Ancillary services market clearing simulation: a comparison between deterministic and heuristic methods

Electricity market players operating in a liberalized environment requires access to an adequate decision support tool, allowing them to consider all the business opportunities and take strategic decisions. Ancillary services represent a good negotiation opportunity that must be considered by market players. For this, decision support tool must include ancillary market simulation. This paper proposes two different methods (Linear Programming and Genetic Algorithm approaches) for ancillary services dispatch. The methodologies are implemented in MASCEM, a multi-agent based electricity market simulator. A test case based on California Independent System Operator (CAISO) data concerning the dispatch of Regulation Down, Regulation Up, Spinning Reserve and Non-Spinning Reserve services is included in this paper.

Derivative-free optimization and filter methods to solve nonlinear constrained problems

In real optimization problems, usually the analytical expression of the objective function is not known, nor its derivatives, or they are complex. In these cases it becomes essential to use optimization methods where the calculation of the derivatives, or the verification of their existence, is not necessary: the Direct Search Methods or Derivative-free Methods are one solution. When the problem has constraints, penalty functions are often used. Unfortunately the choice of the penalty parameters is, frequently, very difficult, because most strategies for choosing it are heuristics strategies. As an alternative to penalty function appeared the filter methods. A filter algorithm introduces a function that aggregates the constrained violations and constructs a biobjective problem. In this problem the step is accepted if it either reduces the objective function or the constrained violation. This implies that the filter methods are less parameter dependent than a penalty function. In this work, we present a new direct search method, based on simplex methods, for general constrained optimization that combines the features of the simplex method and filter methods. This method does not compute or approximate any derivatives, penalty constants or Lagrange multipliers. The basic idea of simplex filter algorithm is to construct an initial simplex and use the simplex to drive the search. We illustrate the behavior of our algorithm through some examples. The proposed methods were implemented in Java.

Local fractional variational iteration and decomposition methods for wave equation on cantor sets within local fractional operators

We perform a comparison between the fractional iteration and decomposition methods applied to the wave equation on Cantor set. The operators are taken in the local sense. The results illustrate the significant features of the two methods which are both very effective and straightforward for solving the differential equations with local fractional derivative.

Diagnóstico e avaliação da segurança de estruturas de madeira existentes

A utilização da madeira enquanto material estrutural é um aspeto abordado com algum receio ou até desconhecimento por parte dos elementos intervenientes no processo de construção civil, sendo ainda uma área pouco lecionada e muitas vezes excluída dos planos curriculares em Engenharia Civil. Assim sendo é importante o surgimento de trabalhos relacionados com esta matéria, relembrando ao sector da construção civil e ao ramo de estudo relacionado, que a madeira já teve e possivelmente voltará a ter um papel importante a desempenhar na área da construção. Um dos aspetos evidenciados nos estudos realizados consiste na importância da reabilitação de edifícios e do seu papel cada vez mais determinante na sociedade. Esta metodologia de intervenção apresenta-se muitas vezes como uma vantagem económica assim como contribui para a preservação do património arquitetónico e cultural, cujo valor histórico é incalculável. A importância da reabilitação de edifícios habitacionais nas zonas históricas, bem como de monumentos de grande importância cultural apresenta-se cada vez mais como um desafio devido à falta de conservação dos mesmos ao longo da sua vida útil, e da necessidade de preservar a identidade do local, beneficiando assim a qualidade do tecido urbano. Assim sendo, este trabalho apresenta um levantamento dos danos possíveis de ocorrer em elementos de madeira, dando especial destaque aos agentes patológicos e às consequências da sua atividade na madeira assim como às metodologias de inspeção e diagnóstico que poderão ser aplicadas em estruturas de madeira existentes, favorecendo assim a vertente da reabilitação ao invés da demolição. Estas metodologias recorrem a ensaios não destrutivos, como é exemplo o Pilodyn, o Resistógrafo, o Ultra-sons, etc., referindo também o recurso a ensaios destrutivos, cuja utilização terá de ser uma questão muito bem ponderada devido às consequências que implica. Por fim, apresenta-se um caso real de estudo em que se analisa um pavimento em madeira através da aplicação de metodologias de ensaio não destrutivas e destrutivas a amostras recolhidas. O objetivo será determinar o estado de conservação da madeira e algumas características físicas tais como a sua densidade e os módulos de elasticidade, sendo posteriormente efetuada uma análise estrutural. Os resultados obtidos permitem efetuar uma avaliação qualitativa do estado geral do pavimento sendo as principais conclusões que o pavimento se encontra atacado por parte de insetos xilófagos e apresenta problemas a nível de verificação a estados limite de utilização, deformação e vibração, fator que condiciona a possível utilização do pavimento.

Assessing and comparing the total antioxidant capacity of commercial beverages: application to beers, wines, waters and soft drinks using TRAP, TEAC and FRAP methods.

This work measures and tries to compare the Antioxidant Capacity (AC) of 50 commercial beverages of different kinds: 6 wines, 12 beers, 18 soft drinks and 14 flavoured waters. Because there is no reference procedure established for this purpose, three different optical methods were used to analyse these samples: Total Radical trapping Antioxidant Parameter (TRAP), Trolox Equivalent Antioxidant Capacity (TEAC) and Ferric ion Reducing Antioxidant Parameter (FRAP). These methods differ on the chemical background and nature of redox system. The TRAP method involves the transfer of hydrogen atoms while TEAC and FRAP involves electron transfer reactions. The AC was also assessed against three antioxidants of reference, Ascorbic acid (AA), Gallic acid (GA) and 6-hydroxy-2,5,7,8-tetramethyl- 2-carboxylic acid (Trolox). The results obtained were analyzed statistically. Anova one-way tests were applied to all results and suggested that methods and standards exhibited significant statistical differences. The possible effect of sample features in the AC, such as gas, flavours, food colouring, sweeteners, acidity regulators, preservatives, stabilizers, vitamins, juice percentage, alcohol percentage, antioxidants and the colour was also investigated. The AC levels seemed to change with brand, kind of antioxidants added, and kind of flavour, depending on the sample. In general, higher ACs were obtained for FRAP as method, and beer for kind of sample, and the standard expressing the smaller AC values was GA.

Combining sparse and dense methods in 6D Visual Odometry

13th International Conference on Autonomous Robot Systems (Robotica), 2013, Lisboa

DITRANS - a multi-agent system for integrated diagnosis of power transformers

This paper describes the development and the implementation of a multi-agent system for integrated diagnosis of power transformers. The system is divided in layers which contain a number of agents performing different functions. The social ability and cooperation between the agents lead to the final diagnosis and to other relevant conclusions through integrating various monitoring technologies, diagnostic methods and data sources, such as the dissolved gas analysis.

Training control centers' operators in incident diagnosis and power restoration using intelligent tutoring systems

The activity of Control Center operators is important to guarantee the effective performance of Power Systems. Operators’ actions are crucial to deal with incidents, especially severe faults like blackouts. In this paper, we present an Intelligent Tutoring approach for training Portuguese Control Center operators in tasks like incident analysis and diagnosis, and service restoration of Power Systems. Intelligent Tutoring System (ITS) approach is used in the training of the operators, having into account context awareness and the unobtrusive integration in the working environment. Several Artificial Intelligence techniques were criteriously used and combined together to obtain an effective Intelligent Tutoring environment, namely Multiagent Systems, Neural Networks, Constraint-based Modeling, Intelligent Planning, Knowledge Representation, Expert Systems, User Modeling, and Intelligent User Interfaces.

A survey of technologies and applications for climbing robots locomotion and adhesion

The interest in the development of climbing robots has grown rapidly in the last years. Climbing robots are useful devices that can be adopted in a variety of applications, such as maintenance and inspection in the process and construction industries. These systems are mainly adopted in places where direct access by a human operator is very expensive, because of the need for scaffolding, or very dangerous, due to the presence of an hostile environment. The main motivations are to increase the operation efficiency, by eliminating the costly assembly of scaffolding, or to protect human health and safety in hazardous tasks. Several climbing robots have already been developed, and other are under development, for applications ranging from cleaning to inspection of difficult to reach constructions. A wall climbing robot should not only be light, but also have large payload, so that it may reduce excessive adhesion forces and carry instrumentations during navigation. These machines should be capable of travelling over different types of surfaces, with different inclinations, such as floors, walls, or ceilings, and to walk between such surfaces (Elliot et al. (2006); Sattar et al. (2002)). Furthermore, they should be able of adapting and reconfiguring for various environment conditions and to be self-contained. Up to now, considerable research was devoted to these machines and various types of experimental models were already proposed (according to Chen et al. (2006), over 200 prototypes aimed at such applications had been developed in the world by the year 2006). However, we have to notice that the application of climbing robots is still limited. Apart from a couple successful industrialized products, most are only prototypes and few of them can be found in common use due to unsatisfactory performance in on-site tests (regarding aspects such as their speed, cost and reliability). Chen et al. (2006) present the main design problems affecting the system performance of climbing robots and also suggest solutions to these problems. The major two issues in the design of wall climbing robots are their locomotion and adhesion methods. With respect to the locomotion type, four types are often considered: the crawler, the wheeled, the legged and the propulsion robots. Although the crawler type is able to move relatively faster, it is not adequate to be applied in rough environments. On the other hand, the legged type easily copes with obstacles found in the environment, whereas generally its speed is lower and requires complex control systems. Regarding the adhesion to the surface, the robots should be able to produce a secure gripping force using a light-weight mechanism. The adhesion method is generally classified into four groups: suction force, magnetic, gripping to the surface and thrust force type. Nevertheless, recently new methods for assuring the adhesion, based in biological findings, were proposed. The vacuum type principle is light and easy to control though it presents the problem of supplying compressed air. An alternative, with costs in terms of weight, is the adoption of a vacuum pump. The magnetic type principle implies heavy actuators and is used only for ferromagnetic surfaces. The thrust force type robots make use of the forces developed by thrusters to adhere to the surfaces, but are used in very restricted and specific applications. Bearing these facts in mind, this chapter presents a survey of different applications and technologies adopted for the implementation of climbing robots locomotion and adhesion to surfaces, focusing on the new technologies that are recently being developed to fulfill these objectives. The chapter is organized as follows. Section two presents several applications of climbing robots. Sections three and four present the main locomotion principles, and the main "conventional" technologies for adhering to surfaces, respectively. Section five describes recent biological inspired technologies for robot adhesion to surfaces. Section six introduces several new architectures for climbing robots. Finally, section seven outlines the main conclusions.

Short-term scheduling considering five-minute and hour-ahead energy resource management

The introduction of new distributed energy resources, based on natural intermittent power sources, in power systems imposes the development of new adequate operation management and control methods. This paper proposes a short-term Energy Resource Management (ERM) methodology performed in two phases. The first one addresses the hour-ahead ERM scheduling and the second one deals with the five-minute ahead ERM scheduling. Both phases consider the day-ahead resource scheduling solution. The ERM scheduling is formulated as an optimization problem that aims to minimize the operation costs from the point of view of a virtual power player that manages the network and the existing resources. The optimization problem is solved by a deterministic mixed-integer non-linear programming approach and by a heuristic approach based on genetic algorithms. A case study considering a distribution network with 33 bus, 66 distributed generation, 32 loads with demand response contracts and 7 storage units has been implemented in a PSCADbased simulator developed in the field of the presented work, in order to validate the proposed short-term ERM methodology considering the dynamic power system behavior.

Construção de um robô trepador com locomoção através de rodas e adesão através de meios magnéticos

Mestrado em Engenharia Electrotécnica e de Computadores

Optimization and validation of organochlorine compounds in adipose tissue by SPE-gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid-phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C18-E), benzenesulfonic acid modified silica cation exchanger (SA), poly (styrene-divinylbenzene (EN) and EN/RP18 SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C18-E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries>70% with standard deviations (SD)<15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′-DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.

Sistema de visão para percepção e navegação de um UAV Quadrotor

Mestrado em Engenharia Electrotécnica e de Computadores

Reorganização dos ajustes posturais antecipatórios em indivíduos após AVE: influência de um programa de intervenção em fisioterapia no registo electromiográfico do tibial anterior e solear

Introdução: As dificuldades encontradas em individuos após Acidente Vascular Encefálico, ao nível da marcha, influenciam significativamente o retorno ao trabalho, a participação na comunidade ou o desempenho nas actividades da vida diária. Objectivo: Neste trabalho, procurou-se verificar qual o efeito de um programa de intervenção em fisioterapia nos ajustes posturais antecipatórios que ocorrem previamente ao movimento voluntário e assim pré-determinar a sua contribuição para a estabilidade postural e o equilíbrio. Material e Métodos: Para testar os pressupostos inerentes, relatam-se dois casos clínicos de sujeitos do sexo masculino com diagnóstico de Acidente Vascular Encefálico. Estes foram submetidos a um programa de intervenção em fisioterapia, durante 10 semanas consecutivas, baseado no Conceito de Bobath e que teve em conta o principal problema de cada indivíduo. Foi monitorizada a actividade electromiográfica do ventre medial do Tibial Anterior e Solear na fase de pré-activação da marcha, em dois momentos distintos, no início e no fim da intervenção. Resultados: Dos resultados obtidos evidenciam-se as diferenças entre os tempos médios de pré-activação, bem como as diferenças entre a percentagem da contracção isométrica voluntária máxima atingida pelos músculos Tibial Anterior e Solear, direito e esquerdo, entre os dois momentos de avaliação, em ambos os sujeitos. Verificou-se, no entanto, que a actividade electromiográfica dos referidos músculos possui grande variabilidade. Conclusão: Os resultados sugerem que o programa de intervenção em fisioterapia parece ter tido influência no recrutamento da actividade muscular do TA e do SO, uma vez que, em termos médios absolutos, ocorreram diferenças após a implementação das estratégias e procedimentos da intervenção.

Deterioração e reabilitação de estruturas de betão armado

Apesar da enorme evolução tecnológica, os prazos na construção são cada vez mais reduzidos e os custos mais controlados, verificando-se uma despreocupação no que diz respeito a aspetos como a qualidade e durabilidade da construção das estruturas. Desperta assim nos técnicos, donos-de-obra, entidades executantes e projetistas a necessidade de avaliar o estado de conservação das estruturas de betão armado. Esta dissertação tem como objetivo principal abordar as anomalias e os mecanismos de deterioração mais correntes, os métodos de ensaio destrutivos ou parcialmente destrutivos mais utilizados e adequados, e abordar algumas das técnicas de reparação e reforço das estruturas de betão armado. Os principais danos apresentados nas estruturas são devidos a agentes físicos, mecânicos, biológicos e químicos. Podem ser devidos a causas diretas (acidentais ou naturais), que acarretam uma ação concreta sobre os elementos estruturais, e causas indiretas (humanas), diretamente ligadas com erros de projeto. É primordial fazer-se o levantamento de todas as anomalias existentes para se recorrer a um método de inspeção e ensaio. Consoante a necessidade de informação e estado da estrutura são selecionados os ensaios a realizar, podendo ser realizados “in situ” ou em laboratório. As técnicas de reparação e reforço são vistas como métodos para melhorar as condições da estrutura ao nível da segurança, desempenho, habitabilidade e durabilidade, prevenindo a evolução dos mecanismos de deterioração.