, relative to the initial state, is confined to a narrow region just behind the shock. Therefore, if such a shock runs over a region with a pre-existing population of relativistic particles, then the boost in radio emissivity, due to pure adiabatic compression, will also be confined to a narrow radial shell.

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Harnisch, Lars-Olav, e Onnen Moerer. "The Specific Bile Acid Profile of Shock: A Hypothesis Generating Appraisal of the Literature". Journal of Clinical Medicine 9, n. 12 (26 novembre 2020): 3844. http://dx.doi.org/10.3390/jcm9123844.

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Background: Bile acid synthesis and regulation of metabolism are tightly regulated. In critical illness, these regulations are impaired. Consequently, the physiologic bile acid pattern in serum becomes disturbed and a disease-specific bile acid profile seems to become evident. Methods: A literature review was performed and trials reporting the broken-down bile acid pattern were condensed with regard to percent differences in bile acid profiles of defined diseases compared to a human control. Results: Ten articles were identified. Most of the studied bile acid profiles differ statistically significant between disease states, furthermore, neither of the reported disease entities show the same broken-down pattern of individual bile acids. Deoxycholic acid (DCA) was found to be decreased in almost all diseases, except for the two shock-states investigated (cardiogenic shock, septic shock) where it was elevated by about 100% compared to the control. Moreover, the pattern of both examined shock-states are very similar, rendering a specific shock-pattern possible, that we argue could eventually maintain or even worsen the pathological state. Conclusion: The specific broken-down bile acid profile of defined diseases might aid in gaining insight into the body’s adaptive reaction and the differential diagnosis, as well as in the therapy of disease states in the early course of the disease.

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MEI, MING. "STABILITY OF SHOCK PROFILES FOR NONCONVEX SCALAR VISCOUS CONSERVATION LAWS". Mathematical Models and Methods in Applied Sciences 05, n. 03 (maggio 1995): 279–96. http://dx.doi.org/10.1142/s0218202595000188.

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This paper is to study the stability of shock profiles for nonconvex scalar viscous conservation laws with the nondegenerate and the degenerate shock conditions by means of an elementary energy method. In both cases, the shock profiles are proved to be asymptotically stable for suitably small initial disturbances. Moreover, in the case of nondegenerate shock condition, time decay rates of asymptotics are also obtained.

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Ceurvorst, L., W. Theobald, M. J. Rosenberg, P. B. Radha, C. Stoeckl, R. Betti, K. S. Anderson et al. "Development of an x-ray radiography platform to study laser-direct-drive energy coupling at the National Ignition Facility". Review of Scientific Instruments 93, n. 10 (1 ottobre 2022): 105102. http://dx.doi.org/10.1063/5.0098982.

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A platform has been developed to study laser-direct-drive energy coupling at the National Ignition Facility (NIF) using a plastic sphere target irradiated in a polar-direct-drive geometry to launch a spherically converging shock wave. To diagnose this system evolution, eight NIF laser beams are directed onto a curved Cu foil to generate He α line emission at a photon energy of 8.4 keV. These x rays are collected by a 100-ps gated x-ray imager in the opposing port to produce temporally gated radiographs. The platform is capable of acquiring images during and after the laser drive launches the shock wave. A backlighter profile is fit to the radiographs, and the resulting transmission images are Abel inverted to infer radial density profiles of the shock front and to track its temporal evolution. The measurements provide experimental shock trajectories and radial density profiles that are compared to 2D radiation-hydrodynamic simulations using cross-beam energy transfer and nonlocal heat-transport models.

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31

RAOOFI, MOHAMMADREZA. "Lp ASYMPTOTIC BEHAVIOR OF PERTURBED VISCOUS SHOCK PROFILES". Journal of Hyperbolic Differential Equations 02, n. 03 (settembre 2005): 595–644. http://dx.doi.org/10.1142/s0219891605000567.

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We investigate the Lp asymptotic behavior (1 ≤ p ≤ ∞) of a perturbation of a Lax or overcompressive type shock wave solution to a system of conservation law in one dimension. The system of the equations can be strictly parabolic, or partially parabolic (real viscosity case, e.g. compressible Navier–Stokes equations or equations of Magnetohydrodynamics). We use known pointwise Green function bounds for the linearized equation around the shock to show that the perturbation of such a solution can be decomposed into a part corresponding to shift in shock position or shape, a part which is the sum of diffusion waves, i.e. the solutions to a viscous Burger's equation, conserving the initial mass and convecting away from the shock profile in outgoing modes, and another part which is more rapidly decaying in any Lp norm.

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32

Liao, Chang Rong, J. H. Hao, D. X. Zhao e K. L. Wang. "Study on Design Method of Magneto-Rheological Fluid Shock Absorber Employing Shear Rate Profiles and Experimental Tests". Applied Mechanics and Materials 121-126 (ottobre 2011): 1095–99. http://dx.doi.org/10.4028/www.scientific.net/amm.121-126.1095.

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The flow differential equation for Magneto-rheological (MR) fluids in annular channels of MR fluid shock absorber is set up and several rational simplifications are made. Analytical shear stress profiles of MR fluids through annular channels are obtained via solution of the flow differential equation. An analytical study on MR fluid shock absorber is present employing shear stress profiles. Both boundary conditions and compatible conditions are established. Both flow velocity profiles and total volumetric flow rate are developed by integration by parts and numerical integration. The prediction method for damping force of MR fluid shock absorber is developed via simultaneous equations. The analytical study on MR fluid shock absorber is validated by means of reformative Herschel–Bulkley constitutive model, in which flow velocity profiles and flow regions boundary radii are drawed. A MR fluid shock absorber, which is designed and fabricated in Chongqing University, is tested by electro-hydraulic servo vibrator in National Center for Test and Supervision of Coach Quality. The experimental results reveal that the methodology is able to predict damping force of MR fluid shock absorber via shear rate profiles and experimental damping forces are in good agreement with analytical those.

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33

Zhu, Z. Y., H. P. Lee e B. T. Cheok. "Finite Element Analysis of Mechanical Shock Responses of RF Connectors". Journal of Electronic Packaging 125, n. 1 (1 marzo 2003): 144–52. http://dx.doi.org/10.1115/1.1536950.

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A numerical study of the effects of mechanical shock on Radio Frequency (RF) connectors is presented. The finite element method is used to analyze the mechanical shock responses of RF connectors. Three commonly used shock profiles, namely the rectangular, the triangular, and the half-sine profiles are considered. The effect of added mass as well as the direction of mechanical shock are also analyzed and discussed.

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34

Kwon, Ryun-Young, e Angelos Vourlidas. "The density compression ratio of shock fronts associated with coronal mass ejections". Journal of Space Weather and Space Climate 8 (2018): A08. http://dx.doi.org/10.1051/swsc/2017045.

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We present a new method to extract the three-dimensional electron density profile and density compression ratio of shock fronts associated with coronal mass ejections (CMEs) observed in white light coronagraph images. We demonstrate the method with two examples of fast halo CMEs (∼2000 km s−1) observed on 2011 March 7 and 2014 February 25. Our method uses the ellipsoid model to derive the three-dimensional geometry and kinematics of the fronts. The density profiles of the sheaths are modeled with double-Gaussian functions with four free parameters, and the electrons are distributed within thin shells behind the front. The modeled densities are integrated along the lines of sight to be compared with the observed brightness in COR2-A, and a χ2 approach is used to obtain the optimal parameters for the Gaussian profiles. The upstream densities are obtained from both the inversion of the brightness in a pre-event image and an empirical model. Then the density ratio and Alfvénic Mach number are derived. We find that the density compression peaks around the CME nose, and decreases at larger position angles. The behavior is consistent with a driven shock at the nose and a freely propagating shock wave at the CME flanks. Interestingly, we find that the supercritical region extends over a large area of the shock and lasts longer (several tens of minutes) than past reports. It follows that CME shocks are capable of accelerating energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere. Our results also demonstrate the power of multi-viewpoint coronagraphic observations and forward modeling in remotely deriving key shock properties in an otherwise inaccessible regime.

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35

Whyte, Lyle G., e William E. Inniss. "Cold shock proteins and cold acclimation proteins in a psychrotrophic bacterium". Canadian Journal of Microbiology 38, n. 12 (1 dicembre 1992): 1281–85. http://dx.doi.org/10.1139/m92-211.

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The synthesis of proteins in the psychrotrophic bacterium Bacillus psychrophilus in response to both cold shock and continuous growth at low temperatures was examined. Cold shocks of 20 to 0, 5, or 10 °C resulted in the induction of nine, seven, and five cold shock proteins, respectively, as determined by 2-dimensional gel electrophoresis and computing scanning laser densitometry. Two cold shock proteins, with molecular masses of 61 and 34 kDa, which were induced in B. psychrophilus by cold shocks of 20 to 0 or 5 °C, were not induced in a cold-sensitive mutant of B. psychrophilus. Analysis of protein profiles of B. psychrophilus during continuous growth at 0, 5, or 10 °C revealed the synthesis of 11, 10, and 4 cold acclimation proteins, respectively. Some of these cold acclimation proteins were similar to cold shock proteins. In addition, the relative synthesis of both cold shock proteins and cold acclimation proteins increased with decreasing temperature. Thus, both types of proteins increased both in number and relative synthesis in response to cold shock and continuous growth at low temperature. Key words: cold shock proteins, cold acclimation proteins, psychrotrophic bacterium.

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36

Coulombel, Jean-Francois, e Pauline Lafitte. "Computation of Shock Profiles in Radiative Hydrodynamics". Communications in Computational Physics 6, n. 5 (2009): 1118–36. http://dx.doi.org/10.4208/cicp.2009.v6.p1118.

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37

Uribe, F. J., R. M. Velasco, L. S. García-Colín e E. Díaz-Herrera. "Shock wave profiles in the Burnett approximation". Physical Review E 62, n. 5 (1 novembre 2000): 6648–66. http://dx.doi.org/10.1103/physreve.62.6648.

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38

Mascia, Corrado, e Kevin Zumbrun. "Spectral Stability of Weak Relaxation Shock Profiles". Communications in Partial Differential Equations 34, n. 2 (12 marzo 2009): 119–36. http://dx.doi.org/10.1080/03605300802553971.

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39

Gómez-Ruiz, A. I., C. Codella, S. Viti, I. Jiménez-Serra, G. Navarra, R. Bachiller, P. Caselli et al. "Diagnosing shock temperature with NH3and H2O profiles". Monthly Notices of the Royal Astronomical Society 462, n. 2 (28 luglio 2016): 2203–17. http://dx.doi.org/10.1093/mnras/stw1811.

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40

Lin, Chunjin, Jean-François Coulombel e Thierry Goudon. "Shock profiles for non-equilibrium radiating gases". Physica D: Nonlinear Phenomena 218, n. 1 (giugno 2006): 83–94. http://dx.doi.org/10.1016/j.physd.2006.04.012.

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41

Zhong, Pei, Yufeng Zhou, Franklin H. Cocks, Charles Marguet, Glenn M. Preminger e John Madden. "Tissue response to modified shock wave profiles". Journal of the Acoustical Society of America 117, n. 4 (aprile 2005): 2383. http://dx.doi.org/10.1121/1.4785659.

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42

Barker, Blake, Marta Lewicka e Kevin Zumbrun. "Existence and Stability of Viscoelastic Shock Profiles". Archive for Rational Mechanics and Analysis 200, n. 2 (7 settembre 2010): 491–532. http://dx.doi.org/10.1007/s00205-010-0363-1.

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43

Smith, Nathan, e Jennifer E. Andrews. "High-resolution spectroscopy of SN 2017hcc and its blueshifted line profiles from post-shock dust formation". Monthly Notices of the Royal Astronomical Society 499, n. 3 (9 ottobre 2020): 3544–62. http://dx.doi.org/10.1093/mnras/staa3047.

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ABSTRACT SN 2017hcc was remarkable for being a nearby and strongly polarized superluminous Type IIn supernova (SN). We obtained high-resolution Echelle spectra that we combine with other spectra to investigate its line-profile evolution. All epochs reveal narrow P Cygni components from pre-shock circumstellar material (CSM), indicating an axisymmetric outflow from the progenitor of 40–50 km s−1. Broad and intermediate-width components exhibit the classic evolution seen in luminous SNe IIn: symmetric Lorentzian profiles from pre-shock CSM lines broadened by electron scattering at early times, transitioning at late times to multicomponent, irregular profiles coming from the SN ejecta and post-shock shell. As in many SNe IIn, profiles show a progressively increasing blueshift, with a clear flux deficit in red wings of the intermediate and broad velocity components after day 200. This blueshift develops after the continuum luminosity fades, and in the intermediate-width component, persists at late times even after the SN ejecta fade. In SN 2017hcc, the blueshift cannot be explained as occultation by the SN photosphere, pre-shock acceleration of CSM, or a lopsided explosion of CSM. Instead, the blueshift arises from dust formation in the post-shock shell and in the SN ejecta. The effect has a wavelength dependence characteristic of dust, exhibiting an extinction law consistent with large grains. Thus, SN 2017hcc experienced post-shock dust formation and had a mildly bipolar CSM shell, similar to SN 2010jl. Like other superluminous SNe IIn, the progenitor lost around 10 M⊙ due to extreme eruptive mass-loss in the decade before exploding.

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44

Bhadra, Sourav, Siddhartha Gupta, Biman B. Nath e Prateek Sharma. "Cosmic rays from massive star clusters: a close look at Westerlund 1". Monthly Notices of the Royal Astronomical Society 510, n. 4 (10 gennaio 2022): 5579–91. http://dx.doi.org/10.1093/mnras/stac023.

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ABSTRACT We study the effect of cosmic ray (CR) acceleration in the massive compact star cluster Westerlund 1 in light of its recent detection in γ-rays. Recent observations reveal a 1/r radial distribution of the CR energy density. Here, we theoretically investigate whether or not this profile can help to distinguish between (1) continuous CR acceleration in the star cluster stellar wind-driven shocks and (2) discrete CR acceleration in multiple supernovae (SNe) shocks – which are often debated in the literature. Using idealized two-fluid simulations and exploring different acceleration sites and diffusion coefficients, we obtain the CR energy density profile and luminosity to find the best match for the γ-ray observations. We find that the inferred CR energy density profiles from observations of γ-ray luminosity and mass can be much different from the true radial profile. CR acceleration at either the cluster core region or the wind termination shock can explain the observations, if the diffusion coefficient is κcr ∼ 1027 cm2 s−1 and a fraction of ${\approx}10-20{{\ \rm per\ cent}}$ of the shock power/post-shock pressure is deposited into the CR component. We also study the possibility of discrete SNe explosions being responsible for CR acceleration and find that with an injection rate of 1 SN in every ∼0.03 Myr, one can explain the observed γ-ray profile. This multiple SN scenario is consistent with X-ray observations only if the thermal conductivity is close to the Spitzer value.

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45

Jacoby, Katherine, Ramiro Saavedra, Matthew Spanier, Joshua Huelster, Alex Campbell, Claire Smith, Barite Dawud e Catherine St. Hill. "Veno-Arterial Extracorporeal Membrane Oxygenation in Adults with Septic Shock". International Journal of Medical Science and Clinical Invention 9, n. 01 (5 gennaio 2022): 5879–90. http://dx.doi.org/10.18535/ijmsci/v9i01.01.

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Survivors and non-survivors were compared for 20 adults supported with veno-arterial extracorporeal membrane oxygenation (VA ECMO) for refractory septic shock from 2012-2018. The primary outcome was hospital survival. Secondary outcomes were ECMO associated complications and survival to decannulation. Median age was 53.5 (IQR 42.0-61.3). At ≤ 24 hours prior to cannulation, median SOFA score was 17.5 (IQR 15 - 19) and 17 patients (85%) had new cardiac dysfunction. Median left ventricular ejection fraction (LVEF) was 20% (IQR 10-38). Thirteen patients had a mixed (cardiogenic and distributive) or cardiogenic shock profile (65%), 7 had a distributive shock profile (35%), and 17 (85%) survived to decannulation. Fourteen (70%) survived to hospital discharge and median cerebral performance category score was 1 (IQR 1-2). No differences were found in age, comorbid conditions, time from shock onset to cannulation, peak flow rate on ECMO, ECMO complications, shock profile, LVEF, or vasoactive-inotrope score (VIS). More patients in the distributive shock profile experienced limb ischemia complications (n=3, 42.9%) compared to the cardiogenic and mixed shock profiles (n=1, 7.7%). Survivors to hospital discharge had a lower SOFA score. VA ECMO support may be a beneficial therapy for refractory septic shock and could be considered in select adult patients.

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46

Takizawa, Motokazu. "X-ray and Radio Observations of the Radio Relic Galaxy Clusters 1RXS J0603.3+4214 and RXC J1053.7+5453". Galaxies 7, n. 1 (22 dicembre 2018): 2. http://dx.doi.org/10.3390/galaxies7010002.

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We study two galaxy clusters with radio relics, 1RXS J0603.3+4214 and RXC J1053.7+5453, through X-ray and radio observations. Radio relics are diffuse non-thermal radio sources found in outskirts of galaxy clusters. Because of their shape and location, they are thought to be related to cluster merger shocks. The galaxy cluster 1RXS J0603.3+4214 has a well-known linear-shape “toothbrush” radio relic. We investigate the temperature structure across the relic to constrain the Mach number of the associated shock. The results are compared with radio spectral results, which suggest that a simple diffusive shock acceleration model does not hold for this relic. The RXC J1053.7+5453 harbors a standard arc-like relic. We also get the Mach number from the temperature profile. In addition, we found an edge-like structure in the X-ray image between the X-ray peak and relic. We investigate the density and temperature profiles across the edge and found that the structure is likely relevant to not a shock but a contact discontinuity.

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47

Jahan, Sharmin, Subrata Banik, Nure Alam Chowdhury, Abdul Mannan e A. A. Mamun. "Electrostatic Shock Structures in a Magnetized Plasma Having Non-Thermal Particles". Gases 2, n. 2 (25 marzo 2022): 22–32. http://dx.doi.org/10.3390/gases2020002.

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A rigorous theoretical investigation has been made on the nonlinear propagation of dust-ion-acoustic shock waves in a multi-component magnetized pair-ion plasma (PIP) having inertial warm positive and negative ions, inertialess non-thermal electrons and positrons, and static negatively charged massive dust grains. The Burgers’ equation is derived by employing the reductive perturbation method. The plasma model supports both positive and negative shock structures in the presence of static negatively charged massive dust grains. It is found that the steepness of both positive and negative shock profiles declines with the increase of ion kinematic viscosity without affecting the height, and the increment of negative (positive) ion mass in the PIP system declines (enhances) the amplitude of the shock profile. It is also observed that the increase in oblique angle raises the height of the positive shock profile, and the height of the positive shock wave increases with the number density of positron. The applications of the findings from the present investigation are briefly discussed.

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48

Rons, N. "Understanding the P Cygni profile". Symposium - International Astronomical Union 162 (1994): 500–501. http://dx.doi.org/10.1017/s007418090021574x.

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Narrow Absorption Components (NACs) have been detected in essentially all unsaturated P Cygni profiles of O-type stars (Howarth & Prinja, 1989). Time-series of observations have revealed their migration through the profile's absorption trough (Prinja et al., 1987, Henrichs et al., 1988). The interpretation of the NACs is essential for the understanding of the dynamic structure of the winds of O stars and of the driving mechanisms behind it. The P Cygni profile substructures caused by isolated reverse and forward shocks were calculated in a ‘line only’ approximation for a spherically symmetric, isothermal stellar wind. The Comoving Frame method was used for an accurate treatment of the complex radiation transfer in the shock environment. The underlying velocity structure follows a β-law (except in the innermost layers where a polynomial law was used) while the ionization was taken to be constant throughout the entire wind.

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49

Webster, James, Jianbiao Pan e Brian J. Toleno. "Investigation of the Lead-free Solder Joint Shear Performance". Journal of Microelectronics and Electronic Packaging 4, n. 2 (1 aprile 2007): 72–77. http://dx.doi.org/10.4071/1551-4897-4.2.72.

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Reflow profile has significant impact on solder joint performance because it influences wetting and microstructure of the solder joint. The purpose of this study is to investigate the effects of reflow profile and thermal shock on the shear performance of eutectic SnPb (SnPb) and Sn3.0Ag0.5Cu (SAC305) solder joints. Test boards were assembled with four different sized surface mount chip resistors (1206, 0805, 0603 and 0402). Nine reflow profiles for SAC 305 and nine reflow profiles for SnPb were developed with three levels of peak temperature (12°C, 22°C, and 32°C above solder liquidus temperature, or 230°C, 240°C, and 250°C for SAC 305; and 195°C, 205°C, and 215°C for SnPb) and three levels of time above solder liquidus temperature (30 sec., 60 sec., and 90 sec.). Half of the test vehicles were then subjected to air-to-air thermal shock conditioning from −40 to 125°C. The shear force data were analyzed using the Analysis of Variance (ANOVA). The fracture surfaces were studied using a Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). It was found that thermal shock degraded both SnPb and SnAgCu joints shear strength, and that the effect of thermal shock on solder joint shear strength is much more significant than that of reflow profile. The SnAgCu solder joints have weaker shear strength than the SnPb solders. The SnAgCu solder joint after thermal shock retains more of its shear strength than that of SnPb for small components and vice versa for larger components.

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50

Fokin, Andrew. "A Full-Amplitude Nonlinear Model for RR Lyr: Pulsations, Shock Waves and Hα Peculiarities". International Astronomical Union Colloquium 139 (1993): 265. http://dx.doi.org/10.1017/s0252921100117555.

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AbstractThe shock phenomena and Hα formation in the atmosphere of RR Lyrae are investigated by means of numerical simulations. The full-amplitude hydrodynamical model is generated, adopting M = 0.578M⊙, L = 62L⊙, Teff = 7175K and Population II composition. The Hα profiles are obtained by solution of the non-LTE line transfer problem for the multilevel hydrogen atom. In the course of pulsations an extended (about 16 static scales) low-density atmosphere is produced with nearly exponential density decrease. Two shocks, propagating outwards, are successively generated during one period. The shock amplitude reaches 140 km/s. No mass loss has been found. These results confirm the earlier results of S. Hill (1972). The main shock develops very high, at mass depths near 0.001 g per area, whereas computations for W Vir yield 100. An analysis of the Fe I and Ti II lines shows that this difference is sufficient to explain the lack of metallic line-doubling in RR Lyrae stars. The bump on the light curve is due to a weak shock, propagating below the photosphere, which is generated with the early shock at the stage of expansion at the H-recombination front. The central intensities, Dopplerian shifts, amplitudes and phases of splitting of the computed Hα profiles agree well with the observed values (Gillet & Crowe 1988). The lack of strong emission also fits the observations, resulting from strong scattering processes near the shock. The predicted Lyman lines show strong emission, reaching maximum at the maximum light.

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