5,086 research outputs found
The Likelihood Ratio Test and Full Bayesian Significance Test under small sample sizes for contingency tables
Hypothesis testing in contingency tables is usually based on asymptotic
results, thereby restricting its proper use to large samples. To study these
tests in small samples, we consider the likelihood ratio test and define an
accurate index, the P-value, for the celebrated hypotheses of homogeneity,
independence, and Hardy-Weinberg equilibrium. The aim is to understand the use
of the asymptotic results of the frequentist Likelihood Ratio Test and the
Bayesian FBST -- Full Bayesian Significance Test -- under small-sample
scenarios. The proposed exact P-value is used as a benchmark to understand the
other indices. We perform analysis in different scenarios, considering
different sample sizes and different table dimensions. The exact Fisher test
for tables that drastically reduces the sample space is also
discussed. The main message of this paper is that all indices have very similar
behavior, so the tests based on asymptotic results are very good to be used in
any circumstance, even with small sample sizes
Full Bayesian analysis for a class of jump-diffusion models
A new Bayesian significance test is adjusted for jump detection in a
diffusion process. This is an advantageous procedure for temporal data having
extreme valued outliers, like financial data, pluvial or tectonic forces
records and others.Comment: 15 pages, 7 figures; real data analysis adde
Photon-number-resolving segmented avalanche-photodiode detectors
We investigate the feasibility and performance of photon-number-resolved
photodetection employing avalanche photodiodes (APDs) with low dark counts. The
main idea is to split n photons over m modes such that every mode has no more
than one photon, which is detected alongside propagation by an APD. We
characterize performance by evaluating the purities of positive-operator-valued
measurements (POVMs), in terms of APD number and photon loss.Comment: 5 pages, 7 figures, submitted for publicatio
Towards the minimization of project duration and cost in stochastic project management environments
There is a general consensus that the rational use of available resources is, nowadays, an important task, since project managers are interested in the maximization of profit and the minimization of risk. In this work, it is proposed a multi-objective model to optimize the use of resources in a stochastic environment. In this multi-objective formulation the aim is to minimize the project duration and the total project cost at the same time. In the future, we intend to solve this problem using multi-objective evolutionary algorithms.Fundação para a Ciência e a Tecnologia (FCT
O contributo dos materiais vernáculos para sustentabilidade do ambiente construído
A utilização de materiais e técnicas locais é uma das principais características da arquitetura
vernácula. Quando comparados com materiais industrializados, os materiais vernáculos têm reduzido
impacte ambiental, sendo uma alternativa para a construção sustentável. No entanto, com a
industrialização os materiais vernáculos caíram em desuso tendo sido preteridos pelos novos materiais
padronizados que conduziram à homogeneização dos diferentes métodos construtivos, dando origem a
uma arquitetura de cariz universal, muitas vezes sem preocupações com o contexto e com significativos
impactes para o ambiente. No que diz respeito à sustentabilidade, os materiais vernáculos têm potencial
para evoluir e adaptarem-se às necessidades contemporâneas, permitindo reduzir a energia
incorporada e os impactes ambientais. Por estas razões, o presente trabalho aborda as potenciais
vantagens da utilização de materiais e técnicas locais no contexto português. Adicionalmente, este
artigo estabelece uma comparação entre os materiais vernáculos e os materiais produzidos
industrialmente ao nível dos indicadores ambientais (energia incorporada e potencial de aquecimento
global).Fundação para a Ciência e a Tecnologia (FCT), com a referência EXPL/ECM-COM/1801/201
Fluorine Abundances in the Globular Cluster M 4
We present chemical abundances for the elements carbon, sodium, and fluorine
in 15 red giants of the globular cluster M 4, as well as six red giants of the
globular cluster Centauri. The chemical abundances were calculated in
LTE via spectral synthesis. The spectra analyzed are high-resolution spectra
obtained in the near-infrared region around 2.3m with the Phoenix
spectrograph on the 8.1m Gemini South Telescope, the IGRINS spectrograph on the
McDonald Observatory 2.7m Telescope, and the CRIRES spectrograph on the ESO
8.2m Very Large Telescope. The results indicate a significant reduction in the
fluorine abundances when compared to previous values from the literature for M
4 and Centauri, due to a downward revision in the excitation
potentials of the HF(1-0) R9 line used in the analysis. The fluorine abundances
obtained for the M 4 red giants are found to be anti-correlated with those of
Na, following the typical pattern of abundance variations seen in globular
clusters between distinct stellar populations. In M 4, as the Na abundance
increases by +0.4 dex, the F abundance decreases by -0.2 dex. A
comparison with abundance predictions from two sets of stellar evolution models
finds that the models predict somewhat less F depletion (-0.1 dex) for
the same increase of +0.4 dex in Na
Metrology with Atom Interferometry: Inertial Sensors from Laboratory to Field Applications
Developments in atom interferometry have led to atomic inertial sensors with
extremely high sensitivity. Their performances are for the moment limited by
the ground vibrations, the impact of which is exacerbated by the sequential
operation, resulting in aliasing and dead time. We discuss several experiments
performed at LNE-SYRTE in order to reduce these problems and achieve the
intrinsic limit of atomic inertial sensors. These techniques have resulted in
transportable and high-performance instruments that participate in gravity
measurements, and pave the way to applications in inertial navigation.Comment: 7 pages, 5 figure
Análise da influência das varandas envidraçadas da arquitetura vernácula beirã no comportamento térmico dos edifícios
A heterogeneidade do território português originou uma profusa manifestação de distintas formas arquitetónicas vernáculas, i.e., construções que se caracterizam por apresentarem uma estreita relação com as condições dos locais onde se encontram inseridas (clima, materiais, economia, cultura, etc.). As estratégias passivas de adaptação ao meio envolvente presentes nestas construções, caraterizadas pela simplicidade, funcionamento passivo e reduzido impacte ambiental, são particularmente relevantes para os desafios que a construção contemporânea enfrenta, permitindo a redução da dependência em energia de fontes não-renováveis. Neste artigo é apresentado um conjunto de estratégias solares passivas comuns na arquitetura vernácula da região da Beira Alta, com destaque para as varandas envidraçadas, e são avaliadas a condições de conforto térmico num caso de estudo. Do estudo, é possível afirmar que nos períodos analisados as condições de conforto térmico no edifício foram asseguradas apenas por meios passivos sem recurso a sistemas mecânicos de climatização
BayGO: Bayesian analysis of ontology term enrichment in microarray data
BACKGROUND: The search for enriched (aka over-represented or enhanced) ontology terms in a list of genes obtained from microarray experiments is becoming a standard procedure for a system-level analysis. This procedure tries to summarize the information focussing on classification designs such as Gene Ontology, KEGG pathways, and so on, instead of focussing on individual genes. Although it is well known in statistics that association and significance are distinct concepts, only the former approach has been used to deal with the ontology term enrichment problem. RESULTS: BayGO implements a Bayesian approach to search for enriched terms from microarray data. The R source-code is freely available at in three versions: Linux, which can be easily incorporated into pre-existent pipelines; Windows, to be controlled interactively; and as a web-tool. The software was validated using a bacterial heat shock response dataset, since this stress triggers known system-level responses. CONCLUSION: The Bayesian model accounts for the fact that, eventually, not all the genes from a given category are observable in microarray data due to low intensity signal, quality filters, genes that were not spotted and so on. Moreover, BayGO allows one to measure the statistical association between generic ontology terms and differential expression, instead of working only with the common significance analysis
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