Nonlinear Pendulum: A Simple Generalization

In this work we solve the nonlinear second order differential equation of the simple pendulum with a general initial angular displacement ($\theta(0)=\theta_0$) and velocity ($\dot{\theta}(0)=\phi_0$), obtaining a closed-form solution in terms of the Jacobi elliptic function $\text{sn}(u,k)$, and of the the incomplete elliptical integral of the first kind $F(\varphi,k)$. Such a problem can be used to introduce concepts like elliptical integrals and functions to advanced undergraduate students, to motivate the use of Computer Algebra Systems to analyze the solutions obtained, and may serve as an exercise to show how to carry out a simple generalization, taking as a starting point the paper of Bel\'endez \emph{et al} \cite{belendez}, where they have considered the standard case $\dot{\theta}(0)=0$

Correlation Dynamics of Yukawa-theory in 1+1 dimensions

Using the method of correlation dynamics we investigate the properties of a field-theory for fermions and scalar bosons coupled via a Yukawa interaction. Within this approach, which consists in an expansion of full equal-time Green functions into connected equal-time Green functions and a corresponding truncation of the hierarchy of equations of motion we carry out calculations up to 4th order in the connected Green functions and evaluate the effective potential of the theory in 1+1 dimensions on a torus. Comparing the different approximations we find a strong influence of the connected 4-point functions on the properties of the system.Comment: LaTeX, 38 pages, 12 figure

E fez-se a luz : contribuições do medium fotográfico para a instauração do realismo literário

The nineteenth century was the scene of deep changes in several areas of society: art, industry, science and others. Officially emerged in 1839, the photographic medium was received, discussed and practiced by many of these areas. This article deals with the arisal and the first receptions of photography in the artistic sphere, considering the shock between painting x photography, the discussion about visible reality and its forms of representation in art. It is also briefly discussed the artistic and social context in which the first realistic publications appeared, the importance of photography in these texts, how they were received in Germany and the fundamental differences between French and German literary realism. Thus, it is intended to point the emergence of the photographic medium as one of the aspects which - through the theoretical and conceptual reconfigurations which have taken place in art - contributed to the establishment of the realistic movement in painting and literature

Detailed investigation of small watershed systems in southern Portugal, implementing a multi-method recharge estimation comparison

Este estudo aborda uma analise completa da recarga dos aquíferos, assim como os seus factores climáticos e hidrológicos, dentro de um pequeno sistema de bacias hidrográficas em Portugal, na região semiárida do Algarve. Foram coletados na região durante os meses de maior pluviosidade vários diferentes conjuntos de dados derivados, obtidos entre novembro de 2020 e abril de 2021. Dentro das séries de dados há factores como, temperatura, precipitação e evapotranspiração, assim como medidas piezométricas em campo. A distribuição dos factores climáticos foi estudada com o uso de métodos de interpolação de dados em grelha, revelando uma mínima variação espacial na região estudada. O estudo estatístico demonstra uma forte correlação entre os factores climáticos e medidas dos níveis dos aquíferos, sugerindo que há uma resposta rápida dos aquíferos às flutuações climáticas. Os coeficientes de correlação foram 0.7 a 0.8 para precipitação e -0.3 a -0.4 para temperatura e potencial de evapotranspiração. Além disso, foi observado que o próprio sistema do aquífero é bem conectado na região estudada, com coeficientes de correlação maiores que 0.9 para as medidas piezométricas. Ainda, utilizando os dados coletados, múltiplas técnicas foram implementadas na área de estudo para estimar o valor de recarga do aquífero durante o período de observação, resultando em dois modelos de recarga que apresentaram um bom desempenho. Os métodos e as incertezas dos dois modelos, BALSEQ e LUMPREM, foram comparados em detalhes a fim de avaliar a significância e as imprecisões em suas simulações do período de observação. O modelo BALSEQ sugere que a recarga varia de 81.58 a 160.32 mm, e de acordo com o modelo LUMPREM, a recarga varia de 16.97 a 93.67 mm. No entanto, a avaliação do desempenho dos modelos sugere que, nas duas abordagens, a variação dos resultados de sobreposição, entre 80 e 90 mm de recarga, é a mais significativa.This study includes a thorough examination of groundwater recharge, as well as its hydrogeological and climatic drivers, within a small watershed system in Portugal’s semi-arid Algarve region. Several different derived data sets were collected over the region’s most significant rain months, over a 5-month period between November 2020 and April 2021. Among the data sets are climate factors including temperature, precipitation, and evapotranspiration, as well as various in field piezometric measurements. Using interpolation methods of gridded data, the geographical distribution of climatic drivers was studied, visualizing and describing the minimal spatial variation within the research region. The statistical study of the climatic factors and measured groundwater levels indicated a strong relationship, suggesting rapid groundwater responses to climate fluctuations, with correlations coefficients of 0.7 to 0.8 regarding the precipitation and -0.3 to -0.4 regarding temperature and potential evapotranspiration. Furthermore, it showed that the groundwater system itself is well connected throughout the region, with most corelation coefficients above 0.9 between the piezometric measurements. Utilizing the gathered data, multiple techniques to estimate the recharge value during the observation period were implemented on the study location, resulting in two distinct recharge models with good performance. The methods and uncertainties of the two models, BALSEQ and LUMPREM were compared in detail in order to assess the significance and inaccuracies in their simulations of the observation period. According to the BALSEQ model, recharge varies from 81.58 to 160.32 mm, and according to the LUMPREM model, recharge ranges from 16.97 to 93.67 mm. However, the evaluation of performances of the models suggests that the overlapping result range of the two approaches, between 80 and 90 mm of recharge, is the most significant

2PI simulations in expanding backgrounds: Doing it anyway!

I set out the 2PI formalism for quantum fields in a Friedmann-Robertson-Walker Universe. I show how one can solve self-consistently for the quantum field evolution and the evolution of the cosmological scale factor, using a renormalised semi-classical Friedmann equation. In a 2PI coupling expansion truncated at O(lambda^2), I perform sample calculations demonstrating kinetic and chemical equilibration in this context.Comment: 4 pages, 5 figures, to appear in the Proceedings of SEWM08, Amsterdam, the Netherlands, August 26-29, 200

First order plus frequency dependent delay modeling : new perspective or mathematical curiosity?

The first-order-plus-dead-time model (FOPDT) is a popular simplified representation of higher order dynamics. However, a well known drawback is the rapid decrease of the frequency response accuracy with increasing process order. This especially applies to the higher frequency range. Literature offers solutions by extending this three parameter model with more parameters. Here, a fractional dead time is proposed. As such, a Frequency-Dependent Delay (FDD) is introduced, which offers a better approximation. As the fractional-order term introduces nonlinear coupling between the phase and the magnitude of the process, the fitting of the function becomes an iterative process, so a constrained multi-objective optimization is needed. This novel model, first-order-plus-frequency-dependent-delay or FOPFDD is fitted on a real electrical ladder network of resistors and capacitors of four and eight parts. The classic model, which is clearly a special case of the new model, is outperformed in the entire bandwidth

Immediate adverse reactions to intravenous iodinated contrast media in computed tomography

Pesquisa quantitativa, exploratório-descritiva, de caráter não experimental, com o objetivo de conhecer as reações adversas imediatas ao contraste iodado intravenoso em pacientes hospitalizados, submetidos a tomografia computadorizada num hospital-escola no Sul do Brasil. Durante o período de estudo, todas as reações adversas manifestaram-se na intensidade leve, com freqüência de 12,5% com o uso de contraste iodado iônico e 1% com contraste não iônico. Extravasamento do meio radiopaco ocorreu em 2,2% das injeções em veia periférica, não havendo complicações em nenhum dos casos. Os resultados encontram-se dentro dos limites citados na literatura internacional e sugere-se que os serviços de tomografia conheçam as próprias taxas de reações adversas ao contraste iodado e as condições em que elas ocorrem, a fim de obter evidências para a avaliação dos respectivos processos assistenciais.Investigación cuantitativa del tipo exploratorio-descriptivo, de carácter no experimental. El objetivo consistía en conocer las reacciones adversas inmediatas al contraste yodado intravenoso en pacientes internados, sometidos a tomografía computarizada en un hospital escuela del sur de Brasil. Durante el período del estudio, todas las reacciones adversas tuvieron intensidad leve y una frecuencia del 12,5% con la utilización del contraste yodado iónico, y 1% con contraste no iónico. La extravasación del contraste ocurrió en un 2,2% de las inyecciones en vena periférica, no ocasionando complicaciones en ninguno de los casos. Los índices evidenciados en el presente estudio se mantuvieron dentro de los límites que constan en la revisión de literatura y, entre las recomendaciones, se sugiere que los servicios de tomografía conozcan los propios índices de reacciones adversas al contraste yodado y las condiciones en que ocurren, con la finalidad de obtener evidencias para evaluación de los respectivos procesos asistenciales.This exploratory-descriptive, non-experimental quantitative research aimed to learn about immediate adverse reactions to intravenous iodinated contrast media in hospitalized patients submitted to computed tomography at a teaching hospital in the South of Brazil. During the study period, all adverse reactions showed mild intensity, at a frequency of 12.5% with ionic iodinated contrast media, and 1% with non-ionic contrast agent. The extravasation of contrast occurred in 2.2% of the injections in a peripheral vein without complications in any of the cases. The results are within the limits cited in international literature and suggest that tomography service professionals should know their own rates of adverse reactions to iodinated contrast agent, as well as the conditions in which they occur, in order to obtain evidence to evaluate the respective care delivery processes