Nonlinear homogenization techniques to solve masonry structures problems

The behaviour of masonry material subjected to different in-plane loading combination is studied in this work. The masonry is considered as a periodic composite material composed by a regular distribution of brick and mortar and it is analyzed using a homogenization technique. The mechanical properties of the masonry, as an orthotropic homogeneous material, depend on the geometrical and mechanical properties of the components based on the study of the equilibrium and compatibility of a basic cell. The masonry is a frictional material and its behaviour depends on the loading direction, for these reasons, a unilateral damage model is chosen for the analysis. This model describes the behaviour of brittle materials subjected to tension-compression cyclic loads based on the introduction of two damage variables and it assumes that the damage is due to the beginning and growth of cracks only in the mortar joints. It is considered that the bricks have a linear elastic constitutive relationship. Numerical applications are performed with a nonlinear finite element code in order to test the proposed procedure by comparing the results with those available in the literature and also with experimental data.     

Hybrid TSSA algorithm-based approach to solve warehouse-scheduling problems

Managing a supply chain efficiently is one of the most promising tasks for enterprises these days. Therefore, all the major factors that contribute to the success of the supply chain have to be handled carefully. Warehousing being the vital component of the supply chain contributes towards the storage and timely and efficient delivery of products. The role of warehouses in the overall success of the supply chain has shifted the inclination of researchers towards finding ways that can ease the complexities prevailing under such a scenario. Motivated by these facts, the present paper deals with the issues pertaining to the modelling of the warehouse management system. The paper emphasizes various matters related to warehouse scheduling and aims for an overall minimization of tardiness. It also proposes a Tabu sample-sort simulated annealing (TSSA) algorithm to solve the complex warehouse-scheduling problems. The comparative result with simulated annealing (SA), Tabu search (TS), and hybrid Tabu-SA algorithms at the end of the proposed work reveals the efficacy and robustness of the TSSA algorithm.     

Regularization and perturbation technique to solve plasticity problems

This paper investigates new procedures to solve plasticity problems by using the asymptotic numerical method (ANM). As the elastic-plastic behavior involves two unilateral conditions, we replace these two conditions by regular functions depending upon the stress field and its time derivative which permits one to take into account elastic-plastic transition and elastic unloading. Several applications in structural plasticity problems are presented to assess the ability of the proposed algorithm.     

Application of statistical methods to solve global reconstruction problems

A solution of the problem of reconstructing a mathematical model using statistical methods to specify the evolution operator is optimized. It is shown that this procedure can be used for modeling with short time series, so that the metric and dynamic characteristics of an attractor can be determined with a knowledge of the reconstructed model equations. Direct methods of analyzing scalar time series are less effective in this situation. Pis’ma Zh. Tekh. Fiz. 23, 7–13 (April 26, 1997)     

Application of statistical approaches to solve impurity propagation problems

The Cauchy problem for an equation of hyperbolic type describing impurity diffusion at a finite velocity is solved by the Monte Carlo method.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 4, pp. 736–740, April, 1981.     

Hydrothermal dynamics on environmental problems using the aspect of earth science

In order to establish a sustainable society, with practical material recycling, it is appropriate to focus on a range of guiding “Earth Principles”, including the character and application of hydrothermal processes. In this paper, it is demonstrated that information obtained from the study of fundamental Earth Principles can be used to inspire the development of new methods for material recycling, such as the following:

Multiagent approach to solve project team work allocation problems

In today's fiercely competitive market, embedded software development teams are driven to do more with less: reduce time to market, costs and risk, while improving quality and predictability. There is also an increasing need to deliberately organise the teams that initially involves the division of the project into tasks; the selection of the right people; and the correct allocation of those tasks for the selected people. Team configuration process is typically performed by a project manager based on his/her past experience and the available (though frequently scarce, uncertain and dynamic) information about the cognitive, emotion and social characteristics of the potential team members. To support this decision-making process we propose the Fuzzy Belief-Desire-Intention architecture, a multiagent approach that given an initial team configuration and a set of tasks, simulates the most possible team performance. Its architecture bases are fuzzy set theory and fuzzy logic and it is implemented using Multiagent Systems technology in Java and Jadex. Tests have been carried out in which the architecture has been applied to a set of tasks involving the embedded software development. The result predicted by our architecture with the performance of an engineering team in a real industrial project is made.     

A simple approach to solve boundary-value problems in gradient elasticity

Summary We outline a procedure for obtaining solutions of certain boundary value problems of a recently proposed theory of gradient elasticity in terms of solutions of classical elasticity. The method is applied to illustrate, among other things, how the gradient theory can remove the strain singularity from some typical examples of the classical theory.     

An algorithm to solve coupled 2D rolling contact problems

This work presents a new approach to the steady‐state rolling contact problem for two‐dimensional elastic bodies, with and without force transmission. The problem solution is achieved by minimizing a general function representing the equilibrium equation and the contact restrictions. The boundary element method is used to compute the elastic influence coefficients of the surface points involved in the contact (equilibrium equations); while the contact conditions are represented with the help of variational inequalities and projection functions. Finally, the minimization problem is solved by the Generalized Newton's Method with line search. Four classic rolling problems are also solved and commented on. Copyright © 2000 John Wiley & Sons, Ltd.     

Using the boundary element method to solve rolling contact problems

A new approach to steady-state rolling, with and without force transmission, based on the boundary element method is presented. The proposed formulation solves the problem in a more general way than semi-analytical methods, with which it shares some approximations. The robustness and accuracy of the proposed method is reflected in the comparative analysis of the results obtained for three different types of rolling problems involving identical, dissimilar and tyred cylinders, respectively.     

Applied column generation-based approach to solve supply chain scheduling problems

More and more enterprises have chosen to adopt a made-to-order business model in order to satisfy diverse and rapidly changing customer demand. In such a business model, enterprises are devoted to reducing inventory levels in order to upgrade the competitiveness of the products. However, reductions in inventory levels and short lead times force the operation between production and distribution to cooperate closely, thus increasing the practicability of integrating the production and distribution stages. The complexity of supply chain scheduling problems (integrated production and distribution scheduling) is known to be NP-hard. To address the issues above, an efficient algorithm to solve the supply chain scheduling problem is needed. This paper studies a supply chain scheduling problem in which the production stage is modelled by an identical parallel machine scheduling problem and the distribution stage is modelled by a capacitated vehicle routing problem. Given a set of customer orders (jobs), the problem is to find a supply chain schedule such that the weighted summation of total job weighted completion time and total job delivering cost are minimised. The studied problem was first formulated as an integer programme and then solved by using column generation techniques in conjunction with a branch-and-bound approach to optimality. The results of the computational experiments indicate that the proposed approach can solve the test problems to optimality. Moreover, the average gap between the optimal solutions and the lower bounds is no more than 1.32% for these test problems.     

Reliable use of determinants to solve non-linear structural eigenvalue problems efficiently

A ‘multiple determinant parabolic interpolation method’ is described and evaluated, principally by using a plane frame test-bed program. It is intended primarily for solving the transcendental eigenvalue problems arising when the ‘exact’ member equations obtained by solving the governing differential equations of members are used to find the eigenvalues (i.e. critical buckling loads or undamped natural frequencies) of structures. The method has five stages which together ensure successful convergence on the required eigenvalues in all circumstances. Thus, whenever checks indicate its suitability, parabolic interpolation is used to obtain eigenvalues more rapidly than would the popular bisection alternative. The checks also ensure a wise choice of the determinant used by the interpolation. The determinants available are all usually zero at eigenvalues, and comprise the determinant of the overall stiffness matrix K _n and the determinants which result, with negligible extra computation, from effectively considering all except the last m (m=1, 2,…, n?1) freedoms to which K _n corresponds as internal substructure freedoms. Tests showed time savings compared to bisection of 31 per cent when finding non-coincident eigenvalues to relative accuracy ? = 10^?4, increasing to 62 per cent when ? = 10^?8. The tests also showed time savings of about 10 per cent compared with an earlier Newtonian approach. The method requires no derivatives and its use in the widely available space frame program BUNVIS-RG has demonstrated how easily it can replace bisection, which was used in the earlier program BUNVIS.     

Computational experiment to solve problems of optimization in pulsed heating regimes

We present the results from numerical solutions of problems in the optimum control of heat conduction in the case of pulsed heating with highly concentrated sources of heat.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 2, pp. 308–314, August, 1990.     

Combining discrete and continuous optimization to solve kinodynamic motion planning problems

A new approach to find the fastest trajectory of a robot avoiding obstacles, is presented. This optimal trajectory is the solution of an optimal control problem with kinematic and dynamic constraints. The approach involves a direct method based on the time discretization of the control variable. We mainly focus on the computation of a good initial trajectory. Our method combines discrete and continuous optimization concepts. First, a graph search algorithm is used to determine a list of intermediate points. Then, an optimal control problem of small size is defined to find the fastest trajectory that passes through the vicinity of the intermediate points. The resulting solution is the initial trajectory. Our approach is applied to a single body mobile robot. The numerical results show the quality of the initial trajectory and its low computational cost.     

Guided particle swarm optimization method to solve general nonlinear optimization problems

The development of hybrid algorithms is becoming an important topic in the global optimization research area. This article proposes a new technique in hybridizing the particle swarm optimization (PSO) algorithm and the Nelder–Mead (NM) simplex search algorithm to solve general nonlinear unconstrained optimization problems. Unlike traditional hybrid methods, the proposed method hybridizes the NM algorithm inside the PSO to improve the velocities and positions of the particles iteratively. The new hybridization considers the PSO algorithm and NM algorithm as one heuristic, not in a sequential or hierarchical manner. The NM algorithm is applied to improve the initial random solution of the PSO algorithm and iteratively in every step to improve the overall performance of the method. The performance of the proposed method was tested over 20 optimization test functions with varying dimensions. Comprehensive comparisons with other methods in the literature indicate that the proposed solution method is promising and competitive.     

Application of the local radial point interpolation method to solve eddy-current problems

This paper introduces the meshless local radial point interpolation method to model eddy-current problems for the first time. The formulation is described and results are compared with those from the ordinary finite-element simulation and the analytical solution.     

An immersed boundary method to solve fluid–solid interaction problems

We describe an immersed-boundary technique which is adopted from the direct-forcing method. A virtual force based on the rate of momentum changes of a solid body is added to the Navier–Stokes equations. The projection method is used to solve the Navier–Stokes equations. The second-order Adam–Bashford scheme is used for the temporal discretization while the diffusive and the convective terms are discretized using the second-order central difference and upwind schemes, respectively. Some benchmark problems for both stationary and moving solid object have been simulated to demonstrate the capability of the current method in handling fluid–solid interactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.