2020
Autores
Leao, AAS; Toledo, FMB; Oliveira, JF; Carravilla, MA; Alvarez Valdes, R;
Publicação
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
Abstract
Irregular packing problems (also known as nesting problems) belong to the more general class of cutting and packing problems and consist of allocating a set of irregular and regular pieces to larger rectangular or irregular containers, while minimizing the waste of material or space. These problems combine the combinatorial hardness of cutting and packing problems with the computational difficulty of enforcing the geometric non-overlap and containment constraints. Unsurprisingly, nesting problems have been addressed, both in the scientific literature and in real-world applications, by means of heuristic and metaheuristic techniques. However, more recently a variety of mathematical models has been proposed for nesting problems. These models can be used either to provide optimal solutions for nesting problems or as the basis of heuristic approaches based on them (e.g. matheuristics). In both cases, better solutions are sought, with the natural economic and environmental positive impact. Different modeling options are proposed in the literature. We review these mathematical models under a common notation framework, allowing differences and similarities among them to be highlighted. Some insights on weaknesses and strengths are also provided. By building this structured review of mathematical models for nesting problems, research opportunities in the field are proposed.
2020
Autores
Schaller, J; Valente, JMS;
Publicação
INTERNATIONAL JOURNAL OF PRODUCTION ECONOMICS
Abstract
This paper considers the problem of scheduling jobs in a no-wait flow shop with the objective of minimizing total earliness and tardiness. An exact branch-and-bound algorithm is developed for the problem. Several dispatching heuristics used previously for other environments and two new heuristics were tested under a variety of conditions. It was found that one of the new heuristics consistently performed well compared to the others. An insertion search improvement procedure with speed up methods based on the structure of the problem was proposed and was found to deliver much improved solutions in a reasonable amount of time.
2020
Autores
Nunes, D; Teixeira, D; Carneiro, D; Sousa, C; Novais, P;
Publicação
Trends and Innovations in Information Systems and Technologies - Volume 2, WorldCIST 2020, Budva, Montenegro, 7-10 April 2020.
Abstract
The European Union has been making efforts to increase energy efficiency within its member states, in line with most of the industrialized countries. In these efforts, the energy consumed by public lighting networks is a key target as it represents approximately 50% of the electricity consumption of European cities. In this paper we propose an approach for the autonomous management of public lighting networks in which each luminary is managed individually and that takes into account both their individual characteristics as well as ambient data. The approach is compared against a traditional management scheme, leading to a reduction in energy consumption of 28%. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2020.
2020
Autores
Vasconcelos, H; de Almeida, JMMM; Saraiva, C; Viveiros, D; Jorge, PAS; Coelho, L;
Publicação
OPTICAL SENSING AND DETECTION VI
Abstract
Biogenic amines, such as putrescine are potential indicators of food storage condition and deterioration. The real time measurement of their concentration in food may become an important method of food control. It was found that putrescine diffuses through a thin layer made from a solution of Poly(ethylene-co-vinyl acetate) (PEVA) and maleic anhydride. Poly(ethylene-co-vinyl acetate) is a common non-chlorinated vinyl capable to adsorb specific analytes as putrescine which upon diffusion, reversibly binds to the maleic anhydride causing the polymer swelling resulting in spectral changes from the optical point of view. Long Period Fiber Gratings coated with 30 nm titanium dioxide, a high refractive index material used to increase the intrinsic sensitivity to the external refractive index, were overcoated with a thin layer of maleic anhydride doped Poly(ethylene-co-vinyl acetate). When exposed to solutions containing small concentrations of putrescine the resonant band corresponding to the LP1,6 cladding mode was found to move to shorter wavelengths. The observed blue shift corresponds to the increasing concentration of putrescine in the fiber sensor structure. Further work is being carried out to improve the sensitivity and the limit of detection of the sensing system as well as to increase range of operation, which is presently limited to 0.3 to 0.5 M.
2020
Autores
Isbeih, YJ; El Moursi, MS; Lotfi, M; Catalão, JPS; Abdel Rahman, MH;
Publicação
IEEE PES Innovative Smart Grid Technologies Europe, ISGT Europe 2020, Delft, The Netherlands, October 26-28, 2020
Abstract
The deployment of large scale photovoltaic (PV) power generation has been witnessed in several countries worldwide with different installed capacities. Accordingly, codes and regulations to ensure secure and economical operation have been revised to address the challenges related with PV integration into electrical networks. This paper presents an H8 mixed sensitivity robust control design for enhancing the overall damping of low frequency oscillations. The presented architecture will implement the output signal of the power oscillator damper (POD) at the control loop of the PV-based solar power plant. The effectiveness of the proposed approach is tested using the New-England, 10machines test system. © 2020 IEEE.
2020
Autores
Torres, A; Miranda, C;
Publicação
EXPLORING SERVICE SCIENCE (IESS 2020)
Abstract
Service Design (SD) and Design Thinking (DT) evolved in the last decade and have become popular in the research field of service science. However, the application of SD and DT research outcomes into practice is still scarce. To help understanding the differences between research and practice, we conducted 20 semi-structured interviews with professionals and trainees from four organizations that are involved in service innovation projects. The results reveal several similarities and complementarities, (dis)advantages, requests and obstacles, which hinder companies from implementing and using structured SD and DT approaches. The findings present some challenges for both researchers and practitioners on actions they could take to overcome barriers and foster the SD and DT practice within organizations.
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