Motion Characteristics Research Articles

Numerical study on the motion characteristics of free fall lifeboats entering calm water and rough sea

As ocean engineering operations extend into deeper seas, the working environment becomes increasingly complex, making free fall lifeboats (FFLBs) more vital for maritime disaster rescues. Unlike traditional davit-launched lifeboats, FFLBs are propelled into the water at a specific velocity and angle, engaging in a complex motion process of launch, impact, submersion, and resurfacing. Therefore, to assess the safety of FFLBs, this paper regarding the lifeboat as a rigid body aims to investigate the six-degree-of-freedom motion characteristics of lifeboat entering the water with different entry angles θ and wave environment, with a specific focus on analyzing the primary causes of capsizing. The numerical simulations of water entry with various θ, wave heights H, and relative entry positions are carried out by combining large eddy simulation and overset mesh technology. The free surface is captured by the volume of fluid method, and the attitude change, acceleration change, motion trajectory, and free surface evolution law of lifeboats are analyzed. The findings suggest that lifeboats can enter calm water safely at θ of 20°–50° and maintain a stable posture. Moreover, in extreme conditions where θ is either 0° or 90°, there is a high risk of entry failure due to excessive vertical acceleration and poor motion attitude, respectively. Furthermore, when facing waves, lifeboats experience reduced horizontal displacement when entering at peak and downward zero point compared to calm water conditions, which poses challenges for avoiding potential dangers.

CO2 retention in high-pressure/high-temperature reservoirs of the Yinggehai Basin, northwestern South China Sea

Global industry drillings targeted at deep-burial hydrocarbons have renewed the record of maximum sustainable overpressure in sedimentary basins. However, the influence of extremely high overpressure on natural fluid accumulation and artificial waste sequestration is not yet completely understood. To better understand the motion characteristics of the highly overpressured CO2-rich fluid, the CO2 retention capacity was quantified, and the CO2-rich fluid motion trails were evaluated in an ideal natural laboratory in the Yinggehai Basin. The hydraulic sealing capacity was higher than the capillary sealing capacity in the highly overpressured stratum. Relative to the situations of no breach or solely breached by capillary failure, the superposition of capillary and hydraulic failures resulted in the caprock integrity breakage by faults (or fractures), diapirs, and pipes. Meanwhile, the high expulsion flux of CO2-rich fluid caused the consumption of chlorite to generate illite in the caprock of dual-breached fields. The CO2-rich fluid flux of capillary invasion was limited by the inherently low permeability of caprock, which may be insufficient for a dramatic change of hydrogen ions or electron activities to induce remarkable chlorite dissolution in the caprock of the sole-breached field.

Stratospheric airship trajectory planning in wind field using deep reinforcement learning

Stratospheric airships, with their long endurance, high flight altitude, and large payload capacity, show promise in earth observation and mobile internet applications. However, challenges arise due to their low flight speed, limited maneuverability and energy constraints when planning trajectories in dynamic wind fields. This paper proposes a deep reinforcement learning-based method for trajectory planning of stratospheric airships. The model considers the motion characteristics of stratospheric airships and environmental factors like wind fields and solar radiation. The soft actor-critic (SAC) algorithm is utilized to assess the effectiveness of the method in various scenarios. A comparison between time-optimized and energy-optimized trajectories reveals that time-optimized trajectories are smoother with a higher speed, while energy-optimized trajectories can save up to 10% energy by utilizing wind fields and solar energy absorption. Overall, the deep reinforcement learning approach proves effective in trajectory planning for stratospheric airships in deterministic and dynamic wind fields, offering valuable insights for flight design and optimization.

EEG correlates of static and dynamic face perception: The role of naturalistic motion

Much of our understanding of how the brain processes dynamic faces comes from research that compares static photographs to dynamic morphs, which exhibit simplified, computer-generated motion. By comparing static, video recorded, and dynamic morphed expressions, we aim to identify the neural correlates of naturalistic facial dynamism, using time-domain and time-frequency analysis. Dynamic morphs were made from the neutral and peak frames of video recorded transitions of happy and fearful expressions, which retained expression change and removed asynchronous and non-linear features of naturalistic facial motion. We found that dynamic morphs elicited increased N400 amplitudes and lower LPP amplitudes compared to other stimulus types. Video recordings elicited higher LPP amplitudes and greater frontal delta activity compared to other stimuli. Thematic analysis of participant interviews using a large language model revealed that participants found it difficult to assess the genuineness of morphed expressions, and easier to analyse the genuineness of happy compared to fearful expressions. Our findings suggest that animating real faces with artificial motion may violate expectations (N400) and reduce the social salience (LPP) of dynamic morphs. Results also suggest that delta oscillations in the frontal region may be involved with the perception of naturalistic facial motion in happy and fearful expressions. Overall, our findings highlight the sensitivity of neural mechanisms required for face perception to subtle changes in facial motion characteristics, which has important implications for neuroimaging research using faces with simplified motion.

SITE-SPECIFIC DISAGGREGATION ANALYSIS OF RECENT EARTHQUAKE ON THE AMBON COAST

Seismic activity in the eastern region of Indonesia, particularly in Ambon, has been a matter of great concern because of its high tectonic activity. The devastating magnitude 6.5 earthquake in September 2019, which resulted in fatalities and significant damage, highlighted the region’s vulnerability and emphasized the importance of understanding the area’s seismic hazards. Although previous studies have been conducted, this study aims to fill critical gaps in the literature by using the latest seismic data until 2022 and updated attenuation equations. Disaggregation analysis is employed to identify ground motion characteristics, that are crucial for calculating synthetic ground motion acceleration. Under risk-targeted maximum considered earthquake (MCER) conditions, the study results show a peak ground acceleration of 0.444 g, with spectral acceleration at 0.2 s reaching 1.093 g, which decreases to 0.350 g at 1.0 s. Notably, background earthquake sources play a dominant role in contributing to the region’s high seismic hazard potential. The results of this study highlight the urgency of updating Indonesia’s national seismic hazard map. The study also recommends future studies to explore additional parameters of newly discovered faults to enhance understanding of fault movements and their impacts in the study area.

Examination of particle motion in fluidized bed flotation columns: Effect of particle shape

The critical analysis of particle dynamics within the flow field is vital for the optimization and enhancement of new fluidized bed flotation columns. Prior research has centered on the kinetic properties of auxiliary fluidized particles (glass spheres) in these columns [1]. However, in real-world applications, these particles undergo wear and transform into irregular shapes. This investigation seeks to explore the motion characteristics of particles of various geometries in a three- phase gas-liquid-solid environment. By quantifying the velocities of particles with different shapes, we aim to improve the evaluation of their dispersion and collision behavior with the column walls. First, the particle concentration distribution within the fluidized zone is continuously monitored through pressure sensors at various axial positions, allowing us to examine the concentration patterns of particles from different shape categories under various operational conditions. Second, the motion dynamics of particles within the fluidization zone are studied using high-speed camera techniques. Particle velocities are determined by correlating tracer particle velocities with black markers for precise measurement. To evaluate the frequency of particle-wall collisions, a modified collision model is applied to ascertain collision rates and to investigate the influence of shape parameters on such interactions. Lastly, the normal and tangential restitution coefficients are measured based on the trajectories of particles before and after collisions with the walls.

Early warning of landslides based on statistical analysis of landslide motion characteristics and AI Earth Cloud InSAR processing system: a case study of the Zhenxiong landslide in Yunnan Province, China

Early warning of landslides based on statistical analysis of landslide motion characteristics and AI Earth Cloud InSAR processing system: a case study of the Zhenxiong landslide in Yunnan Province, China

Theoretical and FEA investigation of the mechanical behaviour for offshore LCO2 floating hose

Injecting liquid CO2 (LCO2) into the seabed for storage utilizing an offshore platform to achieve offshore storage of CO2 is one of the effective measures to realize the reduction of CO2 emissions. To solve the difference in motion characteristics between the LCO2 carrier and the receiving platform due to wind and wave currents, floating hoses can be employed as the pipeline in the CO2 transportation. In this study, an LCO2 floating hose based on the structural form of steel wire reinforced thermoplastic composite pipe is proposed. A mechanical model for this hose is developed to analyze the tensile mechanical properties. It is verified that the method is reliable by comparing with the published experimental results of composite hose containing 4 layers of aramid fiber reinforced layers with a maximum error of 11.48%. A comparative analysis was also carried out by finite element analysis (FEA) with a maximum error of 10.67%. On this basis, the damage states of the hose under internal pressure, tension, bending and torsion load were investigated to analyze mechanical properties. The ultimate tensile load capacity, ultimate bending radius and ultimate unit torsion angle are 463 kN, 1.64m and 14°/m, respectively. The components most prone to failure under different loads were clarified. This study can provide technical reference for the design of floating hoses for offshore LCO2 storage and transportation.

Dynamic rupture modeling in a complex fault zone with distributed and localized damage

Active fault zones have complex structural and geometric features that are expected to affect earthquake nucleation, rupture propagation with shear and volumetric deformation, and arrest. Earthquakes, in turn, dynamically activate co-seismic off-fault damage that may be both distributed and localized, affecting fault zone geometry and rheology, and further influencing post-seismic deformation and subsequent earthquake sequences. Understanding this co-evolution of fault zones and earthquakes is a fundamental challenge in computational rupture dynamics with consequential implications for earthquake physics, seismic hazard and risk. Here, we implement a continuum damage-breakage (CDB) rheology model in our MOOSE-FARMS dynamic rupture simulator to investigate the interplay between bulk damage and fault motion on the evolution of dynamic rupture, energy partitioning, and ground motion characteristics. We demonstrate several effects of damage (accounting for distributed cracking) and breakage (accounting for granulation) on rupture dynamics in the context of two prototype problems addressed currently in the 2D plane-strain setting: (1) a single planar fault and (2) a fracture network. We quantify the spatio-temporal reduction in wave speeds associated with dynamic ruptures in each of these cases and track the evolution of the original fault zone geometry. The results highlight the growth and coalescence of localization bands as well as competition between localized slip on the pre-existing faults vs. inelastic deformation in the bulk. We analyze the differences between off-fault dissipation through damage-breakage vs. plasticity and show that damage-induced softening increases the slip and slip rate, suggesting enhanced energy radiation and reduced energy dissipation. These results have important implications for long-standing problems in earthquake and fault physics as well as near-fault seismic hazard, and they motivate continuing towards 3D simulations and detailed near-fault observations to uncover the processes occurring in earthquake rupture zones.

Phase classification and transient effects of the start-up process of multi-functional pump station in pump mode

In the context of achieving the goal of carbon neutrality, multi-functional pump stations (MFPS) have been greatly developed as a new energy system in recent years. The MFPS can operate in forward direction in pump mode to pump water and in turbine mode in reverse direction to generate electricity. At present, the instability of the MFPS during start-up process (SUP) in pump mode has become the key to restricting the operating life and further development of MFPS. In this paper, based on the motion characteristics of the pump and the cut-off facility (COF), the SUP of the MFPS in pump mode is clearly classified. In order to reveal the transient effect during the SUP, the steady-state full characteristic experiment (SFCE) of the pump was carried out. The occurrence phase of the transient effect during the SUP is analyzed, and the deviation between the steady-state external characteristics and the transient characteristics is revealed. In this study, the evaluation formula of the start-up completion degree (SUCD) of the MFPS in pump mode is proposed for the first time, and the evaluation and identification of the start-up progress at different phases are completed. The results show that the water flow in the system is in a reverse flow state in the Phase I. The SUCD of Phase I is 17 %. In the Phase II, The high-speed jet flow in the pump flows to the inlet of the guide vane (GV), which gradually changes the mainstream direction in the GV. A certain vortex structure can be observed at the exit of the flap gate (FG). The SUCD of Phase II is 61 %. In the Phase I and II, the dimensionless head of transient simulation is much larger than that of SFCE. In the Phase III, the flow state in the impeller will gradually stabilize. The transient effect disappears and the pressure fluctuation intensity decreases. The SUCD of Phase III is 93 %. In the Phase IV, the separation vortex that persists from Phase I-III at the tail of the GV blades disappears. The diversion capacity at the gate increases, and significant annular flow can be observed near the FG.

Expanding the family of plane-symmetric 6R deployable polygon mechanisms by systematically exploring the layout of R-joint axes

In this paper, the impact of parameter variations on the deployable motion characteristics, mobility, input singularity, and deploying/folding performance of plane-symmetric Bricard mechanisms is studied. Firstly, two classes of revolute pair axes used to construct deployable polygon mechanisms (DGMs) are reviewed, and their value ranges are further refined. Secondly, all possible axes arrangement schemes for plane-symmetric 6R DGMs are presented for the first time. Then, an improved schematic synthesis method is proposed, which can be used to design all plane-symmetric 6R DGMs that belong to the plane-symmetric Bricard mechanisms. Thirdly, the improved design method is applied to create a series of single-degree-of-freedom plane-symmetric 6R DGMs. Then, feasible domain searches are performed, and some of them are prototyped. Subsequently, the input singularity of plane-symmetric 6R DGMs is analyzed. Finally, two deploying/folding performance indices are proposed to evaluate the performance of plane-symmetric 6R DGMs with different fully deployed and fully folded states based on actual application scenarios. This work expands the variety and quantity of DGMs, which will also advance the development of robotics, mechanical metamaterials, and kirigami mechanisms.

Kinematic Source Properties of the 2023 Mw 7.7 Türkiye Earthquake Inferred from Near-Fault Strong Ground Motions

Abstract The 2023 Mw 7.7 Türkiye earthquake provided densely observed near-fault ground-motion data, which enabled us to investigate their characteristics and generations. This study aimed to obtain an intuitive understanding of the characteristics of near-fault strong ground motions and their relationship with kinematic source properties using a simple source model. Synthetic ground motions were calculated using the discrete wave number method and compared with observed ground motions. The observed strong motions were used after a time correction based on the first P-wave arrival. Results showed that near-fault pulse-like velocities (0.02–0.6 Hz) were generally explained by the simple kinematic source model that assumed a continuous rupture propagation along the faults. Comparisons at individual sites indicate the various rupture properties of the fault segments. Near-fault ground motions along the Narli segment were explained by the fault plane along the surface trace and not by aftershock distribution. A supershear rupture propagation speed is necessary for a part of the Amanos segment. Rupture stops and restarts were implied near the stepover along the Amanos segment. Empirical site factors estimated by generalized inversion techniques did not show peaks around the frequency of observed large velocity pulses, indicating that the velocity pulses were mainly generated by the source. The model bias and uncertainties were also examined to supplement the simplified subsurface structure used in the simulation. Our results will help to associate the qualitative and quantitative aspects of the kinematic source process with near-fault strong ground motions.

A Study on the Motion Behavior of Metallic Contaminant Particles in Transformer Insulation Oil under Multiphysical Fields.

When using transformer insulation oil as a liquid dielectric, the oil is easily polluted by the solid particles generated in the operation of the transformer, and these metallic impurity particles have a significant impact on the insulation performance inside the power transformer. The force of the metal particles suspended in the flow insulation oil is multidimensional, which will lead to a change in the movement characteristics of the metal particles. Based on this, this study explored the motion rules of suspended metallic impurity particles in mobile insulating oil in different electric field environments and the influencing factors. A multiphysical field model of the solid-liquid two-phase flow of single-particle metallic impurity particles in mobile insulating oil was constructed using the dynamic analysis method, and the particles' motion characteristics in the oil in different electric field environments were simulated. The motion characteristics of metallic impurity particles under conditions of different particle sizes, oil flow velocities, and insulation oil qualities and influencing factors were analyzed to provide theoretical support for the detection of impurity particles in transformer insulation oil and enable accurate estimations of the location of equipment faults. Our results show that there are obvious differences in the trajectory of metallic impurity particles under different electric field distributions. The particles will move towards the region of high field intensity under an electric field, and the metallic impurity particles will not collide with the electrode under an AC field. When the electric field intensity and particle size increase, the trajectory of the metallic impurity particles between electrodes becomes denser, and the number of collisions between particles and electrodes and the motion speed both increase. Under the condition of a higher oil flow velocity, the number of collisions between metal particles and electrodes is reduced, which reduces the possibility of particle agglomeration. When the temperature of the insulation oil changes and the quality deteriorates, its dynamic viscosity changes. With a decrease in the dynamic viscosity of the insulation oil, the movement of the metallic impurity particles between the electrodes becomes denser, the collision times between the particles and electrodes increase, and the maximum motion speed of the particles increases.

Nonlinear Vibrations of the Piezoelectric-Laminated Composite Cantilever Rectangular Plate Subjected to the Transverse and Parametric Excitation

The intelligent structure will be the key to the industrial manufacturing field in the future, piezoelectric materials are the most commonly used active materials in many mechatronic and vibration control systems. In this paper, we illustrated the nonlinear vibration behaviors of the piezoelectric-laminated composite cantilever rectangular plate subjected to transverse and parametric excitation. Two piezoelectric layers are attached to the upper and lower surfaces of graphite/epoxy composite laminated plate. The nonlinear dynamic equations are derived via the classical laminated plate theory, von Karman large deformation theory, the constitutive equation of the piezoelectric materials, and the Hamilton principle. Considering the Galerkin method, the nonlinear ordinary differential equations for the two-order vibration mode of the piezoelectric laminated composite cantilever rectangular plate are achieved. The multiple scale method is applied to obtain the average equations to study the nonlinear vibration characteristic of the stable motion. The primary resonance and the 1:1 internal resonance of the piezoelectric laminated composite cantilever rectangular plate are investigated. The amplitude-frequency response curves, force-amplitude response curves, time histories, phase curves, and bifurcation diagrams are given to investigate the nonlinear dynamic characteristic of the piezoelectric laminated composite cantilever rectangular plate. The detailed parametric analyses show that bubble response curves are separated from the amplitude-frequency response curves with the continuous increase of the external excitation due to the internal resonance. In addition, the results reveal the energy transform between the various order vibration modes of the system. This work is expected to provide theoretical guidance for the nonlinear vibration of the smart piezoelectric laminated composite structure.

A TDOA sequence estimation method of underwater sound source based on hidden Markov model

To address the time difference of arrival (TDOA) estimation problem in the passive positioning system with wideband underwater motion sound sources and distributed hydrophones, a hidden Markov model-based (HMM) TDOA sequence estimation method is proposed in this paper. The method estimates the TDOA with multi-frame output of cross-correlated signals received on hydrophones. The transfer equation of the TDOA is established as a first-order hidden Markov process by analyzing the motion characteristics of the moving sound source and delays obtained from different hydrophones. Dynamic assignment of the HMM parameters is proposed to address the inconsistent change rate of the TDOA. We then achieve an HMM expression of the TDOA sequence by fitting the transfer equation and dynamic assignment of parameters into the HMM. Then, the Viterbi algorithm (VA) is applied to distinguish the optimal sequence of the TDOA among ambiguous estimations. To deal with the problem of data loss or unreliable issues caused by interferences, a data prediction algorithm which could produce possible time delays is added to VA to avoid the impact of outliers on the estimation results. By utilizing multi-frame processing, the proposed method reduces the signal-to-noise ratio (SNR) requirement of single frames since it does not require accurate estimations of TDOA for each frame. Moreover, the method adapts to a lower SNR, which has significant advantages in terms of whole sequence estimation compared with common methods. The results from the simulations and lake experiments validated the proposed TDOA sequence estimation method.

Synchronization and stability of a vibrating system with two rigid frames driven by two groups of coaxial rotating exciters

This article explores the synchronization, stability and motion characteristics of the generalized dynamical model with two rigid frames (RFs) driven by two groups (even number) of coaxial rotating exciters. In light of this system’s generalized coordinates, we use Lagrange’s equations to derive the generalized differential equation of motion. The responses of absolute and relative motion of the generalized system are obtained using the transfer function method. The synchronization and stability criteria of multiple exciters are derived using the average method and Hamilton’s theory, respectively. Taking a dynamical model driven by two pairs of exciters as an example, the localized studies of generalized results are carried out. The stable synchronous solutions for phase differences and excitation frequency, the stability ability coefficient curves and the response curves are graphically presented considering the effect of two crucial dimensionless parameters on the stable synchronous states. The simulation results of the specific system are obtained using the fourth-order Runge-Kutta algorithms and compared with the numerical qualitative analysis results to reveal the high consistency between them and clarify the used methods’ effectiveness. The strength of this work stems from its use in the field of high power and large scale self-synchronization vibrating machines.

Aerodynamic simulation on roof-mounted intelligent awareness system of intelligent vehicle

With the rapid development of intelligent driving technology, it is urgent to conduct research on the distribution and motion characteristics of snow particles in the area of the intelligent vehicle awareness system under harsh snow and wind conditions. In this paper, the Unsteady Reynolds-Averaged Navier-Stokes (URANS) was first used to conduct 1:12 scaled aerodynamic simulation of the intelligent vehicle. It is found that the error of aerodynamic drag coefficient between simulation and test is 5.6%, indicating that the current numerical simulation model can predict the aerodynamic characteristics of intelligent vehicle accurately. Based on this, URANS was used coupled with Lagrangian Multiphase Model (LMP) to investigate the snow accumulation near the roof-mounted intelligent awareness system under different vehicle speeds and snowfall intensities. The study found that with the increase of snowfall intensity from moderate to heavy and vehicle speed at 40 km/h, the incidence of snow particles on various components significantly increases, and the number of adhered particles also increased accordingly. The particle adhesion rate of the awareness system has decreased by 1.24%, while the number of adhered snow particles increased significantly at the back of the roof-mounted intelligent awareness system and the wake window. Under moderate snow condition, as the vehicle speed increased from 40 to 60 km/h, the number of incident particles and adhered particles in the awareness system have significantly decreased by 24,592 and 317,019, respectively, but the particle adhesion rate has increased by a significant 2.88%. Compared to the same snowfall intensity but low speed, the range of particle distribution is significantly reduced and more scattered.

Generation of synthetic spectrum-compatible bi-directional ground motions with specific directionality

Ground motions compatible with the maximum-direction response spectrum (RotD100) condition are emphasized in performance-based design and seismic risk assessment of civil structures in different regions. Due to the complex nature and uncertainty of earthquakes, the comprehensive inclusion of essential characteristics of ground motions is crucial. Recently, the directionality effect of horizontal bi-directional ground motions, representing the variation of the response spectral ordinate amplitude along various directions, on the seismic performance assessment of certain structures or key structural elements has received increasing attention in seismic analysis. However, from the seismic design perspective, there is still a lack of a method that can generate bi-directional ground motions comprehensively reflecting the directionality effect. This study focuses on the correction of ground motion directionality when generating synthetic bi-directional ground motions for a given target response spectrum. An efficient and integrated algorithm is proposed. To demonstrate the applicability of the proposed algorithm, three different target RotD100 response spectra are determined according to modern seismic design codes, and 20 pairs of bi-directional ground motions are generated using the proposed algorithm for each target spectrum. It is shown that with the proposed algorithm, the generated motions present a close match to the target RotD100 response spectrum and meet the specific directionality requirement. In addition, due to the iterative modification of the envelope function, the energy of the generated ground motion is also consistent with the scaled natural records.

Characteristics of strong ground motions and structural damage patterns from the February 6th, 2023 Kahramanmaraş earthquakes, Türkiye

Characteristics of strong ground motions and structural damage patterns from the February 6th, 2023 Kahramanmaraş earthquakes, Türkiye

Design and Implementation of Remote Lab PID Controller Experiment Based on IoT

The education sector has increasingly embraced distance education to ensure a safe and uninterrupted learning process, especially in wars or epidemics. This paper focuses on designing and implementing a PID (Proportional-Integral-Derivative) controller experiment in remote laboratories utilizing the Internet of Things (IoT). Also, a laboratory experiment was developed using a naturally unstable system, specifically a cart-inverted pendulum. The experiments aim to enhance students' understanding of PID controller tuning within a real-world context. This system was chosen due to its dual motion characteristics, with a linear motion for the cart and a circular motion for the pendulum. Two controllers were designed and implemented for the system to enable control and feedback. Additionally, the Blynk platform was integrated into the experiment setup, allowing for real-time visualization of the system's response, control of PID parameters, and the ability to view the video stream via platforms like Skype. For remote connectivity, NodeMCU, an IoT development board, controlled the pendulum, collected system parameters, and transmitted them to the cloud through the Internet. Moreover, the sensors and the system were mathematically modeled, and their transfer functions were extracted. That allows the students to do the PID experiment theoretically and practically and compare the results. This complete setup enables local and remote access to the experiment, ensuring students can experiment regardless of their physical location. As a result of the study, designing and implementing a remote laboratory PID controller experiment utilizing IoT technology provides students with an innovative and immersive learning experience.