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• Combine extrinsic GFDM with absorbing boundary condition for simulating acoustic wave propagation on surfaces. • Accuracy simulation of wave propagation on surfaces with periodic holes or inclusions. • Give convergence analysis for increasing node density and decreasing frequency. • Reveal significant impact of periodic structures. • Investigate effects of filling fraction & surface curvature on transmission. This paper introduces a localized meshless method to analyze time-harmonic acoustic wave propagation on curved surfaces with periodic holes/inclusions. In particular, the generalized finite difference method is used as a localized meshless technique to discretize the surface gradient and Laplace-Beltrami operators defined extrinsically in the governing equations. An absorbing boundary condition is introduced to reduce reflections from boundaries and accurately simulate wave propagation on unclosed surfaces with periodic inclusions. Several benchmark examples demonstrate the efficiency and accuracy of the proposed method in simulating acoustic wave propagation on surfaces with diverse geometries, including complex shapes and periodic holes or inclusions. [ABSTRACT FROM AUTHOR]

In the high-temperature environment, a larger thermal expansion mismatch of a bimaterial leads to pronounced thermal stresses and interface crack growth. In this paper, a generalized fractional heat conduction model is used to determine the instantaneous thermal fracture behaviors of a bimaterial interface crack. An axisymmetric thermoelastic problem is solved with the aid of Goodier's thermoelastic displacement potential and Love's potential functions. A mixed initial-boundary value problem is then converted to a singular integral equation of second kind by using the Hankel and Laplace integral transforms. Numerical results of the intensity factors of heat flux and thermal stresses are evaluated using Stehfest's Laplace inversion scheme. The influence of fractional kernel functions with power and exponential law are analyzed, respectively, for aluminum-steel and steel-epoxy, respectively. The thermal stress intensity factors exhibit more wave-like behaviors based on Riemann-Liouville and Atangana-Baleanu models which is different from Caputo-Fabrizio and the complete diffusion model. • An interface crack between dissimilar materials is analyzed. • Goodier's and Love's potential functions are utilized for solving the problem. • Transient heat flux and thermal stress intensity factors are investigated. • Characteristics for various fractional heat flux kernel are considered. [ABSTRACT FROM AUTHOR]

The utilization of deep learning methodologies for addressing partial differential equations (PDEs) has garnered significant attention in recent years. This paper introduces an improved network structure tailored for the discontinuity-capturing, enabling the resolution of interface problem through a unified neural network framework. Employing the probability space filling argument, we show that our model can generate convergent sequences, where the convergence rate depends on the number of sampling points. Several numerical experiments with regular and irregular interfaces are conducted to elucidate the convergence characteristics, thereby validating the theoretical assertions. Furthermore, we apply our approach to effectively solve the size-modified Poisson-Boltzmann test model, utilizing it for predicting electrostatics and the solvation free energies for proteins immersed in ionic solvents, thus showcasing practical applications of our method. • Improved multi-scale fusion network uses only a single neural network. • Our network model is proposed to solve the elliptical interface problem. • Theoretically give a least convergence rate of our numerical method. • Numerical experiments agree with our theoretical convergence rate. • We calculate the solvation free energies of immersed biomolecules by our method. [ABSTRACT FROM AUTHOR]

• An efficient mid-range approximation method for large-scale problems is proposed. • The improved trust-region strategy has a flexible and controllable performance. • A metamodel assembly technique is developed to alleviate the efficiency issues. • Optimization problems of 512 and 232 design variables are considered respectively. • The method successfully obtains the optimum at a reasonable computational cost. This paper presents an efficient solution for high-fidelity large-scale aerodynamic shape optimization problems based on several developments in the mid-range approximation method within a trust region optimization framework. The mid-range approximation method is an iterative optimization technique that utilizes mid-range approximations to replace the physical experiments or simulations during the optimization based on the selected trust region strategy. It could transform the original optimization problem into a sequence of approximate sub-optimization problems. In this work, an improved trust region strategy is proposed to contain more optimization states with a flexible and controllable performance to suit different types of problems. A metamodel assembly technique and its gradient-enhanced version are developed to further relax the requirements of computational costs in the mid-range approximation method. Its performance is discussed through a detailed comparison of metamodel performance using a mathematical benchmark case named Vanderplaats scalable beam. The wing only of the Common Research Model is offered to the proposed method for aerodynamic shape optimization. The optimization has 1 design objective, 232 design variables, and 135 design constraints. With all constraints satisfied, the optimized configuration has a 4.85 % improvement in wing drag performance. The shock region is greatly reduced and the wing pressure distribution is smooth and nearly parallel. These results show that the proposed method could achieve the design goal successfully within a reasonable computational cost for large-scale problems. [ABSTRACT FROM AUTHOR]

This paper presents a newsvendor model with backorders for customers who are willing to wait to be served. Demand follows a normal probability distribution, with the particularity that the expected value depends on the sale price and the variation coefficient is fixed. Three parameters are considered to characterize this dependence on the expected demand and the sale price: the population size of potential customers, the unit production cost of the item and an elasticity parameter with an isoelastic type. Backorders and lost sales are combined with a fixed proportion for the backorders. The quantities to be determined are the sale price and the order quantity. The goal is the maximization of the expected profit. The optimal solution is obtained in a closed form if there are no lost sales. In the case of a mixture of partial backordering and lost sales, a methodological proposal based on a numerical algorithm is given. The study reveals that the maximum expected profit and the optimal quantities to be determined are highly influenced by the unit purchasing cost and the degree of dependence of the demand concerning the sale price. Other parameters, such as the proportion of backorders and the variation coefficient of demand, are less influential. Numerical examples are used to illustrate the model, and a sensitivity analysis of the optimal solution regarding the nine initial parameters is presented. Some managerial insights deduced from the obtained results are also proposed. • A newsboy model with demand fixed partial backlogged is presented. • Demand follows a normal probability distribution with price-dependent mean. • The decision variables are the lot size and the selling price. • A numerical algorithm is given to obtain the optimal policy. [ABSTRACT FROM AUTHOR]

• Practical fracture limit surfaces (FLSs) considering data flexibility. • A profile function for nonlinear fracture data variations in strain-based FLS. • Stress-based FLS considering evolution of stress anisotropy in the Lagrangian frame. • Both models were validated by experimental data set. • The model effectively represents the flexibility of fracture data. Ductile fracture limits have been extensively studied from the perspectives of material science and mechanics. While these studies have provided scientifically significant insights into ductile fracture limits, the influence of the evolution of anisotropy observed in actual experimental data suggests a need to account for diversity in the experimental data. To address this, it may be possible to further develop the model by investigating more influences from the field of materials science. However, from an engineering perspective, it can be effective to represent the diversity of acquired experimental data as practical functions for use, rather than solely focusing on the material science aspect. This paper presents mathematical formulations representing the strain- and stress-based fracture limit surfaces of ductile materials, to consider diverse data set for the evolution of anisotropy, under plane-stress conditions within the framework of the Lagrangian formulation. The model introduces a strain-based fracture limit surface (FLS), which has an additional anisotropic profile function based on the commonly used two-dimensional strain-based fracture limit curve (FLC). The anisotropic profile function is capable of capturing the evolving anisotropic profile based on the deformation mode and principal loading direction to represent more flexible shapes. With this function, a three-dimensional strain-based FLS, which can present the variation in fracture strains in the space of the deformation mode and principal loading direction, can be constructed. Then, the proposed model transformed this strain-based FLS into a stress-based FLS by converting the presented state vector in the former into the corresponding vector in the latter in the Lagrangian formulation. To achieve this, this study developed a formulation that considers the nonlinear evolution of stress anisotropy independent of the strain anisotropy during stress evolution. The two proposed models were validated by experimental results on a dual-phase steel. These models provide flexible fracture limit functions for ductile materials under varying stress and strain conditions in engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, a novel parabolic system involving nonlinear and nonhomogeneous partial differential operator with variable growth structure is introduced for investigating the image denoising and restoration. More precisely, our model is based on regularizing the classical models involving variable exponent operators by considering a nonlinear operator with double phase flux. We begin by investigating theoretically the solvability to the parabolic system under consideration. Under the setting of Musielak-Orlicz spaces, we build a suitable functional framework to study the proposed system. Therefore, we develop the Faedo-Galerkin approach to demonstrate the existence and uniqueness of a weak solution to our model. To illustrate our theoretical results in the context of image noise removal, we present various numerical implementations on some grayscale images. To enrich these simulations, we test the robustness efficiency of the proposed model in the so-called Magnetic Resonance Images (MRI). The obtained numerical results claim that our model is more efficient and robust against noise, in comparison (visually and quantitatively) to some existing state-of-the-art methods. • A novel nonlinear parabolic system is introduced. • The theoretical results are applied to the image denoising and restoration. • Various numerical implementations on some grayscale images are carried out. [ABSTRACT FROM AUTHOR]

• Double bias fields are introduced into fidelity term to approximate image intensity inhomogeneity. • The proposed energy function is strictly convex, and allows flexible initialization. • A TV (total variation) regularization term is introduced to keep convex level-set function smooth. • The proposed method is robust against to noise and intensity inhomogeneity. The existing active contour models (ACMs) based on bias field (BF) correction mostly rely on a single BF assumption and lack in-depth discussion on the convexity of the energy functional, often leading to the problem of local minima. To address this issue, this paper introduces a dual BF and proposes a convex level-set (LS) method based on multiplicative-additive (MA) model to achieve global minima. Firstly, a MA model is adopted as the fidelity term, and a kernel function is introduced to adjust the size of the intensity inhomogeneous neighborhood, enhancing the adaptability to intensity inhomogeneity. Then, the convex LS function is embedded in the variational framework to ensure convexity of each variable in the energy functional. This transformation turns the segmentation problem into a convex optimization problem. By introducing the total variation regularization term to smooth the LS function, the model's resistance to noise is effectively enhanced. Finally, by minimizing the proposed energy functional, image segmentation and BF correction are successfully achieved. Experimental results validate the global minima property of our model, while also demonstrating good flexibility in the initial contour. The proposed model achieves superior segmentation results compared to other classical ACMs on various types of images. [ABSTRACT FROM AUTHOR]

Quantitative structure-activity relationship modeling techniques are widely employed in diverse areas of chemistry, including environmental risk assessment of compounds and virtual screening of drugs. The modeling process entails optimizing the hyper parameters of the model and selecting appropriate molecular descriptors. It is a typical optimization problem with high-dimensional, nonlinear, continuous and discrete variables coexisting. To address this challenge, this paper proposes an enhanced snake optimizer with multiple strategies. First, new food emergence and temperature change mechanisms are introduced to balance the exploration and exploitation. Second, a death and regeneration mechanism is employed to enhance the algorithm's ability to escape from local optima. Third, new formulas for food searching, fighting, mating and eating are designed to simplify the complexity of the algorithm and improve its search efficiency and accuracy. Fourth, the performance of the proposed algorithm is evaluated using the CEC2017 benchmark functions, eight engineering cases with continuous variables, and six feature selection cases with discrete variables. Experimental results demonstrate that the algorithm significantly outperforms comparison algorithms. Finally, the algorithm was applied to quantitative structure-activity relationship modeling for environmental toxicity prediction. Compared with other algorithms, the algorithm can better configure hyper-parameters and select fewer and more effective features for environmental toxicity prediction model. It will be an effective tool to improve the performance of quantitative structure-activity relationship models. • New food emergence and temperature change mechanisms are presented to better balance exploration and exploitation. • Death and regeneration mechanism is adopted to avoid local optima. • The performance of the proposed algorithm is validated in CEC2017, engineering design and feature selection problems. • A joint optimization approach is proposed for quantitative structure-activity relationship modeling. • An environmental toxicity prediction model is obtained by jointly optimizing hyper-parameters and molecular descriptors. [ABSTRACT FROM AUTHOR]

A spectro-hierarchical algorithm is proposed to determine an approximate solution to the elasto-dynamic problem for periodic heterogeneous materials. Such a homogenization scheme is derived by employing tools from perturbation theory in finite dimension used in the context of the celebrated Theorem of Nekhoroshev. In particular, it is shown how a classical algorithm based on a suitable hierarchy of harmonics can be implemented for the problem at hand, leading to the explicit construction of functions approximating the solution of the original problem with an error that is superexponentially small in the cell dimension. According to this approach, the fully homogenized model turns out to be naturally related to the "integrable case" of perturbation theory. Furthermore, all the featured constants are estimated explicitly. More importantly, a fully detailed bound of the threshold for the cell dimension is presented to ensure the validity of the theory. An example of application of the described theory is given in the final section for the case of a layered material. • The paper deals with the system of PDEs arising from elasto-dynamic problems in Cauchy materials. • Focuses on a novel approach based on perturbation theory to deal with homogenisation-type problems. • Provides an explicit scheme to approximate the solutions of the problem at hand. • Gives explicit estimates of validity of the theory. [ABSTRACT FROM AUTHOR]

Accurate prediction of crack extension is crucial for ensuring the structural integrity of metal components exposed to diverse loads. While the Gurson model and its extensions are widely accepted for delineating ductile fracture stages, especially in porous materials with a rigid-perfectly plastic matrix, their efficacy diminishes in the presence of strain-hardening matrices. To address this limitation, our study introduces a robust numerical implementation and assessment of Perrin's model. In contrast to Gurson's approach, Perrin's model incorporates two distinct strain-hardening parameters derived from an intricate analysis of a strain-hardening hollow sphere subjected to axisymmetric loading. Moving beyond theoretical discussions, this paper actively engages in the rigorous evaluation of Perrin's model under various scenarios, encompassing isotropic, kinematic, and mixed isotropic-kinematic hardening conditions. The model's effectiveness is convincingly demonstrated through meticulous comparisons between numerical simulations and real-world experimental observations conducted on pre-cracked specimens. Facing challenges related to achieving global elastic-plastic convergence in large-scale simulations, our research introduces a sophisticated approach. Leveraging stiffness tangent moduli ensure the maintenance of quadratic convergence in global Newton method iterations. This not only enhances the reliability of our simulations but also underscores the practical applicability of our findings. The study also focuses on the necking and crack propagation of a cylindrical specimen through meticulous computational modeling. Our mesh captures intricate details and addresses stress gradients, revealing coplanar crack propagation contrary to prior beliefs. The confirmation of the cup-cone fracture effect challenges previous interpretations, emphasizing the critical role of void nucleation. This reinforces the credibility and applicability of our approach in advancing the understanding of material fracture behavior. In summary, this study significantly contributes to existing knowledge in fracture prediction models, offering a robust framework for predicting ductile fracture under substantial deformations. The presented findings pave the way for advancements in structural engineering, providing invaluable insights for optimizing the performance and resilience of metal structures in real-world applications. • We present a numerical implementation and assessment of a model for ductile fracture, considering three hardening scenarios. • We discuss the numerical implementation of the model and address the projection problem algorithm for three hardenings • We introduce a numerical integration strategy for handling significant deformations and rotations in complex structures. • We demonstrate the model effectiveness by comparing numerical simulations and experiments in pre-cracked specimens. [ABSTRACT FROM AUTHOR]

Identifying gusts and turbulence events is of primary importance for designing future gust load alleviation systems, calculating airframe load, and analysing incidents. Due to the impossibility of their direct measurement, indirect methods are used and ad hoc experiments are necessary to validate the methodology. This paper employs Convolutional Neural Network and Long Short Term Memory (CNN-LSTM) as well as CNN models for in-flight gust identification. Two aeroelastic models, with different levels of fidelity, representative of a civil and commercial aircraft, are used to generate gust responses to train and test the Deep Learning (DL) models. The results highlight the capability of both LSTM-CNN and CNN models in reconstructing gusts across the entire flight envelope of a civil commercial aircraft. The CNN model demonstrated its ability to identify gusts and turbulence when they occur concurrently, similar to real-world scenarios, in a significantly shorter amount of time. Furthermore, its application to wind tunnel gust response measurements, where the inflow has previously been characterised, demonstrated the effectiveness of the proposed methodology for experimental measurements. • CNN-LSTM and CNN models employed for accurate gust identification. • Methods rigorously applied to both numerical and experimental data. • Utilizing aeroelastic aircraft models with varied fidelity for identification • Identified gusts compared with those from gust generator characterization. • Results showcase significant capability in accurate gust prediction. [ABSTRACT FROM AUTHOR]

Rotating algal biofilm reactors (RABRs) are innovative systems designed to cultivate microalgae biofilms efficiently. In this paper, we have developed a novel mathematical model to accurately capture the growth dynamics of algae biofilms within RABR. By considering the spatial heterogeneity of the RABR, we introduce a PDE-based model that addresses the spatial variations across the substratum, enabling a more accurate simulation of biofilm growth in RABRs. The photosynthesis process is modeled through reactive kinetics, driving the growth of the algae biofilm. To analyze the system's behavior, we employ finite difference numerical methods to solve the complex PDE model. We then conduct extensive numerical simulations to understand algae biofilm growth in the RABR environment under various operational factors and environmental conditions. One primary focus in these simulations is to investigate the impact of various harvesting strategies, harvesting frequencies, light intensity, and light exposure on the overall biomass productivity of the algae biofilm. The numerical results provide valuable insights into optimizing algae biofilm growth and designing harvesting techniques in RABR systems. Our proposed novel mathematical model provides an effective platform for the theoretical investigation and design of RABRs for wastewater treatment. • New mathematical model simulates algae biofilm growth in RABRs accurately. • Incorporates photosynthesis and substratum surface heterogeneity. • Advances RABR efficiency in wastewater treatment and bioproducts. [ABSTRACT FROM AUTHOR]

• Develop an original FE-analytical model of bolt tightening with elastic of bearing cap. • Propose a new assembly accuracy prediction method of planetary gear train. • Consider gear-shaft-bearing-bolt coupling effects on assembly accuracy. • Explore bolt tightening effects on shaft error motion and assembly accuracy. • Carry out the assembly accuracy and vibration tests to verify the proposed method. Planetary gear train (PGT) is a complex transmission system composed of gears, shafts, bearings and bolted joints, of which the assembly accuracy affects the transmission accuracy and dynamic behavior. In this paper, a new assembly accuracy prediction method is proposed for PGT considering gear-shaft-bearing-bolt coupling effects. The new method is formulated by establishing three models for bolt assembly, shaft error motion and assembly accuracy (transmission error) of PGT. The model for bolt assembly is an original FE-analytical model to analyze the bolt assembly effect on elastic deformation of bearing cap, which is developed by finite element (FE) method and analytical method for addressing the elastic effect of bearing cap and elastic interaction between bolts. The models for shaft error motion and assembly accuracy are performed by the three-dimensional contact analysis with errors and preload of bearing cap based on analytical method and kinematic geometry relationship. Combining the three models, the assembly accuracy can be predicted by simulations. The simulations indicate that the proper bolt assembly parameters can alleviate the influence of manufacturing errors on assembly accuracy. The assembly accuracy tests of PGT are conducted. The results well agree with the simulations', and the assembly accuracy is improved by the proper bolt assembly parameters. [ABSTRACT FROM AUTHOR]

• An exact matrix-form solution is proposed for analyzing multiple non-circular tunnels in layered media. • Generalized complex variable theory, conformal mapping and fast Fourier transform are used in derivation. • The proposed solution avoids complicated coefficient determinations and iterative algorithm. • Effects of elastic properties, tunnels' position, equivalent layer and the layer thickness surrounding tunnels are discussed. This paper presents a matrix-form complex variable method that can predict the stress and displacement field around multiple tunnels in layered media. The proposed matrix-form method avoids complicated coefficient determinations and iterative algorithm, which effectively improves the computation efficiency. Firstly, the expressions for the stress and displacement field are given under the generalized complex variable theory. The conformal mapping technique and fast Fourier transform algorithm are used to formulate the matrix-form expressions of boundary conditions. Considering the boundary conditions of the tunnels and soil interfaces, the global matrix solution for multiple tunnels in layered media are obtained by assembling the matrix solutions of all single layers. The present theory is verified by comparison with the existing literature, finite element analysis and field data in engineering practices, and several numerical examples are given to reveal the effects of elastic properties, tunnels' position, equivalent layer and the layer thickness surrounding tunnels. [ABSTRACT FROM AUTHOR]

• A new Weibull log-logistic mixture distribution accumulation generation operator is established. • A novel grey model with multiple interaction effects is established. • The robustness and stability of the proposed method is proved and validated. • A new parameter estimation method is designed. • The proposed method is superior to other seven benchmark models in four case studies. Forecasting the failure of hard disk drives is important in server operation and has attracted increasing attention. However, current disk drive warning systems suffer from high false positive rates and high resource consumption when dealing with hard disk drive overall failure. Therefore, to accurately and stably predict hard disk drive overall failure, this paper develops a new Weibull Log-Logistic grey forecasting model with multiple interaction effects. Firstly, to capture and fit the trend of hard disk failure data flexibly and reduce the volatility, a new accumulation generation operator is established by introducing the Weibull Log-Logistic mixture distribution. Secondly, the proposed model constructs a multiple interaction term to describe the nonlinear relationship of the dependent variables on the system behavior series and the multiple interaction effects between the independent variables. Then, the parameter estimation method is designed to improve the fitting accuracy of the new model, in which linear estimation method, nonlinear estimation method, and meta-heuristic optimization algorithm are used to calculate the parameter values according to their categories. Finally, four varieties of hard disk drive data sets from BackBlaze are selected as study cases to validate the effectiveness of the proposed model. The results show that the mean MAPE of the proposed method is 2.1181 %, 2.2306 %, 8.1712 %, and 4.3417 %, respectively, corresponding to (hard disk drives ST8000NM0055, ST12000NM0007, ST10000NM0086, and ST14000NM0138), and the average value of the evaluation metrics are optimal in all competing models. Furthermore, it is observed that the number of reallocated sectors has the greatest influence in causing the failure of hard disk drives. [ABSTRACT FROM AUTHOR]

In this paper, we formulate mean and dispersion submodels for the class of Bell-Touchard regression models, and so we introduce the Bell-Touchard regression model with varying precision for count response variables. This regression model is, in some aspects, similar to the double generalized linear model framework, allowing for parameter interpretation in terms of the response variable in its original scale. We also provide an iterative process to estimate the regression coefficients in the mean and dispersion submodels, and develop diagnostic measures for this class of regression models. The methods developed are applied in a real data set for illustrative purposes. • Univariate count data modeling. • Two-parameter Bell-Touchard family of distributions. • Regression model for count variables with varying precision. • Overdispersion. [ABSTRACT FROM AUTHOR]

This paper incorporates the shortest passenger travel paths into the first train timetabling problem in urban rail transit networks. We first propose a path-based first train timetabling problem, which is formulated as a mixed-integer nonlinear programming model to reduce the travel time for passengers. To solve this model, we present a tailored branch-and-bound combined with the timetable-based Dijkstra algorithm. To further enhance the efficiency of the exact algorithm, we design a rolling time heuristic algorithm as a substitute for the branch-and-bound algorithm. Then, we proved that the rolling time heuristic combined with the timetable-based Dijkstra algorithm achieves 97.86% and 99.39% reductions in CPU time while sacrificing only 0.007% and 0.057% of optimality gap by two numerical experiments. Finally, the results based on two test networks with different structures demonstrate that the path-based first train timetabling model effectively improves passenger travel efficiency. Specifically, the travel times are reduced by 744 mins and 761 mins, while the transfer waiting times are reduced by 37.87% and 58.91% compared to the existing timetables. Moreover, the results also demonstrate that loop line networks will increase the difficulty of timetabling and lead to many passengers taking detours. To further enhance the efficiency of commuting for passengers who take the first train, URT operators may consider relaxing the limitations on the departure time of the depot stations. • A path-based first train timetabling model to minimize the total travel time in urban rail transit networks. • A tailored branch-and-bound combined with a timetable-based Dijkstra algorithm. • A rolling time heuristic algorithm to solve large-scale networks cases. [ABSTRACT FROM AUTHOR]

• A hybrid method by integrating the advantages of frequency-wavenumber method and finite element method. • The entire process simulation from the source to the local terrain has been achieved. • Seismic response of mountains due to point dislocation source. • The crustal velocity structure and source parameters influence the seismic response. This paper proposes a hybrid method to analyze seismic responses from the source to complex terrain. The hybrid method is based on the domain reduction idea, dividing the overall model into global domain (including the source and propagation path) and local domain (including complex terrain). For the propagation of seismic wave fields in the global domain, a frequency-wavenumber method based on the exact dynamic stiffness matrix is adopted. For the local domain, the finite element method combined with the artificial boundary substructure method is used to analyze the seismic response of complex terrain. The advantage of this hybrid method is that the frequency-wavenumber method can accurately and efficiently calculate the three-component ground motion of the global large-scale model, while the finite element method has a variety of elements and constitutive models, which can finely simulate the local complex terrain. We take the Zigong Xishan Park site as the research object, and verify the correctness of the hybrid method. Based on this, we use the hybrid method to simulate the seismic response of the site, focusing on the propagation process of seismic waves on the mountain surface, the spatial distribution of peak ground displacement, and the effects of crustal velocity structure and source parameters on the seismic response of the mountain. The results show that the propagation of seismic waves and the distribution of peak ground displacement are closely related to changes in terrain, and the crustal velocity structure and source parameters have significant effects on the seismic response of the mountain. [ABSTRACT FROM AUTHOR]

• A numerical approach for obtaining gas-liquid flow parameters utilizing one-dimensional two-fluid model was proposed. • The two-fluid model was discretized by implicit FEM techniques utilizing the proposed algorithm in this paper. • Four cases utilizing different meshes were utilized to illustrate the gas puffing effect on the momentum exchange process. • The transient numerical trends indicate that the gas puffing manifests in two physical forms between different flow regions. The accumulation of liquid condensate in the wet gas pipelines gives negative effects on the piping efficiency and flow managements. Accurate prediction of the condensate behavior is of crucial importance in the pipeline engineering. In this study, the one-dimensional two-fluid model with the stratified modeling in its source term is used to describe the gas-liquid kinetic motion along the pipe and the flow fields obtained from the newly proposed numerical approach are utilized to analyze the flow characteristics. Firstly, four cases with varying inlet liquid fractions, outlet pressures, and different meshes are utilized to investigate the gas-liquid steady-state variations along the pipe. The numerical results indicate that the outlet pressure influences the working pressure of the inlet gas-liquid, subsequently altering the equilibrium state and momentum exchange direction near the inlet, resulting in different condensate distributions in the pipeline. In the transient analysis with initial empty pipe, the inlet gas-liquid mainly impacts the pressure wave propagations in pressure spread stage, the gas kinetic motion in gas filling stage and the motion of the dividing interface between different regions in liquid filling stage, which is validated by the proposed numerical approach through comparison with the simulation tool OLGA designed by Schlumberger. Furthermore, when the liquid condensates appear in the initial state, the transition zones have two physical forms between different flow regions, which include the sudden dividing interface due to the high liquid amount carried by the inlet gas and the transition region resulted from the liquid accumulations. [ABSTRACT FROM AUTHOR]

• The reflection/transmission of seismoelectric waves propagating through a sandwiched structure are studied. • A new fractional order viscoelastic model with two attenuation peaks at seismic and sonic frequencies is established. • The seismoelectric effects have noticeable influences on EM wave while negligible influences on seismic waves. • The porosity and the viscoelasticity of solid frame have evident influences on both elastic waves and EM waves The seismoelectric waves generated in a fluid-saturated porous interlayer and the reflection/transmission characteristics at the interfaces of sandwiched structure are studied in this paper. Aiming to describe the strong attenuation and dispersion simultaneously at seismic and sonic frequencies, a new fractional viscoelastic model for the solid skeleton is introduced to the Pride's seismoelectric coupling theory. Using the interfacial continuity of stress, displacements, magnetic and electric fields, the reflection/transmission coefficients are determined. The numerical results are provided and shown graphically. The effects of seismoelectric coupling and the viscoelastic characteristics of solid skeleton on the reflection and transmission of seismoelectric waves are mainly studied. It is observed that the thickness, porosity and the viscoelastic characteristics of solid skeleton have evident effects not only on the electromagnetic waves but also on the seismic waves. [ABSTRACT FROM AUTHOR]

• This manuscript firstly establishes a half vehicle-pavement-continuous beam bridge (VPCB) coupled system analytical model. • It is innovatively that the bridge and vehicle initial conditions are considered into analytical model. • The pavement road surface local deterioration is simulated by increasing the local roughness level of the road surface. At present, the highway bridge field is in a period of vigorous development, and the application of continuous beam bridges is becoming more extensive, so the related safety research is particularly important. However, there are few studies on the vehicle-bridge coupled interaction of continuous beam bridges, and the influence of pavement is not considered. In order to ensure that the theoretical research can better serve the engineering practice, it is urgent to establish a more refined and more complex vehicle-bridge coupled model. In this paper, a vehicle-pavement-continuous beam bridge (VPCB) coupled system model is established. A half-vehicle model is adopted, the pavement is simulated by a continuous and uniform spring damper, and the bridge is a three-span continuous beam bridge. The motion equation of VPCB system is established and deduced using D 'Alembert principle and modal superposition method. The dynamic responses of VPCB system are calculated by Newmark- β method. Here, the continuous beam bridge mode functions are fitted based on the modal vector of the continuous beam calculated by the finite element model. The correctness of the method is verified by existing literatures. The effects of bridge pavement, vehicle speed, bridge second span length, the pavement equivalent spring stiffness coefficient k p and damping coefficient c p , road roughness on VPCB system are studied. The results show that the pavement can reduce the bridge dynamic amplification factor (DAF) and the vehicle acceleration to improve the ride comfort. The dynamic responses of the vehicle and the bridge contain each other's natural frequencies. The responses of VPCB system increase with the vehicle velocity, the vehicle responses are more affected than the bridge responses. The pavement equivalent stiffness and damping coefficient has little effect on the system. The responses of vehicle and bridge increase with the increase of the bridge second span length. When the vehicle travels each span of the three-span continuous beam bridge, the time history curve of the pavement deformation under the tire resembles a sine wave. When the local roughness level of the road surface increases, the system responses at the deteriorated position suddenly increases, and the responses of the subsequent position will also be affected. The larger the roughness grade, the more obvious the responses increase. The effect on the system responses of the whole pavement damage is more significant than the local pavement damage. [ABSTRACT FROM AUTHOR]

The paper presents a new Lyapunov-type predefined-time stabilization control algorithm for stochastic high-order nonlinear systems with asymmetric output constraints. In contrast to stochastic finite-time and fixed-time stabilization, the average value of the settling-time function for stochastic predefined-time stabilization control is independent of both the initial value and the control factors. To mitigate the significant uncertainties arising from the asymmetric output constraint, a tan-type barrier Lyapunov function is formulated. Furthermore, by harnessing the previously mentioned barrier Lyapunov function and integrating the power integrator technique, a controller design strategy is formulated based on the backstepping method. The rigorous analysis in this study proves that the designed controller ensures both the attainment of predefined-time convergence of the system states to the origin in probability and the satisfaction of the output constraint. Finally, an example of a roll angle subsystem for quadrotor UAVs and a numerical illustration are presented to corroborate the theoretical analysis. • A novel Lyapunov-type stochastic predefined-time stable control algorithm is presented in Theorem 1. • Controller design based on the backstepping method is formulated through the power integrator technique. • The tan-type barrier Lyapunov function extends the order range and absorbs the inherent properties of the nonlinear terms. [ABSTRACT FROM AUTHOR]

• Thermomechanical problem of FGMs sphere with material uncertainties is analyzed. • The interval random uncertainty model is recommended for material parameters. • A data-driven ANN fast calculation for FGMs sphere uncertainties analysis is established. • The volume fraction distribution is optimized for the safety design of the FGMs sphere. Mechanical analysis and optimal design for functionally graded materials (FGMs) structures are significant. The present paper analyzes the parameter uncertainties problem for the thermomechanical response of the FGMs spherical shells with volume fraction power distribution. Here, the interval random uncertainty model is recommended to describe the uncertainties of each component of material parameters in FGMs, and a data-driven artificial neural network (ANN) fast calculation for FGMs spherical shells thermomechanical problems with uncertainties analysis is established and trained. The thermomechanical coupling response analysis and volume fraction optimization analysis of the FGMs spherical shell with material uncertainties are realized for zirconia-titanium FGMs, with the maximum normalized Von Mises stress as the structural safety index and the ANN as the fast calculation method. In addition, the Von Mises stress of the FGMs spherical shell and a ZrO 2 -Ti alloy double-layer spherical shell under different loads is compared. The results show that material parameter uncertainties, especially those in Young's modulus, thermal expansion coefficient, and uniaxial yield limit significantly affect structural safety. The structural safety index λ calculated based on the volume fraction optimization design of FGMs spherical shell is significantly lower than that of the ZrO 2 -Ti alloy double-layer. The ANN method greatly improves the computational efficiency for uncertain problems and maintains high accuracy, compared with the statistical analysis after many calculations by randomly selecting material parameters. This study provides a path for the safety design of FGMs structures with uncertain parameters. [ABSTRACT FROM AUTHOR]

In this paper, a novel non-convex fractional-order image denoising model is proposed to suppress the staircase effect produced by the TV model while maintaining a neat contour. The model combines ℓ q (0 < q < 1) quasi-norm and fractional-order regularization, and employs a diffusion coefficient with a faster convergence rate to preserve more image edges and details. Additionally, an adaptive regularization parameter is designed to adjust the denoising performance of the algorithm. To obtain the optimal approximate solution of the model, an enhanced primal-dual algorithm is adopted and the complexity and convergence of the algorithm are theoretically analyzed. Finally, the effectiveness of the proposed method is demonstrated through numerical experiments. • A new non-convex FOTV model is proposed. • A new diffusion coefficient is introduced to retain more edge details of the image. • The existing primal-dual algorithm is improved, and the convergence of this algorithm is analyzed. • An adaptive regularization parameter is designed. [ABSTRACT FROM AUTHOR]

• Unconventional subloading surface model is used for finite strain elastoplasticity. • Time integration schemes are proposed in reference and intermediate configurations. • Further decomposition of deformation gradient is utilized in kinematic hardening. • Diverse cases such as simple shear in tension and tension-compression are studied. • The results are in good agreement with experimental data available in literature. In this paper, the elastoplastic behavior of isotropic materials under finite strains is modelled and simulated under consideration of the subloading surface concept. Using the subloading surface model has many advantages, such as the ability of modeling more smoothly transition from elastic to plastic state and also more realistic modeling of the Bauschinger effect. For this purpose, three time integration algorithms are utilized in the reference and intermediate configurations in the present study. The first algorithm is based on a time integration scheme, available in the literature, and the second time integration is proposed by tensor exponential-based time integration and the third one is represented by a standard backward Euler time integration scheme. In the second proposed time integration, which is defined in the intermediate configuration, there is no need to use co-rotational objective time rates. However, in the third one, although it is based on the intermediate configuration, the Zaremba–Jaumann co-rotational rate is employed. Besides, in the second two time integrations, the constitutive equations are derived based on the unknown tensors defined in the intermediate configuration and as a consequence there is no restriction of using different hyperelastic models. For case studies, diverse deformation gradient tensors with and without volume changes are considered. These studied cases are accomplished for SUS 304 stainless steel and a glassy polymer (oriented PET). The obtained results of some cases are compared with available results in the literature. The agreement among the predicted results in this paper and the results from literature is good. [ABSTRACT FROM AUTHOR]

• We proposed a methodology to perform vibration analysis of rotor systems that exhibit localized nonlinearities. • The motion equation of the whole system uses hybrid coordinates. • The stability analysis of the obtained solutions is performed by the floquet theory. In this paper, the differential quadrature finite element method (DQFEM), component mode synthesis (CMS) method and incremental harmonic balance (IHB) method are combined to propose a methodology to perform vibration analysis and stability analysis of rotor systems supported on fluid-film bearings that exhibit localized nonlinearities such as squeeze-film damper (SFD). In multi-degree of freedom systems with SFD, a method for dynamic analysis of the system by reducing the degrees of freedom is first suggested in this paper. DQFEM are used to create the mass matrix, stiffness matrix, and gyroscopic matrix of the system. Then, the system is divided into linear system and nonlinear system, and the motion equation of the linear system reduces the degrees of freedom using the free interface CMS method, and the motion equation of the nonlinear system is written without reducing the degrees of freedom. By synthesizing the equations of motion of each component, the motion equation of the entire system is created. That is, the motion equation of the whole system uses hybrid coordinates. The motion equation of the system is solved using the modified IHB method. To evaluate the effectiveness of the suggested method, the computed solutions are compared with the results presented in the previous literature, and the results are very consistent. Also, stability analysis of the obtained solutions is performed by the Floquet theory. The method suggested in the paper can be effectively used to analyze the dynamic behavior of rotor systems exhibiting localized nonlinearities such as SFD. [ABSTRACT FROM AUTHOR]

• Motion planning of a spin-rolling sphere on a plane. • A novel geometric path planning approach with a Darboux frame parametrization. • Planning the spin-rolling sphere on the shortest path on the plane. • Evaluation of the capabilities and performance of the approach in the simulation. The paper deals with motion planning for a spin-rolling sphere when the sphere follows an optimal straight path on a plane. Since the straight line constrains the sphere's motion, controlling the sphere's spin motion is essential to converge to a desired full configuration of the sphere. In this paper, we show a new geometric-based planning approach that is based on a full-state description of this nonlinear system. First, the problem statement of the motion planning is posed. Next, we develop a geometric controller implemented as a virtual surface by using the Darboux frame kinematics. This virtual surface generates arc-length-based inputs for controlling the trajectories of the sphere. Then, an iterative algorithm is designed to tune these inputs for the desired configurations. Finally, the feasibility of the proposed approach is verified by simulations. [ABSTRACT FROM AUTHOR]

• This paper presents a drained expansion solution of a cylindrical cavity with fabric change effect in the sand. • The problem is formulated as a system of first-order differential equations with the known variables. • A user-defined SANISAND model is implemented as a subroutine, which is applied to FEM simulation. Sandy soil exhibits inherently anisotropy due to its microstructure, also known as 'fabric'. However, the drastic change in fabric observed during the dilatant phase is often overlooked in current cavity expansion research. This paper presents a drained expansion solution of a cylindrical cavity with fabric change effect in the sand using a simple non-associated and anisotropic model, SANISAND. The problem is formulated as a set of first-order differential equations with the unknown variables as functions of an auxiliary coordinate, which can be solved as an initial value problem. A subroutine is implemented into the FEM simulation to verify the proposed method. Additionally, cavity expansion solutions in sand are compared with those based on state-dependent dilatancy. The anisotropic fabric of the sand is studied to investigate the impact of the initial void ratio, initial mean stress, and at-rest coefficient on the void ratio path, stress distributions and paths, and bounding surfaces. The proposed solution provides a framework for the potential use of cavity expansion in sand, considering the fabric change effect, and a benchmark for further developments and numerical calculations by using the SANISAND model. [ABSTRACT FROM AUTHOR]

• Developing a nondestructive approach for the critical pressure of functionally graded combined shells with hydrostatic pressure. • Equivalent model of hydrostatic pressure for functionally graded combined shells is proposed. • The validity of the developed computational model is verified by numerical examples. • The effects of power-law exponents, geometric parameters, boundary conditions on critical pressure are discussed. This paper describes a unified nondestructive semi-analytical formulation for the critical pressure of underwater functionally graded combined shells subjected to external hydrostatic pressure. The structural model of combined shells is constructed from the first-order shear deformation theory, Voigt mixing law, and virtual spring technology. The admissible displacement functions are uniformly expressed with Legendre polynomials along the generatrix direction and Fourier series along the circumferential direction. The Kirchhoff-Helmholtz boundary integral equation is discretized by using the Legendre-Gauss spectral boundary element method, and the external acoustic field model is derived by expanding the Green's function, sound pressure, and displacement of combined shells with one-dimensional Fourier transformation. The linear elastic material theory is applied to deduce the work done by the hydrostatic pressure. The key technology to predict the critical pressure is to create an accurate equivalent model of the hydrostatic pressure. Through solving the final coupled governing equation, the critical pressure is obtained from the linear relationship between the hydrostatic pressure and the square of natural frequency. The convergence and correctness are verified by comparison with the results from published papers and numerical methods. The effects of different hydrostatic pressures, power-law exponents, geometric parameters, and boundary conditions on the critical pressure are investigated in several examples. Computed results can provide security guidance for the nondestructive prediction of underwater functionally graded combined shells at the beginning of engineering application design. [ABSTRACT FROM AUTHOR]

In the previous exoskeleton research, the development method of the exoskeleton-function-expectation prediction in the initial design stage is lacking, which is not conducive to reviewing the system-parameter influences on exoskeleton performances, nor to exploring the exoskeleton optimization direction. In this paper, a human-exoskeleton oscillation model is designed by integrating the main functions of one load-supporting exoskeleton in the gravity direction into the double-mass coupled oscillator model. The model simplifies the human-exoskeleton coupling motion into the human-exoskeleton oscillation motion in the gravity direction, and in the oscillation process qualitatively calculates the multiple functional expectations of the exoskeleton, such as the load-supporting capability, the human-exoskeleton interaction force, the oscillation response of the backpack and the power-assistance ability. By comparing the test results of the model with previous research, the model performance was analyzed. And further, the reasons for the unsatisfying load-supporting efficiency of previous exoskeletons were explained and the influences of system parameters for the system expectations were evaluated, which helps to provide a theoretical basis for improving the exoskeleton load-supporting efficiency and human-body comfort. In addition, the combination of the exoskeleton supporting static load and the suspension system buffering dynamic load is a new direction, and the model of the paper is also beneficial to evaluate the interference degree of the exoskeleton to the suspension system. [ABSTRACT FROM AUTHOR]

• A shape feature controlled topology optimization method of PZT for structure vibration control is proposed. • A modified K-means clustering method is proposed to obtain the explicit shape control functions. • An explicit optimization model with SPI as its objective and shape control functions as its constraints is presented. • Sensitivity analysis is performed based on chain rule, the Lyapunov equation and the adjoint method. This paper proposes a method for shape feature controlled topology optimization of attached piezoelectric actuators of thin-walled smart structures, aiming at both vibration control performance as well as possible manufacturing constraints. This paper first proposes a modified K-means clustering method to derive the shape feature control functions. Then, an optimization model with system performance index (SPI) as its objectiveness and shape feature control functions as its explicit constraints is organized. Based on the Lyapunov equation, the adjoint method and the chain rule, the sensitivity analysis of both objective and constraints in optimization model is performed. A mathematical programming method is applied to solve the optimization model once the sensitivities is calculated. Then the LQR control algorithm is used in the optimized structure for vibration control. Numerical examples as well as engineering application are applied to prove effectiveness of the proposed methods. The results show feasibility of the proposed methods. [ABSTRACT FROM AUTHOR]

• The nonlinear dynamics and thermal bidirectional coupling model of a rotor-ball bearing system is constructed. • The coupling characteristics of the interaction between vibration response and temperature variation are obtained. • The complicated jump phenomena and motion patterns in vibration response and temperature variation are demonstrated. • The characteristics affected by initial radial clearance, rotor eccentricity and lubricant viscosity are discussed. This paper focuses on the nonlinear dynamics and thermal bidirectional coupling characteristics of a rotor-ball bearing system. The motion equations of the rotor system are formulated by the Lagrange method, where the radial clearance of the ball bearing affected by thermal characteristics is considered. The heat transfer model of the ball bearing is established by combining the lumped parameter with the full thermal network, in which the frictional heat generation induced by the dynamic load of the ball bearing is considered. The heat transfer model is coupled with the motion equations of the rotor system via the mechanical model of the ball bearing. The dynamics and thermal bidirectional coupling model is solved by the step-by-step iterative solving procedure to detect the interaction between the vibration response of the rotor and the temperature variation of the ball bearing. The results show that the thermal expansion of the ball bearing results in the dynamical variation of the effective radial clearance, which makes a significant influence on nonlinear dynamics and thermal characteristics of the rotor-ball bearing system. On the other hand, the nonlinear dynamic response of the rotor leads to the nonlinear thermal characteristics of the ball bearing through the influence of the dynamic load. It is observed that there are more complicated jump phenomena and motion patterns in the vibration response and temperature variation compared to the case without thermal effects. Moreover, the jump phenomena affected by the initial radial clearance, rotor eccentricity, and lubricant viscosity are analyzed in detail. The results obtained in this paper can provide more insight into the bidirectional coupling mechanism of the nonlinear dynamics and thermal characteristics. [ABSTRACT FROM AUTHOR]

• A type of metamaterial isolation beam consisting a cantilever beam with flexoelectric film attached is provided. • A closed-form analytical expression for the bandgap range is derived. • The operating bandgap of the metamaterial isolation beam is widened by flexoelectric effect. • Parameter analysis and simulation validation of the model are performed, and optimal values are provided. • The flexoelectric beam significantly outperforms piezoelectric beams in microscale high-frequency passive isolation. In this paper, a type of metamaterial isolation beam consisting a cantilever beam with flexoelectric film attached is provided. Electrodes interconnect on the surface to create parallel resonant shunt circuits, enabling band-stop filtering. The electromechanical control equations are derived using the Hamiltonian principle. A closed-form analytical expression for the bandgap range is obtained via the root locus method. Theoretical results are validated through finite element methods. Findings reveal that the operational bandgap of millimeter-scale flexoelectric metamaterial isolation beams is 5.2 times greater than that of conventional piezoelectric metamaterial beams. Furthermore, the vibration excitation amplitude is reduced by 99.9%. These results highlight the significant advantages of flexoelectric materials for microscale high-frequency passive isolation, providing superior stability in complex vibration environments. The research investigates the effects of end mass, electrode plate count, and external resistance on the vibration isolation performance of flexoelectric metamaterial beams. The study also examines the variations in relative bandgap width between flexoelectric and piezoelectric metamaterial beams concerning material, size, and structural parameters, identifying optimal values. Notable differences in bandgap characteristics are observed between flexoelectric and piezoelectric beams; for instance, while piezoelectric beams have an optimal substrate elastic modulus, flexoelectric beams do not, and the optimal film thickness for flexoelectric beams is 2.2 times that for piezoelectric beams. [ABSTRACT FROM AUTHOR]

This study introduces a non-convex fractional-order hyper-Laplacian variational model for Gaussian noise removal. It employs first the primal-dual hybrid gradient algorithm to solve problems involving overlapping group sparse structures. Additionally, this paper designs a new algorithm leveraging the framework of the Chambolle-Pock algorithm with convergence and aims to recover high-quality images. The model, integrating the overlapping group sparse structure of the hyper-Laplacian prior with the non-convex fractional-order total variation, exhibits superior performance in reducing the staircase effect and maintaining sharp edge contours. To further improve the performance of the algorithm, a semi-adaptive p (x) non-convex penalty weight assignment mechanism is designed by introducing the structure tensor, which according to the characteristics of each region of the image and the noise level. The effectiveness and superiority of the proposed algorithm in image denoising with simulation experiments and comparative analyses are fully verified. • A new non-convex fractional-order hyper-Laplace variation model is proposed. • The PDHG algorithm is introduced to solve optimization problems involving OGS-HL for the first time. • The convergence and complexity of the new design algorithm are analyzed. • A semi-adaptive p (x) determined by the structure of the image and the noise level is designed. [ABSTRACT FROM AUTHOR]

• Analytic algorithm for SH wave scattering near semi-elliptical crater. • The boundary of the crater is endowed with surface elasticity. • DSCF relative to wave frequency, incident angle and crater's aspect ratio. Cratering occurs inevitably on the surface of materials at all scales due to comprehensive factors. The presence of craters may have a significant influence on the mechanical performance of the surface of an elastic body. In this paper, we study the SH wave propagation in an elastic semi-infinite medium whose surface has a semi-elliptical crater. We explore the scattering of the SH wave by the crater when surface elasticity is incorporated in the model of deformation to account for possible small-scale effects of the crater. We obtain a series solution for the scattered wave function by employing the Mathieu functions in the corresponding elliptical coordinate system. We discuss in some numerical examples the dynamic stress concentration around the crater relative to the wave frequency and few geometric parameters. [ABSTRACT FROM AUTHOR]

Failure in cancer treatment often stems from drug resistance, which can manifest as either intrinsic (pre-existing) or acquired (induced by drugs). Despite extensive efforts, overcoming this resistance remains a challenging task due to the intricate and highly individualized biological mechanisms involved. This paper introduces an innovative extension of an already well-established mathematical model to account for tumour resistance development against chemotherapy. This study examines the existence and local stability of model solutions, as well as exploring the model asymptotic dynamics. Additionally, a numerical analysis of the optimal control problem is conducted using an objective functional. The numerical simulations demonstrate that a constant anti-angiogenic treatment leads to a concatenation of bang-bang and singular intervals in chemotherapy control, resembling a combined protocol comprising maximal tolerated dose and metronomic protocols. This observation lends support to the hypothesis that mean-dose chemotherapy protocols may help circumvent acquired drug resistance. Lastly, a sensitivity analysis is undertaken to scrutinize the dependence of model parameters on the outcomes of the previously examined therapeutic protocols. • We consider a heterogeneous tumour consisting of two cellular subpopulations: sensitive and resistant to chemotherapy. • We change the therapy paradigm from total tumour eradication to controlling tumour growth and preventing drug resistance. • An optimal chemotherapy scheduling directly penalizes the subpopulation of resistant cells. • Penalizing chemoresistance gives rise to singular controls, supporting the metronomic chemotherapy administration scheme. • Sensitivity analysis shows how the optimal control structure depends on model parameters and initial conditions. [ABSTRACT FROM AUTHOR]

This paper studies the estimation problem of multiplicative models for large-scale positive response data with growing dimensions. First, we propose a communication-efficient least product relative error estimator which is the minimizer of a surrogate loss function that approximates the global least product relative error loss. Then, a practically efficient distributed Newton-Raphson algorithm is proposed to solve the problem. Theoretically, we show that the distributed estimator achieves the same statistical efficiency as the global estimator under regularity conditions when the dimension is fixed and increases with the local sample size, respectively. Second, by incorporating an adaptive lasso penalty into the surrogate loss, we develop a communication-efficient penalized least product relative error estimator for high-dimensional variable selection on massive positive response data. Accordingly, we propose a distributed algorithm based on the alternating direction method of multipliers. It is shown that the distributed penalized estimator has the oracle property in the growing-dimensional setting. Finally, extensive simulations and two real-world applications are conducted to demonstrate the superiority of our proposal. • A model is proposed to handle massive positive response data with growing dimensions. • Two new distributed estimators based on a relative error loss are proposed. • Two communication-efficient distributed algorithms are designed. • The convergence rate and asymptotic normality of the new estimators are derived. [ABSTRACT FROM AUTHOR]

• An analytical solution to the responses of a vehicle passing through continuous beams. • The quantitative relationship between vehicle acceleration and the damage. • Detailed comparison of the damage relationships for simply-supported and continuous beams. Damage detection for bridges using a passing vehicle has drawn much interest. Recent studies demonstrate that the tap-scan method is an efficient way to detect the change of beam bending stiffness. A quantitative relationship between the change of beam bending stiffness and the acceleration of a vehicle can be evaluated. However, the reported relationship is calibrated for a simply-supported beam, which may be unsuitable for continuous beams due to inherent structural differences. Addressing this, an analytical solution for damage detection for continuous beams using the tap-scan method is presented in this paper. Case studies reveal that damage relationships across different spans of continuous beams show negligible dependence on modal parameters and beam lengths. Consequently, the damage identification within any span of a continuous beam can be accomplished using the same damage relationship calibrated on a simply-supported beam. But it should be noticed that the damage relationship might differ by beam structural forms. The above result holds substantial implications for practical engineering scenarios, notably by diminishing the labor and complexity associated with the calibration of damage relationships for continuous beams. [ABSTRACT FROM AUTHOR]

This paper focuses on the applicability of Zermelo's equation within the context of 3D commercial aircraft trajectory optimization problems. The associated optimal control problem includes two singular controls, specifically aerodynamic path angle and throttle setting, and one regular control, specifically heading angle. Using Pontryagin's maximum principle and the direct adjoining method, we show that the optimal heading angle is defined by Zermelo's equation. The significance of the presented analysis is that Zermelo's equation holds for 3D commercial aircraft flights, even in the presence of standard state-inequality constraints and a more general objective function. With the help of Zermelo's equation, the control problem is initially analyzed for a 3D time-optimal climb-phase scenario, which is solved by an indirect approach. Through the analysis of the switching function, we demonstrate the dependency of the optimal aerodynamic path angle on the optimal heading angle. Next, by tackling a 3D time-fuel-optimal free-routing flight, solved by a direct approach, we show that Zermelo's equation can help reduce the overall dimension of the associated nonlinear programming. To successfully handle the initial guess in both indirect and direct problems, it is proposed a diminutive nonlinear programming technique as a fast and robust initializer. This simple-yet-effective initializer provides sufficient information about the optimal controls and state dynamics required for initializing a direct optimization, as well as the optimal switching times and co-states required for initializing an indirect optimization. • Demonstrating the applicability of Zermelo's equation to constrained optimization of 3D aircraft flights. • Solving 3D time-optimal problem in climb phase with Zermelo's identity using an Indirect method. • Solving 3D time-fuel-optimal free-routing problem with Zermelo's identity using a new Direct transcription method. • Brief discussion on aNLP for initialization of both Indirect and Direct methods. [ABSTRACT FROM AUTHOR]

• A novel human-based algorithm: the flavoring search algorithm. • Flavoring search algorithm corresponds to the real-world flavoring process. • Flavoring search algorithm proposes a unique flavor factor. • A Markov model of the flavoring search algorithm is developed. • Flavoring search algorithm is applied to engineering problems and robot path planning. In this paper, a human-based meta-heuristic algorithm, the Flavoring Search Algorithm, is proposed and mathematically modeled with the aim of providing an alternative optimization method for solving practical engineering problems. Flavoring Search Algorithm is inspired by the human behavior of flavoring in everyday life, including basic flavoring, formal flavoring, and auxiliary flavoring. By introducing a unique taste factor, it not only succeeded in making the Flavoring Search Algorithm corresponds to the real flavoring process but also balanced the exploration and exploitation of the algorithm. With the help of the taste factors, Flavoring Search Algorithm performs basic flavoring (initial flavoring and random flavoring) in the exploration phase and formal flavoring and auxiliary flavoring in the exploitation phase. In addition, theoretical analysis and experiments have led to the conclusion that the taste factor can be used as an effective and practical new threshold conversion mechanism for meta-heuristic algorithms. This study also establishes a Markov model to rigorously analyze the Flavoring Search Algorithm as a globally convergent algorithm from a mathematical point of view. Through experimental and analytical comparisons with other excellent optimizers on 30 test functions, as well as on 3 real-world engineering design problems and 1 path planning problem. The results show that the Flavoring Search Algorithm generally outperforms the tested competitors in solving benchmark functions and engineering problems, validating the utility of the proposed optimizer in solving challenging real-world problems. [ABSTRACT FROM AUTHOR]

• An atmospheric corrosion model of clearance joint is developed based on COMSOL simulation software. • A dynamic modeling and analysis method for ALGRM considering atmospheric corrosion is explored. • The effects of corrosion time and different bearing materials on ALGRM are investigated. • The dynamic behavior and nonlinear characteristics of ALGRM are discussed. Atmospheric corrosion poses a significant challenge for the components of aircraft exposed to prolonged harsh weather conditions, critically impacting the safety property of aircraft landing gear retraction mechanism (ALGRM). This paper focuses on the ALGRM of a specific aircraft type, presenting a new modeling and analysis approach to assess the influence of atmospheric corrosion on dynamic behavior and nonlinear characteristics of mechanism. Initially, the dynamic model of ALGRM incorporating clearance joints is established using Lagrangian method. Numerical solutions are then obtained using the Runge-Kutta method. Subsequently, COMSOL simulation software is employed to simulate the corrosion morphology of the bearing under atmospheric corrosion, integrating the corroded bearing surfaces into the dynamic model of the mechanism. Finally, the study investigates the effects of corrosion time and different bearing materials on the dynamic behavior and nonlinear characteristics of ALGRM considering atmospheric corrosion. The results indicate that as corrosion time increases, the degradation of the dynamic behavior of ALGRM becomes more pronounced, and there are significant variations for corrosion morphology of bearing made of different materials under atmospheric corrosion. The findings of this study contribute to a broader understanding of the complex interactions between the dynamic behavior of aircraft and environmental degradation, providing some insights for designing ALGRM that are more durable and adaptable to atmospheric corrosion environments. [ABSTRACT FROM AUTHOR]

• A quasi-zero-stiffness (QZS) metamaterial cylindrical shell is proposed;. • Quasi-zero stiffness is fulfilled by compliant mechanisms;. • QZS resonator is devised to open low-frequency band gaps;. • QZS metamaterial shell enables wave attenuation at low frequency. Low-frequency vibrations widely exist in various shell structures of aircrafts, ships or rockets, and propagate along shell structures in elastic waves. Aimed at the vibration issue, this paper proposes a novel metamaterial cylindrical shell with quasi-zero-stiffness (QZS) resonators to achieve low-frequency wave attention within band gaps. Firstly, the resonator is devised to exhibit the QZS feature under appropriate pre-deformation. A simplified dynamic model is established to replace the metamaterial cylindrical shell and derive dispersion relations. Then, the band gap is revealed theoretically by both the plane wave expansion method (PWEM) and the finite element method (FEM). Additionally, the finite element model of the metamaterial cylindrical shell is built to analyze the structural responses and evaluate the transmittance of flexural waves. The results show that the QZS metamaterial cylindrical shell is capable of opening low-frequency band gaps and effectively attenuating flexural waves at low frequencies. [ABSTRACT FROM AUTHOR]

• The strongly nonlinear dynamical system is solved through the homotopy analysis method. • The system exhibits hardening/softening behavior for superharmonic/subharmonic resonance. • The time delay parameters influence the generation and disappearance of subharmonic resonance. The present work discusses the strongly nonlinear dynamical characteristics of the secondary resonance in a cantilever beam system with concentrated mass regulated through displacement and velocity time delay. Through the homotopy analysis method, the potential superharmonic and subharmonic resonance issues are resolved. A detailed analysis is conducted to investigate the influences of the time delay, feedback gain coefficient, excitation amplitude, and damping coefficient on the nonlinear response. The results show that the system exhibits hardening behavior for superharmonic resonance with one or two peaks and softening behavior for subharmonic resonance. In time delay control systems, increasing the damping coefficient occasionally causes an increase in amplitude. Due to the complexity of the system, it is challenging to definitively determine whether displacement or velocity time delay control is more suitable. Only when specific working conditions are given can it be compared which way is better. Prudently choosing the velocity and displacement time delay factors can restrain the amplitude of the system, adjust the response region, jump frequency and the number of solutions. The findings of this paper are thought to be useful in the design of time delay feedback controllers. [ABSTRACT FROM AUTHOR]

• A predefined time control is proposed for morphing aircraft with state constraints. • The unknown disturbances can be estimated faster and more accurately. • The feasibility conditions are not required. • The system state can be limited to preset constraints. • The practical predefined time stability of attitude tracking error is guaranteed. This paper proposes a predefined time control method for morphing aircraft based on an adaptive full-feedback recurrent neural network and a universal barrier function. This method allows morphing aircrafts to track their attitude accurately even under the influence of morphing disturbance, aerodynamic uncertainties and asymmetric time-varying constraints. Specifically, a new universal barrier function is applied to directly perform unconstrained transformations of state variables, which avoids feasibility conditions. Additionally, an adaptive full-feedback recurrent neural network structure is proposed to quickly and accurately approximate additional disturbances and unknown dynamics. Moreover, a backstepping framework is applied to design the predefined time control law, and a command filter is used to prevent the "explosion of complexity" problem. According to stability analyses, the states of the closed-loop system converge within the preset time without violating the state constraints. Finally, the effectiveness of the control algorithm is verified via simulation experiments. [ABSTRACT FROM AUTHOR]

Due to the multiple physics involved and their mutual and complex interactions, nuclear engineers and researchers are constantly working on developing highly accurate Multi-Physics models, focusing in particular on the core coupling of Neutronics and Thermal-Hydraulics. Nevertheless, the development of accurate and stable models remains a challenging task despite the advancements in computational hardware and software. This work investigates the possibility of combining the available mathematical model with data collected on physical systems, with a two-fold goal: improvement of the performance of the former from the computational point of view without sacrificing accuracy and performing model bias correction with the knowledge coming in real-time from the system. In particular, two Data-Driven Reduced Order Modelling techniques, the Generalised Empirical Interpolation Method and the Parametrised-Background Data-Weak formulation, are applied to literature benchmark nuclear case studies, as they were observed to be quite well suited for the chosen cases. The main goal of this work is to assess the possibility of using external data to perform model bias correction: starting from a purposefully less accurate, but computationally cheaper base model, then using high-fidelity data to update and correct the model efficiently. Indeed, the numerical results obtained in this paper are promising, confirming the feasibility of this approach to develop computationally cheap and accurate multi-physics models; furthermore, investigation of Data-Driven Reduced Order Modelling approach to nuclear industrial cases, in the context of model bias correction, is foreseen. • State estimation using Data-Driven Reduced Order Modelling. • Solution of low-fidelity Multi-Physics models embedding Reduced Order Modelling approaches. • Update/correction of Multi-Physics models using higher-fidelity data. • Enhancing Multi-Physics modelling of nuclear reactors with data from different fidelity levels. [ABSTRACT FROM AUTHOR]

• The analytical solution of multipoint ground motion in multilayer submarine field is derived for the first time. • The transfer function and coherence function of multipoint ground motion at this site are derived for the first time. • The influence of soil stiffness and sea water height on ground motion is analyzed. In ocean engineering anti-seismic filed, the marine environment is usually regarded as the coupling field of seawater-layered porous seabed-elastic bedrock. This paper presents a theoretical method to study the spatially variable seismic underground motions in stratified seabed system. Based on the potential flow theory, Biot's porous model and random vibration theory, the transfer function and coherence function model of the underground seismic motions in the marine coupling field are derived. On the basis of the above theoretical derivation, the program of the spatial variability seismic underground motions of the coupling field is simulated and developed, and its accuracy and effectiveness are verified. Moreover, the effects of soil stiffness and overlying seawater level on the seismic response are also analyzed. Numerical results show that spatially variable seismic underground motions are significantly different from those on the ocean bottom. The simulation of spatially variable seismic underground motions for layered seabed field is significant for both theoretical study and ocean engineering application. [ABSTRACT FROM AUTHOR]

• Proposed fuzzy small displacement torsor model for tolerance classification representation. • Established an assembly reliability index for evaluating assembly precision. • Developed constrained transformation method for efficient and high-accuracy calculation. • Proposed a novel fuzzy algorithm for assembly precision management. The assembly precision of a specified product is subject to epistemic uncertainty due to manufacturing and measurement errors. The efficient and accurate assembly precision management is essential for realizing smart production lines, which rely on the robust assembly precision analysis model and calculation method. Parametric models are extensively used for assembly precision analysis in industrial products, typically integrating worst-case and statistical methods for calculations. Nevertheless, the combined application of these methods presents inherent limitations. Therefore, a novel fuzzy algorithm for assembly precision management is proposed in this paper by using fuzzy sets to quantify epistemic uncertainty in assembly precision, which integrates the proposed fuzzy-based assembly precision analysis model and fuzzy-based calculation method. The proposed fuzzy small displacement torsor model is a fuzzy-based model for deviation representation and tolerance classification using decomposed fuzzy numbers, where an assembly reliability index is always established for the hierarchical evaluation and management of assembly precision. Subsequently, a comprehensive assembly precision analysis model is developed for precision prediction and contribution quantification by integrating the Jacobian model for deviation propagation. A new constrained transformation method is proposed as a fuzzy-based calculation method, offering efficient and highly accurate assembly precision computation. It accounts for torsor parameter constraints to ensure greater prediction accuracy than the worst-case method and improves computational efficiency compared to statistical methods. An assembly case of the centering pin mechanism is applied to verify the superiority of the proposed novel fuzzy algorithm compared with the Jacobian-Torsor model with worst-case or statistical methods. [ABSTRACT FROM AUTHOR]