Dynamic Behavior Research Articles

Experimental study on the dynamic mechanical and progressive fracture behavior of multi-jointed rock mass under repetitive impact loading

The failure of rock masses is often controlled by structural planes, and the study on the dynamic mechanical behavior of multi-jointed rock masses under repetitive dynamic loading is still few. A series of repetitive impact tests on multi-jointed gabbro (MJG) are conducted with the split Hopkinson pressure bar (SHPB) testing apparatus. The effects of repetitive impact and joint inclination angles (α) on the dynamic mechanical behavior of MJG from the perspectives of impact number, stress equilibrium, dynamic mechanical properties, energy evolution, and macro and micro failure modes are deeply investigated. The results show that the joint inclination angle affects the impact resistance of the MJG. Under repetitive impact loadings, the mechanical behavior of the MJG is consistent, with tensile wing cracks initiating from the joint tips and propagating along the loading direction until specimen failure. During this process, cracks propagate along the weakest paths, thereby consuming the energy generated by the impact and preventing the activation of other minor defects. The macroscopic failure of the MJG undergoes four stages: the appearance of white patch, crack coalescence, crack penetration, and fracture, with the final failure mode being splitting. The microscopic formation stage of white patch is divided into microcrack activation and microcrack widening.

Dynamic globularization behavior of the dual-phase TiZrV medium entropy alloy during hot working

Globularization is an advantageous way to improve the formability of dual-phase materials. Dynamic globularization behavior of the TiZrV medium entropy alloy (MEA) with dual-phase was investigated at the temperature range of 500 ℃ ~ 700 ℃ and strain rate of 0.1s-1 ~ 10s-1 by the double-cone compression test. The finite element software was used to simulate the hot compression process of the double-cone specimen. Transmission electron microscope (TEM) was used to study the deformation microstructure features. The double-cone test can produce a wide strain range and corresponding deformation microstructure. The highest globularization ratio of 72.4% was obtained under the strain of about 0.88 at 500 ℃ and 10s-1. The hot deformation mechanism map in the temperature range of 500 ℃ ~ 700 ℃ and the strain range of 0.2 ~ 1.2 at 10s-1 was constructed by combining the double-cone test with finite element simulation. The hot deformation mechanism map is divided primarily into two parts. At 500 ℃, in the strain region of 0.2 ~ 0.88, the deformation mechanism is dynamic recovery (DRV), and in the strain region of 0.88 ~ 1.2, the deformation mechanism is dynamic recrystallization (DRX). It is considered that DRX plays a key role in dynamic globularization of the TiV phase during hot working and its production is summarized.

Research on microplastic deformation of Inconel718 under the conditions of high temperature and high strain rate

The compression experiments of the nickel-based superalloy Inconel718 were carried out with the help of split Hopkinson pressure bar device, and the microstructure evolution law in the compression deformation of the alloy was studied by means of optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Based on the dislocation theory, a three-dimensional discrete dislocation dynamics model is established. By simulating the dynamic evolution of the discrete dislocation, the interaction of the dislocation itself and the formation of the dislocation microstructure were captured, and further explore the microplastic deformation process of Inconel718. The results show that deformation conditions significantly affect the rheological behavior and dynamic recrystallization behaviour. The cross slip of dislocations is closely related to temperature and strain rate, which in turn affect the dislocation configuration. The deformation mechanism of Inconel718 under the conditions of high temperature and high strain rate is jointly dominated by dislocation slip and twin deformation. As the temperature increases, the average Schmidt factor increases, and more dislocation slip systems are activated. As the strain rate increases, the number of deformation twins increases, while the thickness of deformation twins decreases.

Wetting permeability of surface active agent droplets impacting on a layer of coal dust

The wetting and penetration of the coal dust layer by liquid droplet is crucial for suppressing coal dust. A combination of experimental and simulation methods was employed to investigate the impact of surfactant concentration, droplet velocity, and particle size on the penetration properties and their underlying mechanisms. Droplet impact wetting experiments were employed to evaluate their dynamic wetting behavior on the coal dust layer. The experimental results show that increasing the impact velocity of droplets is advantageous for enhancing the maximum dimensionless wetting length. Increasing the surfactant concentration can expedite the droplet reaching maximum dimensionless wetting volume in the dust layer. The larger the particle size of coal dust, the shorter time required for droplet to reach maximum wetting volume. The research results provide a theoretical basis for selecting and efficiently applying surfactants in treating coal dust.

Experimental Study on Dynamic Bond Behavior between Reinforcement and Concrete under Fire

Experimental Study on Dynamic Bond Behavior between Reinforcement and Concrete under Fire

Influence of Water Saturation on Dynamic Tensile and Compressive Behaviors of Concrete

Influence of Water Saturation on Dynamic Tensile and Compressive Behaviors of Concrete

Dynamical behaviors of autonomous and nonautonomous models of generalist predator–prey system with fear, mutual interference and nonlinear harvesting

In this study, we explore a predator–prey model to evaluate the impacts of fear, mutual interference, and harvesting, as these factors play crucial roles in modifying population dynamics, trophic cascades, and species interactions. Additionally, we enhance the model to incorporate the seasonality of specific ecological factors across time. The autonomous and associated nonautonomous models have undergone thorough mathematical analysis and extensive numerical simulations in the course of the study. We conduct a fundamental differential sensitivity analysis to discern the key parameters influencing both prey and predator populations within the ecosystem. Through numerical investigations of the autonomous model, we notice that in the presence (absence) of harvesting, the mutual interference among predators destabilizes (stabilizes) the coexisting equilibrium. The fear effect significantly reduces the densities of prey and predator populations, and destabilizes the coexisting equilibrium by producing multiple stability switches. The survival of predators substantially depends on the focal prey if their growth from other food sources is relatively low. Notably, the harvesting of predators is beneficial and promotes the coexistence of species only when their growth from other food sources is too much. Moreover, the system shows bistability, tristability, and multiple limit cycles under identical ecological conditions. We also show various phenomena that manifest within the seasonally forced model, including the emergence of periodic solutions, higher periodic solutions, bursting patterns, and chaotic dynamics. Remarkably, the influence of seasonal forcing possesses the capability to govern the chaotic dynamics by giving rise to an exceedingly quasi-periodic arrangement in the prey and predator densities.

Analysis of the Dynamical Behavior of a Modified Cubic-Map with a Discrete Memristor

Analysis of the Dynamical Behavior of a Modified Cubic-Map with a Discrete Memristor

A simplified three-parameter model for analyzing torsional vibration of rectangular foundations on layered soil

Dynamic soil-structure interaction (SSI) significantly impacts structural vibration. Over the past few decades, numerous simplified models were developed to analyze dynamic SSI on homogeneous soil. In this study, however, a lumped-parameter model is adopted to investigate the dynamic behavior of rectangular foundations overlying nonuniform soil. The simplified three-parameter model is utilized to analyze the torsional vibration of rectangular foundations on layered soil with linearly varying shear-wave velocities. Non-dimensional parameters (shear-wave velocity ratios, layer depth ratios, and mass ratios) are also investigated herein. The frequency-magnification curves of the foundation using three-parameter model are found to agree well with theoretical solutions. Consistent agreements are also observed at the resonant response and its corresponding frequency ratio. Additionally, the resultant resonant magnification factors against mass ratios clearly show the impacts of the whipping effect resulting from soil-foundation interactions. The proposed model excels in simulating layered soil and includes fewer parameters than existing lumped-parameter models. The proposed model also demonstrates the adaptivity and reliability to simulate the dynamic responses calculated from the published in-situ experimental data. The time-domain application based on the proposed model effectively estimates the structural displacement of the soil-foundation-superstructure system. This research could contribute to the SSI analysis regarding the torsional vibration of a foundation on nonuniform soil.

Cloud Cover Segmentation and Motion Prediction from Satellite Imagery

Abstract: This research project is dedicated to achieving precise identification, segmentation, and motion prediction of cloud formations in satellite imagery. Leveraging the powerful U-Net, a renowned deep learning architecture for image segmentation, is crucial in addressing the intricate challenge of cloud detection and segmentation within remote sensing imagery. The automation of cloud identification processes within the project not only enhances weather forecasting capabilities but also contributes significantly to advancements in climate monitoring and environmental analysis. The incorporation of Long ShortTerm Memory (LSTM) networks facilitates cloud motion prediction, providing insights into the dynamic behavior of cloud formations over time. The robustness of the U-Net model, coupled with the enhanced capability of capturing intricate patterns and predicting cloud motion, establishes it as a valuable and comprehensive tool. This contributes to improving the accuracy and efficiency of cloud segmentation in satellite imagery, fostering progress in critical domains such as environmental research and meteorological applications

In situ monitoring of polymeric patchy micelles upon non-covalent post-assembly modification

ABSTRACT Polymeric patchy micelles (PPMs) are nanostructures with distinct regions on their surfaces, offering unique properties for various applications. Herein, we present a straightforward method for monitoring the structure of PPMs formed via non-covalent post-assembly modification (NCPAM). By employing 1-pyrenemethylamine, a pyrene-based molecule, as both a modifier and fluorescent probe, we demonstrate that the formation of PPMs with a higher order aggregation state of pyrene induces a stronger pyrene excimer emission. This leads to variations in the excimer-to-monomer emission ratio, serving as a parameter for studying structural changes in PPMs during NCPAM. In situ monitoring of PPM formation and temperature-dependent transformations is achieved using fluorescent analytical method, providing valuable insights into their structural evolution and dynamic behaviour. This study offers a straightforward approach to understanding and controlling PPM structures, facilitating the design of advanced nanomaterials for diverse applications.

Single-Digit Nanobubble Sensing via Nanopore Technology.

Nanobubbles play an important role in diverse fields, including engineering, medicine, and agriculture. Understanding the characteristics of individual nanobubbles is essential for comprehending fluid dynamics behaviors and advancing nanoscale science across various fields. Here, we report a strategy based on nanopore sensors for characterizing single-digit nanobubbles. We investigated the sizes and diffusion coefficients of nanobubbles at different voltages. Additionally, the finite element simulation and molecular dynamics simulation were introduced to account for counterion concentration variation around nanobubbles in the nanopore. In particular, the differences in stability and surface charge density of nanobubbles under various solution environments have been studied by the ion-stabilized model and the DLVO theory. Additionally, a straightforward method to mitigate nanobubble generation in the bulk for reducing current noise in nanopore sensing was suggested. The results hold significant implications for enhancing the understanding of individual nanobubble characterizations, especially in the nanofluid field.

Research on the influence of flexible wheelset rotation effect on wheel rail contact force

PurposeUnder the high-speed operating conditions, the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition. In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction, it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approachThe wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper. As for the wheel-rail contact forces, which is a particular force element in vehicle multibody system, a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation. Based on the flexible wheelset modeling approach in this paper, two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established, two kinds of track excitations, namely normal measured track irregularities and short-wave irregularities are used, wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.FindingsUnder normal track irregularity excitations, the amplitudes of vertical, longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model, and the virtual penetration and equivalent contact patch are also slightly smaller. For the flexible wheelset model, the wheel rail longitudinal and lateral creepages will also decrease. The higher the vehicle speed, the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model. Under track short-wave irregularity excitations, the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset. However, unlike the excitation case of measured track irregularity, under short-wave excitations, for the speed within the range of 200 to 350 km/h, the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase. This is partly due to the contribution of wheelset’s elastic vibration under short-wave excitations. For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above, as well as high-frequency wheel-rail interaction analysis problems under various speed conditions, the flexible wheelset model will give results agrees better with the reality.Originality/valueThis study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system. Furthermore, by comparative research, the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained, which is useful to the application scope of rigid and flexible wheelset models.

Computational study on the binding mechanism of allosteric drug TNO155 inhibiting SHP2E76A.

E76A mutations of SHP2 have been reported to associate with genetic developmental diseases and cancers, and TNO155 is one of the effective inhibitors targeted to the allosteric site 1, which has already entered the clinical stage. However, the detailed binding mechanism between them still needs further clarification at micro-atomic level. In this study, the binding mechanism of TNO155 inhibiting SHP2E76A and the superiorities of TNO155 at binding affinity and dynamic interactive behavior with SHP2E76A were probed utilizing a series of computational drug design technologies. The results show that SHP2E76A forms tighter interaction with TNO155 compared to SHP099. SHP2E76A-TNO155 exhibits the largest electrostatic interaction among all complex systems, which can be manifested by the strong hydrogen bond interactions formed by two electrically charged residues, Arg111 and Glu250. Notably, in SHP2E76A-TNO155 system, Asp489 makes an additional substantial beneficial contribution. The E76A mutation brings stronger residue positive correlation and a larger conformation fluctuation between N-CH2 and PTP domains, resulting in tighter binding betweenTNO155and SHP2E76A. This study offers valuable insights for the further design and development of novel SHP2E76A allosteric inhibitors.

Backstepping synchronization control for four-dimensional chaotic system based on DNA strand displacement

Backstepping control is an important nonlinear control design method, which realizes the control of complex systems by constructing control law step by step, and has significant advantages for dealing with complex nonlinear systems. This article proposes a synchronization technique for four-dimensional chaotic systems using a combination of backstepping control method and DNA strand displacement technology. By relying on theoretical knowledge of DNA molecules, five basic chemical reaction modules such as trigger reaction, reference reaction, catalytic reaction, annihilation reaction and degradation reaction are given to construct a four-dimensional DNA chaotic system. On the basis of the relevant theory of chaotic dynamics, the constructed system is analyzed by Lyapunov exponent diagram and spectral entropy complexity algorithm, and the results come to the conclusion that the system reveals extremely complex and varied dynamic behaviors. Combining DNA strand displacement technology with backstepping control method, four controllers are developed to ensure that the trajectories of two homogeneous chaotic systems are synchronized. The numerical simulation results validate the feasibility and applicability of the proposed method. The method proposed in this paper may provide some references in the field of DNA molecular chaos synchronization control.

Discrete-Time Impedance Control for Dynamic Response Regulation of Parallel Soft Robots

Accurately controlling the dynamic response and suppression of undesirable dynamics such as overshoots and vibrations is a vital requirement for soft robots operating in industrial environments. Pneumatically actuated soft robots usually undergo large overshoots and significant vibrations when deactuated because of their highly flexible bodies. These large vibrations not only decrease the reliability and accuracy of the soft robot but also introduce undesirable characteristics in the system. For example, it increases the settling time and damages the body of the soft robot, compromising its structural integrity. The dynamic behavior of the soft robots on deactuation needs to be accurately controlled to increase their utility in real-world applications. The literature on pneumatic soft robots still does not sufficiently address the issue of suppressing undesirable vibrations. To address this issue, we propose the use of impedance control to regulate the dynamic response of pneumatic soft robots since the superiority of impedance control is already established for rigid robots. The soft robots are highly nonlinear systems; therefore, we formulated a nonlinear discrete sliding mode impedance controller to control the pneumatic soft robots. The formulation of the controller in discrete-time allows efficient implementation for a high-order system model without the need for state-observers. The simplification and efficiency of the proposed controller enable fast implementation of an embedded system. Unlike other works on pneumatic soft robots, the proposed controller does not require manual tuning of the controller parameters and automatically calculates the parameters based on the impedance value. To demonstrate the efficacy of the proposed controller, we used a 6-chambered parallel soft robot as an experimental platform. We presented the comparative results with an existing state-of-the-art controller in SMC control of pneumatic soft robots. The experiment results indicate that the proposed controller can effectively limit the amplitude of the undesirable vibrations.

Modeling Excitable Cells with Memristors

This paper presents an in-depth analysis of an excitable membrane of a biological system by proposing a novel approach that the cells of the excitable membrane can be modeled as the networks of memristors. We provide compelling evidence from the Chay neuron model that the state-independent mixed ion channel is a nonlinear resistor, while the state-dependent voltage-sensitive potassium ion channel and calcium-sensitive potassium ion channel function as generic memristors from the perspective of electrical circuit theory. The mechanisms that give rise to periodic oscillation, aperiodic (chaotic) oscillation, spikes, and bursting in an excitable cell are also analyzed via a small-signal model, a pole-zero diagram of admittance functions, local activity, the edge of chaos, and the Hopf bifurcation theorem. It is also proved that the zeros of the admittance functions are equivalent to the eigen values of the Jacobian matrix, and the presence of the positive real parts of the eigen values between the two bifurcation points lead to the generation of complicated electrical signals in an excitable membrane. The innovative concepts outlined in this paper pave the way for a deeper understanding of the dynamic behavior of excitable cells, offering potent tools for simulating and exploring the fundamental characteristics of biological neurons.

A comprehensive analysis of COVID-19 nonlinear mathematical model by incorporating the environment and social distancing

This research conducts a detailed analysis of a nonlinear mathematical model representing COVID-19, incorporating both environmental factors and social distancing measures. It thoroughly analyzes the model’s equilibrium points, computes the basic reproductive rate, and evaluates the stability of the model at disease-free and endemic equilibrium states, both locally and globally. Additionally, sensitivity analysis is carried out. The study develops a sophisticated stability theory, primarily focusing on the characteristics of the Volterra–Lyapunov (V–L) matrices method. To understand the dynamic behavior of COVID-19, numerical simulations are essential. For this purpose, the study employs a robust numerical technique known as the non-standard finite difference (NSFD) method, introduced by Mickens. Various results are visually presented through graphical representations across different parameter values to illustrate the impact of environmental factors and social distancing measures.

Dynamics of transformed nonlinear waves for the (2+1)-dimensional pKP-BKP equation: interactions and molecular waves

Abstract In this paper, the dynamical behaviors of transformed nonlinear waves for the (2+1)-dimensional combined potential Kadomtsev-Petviashvili and B-type Kadomtsev-Petviashvili (pKP-BKP) equation are investigated, which can be used to reveal the nonlinear wave phenomena in nonlinear optics, plasma physics and hydrodynamics. The breath-wave and the lump solutions are constructed by means of the soliton solutions. The conversion mechanism for the breath-waves is systematically analyzed, which leads to several new kink-shaped nonlinear waves. The gradient relationships of these transformed waves are revealed by a Riemannian circle. Through the analysis of the nonlinear superposition between the periodic wave component and the kink solitary wave component, the dynamical characteristics including the formation mechanism, oscillation and locality for the nonlinear waves are investigated. The time-varying properties of transformed waves are showed by the study of time variables. By virtue of the two breath-wave solution, several interactions including elastic and inelastic collisions between two nonlinear waves are studied. In particular, some transformed molecular waves encompassing the non-, semi- and full-transition modes are presented with the aid of velocity resonance. The results can help us further understand the complex nonlinear waves existing in the integrable systems.

Linear and Nonlinear Electro-optic Response of MHPOCBC

This study investigated the linear and second-order electro-optic responses in chiral smectic liquid crystal 4-(1-methylheptyloxycarbonyl) phenyl 4-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC). The result revealed a single Debye-type relaxation in the linear electro-optic frequency dispersion, with a relaxation frequency extending up to one hundred kHz. Conversely, the second-order electro-optic response exhibited intricate temperature-dependence, accurately depicted by a phenomenological Landau theory around the SmA–SmCa* phase transition point. Notably, in the SmCa* phase, critical slowing down of the amplitude mode occurred near the transition to the SmA phase, while at lower temperatures of the SmCa* phase, a distinct low-frequency relaxation mode emerged. Furthermore, the relaxation frequency of the antiferroelectric Goldstone mode in the SmCA* phase remained constant across the entire temperature range. These findings should significantly contribute to the understanding of dynamic behaviors in chiral smectic liquid crystals, shedding light on their complex phase transitions and electro-optic properties.