Cookies Policy
The website need some cookies and similar means to function. If you permit us, we will use those means to collect data on your visits for aggregated statistics to improve our service. Find out More
Accept Reject
  • Menu
Publications

2022

Metaheuristics for the permutation flowshop problem with a weighted quadratic tardiness objective

Authors
Silva, AF; Valente, JMS; Schaller, JE;

Publication
COMPUTERS & OPERATIONS RESEARCH

Abstract
In this paper, we consider a permutation flowshop problem, with a weighted squared tardiness objective function, which addresses an important criterion for many customers. Our objective is to find metaheuristics that can, within acceptable computational times, provide sizeable improvements in solution quality over the best existing procedure (a dispatching rule followed by an improvement method). We consider four metaheuristics, namely iterated local search (ILS), iterated greedy (IG), variable greedy (VG) and steady-state genetic algorithms (SSGA). These are known for performing well on permutation flowshops and/or on tardiness criteria. For each metaheuristic, four versions are developed, differing on the choice of initial sequence and/or local search. Additionally, four different time limits are considered. Therefore, a total of 64 sets of results are obtained. The results show that all procedures greatly outperform the best existing method. The IG procedures provide the best results, followed by the SSGA procedures. The VG methods are usually inferior to SSGA, while the ILS metaheuristics tend to be the worst performers. The four metaheuristics prove to be robust in what regards initial solution and local search method, since both have little effect on the performance of the metaheuristics. Increasing the time limit does improve the performance of all procedures. Still, a sizeable improvement is obtained even for the lowest time limit. Therefore, even under restrictive time limits, the metaheuristics greatly outperform the best existing procedure.

2022

Path Planning with Hybrid Maps for processing and memory usage optimisation

Authors
Santos, LC; Santos, FN; Aguiar, AS; Valente, A; Costa, P;

Publication
2022 IEEE INTERNATIONAL CONFERENCE ON AUTONOMOUS ROBOT SYSTEMS AND COMPETITIONS (ICARSC)

Abstract
Robotics will play an essential role in agriculture. Deploying agricultural robots on the farm is still a challenging task due to the terrain's irregularity and size. Optimal path planning solutions may fail in larger terrains due to memory requirements as the search space increases. This work presents a novel open-source solution called AgRob Topologic Path Planner, which is capable of performing path planning operations using a hybrid map with topological and metric representations. A local A* algorithm pre-plans and saves local paths in local metric maps, saving them into the topological structure. Then, a graph-based A* performs a global search in the topological map, using the saved local paths to provide the full trajectory. Our results demonstrate that this solution could handle large maps (5 hectares) using just 0.002 % of the search space required by a previous solution.

2022

Is FFT Fast Enough for Beyond 5G Communications? A Throughput-Complexity Analysis for OFDM Signals

Authors
Queiroz, S; Vilela, JP; Monteiro, E;

Publication
IEEE ACCESS

Abstract
In this paper, we study the impact of computational complexity on the throughput limits of the fast Fourier transform (FFT) algorithm for orthogonal frequency division multiplexing (OFDM) waveforms. Based on the spectro-computational complexity (SC) analysis, we verify that the complexity of an N-point FFT grows faster than the number of bits in the OFDM symbol. Thus, we show that FFT nullifies the OFDM throughput on N unless the N -point discrete Fourier transform (DFT) problem verifies as Omega(N) , which remains a fascinating open question in theoretical computer science. Also, because FFT demands N to be a power of two 2(i) (i > 0), the spectrum widening leads to an exponential complexity on i , i.e. O (2(i)i) . To overcome these limitations, we consider the alternative frequency-time transform formulation of vector OFDM (V-OFDM), in which an N -point FFT is replaced by N/L (L > 0) smaller L-point FFTs to mitigate the cyclic prefix overhead of OFDM. Building on that, we replace FFT by the straightforward DFT algorithm to release the V-OFDM parameters from growing as powers of two and to benefit from flexible numerology (e.g., L = 3 , N = 156). Besides, by setting L to Theta (1) , the resulting solution can run linearly on N (rather than exponentially on i) while sustaining a non null throughput as N grows.

2022

Integrating Laser-induced breakdown spectroscopy and photogrammetry towards 3D element mapping

Authors
Rodrigues, P; Lopes, T; Cavaco, R; Capela, D; Ferreira, MFS; Jorge, PAS; Silva, NA;

Publication
Journal of Physics: Conference Series

Abstract
The possibility to map the element distribution on a sample surface is one of the interesting applications of laser-induced breakdown spectroscopy that has been extensively explored in recent years. In this manuscript, we explore the combination of photogrammetry and LIBS techniques for the creation of a three-dimensional model of the map of the elements on the surface of the sample. Using a dedicated photogrammetry solution and software, we reconstruct the three-dimensional model of the mineral sample whose mesh is later exploited for the interactive interpretation of the results. Then, making use of Paraview software, which integrates production algorithms and computing performance in a unified solution for scientific purposes, we establish a process pipeline that allows the creation of an interactive three-dimensional model with the spatial distribution of the target elements on top of the sample surface. Our results demonstrate that combining these two techniques can give us a valuable resource for better qualitative analysis and insight, providing an innovative three-dimensional modeling solution that may open the door to a new range of possibilities, from quality control technology involving alloys and mechanical parts to interactive teaching environments for geo and biosciences, just to name a few examples. © Published under licence by IOP Publishing Ltd.

2022

DESIGN AND IMPLEMENTATION OF A CHATBOT AS A TOOL TO ASSIST A HELPDESK TEAM

Authors
Ribeiro, DP; Anjo, A; Henriques, PR;

Publication
International Conference on Applied Computing 2022 and WWW/Internet 2022

Abstract
The existence of internal helpdesk teams is a common occurrence in companies nowadays, especially when considering the IT sector. These teams are an expensive resource and are only able to serve a limited number of users at a given moment, which evidences the importance of helpdesk teams operating as efficiently as possible. A common occurrence in the daily operations of these teams consists in the existence of a set of repeated tasks that could be automated through the usage of a chatbot capable of acting on behalf of helpdesk team members. By allowing a chatbot to perform some of these repeated actions, helpdesk teams are able to focus on other tasks, thus allowing to increase their productivity. Additionally, the usage of chatbots to assist a helpdesk team creates a highly available tool, capable of giving answers in a short time frame. In this paper, the design and implementation of such a tool is presented, including concepts and approaches related to chatbot development. As a result, a fully functional chatbot named Triton was produced, capable of helping employees of a consulting company with helpdesk-related problems and questions. Copyright © (2022) by International Association for Development of the Information Society (IADIS). All rights reserved.

2022

Smart system for monitoring and controlling energy consumption and ambient conditions

Authors
Dias, Paloma; Brito, Thadeu; Lopes, Luís; Lima, José;

Publication
CIEEMAT 2022 VII Ibero-American Congress on Entrepreneurship, Energy, Environment and Technology

Abstract
In the current energy context, alternatives are sought that provide a more conscious use of energy and the development of technology aimed at efficiently meeting the needs of energy consumers and the utility company. In this scenario, smart systems for monitoring and controlling the energy consumption of residential loads stand out. In [1], the authors worked on a system from which the user could monitor their energy consumption in real time. Through a website, the consumer accessed their information using visualizations in graphics, for example. Consumption data was obtained by a smart plug. Furthermore, the option to remotely turn devices on and off has been included in the system so that the user has the ease of controlling their devices.

  • 849
  • 4387