Assessing Inconspicuous Smartphone Authentication for Blind People

As people store more personal data in their smartphones, the consequences of having it stolen or lost become an increasing concern. A typical counter-measure to avoid this risk is to set up a secret code that has to be entered to unlock the device after a period of inactivity. However, for blind users, PINs and passwords are inadequate, since entry 1) consumes a non-trivial amount of time, e.g. using screen readers, 2) is susceptible to observation, where nearby people can see or hear the secret code, and 3) might collide with social norms, e.g. disrupting personal interactions. Tap-based authentication methods have been presented and allow unlocking to be performed in a short time and support naturally occurring inconspicuous behavior (e.g. concealing the device inside a jacket) by being usable with a single hand. This paper presents a study with blind users (N = 16) where an authentication method based on tap phrases is evaluated. Results showed the method to be usable and to support the desired inconspicuity.Comment: 4 pages, 1 figur

Distributed learning of CNNs on heterogeneous CPU/GPU architectures

Convolutional Neural Networks (CNNs) have shown to be powerful classification tools in tasks that range from check reading to medical diagnosis, reaching close to human perception, and in some cases surpassing it. However, the problems to solve are becoming larger and more complex, which translates to larger CNNs, leading to longer training times that not even the adoption of Graphics Processing Units (GPUs) could keep up to. This problem is partially solved by using more processing units and distributed training methods that are offered by several frameworks dedicated to neural network training. However, these techniques do not take full advantage of the possible parallelization offered by CNNs and the cooperative use of heterogeneous devices with different processing capabilities, clock speeds, memory size, among others. This paper presents a new method for the parallel training of CNNs that can be considered as a particular instantiation of model parallelism, where only the convolutional layer is distributed. In fact, the convolutions processed during training (forward and backward propagation included) represent from $60$-$90$\% of global processing time. The paper analyzes the influence of network size, bandwidth, batch size, number of devices, including their processing capabilities, and other parameters. Results show that this technique is capable of diminishing the training time without affecting the classification performance for both CPUs and GPUs. For the CIFAR-10 dataset, using a CNN with two convolutional layers, and $500$ and $1500$ kernels, respectively, best speedups achieve $3.28\times$ using four CPUs and $2.45\times$ with three GPUs. Modern imaging datasets, larger and more complex than CIFAR-10 will certainly require more than $60$-$90$\% of processing time calculating convolutions, and speedups will tend to increase accordingly

Seguimento de pessoas com drones em espaços inteligentes

Recent technological progress made over the last decades in the field of Computer Vision has introduced new methods and algorithms with ever increasing performance results. Particularly, the emergence of machine learning algorithms enabled class based object detection on live video feeds. Alongside these advances, Unmanned Aerial Vehicles (more commonly known as drones), have also experienced advancements in both hardware miniaturization and software optimization. Thanks to these improvements, drones have emerged from their military usage based background and are now both used by the general public and the scientific community for applications as distinct as aerial photography and environmental monitoring. This dissertation aims to take advantage of these recent technological advancements and apply state of the art machine learning algorithms in order to create a Unmanned Aerial Vehicle (UAV) based network architecture capable of performing real time people tracking through image detection. To perform object detection, two distinct machine learning algorithms are presented. The first one uses an SVM based approach, while the second one uses an Convolutional Neural Network (CNN) based architecture. Both methods will be evaluated using an image dataset created for the purposes of this dissertation’s work. The evaluations performed regarding the object detectors performance showed that the method using a CNN based architecture was the best both in terms of processing time required and detection accuracy, and therefore, the most suitable method for our implementation. The developed network architecture was tested in a live scenario context, with the results showing that the system is capable of performing people tracking at average walking speeds.O recente progresso tecnológico registado nas últimas décadas no campo da Visão por Computador introduziu novos métodos e algoritmos com um desempenho cada vez mais elevado. Particularmente, a criação de algoritmos de aprendizagem automática tornou possível a detecção de objetos aplicada a feeds de vídeo capturadas em tempo real. Paralelo com este progresso, a tecnologia relativa a veículos aéreos não tripulados, ou drones, também beneficiaram de avanços tanto na miniaturização dos seus componentes de hardware assim como na optimização do software. Graças a essas melhorias, os drones emergiram do seu passado militar e são agora usados tanto pelo público em geral como pela comunidade científica para aplicações tão distintas como fotografia e monitorização ambiental. O objectivo da presente dissertação pretende tirar proveito destes recentes avanços tecnológicos e aplicar algoritmos de aprendizagem automática de última geração para criar um sistema capaz de realizar seguimento automático de pessoas com drones através de visão por computador. Para realizar a detecção de objetos, dois algoritmos distintos de aprendizagem automática são apresentados. O primeiro é dotado de uma abordagem baseada em Support Vector Machine (SVM), enquanto o segundo é caracterizado por uma arquitetura baseada em Redes Neuronais Convolucionais. Ambos os métodos serão avaliados usando uma base de dados de imagens criada para os propósitos da presente dissertação. As avaliações realizadas relativas ao desempenho dos algoritmos de detecção de objectos demonstraram que o método baseado numa arquitetura de Redes Neuronais Covolucionais foi o melhor tanto em termos de tempo de processamento médio assim como na precisão das detecções, revelando-se portanto, como sendo o método mais adequado de acordo com os objectivos pretendidos. O sistema desenvolvido foi testado num contexto real, com os resultados obtidos a demonstrarem que o sistema é capaz de realizar o seguimento de pessoas a velocidades comparáveis a um ritmo normal humano de caminhada.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

La modernidad y la contemporaneidad en diálogo con el patrimonio: La vida de dos espacios de culto en Lisboa: la iglesia de Santa Isabel y la capilla do Rato

Since the 1960s, the artistic and architectural interventions carried out in the church of Santa Isabel and Rato Chapel, in Lisbon, brought to the debate the overlap of different narratives in these two different spaces of worship: the first, is a parish church preserved by the earthquake of Lisbon (1755), which had its liturgical space redesigned before the Second Vatican Council; the second, is a private chapel annexed to a 18th century palace that became a symbolic worship space for students and engaged young professionals since the 1970s. Enriched with the work of either well-known artists or, sometimes, anonymous architects, the two case studies show us the life of monuments, where Modern and Contemporary Art and Architecture participate in preserving and enhancing their cultural value. At the same time, the liturgical and pastoral activities are shown to be the engine behind successive interventions.Desde la década de 1960, las intervenciones artísticas y arquitectónicas realizadas en la iglesia de Santa Isabel y la capilla do Rato, en Lisboa, trajeron al debate la superposición de diferentes narrativas en estos dos diferentes espacios de culto: el primero es una iglesia parroquial que sobrevivió al terremoto de Lisboa (1755), cuyo espacio litúrgico se rediseñó antes del Concilio Vaticano II; la segunda es una capilla privada anexa a un palacio del siglo XVIII que se convirtió en un espacio de culto simbólico para estudiantes y jóvenes profesionales comprometidos a partir de la década de 1970. Enriquecidos con el trabajo de artistas conocidos, o a veces, de arquitectos anónimos, los dos estudios de caso nos muestran la vida de los monumentos, donde el arte y la arquitectura moderna y contemporánea participan en la preservación y mejora de su valor cultural. Al mismo tiempo, se muestra que las actividades litúrgicas y pastorales son el motor de las sucesivas intervenciones

Distribution-Based Categorization of Classifier Transfer Learning

Transfer Learning (TL) aims to transfer knowledge acquired in one problem, the source problem, onto another problem, the target problem, dispensing with the bottom-up construction of the target model. Due to its relevance, TL has gained significant interest in the Machine Learning community since it paves the way to devise intelligent learning models that can easily be tailored to many different applications. As it is natural in a fast evolving area, a wide variety of TL methods, settings and nomenclature have been proposed so far. However, a wide range of works have been reporting different names for the same concepts. This concept and terminology mixture contribute however to obscure the TL field, hindering its proper consideration. In this paper we present a review of the literature on the majority of classification TL methods, and also a distribution-based categorization of TL with a common nomenclature suitable to classification problems. Under this perspective three main TL categories are presented, discussed and illustrated with examples

Characterizing the timing behaviour of power-line communication by means of simulation

Although power-line communication (PLC) is not a new technology, its use to support communication with timing requirements is still the focus of ongoing research. Recently, a new infrastructure was presented, intended for communication using power lines from a central location to geographically dispersed nodes using inexpensive devices. This new infrastructure uses a two-level hierarchical power-line system, together with an IP-based network. Within this infrastructure, in order to provide end-toend communication through the two levels of the powerline system, it is necessary to fully understand the behaviour of the underlying network layers. The masterslave behaviour of the PLC MAC, together with the inherent dynamic topology of power-line networks are important issues that must be fully characterised. Therefore, in this paper we present a simulation model which is being used to study and characterise the behaviour of power-line communication.C

REMPLI discreet event simulation results

This document makes a brief review on the results of the REMPLI Discreet Event Simulation system used to test the REMPLI Transport Layer. An introduction on the REMPLI Discreet Event Simulation system is made on HURRAY-TR-070903

A evolução da Previdência Social em perspectiva comparada: 1935-1974

Mestrado em Governação, Competitividade e Políticas PúblicasEste trabalho pretendeu analisar a importância e o contributo do sistema português de Previdência Social no processo de institucionalização do Estado Social em Portugal, e compreender a evolução da Previdência Social através de uma comparação com o contexto internacional. Para efectuar essa comparação recorreu-se à análise da evolução e composição da despesa social em percentagem do Produto Interno Bruto. O período histórico analisado inicia-se em 1935, com a criação da Previdência Social, e termina em 1974, com o fim do Estado Novo. Com base nos elementos e dados recolhidos foi possível tirar algumas conclusões acerca da importância da Previdência Social na institucionalização do actual Estado Social português, nomeadamente na configuração do sistema português de segurança social desenvolvido a partir de 1974. Como resultados mais relevantes, concluiu-se que: em primeiro lugar, o Estado desempenhou o principal papel na institucionalização do Estado Social em Portugal; em segundo lugar, a génese do actual Estado Social português começou durante o período do Estado Novo, assim, Portugal começou a construir um sistema de protecção social embora com algum atraso em relação à realidade existente nesse domínio na maioria dos países desenvolvidos; em terceiro lugar, a evolução da despesa social ao longo do Estado Novo apresenta uma tendência crescente dos valores de despesa social, mas o sistema de Previdência Social nunca se transformou num sistema moderno de segurança social nem chegou próximo dos níveis de despesa social existentes na maioria dos países desenvolvidos.This work analyses the relevance and the contribution of the portuguese social protection system called Previdência Social in the implementation process of the Welfare State in Portugal, and attempts to understand the evolution of Previdência Social in the international context. To this effect, the comparison is focused on the evolution and composition of social expenditure relative to GDP. The historical period analyzed begins in 1935 when the social protection scheme called Previdência Social was created and ends in 1974 with the demise of the Estado Novo regime. The research allowed some conclusions about the relevance of Previdência Social to the configuration of the Social Security system and the Welfare State in Portugal. The most relevant conclusions are: first, the state played the main role in the implementation of the Welfare State in Portugal; second, the origins of the current portuguese Welfare State began during the Estado Novo period; third, the evolution of social expenditure during Estado Novo presents a growth trend divided into three periods, but the Previdência Social system never changed into a modern social security system neither did it reach the social expenditure levels of welfare systems in most developed countries