Search

Thermal shock resistance and mechanical reliability of aluminum nitride (AlN) ceramic substrates are essential in electronic device modules. In this study, the thermal shock behavior of AlN doped with aluminum - yttrium oxide (Al - Y 2 O 3) was explored. The results indicate that adding Al to AlN ceramics increases its flexural strength, thermal conductivity, and thermal expansion coefficient. The microcracks caused by thermal mismatch between the AlN matrix and the secondary phases relieved internal stress, thereby improving thermal shock resistance of AlN ceramics. Furthermore, the addition of Al isolates and homogenizes the secondary phases, resulting in a more uniform microstructure and strengthened grain boundaries, which enhance the flexural strength, Weibull modulus, and thermal shock resistance. After introducing 0.5 wt% Al, the Weibull modulus of AlN ceramics increased by 73.37 %, and their critical thermal shock temperature difference exceeded 800 °C, with a maximum residual strength of 488.01 ± 48.26 MPa at 600 °C. Overall, an appropriate amount of Al improves the reliability and thermal shock resistance of AlN ceramics. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusions Impella 5.5 is a temporary left ventricular assist device utilized to support patients with cardiogenic shock and those undergoing high‐risk cardiac interventions.From October 2019 to January 2023, 226 patients received Impella 5.5 support at Cleveland Clinic main campus. Patients were stratified by Society for Cardiovascular Angiography and Interventions (SCAI) shock stages. Immediate post‐Impella 5.5 trajectories were compared across groups. Trajectories were defined as mortality on Impella 5.5, transition to advanced heart failure therapies (durable left ventricular assist device/heart transplantation), or survival to Impella 5.5 removal without advanced therapies.Overall, 148 (65%) patients with cardiogenic shock and 78 (35%) undergoing high‐risk cardiac interventions received Impella 5.5 support. SCAI stage was A in 63 (28%), B in 10 (4.4%), C in 29 (13%), D in 104 (46%), and E in 20 (8.8%). Mortality on Impella 5.5 was highest in SCAI stage E (A: 3.2%, B: 10%, C: 14%, D: 27%, E: 35%; p < 0.01). Transition to advanced therapies (durable left ventricular assist device or heart transplantation) was highest in SCAI stages C‐D (A: 1.6%, B: 0.0%, C: 45%, D: 36%, E: 20%; p < 0.01). Survival to Impella removal without advanced therapies was highest in SCAI stages A‐B (A: 95%, B: 90%, C: 41%, D: 38%, E: 45%; p < 0.01).Stratification by presentation acuity in candidates for Impella 5.5 insertion may help identify which patients may and may not benefit from this escalation of tailored temporary mechanical circulatory support. [ABSTRACT FROM AUTHOR]

Background: We report a rare case of new onset autoimmune adrenal insufficiency in childhood, presenting with severe shock requiring mechanical circulatory support. In the current era of readily available imaging, laboratory and other diagnostic investigations, medical history and careful physical exam can often provide valuable diagnostic information for timely therapy. Case presentation: A 7-year-old boy with a history of mild intermittent asthma, presented with severe cardiogenic shock requiring extracorporeal membrane oxygenation (ECMO). Bronzing of his entire body was noted on physical exam. Stress dose hydrocortisone was given for suspected adrenal insufficiency. After weaning from ECMO and extensive rehabilitation, the patient recovered and was discharged home. Conclusion: Primary adrenal insufficiency (PAI) should be considered in the context of physical exam and laboratory findings, even in the presence of circulatory shock. [ABSTRACT FROM AUTHOR]

Use of Intra-Aortic Balloon Pump (IABP) in combination with Impella has been described as an alternative strategy for mechanical circulatory support (MCS) in patients with cardiogenic shock (CS). We provide a systematic review aimed to explore the effectiveness of this paired MCS approach. We conducted a comprehensive systematic search in MEDLINE, Scopus, and Cochrane databases to identify all studies that investigated dual MCS with IABP and Impella. Our search strategy identified 12 articles, including 1 randomized controlled trial, 1 retrospective study, 1 case series, 7 case report and 2 animal studies. Rationale for this combined MCS strategy stems from an observed reduction in myocardial oxygen demand/supply ratio compared to the use of each device alone, without determining significant variations in left ventricular work. Nonetheless, this combined approach also leads to a 30–40 % decline in Impella flow, increasing the risk of bleeding, Impella displacement, as well as triggering positioning and pressure alarms. Additionally, hemolytic risk data yielded inconclusive results. Importantly, there were no notable disparities in mortality rates when comparing the combined strategy to the use of each device individually. At the current state-of-the-art, there are no conclusive data demonstrating net clinical benefits of combining Impella with IABP. Considering the substantial risks of morbidity associated, we recommend against its use in clinical practice. [Display omitted] • MCS combination is an interesting strategy but need a strong rationale due to side effects. • Impella functioning is severely worsened when combined with IABP. • Hemodynamic benefit of IABP and Impella combination does not justify increased risk. • Expansion of registries on major outcomes is needed to examine dual MCS strategies. [ABSTRACT FROM AUTHOR]

The rapid, energy‐efficient, scalable preparation of high‐strength, flexible, multifunctional nanostructured aerogels is highly desired yet challenging. Here, an ambient‐pressure‐dried (APD) strategy is developed involving self‐foaming, dip‐coating, and graphene oxide (GO)‐assisted multiple cross‐linking treatments for the prompt, large‐area preparation of polyurea/transition metal carbides/nitrides (MXenes) aerogels. The APD MXene‐based aerogels showcase low density, remarkable mechanical strength, and ultraflexiblity involving stretchability, good conductivity, hydrophobicity, and high resistance to various solvents. Synergies of robust, elastic cell walls and porous structure contribute to high‐efficiency absorption of high‐frequency, high‐speed mechanical shock waves for the aerogels, significantly transcendinging the biomasses, plastics, elastomers, ceramics, and metals. In addition to the excellent microwave shielding performance of over 40 dB in ultrabroadband frequencies of 4–40 GHz, the oxidation stability is elevated for APD MXene aerogels, consequently yielding applicability in harsh conditions. Furthermore, the superior light absorption capability of aerogels leads to the efficient photothermal conversion, therapy, antibacterial, desalination, water purification, deicing, and thick oil absorption. This work provides a facile, time‐ and energy‐efficient, scalable APD methodology for manufacturing large‐area, high‐strength, ultraflexible, multifunctional MXene‐based aerogels, enlighting a novel synergistic defense against mechanical shock and electromagnetic waves, and promoting them as a prospective candidate in aerospace, device protection, and next‐generation electronics. [ABSTRACT FROM AUTHOR]

This study aims to develop thermoplastic (TP) and thermoset (TS) based mixed matrix composite using design dependent physical compatibility. Using thermoplastic-based (PLA) skeletal lattices with diverse patterns (gyroid and grid) and different infill densities (10% and 20%) followed by infiltration of two different thermoset resin systems (epoxy and polyurethane-based) using a customized FDM 3D printer equipped with a resin dispensing unit, the optimised design and TP-TS material combination was established for best mechanical performance. Under uniaxial tensile stress, the failure modes of TP gyroid structures with polyurethane-based composites included 'fiber pull-out', interfacial debonding and fiber breakage, while epoxy based mixed matrix composites with all design variants demonstrated brittle failure. Higher elongation (higher area under curve) was observed in 20% infilled gyroid patterned composite with polyurethane matrix indicating the capability of operation in mechanical shock absorption application. Electron microscopy-based fractography analysis revealed that thermoset matrix properties governed the fracture modes for the thermoplastic phase. This work focused on the strategic optimisation of both toughness and stiffness of mixed matrix composite components for rapid fabrication of construction materials. [ABSTRACT FROM AUTHOR]

AbstractIn this study, the nonlinear forced vibration of graphene/piezoelectric sandwich nanosheets under mechanical impact was investigated. For the first time, linear (displacement and velocity) and nonlinear (displacement) time-delay proportional derivative (PD) controllers were applied to graphene/piezoelectric sandwich nanosheets, and the primary/secondary resonance under different time-delay parameters were analyzed. An approximate analytical solution for the nonlinear forced vibration control equation was obtained using the multiple scale perturbation method, and the stability of graphene/piezoelectric sandwich nanosheets under primary/secondary resonance conditions was discussed using the Ross Herwitz theorem. Finally, the results of this study were compared with those of other studies. The feasibility of the research methodology was demonstrated. On this basis, the research results indicate that linear displacement delay, nonlinear displacement delay, and velocity delay parameters can suppress the unsteady vibration characteristics of the main system. And comparing the linear and nonlinear displacement time-delay, it is found that the nonlinear displacement time-delay has a greater effect on the system. Specifically, the presence of nonlinear displacement time-delay changes the vibration characteristics of the curve from hard spring characteristics to soft spring characteristics. Comparison of displacement time-delay and velocity time-delay reveals that velocity time-delay gives better control over the system. In addition, the results show that the excitation amplitude, nonlocal parameters, and external voltage enhance the nonlinear characteristics of the system under the main and superharmonic resonance conditions before the time-delay control. Subharmonic resonance conditions, the system parameters make the vibration range wider. After the time-delay control, the influence of these three factors on the system vibration is significantly reduced for the three resonance conditions, especially for the non-local parameters. The results of the study can provide guidance for active control of time delay in different types of nanodevices for engineering applications. [ABSTRACT FROM AUTHOR]

Cardiogenic shock (CS) remains a high-mortality condition despite technological and therapeutic advances. One key to potentially improving CS prognosis is understanding patient heterogeneity and which patients may benefit most from different treatment options, a key element of which is sex differences. While cardiovascular diseases (CVDs) have historically been considered a male-dominant condition, the field is increasingly aware that females are also a substantial portion of the patient population. While estrogen has been implicated in protective roles against CVD and tissue hypoxia, its role in CS remains unclear. Clinically, female CS patients tend to be older, have more severe comorbidities and are more likely to have non-acute myocardial infarction etiologies with preserved ejection fractions. Female CS patients are more likely to receive pharmacotherapy while less likely to receive mechanical circulatory support. There is increased short-term mortality in females, although long-term mortality is similar between the sexes. More sex-specific and age-stratified research needs to be done to fully understand the relevant pathophysiological differences in CS, to better recognize and manage CS patients and reduce its mortality. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This standard provides definitions for a wide variety of terms, abbreviations, and letter symbols used in acoustics and electroacoustics. Terms of general use in all branches of acoustics are defined, as well as many terms of special use for architectural acoustics, acoustical instruments, mechanical vibration and shock, physiological and psychological acoustics, underwater sound, sonics and ultrasonics, and music. [ABSTRACT FROM AUTHOR]

Aims Methods and results Conclusions To describe the use and the relation to outcome of different ventilation strategies in a contemporary, large, prospective registry of cardiogenic shock patients.Among 657 patients enrolled from March 2020 to November 2023, 198 (30.1%) received oxygen therapy (OT), 96 (14.6%) underwent non‐invasive ventilation (NIV), and 363 (55.3%) underwent invasive mechanical ventilation (iMV). Patients in the iMV group were significantly younger compared to those in the NIV and OT groups (63 vs. 69 years, p < 0.001). There were no significant differences between groups regarding cardiovascular risk factors. Patients with SCAI B and C were more frequently treated with OT and NIV compared to iMV (65.1% and 65.4% vs. 42.6%, respectively, p > 0.001), while the opposite trend was observed in SCAI D patients (12% and 12.2% vs. 30.9%, respectively, p < 0.001). All‐cause mortality at 24 h did not differ amongst the three groups. The 60‐day mortality rates were 40.2% for the iMV group, 26% for the OT group, and 29.3% for the NIV group (p = 0.005), even after excluding patients with cardiac arrest at presentation. In the multivariate analysis including SCAI stages, NIV was not associated with worse mortality compared to iMV (hazard ratio 1.97, 95% confidence interval 0.85–4.56), even in more severe SCAI stages such as D.Compared to previous studies, we observed a rising trend in the utilization of NIV among cardiogenic shock patients, irrespective of aetiology and SCAI stages. In this clinical scenario, NIV emerges as a safe option for appropriately selected patients. [ABSTRACT FROM AUTHOR]

Background: The efficacy of extracorporeal membrane oxygenation (ECMO) as a bridge to left ventricular assist device (LVAD) remains unclear, and recipients of the more contemporary HeartMate 3 (HM3) LVAD are not well represented in previous studies. We therefore undertook a multicenter, retrospective study of this population. Methods and Results: INTERMACS 1 LVAD recipients from five U.S. centers were included. In‐hospital and one‐year outcomes were recorded. The primary outcome was the overall mortality hazard comparing ECMO versus non‐ECMO patients by propensity‐weighted survival analysis. Secondary outcomes included survival by LVAD type, as well as postoperative and one‐year outcomes. One hundred and twenty‐seven patients were included; 24 received ECMO as a bridge to LVAD. Mortality was higher in patients bridged with ECMO in the primary analysis (HR 3.22 [95%CI 1.06–9.77], p = 0.039). Right ventricular assist device was more common in the ECMO group (ECMO: 54.2% vs non‐ECMO: 11.7%, p < 0.001). Ischemic stroke was higher at one year in the ECMO group (ECMO: 25.0% vs non‐ECMO: 4.9%, p = 0.006). Among the study cohort, one‐year mortality was lower in HM3 than in HeartMate II (HMII) or HeartWare HVAD (10.5% vs 46.9% vs 31.6%, respectively; p < 0.001) recipients. Pump thrombosis at one year was lower in HM3 than in HMII or HVAD (1.8% vs 16.1% vs 16.2%, respectively; p = 0.026) recipients. Conclusions: Higher mortality was observed with ECMO as a bridge to LVAD, likely due to higher acuity illness, yet acceptable one‐year survival was seen compared with historical rates. The receipt of the HM3 was associated with improved survival compared with older generation devices. [ABSTRACT FROM AUTHOR]

Medium-voltage (MV) switchgear and gas insulated switchgear (GIS) are essential components of power-grid systems. Their safe operation is crucial for the electricity consumption of users. However, insulation faults often occur during the operation of MV switchgear and GIS because of pollution, humidity, heat, mechanical shock, and other factors. Partial discharge (PD) measurements are the most effective indicator to prevent insulation failure. Transient earth voltage (TEV) and ultrasonic methods are the most popular PD measurement methods for switchgear. Currently, these two methods are used widely and independently. In this study, a novel TEV-ultrasonic integrated sensor is proposed based on the independent structure of the TEV and the ultrasonic sensor. The performance parameters of the proposed sensor were tested on test platforms. PD measurement experiments were conducted in a 10 kV switchgear and 220 kV GIS to analyze the performance of the integrated sensor. The results show that the sensor can simultaneously measure the TEV and ultrasonic signals in the same location. The integrated sensor can realize effective and sensitive detection, precise location, and accurate diagnosis of PD in the MV switchgear and GIS. [ABSTRACT FROM AUTHOR]

High‐density interconnect (HDI) technology for liquid metal (LM)‐based stretchable printed circuit boards is crucial for expanding their applicability. HDI technology provides high‐resolution multilayer circuits with a high density of components, as required for next generation of neuroprobes and ultrasonic and sensor arrays. This study presents a HDI technique utilizing laser engraved micro grooves in silicone with a protective lift‐off mask of polyvinyl alcohol (PVA) and subsequent microscale LM particle spray deposition. This approach achieves high‐resolution LM patterns and enables multilayer connectivity and high‐density integration of components simultaneously, that is, realizing HDI technology. It is demonstrated using a stretchable 0201 LED display with a density of six leads per mm2 and a cochlear implant (CI) electrode array. The demonstrated manufacturing of the CI has the potential to enable fully automated printed circuit board manufacturing of such implants with increased precision and throughput. Implants in guinea pigs show that the CI is capable of activating the auditory neuron with electrical auditory brainstem response (eABR) and electrical compound action potential (eCAP) of high quality. Moreover, the U‐shaped cross section of the LM interconnects provides a higher mechanical shock resistance of the circuit than that of normal rectangular cross sections. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: Cardiogenic shock (CS) is a complex life-threatening condition that results from primary cardiac dysfunction, leading to persistent hypotension and systemic hypoperfusion. Among the therapeutic options for CS are various percutaneous mechanical circulatory support (MCS) devices that have emerged as an increasingly effective hemodynamic support option. Percutaneous therapies can act as short-term mechanical circulatory assistance and can be split into intra-aortic balloon pump (IABP) and non-IABP percutaneous mechanical devices. Areas covered: This review will evaluate the MCS value while considering the mortality rate improvements. We also aim to outline the function of pharmacotherapies and percutaneous hemodynamic MCS devices in managing CS patients to avoid the onset of end-organ dysfunction and improve both early and late outcomes. Expert opinion: Given the complexity, acuity and high mortality associated with CS, and despite the availability and efficacy of pharmacological management, MCS is required to achieve hemodynamic stability and improve survival. Various percutaneous MCS devices are available with varying indications and clinical outcomes. The rates of early mortality and complications were found to be comparable between the four devices, yet, IABP seemed to show the most optimal clinical profile whilst ECMO demonstrated its more long-term efficacy. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is an efficient method to fabricate components with complex geometries. However, high levels of tensile residual stress generated in the near-surface layer of the fabricated components due to the high cooling rate and large thermal gradients during the AM process have limited their applications. Laser shock processing (LSP) is a novel surface-strengthening technique applied to modify the near-surface of metallic materials with the purpose of improving mechanical properties such as microhardness, residual stress, wear resistance, and fatigue performance. There are more and more investigations to report the combining manufacturing process of metallic alloys through AM and LSP. In this perspective, the fundamental mechanisms of AM and LSP were summarized in detail. The combining manufacturing process with LSP and AM was introduced from the aspect of residual stress, microhardness, fatigue performance, wear resistance, and microstructure evolution. Also, the microstructure-property relationship was discussed to explain the strengthening mechanism of AMed components by LSP. This work has important reference value and guidance significance for researchers to widespread the accepted LSP as a postprocessing method in the fields of AM. [ABSTRACT FROM AUTHOR]

Due to the importance of safety in the process of structural designing of the modern buildings' ceiling, this study gravitates on a novel topic of analyzing thermoelastic response of the concrete ceiling reinforced with nanoparticles of graphene-platelets (GPL). To this end, the mentioned ceiling is considered as a fully-clamped rectangular plate exposed to simultaneous impact of thermal and mechanical loads. The exact form of the elasticity theory in conjunction with the differential quadrature method is employed for acquiring the behavior of the system. Then, an artificial intelligence-based method is used to accelerate the computational process. Efficiency and accuracy of the employed solution are examined and verified by means of a comparative study. The results of this article would be broadly employed in the structural design of the modern constructions in the near future. [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]

In this study, both the optical and piezoelectric properties of polyvinylidene fluoride (PVDF) electrospun nanofibers were investigated at different needle-to-collector distances of the electrospinning process at constant applied high voltage. For piezoelectric characterization, the fabricated nanofiber mats were subjected to applied forces, including cyclic force, variable frequency-based loads, and free-falling masses (impulse loading), along with power density analysis for different load resistance values. In addition, both optical absorbance and transmittance measurements were conducted to evaluate the optical properties of the fabricated nanofibers. The piezoelectric analysis demonstrated the best piezoresponse of the fabricated nanomats at a needle-to-collector distance of 15 cm and high voltage of 22 kV. However, a trade-off between piezoelectric response and optical transmissivity was observed based on the electrospinning distance parameter. The relatively higher optically transparent sample exhibited only moderate piezoelectric response, while the less transparent sample displayed the highest piezoelectric activity. Based on the optimized sample and piezoelectric analysis, the synthesized nanofiber mat was subjected to applied mechanical stress in the form of variable velocity and momentum loads. A maximum potential of approximately 16 V was harvested through velocity and momentum impact, especially with the addition of a double-layer PVDF membrane. Furthermore, the sensing effect of airflow pressure on single/double-layer PVDF was studied. The single-layer PVDF membrane generated 79 mV under an airflow speed of 21 km/h, while the double-layer membrane produced 114 mV potential under the same airflow. This study highlights the diverse applications of PVDF nanofiber mats as multifunctional sensors and energy harvesting applications from mechanical shocks and airflow impact. [ABSTRACT FROM AUTHOR]

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]

Collisionless shock waves are efficient ion accelerators. Previous numerical and observational studies have shown that quasi‐parallel (Q‖) shocks are more effective than quasi‐perpendicular (Q⊥) shocks at generating energetic ions under steady upstream conditions. Here, we use a local, 2D, hybrid particle‐in‐cell model to investigate how ion acceleration at super‐critical Q⊥ shocks is modulated when tangential discontinuities (TDs) with large magnetic shear are present in the upstream plasma. We show that such TDs can significantly increase the ion acceleration efficiency of 2D Q⊥ shocks, up to a level comparable to Q‖ shocks. Using data from the hybrid model and test particle simulations, we show that the enhanced energization is related to the magnetic field change associated with the discontinuity. When shock‐reflected ions cross the TD during their upstream gyromotion, the sharp field change causes the ions to propagate further upstream, and gain additional energy from the convection electric field associated with the upstream plasma flow. Our findings illustrate that the presence of upstream discontinuities can lead to bursts of energetic ions, even when they do not trigger the formation of foreshock transients. These results emphasize the importance of time‐variable upstream conditions when considering ion energization at shocks. Key Points: Bursts of energetic ions can appear upstream of quasi‐perpendicular shocks due to highly sheared upstream tangential discontinuitiesThe magnetic field change of the discontinuity enables the shock‐reflected ions to be further energized by the convection electric fieldThis process results in a local acceleration efficiency comparable to that of quasi‐parallel shocks under steady upstream conditions [ABSTRACT FROM AUTHOR]

Micro-Raman spectroscopy was carried out to evaluate the localized residual stresses in commercial Gallium-Nitride-based devices, specifically, AlGaN/GaN high-electron-mobility Transistors (HEMTs) with a novel packaging design provided by STMicroelectronics S.r.l. (Catania, Italy). The packaging plays a key role in protecting the device core against the external environment, thus minimizing damages caused by mechanical shocks, exposure to light, and contact with chemicals, conjointly achieving an efficient heat dissipation rate. Even though the packaging is a required step for the proper functioning of ready-to-use electronic devices, its application typically may introduce mechanical stress to AlGaN/GaN HEMTs, which can result in various reliability issues. In this paper, we investigate the impact of packaging on residual stress by analyzing the frequency shift of the E2 Raman peak along GaN layers and at the GaN/Si interface. An extensive evaluation was conducted using both a packaged device and a wafer-level device. The correlation between Raman frequency shifts of the E2 mode was accurately quantified, revealing a stress mitigation of approximately 0.1 GPa. This reduction is ascribed to the compressive stress introduced by the packaging, which partially offsets the intrinsic tensile stress of the wafer-level device. The proposed methodology could, in principle, be implemented to improve the development of packaging. [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]

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]

When a dielectric material undergoes mechanical impact, it generates a shock wave, causing changes in its refractive index. Recent demonstrations have proven that the modified refractive index can be determined remotely using a millimeter-wave interferometer. However, these demonstrations are based on the resolution of an inverse electromagnetic problem, which assumes that the losses in the material are negligible. This restrictive assumption is overcome in this article, in which a new approach is proposed to solve the inverse electromagnetic problem in lossy and shocked dielectric materials. Our methodology combines a one-dimensional convolutional neural network architecture, namely Inverse problem of Lossless or Lossy Shocked Wavefront Network (ILSW-Net), with a nonlinear optimization technique based on the Nelder–Mead algorithm to estimate losses within dielectric materials under a mechanical impact. Experimental results for both simulated and real signals show that our method can successfully predict the velocities and the refractive index while accurately estimating the shock wavefront. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A large deformation, coupled finite‐element (FE) model is developed to simulate the multiphase response of soft porous materials subjected to high strain‐rate loading. The approach is based on the theory of porous media (TPM) at large deformations. Simplifications to the one‐dimensional regime studied in the numerical simulations follow. An overview of several different time integration schemes is presented for the purpose of solving the nonlinear dynamic coupled balance of momenta (mixture and fluid) and balance of mass of the mixture equations. Numerical examples are presented for (i) verification against closed‐form analytical solutions assuming small loads, (ii) demonstrating large deformation effects at high strain‐rate, and (iii) showing differences in deformations between a single‐phase elastodynamics model with occluded compressible pore fluid and a multiphase poroelastodynamics model at high strain‐rate. The multiphase model shows that the relative motion of the pore fluid significantly dampens the deformation response of the solid skeleton as compared to the single‐phase model, and makes it possible to extract quantitative values for the stresses of the different constituents, thereby allowing one to form preliminary conclusions about the onset of damage in the solid skeleton. The novelty of the current work is developing a multiphase, large deformation, mixture theory numerical model for high strain‐rate loading of soft porous materials. It was discovered that explicit, adaptive time‐stepping Runge–Kutta schemes offer high accuracy at relatively low cost when compared to traditional implicit or explicit central difference time‐stepping schemes for shock‐like loadings. Shock viscosity is added to the mixture momentum balance equation to regularize the shock front, and a stabilization term is added to the mixture mass balance equation to stabilize equal order interpolation finite elements for the coupled finite element solution of multiphase materials. [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]

Refractories are characterized by their ability to withstand high temperatures that reach 2800°C, their ability to withstand sudden changes in temperature, resist mechanical shocks, due to the formation of glass at a temperature of 1050-1100°C, it is required that the molds manufactured from refractories withstand that temperature. This is in addition to the ability of the refractory material to show the fine details and the prominent and recessed sculptural surfaces (smooth - rough) in the glass product, and to achieve the uniqueness and excellence of the glass product.This is due to the requirements of refractory mold in its manufacture and assortment with manual blowing in terms of its ability to withstand pressures, non-fragmentation, thermal endurance that reaches (1500 - 1750°C), and a low rate of expansion and contraction that reaches ± 0.05 mm, as well as its flat smoothness, which is considered as a mirror of a model formation.Since the glass material is acidic, it requires that the components of the refractory composition of the mold be acidic or neutral as well. To prevent the adhesion with the glass components thus, some refractories were selected that enter into the work of refractory formulations that can achieve chemical and natural properties suitable in the manufacture of glass forming molds by manual blowing. (16) Refractory compositions were made, and the research reached to find new refractories that meet the requirements. Thus, it is recommended to use refractories for producing the prototype of the glass products which are characterized by aesthetic products.

This document is an amendment to ANSI/ASA S2.73-2014/ISO 10819:2013 (R2019). The committee has decided that the contents of this amendment and the base publication will remain unchanged until the ISO stability date indicated on the ISO website in the data related to this publication. Since these documents are identical national adoptions, ASA will follow the same process. [ABSTRACT FROM AUTHOR]

This American National Standard specifies a method for the laboratory measurement, data analysis, and reporting of the vibration transmissibility of a glove with a vibration-reducing material that covers the palm, fingers, and thumb of the hand. ANSI/ASA S2.73-2014 / ISO 10819:2013 specifies vibration transmissibility in terms of vibration transmitted from a handle through a glove to the palm of the hand in hrough a glove to the palm of the hand in one-third-octave frequency bands with center frequencies of 25 Hz to 1,250 Hz. [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]

Crack propagation in ceramics is a highly quick, complex, and nonlinear process that occurs under thermal shock. It is challenging to directly observe the evolution process of cracks in experiments due to the high speed and unpredictability of crack propagation. Based on the phase-field fracture method, a phase-field numerical model combined with thermal and mechanical damage is established to analyze the crack propagation path, velocity, and morphology of pre-cracked ceramic plates under flame thermal shock loading. This research primarily focuses on the impact of prefabricated crack angle and length on crack propagation. According to the findings of the numerical simulation, ceramic plates with varied prefabricated crack angles are loaded via flame thermal shock, and thermal stress is caused by the rapid rise in the temperature difference between the top edge and the inside of the ceramic plate. Hence, the crack propagation rate seems to be quick at first, and then, slows down when the wing-like cracks at the crack tips spread to both ends. The crack tip on the side closer to the flame thermal loading is more likely to generate wing-shaped cracks as the length of the pre-existing crack increases. However, the crack tip on the side further away from the flame thermal loading exhibits the reverse tendency. The complex evolution process of crack initiation, propagation, and coalescence in ceramic materials brought on by flame thermal shock can be predicted by the thermo-mechanical coupled phase-field model, which is a valuable reference for designing and optimizing the thermal shock resistance and mechanical failure prediction of ceramic materials. [ABSTRACT FROM AUTHOR]

In the presented work the impact of a laser shock wave on the mechanical properties of a Titanium Grade 1 was investigated. Based on a series of experimental studies related to the impact of the laser shock wave on the tested material, the impact of the given treatment on the structure and mechanical properties was assessed. The influence of the environment on the distribution of plasma temperature and pressure in the material during the implementation of the laser shock wave was analyzed. The effect of the laser treatment on the structure and micromechanical properties was initially estimated on the basis of the analysis of experimental results in the form of static strength test of samples after laser treatment. A slight increase in material strength was detected with a minimal decrease in ductility. In order to comprehensively understand the observed phenomenon, a number of fractographic tests were performed, especially the analysis of the porosity of the fracture surfaces. A decrease in the porosity of the material after impact laser treatment was observed as a result of local plastic deformation. [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]

A firefighter's helmet is used as a basic personal protective equipment item. The purpose of the helmet is to absorb a part of mechanical impact acting towards the rescuer's cervical spine, which may lead to its injury. The aim of the study was to determine the effect of changes in the helmet design on the threshold passive forces transferred to the firefighter's cervical spine. The test subjects were firefighter's helmets compliant with the European standard for helmets used by fire brigades. The study was carried out under model conditions, using special equipment with a head model and an additional force sensor placed under it, where the cervical spine is anatomically located. The central impact energy was assumed to be 60 J. A semi-spherically ended beater was used. The experimentally determined force-displacement characteristics revealed two phases of force increase. Using polyurethane foam as a cushioning insert instead of the expanded polyester used in older designs reduced values of forces in the first phase of the characteristic. There were many cases where the critical passive force value was exceeded, which would have resulted in the cervical spine injury. Modifications in material selection and component manufacturing technology affect the protective capabilities of firefighter's helmets and result in their improvement. Nevertheless, helmets that are currently in use are still affected by forces whose values exceed the ones that are considered to be safe for a firefighter. [ABSTRACT FROM AUTHOR]