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The Closest String Problem (CSP) calls for finding an n-string that minimizes its maximum distance from m given n-strings. Integer linear programming (ILP) proved to be able to solve large CSPs under the Hamming distance, whereas for the... more
The Closest String Problem (CSP) calls for finding an n-string that minimizes its maximum distance from m given n-strings. Integer linear programming (ILP) proved to be able to solve large CSPs under the Hamming distance, whereas for the Levenshtein distance, preferred in computational biology, no ILP formulation has so far be investigated. Recent research has however demonstrated that another metric, rank distance, can provide interesting results with genomic sequences. Moreover, CSP under rank distance can easily be modeled via ILP: optimal solutions can then be certified, or information on approximation obtained via dual gap. In this work we test this ILP formulation on random and biological data. Our experiments, conducted on strings with up to 600 nucleotides, show that the approach outperforms literature heuristics. We also enforce the formulation by cover inequalities. Interestingly, due to the special structure of the rank distance between two strings, cover separation can be done in polynomial time.
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This chapter presents a real-time emergency evacuation handling system based on internet of things (IoT) technologies. The IoT infrastructure has a core computational component that is in charge of minimizing the time necessary to... more
This chapter presents a real-time emergency evacuation handling system based on internet of things (IoT) technologies. The IoT infrastructure has a core computational component that is in charge of minimizing the time necessary to evacuate people from a building. The space and time dimension are discretized according to metrics and models in literature, as well as original methods. The component formulates and solves a linearized, time-indexed flow problem on a network that represents feasible movements of people at a suitable frequency. Accurate parameter setting makes the computational time to solve the model compliant with real-time use. An application of the proposed IoT system and its core algorithm to handle safe evacuation test in Palazzo Camponeschi—a building in L’Aquila (Italy) now and then used for exhibitions—is described, and diverse uses of the methodology are presented.
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Distributing material flows among the workstations of a plant is a crucial problem in order to reduce both production and logistics costs, especially when product mix and volume production are very large. Optimal solutions should meet due... more
Distributing material flows among the workstations of a plant is a crucial problem in order to reduce both production and logistics costs, especially when product mix and volume production are very large. Optimal solutions should meet due dates requirements while assigning operations in accordance to the production capacity available at the moment. Pursuing this objective is however complicated in case of a large product mix, due to the possibly large number of machine set-ups required. This paper deals with a real production process consisting in the assembly of micropumps and dispensers carried out by a major international manufacturer in its plants in Centre Italy. Two articulated methods based on column generation are devised for tackling situations of different size and complexity, and a sample of their potential effectiveness is exhibited.
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We address a 1-dimensional cutting stock problem where, in addition to trimloss minimization, we require that the set of cutting patterns forming the solution can be sequenced so that the number of stacks of parts maintained open... more
We address a 1-dimensional cutting stock problem where, in addition to trimloss minimization, we require that the set of cutting patterns forming the solution can be sequenced so that the number of stacks of parts maintained open throughout the process never exceeds a given s. For this problem, we propose a new integer linear programming formulation whose constraints grow quadratically with the number of distinct part types.
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We formulate a spatial pricing problem as bilevel non-capacitated location: a leader first decides which facilities to open and sets service prices taking competing offers into account; then, customers make individual decisions minimizing... more
We formulate a spatial pricing problem as bilevel non-capacitated location: a leader first decides which facilities to open and sets service prices taking competing offers into account; then, customers make individual decisions minimizing individual costs that include access charges in the spirit of Hotelling. Both leader and customers are assumed to be risk-neutral. For non-metric costs (i.e., when access costs do not satisfy the triangle inequality), the problem is NP-hard even if facilities can be opened at no fixed cost. We describe an algorithm for solving the Euclidean 1-dimensional case (i.e., with access cost defined by the Euclidean norm on a line) with fixed opening costs and a single competing facility.
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One of the main issues in the glass industry is the minimization of the trim loss generated when cutting large parts (stocks) into small items. In our application stocks are produced in the plant. Many distinct stock sizes are feasible,... more
One of the main issues in the glass industry is the minimization of the trim loss generated when cutting large parts (stocks) into small items. In our application stocks are produced in the plant. Many distinct stock sizes are feasible, and technical constraints limit the variety of cutting patterns to those producing a single type of item per stock. Consequently, the focus is not on seeking an optimal subset of cutting patterns, but rather on choosing an optimal subset of a limited number of stock sizes. In this paper we discuss a 0-1 linear programming formulation for this problem based on a p-median model. Tested on data from the field, the formulation shows an impressive reduction of the trim loss produced in the present plant operation and definitely outperforms traditional exact approaches in terms of computation time.
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This paper describes the design of an Internet of Things (IoT) system for building evacuation. There are two main design decisions for such systems: i) specifying the platform on which the IoT intelligent components should be located; and... more
This paper describes the design of an Internet of Things (IoT) system for building evacuation. There are two main design decisions for such systems: i) specifying the platform on which the IoT intelligent components should be located; and ii) establishing the level of collaboration among the components. For safety-critical systems, such as evacuation, real-time performance and evacuation time are critical. The approach aims to minimize computational and evacuation delays and uses Queuing Network (QN) models. The approach was tested, by computer simulation, on a real exhibition venue in Alan Turing Building, Italy, that has 34 sets of IoT sensors and actuators. Experiments were performed that tested the effect of segmenting the physical space into different sized virtual cubes. Experiments were also conducted concerning the distribution of the software architecture. The results show that using centralized architectural pattern with a segmentation of the space into large cubes is the ...
The paper describes models for scheduling the patterns that form a solution of a cutting stock problem. We highlight the problem of providing the required final products with the necessary items obtained from the cut, choosing which... more
The paper describes models for scheduling the patterns that form a solution of a cutting stock problem. We highlight the problem of providing the required final products with the necessary items obtained from the cut, choosing which pattern feeds which lot of parts. This problem can be solved prior to schedule cuts, or in an integrated way. We present integer programming models for both approaches.
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ABSTRACT Two NP-complete unweighted graph partitioning problems are considered: Simple Max Partitioning (SMP) and Uniform Graph Partitioning (UGP). For both problems, polynomial-time algorithms are available for special classes of graphs.... more
ABSTRACT Two NP-complete unweighted graph partitioning problems are considered: Simple Max Partitioning (SMP) and Uniform Graph Partitioning (UGP). For both problems, polynomial-time algorithms are available for special classes of graphs. In the present paper, the class of line-graphs is considered and a polynomial algorithm is proposed to solve both UGP and SMP in this class.
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ABSTRACT A mixed hypergraph is a pair H =(V, E ∪ A), where V is the vertex set and E (A) the edge (the co-edge) set of H. A legal colouring of H gives the same (different) colour(s) to at least two vertices of any co-edge (of any edge).... more
ABSTRACT A mixed hypergraph is a pair H =(V, E ∪ A), where V is the vertex set and E (A) the edge (the co-edge) set of H. A legal colouring of H gives the same (different) colour(s) to at least two vertices of any co-edge (of any edge). The upper chromatic number of H is the maximum number X̄(H) of colours that can be used in a legal colouring. An incomplete Steiner triple system T over a set V is a collection of triples such that no two triples share more than one element of V. Consider the mixed hypergraph S =(V, φ ∪ T). We prove that computing X̄(S) is in general NP-hard, but there exists a polynomial-time algorithm returning a colouring with 7X̄(S) colours.
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One of the main issues in the glass industry is the minimization of the trim loss generated when cutting large parts (stocks) into small items. In our application stocks are produced in the plant. Many distinct stock sizes are feasible,... more
One of the main issues in the glass industry is the minimization of the trim loss generated when cutting large parts (stocks) into small items. In our application stocks are produced in the plant. Many distinct stock sizes are feasible, and technical constraints limit the variety of cutting patterns to those producing a single type of item per stock. Consequently, the focus is not on seeking an optimal subset of cutting patterns, but rather on choosing an optimal subset of a limited number of stock sizes. In this paper we discuss a 0-1 linear programming formulation for this problem based on a p-median model. Tested on data from the field, the formulation shows an impressive reduction of the trim loss produced in the present plant operation and definitely outperforms traditional exact approaches in terms of computation time.
In this paper we introduce an extension of the well known Rural Postman Problem, which combines arc routing with profits and facility location. Profitable arcs must be selected, facilities located at both end-points of the selected arcs,... more
In this paper we introduce an extension of the well known Rural Postman Problem, which combines arc routing with profits and facility location. Profitable arcs must be selected, facilities located at both end-points of the selected arcs, and a tour identified so as to maximize the difference between the profit collected along the arcs and the cost of traversing the arcs and installing the facilities. We analyze properties of the problem, present a mathematical programming formulation and a branch-and-cut algorithm. In an extensive computational experience the algorithm could solve instances with up to 140 vertices and 190 arcs and up to 50 vertices and 203 arcs.
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ABSTRACT The graph ordering problem here addressed derives from industrial applications where one can associate vertices with process steps and edges with jobs. A linear layout of the vertices corresponds then to a production schedule,... more
ABSTRACT The graph ordering problem here addressed derives from industrial applications where one can associate vertices with process steps and edges with jobs. A linear layout of the vertices corresponds then to a production schedule, and one wants to find a layout minimizing the average completion time of the jobs. We prove that the problem is NP-hard in general and is polynomial on trees. We then provide a 2-approximate algorithm and investigate necessary conditions for optimality. On this basis, we devised a combinatorial branch-and-bound algorithm and tested it on random graphs with up to 100 nodes.
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ABSTRACT This paper presents a decision support tool for solving a cutting and reuse problem arising in a European plant devoted to the production of gear belts. In this production, rectangular pieces of rubberised nylon are cut using... more
ABSTRACT This paper presents a decision support tool for solving a cutting and reuse problem arising in a European plant devoted to the production of gear belts. In this production, rectangular pieces of rubberised nylon are cut using machines employing parallel blades, so as to obtain rectangular components of identical height and (possibly) different width. A component is then used to produce a set of belts with the same girth; but, if necessary, the girth required can also be obtained by sewing together two components. The major objectives of optimisation are: trim loss minimisation, quality control, workload equalisation, setup minimisation. The problem, a particular one-dimensional cutting stock with both cutting and reuse decision variables, has been formulated in terms of integer linear programming and then efficiently solved by applying standard packages within a column generation scheme. A significant improvement of performance has been obtained in terms of both economic savings and product quality. This has convinced the management to implement the model in the plant operation.
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ABSTRACT Classical stock cutting calls for fulfilling a given demand of parts minimizing raw material needs. With the production of each part type regarded as a job due within a specific date, a problem arises of scheduling cutting... more
ABSTRACT Classical stock cutting calls for fulfilling a given demand of parts minimizing raw material needs. With the production of each part type regarded as a job due within a specific date, a problem arises of scheduling cutting operations. We here propose an exact integer linear programming formulation, and develop primal heuristics, upper bounds and an implicit enumeration scheme. A computational experience carried out for the one-dimensional problem shows that our primal heuristics outperform known ones, and that the formulation has good features for finding exact solutions of non-trivial instances.
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Aim of this paper is to study the complexity of the Deadlock-Safety problem for Store-and-Forward networks. The following results are shown: 1. the problem is in general NP-complete, even for tree-like networks. It is still NP-comptete... more
Aim of this paper is to study the complexity of the Deadlock-Safety problem for Store-and-Forward networks. The following results are shown: 1. the problem is in general NP-complete, even for tree-like networks. It is still NP-comptete for various "simple" topologies (including ...
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Let G be the graph obtained as the edge intersection of two graphs G 1 ; G 2 on the samevertex set V . We show that if at least one of G 1 ; G 2 is perfect, then (G) (G 1 ) (G 2 ),where () is the cardinality of the largest stable set.... more
Let G be the graph obtained as the edge intersection of two graphs G 1 ; G 2 on the samevertex set V . We show that if at least one of G 1 ; G 2 is perfect, then (G) (G 1 ) (G 2 ),where () is the cardinality of the largest stable set. Moreover, for general G
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Research studies on multi-agent systems have been recently boosted by manufacturing and logistics with deep motivations like the presence of independent human deciders with individual goals, the aspiration to dominate the complexity of... more
Research studies on multi-agent systems have been recently boosted by manufacturing and logistics with deep motivations like the presence of independent human deciders with individual goals, the aspiration to dominate the complexity of decision-making in large organizations, the simplicity and robustness of self-reacting distributed systems. After a survey of the multi-agent paradigm and its applications, the paper introduces the notion of hybrid holonic system to study the effect of supervision on a system whose elements negotiate and cooperate in a rule-settled environment to obtain resources for system operation. The supervisor can spur or disincentive agents by assigning/denying resources to them. A simple single-decider optimization model referred to a real application is described, and solution methodologies for optimal resource allocation fitting different scenarios (centralized, distributed, multi-agent) are discussed, identifying ranges of autonomy, quantifying rewarding and defining a negotiation protocol between the agents and the supervisor. Aim of the paper is to describe through an example a general methodology for quantitative decision-making in multi-agent organizations.
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ABSTRACT The management of a work cell consisting of multichamber systems Endura 5500 PVD is addressed with the goals of maximizing production volume and facilitating maintenance plans. These objectives are pursued through suitable system... more
ABSTRACT The management of a work cell consisting of multichamber systems Endura 5500 PVD is addressed with the goals of maximizing production volume and facilitating maintenance plans. These objectives are pursued through suitable system configuration and loading. A mixed integer linear programming model incorporating such requirements as workload equalization and fault tolerance is devised to find optimal chamber assembly. The nominal productivity under distinct feasible production modes is evaluated by simulating Endura operation scheduling, and then utilized as problem input to compute nominal work cell productivity under steady-state inventory conditions. This method has been successfully adopted in an actual wafer fab to determine sputtering capacity allocation
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A cook has to prepare n cakes using an oven with two racks. According to the recipe, the i-th cake has to be baked for exactly ai minutes. Cakes to be cooked are taken from a table and carried to the oven, and once cooked are carried back... more
A cook has to prepare n cakes using an oven with two racks. According to the recipe, the i-th cake has to be baked for exactly ai minutes. Cakes to be cooked are taken from a table and carried to the oven, and once cooked are carried back to the table by means of a trolley that can carry two
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This paper deals with glass cutting in an Italian plant producing parts for the automotive market. Glass cutting is basically organised in two phases: first, large rectangular sheets of the same type are obtained from a ribbon of flat... more
This paper deals with glass cutting in an Italian plant producing parts for the automotive market. Glass cutting is basically organised in two phases: first, large rectangular sheets of the same type are obtained from a ribbon of flat glass and sent to warehouse; then, sheets of various types are taken from the warehouse and cut into small rectangular parts
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The Pattern Minimization Problem (PMP) consists in finding, among the optimal solutions of a cutting stock problem, one that minimizes the number of distinct cutting patterns activated. The Work-in-process Minimization Problem (WMP) calls... more
The Pattern Minimization Problem (PMP) consists in finding, among the optimal solutions of a cutting stock problem, one that minimizes the number of distinct cutting patterns activated. The Work-in-process Minimization Problem (WMP) calls for scheduling the patterns so as to maintain as few open stacks as possible. This paper addresses a particular class of problems, where no more than two
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Rita Macedo a, Elsa Silva a, Cláudio Alves ab , Filipe Pereira e Alvelos ab, JM Valério de Carvalho ab, Claudio Arbib c , Fabrizio Marinelli d, Ferdinando Pezzella d,Luigi De Giovannid, Luca Gambella d ... Università Politecnica delle... more
Rita Macedo a, Elsa Silva a, Cláudio Alves ab , Filipe Pereira e Alvelos ab, JM Valério de Carvalho ab, Claudio Arbib c , Fabrizio Marinelli d, Ferdinando Pezzella d,Luigi De Giovannid, Luca Gambella d ... Università Politecnica delle Marche Via Brecce Bianche, I-60131, Ancona, Italy