Dynamic Behavior Research Articles

EXPLICIT-IMPLICIT SCHEMES FOR CALCULATING DYNAMICS OF ELASTOVISCOPLASTIC MEDIA WITH SOFTENING

The paper examines the dynamic behavior of elastoviscoplastic media under the action of an external load. For the case of a linear viscosity function and a nonlinear softening function, an explicit-implicit calculation scheme has been constructed that makes it possible to obtain a numerical solution to the original semilinear hyperbolic problem. This approach does not involve the use of the method of splitting into physical processes. Despite this, an explicit computational algorithm was obtained that can be effectively implemented on modern computing systems.

An Investigation of Dynamic Behavior of Electric Vehicle Gear Trains

Abstract The automotive industry has been experiencing a significant transition toward electrified powertrains in recent years. A torsional model of a common type of electric vehicle (EV) drivetrains is proposed to demonstrate certain dynamic behaviors that are unique to such high-speed applications. This two-stage helical gear drive train is supported by three shafts and connects the electric motor to the vehicle axle. The gear mesh interfaces are modeled by periodically time-varying stiffnesses subjected to backlash and displacement excitations to represent gear tooth errors and modifications. In addition to these internal excitations, torque fluctuations caused by electric motor are included as the external excitations. Two different operating conditions are studied here: (i) steady-state response as the vehicle is operated under steady torque conditions and (ii) transient response during EV system transitions between the drive and regenerative (regen) braking modes of operation. The torsional model predictions are verified through comparisons to simulations from a deformable-body contact model. Parameter sensitivity studies are performed to demonstrate nonlinear behavior of a helical gear train caused by external torque fluctuations as well as the interactions between external and internal excitations. Finally, drivetrain structural modes are shown to respond to drive-regen transitions resulting in certain transient (vibro-impact) behavior with elevated dynamic mesh forces.

Non-autonomous exact solutions and dynamic behaviors for the variable coefficient nonlinear Schrödinger equation with external potential

Abstract The nonlinear Schrödinger(NLS) equation represents a nonlinear dynamical system, which is usually used to describe nonlinear waves in deep water, self-focusing of intense lasers contained in electrolytes, and so on. The exact solutions of the variable coefficient nonlinear Schrödinger equation with external potential are considered. The variable coefficient nonlinear Schrödinger equation is transformed into a constant coefficient nonlinear equation by using the similarity transformation method, the exact solutions of the constant coefficient nonlinear equation are generated by using the homogeneous balance method. We obtain one-soliton, two-soliton, kink type soliton, bright soliton, parabolic soliton and rogue wave solutions. A ‘stepped’ type soliton solution is obtained in this paper, which is a novel type solution and different from the solutions of most nonlinear Schrödinger equations. Some special dynamic behaviors of solitons of the variable coefficient nonlinear Schrödinger equation with external potential are obtained via selecting some free functions. We found that the numerical simulation result is consistent with the exact solution through illustrating the time evolution of bright soliton solution.

Interfacial Characteristics of Ice-Supporting Substrates via Molecular Dynamics Simulations.

Ice accumulation on aircraft surfaces poses significant safety and performance risks, necessitating the development of coatings to prevent ice adhesion. The present work focuses on characterizing the interfacial properties of ice on various substrates through molecular descriptors. We follow the hypothesis that has been previously proposed in several experimental works according to which a disordered, quasi-liquid layer (QLL) of water at the substrate/ice interface is developed, which in turn acts as a self-lubricant reducing material's ice adhesion strength. To put this idea into the test, we conducted extensive molecular dynamics (MD) simulations on ice supported by different types of substrates, such as graphite, boron nitride, and a cross-linked epoxy polymer. Our findings reveal that the ice structure becomes disordered near the interface for all substrates, with a more pronounced effect in the polymer substrate. The formation of QLL at the interface was quantified using metrics such as local density, Q6 order parameter, and hydrogen bonding. The polymer substrate showed a thicker QLL compared to the two flat surfaces, as this was verified by both the significant differences in the local water density profiles and the distribution of the employed order parameter. The latter ones were directly correlated to the development of hydrogen bonds between the interfacial water molecules and the polymer substrate's polar atoms, which was found to induce a more intense disruption of ice's crystal structure. Moreover, our analysis revealed that the polymer's oxygen atoms contribute more to hydrogen bonding with the water molecules than the nitrogen atoms, with hydroxyl oxygens (-OH) contributing more compared to the epoxy ones (-O-). The analysis related to the dynamics of the interfacial water molecules revealed a substantial reduction in mobility on the epoxy, exceeding the slowdown observed on boron nitride, with graphite demonstrating the least reduction in dynamic behavior among the substrates studied.

A Multi‐Time Stepping Algorithm for the Modelling of Heterogeneous Structures With Explicit Time Integration

ABSTRACTHeterogeneous solids often exhibit complex dynamic behavior, requiring simulations to use varying time steps. However, the conventional use of a single‐time step for the entire domain can be inefficient. This article proposes a multi‐time stepping algorithm that addresses this challenge by relaxing the constraint for an integer or constant time step ratio between subdomains and eliminating the need for kinematic interpolation. The algorithm ensures the satisfaction of the Courant‐Friedrichs‐Lewy condition, deviating only to allow subdomains to remain in synchronization. Consequently, less integration steps are performed in comparison to state‐of‐the‐art asynchronous integrators. We extend to the coupling of multiple subdomains, where each subdomain has its time step. Simulating stress wave propagation in metamaterials demonstrates that the proposed algorithm significantly accelerates simulation time, without sacrificing accuracy.

Reconfigurable skyrmion logic gates and diodes in the same synthetic antiferromagnetic nanotrack based on potential well inducting effect

Abstract Magnetic skyrmions are nanoscale spin configurations with topological protection properties, which have broad application potential in the next generation of spintronic devices. Here, we report on the current-driven dynamics of skyrmions in synthetic antiferromagnetic nanotracks with voltage-controlled magnetic anisotropy. This research reveals that, compared to a single skyrmion, when two skyrmions are createdsimultaneously, the inducting effect of the potential well generated by the voltage gateon the skyrmions is partially counteracted by the interaction between the skyrmions,resulting in a reduction in the critical current required for the skyrmions to pass thevoltage gate. Moreover, the critical current required for the forward moving skyrmions to depin from the voltage gate is significantly lower than that required for the reverse moving skyrmions. Based on the dynamic behavior of skyrmions, we have proposed and achieved the skyrmion logic AND, OR, NOT, NAND, NOR gates and the diodes on the same synthetic antiferromagnetic nanotrack by micromagnetic simulation, in which the logic NOT, NAND, and NOR gates are realized in a reconfigurable way. Our results are beneficial for the design and development of non-volatile spintronic devices with integrated multifunctionality and ultra-low energy consumption.

Numerical Simulation of the Dynamic Behavior of Low Permeability Reservoirs Under Fracturing-Flooding Based on a Dual-Porous and Dual-Permeable Media Model

In recent years, fracturing-flooding technology has achieved a series of successful practices in the development of low-permeability oil reservoirs. However, research on the dynamic behavior of fracturing-flooding remains limited. In this paper, a dual medium model considering anisotropic characteristics is established for the target blocks. Multiple sets of conventional water injection transitions and multi-cycle fracturing-flooding operations are designed for simulation to explore the subsequent optimal operational schemes. Simulations are conducted on the optimal transitions between conventional water injection and multi-cycle fracturing-flooding schemes for different reservoir models with varying physical properties to study the dynamic behavior of fracturing-flooding in oil reservoirs with different properties. The results indicate that, for conventional water injection schemes, the optimal transition time for both the target well group and other reservoirs with different properties corresponds to a formation pressure coefficient between 1.2 and 1.3, with the optimal injection–production ratio being 1:1. From the perspective of water cut, the accumulated oil production of multi-cycle fracturing-flooding is higher than that of conventional water injection. The optimal multi-cycle fracturing-flooding schemes for both the target well group and other reservoirs with different properties are to start fracturing-flooding when the formation pressure coefficient is around 0.8 and to begin production when it reaches 1.4.

Holistic Dynamic Modeling and Simulation of Alkaline Water Electrolysis Systems Based on Heat Current Method

Hydrogen production technology is becoming increasingly important with the rapid development of hydrogen energy. Among existing hydrogen production technologies, alkaline water electrolysis (AWE) is drawing wide attention due to its advantages such as high maturity and low cost, and its performance analysis and optimization are important for applications. However, the AWE system contains processes with different physical and mathematical properties such as electrochemical reaction and heat transport processes, bringing difficulties to the system modeling. Moreover, the electrical and thermal processes have different characteristic time scales, and the system shows a sophisticated dynamic behavior, which has not been well studied yet. Here, a homomorphic dynamic model of the AWE system in the form of electrical circuit is built to describe the thermal and electrochemical processes uniformly, where the two parts are integrated via the energy conservation seamlessly. The model is verified by comparing with the experimental data and shows a high accuracy. The dynamic simulation analysis is conducted to investigate the dynamic response characteristics of the system under current step changes and fluctuations. The temperature overshoot and oscillation phenomena caused by delays in heat transport processes are studied. Results show that the time delay yields a maximum temperature overshoot of 10 °C, which would reduce the lifespan of the stack. This also highlights the importance of dynamic system analysis.

Touch-down condition control for the bipedal spring-mass model in walking

Behaviors of animal bipedal locomotion can be described, in a simplified form, by the bipedal spring-mass model. The model provides predictive power, and helps us understand this complex dynamical behavior. In this paper, we analyzed a range of gaits generated by the bipedal spring-mass model during walking, and proposed a stabilizing touch-down condition for the swing leg. This policy is stabilizing against disturbances inside and outside the same energy level and requires only internal state information. In order to generalize the results to be independent of size and dimension of the system, we nondimensionalized the equations of motion for the bipedal spring-mass model. We presented the equilibrium gaits (a.k.a fixed point gaits) as a continuum on the walking state space showing how the different types of these gaits evolve and where they are located in the state space. Then, we showed the stability analysis of the proposed touch-down control policy for different energy levels and leg stiffness values. The results showed that the proposed touch-down control policy can stabilize towards all types of the symmetric equilibrium gaits. Moreover, we presented how the peak leg force changes within an energy level and as it varies due to the type of the gait since peak force is important as a measurement of injury or damage risk on a robot or animal. Finally, we presented simulations of the bipedal spring-mass model walking on level ground and rough terrain transitioning between different equilibrium gaits as the energy level of the system changes with respect to the ground height. The analysis in this paper is theoretical, and thus applicable to further our understanding of animal bipedal locomotion and the design and control of robotic systems like ATRIAS, Cassie, and Digit.

Experimental determination of lateral sway of a pneumatic spring when passing through a railroad switch in conditions of provision of high-speed trains` safety

Experimental determination of lateral sway of a pneumatic spring when passing through a railroad switch in conditions of provision of high-speed trains` safety

Exploring epidemics using non-monotonic incidence function: Effects of sociological factors and hospital bed availability

This study investigates the dynamics of an epidemic employing an (Susceptible-Infected-Hospitalized-Recovered-Susceptible (SIHRS) epidemiological model highlighting the crucial importance of hospital bed availability and a non-monotone incidence function, which incorporates the influences of stringent governmental measures, social behavior dynamics and public responses in both autonomous and non-autonomous scenarios. The analysis investigates the conditions for existence of infection-free and endemic steady states based on the basic reproduction number as it surpasses unity. Sensitivity analysis has been conducted to evaluate the impact of different system parameters on disease transmission. This work also investigates alterations in stability of the system caused by transcritical, Hopf and saddle-node bifurcations. Additionally, two-parameter bifurcation identifies the regions where the stability of both the equilibrium points has been examined. Numerical simulations are shown to illustrate all the theoretically obtained results. Also, the model examines the dynamical behavior of the epidemic when the quantity of available hospital beds varies periodically. This aspect of the study highlights the significant impact of hospital bed availability. Such factors are crucial in preventing disease spread during an epidemic. The results provide valuable insights into how dynamic patterns of disease transmission are influenced by healthcare infrastructure and public health interventions. This comprehensive exploration underscores the importance of integrated approaches combining medical resources and societal measures in managing and mitigating the effects of epidemics.

Advanced Control Strategies for Cleaner Energy Conversion in Biomass Gasification

The escalating climate crisis necessitates urgent and decisive action to mitigate greenhouse gas emissions. Gasification stands out as a highly adaptable process for energy conversion, capable of handling a wide range of feedstocks, from coal to biomass. The process plays a significant role in improving sustainability by converting these feedstocks into synthesic gas (syngas), which can be used as a cleaner energy source or as a building block for producing various chemicals. The utilization of syngas obtained through gasification not only reduces the reliance on fossil fuels but also helps in reducing greenhouse gases (GHGs), thereby contributing to a more sustainable energy landscape. To maintain optimal operational conditions and ensure the quality and safety of the product, an effective control system is crucial in the gasification process. This paper presents a comparative analysis of three control strategies applied to a numerical model of rice husk gasification: classical control, fuzzy logic control, and dynamic matrix control. The analysis is based on a comprehensive model that includes the equations necessary to capture the dynamic behavior of the gasification process across its various stages. The goal is to identify the most effective control strategy, and the performance of each control strategy is evaluated based on the integral of the absolute value of the error (IAE). The results indicatethat fuzzy logic control consistently outperforms classical control techniques, demonstrating superior disturbance rejection, enhanced stability, and overall improved control accuracy. These findings highlight the importance of selecting an appropriate advanced control strategy to optimize sustainable gasification processes.

Dark solitons on elliptic function background for the defocusing Hirota equation

We investigate dark solitons lying on elliptic function background in the defocusing Hirota equation with third-order dispersion and self-steepening terms. By means of the modified squared wavefunction method, we obtain the Jacobi’s elliptic solution of the defocusing Hirota equation, and solve the related linear matrix eigenvalue problem on elliptic function background. The elliptic N-dark soliton solution in terms of theta functions is constructed by the Darboux transformation and limit technique. The asymptotic dynamical behaviors for the elliptic N-dark soliton solution as t → ± ∞ are studied. Through numerical plots of the elliptic one-, two- and three-dark solitons, the amplification effect on the velocity of elliptic dark solitons, and the compression effect on the soliton spatiotemporal distributions produced by the third-order dispersion and self-steepening terms are discussed.

Solutions of Local and Nonlocal Discrete Complex Modified Korteweg–De Vries Equations and Continuum Limits

ABSTRACTCauchy matrix approach for the discrete Ablowitz–Kaup–Newell–Segur equations is reconsidered, where two “proper” discrete Ablowitz–Kaup–Newell–Segur equations and two “unproper” discrete Ablowitz–Kaup–Newell–Segur equations are derived. The “proper” equations admit local reduction, while the “unproper” equations admit nonlocal reduction. By imposing the local and nonlocal complex reductions on the obtained discrete Ablowitz–Kaup–Newell–Segur equations, two local and nonlocal discrete complex modified Korteweg–de Vries equations are constructed. For the obtained local and nonlocal discrete complex modified Korteweg–de Vries equations, soliton solutions and Jordan‐block solutions are presented by solving the determining equation set. The dynamical behaviors of 1‐soliton solution are analyzed and illustrated. Continuum limits of the resulting local and nonlocal discrete complex modified Korteweg–de Vries equations are discussed.

Digital Twin-Based Smart Feeding System Design for Machine Tools

With the continuous development of intelligent manufacturing technology, the application of intelligent feed systems in modern machine tools is becoming increasingly widespread. Digital twin technology achieves the monitoring and optimization of the entire life cycle of a physical system by constructing a virtual image of the system, while neural network controllers, with their powerful nonlinear fitting ability, can accurately capture and simulate the dynamic behavior of complex systems, providing strong support for the optimization control of intelligent feed systems. This article discusses the design and implementation of an intelligent feed system based on digital twins and neural network controllers. Firstly, this article establishes a mathematical model based on the traditional ball screw structure and analyzes the dynamic characteristics and operating mechanism of the system. Subsequently, the mathematical model is fitted using a neural network controller to improve control accuracy and system response speed. The experimental results demonstrate that the neural network controller shows good consistency in fitting traditional mathematical models, not only effectively capturing the nonlinear characteristics of the system but also maintaining stable control performance under complex operating conditions.

Predicting multi-parametric dynamics of an externally forced oscillator using reservoir computing and minimal data

AbstractMechanical systems exhibit complex dynamical behavior from harmonic oscillations to chaotic motion. The dynamics undergo qualitative changes due to changes to internal system parameters like stiffness and changes to external forcing. Mapping out complete bifurcation diagrams numerically or experimentally is resource-consuming, or even infeasible. This study uses a data-driven approach to investigate how bifurcations can be learned from a few system response measurements. Particularly, the concept of reservoir computing (RC) is employed. As proof of concept, a minimal training dataset under the resource constraint problem of a Duffing oscillator with harmonic external forcing is provided as training data. Our results indicate that the RC not only learns to represent the system dynamics for the external forcing seen during training, but it also provides qualitatively accurate and robust system response predictions for completely unknown multi-parameter regimes outside the training data. Particularly, while being trained solely on regular period-2 cycle dynamics, the proposed framework correctly predicts higher-order periodic and even chaotic dynamics for out-of-distribution forcing signals.

Contributions on the Use of Dynamic Absorbers in a Vehicle Engine

In the study presented in the paper, a theoretical calculation will be made regarding engine vibration dampers. These will be validated with the experimental model. These validations bring results in static and dynamic balance through the reduction of torsional vibrations in the engine. Torsional vibrations are caused by various factors as well as engine operating conditions. The paper focuses on the reduction of torsional vibrations from a theoretical and experimental point of view. Therefore, in this study, a dynamic absorber was considered which was integrated into the system considered by the paper and was analyzed both from the point of view of its static and dynamic behavior.

Rapid and Versatile Functionalization of Poly-Ethylene Imine via Dynamic Aminal Formation.

The study of dynamic covalent chemistry (DCC) is growing rapidly in polymer chemistry. The dynamic covalent chemistry of polyaminals formed by the reaction of linear polyethyleneimine (L-PEI) with various functional aldehydes is explored. The study demonstrates the pH-dependent kinetics of polyaminal formation and the versatility of polyaminals in controlling the release of aldehydes under ambient conditions. Additionally, the controlled temperature-induced release of aldehydes and the dynamic shuffling behavior of aminals in polymer systems are investigated, emphasizing the potential for dynamic, covalently bonded polymers through dynamic aminal chemistry. The research showed the dynamic covalent aminal exchange for creating a range of new polymer materials.

Methane upgrading on pelletised Maxsorb activated carbon by gas-phase simulated moving bed

To study the separation of methane and nitrogen mixtures by gas-phase simulated moving bed (SMB), Maxsorb activated carbon was pelletised by extrusion with 10% binder. Both argon and carbon dioxide were used as potential desorbent gases. The effectiveness of the adsorbent was assessed by analysing the adsorption equilibrium data and conducting fixed-bed experiments to determine the single and multicomponent dynamic adsorption behaviour. Pure component N2, CH4, Ar, and CO2 isotherms were measured at three different temperatures, up to 2.5 bar, using a volumetric method. The results show that CO2 exhibits the highest affinity to the solid phase, followed by CH4, N2, and Ar. Single, binary, and ternary fixed-bed experiments were performed, allowing the validation of the proposed mathematical model. Two SMB cycles were designed to separate a CH4/N2 mixture using each desorbent gas. The respective separation regions were drawn. Both processes achieved a high purity level for the methane stream (above 99%) and exhibited high recovery (above 97%). The obtained results were crossed with the previously studied BPL material, and the Maxsorb adsorbent showed better performance overall.

Dynamic Response to Moving Load of Prestressed Damped Shear Beam Resting on Bi-Parametric Elastic Foundation

The dynamic behaviour of damped shear beam resting on bi-parametric elastic foundation when traversed by moving load travelling at constant velocity is investigated in this present study. The beam-type structure has a uniform cross-sectional area and it is assumed to be simply supported. The governing equations are coupled second order partial differential equations. The method of integral transformation called Finite Fourier series was first used to reduce the sets of coupled second order partial differential equations governing the motion of this class of dynamical problem to sequence of coupled second order ordinary differential equations. Thereafter, the simplified coupled equations describing the motion of the beam-load system were then solved by Laplace transformation in conjunction with convolution theory to obtain the solution. The closed form solution obtained was analyzed to obtain the conditions under which the beam-load system will experience resonance phenomenon and speeds at which this may occur are also established. The effects of pertinent structural parameters on the response of a damped shear beam when under the action of the moving load were presented in plotted curves. From the graphs, it is interestingly found that increase in the values of vital structural parameters, such as axial force Nf, circular frequency CF, foundation stiffness K and shear modulus G, reduces the transverse displacement of the damped shear beam when under the action of the moving load. Practically speaking, increase in the values of these structural parameters significantly enhances the stability of the beam and increases the critical speed of the dynamical system. Consequently, the resonance risk of the vibrating system is reduced and thus the safety of the occupant of this structural member is guaranteed.