Shock Energy Research Articles

Experimental study on seismic performance of prefabricated viscoelastic damping bolted joints

Aiming at the defect of insufficient bearing capacity of prefabricated concrete beam-column joint with bolted connection, a prefabricated viscoelastic damping bolted joint (VDBJ) is proposed with good seismic performance. The damping principle is based on that viscoelastic (VE) dampers can provide energy dissipation and additional stiffness for the structures. Three full-scale beam-column joint specimens were designed, including one cast-in-place joint specimen, one prefabricated bolted joint specimen without VE dampers and one prefabricated bolted joint specimen with VE dampers. Since the viscoelastic damper is a passive energy dissipation device with velocity correlation, comparison and analysis of three specimens under high-frequency cyclic loading are performed on the failure modes and seismic performance indexes such as hysteretic energy dissipation, displacement ductility, stiffness degradation and ultimate bearing capacity. The analysis of the test results indicate that the proposed prefabricated viscoelastic damping bolted joint has stronger ultimate bearing capacity and displacement ductility than the cast-in-place joint. The arrangement of VE dampers effectively controls the appearance and expansion of concrete cracks, which not only achieves the expected effect of shock absorption and energy dissipation, but also can realizes the rapid replacement of components after the earthquakes.

Effect of nanopores on plasticity and their collapse mechanism in magnesium single crystal under shock loading

The influence of defects on the plastic properties of materials always captures much attention for ultrahigh strain-rate loading. By virtue of the planar shock compression in [0001], [101¯0], and [1¯21¯0] directions, our large-scale molecular dynamics simulations reveal that the prismatic nanopores facilitate the inelastic deformation, such as basal and prismatic glides, reorientation, and amorphization. And that, the nanopores with different center axial directions contribute to activation of various slip systems, such as basal and prismatic dislocation slip. The inelastic deformation induced nanopore collapse is an important mechanism of nanopore collapse at weak shock intensity. Three modes of collapse are obtained: a transverse and a longitudinal collapse from the basal glide, and an inclined collapse from the amorphization at the tip of the prismatic nanopore. The shear stress is highly concentrated at the elastic region about to be plastic deformation, and then attenuates mainly during inelastic deformation and nanopore collapse. The shock energy dissipation is correlated to the conversion between kinetic energy and internal energy, which leads to a higher local temperature around the prismatic nanopore.

Predictive Helmet Optimization Framework Based on Reduced-Order Modeling of the Brain Dynamics.

Sports-related traumatic brain injuries (TBIs) are among the leading causes of head injuries in the world. Use of helmets is the main protective measure against this epidemic. The design criteria for the majority of the helmets often only consider the kinematics of the head. This approach neglects the importance of regional deformations of the brain especially near the deep white matter structures such as the corpus callosum (CC) which have been implicated in mTBI studies. In this work, we develop a dynamical reduced-order model of the skull-brain-helmet system to analyze the effect of various helmet parameters on the dynamics of the head and CC. Here, we show that the optimal head-helmet coupling values that minimize the CC dynamics are different from the ones that minimize the skull and brain dynamics (at some kinematics, up to two times stiffer for the head motion mitigation). By comparing our results with experimental impact tests performed on seven different helmets for five different sports, we found that the football helmets with an absorption of about 65-75% of the impact energy had the best performance in mitigating the head motion. Here, we found that none of the helmets are effective in protecting the CC from harmful impact energies. Our computational results reveal that the origin of the difference between the properties of a helmet mitigating the CC motion vs. the head motion is nonlinear vs. linear dynamics. Unlike the globally linear behavior of the head dynamics, we demonstrate that the CC exhibits nonlinear mechanical response similar to an energy sink. This means that there are scenarios where, at the instant of impact, the CC does not undergo extreme motions, but these may occur with a time delay as it absorbs shock energy from other parts of the brain. These findings hint at the importance of considering tissue level dynamics in designing new helmets.

The "Defibrillation Testing, Why Not?" survey. Testing of subcutaneous and transvenous defibrillators in the Italian clinical practice.

BackgroundDefibrillation testing (DT) can be omitted in patients undergoing transvenous implantable cardioverter–defibrillator (T-ICD) implantation, but it is still recommended for patients at risk for a high defibrillation threshold and for ICD generator changes. Moreover, DT is still recommended on implantation of subcutaneous ICD (S-ICD). The aim of the present survey was to analyze the current practice of DT during T-ICD and S-ICD implantations.MethodsIn March 2021, an ad hoc questionnaire on the current performance of DT and the standard practice adopted during testing was completed at 72 Italian centers implanting S-ICD and T-ICD.Results48 (67%) operators reported never performing DT during de-novo T-ICD implantations, while no operators perform it systematically. The remaining respondents perform it for patients at risk for a high defibrillation threshold. DT is never performed at T-ICD generator change. At the time of de-novo S-ICD implantation, DT is never performed by 9 (13%) operators and performed systematically by 48 (66%). The remaining operators frequently omit DT in patients with more severe systolic dysfunction. DT is not performed at S-ICD generator change by 92% of operators. DT is conducted by delivering a first shock energy of 65 J by 60% of operators, while the remaining 40% test lower energy values.ConclusionsIn current clinical practice, most operators omit DT at T-ICD implantation, even when still recommended in the guidelines. DT is also frequently omitted at S-ICD implantation, and a wide variability exists among operators in the procedures followed during DT.

Time Defendability of Ground Resistance Properties and Its Application of Vitric Tuff on the Development of Ground Enhancement Material

Ground repair material is an essential part of the grounding system as a lightning rod to reduce the risk of lightning activity. Grounding repair materials consist of conductive and superconductive materials, commonly known as Ground Enhancement Materials (GEM). GEM has a low resistivity, very effectively supporting lightning shock energy to earth. Vitric tuff, a pyroclastic rock, is composed of an aluminosilicate (phyllosilicate) mineral group developed as a grounding improvement material. The primary purpose of this study was to determine the decrease in resistivity of vitric tuff in its development as a GEM. The research method consisted of field observations and laboratory experiments (treatment with chemical-physical activation and formulation with additives). The results showed that moisture content, SiO2/Al2O3 ratio (quartz and feldspar mineral/albite), clay mineral, crystal quality (impurities), carbon, and salt were influenced by vitric tuff resistivity. With the vitric tuff formulation and additives, the resistivity reduction is above 99%. Based on experiments, the best formulation of GEM made from tuff is 65% activated vitric tuff, 27% activated charcoal, 6% NaCl, and 2% Cement Material Cellulose. The formula produces a resistivity value of 0.0124 Ω-m, which is stable with time and meets GEM requirements (ρ ≤ 0.20 Ω-m).

Paper tube-guided blast response of sandwich panels with auxetic re-entrant and regular hexagonal honeycomb cores – An experimental study

Auxetic honeycomb structures have drawn increasing attention for impact/blast protection purposes owing to their superior indentation resistance and energy absorption capability. However, few comparative study on the blast performance among sandwich structures with different auxetic and non-auxetic cores has been performed to date. In this paper, the dynamic behaviors of metallic sandwich panels with auxetic re-entrant and regular hexagonal honeycomb cores (i.e. RHSPs and HHSPs) under the paper tube-guided explosions were investigated by a series of blast tests. The failure modes and underlying mechanisms of the target panels with different core relative densities under different impulse levels were classified and analyzed in detail. The panel blast resistance was evaluated by means of the back-face maximum permanent deflections, introducing the testing results of double arrowhead honeycomb sandwich panels (DAHSPs) in a separate paper. It indicates that the introduction of the paper tube achieved the concentration of shock energy, thus aggravating the panel central damage levels remarkably. For the RHSPs with NPR effect, the predominated failure modes of front faces transitioned essentially from the complete petal-like tearing to a local inner dome as the blast impulse decreased. The ones for the back faces ranged from partial tearing to pure global bending deformation, while the core failure modes tuned from central crushing and peripheral buckling to global compression deformation with central shrinkage and boundary adduction. Relative to the RHSPs, the equivalent HHSPs with a higher compressive strength were less insensitive to the blast intensity. Within the scope of present study, the DAHSPs could experience lower back face deflections than those of RHSPs regardless of core relative density. The auxetic honeycomb sandwich panels not always exhibited better over the non-auxetic HHSPs, which depended greatly on the blast impulse and core density level. This comparative research provides a useful reference for the auxetic sandwich honeycomb core design in protection applications.

How large is the economy-wide rebound effect in middle income countries? Evidence from Iran

Recent research suggests that the economy-wide rebound effect is near 100% in several high-income countries. Is it similarly large in middle-income countries? Iran is a middle-income country that is also a large oil producer. We estimate the economy-wide rebound effect for Iran using a structural vector autoregressive model and quarterly data from 1988:3 to 2018:1. We identify the structural shocks by independent component analysis, a statistical identification technique that does not require us to impose restrictions based on economic theory on the model. The results show that in response to an energy efficiency shock energy use falls initially but returns to near its original level over time. The economy-wide rebound effect in Iran is 84% after 6 years and its confidence interval includes 100%. This implies that policies that encourage energy efficiency innovation will have limited long-term impact on energy use.

A new composite made from Luffa Cylindrica and ethylene vinyl acetate (EVA): Mechanical and structural characterization for its use as Mouthguard (MG)

The use of Mouthguards (MGs) in contact sports is an interesting biomedical topic. MGs are protective personal equipment made principally from the copolymer ethylene vinyl acetate (EVA). EVA is a thermoplastic whose thickness and rigidity are variables of concern for a good shock energy absorption capability in an MG. A natural fiber polymer composite is an interesting attempt for tackling these variables. Luffa cylindrica (luffa) is a sponge gourd that grows in 3D structure, which is used mainly as an ornament, a filling, or is trimmed for its use as a bathing product. In this work, a new EVA-luffa composite (EVLc) was made from commercial EVA sheets and luffa mat acting as reinforcement. FTIR, DSC, and TGA tests of EVA revealed its nature compared to literature data. A mechanical testing was applied to eight EVLc ASTM D-638 type V dumbbells (D1-D8) that showed low tensile strength values compared to EVA resistance ranges in literature. SEM images of EVLc's D1-D8 confirmed good adhesion between the reinforcement and matrix without surface treatment, and a descriptive statistical analysis indicated an intrinsic variation.

Numerical analysis of shock energy dissipation in microbubble clouds

In this study, energy dissipation via shock–bubble interaction (SBI) is investigated. With the SBI model developed herein, shock propagation in a bubbly mixture where shockwaves move in a steady state with constant shock velocity and shock strength are obtained as forms of time histories of gas and liquid pressure, bubble radius, and gas temperature. Shock energy is dissipated through thermal heat transfer between the gas and the liquid during bubble oscillation after the shockwave passes in a certain location. The dissipation energy (DE) and damping time (DT) were obtained in the form of dimensionless functions with SBI initial values of the gas volume fraction, bubble radius, and shock strength. Finally, the dissipation power is estimated by combining the concepts of DE and DT that evaluates the ability of energy mitigation in a given SBI system.

Shock energy attenuation of liquid aqueous methylcellulose hydrogels

Liquid methylcellulose (MC) solutions have been shown to effectively attenuate the momentum associated with structural shock. Yet, the energy attenuation remains to be characterized and this is the point of this paper. By measuring the velocity of a momentum trap in contact with the gel container, the ratio between through-the-gel and incoming kinetic shock energies is measured and correlated with the MC concentration, for a fixed 40 mm thick gel layer. The percentage of transferred energy decreases exponentially with the gel concentration, saturating around 15 wt%. While the contribution of the gel’s metallic container cannot be evaluated separately, it is proposed that the reported figures are of a lower bound type since the container itself is not deemed to have a significant effect on shock attenuation while providing a contrario a low resistance path for wave propagation. Whereas the choice of gel compositions is limited in a sense, the thickness of the layer is not, which provides a degree of freedom for the design of energy absorbing devices.

A simplified homogenization model applied to viscoelastic behavior of cortical bone at ultrasonic frequencies

Cortical bone is a complex multiscale medium and its study is of importance for clinical fracture prevention. In particular, cortical attenuation is known to be linked with shock energy absorption and ability to resist fracture. However, the links between cortical bone absorption and its multiscale structure are still not well understood. This work is about the use of homogenized tensors in order to characterize the viscoelastic behavior of cortical bone at ultrasonic frequencies, i.e., about 0.1 to 10 MHz. Such tensors are derived from the cell problem via two-scale homogenization theory for linear elastic and Kelvin–Voigt viscoelastic descriptions. The elliptic formulations obtained from the cell problems are implemented within the range of medically-observed porosities. Microstructure is assessed considering cubic cells with cylindrical inclusion and transverse isotropic assumption. A simplified model, adding one temporal parameter τ per phase, allows a good agreement with experimental data. The corresponding attenuation is proportional to the square of the frequency, in agreement with Kramer–Kronig relations. This development is proposed in the context of robust clinical inverse problem approaches using a restricted number of parameter. Two main properties for the material filling the pores are adjusted and discussed: absorption and shear contribution. Best agreement with experimental data is observed for material inside the pores being solid and highly attenuating.

Combatting medical plastic waste through visual elicitation: Insights from healthcare professionals

In spite of the focus on improving treatment methods and determining the economic and environmental impacts of medical waste management, little research has been conducted to understand consumer perceptions of medical waste reduction. In healthcare setting, our research seeks to address this urgent need by investigating how visual cues can be used to elicit healthcare professionals' willingness to reduce medical plastics. By employing the vignette-based experimental method, we collected data from 1,139 healthcare professionals to examine how visual characteristics (i.e., visual clutter, colorfulness, the presence of human face, the presence of animal) in images of medical plastic pollution were used to arouse moral shock and emotional energy in healthcare professionals. The results of our study suggest that visual displays should be cluttered, colorful, and characterized by human presence. By displaying these visuals in an image of anti-plastic pollution, healthcare professionals are most likely to express their sadness, rage, and despair, and enhance their intention to refuse medical plastics to the fullest extent. By contrast to the previous study, we found that healthcare professionals’ moral shock and willingness to refuse medical plastics were not significantly impacted by the presence of animals on the images.

Strain hardening and shock mitigation response of polyurethane under high strain rates

Polyurethane is a promising candidate for the potting of embedded electronics due to its shock absorbing properties. This paper discusses the less known strain hardening and shock mitigation properties of 4,4′-methylenediphenyl diisocyanate based polyurethane under dynamic loading. This study is reported in a strain rate range of 1600–2900 s−1 under compression using a split-Hopkinson pressure bar (SHPB). The experimental stress–strain behavior of polyurethane was modeled with Hollomon’s equation to analyze its hardening behavior in dynamic environments. Jointly, the incident, reflected, and transmitted strain signals of the SHPB are analyzed in time and frequency domains to understand the shock absorbing properties of polyurethane. Polyurethane was found to absorb more shock for more intense loading. It was observed to mitigate 81% of shock energy with frequencies up to 10 kHz.

An in-silico assessment of efficacy of two novel intra-cardiac electrode configurations versus traditional anti-tachycardia pacing therapy for terminating sustained ventricular tachycardia

The implanted cardioverter defibrillator (ICD) is an effective direct therapy for the treatment of cardiac arrhythmias, including ventricular tachycardia (VT). Anti-tachycardia pacing (ATP) is often applied by the ICD as the first mode of therapy, but is often found to be ineffective, particularly for fast VTs. In such cases, strong, painful and damaging backup defibrillation shocks are applied by the device. Here, we propose two novel electrode configurations: “bipolar” and “transmural” which both combine the concept of targeted shock delivery with the advantage of reduced energy required for VT termination. We perform an in silico study to evaluate the efficacy of VT termination by applying one single (low-energy) monophasic shock from each novel configuration, comparing with conventional ATP therapy. Both bipolar and transmural configurations are able to achieve a higher efficacy (93% and 85%) than ATP (45%), with energy delivered similar to and two orders of magnitudes smaller than conventional ICD defibrillation shocks, respectively. Specifically, the transmural configuration (which applies the shock vector directly across the scar substrate sustaining the VT) is most efficient, requiring typically less than 1 J shock energy to achieve a high efficacy. The efficacy of both bipolar and transmural configurations are higher when applied to slow VTs (100% and 97%) compared to fast VTs (57% and 29%). Both novel electrode configurations introduced are able to improve electrotherapy efficacy while reducing the overall number of required therapies and need for strong backup shocks.

The effect of patient weight and amiodarone use on the energy of a successful shock in cardioversion of atrial arrhythmias – single-center experience study

Abstract Background Electrical cardioversion (DCCV) is an effective method of sinus rhythm restitution. Recently published data suggest higher efficiencies of higher discharge energies. The influence of individual parameters on the success of cardioversion is still studying. Purpose To evaluate the influence of individual patient parameters on the energy of a successful external defibrillator shock during cardioversion of atrial arrhythmias Methods The retrospective analysis cohort of all patients treated by DCCV due to atrial arrhythmias between 10/2015 and 1/2020. To evaluate potential predictors for the choice of a higher initial discharge using one-dimensional logistic regression and to include parameters significant at the 10% level of significance (p<0.1) in the multidimensional logistic regression model. Results 1986 electrical cardioversions of 984 patients (382 repeated procedures of the same patients in a cohort). 1292 (65.1%) men and 694 (34.9%) women aged 67.0 (±10.2) years. Mean energy of the first shock 118.9 (±19.2) J with a success rate of 77.8%, energy of the second shock 154.0 (±26.3) J, which increased the overall success to 80.0%, and mean high of the third shock 173.9 (±25.6) J, when the total efficacy of DCCV in sinus rhytm restitution reached 89.8%. From the univariate binary regression, parameters significant at the 10% level of significance (p<0.1) were selected and included in a multidimensional logistic regression model. Only the patient's weight and the use of amiodarone proved to be statistically significant. Weight with OR 1.21 and use of amiodarone with OR 1.43. Conclusion Patient weight and amiodarone use are predictors of the need to use higher energy electric cardioversion. Discussion Amiodarone medication does not appear to increase the defibrillation threshold, but rather is a feature that represents the group of patients treated with more aggressive antiarrhythmic therapy for advanced atrial arrhythmias with more significant structural impairment, but this attitude requires further study. Funding Acknowledgement Type of funding sources: Private hospital(s). Main funding source(s): VAVIA: IGS202009 - Racionální algoritmus při elektivní elektrické kardioverzi fibrilace síní.

Defibrillation testing of subcutaneous versus transvenous defibrillators in the clinical practice: a nationwide survey in Italy

Abstract Aims According to current guidelines, defibrillation testing (DT) for efficacy can be omitted in patients undergoing transvenous implantable cardioverter–defibrillator (T-ICD) implantation. DT is still recommended for patients at risk for a high defibrillation threshold (e.g. hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, right-sided implantations) and for ICD generator changes. Moreover, a class I recommendation remains to perform DT during the implantation of subcutaneous ICD (S-ICD). The aim of the present survey was to analyze the current practice of DT during T-ICD and S-ICD implantations in Italy. Methods In March 2021, an ad hoc questionnaire on the current performance of DT and the standard practice adopted during testing was completed by 72 operators at Italian centers implanting S-ICD and T-ICD. Results 48 (67%) operators reported never performing DT during de-novo T-ICD implantations, while no operators perform it systematically. The remaining respondents perform it in specific cases: right sided implantations (54%), poor signal sensing (46%), secondary prevention patients (42%), arrhythmic syndromes (13%), hypertrophic cardiomyopathy (8%). DT is never performed at T-ICD generator change. At the time of de-novo S-ICD implantation, DT is never performed by 9 (13%) operators and performed systematically by 48 (66%). The remaining operators perform DT in cases of: secondary prevention patients (73%), sub-optimal S-ICD placement (33%), non-compromised ejection fraction (33%) or obese patients (7%). DT is not performed at S-ICD generator change by 92% of operators. DT is conducted by delivering a first shock energy of 65J by 60% of operators, while the remaining 40% test lower energy values. The most frequently reported conditions for revising the system at the end of de- novo implantation procedure is high shock impedance (54%) and sub-optimal S-ICD placement or high PRAETORIAN score (50%). With adequately low shock impedance and optimal system placement, 37% of operators would accept a defibrillation margin <15J. Conclusion In current clinical practice, the vast majority of operators omit DT at T-ICD implantation, even when still recommended in the guidelines. DT is also frequently omitted at S-ICD implantation. We also report a wide variability among operators in the procedures followed during DT and in the criteria applied for defining the procedural success. Funding Acknowledgement Type of funding sources: None.

Classification of emerging patterns in self-assembled two-dimensional magnetic lattices.

Self-assembled granular materials can be utilized in many applications such as shock absorption and energy harvesting. Such materials are inherently discrete with an easy path to tunability through external applied forces such as stress or by adding more elements to the system. However, the self-assembly process is statistical in nature with no guarantee for repeatability, stability, or order of emergent final assemblies. Here we study both numerically and experimentally the two-dimensional self-assembly of free-floating disks with repulsive magnetic potentials confined to a boundary with embedded permanent magnets. Six different types of disks and seven boundary shapes are considered. An agent-based model is developed to predict the self-assembled patterns for any given disk type, boundary, and number of disks. The validity of the model is experimentally verified. While the model converges to a physical solution, these solutions are not always unique and depend on the initial position of the disks. The emerging patterns are classified into monostable patterns (i.e., stable patterns that emerge regardless of the initial conditions) and multistable patterns. We also characterize the emergent order and crystallinity of the emerging patterns. The developed model along with the self-assembly nature of the system can be key in creating re-programmable materials with exceptional nonlinear properties.

Membrane lipid metabolism, heat shock response and energy costs mediate the interaction between acclimatization and heat-hardening response in the razor clam Sinonovacula constricta.

Thermal plasticity on different time scales, including acclimation/acclimatization and heat-hardening response - a rapid adjustment for thermal tolerance after non-lethal thermal stress, can interact to improve the resilience of organisms to thermal stress. However, little is known about physiological mechanisms mediating this interaction. To investigate the underpinnings of heat-hardening responses after acclimatization in warm seasons, we measured thermal tolerance plasticity, and compared transcriptomic and metabolomic changes after heat hardening at 33 or 37°C followed by recovery of 3 or 24 h in an intertidal bivalve Sinonovacula constricta. Clams showed explicit heat-hardening responses after acclimatization in a warm season. The higher inducing temperature (37°C) caused less effective heat-hardening effects than the inducing temperature that was closer to the seasonal maximum temperature (33°C). Metabolomic analysis highlighted the elevated content of glycerophospholipids in all heat-hardened clams, which may help to maintain the structure and function of the membrane. Heat shock proteins (HSPs) tended to be upregulated after heat hardening at 37°C but not at 33°C, indicating that there was no complete dependency of heat-hardening effects on upregulated HSPs. Enhanced energy metabolism and decreased energy reserves were observed after heat hardening at 37°C, suggesting more energy costs during exposure to a higher inducing temperature, which may restrict heat-hardening effects. These results highlight the mediating role of membrane lipid metabolism, heat shock responses and energy costs in the interaction between heat-hardening response and seasonal acclimatization, and contribute to the mechanistic understanding of evolutionary change and thermal plasticity during global climate change.

Soil biological activity of short rotation crop at the maximum saturation with sunflower

Soil biological activity of short rotation crop at the maximum saturation with sunflower

Strengthening effect of laser shock: convex model with and without reflection

In this paper, the total reflection convex model and non-reflective convex model are established by simulation method, and the influence of shock pressure/laser energy and longitudinal wave reflection on the strengthening effect of laser shock 7050-T7451 aluminum alloy convex model is analyzed, and the relevant experiments are carried out to verify. When the shock pressure is 1500 MPa or the laser energy is 2.71 J, the shock energy is small, and the reflection of longitudinal wave has no effect on the material surface. When the shock pressure is greater than 1500 MPa or the laser energy is greater than 2.71 J, the reflection of longitudinal wave begins to affect the material surface, and the residual stress and deformation in the spot follow the rule that the position of spot edge in the circumferential direction is the largest, and the position of spot edge in the center and generatrix direction is smaller. Combined with the experimental results and simulation analysis, the residual stress distribution and surface integrity were evaluated comprehensively. When the convex model with 1/5 curvature was strengthened by laser shock, 4.82 J laser energy was applied on the surface of 4 mm spot to obtain better strengthening effect.