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To realize the double-roll thin strip continuous casting process for the production of high-quality steels, it is necessary to seek a new type of refractory material tailored for delivery device employed in this process. Therefore, the present study aimed to design and prepare MgAl 2 O 4 –C refractories for this purpose as well as to study their physical and mechanical properties, thermal shock resistance, oxidation kinetics, and to perform molten steel experiments after pre-oxidation treatment. The results of the present study demonstrated that the specimens could maintain high mechanical and thermal shock properties even after pre-oxidation treatment. After pre-oxidation at 1100 °C/1 h, the cold compressive strength of the specimen reached 17.63 MPa, with a residual strength ratio (thermal shock resistance) of 77.99%. Analysis of oxidation kinetics based on the shrinking core model indicated an increase in the effective diffusion coefficient and complete oxidation time with higher pre-oxidation temperature. Pre-oxidation of MgAl 2 O 4 –C refractories has been shown to be effective in reducing carbon penetration into the molten steel from carbon-containing refractories, thus maintaining the stability of the molten steel composition. This effect was attributed to enhanced contact and wettability between the steel and refractories, an augmented thickness of the pre-oxidized decarburized layer, the formation of a dense magnesium oxide layer, and the emergence of the MgAl 1·9 Fe 1 O 4 phase. Consequently, an MgAl 2 O 4 –C refractories designed for the delivery device was proposed along with anticipated applicability in the double-roll continuous casting process. [ABSTRACT FROM AUTHOR]

In the current work, the thermoelastic wave propagation and the thermal shock problems are studied based on the dipolar gradient elasticity and fractional order generalized thermoelasticity in order to take into account the microstructure effect and the thermal effect at a small scale. First, the fractional-order governing equations for coupled thermoelastic wave propagation are derived and the effects of microstructure parameters and fractional order on the dispersion and the attenuation are discussed; next, the transient problems by the thermal shock and the mechanical shock on the surface of half-space are studied. The Laplace transformation method and the state transfer equation method are used to solve this problem. The numerical results for the temperature, the displacement, the stress and the high order stress distributions are provided and shown graphically. The effects of the fractional order and the microstructure parameter on the thermoelastic behavior are investigated. Some interesting phenomenons and conclusions are presented at last. [ABSTRACT FROM AUTHOR]

A novel nonlinear coupled finite-strain electro-magneto-thermo-hyperelasticity (EMTHE) model is developed for the first- and second-sound wave propagation and reflection investigations in media that are exposed to electromagnetic fields and mechanical shocks. In contrast to the previous studies which studied behaviors of the finite-strain elastic or incompressible materials with small deformations, the current research proposes a much more complicated but much more accurate novel practical model for wave propagation and reflection analyses in near-incompressible finite-strain materials. Furthermore, to evaluate the effects of the electro-magneto-thermomechanical coupling, the strain energy density function of the hyperelastic material is expanded in a new way. The governing equations are obtained according to a nonlinear version of the Helmholtz free energy. The energy equations comprise the first- and second-order time rates of the temperature to enable the modeling of the finite-speed heat transfer; i.e., the establishment of a second-sound model. A nonlinear iterative finite element solution algorithm is proposed and implemented for the resulting coupled time-dependent generalized electro-magneto-thermo-hyperelasticity equations. The results show significant differences between the predicted wave propagation and reflection characteristics and behaviors of the near-incompressible and incompressible finite-strain models. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies on the evolution of shock-accelerated SF6/air interface with small initial amplitude are conducted. The effect of compressibility on the early development of perturbation is highlighted by varying shock intensity and fluid properties. The startup process is analyzed when rarefaction waves are reflected and the characteristic time of the startup process is provided. The relationship between the phase inversion process and the startup process under different incident shock strengths is clarified. According to the startup time, a new start point for normalization is given, which can better normalize the amplitude growth at the early stage. In addition, the effects of incident shock strength and physical properties of fluids on the linear growth rate are highlighted through numerical simulations. The incompressible linear model loses validity when the incident shock is strong, and the existing rotational model is verified to provide excellent predictions under any shock strengths. The decrease in adiabatic exponent of the heavy fluid or the increase in adiabatic exponent of the light fluid can reduce the linear growth rate. As the absolute value of Atwood number increases, the adiabatic exponent of the heavy fluid has a more significant effect on the linear growth than that of the light fluid. [ABSTRACT FROM AUTHOR]

Investigating the resistance of materials in some applications, such as aerospace, to ballistic shocks is of great importance. This article used molecular dynamics simulation to study the effect of mechanical shock under impact loads. In the ballistic shock simulation of aluminum-graphene nanocomposites, the Mishin, Tersoff, and Lennard–Jones potentials were used for aluminum, carbon in the projectile, and aluminum-carbon nanocomposites. The study results show that the presence of graphene sheets in aluminum increases its mechanical properties, including Young's modulus and yield strength. Adding graphene prevents projectile penetration into the material, so aluminum with a higher percentage of graphene will have maximum absorption in less time. Furthermore, the effect of adding more graphene layers to aluminum was also investigated. Specifically, single to five-layer graphene sheets absorb 11, 28, 53.5, and 90% of the projectile's energy, respectively. Furthermore, some optimal configuration for withstanding along the external projectile was discussed here. [ABSTRACT FROM AUTHOR]

In the field of healthcare logistics, the reliance on conventional transport methods such as cars for the delivery of monoclonal antibodies (mAbs) is susceptible to challenges posed by traffic and infrastructure, leading to increased and unpredictable transport times. Recognizing the potential role of drones in mitigating these challenges, we aimed to investigate the impact of medical drone transport on the stability of mAbs. Compromised stability could lead to aggregation and immunogenicity, thereby jeopardizing the efficacy and safety of mAbs. We studied the transportation of vials as well as ready-to-administer infusion bags with blinatumomab, tocilizumab, and daratumumab. The methodology involved the measurement of both temperature and mechanical shock during drone transport. Moreover, the analytical techniques High Performance Size-Exclusion Chromatography (HP-SEC), Dynamic Light Scattering (DLS), Light Obscuration (LO), Micro-Flow Imaging (MFI), and Nanoparticle Tracking Analysis (NTA) were employed to comprehensively assess the presence of aggregates and particle formation. The key findings revealed no significant differences between car and drone transport, indicating that the stability of mAbs in both vials and infusion bags was adequately maintained during drone transport. This suggests that medical drones are a viable and reliable means for the inter-hospital transport of mAbs, paving the way for more efficient and predictable logistics in healthcare delivery. [ABSTRACT FROM AUTHOR]

The damage impact of mechanical shocks on stator bar insulation is a key factor in high-voltage motor accidents. This study conducted electrical aging acceleration and breakdown experiments on damaged stator insulating materials to understand failure causes and evaluation methods. The relationship between sample defect area and depth and electrical properties was analyzed, along with the morphology of the damaged surface using a scanning electron microscope. Results show that the defect area correlates with impact mode but does not directly impact electrical performance. Effective insulation thickness is positively linked to electrical performance. This study serves as a valuable reference for evaluating mechanical impact faults in high-voltage motors. [ABSTRACT FROM AUTHOR]

Shock–bubble interactions (SBIs) are important across a wide range of physical systems. In inertial confinement fusion, interactions between laser-driven shocks and micro-voids in both ablators and foam targets generate instabilities that are a major obstacle in achieving ignition. Experiments imaging the collapse of such voids at high energy densities (HED) are constrained by spatial and temporal resolution, making simulations a vital tool in understanding these systems. In this study, we benchmark several radiation and thermal transport models in the xRAGE hydrodynamic code against experimental images of a collapsing mesoscale void during the passage of a 300 GPa shock. We also quantitatively examine the role of transport physics in the evolution of the SBI. This allows us to understand the dynamics of the interaction at timescales shorter than experimental imaging framerates. We find that all radiation models examined reproduce empirical shock velocities within experimental error. Radiation transport is found to reduce shock pressures by providing an additional energy pathway in the ablation region, but this effect is small (∼1% of total shock pressure). Employing a flux-limited Spitzer model for heat conduction, we find that flux limiters between 0.03 and 0.10 produce agreement with experimental velocities, suggesting that the system is well-within the Spitzer regime. Higher heat conduction is found to lower temperatures in the ablated plasma and to prevent secondary shocks at the ablation front, resulting in weaker primary shocks. Finally, we confirm that the SBI-driven instabilities observed in the HED regime are baroclinically driven, as in the low energy case. [ABSTRACT FROM AUTHOR]

The present paper investigates the von-Karman geometrically nonlinear structural responses of ceramic-metal functionally graded shell panels under the effect of the cases of mechanical and thermal shocks on their ceramic-rich surface. The constituents in the FGM are temperature-dependent and are graded as per the recently proposed four-parameter power laws while their effective properties in the shells are obtained using the Mori-Tanaka homogenization scheme. The transient thermoelastic problem is solved by importing the temporally varying temperature distribution from the nonlinear 1D heat equation as thermal loads into the FE code developed for thin and moderately thick shells based on higher-order shear deformation theory. The nonlinearity in the heat equation is linearized using Picard method in each Crank-Nicholson time-step while the linearization step in the geometric nonlinear problem uses Newton-Raphson method in each Newmark time-step. The new results presented in the manuscript study the effect of geometric nonlinearity on the responses of FG shell panels and the effect of different parameters of four-parameter FG laws. It was observed that including geometric nonlinearity significantly affects the responses of the shell panel structures when the loading direction, either mechanical or thermal, along with the gradation direction is reversed. [ABSTRACT FROM AUTHOR]

The effectiveness of clear aligners in correcting malocclusions is closely linked to the properties of the materials used to make them. The polymers used in the manufacture of clear aligners have well-established properties. However, the process of manufacturing clear aligners, known as thermoforming, involves thermal and mechanical shocks that may alter these properties. The objective of this study was to evaluate the effects of thermoforming on the mechanical, optical, chemical, and morphological properties of sixty PET-G specimens. The study compared the thickness, weight, absorbance, chemical structure, surface roughness, elastic modulus, yield strength, and breaking load of thirty thermoformed specimens with thirty non-thermoformed specimens. The study introduces a new approach by using standardized samples to analyze both chemical and physical properties. The results showed statistically significant differences in thickness (−15%), weight (−11%), and surface roughness (+1233% in roughness average; +1129% in RMS roughness) of the material. Additionally, a correlation was found between reduction in thickness and increase in opalescence. There was no significant change in the functionality of the aligners after thermoforming, as no significant mechanical changes were found. However, the increase in surface roughness may lead to plaque and fluid accumulation and worsen the fit of the aligners. [ABSTRACT FROM AUTHOR]

The heat extraction process of the Enhanced Geothermal System (EGS) faces the problem of mechanical property degradation caused by artificial cracks and surrounding rock caused by water-cooling shock. However, there are few studies considering the effect of water-cooling shock on fracture deformation and heat production performance. Therefore, a comprehensive numerical model considering water-cooling shock was established to simulate the heat extraction process of EGS. Four different scenarios were designed to analyze the influence of water-cooling shock on the heat production performance of EGS. The sensitivity analysis of several important variables affecting fracture aperture and heat production performance is carried out. The results show that compared with EGS without considering water-cooling shock, the heat extraction performance of EGS considering water-cooling shock is more reasonable. For a reservoir with an initial temperature of 300°C, the decrease of production temperature after 40 years is 3.35°C. Water-cooling shock changes the fracture aperture by degrading the elastic modulus of rocks and fractures, which affects the heat production performance of EGS. The decrease of fracture elastic modulus means that the fracture aperture increases under the same injection water pressure and confining pressure. The decrease of elastic modulus of bedrock leads to the decrease of stress sensitivity index, which inhibits the expansion of fracture aperture. Comprehensively considering water-cooling shock on reservoirs and fractures will more reasonably predict the heat production performance of EGS. [ABSTRACT FROM AUTHOR]

Noninvasive optical measurements of the shockwave propagation velocity using multiple pulse illumination allow deducing the shockwave pressure amplitude through Hugoniot relations and an appropriate equation of state of the medium. This technique is particularly useful for spatially resolved measurements near the shockwave emission site. Due to diffraction, however, a shockwave front can significantly change its morphology, rendering precise velocity measurements non-trivial. As solution we propose a wave front evolution (WaFE) velocimetry technique, which applies Huygens principle. We take a shadowgraph of the wave front at subsequent times as initial condition for the acoustic Helmholtz equation and numerically propagate the fronts in time. From the instance of time, when two subsequently taken wave front shadows numerically interfere and form one sharp wave front, the local shock velocity is obtained and the local shock pressure amplitude measured. With artificial test images, it is shown that this technique has excellent sub-pixel accuracy, robustness to noise, and can work with low contrast images and even overlapping and interfering wave fronts. The software is made available freely and can be applied to general shock front velocity measurements. We apply WaFE to determine the anisotropic shockwave emission from an elongated laser-induced plasma in water from shadowgraphs of the shockwave front imaged four times onto the same camera frame using multiple pulse illumination at a repetition rate of 60 MHz. The direction dependence of attenuation of the shockwave pressure amplitude is measured at distances of 50–300 μm to the plasma. [ABSTRACT FROM AUTHOR]

Safe storage and transportation of liquid oxygen (LOX) are critical for many engineering, medical, and defense applications. Double-walled, vacuum-insulated cryogenic tanks are commonly used, but they require supports that minimize heat transfer while bearing mechanical stresses. This study examines a novel polyamide-steel composite support for cryogenic tanks using COMSOL simulations. The significance lies in improving storage by reducing heat flux to LOX. The study also evaluates the effects of dynamic loading, resulting from mechanical shocks three times larger than the mass of the inner shell carrying LOX, applied to the ends of the internal supports. The significant contributions of this research lie in two main areas. Firstly, the study demonstrates the advantages of the new support design, particularly its enhanced ability to minimize heat transfer from the external environment to the cryogenic tank, thereby contributing to improved temperature control and safety. Secondly, the developed composite supports exhibit superior heat transfer characteristics, displaying efficiency in both static and dynamic loading conditions. Results demonstrated that the composite support reduced heat transfer compared to conventional designs under static and dynamic loads. This new support design enables safer LOX storage by limiting temperature increases. The coupled thermal–mechanical modeling methodology provides an effective tool for optimizing support designs in cryogenic systems. [ABSTRACT FROM AUTHOR]

Abstract For the first time, in the current work, the quasi-3D new refined theory (Q3D-NRT) is used to analyze the dynamic reactions of functionally graded (FG) annular sector plates made of graphene origami (GOri)-enabled auxetic metal metamaterials to the mechanical shock loading. The auxetic property of the annular plates is effectively controlled by graphene content and GOri folding degree that is graded across the thickness direction of the annular plates in a layer-wise manner, as Poisson’s ratio and other material properties are position-dependent and can be estimated by genetic programming-assisted micromechanical models (MM). Hamilton’s concept is used to find the structure’s governing equations. The differential quadrature technique and the Laplace transform are used at design sites to solve the time-varying equations of motion. The system response is translated from the Laplace domain to the time domain using a modified version of the Dubner and Abate approach. To investigate the impact of different geometrical and physical factors on the dynamic reactions of the annular sector plates, thorough parametric research is conducted. The findings of the present mathematical modeling are compared with those of the earlier publications and also with those of the machine learning approach. Utilizing this learning strategy, differential equations may be solved with very cheap computer costs while also overcoming formulation complexity. It needs a valid dataset from experimental or numerical analysis to use machine learning techniques. This dataset was compiled using the study’s numerical findings. Additionally, the machine learning approach demonstrates the capacity to deliver findings with a high degree of accuracy when predicting the mechanical characteristics of the existing structure under novel loading and boundary circumstances. [ABSTRACT FROM AUTHOR]

The Shock Academic Research Consortium is a multi-stakeholder group, including representatives from the US Food and Drug Administration and other government agencies, industry, and payers, convened to develop pragmatic consensus definitions useful for the evaluation of clinical trials enrolling patients with cardiogenic shock, including trials evaluating mechanical circulatory support devices. Several in-person and virtual meetings were convened between 2020 and 2022 to discuss the need for developing the standardized definitions required for evaluation of mechanical circulatory support devices in clinical trials for cardiogenic shock patients. The expert panel identified key concepts and topics by performing literature reviews, including previous clinical trials, while recognizing current challenges and the need to advance evidencebased practice and statistical analysis to support future clinical trials. For each category, a lead (primary) author was assigned to perform a literature search and draft a proposed definition, which was presented to the subgroup. These definitions were further modified after feedback from the expert panel meetings until a consensus was reached. This manuscript summarizes the expert panel recommendations focused on outcome definitions, including efficacy and safety. [ABSTRACT FROM AUTHOR]

Shock waves are common in astrophysical environments. On many occasions, they are collisionless, which means they occur in settings where the mean free path is much larger than the dimensions of the system. For this very reason, magnetohydrodynamic (MHD) is not equipped to deal with such shocks, be it because it assumes binary collisions, hence temperature isotropy, when such isotropy is not guaranteed in the absence of collisions. Here, we solve a model capable of dealing with perpendicular shocks with anisotropic upstream pressure. The system of MHD conservation equations is closed assuming the temperature normal to the flow is conserved at the crossing of the shock front. In the strong shock sonic limit, the behaviour of a perpendicular shock with isotropic upstream is retrieved, regardless of the upstream anisotropy. Generally speaking, a rich variety of behaviours is found, inaccessible to MHD, depending on the upstream parameters. This work can be viewed as the companion paper of MNRAS 520, 6083-6090 (2023), where the case of a parallel shock was treated. Differences and similarities with the present case are discussed. [ABSTRACT FROM AUTHOR]

We directly compare hybrid kinetic simulations and in situ observations of a high Mach number high-β shock in the Solar wind. We launch virtual probes to demonstrate that the model quantitatively reproduces the observations. The observed wave properties are caused by the ion Weibel instability in the shock foot. Parameters of reflected ions in the shock foot are extracted from simulations, and their coordinate dependencies are linearly approximated. These approximations could be used in analytical models. Due to strong magnetic variations at ramp the reflected ions density can be locally very high (nearly that of the incoming flow), which makes favourable conditions for the instability. [ABSTRACT FROM AUTHOR]

The capybara (Hydrochoerus hydrochaeris) is currently the largest known representative of the Rodentia order. It is an important herbivorous animal from the zootechnical point of view, found in different countries in South America, mainly in Brazil, where it can be found in all its States. The study of the anatomy of the lumbosacral plexus and medullary cone of the species could contribute to the development of comparative anatomy, and to adoption of future clinical and surgical procedures in the species. The present study proposed to conduct an exploration of the nerves of the lumbosacral plexus in capybara to highlight their relationship with the adjacent muscle tissues. Four adult capybaras, two males and two females, were used for dissection of the muscles innervated by the nerves that make up the lumbosacral plexus. The results allowed to verify that the lumbosacral plexus is formed by ventral roots originating in the six lumbar vertebrae and the three sacral vertebrae. The medullary cone was found between L6 and S1 in the sixth lumbar vertebra (L6) and the first sacral vertebra (S1). The identification and the recognition of these nerves in capybaras are important to improve the assessment of possible injuries caused by inadequate management, accidental mechanical shocks, or peripheral nervous system disorders. Additionally, the study included the topographic analysis of the medullary cone, essential for improving the anesthetic techniques by epidural route. The expansion of this type of research with capybaras can be useful for developing management techniques that preserve the species health and well-being. [ABSTRACT FROM AUTHOR]

It is shown that the ratio of the proton convective gyroradius r Ep, to the width of the shock ramp D , controls the thermalization process of ions in quasi-perpendicular shocks. When r Ep/ D > 1, the solar wind beam energy is rapidly converted to gyration (thermal) energy by a universal, transit time thermalization (TTT) mechanism that does not require any collisions, waves, or instabilities. The TTT of ions on magnetic field gradients is followed by stochastic wave energization (SWE) on electric field gradients. Ions heated by TTT and SWE processes are subject to additional ballistic surfing acceleration caused by the convection field in the shock front. These three fundamental ion energization mechanisms are studied with test-particle simulations in a realistic shock model, and are shown to be consistent with magnetospheric multiscale measurements in the Earth's bow shock. It is also shown that shock reflected ions are produced by the SWE process and not by the cross-shock potential. An explanation for downstream oscillations in quasi-perpendicular shocks is also provided. [ABSTRACT FROM AUTHOR]

In this paper, we construct counterexamples to the local existence of low-regularity solutions to elastic wave equations in three spatial dimensions (3D). Inspired by the recent works of Christodoulou, we generalize Lindblad's classic results on the scalar wave equation by showing that the Cauchy problem for 3D elastic waves, a physical system with multiple wave-speeds, are ill-posed in H3(R3). We further prove that the ill-posedness is caused by instantaneous shock formation, which is characterized by the vanishing of the inverse foliation density. The main difficulties of the 3D case come from the multiple wave-speeds and its associated non-strict hyperbolicity. We obtain the desired results by designing and combining a geometric approach and an algebraic approach, equipped with detailed studies and calculations of the structures and coefficients of the corresponding non-strictly hyperbolic system. Moreover, the ill-posedness we depict also applies to 2D elastic waves, which corresponds to a strictly hyperbolic case. [ABSTRACT FROM AUTHOR]

Abstract—In order to provide fast, accurate, and low cost shock sensitivity calibration of acceleration sensors, a pneumatically operated piston shock calibrator based on ISO 16063-22 is designed. comparative calibration method is used to calibrate the shock sensitivity of tested sensor within a shock peak amplitude of 25 to 2000 g and a pulse duration of 0.1 to 3 ms. The pneumatically operated piston shock calibrator includes modules of mechanical shock, shock signal generation, and measurement control based on the NI data acquisition card and LabVIEW control program. Numerical analysis and calculation of the pneumatic ejection process by MATLAB is performed to analyze the influence factors and levels of the impact velocity. Moreover, experiments on key performance indexes and test data processing are carried out. The repeatability of shock peak amplitude and pulse duration are better than 1.24 and 2.19%, respectively, which reaches the level of the commercially available calibrator of the same type. Meanwhile, the calibrated uncertainty is 2.56% (k = 2), which meets the ISO 16063-22 requirement with the accuracy of less than 5%. [ABSTRACT FROM AUTHOR]

Properties of dust-ion acoustic waves (DIAWs) in an unmagnetized dusty plasma consisting of mobile ions, superthermal electrons, and negatively charged dust clouds with charge fluctuation are investigated. Burgers' equation is derived from the fluid equation of the plasmas by considering the reductive perturbation technique. The Lax pair of the evolution equation is obtained, and the characteristics of the DIAWs are investigated by employing the Darboux transformation. Some new waves (one-soliton, two-soliton-shocks, etc.) other than usual shocks are observed as the Darboux transformation is used through the Lax pair. It is also shown that all the physical plasma parameters have a significant effect on the structure of the nonlinear waves. [ABSTRACT FROM AUTHOR]

Type II solar bursts are radio signatures of shock waves in the solar corona driven by solar flares or coronal mass ejections (CMEs). Therefore, these bursts present complex spectral morphologies in solar dynamic spectra. Here, we report meter–decameter radio observations of a type II burst on 2014 July 25 made with the Ukrainian radio telescopes UTR-2 (8.25–33 MHz) and GURT (8.25–78 MHz). The burst demonstrates fundamental and harmonic components, band splitting, a herringbone structure, and a spectral break. These specific spectral features, observed jointly in a single type II burst, are rarely detected. To contribute to our understanding of such puzzling type II events, we carried out a detailed analysis of the recorded type II dynamic spectrum. In particular, the herringbone pattern has been exploited to study electron density turbulence in the solar corona. We calculated the power spectral densities of the flux variations in selected herringbones. The spectral index is in the range of α = −1.69 to −2.00 with an average value of −1.897, which is slightly higher than the Kolmogorov spectral index of −5/3 for fully developed turbulence. We also recognized that the second type II burst consists of three drifting lanes. The lane onset times coincide with the spectral break in the first type II burst. We regard that the CME/shock passage through a streamer caused the spectral break and triggered the multilane type II radio emission. Thus, we support one of the proposed scenarios for type II burst occurrence as being the result of CME/shock–streamer interaction. [ABSTRACT FROM AUTHOR]

Transparent ceramics are promising materials in the fields of high pressure and high temperature. Based on a lattice-spring simulation method, a novel polycrystalline model for shock-wave compression is established to explore the dynamic response and damage evolution of yttrium aluminum garnet (YAG) under shock loading. The macro-response and micro-fracture process under impact loading can be obtained simultaneously, and a correlation between the macroscopic response and mesoscale damage is shown. The process of crack propagation along a grain boundary and through grain-boundary deflection is observed in the simulation. A change in deformation behavior from intergranular fracture to transgranular fracture in the vicinity of grain boundaries, associated with the transition from an elastic response to a plastic response, is observed, as the shock stress increases from below to above the Hugoniot elastic limit. Computational results demonstrate a clear, exponential attenuation of the elastic precursor wave with the propagation of shock waves. The reasons for the elastic precursor decay and the transition from an elastic response to a plastic response are the stress relaxation and energy dissipation caused by internal transgranular fracture. The polycrystalline model will aid in microstructure design and provide a reference for the development of polycrystalline transparent ceramics in the fields of engineering and scientific research. [ABSTRACT FROM AUTHOR]

Erythritol has been proposed as an inert surrogate for developing theoretical and computational models to study aging in energetic materials. In this work, we present a comparison of mechanical and shock properties of erythritol computed using the ReaxFF reactive force field and from ab initio calculations employing density functional theory (DFT). We screened eight different ReaxFF parameterizations, of which the CHO parameters developed for hydrocarbon oxidation provide the most accurate predictions of mechanical properties and the crystal structure of erythritol. Further validation of the applicability of this ReaxFF parameterization for modeling erythritol is demonstrated by comparing predictions of the elastic constants, crystal structure, vibrational density of states, and Hugoniot curves against DFT calculations. The ReaxFF predictions are in close agreement with the DFT simulations for the elastic constants and shock Hugoniot when the crystal is loaded along its c axis but show as much as 30% disagreement in the elastic constants in the a b plane and 12% difference in shock pressures when shocked along the a or b crystal axes. Last, we compare thermomechanical properties predicted from classical molecular dynamics with those calculated using the quasi-harmonic approximation and show that quantum mechanical effects produce large discrepancies in the computed values of heat capacity and thermal expansion coefficients compared with classical assumptions. Combining classical molecular dynamics predictions of mechanical behavior with phonon-based calculations of thermal behaviors, we show that predicted shock-induced temperatures for pressures up to 6.5 GPa do not exceed the pressure-dependent melting point of erythritol. [ABSTRACT FROM AUTHOR]

Soda-lime glass (SLG) and other silica glasses exhibit the failure wave phenomenon under shock compression. The mechanism responsible for this peculiar behavior of glasses is still unresolved. In this study, a series of plate impact experiments was performed at three different impact stresses of 6.4, 8.3, and 10.8 GPa to better understand the mechanisms underlying the failure wave phenomenon. Specifically, spall experiments were conducted to probe the speed and existence of failure waves at different stresses in SLG. A layered glass target was used to probe the possibility of a "renucleation" of the wave at the SLG–SLG interface. When it existed, the failure wave was inferred to propagate at a speed of 1.3 km/s. However, it was observed that the failure wave phenomenon ceases to exist for impact stresses higher than 10 GPa. In experiments with a 6.4 GPa impact stress, the peak free surface velocity was significantly less than what is predicted by stress-Hugoniot calculations. This velocity deficit and other important features of the measured free surface velocity profiles were simulated using finite element analysis by incorporating an abrupt densification of SLG at a critical stress in the equation of state. This densification feature is similar to what would be expected of a phase transition. Although unable to unambiguously reveal the mechanism causing the failure wave phenomenon, the results of the present work clearly indicate that the failure wave causes a secondary compression and densification in SLG. [ABSTRACT FROM AUTHOR]

Engineering structures or materials are often subjected to multiple shock loadings. Mechanical response and its physical mechanism under such loadings are extremely complex and need to be studied in depth. To reveal double shock-induced deformation and microstructural evolution in the key structural material Ta, large-scale non-equilibrium molecular dynamics simulations of monocrystalline and polycrystalline Ta under double shock loading were performed. The results show that the activation and re-evolution of twins and dislocations introduced by the first shock dominate the plastic deformation during the second one. Some crystallographic orientation dependent mechanisms of plastic deformation under the second shock are revealed. Twin-dislocation conversion is dominant in the ⟨100⟩-orientated monocrystalline and polycrystalline Ta, while dislocation slipping is dominant in the ⟨110⟩- and ⟨111⟩-orientated Ta. The dependence of flow strength on the loading-paths of single and double shocks was also investigated. Shock-induced amorphization and recrystallization are observed in the single shock-loaded Ta models, leading to lower flow strengths than those of the double shock-loaded ones. These results help understand the complex relationship between the dynamic strength and intrinsic deformation mechanism of Ta under multiple shock loadings. [ABSTRACT FROM AUTHOR]

Shock temperature, stress, and dynamic emissivity for cerium shocked from 8.4 to 23.5 GPa were measured. In addition, the isentropic shock release temperature as a function of release stress was determined at a window interface. Cerium samples were shock compressed by plate impact on a single-stage gun. We made time-resolved measurements of thermal radiance, reflectance, and interface velocity of samples glued to lithium fluoride windows. Reflectance was measured with an integrating sphere and velocity with photonic Doppler velocimetry. From these measurements, we determined the temperature, emissivity, and stress at the interface. For shock stresses below 10.24 GPa, the samples were shocked from the γ phase into the α phase; at higher stresses, the cerium presumably melted or entered a mixed phase upon shock. The shock Hugoniot temperature as a function of stress follows a straight line over the entire range of our measurements, disagreeing with previously published predictions that the Hugoniot would follow the melt boundary from 10.24 up to around 16–18 GPa. Between 11.9 and 16.8 GPa, all the release isentropes converged (within experimental uncertainty) to a point around 4 GPa and 900 K, near the published melt curve. For experiments shocked above ∼16 GPa, the release isentropes behave differently. This suggests that within this 12–16 GPa range, there is a phase transition taking place, probably melt, and that it is occurring somewhere along the shock and release path. We could not identify a single-valued phase boundary from our experiments. Potential reasons for this are discussed. [ABSTRACT FROM AUTHOR]

Optical pyrometry is a well-developed, broadly applicable method to determine temperature in dynamic compression experiments. However, it measures radiation from only the skin depth of the radiant material, is highly susceptible to spurious backgrounds, and requires an often-unmeasurable free parameter—the sample dynamic emissivity. Raman spectroscopy offers a method to determine temperature directly from fundamental theory, but it is practically limited in applications to a small subset of shock experiments. In this work, we describe an experiment allowing simultaneous application of Raman and pyrometric temperature techniques to benchmark a specific instance of pyrometry. We attempted both measurements on multiple experiments and compare the successful temperature results between the separate but highly repeatable shots. We find that dynamic shock temperatures inferred from Raman spectroscopy and pyrometry generally agree within the uncertainties of each measurement, although those uncertainties are larger than typical for a specially designed pyrometry experiment on a shocked metal sample. [ABSTRACT FROM AUTHOR]

A general methodology to prepare MXene quantum dots (MxQDs) with yields over 20% by liquid‐phase laser ablation of the MAX phase is reported. Mechanical and thermal shock by 532 nm laser pulses (7 ns fwhp, 50 mJ × pulse−1, 1 Hz pulse frequency) produces MAX etching and exfoliation to form MXene QDs, avoiding the use of HF. The process can be followed by absorption and emission spectroscopy and by dynamic laser scattering and it appears to be general, being applied to Ti3AlC2, Ti2AlC, Nb2AlC, and V2AlC MAX phases. Density functional theory calculations indicate that, depending on the surface terminal groups, the diminution of the MXene size to the nanometric scale makes it possible to control the band gap of the MXene. The photocatalytic activity of these MXene QDs for hydrogen evolution has been observed, reaching an H2 production for the most efficient Ti3C2 QDs as high as 2.02 mmol × g−1 × h−1. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to combine the entropy weight method with the cloud model and establish a fire risk assessment method for airborne lithium battery. Design/methodology/approach: In this paper, the fire risk assessment index system is established by fully considering the influence of the operation process of airborne lithium battery. Then, the cloud model based on entropy weight improvement is used to analyze the indexes in the system, and the cloud image is output to discuss the risk status of airborne lithium batteries. Finally, the weight, expectation, entropy and hyperentropy are analyzed to provide risk prevention measures. Findings: In the risk system, bad contact of charging port, mechanical extrusion and mechanical shock have the greatest impact on the fire risk of airborne lithium battery. The fire risk of natural factors is at a low level, but its instability is 25% higher than that of human risk cases and 150% higher than that of battery risk cases. Practical implications: The method of this paper can evaluate any type of airborne lithium battery and provide theoretical support for airborne lithium battery safety management. Originality/value: After the fire risk assessment is completed, the risk cases are ranked by entropy weight. By summarizing the rule, the proposed measures for each prevention level are given. [ABSTRACT FROM AUTHOR]

In this paper, a neural network approach is applied for solving an electromagnetic inverse problem involving solid dielectric materials subjected to shock impacts and interrogated by a millimeter-wave interferometer. Under mechanical impact, a shock wave is generated in the material and modifies the refractive index. It was recently demonstrated that the shock wavefront velocity and the particle velocity as well as the modified index in a shocked material can be remotely derived from measuring two characteristic Doppler frequencies in the waveform delivered by a millimeter-wave interferometer. We show here that a more accurate estimation of the shock wavefront and particle velocities can be obtained from training an appropriate convolutional neural network, especially in the important case of short-duration waveforms of few microseconds. [ABSTRACT FROM AUTHOR]

Purpose: Jarring events, be they global crises such as COVID-19 or technological events such as the Cambridge Analytica data incident, have bullwhip effects on billions of people's daily lives. Such "shocks" vary in their characteristics. While some shocks cause, for example, widespread adoption of information systems (IS) as diverse as Netflix and Teams, others lead users to stop using IS, such as Facebook. To offer insights into the multifaceted ways shocks influence user behavior, this study aims to assess the status quo of shock-related literature in the IS discipline and develop a taxonomy that paves the path for future IS research on shocks. Design/methodology/approach: This study conducted a literature review (N = 70) to assess the status quo of shock-related research in the IS discipline. Through a qualitative study based on users who experienced shocks (N = 39), it confirmed the findings of previous literature in an illustrative IS research context. Integrating the findings of the literature review and qualitative study, this study informs a taxonomy of shocks impacting IS use. Findings: This study identifies different ways that shocks influence user behavior. The taxonomy reveals that IS research could profit from considering environmental, private and work shocks and shedding light on positive shocks. IS research could also benefit from examining the urgency of shocks, as there are indications that this influences how and when individuals react to a specific shock. Originality/value: Findings complement previous rational explanations for user behavior by showing technology use can be influenced by shocks. This study offers a foundation for forward-looking research that connects jarring events to patterns of technology use. [ABSTRACT FROM AUTHOR]

We have synthesized the well-performance bulk diamond–SiC composite by the high-temperature and high-pressure method and employed the light gas gun launched flyer plates to investigate shock compression response of the diamond–SiC composite. The plots of shock velocity vs particle velocity demonstrate the presence of double elastic waves in the diamond–SiC composite under shock compression. The first elastic wave travels at 13.1 ∼ 13.6 km / s and leads to yielding at ∼ 12.75 GPa. The second elastic wave propagates at 12.8 ∼ 13.0 km / s and does not display the yielding up to ∼ 110 GPa. Such a Hugoniot elastic limit is apparently higher than that of the single crystal diamond. The strengthening mechanism underlying the diamond–SiC composite has been discussed. By simulations of the lattice-spring model, the results revealed that under shock compression, the silicon carbide matrix yields first in the composite, resulting in damage to the substructure surrounding the diamond particles. This damage releases the intense shear stress and protects the diamond from severe crushing. Due to diamonds being hydrostatically confined by the silicon carbide matrix, both dislocation migration and slip band sliding are suppressed significantly, which enhances the strength of diamonds. [ABSTRACT FROM AUTHOR]

With the advent of additive manufacturing (AM) techniques, a new class of shockwave mitigation and structural supports has been realized through the hierarchical assembly of polymer materials. To date, there have been a limited number of studies investigating the role of structure on shockwave localization and whether AM offers a means to tailor shockwave behavior. Of particular interest is whether the mesoscopic structure can be tailored to achieve shockwave properties in one direction of impact vs the other. Here, we illustrate directional response in engineered polymer foams. In situ time-resolved x-ray phase contrast imaging at the Advanced Photon Source was used to characterize these diode-like structures. This work offers a breakthrough in materials technology for the development of protective structures that require augmentation of shock in one direction while diminishing transmission in the opposite direction. [ABSTRACT FROM AUTHOR]

In previous studies of shock compression, pressure P , specific volume v , specific internal energy e , shock velocity U s , and particle velocity u p have typically been presented in a dimensional form. For different materials, the plots of P − v , P − u p , or U s − u p , often called Hugoniot curves, are different. Here, we predict the behavior of shock-compressed liquids through proper scaling of the Rankine–Hugoniot (RH) equations and dimensionless Hugoniot curves. The characteristic density and velocity scales are the density ρ 0 and bulk speed of sound c b 0 of the undisturbed liquid, respectively. Two dimensionless numbers arise from the scaled RH equations, one for the initial condition of pressure and the other for the initial condition of internal energy. Under normal conditions, these two numbers do not affect the solutions of the dimensionless RH equations. The dimensionless Hugoniot curves P / (ρ 0 c b 0 2) vs v ρ 0 , U s / c b 0 vs u p / c b 0 , and P / (ρ 0 c b 0 2) vs u p / c b 0 of different liquids merge reasonably well onto a single curve. The dimensionless Hugoniot curve v ρ 0 vs U s / c b 0 or v ρ 0 vs u p / c b 0 , often omitted in the previous work, is thus found to be useful in the understanding of shock compression. The v ρ 0 vs U s / c b 0 curve clearly shows that the dependence of the specific volume ratio v ρ 0 on U s / c b 0 is different for moderate and strong shocks. For a moderate strength shock (U s / c b 0 ≲ 10), a new approximation relation is proposed for shock velocity U s and particle velocity u p as (U s − u p) / c b 0 ≈ (U s / c b 0 ) n , where the exponent is determined empirically as n = 0.55 − 0.6. This new approximation relation is different from the commonly used linear relation between U s and u p and better predicts the behavior of shock-compressed liquids. Using the new approximation relation, the ratio v ρ 0 under moderate strength shocks can be approximated by a power law v ρ 0 ≈ (U s ∗) n − 1 . For stronger shocks, the decrease in the specific volume ratio is slower and is bounded. [ABSTRACT FROM AUTHOR]

When a shock wave of several tens of GPa breaks out at a free surface, a material is ejected ahead of this surface. The amount and velocity of such ejecta depend on the breakout pressure, state of the released material (solid, liquid, or mixed), whether the shockwave is supported or unsupported, and the initial geometrical perturbation (or roughness) of the free surface. If surface defects consist of small grooves, pits, or scratches, material ejection occurs in the form of jets breaking up into tiny particles (so-called microjetting), with jet tip velocities up to several times higher than the free surface velocity. The laser-based experiments presented in this paper focus on microjetting in shock-melted tin with periodic surface perturbations. Several complementary diagnostics are combined to measure the velocity and mass of ejecta during the early stages of the jetting process. One relevant advancement is the use of ps-laser x-ray radiography to probe the density of the ejecta in distinct jets a few tens of μ m -wide. The effects of the depth and wavelength of the initial perturbation are investigated in both linear and near-linear growth regimes. The results are compared with predictions derived from the Richtmyer–Meshkov Instability theory. [ABSTRACT FROM AUTHOR]

A series of planar impact tests were performed aiming at measuring the compressibility of the paraffin–poly-methylmethacrylate (PMMA) mixture up to a pressure of 2.5 GPa. It was found that compressive waves in the mixture consist of the initial part, characterized by a virtually linear increase of parameters, followed by the part associated with their relaxation. The dependence of the maximum strain rate of compression of the mixture on the final shock pressure was found to be much weaker than observed in metals and liquids. This inconsistency was explained by the difference of the viscosity mechanisms in these media. Based on an assumption of additivity of volumes of the mixture constituents, the estimates of bulk PMMA compressibility were obtained. [ABSTRACT FROM AUTHOR]

Spall fracture is a high strain-rate damage phenomenon associated with shock or impulsive loading events. When a material that has been subjected to shock compression is allowed to release, rarefaction waves propagate into the sample and reduce the internal stress to zero. If multiple rarefaction waves intersect, they generate tension which, if sufficient, can nucleate voids in the material. It has been observed in several works investigating spall fracture that although the shock-wave profiles suggested spall occurred, imaging of the recovered sample revealed no voids or cracks. In this study, we aim to determine whether a second shock event could recompact existing spall damage, and if so, what form does the microstructure at the recompaction interface have? Through a series of gas-gun flyer-plate impact experiments, we demonstrate that modest shock stresses of 2 GPa–3 GPa are enough to both fully compact a damaged copper target back to a state of zero porosity and, furthermore, drive recrystallization of the interface such that there is a new bond formed where the free surfaces were brought together. [ABSTRACT FROM AUTHOR]

To investigate the role of crystal anisotropy on the elastic–plastic deformation of BCC single crystals at high shock stresses, molybdenum (Mo) single crystals were shock compressed along the [100], [111], and [110] orientations at elastic impact stresses between 20 and 110 GPa. Laser interferometry was used to measure shock wave velocities and particle velocity histories. Along the [100] and [111] orientations, elastic–plastic waves (two wave structure) were observed up to 110 GPa. Along the [110] orientation, the two wave structure was observed only up to 90 GPa. The measured elastic wave amplitudes were analyzed to determine crystal anisotropy effects, impact stress dependence, and the activated slip systems on the Hugoniot elastic limit. The findings from our work have provided insight into the role of crystal anisotropy on the elastic–plastic deformation under shock compression at high stresses. [ABSTRACT FROM AUTHOR]

A Talbot–Lau x-ray deflectometer can map electron density gradients in high energy density plasmas, as well as provide information about plasma elemental composition through single-image x-ray refraction and attenuation measurements. A new adaptation to a pulsed power environment used backlighting from copper X-pinches, allowing for electron density mapping of a low-Z object. Even though the X-pinch backlighter is not properly optimized for emitting x-rays in terms of source size and photon fluence, Moire fringe patterns with contrast up to 14% and fringe shift due to refraction on a beryllium object are obtained. Due to the proximity of the deflectometer with the X-pinch (∼6 cm), it is shown that a protective filter is required to avoid damage in the closest (i.e., source) grating due to both plasma debris and mechanical shock. Regarding grating survival, these did not show any damage due to the intense magnetic field or heating induced by plasma radiation. Electron density on beryllium was measured with a difference lower than 16%. The areal electron density mapping of the sample was limited by source size characteristics, in similarity to transmission radiography. These results show the potential of plasma electron density as well as material mapping through Talbot–Lau x-ray deflectometry in a pulsed power environment. [ABSTRACT FROM AUTHOR]

The ability to understand and predict the response of matter at extreme conditions requires knowledge of a material's equation-of-state including the location of phase boundaries, transition kinetics, and the evolution of material strength. Cerium is a material with a complex phase diagram that continues to attract significant scientific interest. Recent dynamic experiments have provided information on the low-pressure γ – α phase transition, sound speed, and Hugoniot data for the higher-pressure α phase, as well as the incipient shock melt transition. Despite these efforts, there are still regions of the phase diagram that are largely unexplored dynamically, including the high-pressure region below the melt boundary. Along a room temperature isotherm, diamond anvil cell data report a transition to the ϵ phase between 13 and 17 GPa. At higher temperatures, similar diamond anvil cell data show significant disagreement regarding the existence, location, and slope of the ϵ -phase boundary. In this work, double-shock loading was used to access the α – ϵ region of the phase diagram to obtain equation-of-state information and to determine the location of the ϵ -phase boundary for shock loading. [ABSTRACT FROM AUTHOR]

Double elastic shock waves are rarely observed in two-dimensional (2D) materials and normally unexpected for elastically isotropic 2D crystals such as graphene. With large-scale molecular dynamics simulations, we show that in single-crystal graphene shock-loaded along nonzigzag and nonarmchair directions, double elastic shock waves (quasilongitudinal and quasitransverse) can emerge. Quantitative acoustic wave equation analysis reveals that shock-induced symmetry reduction in lattice, as well as in elastic stiffness tensor, gives rise to the normally unexpected quasitransverse wave following the quasilongitudinal wave. [ABSTRACT FROM AUTHOR]

Shock-induced consolidation of tungsten nanoparticles to form a bulk material was modeled using molecular dynamics simulation. By arranging the nanoparticles in a three-dimensional model of body-centered cubic super-lattice, the calculated shock velocity-particle velocity Hugoniot data are in good agreement with the experiments. Three states, including solid-undensified, solid-densified, and liquid-densified, can be sequentially obtained with the increase of the impact velocity. It is due to the flow deformation at the particle surface that densifies the cavity, and the high pressure and temperature that join the particles together. Melting is not a necessary factor for shock consolidation. Based on whether or not melting takes place, the consolidation mechanisms are liquid-diffusion welding or solid-pressure welding. [ABSTRACT FROM AUTHOR]

Gd 3 Ga 5 O 12 single crystals [gadolinium gallium garnet (GGG)] were shock compressed to elastic deformation, elastoplastic transformation, and structural phase-transition regimes with the corresponding single, two-wave, and three-wave structures. Velocity profiles at the front interface and the rear free surface of the sample are measured by a Doppler pin system. Results of these measurements are analyzed in detail, and the refractive index, n , at 1550 nm is obtained as a function of shock pressure or density. Incorporating previously published single-wave data above 100 GPa, characteristic variations in the refractive index are presented and discussed within the context of shock-induced polymorphism of the GGG. [ABSTRACT FROM AUTHOR]

To gain insights into the relative contributions of different plastic deformation mechanisms, particularly basal slip, for shocked hexagonal close-packed (hcp) metals, magnesium (Mg) single crystals were subjected to shock compression and release along a low-symmetry (LS) orientation to 1.9 and 4.8 GPa elastic impact stresses. LS-axis is a "nonspecific" direction resulting in propagation of quasilongitudinal and quasishear waves. Wave profiles, measured using laser interferometry, show a small elastic wave followed by two plastic waves in compression; release wave profiles exhibited a structured response for the higher stress and a smooth response for the lower stress. The LS-axis wave profiles are significantly different than profiles published previously for c- and a-axes, demonstrating that Mg single crystals exhibit strong anisotropy under shock compression/release. Numerical simulations, using a time-dependent anisotropic modeling framework, show that shock wave loading along the LS-axis involves the simultaneous operation of multiple deformation mechanisms. Shock compression along LS-axis is dominated by basal slip while prismatic slip and pyramidal I { 10 1 ¯ 1 } ⟨ 11 2 ¯ 3 ⟩ slip play a smaller role; coupling between longitudinal and shear deformations was observed. The unloading response is dominated by basal slip with some contribution from prismatic slip; pyramidal I slip is not activated. The present results, unlike results obtained for c- and a-axes, show that the deformation mechanism observed under quasistatic loading conditions along LS-axis is not sufficient to determine the shock response along this orientation. Although requiring numerical simulations for wave analysis, shock propagation along a LS-orientation provides new insights into the plastic deformation response of hcp metal single crystals. [ABSTRACT FROM AUTHOR]

Shock-induced plasticity and phase transition in single crystal lead are investigated by nonequilibrium molecular dynamics simulations. Under dynamic shock loading, the appearance of plasticity in materials precedes that of phase transition. Plasticity mainly causes two effects: one is that plasticity has a significant relaxation effect on shear stress, and the other is that deformation twinning serves as important nucleation sites for the phase transition. This twinning is caused by mutual impediments among different cross-slips and {111} slips. There are three main stages in the dynamic phase transition process of lead: fcc → bcc-like phase transition, plasticity, and hcp phase formation and growth. Moreover, phase transition has a more significant relaxation effect on shear stress, which relaxes the shear stress to a minimum value. The spall strength of lead decreases as the shock intensity increases, but its rate of decrease under different shock intensities is different. Plasticity, especially phase transition, would obviously result in a lower rate of decrease in spall strength. [ABSTRACT FROM AUTHOR]

With the aim of expanding the measurable range of high-rate deformation, experiments were conducted in which AD1 aluminum [A199.3 under the international classification and AA1135 in the USA (American National Standards Institute)] was subjected to stepwise shock compression at both room temperature and in the range of 498–530 °C. Measurements of the width of the plastic shock waves revealed that the anomalous thermal hardening at strain rates exceeding 105 s−1 is maintained upon increasing the deformation up to at least 6.5%. The hysteresis during shock compression and unloading cycles of the elastic–plastic body was analyzed. The results indicated that determination of the stress states behind the plastic shock wave utilizing this method requires higher than usual measurements and calculation accuracies. [ABSTRACT FROM AUTHOR]