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1.
The multilevel MINLP optimization approach to structural synthesis: the simultaneous topology, material, standard and rounded dimension optimization
Stojan Kravanja, Simon Šilih, Zdravko Kravanja, 2005, original scientific article

Abstract: The paper describes the simultaneous topology, material, standard and rounded dimension optimization of mechanical structures, performed by the Mixed-Integer Non-linear Programming (MINLP) approach. Beside the generation of an MINLP mechanical superstructure, the development of a general multilevel MINLP formulation for a mechanical superstructure is presented. The consideration of the discrete materials as well as standard and particularly rounded dimensions in structural synthesis significantly increases the combinatorics of the discrete optimization, which as a result may become too difficult to solve. A Linked Multilevel Hierarchical Strategy (LMHS) has been introduced for the solving of such large combinatorial problems. In order to decrease the effect of non-convexities, the Modified Outer-Approximation/Equality-Relaxation (OA/ER) algorithm has been applied. Four numerical examples of different complexities are presented to illustrate the proposed multilevel MINLP optimization approach: the optimization of two steel trusses, a composite I beam and a hydraulic steel roller gate Intake gate, erected in Aswan II, Egypt.
Keywords: structural optimization, structural synthesis, MINLP, topology opitmization, material optimization, discrete variable optimization, multilevel MINLP strategy, truss, composite beam, roller gate
Published: 01.06.2012; Views: 1618; Downloads: 60
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2.
Chinese postman problem with priorities (high cost of delays)
Tomaž Kramberger, Janez Žerovnik, 2008, published scientific conference contribution

Abstract: Several real-world problems, such as street sweeping, mail delivery, solid waste collection, salt gritting and snow plowing can be modeled as Chinese postman problems with some additional constraints. In the paper we present a formal definition of the special case of CPP problem where a subset of priority nodes are given that must be visited as soon as possible, i.e. the cost of delays is much bigger than the cost of additional edges traversed. A heuristical algorithm is proposed which gives near optimal feasible solutions.
Keywords: combinatorial optimization, discrete optimization
Published: 05.06.2012; Views: 851; Downloads: 33
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3.
Mixed-integer nonlinear programming based optimal time scheduling of construction projects under nonconvex costs
Rok Cajzek, Uroš Klanšek, 2016, original scientific article

Abstract: Optimal project scheduling under nonconvex time-cost relations represents a challenging problem in construction management. The nonconvex time-cost relations may appear in a construction project when several different duration options are available for its activities due to alternative technological processes enabled for their realization or wide accessibility of production resources. The source of nonconvexity of the project scheduling optimization problem can also be the project penalty- or bonus-duration relations arranged within the construction contract. The aim of this paper is to present the mixed-integer nonlinear programming (MINLP) based optimal time scheduling of construction projects under nonconvex costs. For this purpose, the MINLP model was developed and applied. A numerical example from literature and an example of construction project time-cost trade-off analysis under practical nonconvex penalty function are given in the paper to demonstrate advantages of MINLP optimization. The example from literature first presented the capability of the MINLP approach to obtain the optimal solution for difficult, highly combinatorial nonconvex discrete project scheduling problem. Thereupon, the following example revealed that the optimal project time-cost curve may take very nonuniform shape on account of discrete nature of activity direct cost options and nonconvex relation between project duration and total cost. In this way, the presented study intends to provide practitioners with new information from the field of optimization techniques for project scheduling as well as an alternative view on performance of total cost when project duration is changed.
Keywords: extreme environments, construction management, discrete optimization, mixed-integer nonlinear programming, nonconvex costs, time scheduling
Published: 12.07.2017; Views: 328; Downloads: 207
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4.
On vulnerability measures of networks
Rija Erveš, Darja Rupnik Poklukar, Janez Žerovnik, 2013, published scientific conference contribution

Abstract: As links and nodes of interconnection networks are exposed to failures, one of the most important features of a practical networks design is fault tolerance. Vulnerability measures of communication networks are discussed including the connectivities, fault diameters, and measures based on Hosoya- Wiener polynomial. An upper bound for the edge fault diameter of product graphs is proved.
Keywords: discrete optimization, communication network, vulnerability
Published: 21.07.2017; Views: 277; Downloads: 52
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5.
Discrete optimization with fuzzy constraints
Primož Jelušič, Bojan Žlender, 2017, original scientific article

Abstract: The primary benefit of fuzzy systems theory is to approximate system behavior where analytic functions or numerical relations do not exist. In this paper, heuristic fuzzy rules were used with the intention of improving the performance of optimization models, introducing experiential rules acquired from experts and utilizing recommendations. The aim of this paper was to define soft constraints using an adaptive network-based fuzzy inference system (ANFIS). This newly-developed soft constraint was applied to discrete optimization for obtaining optimal solutions. Even though the computational model is based on advanced computational technologies including fuzzy logic, neural networks and discrete optimization, it can be used to solve real-world problems of great interest for design engineers. The proposed computational model was used to find the minimum weight solutions for simply-supported laterally-restrained beams.
Keywords: uncertainty, discrete optimization, neuro-fuzzy technique, structural optimization
Published: 09.08.2017; Views: 409; Downloads: 165
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