Shock Environment Research Articles

Surface Evolution of Vermicular Cast Iron in High Frequent Cyclic Plasma and Different Facial Cooling Airflows

The surface evolution of vermicular cast iron in a high frequent cyclic plasma and facial cooling airflow was studied to understand the behavior and mechanism in different cooling conditions under a unique thermal shock environment. Results indicated that both the mass and linear loss presented titled inverted V-shaped relationships with the flux of the cooling airflow, while the change in roughness decreased continuously. As the cooling airflow rose, the eroded zone was reduced, the iron oxides lessened, and fluctuation of the surface temperature weakened. In combination with the thermodynamic calculations and thermal analysis, it was confirmed that the oxidation and mechanical erosion had contrary tendencies with the rising flux in the facial cooling airflow. The transformation of the dominant factor from oxidation to peeling off by thermal stress and scouring resulted in the evolution of mass and thickness. The surface oxides dominated the change in the roughness.

Key technologies disclosure for the high-g shock tester based on collision principle and experimental study.

The shock tester based on a three-body, single-level velocity amplifier is especially suitable for high-g shock tests of lightweight and compact pieces. This study focuses on disclosing some key technologies that affect whether the velocity amplifier could achieve a high-g level shock experimental environment. Equations describing the first collision are deduced and some key design criteria are proposed. The key conditions for formation of the opposite collision are proposed for the second collision, which is the most important point, to obtain a high-g shock environment. A test platform was constructed, and experiments were conducted with different shock rods, pulse shapers, and initial velocities. The test results fully demonstrated the powerful ability of the single-level velocity amplifier for high-g shock experiments and tell us that a duralumin alloy or carbon fiber is suitable to design shock rods.

Harvesting energy from shock environments via functionally graded magneto-electro-elastic materials

Given the fact that the environmental kinetic energy may appear in the form of shock pulse excitation, this paper aims to investigate the response of a shock excited cantilever beam equipped with two symmetric functionally graded magneto-electro-elastic layers. To this end, employing a hybrid procedure including the Ritz method together with the geometric nonlinear Euler-Bernoulli beam theory, the coupled magneto-electro-mechanical reduced equations of motion are obtained. The model predictions are compared and successfully validated by those available in the literature. Having the vibration frequency of the system, which is obtained by the method of multiple time scales, the optimal duration maximizing the influence of shock pulse acceleration is predicted using the power shock spectrum introduced in this study for the first time. The results reveal that the harvested power maximizes when the system fundamental frequency becomes 1.36 times the equivalent shock frequency.

Theoretical and experimental study of the “superelastic collision effects” used to excite high-g shock environment

The excitation technology for high-g-level shock environment experiments is currently a topic of interest, for which velocity amplification by collisions of vertically stacked bodies has been used to develop high-g shock tests with great success. This study investigated the superelastic collision effects generated during high-velocity one-dimensional three-body impacts. Theoretical formulae were derived in brief for an analytical investigation of the collisions. Four experiments were performed with different initial velocities obtained from free-falls from different heights. Velocity gains larger than 5 were obtained for the three-body collisions, and coefficients of restitution larger than 2.5 were observed for the second impact. The experimental results well verified the existence of superelastic collision effects in the one-dimensional three-body impacts.

Intense Whistler-mode Waves at Foreshock Transients: Characteristics and Regimes of Wave−Particle Resonant Interaction

Thermalization and heating of plasma flows at shocks result in unstable charged-particle distributions that generate a wide range of electromagnetic waves. These waves, in turn, can further accelerate and scatter energetic particles. Thus, the properties of the waves and their implication for wave−particle interactions are critically important for modeling energetic particle dynamics in shock environments. Whistler-mode waves, excited by the electron heat flux or a temperature anisotropy, arise naturally near shocks and foreshock transients. As a result, they can often interact with suprathermal electrons. The low background magnetic field typical at the core of such transients and the large wave amplitudes may cause such interactions to enter the nonlinear regime. In this study, we present a statistical characterization of whistler-mode waves at foreshock transients around Earth’s bow shock, as they are observed under a wide range of upstream conditions. We find that a significant portion of them are sufficiently intense and coherent (narrowband) to warrant nonlinear treatment. Copious observations of background magnetic field gradients and intense whistler wave amplitudes suggest that phase trapping, a very effective mechanism for electron acceleration in inhomogeneous plasmas, may be the cause. We discuss the implications of our findings for electron acceleration in planetary and astrophysical shock environments.

The effect of collisions on the multi-fluid plasma Richtmyer–Meshkov instability

The Richtmyer–Meshkov instability (RMI) results from the impulsive acceleration of a density interface where the RMI itself or the acceleration is perturbed. The RMI is ubiquitous in shock environments and may arise due to an interface of fluid species, isotopes, temperature, or more. The plasma RMI can be significantly influenced by electromagnetic effects and can be modeled more accurately by a multi-fluid plasma (MFP) model rather than conventional magnetohydrodynamics, though with increased computational expense. MFP modeling of the plasma RMI has revealed many phenomena but has only been completed within the ideal regime. Modeling the effects of elastic collisions is vital for understanding the behavior of the instability in a dense plasma. The Braginskii transport coefficients provide theoretically based relations modeling thermal equilibration, inter-species drag, viscous momentum- and energy-transfers, and thermal conductivity. Our numerical simulations of the MFP RMI with these relations show that the key changes from the ideal case are (1) reduction of relative motion between the ion and electron fluids (consequently affecting the self-generated electromagnetic fields), (2) introduction of anisotropy in momentum and energy via transport coefficients, and (3) damping of high frequency electromagnetic waves and plasma waves. Under the conditions studied, the net effect is a reduction in the MFP RMI amplitude width and the growth rate to levels approaching the neutral fluid instability, as well as a reduction in large scale perturbations along the ion fluid density interface, a positive for inertial confinement fusion efforts. There are, however, two important caveats: small-scale density interface perturbations remain, and the conditions simulated are a few relevant points in a large parameter space that requires further investigation.

Phase-space Energization of Ions in Oblique Shocks

Examining energization of kinetic plasmas in phase space is a growing topic of interest, owing to the wealth of data in phase space compared to traditional bulk energization diagnostics. Via the field-particle correlation (FPC) technique and using multiple means of numerically integrating the plasma kinetic equation, we have studied the energization of ions in phase space within oblique collisionless shocks. The perspective afforded to us with this analysis in phase space allows us to characterize distinct populations of energized ions. In particular, we focus on ions that reflect multiple times off the shock front through shock-drift acceleration, and how to distinguish these different reflected populations in phase space using the FPC technique. We further extend our analysis to simulations of three-dimensional shocks undergoing more complicated dynamics, such as shock ripple, to demonstrate the ability to recover the phase-space signatures of this energization process in a more general system. This work thus extends previous applications of the FPC technique to more realistic collisionless shock environments, providing stronger evidence of the technique’s utility for simulation, laboratory, and spacecraft analysis.

Reliability Analysis for k-out-of-N: F Load Sharing Systems Operating in a Shock Environment

This paper studies a reliability modeling for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -out-of- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> : <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F$ </tex-math></inline-formula> load sharing system that operates in a shock environment. Such a system consists of a protective device and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> components with load sharing. The base hazard rate of the loading sharing system is affected by random shocks and the protective device. Random shocks can be classified into two types: invalid shock and valid shock. An invalid shock has no influence on the system whereas a valid shock makes the base hazard rate larger. The system fails, if the number of failed components is at least <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> , the system suffers at least <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> random shocks or the protective device fails, whichever occurs first. A Markov process is used to evaluate system reliability in this paper. A distributed computer system is given to show application of the proposed model.

Analysis of Survivabilty of the Ship Propulsion System in a Severe Shock Environment, Based on the Fuzzy Theory and Analytic Hierarchy Process

Analysis of Survivabilty of the Ship Propulsion System in a Severe Shock Environment, Based on the Fuzzy Theory and Analytic Hierarchy Process

The obscured nucleus and shocked environment of VV 114E revealed by JWST/MIRI spectroscopy

ABSTRACT Compact Obscured Nuclei (CONs) potentially hide extreme supermassive black hole (SMBH) growth behind large column densities of gas/dust. We present a spectroscopic analysis of the heavily obscured nucleus and the surrounding environment of the eastern region of the nearby (z = 0.02007) interacting galaxy VV 114 with the JWST Mid-InfraRed Instrument (MIRI). We model the spectrum from 4.9 to 28 μm to extract polycyclic aromatic hydrocarbon (PAH) emission and the underlying obscured continuum. We find that the NE nucleus (A) is highly obscured where the low PAH equivalent width (EW) ratio, EW(12.7)/EW(11.3), reveals a dust enshrouded continuum source. This is confirmed by decomposing the continuum into nuclear and star-forming where the nuclear component is found to be typical of CONs. The 11.3/6.2 PAH flux ratio is consistent with originating in star-forming regions rather than typical AGN. The second nucleus (B) is much less obscured, with PAH flux ratios also typical of star-forming regions. We do not detect any high ionization lines such as [Ne v] or [Ne vi] which suggests that if an AGN is present it must be highly obscured. Additionally, we detect a shock front south of the secondary nucleus (B) in the [Fe ii] (5.34 μm) line and in warm molecular hydrogen. The 6.2 PAH emission does not spatially coincide with the low-J transitions of H2 but rather appears strong at the shock front which may suggest destruction of the ionized PAHs in the post-shock gas behind the shock front.

Analysis of investment and decision-making based on ESG token platform under jump-diffusion

Token financing is operated by a platform based on blockchain technology. This paper mainly studies the influence of ESG factors on the decision-making of various participants on the platform and analyses the influence of the persistent shock environment on the operation of the token platform. We first characterise developers' token holdings by a jump-diffusion stochastic differential equation. Besides, the nonpecuniary benefits specific to the ESG environment is introduced to the developers' objective function and an incentive of government capital gain tax for green platform developers is also considered. Moreover, the Hamilton–Jacob–Bellman (HJB) equation satisfied by the developers' value function is derived while the equilibrium price of the token is obtained. Then, we compare the differences between some features, which include users' transaction volume, speculators' transaction volume and expected token returns, on the green platform (ESG score greater than 0) and the same features on the brown one (ESG score less than 0). We also analyse the impact of speculators' ESG preferences on the expected token returns, users' and speculators' transaction volume. Finally, by using numerical simulation, we illustrate the impact of the intensity of persistent shock and investment risk (token return volatility) on the operation of the token platform.

Generalized mixed shock model for multi-component systems in the shock environment with a change point

The reliability of various systems under shock models has been explored extensively in the literature, where the constant mechanism of shock impact has always been studied. Nevertheless, engineering systems operate in a more complicated shock environment due to developments, and it is worth studying the reliability of such multi-component systems in a variable shock environment. Driven by the research gaps and practical situations, this paper constructs a reliability model of multi-component systems under a generalized mixed shock model with a change point. The multi-state components operate in the shock environment I initially and it may continue to run in the shock environment II after the random change point of the environment. Two novel shock impact mechanisms of the variable environment are put forward, where a series of failure criteria based on shocks are included. Four different structures of multi-component systems are considered in this paper. It can be proved that the proposed mixed shock model is a generalization of some transformed models. A multi-stage finite Markov chain imbedding approach is established to derive the probabilistic indices of the components and entire systems. Based on the engineering applications, illustrative examples are provided to verify the effectiveness of the proposed model.

Damage boundaries on shock response spectrum based on an elastic single-degree-of-freedom structural model

Damage boundary based on a single-degree-of-freedom (SDOF) structural model under shock environment is studied in the present paper. Shock environment applied to the SDOF structure is characterized by different shock-waveforms. For an SDOF model with small damping, its shock damage boundary consists of three characteristic lines intersecting at a point, i.e. the isodamage absolute acceleration asymptote, pseudo velocity horizontal line and relative displacement asymptote in different frequency regimes. The upper and lower damage bounds on 4-coordinate pseudo velocity shock response spectrum (PVSRS) graph are proposed, which are associated with generic shock-waveforms with sufficiently large and small shock-waveform coefficients, respectively. The validity of the upper and lower damage bounds proposed in this study is demonstrated using an idealized mass-plate model with pins subjected to shock loads characterized by various shock-waveforms. Particularly, the lower damage bound underpins the use of PVSRS ‘damage metric’ as a rule-of-thumb in various engineering fields. It also shows that the proposed method is suitable for real shock environment.

Self healing behavior of enamel incorporated with nickel particles of various sizes during high temperature oxidation process

The self-healing nickel-enamel composite coating can spontaneously heal cracks at a certain temperature, thus ensuring its high-temperature service ability in thermal shock environment. In this study, nickel particles of various sizes (50 nm, 2 µm and 20 µm) were incorporated into a silicate enamel. Flexural strength of the pure enamel and its composites was investigated to analyze their thermal shock and crack healing behavior. Results indicated that nickel particles incorporation enhanced strength and thermal shock resistance of enamel, but such an enhancement depended on the size of particles. When nickel particles were in a scale of 2 µm, the composite performed the highest flexural strength, 34% higher than the enamel free of nickel particles. Moreover, its critical thermal shock temperature (ΔTC) was increased by 100 ℃. In the meantime, the composite was endowed with the optimum ability of cracks self-healing. After cracks nucleation in the process of thermal shock, they were largely healed in subsequent oxidation stage. Flexural strength was recovered to 87.9% of the value before thermal shock.

Hypersonic Shockwave Robustness in Infrared Plasmonic Doped Metal Oxide Nanocrystal Cubes: Implications for High-Speed Ballistics Transport Applications

We report that, in doped metal oxide nanocrystal cubes, the infrared plasmonic absorption optical property is robust under exposure to repeated hypersonic shockwaves at Mach 6.2. Fluorine–tin co-doped indium oxide (F,Sn:In2O3) shock-exposed nanocrystals demonstrate morphological and optical property robustness, including infrared localized surface plasmonic resonance absorption at 4164 cm–1 (2401 nm) and cubic shape retention at 14 nm in size. Surface oxidation from reduced indium to oxidated (In2O3) and hydroxylated (In-OH) indium states is observed. Yet, free electron carrier concentration at 8.18 × 1020 cm–3, estimated to be 2245 electrons per nanocrystal, is retained in the nanocrystal core at 15 shock cycles. This demonstrates preservation of the plasmonic absorption property under an extreme hypersonic shock environment. We expect that doped infrared plasmonic metal oxides can serve as a keystone for nanomaterial scientists in potential applications for high performance infrared optical filters and sensor devices in surface exposed hypersonic aerospace vehicles.

Semi-analytical models for deriving shock signals and response spectra on immersed and fluid-filled hulls subjected to shock waves

A semi-analytical model for a naval shock problem is proposed in this paper. It is applied to calculate the signals and response spectra which characterize the dynamic response of submarine hulls bearing equipment, when the latter is subjected to a pressure wave triggered by a far-field underwater explosion. It is also used to compare the configurations in which the hull may be filled or not with an inner fluid. The proposed model corresponds to a simplification of actual configurations, in the sense that the hull is simplified to a cross-section of a circular cylinder and that the equipment is simplified to a mass point. However, it allows to derive meaningful data – in particular the spectral response of the equipment and associated design shock response characteristics – which are representative of naval shock environment and useful for architects as design values in the early stages of naval projects. The details of the mathematical model are exposed, together with data validating them. The model proves useful to highlight the parameters of primary importance for the physics at stake and to investigate their influences on the acceleration and velocity levels of both the hull and the on-board equipment. Simple mathematical expressions are derived, and may prove useful for designers.

P2.02: Save the Environment: Liver Transplantation Restores A Circulating Environment That Supports Healthy Platelet Aggregation Within Two Hours of Reperfusion

Introduction: Thrombocytopenia in patients with cirrhosis is common and likely multifactorial secondary to splenic sequestration, decreased thrombopoietin production, shear stress of portal hypertension, and toxic suppression of megakaryocytopoiesis. However, there is no clear association of absolute platelet count with risk of hemorrhage. Rather, platelet dysfunction, in the pro-inflammatory vasodilatory state of chronic liver disease, may be of greater importance. There is evidence that the circulating environment of severe tissue injury and shock impairs platelet aggregation in trauma patients. Using this model as our template, we hypothesized that healthy platelets treated with serum from cirrhotic patients pre-transplant would have impaired aggregation compared to those treated with serum post-portal reperfusion. Methods: Serum was collected from liver transplant recipients prior to incision, and two hours following portal reperfusion as part of the Mild Hypothermia and Acute Kidney Injury in Liver Transplantation trial (NCT03534141). Platelets (from male and female healthy platelet donors) were isolated by centrifugation, pelleted, and mixed with each of the following sera (6 of each group): buffer, autologous, gender matched healthy (heterologous), gender matched pre-transplant, and gender matched post-portal reperfusion (12% v/v) for 20min (Fig1A). Baseline aggregation was measured for 10min via multiple impedance aggregometer, then stimulated with a thrombin analog and measured for 15min. Aggregometry responses were quantified by the area under the impedance aggregation curve (AUC), normalized to autologous treated platelets. Statistical analysis was performed using one way ANOVA, with Tukey’s Honest Significant Difference testing post-hoc for pairwise comparisons. Results: Healthy platelet aggregation was markedly impaired upon treatment with pre-transplant serum, but was restored when treated with serum from the same cohort of patients two hours post-portal reperfusion (to levels similar to treatment with healthy sera, Fig1B). Healthy platelet aggregation upon treatment with post-portal reperfusion serum was significantly higher than with pre-transplant serum treatment (median relative AUC 1.4x vs -0.1x, p<0.05; Fig2). Conclusion: Healthy platelets treated with serum from cirrhotic patients immediately prior to liver transplant have impaired aggregation, while treatment with serum from the same patients two hours post-portal reperfusion restores aggregation. This suggests the circulating environment of cirrhosis may induce platelet dysfunction through soluble inhibitors, and that liver transplantation and the healthy plasma administration accompanying the reperfusion phase, may induce swift recovery of platelet aggregation capacity. Future investigations should focus on implications of this including that platelet transfusion may not achieve hemostasis until post portal-reperfusion.

Effect of interface structure on thermal conductivity and stability of diamond/aluminum composites

Diamond/aluminum composites were fabricated by gas pressure infiltration with pure aluminum and pristine diamond, nanoscale W or WC coated diamond as raw materials. The influence of interfacial phase type and size on the thermal conductivity of the composites was investigated. The evolution of microstructure and properties of composites under temperature shock environment was also analyzed. The introduction of W and WC coatings inhibits the formation of interfacial phase Al4C3, while the generation of amorphous carbon in WC-coated diamond/aluminum composite causes a weak interface bonding and huge acoustic impedance difference with diamond, leading to a decrease in thermal conductivity. The W-coated diamond/aluminum composite shows the optimal thermal properties after 1000 cycles of temperature shock treatment. The introduction of W coating can improve performance stability while maintaining high thermal conductivity, making them promising thermal management composites.

Interstellar Complex Organic Molecules in SiO-traced Massive Outflows

The interstellar medium contains dust and gas, in which molecules can proliferate at high densities and in cold conditions. Interstellar complex organic molecules (iCOMs) are C-bearing species that contain at least six atoms. As they are detected in young stellar objects, iCOMs are expected to inhabit early stages of star formation evolution. In this study, we try to determine which iCOMs are present in the outflow component of massive protostars. To do this, we analyzed the morphological extension of blue- and redshifted iCOM emission in a sample of 11 massive protostars employing mapping observations at 1 mm within a ∼1 GHz bandwidth for both the IRAM-30 m and APEX telescopes. We modeled the iCOM emission of the central pointing spectra of our objects using the XCLASS local thermal equilibrium radiative transfer code. We detected the presence of several iCOMs such as CH3OH, 13CH3OH, CH3OCHO, C2H5C15N, and (c-C3H2)CH2. In G034.41+0.24, G327.29-0.58, G328.81+0.63, G333.13-0.43, G340.97-1.02, G351.45+0.66, and G351.77-0.54, the iCOM lines show a faint broad-line profile. Due to the offset peak positions of the blue- and redshifted emission, covering from ∼0.1 to 0.5 pc, these wings are possibly related to movements external to the compact core, such as large-scale low-velocity outflows. We have also established a correlation between the parent iCOM molecule CH3OH and the shock tracer SiO, reinforcing the hypothesis that shock environments provide the conditions to boost the formation of iCOMs via gas-phase reactions.

Compensation of fiber optic gyroscope vibration error based on VMD and FPA-WT

With the advantages of all-solid-state, high-precision, and small size, the fiber optic gyroscope (FOG) is widely used in aerospace, unmanned driving, and robotics. However, the optoelectronic devices inside the FOG will produce non-negligible errors under the action of stress, resulting in zero-bias drift and increased noise, thereby limiting the application of the FOG in vibration and shock environments. In order to solve this problem, our paper proposes a new algorithm based on the variational mode decomposition (VMD) and flower pollination algorithm-wavelet transformation (FPA-WT). We combine the advantages of VMD and WT, use VMD to decompose non-stationary vibration signals to separate the effective signal component and zero-bias drift, and then use WT to denoise each component. Since the denoising effect of WT largely depends on the selection of initial parameters, we use the FPA to find the best parameters for WT. In order to better analyze the influence of vibration on FOG, we carry out the axial vibration and radial vibration experiments at the same time. The experimental results verify the effectiveness of our method, which can reduce the vibration error and improve the performance of the FOG in vibration and shock environments.