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Publicações

2018

Single Particle Differentiation through 2D Optical Fiber Trapping and Back-Scattered Signal Statistical Analysis: An Exploratory Approach

Autores
Paiva, JS; Ribeiro, RSR; Cunha, JPS; Rosa, CC; Jorge, PAS;

Publicação
SENSORS

Abstract
Recent trends on microbiology point out the urge to develop optical micro-tools with multifunctionalities such as simultaneous manipulation and sensing. Considering that miniaturization has been recognized as one of the most important paradigms of emerging sensing biotechnologies, optical fiber tools, including Optical Fiber Tweezers (OFTs), are suitable candidates for developing multifunctional small sensors for Medicine and Biology. OFTs are flexible and versatile optotools based on fibers with one extremity patterned to form a micro-lens. These are able to focus laser beams and exert forces onto microparticles strong enough (piconewtons) to trap and manipulate them. In this paper, through an exploratory analysis of a 45 features set, including time and frequency-domain parameters of the back-scattered signal of particles trapped by a polymeric lens, we created a novel single feature able to differentiate synthetic particles (PMMA and Polystyrene) from living yeasts cells. This single statistical feature can be useful for the development of label-free hybrid optical fiber sensors with applications in infectious diseases detection or cells sorting. It can also contribute, by revealing the most significant information that can be extracted from the scattered signal, to the development of a simpler method for particles characterization (in terms of composition, heterogeneity degree) than existent technologies.

2018

The Two-Dimensional Strip Packing Problem: What Matters?

Autores
Neuenfeldt Junior, A; Silva, E; Miguel Gomes, AM; Oliveira, JF;

Publicação
OPERATIONAL RESEARCH

Abstract
This paper presents an exploratory approach to study and identify the main characteristics of the two-dimensional strip packing problem (2D-SPP). A large number of variables was defined to represent the main problem characteristics, aggregated in six groups, established through qualitative knowledge about the context of the problem. Coefficient correlation are used as a quantitative measure to validate the assignment of variables to groups. A principal component analysis (PCA) is used to reduce the dimensions of each group, taking advantage of the relations between variables from the same group. Our analysis indicates that the problem can be reduced to 19 characteristics, retaining most part of the total variance. These characteristics can be used to fit regression models to estimate the strip height necessary to position all items inside the strip.

2018

An electronic marketplace for airlines

Autores
Reis, L; Rocha, AP; Castro, AJM;

Publicação
Communications in Computer and Information Science

Abstract
In this paper we propose an airline marketplace, modeled as a multi-agent system with an automated negotiation mechanism, where airlines can announce availability of resources (aircraft or aircraft and crew) for lease and other airlines can go there to contract resources to fill gaps in the operation, typically due to disruptions and/or an unexpected increase on the operation. The proposed negotiation occurs in several rounds, where qualitative comments made by the buyer agent on proposals sent by the sellers enables these to learn how to calculate new proposals, using a case-based reasoning methodology. © 2018, Springer International Publishing AG, part of Springer Nature.

2018

Automatic Generation of Disassembly Sequences and Exploded Views from SolidWorks Symbolic Geometric Relationships

Autores
Costa, CM; Veiga, G; Sousa, A; Rocha, L; Oliveira, E; Cardoso, HL; Thomas, U;

Publicação
2018 IEEE INTERNATIONAL CONFERENCE ON AUTONOMOUS ROBOT SYSTEMS AND COMPETITIONS (ICARSC)

Abstract
Planning the optimal assembly and disassembly sequence plays a critical role when optimizing the production, maintenance and recycling of products. For tackling this problem, a recursive branch-and-bound algorithm was developed for finding the optimal disassembly plan. It takes into consideration the traveling distance of a robotic end effector along with a cost penalty when it needs to be changed. The precedences and part decoupling directions are automatically computed in the proposed geometric reasoning engine by analyzing the spatial relationships present in SolidWorks assemblies. For accelerating the optimization process, a best-first search algorithm was implemented for quickly finding an initial disassembly sequence solution that is used as an upper bound for pruning most of the non-optimal tree branches. For speeding up the search further, a caching technique was developed for reusing feasible disassembly operations computed on previous search steps, reducing the computational time by more than 18%. As a final stage, our SolidWorks add-in generates an exploded view animation for allowing intuitive analysis of the best solution found. For testing our approach, the disassembly of two starter motors and a single cylinder engine was performed for assessing the capabilities and time requirements of our algorithms.

2018

Wine productivity per farm size: A maximum entropy application

Autores
Galindro, A; Santos, M; Santos, C; Marta Costa, A; Matias, J; Cerveira, A;

Publicação
Wine Economics and Policy

Abstract
The size of a farm is one of the factors that influence its productivity, in an ambiguous relationship that is often discussed in the industrial economy. In Portugal, the Demarcated Douro Region (DDR) is characterized by very small farms. Usually, this trend is considered a limitating factor in the profitability of the wine farms. In order to assess the correctness of this sentence, the variation of wine productivity per land size, from 2010 to 2016, was studied in the DDR, considering its three distinctive areas: Baixo Corgo, Cima Corgo and Douro Superior. The farms were categorized in nine different size ranges; as these variables outnumber the available seven observations, the Generalized Maximum Entropy (GME) estimator was used, since it suits the need to solve an ill-conditioned problem. GME was applied with the MATLAB (MATrix LABoratory) software along with the Bootstrap technique. According to the simulations, larger farms (with an area greater than 20 ha) on Douro Superior and Cima Corgo reveal higher marginal productivity given the current state of the region. On the other hand, Baixo Corgo's results suggest that medium-sized farms (with area ranges between 2 and 5 ha) display higher marginal increments to the region wine productivity. © 2018 UniCeSV, University of Florence

2018

Development of a dynamic model for twin hull ASVs

Autores
Pinto, AF; Cruz, NA; Pinto, VH; Ferreira, BM;

Publicação
2018 OCEANS - MTS/IEEE KOBE TECHNO-OCEANS (OTO)

Abstract
This paper presents an overview of a generalized 6 degrees of freedom model for surface vessels and explains how it can be extended for twin hull surface vehicles. The extended model takes into account the hull characteristics (dimensions and location), which are important to improve the accuracy of simulations and the performance of controllers. The method involves the calculation of the submerged volume of each hull, location of each hull's center of buoyancy and restoring forces/ torques due to buoyancy contributions. To evaluate the proposed model, some simulations were performed, using an example of allocation of propulsion system and realistic hydrodynamic coefficients (added mass and damping) and inertial tensors.

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