Intense Shock Research Articles

Impact of Various High Intensity Earthquake Characteristics on the Inelastic Seismic Response of Irregular Medium-Rise Buildings

In the twenty-first century, the seismic design of buildings seems to have become a fully recognized topic. There are guidelines and standards which should be taken into account by designers in seismic areas. Designers using modern international guidelines have ascertained that the behavior of structures is not as expected. New challenges in the construction industry result in the construction of structures with new, unusual shapes. These are structures that do not meet the assumptions of safe construction in seismic areas. Contemporary buildings are also characterized by their irregular distribution of structural elements. Such solutions are not beneficial from the point of view of seismic engineering and can lead to reduced dynamic resistance and damage in such structures. In this paper, a five-storey, irregular-shaped reinforced concrete (RC) building model was subjected to different earthquakes with varying magnitudes, PGA (peak ground acceleration) and PGV (peak ground velocity) values, and durations of the intense shock phase. Once the model was verified using previous in situ measurements, the building model was subjected to five earthquakes. A numerical nonlinear analysis of the building was performed using a verified FEA (finite element analysis) model in the time domain through non-linear time history analysis with the Broyden–Fletcher–Goldfarb–Shanno (BFGS) method. The building’s dynamic properties were measured using various methods of excitation. The model was influenced, among others, by two far-field representative events caused by the last earthquake in Turkey, which resulted in strong ground motion. The analysis results identified the locations of structural damage and allowed for the assessment of the structure’s dynamic resistance. The results of the calculations prove that the duration of the intensive phase of extortion is one of the reasons for building damage in earthquake-prone areas. Building damage occurs with earthquakes that are characterized by an intensive phase of excitation with a long duration and high values of velocity in the earthquake components. The article highlights the inadequate dynamic resistance of the building, leading to excessive displacements and unfavorable structural solutions. Damage to buildings at this earthquake intensity caused damage to the load-bearing structure, which was not designed for such intensities. This paper is a research report with a specific case study of medium-rise irregular RC buildings.

Quantitative analysis of deformation characteristics and corrosion properties of high energy laser shock peened Ni-based superalloy

This study examines the influence of high-energy laser shock peening (LSP) using 7 J and 10 J pulse energies on the sub-surface deformation characteristics of Inconel 718 superalloy. High-magnitude compressive residual stresses were induced into the samples after LSP with large residual stress depths of the order of 2 mm – the experimental observations were in good agreement with finite element analyses of the LSP process. The propagation of intense shock waves led to an increased strain hardening and dislocation densities that were experimentally quantified by synchrotron diffraction and transmission electron microscopy. Microscopic analyses revealed highly refined grain structure only at the surface without much refinement observed in the residual depth region. Alongside high degree of strain hardening, a profuse amount of adiabatic shear bands was observed in the hardened depth, indicative of simultaneous strain localisation under such high laser pulse energy. These bands occurred along common slip planes in the Ni γ-matrix and could be potential areas of instability leading to failure. The LSP-treated samples exhibited improved corrosion resistance, with higher laser pulse energy peened samples performing better.

Design, Fabrication, and Commissioning of Transonic Linear Cascade for Micro-Shock Wave Analysis

Understanding shock wave behavior in supersonic flow environments is critical for optimizing the aerodynamic performance of turbomachinery components. This study introduces a novel transonic linear cascade design, focusing on advanced blade manufacturing and experimental validation. Blades were 3D-printed using Inconel 625, enabling tight control over the geometry and surface quality, which were verified through extensive dimensional accuracy assessments and surface finish quality checks using coordinate measuring machines (CMMs). Numerical simulations were performed using Ansys CFX with an implicit pressure-based solver and high-order numerical schemes to accurately model the shock wave phenomena. To validate the simulations, experimental tests were conducted using Schlieren visualization, ensuring high fidelity in capturing the shock wave dynamics. A custom-designed test rig was commissioned to replicate the specific requirements of the cascade, enabling stable and repeatable testing conditions. Experiments were conducted at three different inlet pressures (0.7-bar, 0.8-bar, and 0.9-bar gauges) at a constant temperature of 21 °C. Results indicated that the shock wave intensity and position are highly sensitive to the inlet pressure, with higher pressures producing more intense and extensive shock waves. While the numerical simulations aligned broadly with the experimental observations, discrepancies at finer flow scales suggest the need for the further refinement of the computational models to capture detailed flow phenomena accurately.

Fracture toughness and cavitation erosion behavior of Fe-based amorphous composite coatings with Ni-coated Al2O3 addition

Fe-based amorphous composite coatings were prepared on 304 stainless steel substrates using atmosphere plasma spraying (APS), aiming to investigate the effect of Ni-coated Al2O3 particles addition on fracture toughness and cavitation erosion behavior of Fe-based composite coatings. The microstructure, phase composition, elastic modulus, microhardness and fracture toughness of the coating were characterized using scanning electron microscopy with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness tester and nanoindentation. The cavitation erosion behavior of Fe-based coatings was investigated by ultrasonic vibration cavitation method. Fe-based amorphous composite coatings exhibit a characteristic lamellar microstructure and reveal the presence of amorphous phases along with α-(Fe, Cr), NiO, Ni and Al2O3 crystalline phases. When the content of Ni-coated Al2O3 in coating increases from 0 wt% to 3 wt%, there is slight deterioration in porosity from 3.64 % to 4.75 % and fracture toughness from 2.579 MPa·m1/2 to 2.392 MPa·m1/2, yet an increase in microhardness from 925.4 HV0.5 to 1090.3 HV0.5. The composite coating with 3 wt% Ni-coated Al2O3 demonstrates the peak cavitation resistance and its cumulative mass loss is significantly reduced by 36.4 % compared to the pure Fe-based coating. The cavitation erosion failure of Fe-based amorphous composite coatings is predominantly characterized by the brittle fracture mechanism. The fundamental process driving cavitation erosion damage involves the material peeling and coating delamination instigated by intense micro-jet impact and shock wave propagation. The proposed Fe-based amorphous composite coatings can be applied to improve the anti-cavitation performance of components in contact with high-speed fluids, such as ship propellers and centrifugal pump blades.

Fear generalization modulated by shock intensity and protein synthesis inhibitor.

Maladaptive fear responses, including sensitized threat reactions and overgeneralization, contribute to anxiety disorders such as generalized anxiety disorder and post-traumatic stress disorder. Although stress intensity influences the generation and extent of these maladaptive fears, the underlying mechanisms remain unclear. The present study examined whether varying footshock stress intensity and inhibition of protein synthesis have differential effect on fear sensitization and generalization in mice. Mice were subjected to a classic fear conditioning protocol involving five different levels of footshock intensities. Prior to fear acquisition, the protein synthesis inhibitor cycloheximide (CHX) was administered intraperitoneally. Fear sensitization to white noise and fear generalization to tones with frequencies differing from the conditioned tone were assessed at either 2 or 4 days after fear acquisition. The results showed that, although varying shock intensities (except the lowest) led to a similar pattern of increased freezing during auditory cues in fear acquisition, the extent of both fear sensitization and generalization increased with the intensity of the footshock in the following days. As shock intensities increased, there was a proportional rise in sensitized fear to white noise and generalized freezing to tones with frequencies progressively closer to the conditioned stimulus. Mildest shocks did not induce discriminative conditioned fear memory, whereas the most intense shocks led to pronounced fear generalization. Administration of CHX before fear acquisition did not affect sensitized fear but reduced generalization of freezing to tones dissimilar from the conditioned stimulus in the group exposed to the most intense shock. Our results suggest that maladaptive fear responses elicited by varying stress intensities exhibit distinct characteristics. The effect of CHX to prevent overgeneralization without affecting discriminative fear memory points to potential therapeutic approaches for fear-related disorders, suggesting the possibility of mitigating overgeneralization while preserving necessary fear discrimination.

Ion kinetic effects on the formation of intense laser-driven shock waves

The ion kinetic effect on the formation of intense laser-driven collisional shock waves is investigated via hybrid fluid-particle-in-cell simulations. It is found that the ion heat flux dominates the shock formation, which is considerably larger than the electron heat flux in the shock region. The rise of the temperature due to the laser energy deposition drives a heatwave into the overdense plasma, creating an electron–ion energy exchange zone between the critical surface and heat wave front. The heated ions, which are generated at the electron–ion energy exchange zone via the friction force, are found to travel to the high-density region and cause a tail distribution gain. Despite the small quantity, the heated tail ions contribute most of the ion heat flux during the shock formation. Additionally, as the electron heat flux decreases, the population of the heated tail ions is reduced, leading to a fall in the ion heat flux. This results in the delay or even suppression of the shock formation, because the ions are in a non-equilibrium state in the vicinity of the shock region, the ratio of the downstream ion temperature to the upstream ion temperature tends to a modestly decrease in comparison to the theory. The study provides a clear picture of the formation process of laser-driven shock waves.

ЧИСЕЛЬНЕ МОДЕЛЮВАННЯ ПРОЦЕСУ ВПЛИВУ ПРОДУКТІВ ДЕТОНАЦІЇ НА НАДЗВУКОВИЙ ПОТІК ПОВІТРЯ

Currently, there is a large number of control bodies used in modern rocket technol-ogy. Gasdynamic systems are usually used in rocket engines to change the thrust vector, less often - to create asymmetric air flow around the case. But the application of the det-onation process for such scheme can have better energy and dynamic characteristics compared to existing systems. The driving force in such scheme is created not only by the reactive mass force of detonation products ejected from the gas generator, but also by the effect of an intense shock wave on the pattern of supersonic flow around the rocket. Therefore, it is necessary to evaluate the performance and efficiency of the experiment. The purpose of the study is a priori numerical study of the detonation wave effect on the supersonic flow in the nozzle. Modeling was carried out in the Solid Works application software package. The geometric parameters of the model coincide with the experimental model. It is a flat nozzle, one of the walls is longer than the other and imitates the surface of the rocket. Air, accelerating in the nozzle to supersonic speeds with Mach number M=1.3...2, flows around this wall. Setting devices affecting the flow in it, it is possible to investigate their influence and the possibility of creating a lateral (controlling) force. When detonation is used to disturb the flow, an intense shock wave is generated in it, which changes the pres-sure distribution on the wall surface. Some holes for pressure sensors are made in the wall to fix this disturbance over time. A priori numerical modeling was carried out in order to estimate the parameters of the interaction of detonation products with the supersonic air flow. The pressure range and duration of the process have been determined, which allows selection of equipment and planning of the experiment. Patterns of velocity and pressure distribution in the model over time were obtained.

Male and Female Circumcision or Genital Mutilation in Men and Women

Circumcision is the surgical removal of a large section of the male genitalia or the cutting, usually non-surgical, of a large section of the female genitalia. Male and female circumcision implies aggression to the genitals of minors of both sexes, whether due to tradition, social pressures, religious prejudices or business, causing unnecessary damage to the organism of children such as intense pain, fear, bleeding, infection, deformations, sexual dysfunctions, infertility, necrosis, shock, gangrene or death. This vicious cycle must stop worldwide

Long noncoding RNAs heat shock RNA omega nucleates TBPH and promotes intestinal stem cell differentiation upon heat shock

In Drosophila, long noncoding RNA Hsrω rapidly assembles membraneless organelle omega speckles under heat shock with unknown biological function. Here, we identified the distribution of omega speckles in multiple tissues of adult Drosophila melanogaster and found that they were selectively distributed in differentiated enterocytes but not in the intestinal stem cells of the midgut. We mimicked the high expression level of Hsrω via overexpression or intense heat shock and demonstrated that the assembly of omega speckles nucleates TBPH for the induction of ISC differentiation. Additionally, we found that heat shock stress promoted cell differentiation, which is conserved in mammalian cells through paraspeckles, resulting in large puncta of TDP-43 (a homolog of TBPH) with less mobility and the differentiation of human induced pluripotent stem cells. Overall, our findings confirm the role of Hsrω and omega speckles in the development of intestinal cells and provide new prospects for the establishment of stem cell differentiation strategies.

Intense thermal shock generators made of micron-thick SnO2 layers for the on-chip rapid thermal processing in air

Thermal shock-resistant heaters are essential in various electronic devices, including chemical sensors and pyroelectric electron emitters. The advent of ultrafast high-temperature sintering and shock synthesis of nanomaterials has increased the demand for air-operating high-rate joule heaters. Moreover, incorporating such heaters at the chip level would revolutionize current rapid thermal processing methods in semiconductor technology. Here, transparent micron-thick SnO2 resistors are grown by spray pyrolysis on alumina, silica, and oxidized silicon chips and used as thermal shock-resistant air-operating heaters. These heaters can generate repeated heating cycles at rates of 15,000 °C/s up to 900 °C/s. Tin is a group IV element and its impact on Si- and SiO2-based devices is minimal making the presented device silicon compatible. The superior performance of the presented heaters is attributed to the tin oxide’s unique combination of physicochemical properties including high-temperature chemical stability in oxidizing atmospheres, suitable intrinsic conductivity, and optimal negative temperature coefficient of resistance. The application of the SnO2 heaters for the rapid on-chip high-temperature oxidation and sintering of low-melting-point metal thin films, while preserving the metal layer’s nanotexture, is demonstrated.

An overpressure monitoring system based on PVDF integrated Electronic sensor with enhanced noise attenuation capability

The measurement of shockwave overpressure is of great significance for the safe use of explosives. The traditional overpressure monitoring systems are based on Integrated Electronics Piezo-Electric (IEPE) ceramic sensors. However, the brittleness of piezoelectric ceramic limits the application of overpressure monitoring system in high impact overpressure testing. Herein, a novel overpressure monitoring system based on Integrated Electronic Poly (vinylidene fluoride) (PVDF) (PFIE) sensor with electromagnetic interference shielding capability and parasitic vibration noise elimination function was designed for intense overpressure acquiring. PVDF, as a polymer, can endure much higher impact pressures compared to piezoelectric ceramics. However, its larger internal resistance makes it more prone to electromagnetic interference. To address this, an electromagnetic shielding structure was designed, incorporating an impedance matching circuit that effectively reduces the sensor's output impedance. Additionally, to mitigate excessive vibration noise during overpressure testing, the differential noise reduction technique has been implemented. Both the laboratory testing and the real blast testing with 10 kg trinitrotoluene were performed to validate the PFIE overpressure monitoring system. The result shows that the electromagnetic noise suppression ability of the PFIE overpressure sensors developed for the monitoring system was improved by 45 dB, and the parasitic vibration noise could be attenuated from 30 % to 1 %, what’s more the RMS errors of the overpressure dynamic parameters obtained by the monitoring system were below 10 %. This work has successfully addressed the noise sensitivity issue inherent in PVDF when used as a pressure sensor, capitalizing on its robust impact resistance. This approach has provided a viable solution for measuring overpressure in scenarios involving intense shock pressures, leveraging the strengths of PVDF in such demanding applications.

Transportation of mAb Dosing Solution in Intravenous Bag: Impact of Manual, Vehicle, and Pneumatic Tube System Transportation Methods on Product Quality.

Monoclonal antibody (mAb) products for intravenous (IV) administration generally require aseptic compounding with a commercial diluent within a pharmacy. The prepared dosing solution in the IV bag may be transported to the dosing location via manual, vehicular, pneumatic tube system (PTS), or a combination of these methods. In this study, the type and level of physical stresses associated with these three methods and their product quality impact for relatively sensitive and stable mAbs were assessed. Vibration was found to be the main stress associated with manual and vehicle transportation methods, although this was at a relatively low level (<1 GRMS/Root-Mean-Square Acceleration). Shock and drop events, at relatively low levels, were also observed with these methods. PTS transportation showed substantially more intense shock, vibration, and drop stresses and the measured levels were up to 91 G/force of acceleration or deceleration, 3.7 GRMS and 39 G, respectively. Using a foam padding insert for PTS transportation reduced the shock level considerably (91 G to 59 G). Transportation of mAb dosing solutions in IV bags via different methods including PTS transportation variables caused a small increase in the subvisible particle counts and there was no change in submicrometer particle distribution. No visible particles and no significant change to soluble aggregate levels were observed after transportation. Strategies such as removal of IV bag headspace prior to transport and in-line filtration poststress reduced the subvisible particles counts. All tested transportation conditions showed negligible impact on other product quality attributes tested. Removal of IV bag headspace prior to PTS transport prevented formation of micro air bubbles and foaming compared to the unaltered IV bag. This study shows examples where manual, vehicle, and PTS transport methods did not significantly impact product quality, and provides evidence that mAb products that are appropriately stabilized in the dosing solution (e.g., with a surfactant) can be transported via a PTS.

Advancing high-speed flow simulations: SAUSM – an innovative hybrid numerical scheme for shock stability and accuracy

This paper introduces a novel hybrid numerical method, SAUSM, designed for accurate and robust simulation of compressible flows governed by the Euler equations. While the AUSM[Formula: see text] scheme provides proper resolution of smooth flow features, it is susceptible to anomalies, particularly the carbuncle phenomenon near strong shock discontinuities. Conversely, the AUFS scheme offers inherent stability in capturing shocks; however, it lacks the accuracy of AUSM[Formula: see text] in smooth regions. The proposed SAUSM method combines AUSM[Formula: see text] and AUFS through an adaptive weighting function, facilitating a seamless transition between the schemes. This approach preserves the accuracy of AUSM[Formula: see text] in smooth regions while ensuring robust shock-capturing capabilities near discontinuities. The effectiveness of the SAUSM method is rigorously demonstrated through a comprehensive suite of progressively complex test cases. Numerical experiments demonstrate SAUSM’s proficiency in resolving intense shock patterns and discontinuities without introducing anomalies. In the selected test cases, SAUSM agrees with reference solutions and effectively mitigates anomalies observed in AUSM[Formula: see text], including kinked Mach stems. In the challenging test case involving hypersonic blunt body flow over a cylinder, SAUSM adapts dissipation effectively by utilizing its adaptive weighting function to generate smooth pressure distributions, thereby eliminating the carbuncle instability linked to AUSM[Formula: see text] when applied to a high aspect ratio grid. The consistent formulation of flux splitting and the adaptive weighting in SAUSM prevent excessive dissipation away from discontinuities, thus preserving accuracy comparable to that of exact Riemann solvers. Consequently, SAUSM emerges as a promising and innovative approach to accurately and robustly simulate a wide range of compressible Euler flows. The comprehensive results obtained from the validation tests firmly establish SAUSM as a highly effective general-purpose technique for computational fluid dynamics in academic research.

Self-Start Characteristics of Hypersonic Inlet When Multiple Unstart Modes Exist

Intense shock boundary-layer interaction may lead to multiple unstart modes existing in a hypersonic inlet. Thus, self-start problems become complex and cannot be explained using the classical double-solution theory of air inlet. The essence of the self-start process of a hypersonic inlet is the vanishment of separations near or in the inlet. To clarify self-start characteristics, experiments were conducted on three distinct types of unstart mode: the flow mode of small separation on body (SSB), large separation on body (LSB), and dual separations on both body and lip (DSBL); researchers recently discovered these as the unstart modes of hypersonic inlet. The results from the current experiment are as follows: (1) The SSB vanishes by raising the angle of attack (alpha). Before the vanishing point is reached, there is a dwindling process for this separation. (2) The LSB vanishes through acceleration or a decreasing alpha. (3) DSBL are difficult to vanish directly, which results in poor self-start performance. However, the DSBL flow mode may convert to LSB unstart form—which is easier to self-start—by decreasing the alpha. The Flow Field Reconstruction Method was designed to improve the self-start of the DSBL flow mode, and it was validated through experiments. Analysis of the flow mechanism revealed the reason for the poor self-start performance of the DSBL unstart mode: large-scale separation on the lip side cannot be promoted to vanish through broadwise spillage due to the resistance of sideboards. The results of this study could greatly enrich the existing theory of start problems for hypersonic inlets.

Impact of cavity and ramp configuration on the combustion performance of a strut-based scramjet combustor

Abstract The flow performance of a dual wall-mounted cavity in a strut-injector scramjet combustor in steady reacting flow conditions is computationally analyzed. A baseline configuration corresponding to DLR experiments and two proposed configurations with varying bottom wall cavity depth and fixed top wall ramp is considered. Steady-flow computations are performed using the 2-D Reynolds Averaged Navier–Stokes method with k-ω SST turbulence closure coupled and single-step reaction chemistry. The calculated flow patterns, density, pressure, and temperature fields are compared with shadowgraph and wall pressure measurements from DLR experiments. The cavity and strut are mounted downstream of the strut to analyze the shock patterns and their interference with the shear layer mixing features. The estimated flow patterns, density, pressure, and temperature fields are compared with shadowgraph and wall pressure measurements from DLR experiments. Incorporating cavity and ramp configuration provides earlier complete combustion compared to the baseline model, with a marginal rise in the total pressure caused by additional shock wave formation that emanates from the corners of the cavity and ramp. The combustion zone widens in the lateral direction as the cavity shifts the shock train downstream of the strut injector owing to intense shock shear layer interactions.

Effect of ultrasonic intensity on microstructure and mechanical properties of steel alloy in direct energy deposition-Arc

To study the effect of ultrasonic intensity on the microstructure and mechanical properties during the direct energy deposition-Arc (DED-Arc) of ER70S-6 steel alloy, an ultrasound assisted DED-Arc system was developed by coupling ultrasonic energy with the electric arc deposition process. The propagation and vibration distribution of ultrasound in the substrate were analyzed by numerical simulation method. Deposition layers were fabricated using different ultrasonic amplitudes, and the microstructure, microhardness and tensile properties of the fabricated parts were systematically investigated. The results show that as the ultrasonic intensity increased, the grain refinement area expanded from the center of the molten pool to the surrounding area, and the grain morphology transforms from coarse columnar grains to fine equiaxed grains. When the ultrasonic amplitude was 15 μm, the grain refinement area of the cross-section was 94.6%, the average grain size was significantly increased to about grade 6. The microhardness increased by 10.6%. Thousands of ultrasonic cavitation events not only enhance the supercooling and wettability of the melt pool to promote nucleation, but also break the columnar grains into small grains by intense shock waves, which significantly improve the microstructure homogeneity and mechanical properties. The research provides an alternative approach to overcoming the long-standing problem of coarse columnar grains in the field of DED-Arc.

Experimental determination of vibration conductivity by rocket sled structural elements in high-speed track tests of aircraft equipment

The development of new ballistic-type aircraft is characterized primarily by improved aerodynamic characteristics and higher speed limits. Ground track testing of aviation and rocket technology is a stage whose task is to confirm the efficiency and effectiveness of new developments. Track tests make it possible to simulate real loads, they are simpler and much cheaper than flight tests. Experimental installation "Rocket rail track 3500" of Scientific Test Range of Aviation Systems named after L. K. Safronov is constantly being upgraded in order to conduct track tests of products at a speed greater than 3M. The experimental setup includes a two-rail track, made on a special foundation, which excludes unacceptable rail deflection with a mass of up to 3000 kg. The rail track has an acceleration section with an angle of attack 2500 m long and a deceleration section. A tray filled with water is made on the braking section between the track rails. It is designed for hydrodynamic braking to a complete stop of the rocket sled with stored equipment. The movable rocket track sled is made of a massive steel plate to which three cross beams are welded. The front and rear beams end with axles on which sliding supports are pivotally mounted. On the rear and middle beams there are lodgements for fastening rocket engines of solid fuel. Depending on the required test speed, from one to five motors can be placed on the cradles. The test object is usually mounted on the front and middle beams along the axis of the sled and fixed in a cantilever, with the head part extended forward. The design of the supports - shoes is made to encircle the rail head in such a way that it provides sliding contact along the upper plane of the rail head, and in the event of a lifting force exceeding the weight of the sled at high speeds, it keeps the structure from free flight by contacting the lower surface of the rail head. Track high-speed tests of special equipment objects are always accompanied by intense vibration and shock effects of structural elements. Due to the desire to conduct track testing of products at a faster rate, it becomes necessary to reduce the level of dynamic loads and eliminate resonant interactions. The article presents an algorithm and methodology! for statistical processing of random signals of three-axis vibration acceleration sensors installed on the shoes of the rocket track sled and on the fairing of the test object. Due to the placement of registration data storage devices on the sled, experimental vibration data were stored when testing the product at a speed of more than IM. The autocorrelation functions of the signals of vibration accelerations of sensors placed on various elements of the rocket sled, the functions of mutual correlation of the corresponding signals, the density of the amplitude spectra, the density of the power spectra and the transfer functions that characterize the dynamic conductivity of vibrations from the shoes sliding along the rail guides to the test object were determined.

A pilot study examining financial stress during COVID-19 and executive function in mental health in parents and children

Families have endured intense economic shock throughout the COVID-19 pandemic, which may be linked to reduced cognitive performance as well as mental health outcomes of parents and children. The present study investigated how COVID-19-related financial stress and parental job loss impact executive functions and mental health in both parents and adolescents. Participants in the study were 83 adolescent-parent dyads (Adolescent Age M = 13.01 years, SD = 2.27, Parent Age M = 43.26, SD = 5.07) who participated remotely between April 25th and June 1st 2021. Both parents and adolescents completed three measures of executive function and also reported on their mental health symptoms using the MHI-5 and RCADS-short, respectively. Parents also reported on financial stress and whether they or their partner had lost employment during the pandemic (37.8% lost employment). Parental job loss was correlated with greater financial stress (r =.342, p =.002). Financial stress was correlated with worse adolescent inhibitory control (r = -.232, p =.036), but better parent working memory (r =.261, p =.018). Greater financial stress was associated with more mental health symptoms (r =.288, p =.009) for parents, but not adolescents. These results suggest that financial stress may impact child executive function and parent mental health. Further research is needed, as the long-term repercussions of economic stress on mental health and executive functions may become more apparent as the pandemic progresses.

Fast Deflagration-to-Detonation Transition in Helical Tubes

When designing a new type of power plants operating on pulsed detonations of gaseous or liquid fuels, the concept of fast deflagration-to-detonation transition (FDDT) is used. According to the concept, a flame arising from a weak ignition source must accelerate so fast as to form an intense shock wave at a minimum distance from the ignition source so that the intensity of the shock wave is sufficient for fast shock-to-detonation transition by some additional arrangements. Hence, the FDDT concept implies the use of special means for flame acceleration and shock wave amplification. In this work, we study the FDDT using a pulsed detonation tube comprising a Shchelkin spiral and a helical tube section with ten coils as the means for flame acceleration and shock amplification (focusing), respectively. To attain the FDDT at the shortest distances for fuels of significantly different detonability, the diameter of the pulsed detonation tube is taken close to the limiting diameter of detonation propagation for air mixtures of regular hydrocarbon fuels (50 mm). Experiments are conducted with air mixtures of individual gaseous fuels (hydrogen, methane, propane, and ethylene) and binary fuel compositions (methane–hydrogen, propane–hydrogen, and ethylene–hydrogen) at normal pressure and temperature conditions. The use of a helical tube with ten coils is shown to considerably extend the fuel-lean concentration limits of detonation as compared to the straight tube and the tube with a helical section with two coils.

Mental Health Status Of A Population During COVID-19 Pandemic in Bangladesh: A Cross-Sectional Study

Background: The current Pandemic situation has the potential to impact mental health unfavourably. As a by and large new infection, much still needs to be had some significant awareness of Coronavirus. Following openness to the SARS-CoV-2 infection contamination, the vast majority of the people stay asymptomatic or foster gentle indications. Coronavirus cases can make complexities that will require hospitalization. Coronavirus patients revealed conditions like intense respiratory pain disorder, cardiovascular breakdown, liver harm, renal disappointment, shock, and multiorgan disappointment. During the current Coronavirus pandemic, general clinical issues have pulled in more highlight. Diverged from that, the psychological wellness outcomes of Coronavirus pandemic have gotten less thought. Methods: This study will follow a cross-sectional study aimed to determine the prevalence of depression, anxiety, and stress during the initial stage of the COVID-19 pandemic among the Bangladeshi population. Results:Self-reported information on socio-demographics, illness and mental health status was obtained predominantly through a Facebook-based Coronavirus related page named 'Coronabarta' from 30th April to eight May 2020. Mental health status was assessed using the Depression, Anxiety and Stress Scale (DASS-21). A total of 420 individuals participated in this study who were relatively young and highly educated. The study finding suggests that COVID-19 pandemic may increase the risk of depression, anxiety, and stress in Bangladesh. The prevalence of depression, anxiety, and stress were 46.7% (95% Confidence Interval, CI:42.1% - 51.8%), 39.1(95% CI:34.3% – 43.9%), and 34.8% (95% CI:30.2 – 39.5%), respectively. Females and individuals with physical illness are at higher risk of developing adverse psychological consequences. Gossiping with family members is protective against depression (OR: 0.5, 95% CI:0.3 – 0.7). Watching television reduces stress (OR:0.6, 95% CI:0.4-0.9). Large cohort studies are recommended to confirm the association between COVID-19 pandemic and adverse mental health status. Necessary measures should be considered to improve psychological well-being during the COVID-19 pandemic. Conclusion: To find out the mental health status of the population during COVID-19 pandemic in Bangladesh, this study finding may form a basis for the development of a mental health support strategy in Bangladesh. Bangladesh Medical Res Counc Bull 2022; 48(3): 195-202