2015
Authors
Rodrigues, AM; Ferreira, JS;
Publication
Studies in Big Data
Abstract
Sectorization means dividing a whole into parts (sectors), a procedure that occurs in many contexts and applications, usually to achieve some goal or to facilitate an activity. The objective may be a better organization or simplification of a large problem into smaller sub-problems. Examples of applications are political districting and sales territory division. When designing/comparing sectors some characteristics such as contiguity, equilibrium and compactness are usually considered. This paper presents and describes new generic measures and proposes a new measure, desirability, connected with the idea of preference. © 2015, Springer International Publishing Switzerland.
2015
Authors
Costa, E; Soares, AL; de Sousa, JP;
Publication
RISKS AND RESILIENCE OF COLLABORATIVE NETWORKS
Abstract
There is growing evidence that internationalization of small and medium enterprises (SMEs) has become a priority to gain competitive advantage. However, SMEs still face major challenges and obstacles during these processes. This paper proposes a model of collaborative networks for internationalization processes of SMEs, mediated by industrial enterprise associations (IEAs), in order to improve decision-making processes. First, a systematic literature review (SLR) was performed to study the impact that networks and collaboration have in the decision-making process of internationalization. Then, the model was developed using adequate information and knowledge management tools. Finally, to understand the relevance of the proposed model, data were gathered through interviews to key persons in companies of the IT/electronics and textile industries. Results showed that collaborative networks can represent an important facilitator in the internationalization of SMEs and that IEAs can have a fundamental role for promoting collaboration in this domain, between associated SMEs.
2015
Authors
Parragh, SN; de Sousa, JP; Almada Lobo, B;
Publication
TRANSPORTATION SCIENCE
Abstract
In this paper we introduce the dial-a-ride problem with split requests and profits (DARPSRP). Users place transportation requests, specifying a pickup location, a delivery location, and a time window for either of the two. Based on maximum user ride time considerations, the second time window is generated. A given fleet of vehicles, each with a certain capacity, is available to serve these requests, and maximum route duration constraints have to be respected. Each request is associated with a revenue and the objective is to maximize the total profit, that is, the total revenue minus the total costs. Transportation requests involving several persons may be split if it is beneficial to do so. We formulate the DARPSRP as a mixed-integer program using position variables and in terms of a path-based formulation. For the solution of the latter, we design a branch-and-price algorithm. The largest instance solved to optimality, when applied to available instances from the literature, has 40 requests; when applied to newly generated instances, the largest instance solved to optimality consists of 24 requests. To solve larger instances a variable neighborhood search algorithm is developed. We investigate the impact of request splitting under different geographical settings, assuming favorable settings for request splitting in terms of the number of people per request. The largest benefits from request splitting are obtained for problem settings exhibiting clustered customer locations.
2015
Authors
Sadic, S; de Sousa, JP; Crispim, JA;
Publication
RISKS AND RESILIENCE OF COLLABORATIVE NETWORKS
Abstract
The term Dynamic Manufacturing Network (DMN) refers to a new collaborative business model that relies on real-time information sharing, synchronized planning and common business processes. DMNs are operational networks formed among autonomous and globally dispersed partners, and can be seen as the manufacturing industry application of the Virtual Enterprise (VE) concept. Despite their numerous practical benefits such as optimized processes and access to new and global markets, they are particularly vulnerable to disruptions. Any disruption in manufacturing or transportation of products may obviously result in failed orders, thus impacting the whole DMN reliability. Instead of developing stochastic models to deal with uncertainty, as it is usually done, we have rather integrated the concept of flexibility into the tactical and operational planning of such networks. We therefore propose in this work, a multi-objective optimization model that simultaneously maximizes reactive flexibility measures while minimizing total operating costs.
2015
Authors
Sato, AK; Guerra Tsuzuki, MDG; Martins, TD; Gomes, AM;
Publication
IFAC PAPERSONLINE
Abstract
Irregular nesting is a subgroup of cutting and packing problems in which a set of irregular items must be inserted in a rectangular container with a variable width. It is often found ill industries such as textile, wood and shipbuilding and an efficient solution usually renders an economical and environmental positive impact. Due to the complex geometry of items, the no overlapping rule is hard to guarantee and, therefore, geometric tools are usually employed. In this work, a raster method is proposed to solve the overlap minimization problem, which can be adapted to solve the irregular nesting problem. A map of overlap values is created and is employed to find the minimum overlap placement for each item A multiresolution approach is used to reduce the size of the map and, consequently, accelerate the search process. The results from tests performed using 4 benchmark tests indicates that more compact layouts can be obtained using multiple resolutions. Moreover, the results are competitive when compared to other solutions in the literature. Copyright (C)2015 IFAC.
2015
Authors
Rocha, P; Rodrigues, R; Miguel Gomes, AM; Toledo, FMB; Andretta, M;
Publication
IFAC PAPERSONLINE
Abstract
This paper presents an approaches. that assists in producing highly compacted Nesting layouts with irregular pieces using free rotations. This approach consists in the selection and compaction of big pieces in a first phase, while in a second phase, places the remaining small pieces between the big pieces, compacting all of them. The effect of several parameters are analyzed, such as minimum length to be achieved in the first phase, attraction of the pieces to the edges of the container, attraction between each pair of pieces, among others. This approach can provide good compaction results, while improving computational cost in some cases, which cart allow to tackle real world problems more effectively mkt efficiently.
The access to the final selection minute is only available to applicants.
Please check the confirmation e-mail of your application to obtain the access code.