A contribution on modeling methodologies for multibody systems.

Multibody System Dynamics has been responsible for revolutionizing Mechanical Engineering Design by using mathematical models to simulate and optimize the dynamic behavior of a wide range of mechanical systems. These mathematical models not only can provide valuable informations about a system that could otherwise be obtained only by experiments with prototypes, but also have been responsible for the development of many model-based control systems. This work represents a contribution for dynamic modeling of multibody mechanical systems by developing a novel recursive modular methodology that unifies the main contributions of several Classical Mechanics formalisms. The reason for proposing such a methodology is to motivate the implementation of computational routines for modeling complex multibody mechanical systems without being dependent on closed source software and, consequently, to contribute for the teaching of Multibody System Dynamics in undergraduate and graduate levels. All the theoretical developments are based on and motivated by a critical literature review, leading to a general matrix form of the dynamic equations of motion of a multibody mechanical system (that can be expressed in terms of any set of variables adopted for the description of motions performed by the system, even if such a set includes redundant variables) and to a general recursive methodology for obtaining mathematical models of complex systems given a set of equations describing the dynamics of each of its uncoupled subsystems and another set describing the constraints among these subsystems in the assembled system. This work also includes some discussions on the description of motion (using any possible set of motion variables and admitting any kind of constraint that can be expressed by an invariant), and on the conditions for solving forward and inverse dynamics problems given a mathematical model of a multibody system. Finally, some examples of computational packages based on the novel methodology, along with some case studies, are presented, highlighting the contributions that can be achieved by using the proposed methodology.

Sistemática de transformação: desenvolvimento teórico para o alinhamento entre estratégia e cultura organizacional nos projetos de Lean

Desde o final do Século XX e início do Século XXI, estudos analisam a elevada taxa de insucesso ou insatisfação com os Programas de Lean. Esta taxa tem se demonstrado demasiadamente elevada, variando entre 66% e 90%. Como efeito deste insucesso, tem-se o desperdício de tempo, dinheiro, recursos e, talvez o pior, tem-se a propagação do medo nos agentes de mudança em empreitar novas iniciativas de mudança. Estudos apontam a falta de alinhamento de tais projetos com a Cultura Organizacional como uma das questões fundamentais deste insucesso. Partindo desta temática de pesquisa, este ensaio teórico pode ser caracterizado como uma abordagem qualitativa de análise do problema, de natureza básica de pesquisa buscando gerar conhecimentos novos e úteis às organizações, sem aplicação prática prevista neste primeiro estágio de pesquisa. A fonte de evidências para sustentar o modelo proposto foi revisão dos estudos de caso encontrados na literatura, sendo utilizadas tanto uma Revisão Bibliográfica Sistemática (RBS) quanto Exploratória, de tal maneira a buscar o \"estado da arte\" no campo de estudo. A Fundamentação Teórica do trabalho é baseada na literatura de quatro grandes campos de estudo: (i) Estratégia, (ii) Lean, (iii) Cultura Organizacional e (iv) Gestão de Mudanças. A RBS tem foco nas interseções destes grandes campos, agregando 190 trabalhos internacionais. Por sua vez, a Revisão Exploratória traz algumas das principais referências dos três campos de estudo, como: Edgar Schein, John Kotter, Kim Cameron, Robert Quinn, David Mann, dentre outros. Desta maneira, este trabalho estudou a influência da cultura organizacional nos projetos de transformação e, a partir da ruptura com a teoria atual, construiu e propôs uma sistemática teórica, intitulada de \"Sistemática de Transformação\" (ou simplesmente \"Sistemática T\"), a qual propõe o alinhamento entre três dimensões: Estratégia, Projeto de Transformação e Cultura Organizacional. Fazendo uso desta sistemática, é esperado que os agentes de mudança consigam ter um planejamento mais eficaz do processo de diagnóstico, avaliação e gestão da cultura organizacional alinhado à Estratégia e também ao Projeto de Transformação da organização, com ênfase nos Programas de Lean. A proposição e uso desta sistemática pode favorecer tanto a discussão acadêmica na área de Gestão de Operações sobre o tema, quanto fornecer subsídios para aplicações práticas mais eficazes.

Desenvolvimento de algoritmo de controle de tração para regeneração de energia metroviária - ACTREM: melhoria da eficiência energética de sistemas de tração metroviária.

Esta tese propõe um modelo de regeneração de energia metroviária, baseado no controle de paradas e partidas do trem ao longo de sua viagem, com o aproveitamento da energia proveniente da frenagem regenerativa no sistema de tração. O objetivo é otimizar o consumo de energia, promover maior eficiência, na perspectiva de uma gestão sustentável. Aplicando o Algoritmo Genético (GA) para obter a melhor configuração de tráfego dos trens, a pesquisa desenvolve e testa o Algoritmo de Controle de Tração para Regeneração de Energia Metroviária (ACTREM), usando a Linguagem de programação C++. Para analisar o desempenho do algoritmo de controle ACTREM no aumento da eficiência energética, foram realizadas quinze simulações da aplicação do ACTREM na linha 4 - Amarela do metrô da cidade de São Paulo. Essas simulações demonstraram a eficiência do ACTREM para gerar, automaticamente, os diagramas horários otimizados para uma economia de energia nos sistemas metroviários, levando em consideração as restrições operacionais do sistema, como capacidade máxima de cada trem, tempo total de espera, tempo total de viagem e intervalo entre trens. Os resultados mostram que o algoritmo proposto pode economizar 9,5% da energia e não provocar impactos relevantes na capacidade de transporte de passageiros do sistema. Ainda sugerem possíveis continuidades de estudos.

Aplicação de modelos de defeitos na geração de conjuntos de teste completos a partir de Sistemas de Transição com Entrada/Saída

O Teste Baseado em Modelos (TBM) emergiu como uma estratégia promissora para minimizar problemas relacionados à falta de tempo e recursos em teste de software e visa verificar se a implementação sob teste está em conformidade com sua especificação. Casos de teste são gerados automaticamente a partir de modelos comportamentais produzidos durante o ciclo de desenvolvimento de software. Entre as técnicas de modelagem existentes, Sistemas de Transição com Entrada/Saída (do inglês, Input/Output Transition Systems - IOTSs), são modelos amplamente utilizados no TBM por serem mais expressivos do que Máquinas de Estado Finito (MEFs). Apesar dos métodos existentes para geração de testes a partir de IOTSs, o problema da seleção de casos de testes é um tópico difícil e importante. Os métodos existentes para IOTS são não-determinísticos, ao contrário da teoria existente para MEFs, que fornece garantia de cobertura completa com base em um modelo de defeitos. Esta tese investiga a aplicação de modelos de defeitos em métodos determinísticos de geração de testes a partir de IOTSs. Foi proposto um método para geração de conjuntos de teste com base no método W para MEFs. O método gera conjuntos de teste de forma determinística além de satisfazer condições de suficiência de cobertura da especificação e de todos os defeitos do domínio de defeitos definido. Estudos empíricos avaliaram a aplicabilidade e eficácia do método proposto: resultados experimentais para analisar o custo de geração de conjuntos de teste utilizando IOTSs gerados aleatoriamente e um estudo de caso com especificações da indústria mostram a efetividade dos conjuntos gerados em relação ao método tradicional de Tretmans.

A Discursive Perspective on China's Global Politics of Climate Change, 1992-2013

This dissertation investigates China’s recent shift in its climate change policy with a refined discourse approach. Methodologically, by adopting a neo-Gramscian notion of hegemony, a generative definition of discourse and an ontological pluralist position, the study constructs a theoretical framework named “discursive hegemony” that identifies the “social forces” for enabling social change and focuses on the role of discursive mechanisms via which the forces operate and produce effects. The key empirical finding of this study was that it was a co-evolution of conditions that shaped the outcome as China’s climate policy shift. In examining the case, a before-after within-case comparison was designed to analyze the variations in the material, institutional, and ideational conditions, with methods including interviews, conventional narrative/text analysis and descriptive statistics. Specifically, changes in energy use, the structure of decision-making body, and the narratives about sustainable development reflected how the above three types of social force processed in China in the first few years of the 21st century, causing the economic development agenda to absorb the climate issue, and turning the policy frame for the latter from mainly a diplomatic matter to a potential opportunity for better-quality growth. With the discursive operation of the “Science-based development”, China’s energy policy has been a good example of the Chinese understanding of sustainability characterized by economic primacy, ecological viability and social green-engineering. This way of discursive evolution, however, is a double-edged sword that has pushed forward some fast, top-down mitigation measures on the one hand, but has also created and will likely continue creating social and ecological havoc on the other hand. The study makes two major contributions. First and on the empirical level, because China is an international actor that was not expected to cooperate on the climate issue according to major IR theories, this study would add one critical case to the studies on global (environmental) governance and the ideational approach in the IR discipline. Second and on the theory-building level, the model of discursive hegemony can be a causally deeper mode of explanation because it traces the process of co-evolution of social forces.

Potential Adverse Effects of the Alaska Natural Gas Pipeline on Arctic Caribou and Proposed Mitigation

The Alaska Natural Gas Pipeline (ANGP) is proposed for construction on the North Slope in 2016. It will be aligned through Arctic caribou habitat and evidence shows that caribou are negatively affected by human development. This Capstone identifies potential adverse affects of ANGP on Arctic caribou using interviews from expert caribou biologists and the 1977 Trans-Alaska Pipeline System (TAPS) as a model. Based on a synthesis of the interviews and TAPS analysis, this capstone proposes and examines a set of seventeen conservation measures to be implemented during construction and operation of ANGP to minimize adverse impacts on caribou herds. These conservation measures can be used as a baseline for future developments on the North Slope to promote caribou herd management.

The role of authenticity in tourism planning: empirical findings from southeast Spain

Tourism is the main economic activity in many towns in the province of Alicante in southeast Spain and has turned this area into a paradigmatic example of mass tourism on the Mediterranean coast. Since the 1960s, the province's coastal towns have opted for a development model centred on what is known as 'residential tourism' or 'second-home tourism', with few exceptions, such as Benidorm. We wish to put forward the argument that the main social agents in the tourism sector have not perceived the 'search for authenticity' as a factor that may attract tourists to this area. To this end, we will start by reviewing critically the theoretical discourse about the role played by authenticity in the motivation of tourists. Then we will discuss some of the results obtained from empirical, qualitative research that included 37 in-depth interviews. As a guide for our empirical research, we use a model based on the stakeholder theory. The epistemological difficulties faced by researchers do not justify certain critical arguments that try to highlight the impossibility of operationalising essential concepts and approaches such as that of authenticity. Therefore, it is necessary that empirical research continues to delve into the sociological keys that determine the 'search for authenticity' in the tourists' experience.

Multi-agent system for control of robots inspired on the distributed activity and hormonal regulation of humans

Robotics is an emerging field with great activity. Robotics is a field that presents several problems because it depends on a large number of disciplines, technologies, devices and tasks. Its expansion from perfectly controlled industrial environments toward open and dynamic environment presents a many new challenges. New uses are, for example, household robots or professional robots. To facilitate the low cost, rapid development of robotic systems, reusability of code, its medium and long term maintainability and robustness are required novel approaches to provide generic models and software systems who develop paradigms capable of solving these problems. For this purpose, in this paper we propose a model based on multi-agent systems inspired by the human nervous system able to transfer the control characteristics of the biological system and able to take advantage of the best properties of distributed software systems. Specifically, we model the decentralized activity and hormonal variation.

Spectral BRDF-based determination of proper measurement geometries to characterize color shift of special effect coatings

A reduced set of measurement geometries allows the spectral reflectance of special effect coatings to be predicted for any other geometry. A physical model based on flake-related parameters has been used to determine nonredundant measurement geometries for the complete description of the spectral bidirectional reflectance distribution function (BRDF). The analysis of experimental spectral BRDF was carried out by means of principal component analysis. From this analysis, a set of nine measurement geometries was proposed to characterize special effect coatings. It was shown that, for two different special effect coatings, these geometries provide a good prediction of their complete color shift.

Turismo y negocio inmobiliario: la crisis de un modelo de desarrollo. Tres estudios de casos de Canadá, Argentina y España

La vinculación del negocio turístico-inmobiliario con las migraciones por amenidad o por estilos de vida tiende a incubar problemas de racionalidad que, además de los ligados a la falta de sustentabilidad ambiental, acaban por volver inviable la lógica socio-económica del proceso. Para ilustrar este argumento se propone una reflexión crítica basada en la experiencia de lo acontecido en tres regiones del mundo en las que el desarrollo del modo de producción inmobiliario -basado en la captación y promoción de los tipos de movilidad residencial orientados por la búsqueda de experiencias de ocio- ha promovido efectos regresivos en relación al desarrollo local: las áreas montañosas del Oeste de Canadá, la Norpatagonia, en Argentina, y el sudeste de España, con atención a la provincia de Alicante. El artículo indaga en la falta de sustentabilidad de un modelo de desarrollo basado en el negocio turístico-inmobiliario; al tiempo que identifica patrones comunes y diferencias entre los casos analizados.

μ-MAR: Multiplane 3D Marker based Registration for depth-sensing cameras

Many applications including object reconstruction, robot guidance, and. scene mapping require the registration of multiple views from a scene to generate a complete geometric and appearance model of it. In real situations, transformations between views are unknown and it is necessary to apply expert inference to estimate them. In the last few years, the emergence of low-cost depth-sensing cameras has strengthened the research on this topic, motivating a plethora of new applications. Although they have enough resolution and accuracy for many applications, some situations may not be solved with general state-of-the-art registration methods due to the signal-to-noise ratio (SNR) and the resolution of the data provided. The problem of working with low SNR data, in general terms, may appear in any 3D system, then it is necessary to propose novel solutions in this aspect. In this paper, we propose a method, μ-MAR, able to both coarse and fine register sets of 3D points provided by low-cost depth-sensing cameras, despite it is not restricted to these sensors, into a common coordinate system. The method is able to overcome the noisy data problem by means of using a model-based solution of multiplane registration. Specifically, it iteratively registers 3D markers composed by multiple planes extracted from points of multiple views of the scene. As the markers and the object of interest are static in the scenario, the transformations obtained for the markers are applied to the object in order to reconstruct it. Experiments have been performed using synthetic and real data. The synthetic data allows a qualitative and quantitative evaluation by means of visual inspection and Hausdorff distance respectively. The real data experiments show the performance of the proposal using data acquired by a Primesense Carmine RGB-D sensor. The method has been compared to several state-of-the-art methods. The results show the good performance of the μ-MAR to register objects with high accuracy in presence of noisy data outperforming the existing methods.

Kinetic Model for Micro Algae Cell Concentration and Size Distribution: Application to Nannochloropsis gaditana

The cell concentration and size distribution of the microalgae Nannochloropsis gaditana were studied over the whole growth process. Various samples were taken during the light and dark periods the algae were exposed to. The distributions obtained exhibited positive skew, and no change in the type of distribution was observed during the growth process. The size distribution shifted to lower diameters in dark periods while in light periods the opposite occurred. The overall trend during the growth process was one where the size distribution shifted to larger cell diameters, with differences between initial and final distributions of individual cycles becoming smaller. A model based on the Logistic model for cell concentration as a function of time in the dark period that also takes into account cell respiration and growth processes during dark and light periods, respectively, was proposed and successfully applied. This model provides a picture that is closer to the real growth and evolution of cultures, and reveals a clear effect of light and dark periods on the different ways in which cell concentration and diameter evolve with time.

Teaching as a fractal: from experience to model

The aim of this work is to improve students’ learning by designing a teaching model that seeks to increase student motivation to acquire new knowledge. To design the model, the methodology is based on the study of the students’ opinion on several aspects we think importantly affect the quality of teaching (such as the overcrowded classrooms, time intended for the subject or type of classroom where classes are taught), and on our experience when performing several experimental activities in the classroom (for instance, peer reviews and oral presentations). Besides the feedback from the students, it is essential to rely on the experience and reflections of lecturers who have been teaching the subject several years. This way we could detect several key aspects that, in our opinion, must be considered when designing a teaching proposal: motivation, assessment, progressiveness and autonomy. As a result we have obtained a teaching model based on instructional design as well as on the principles of fractal geometry, in the sense that different levels of abstraction for the various training activities are presented and the activities are self-similar, that is, they are decomposed again and again. At each level, an activity decomposes into a lower level tasks and their corresponding evaluation. With this model the immediate feedback and the student motivation are encouraged. We are convinced that a greater motivation will suppose an increase in the student’s working time and in their performance. Although the study has been done on a subject, the results are fully generalizable to other subjects.

Análise da qualidade de energia de um parque eólico com ligação à rede eléctrica

Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2016

The Labour Allocation Decisions of Farm Households: Defining a theoretical model. Factor Markets Working Paper No. 31, October 2012

This paper presents a theoretical model for the analysis of decisions regarding farm household labour allocation. The agricultural household model is selected as the most appropriate theoretical framework; a model based on the assumption that households behave to maximise utility, which is a function of consumption and leisure, and is subject to time and budget constraints. The model can be used to describe the role of government subsidies in farm household labour allocation decisions; in particular the impact of decoupled subsidies on labour allocation can be examined. Decoupled subsidies are a labour-free payment and as such represent an increase in labour-free income or wealth. An increase in wealth allows farm households to work less while maintaining consumption. On the other hand, decoupled subsidies represent a decline in the return to farm labour and may lead to a substitution effect, i.e., farmers may choose to substitute non-farm work for farm work. The theoretical framework proposed in this paper allows for the examination of these two conflicting effects.