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An Analytical Hierarchy Process-Based Approach to Solve the Multi-Objective Multiple Traveling Salesman Problem
No full textWe consider the problem of assigning a team of autonomous robots to target locations in the context of a disaster management scenario while optimizing several objectives. This problem can be cast as a multiple traveling salesman problem, where several robots must visit designated locations. This paper provides an analytical hierarchy process (AHP)-based approach to this problem, while minimizing three objectives: the total traveled distance, the maximum tour, and the deviation rate. The AHP-based approach involves three phases. In the first phase, we use the AHP process to define a specific weight for each objective. The second phase consists in allocating the available targets, wherein we define and use three approaches: market-based, robot and task mean allocation-based, and balanced-based. Finally, the third phase involves the improvement in the solutions generated in the second phase. To validate the efficiency of the AHP-based approach, we used MATLAB to conduct an extensive comparative simulation study with other algorithms reported in the literature. The performance comparison of the three approaches shows a gap between the market-based approach and the other two approaches of up to 30%. Further, the results show that the AHP-based approach provides a better balance between the objectives, as compared to other state-of-the-art approaches. In particular, we observed an improvement in the total traveled distance when using the AHP-based approach in comparison with the distance traveled when using a clustering-based approach.info:eu-repo/semantics/publishedVersio
Introduction to the special section on Real time computing and distributed systems
No full textModern distributed systems are increasingly complex both on their architectural design and on the computational logic that they execute. Their timely operation is challenged, which is critical for some domains such as cyber-physical systems where timeliness and dynamic behavior must be satisfied simultaneously. Providing real-time operation whereas supporting the inherent dynamic behavior of cyber-physical systems requires solutions that are not yet available. A number of challenging scientific and engineering problems that span across a variety of research areas are raised. The new challenges go far beyond those of traditional networked real-time systems; cyber-physical systems are autonomous, open, large-scale, real-time, embedded, and control systems that make intensive use of networks, distribution, and wireless technology. Such complex systems have different [sub]parts/systems with different levels of real-time requirements.info:eu-repo/semantics/publishedVersio
Towards a Realistic Simulation Framework for Vehicular Platooning Applications
No full textCooperative vehicle platooning applications increasingly demand realistic simulation tools to ease their validation, and to bridge the gap between development and real-word deployment. However, their complexity and cost, often hinders its validation in the real-world. In this paper we propose a realistic simulation framework for vehicular platoons that integrates Gazebo with OMNeT++ over Robot Operating System (ROS) to support the simulation of realistic scenarios of autonomous vehicular platoons and their cooperative control.info:eu-repo/semantics/publishedVersio
The Reverse Logistics of Unsold Medications in Pharmacies in Campania, Italy
No full textThis paper is a study in Reverse Logistics (RL) that aims to analyse the reverse flow of medications with expired dates, in the pharmacies of the Campania region in Italy. The main objective is to analyse the final destination of medications that are not sold and are collected in pharmacies. The analysis of how the company responsible for the collection of the medications works was made using semi-structured interviews, and a subsequent factor analysis of the collected data. The pharmacies of the main cities of this region were investigated, in order to understand their importance in this process, as well as to understand their main difficulties and challenges. A statistical analysis of the data allowed us to verify how pharmacies are accustomed to the current legislation and are aware of the importance of their role in the RL of the medications that are not sold due to expired date. It was observed that pharmacies are very satisfied with the company responsible for the collection and referral of medications and their materials to an adequate final destination. Both of them work in tune, respond well to current legislation and respect the environment.We acknowledge the financial support of CIDEM, R&D unit funded by the FCT-Portuguese Foundation for the Development of Science and Technology, Ministry of Science, Technology and Higher Education, under the Project UID/EMS/0615/2016.info:eu-repo/semantics/publishedVersio
Solar irradiance modelling using an offline coupling procedure for the Weather Research and Forecasting (WRF) model
No full text.The research proposed herein seeks to improve solar irradiance magnitude and variability results produced by
the Weather Research and Forecasting (WRF) model using a novel offline coupling procedure (OCP). The OCP
includes simulations in clear sky conditions, where the effects from varying atmospheric composition depend on
the broadband clear sky model used, on cloud attenuation and on decomposition techniques to accurately separate the global irradiance into direct and diffuse components. Furthermore, shadowing and slope effects from
orographic features and other obstacles are included with much greater detail. Benefits of the offline coupling
procedure were quantified by comparison against local solar radiation measurements over a period of one year.
A baseline test to explore the different configuration options was implemented. It considers two aerosol databases, three broadband clear sky models, two cloud attenuation corrections based on clear sky index (either
global or by components) and four decomposition models. Given the amount of results from baseline tests, the
relative root-mean-square error (rRMSE) was used as the criterion to identify the most suitable OCP configuration, which was subsequently used in the performance analysis. The current baseline test comprises seven
sites selected from the Baseline Radiation Network (BSRN) in different terrain complexities and atmospheric
conditions. Statistical indicators associated with the annual global horizontal irradiance reveal that OCP improved WRF results by 88.4% in terms of the relative mean bias error (rMBE) and by 5.0% in the value of the
Nash-Sutcliffe efficiency (NSE). A standard OCP configuration to model global horizontal irradiance only is
proposed. The rMBE of annual hourly global horizontal irradiance oscillated between −3.6% and 3.9%, whilst
the NSE varied between 0.608 and 0.939. The analogous quantities for diffuse horizontal irradiance were
19.3% rMBE 4.6%
and
0.371 NSE 0.717
, while for direct normal irradiance
6.5% rMBE 23.2%
and
0.101 NSE 0.656.info:eu-repo/semantics/publishedVersio
Comparative study of PVD and CVD cutting tools performance in milling of duplex stainless steel
No full textThe machining process evolution has been accompanied by the improvement of tool performance, being this mainly due to the development of thin coatings, mono and multi-layered, providing the most appropriate set of properties for each machining condition. On the other hand, duplex stainless steels have registered a strong increase in demand, which, in many cases, requires the use of machining processes in order to obtain the final shape accurately. Taking into account these two aspects, this paper aims essentially to evaluate the performance of two cutting inserts with PVD and CVD coatings, used in rough milling operations of duplex stainless steel. The cutting parameters and machining conditions were those recommended by the manufacturer and were kept unchanged in all performed tests. The behavior of the PVD- and CVD-coated cutting tools was assessed using three different facets: (a) surface roughness analysis, (b) tool wear evaluation, and (c) the monitoring of vibration levels produced during each test. CVD (TiN/TiCN/Al2O3)-coated inserts showed very good suitability to be used as tools for roughing milling operations when machining super duplex stainless steels.The authors would like to thank Daniel Figueiredo from PALBIT Company for the tools assigned to carry out this work. Authors also thank the ARSOPI Company for the duplex stainless steel assigned to this investigation. F. J. G. Silva also thanks Rui Rocha from CEMUP, for his dedication and professionalism in the SEM and EDS equipment operation and analysis.info:eu-repo/semantics/publishedVersio
Trust and Reputation Smart Contracts for Explainable Recommendations
No full textRecommendation systems are usually evaluated through accuracy and classification metrics. However, when these systems are supported by crowdsourced data, such metrics are unable to estimate data authenticity, leading to potential unreliability. Consequently, it is essential to ensure data authenticity and processing transparency in large crowdsourced recommendation systems. In this work, processing transparency is achieved by explaining recommendations and data authenticity is ensured via blockchain smart contracts. The proposed method models the pairwise trust and system-wide reputation of crowd contributors; stores the contributor models as smart contracts in a private Ethereum network; and implements a recommendation and explanation engine based on the stored contributor trust and reputation smart contracts. In terms of contributions, this paper explores trust and reputation smart contracts for explainable recommendations. The experiments, which were performed with a crowdsourced data set from Expedia, showed that the proposed method provides cost-free processing transparency and data authenticity at the cost of latency.info:eu-repo/semantics/publishedVersio
Effect of drill speed on bone damage during drilling
No full textProceedings of the IV International Conference on Biodental EngineeringThe most usual causes of the failure in dental implant osseointegration are the mechanical damage linked with excessive levels of penetration force during drilling and thermal injury, because produce irreversible osteonecrosis. The result is weakened contact of implants with bone and loss of rigid fixation, which lead to delay the healing process. The main goal of this paper is to investigate the effect of drill speed on mechani-cal damage during drilling of solid rigid foam materials with similar mechanical properties to the human bone. Experimental tests were performed on biomechanical blocks instrumented with strain gauges in dif-ferent surface positions during the drilling process. A three-dimensional finite element model was devel-oped to simulate the drilling process and validated with experimental tests. Results of this study suggests that a drill bit with lower drill speed can reduce the strains and stresses in bone during drilling. The pro-posed numerical model reflected adequately the experimental results and could be useful in determination of optimal drilling conditions that minimize the bone injuries.info:eu-repo/semantics/publishedVersio
Thermo-mechanical stresses distribution on bone drilling: Numerical and experimental procedures
No full textIn bone drilling, the temperature and the level of stresses at the bone tissue are function of the drilling parameters. If certain thresholds are exceeded, irreversible damages may occur on the bone tissue. One of the main challenges in the drilling process is to control the associated parameters and even more important, to avoid the surrounding tissue damage. In this study, a dynamic numerical model is developed to determine the thermo-mechanical stresses generated during the bone drilling, using the finite element method. The numerical model incorporates the geometric and dynamic characteristics involved in the drilling processes, as well the developed temperature inside the material. The numerical analysis has been validated by experimental tests using polyurethane foam materials with similar mechanical properties to the human bone. Results suggest that a drill bit with lower drill speed and higher feed rate can reduce the strains and stresses in bone during the drilling process. The proposed numerical model reflected adequately the experimental results and could be useful in determination of optimal drilling conditions that minimise the bone injuries.info:eu-repo/semantics/publishedVersio
A Flexibility Home Energy Management System to Support Agreggator Requests in Smart Grids
No full textEnergy flexibility will play a key role in the proper functioning of energy systems, introducing a set of benefits to all involved stakeholders and changing the shape of electricity markets as we know them. It is expected that new players with different interests will emerge in this context. Particularly, the aggregators might allow end-users to be aware of their consumption flexibility value, or merely facilitate consumer's participation, for instance through the use of demand response. To this end, a prompt system response allowing the interaction between aggregators and residential users is needed. Therefore, the so-called Home Energy Management System (HEMS) becomes an active tool to communicate end-users with aggregators, performing the necessary changes in the consumption profiles in benefit of all involved parts. In this paper, a model with the objective of achieving a match between the flexibility required by an aggregator and the flexibility offered by residential users through the HEMS capability of shifting specific appliances is proposed. The model is then solved using a well-known swarm intelligence algorithm, the particle swarm optimization (PSO). An illustrative example of how the model is optimized using PSO, re-scheduling appliances to meet a flexibility curve, is presented. After that, a case study with 15 appliances based on real profiles of home devices is solved showing the effectiveness of the proposed approach to procure flexibility.This work has received funding from the Project NetEffiCity (ANI|P2020 18015), and from FEDER Funds through COMPETE program and from National Funds through FCT under the project UID/EEA/00760/2013.info:eu-repo/semantics/publishedVersio