A comment on "The effect of a common currency on the volatility of the extensive margin of trade"

In this paper I comment on Auray, Eyquem, and Pontineau (2012). I show that their introduction of sticky-prices into Ghironi \& Melitz (2005) framework is incorrect and generates a bias in simulation results. Additionally, I find that, by introducing sticky-prices into Ghironi \& Melitz (2005) framework in a correct way, the model is able to account for the empirical findings of Auray, Eyquem, and Pontineau (2012). Finally, I also find that if central banks target a data-consistent CPI inflation, results improve quantitatively.Pricing-to-market; Local currency pricing; Extensive Margin; Monetary Union; Monetary Policy

A logic for n-dimensional hierarchical refinement

Hierarchical transition systems provide a popular mathematical structure to represent state-based software applications in which different layers of abstraction are represented by inter-related state machines. The decomposition of high level states into inner sub-states, and of their transitions into inner sub-transitions is common refinement procedure adopted in a number of specification formalisms. This paper introduces a hybrid modal logic for k-layered transition systems, its first-order standard translation, a notion of bisimulation, and a modal invariance result. Layered and hierarchical notions of refinement are also discussed in this setting.Comment: In Proceedings Refine'15, arXiv:1606.0134

Técnicas para avaliação e minimização de acoplamento em sistemas de agregados de antenas

The evolution of modern MIMO systems has led them to increasingly operate at frequencies around millimeter waves in the search for greater bandwidth, as well as in the search for greater antenna gains, and beamforming or spatial filtering capabilities. For this, the high density of antennas in a short space alerts to the appearance of undesirable phenomena, such as the mutual coupling between the elements, which degrade the performance of these systems, making it necessary to find techniques to minimize this effect. In this dissertation, this problem was analyzed, and solutions are presented that allow the reduction of this negative effect in antenna aggregates. In this sense, two printed structures were developed, with properties associated with metamaterials, one in the shape of a U and the other with a variation resulting from the joining of two rings. Subsequently, a comparative study was carried out in simulation of the impact of the two structures in different situations (with patch antennas calibrated to 8.4GHz), finally the results obtained by simulation were compared with the measurements obtained in the laboratory for arrays of 4 elements with and without the U-shaped metamaterials, and the effect of these structures on the array was analysed.A evolução dos sistemas MIMO modernos tem levado estes a operar cada vez mais em frequências em torno de ondas milimétricas na procura de maiores larguras de banda, assim como na procura por maiores ganhos das antenas, e capacidade de beamforming ou filtragem espacial. Para isso, essa elevada densidade de antenas num curto espaço alerta para o aparecimento de fenómenos indesejáveis, como são o acoplamento mútuo entre os elementos, que degradam a performance destes sistemas, tornando-se necessário encontrar técnicas para minimizar esse efeito. Nesta dissertação esta problemática foi analisada, e são apresentadas soluções que possibilitam a redução deste efeito negativo em agregados de antenas. Nesse sentido, foram desenvolvidas duas estruturas impressas, com propriedades associadas aos metamateriais, propriedades estas que têm ganho bastante relevo nas últimas décadas na melhoria de sistemas MIMO em vários aspetos, uma em forma de U e outra com uma variação resultante da junção de dois anéis. Posteriormente foi feito um estudo comparativo em simulação do impacto das duas estruturas em diferentes situações (estando as antenas patch calibradas para 8.4GHz), sendo finalmente comparados os resultados obtidos por simulação com as medidas obtidas em laboratório para arrays de 4 elementos com e sem os metamateriais em forma de U e analisou-se o efeito destas estruturas no agregado.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Refinement by interpretation in {\pi}-institutions

The paper discusses the role of interpretations, understood as multifunctions that preserve and reflect logical consequence, as refinement witnesses in the general setting of pi-institutions. This leads to a smooth generalization of the refinement-by-interpretation approach, recently introduced by the authors in more specific contexts. As a second, yet related contribution a basis is provided to build up a refinement calculus of structured specifications in and across arbitrary pi-institutions.Comment: In Proceedings Refine 2011, arXiv:1106.348

The Effect of Recency to Human Mobility

In recent years, we have seen scientists attempt to model and explain human dynamics and, in particular, human movement. Many aspects of our complex life are affected by human movements such as disease spread and epidemics modeling, city planning, wireless network development, and disaster relief, to name a few. Given the myriad of applications it is clear that a complete understanding of how people move in space can lead to huge benefits to our society. In most of the recent works, scientists have focused on the idea that people movements are biased towards frequently-visited locations. According to them, human movement is based on an exploration/exploitation dichotomy in which individuals choose new locations (exploration) or return to frequently-visited locations (exploitation). In this work, we focus on the concept of recency. We propose a model in which exploitation in human movement also considers recently-visited locations and not solely frequently-visited locations. We test our hypothesis against different empirical data of human mobility and show that our proposed model is able to better explain the human trajectories in these datasets

Object detection with artificial vision and neural networks for service robots

Dissertação de mestrado em Engenharia Eletrónica Industrial e ComputadoresThis dissertation arises from a major project that consists on developing a domestic service robot, named CHARMIE (Collaborative Home Assistant Robot by Minho Industrial Electronics), to cooperate and help on domestic tasks. In general, the project aims to implement artificial intelligence in the whole robot. The main contribution of this dissertation is the development of the vision system, with artificial intelligence, to classify and detect, in real time, the objects represented on the environment that the robot is placed. This dissertation is within two broad areas that revolutionized the robotics industry, namely the artificial vision and artificial intelligence. Knowing that most of the existent information is presented on the vision and with the evolution of robotics, there was a need to introduce the capacity to acquire and process this kind of information. So, the artificial vision algorithms allowed them to acquire information of the environment, namely patterns, objects, formats, through vision sensors (cameras). Although implementing artificial vision can be very complex if it is intended to detect objects, due to image complexity. The introduction of artificial intelligence, more precisely, deep learning, brought the capability of implementing systems that can learn from provided data, without the need of hard coding it, reducing slightly the complexity and the time consumption of implementing complex problems. For artificial vision problems, like this project, there is a deep neural network that is specialized in learning from three dimensional vectors, namely images, named Convolutional Neural Network (CNN). This network uses image data to learn patterns, edges, formats, and many more, that represents a certain object. This type of network is used to classify and detect the objects presented in the image provided by the camera and is implemented with the Tensorflow library. All the image acquisition from the camera is performed by the OpenCv library. At the end of the dissertation, a model that allows real-time detection of objects from camera images is provided

Otimização do teor de corte e do sequenciamento de minas subterrâneas

Orientador: Priscila Cristina Berbert RampazzoDissertação (mestrado profissional) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação CientíficaResumo: Métodos de lavra subterrânea são aplicados na extração de vários metais e minerais. O planejamento de métodos subterrâneos difere do planejamento de métodos de superfície pelo fato de que não é necessário extrair todas as áreas de produção dentro dos limites econômicos finais para se ter uma sequência factível, ou seja, nos métodos subterrâneos é fisicamente possível que algumas áreas permaneçam não lavradas mesmo estando dentro do limites econômicos finais. O planejamento estratégico é a área central do planejamento de longo prazo de uma mina e visa definir estratégias de escala de produção, métodos de lavra e de beneficiamento mineral, selecionar as áreas que serão lavradas e otimizar a sequência de lavra destas áreas de produção. Para garantir a viabilidade econômica do empreendimento, o planejamento estratégico deve considerar as características-chave dos empreendimentos de mineração, que são: a necessidade de capital intensivo, o longo período de retorno do investimento e o ativo (reserva) limitado. Essas características devem ser consideradas durante o processo de valoração de um empreendimento mineiro, que normalmente é feito através do cálculo do VPL, valor presente líquido. Dentre as principais alavancas do planejamento estratégico, o teor de corte utilizado na seleção dos blocos que serão lavrados e o sequenciamento de mina são os que geram maior número de opções, fazendo com que avaliações de cenários demandem muito tempo e se tornem inviáveis na prática dada a necessidade de respostas rápidas para tomadas de decisão. Neste trabalho, três diferentes modelos matemáticos são propostos para abordar, de forma conjunta, o problema da seleção dos blocos de lavra de uma mina subterrânea e a otimização do sequenciamento destes blocos. Tais modelos consideram o VPL como principal objetivo a ser maximizado e resultam no uso do teor de corte como fator que equilibra as capacidades de produção dos diferentes estágios de um sistema de mineração. A abordagem matemática adapta a modelagem clássica de problemas de sequenciamento considerando os blocos de lavra como tarefas e as atividades de escavação de galerias (desenvolvimento de acessos) e de produção de minério (lavra) como máquinas. Os modelos propostos são testados com base em casos reais, utilizando-se métodos de solução exata e um algoritmo genético. Os resultados computacionais mostram que o algoritmo genético é mais eficiente do que os métodos exatos, sobretudo para instâncias maiores, mais próximas da realidadeAbstract: Underground mining methods are used at the extraction of many metals and minerals. Underground mining planning differs from surface mining planning mainly because, in the first case, it is not necessary to extract all mining blocks within the ultimate economic limits to have a feasible sequence, i.e., it is physically possible to an underground mine to have some areas left \textit{in situ} even if they are inside the ultimate economic limits. Strategic planning is the core area of long-term mining planning and aims to define the scale of production, mining and processing methods, to select areas that will be mined, and to optimize the mining sequence. To guarantee the economic feasibility of a mining asset, strategic planners must also consider the key aspects of mining businesses, which are: capital-intensive requirements, long-term payback, and limited asset (reserves) life. These characteristics must be considered during the valuation process of a mining asset, which is normally conducted through NPV, net present value, calculations. Among the main strategic planning levers, cut-off grades (used at the selection of blocks that will be mined) and the mine sequencing are the ones that generate the greatest number of options. As scheduling multiple scenarios requires a great deal of time, this is infeasible in real situations given the need for quick responses. In this dissertation, three mathematical models are proposed to tackle, at the same time, two problems: the selection of the mining blocks in an underground mine, and the optimization of their sequence. These models consider NPV as the main objective to be maximized and result in using cut-off grades as a factor that balances the main capabilities of a mining system. The mathematical approach adapts classical scheduling models considering mining blocks as jobs; and tunnels excavation (access development) and ore production (mining) activities as machines. The proposed models are tested, with real cases, using exact-solution methods and a genetic algorithm. Results show that the genetic algorithm is more efficient than the exact methods, especially for greater instances that are similar to real problemsMestradoMatematica Aplicada e ComputacionalMestre em Matemática Aplicada e Computaciona