Single Impact Research Articles

ENVIRONMENTAL IMPACTS OF COMMUNITARY CROPS OF SWEET QUINOA (CHENOPODIUM QUINOA WILLD. VAR. TUKAHUAN) AT ANDEAN REGION IN ECUADOR

Quinoa (Chenopodium Quinoa) is a trendsetter crop as it is a great source of vitamins, proteins and minerals and it is a gluten-free pseudocereal. Agriculture is a sector that contributes to climate change through greenhouse gas emissions. In Ecuador, agriculture contributed to 18.03% of emissions. The purpose of this research was to determine the Life Cycle Analysis (LCA) of communitarian systems that produce Sweet Quinoa in Ecuador. It was carried out by an inventory of the LCA. The data collected were through interviews and surveys, chemical analysis of soil samples, plant structure and manure applied. A bag of 25 kg of Quinoa has been selected as a functional unit. Impact indicators were defined as Quinoa yield per single environmental impact index, including GWP, aquatic eutrophication potential and aquatic ecotoxicology. The results indicate that a Quinoa yield obtained by a suitable application of manure is lower or equal to Wheat. The mitigation of aquatic eutrophication caused by the excessive use of N-fertilizer is an important factor in improving the eco-efficiency of the Quinoa productive chain. The importance of the LCA of an agro-product lies in knowing and reducing different environmental impacts and encouraging sustainable production.

Thermal transport during drop-on-drop impact on a heated superhydrophobic substrate

Interaction of multiple liquid droplets is ubiquitous in various engineering systems, for example, spray cooling in various forms, which is an attractive option to manage high heat flux applications. Thermal transport phenomena ensuing during drop-on-drop impact is numerically investigated here. One drop (Droplet #1) is kept stationary and in quasi-equilibrium on a heated superhydrophobic solid substrate, while the second drop (Droplet #2) is impacted vertically on it with a certain Weber number (We Droplet #2 = 1.0, 4.0, and 8.2). The evolution of both droplets in different phases of impact, such as spreading, receding, and bounce-off regimes, along with associated heat transfer is scrutinized. The dependence of transport characteristics on various control parameters such as impact velocity of drop, volume ratio, fluid properties, and wall temperature are investigated. Distinct heat transfer trends are observed with the considered We number of impacting droplet (Droplet #2) being = 1.0, 4.0, and 8.2, respectively. Smaller droplet impacting with higher impact velocity results in more effective heat transfer as compared to a large droplet with small velocity, both having identical We number. To ease the analysis, comparison of heat transfer during drop-on-drop impact with a single droplet impact, having an equivalent diameter and velocity scales of the former drop-on-drop case, is also presented. It is revealed that the resulting heat transfer, with velocity scale based on momentum balance, is underpredicted, as compared to drop-on-drop impact. If the actual impact velocity of impacting droplet is taken, then the heat transfer gets overpredicted. Accordingly, analysis suggests that the appropriate representative velocity scale will be in-between these two bounds, which will accurately predict the heat transfer during drop-on-drop impact.

Numerical Investigation of Plastic Deformation of Flat Plate for Slamming Impact by Coupled Eulerian–Lagrangian Method

Ships and offshore structures are subjected to impact loads, such as slamming and sloshing. High impact pressures can cause permanent hull deformation by a single impact event. In addition, significant fatigue damage can be accumulated via repeated impact pressures. In this study, the plastic deformation behavior of flat plates under slamming impact is numerically investigated using a coupled Eulerian–Lagrangian method. The dynamic impact pressure of the flat plates by weight and drop height is investigated under the assumption of viscous and compressible fluids. To evaluate the plastic deformation of the plate, contact between water and the plate is removed after a certain duration after dropping, and then the remaining deformation is measured. Optimized finite element models for drop simulations are selected via a mesh sensitivity study, and the simulation results are calibrated and compared with experimental data. Results of the simulation and the experiment show good agreement in general in terms of deflection range. However, because the initial condition of the plate is not reflected in the simulation, some discrepancy is observed in maximum deflections. Finally, a discussion is presented for a more accurate fluid impact analysis model based on the comparison results with the experimental data.

A VFM-based identification method for the dynamic anisotropic plasticity of sheet metals

The anisotropic plasticity of sheet metals at high strain rates is a critical factor that can influence the fabrication and service safety of engineering parts under dynamic loading conditions. The characterization of dynamic anisotropic plasticity using conventional testing methods usually suffers from the limitations resulted from the homogeneous deformation state and one-dimensional wave propagation preconditions. In this work, a highly efficient approach is proposed for the simultaneous identification of the anisotropic yielding and hardening constitutive parameters at high strain rates based on the heterogeneous impact test and the virtual fields method. First, the identification framework that combines the selected anisotropic plasticity constitutive models and the principle of virtual work concerning the dynamic kinematics term is introduced. In order to validate the proposed identification algorithm, simulated virtual impact tests were performed to provide reference parameters and unpolluted inertial acceleration/strain/strain rate field data. These data were then processed to extract the target dynamic anisotropic parameters. The results show that using the double-notched impact configuration and the proposed identification algorithm the selected anisotropic yielding and hardening parameters can be reasonably identified from a single impact test, significantly simplifying the testing procedures compared to conventional dynamic testing methods. Also, the effects of different processing parameters and influential factors on the identification accuracy have been investigated. From the sensitivity studies, the preferred ranges of the processing parameters have been determined and the robustness of the proposed method within these verified.

Assessment of HVAC system operational fault impacts and multiple faults interactions under climate change

The effect of climate change on heating, ventilation and airconditioning (HVAC) system performances has become prominent, and HVAC fault impacts may also vary with climate change. This paper evaluates the impacts of HVAC operational faults on system energy and occupant thermal comfort under the current, 2030s and 2050s climates using a validated model. The energy and thermal comfort impact indicators were proposed to rank single and multiple faults under each climate period. Supply fan stuck at maximum speed, and the combinations associated with this fault were ranked first in energy and thermal comfort rankings, respectively. Based on the investigations of multiple faults interactions, it is found that the synergetic/antagonistic effect of multiple faults combinations can lead to a significantly higher/lower combined impact than any single fault impact among the combination when the single faults present opposite impacts. Moreover, heating coil supply air temperature sensor negative bias, and the combination of thermostat positive offset and outdoor air damper stuck fully open led to the most increase system total electricity by 34.3 GJ and 35.3 GJ from current to 2050s period. The results are useful for researchers to prioritise the faults with significant impacts for developing fault detection and diagnosis framework.

A Numerical Study on the Crack Propagation of Homogenized Micro-Crack Crushing for Concrete Pavement

Homogenized micro-crack crushing is a new method of concrete pavement rehabilitation that makes full use of the bearing capacity of the original concrete pavement, whereby the treated pavement can be directly overlaid with hot mixed asphalt concrete. In order to solve the problem of longitudinal crack extension of a cracked core in the weak position of local pavement, the crack propagation mode of concrete slabs under low-velocity impact from different numbers and distributions of impact heads was studied using numerical simulation. Moreover, field tests were also carried out to determine the optimal layout of drop hammer impact heads, and the numerical simulation results were compared with the experimental data. The results show that, when a concrete slab is impacted by a single impact head, the bottom of the slab first cracks and then the crack develops upward until the main crack runs through the concrete slab. However, when the concrete slab is impacted by multiple-impact heads, including three or four impact heads, the concrete slab forms a triangular or quadrilateral fracture core, respectively. The numerical simulation results are in good agreement with the laboratory experiments. Through the optimized arrangement of the hammer’s impact heads, the problem of longitudinal crack extension of a cracked core can be effectively solved, and the probability of reflection cracks can be reduced.

Mechanical shock-induced nucleation in solution: Is cavitation necessary?

Mechanical shock-induced nucleation (MSIN) of crystals from aqueous supersaturated solutions of ammonium chloride is reported. A simple apparatus was constructed to expose solutions in glass vials to a single impact, while images were recorded using a fast camera. A strong correlation between cavitation in the liquid and nucleation of solid ammonium chloride was revealed. The measured fraction of solutions nucleated as a function of impact height was fitted using a Poisson model. The mean number of solution samples nucleated increased quadratically with impact height above a threshold height. Analysis of images showed that the accelerations achieved were sufficient to induce cavitation based on the cavitation number proposed by Pan et al. [Proc. Natl. Acad. Sci. USA 114 (2017) 8470]. The use of a hydrophobic coating on the internal glass surface was shown to significantly increase both the number of cavities observed and the probability of MSIN of solid crystals. The results presented suggest that MSIN of ammonium chloride salt is mediated by cavitation.

Characterization of Single Particles By Electrochemical Impedance

The ubiquity of nanomaterials in electrochemical energy conversion technologies has driven intense interest in unravelling the material’s structure- function relationships. In response, single- entity electrochemistry has been developed as a technique to study the properties of individual nanoparticles, one at a time. This approach engenders a bottom-up understanding, linking the activities of the single particles to the emergent properties of the ensemble.The “nano-impact” technique, a subset of single-entity electrochemistry, uses low-noise instrumentation to measure current transients arising from individual particles which stochastically collide with an ultramicroelectrode. These transients have been successfully used to measure the size of both insulating and redox-active nanoparticles, as well as the activity of single electrocatalysts. However, it remains challenging to study certain classes of materials on a single-entity basis. One such class is pseudocapacitors – materials which mix electronic and ionic conductivity, critical components of ion batteries and other next-generation energy storage technologies. While careful experimental design and data analysis have allowed the detection and qualitative characterization of single ion-intercalating particles, their nature as mixed conductors makes quantitative information difficult to obtain amperometrically.This hurdle is due to the measured current response being dictated by one or more possible factors: electron transfer, ion diffusion within the particle or across the particle/electrolyte interface, or ion transfer in the bulk. To overcome this, electrochemical impedance spectroscopy (EIS) is commonly used to characterize bulk pseudocapacitors. In EIS, a small-magnitude sinusoidal (AC) voltage is applied to the working electrode and the current response is recorded. Different timescales can be probed by varying the AC frequency – the high frequency response is dominated by fast processes, such as capacitance, while the low frequency response contains information on electron transfers and mass transport. In this way, EIS gives a full picture of the electroactive material and can unravel the coexisting electronic and ionic conductivity of mixed conductors.In this presentation, I will discuss our development of an EIS-based technique to detect and characterize single particles. We implemented fast-Fourier transform based EIS to rapidly acquire impedance spectra spanning several decades of frequencies. The spectra are fit to an equivalent circuit model and monitored as a function of time. Discrete changes in various equivalent circuit parameters are observed, corresponding to single particle-electrode impact events. Using a model system of polystyrene microbeads, we demonstrate that discrete increases in the charge-transfer resistance can be used to accurately measure the contact area between the individual bead and the ultramicroelectrode. I will also discuss our recent progress towards detecting single ion-intercalating nanoparticles and characterizing their charge storage ability on a single particle basis. These advances expand both the scope of single-entity electrochemistry and the depth of information gleaned from a single measurement of a single particle.

(Invited) Detection of Bacterial Rhamnolipid Toxin By Redox Liposome Single Impact Electrochemistry

The single-entity impact method is a very sensitive and powerful electroanalytical tool for biological and environmental purposes such as electrochemical detection of pathogens.[1] The versatility of ultramicroelectrodes (UMEs) gives unique and essential properties for electroanalytical sensing owing to their small size, high sensitivity, fast steady-state response, low double-layer charging current and minimal ohmic loss. The observation of these stochastic events can provide information on various single nanoparticles contrary to ensemble (bulk) measurements. The main advantage of studying collisions of single entities is the low limit of detection (in principle, one single species) inherent to this electroanalytical method and the ability to study single entities (cells, viruses, nanoparticles...) in real time (dynamic measurement).[2–4]Electrochemistry of single redox liposome impacts at an UME consists in detecting the electrolysis of a redox probe encapsulated inside a liposome when it is released at the UME after impact (or collision). The UME is polarized at the oxidation or reduction potential of the encapsulated redox probe and a concentration of several pico-molar of redox liposomes added to the aqueous buffer electrolyte is enough to detect “current spikes” in the chronoamperometry (i-t) curve corresponding to discrete collision events.[3,4] The electron transfer does not readily occur across a lipid bilayer, thus the electrolysis of the liposome redox active content after collision and membrane rupture or opening at the UME surface led to many studies dealing with the membrane permeation mechanism.[3,4]Here, our work is based on the previous results where no current spike was observed in the chronoamperometry curve because the redox DMPC liposomes did not break during impact (or collision) onto the UME surface.[3,4] Hence, the electrochemical sensing principle is based on the weakening of the liposomes lipid membrane upon interaction with a destructive bacterial virulence factor which leads upon impact at an UME to the breakdown of the liposomes and the release/electrolysis of its encapsulated redox probe, as previously reported.[5] In the presence of RL toxin in solution (acting like a surfactant in the lipid membrane), current spikes corresponding to the electrolysis of the encapsulated redox probe released from weakened liposomes are detected (see Figure). Thanks to the redox liposome single impact electrochemistry, the highest detection limit of RL toxin (500 nM) has been reached in comparison to several micromoles per liter previously reported.[5][1] Lebègue, E.; Costa, N.L.; Louro, R.O.; Barrière, F. Communication—Electrochemical Single Nano-Impacts of Electroactive Shewanella Oneidensis Bacteria onto Carbon Ultramicroelectrode. J. Electrochem. Soc. 2020, 167, 105501, doi:10.1149/1945-7111/ab9e39.[2] Dick, J.E.; Lebègue, E.; Strawsine, L.M.; Bard, A.J. Millisecond Coulometry via Zeptoliter Droplet Collisions on an Ultramicroelectrode. Electroanalysis 2016, 28, 2320–2326, doi:10.1002/elan.201600182.[3] Lebègue, E.; Anderson, C.M.; Dick, J.E.; Webb, L.J.; Bard, A.J. Electrochemical Detection of Single Phospholipid Vesicle Collisions at a Pt Ultramicroelectrode. Langmuir 2015, 31, 11734–11739, doi:10.1021/acs.langmuir.5b03123.[4] Lebègue, E.; Barrière, F.; Bard, A.J. Lipid Membrane Permeability of Synthetic Redox DMPC Liposomes Investigated by Single Electrochemical Collisions. Anal. Chem. 2020, 92, 2401–2408, doi:10.1021/acs.analchem.9b02809.[5] Luy, J.; Ameline, D.; Thobie-Gautier, C.; Boujtita, M.; Lebègue, E. Detection of Bacterial Rhamnolipid Toxin by Redox Liposome Single Impact Electrochemistry. Angew. Chem. Int. Ed. 2021, accepted , doi: 10.1002/anie.202111416. Figure 1

Theoretical and experimental determination of number of impacts required for caryopsis destruction

The article presents theoretical and experimental studies to determine the number of impacts to destroy the caryopsis. To substantiate the number of shock impacts, the Rebinder’s equation for determining the work on grinding was taken as the basis for theoretical studies. The transformation and development of the Rebinder’s equation enabled to theoretically obtain expressions for determining the amount of work required for guaranteed destruction of the caryopsis when a single impact was applied. An equation for determining the work of a particle destruction during a multiple number of impacts was also obtained. Its transformation enabled to obtain a function and implement a theoretical nomogram. The performed theoretical analysis of the obtained nomogram enabled to consider the energy costs when determining the required number of impacts for guaranteed caryopsis destruction at certain voltages. To validate the theoretical studies, the experiments on breaking down whole grains of wheat and barley were carried out. To conduct the experiments, an experimental setup to perform a series of experiments was developed. As a result of experimental studies, the value of the limiting stresses, at which no grain destruction is observed with any number of impacts, was determined. The magnitude of the stress for a single impact for guaranteed destruction of the caryopsis was determined. The main result of the experiments is the determination of the number of impacts for the destruction of barley and wheat kernels with minimal energy consumption.

Modeling impact fracture of rock by hydraulic hammer pick with regard to its bluntness

Destruction of rocks and artificial composites is carried out in various ways. One of the most common methods is the impact fracture. The conical pick of JCB HM380 hydraulic breaker was used as the impact tool. The experimental study of rock fracture was carried out on an artificial composite—concrete. The depth of penetration of the pick into concrete was used as the test parameter. The model was based on the model of Professor V. B. Sokolinsky. The model developed in this work takes into account the degree of bluntness of the tool insingle and multiple impact. The system was considered as a two-component system due to the high stiffness of the pick–granite contact (as against the hammer piston–pick stiffness). The wave processes in the pick were disregarded because of the small length of the pick. The pick penetration depth in rocks was calculated theoretically, using the developed mathematical model, at each impact of the pick, and then was compared with the experimental data. The fracture tests also used JCB HM380 breaker and concrete. The penetration depth was determined from the step-frame analysis of video filming of the process. It is found that the pick blunting causes a monotonic increase in the rock resistance to the pick penetration, both in single and multiple impact, while the depth of the tool penetration and the blow time decrease (as compared with the initial state of the tool, by 28% and 20%, respectively).

Experimental and Numerical studies of Fiber Metal Laminates comprising Ballistic fabrics subjected to Shock Impact

The scope of fiber metal laminates (FMLs) in the applications for shock and blastwave mitigation has been gaining a lot of focus recently. The response of the FML structures to side-on interaction with shock waves was experimentally investigated using a shock tube. The influence of incorporating ballistic grade fabrics as sandwiched plies between metallic skins in addition to low acoustic impedance materials was explored in the current work. Five sequences of laminates were fabricated employing AA6061-T6 skins, with aramid-epoxy, ultra-high molecular weight polyethylene-epoxy, and paperboard-epoxy as sandwiched layers. The deformation profiles of different sequences were investigated and the stackups with the best shock mitigation response were identified. A numerical model for the laminate transverse deformation was developed. The deformations of the faceplate and the backplate of each sequence were compared to the numerical results. Among the five sequences, BRSP-II and BRSP-IV showed the least backplate deformation of ∼−0.25 mm after single shock impact, while the same configurations showed lowest backplate deformation ∼−0.6 mm after the second shock impact, as compared to the other sequences. The twin shock impacted specimens of various sequences were subjected to Cone beam computed tomography (CBCT) for layerwise investigation of shock impact. The four sequences BRSP-I, BRSP-II, BRSP-III and BRSP-IV showed deformations in all the plies with no delamination. However, delamination was observed at the center in BRSP-V between the backplate and the penultimate ply.

어린이의 뛰어다님을 재현하는 연속성 충격원 시작품의 충격음 특성

Bang machines and rubber balls, which are currently used as heavy-weight impact sources for floor impact sound measurement, have characteristics that differ from the actual impact patterns of children. This is because the current impact source is larger than the actual impact force of the child, and there is a single impact pattern, so a child

An Experimental and Numerical Simulation Study of Single Particle Impact during Detonation Spraying

A comparison of the numerical simulation and an experimental study of the collision of the particles and the substrate during detonation spraying is presented. The spraying regimes were chosen to provide unmelted, partially melted, and completely molten particles. The numerical simulation was performed using the smoothed particle hydrodynamics (SPH) method with velocity and temperature settings as initial conditions. Good agreement was obtained between the simulation results and the experimental data, making the SPH simulation suitable for analysis of the deformation of particles and the substrate during detonation spraying. Information about the particle’s shape evolution during the collision is presented. An increase in temperature and plastic strain is analyzed at different points of the particle and substrate. Under certain spraying regimes, it is possible to melt a solid particle due to its high-strain-rate deformation, but no melting of the substrate was observed during the simulation.

Conversion Study on the Formation of Mechanochemically Synthesized BaTiO3

Mechanochemistry is a method that can cover the energy demand of reaction pathways between solid materials. This requires enough energy to maintain the reactions between the starting materials. This is called “high-energy milling”. In our case, a planetary ball mill provided the required energy. Using the Burgio-equation, the required energy is determinable; the energy released during a single impact of a milling ball (Eb), as well as during the whole milling process (Ecum). The aim of this work was the one-step production of BaTiO3 from BaO and TiO2 starting materials. Whereas during mechanochemical reactions it is possible to produce nanoparticles of up to 10 nm, the essence of this study is to develop the preparation of BaTiO3 with a perovskite structure even without subsequent heat treatment, since sintering at high temperatures is associated with a rapid increase in the size of the particles. By describing the synthesis parameters and their energy values (Eb and Ecum), it is possible to transpose experimental conditions, so that in the case of other types of planetary ball mills or grinding vessel made of other materials, the results can be used. In this study, the mechanical treatment was carried out with a Fritsch Pulverisette-6 planetary ball mill and the transformation of the starting materials was investigated by X-ray diffractometric, Raman and Energy-dispersive X-ray spectroscopic, and transmission electron microscopic measurements.

Damage mechanism of composite laminates under multiple ice impacts at high velocity

Unlike most research on ice impact threats with single impact and multiple repeated impact, different impact schemes such as single-point repeated impact and multi-point sequential impact were carried out in this article, considering the actual circumstance of hail impacts on aerospace structures. To study the response of CFRP laminates to multiple ice impacts, ice projectiles with a diameter of 25 mm were projected onto laminates. Three different routes, including visual analysis, C-Scan analysis and X-ray tomography, were then used to observe the intralaminar and interlaminar damage patterns. An innovative damage category induced by different impact schemes was summarized from the whole experimental results through the visual analysis. The extent of delamination damage was characterized by C-Scan and CT. Both the damage mode and the area of delamination are not only related to the magnitude of single impact energy, but also to the density of impact points. For numerical approach, a strain-rate dependent continuum damage model with interlayer cohesive element was used to predict the damage evolution in CFRP laminates. It was first verified and then combined with the test data to reveal different damage mechanisms of single-point repeated impact and multi-point sequential impact.

432-P: Single and Joint Impact of Type 2 Diabetes and of Coronary Artery Disease on Albuminuria

Albuminuria is a characteristic feature of diabetic nephropathy, and increased urine albumin excretion is associated with an increased risk of coronary artery disease (CAD) . However, type 2 diabetes (T2DM) and CAD frequently coincide, and the single and joint effects of T2DM and angiographically determined CAD with albuminuria are unclear. This issue therefore was addressed in the present study. We investigated 831 patients with angiographically proven CAD, of whom 261 had T2DM (CAD+/T2DM+) and 570 did not have diabetes (CAD+/T2DM-) and 263 controls without CAD, of whom 63 had T2DM (CAD-/T2DM+) and 200 did not have diabetes (CAD-/T2DM-) . The albumin / creatinine ratio (ACR) was 37±1in CAD-/T2DM- patients. Compared to this group it was higher in CAD-/T2DM+ patients (193±642; p<0,001) , but not in CAD+/T2DM- patients (52±184; p=0,421) , in whom it was significantly lower than in CAD-/T2DM+ patients (p<0.001) . In CAD+/T2DM+ patients the ACR (162±466) was higher than in CAD-/T2DM- (p<0,001) and in CAD+/T2DM- patients (p<0,001) , but did not differ significantly to that in CAD-/T2DM+ patients (p=0,225) . In multivariate analysis of covariance, T2DM but not CAD proved to be an independent predictor of ACR after adjustment for age, sex, body mass index, LDL-C, smoking, hypertension and the use of ACE inhibitors /AT2-antagonists and statins (F=22.06; p<0.0 and F=0.520; p=0.471, respectively) . We conclude that T2DM but not CAD is an independent determinant of albuminuria. Disclosure M.Maechler: None. L.Sprenger: None. A.Mader: None. B.Larcher: None. A.Vonbank: None. A.Leiherer: None. A.Muendlein: None. H.Drexel: None. C.H.Saely: None.

Tensile strength deterioration of PVC coated PET woven fabrics under single and multiplied artificial weathering impacts and cyclic loading

This paper investigates the tensile strength degradation of architectural PVC coated PET woven fabrics exposed to single and combined artificial weathering impacts and cyclic loading. The uniaxial tensile strength sensitivity to different weathering stressors such as UV light, humidity, and temperature plus cyclic loading was determined. Furthermore, the physicochemical changes were traced by Fourier transform infrared spectroscopy and scanning electron microscopy. The results reveal the key role of photodegradation on the tensile strength deterioration of PET yarns, while incorporation of cyclic loading cannot exacerbate this degradation rate remarkably. Weathering impacts decrease the stiffness (Esecant) either individually or collectively while a single impact of humidity or temperature leads to comparably low changes of the tensile strength. Strength modification factors based on the draft standard prCEN/TS 19102:2022-05 have been calculated covering all surveyed artificial weathering test results. The presented study provides a better understanding of the weathering performance of PET-PVC fabrics under various attacks.

Simulation Research on Impact Contact Behavior between Coal Gangue Particle and the Hydraulic Support: Contact Response Differences Induced by the Difference in Impacted Location and Impact Material.

In the process of top coal caving, coal gangue particles may impact on various parts of the hydraulic support. However, at present, the contact mechanism between coal gangue and hydraulic support is not entirely clear. Therefore, this paper first constructed the accurate mathematical model of the hydraulic cylinder equivalent spring stiffness forming by the equivalent series of different parts of emulsion and hydraulic cylinder, and then built the mesh model of the coal gangue particles and the support’s force transmission components; on this basis, the rigid–flexible coupling impact contact dynamic model between coal gangue and hydraulic support was established. After deducing contact parameters and setting impact mode, contact simulations were carried out for coal particles impacting at the different parts of the support and coal/gangue particles impacting at the same component of the support, and the contact response difference in the support induced by the difference in impacted component and coal/gangue properties was compared and studied. The results show that the number of collisions, contact force, velocity and acceleration of impacted part are different when the same single coal particle impact different parts of the support. Various contact responses during gangue impact are more than 40% larger than that of coal, and the difference ratio can even reach 190%.

Multi-Dimensional Factor Correlation, Multiple Interbank Network Contagion, and Conditional VaR of Banks

The systemic risk of banks is a multi-dimensional factor correlation and multi-interbank contagion, forming a multi-dimensional multi-correlation (MDMC) contagion risk. After superposition, the multiplier effect magnifies the destructive power of a single impact. In this study, the weighted average method is used to integrate the four interbank contagion paths of jump-diffusion, interbank lending, stock price information, and common assets, establish the multi-level interbank contagion matrix, apply the quantile estimation of the spatial Dubin panel model, estimate the MDMC infectious bank conditional risk value, and decompose and identify the systemically important risk factors, systemically important banks, and systemically vulnerable banks. The following conclusions were drawn. First, the superposition contagion effect of MDMC networks is significant. Second, the systemic importance of default risk, interest rate risk, liquidity risk, and the GDP growth rate of the banking industry is high, followed by changes in stock market returns and investor sentiment. Third, the four major state-owned banks have an MDMC network contagion effect, which has the characteristics of systemic importance and vulnerability.