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To adapt to higher and steeper slope environments, this paper proposes a new type of support structure called an anchored frame pile. The study designed and conducted a series of shaking table tests with three-way loading. The acceleration field of the slope, bedrock and overburden layer vibration variability, Fourier spectra, pile dynamic earth pressure, anchor cable force, and damage were analyzed in detail. The results indicate that the overall effectiveness of anchored frame piles for slope reinforcement is superior, and the synergistic impact of front and back piles is evident. Anchor cables effectively reduce the variability of bedrock and overburden layer vibrations. A zone of acceleration concentration always exists at the shoulder of a slope under seismic action. The dominant Fourier frequency in the Y direction of the slope is 11.7687 Hz under Wolong seismic, and the high-frequency vibrations of the upper overburden layer are significantly stronger than those of the bedrock. Slopes under 0.4 g earthquakes first form cracks at the top and then expand downward through them. Under seismic action, the peak dynamic earth pressure in front of the front pile occurs near the bottom of the pile, and the dynamic earth pressure behind the pile occurs near the slip surface. The peak dynamic earth pressure of the back pile occurs at the top of the bedrock. The slope damage is significant at 0.6 g. At this point, the peak dynamic soil pressure at the top of the front pile measures 9.5 kPa, while the peak dynamic soil pressure at the bottom reaches 24.3 kPa. Below the sliding surface of the front pile and on top of the bedrock of the back pile are the critical areas for prevention and control. Elevating the prestressing of the anchor cables will help enhance the synergy between the anchor cables and the piles. Simultaneously, it will reduce the variability of vibration in the bedrock and overburden, thereby improving the stability of the slopes. [ABSTRACT FROM AUTHOR]

Plasma flows with enhanced dynamic pressure, known as magnetosheath jets, are often found downstream of collisionless shocks. As they propagate through the magnetosheath, they interact with the surrounding plasma, shaping its properties, and potentially becoming geoeffective upon reaching the magnetopause. In recent years (since 2016), new research has produced vital results that have significantly enhanced our understanding on many aspects of jets. In this review, we summarise and discuss these findings. Spacecraft and ground-based observations, as well as global and local simulations, have contributed greatly to our understanding of the causes and effects of magnetosheath jets. First, we discuss recent findings on jet occurrence and formation, including in other planetary environments. New insights into jet properties and evolution are then examined using observations and simulations. Finally, we review the impact of jets upon interaction with the magnetopause and subsequent consequences for the magnetosphere-ionosphere system. We conclude with an outlook and assessment on future challenges. This includes an overview on future space missions that may prove crucial in tackling the outstanding open questions on jets in the terrestrial magnetosheath as well as other planetary and shock environments. [ABSTRACT FROM AUTHOR]

Mars Atmosphere and Volatile EvolutioN (MAVEN) mission reveals the existence of magnetosheath jets in the Martian plasma environment. The jets, which contrast with the surrounding plasma in the magnetosheath region, are transitory, locally limited plasma structures with high dynamic pressure. For the first time, MAVEN's high-time resolution burst mode data are utilized to analyse plasma waves in these jets. Our investigation reveals the simultaneous presence of solitary waves, double layers, electron acoustic waves, and mirror modes. These waves in the Martian magnetosheath jets show similar wave characteristics to those observed in the Earth's magnetosheath jets. These plasma wave observations will help us comprehend the genesis of jets in the Martian plasma environment as they are carriers of momentum and energy across different regions. [ABSTRACT FROM AUTHOR]

In this study, we optimized design of a series of sports leggings O1/O2/O3 with graded pressures, evaluated a mannequin static, four-subjects static and dynamic dressing pressure, and compared with the commercial L-brand sports leggings L1/L2/L3. The results showed that the optimized design sports leggings had lower dressing pressure at the waist, abdomen, and hip than the commercial sports leggings, in which the dressing pressure of a mannequin static, four-subjects static and dynamic at the pressure-significant hip point P8 were reduced by 2.34–14.02%, 16.26–21.78%, and 5.26–11.88%, respectively. The four circumferential directions P4–7, P9–12, P13–16, and P17–20 from the groin to the ankle showed graded pressure trends, while the pressure of commercial sports leggings fluctuated with no significant pattern. In addition, the blood flow of O1/O2/O3 was higher than that of when naked and L1/L2/L3 in both static and dynamic dressing. The blood flow showed a decreasing trend with time, but O1/O2/O3 still had a relatively large blood flow, especially wearing O1 (76.671 PU, 64.054 PU) had a significant dynamic blood flow in both time stages, which had a positive effect on the promotion of blood circulation of the legs. L1/L2/L3 had lower blood flow in the inner calf P15 than when naked, a condition that may inhibit blood flow in the legs and lead to increased fatigue in the human legs, which is detrimental to physical exercise and human health. [ABSTRACT FROM AUTHOR]

Using observations of mass density inferred from standing Alfvén wave frequencies and electron density inferred from plasma wave frequencies, predominantly for the Combined Release and Radiation Effects Satellite (CRRES) and Van Allen Probes spacecraft, we used symbolic nonlinear regression to find analytical formulas for the equatorial electron density, n e , mass density, ρ m , and average ion mass, M ≡ ρ m / n e . We separate the data into plasmasphere and plasmatrough populations based on the observed values of n e in order to find formulas for plasmasphere, plasmatrough, and both plasmasphere and plasmatrough. Our models depend on position, the solar extreme ultraviolet (EUV) F10.7 flux, geomagnetic activity parameters such as Kp, AE, Dst, and the solar wind dynamic pressure. Formulas for M are presented with or without n e as an input parameter. By examining formulas of varying complexity, we are able to determine the relative importance of the various dependencies. The most important dependencies for n e and ρ m are that they decrease with respect to L shell and geomagnetic activity as specified by parameters such as Kp. The most important dependence of M is that M increases with respect to increasing F10.7. The value of M is close to unity within the plasmasphere, but can be significantly above 1 in the plasmatrough. Although n e and ρ m have maximum value at dusk local time, M has maximum value at dawn local time. The O+ concentration is larger at dawn local time, but the O+ density can be comparable at dawn and dusk because of larger n e at dusk. [ABSTRACT FROM AUTHOR]

Background: This study compared the ventilatory variables and computed tomography (CT) features of patients with coronavirus disease 2019 (COVID-19) versus those of patients with pulmonary non–COVID-19-related acute respiratory distress syndrome (ARDS) during the early phase of ARDS. Methods: This prospective, observational cohort study of ARDS patients in Taiwan was performed between February 2017 and June 2018 as well as between October 2020 and January 2024. Analysis was performed on clinical characteristics, including consecutive ventilatory variables during the first week after ARDS diagnosis. Analysis was also performed on CT scans obtained within one week after ARDS onset. Results: A total of 222 ARDS patients were divided into a COVID-19 ARDS group (n = 44; 19.8%) and a non–COVID-19 group (all pulmonary origin) (n = 178; 80.2%). No significant difference was observed between the two groups in terms of all-cause hospital mortality (38.6% versus 47.8%, p = 0.277). Pulmonary non–COVID-19 patients presented higher values for mechanical power (MP), MP normalized to predicted body weight (MP/PBW), MP normalized to compliance (MP/compliance), ventilatory ratio (VR), peak inspiratory pressure (Ppeak), and dynamic driving pressure (∆P) as well as lower dynamic compliance from day 1 to day 7 after ARDS onset. In both groups, non-survivors exceeded survivors and presented higher values for MP, MP/PBW, MP/compliance, VR, Ppeak, and dynamic ∆P with lower dynamic compliance from day 1 to day 7 after ARDS onset. The CT severity score for each of the five lung lobes and total CT scores were all significantly higher in the non–COVID-19 group (all p < 0.05). Multivariable logistic regression models revealed that Sequential Organ Failure Assessment (SOFA) score was independently associated with mortality in the COVID-19 group. In the non–COVID-19 group, body mass index, immunocompromised status, SOFA score, MP/PBW and total CT severity scores were independently associated with mortality. Conclusions: In the early course of ARDS, physicians should be aware of the distinctions between COVID-19-related ARDS and non–COVID-19-related ARDS in terms of ventilatory variables and CT imaging presentations. It is also important to tailor the mechanical ventilation settings according to these distinct subsets of ARDS. [ABSTRACT FROM AUTHOR]

Pulsation noise in the piping system generated by the excitation of the pump source seriously affects the reliability of the pipeline system and mechanical equipment. The active noise control can effectively suppress the low-frequency noise in the liquid-filled pipeline. Active control methods with intrusive secondary sources generally use dynamic pressure sensors or hydrophones to collect signals, which destroy the structure of the pipe. In this paper, we propose an active noise control method utilizing signals acquired by accelerometers, which adopts offline modeling of the secondary path and the notch narrowband FxLMS algorithm for controlling the secondary source actuation. The feasibility of this method is verified by LabVIEW simulation and active noise control test of the liquid-filled pipeline. The test results show that this method can achieve more than 4 dB reduction for low-frequency (10~200 Hz) line spectrum noise under most operating conditions. [ABSTRACT FROM AUTHOR]

Wind tunnel test results can be influenced by various factors such as the blockage ratio and scaling ratio. These factors may introduce errors in the experimental outcomes, impacting the accuracy and reliability of the data obtained. This study quantitatively assesses consistency and identifies uncertainty sources to enhance result uniformity across various wind tunnel laboratories. This study conducted a systematic comparison between different wind tunnels in terms of rigid model pressure measurement wind tunnel experiments on the same Commonwealth Advisory Aeronautical Research Council (CAARC) standard tall building model. The study analyzes and discusses the results of mean and root-mean-square (RMS) wind pressure coefficients, peak factors, extreme wind pressure coefficients, probability density distributions, and base overturning force coefficients. The results indicated that in the open-circuit wind tunnel laboratory, the mean wind pressure coefficient is underestimated in the positive pressure region and overestimated in the negative pressure region. This is due to the static pressure which significantly decreases the streamwise direction within the test section, and the difference in static pressure is logarithmically proportional to the mean wind speed. Additionally, dynamic pressure is uniformly distributed along the test section axis. The inaccurate measurement of static pressure leads to these results. To address this issue, an indirect measurement method was employed to correct the static pressure results and reduce the error in the mean wind pressure coefficient to within 10%. Furthermore, differences in turbulence integral scale result in an error of up to 16% in the RMS wind pressure coefficient. Therefore, when conducting rigid model pressure measurement wind tunnel experiments, especially in open-circuit wind tunnel laboratories, careful consideration should be given to the influence of static pressure drop and integral length scale of turbulence. [ABSTRACT FROM AUTHOR]

Prokaryotes (Bacteria and Archaea) encode a highly diversified arsenal of defence systems that protect them against mobile genetic elements, such as phages and plasmids. In turn, mobile genetic elements encode anti-defence systems that allow them to escape the activity of these defence systems. This has resulted in an evolutionary arms race in which defence systems and anti-defence systems evolve and adapt continuously, driving intriguing innovation and enormous diversification on both sides. Over 150 prokaryotic defence systems have been identified to date. Anti-defence systems are known for only a subset of these, but more are being discovered at a steady rate. Despite an increasing understanding of the highly diverse molecular mechanisms of anti-defence systems, their diverse evolutionary origins, the selective pressures they are subjected to, and their ecological importance and implications often remain obscure. In this review, we describe the diverse strategies that phage and plasmid anti-defence systems employ to escape host defence systems. We explore the evolutionary origins of anti-defence systems and describe different factors that exert selective pressure, affecting their maintenance and diversification. We describe how, in turn, defence systems themselves evolved to act upon anti-defence mechanisms, thereby adding a new layer to the co-evolutionary battle between prokaryotes and their mobile genetic elements. We discuss how the continuous selective pressures found in dynamic microbial communities promote the retention and diversification of these anti-defence systems. Finally, we consider the ecological implications for both hosts and their mobile genetic elements, noting how the balance of defence and anti-defence strategies can shape microbial community composition, influence horizontal gene transfer, and impact ecosystem stability. In this Review, Niault et al. discuss how anti-defence systems allow phages and plasmids to escape prokaryotic defence systems, with a focus on their evolutionary origins, the selective pressures that promote their retention and diversification, and the ecological factors that influence their interactions with defence systems. [ABSTRACT FROM AUTHOR]

This work investigates the effect of a number of perforated fin configurations on the convective flow characteristics within a heated trapezoidal channel. By improving the flow characteristics, pressure distribution, velocity profiles, and temperature patterns, it is intended to investigate optimum performance by using different geometrical fin designs. Numerical simulations are performed for solid and perforated fins with Reynolds numbers from 100 000 up to 200 000. Most importantly, the results highlight that perforations cause significant changes in flow behavior, such as the formation of distinct recirculation zones and dynamic pressure profile variations, which influence the thermal characteristics. This study identifies that optimization of perforated fin geometries is a key strategy to achieve high efficiency in thermal management systems for effective cooling of engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, an unsteady Reynolds-averaged N–S equations (URANS) method is developed to calculate the surge dynamic process of compressor. Using this method, the surge dynamic process of a four-stage high-speed axial compressor at 70% design speed under different B parameters is numerically simulated. The simulation results show that the classical surge is induced when the B parameter is 0.35 and 0.4, and the deep surge is induced when the B parameter is 1.0 and 1.44. The surge frequency decreases with the increase in the B parameter, and the surge frequency obtained when the B parameter is 1.44 is very close to the experimental results. The body-force model (BFM) is another numerical simulation method with low computational cost and can capture the details of the flow field to a certain extent. For the same high-speed four-stage compressor, under the condition that the surge frequency is almost the same as that in the experiment, the calculation results of the surge dynamic process by the URANS method and the previously developed BFM are compared. The results show that the prediction of the dynamic pressure of the wall by the two methods is in good agreement with the experimental data, and the two methods have also achieved similar results in the prediction of the blade force. The meaningful comparison results show that the URANS method can be used as a supplement to the experiment in many aspects and provide more abundant calibration data for the further development of BFM. [ABSTRACT FROM AUTHOR]

The objective of this research is to delve into the leakage, deflection, and oscillation characteristics of brush seals. To achieve this, the flow characteristics of a brush seal were first analyzed through numerical simulation. Subsequently, a static brush seal test rig was utilized to measure the leakage performance and hysteresis characteristics of brush seals with varying geometric structures under pressure ratios ranging from 1.1 to 3.8. The deflections of bristle during operation were observed using an endoscope, and dynamic pressure sensors were employed to collect data on the airflow dynamic pressure in the free end area of bristles, facilitating the analysis of bristle oscillation characteristics. The results indicated that considering the parameters of this study, the leakage increases with the rise in pressure ratio and radial gap. The long front plate configuration was found to contribute to an increase in leakage. Specifically, under the three radial gap conditions of 0, 0.1, and 0.2 mm, the maximum leakage difference between brush seals with and without the front plate configuration was 4.9%, 4.6%, and 2.6%, respectively. The increase in radial gap and the existence of the front plate were observed to diminish the hysteresis effect of brush seals. At a pressure ratio of π = 2.0, the hysteresis indicator H for structures with a radial gap of 0.2 and 0.1 mm decreased by 45.5% and 63.6%, respectively, compared to the 0 mm gap structure. The existence of the front plate resulted in a 33.3% reduction in H compared to its absence. Additionally, an increase in pressure ratio and radial gap was correlated with an increase in brush oscillation frequency. Under identical pressure ratio conditions, brush seals with the front plate also exhibited higher brush oscillation frequencies than those without. [ABSTRACT FROM AUTHOR]

The pilot stage plays a crucial role in central-staged combustion technology. This study aimed to investigate the impact of the jet-type pilot stage on the flame structure and combustion instability in a novel strong coupled centrally staged swirl gas turbine combustor, using both experiments and large eddy simulations (LES). Nonlinear dynamic analyses of dynamic pressure, including phase and recurrence plots, were performed alongside a proper orthogonal decomposition of the dynamic flame structures. It is indicated that a richer pilot stage worsens the instability of the centrally staged combustion system. An increase in the equivalence ratio of the pilot stage leads to enhanced non-premixed combustion and a downstream shift in the heat release region. The transition results in the shift of flame shape from an attached V-shaped flame to an intermittent lifting U-shaped flame. The flame surface statistics from LES results including the strain rate and progress variable gradient of lean and rich pilot conditions were compared. Under richer pilot conditions, the lifting U-shaped flame demonstrates increased sensitivity to flow field fluctuations, intensifying vortex–flame interactions. This interaction causes the large-scale flame surface stretching and even extinction of the pilot stage flame, exacerbating combustion instability observed in this study. These insights offer a deeper understanding of the impact of the jet-type pilot stage on the novel multi-staged central combustion systems. [ABSTRACT FROM AUTHOR]

The object of this article is two parallel underwater vehicles with ventilated partial cavitation, which results in partial deformation of the ventilated cavity and is accompanied by nonlinear changes in the internal flow structure. In our experiments, a high-speed camera system was used to observe transient cavity evolution, and dynamic pressure measurement systems were employed to measure pressure fluctuations under different ventilation flow rates and parallel distances. The results indicated that cavity evolution goes through three stages after ventilation begins: the growth stage, the shortening stage, and the periodic shedding stage, with their periods being influenced by different variables. The dominant frequencies of grayscale variation in the three stages are significantly different, as are the pressure variations. Moreover, the dominant frequency of periodic shedding in the two cavities decreases as ventilation flow rates increase. A critical distance of d* = 1.6 was identified under the experimental conditions, which differentiates the pressure fluctuation characteristics at different parallel distances. Furthermore, the two main mechanisms of pressure fluctuation during the periodic shedding stage were clarified. [ABSTRACT FROM AUTHOR]

This numerical study investigates the collapse of various arrangements of gas bubbles immersed in water in the vicinity of a rigid wall and impacted by a planar shock wave. Multiple bubble configurations, from 2 to 5 bubbles, are compared, focusing primarily on the pressure loads on the wall and the potential amplification in comparison with the single-bubble case. The three-dimensional simulations are performed using a massively parallel compressible diffuse interface solver. The effects of the grid resolution and the mass transfer term are discussed. The main characteristics of the flows are described, and the dynamic behaviors in pressure wave propagation are illustrated. A power-law is proposed for the evolution of the maximum pressure peak on the wall as a function of the density ratio of the bubble array. An amplification of a factor 30 is highlighted for a pyramidal arrangement. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative approach to optimizing flight corridors under complex constraints, particularly focusing on the Terminal Area Energy Management (TAEM) phases of reusable vehicles, where nominal trajectories may be inadequate due to initial condition and aerodynamic deviations. Leveraging the elegant principles of symmetry, the proposed optimal flight corridor design method, based on the Lagrange multiplier technique, offers a harmonious balance between trajectory accuracy and adaptability. By describing the TAEM flight corridor through a range–altitude profile and utilizing iterative optimization to uphold physical constraints such as dynamic pressure, overload, and roll angle, this method ensures symmetrical alignment of the design parameters. Through a comprehensive analysis of aerodynamic and initial position uncertainties, this method showcases exceptional symmetry in adapting to trajectory design uncertainties. The simulation results demonstrate the resilient nature of the designed flight corridor, capable of seamlessly accommodating initial state deviations and aerodynamic uncertainties. This symmetrical optimization of flight corridors not only enhances trajectory planning and control capabilities during the terminal energy management phase, but also showcases a paradigm shift towards precision and balance in aerospace engineering. Our simulation findings underscore the efficiency of this approach by reducing the flight corridor range by 50% compared to the nominal state while maintaining robustness across deviation conditions, embodying the symmetrical resilience needed for optimal trajectory design. [ABSTRACT FROM AUTHOR]

Introduction: In this study, we use 7 years (2012–2019) of pitch angle resolved electron flux measurements from Van Allen Probe-B spacecraft to study the variation of near-equatorial pitch angle distributions (PADs) of outer radiation belt (L ≥ 3) relativistic electrons (E ≥ 0.5 MeV) with different levels of geomagnetic activity. Methods: We calculate a pitch angle anisotropy index (PAI) to categorize the PADs into three types: pancake, PAI ≥ 1.05; butterfly, PAI ≤ 0.95; and flattop, 0.95 < PAI < 1.05. Results and Discussion: Our statistical results show that L shells ≥ 5 are dominated by pancake PADs on the dayside (9 < MLT < 15), butterfly PADs on the nightside (21 < MLT < 3), and flattop PADs in the dawn (3 < MLT < 9) and dusk (15 < MLT < 21) sectors, across almost all relativistic energies. In the inner L shells, the pancake and flattop PADs exhibit dependence on both L-shell and energy, with the occurrence rate increasing with decreasing L and increasing energy. For the butterfly PADs, we discovered a second population of low-L butterflies that are present at almost all local times. When the variation of electron PAI is compared with solar wind dynamic pressure P dyn and geomagnetic indices SYM-H and AL, P dyn is found to be the dominant parameter in driving the outer radiation belt pitch angle anisotropy. During periods of enhanced P dyn , pancake PADs on the dayside become more 90 ° -peaked, butterfly PADs on the nightside exhibit enhanced flux dips around 90 ° pitch angle along with an enhanced azimuthal and radial extent, and flattop PADs turn into either pancake or butterfly PADs. [ABSTRACT FROM AUTHOR]

The translational effects of gas streams, which form after the triple-shock configurations at Mach reflection of blast waves with normal main shock (so-called stationary Mach configurations), were analyzed. Unlike in the case of an elevated explosions of fuel as rocket starts in initially stagnant air, which is considered here as a private case, it was supposed that this shock-wave structure moves in a preceding flow with arbitrary velocity (and corresponding flow Mach number). Analyzing relations of the dynamic pressures across the slipstream, which emanates from the triple point of the Mach reflection, it was shown that the flows after the triple-shock configuration usually differ much in their translational action on surrounding objects. It was found and discussed that some configurations drag the objects initially situated above and below the triple-point trajectory in opposite directions. Moreover, the "trigger" structure was found that remains previous flow drag action on the object above the triple-point trajectory, but switches it to exactly opposite one, if the object is situated below the triple point. • Triple-shock configurations appear at the internal blast inside of a spaceship. • They divide gas stream into two regions with very different velocity pressures. • Blast safety of an object aboard depends on its position above or below triple point. • Triple configurations are found with extreme drag force above or below the slipstream. • Some of them drag objects above and below the slipstream in opposite directions. [ABSTRACT FROM AUTHOR]

With the improvement of dry gas seal efficiency in high-parameter fields, the flow pattern of gas film lubrication is complicated. Based on gas lubrication theory, the Reynolds equation of compressible gas was established with a bidirectional T-groove dry gas seal as the research object. The Reynolds equation was solved to obtain a modified turbulent film pressure distribution law that affects gas lubrication. The effectiveness of the calculation program was verified by experimental tests. The results show that with an increase in operating parameters, the turbulence effect caused the gas film pressure fluctuation in the T-groove region to intensify, resulting in gas film flow instability. In addition, the inertia effect improved, which slowed down the leakage and affected the change law of stiffness and the rigid leakage ratio. When the fluid speed and gas pressure were low, the inertia effect could be ignored. When the groove depth was increased to 8 μm, the height difference between the trough and non-T-groove region became larger due to the combination of the turbulence and inertia effects. Further, when the gas film thickness was 3 μm, the opening force and gas film stiffness were high due to the dynamic pressure effect in the small film thickness groove. An increase in the gas film thickness weakened the turbulence effect and reduced the gas film pressure fluctuation. [ABSTRACT FROM AUTHOR]

Deep shale formations pose significant challenges in forming high-conductivity fractures, leading to low ultimate recoverable reserves (EUR) per well under conventional fracturing techniques. Dense-cutting fracturing is a commonly employed method to enhance the EUR of individual wells; however, the critical process parameters influencing EUR remain unclear. This study develops a novel EUR calculation model tailored for deep shale gas dense-cutting, integrating the Warren-Root model with the constant-volume gas reservoir material balance equation. The model comprehensively incorporates Knudsen diffusion and adsorption-desorption phenomena in deep shale gas, corrects apparent permeability, and employs the finite element method to simulate dynamic pressure depletion during production. The study examines the impact of fracture half-lengths, cluster spacing, fracture conductivity and horizontal section lengths on EUR under tight-cutting fracturing. Orthogonal experiments combined with multiple linear regression analysis reveal the hierarchy of influence among the four factors on EUR: horizontal section length > fracture half-length > cluster spacing > fracture conductivity. The study derives EUR correlation expressions that incorporate the effects of crack half-length, cluster spacing, fracture conductivity, and horizontal segment length. The orthogonal experimental results indicate that EUR exhibits positive correlations with crack half-length, fracture conductivity, and horizontal segment length, while showing a negative correlation with cluster spacing. The multiple regression equation achieves a coefficient of determination (R2) of 0.962 and an average relative error of 3.79%, outperforming traditional prediction methods in both accuracy and computational simplicity. The findings are of substantial significance for the rapid estimation of EUR in individual wells following deep shale gas fracturing and offer valuable theoretical insights for practical engineering applications. [ABSTRACT FROM AUTHOR]

This paper aims to address the issue of hydraulic support crushing accidents or support failures in the retracement roadway (RR) that frequently occurs when a fully mechanized mining face is retraced during the end-mining stage. The deformation and instability mechanism of surrounding rock in the RR during the end mining of a fully mechanized mining face at the Hanjiawan Coal Mine located in the northern Shaanxi mining area is explored through field measurement, theoretical analysis, similar simulation, and numerical simulation. The results reveal that the stability of the remaining coal pillar (RCP) and the fracture position of the main roof are the main factors contributing to large-scale dynamic load pressure in the RR during the end-mining stage. The plastic zone width limit of the RCP is identified to be 5.5 m. Furthermore, the stress distribution within the RCP during the end-mining stage is determined, and the linear relationship between the load borne by the RCP and the strength of the coal pillar is quantified. A similar simulation experiment is conducted to examine the collapse and instability characteristics of the overlying rock structure during the end-mining stage. UDEC (v.5.0) software is utilized to optimize the roof support parameters of the RR. A surrounding rock control technology that integrates the anchor net cable and hydraulic chock is proposed to ensure RR stability. Meanwhile, a method involving ceasing mining operations and waiting pressure is adopted to ensure a safe and smooth connection between the working face and the RR. This study provides a reference for the surrounding rock control of the RR during end mining in shallow, closely-spaced coal seams under similar conditions. [ABSTRACT FROM AUTHOR]

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We investigated, for the first time, the impact of the disappearing solar wind (DSW) event [26–28 December 2022] on the deep nightside ionospheric species using MAVEN data sets. An enhanced plasma density has been observed in the Martian nightside ionosphere during extreme low solar wind density and pressure periods. At a given altitude, the electron density surged by ∼2.5 times, while for ions (NO+, O2+, CO2+, C+, N+, O+, and OH+), it enhanced by > 10 times, respectively, compared to their typical average quiet‐time periods. This investigation suggests that an upward ionospheric expansion likely took place in a direct consequence to the contrasting low dynamic/magnetic pressure and relatively higher nightside ionospheric pressure (by 1–2 orders) causing an increased ionospheric density. Moreover, the day‐to‐night plasma transport may also be a contributing factor to the increased plasma density. Thus, this study offers a new insight about planetary atmosphere/ionosphere during extreme quiescent solar wind periods. Plain Language Summary: The evolution of the Mars climate over time depends upon the solar wind‐Mars interactions. The varying activity over the Sun intermittently produce extreme low density solar wind or also called as disappearing Solar Wind (DSW), which can affect the planetary environment in many ways. Beyond Earth, the effect of DSW on other planetary atmospheres is not well studied. In order to understand this aspect, we have explored the behavior of Martian nightside plasma environment (species: e−, NO+, O2+, CO2+, C+, N+, O+, and OH+) during the DSW event. A dense ionosphere is observed during DSW compared to non‐DSW periods. During DSW, the magnitude of peak nightside electron and ions density are increased by ∼2.5 and more than 10 times, respectively compared to their typical average quiet‐time scenario. The higher plasma density could be due to an expansion from the lower to the topside ionosphere, in consequence to the higher ionospheric pressure as compared to the low solar wind pressure. Furthermore, it could also be enhanced by the transport of plasma from dayside to nightside. Hence, this study, for the first instance, guides us to a new understanding of the impact of a rarest solar wind phenomenon on the Martian ionosphere. Key Points: An increased plasma density is observed in the nightside ionosphere during the disappearing solar wind periods around MarsThe electron and ions abundance surged by a factor of ∼2.5 and >10 respectively, compared to the average quiet‐time periodsThe contrast between the higher nightside ionospheric pressure and the dynamic/magnetosheath pressure led to increased plasma densities [ABSTRACT FROM AUTHOR]

The Martian magnetotail is largely controlled by the solar wind (SW) and is modulated by variations in the upstream drivers. However, due to the limitations of single‐spacecraft observations, the effects of SW variations on the Martian magnetotail have not been fully understood so far. Here, using Tianwen‐1 and MAVEN data, we report for the first time the rapid response of Martian magnetotail to the SW disturbance. In our study, Tianwen‐1 detected the flapping of Martian magnetotail, while MAVEN monitored disturbances in the upstream SW. The results indicate that a 20% increase (or decrease) in SW dynamic pressure and a 30° (or 50°) rotation of interplanetary magnetic field clock angle could cause the Martian magnetotail to swing rapidly. These two SW disturbances could lead to oscillations of the Martian magnetotail. This study reveals the importance of joint observations for studying the interaction between the SW and Mars. Plain Language Summary: Mars lacks an intrinsic global magnetic field and as a result solar wind (SW) interacts directly with its ionosphere and atmosphere, leading to a high dependence of the Martian induced magnetosphere on SW conditions. Understanding the interaction between the SW and Mars can provide critical information for studies of planetary evolution, especially the effect of the SW on the Martian magnetotail. In previous studies, using single satellite observations, we limit ourselves to studying some local physical processes or statistical properties. Here, based on the joint measurements by Tianwen‐1 and MAVEN, we observed the rapid response of Martian magnetotail to the SW disturbance, finding that a 20% increase (or decrease) in SW dynamic pressure and a 30° (or 50°) rotation of IMF clock angle could cause the Martian magnetotail to swing rapidly. These two SW disturbances could lead to oscillations of the Martian magnetotail. These results can help us understand the SW interaction with the Martian induced magnetosphere. Key Points: We report for the first time the rapid response of Martian magnetotail to the solar wind (SW) disturbance by using Tianwen‐1 and MAVEN dataA 20% increase (or decrease) in PSW and a 30° (or 50°) rotation of interplanetary magnetic field clock angle could cause the Martian magnetotail to swingThese two SW disturbances could lead to oscillations of the Martian magnetotail [ABSTRACT FROM AUTHOR]

Water flows through microscopic orifices have attracted much research interest recently because of their many potential industrial, biological, and medical applications, as well as their importance in the physics of fluids. In this study, by using circular nickel micro-orifices with diameters of 5–100 µm and applying pressures from 0.5 Pa to 0.6 MPa, the following anomalies were revealed. The velocity of water flowing through the 5–25 µm micro-orifices was 1.4–2.5 times higher than that through macro-orifices under low pressures and was close to the velocity of inviscid fluid under high pressures. The pressure divided by the dynamic pressure was frequently independent of the thickness of the orifice and close to that of the infinitely thin orifice under low pressures, whereas it was almost unity under high pressures. Notably, the flow rate often decreased gradually or steeply to negative values under applied pressures, whereupon either nickel or nickel and organic substances were found in and around the orifice. The velocity through the circular polyimide micro-orifice was substantially lower than that through macro-orifices, and a polyimide-like substance developed in the orifice. The effect of the organic substances found in the orifice on the flow properties was discussed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology 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.)

The lunar environment heliospheric X-ray imager (LEXI) and solar wind–magnetosphere–ionosphere link explorer (SMILE) will observe the magnetopause motion in soft X-rays to understand dayside reconnection modes as a function of solar wind conditions after their respective launches in the near future. To support their successful science mission, we investigate the relationship between the magnetopause position and the dayside reconnection rate by utilizing super dual auroral radar network (SuperDARN) observations and widely used empirical models of magnetopause position (Shue et al. in J Geophys Res 103:17691–17700. https://doi.org/10.1029/98JA01103, 1998 and Lin et al. in J Geophys Res 115:A04207. https://doi.org/10.1029/2009JA014235, 2010). We select three cases when the interplanetary magnetic field rotates during periods of quasi-steady solar wind dynamic pressure. We first estimate the dayside reconnection rate by calculating the electric field along the open–closed magnetic field boundary (OCB) in the OCB moving reference frame. Then, we estimate the magnetopause position near the local noon by inputting NASA OMNI solar wind data into the empirical magnetopause models. The reconnection rate shows anti-correlation with the magnetopause position that it generally increases as the magnetopause located closer to Earth and vice versa. Our result also confirms that the reconnection rate increases as the empirical coupling efficiency between solar wind and the magnetosphere increases. [ABSTRACT FROM AUTHOR]

Combining experimental research and numerical simulation, this paper studies the effects of obstacle position and blockage ratio on hydrogen flame evolution and explosion characteristic. The mechanism of obstacle-induced turbulence on the hydrogen flame acceleration is revealed. The results show that in a double obstacle tube, When the obstacle spacing is larger, the turbulent combustion intensity and pressure rise rate is relatively higher, and the pressure oscillation is enhanced. The sufficient turbulent combustion promotes the formation of stronger vortex motion at the downstream obstacle. As the blockage ratio increases, the turbulent combustion intensity, flame front speed, and pressure rise rate increases significantly. While obstacles with a high blockage ratio have a blocking effect on the pressure, slightly weakening the pressure oscillation. As the blockage ratio increases, the jet speed at the obstacle increases, the scale and speed of vortex increase, and the vorticity magnitude of unburned and burned area increases. • Effects of obstacle position and blockage ratio on hydrogen explosion are investigated. • A numerical model is developed to analyze the flame evolution and pressure dynamic. • Mechanism of obstacle-induced turbulence on the hydrogen flame acceleration is revealed. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) 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.)

To overcome the shortcomings of traditional NLP methods for trajectory planning problems, an intelligent trajectory real-time planning method is designed for hypersonic gliding vehicles (HGVs), which is composed of two stages: the agent training stage and the real-time trajectory generation stage. During the training stage, the HGV model is considered as an agent, and an environment containing flight information and relative information is constructed. Given the trajectory planning problem possessing continuous state-action space, the twin delayed deep deterministic policy gradient (TD3) is employed, based on which the HGV agent is trained in the environment. To match the real flight environment for HGVs, the process and terminal constraints are taken into consideration, such as the limit of dynamic pressure, overload, and the terminal miss distance, etc. The reward shaping technique is adopted to tackle the multiple constraints. The second stage is the real-time trajectory generation stage, during which a trajectory satisfying the multiple constraints is generated online by the TD3-based method. The simulation results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The use of pile-supported breakwaters can be a cost-effective solution for wave energy dissipation when traditional rubble mound breakwaters are not suitable. For a cost-effective design of these barriers, it is essential to obtain accurate estimates of dynamic pressures and wave forces. Laboratory experiments were conducted to investigate the dynamic pressures and forces on a novel pile-supported breakwater with inclined perforated plates. The analysis focused on various wave and structural parameters, including incident wave height, wave period, plate porosity, and plate configuration. For double-layer configurations with the same porosity, dynamic pressures on the single-layer or front plate were significantly higher than on the rear plate, with rear plate forces being 20% to 60% less. The dynamic pressure on the rear plate exhibited a uniform vertical distribution. Varying plate porosity at different locations significantly impacted structural forces. Gradually decreasing porosity improved wave dissipation and reduced forces on the plates, with front and back plate forces reaching approximately 70% of those on single-layer plates. Optimal protection across various wave periods can be achieved by adjusting porosity and plate arrangement. These findings provide valuable insights for designing pile-supported breakwaters in coastal protection engineering. [ABSTRACT FROM AUTHOR]

In order to study the instability characteristics of interlayer rock strata (IRS) in shallow buried close-distance coal seams under insufficient mining areas, based on the background of interval mining under goaf in Nanliang Coal Mine, this paper studies the instability characteristics of interlayer strata in interval mining under goaf by means of similar simulation, numerical simulation, and field measurement. The results indicated that the first weighting interval of the main roof during mining in the lower coal seam was 49 m, while small and large periodic weightings with intervals of 10–14 m and 15–19 m were identified. During periodic weighting, the support resistance ranged from 6813 to 10,935 kN, with a dynamic load factor of 1.07–1.74, and the peak abutment pressure in front of the working face was 5.85–9.85 MPa. The mining under the interval coal pillar (ICP) was the 'stress increase zone', and the mining under the temporary coal pillars (TCPs) and the interval goaf was the 'stress release zone'. During the working face mining out of the ICP, the support resistance reached 10,934 kN, the dynamic load factor reached 1.74, and the abutment pressure (AP) reached 9.85 MPa, which was 60% higher than the AP mining under the "stress release zone". Analysis suggests that the cutting instability of the IRS was the root cause of the increased AP in the working face of the lower coal seam. A numerical simulation was performed to verify the instability characteristics of the IRS in the interval goaf. The relationship between support strength and roof subsidence during the period of the working face leaving the coal pillar was established. A dynamic pressure prevention method involving pre-splitting and pressure relief of the ICP was proposed and yields superior field application performance. The findings of the study provide a reference for rock strata control during mining under the subcritical mining area in shallow and closely spaced coal seams. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare the distribution of plantar pressure and anterior-posterior (AP) or medial-lateral (ML) shear forces in healthy younger (HY) people, healthy older (HO) people, and diabetic patients, both in static standing and during gait. Materials and methods: A total of 20 HY adults, 16 HO adults and 15 diabetic patients were included. The static mechanical distribution measurements included: static horizontal, AP slope plane, and left/right slope standing. Data collected during the gait cycle encompassed the plantar pressure-time integral (PTI), peak pressure (PP), AP/ML shear force-time integral (AP-STI/ML-STI), and AP/ML peak shear force (AP-PS/ML-PS). The plantar surface was segmented into regions including hallux (HL), 2nd~5th toes (T2-5), 1st metatarsal head (M1), 2nd~3rd metatarsal heads (M2-3), 4th~5th metatarsal heads (M4-5), lateral foot arch (LA), and heel regions. Results: The HO group exhibited increased static pressure in M2-3 and heel regions and AP shear force in the entire plantar and M1 regions, in comparison to the HY group. The diabetes group showed increased static pressure in entire plantar, M1, M2-3 and heel regions and AP shear force in the entire plantar, T2-5, M1, M2-3 and heel regions. During gait, the HO group exhibited increased PTI in the whole plantar, T2-5, M2-3, and M4-5 regions, while the diabetes group showed increased PTI in the whole plantar, M1 and M2-3 regions. The HO group showed increased PP in the whole plantar, M1 and heel regions, while decreased in the M2-3 region. The diabetes group showed increased PP in the whole plantar, T2-5, M2-3, M4-5 and heel regions. The HO group showed increased AP-STI in the T2-5, M1, and M2-3 regions, while the diabetes group showed increased AP-STI in the whole plantar, M2-3 and heel regions. Conclusions: Our findings indicate that both static and dynamic plantar pressures and shear forces are significantly greater in diabetic patients and HO individuals compared to HY adults. The most substantial increases was occurred under the M2-3 and heel regions. [ABSTRACT FROM AUTHOR]

Due to the difficulty in predicting the occurrence of rockburst in deep mining areas,this paper proposes that the use of Peridynamics to analyze the mechanical characteristics of coal-rock composite structures under loading conditions from the perspective of energy, Determine the impact tendency of coal rock composite structures by combining rock elastic deformation energy index (WET) and rock impact energy index (WCF); Use Lammps software to simulate the loading of composite structural materials and compare and verify with experimental results, to more accurately determine the tendency of rockburst occurrence in different coal-rock composite structures.The results indicate that after the specimen reaches the yield stress, the sample exhibits an "X" shaped failure. The coal body has a significant impact on the overall model's fragmentation, and different combination states and ratios can affect the degree of damage in the coal-rock composite structure. which has important theoretical value for rock mechanics research. The research results can reduce the occurrence of rockburst accidents, the difficulty of mine support, and the cost of mining engineering, as well as improve mine safety levels. [ABSTRACT FROM AUTHOR]

These days petroleum and condensate formations, especially offshore ones, are actively being developed. The main feature of such formations is multiphase flow in tubing and riser. During production flow liquid slugs, adverse pressure pulses, and often hitting impacts are detected as a result of high gas content, interphase tension forces and complicated pipeline geometry, leading to pressure surges. The energy and very functioning efficiency of both gaslift and fountain operated wells is thus drastically reduced with the disturbance of the optimal production regime. In this paper it has been determined that a novel approach to multiphase flow management allows for decrease in emergency failures and operational expenses. Thus, right modelling and optimization of phase slippages can become a good guaranteur of safe and secure well operations. [ABSTRACT FROM AUTHOR]

In order to explore the variation law of dynamic pressure effect in the wedge space of five-leaf foil bearings, and to study the influence of different eccentricities, deviation angles and rotation speeds on the static characteristics of the bearings, and the fluid domain of the wedgeshaped space of the bearings was simulated and analyzed by using the CFD software FLUENT. Starting from the compressible fluid lubrication equation and the continuity equation, the basic form of bearing capacity calculation is obtained. The results show that when the thickness of the air film Cr is 10, 20 and 30μm, the pressure of the rotating wall of the bearing is symmetrically distributed along the center, and gradually decreases from the maximum pressure to the ambient pressure. With the increase of rotational speed, the pressure value of the minimum film thickness Cr increases, showing a positive correlation. At the eccentricity of β=0°, the pressure distribution area in the wedge space is larger when the eccentricity is ε=0.6, and the pressure distribution area in the wedge space is smaller when the eccentricity is ε=0.9. When the eccentricity is ε=0.8, the dynamic pressure effect area of the eccentricity angle β=0° is less than that of β= 36°. Meanwhile, under this condition, the higher the rotational speed, the smaller the peak value of the circumferential distribution limit wave of pressure along the central section is. [ABSTRACT FROM AUTHOR]

The fracture toughness and wear resistance of WC-based ceramics are crucial factors that determine their subsequent applications. In this study, the mechanical and tribological properties of expanded graphite (EG) reinforced WC ceramics consolidated by oscillatory pressure sintering (OPS) were investigated. The results demonstrated that the combination of dynamic pressure and EG had a synergistic effect, resulting in a much higher relative density of 0.2 wt% EG/WC ceramics reaching up to 99.78%. Simultaneously, 0.2 wt% EG/WC ceramics demonstrated a reduced grain size, with fracture toughness, flexural strength and wear rate reaching 7.54 MPa m1/2, 1262 MPa and 2.16 × 10−7 mm3·N−1·m−1, respectively. EG was present in the form of graphene nanoplatelets (GNPs) within WC ceramics. The primary toughening mechanisms involved the bridging and pulling out of GNPs, as well as the generation of microcracks induced by GNPs. Additionally, the exceptional thermal conductivity of GNPs can facilitate heat dissipation and reduce thermal damage. The wear resistance of WC-EG ceramics was primarily enhanced through improving overall mechanical properties and decreasing the occurrence of oxidation and adhesive wear. [ABSTRACT FROM AUTHOR]

During the expansion phase of a substorm, the poleward jump of auroras (breakup) and the expansion of the auroral bulge are observed. The expansion is accompanied by a negative magnetic bay under the aurora and a positive magnetic bay at mid-latitudes. The magnitude of the negative bay is characterized by the auroral AL-index. The Mid-Latitude Positive Bay index (MPB-index) was previously proposed in order to characterize the positive bay. In this article, the statistical relationship of the MPB-index with the geomagnetic activity at different latitudes and with the parameters of the solar wind and interplanetary magnetic field is investigated. It is shown that all extremely high values of the MPB-index (above 10 000 nT2) are observed during strong geomagnetic storms (when the Dst-index falls below –100 nT), all extremely strong geomagnetic storms (when the Dst-index falls below –250 nT) are accompanied by extremely high values of the MPB-index. Statistically, the MPB-index increases with increasing geomagnetic activity at any latitude. On average, the MPB-index increases with increasing interplanetary magnetic field magnitudes and any of its components. However, for the Bz-component, large values of the MPB-index are observed at its southward orientation. For the plasma parameters of the solar wind, the MPB-index increases most strongly with the increase of its speed. The dependence on the dynamic pressure and on the value of the EY-component of the electric field of the solar wind is also strong. However, the MPB-index weakly depends on the density and temperature of the solar wind. [ABSTRACT FROM AUTHOR]

The dispersion prediction model called CONTAM has been widely used to predict airflow rates in multi-zone indoor environments. However, as CONTAM adopts the lumped system approach under the assumption that the air in each room is well mixed, and thus the pressure and temperature are homogeneous, its prediction may be inaccurate in certain cases. Thus, this study proposed an efficient algorithm that yielded improved flow rates by reflecting the non-uniform distribution of pressure or the presence of dynamic pressure based on single-zone computational fluid dynamics. The proposed method selectively applied a large-eddy simulation to obtain information on velocity, pressure, and temperature, which can be used for the accurate prediction of flow rates across multi-zone environment. [ABSTRACT FROM AUTHOR]

Although diabetic polyneuropathy (DPN) has a very high prevalence among people with diabetes, gait analysis using cyclograms is very limited, and cyclogram research, in general, is limited to standard measures available in software packages. In this study, cyclograms (movements of the centre of pressure, COP, on and between the plantar surfaces) of diabetics and healthy individuals recorded with a smart insole were compared in terms of geometry and balance index, BI. The latter was calculated as the summed product of standard deviations of cyclogram markers, i.e., start/end points, turning points, and intersection points of the COP. The geometry was assessed by the positions of, and distances between, these points, and the distance ratios (14 parameters in total). The BI of healthy and diabetic individuals differed significantly. Of the fifteen parameters (including the BI), three were suitable as classifiers to predict DPN, namely two distances and their ratio, with false negatives ranging from 1.8 to 12.5%, and false positives ranging from 2.9 to 7.1%. The standard metric of the cyclogram provided by the software packages failed as a classifier. While the BI captures both DPN-related balance and other balance disorders, the changing geometry of the cyclogram in diabetics appears to be DPN-specific. [ABSTRACT FROM AUTHOR]

To study the key factors on integrated curtain formation and breakup in curtain coating production process, we used the numerical simulation method to analyze the various stages of the curtains from full curtain to full thread state by changing the inlet flow rate, which is, changing the Weber number (We). The numerical model was based on an actual production machine, and the physical properties of the lacquer were accurately measured for the simulation. It is found that with the gradual breakup of the curtain, the oscillation of the curtain gradually increased, there was obvious distortion and increase in Turbulent Viscosity Ratio (TVR) at the breakup, and there was a decrease in Dynamic Pressure (DP) at the top of the breakup. Different curtain state reflects a shift from inertia force dominance to a balance of forces and finally to surface tension dominance. The finding from the simulation, also the comparison between the results of simulation and experiments provided the basis to understand the mechanism of curtain coating, also inspired the engineers to optimize the geometry of curtain coater and the coating production parameters for easier integrated curtain forming. [ABSTRACT FROM AUTHOR]

The drag experienced by the nose of an aircraft varies significantly under different incoming flow conditions. In order to reduce the aerodynamic force on the nose of the (hypersonic) supersonic vehicle, the numerical simulation approach has been used to analyze the drag reduction laws and mechanisms of a blunt-body vehicle with the aerospike-counterflowing jet composite approach under different incoming flow dynamic pressures. The effects of two environments with H = 0.1 km and H = 30 km, as well as the influence of different incoming Mach numbers on the drag reduction at H = 0.1 km were investigated. The research has shown that there exists a minimum overall drag value for the vehicle under different dynamic pressures, while the variation in the wall pressure is related to the actual operating conditions. The recirculation zones at the aerospike and in front of the blunt body are important flow structures that affect the drag reduction. When the jet total pressure ratio increases, the position of the recirculation zone at the head of the drag reduction rod moves away from the central axis of the model. When the incoming flow dynamic pressure is higher, the separation point of the recirculation zone in front of the blunt body is located further downstream, and the reattachment point is related to the incoming flow and jet conditions, aligning with the trend of variation of the position of the maximum pressure on the blunt body wall. As it can effectively push away the shock wave, the enhanced drag reduction effect of the jet is significant when the incoming flow dynamic pressure is higher. However, the high jet pressure resulting from high dynamic pressure needs to be considered in the actual design. Furthermore, the complex turbulent flow field formed by the high dynamic pressure incoming flow and the jet is worthy of further study by means of the large eddy simulation. • Drag reduction induced by the aerospike-jet composite approach was investigated numerically. • Different incoming dynamic pressures were considered for practical implementation. • High jet pressure resulting from high dynamic pressure should be considered in actual design. • The reattachment point is related to the incoming flow and jet conditions. [ABSTRACT FROM AUTHOR]

Nonlinear solitary waves influence the Earth's crust because wave pressure on the ocean bottom contains non-hydrostatic components. Our physical-mathematical model allows us to calculate the surplus super-hydrostatic pressure on the Earth's crust. It depends on the amplitudes of solitary waves and the depth of an ocean. The surplus wave pressure averages 50% from hydrostatic pressure on the shallow ocean shelves. Thus, the solitary wave's tsunami class can provoke novel (repeated) earthquakes (or landslides) because surplus stresses affect the seismic focus. Theoretical results and experimental physical modeling of soliton waves have shown good agreement. A calculated example of the mega-tsunami in Lituya Bay and a described example of Dickson Fjord (AK, USA) indicate changes in the dynamic pressure after the onset of the tsunami. The presented studies demonstrate a first attempt at creating a numerical model of this phenomenon. [ABSTRACT FROM AUTHOR]

This study presents a three-dimensional numerical model with the novel rigid fluid method (RFM) to simulate slide-type landslides. RFM, coupled with the Navier–Stokes solver Splash3D, is developed to calculate the movement and rotation of a moving solid. With the pressure and shear stress data in each grid collected by the discrete element method, the moving solid is granted to be involved in the simulation. The model is validated against a three-dimensional experiment of a sphere entering water, demonstrating good agreement in terms of displacement and air column pinch-off time. Subsequently, the model is applied to simulate the process of a semispherical landslide tsunami, using a semispherical laboratory experiment as a benchmark. The numerical results show excellent agreement with the experimental data in terms of sliding track, velocity, dynamic pressure, and wave height. To investigate the applicability of the model to real-world scale events, the above-mentioned case is scaled up proportionally, and the time, flow velocity, dynamic pressure, and resultant force are compared to verify the Froude number similarity. The results indicate that the model can effectively capture the essential features of landslide-induce tsunamis and has the potential to be used for further studies on the impacts of such events. [ABSTRACT FROM AUTHOR]

We report a specular loss event of radiation belt electrons induced by a moderate geomagnetic storm on April 4, 2017, by using Van Allen Probe observations. During the initial phase, when the solar wind dynamic pressure (Pdyn) reached 12 nPa, the radiation belt electrons at Ek > ∼200 keV experienced a partial loss, followed by noticeable energy dispersion, which pronouncedly occurred at larger pitch angles on higher L shells. During the main phase, both probes witnessed a significant electron flux depletion at all energies from 54 to 2.6 MeV on the dusk-night side (MLT = magnetic local time around 20). Moreover, the corresponding phase space density (PSD) shows a local dip within L* = 4.44–4.87 (drift shell under adiabatic coordinate), which is not the outermost of L*, lasting for one pass (semi-period) of the spacecraft and quickly disappearing. By comparing the characteristics of electron loss in response to variations of the solar wind and geomagnetic indices, the movement of the estimated magnetopause location and the last closed drift shells, as well as the distribution of the plasma waves, we find that the partial dropout was essentially induced by the magnetopause shadowing effect, while the potential effect of the subsequent local PSD dip cannot be clearly explained by the present theory as far as we know. By showing the specular dropout event in the present work, we underline that the different loss effects should draw special attention from the space physics community. [ABSTRACT FROM AUTHOR]

Accurate flow models are crucial for simulating shallow water hydrodynamics, particularly in predicting and mitigating the impacts of extreme events involving free-surface flows. Many of these extreme scenarios in river environments involve fluid dynamics with significant dynamic pressures, invalidating the use of standard Saint-Venant-type models. This study presents a robust and accurate novel alternative based on the Reynolds-averaged Navier–Stokes (RANS) equations solved through variational methods. Despite their potential, variational methods have been underutilized in the literature, and their application has been limited to low-level expansions. Moreover, they are rarely validated against experiments that simulate complex flows. This study addresses both challenges. First, a general mathematical framework is developed for the variational RANS (VR) model of arbitrary high-level. The VR level III model is presented and is solved numerically using a robust finite volume-finite difference solver for turbulence flow modeling. Second, an extensive experimental program was conducted to validate this new flow modeling tool, focusing on two challenging flow scenarios. The first scenario involves the propagation of turbulent breaking waves over an irregular, uneven bathymetry—conditions similar to those observed during bedform development in riverine environments. This scenario involved the experimental characterization of unsteady surges over an array of obstacles in series. The second scenario investigated sill-controlled released discharges, similar to those occurring in estuary inlets with sediment bars. Comparisons between the new experimental data and the predictions from the VR level III model reveal the model's accuracy and robustness, making it a highly suitable tool for simulating free-surface flows. [ABSTRACT FROM AUTHOR]

To elucidate the effect of fluid pressurization rate on the shear slip behavior of shale fractures during reservoir hydraulic pressure fluctuations, shale slip experiments with constant axial stress were conducted at 0.5, 2, 8, and 30 MPa/min pressurization rates based on the pressure fluctuation characteristics of hydraulically fractured reservoirs of deep shale gas in the Sichuan Basin. The results indicated that quasi-static slip exhibited higher average velocities than creep slip by 2–3 orders of magnitude at equivalent pressurization rates. Additionally, at 30 MPa/min pressurization rates, the slip type transitioned directly from creep to dynamic slip. The slip velocity increases with increasing pressurization rate, and the average velocities of quasi-static slip are 7.10 × 10−4, 2.20 × 10−3, and 5.40 × 10−3 mm/s, respectively. Dynamic slip exhibited the highest critical slip pressure of 7.14 MPa and the largest friction coefficient increased by 55% at a pressurization rate of 2 MPa/min. Friction strength primarily increased by 42% during creep slip at a pressurization rate of 0.5 MPa/min, while the friction coefficient minimally decreased by 0.03% during dynamic slip. Notably, dynamic slip exhibited a significant increasing trend in the percentage of friction coefficient increment. The critical dynamic slip pressure and energy released during slip exhibited an initially increasing and then decreasing pattern over the range of pressurization rates in this experiment, which is a result of the degree of inhomogeneity of the fluid increasing and then decreasing with the pressurization rate. Consequently, this led to maximum accumulation and energy release at the fracture surface, resulting in minimal quasi-static slip displacement, and is not conducive to improved reservoir permeability characteristics and safe shale gas recovery. [ABSTRACT FROM AUTHOR]

The water entry cavity and load characteristics obtained through scaled-down tests are correlated with the atmospheric pressure and density at the free surface. The evaluation of the influence of the cavitation number and atmospheric density coefficient is highly essential for scale tests to improve the prototype prediction accuracy. Focusing on the similarity criterion simulations and load prediction of the scaled-down tests, this study conducts the simulation tests of the water entry characteristics of the scaled-down model under different environments: normal pressure, reduced pressure, and reduced pressure and heavy gas replacement. Moreover, the influence of the cavitation number and atmospheric density coefficient on the multiphase flow, slamming load, and air cushion effect is discussed. The "air cushion effect" is formed at the top of the vehicle during water entry process, which affects the peak narrow pulse width slamming load. Furthermore, the "air cushion" experiences expansion–stability–rupture–escape with increasing water invasion depth. As the atmospheric pressure decreases, the gas tends to thin and the retention inertia weakens. The decrease in the "air cushion" buffering capacity leads to the increase in the slamming load and the expansion of the cavity scale formed by the liquid. Excessive simulation of the dynamic pressure results in the delayed closure of the cavity surface and the slow fall of the water curtain. As the atmospheric density increases, the retention inertia of gas increases because of the increase in the molecular mass, the slamming load gradually decreases, and the closure time of the cavitation and water curtain decreases. The research results of this paper provide some reference for the similarity transformation of the scaled-down test and the pre-research of the prototype. [ABSTRACT FROM AUTHOR]