Measurement of the average electromagnetic longitudinal shower profile at the Pierre Auger Observatory

In addition to the standard X$_{max}$ and energy, the longitudinal profiles of extensive air showers contain some more interesting information. For energies above 10$^{17:8}$ eV, we present the average profiles as a function of atmospheric depth measured for the first time at the Pierre Auger Observatory. The profile shapes for different energy ranges are all well reproduced by a Gaisser- Hillas function within the range studied. A detailed analysis of the systematic uncertainties is performed using data and a full detector simulation, and the results are compared with predictions of hadronic interaction models for different primaries.Peer Reviewe

Analyzing the senior consumers’ attitude toward advertising: traditional and new media

Senior consumers have received limited attention from researchers and practitioners. Therefore, advertising managers become reliant on limited research and standing stereotypes to set their strategies. At the same time, more and more people start spending more time in later adulthood than in any other traditional marketing life stage. These senior consumers are healthier and wealthier than their ancestors were at their age. This reality is not exclusive to western countries, in fact in a few years this aging of the population will take over many of the current stars of economic growth: Places like China and South Korea also face serious population aging. This dissertation focuses on the perceptions of seniors about ads presented on the new media. Two studies were conducted to explore the way senior consumers perceive ads presented on TV (traditional media) and YouTube (new media), the first study was a experiment conducted in a senior university which gathered 107 observations, and the second a focus group interview. Firstly, it was discovered that seniors seem to be more efficient at avoiding ads on TV than on YouTube; secondly it was found that due to the different ways and purposes seniors use TV and YouTube for, ads presented on YouTube may cause more irritation than on TV; thirdly it was learnt that skepticism toward advertising messages may be higher for ads presented on YouTube than on TV; finally, it was also discovered that for seniors, attitude toward advertising does not seem to vary across different media.Os consumidores seniores têm recebido pouca atenção por parte de investigadores e gestores de publicidade. Este facto leva a que os gestores a desenharem estratégias tendo por base um número limitado de estudos e estereótipos. Por outro lado, um número cada vez maior de pessoas vive mais tempo no fim da fase adulta da sua vida. Os consumidores seniores da atualidade são mais saudáveis e mais abastados do que os seus antepassados eram com a mesma idade. Esta realidade não é exclusiva do mundo ocidental, em poucos anos o envelhecimento da população irá afetar as atuais estrelas do crescimento económico: lugares como a China e a Coreia do Sul também enfrentam um grave envelhecimento da população. Esta dissertação foca-se nas perceções dos seniores acerca de publicidade apresentada nos novos meios de comunicação social. Dois estudos foram efetuados para determinar a maneira como os consumidores seniores percecionam anúncios apresentados na TV e no YouTube; o primeiro estudo foi um experimento efetuado numa universidade sénior que resultou em 107 observações, e o segundo um focus group interview. Quatro descobertas foram feitas: primeiro, descobriu-se que os seniores tendem a ser mais eficientes a evitar anúncios na TV do que no YouTube; segundo, descobriu-se que os anúncios apresentados no YouTube poderão ser mais irritantes para os seniores do que os apresentados na TV; terceiro, descobriu-se que o ceticismo em relação às mensagens publicitárias pode ser maior para anúncios apresentados no YouTube do que na TV; e, finalmente, descobriu-se que para os seniores a atitude em relação à publicidade não varia para diferentes media

An architecture to generate classified datasets and improve performance of intrusion detection systems

Mestrado em Ciberseguran?a na Escola Superior de Tecnologia e Gest?o do Instituto Polit?cnico de Viana do CasteloNowadays, a set of services are available online with various associated data. It is essential to ensure the availability, integrity and confidentiality of all data. However, cyberattacks are a major threat. In this sense, an Intrusion Detection System (IDS) is an important tool to prevent potential threats to systems and data. It is necessary to implement new mechanisms with intelligence to successfully defend the complexity and intelligence of attacks, that is, to increase their efficiency. Anomaly-based IDSs may deploy machine learning algorithms to classify events either as normal or anomalous and trigger the adequate response. When using supervised learning, these algorithms require classified, rich, and recent datasets. Thus, to foster the performance of these machine learning models, datasets can be generated from different sources in a collaborative approach, and trained with multiple algorithms. This document proposes a vote-based architecture to generate classified datasets and improve performance of supervised learning-based IDSs. In a regular basis, multiple IDSs in different locations (companies) send their logs to a central system that combines and classifies them using different machine learning models and a majority vote system. Then, it generates a new and classified dataset, which is trained to obtain the best updated model to be integrated into the IDS of the companies involved. In this way, intrusion detection systems are frequently updated with the best machine learning model to increase their efficiency. The proposed architecture trains multiple times with several algorithms and, to shorten the overall runtimes, the proposed architecture was deployed in Fed4FIRE+, a federated testbed, with Ray to distribute the tasks by the available resources. This implementation allowed a reduction of the time in the classification between 31% and 33%, and in the training time of 43%. A set of machine learning algorithms and the proposed architecture were assessed. When compared with a baseline scenario, the proposed architecture enabled to increase the accuracy by 11.5% and the precision by 11.2%

The portuguese judicial system : descriptive enquiry on problems faced and a model for productivity

Mestrado em Economia Monetária e FinanceiraEsta tese pretende estudar o sistema judicial Português, em particular a produtividade judicial dos tribunais Portugueses. O trabalho divide-se em duas grandes áreas. Primeiro, oferece uma visão sobre o estado do sistema judicial Português e oferece uma narrativa sobre as razões que levam o sistema judicial Português a ser visto como um bloqueio ao desenvolvimento económico em Portugal. Na segunda parte do trabalho é desenvolvido um modelo econométrico que ajude a explicar a produtividade judicial. O principal contributo da segunda parte do trabalho para a literatura é a capacidade de resolver problemas de endogeneidade não estudados em trabalhos anteriores.There seems to be a wide agreement in Portuguese society that the legal system is one of the main structural problems and one reason for the anemic economic growth experienced in recent years. The objective of this paper is twofold. First, it offers a view on the state of the Portuguese judicial system over the past two decades and contributes with a perspective on the reasons Portuguese justice can be perceived as a roadblock on economic development. Second, it goes further and tries to explore potential answers by constructing na econometric model that connects judge?s productivity with its potential determinants. Furthermore, this econometric model also deals with endogeneity issues not dealt with in similar studies

The foster family process to maintain the will to remain in foster care — implications for a sustainable programme

There were 7032 children in out-of-home care in 2018 in Portugal. Of these, only 2.8% were in foster care, despite this being the recommended response according to legal regulations. It is critical that more families be encouraged to become foster carers and also that experienced carers stay in the system to create a sustainable programme. How is the will to foster a child maintained? What can we learn from foster families’ experiences to improve childcare and the child protection system? The methodology of this study was based on interviews with foster carers. The analysis was inspired by grounded theory. We found three types of foster families, classified according to their will to leave or remain in foster care—unconditional, hesitant, or retired. The results suggest that the key elements for foster carers to remain in the foster care system are (i) their level of satisfaction with how the previous placement concluded, (ii) keeping in touch with the ex-foster child, (iii) the feeling of acknowledgement by all the stakeholders, and (iv) the quality of social services as well as the support of the professional teams.info:eu-repo/semantics/publishedVersio

Implied volatility as a forecast for future volatility : evidence from european market

Mestrado em FinançasO objetivo principal deste estudo é o de testar se a Volatilidade Implicita em instrumentos financeiros, nomeadamente Opções financeiras, é um estimador preciso da Volatilidade Futura. Os dados usados dizem respeito ao Índice Euro Stoxx 50, mais concretamente cotações de fecho e Volatilidade Implicita em opções ATM com um mês até à maturidade, o que permite conduzir uma análise ao mercado Europeu. A amostra selecionada cobre o periodo de Janeiro de 2002 a Abril de 2012. Os testes realizados permitiram-nos concluir que a Volatilidade Implicita pode ser considerada um estimador centrado e eficiente para a Volatilidade Futura e ainda, que contém mais capacidade explicativa quando comparada com a Volatilidade Histórica, o que pode ser uma indicação de Eficiência de Mercado.The main purpose of this master thesis is test whether implied volatility is an accurate estimator for future volatility. We collect data regarding to the Euro Stoxx 50 index, namely closing index prices and implied volatility from one-month ATM options, in order to conduct an analysis of the European Market. The Sample selected covers the period from January 2002 to April 2012. The tests conducted allow us to conclude that implied volatility can be considered an unbiased and efficient estimator for future volatility and also that has more predictive ability than historical volatility, which is an indication of market efficiency

Approaching the Optimal Performance of Nonlinear OFDM With FWA Techniques

Telecommunications are part of people’s daily lives. Also, nowadays, a complete "technological illiteracy" is hard to be found in the so-called developed countries. To the point of being almost a necessity in everyday life, telecommunications must evolve to meet this need. One of the most widely used transmission techniques in mobile communications today is Orthogonal Frequency-Division Multiplexing (OFDM). Adopted in the fourth generation of mobile communications (4G), much for its ability to deal with frequency-selective channels and good spectral efficiency, it is one of the candidate schemes to be in the fifth generation of mobile communications (5G). Despite the advantages, OFDM signals have high envelope fluctuations, making them sensitive to nonlinear effects. Several techniques were proposed to reduce these fluctuations, however they required nonlinear operations that worsened the performance of receivers. Nevertheless, it has recently been shown that the distortion effects caused by nonlinearity is no longer seen as a problem, but as information. In fact, with this discovery, it becomes possible to employ optimal receivers in order to improve the performance. Despite that, these receivers have a very high complexity and, to try to solve this problem, sub-optimal receivers have been proposed. The sub-optimal receiver presented in this thesis is based on an optimization algorithm called Fireworks Algorithm (FWA). The thesis includes: a study of the parameters of the algorithm in order to understand its true impact on Bit Error Rate (BER) performance; a comparison of the BER for different channels: Additive White Gaussian Noise (AWGN) and Frequency-Selective; and a proposal for an FWA variant that tries to reduce the receiver’s complexity even more

3D Printing of Nanoreinforced Pectin-Based Hydrogels with Tunable Flow Properties for Bone Regeneration

Hydrogels have proved to be highly attractive biocompatible materials which can be used for tissue engineering applications. Among the hydrogels, Polysaccharides due to their superior mechanical properties, stability, and resemblance of the native extracellular bone matrix (ECM) are appealing to use as cell-based regenerative therapy. To impart complex 3-dimensional architectural features, printing methodology is a versatile approach due to its capability to fabricate customizable scaffolds. Pectin stands out since its solubility can be more easily modulated compared with the other natural polymers. One of the big burdens in this regard is that the lack of multifunctional printable materials which can resemble ECM of bone tissue. In order to make pectin printable for bone tissue engineering, nanosilicates can be used to modify the flow behavior of pectin. Moreover, nanosilicates provide osteogenic properties, mechanical reinforcement, and triggering of cell phenomena, making up for the absence of such properties in polysaccharides. Here, we hypothesized that the incorporation of laponite (LAP) nanosilicates within methacrylated-pectin (PEMA) enhance the shape fidelity and mechanical properties. Therefore, pectin was modified through a methacrylation process creating a UV-crosslinkable methacrylated-pectin (PEMA) hydrogel. Polymer concentration was kept unchanged while laponite amount was tuned in order to study its influence on disc-shaped scaffolds and to define a printability window. Using an extrusion-based process, the compositions of PEMA/LAP were printed and their printability properties quantified and a detailed study on the rheological properties of the PEMA/LAP hydrogels was conducted. Remarkably, elastic modulus in the range of 8-48 kPa were obtained, which is ideal to promote osteogenesis. Rheological properties, as well as mechanical properties, confirmed the existence of a saturation limit for LAP, from which scaffolds properties deteriorate. This nanocomposite platform highlights the potential of printed PEMA/LAP for bone tissue engineering, proposing a 3D-printable, low cost, tunable, biocompatible and highly promising alternative in this field

A Study of the Magnetic Field inside the Discharge Chamber of an Ion Thruster

One of the characteristics that ion thrusters are known for is its high efficiency.  In the process of designing an ion thruster the study of the magnetic field alongside the discharge chamber is crucial to achieve optimal efficiency. This work shows the importance of taking into consideration the materials in the vicinities of the magnets as well as the expected intensity of the magnetitic field inside the thrusters in study. The procedures used to study the magnetic field in the open software used are described in this work. The thruster in study is an oversizing done of a previous one, so the desired results are to obtain the ones obtained for the original engine. Keywords: Ion thruster, High efficiency, Magnetic fiel