Shock Wave

In this study, the Landau and cyclotron growth rates of whistler mode waves in earth's bow shock are calculated by using electron distribution functions obtained with the fast plasma experiment on ISEE 2. Three electron distribution functions measured within the transition region of the shock are analyzed. An important feature of these electron distribution functions is the presence of a field‐aligned beam with a T⊥ > T∥ anisotropy. The beam velocity vector is directed toward the magnetosheath. The calculations show that the electron distribution functions spontaneously generate whistler mode waves with plasma rest frame frequencies between about 0.1 and 100 Hz. The wave normal angles of the generated whistlers range from 0° to the resonance cone angle. Electromagnetic Landau resonance and/or cyclotron resonance contribute to wave growth over the range of velocity distributions observed. The waves that are generated by the normal cyclotron resonance have wave vectors directed...

How does the mass of an asteroid change the size of its impact crater? Background information: When a object collides with a surface, it creates a crater. This is because of kinetic energy generated by the projectile's weight (mass) and velocity (speed) being transferred into the colliding surface, displacing material and forming a crater. Kinetic energy can be calculated with the formula KE = ½MV^2, where M is the mass of an object and V is the velocity of an object. When velocity is kept the same, an increase in mass results in more kinetic energy being transferred on impact, displacing more material, and making a larger crater. This is a well-established concept in physics and is backed by many reputable sources such as NASA and scientists like astrophysist Neil deGrasse Tyson. Asteroid research has also shown that real asteroid impacts follow extremely similar principles as smaller-scale models. In this experiment, objects of the same diameter but different masses are dropped from the same height into a tray of flour, replicating a realistic scaled down surface. By isolating mass as the only changing factor we can clearly observe how mass by itself affects crater size, achieving the aim of this investigation.

Homogeneous second-order Aw-Rascle-type models have demonstrated greater effectiveness than their non-homogeneous counterparts in traffic flow modeling. This study addresses the numerical solution of hyperbolic conservation laws governing these models by coupling the second-order HLLE Riemann solver, a Godunov-type finite volume approach, with the wave propagation algorithm. A novel wave-speed selection strategy is proposed by comparing characteristic velocities with Roe speeds, yielding solutions with guaranteed positive density and speed. The proposed IWP-HLLE method is applied to simulate shock, rarefaction, and contact discontinuity waves under homogeneous long-road conditions, eliminating the influence of external source terms and ensuring the homogeneity of the governing hyperbolic equations. Its performance is benchmarked against the MacCormack scheme supplemented by two standard stabilization techniques, namely artificial viscosity (AV) and central differencing (CD). Spatiotemporal distributions and density profiles are examined across four representative traffic scenarios: free flow, congested traffic flow, queue dissolution, and congested flow with non-equilibrium velocity and uniform density. The results demonstrate that the IWP-HLLE approach substantially suppresses numerical oscillations compared to both AV and CD methods while maintaining stability across all test cases.

Material selection for aircraft components is a fundamental aspect of aerospace engineering because it directly influences structural performance, operational safety, durability, and fuel efficiency. Aircraft parts are subjected to demanding service conditions, including high mechanical loads, temperature variations, and corrosive environments. Therefore, selecting an appropriate material requires balancing multiple properties such as low density, high stiffness, adequate elongation, and elevated temperature resistance. The present study investigates the material selection problem for aircraft parts by evaluating five candidate materials: aluminum, Aluminum 7075-T6, maraging steel, steel, and titanium. A structured decision-making methodology is employed to compare these alternatives based on key engineering criteria, namely density (kg/m³), elastic modulus (GPa), elongation (%), and temperature limit (°C). The evaluation process integrates material property analysis with multi-criteria assessment techniques to identify the most suitable material for aerospace applications. The results indicate that Aluminum 7075-T6 achieves the highest overall ranking due to its favorable combination of lightweight characteristics, mechanical strength, and performance under operational conditions. In contrast, conventional aluminum receives the lowest ranking among the evaluated alternatives because of its comparatively lower performance across the selected criteria. The findings demonstrate the importance of systematic material evaluation in optimizing aircraft design and performance. Effective material selection contributes to enhanced reliability, reduced structural weight, improved fuel economy, and lower maintenance requirements, thereby supporting the development of safer and more sustainable aerospace systems.

Using quantum magneto-hydrodynamic theory, the nonlinear propagation of magnetoacoustic waves have been investigated in a quantum magneto-plasma having dissipative ions fluid as well as quantum electrons and positrons, including exchange-correlation and electrons/positrons spin effects. The Korteweg-devris-Burger equation is derived employing the reductive perturbation method. It has been found that the quantum magneto-plasma system under consideration supports buth magnetoacoustic solitary and shock waves depending on the values of the plasma parameters. The effects of quantum plasma parameters (such as exchange-correlation coefficients, magnetic field strength, kinematic viscosity and the concentrations of electrons and positrons) on the magnetoacoustic shock waves (both monotonic shock waves and oscillatory shock waves) are examined. The profiles of both monotonic and oscillatory shock waves are found to be significantly affected by these parameters.The results of the current study may be useful to understand the properties of magnetoacoustic waves propagating in dense space plasma environments where the quantum mechanical effects of electrons and positrons are included.

Using quantum magneto-hydrodynamic theory, the nonlinear propagation of magnetoacoustic waves have been investigated in a quantum magneto-plasma having dissipative ions fluid as well as quantum electrons and positrons, including exchange-correlation and electrons/positrons spin effects. The Korteweg-devris-Burger equation is derived employing the reductive perturbation method. It has been found that the quantum magneto-plasma system under consideration supports buth magnetoacoustic solitary and shock waves depending on the values of the plasma parameters. The effects of quantum plasma parameters (such as exchange-correlation coefficients, magnetic field strength, kinematic viscosity and the concentrations of electrons and positrons) on the magnetoacoustic shock waves (both monotonic shock waves and oscillatory shock waves) are examined. The profiles of both monotonic and oscillatory shock waves are found to be significantly affected by these parameters.The results of the current stu...

Objective. A study was conducted to investigate the possible eects of fatigue on the heel strike-initiated shock accelerations and on attenuation of these shocks along the body during eccentric muscle contractions. Design. Level and decline running on a treadmill were used to acquire the experimental data on the foot strike-initiated shock accelerations. Background. Eccentric contractions of the lower limb muscles in combination with shock generation and propagation during downhill running and muscle fatigue may diminish their ability to dissipate and attenuate loading on the system. Methods. Fourteen young healthy males ran on a treadmill at a speed exceeding their anaerobic threshold by 5% for 30 min, as follows: (a) level running and (b) downhill running with a decline angle of À4°. The foot strike-induced shock accelerations were recorded every ®ve minutes on the tibial tuberosity and sacrum. Fatigue was monitored by means of the respiratory parameters. Results. The downhill running related with eccentric muscle contractions was associated with increased shock propagation from the tibial tuberosity to the sacrum levels, even though fatigue did not develop. Conclusions. Shock propagation from the tibial tuberosity to the sacrum is augmented due to the eccentric action of the muscles, without metabolic fatigue development. Eccentric muscle contraction in downhill running reduces the musculoskeletal ability to attenuate the heel strike-induced shock waves. Knowledge about the eect of fatigue on the shock propagation between the shank and the sacrum levels may help in understanding the mechanism of stress fractures and joint damage.

The assessment of Ground Reaction Forces (GRF) is important for gait analysis for sports, pathological gaits and rehabilitation. To capture GRF, force plates and foot pressure insoles are commonly used. Due to cost and portability issues, such systems are mostly limited to lab-based studies. Longterm, continuous and pervasive measurement of GRF is not feasible. This paper presents a novel concept of using an earworn sensor for pervasive gait analysis. By emulating the human vestibular system, the bio-inspired design sensor effectively captures the shock wave generated by the GRF. A hierarchical Bayesian network is developed to estimate the plantar force distribution from the ear sensor signals. The accuracy of the ear sensor for detecting GRF is demonstrated by comparing the results with a high-accuracy commercial foot pressure insole system.

In this paper the results are presented on the quest for an intensified steam cracking process. The main focus is to improve the efficiency of the steam cracking process. The first part of the investigation is to examine which of the current available processes is close to the ideal steam cracking process. Two possible technologies have potential, namely the shock

Recent simulation results have revealed that energetic electron bursts are produced cyclically at the shock reformation period upstream of reforming shocks and are qualitatively very different from the continuous beam expected from time‐stationary shocks (Yuan et al., 2007a). This paper extends our previous studies by numerically investigating the dependence of electron burst events on shock parameters (the upstream plasma β and Mach number MA). The test particle approximation is made for electrons, and the electron trajectories are traced exactly in the time‐dependent electromagnetic field profiles, generated by one‐dimensional hybrid simulation code. Simulation results indicate that the upstream incoming electrons can be reflected nonuniformly or continuously depending on the shock parameters. Bursty energetic electron events take place when the plasma beta is low (β ≤ 0.4) and the shock Mach number is high (MA ≥ 6). Time‐varying loss cone, beam, and ring beam features are observe...

Particle dynamics and energization at the earth bow shock. 1 RICHARD MARCHAND, FRANCES MACKAY, JIANYONG LU, KONSTANTIN KABIN, ROBERT RANKIN, University of Alberta -Simulation results are presented for the dynamics and energization of plasma particles as they cross the earth bow shock. The model is based on a kinetic description of particle dynamics, in which single particle trajectories are calculated using a symplectic integration scheme. Particle distribution functions are calculated at different positions in the magnetosheath using Louville's theorem with a Hamiltonian formulation of single particle equations of motion and time reversed particle tracing. As a first approximation, the bow shock is assumed to be represented by a prescribed local plane shock. A more detailed representation of the shock and magnetosheath regions is then considered, as obtained from a global MHD simulation model. Comparisons are made between the two models, for different possible angles between the incident plasma flow velocity and the shock front. Various scenarios of energization are also considered for majority (H) and minority (He and heavier elements) ion species.

The AURAL-M governance framework, built on contact Hamiltonian mechanics and the Constitutional Projection Operator, is shown to have been physically instantiated in the Rayleigh-Plesset equation governing acoustic-fluid cavitation dynamics since its first derivation by Besant in 1859. The surface tension, viscosity, and ambient pressure terms in the Rayleigh-Plesset equation are identified as physical constraint forces that project the bubble trajectory onto an admissible region at every timestep-precisely the function of the admissible projection operator Π_A. The sonoluminescence stability island in parameter space is identified as the admissible set A defined by the intersection of five constraint surfaces. The sonoluminescent collapse event, in which a cavitating bubble produces a plasma hot spot exceeding 10,000 K and emits photons, is identified as a physical instantiation of the governance horizon crossing event. The four-phase acoustic cavitation cycle (expansion, compression, collapse, after-bounce) maps one-to-one onto the four-phase AURAL-M engine cycle (exploration, transition, consolidation, regulation). The thermodynamic efficiency is bounded by the Lopez-Carnot Intelligence Bound. The photon emission at the collapse boundary is a physical instance of the governance holographic bound. A quantum lift of the Rayleigh-Plesset equation through the Lopez Quantum Master Equation extends these results to density-matrix space and establishes structural identity with the Lopez Governed Polariton Engine. Application to the Lopez Quantum Turbine propulsion architecture identifies acoustic cavitation as the physical compression mechanism, enabling bench-scale prototyping with off-the-shelf ultrasonic transducers. Numerical simulation confirms 100% admissibility under governed evolution, four-phase cycle fidelity, and SHA-256 cryptographic proof of execution.

The significance of nonlinear propagation effects on infrasound is studied using the Nonlinear Progressive Wave Equation (NPE) [B. E. McDonald and W. A. Kupperman, J. Acoust. Soc. Am., 81, 1406--1417 (1987)]. The NPE model accounts for nonlinear effects associated with a weak shock front, including shock-driven energy loss and self refraction. Numerical implementation is accomplished using a pseudospectral approach, which provides excellent computational efficiency while still maintaining acceptably small numerical errors. The nonlinear effects are isolated by generating NPE predictions with the nonlinear terms turned on and off. With the nonlinear terms off, the NPE reduces to a standard linear PE formulation. Waveform predictions through a realistic atmosphere are compared to ground truth observations to evaluate the NPE model performance and assess the influence of the nonlinear effects along the propagation path.

The mechanical properties of Chelyabinsk LL5 chondrite (Chelyabinsk meteorite) were studied by uniaxial compression and diametral compression/indirect tension test. Twenty cylindrical samples, 10 for compression and 10 for tension, with the diameter 3.3 mm and 1.65 mm in height have been prepared for testing. It was shown that the strength of the tested samples under compression almost 45 times greater than it is at tension: 372 ± 10 MPa and 8.2 ± 0.7 MPa, respectively. Fracture behaviour under compression and tension was similar and can be characterised as brittle. The obtained compression strength of the Chelyabinsk meteorite lies close to the maximal values of strength for many other chondrites, whereas its tensile strength magnitude resides in the bottom quarter of the range of similar measurements. It may be caused by the small sizes of the investigated samples together with a large number of tiny cracks between the grains in the Chelyabinsk chondrite. Our estimations have shown that if one assumes that the initial shape of the Chelyabinsk fireball was spherical or ellipsoidal, then its fragmentation stress is close to the experimental tensile strength and much lower than the compression strength. Hence, a stress state equivalent to one appearing at the indirect tension test could occur in the Chelyabinsk fireball during its fall in the Earth atmosphere.

The surfaces of Ni50Ti50 shape memory alloys (SMAs) were patterned by laser scribing. This method is more simplistic and efficient than traditional indentation techniques, and has also shown to be an effective method in patterning these materials. Different laser energy densities ranging from 5 mJ/pulse to 56 mJ/pulse were used to observe recovery on SMA surface. The temperature dependent heat profiles of the NiTi surfaces after laser scribing at 56 mJ/pulse show the partiallyrecovered indents, which indicate a "shape memory effect (SME)" Experimental data is in good agreement with theoretical simulation of laser induced shock wave propagation inside NiTi SMAs. Stress wave closely followed the rise time of the laser pulse to its peak values and initial decay. Further investigations are underway to improve the SME such that the indents are recovered to a greater extent.

The surfaces of Ni50Ti50 shape memory alloys (SMAs) were patterned by laser scribing. This method is more simplistic and efficient than traditional indentation techniques, and has also shown to be an effective method in patterning these materials. Different laser energy densities ranging from 5 mJ/pulse to 56 mJ/pulse were used to observe recovery on SMA surface. The temperature dependent heat profiles of the NiTi surfaces after laser scribing at 56 mJ/pulse show the partiallyrecovered indents, which indicate a "shape memory effect (SME)" Experimental data is in good agreement with theoretical simulation of laser induced shock wave propagation inside NiTi SMAs. Stress wave closely followed the rise time of the laser pulse to its peak values and initial decay. Further investigations are underway to improve the SME such that the indents are recovered to a greater extent.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Gravity Engineering Ltd -The response of aluminium foams to impact can be categorised by the impact velocity. Tests are reported ranging from quasi-static to impact velocities greater than the speed of sound in the foam. The techniques used ranging from drop-hammer and pneumatic launcher tests, to plate impact at velocities greater than 1000 m s-1. The quasi-static compression behaviour was elastic, perfectly-plastic, locking. For static and dynamic compression at low impact velocities, post-impact examination of partially crushed specimens showed that deformation was through the cumulative multiplication of crush bands. If the impact velocity is less than the velocity of sound, but above a certain critical impact velocity, the plastic compression occurs in a shock-like manner and the specimens deform by progressive cell crushing. At higher impact velocities the compaction front is not preceded by an elastic wave. Laboratory X-ray microtomography has been employed to acquire tomographic datasets of aluminium foams before and after tests. The morphology of the underformed foam was input as the input dataset to an Eulerian code. Hydrocode simulations were then carried out on real microstructure. These simulations provide insight to mechanisms associated with the localization of deformation.

Cellular materials have applications for impact and blast protection. Under impact/impulsive loading the response of the cellular solid can be controlled by compaction (or shock, see ) waves. Different analytical and computational solutions have been produced to model this behaviour but these solutions provide conflicting predictions for the response of the material in certain loading scenarios. The different analytical approaches are discussed using two simple examples for clarity. The differences between apparently similar "models" are clarified. In particular, it is argued that mass-spring models are not capable of modelling the discontinuities that exist in a compaction wave in a cellular material.

Dispersive shock waves in thermal optical media belong to the third-order nonlinear phenomena, whose intrinsic irreversibility is described by time asymmetric quantum mechanics. Recent studies demonstrated that nonlocal wave breaking evolves in an exponentially decaying dynamics ruled by the reversed harmonic oscillator, namely, the simplest irreversible quantum system in the rigged Hilbert spaces. The generalization of this theory to more complex scenarios is still an open question. In this work, we use a thermal third-order medium with an unprecedented giant Kerr coefficient, the M-Cresol/Nylon mixed solution, to access an extremely-nonlinear highly-nonlocal regime and realize anisotropic shock waves. We prove that a superposition of the Gamow vectors in an ad hoc rigged Hilbert space describes the nonlinear beam propagation beyond the shock point. Specifically, the resulting rigged Hilbert space is a tensorial product between the reversed and the standard harmonic oscillators spaces. The anisotropy turns out from the interaction of trapping and antitrapping potentials in perpendicular directions. Our work opens the way to a complete description of novel intriguing shock phenomena, and those mediated by extreme nonlinearities.

We investigate the propagation of a dark beam in a defocusing medium in the strong nonlinear regime. We observe for the first time a shock fan filled with non-interacting one-dimensional grey solitons that emanates from a gradient catastrophe developing around a null of the optical intensity. Remarkably this scenario turns out to be very robust, persisting also when the material nonlocal response averages the nonlinearity over dimensions much larger than the emerging soliton filaments.

We present analytic formulas for the nonlinear evolution of the bubble amplitude in Rayleigh-Taylor and Richtmyer-Meshkov instabilities in two and three dimensions. Direct numerical simulations of He͞Xe shock tube experiments are also presented and the results are found to agree well with the analytic formulas which are based on an extension of Layzer's theory [Astrophys. J. 122, 1 (1955)].

Dielectric barrier discharge (DBD) plasma actuators are widely used for active flow control due to their ability to generate plasma without moving parts. In this study, a two-dimensional electrostatic model of an asymmetric DBD plasma actuator is developed using COMSOL Multiphysics to investigate the effect of different excitation conditions on electric field distribution. Three excitation cases, namely AC, nanosecond pulsed (NS), and hybrid AC+NS, are considered using simplified voltage approximations. The results show that the electric field is strongly concentrated near the edge of the exposed electrode for all cases. While the spatial distribution of the electric field remains similar, its magnitude increases with the applied voltage. The hybrid case produces the highest electric field intensity, indicating improved potential for plasma generation. The study demonstrates that a simplified electrostatic approach can provide a qualitative understanding of DBD actuator behavior and serve as a basis for more advanced plasma modeling.

This study examines the layer-dependent scaling between propagation an gle and oscillation period of Alfvén waves in a gravitationally stratified solar atmosphere using a linearized ideal magnetohydrodynamic (MHD) framework. A dispersion relation is derived and evaluated for plasma conditions representative of the photosphere , chromosphere, and corona, and the propagation angle is computed as a function of oscillation period across these layers. The results show that the angle-period relationship follows an arctangent scaling of the form , where the scaling parameter depends on the Alfvén speed and plasma properties. This scaling captures a clear transition in wave behaviour with height. In the lower atmospheric layers, where , the propagation angle varies approximately linearly with oscillation period, indicating strong coupling. In the chromosphere, a transitional regime () is observed, where the dependence weakens. In the corona, where , the propagation angle approaches , indicating saturation and predominantly transverse propagation. These results show that gravitational stratification governs the scaling through its influence on the parameter and provide a quantitative description of how wave propagation geometry and energy transport evolve across the solar atmosphere.

Acoustic Inertial Confinement Fusion (AICF), commonly known as sonofusion, presents a theoretical pathway to achieving thermonuclear fusion by exploiting the adiabatic heating of cavitating bubbles in a deuterated liquid. However, the realization of sufficient core temperatures is fundamentally limited by Rayleigh-Taylor (RT) instabilities, which cause the microscopic bubbles to shatter asymmetrically during supersonic collapse. This paper proposes a novel theoretical framework to suppress these instabilities using a "Cymatic Geodesic" approach. By superimposing an ultra-high-frequency ultrasonic locking wave (e.g., 10 MHz) over the primary low-frequency driving wave (e.g., 20 kHz), a parametric resonance is induced on the fluid boundary. This creates a ponderomotive force that traps surface perturbations within an oscillatory well, maintaining perfect spherical symmetry. Theoretical calculations demonstrate that this stabilized adiabatic collapse can achieve core temperatures exceeding 3 × 10 7 K, comfortably crossing the threshold for Deuterium-Deuterium (D-D) fusion.

Electric field measurements from a single spacecraft have been used to study ion‐sound turbulence observed within the Earth's bow shock. The observed frequency of the ion‐sound waves can be both lower and higher than the local electron cyclotron frequency depending upon the direction of wave propagation in the plasma rest frame. The ion‐sound waves observed upstream of the ramp can not be generated either by an instability related to the gradient in the electron temperature or an electric current within the ramp. A comparison of wave vectors for distinctive wave packets indicate that non‐stationary, short scale current layers formed in the processes of the ramp evolution might be the source of the free energy for such waves.

We study spectral phase transitions in discrete operator systems of the form where L 0 is symmetric and ∆ is antisymmetric transport. We derive a transport-spectral phase classification governed by a pseudospectral exponent κ. The resulting framework separates stable diffusive geometries, critical scale-invariant geometries, and transport-dominated unstable geometries.

The unfixed flame propagation velocity of a gas explosion and the fixed response time of explosion suppression devices are the important reasons for the poor protective effect of active explosion suppression. A flexible explosion suppression method based on buffer energy absorption is detailed in this study. The explosion suppression system consists of an explosive characteristic monitoring system, an explosion suppression agent system, and an explosion suppression airbag. An empty pipe experiment and an explosion suppression experiment with a flexible-airbag gas-explosion suppression device were conducted in a 20.5 m-long pipe with an inner diameter of 180 mm. The flame propagation velocity and maximum overpressure values were compared between the two groups of experiments. The experimental results show that the flame wave propagation can be completely suppressed by the explosion suppression device under certain pressure. The occurrence time of maximum overpressure at each pressure...

This effort investigates surface-preparation methods to enhance dynamic surface-property measurements of shocked metal surfaces. To assess the ability of making reliable and consistent dynamic surface-property measurements, the amount of material ejected from the free surface upon shock release to vacuum (ejecta) was monitored for shocked Al-1100 and Sn targets. Four surface-preparation methods were considered: Fly-cut machine finish, diamond-turned machine finish, polished finish, and ball rolled. The samples were shock loaded by in-contact detonation of HE PBX-9501 on the front side of the metal coupons. Ejecta production at the back side or free side of the metal coupons was monitored using piezoelectric pins, optical shadowgraphy, and x-ray attenuation radiography.

Fourier-transform infrared and Raman studies are performed on Ar(H 2 ) 2 compound single crystals over a large pressure ͑5-30 GPa͒ and temperature ͑30-300 K͒ range in a diamond-anvil cell. The effect of polarization on the infrared absorption is investigated. On the basis of the spectroscopic features and comparing to the cases of pure solid H 2 and of matrix isolated H 2 in argon crystal, we assign the quite complex infrared spectra to the pure vibron and vibron plus phonons and vibron plus rotons combination bands. The difference of the infrared and Raman vibron frequency, as a function of pressure, is interpreted quantitatively with reference to vibrational coupling between hydrogen molecules, as in the hydrogen crystal case. Information on the structural properties can thus be derived. Finally, this study highlights the similarity in the molecular problems for the Ar(H 2 ) 2 compound and for solid hydrogen. ͓S0163-1829͑99͒12529-3͔

The isotopic shift in the melting curve of He has been measured between 70 and 260 K. An exponential divergence from accurate path-integral Monte Carlo calculations is observed which leads to an oppo- site isotopic shift above 200 K. The same measurements have also been performed in isotopic H2 at 296 K where a reasonable agreement with theory is obtained. Tentative explanations of this puzzling discrepancy in He are discussed: importance of many-body forces, breakdown of the Born-Oppenheimer approximation, and importance of statistics.

The binary phase diagram of He-Ne mixtures has been measured at 296 K in a diamond anvil cell. It is of the eutectic type with no Auid-Auid separation of phases. A homogeneous solid mixture is shown to be stable for a mole fraction of He equal to 3 . Single-crystal synchrotron x-ray measurements indicate that this solid is ordered with 12 atoms in the unit cell. Gibbs free energy calculations support the attribution to the MgZn2 type structure, It is the first Laves phase observed in a van der Waals molecular compound.

X-ray 1-3 and radio 4-6 observations of the supernova remnant Cassiopeia A reveal the presence of magnetic fields about 100 times stronger than those in the surrounding interstellar medium. Field coincident with the outer shock probably arises through a nonlinear feedback process involving cosmic rays 2,7,8 . The origin of the large magnetic field in the interior of the remnant is less clear but it is presumably stretched and amplified by turbulent motions. Turbulence may be generated by hydrodynamic instability at the contact discontinuity between the supernova ejecta and the circumstellar gas 9 . However, optical observations of Cassiopeia A indicate that the ejecta are interacting with a highly inhomogeneous, dense circumstellar cloud bank formed before the supernova explosion 10-12 . Here we investigate the possibility that turbulent amplification is induced when the outer shock overtakes dense clumps in the ambient medium . We report laboratory experiments that indicate the magnetic field is amplified when the shock interacts with a plastic grid. We show that our experimental results can explain the observed synchrotron emission in the interior of the remnant. The experiment also provides a laboratory example of magnetic field amplification by turbulence in plasmas, a physical process thought to occur in many astrophysical phenomena. High-resolution X-ray images and radio polarization maps of Cassiopeia A show two distinct strong magnetic field regions . Narrow X-ray filaments, a fraction of a parsec in width, are observed at the outer shock rim at a radius of about 2.5 pc. These structures are produced by synchrotron radiation from ultrarelativistic electrons (with teraelectronvolt energy) and can be explained by magnetic fields of the order of 100 µG or more 2,3 . The interior of the remnant contains a disordered shell (about 0.5 pc in width at a radius of 1.7 pc) of radio synchrotron emission by gigaelectronvolt electrons 4 . The inferred magnetic field in these radio knots is a few milligauss, about 100 times higher than expected from the standard shock compression of

Radiative-shocks induced by laser–cluster interactions are modeled using radiation-hydrodynamic simulations. A good agreement—in both shock velocity and density profiles—is obtained between experiment and simulations, indicating that non-local thermodynamic equilibrium (NLTE) radiative effects are important in the experimental regime examined, particularly at early times (≤30 ns) due to the elevated temperatures (≥35 eV). The enhanced NLTE radiative emission causes the shock to be reduced in amplitude, increased in width, and reduced in propagation velocity, while the amplitude of the radiative precursor is increased. As the density and temperature conditions are relatively modest, this potentially has important implications for the scalings that are used in laboratory–astrophysics to transform between laboratory and astrophysical scales, which do not hold for non-LTE systems.

Studies of a blast wave produced from carbon rods and plastic spheres in an argon background gas have been conducted using the Vulcan laser at the Rutherford Appleton Laboratory. A laser of 1500 J was focused onto these targets, and rear-side observations of an emission front were recorded using a fast-framing camera. The emission front is asymmetrical in shape and tends to a more symmetrical shape as it progresses due to the production of a second shock wave later in time, which pushes out the front of the blast wave. Plastic spheres produce faster blast waves, and the breakthrough of the second shock is visible before the shock stalls. The results are presented to demonstrate this trend, and similar evolution dynamics of experimental and simulation data from the FLASH radiation-hydrodynamics code are observed.

The 25 April 1992 magnitude 7.1 Cape Mendocino thrust earthquake demonstrated that the North America-Gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the Cascadia region. The shock occurred just north of the Mendocino Triple Junction and caused strong ground motion and moderate damage in the immediate area. Rupture initiated onshore at a depth of 10.5 kilometers and propagated up-dip and seaward. Slip on steep faults in the Gorda plate generated two magnitude 6.6 aftershocks on 26 April. The main shock did not produce surface rupture on land but caused coastal uplift and a tsunami. The emerging picture of seismicity and faulting at the triple junction suggests that the region is likely to continue experiencing significant seismicity. On 25 April 1992 at 18:06 (UTC), a surface wave magnitude (Ms) 7.1 earth- quake occurred near the town of Petrolia, California (Fig. ). The main shock was followed the next day by two MS 6.6 after- shocks at 07:41 and 11:41, located offshore about 25 km west-northwest of Petrolia. These three earthquakes and more than 2000 recorded aftershocks illuminated the configuration of the Mendocino Triple Junction, where the Pacific, North Ameri- ca, and southernmost Juan de Fuca (Gorda) plates meet. The occurrence of a M 7 earthquake is not unusual at the triple junction; over 60 earthquakes of Modified Mercalli intensity > VI (1) or M > 5.5 have occurred there since 1853 (2). However, this earthquake sequence may have provided the first direct evidence of inter- plate seismicity and thus impacts regional hazard assessment. In this article, we de- scribe geophysical and seismological obser- vations and discuss implications for seismic hazards in the Pacific Northwest.

This article introduces a novel model of dark matter, conceptualized as a new physical element-termed dark substance-which is not composed of classical particles. This dark substance is proposed to pervade the universe, constituting what is commonly regarded as the vacuum. By assigning simple physical properties to this dark substance, we provide a theoretical justification for the flat rotation curves observed in galaxies and the baryonic Tully-Fisher relation. Subsequently, we examine the potential distributions of dark matter within galaxies and galaxy clusters, along with the associated galaxy velocities in clusters, within the framework of our proposed dark matter theory. Furthermore, leveraging this new dark matter model, we propose a New Cosmological Model (NCM) of the Universe, which is finite and flat. The NCM comprises two distinct mathematical formulations. The first closely resembles the Standard Cosmological Model (ΛCDM), while clarifying the nature of dark matter and dark energy, and offering an interpretation of the CMB rest frame and cosmological time. The second mathematical model is significantly simpler than the SCM, yet yields theoretical predictions consistent with astronomical observations at sufficiently low redshifts. In the concluding sections, we demonstrate that both the proposed dark matter model and the NCM can interpret observations related to the primordial universe and the CMB power spectrum. Finally, we show that these two mathematical models can be utilized to address the Hubble tension, leading to the definition of a third mathematical framework, referred to as the Δ model. An earlier version of this work, lacking recent astronomical data and covering fewer topics (particularly concerning the ΛCDM model, primordial universe, CMB power spectrum, and Hubble tension), was published in an applied physics journal (DELORT 2018).

This paper describes the calibration of the Arrhenius Wescott-Stewart-Davis (AWSD) reactive flow model for the recently developed high explosive PBX 9701, which consists of 97% 3,3'-diamino-4,4'-azoxyfurazan (DAAF) and 3% FK-800 binder by weight. DAAF-based explosive formulations have several desirable qualities as they are relatively insensitive to non-shock insults but have higher performance than triaminotrinitrobenzene (TATB) based formulations. Equations of state for the explosive reactants and products are calibrated using a combination of existing and new experimental data and theoretical calculations. The AWSD rate law calibration utilizes both one-dimensional shock-to-detonation and multidimensional rate stick experiments to capture the shock initiation and propagating detonation regimes. Validation of the calibrated model is demonstrated through comparison with recent gas-gun experiments.

Steady compaction waves in an inert porous material are investigated using a p -α model. In a steady traveling wave reference frame, the one-dimensional Euler equations are reduced to a set of ordinary differential equations. A Mie-Grüneisen equation of state (EOS) is used with parameters calibrated for polyurea aerogel (PUA). Analytic solutions for non-equilibrium compaction are developed which compliment numerical simulations and are able to predict the complete wave structure, including the compaction wave speed, zone length, and final compacted solid volume fraction. The dynamic compaction of PUA is studied for a range of piston velocities. Three regions of behavior are identified: supersonic, subsonic-complete, and subsonic-partial compaction. Below a critical piston velocity, a subsonic compaction wave is produced without a leading shock. At even lower piston velocities, there is partial compaction and a greater dependence on the dynamic compaction relation. Some features and limitations of the current model are discussed.

The aquarium test provides optical data on important aspects of detonation performance, namely the detonation velocity, shock wave shape in the surrounding water, and expansion rate of the condensed phase explosive products. It is commonly used for calibrating reaction rate laws and products equations of state (EOS). An important aspect, with regards to the analysis, is an adequate representation of the confining material to avoid inaccuracies. We conduct a series of two-dimensional axisymmetric reactive flow simulations for an ANFO-PMMA-water system using the Ghost Fluid Method. The goal is to evaluate the results obtained using three different EOSs for water: Tait, Murnaghan, and Tillotson. The numerical calculations are compared to large-scale aquarium experiments where the HE-water interface and the water shock front locations are directly measured from time-resolved image data.

A multidimensional implementation of DSD, formulated with the level set method, is applied to track the propagation of a detonation wave in a heterogeneous explosive consisting of an array of inert cylindrical obstacles with a liquid explosive in the interstitial space. With the Huygens assumption, the average detonation velocity through the explosive is less than that for the liquid explosive alone, due to the increased path length. When the normal detonation velocity is assumed to depend on front curvature, there is an additional, smaller reduction in the detonation velocity, which depends on the cylinder material. The detonation velocity deficits obtained in the computations are of the same order as those observed experimentally for a heterogeneous explosive consisting of a packed bed of spherical inert beads saturated with sensitized nitromethane. The DSD computations are relevant to the experimental results in the large-bead limit in which the pore dimension is large enough to support the propagation of discrete detonation wavelets in the interstitial liquid between the beads.

A highly accurate numerical shock and material interface fitting scheme composed of fifth-order spatial and third-or fifth-order temporal discretizations is applied to the two-dimensional reactive Euler equations in both slab and axisymmetric geometries. High rates of convergence are not typically possible with shock-capturing methods as the Taylor series analysis breaks down in the vicinity of discontinuities. Furthermore, for typical high explosive (HE) simulations, the effects of material interfaces at the charge boundary can also cause significant computational errors. Fitting a computational boundary to both the shock front and material interface (i.e. streamline) alleviates the computational errors associated with captured shocks and thus opens up the possibility of high rates of convergence for multi-dimensional shock and detonation flows. Several verification tests, including a Sedov blast wave, a Zel'dovich-von Neumann-Döring (ZND) detonation wave, and Taylor-Maccoll supersonic flow over a cone, are utilized to demonstrate high rates of convergence to nontrivial shock and reaction flows. Comparisons to previously published shock-capturing multi-dimensional detonations in a polytropic fluid with a constant adiabatic exponent (PF-CAE) are made, demonstrating significantly lower computational error for the present shock and material interface fitting method. For an error on the order of 10 m/s, which is similar to that observed in experiments, shock-fitting offers a computational savings on the order of 1000. In addition, the behavior of the detonation phase speed is examined for several slab widths to evaluate the detonation performance of PBX 9501 while utilizing the Wescott-Stewart-Davis (WSD) model, which is commonly used in HE modeling. It is found

Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodology of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results, are presented.

An ultra-fine, sub-micron discrete grid is used to capture the unsteady dynamics of a one-dimensional detonation in an inviscid O -O2 -O3 mixture. The ultra-fine grid is necessary to capture the length scales revealed by a complementary analysis of the steady detonation wave structure. For the unsteady calculations, shock-fitting coupled with a high order spatio-temporal discretization scheme combine to render numerical corruption negligible. As a result, mathematically verified solutions for a mixture initially of all O3 at one atmosphere and 298.15 K have been obtained; the solutions are converging at a rate much faster than the sub-first order convergence rate of all shock-capturing schemes. Additionally, the model has been validated against limited experimental data. Transient calculations show that strongly overdriven waves are stable and moderately overdriven waves unstable. New limit cycle behavior is revealed, and the first high resolution bifurcation diagram for detonation with detailed kinetics is found.

An ultra-fine, sub-micron discrete grid is used to capture the unsteady dynamics of a one-dimensional detonation in an inviscid O -O2 -O3 mixture. The ultra-fine grid is necessary to capture the length scales revealed by a complementary analysis of the steady detonation wave structure. For the unsteady calculations, shock-fitting coupled with a high order spatio-temporal discretization scheme combine to render numerical corruption negligible. As a result, mathematically verified solutions for a mixture initially of all O3 at one atmosphere and 298.15 K have been obtained; the solutions are converging at a rate much faster than the sub-first order convergence rate of all shock-capturing schemes. Additionally, the model has been validated against limited experimental data. Transient calculations show that strongly overdriven waves are stable and moderately overdriven waves unstable.