Maximum Acceleration Research Articles

Research on seismic response and dynamic lateral pressure of the silo model under dynamic interaction between granular materials and the silo wall

AbstractThe purpose is to study seismic response and dynamic lateral pressure of the silo wall with different storage conditions under the earthquake. FEM was used to conduct dynamic time history analysis of the silo. The seismic response of the empty silo was smaller than that of the filled silos, and for the latter, under seismic action, the bulk sand particles and the silo wall had a more complex dynamic interaction, and nodes displacements on the wall and columns mainly fluctuated rising. For the deformation of the bulk sand, it was similar to a parabolic pattern in section, the closer to the silo center the greater the deformation was, and the farther away from the silo center the smaller the deformation was. The maximum acceleration was near the top of the wall in the empty silo, near the middle of the wall in contact with bulk sand in the filled silos. Nodes maximum overpressure coefficient was 1.6 and 2.9 in half fully and fully filled silos, respectively, but the coefficient 2.9 was greater than the standardized value of 2.0, therefore, the suggested overpressure coefficient was proposed. Meanwhile, Mises stress was investigated, and it was smaller in the empty silo, but larger in the filled silos, particularly in and around the ring beam due to the dynamic interaction between the sand and the silo wall, where the stiffness had a sudden change, and the maximum stress at the ring beam increased gradually with the seismic action.

First direct machine-specific parameters incorporated in Spot-scanning Proton Arc (SPArc) optimization algorithm.

Spot-scanning Proton Arc (SPArc) has been of significant interest in recent years because of its superior plan quality. Currently, the primary focus of research and development is on deliverability and treatment efficiency. To address the challenges in generating a deliverable and efficient SPArc plan for a proton therapy system with a massive gantry, we developed a novel SPArc optimization algorithm (SPArcDMPO) by directly incorporating the machine-specific parameters such as gantry mechanical constraints and proton delivery sequence. SPArc delivery sequence model (DSMarc) was built based on the machine-specific parameters of the prototype arc delivery system, IBA ProteusONE®, including mechanical constraint (maximum gantry speed, acceleration, and deceleration) and proton delivery sequence (energy and spot delivery sequence, and irradiation time). SPArcDMPO resamples and adjusts each control point's delivery speed based on the DSMarc calculation through the iterative approach. In SPArcDMPO, users could set a reasonable arc delivery time during the plan optimization, which aims to minimize the gantry momentum changes and improve the delivery efficiency. Ten cases were selected to test SPArcDMPO. Two kinds of SPArc plans were generated using the same planning objective functions: (1) original SPArc plan (SPArcoriginal); (2) SPArcDMPO plan with a user-pre-defined delivery time. Additionally, arc delivery sequence was simulated based on the DSMarc and was compared. Treatment delivery time was compared between SPArcoriginal and SPArcDMPO. Dynamic arc delivery time, the static irradiation time, and its corresponding time differential (time differential=dynamic arc delivery time-static irradiation time) were analyzed, respectively. The total gantry velocity change was accumulated throughout the treatment delivery. With a similar plan quality, objective value, number of energy layers, and spots, both SPArcoriginal and SPArcDMPO plans could be delivered continuously within the±1 degree tolerance window. However, compared to the SPArcoriginal, the strategy of SPArcDMPO is able to reduce the time differential from 30.55±11.42%(90±32 s) to 14.67±6.97%(42±20 s), p<0.01. Furthermore, the corresponding total variations of gantry velocity during dynamic arc delivery are mitigated (SPArcoriginal vs. SPArcDMPO) from 14.73±9.14 degree/s to 4.28±2.42 degree/s, p<0.01. Consequently, the SPArcDMPO plans could minimize the gantry momentum change based on the clinical user's input compared to the SPArcoriginal plans, which could help relieve the mechanical challenge of accelerating or decelerating the massive proton gantry. For the first time, clinical users not only could generate a SPArc plan meeting the mechanical constraint of their proton system but also directly control the arc treatment speed and momentum changes of the gantry during the plan optimization process. This work paved the way for the routine clinical implementation of proton arc therapy in the treatment planning system.

Stability analysis of braking and control system of pipeline intelligent plugging robot

In the maintenance and emergency repair of oil and gas long-distance pipelines, the pipeline intelligent plugging robot is a new type of intelligent and efficient plugging device inside the pipeline. The stability of its braking and control system determines whether it can successfully seal high-pressure oil and gas inside the pipeline. This research is about intelligent plugging robots for pipelines that use the friction between the rubber hose and the pipe wall for braking. A hydraulic control system is designed, and a braking model for the robot is established. The hydraulic control system is simulated using a numerical simulation method, and the influence of different braking distances on system stability is investigated for various initial velocities of the robot. The results indicate that the fuzzy PID control hydraulic system exhibits a faster response with a maximum overshoot acceleration of −12.8 m/s2. The system achieves the desired acceleration of −0.14 m/s2 within 7 seconds and successfully completes the braking process. The fuzzy PID control approach effectively reduces parameter fluctuations, improves system stability, and decreases acceleration variations when faced with different initial speeds and braking distance signals. Consequently, the positioning accuracy of the robot is enhanced, and power consumption is reduced. This research provides important guidance for the development of new technologies in pipeline maintenance and emergency repair, particularly in the area of plugging operations under pressure.

The Influence of a Booster Seat on the Motion of the Reclined Small Female Anthropomorphic Test Device in Low-Acceleration Far-Side Lateral Oblique Impacts.

Belt-positioning booster (BPB) seats may prevent submarining in reclined child occupants in frontal impacts. BPB-seated child volunteers showed reduced lateral displacement in reclined seating in low-acceleration lateral-oblique impacts. As submarining was particularly evident in reclined small adult female occupants, we examined if a booster seat could provide similar effects on the kinematics of the small female occupant to the ones found on the reclined child volunteers in low-acceleration far-side lateral oblique impacts. The THOR-AV-5F was seated on a vehicle seat on a sled simulating a far-side lateral-oblique impact (80 deg from frontal, maximum acceleration ∼2 g, duration ∼170 ms). Lateral and forward head and trunk displacements, trunk rotation, knee-head distance, seatbelt loads, and head acceleration were recorded. Three seatback angles (25 deg, 45 deg, 60 deg) and two booster conditions were examined. Lateral peak head and trunk displacements decreased in more severe reclined seatback angles (25-36 mm decrease compared to nominal). Forward peak head, trunk displacements, and knee-head distance were greater with the seatback reclined and no BPB. Knee-head distance increased in the severe reclined angle also with the booster seat (>40 mm compared to nominal). Seat belt peak loads increased with increased recline angle with the booster, but not without the booster seat. Booster-like solutions may be beneficial for reclined small female adult occupants to reduce head and trunk displacements in far-side lateral-oblique impacts, and knee-head distance and motion variability in severe reclined seatback angles.

Reassessment of the Stability Conditions in the Lignite Open Pits of Oltenia (Romania) in Relation to the New Local Seismic Context as an Imperative for Sustainable Mining

Responsible mining considers the three pillars of sustainability, namely the environment, the economy and social welfare. As a result, exploitation of deposits of useful mineral substances, as an economic activity, must be carried out taking into account several requirements, among which is the generation of a reduced impact on the environment and local communities. Sliding of open pits and waste dumps slopes represents a major risk, which endangers workers and machinery, as well as the components of the natural and built environment in the influenced area. In order to avoid such phenomena and their consequences, it is imperative to analyze the stability conditions whenever their possible triggering factors appear (such as earthquakes). Between February and March of 2023, the region of Oltenia (south-west Romania) was affected by intense seismic activity, out of normal patterns. Considering this series of seismic events, in this paper we aimed at reevaluating the stability conditions of the slopes of the working fronts and of the internal dumps in the lignite open pits located in the region in this new context. Research focused on three lignite open pits, namely Peșteana North (Rovinari mining perimeter), Jilț North (Jilț mining perimeter), Berbești–Alunu (Berbești mining perimeter). After describing the general geology and tectonics of the areas under study, the seismic episode that affected the region at the beginning of 2023 (which in fact extended until November) is highlighted, with increased attention given to the earthquakes of 13 and 14 February 2023, with a local magnitude ML ≥ 5. The most important part of the study is represented by the stability analyses, carried out for normal conditions (considering the characteristics of the rocks at natural humidity and in the absence of the influence of external factors) and under seismic conditions, characterized by a peak ground acceleration equal to the maximum acceleration considered for the location area of the mining perimeters taken into study. The results of the study showed that, for most of the analyzed situations, a renewal of the technical exploitation documentation is required, which, taking into account the results of this study, must adopt new geometries of the excavation and deposition fronts, so that the objectives in terms of operational and workplace safety imposed by legislation are respected.

CO2 Measurement under Different Pressure and Vibration Conditions Using Tunable Diode Laser Absorption Spectroscopy

The greenhouse effect resulting from fuel combustion has drawn growing attention, and CO2 emissions from fossil fuel power stations are one of the main sources of greenhouse gases. It is crucial to monitor the concentration of CO2 in the flue gas ducts of these stations. However, pressure and vibration caused by the combustion of boilers make the measurement of CO2 in flue gas ducts extremely challenging. In this study, tunable diode laser absorption spectroscopy (TDLAS) combined with Wave Modulation Spectroscopy (WMS) was employed to measure the concentration of CO2 under different pressure and vibration conditions in the laboratory. The absorption line of CO2 at the wavenumber 6357.38 cm−1 was recorded under varying pressure conditions ranging from 0 to 1.4 atm, acceleration conditions ranging from 0 to 7.7 m/s2, and a combination of both. Firstly, a negative linear correlation was found between the pressure and the amplitude of the second harmonic, with a maximum relative error of 4.645% observed at a pressure of 1.4 atm. Secondly, the maximum acceleration that the system can withstand was determined to be 7.3 m/s2, as it was not possible to provide a sufficiently low fitting error at higher accelerations. For the combined effects of the pressure and vibration, a dramatic increase in the relative error of amplitude can be observed within the acceleration range of 5.0~6.0 m/s2 while under the pressure conditions of 0.6 atm, 1.0 atm, and 1.4 atm. Moreover, the maximum endurable acceleration decreases with the increase in pressure, which infers that effective measurements can be achieved when the acceleration is below 5 m/s2 within the pressure range of 0~1.4 atm. This suggests that TDLAS combined with WMS possesses a potential for online measuring of CO2 concentrations in flue gas ducts within a certain acceleration range. This work can provide some insights for stable gas detection using TDLAS under varied pressure and vibration conditions.

Rotational Thromboelastometry and Clot Waveform Analysis as Point-of-Care Tests for Diagnosis of Disseminated Intravascular Coagulation in Critically Ill Children in Thailand.

This study aimed to determine the test performances of rotational thromboelastometry (ROTEM) and activated partial thromboplastin time-based clot waveform analysis (aPTT-CWA) compared with the International Society on Thrombosis and Hemostasis disseminated intravascular coagulation (ISTH-DIC) score for diagnosis of overt disseminated intravascular coagulation (ODIC) in critically ill children. Prognostic indicators of DIC complications were also evaluated. A prospective cross-sectional observational study was conducted. ROTEM and aPTT-CWA were assessed alongside standard parameters based on the ISTH-DIC score and natural anticoagulants. Both conventional and global hemostatic tests were repeated on days 3-5 for nonovert DIC. PICU of the Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand. Infants and children who were admitted to PICU with underlying diseases predisposed to DIC, such as sepsis, malignancy, major surgery, trauma, or severe illness, were included in the study between July 1, 2021, and November 30, 2022. None. Sixty-four children were enrolled in this study. The prevalence of ODIC was 20.3%. Regarding ROTEM parameters, using EXTEM clot formation time (CFT) cutoff of greater than 102 seconds provided sensitivity and specificity of 90.9% and 80.9%, respectively, for diagnosing ODIC, with the area under the curve (AUC) of 0.86. In the case of aPTT-CWA performance, no biphasic waveform was observed, whereas both maximum coagulation acceleration (Min2) of less than 0.35%/s 2 and maximum coagulation deceleration of less than 0.25%/s 2 demonstrated identical sensitivities of 76.9% and specificities of 79.6%. Combining two global hemostatic tests significantly improved the diagnostic performance (INTEM CFT + EXTEM CFT + Min2 AUC 0.92 [95% CI, 0.80-1.00] vs. EXTEM CFT AUC 0.86 [95% CI, 0.75-0.96], p = 0.034). Bleeding was the most common consequence. In multivariable logistic regression analysis, Min2 of less than 0.36%/s 2 was an independent risk factor for bleeding complications, with an adjusted odds ratio of 15.08 (95% CI, 1.08-211.15, p = 0.044). ROTEM and aPTT-CWA were valuable diagnostic tools in critically ill children who might require point-of-care tests. Min2 showed significant clinical implications for predicting bleeding events in this population.

Laser-machined two-stage nozzle optimised for laser wakefield acceleration

In this paper, the modelling and manufacturing of a two-stage supersonic gas jet nozzle enabling the formation of adaptive plasma concentration profiles for injection and acceleration of electrons using few-cycle laser beams are presented. The stages are modelled using the rhoSimpleFoam algorithm of the OpenFOAM computational fluid dynamics software. The first 200–300 ${\rm \mu}$ m diameter nozzle stage is dedicated to 1 % N2 + He gas jet formation and electron injection. By varying the pressure between the first and second stages of the injectors, the electron injection location could be adjusted, and the maximum acceleration distance could be ensured. By changing the concentration of the nitrogen in the gas mixture, the charge of the accelerated electrons could be controlled. The second nozzle stage is designed for acceleration in fully ionised He or hydrogen gas and forms the optimal plasma concentration for bubble formation depending on the laser pulse energy, duration and focused beam diameter. In order to reduce the diameter of the plasma profile formed by the first nozzle and the concentration drop gap between the two nozzles, a one-side straight section was introduced in the first nozzle. The shock wave reflected from the straight section of the wall propagates parallel to the shock wave of the intersecting supersonic jets and ensures a minimal gap between the jets. The second-stage longitudinal plasma concentration profile could have an increasing gas density gradient to compensate for dephasing between the electron bunch and the plasma wave due to wave shortening with increasing plasma concentration.

Dynamic soil–structure interaction of a three-span railway bridge subject to high-speed train passage

In this study, the influence of Soil-Structure Interaction (SSI) on the dynamic behavior of a three-span concrete slab railway bridge with integrated retaining walls is investigated. The bridge is subjected to controlled excitations using a hydraulic actuator with different frequencies and load amplitudes. A 3D model of the railway bridge-soil system is implemented and calibrated using the experimental frequency response functions at each sensor location. A soil-free model is also created to compare with the calibrated model. It is observed that the dynamic behavior of the railway bridge is substantially altered by the presence of the surrounding soils, and neglecting SSI can lead to underestimation and inaccurate results. Additionally, the calibrated model is used for further train-passage analyses. For the studied bridge, neglecting SSI increases the maximum acceleration response of the bridge during high-speed train passages from 5.5 m/s2 up to 14.5 m/s2. It is also shown that the response of the bridge during train passage is predominantly influenced by its first bending mode, with higher modes inducing no discernible effect. Finally, parametric studies are performed in order to study the uncertainties related to the soil properties.

Research on Flexible Braking Control of a Crawler Crane during the Free-Fall Hook Process

Due to the large inertia and strong impact accompanying the free-falling hook process of crawler cranes, it is difficult to meet the demand for flexible and smooth braking control under different weight load conditions. Therefore, this paper takes the free-fall hook system as the research object and combines system operation characteristics and control theory to carry out research on flexible braking control of the free-fall hook system. Firstly, a joint simulation platform of MATLAB (version 2018b) and AMESim (version 2019.1) software is built to theoretically analyze the key components of the free-fall hook system (proportional pressure-reducing valve, winch reducer, and wet clutch). Secondly, a mathematical model of the braking process is established, and the pressure control demand is clarified to analyze the reasons for the existence of dead zones and hysteresis loops in the system. Meanwhile, it is found that the dead zones and hysteresis loops existing in the pressure output of the pressure-reducing valve are the main factors of flexibility with load braking. Then, in this paper, a closed-loop control strategy is formulated based on the automatic adaptation of the braking gear in combination with the fuzzy PID pressure. Finally, the effectiveness of the control strategy proposed in this paper is verified with simulation and experimental testing using the pressure hysteresis loop of the free-fall hook process and the load-braking acceleration as the judging criteria. The results show that the system pressure hysteresis loop is reduced by 50%–60% and the maximum braking acceleration is reduced by 24%–30% under the conditions of 6.44 tonnes and 10.44 tonnes, which improves the accuracy of pressure control and achieves flexible and smooth braking with loads for different tonnages of free-fall hooks.

Joint electric vehicle routing and battery health management integrating an explicit state of charge model

Although fleet management has been extensively explored in transportation science, the rise of electromobility imposes several scientific challenges and opportunities. So far, few attempts were made to include battery degradation in the Electric Vehicle Routing Problem (EVRP). To do it realistically, it is necessary to model State of Charge (SoC), however most versions of routing problems use oversimplified SoC models or consider only energy consumption which leads to less robust solutions overall. In this work, a method for estimating battery degradation, which relies on a realistic SoC model is presented and incorporated into a new version of the electric vehicle routing problem. In this version, not only battery degradation is integrated, but also the possibility of limiting different vehicle parameters, such as maximum vehicle speed and acceleration. Due to the extra computational complexity related to the SoC and degradation models, a genetic algorithm capable of solving the aforementioned extended EVRP is presented. Finally, through different numerical experiments, the advantages of the proposed methodology are shown.

Comprehensive Assessment of the Seismic Performance of an Innovative Hybrid Semiactive and Passive State Control System for a Low-Degree-of-Freedom Structure Using Real-Time Hybrid Simulation

The dynamic performance of base isolation systems provides an effective means to reduce the seismic vulnerability of buildings. However, large displacements in the base isolation during seismic events pose a major challenge for this control system. Recently, novel control systems have been implemented to control and reduce the excessive displacements. This study presents an evaluation of the seismic performance of unconnected-fiber-reinforced elastomeric isolators (U-FREI) and variable orifice damper (VOD) devices used together as a hybrid control system for a low-degree-of-freedom reference structure by employing real-time hybrid simulation (RTHS) testing technique. This physical cybernetic testing methodology allows a dynamic system of interest to be substructured into two components: numerical and experimental. In this study, the numerical substructure corresponds to a 2-degree of freedom model, representing a reference structure, and an experimental substructure was formed using the hybrid control system described. To develop an interface between the two substructures, a horizontal transfer system (HTS) was implemented and coupled with a vertical transfer system (VTS). Using RTHS, the performance of the reference structure and the hybrid control system was evaluated under six seismic events: CAM, CAT, El Centro, Loma Prieta, Pizarro, and Chihuahua, at a maximum acceleration of 0.10 g (0.981 m·s−2). The experimental behavior of the hybrid control system allows the reference structure to reduce its maximum drift by more than 24% compared to the fixed structure. Finally, the performance and accuracy of the RTHS tests were calculated.

Study on the correlation between indoor accelerated corrosion testing of concrete epoxy polysiloxane coating and real-sea environmental testing in the East China Sea

In order to reveal the correlation between the accelerated corrosion test of epoxy polysiloxane coating and the real sea environmental test, the real sea environmental test was carried out in the atmosphere and tidal range area of Zhairuoshan Island in the East China Sea, and the multi-factor coupling test I (Cycle of 7-day xenon lamp aging test + 7-day Wetting-drying test) and test II (Cycle of 7-day xenon lamp aging test + 3-day damp heat test + 4-day salt spray test) were designed with reference to the environment of the East China Sea. The correlation between indoor accelerated corrosion test and real sea environmental test was analyzed by using Grey Relation Analysis, Spearman's rank correlation coefficient and Acceleration factor conversion method. The results show that both the indoor accelerated corrosion test and the real sea environmental test have corrosive effects on the epoxy polysiloxane coating of concrete. In the indoor accelerated corrosion test, it was found that the Wetting-drying test caused the highest loss of light rate. In the real sea environmental test, the loss of light rate of the coating in the atmosphere is higher than that in the tidal area, and the color difference is slightly lower. When the loss of light rate is used as the criterion, the grey correlation coefficient between the multi-factor coupling test I and the tidal range test is 0.63, and the maximum acceleration factor during the test is 5.3, indicating a good correlation between the two tests. Through this study, an effective indoor accelerated corrosion test method with good correlation and acceleration characteristics to the loss of light rate of concrete epoxy polysiloxane coating in a real sea environment was obtained.

Vibration control of an eleven-story structure with MR and TMD dampers using MAC predictive control, considering nonlinear behavior and time delay in the control system

In the last two decades, model predictive control has made significant progress in research and industrial process control. This achievement is through the high ability of model predictive control to solve industrial process control problems in the time domain. It is applicable in many control systems, such as delayed systems, univariate and multivariable systems, non-minimum phase systems, and unstable systems. This strategy is essentially for controlling delayed systems. It is possible to create a time delay in transmitting structure movement data in the systems that use sensors and receivers of sensor-recorded data, which is a factor to reduce the efficiency of the control system and even the instability of the structure. In this study, to investigate and compensate the effect of time delay in the hybrid vibration control system, an 11-story structure with a tuned mass damper and an MR damper was used by model algorithmic control (MAC) and nonlinear behavior of the structure in the control process. The linear and nonlinear structural models are created in OpenSEES, the control system in MATLAB; and the TCP/IP connection method was used to connect two programs. The fuzzy decision system is based on accelerating and decelerating movement. The structure has been subjected to seven earthquakes with maximum accelerations of 0.1 g to 1.0 g with an incremental step of 0.1 g. According to the results of incremental dynamic analysis, the average percentage of the fuzzy control system performance reduction, considering the time delay, is 15.28% and 38.57% for the maximum displacement and base shear in the linear structure, and 8.04% and 5.97% for the nonlinear structure, respectively. The assumed time delays have been effectively overcome using the model algorithmic control system (MAC), determining the prediction horizon of the structural behavior, and optimizing the control force in the control horizon. The performance of the MAC control system has been better than the fuzzy control system and the passive control with TMD. The average improvement percentage of the results of the maximum linear and nonlinear structural displacement response is respectively equal to 10.2 and 11.8 with the MAC control system, compared to the fuzzy control system without time delay. For the maximum base shear, it is equal to 8.32 and 2.49, respectively.

Correlation of 3D Morphometric Changes, Kinematics, and Muscle Activity During Smile.

Knowing the morphological, kinematic, and electrophysiological parameters of the smile in healthy individuals may contribute to evaluating, planning, and monitoring the smile reanimation. This study aimed to determine the correlation between 3D morphometric changes, movement kinematics, and muscle activity in the facial soft tissue of healthy individuals. In this cohort study, 20 volunteers were selected from healthy individuals with no facial disorders. During smiling, three-dimensional face scanning, facial motion capture, and surface electromyography (sEMG) were performed. The average displacement, velocity, and acceleration during facial movements were measured. The mean change in 3D surface morphometry and activation of the zygomaticus major were determined. The volunteers, comprising 10 males and 10 females, had a mean age of 24 ± 10 years; for female, mean age was 23 ± 5 years and for men 26 ± 13 years. Significant correlations were found between kinematic and morphometric data (r = 0.51, p < 0.001), sEMG and morphometric (r = 0.50, p < 0.001) data, and sEMG and kinematic data (r = 0.49, p < 0.002). The maximum acceleration occurred during approximately 65% of the muscle activation time and 64% of the peak muscle activation value. Additionally, the maximum velocity was reached at around 73% of the muscle activation time and 67% of the peak muscle activation value. Furthermore, the maximum displacement values were observed at approximately 88% of the muscle activation time and 76% of the peak muscle activation value. The findings may provide insights into the smile's functional parameters, contribute to understanding facial muscle-related disorders, and aid in improving the diagnosis and treatment of the smile. NA Laryngoscope, 134:3112-3119, 2024.

Numerical study on thermodynamic characteristics of large-scale liquid hydrogen tank with baffles under sloshing conditions

The control of the evaporation rate is essential to the long-distance transportation of liquid hydrogen (LH2). This paper conducts a numerical investigation of the thermodynamic characteristics in tanks with baffles under LH2 sloshing conditions by establishing a computational fluid dynamics (CFD) model. The pressurization rate and vapor-liquid interface sloshing behavior predicted by the numerical model is validated against experimental data. The effects of baffles, amplitude, frequency, and storage pressure on thermodynamic characteristics such as temperature, pressurization rate, and evaporation rate of the LH2 tank under sinusoidal sloshing are analyzed in detail. The simulation results suggest that adding baffles can effectively suppress the pressure fluctuation of LH2 under sloshing conditions, but baffles as a "thermal bridge" accelerate the pressurization rate in the tank. Adding baffles during smooth transportation accelerates the pressurization rate. The baffles gradually demonstrate the effect of suppressing the pressurization rate as the acceleration amplitude increases. Assuming that the LH2 evaporation rate is stable for a certain value, the daily evaporation rates in the LH2 tank account for 2.59 % and 5.13 % when the maximum acceleration is 5.92 m/s2 and 9.87 m/s2, respectively, which contradicts the long-term storage goal of LH2. The slower the sloshing frequency, the higher the maximum liquid phase level in the tank, and the faster the evaporation rate. The sloshing frequency has little effect on the LH2 pressurization and evaporation rates compared to the amplitude. The growth of pressure decreases from 139.9 Pa to 85.62 Pa for a period of 15 s when the storage pressure in the tank increases from 0.1 MPa to 0.6 MPa. This study provides guidlines for the in-depth investigation of the thermodynamic behavior in LH2 tanks during transportation.

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.

A risk-aware reference trajectory resampling method for quadrotor tracking accuracy improvement

PurposeMany existing trajectory optimization algorithms use parameters like maximum velocity or acceleration to formulate constraints. Due to the ignoring of the quadrotor actual tracking capability, the generated trajectories may not be suitable for tracking control. The purpose of this paper is to design an online adjustment algorithm to improve the overall quadrotor trajectory tracking performance.Design/methodology/approachThe authors propose a reference trajectory resampling layer (RTRL) to dynamically adjust the reference signals according to the current tracking status and future tracking risks. First, the authors design a risk-aware tracking monitor that uses the Frenét tracking errors and the curvature and torsion of the reference trajectory to evaluate tracking risks. Then, the authors propose an online adjusting algorithm by using the time scaling method.FindingsThe proposed RTRL is shown to be effective in improving the quadrotor trajectory tracking accuracy by both simulation and experiment results.Originality/valueInfeasible reference trajectories may cause serious accidents for autonomous quadrotors. The results of this paper can improve the safety of autonomous quadrotor in application.

ТЯГОВІ ВИПРОБУВАННЯ МОБІЛЬНИХ МАШИН ІЗ ВИКОРИСТАННЯМ ПРИНЦИПІВ КІНЕМОДИНАМІКИ

The study aims to develop a method for traction testing of mobile machines using the principles of kinemodynamics. To achieve these goals, it is necessary to: justify the method of traction testing of mobile machines using the principles of kinemodynamics; and carry out experimental validation of the proposed test method. Methods and materials. The methodological basis of the work is the principles of kinemodynamics, namely partial accelerations. The development of a test method consists of determining the possibility of measuring the established indicators and assessing the method’s suitability. To determine the power and energy characteristics of mobile machines, it is proposed to use a measuring complex consisting of a linear accelerometer and special software for processing the measured data. Results. A method for traction testing of mobile machines using the principles of kinemodynamics has been developed; experimental validation of the proposed test method was carried out. The essence of the method is the direct measurement of longitudinal accelerations that occur during the acceleration of a car and the subsequent processing of the results of these measurements, using an energy approach based on determining the change (difference) in the kinetic energy of the car over a certain period. This made it possible to determine the force on the wheels of the car, which leads to its acceleration (or maintaining uniformly accelerated motion) and the share of engine power spent on this car. An experimental validation of the developed method was carried out, which consisted of determining the coefficient of agreement of test results with variations in certain specific factors. Conclusions. The use of the principles of kinemodynamics allows us to determine the fraction of force that leads to acceleration during the acceleration of the car and the fraction of engine power expended. Based on the test results obtained by the proposed method, the following analysis can be made: determine the conditions (gear ratio in the gearbox) under which maximum acceleration is possible, determining the share of the maximum possible design force in each gear used to accelerate the machine; determine the weighted average power reserve of the machine engine, which can be used to overcome additional interference. Experimental validation of the proposed method in terms of agreement showed satisfactory results. Keywords: traction tests, method, coincidence coefficient, power, traction force, acceleration.

Inertial Measurement Unit-Based Romberg Test for Assessing Adults With Vestibular Hypofunction.

This work aims to explore the utility of wearable inertial measurement units (IMUs) for quantifying movement in Romberg tests and investigate the extent of movement in adults with vestibular hypofunction (VH). A cross-sectional study was conducted at an academic tertiary medical center between March 2021 and April 2022. Adults diagnosed with unilateral vestibular hypofunction (UVH) or bilateral vestibular hypofunction (BVH) were enrolled in the VH group. Healthy controls (HCs) were recruited from community or outpatient clinics. The IMU-based instrumented Romberg and tandem Romberg tests on the floor were applied to both groups. The primary outcomes were kinematic body metrics (maximum acceleration [ACC], mean ACC, root mean square [RMS] of ACC, and mean sway velocity [MV]) along the medio-lateral (ML), cranio-caudal (CC), and antero-posterior (AP) axes. A total of 31 VH participants (mean age, 33.48 [SD 7.68] years; 19 [61%] female) and 31 HCs (mean age, 30.65 [SD 5.89] years; 18 [58%] female) were recruited. During the eyes-closed portion of the Romberg test, VH participants demonstrated significantly higher maximum ACC and increased RMS of ACC in head movement, as well as higher maximum ACC in pelvic movement along the ML axis. In the same test condition, individuals with BVH exhibited notably higher maximum ACC and RMS of ACC along the ML axis in head and pelvic movements compared with HCs. Additionally, BVH participants exhibited markedly increased maximum ACC along the ML axis in head movement during the eyes-open portion of the tandem Romberg test. Conversely, no significant differences were found between UVH participants and HCs in the assessed parameters. The instrumented Romberg and tandem Romberg tests characterized the kinematic differences in head, pelvis, and ankle movement between VH and healthy adults. The findings suggest that these kinematic body metrics can be useful for screening BVH and can provide goals for vestibular rehabilitation.