Primary Shock Research Articles

Tempestuous life beyond R500: X-ray view on the Coma cluster with SRG/eROSITA

This is the first paper in a series of studies of the Coma cluster using the SRG/eROSITA X-ray data obtained in the course of the calibration and performance verification observations. The data cover a ~3° × 3° area around the cluster with a typical exposure time of more than 20 ks. The stability of the instrumental background and operation of the SRG observatory in the scanning mode provided us with an excellent data set for studies of the diffuse emission up to a distance of ~1.5R200 from the Coma center. In this study, we discuss the rich morphology revealed by the X-ray observations (also in combination with the SZ data) and argue that the most salient features can be naturally explained by a recent (ongoing) merger with the NGC 4839 group. In particular, we identify a faint X-ray bridge connecting the group with the cluster, which is convincing proof that NGC 4839 has already crossed the main cluster. The gas in the Coma core went through two shocks, first through the shock driven by NGC 4839 during its first passage through the cluster some gigayear ago and, more recently, through the “mini-accretion shock” associated with the gas settling back to quasi-hydrostatic equilibrium in the core. After passing through the primary shock, the gas should spend much of the time in a rarefaction region, where radiative losses of electrons are small, until the gas is compressed again by the mini-accretion shock. Unlike “runway” merger shocks, the mini-accretion shock does not feature a rarefaction region downstream and, therefore, the radio emission can survive longer. Such a two-stage process might explain the formation of the radio halo in the Coma cluster.

Causes and Consequences of Sea Ice Initialization Shock in Coupled NWP Hindcasts with the GC2 Climate Model

AbstractWe present a coupled retrospective forecast (hindcast) study using the Met Office Global Coupled Model, version 2 (GC2), in which we identify and mitigate causes of initialization shock that lead to rapid error growth in sea ice forecasts. Sea ice state variables and volume budget terms as a function of forecast lead time are evaluated relative to analyses from an uncoupled Met Office ocean–sea ice analysis system [Forecast Ocean Assimilation Model, version 13 (FOAMv13)]. Two sources of initialization shock are highlighted and addressed, both of which are related to effective differences in physics between the analysis system and coupled forecast model. The primary shock to sea ice state variables arises from the use of a salinity-independent freezing temperature for seawater in GC2 as opposed to a salinity-dependent formulation in FOAMv13. A secondary effect arises from differences in the sea ice roughness and hence air–ice drag in the GC2 forecast model compared to the FOAMv13 analysis system. Generalizing from the findings of this study, we suggest that using nonnative analyses as initial conditions for coupled numerical weather prediction (NWP) studies will likely make them prone to initialization shock in some model components, to the detriment of forecast skill. To reduce the undesirable impacts of initialization shock on short-range forecast skill noted in this study we would therefore recommend the use of initial conditions (analyses) physically consistent with the native model components of the coupled forecast model, a native coupled analysis likely being the optimal initialization method.

Clinical efficacy of direct or indirect left ventricular unloading during venoarterial extracorporeal membrane oxygenation for primary cardiogenic shock

ObjectiveLeft ventricular (LV) distention is a feared complication in patients receiving venoarterial (VA) extracorporeal membrane oxygenation (ECMO). LV unloading can be achieved indirectly with intra-aortic balloon pump (IABP) or directly with an Impella device (Abiomed, Danvers, Mass). We sought to assess the clinical and hemodynamic effects of IABP and Impella devices on patients supported with VA ECMO. MethodsWe conducted a retrospective review of VA ECMO patients at our institution from January 2015 to June 2020. Patients were categorized as either ECMO alone or ECMO with LV unloading. LV unloading was characterized as either ECMO with IABP or ECMO with Impella. We recorded baseline characteristics, survival, complications, and hemodynamic changes associated with device initiation. ResultsDuring the study, 143 patients received ECMO alone whereas 140 received ECMO with LV unloading (68 ECMO with IABP, 72 ECMO with Impella). ECMO with Impella patients had a higher incidence of bleeding events compared with ECMO alone or ECMO with IABP (52.8% vs 37.1% vs 17.7%; P < .0001). Compared with ECMO alone, ECMO with IABP patients had better survival at 180 days (log rank P = .005) whereas survival in ECMO with Impella patients was not different (log rank P = .66). In a multivariable Cox hazard analysis, age (hazard ratio [HR], 1.02; 95% confidence interval [CI], 1.00-1.03; P = .015), male sex (HR, 0.54; 95% CI, 0.38-0.80; P = .002), baseline lactate (HR, 1.06; 95% CI, 1.02-1.11; P = .004), baseline creatinine (HR, 1.06; 95% CI, 1.00-1.11; P = .032), need for extracorporeal membrane oxygenation-cardiopulmonary resuscitation (HR, 2.09; 95% CI, 1.40-3.39; P = .001), and presence of pre-ECMO IABP (HR, 0.45; 95% CI, 0.25-0.83; P = .010) were associated with reduced mortality. There was no significant difference in hemodynamic changes in the ECMO with IABP versus ECMO with Impella cohorts. ConclusionsConcomitant support with IABP might help reduce morbidity and improve 180-day survival in patients receiving VA ECMO for cardiogenic shock.

Deflagration-to-detonation Transition in Stratified Oxygen – Liquid Fuel Film Systems

ABSTRACT Deflagration-to-detonation transition (DDT) in gas (oxygen)–liquid n-heptane film and gas (oxygen)–liquid n-decane film systems is registered experimentally using a fused or exploding wire as a weak ignition source that generates a primary shock wave with a Mach number ranging from 1.02 to 1.6. In a straight smooth-walled channel of rectangular cross section 54 × 24 mm, 3 and 6 m long with one open end, the DDT is obtained at distances 900 to 4000 mm from the ignition source 3 to 1700 ms after ignition. The DDT is obtained for n-heptane and n-decane films 0.2 to 0.7 mm thick, which corresponds to the overall fuel-to-oxygen equivalence ratios of 15 to 40. The registered detonation velocities range from 1400 to 2000 m/s. In several experiments, a high-velocity quasi-stationary deflagration front propagating at an average velocity of 700–1100 m/s is recorded. The structure of this front includes the leading shock wave followed by the reaction zone separated from each other by a time delay of 90 to 190 μs. The results obtained are important for explosion safety and for better understanding of the operation process in the continuous-detonation and pulse-detonation combustors of advanced rocket and air-breathing engines with the supply of liquid fuel in the form of a wall film.

The connectedness between Sukuk and conventional bond markets and the implications for investors

PurposeThe purpose of this paper is to examine the connectedness across a variety of Sukuk and conventional bond indices and the implications for optimal asset allocation for the period January 1, 2010–April 30, 2020.Design/methodology/approachThe data set consists of five major Sukuk (Dow Jones Sukuk, Thompson Reuters BPA Malaysia Sukuk, Indonesia Government Sukuk, S&P MENA Sukuk and Tadawul Sukuk and Bonds Index) and five conventional bond indexes, one for developed (USA) and four for emerging markets (Malaysia, Indonesia, Africa and Qatar). This study investigates the connectedness and volatility spillover effects across the aforementioned indices, by following the Diebold and Yilmaz (2012) approach, based on the time-varying parameter vector autoregressive (TVP-VAR) model. In addition, this paper provides optimal hedge ratios and portfolio weights for investors.FindingsThe empirical results show that Sukuk and conventional bond markets are highly integrated and that total connectedness exhibits sensitivity to exogenous shocks. The Dow Jones and the Malaysian Sukuk indices are the primary shock transmitters to other markets. However, the weak volatility spillovers between the Dow Jones and conventional bonds suggest that opportunities for optimal asset allocation may in fact exist. The highest (lowest) hedging effectiveness can be achieved by taking a short position in Malaysian (Qatarian) bonds.Originality/valueTo the best of the knowledge, this is the largest sample taken into account to investigate the connectedness between Sukuk and conventional bonds.

Experimental investigation of shock train behavior in a supersonic isolator

For a better understanding of the shock train structure and its dynamic oscillation features, wind tunnel experiments with linear and stepwise increase backpressure were conducted with supersonic isolator flows at Mach 1.85 and 2.70. High-frequency wall static pressure measurements were performed along the primary and corner regions to capture the behavior of the primary and corner shock train. The fine structures of the shock train were recorded using schlieren visualization with circular, horizontal, vertical, and color knife edges. The pressure results show that the shock train leading shock at Mach 2.70 is more three-dimensional. The flow field exhibits the following features near the corner: the pressure fluctuation amplitude is smaller, the shock train leading shock is closer to the upstream regions, and the oscillation of the shock train leading shock can propagate a longer distance downstream. Schlieren snapshots obtained using horizontal and vertical knife edges show shock train structures with alternating distributions of the vertical and horizontal density gradients. Further application of color knife edges clearly distinguishes these regions. The power spectra analysis of a series of schlieren snapshots was performed to characterize the dominant oscillation structures in the flow field with different visualization variables, and the motion relationship between the structures in the shock train was clarified based on the coherence and phase analyses of the schlieren images. The disturbance downstream first causes the movement of the shock train leading shock, and the closer the downstream shock is to the shock train leading shock, the earlier it moves.

Public debt, sovereign spreads and the unpleasant arithmetic of fiscal consolidations

AbstractIn response to severe fiscal consolidation policies implemented after the Great Recession and the euro area sovereign debt crisis, many have questioned the effectiveness of fiscal consolidations in reducing the burden of public debt. This paper revisits this fundamental policy debate qualitatively and quantitatively, studying conditions under which primary budget balance changes can successfully reduce government debt‐to‐GDP ratios. We first illustrate these conditions through a partial equilibrium setting. We then investigate the conditions quantitatively using a medium‐scale New Keynesian DSGE model calibrated on periphery countries of the euro area. The analysis highlights the critical role of sovereign spreads in driving the debt‐to‐GDP dynamics following a restrictive primary balance shock. Fiscal consolidations turn out to successfully reduce the debt‐to‐GDP even for fairly low elasticities of spreads to fiscal variables. However, their effectiveness is quantitatively moderate and varies crucially with the initial spread level, with the degree of monetary policy accommodation, and with the responsiveness of market investors to economic fundamentals.

Numerical optimisation of a micro-wave rotor turbine using a quasi-two-dimensional CFD model and a hybrid algorithm

Wave rotors are unsteady flow machines that exchange energy through pressure waves. This has the potential for enhancing efficiency over a wide spectrum of applications, ranging from gas turbine topping cycles to pressure-gain combustors. This paper introduces an aerodynamic shape optimisation of a power generating non-axial micro-wave rotor turbine and seeks to enhance the shaft power output while preserving the wave rotor’s capacity to function as a pressure-exchanging device. The optimisation considers six parameters including rotor shape profile, wall thickness, and number of channels and is done using a hybrid genetic algorithm that couples an evolutionary algorithm with a surrogate model. The underlying numerical model is based on a transient, reduced-order, quasi-two dimensional computational fluid dynamics model at a fixed operating condition. The numerical results from the quasi-two-dimensional optimisation indicate that the best candidate design increases shaft power by a factor of 1.78 and imply a trade-off relationship between torque generation and pressure exchange capabilities. Further evaluation of the optimised design using three-dimensional computational fluid dynamics simulations confirms the increase in power output at the cost of increased entropy production. It is further disclosed that increased incidence losses during the initial opening of the channel to the high-pressure inlet duct compromise the shock strength of the primary shock wave and account for the decrease in pressure ratio. Finally, the numerical trends are validated using experimental data.

Analysis of the blast waves from the explosions of stoichiometric, rich, and lean propane/oxygen mixtures

The blast waves from a series of explosions of stoichiometric, rich, and lean propane/oxygen mixtures have been analysed. The explosive mixtures were contained in hemispherical soap bubbles, 0.05 m in radius, with total masses in the order of 1 g. The blast waves were measured with a series of piezoelectric transducers, flush mounted in the horizontal surface supporting the charges, at various distances from the centres of the explosions. The measured time history of hydrostatic overpressure from each transducer was least-squares-fitted to the modified Friedlander equation to provide the best estimates of the peak hydrostatic overpressure immediately behind the primary shock and the positive phase duration. The times-of-arrival (TOA) of the primary shocks at each gauge location were used to determine the shock Mach numbers as functions of distance, and these values were used in a Rankine–Hugoniot relationship to calculate the peak hydrostatic overpressures, also as functions of distance. For all explosive mixtures, there was excellent agreement between the direct gauge measurements and the values from the TOA analyses. In order to compare the relative strengths of the blast waves from the three mixtures, the measured results were scaled to those for a 1-kg charge using the masses of propane and applying Hopkinson’s cube root scaling. This analysis showed that the blast wave from the lean mixture, for which there was an excess of oxygen, was stronger than that from a stoichiometric mixture, indicating a more efficient detonation. The blast wave from the rich mixture, for which there was a deficiency of oxygen, was weaker than that from the stoichiometric mixture, but gradually strengthened relatively, probably due to the afterburning of the undetonated propane in the presence of atmospheric oxygen. The peak overpressures as functions of distance and the overpressure time histories from the three types of explosive were compared with predictions by a Propane Blast interface and in all cases showed excellent agreement. The interface predictions were based on measurements from a nominal 20-ton propane/oxygen explosion, and the agreement with results from charges with masses of less than 1 g indicates the validity of Hopkinson’s cube root scaling applied to propane/oxygen explosions over a range of charge masses in excess of six orders of magnitude.

Shock Wave Physics as Related to Primary Non-Impact Blast-Induced Traumatic Brain Injury.

Blast overpressure exposure, an important cause of traumatic brain injury (TBI), may occur during combat or military training. TBI, most commonly mild TBI, is considered a signature injury of recent combat in Iraq and Afghanistan. Low intensity primary blast-induced TBI (bTBI), caused by exposure to an explosive shock wave, commonly leaves no obvious physical external signs. Numerous studies have been conducted to understand its biological effects; however, the role of shock wave energy as related to bTBI remains poorly understood. This report combines shock wave analysis with established biological effects on the mouse brain to provide insights into the effects of shock wave physics as related to low intensity bTBI outcomes from both open-air and shock tube environments. Shock wave peak pressure, rise time, positive phase duration, impulse, shock velocity, and particle velocity were measured using the Missouri open-air blast model from 16 blast experiments totaling 122 mice to quantify physical shock wave properties. Open-air shock waves were generated by detonating 350-g 1-m suspended Composition C-4 charges with targets on 1-m elevated stands at 2.15, 3, 4, and 7 m from the source. All mice sustained brain injury with no observable head movement, because of mice experiencing lower dynamic pressures than calculated in shock tubes. Impulse, pressure loading over time, was found to be directly related to bTBI severity and is a primary shock physics variable that relates to bTBI. The physical blast properties including shock wave peak pressure, rise time, positive phase duration, impulse, shock velocity, and particle velocity were examined using the Missouri open-air blast model in mice with associated neurobehavioral deficits. The blast-exposed mice sustained ultrastructural abnormalities in mitochondria, myelinated axons, and synapses, implicating that primary low intensity blast leads to nanoscale brain damage by providing the link to its pathogenesis. The velocity of the shock wave reflected back from the target stand was calculated from high-speed video and compared with that of the incident shock wave velocity. Peak incident pressure measured from high sample rate sensors was found to be within 1% of the velocity recorded by the high-speed camera, concluding that using sensors in or close to an animal brain can provide useful information regarding shock velocity within the brain, leading to more advanced knowledge between shock wave physics and tissue damage that leads to bTBIs.

The TNT and ANFO equivalences of the Beirut explosion

On 4 August 2020, an estimated 2.75 kt of ammonium nitrate exploded in the Port of Beirut, Lebanon. Rigby et al. (Shock Waves 30:671–675, 2020) used observations from numerous video recordings of the explosion to estimate the time-of-arrival of the primary shock at 38 positions, the distances of which from the centre of the explosion were determined from Google maps. These data were analysed to make a preliminary estimate of the TNT equivalence of the explosion, with a best estimate of 0.5 kt and an upper limit of 1.12 kt. Rigby et al. have made their data available for other users, and the present paper describes how these data have been further analysed to obtain the TNT and ANFO equivalences as functions of radial distances from the centre of the explosion. The TNT equivalence varies from 0.15 to 0.7 kt, with a median value of about 0.5 kt, in agreement with the Rigby et al. result. The ANFO equivalence varies from 0.2 to 1.0 kt with a median value of about 0.75 kt. Some additional thoughts about the Beirut explosion are appended.

Primary shock calibration with fast linear motor drive

This paper describes the implementation of a new, fast and precise linear motor drive for PTB’s primary shock calibration device. This device is used for monopole shock calibrations of accelerometers using the “hammer-anvil” principle according to ISO 16063-13:2001 and operates in a peak acceleration range from 50 m/s² to 5000 m/s². &lt;br /&gt;The main challenge of implementing this kind of shock generator is accelerating a hammer to velocities up to 5 m/s within distances of less than 70 mm. &lt;br /&gt;In this paper, a few helpful improvements are described which lead to an enhanced repeatability of pulse generation over the full shock intensity range as well as a substantial decrease of harmonic disturbing signals.

Numerical study on spray collapse process of ECN spray G injector under flash boiling conditions

This work features a numerical study of the spray collapse process that occurs under flash-boiling, gasoline-direct-injection conditions. The Engine Combustion Network’s Spray G injector was modeled, and iso-octane, n-hexane, and propane were used as fuels with the goal to investigate fuel property effects. The development of individual jets and jet-to-jet interaction were analyzed to reveal the physical mechanisms of spray collapse. The results agreed qualitatively well with the experimental data of propane available from the literature and the predictions revealed the model’s ability to capture the near-nozzle shock structures witnessed in the experiments. Simulations showed that the flow development of flashing sprays was strongly tied with the fuel properties. Specifically, under-expanded jets were not observed with iso-octane due to the fuel’s low vapor pressure. In the case of n-hexane, the jets were under-expanded, and a low-pressure core was observed inside the jets due to the flow expansion. With propane, the very strong expansion caused the flow to become transonic and generate a unique shock structure near the nozzle exit. The shock structure revealed the formation of primary shock cells within the jets and secondary shock cells induced by jet-to-jet interaction. Based on the results, the spray collapse under flash boiling conditions was mainly attributed to two effects, i.e., the decrease in pressure at the spray center induced by the low-pressure cores inside and between the jets, and the isolation effect due to the jet-to-jet interaction which contributed to maintain the pressure differential between the spray center and the ambient.

A comparative study of laser-induced gas breakdown ignition and laser ablation ignition in a supersonic combustor

Cavity ignition was achieved in a supersonic combustor by laser-induced gas breakdown (LIGB) and laser ablation (LA). High-speed photography and schlieren imaging were employed to characterize the ignition processes. schlieren imaging was also applied to visualize LIGB and LA in quiescent air. The input energy was approximately 200 mJ. The distance between the focal point of the convex lens and the target plate (d) varied from 10 mm above the target plate (d = 10 mm) to 5 mm below the target plate (d = −5 mm). The experiments performed in quiescent air indicated that the plasma of LA (d = −5 mm) was relatively small. Compared to LIGB, the expansion of the hot plume resulting from LA was less significant because the plate prevented the formation of the third lobe. The primary shock wave of LA propagated faster than that of LIGB because of high pressure ratio between the plasma and the ambient air. In the supersonic combustor with d = 5 or 10 mm, the laser induced a plasma by LIGB at the focal point and induced another plasma by LA at the cavity floor. These two tests were the combination of LIGB ignition and LA ignition. LA ignition was achieved in the test with d = −5 mm. The ignition process of the test with d = 10 mm was the slowest because of severe plasma quenching at the focal point. For the early stage of ignition, the flame kernels of the tests with d = 5 and −5 mm were different. However, the differences gradually vanished after the flame kernels reached the cavity leading edge. The ignition times of these two tests were almost the same. Therefore, the plasma resulting from LA was as effective as the plasma generated by LIGB in terms of ignition. Laser ablation ignition was a promising ignition method in a supersonic combustor.

Formation of Foreshock Transients and Associated Secondary Shocks

Abstract Upstream of shocks, the foreshock is filled with hot ions. When these ions are concentrated and thermalized around a discontinuity, a diamagnetic cavity bounded by compressional boundaries, referred to as a foreshock transient, forms. Sometimes, the upstream compressional boundary can further steepen into a secondary shock, which has been observed to accelerate particles and contribute to the primary shock acceleration. However, secondary shock formation conditions and processes are not fully understood. Using particle-in-cell simulations, we reveal how secondary shocks are formed. From 1D simulations, we show that electric fields play a critical role in shaping the shock’s magnetic field structure, as well as in coupling the energy of hot ions to that of the shock. We demonstrate that larger thermal speed and concentration ratio of hot ions favor the formation of a secondary shock. From a more realistic 2D simulation, we examine how a discontinuity interacts with foreshock ions leading to the formation of a foreshock transient and a secondary shock. Our results imply that secondary shocks are more likely to occur at primary shocks with higher Mach number. With the secondary shock’s previously proven ability to accelerate particles in cooperation with a planetary bow shock, it is even more appealing to consider them in particle acceleration of high Mach number astrophysical shocks.

Microwave pretreatment followed by associated microwave-hot air drying of Gundelia tournefortii L.: drying kinetics, energy consumption and quality characteristics

Gundelia tournefortii L. is a well-known medicinal plant. Here, drying characteristics of it were investigated using combined microwave-hot air (CMWHA) drying method which consists of microwave pretreatment (specific powers of 450, 600 and 750 W), called primary shock, followed by associated microwave-hot air drying (180, 300 and 450 W assisted with 60, 70, and 80 °C inlet air temperature). Drying kinetics of the proposed method was modeled. Thus, experimental moisture ratio data was fitted to 10 thin layer models. It was found that Midilli et al. model had the best fit to show kinetics behavior. According to the results, drying rate was increased by increasing microwave power at a certain temperature. The maximum drying rate was obtained in the combined condition of 450 W and 80 °C with a primary shock of 750 W. Effective moisture diffusivity (Deff) ranged between 1.21 × 10−6 and 6.19 × 10−6 (m2/s); however it was 8.74 × 10−7 for hot air drying. Moreover, activation energy was in the range of 12.86 to 15.82 (kJ/mol). Comparison between energy consumptions showed that the lowest value was attributed to combined conditions of 180 W, 80 °C and a primary shock of 600 W which lead to 69% energy saving compared to hot air method. Quality of dried products was evaluated by measurement of colour parameters (L*, a*, and b*), total colour difference (∆E), browning index (BI), Chroma, Hue angle, rehydration, and ratio of shrinkage. Generally, it was found that CMWHA method is the best choice to dry Gundelia tournefortii L. in terms of time, mass transfer rate, energy, and quality.

Quantitative analysis of the global proteome in lung from mice with blast injury

Aim of the Study The mechanism by which primary shock wave causes lung injury is unclear. The aim of this study is to find the changes of protein that can be helpful in understanding blast-induced lung injury Material and Methods A quantitative analysis of their global proteome was conducted in lung from mice with blast injury using LC-MS/MS. Protein annotation, unsupervised hierarchical clustering, functional classification, functional enrichment and cluster, and protein-protein interaction analyses were performed. Furthermore, western blotting was used to validate the changed protein levels. Results A total of 6498 proteins were identified, of which 5520 proteins were quantified. The fold-change cutoff was set at 1.2; 132 proteins were upregulated, and 104 proteins were downregulated. The bioinformatics analysis indicated that the differentially expressed proteins were involved in the cholesterol metabolism, asthma, nonalcoholic fatty liver disease. Remarkably, the processes related to the change of oxidative phosphorylation including the NADH dehydrogenase, Cytochrome C reductase, Cytochrome C oxidase and F-type ATPase were significantly upregulated, which were further verified by western blotting. Conclusion These results confirmed that the oxidative phosphorylation is critical to blast-induced lung injury. LC/MS-based profiling presented candidate target/pathways that could be explored for future therapeutic development.

Calculation of Shock Waves in an Explosion of a Liquid Gas Pressure Reservoir

Rapid phase transitions occurring with a sharp increase in a specific volume can be accompanied by explosive gas-dynamic phenomena. A model is presented for calculating shock waves generated in the atmosphere during an explosion of a liquid gas pressure reservoir, based on the assumption of a thermodynamically equilibrium state of a vapor–liquid mixture in which both vapor and liquid have equal velocities and are in a state of saturation at local pressure. The spherically symmetric expansion of a boiling liquid cloud is calculated, pressure profiles under various initial conditions are compared, and the primary shock wave parameters are validated according to the results of available experimental data. Two-dimensional calculations of shock waves during the fracture of a cylindrical tank near the underlying surface at various degrees of filling are presented.

High velocity projectile impact of a composite rubber/aluminium fluid-filled container

When penetrated by a high-velocity projectile, a fluid-filled container can be severely damaged and ruptured due to the intense impact loading from Hydrodynamic Ram (HRAM), which causes a primary shock wave, and then a subsequent loading phase when a cavity evolves in the fluid. In the design of fuel tanks for aircraft, and other transport vehicles, the HRAM pressure is a major concern for the reliability of the structure. In this paper, experiments of high-velocity projectiles impacting two different types of fluid-filled containers, including an aluminium wall and a composite aluminium/rubber wall, were performed to study the mitigation effect of the rubber layer on the damage of the structure and the impact loading from Hydrodynamic Ram. A high-speed camera was employed to record the formation process of the cavity, and the shock wave pressure-time histories in the fluid were also obtained by pressure transducers. By comparing and analysing the experimental results, it is shown that the rubber layer of the composite wall container was able to reduce the reflected shock pressure and the deformation of the structure.

Physical Conditions in Shocked Interstellar Gas Interacting with the Supernova Remnant IC 443*

Abstract We present the results of a detailed investigation into the physical conditions in interstellar material interacting with the supernova remnant (SNR) IC 443. Our analysis is based on a comprehensive examination of high-resolution far-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope of two stars behind IC 443. One of our targets (HD 43582) probes gas along the entire line of sight through the SNR, while the other (HD 254755) samples material located ahead of the primary supernova shock front. We identify low-velocity quiescent gas in both directions and find that the densities and temperatures in these components are typical of diffuse atomic and molecular clouds. Numerous high-velocity components are observed in the absorption profiles of neutral and singly ionized atomic species toward HD 43582. These components exhibit a combination of greatly enhanced thermal pressures and significantly reduced dust-grain depletions. We interpret this material as cooling gas in a recombination zone far downstream from shocks driven into neutral gas clumps. The pressures derived for a group of ionized gas components at high positive velocity toward HD 43582 are lower than those of the other shocked components, pointing to pressure inhomogeneities across the remnant. A strong, very high velocity component near −620 km s−1 is seen in the absorption profiles of highly ionized species toward HD 43582. The velocity of this material is consistent with the range of shock velocities implied by observations of soft thermal X-ray emission from IC 443. Moderately high velocity gas toward HD 254755 may represent shocked material from a separate foreground SNR.