Minimization of open orders using interval graphs

In this paper we address an order processing optimization problem known as the Minimization of Open Stacks Problem (MOSP). This problem consists in finding the best sequence for manufacturing the different products required by costumers, in a setting where only one product can be made at a time. The objective is to minimize the maximum number of incomplete orders from costumers that are being processed simultaneously. We present an integer programming model, based on the existence of a perfect elimination order in interval graphs, which finds an optimal sequence for the costumers orders. Among other economic advantages, manufacturing the products in this optimal sequence reduces the amount of space needed to store incomplete orders.

Sequencing cutting patterns with colored interval graphs

The problem addressed here originates in the industry of flat glass cutting and wood panel sawing, where smaller items are cut from larger items accordingly to predefined cutting patterns. In this type of industry the smaller pieces that are cut from the patterns are piled around the machine in stacks according to the size of the pieces, which are moved to the warehouse only when all items of the same size have been cut. If the cutting machine can process only one pattern at a time, and the workspace is limited, it is desirable to set the sequence in which the cutting patterns are processed in a way to minimize the maximum number of open stacks around the machine. This problem is known in literature as the minimization of open stacks (MOSP). To find the best sequence of the cutting patterns, we propose an integer programming model, based on interval graphs, that searches for an appropriate edge completion of the given graph of the problem, while defining a suitable coloring of its vertices.

Using interval graphs in an order processing optimization problem

In this paper we address an order processing optimization problem known as minimization of open stacks (MOSP). We present an integer pro gramming model, based on the existence of a perfect elimination scheme in interval graphs, which finds an optimal sequence for the costumers orders.

Generalized Extraction of Real-Time Parameters for Homogeneous Synchronous Dataflow Graphs

23rd Euromicro International Conference on Parallel, Distributed, and Network-Based Processing (PDP 2015). 4 to 6, Mar, 2015. Turku, Finland.

Sistema de suporte à negociação numa empresa de prestação de serviços médicos

Nesta dissertação foram estudados métodos de apoio à negociação com o objectivo de encontrar o melhor modelo de negociação para uma empresa prestadora de serviços médicos. O modelo utilizado foi o WinWin e para testar o modelo foi desenvolvido um sistema de apoio à negociação com os clientes. A aplicação foi desenvolvida com o objectivo de conseguir optimizar percursos e reduzir custos, dentro de certas condições, da forma mais eficiente possível, e que fosse de acordo aos interesses do processo de negociação e do contrato com o cliente. Com isto, a aplicação foi testada com 70 contratos, tendo conseguido simular vários grafos que conseguiam alocar todas as consultas dos contratos de forma a respeitar os objectivos impostos por este, e sendo eficientes no sentido de reduzir os custos e tempo de deslocação, diminuindo consequentemente os custos do contrato para o cliente. A redução dos custos para o cliente permite à empresa prestadora de serviços médicos ser mais competitiva face aos seus concorrentes, assim como possuir uma maior margem de manobra face ao processo de negociação, pois também através das simulações conseguem ter uma noção mais precisa dos custos totais de um contrato, diminuindo assim possíveis riscos de um contrato mal estimado.

Desenvolvimento de um pedómetro para telemóvel

Esta tese descreve o desenvolvimento do hardware e do software de um sistema com a capacidade de reconhecer o número de passos que uma pessoa efectua durante uma actividade física. O sistema consiste num acelerómetro controlado por um microcontrolador, que comunica com um dispositivo móvel através de Bluetooth. De modo a realizar o sistema foi necessário analisar uma vasta bibliografia, para conhecer o estado da arte desta tecnologia, entender o princípio de funcionamento do protocolo Bluetooth e os conceitos biomecânicos por detrás da marcha humana. A proposta deste trabalho apresentava como elemento diferenciador do estado da arte o uso de um acelerómetro em conjunto com sensores de pressão. Com a conjugação destes sensores pretendia-se aumentar a precisão de um equipamento que normalmente não é reconhecido por essa característica. Contudo, a indisponibilidade dos sensores de pressão levou a que o sistema só fosse constituído pelo acelerómetro. Embora, o sistema foi projectado considerando que os sensores de pressão serão incluídos num futuro desenvolvimento. Neste trabalho foram desenvolvidos dois algoritmos para detectar os passos que uma pessoa executa, com pé onde é colocado o sensor, quando caminha ou corre. Num dos testes realizados o algoritmo da “aceleração composta” detectou 84% dos passos, enquanto o algoritmo da “aceleração simples”detectou 99%. A plataforma para a interface gráfica pretendia-se que fosse um telemóvel, contudo não foi possível obter um telemóvel que suporta-se o perfil SPP (Serial Port Profile), necessário para a comunicação com o módulo Bluetooth usado. A solução passou por usar como plataforma um computador portátil com Bluetooth, para o qual foi desenvolvido a aplicação “Pedómetro ISEP” em Visual Basic. O “Pedómetro ISEP” apresenta várias funcionalidades, entre elas destaca-se o cálculo da distância percorrida, da velocidade, e das calorias consumidas, bem como, o registo desses valores em tabelas e da possibilidade de desenhar os gráficos representativos do progresso do utilizador.

Estudo comparativo entre criança com e sem joelhos valgos praticantes de hóquei em patins utilizando diferentes sistemas de análise

O presente estudo tem como objetivo comparar experimentalmente duas crianças praticantes de Hóquei em Patins, uma normal e uma com a patologia dos joelhos valgos, avaliando qualitativamente as diferenças posturais, estáticas e dinâmicas, decorrentes da utilização dos patins específicos desta modalidade, através do sistema de análise da Força de Reação do Solo (FRS), de Eletromiografia (EMG), de captura de movimento, e de modelação e simulação. Para atingir o objetivo definiu-se um protocolo de ensaios com as seguintes tarefas: repouso com e sem patins, marcha, corrida, deslizar com os dois pés apoiados e deslizar com o pé esquerdo levantado. No repouso avaliou-se a variação do ponto de aplicação da FRS da criança normal e patológica, com e sem patins. Ainda na tarefa de repouso avaliou-se também as componentes médio-lateral, antero-posterior individualmente e a componente vertical da FRS, juntamente com a atividade muscular dos músculos Gastrocnémio Medial (GM), Recto Femoral (RF), Vasto Medial (VM), Vasto Lateral (VL), Bicípete Femoral (BF), Semitendinoso (ST), Tensor da Fascia Lata (TFL), Gastrocnémio Lateral (GL), de forma a comparar os valores de intensidade de FRS e da atividade muscular dos diferentes instantes de tempo desta tarefa. Para as restantes tarefas apenas se avaliou individualmente as componentes médio-lateral e antero-posterior da FRS e a componente vertical da FRS juntamente com a atividade muscular dos referidos músculos, salientando as diferenças evidentes entre as curvas da criança normal e as curvas da criança patológica durante os diferentes instantes do movimento. Todas as tarefas referidas, exceto a tarefa de repouso com patins, foram ainda simuladas recorrendo a modelos músculo-esqueléticos. A partir destas simulações do movimento obtiveram-se os ângulos articulares e efetuou-se a respetiva análise. No final dos resultados obtidos apresentou-se uma tabela de resumo com o cálculo dos coeficientes de variação de cada grandeza, exceto nos gráficos da posição no espaço da FRS, onde se constatou que existe uma grande variabilidade inter-individuo em cada tarefa. A análise dos resultados de cada tarefa permite concluir que a utilização de patins pode trazer uma maior ativação muscular para a criança patológica, embora se verifique instabilidade articular. Apesar dessa instabilidade pode-se inferir que, uma maior ativação muscular decorrente da utilização de patins, tal como acontece na prática do hóquei em patins, pode trazer uma melhoria, a longo prazo, na estabilidade da articulação do joelho e na sustentação corporal, proporcionada pelo fortalecimento muscular.

Comparative study about heating systems for pultrusion process

Different heating systems have been used in pultrusion, where the most widely used heaters are planar resistances. The primary objective of this study was to develop an improved heating system and compare its performance with that of a system with planar resistances. In this study, thermography was used to better understand the temperature profile along the die. Finite element analysis was performed to determine the amount of energy consumed by the heating systems. Improvements were made to the die to test the new heating system, and it was found that the new system reduced the setup time and energy consumption by approximately 57%.

Analysis of stock market indices through multidimensional scaling

We propose a graphical method to visualize possible time-varying correlations between fifteen stock market values. The method is useful for observing stable or emerging clusters of stock markets with similar behaviour. The graphs, originated from applying multidimensional scaling techniques (MDS), may also guide the construction of multivariate econometric models.

A fractional approach for the motion planning of redundant and hyper-redundant manipulators

The trajectory planning of redundant robots through the pseudoinverse control leads to undesirable drift in the joint space. This paper presents a new technique to solve the inverse kinematics problem of redundant manipulators, which uses a fractional differential of order α to control the joint positions. Two performance measures are defined to examine the strength and weakness of the proposed method. The positional error index measures the precision of the manipulator's end-effector at the target position. The repeatability performance index is adopted to evaluate if the joint positions are repetitive when the manipulator execute repetitive trajectories in the operational workspace. Redundant and hyper-redundant planar manipulators reveal that it is possible to choose in a large range of possible values of α in order to get repetitive trajectories in the joint space.

Multidimensional scaling analysis of electricity market prices

This paper studies the impact of energy and stock markets upon electricity markets using Multidimensional Scaling (MDS). Historical values from major energy, stock and electricity markets are adopted. To analyze the data several graphs produced by MDS are presented and discussed. This method is useful to have a deeper insight into the behavior and the correlation of the markets. The results may also guide the construction models, helping electricity markets agents hedging against Market Clearing Price (MCP) volatility and, simultaneously, to achieve better financial results.

An evolutionary approach for the motion planning of redundant and hyper-redundant manipulators

The trajectory planning of redundant robots is an important area of research and efficient optimization algorithms are needed. The pseudoinverse control is not repeatable, causing drift in joint space which is undesirable for physical control. This paper presents a new technique that combines the closed-loop pseudoinverse method with genetic algorithms, leading to an optimization criterion for repeatable control of redundant manipulators, and avoiding the joint angle drift problem. Computer simulations performed based on redundant and hyper-redundant planar manipulators show that, when the end-effector traces a closed path in the workspace, the robot returns to its initial configuration. The solution is repeatable for a workspace with and without obstacles in the sense that, after executing several cycles, the initial and final states of the manipulator are very close.

Optimising the energy consumption on pultrusion process

This study is based on a previous experimental work in which embedded cylindrical heaters were applied to a pultrusion machine die, and resultant energetic performance compared with that achieved with the former heating system based on planar resistances. The previous work allowed to conclude that the use of embedded resistances enhances significantly the energetic performance of pultrusion process, leading to 57% decrease of energy consumption. However, the aforementioned study was developed with basis on an existing pultrusion die, which only allowed a single relative position for the heaters. In the present work, new relative positions for the heaters were investigated in order to optimise heat distribution process and energy consumption. Finite Elements Analysis was applied as an efficient tool to identify the best relative position of the heaters into the die, taking into account the usual parameters involved in the process and the control system already tested in the previous study. The analysis was firstly developed based on eight cylindrical heaters located in four different location plans. In a second phase, in order to refine the results, a new approach was adopted using sixteen heaters with the same total power. Final results allow to conclude that the correct positioning of the heaters can contribute to about 10% of energy consumption reduction, decreasing the production costs and leading to a better eco-efficiency of pultrusion process.

Saving energy in the GFRP pultrusion process

This study addresses to the optimization of pultrusion manufacturing process from the energy-consumption point of view. The die heating system of external platen heaters commonly used in the pultrusion machines is one of the components that contribute the most to the high consumption of energy of pultrusion process. Hence, instead of the conventional multi-planar heaters, a new internal die heating system that leads to minor heat losses is proposed. The effect of the number and relative position of the embedded heaters along the die is also analysed towards the setting up of the optimum arrangement that minimizes both the energy rate and consumption. Simulation and optimization processes were greatly supported by Finite Element Analysis (FEA) and calibrated with basis on the temperature profile computed through thermography imaging techniques. The main outputs of this study allow to conclude that the use of embedded cylindrical resistances instead of external planar heaters leads to drastic reductions of both the power consumption and the warm-up periods of the die heating system. For the analysed die tool and process, savings on energy consumption up to 60% and warm-up period stages less than an half hour were attained with the new internal heating system. The improvements achieved allow reducing the power requirements on pultrusion process, and thus minimize industrial costs and contribute to a more sustainable pultrusion manufacturing industry.

How to reduce energy consumption on pultrusion

The global warming due to high CO2 emission in the last years has made energy saving a global problem nowadays. However, manufacturing processes such as pultrusion necessarily needs heat for curing the resin. Then, the only option available is to apply all efforts to make the process even more efficient. Different heating systems have been used on pultrusion, however, the most widely used are the planar resistances. The main objective of this study is to develop another heating system and compares it with the former one. Thermography was used in spite of define the temperature profile along the die. FEA (finite element analysis) allows to understand how many energy is spend with the initial heating system. After this first approach, changes were done on the die in order to test the new heating system and to check possible quality problems on the product. Thus, this work allows to conclude that with the new heating system a significant reduction in the setup time is now possible and an energy reduction of about 57% was achieved.