Dynamic Boundary Research Articles

Unveiling attenuation structures in the northern Taiwan volcanic zone.

This cutting-edge study delves into regional magmatism in northern Taiwan through advanced 3-D P- and S-wave frequency-dependent attenuation tomography. Positioned at the dynamic convergence boundary between the Philippine Sea Plate and the Eurasian Plate, Taiwan experiences moderate earthquakes and intriguing volcanic activity, with a focus on the Tatun volcano group. Employing the Formosa seismic array for high-resolution results, our research identifies high-attenuation anomalies (low Q) beneath the northern Taiwan volcanic zone (NTVZ) and offshore submarine volcanoes, indicative of potential hydrothermal activities and magma reservoirs at varying depths. Additionally, we explore low-attenuation anomalies (high Q) in the forearc region of the Ryukyu subduction zone, suggestive of partial saturation linked to serpentinization processes resulting from seawater infiltration or forearc mantle hydration. These findings shed light on the complex geological features and provide essential insights into the crustal properties of northern Taiwan, contributing to a deeper understanding of its magmatic evolution and tectonic processes.

Численное моделирование водородопроницаемости с концентрационной зависимостью коэффициента диффузии

The paper presents a nonlinear mathematical model of alloys hydrogen permeability for membrane technologies of high-purity hydrogen production. Diffusion processes in the material bulk are taken into account as well as physical and chemical phenomena at the surface: adsorption, desorption and relatively fast dissolution. The iterative computational algorithm and software in Scilab have been developed to model the hydrogen permeability with dynamic boundary conditions and concentration-dependent diffusion coefficient.

Adaptive Dynamic Boundary Sliding Mode Control for Robotic Manipulators under Varying Disturbances

This paper introduces an Adaptive Dynamic Bounded Sliding Mode Control (ADBSMC) method that incorporates a disturbance observer to enhance the response characteristics of the robot manipulator while eliminating the reliance on a priori knowledge. The proposed method utilizes nonlinear sliding mode manifolds and fast-terminal-type convergence laws to address errors and parameter uncertainties inherent in the nonlinear system models. The adaptive law is designed to cover all boundary conditions based on the model’s state. It can dynamically determine upper and lower bounds without requiring prior knowledge. Consequently, the ADBSMC control method amalgamates the benefits of adaptive law and fast terminal sliding mode, leading to significant enhancements in control performance compared with traditional sliding mode control (SMC), exhibiting robustness against uncertain disturbances. To mitigate external disturbances, a system-adapted disturbance observer is devised, facilitating real-time monitoring and compensation for system disturbances. The stability of ADBSMC is demonstrated through the Lyapunov method. Simulation and experimental results validate the effectiveness and superiority of the ADBSMC control scheme, showcasing its potential for practical applications.

A novel unresolved/semi‐resolved CFD‐DEM coupling method with dynamic unstructured mesh

AbstractThe greatest challenge when performing large deformation simulations using the CFD‐DEM coupling method lies in the dynamical update of the fluid meshes. To address this problem, a novel CFD‐DEM coupling method integrated with the dynamic unstructured grid is proposed in this work. The mesh initialization and reconstruction are performed by the Constrained Delaunay triangulation (CDT) implemented by the tetgen algorithm. Moreover, the equation of state (EOS) is introduced to consider the impact of fluid compressibility. The reliability of this coupling method is preliminarily verified by the particle sedimentation test. Additionally, undrained triaxial shear and one‐dimensional consolidation tests are conducted to examine the applicability of the proposed method in simulating geotechnical cases. From our analysis, it is found that the shear responses in the undrained triaxial shear test obtained from the proposed method with dynamic mesh are in direct accordance with those led by the constant volume (CV) method. However, difficulties arise in accurately describing the moving boundary by the fixed mesh, leading to unreliable results. Moreover, in the one‐dimensional consolidation test, both the dynamic and fixed grids can capture the Mandel—Cryer effect, which is more pronounced under the dynamic grid, mainly due to the dual impact of the loading device and particle skeleton on the fluid. A greater compressibility specified under the dynamic grid led to a weakening of this effect, whereas its duration is increased. Our work provides valuable insights for effectively dealing with dynamic fluid boundaries.

EAO: Enhanced aquila optimizer for solving optimization problem

The Aquila optimization (AO) algorithm has the drawbacks of local optimization and poor optimization accuracy when confronted with complex optimization problems. To remedy these drawbacks, this paper proposes an Enhanced aquila optimization (EAO) algorithm. To avoid elite individual from entering the local optima, the elite opposition-based learning strategy is added. To enhance the ability of balancing global exploration and local exploitation, a dynamic boundary strategy is introduced. To elevate the algorithm’s convergence rapidity and precision, an elite retention mechanism is introduced. The effectiveness of EAO is evaluated using CEC2005 benchmark functions and four benchmark images. The experimental results confirm EAO’s viability and efficacy. The statistical results of Freidman test and the Wilcoxon rank sum test are confirmed EAO’s robustness. The proposed EAO algorithm outperforms previous algorithms and can useful for threshold optimization and pressure vessel design.

An Empirical Model for Mercury’s Field‐Aligned Currents Derived From MESSENGER Magnetometer Data

AbstractMercury is the only planetary magnetosphere which does not possess a significantly conducting ionosphere, yet magnetic field observations by the Mariner 10 and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) missions revealed a stable presence of large‐scale field‐aligned currents (FACs). Several empirical magnetic field models have been developed to describe Mercury’s magnetospheric currents and their associated magnetic fields, but none attempted to include an explicit description of large‐scale FACs. Here, we describe a dynamic FAC magnetic field model for Mercury based on the analytical solution to conical currents, which are shielded by a dynamic magnetopause boundary. The model contains free parameters setting the FACs' latitudinal extent and amplitude as functions of magnetospheric activity. The parameters are fit by minimizing the root‐mean‐square (RMS) differences between the model and MESSENGER Magnetometer data. During magnetically quiet conditions, the modeled FACs have an intensity of ∼10 nA/m2 and extend in latitude from ∼83°N to ∼40°N. They intensify to ∼20 nA/m2 and expand equatorward to ∼28°N during the most active times. The inclusion of the FAC model reduces low‐altitude RMS residuals by 8.1% when compared to prior models. The model effectively captures the azimuthal component of the magnetic field present in the MESSENGER low‐altitude data, but largely misses the radial and co‐latitudinal components, indicating other large‐scale physics remain missing in the mathematical descriptions of Mercury's magnetosphere.

Magmatic Evolution of the Fossil Melanesian Island Arc: Evidence From Lower Miocene Lavas of Malekula Island (Vanuatu)

AbstractThe subduction zones in the SW Pacific Ocean are some of the most dynamic plate boundaries on Earth with changes in subduction polarity and subduction initiation processes. The New Hebrides island arc formed some 10 million years ago after the Melanesian island arc was abandoned due to the cessation of subduction of the Pacific Plate after collision of oceanic plateaus with the island arc. Parts of the Melanesian island arc occur within the New Hebrides island arc and we show that Miocene volcanic rocks exposed on Malekula island in the New Hebrides island arc consist of island arc tholeiites to alkaline basalts with variable slab contribution. The lava erupted between 22.5 and 16.3 Ma, similar to the Wainimala Group lavas on Fiji representing the eastern portion of the Melanesian island arc. Partial melts from subducted sediments affected a Pacific MORB‐type mantle, but we do not find evidence for a slab component derived from the Ontong Java Plateau or for assimilation of continental crust. Thus, no Miocene subduction of the Ontong Java Plateau occurred beneath Malekula and the basement of the island probably does not consist of continental crust rifted from Australia. The Malekula lava succession resembles that of other portions of the Miocene Melanesian island arc between New Britain and Fiji, indicating continuous subduction of the Pacific plate along this arc.

Strategy of directional oil transport for splash lubrication systems

Supplying oil to bearings rapidly over long distances presents a challenge for splash lubrication systems in drive axle main reducers (DAMRs), mainly because of inadequate driving forces. To mitigate this issue, a novel strategy was introduced to control the splash oil flow via a shroud, which enabled directional oil transport. We developed a transient modeling framework to comprehensively investigate the temporal and spatial evolution mechanisms of splash oil. This framework, validated through empirical studies, navigates the uncertainties and multiscale properties of the multifaceted physics induced by the dynamic boundaries of a shrouded gear. Several operating scenarios were simulated to investigate the driving mechanism of directional oil transport within the shroud, as well as the effect of shroud design and rotational speed on splash lubrication performance. Results demonstrate that the pressure gradients inside and outside the shroud govern the directional transport of the splash oil flow. The bearings located distally on the sump receive a considerable volume of oil (maximum flow rate exceeding 11 L/min) from the upper passage. Concurrently, the churning losses in the DAMR are reduced by >30 % when the wheel is shrouded in comparison to an unshrouded scenario. Moreover, interactions involving friction and collision between the gear and fluid particles intensify with increasing speed and enhance shroud sealing. This study provides a valuable mechanism for investigating oil transport in splash-lubricated DAMRs.

Numerical Reconstruction of the Source in Dynamical Boundary Condition of Laplace’s Equation

In this work, we consider Cauchy-type problems for Laplace’s equation with a dynamical boundary condition on a part of the domain boundary. We construct a discrete-in-time, meshless method for solving two inverse problems for recovering the space–time-dependent source and boundary functions in dynamical and Dirichlet boundary conditions. The approach is based on Green’s second identity and the forward-in-time discretization of the non-stationary problem. We derive a global connection that relates the source of the dynamical boundary condition and Dirichlet and Neumann boundary conditions in an integral equation. First, we perform time semi-discretization for the dynamical boundary condition into the integral equation. Then, on each time layer, we use Trefftz-type test functions to find the unknown source and Dirichlet boundary functions. The accuracy of the developed method for determining dynamical and Dirichlet boundary conditions for given over-determined data is first-order in time. We illustrate its efficiency for a high level of noise, namely, when the deviation of the input data is above 10% on some part of the over-specified boundary data. The proposed method achieves optimal accuracy for the identified boundary functions for a moderate number of iterations.

Influence of the Elastic-Plastic Dynamic Artificial Boundary on the Progressive Collapse Performance of Truss Structures

The traditional fixed boundary could not transmit the elastic-plastic stress waves in the progressive collapse analysis of the truss structures, leading to discrepancies in understanding the true response of structures. To solve the critical problem, a new dynamic artificial boundary is proposed and integrated into the truss structure to transmit elastic-plastic stress waves. The new dynamic artificial boundary is established through the integration of the elastic-plastic constitutive model into the governing equation of the stress wave. This boundary is subsequently implemented within the ABAQUS finite element software for the purpose of conducting progressive collapse analysis of the truss structures. The progressive collapse simulation of the truss structures involves a comparative analysis between the new dynamic artificial boundary and the traditional fixed boundary. Numerical analysis demonstrates that the dynamic artificial boundary led to varied initial failure and collapse compared to the fixed boundary. The failure typically occurs at the mid-span under the dynamic boundary. In contrast, additional failures occur near the support columns under the fixed boundary due to stress wave reflections. The dynamic artificial boundary more closely reflects the physical reality and provides a new method for the progressive collapse analysis of the truss structures in practical applications.

Dynamic behaviors of delaminated nanofilms partly bonded on substrates with sub-nanoscale van der Waals dynamic boundaries

Abstract Dynamic buckling-induced delamination of nanofilms on substrates is a universal and essential phenomenon in nanoelectromechanical systems (NEMS). Van der Waals (vdWs) interactions play an important role in the dynamic buckling-induced delamination of nanofilms on substrates due to the interaction distances at nanoscale or even sub-nanoscale in NEMS. Therefore, it is interesting yet challenging to reveal the effect of intermolecular vdWs interactions on dynamic buckling-induced delamination of nanofilms on substrates. By considering sub-nanoscale dynamic boundary effects induced by intermolecular vdWs interactions, a parametric excitation nonlinear vibration model for dynamic buckling-induced delamination of nanofilms partly bonded on substrates is established. Effects of sub-nanoscale vdWs dynamic boundaries on transient and steady-state responses of dynamically delaminated nanofilms on substrates are analyzed. The sub-nanoscale vdWs dynamic boundaries lead the dynamic responses of delaminated-nanofilm/substrate systems very sensitive to initial conditions. The bending and shifting frequency response results demonstrated that the system nonlinearities can be greatly amplified by the sub-nanoscale vdWs dynamic boundary effect. Moreover, the spontaneous symmetry breaking and violent interfacial tearing/healing phenomena can be also triggered in the systems. Based on spontaneous symmetry breaking, a trans-scale relationship between nanofilm equilibrium positions and intermolecular vdWs interactions is established, which can provide a promising route for trans-scale measurements of molecular scale interfacial interactions. The work can also be helpful for the dynamic design of resonant NEMS devices based on nanofilm/substrate systems.

Strange non-local operators homogenizing the Poisson equation with dynamical unilateral boundary conditions: asymmetric particles of critical size

We study the homogenization of a nonlinear problem given by the Poisson equation, in a domain with arbitrarily shaped perforations (or particles) and with a dynamic unilateral boundary condition (of Signorini type), with a large coefficient, on the boundary of these perforations (or particles). This problem arises in the study of chemical reactions of zero order. The consideration of a possible asymmetry in the perforations (or particles) is fundamental for considering some applications in nanotechnology, where symmetry conditions are too restrictive. It is important also to consider perforations (or particles) constituted by small different parts and then with several connected components. We are specially concerned with the so-called critical case in which the relation between the coefficient in the boundary condition, the period of the basic structure, and the size of the holes (or particles) leads to the appearance of an unexpected new term in the effective homogenized equation. Because of the dynamic nature of the boundary condition this ``strange term'' becomes now a non-local in time and non-linear operator. We prove a convergence theorem and find several properties of the ``strange operator'' showing that there is a kind of regularization through the homogenization process.
 For more information see https://ejde.math.txstate.edu/Volumes/2024/03/abstr.html

An improved chaos sparrow search algorithm for UAV path planning

This study suggests an improved chaos sparrow search algorithm to overcome the problems of slow convergence speed and trapping in local optima in UAV 3D complex environment path planning. First, the quality of the initial solutions is improved by using a piecewise chaotic mapping during the population initialization phase. Secondly, a nonlinear dynamic weighting factor is introduced to optimize the update equation of producers, reducing the algorithm's reliance on producer positions and balancing its global and local exploration capabilities. In the meantime, an enhanced sine cosine algorithm optimizes the update equation of the scroungers to broaden the search space and prevent blind searches. Lastly, a dynamic boundary lens imaging reverse learning strategy is applied to prevent the algorithm from getting trapped in local optima. Experiments of UAV path planning on simple and complex maps are conducted. The results show that the proposed algorithm outperforms CSSA, SSA, and PSO algorithms with a respective time improvement of 22.4%, 28.8%, and 46.8% in complex environments and exhibits high convergence accuracy, which validates the proposed algorithm's usefulness and superiority.

Adaptive prescribed performance control for wave equations with dynamic boundary and multiple parametric uncertainties

<abstract><p>In modern engineering, the dynamics of many practical problems can be described by hyperbolic distributed parameter systems. This paper is devoted to the adaptive prescribed performance control for a class of typical uncertain hyperbolic distributed parameter systems, since uncertainties are inevitable in practice. The systems in question simultaneously have unknown in-domain spatially varying damping coefficient and unknown boundary constant damping coefficient. Moreover, dynamic boundary condition is considered in the present paper. These characteristics make the control problem in the paper essentially different from those in the related works. To solve the problem, using adaptive technique based projection operator, backstepping method developed for ODEs and Lyapunov stability theories, a powerful adaptive prescribed performance control scheme is proposed to successfully guarantee that all states of the resulting closed-loop system are bounded, furthermore, the original system state converges to an arbitrary prescribed small neighborhood of the origin. Compared with the existing results, the developed control schemes can not only effectively handle the serious uncertainties, but also overcome the technical difficulties in the infinite-dimensional backstepping control design method caused by the dynamic boundary condition and guarantee prescribed performance.</p></abstract>

Dynamic Event-Triggered Boundary Control for Cyber-Physical Flexible Riser Systems Subject to Spoofing Attacks

Dynamic Event-Triggered Boundary Control for Cyber-Physical Flexible Riser Systems Subject to Spoofing Attacks

Study on coupled problems of thermoelasticity in Strains

In the work, within the framework of the strain compatibility conditions of Saint-Venant, two equivalent dynamic boundary value problems of thermoelasticity with respect to strains are formulated. In the case of the first boundary value problem, the dynamic equations of thermoelasticity are obtained from the compatibility conditions, in the second case, instead of the first three equations of thermoelasticity, the equations of motion expressed with respect to deformations are considered. Discrete analogues of boundary value problems are constructed using the finite-difference method in the form of explicit and implicit schemes. The solution of explicit schemes is reduced to recurrent relations with respect to deformations and temperature. Implicit schemes are solved by sequential application of the elimination method. The validity of the formulated thermoelastic boundary value problems is substantiated by comparing the numerical results of the problem of a thermoelastic parallelepiped obtained by different methods, as well as solving a similar problem in displacements.

Adaptive Load Shedding as Part of Primary Frequency Response To Support Networked Microgrid Operations

Global changes in the deployment of distributed energy resources, control and communications technologies, business models, and regulatory policy are increasing the operational options for future distribution systems. One such option is the coordinated operation of distributed resources to form microgrids and networks of microgrids to support traditional bulk power systems during normal operations and critical end-use loads during outages. While individual standalone microgrids have been extensively studied and deployed, the coordinated operation of networked microgrids is operationally more challenging due to the dynamic boundaries and changing mix of generation resources. This paper presents a method of using a distributed control architecture to support primary frequency response in networked microgrids operations. The support of primary frequency response is accomplished using the Open Field Message Bus reference architecture and Grid Friendly Appliance controllers.

Null controllability for parabolic systems with dynamic boundary conditions

Null controllability for parabolic systems with dynamic boundary conditions

A Direct Discontinuous Galerkin Method for Time Fractional Diffusion Equations with Fractional Dynamic Boundary Conditions

A Direct Discontinuous Galerkin Method for Time Fractional Diffusion Equations with Fractional Dynamic Boundary Conditions

Structure-preserving schemes for Cahn–Hilliard equations with dynamic boundary conditions

Structure-preserving schemes for Cahn–Hilliard equations with dynamic boundary conditions