Acceleration Force Research Articles

Seismic Structure-Soil-Structure Interaction (SSSI) between piled neighboring bridges: Influence of height ratio

Abstract This paper explores the impact of height ratios on the seismic Structure-Soil-Structure Interaction (SSSI) for three adjacent bridges with varying superstructure masses (Mst = 350, 1050, 350 t) through 3D numerical simulations. A comprehensive series of numerical analyses has been conducted across different height ratios (R = 1, 1.1, 1.15, 1.2, 1.25, 1.5, 2, and 3) to assess their influence on superstructure acceleration and the internal forces within the foundation piles. The bridges under investigation are supported by groups of piles embedded in nonlinear clay. The numerical simulations were executed using fast Lagrangian analysis of continua in three dimensions (FLAC 3D), a three-dimensional finite differences modeling software. The findings revealed that variations in mass ratios significantly impact the SSSI effects on superstructure acceleration and pile internal forces. Notably, adverse effects were more pronounced for mass ratios of R = 1.1 and 1.2, leading to an increase in bending moment, shear force, and superstructure acceleration by up to 237.8%, 291.4%, and 70.33%, respectively. In contrast, a mass ratio of R = 3 resulted in a decrease in bending moment, shear force, and superstructure acceleration by up to 72%, 82.14%, and 81.13%, respectively. This implies that a careful arrangement of adjacent structures with different masses can be employed effectively to manage the (SSSI) effects.

Effects of training flights of combat jet pilots on parameters of airway function, diffusing capacity and systemic oxidative stress, and their association with flight parameters

BackgroundFighter aircraft pilots are regularly exposed to physiological challenges from high acceleration (Gz) forces, as well as increased breathing pressure and oxygen supply in the support systems. We studied whether effects on the lung and systemic oxidative stress were detectable after real training flights comprising of a wide variety of exposure conditions, and their combinations.MethodsThirty-five pilots of the German Air Force performed 145 flights with the Eurofighter Typhoon. Prior to and after flight lung diffusing capacity for carbon monoxide (DLCO) and nitric oxide (DLNO), alveolar volume (VA), and diffusing capacities per volume (KCO, KNO) were assessed. In addition, the fractional concentration of exhaled nitric oxide (FeNO) was determined, and urine samples for the analysis of molecular species related to 8-hydroxy-2’-deoxyguanosine (8-OHdG) were taken. For statistical analysis, mixed ANOVA models were used.ResultsDLNO, DLCO, KNO, KCO and VA were reduced (p < 0.001) after flights, mean ± SD changes being 2.9 ± 5.0, 3.2 ± 5.2, 1.5 ± 3.7, 1.9 ± 3.7 and 1.4 ± 3.1%, respectively, while FeNO decreased by 11.1% and the ratio of 8-OHdG to creatinine increased by 15.7 ± 37.8%. The reductions of DLNO (DLCO) were smaller (p < 0.001) than those of KNO (KCO). In repeated flights on different days, baseline values were restored. Amongst various flight parameters comprising Gz-forces and/or being indicative of positive pressure breathing and oxygenation support, the combination of long flight duration and high altitude appeared to be linked to greater changes in DLNO and DLCO.ConclusionsThe pattern of reductions in diffusing capacities suggests effects arising from atelectasis and increased diffusion barrier, without changes in capillary blood volume. The decrease in exhaled endogenous NO suggests bronchial mucosal irritation and/or local oxidative stress, and the increase in urinary oxidized guanosine species suggests systemic oxidative stress. Although changes were small and not clinically relevant, their presence demonstrated physiological effects of real training flights in a modern 4th generation fighter jet.

Kinetic and Kinematic Characteristics Underpinning Change of Direction Performance in Basketball: A Comparative Study Between Sexes and Tests.

Baena-Raya, A, Díez-Fernández, DM, Martínez-Rubio, C, Conceição, F, and López-Sagarra, A. Kinetic and kinematic characteristics underpinning change of direction performance in basketball: A comparative study between sexes and tests. J Strength Cond Res 38(4): e182-e188, 2024-This study (a) evaluated the sex-specific kinetic and kinematic outcomes underpinning change of direction (COD) performance, (b) compared these outcomes across 3 different COD tests, and (c) examined the sex-specific and test-specific outcome most strongly related to COD performance in basketball players. Thirty young basketball players (17 males and 13 females) competing at the national level were assessed for the modified 505 test, modified T test, and V-cut test. The Local Positioning System technology (WIMU PRO, Realtrack Systems S.L., Almería, Spain) was used to measure the maximum values of acceleration (ACC max ), deceleration (DEC max ), velocity (VEL max ), and centripetal force (CentF max ) in each COD test. Male players displayed greater ACC max , VEL max , DEC max , and CentF max outputs for each section of the 505 test, T test, and V-cut test (all p < 0.05), resulting in a faster COD performance than females across tests (all ES > -1.42; 95% CI = -3.45 to -0.57). The 505 test demanded significantly greater kinematic outputs than T test and V-cut test for both sexes ( p < 0.01). The ACC max explained ∼26-58% of the variability in COD time for males across tests ( p < 0.05) and 40% in females' modified 505-test time ( p < 0.05). Likewise, in females, DEC max explained 38% of the modified T -test time variability, whereas VEL max explained 53% in the V-cut test time (both p < 0.05). These findings suggest that (a) COD data should not be used interchangeably across sexes, (b) test specificities should be considered for designing COD training, and (c) the kinematic outcomes explaining COD performance might vary across sexes.

Particle agglomeration via resonant acoustic mixer for dry powder inhalation

The work presented in this paper employed a resonant acoustic mixing (RAM) process to optimize the fine particle agglomeration process for dry powder inhalation to achieve efficient pulmonary delivery of melatonin. The formulation prepared by acoustic mixing with the double layer grids demonstrated superior agglomerate particle size distribution and approximately 90% of the metered dose in the dosing chamber was emitted from Turbuhaler® (90% emitted dose). Acceleration force during acoustic mixing significantly affected the packing fraction of mixtures and mechanical strength of agglomerates resulting in improved fine particle fraction. The particle agglomeration via RAM can improve the efficiency of agglomerate production by utilizing the internal space of the mixer to induce more particle collision. The agglomerates formulation exhibited ideal fine particle fraction of 47.65 ± 1.46% and 56.02 ± 2.55% at flow rates of 30 and 60 L/min, respectively. The fine particle deposition was only slightly affected at the lower air-flow rate, suggesting a reliable inhalation performance in vivo.

Longitudinal Seismic Response of Metro Tunnels Crossing a Fault with Multi-Slip Surfaces

There are multiple seismic fault zones near Xi’an in China, among which the Li Piedmont Fault has multiple slip surfaces. A 3D finite element dynamic Soil–Fault–Tunnel model was established based on the engineering background of the Xi’an Metro tunnel orthogonally crossing the Li Piedmont Fault. The input seismic loads used the Chi-Chi, El-Centro, and artificial seismic waves, and the latter was artificially synthesized based on seismic conditions and site conditions of actual engineering. The Chi-Chi seismic wave with larger PGV/PGA and wider acceleration-sensitive area is a near-field seismic wave, while the others are far-field seismic waves. The seismic loads were transformed into the equivalent nodal force on the boundary nodes of the model, and nonlinear dynamic calculation was carried out to obtain the longitudinal seismic response of the structure. The main results show that the fault amplifies the seismic response of the tunnel, and the tunnel at the position of the fault slip surfaces is more vulnerable to failure, especially near the slip surface between the hanging wall and the fault, where the maximum acceleration, soil pressure, and internal force of the tunnel structure occur. In addition, the seismic response of the tunnel and soil caused by near-field seismic motion is significantly stronger than that caused by far-field seismic motion.

Inter-study reproducibility of cardiovascular magnetic resonance-derived hemodynamic force assessments

Cardiovascular magnetic resonance (CMR)-derived hemodynamic force (HDF) analyses have been introduced recently enabling more in-depth cardiac function evaluation. Inter-study reproducibility is important for a widespread clinical use but has not been quantified for this novel CMR post-processing tool yet. Serial CMR imaging was performed in 11 healthy participants in a median interval of 63 days (range 49–87). HDF assessment included left ventricular (LV) longitudinal, systolic peak and impulse, systolic/diastolic transition, diastolic deceleration as well as atrial thrust acceleration forces. Inter-study reproducibility and study sample sizes required to demonstrate 10%, 15% or 20% relative changes of HDF measurements were calculated. In addition, intra- and inter-observer analyses were performed. Intra- and inter-observer reproducibility was excellent for all HDF parameters according to intraclass correlation coefficient (ICC) values (> 0.80 for all). Inter-study reproducibility of all HDF parameters was excellent (ICC ≥ 0.80 for all) with systolic parameters showing lower coeffients of variation (CoV) than diastolic measurements (CoV 15.2% for systolic impulse vs. CoV 30.9% for atrial thrust). Calculated sample sizes to detect relative changes ranged from n = 12 for the detection of a 20% relative change in systolic impulse to n = 200 for the detection of 10% relative change in atrial thrust. Overall inter-study reproducibility of CMR-derived HDF assessments was sufficient with systolic HDF measurements showing lower inter-study variation than diastolic HDF analyses.

Prototype silicone rubber based passive seismic damper: Development, characterization and implementation

Passive damping devices are mostly preferred owing to their relatively lower cost, low maintenance, and stability over a wide range of frequencies during seismic events. Currently, these devices with temperature in-sensitive viscoelastic material are being explored. The paper aims to develop a prototype piston-cylinder based passive damper with silicone rubber particles and characterize it with varied amplitude and frequency of sinusoidal input. The device Silicone Rubber Particle Packed Damper, so developed, was then implemented in the benchmark building for seismic response control. Silicone rubber particles with lower hardness were produced through compressed molding technology to improve the damping efficiency of the device. The device was later converted to an Air Damping Device by removing silicone rubber particles for a natural comparison of efficacy. Hysteresis curves of devices, elliptical in shape, obtained through characterization were mathematically modelled using the Kelvin-Voigt model, and parameters were identified using multivariable linear regression to implement them with the benchmark building. Uncontrolled and controlled responses of benchmark building fitted with, both, damping devices were determined under strong motion (El Centro, Hachinohe) and pulse-type (Kobe, Northridge) seismic excitations. Seismic response parameters; peak displacement, peak interstorey drift, peak acceleration, and peak damper force was estimated. Each seismic response parameter yields substantial reduction for controlled benchmark building with Silicone Rubber Particle Packed Damper. The efficacy of damping devices was established by Performance Indices in terms of peak interstorey ratio, level acceleration, base shear, and control force. Though both passive damping devices were found effective in seismic response control of benchmark building, Silicone Rubber Particle Packed Damper outperforms Air Damping Device. The developed prototype damping devices are a low cost and easy to maintain.

Assessing playability limits of bowed-string transients using experimental measurements

Understanding the dynamics of bowed-string attacks involves exploring the relationship between bow acceleration, bow force, and the generation of Helmholtz motion during transients. This study addresses the following research question: How do theoretical limits of “playability” predict these parameters? Motivated by the need for experimental evidence in this domain, we present a comprehensive investigation into bowed-string transients within the bow acceleration and bow force parameter space, known as the Guettler diagram. This study exclusively employs an experimental methodology. The setup, employing a robotic arm, permits the collection of transient data under varying bowing conditions. Analysis of the bridge force waveform allows for the extraction of pre-Helmholtz transient times. Our results reveal a triangular playable region in the Guettler diagram, consistent with theoretical predictions and previous experimental findings. However, Guettler’s analytical limits for playable regions during transients show limitations. We investigate the role of friction, a key parameter idealized in the model used for obtaining these limits. Measured friction coefficients from transients reveal discrepancies with prior experimental studies, highlighting the need for further investigations in this direction.

The Use of Transition Curves in Airport Runway Rapid Exit Taxiways (RETs)

This paper describes a study result focused on the transition curves used in airport rapid exit taxiways (RETs). Such geometric elements are not currently made explicit by standards, and major international government agencies, such as the International Civil Aviation Organization and the Federal Aviation Administration, are limited to providing some layouts consisting of only constant curvature elements, although the aircrafts speed in RETs is variable. In addition to the clothoid that has unitary shape parameter “n” and the multiparameter clothoids (generalized Cornu spirals), the study analyzes the Bloss curve employment. Regarding the multiparameter clothoids, four schemes with shape parameter equal to 1.25, 1.50, 1.75, and 2.00 were considered, respectively. The proposed curves’ effectiveness was evaluated by analyzing the main geometric and kinematic variables trend, that is, curvature, transversal acceleration, lateral jerk, speed, travel time, longitudinal deceleration, and centrifugal force. To ensure the analysis effectiveness, the study layouts were designed from those used for runways codes 1‐2 and 3‐4 maintaining the main geometric elements dimensions unchanged (length of straight lines, radii of circular curves, exit angles, etc.). The kinematic variables values along the design RETs were calculated “point by point” by MATLAB software to take into account nonuniform motion regimen. The obtained results show that both the Bloss curve and the multiparameter clothoid having a shape factor equal to 2 are capable of better contribution in terms of safety and comfort. Implications in the airport construction field are related to the possibility of using lower deceleration values compared to current standards, that is, allowing higher exit speed for the same deceleration. This allows aircrafts to vacate the runway more quickly and, therefore, to increase runway capacity without taking expensive RETs repositioning.

Retinal hemorrhage variation in inertial versus contact head injuries

BackgroundAbusive head trauma (AHT) is frequently accompanied by dense/extensive retinal hemorrhages to the periphery with or without retinoschisis (complex retinal hemorrhages, cRH). cRH are uncommon without AHT or major trauma. ObjectiveThe study objectives were to determine whether cRH are associated with inertial vs. contact mechanisms and are primary vs. secondary injuries. Participants and settingThis retrospective study utilized a de-identified PediBIRN database of 701 children <3-years-old presenting to intensive care for head trauma. Children with motor vehicle related trauma and preexisting brain abnormalities were excluded. All had imaging showing head injury and a dedicated ophthalmology examination. MethodsContact injuries included craniofacial soft tissue injuries, skull fractures and epidural hematoma. Inertial injuries included acute impairment or loss of consciousness and/or bilateral and/or interhemispheric subdural hemorrhage. Abuse was defined in two ways, by 1) predetermined criteria and 2) caretaking physicians/multidisciplinary team's diagnostic consensus. ResultsPediBIRN subjects with cRH frequently experienced inertial injury (99.4 % (308/310, OR = 53.74 (16.91–170.77)) but infrequently isolated contact trauma (0.6 % (2/310), OR = 0.02 (0.0004–0.06)). Inertial injuries predominated over contact trauma among children with cRH sorted AHT by predetermined criteria (99.1 % (237/239), OR = 20.20 (6.09—67.01) vs 0.5 % (2/339), OR = 0.04 (0.01–0.17)).Fifty-nine percent of patients with cRH, <24 h altered consciousness, and inertial injuries lacked imaging evidence of brain hypoxia, ischemia, or swelling. ConclusionscRH are significantly associated with inertial angular acceleration forces. They can occur without brain hypoxia, ischemia or swelling suggesting they are not secondary injuries.

Enhancing vehicle ride comfort through deep reinforcement learning with expert-guided soft-hard constraints and system characteristic considerations

Currently, the research on controlling vehicle ride comfort primarily revolves around utilizing traditional algorithms for active or semi-active control of suspension systems. However, these methods often lack adaptability and necessitate a substantial allocation of human and material resources for system calibration and parameter tuning. With the advancement of cutting-edge computational methods, such as artificial intelligence (AI), being applied in engineering, new opportunities have arisen to tackle knowledge-intensive tasks like suspension control. This study aims to enhance vehicle ride comfort by proposing an active suspension control method that integrates deep reinforcement learning (DRL) while considering system characteristics. Firstly, we construct a Twin Delayed Deep Deterministic Policy Gradient (TD3) architecture to systematically explore control policies. Secondly, we propose an expert-guided soft-hard constraints model (TD3-SH) that synergistically incorporates multi-scale information such as displacement, velocity, acceleration, and control force. Additionally, in practical engineering applications, we introduce action delay mechanisms and hard constraint modules to address time delay and actuator dynamic constraints, thereby alleviating the challenges associated with subsequent parameter adjustments and other knowledge-intensive tasks. Finally, simulations demonstrate the effective mitigation of body vibrations in the low-frequency range and the subsequent improvement of ride comfort by TD3-SH. In comparison to the deep deterministic policy gradient (DDPG), TD3, and model predictive control (MPC) baselines, the proposed method showcases control performance improvements of 54.8%, 35.5%, and 18.3%, respectively. Moreover, the method exhibits ride comfort optimization exceeding 85% across diverse road conditions, showcasing its exceptional generalization and adaptive capacity. Furthermore, the optimization amount exceeding 58% can be sustained despite the constraints of time delay and actuator dynamics. Evidently, the proposed algorithm holds significant potential for engineering applications and is uniquely suited for complex tasks in the vehicle industry characterized by high uncertainty.

FUNCTIONAL STABILITY OF THE INVERTED PENDULUM AND ITS RELATION TO UNCREWED AERIAL VEHICLE WINGS THROUGH SYSTEM MATHEMATICAL MODELING AND SIMULATION

The flight instability of an uncrewed aerial vehicle (UAV) can be considered critical, and investigations of stability can be compared to the study of the stabilization of an inverted pendulum. This study investigated the stability of two dynamic systems, represented by an inverted pendulum and a simple approximation of an aircraft wing surface exposed to aerodynamic forces. This study illustrates the advantages of time-domain simulation for solving the differential equation of motion. The simulation used the Euler integration approach for various system parameters. Essentially, an aircraft in flight must constantly maintain pitch stability, which, in practical considerations, can be compared to the mechanism of a rotary motion represented by the up-swinging motion of an inverted pendulum. The pendulum may conserve the same concept as an aircraft’s acceleration, as both are affected by the same gravity and acceleration forces, in which the longitudinal stability of the aircraft must be ensured immediately upon takeoff. An inverted pendulum and a UAV aircraft system simulation were developed with basic MATLAB software. The inverted pendulum simulation showed that as the value of the spring’s stiffness at the limit of stability (klim) increased, the system became more convergent and, as a result, more stable. The stiffness of the spring at the limit of stability, klim = 32.69 N m-1 (i.e., equivalent to an initial angular rotation θ = 5 °), and the system’s stability were observed up to the value of klim = 179.79 N m-1, which resulted in an unstable short initial period. In addition, for the aircraft’s wing, the damping coefficient (clim) value was in the range of clim ≥ 10,000 N s m-1. Therefore, with the damping ratio ζ being equal to zero, the system vibrated consistently at its natural frequency (wn), never deviating drastically to become unstable.

Increased H3K9me3 and F-Actin Reorganization in the Rapid Adaptive Response to Hypergravity in Human T Lymphocytes.

Our study explored the impact of hypergravity on human T cells, which experience additional acceleration forces beyond Earth's gravity due to various factors, such as pulsatile blood flow, and technology, such as high-performance aircraft flights or spaceflights. We investigated the histone modifications Histone 3 lysine 4 and 9 trimethylation (H3K4me3 and H3K9me3, respectively), as well as the structural and cytoskeletal organization of Jurkat T cells in response to hypergravity. Histone modifications play a crucial role in gene regulation, chromatin organization and DNA repair. In response to hypergravity, we found only minimal changes of H3K4me3 and a rapid increase in H3K9me3, which was sustained for up to 15 min and then returned to control levels after 1 h. Furthermore, rapid changes in F-actin fluorescence were observed within seconds of hypergravity exposure, indicating filament depolymerization and cytoskeletal restructuring, which subsequently recovered after 1 h of hypergravity. Our study demonstrated the rapid, dynamic and adaptive cellular response to hypergravity, particularly in terms of histone modifications and cytoskeletal changes. These responses are likely necessary for maintaining genome stability and structural integrity under hypergravity conditions as they are constantly occurring in the human body during blood cell circulation.

Selected Exogenous (Occupational and Environmental) Risk Factors for Cardiovascular Diseases in Military and Aviation

Cardiovascular diseases are a group of disorders of heart and blood vessels which are the leading cause of death globally. They are also a very important cause of military unsuitability especially among military pilots. Some of the risk factors cannot be modified, but a large group of them can be modified by introducing healthy habits or behaviors, such as regular physical activity, quitting of tobacco smoking, cessation of harmful alcohol consumption, or stress avoidance. Specific occupational and environmental factors, such as acceleration, pressure changes, hypoxia, thermal stress, noise, vibration, prolonged sedentary posture, difficulties in moving the limbs, shifts, work shift irregularities, circadian dysrhythmia, variations in the microclimate, motion sickness, radiation, toxicological threats, occupational stress, emotional tension, highly demanding tasks especially during take-off and landing, predominance of intellectual over physical activity, and forced operation speed against time shortage are considered as characteristic for military personnel, especially military aircrews. They are of special concern as some of them are considered as potential CVD risk factors. The aim of this study was to discuss the influence of selected occupational and environmental factors (noise, altitude, hypoxia, acceleration forces, tobacco smoking, oral health, and stress) regarding their importance for CVD risk in military professionals and military aviators. The performed revision confirmed that they are exposed to certain characteristic conditions, which may influence the CVD risk but the number of solid scientific data regarding this subject are limited. There is a great need to perform complex studies on environmental and occupational risk factors for CVDs in military personnel and military aviators as well as how to minimize their influence to prolong the state of health and military suitability of this professional groups.

MATHEMATICAL MODELING OF THE PROCESS OF MOVEMENT OF GRAIN MATERIAL ON THE SURFACE OF A SIEVE OF A VIBRATING PNEUMATIC PULSE SEPARATOR

The results of a theoretical study of the movement of grain material on the surface of a unfailing sieve of a vibrating pulse separator are presented. The paper presents the power and kinematic model, geometric characteristics of the surface of the sieve of a vibrating pneumatic pulse separator in static, and kinematic processing parameters. Calculations based on the proposed model allow determining the forces of movement, velocity, and acceleration of seeds in the grain medium under the combined action of vibrations and pneumatic pulse flow. The following conclusions were drawn as a result of the research and analysis of the generated forces according to the developed mathematical model: the greatest influence on the process of moving grain material, both in the horizontal and vertical directions, is exerted by the force of impulse (pulsation) of the air flow, the pressure force above the overlying layers of grain material (for seeds in the middle part and on the surface of the sieve without a dip), friction forces, seed weight, and the Archimedean force; in order to intensify the process of fractionation of the grain medium, increase the productivity of the vibrating pneumatic pulse separator, it is necessary to increase the force of the pulsating air flow, the inertia of the oscillatory motion, friction and lateral pressure on the seeds in the grain medium. To solve this problem, it is necessary to optimize the amplitudes and frequencies of oscillations of the unfailing sieve of the vibrating pneumatic pulse separator. The analysis of the mathematical model showed the feasibility of using a vibrating unfailing sieve surface with the simultaneous interaction of the injecting pulsating air flow under the sieve to separate grain material by seed density. It has been established that in order to intensify the separation of grain material into fractions, while increasing the productivity of the technical means, it is necessary to increase the force of the pulsating air flow, friction forces, and lateral pressure. The dynamic model of the movement of grain material displacement and recombination is scientifically substantiated and technological recommendations for the separation of grain material into fractions by seed density using the proposed technical means of a vibrating pneumatic pulse separator with the use of a patented method of its separation are developed.

The Influence of Vertical Seismic Acceleration on the Triggering of Landslides Constrained by Bedding Faults under an Inertial Frame Reference: The Case of the Daguangbao (DGB) Landslide

The Daguangbao (DGB) landslide was the largest landslide that was triggered by the 2008 Wenchuan earthquake with a magnitude of Ms8.0. The sliding surface of this landslide was constrained on a bedding fault 400 m below the ground surface. Seismic records show that the landslide suffered not only from strong horizontal but also vertical ground shaking that was almost equal to the horizontal component. In this study, to reveal the landslide triggering mechanism of the DGB landslide, this study ignores the steep dipping tension fracture section and the leading edge-locking section of the trailing edge of the DGB landslide, and the geological model of the large optical package landslide is generalized into a block model with the bottom controlled slip soft zone as the interface. Based on the improved Newmark method that considers vertical ground motion, the three-way seismic acceleration data and the shear strength parameter of the sliding surface being taken as a variable are used to calculate the cumulative permanent displacement of the slider. Then, by considering the cumulative permanent displacement ratio of vertical seismic acceleration or not and the cumulative permanent displacement ratio value considering the inertial force as the index, the response characteristics of the cumulative permanent displacement of the block-to-vertical ground motion and inertial forces were analyzed. The results show that both the horizontal inertial force and the vertical acceleration significantly increased the permanent displacement. The permanent displacement is 4.9 cm when considering the vertical acceleration, whereas it is only 2.0 cm without taking this into account. The contribution of vertical acceleration is significantly enlarged (87.8–90.7%) by the decreasing of the internal friction angle of the slide surface, while it is less influenced (5–27.4%) by the cohesion. Compared with the lower shear strength parameter of the sliding surface, the contributions of vertical acceleration and inertial force to the permanent displacement are more obvious when the shear strength parameter of the sliding surface is higher. When ϕ &gt; 18°, the D/D* is greater than 1, and the maximum D/D* reaches 7. The fast accumulation event of permanent displacement is triggered in the concentration stage of the seismic energy release. In the DGB landslide area, 50% of the energy is released within 30–50 s, as indicated by the acceleration peaks recorded at the nearest seismic station, Qingping station. It is assumed that the DGB landslide may be triggered at 30–50 s due to half of the seismic energy being released during that time span.

Research on fatigue evaluation method of high-speed train axle based on axle box acceleration

As a key safety component of the high-speed train, fatigue fracture of the axle would lead to major accidents such as derailment or overturning. The complexity of the axle dynamic stress test seriously enhances the difficulty of axle fatigue damage analysis. In this paper, the dynamic stress test of the high-speed train axle was carried out, the axle box acceleration was monitored on-track during the test, and the relationship between the axle stress spectrum and acceleration was analyzed on-track. The results show that the relationships between the axle equivalent stresses and the Root Mean Square (RMS) values of the axle box vertical acceleration and lateral acceleration exhibit a strong joint probability density distribution. The concept of the virtual surface density of wheel-rail contact is also proposed to realize the purpose of using axle box acceleration to deduce axle equivalent force. The results quantify the relationship between axle box acceleration and axle equivalent force, provide a new method for predicting the axle damage using the acceleration RMS values, and open up a new approach for structural health monitoring of high-speed train axles.

Experimental Investigations of the Detachment of Different Particle Structures from a Magnetizable Fiber in the Gas Phase

A current subject of research is the application of magnetic effects for the detachment of accumulated particles of fibrous collectors in gas particle separation. Initial studies have already shown the magnetically induced detachment behavior of a compact particle structure after a single deflection from a single fiber. In this study, the detachment behavior of particle structures with different morphologies from a single fiber is investigated as a function of the particle loading stage on the fiber, the external magnetic flux density, the inflow velocity and the number of regenerations of the fiber for a certain parameter range. Diffusive and more compact particle structures with non-magnetic properties are deposited on the magnetizable single fiber. By applying an external magnetic field, the fiber is magnetized and experiences a torsional moment. The deposited particle structures on the fiber are detached by the acceleration forces. The detachment of the particle structures is observed using a high-speed camera and the image sequences are analyzed. By determining the projection area before and after the fiber deflection, a degree of regeneration is calculated. With magnetic-induced regeneration, high degrees of regeneration close to 100% can be achieved. Repetitive fiber deflections improve the detachment of the particle structures. The magnetic-induced regeneration is suitable for applications where flow reversal is not possible and can be performed either online or offline. Due to the gentle regeneration, fewer emissions are produced on the clean gas side than, for example, with jet pulse cleaning. It makes it easier to achieve emission limits and simplifies product recovery.

Effects of Infill Panels with Various Configurations on the Non-Linear Dynamic Responses of Reinforced Concrete Structures

Abstract: This study presents the effects of including infill panels on the non-linear dynamic response of a hypothetical reinforced concrete frame when subjected to an earthquake. Infill panels are represented by equivalent diagonal struts using three different configurations, i.e., single, double with three different connection locations with the beams, and triple struts. The main goal is to determine the simplest and most appropriate representation of the infill panels by analogous struts. The effect of panel sizes on the non-linear dynamic response of the structure is also presented in this work. The main results showed that including infill panels in the analysis reduced the natural period, roof displacement, and story drift ratio, increasing the roof acceleration and shear forces at the structure base. Utilizing the triple model and the double strut joined at the midspan of the beams showed a good agreement with those using the complete infill model.

Effect of high-gravity acceleration forces and anti-gravity maneuver for cardiac function in fighter pilots

Abstract Background Environmental factors such as hypoxia and gravity affect to the human cardiovascular system. It’s more important for fighter pilots who are exposed to high altitude, harsh gravitational (G) acceleration, and perform anti-G maneuvers similar to the Valsalva maneuver. Experimental studies examining how high gravitational acceleration and anti-gravity maneuver affect cardiac function are rare. Purpose This study aimed to investigate the effect on cardiac function of fighter pilots exposed to high G acceleration forces. Methods From July 2019 to June 2020, fighter pilots underwent regular health check-up and echocardiogram. Data from trainees who did not experience a flight were used for control group. Echocardiographic data included left ventricle (LV) chamber size, systolic function, and diastolic function, as well as right ventricle systolic pressure (RVSP), inferior vena cava (IVC) collapsibility, and the tricuspid annular plane systolic excursion (TAPSE) to evaluate right heart function. The multiple linear regression analysis for TAPSE was performed with total flight time as an independent continuous variable in fighter pilots. Results We enrolled 29 fighter pilots (41±10years-old; male, 100%; mean flight time 1821±1186 hours) and 16 trainees (36±17years-old; male, 100%). There was no significant difference in age, blood pressure, LVEF, RVSP, and the IVC collapsibility between fight pilots and trainees. In multivariate linear regression analysis for fighter pilots, TAPSE was affected by total flight time with positive correlation. Conclusion The experience of fighter pilots exposed to the high G acceleration forces and anti-G maneuver might be associated with right heart function change, but not associated with the prominent cardiac structural changes.