Modelagem computacional para Avaliação da Age of Information (AoI) em sistemas ciberfísicos

Dissertação (Mestrado Profissional em Computação Aplicada) — Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, Brasília, 2022.A Age of Information (AoI) é um conceito que define métricas relacionadas ao grau de atualização que um monitor possui em relação a uma ou mais fontes de informação, as quais enviam pacotes sequenciais de atualização. O presente estudo propõe a utilização da AoI para a avaliação e otimização de um Sistema Ciberfísico (SCF) caracterizado como um sistema de monitoramento e decisão no contexto da atividade de comando e controle (C2) militar. Nesse tipo de sistema, agentes enviam periodicamente suas posições georreferenciadas para um centro de operações e os cenários de uso podem ter diferentes graus de criticidade. Para atingir esse objetivo, este trabalho desenvolveu um modelo computacional para cálculo da Age of Information (AoI), o qual foi usado como base para a implementação de uma ferramenta de simulação. Além da referida ferramenta, este trabalho contribuiu para a melhoria das atuais técnicas de gerenciamento de pacotes para a otimização da AoI, ao propor duas novas técnicas: a Last Generated - First Served - Conditional (LGFS-C), para modelos de uma fonte e um servidor e a Max Age First - Last Generated - First Served - Multiple preemption in Waiting (MAF-LGFS-MW), para modelos de múltiplas fontes e múltiplos servidores. Ambas as técnicas, quando avaliadas, mostraram resultados iguais ou melhores do que as atuais técnicas no estado da arte, a depender dos parâmetros do modelo. Como última contribuição, o trabalho aplica uma metodologia de avaliação com o uso da ferramenta desenvolvida em três tipos de cenários de uso, em que é demonstrado o uso das simulações para melhorar o dimensionamento da infraestrutura em função dos requisitos de desempenho.Age of Information (AoI) is a concept that defines a metric related to the degree of update that a monitor has in relation to one or more information sources, which send sequential update packets. The present study proposes the use of AoI to evaluate and optimize a Cyber Physical System characterized as a monitoring and decision-making system in the context of military command and control (C2) activity. In this type of system, agents periodically send their georeferenced positions to an operations center and common scenarios may have different degrees of criticality. To achieve this goal, this work developed a computational model to calculate the Age of Information (AoI), which was used as a basis for the implementation of a simulation tool. In addition to the aforementioned tool, this work contributed to the improvement of current package management techniques for the optimization of AoI, by proposing two new techniques: Last Generated - First Served - Conditional (LGFS-C ), for single-source, single-server models, and Max Age First - Last Generated - First Served - Multiple preemption in Waiting (MAF-LGFS-MW), for multiple-source, multiple-server models. Both techniques, when evaluated, showed results equal or better than current state of the art techniques, depending on the model parameters. As a last contribution, this research applies an evaluation methodology, using the developed tool and AoI in three types of critical scenarios, in which the use of the tool is demonstrated to improve the infrastructure planning according to performance requirements

Influence of Urbanization on the Dynamics of the Urban Vegetation Coverage Index (VCI) in Erechim (RS)

ABSTRACT Vegetation fragments located in urban perimeters provide better environmental conditions for biological diversity and human well-being. The aim of this study was to evaluate the Vegetation Coverage Index (VCI) of the urban perimeter of Erechim, RS, between years 2010 and 2015. Mapping was carried out using World View 2 and Pleiades satellites images with spatial resolution of 0.5 m. Significant difference was found between VCI values of 2010 and 2015, as well as a decrease in the recommended rate in the range of 30% per neighborhood. Due to the influence of increased urbanization, there was reduction of 229.98 hectares in the vegetation coverage area of the urban perimeter during the study period. The expansion of urban areas reduced vegetation fragments and has contributed in an effective manner to the disordered occupation of the city, generating negative impacts to the environment and to the quality of life of the local population

A novel approach based on X-ray fluorescence and photon attenuation to the analysis of soils for forensic investigation

Use of soil in forensic science is related to its several chemical, physical, and biological properties associated with its capacity to adhere to different materials and surfaces. Forensic soil experts and police investigators have been using soil samples as an aid in criminal investigations. Soils can act as fingerprints because they present contrasting physical, chemical, biological, and mineralogical properties. However, depending on the analytical tools utilized to characterize the soil, differentiating the samples when they have similar properties might be impossible. Thus, soil utilization as a fingerprint material requires increasing the number of variables measured as well as the accuracy and precision of the measurements. This study presents the feasibility of methods based on X-ray fluorescence (XRF) and radiation interaction parameters to discriminate soils for forensic investigations. Analyses of soil particle size, elemental composition (XRF), mass attenuation coefficient (μ), atomic (σ a ) and electronic (σ e ) cross-sections, effective atomic number (Z eff ), and electron density (N el ) were carried out to evaluate the potential of nuclear parameters to differentiate soils. Ten different soil types collected at 0.00-0.05 m layer were studied. The radiation interaction parameters were obtained through the XCOM computer code, while the experimental measurements were carried out by the traditional gamma-ray attenuation method utilizing the radioactive sources of 241 Am and 137 Cs. The results showed that the soils presented broad differences in terms of clay, silt, and sand contents as well as in the major oxides. These differences influenced the radiation attenuation properties as verified through the multivariate analysis. For the lowest photon energy studied (10 and 30 keV), σ e was the most interesting parameter to discriminate the soils. For energies above 59.5 keV, Z eff and N el were the most important parameters. Good agreement was found between the calculated and measured parameters. The findings of this study indicate that radiation interaction parameters have great potential for crime scene investigation providing new parameters for better discrimination of soils. The main advantage of the method presented here is that it is fast, easy to implement, does not require powerful computers, and the XCOM code can be run online at the NIST (National Institute of Standards and Technology, USA) website