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A grid-characteristic numerical method for solving a multidimensional transport equation on an unstructured grid with an order higher than one is proposed; this method does not use auxiliary points on edges and faces. The avoidance of auxiliary points on edges and faces simplifies the topology of the computational grid during its motion, which is important for solving dynamic problems of mechanics of deformable solids. To increase the approximation order, an analog of the grid stencil extension implemented for an unstructured grid is used. Results of testing the proposed numerical scheme for continuously differentiable, continuous, discontinuous solutions are presented. [ABSTRACT FROM AUTHOR]

An algorithm based on the Paterson-Stockmeyer (PS) scheme and filtering technology is developed to compute the large matrix functions in dynamic problems accurately and efficiently. With the assistance of analysis on truncation error and error caused by filtering, the error growth law during the computation is studied, based on which an adaptive filtering threshold is proposed to help the proposed algorithm more efficiently achieve similar accuracy as the original PS scheme. Numerical examples, including 30 random matrices with different bandwidths, 10 adjacency matrices in the complex network dynamic problems, and a trampoline vibration problem, are given to verify the efficiency and accuracy of the proposed algorithm. Numerical results suggest that the proposed algorithm can achieve good accuracy and efficiency in computing the matrix function in the considered dynamic problems. [ABSTRACT FROM AUTHOR]

This paper focuses on the dynamic workforce scheduling and routing problem for the maintenance work of harvesters in a sugarcane harvesting operation. Technician teams categorized as mechanical, hydraulic, and electrical teams are assumed to have different skills at different levels to perform services. The jobs are skill-constrained and have time windows. During a working day, a repair request from a sugarcane harvester may arrive, and as time passes, the harvester's position may shift to other sugarcane fields. We formulated this problem as a multi-visit and multi-period dynamic workforce scheduling and routing problem (MMDWSRP) and our study is the first to address the workforce scheduling and routing problem (WSRP). A mixed-integer programming formulation and a hybrid particle swarm and whale optimization algorithm (HPSWOA) were firstly developed to solve the problem, with the objective of minimizing the total cost, including technician labor cost, penalty for late service, overtime, travel, and subcontracting costs. The HPSWOA was developed for route planning and maintenance work for each mechanical harvester to be provided by technician teams. The proposed algorithm (HPSWOA) was validated against Lingo computational software using numerical experiments in respect of static problems. It was also tested against the current practice, the traditional whale optimization algorithm (WOA), and traditional particle swarm optimization (PSO) in respect of dynamic problems. The computational results show that the HPSWOA yielded a solution with significantly better quality. The HPSWO was also tested against the traditional genetic algorithm (GA), bat algorithm (BA), WOA, and PSO to solve the well-known CEC 2017 benchmark functions. The computational results show that the HPSWOA achieved more superior performance in most cases compared to the GA, BA, WOA, and PSO algorithms. [ABSTRACT FROM AUTHOR]

Based on the differential cubature (DC) principle, a dynamic procedure for simultaneous discretization of time and space is developed. A spatial–temporal differential cubature analysis method for dynamic problems is established with the Timoshenko shear beam; the reliability of analysis results obtained by which is verified, and the stability of the numerical scheme is studied. This method is extended to the two-dimensional structure, and the forced vibration analysis is carried out with the thin plate as an example. The research shows that the method can acquire highly accurate numerical results, and the calculated time-history numerical solution of beam displacement is extremely consistent with the analytical solution, which can adopt to the changes in beam properties and load parameters. With fewer nodes and longer time step than the finite element method (FEM), the method in this paper can still obtain stable and accurate results when solving displacement responses of plate under forced vibration. The numerical stability of this method is closely related to the grid form and the size of time step, and the increase in the number of nodes in the time domain is conducive to increasing the stability range. [ABSTRACT FROM AUTHOR]

Introducing functional gradients into thermoelectric materials can affect their conversion efficiency and mechanical properties. In this paper, the problem of thermal shock of an exponentially thermoelectric graded material is considered. Using the superposition principle and the method of separation of variables, expressions for the temperature and other physical quantities of the thermoelectric field are obtained. Then, other physical expressions for the thermoelectric field are derived from the expression for temperature. The effective thermoelectric coefficients of a static functionally graded material are obtained by using the equivalence principle. The numerical results describe the changes of physical quantities related to temperature with time and position. Meanwhile, the basic condition for thermoelectric conversion is analyzed based on the thermoelectric figure of merit, thermoelectric conversion efficiency, effective thermoelectric coefficient, and effective thermoelectric figure of merit. The results show that higher thermoelectric conversion efficiency can be achieved by changing the grading parameters. These results provide a theoretical basis for the production and performance optimization of thermoelectric materials. [ABSTRACT FROM AUTHOR]

In recent years, the popularity of fiber-reinforced materials in the aerospace and automobile industries grows due to their high stiffness-to-weight ratios. Thus, a structural design methodology is needed to bring out the celebrated mechanical properties of these materials as much as possible. From this aspect, topology optimization has been considered as an effective method for such a method. As a natural consequence of the trend, intensive researches on topology optimization methodologies to handle the anisotropy of fibrous materials has been conducted. However, these researches were limited to the static problem, i.e., compliance minimization problem. In the present work, we propose a dynamic topology optimization method for fiber-reinforced materials which is capable of optimizing element-by-element orientations. Our method builds upon a framework of SIMP type topology optimization and can optimize each element’s density and orientation as design variables. Numerical analysis is done by Finite Element Method and Method of Moving Asymptotes is implemented as an updating scheme of design variables. The effectiveness of our method is validated through the eigenfrequency maximization problem and eigenfrequency gap maximization problem.

This paper focuses on the dynamic workforce scheduling and routing problem for the maintenance work of harvesters in a sugarcane harvesting operation. Technician teams categorized as mechanical, hydraulic, and electrical teams are assumed to have different skills at different levels to perform services. The jobs are skill-constrained and have time windows. During a working day, a repair request from a sugarcane harvester may arrive, and as time passes, the harvester’s position may shift to other sugarcane fields. We formulated this problem as a multi-visit and multi-period dynamic workforce scheduling and routing problem (MMDWSRP) and our study is the first to address the workforce scheduling and routing problem (WSRP). A mixed-integer programming formulation and a hybrid particle swarm and whale optimization algorithm (HPSWOA) were firstly developed to solve the problem, with the objective of minimizing the total cost, including technician labor cost, penalty for late service, overtime, travel, and subcontracting costs. The HPSWOA was developed for route planning and maintenance work for each mechanical harvester to be provided by technician teams. The proposed algorithm (HPSWOA) was validated against Lingo computational software using numerical experiments in respect of static problems. It was also tested against the current practice, the traditional whale optimization algorithm (WOA), and traditional particle swarm optimization (PSO) in respect of dynamic problems. The computational results show that the HPSWOA yielded a solution with significantly better quality. The HPSWO was also tested against the traditional genetic algorithm (GA), bat algorithm (BA), WOA, and PSO to solve the well-known CEC 2017 benchmark functions. The computational results show that the HPSWOA achieved more superior performance in most cases compared to the GA, BA, WOA, and PSO algorithms.

We consider the problem of modeling hydroelastic oscillations of liquid fuel in the tanks of launch vehicles with the use of mechanical analogs. Here, it is important to ensure the applicability of the computational model with mechanical analogs to the real object in terms of the mass-inertial and dynamic characteristics. In addition, it is necessary to ensure the correct modeling of the external active forces acting on a tank when it is modeled by mechanical analogs. The proposed approach can be applied in a simulation of fire stand tests (FSTs) of propulsion systems, when the engine is mounted on the truss structure to the tank's dome and in the analysis of loads on the prospective reusable stages of launch vehicles. [ABSTRACT FROM AUTHOR]

Based on the differential cubature (DC) principle, a dynamic procedure for simultaneous discretization of time and space is developed. A spatial–temporal differential cubature analysis method for dynamic problems is established with the Timoshenko shear beam; the reliability of analysis results obtained by which is verified, and the stability of the numerical scheme is studied. This method is extended to the two-dimensional structure, and the forced vibration analysis is carried out with the thin plate as an example. The research shows that the method can acquire highly accurate numerical results, and the calculated time-history numerical solution of beam displacement is extremely consistent with the analytical solution, which can adopt to the changes in beam properties and load parameters. With fewer nodes and longer time step than the finite element method (FEM), the method in this paper can still obtain stable and accurate results when solving displacement responses of plate under forced vibration. The numerical stability of this method is closely related to the grid form and the size of time step, and the increase in the number of nodes in the time domain is conducive to increasing the stability range.

We formulate a dynamic problem which governs the displacement of a viscoelastic body which, on one hand, can come into frictional contact with a penetrable foundation, and, on the other hand, may undergo material damage. We formulate and prove the theorem on the existence and uniqueness of the weak solution to the formulated problem. [ABSTRACT FROM AUTHOR]

We present the exact solution of a nonstationary problem for the infinite elastic layer containing a rigid cylindrical inclusion with conditions of smooth contact imposed on the cylindrical surface. One surface of the layer is subjected to the action of an axisymmetric normal nonstationary compressive load. The other surface either is perfectly coupled with an absolutely rigid foundation or is supported by a smooth foundation without friction. To construct the fields of displacements and stresses in the layer, we successively apply the Laplace and Weber integral transformations to the axisymmetric equations of motion. This gives an inhomogeneous vector boundary-value problem for the unknown transforms of displacements. The problem is solved with the help of the matrix differential calculus. The normal stresses are analyzed on the cylindrical surface of the inclusion and on the bottom surface of the elastic layer. The obtained solution is studied in detail for the case of quasistatic vibration. [ABSTRACT FROM AUTHOR]

Due to the high rate of Traffic accident and death toll in Iran, recently the case has altered into a major national hitch. Through System Dynamics point of view and examining significant factors like the yearly death toll of vehicle accidents in Iran, the importance of the case gets more vivid. Generally the case beholds various dimensions (Multi Dimensional Case) and special complexities. The study applies “System Dynamics” approach. Having defined the Dynamic problem, considering the “literature review”, and exploring the interviews four groups of major factors were scrutinized as effective and significant. Concentrating on the four main factors, the “Casual Loop Model” was developed. The system was divided to several subsystems (several main sections). Afterward “Casual Loop diagram” was presented for each subsystem. Finally the three proposed strategic policies were introduced to enhance the behavior of main system variables such as set-up “In-charge organization” or leading organization.

A coupling peridynamic approach is developed for the consolidation and dynamic analyses of saturated porous media. In this method, the coupling state-based peridynamic equations of solid skeleton and pore fluid are derived based on the u–p form governing equations. Then, the corresponding implicit incremental formulations are obtained according to the linearization method on the basis of the first-order Taylor's expansion technique and the Newton–Raphson method. There are two advantages of the present implicit algorithm comparing with the explicit one. First, the former can handily deal well with various boundary conditions without setting up additional boundary layers. Next, the former is more reasonable and efficient to solve the consolidation problems whereas it often needs very small time step for the explicit peridynamic method combining with an additional damping under a quasi-static loading. Finally, both the consolidation and dynamic examples are given out and the results certify the validity and accuracy of the developed method by comparing it with the finite element method. [ABSTRACT FROM AUTHOR]

The problem of determining the steady-state dynamic response of a granular elastic half-plane to a load moving on its surface is solved analytically. The granular material is modeled as a gradient elastic solid with one material constant with length dimensions in addition to the two classical elastic moduli. The load is uniformly distributed of constant magnitude and moves with constant speed. The resulting two partial differential equations of motion are of the sixth order with respect to the horizontal x and vertical y coordinates and of the second order with respect to time t. These equations are solved with the aid of complex Fourier series involving x and t, which reduce them to a system of two ordinary differential equations, which can be easily solved. The so-obtained solution is used to easily assess the microstructural effect on the various response quantities through parametric studies. [ABSTRACT FROM AUTHOR]

Highlights • A price-responsive early charging control (PRECC) is proposed, which uses an adaptive speedup factor to tackle the dynamic problem caused by the uncertainty of EV behavior. • PRECC considers price preference in early charging to further narrow the gap between online and offline charging optimizations. Besides, it is not limited by EV states, therefore effectively coping with base load variations. • No iterative optimization is required to obtain the control factor, thus PRECC comes with low computational cost. This is very meaningful for reducing the overall costs of charging coordination. Abstract The uncertainty of electric vehicle (EV) behavior is deemed as a major challenge in online charging scheduling. It may lead to charging congestion to compromise the whole benefits of EV owners and aggregators. Early charging is the most efficient way to tackle the dynamic problem. However, it is very challenging for early charging to achieve the adaptive control and minimize electricity bill. In this paper, a price-responsive early charging adaptive control (PRECC) is proposed. The speedup factor is designed as a subtotal of charging demand categorized by electricity price, and it can be determined with only one offline charging optimization through a data-mining method. Due to the strong correlation with electricity price, PRECC can help online scheduling algorithms minimize early charging cost. Since it is not limited by the states of EVs, it can rapidly respond to the variations of base load and electricity price. Besides, with the independent design, it can well match online scheduling algorithms. Computer simulations are made to verify the proposed control. The results show that PRECC can improve the optimality of online scheduling by an average of 5.4%. Compared with the traditional early charging strategies, it has obvious advantages in terms of optimality, power capacity utilization, and profitability. [ABSTRACT FROM AUTHOR]

A spline-interpolation solution of static and dynamic elasticity theory problems is suggested. The method allows to solve the problems for solids with plane sections parallel to the plane XOY. We reduce space and dynamic problems to the series of plane boundary-value problems. The recursive formulas are obtained to determine the spline coefficients. The convergence of the constructed approximate solutions to the exact solutions is proved.

In this study, we propose a parameter-free optimization method to control time-dependent responses of a shell structure, where the optimal thickness distribution is determined without design parameterization. The design objective is to minimize the vibration displacements or to control the dynamic responses at arbitrary domains and times for an arbitrary time-dependent loading under the volume constraint. The unsteady optimum design problems are formulated as distributed-parameter optimization problems and the sensitivity functions with respect to the thickness variation are derived based on the variational method, Lagrange multiplier method and the adjoint variable method. The derived sensitivity function is applied to the H1 gradient method with Poisson's equation, a gradient method in the function space newly proposed in this study to determine the optimal variation of the thickness distribution. With the proposed method, the optimal thickness distribution for time-dependent response problems such as a forced-vibration, a free-vibration or a transient response is obtained while minimizing the objective functional and maintaining the smooth thickness distribution of a shell structure. Several numerical design examples including a continuous dynamic force or an impulse force as an input force are demonstrated to show the effectiveness of the proposed method, and the results are discussed.

Summary: A mesh superposition technique is developed based on the superimposed version FEM (s‐version FEM) for dynamic analysis of damage to structures. In the proposed technique, the concerned area is discretized as a rough global mesh and is overlaid into a fine local mesh of the proposed s‐version FEM. To describe the small‐scale stress wave, the governing equations for the internal part and boundary of the local region are proposed. The damage evolving constitutive model is substituted into these governing equations to describe the distributions of damage on a small scale. L‐shape domain problem, modal, time history, and damage examples are given for the validations. The results show that the proposed s‐version FEM can refine a global mesh and accurately describe the damage, stress, and deformation of a concerned area of structure on the small scale. The proposed s‐version FEM can be applied to not only a dynamic problem but also a damage analysis of structures. [ABSTRACT FROM AUTHOR]

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