A formal proof of the optimal frame setting for Dynamic-Frame Aloha with known population size

In Dynamic-Frame Aloha subsequent frame lengths must be optimally chosen to maximize throughput. When the initial population size ${\cal N}$ is known, numerical evaluations show that the maximum efficiency is achieved by setting the frame length equal to the backlog size at each subsequent frame; however, at best of our knowledge, a formal proof of this result is still missing, and is provided here. As byproduct, we also prove that the asymptotical efficiency in the optimal case is $e^{-1}$, provide upper and lower bounds for the length of the entire transmission period and show that its asymptotical behaviour is $\sim ne-\zeta \ln (n)$, with $\zeta=0.5/\ln(1-e^{-1})$.Comment: 22 pages, submitted to IEEE Trans. on Information Theor

On the Hardness-Intensity Correlation in Gamma-Ray Burst Pulses

We study the hardness-intensity correlation (HIC) in gamma-ray bursts (GRBs). In particular, we analyze the decay phase of pulse structures in their light curves. The study comprises a sample of 82 long pulses selected from 66 long bursts observed by BATSE on the Compton Gamma-Ray Observatory. We find that at least 57% of these pulses have HICs that can be well described by a power law. The distribution of the power law indices, obtained by modeling the HIC of pulses from different bursts, is broad with a mean of 1.9 and a standard deviation of 0.7. We also compare indices among pulses from the same bursts and find that their distribution is significantly narrower. The probability of a random coincidence is shown to be very small. In most cases, the indices are equal to within the uncertainties. This is particularly relevant when comparing the external versus the internal shock models. In our analysis, we also use a new method for studying the HIC, in which the intensity is represented by the peak value of the E F_E spectrum. This new method gives stronger correlations and is useful in the study of various aspects of the HIC. In particular, it produces a better agreement between indices of different pulses within the same burst. Also, we find that some pulses exhibit a "track jump" in their HICs, in which the correlation jumps between two power laws with the same index. We discuss the possibility that the "track jump" is caused by strongly overlapping pulses. Based on our findings, the constancy of the index is proposed to be used as a tool for pulse identification in overlapping pulses.Comment: 20 pages with 9 eps figures (emulateapj), ApJ accepte

Determining Bolometric Corrections for BATSE Burst Observations

We compare the energy and count fluxes obtained by integrating over the finite bandwidth of BATSE with a measure proportional to the bolometric energy flux, the phi-measure, introduced by Borgonovo & Ryde. We do this on a sample of 74 bright, long, and smooth pulses from 55 GRBs. The correction factors show a fairly constant behavior over the whole sample, when the signal-to-noise-ratio is high enough. We present the averaged spectral bolometric correction for the sample, which can be used to correct flux data.Comment: 3 pages, 3 figures, to appear in AIP proc. "Gamma-Ray Burst and Afterglow Astronomy 2001" Woods Hole, Massachusett

Infiltração marginal de dentes selados com materiais restauradores rovisórios

TCC (graduação) - Universidade Federal de Santa Catarina, Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Curso de Odontologia.O objetivo deste estudo, in vitro, foi comparar a capacidade seladora de diferentes materiais restauradores provisórios usados em Endodontia: Bioplic®, XTemp®, XTemp LC®, Maxxion R®, Riva LC® e Coltosol®. Quarenta e dois molares foram selecionados e divididos em 7 grupos de 6 elementos, sendo um deles o controle negativo. Após a abertura coronária, uma camada de resina composta foi fotopolimerizada nas entradas dos canais. Sobre ela foi colocada uma bolinha de algodão de forma a padronizar a altura da câmara pulpar em 4mm. Os materiais foram inseridos de acordo com as instruções dos fabricantes e os dentes impermeabilizados, exceto 1mm ao redor do bordo cavo superficial. Após termociclagem (125 ciclos) somente a coroa, e a porção mais cervical da raiz, foi submersa em azul de metileno a 2% e mantidos a 37º. Decorridas 72 h os dentes foram seccionados longitudinalmente e a infiltração marginal avaliada pelos escores: 0 = sem infiltração ou apenas superficial, 1 = até a metade da parede cavitária e do selamento, 2 = em toda a extensão da parede cavitária e do selamento, 3 = em toda a extensão da parede cavitária e do selamento atingindo a bolinha de algodão. Os dados foram analisados pelo teste de Kruskal-Wallis que detectou diferença significativa entre os materiais (p>0,05). Para comparações individuais foi empregado o teste U de Mann-Whitney. O Bioplic® apresentou o melhor resultado, 83,33% das amostras receberam escore 0. O Coltosol com 33,33% das amostras em escore 0 não mostrou diferença estatisticamente significativa com o Bioplic. Os outros materiais receberam escores que variaram entre 1 e 3. Concluiu-se que o Bioplic® foi o material que proporcionou o melhor selamento, porém nenhum material foi capaz de impedir totalmente a infiltração marginal do corante

The Temporal and Spectral Characteristics of "Fast Rise and Exponential Decay" Gamma-Ray Burst Pulses

In this paper we have analyzed the temporal and spectral behavior of 52 Fast Rise and Exponential Decay (FRED) pulses in 48 long-duration gamma-ray bursts (GRBs) observed by the CGRO/BATSE, using a pulse model with two shape parameters and the Band model with three shape parameters, respectively. It is found that these FRED pulses are distinguished both temporally and spectrally from those in long-lag pulses. Different from these long-lag pulses only one parameter pair indicates an evident correlation among the five parameters, which suggests that at least $\sim$4 parameters are needed to model burst temporal and spectral behavior. In addition, our studies reveal that these FRED pulses have correlated properties: (i) long-duration pulses have harder spectra and are less luminous than short-duration pulses; (ii) the more asymmetric the pulses are the steeper the evolutionary curves of the peak energy ($E_{p}$) in the $\nu f_{\nu}$ spectrum within pulse decay phase are. Our statistical results give some constrains on the current GRB models.Comment: 18 pages, 7 figures, accepted for publication in the Astrophysical Journa

Fighting the curse of sparsity: probabilistic sensitivity measures from cumulative distribution functions

Quantitative models support investigators in several risk analysis applications. The calculation of sensitivity measures is an integral part of this analysis. However, it becomes a computationally challenging task, especially when the number of model inputs is large and the model output is spread over orders of magnitude. We introduce and test a new method for the estimation of global sensitivity measures. The new method relies on the intuition of exploiting the empirical cumulative distribution function of the simulator output. This choice allows the estimators of global sensitivity measures to be based on numbers between 0 and 1, thus fighting the curse of sparsity. For density-based sensitivity measures, we devise an approach based on moving averages that bypasses kernel-density estimation. We compare the new method to approaches for calculating popular risk analysis global sensitivity measures as well as to approaches for computing dependence measures gathering increasing interest in the machine learning and statistics literature (the Hilbert–Schmidt independence criterion and distance covariance). The comparison involves also the number of operations needed to obtain the estimates, an aspect often neglected in global sensitivity studies. We let the estimators undergo several tests, first with the wing-weight test case, then with a computationally challenging code with up to k = 30, 000 inputs, and finally with the traditional Level E benchmark code

Surf Biomechanics and Bioenergetics.

O surf moderno vem sendo descrito como uma atividade física intermitente, que varia em duração e intensidade, seguida de períodos de recuperação consideráveis. Atualmente, a análise e avaliação das sessões de surf são baseadas em conhecimento empírico, experiência e observação. Em outras palavras, procedimentos que envolvem grandes erros de medição. No entanto, é extremamente difícil obter informações analíticas sobre os parâmetros de desempenho. As primeiras investigações científicas no mundo do surf enfrentam uma dificuldade clássica do mundo da ciência, que é medir sem interferir. Além disso, o ambiente marítimo, particularmente devido à água salgada, é extremamente hostil aos componentes eletrônicos, que atualmente são a nossa maior fonte de informações quantitativas.O objetivo desta pesquisa foi investigar a fase horizontal do surf, especificamente a remada de potência, a remada de longa duração e a técnica de transição para ficar de pé na prancha de surf. Todo este pacote sob a perspetiva da biomecânica, associado a alguns parâmetros bioenergéticos. A abordagem geral foi apoiada por um processo de desconstrução dos movimentos e técnicas em partes didáticas, a fim de reconstruir um conhecimento global e uma melhor compreensão do surf. Olhando para o futuro, agregámos a este projeto o desenvolvimento de recursos tecnológicos que possibilitam explorar o surf diretamente no oceano. Tudo isso ganha ainda muito mais peso, desde que o Surf foi selecionado como novo desporto olímpico para os Jogos de Tóquio, em 2020. Os Jogos Olímpicos passam a ser uma excelente oportunidade, onde o surf se tornará mais profissionalizado e organizado. Neste contexto, as métricas para avaliação de desempenho são importantes para ajudar a validação de metodologias de ensino-aprendizagem, treinamento e julgamentos competitivos.Palavras-chave: biomecânica do surf, surfing, remadas do surf, ficar de pé, medições.Modern surfing has been described as an intermittent physical activity, which varies in duration and intensity, followed by considerable recovery periods. Currently, the analysis and judgment of surf sessions are based on empirical knowledge, experience, and observation. In other words, procedures that involve great measurement errors. However, it is extremely difficult to obtain analytical information on performance parameters. The first scientific investigations in the surf world faced a classic difficulty of the world of science, which is to measure without interfering. In addition, the maritime environment, particularly due to salt water, is extremely hostile to electronic components, which are currently our largest source of quantitative information.This research aimed to investigate the horizontal phase of surfing, specifically the sprint paddling, endurance paddling and the transition pop-up - standing technique. The whole pack under a biomechanics perspective, associated with bioenergetic parameters. The general approach was supported by process of deconstruction of movements and techniques in didactic parts, in order to reconstruct a global knowledge, and a better understanding of surfing. Looking to the future, we aggregate to this project the development of technological resources that make it possible to explore surf directly in the ocean. All this gained even more relevance since Surf has been selected as the new Olympic sport for the next Games of Tokyo 2020. The Olympic Games are an excellent opportunity where surfing will become more professional and organised. In this context, the metrics for performance evaluation are important to help validating teaching-learning methodologies, support training and competitive judgments