Página 1 dos resultados de 5635 itens digitais encontrados em 0.168 segundos

Um modelo para planejamento de canais de distribuição no setor de alimentos.; A model for the distribution channels in the food sector.

Neves, Marcos Fava
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/12/1999 Português
Relevância na Pesquisa
36.57402%
São muitas as empresas que estão insatisfeitas com a distribuição de seus produtos. Logo a distribuição, ainda uma forte fonte de vantagem competitiva sustentável disponível para as empresas. No produto, a rápida transferência de tecnologia entre empresas e a competição global possibilitam que empresas competidoras consigam igualdade de condições em design, atributos e qualidade. Em preços, a habilidade das empresas de operar em todos os lugares do mundo cria condições de oferta aos menores preços possíveis. Nas comunicações (promoção), a massiva exposição das pessoas estabelece certa barreira a esse excesso, reduzindo o impacto das mensagens. Portanto, a distribuição, dentro do conceito clássico do composto de marketing (4P´s - Produto, Preço, Promoção ou Comunicações e Ponto de Venda ou Distribuição) é um item importante de diferenciação. Os canais de distribuição oferecem a construção de vantagens competitivas sustentáveis, por suas características de longo prazo, tanto no planejamento como na implementação, por exigirem estrutura de organizações consistentes e terem base em pessoas e relacionamentos. Esta tese propõe um modelo para planejamento de canais de distribuição mais focado em empresas de alimentos e bebidas. Ou seja...

Fornecimento de uréia na dieta de catetos (Pecari tajacu) e uso de isótopo estável 15N como marcador para estimativa da síntese de nitrogênio microbiano; Provision of urea in diet peccary collared (Pecari tajacu) and use of stable isotope 15N how to marker to estimate of microbial nitrogen synthesis

Mendes, Alcester
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/10/2008 Português
Relevância na Pesquisa
36.675493%
A utilização racional da fauna silvestre é um processo benéfico, por resultar em vantagens econômicas e sociais, e ao mesmo tempo auxiliar no processo de conservação das espécies silvestres. Entre as espécies silvestres brasileiras com potencial zootécnico, destaca-se o cateto (Pecari tajacu), um animal que consome diversos tipos de alimentos e que produz carne e couro com elevada demanda nos mercados nacional e internacional, respectivamente. Uma característica desta espécie é a presença de um pré-estômago, onde ocorre fermentação microbiana que confere a esta espécie capacidade para digerir alimentos volumosos. Objetivou-se com o presente trabalho: (i) medir a capacidade digestiva usando doses crescentes de uréia como fonte de nitrogênio não protéico (NNP) na dieta de catetos; (ii) avaliar a eficiência da microbiota do pré-estômago de catetos em proceder à fermentação anaeróbica da dieta, através da técnica de produção de gases para diferentes doses de uréia; (iii) estimar a síntese de nitrogênio microbiano in vitro utilizando o isótopo estável 15N como marcador. O trabalho foi dividido em três capítulos. No primeiro foi utilizado delineamento com distribuição inteiramente aleatória, no qual as possíveis seqüências dos tratamentos (doses de uréia: 0...

Poluentes orgânicos e isótopos estáveis no ecossistema da Baía do Almirantado, Ilha Rei George, Antártida; Organic pollutants and stable isotopes in the ecosystem of Admiralty Bay, King George Island, Antarctica

Cipro, Caio Vinicius Zecchin
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/11/2011 Português
Relevância na Pesquisa
36.560986%
Apesar da pequena influência antrópica direta em seu território, a Antártida não pode ser considerada livre do alcance de poluentes. No presente estudo, avaliou-se a distribuição e transferência de poluentes orgânicos (PCBs, pesticidas organoclorados e PBDEs) em compartimentos abióticos (neve e água de degelo) e bióticos (liquens, musgos, invertebrados, peixes, ovos de aves e tecidos de aves e pinípedes, para os quais também foi aplicada análise isotópica de nitrogênio-15 e carbono-13) do ecossistema da Baía do Almirantado. Os compartimentos abióticos tiveram concentrações entre 1,4 e 156 pg L-1, apenas para grupos de organoclorados, com variação intra-sazonal importante e compatibilidade com níveis tróficos inferiores e amostras de vegetação, que por sua vez refletiram a importância de fontes secundárias de poluentes. Nos animais, grosso modo, os compostos prevalecentes (em ng g-1 peso úmido) foram PCBs, (6,82-1821), HCB (0,060-136) e DDTs, (0,410-524), níveis de duas a três ordens de grandeza superiores aos encontrados em vegetação. PBDEs ocorreram, de modo geral, em níveis uma ou duas ordens de grandeza abaixo dos organoclorados. A análise isotópica mostrou-se útil como ferramenta indicadora de nível trófico e origem de matéria orgânica consumida...

Passeios aleatórios estáveis em Z com taxas não-homogêneas e os processos quase-estáveis; Stable random walks on Z with inhomogeneous rates and quasistable processes

Souza, Wagner Barreto de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/12/2012 Português
Relevância na Pesquisa
36.730496%
Seja $\mathcal X=\{\mathcal X_t:\, t\geq0,\, \mathcal X_0=0\}$ um passeio aleatório $\beta$-estável em $\mathbb Z$ com média zero e com taxas de saltos não-homogêneas $\{\tau_i^: i\in\mathbb Z\}$, com $\beta\in(1,2]$ e $\{\tau_i: i\in\mathbb Z\}$ sendo uma família de variáveis aleatórias independentes com distribuição marginal comum na bacia de atração de uma lei $\alpha$-estável, com $\alpha\in(0,2]$. Nesta tese, obtemos resultados sobre o comportamento do processo $\mathcal X_t$ para tempos longos, em particular, obtemos seu limite de escala. Quando $\alpha\in(0,1)$, o limite de escala é um processo $\beta$-estável mudado de tempo pela inversa de um outro processo, o qual envolve o tempo local do processo $\beta$-estável e um independente subordinador $\alpha$-estável; chamamos o processo resultante de processo quase-estável. Para o caso $\alpha\in[1,2]$, o limite de escala é um ordinário processo $\beta$-estável. Para $\beta=2$ e $\alpha\in(0,1)$, o limite de escala é uma quase-difusão com medida de velocidade aleatória estudada por Fontes, Isopi e Newman (2002). Outros resultados sobre o comportamento de $\mathcal X$ para tempos longos são envelhecimento e localização. Nós obtemos resultados de envelhecimento integrado e não-integrado para $\mathcal X$ quando $\alpha\in(0...

Análise da estrutura populacional da abrótea-de-profundidade, Urophycis mystacea Ribeiro, 1903 (Teleostei: Phycidade) da região sudeste-sul do Brasil. Morfologia e relação entre isótopos estáveis dos otólitos sagittae; Analysis of the population structure of deep-hake , Urophycis mystacea Ribeiro, 1903 ( Teleostei: Phycidae ) from the Southeastern Brazil. Morphology and relationship between stable isotopes of sagitta otoliths

Romero, Cesar Santificetur
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/10/2013 Português
Relevância na Pesquisa
36.75083%
Estudos sobre a análise populacional da abrótea-de-profundidade, Urophycis mystacea, uma ferramenta importante para a gestão de estoques, nunca haviam sido realizados. Na presente dissertação, através da análise da distribuição em comprimentos de exemplares coletados ao longo da região sudeste-sul do Brasil, da análise quali-quantitativa das características morfológicas e morfométricas dos otólitos sagittae e da análise das razões de isótopos estáveis dos mesmos, foi avaliada a homogeneidade do estoque, que constitui importante recurso pesqueiro na região. Para as análises, a região entre o cabo de São Tomé e o Chuí foi dividida em três áreas. As análises morfológicas foram feitas seguindo metodologia de TUSET et. al (2008) e ASSIS (2002), usando quinze feições da sagittae. O teste qui-quadrado foi aplicado para verificar a homogeneidade da distribuição dos caracteres em relação a ontogenia. As análises morfométricas foram realizadas em um estereomicroscópio, com otólitos de peixes da faixa entre 300 e 499 mm de comprimento total, comum às três áreas. Foram obtidas variáveis morfométricas (Co, Ao, Eo, Po, Ar e Pe) e calculadas relações morfométricas e os indicadores de forma. Testes estatísticos foram aplicados para verificar diferenças dos caracteres entre as áreas pré-estabelecidas. Para a análise isotópica foram análizados dez otólitos por área...

On Nonstable and Stable Population Momentum

Espenshade, Thomas J.; Olgiati, Analia S.; Levin, Simon A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/2011 Português
Relevância na Pesquisa
36.98785%
This article decomposes total population momentum into two constituent and multiplicative parts: “nonstable” momentum and “stable” momentum. Nonstable momentum depends on deviations between a population’s current age distribution and its implied stable age distribution. Stable momentum is a function of deviations between a population’s implied stable and stationary age distributions. In general, the factorization of total momentum into the product of nonstable and stable momentum is a very good approximation. The factorization is exact, however, when the current age distribution is stable or when observed fertility is already at replacement. We provide numerical illustrations by calculating nonstable, stable, and total momentum for 176 countries, the world, and its major regions. In short, the article brings together disparate strands of the population momentum literature and shows how the various kinds of momentum fit together into a single unifying framework.

Spatial Variability of Erosion Rates Inferred from the Frequency Distribution of Cosmogenic 3He in Olivines from Hawaiian River Sediments

Meade, Brendan; Mukhopadhyay, Sujoy; Gayer, Eric
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.61768%
To constrain the spatial distribution of erosion rates in the Waimea river watershed, on the western side of the island of Kauai, Hawaii, we calculate the frequency distribution of cosmogenic He-3 concentrations ([He-3],) from helium isotopic measurements in olivine grains from a single sample of river sediment. Helium measurements were made in 26 aliquots of similar to 30 olivine grains each. The average [He-3], from the 26 aliquots was used to estimate a basin-wide average erosion rate of 0.056 mm/yr, a value that is similar to erosion rates obtained from geochemical analyses of river sediments from tectonically stable landforms. However, forward models of cosmogenic nuclide production and sediment generation rates are inconsistent with the hypothesis that the observed [He-3], frequency distribution is the result of a homogeneous, basin wide, erosion rate. Instead, a distribution of erosion rates, from similar to 0 to 4 mm/yr, may account for the observed frequency distribution. The distribution of erosion rates can be modeled by both non-linear slope- and curvature-dependent erosion rates with power law exponents ranging from 2.0 to 2.5. However, the spatial distribution of cosmogenic nuclides for slope- and curvature-dependent erosion rates are distinct...

The role of hydrology in determining the distribution patterns of invasive willows (Salix) and dominant native trees in the lower River Murray (South Australia).

Gehrig, Susan L.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010 Português
Relevância na Pesquisa
36.785103%
This thesis explores the hydrological factors that may contribute to the observed distribution patterns of invasive willows (Salix) and native trees (Eucalyptus camaldulensis, E. largiflorens and Acacia stenophylla) along the Lower River Murray (LRM) in southern Australia. An initial survey, establishing the diversity and flowering biology of Salix taxa was carried out to ascertain the extent of invasion, and the likelihood of hybridisation, which may accelerate invasion. S. babylonica, S. fragilis, S. × chrysochoma and S. × rubens occur in the study region, each represented by a single gender. None were present on floodplains, but the most dominant taxon, S. babylonica, occurred along the entire length of the main channel. No seed or seedlings were observed; hence reproduction is likely to be asexual. More detailed survey work was then carried out to characterise the distribution patterns of the dominant S. babylonica and co-occurring natives (Eucalyptus camaldulensis, E. largiflorens and Acacia stenophylla) along a hydrologic gradient produced by the extensive weir system in the LRM. In weir pools, variation in daily water levels of weir pools is low (± 0.1 m) immediately upstream of the weir...

The influence of salinity on various life stages of Ruppia tuberosa and implications for its distribution in the Coorong, South Australia.

Kim, Dae Heui
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014 Português
Relevância na Pesquisa
36.62746%
Despite the obvious decline in the distribution of Ruppia in the Coorong, there have been few extensive studies investigating the factors that control the distribution of this genus. In particular, few studies have focused on how salinity causes changes in the distribution and abundance of various life stages of Ruppia tuberosa J. Davis and Tomlinson. To enable the appropriate and restorative management of R. tuberosa in the Coorong, it is necessary to improve our understanding of the environmental factors that impact this species. The primary aim of this study was to determine the principle factors in controlling the germination, growth and reproduction of R. tuberosa in the Coorong, which ultimately controls its distribution. This was examined through a range of techniques, including field distribution surveys, germination experiments, pond experiments and transplantation experiments to enable for the management of this species in the Coorong. The first objective (Chapter 2) was to determine the effect of physico-chemical conditions on the distribution and abundance of various life stages of R. tuberosa in the Coorong region. In investigating this aim, salinity thresholds for various R. tuberosa life stages were assessed. The distribution and abundance of shoots...

Indirect Estimation of Elliptical Stable Distributions

LOMBARDI, Marco J.; VEREDAS, David
Fonte: European University Institute Publicador: European University Institute
Tipo: Trabalho em Andamento Formato: application/pdf; digital
Português
Relevância na Pesquisa
36.75083%
We present an indirect estimation approach for elliptical stable distributions which relies on the use of a multivariate Student-t distribution as auxiliary model. This distribution is also elliptical and we show that its parameters have a one-to-one relationship with those of the elliptical stable, therefore making the proposed indirect approach particularly suitable. We analyze the finite sample behaviour of the estimators via a comprehensive Monte Carlo study. An application to 27 emerging markets stock indexes concludes the paper.

Statistical description of the error on wind power forecasts via a Lévy a-stable distribution

BRUNINX, Kenneth; DELARUE, Erik; D’HAESELEER, William
Fonte: Instituto Universitário Europeu Publicador: Instituto Universitário Europeu
Tipo: Trabalho em Andamento Formato: application/pdf; digital
Português
Relevância na Pesquisa
37.056538%
As the share of wind power in the electricity system rises, the limited predictability of wind power generation becomes increasingly critical for operating a reliable electricity system. In most operational & economic models, the wind power forecast error (WPFE) is often assumed to have a Gaussian or so-called B-distribution. However, these distributions are not suited to fully describe the skewed and heavy-tailed character of WPFE data. In this paper, the Lévy a-stable distribution is proposed as an improved description of the WPFE. Based on 6 years of historical wind power data, three forecast scenarios with forecast horizons ranging from 1 to 24 hours are simulated via a persistence approach. The Lévy a-stable distribution models the WPFE better than the Gaussian or so-called B-distribution, especially for short term forecasts. In a case study, an analysis of historical WPFE data showed improvements over the Gaussian and B-distribution between 137 and 567% in terms of cumulative squared residuals. The method presented allows to quantify the probability of a certain error, given a certain wind power forecast. This new statistical description of the WPFE can hold important information for short term economic & operational (reliability) studies in the field of wind power.

Limiting behavior of the search cost distribution for the move-to-front rule in the stable case

Leisen, Fabrizio; Lijoi, Antonio; Paroissin, Christian
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: info:eu-repo/semantics/draft; info:eu-repo/semantics/workingPaper Formato: application/pdf
Publicado em /07/2011 Português
Relevância na Pesquisa
46.652515%
Move-to-front rule is a heuristic updating a list of n items according to requests. Items are required with unknown probabilities (or popularities). The induced Markov chain is known to be ergodic. One main problem is the study of the distribution of the search cost defined as the position of the required item. Here we first establish the link between two recent papers of Barrera and Paroissin and Lijoi and Pruenster that both extend results proved by Kingman on the expected stationary search cost. Combining results contained in these papers, we obtain the limiting behavior for any moments of the stationary seach cost as n tends to infinity.

Exact Skewness-Kurtosis Tests for Multivariate Normality and Goodness-of-fit in Multivariate Regressions with Application to Asset Pricing Models

DUFOUR, Jean-Marie; KHALAF, Lynda; BEAULIEU, Marie-Claude
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 225374 bytes; application/pdf
Português
Relevância na Pesquisa
37.05894%
We study the problem of testing the error distribution in a multivariate linear regression (MLR) model. The tests are functions of appropriately standardized multivariate least squares residuals whose distribution is invariant to the unknown cross-equation error covariance matrix. Empirical multivariate skewness and kurtosis criteria are then compared to simulation-based estimate of their expected value under the hypothesized distribution. Special cases considered include testing multivariate normal, Student t; normal mixtures and stable error models. In the Gaussian case, finite-sample versions of the standard multivariate skewness and kurtosis tests are derived. To do this, we exploit simple, double and multi-stage Monte Carlo test methods. For non-Gaussian distribution families involving nuisance parameters, confidence sets are derived for the the nuisance parameters and the error distribution. The procedures considered are evaluated in a small simulation experi-ment. Finally, the tests are applied to an asset pricing model with observable risk-free rates, using monthly returns on New York Stock Exchange (NYSE) portfolios over five-year subperiods from 1926-1995.; Dans cet article, nous proposons des tests sur la forme de la distribution des erreurs dans un modèle de régression linéaire multivarié (RLM). Les tests que nous développons sont fonction des résidus obtenus par moindres carrés multivariés...

Simulation-Based Finite-Sample Tests for Heteroskedasticity and ARCH Effects.

DUFOUR, Jean-Marie; KHALAF, Lynda; BERNARD, Jean-Thomas; GENEST, Ian
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 342447 bytes; application/pdf
Português
Relevância na Pesquisa
36.774937%
A wide range of tests for heteroskedasticity have been proposed in the econometric and statistics literature. Although a few exact homoskedasticity tests are available, the commonly employed procedures are quite generally based on asymptotic approximations which may not provide good size control in finite samples. There has been a number of recent studies that seek to improve the reliability of common heteroskedasticity tests using Edgeworth, Bartlett, jackknife and bootstrap methods. Yet the latter remain approximate. In this paper, we describe a solution to the problem of controlling the size of homoskedasticity tests in linear regression contexts. We study procedures based on the standard test statistics [e.g., the Goldfeld-Quandt, Glejser, Bartlett, Cochran, Hartley, Breusch-Pagan-Godfrey, White and Szroeter criteria] as well as tests for autoregressive conditional heteroskedasticity (ARCH-type models). We also suggest several extensions of the existing procedures (sup-type of combined test statistics) to allow for unknown breakpoints in the error variance. We exploit the technique of Monte Carlo tests to obtain provably exact p-values, for both the standard and the new tests suggested. We show that the MC test procedure conveniently solves the intractable null distribution problem...

Exact Multivariate Tests of Asset Pricing Models with Stable Asymmetric Distributions

BEAULIEU, Marie-Claude; DUFOUR, Jean-Marie; KHALAF, Lynda
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica Formato: 204421 bytes; application/pdf
Português
Relevância na Pesquisa
36.999365%
In this paper, we propose exact inference procedures for asset pricing models that can be formulated in the framework of a multivariate linear regression (CAPM), allowing for stable error distributions. The normality assumption on the distribution of stock returns is usually rejected in empirical studies, due to excess kurtosis and asymmetry. To model such data, we propose a comprehensive statistical approach which allows for alternative - possibly asymmetric - heavy tailed distributions without the use of large-sample approximations. The methods suggested are based on Monte Carlo test techniques. Goodness-of-fit tests are formally incorporated to ensure that the error distributions considered are empirically sustainable, from which exact confidence sets for the unknown tail area and asymmetry parameters of the stable error distribution are derived. Tests for the efficiency of the market portfolio (zero intercepts) which explicitly allow for the presence of (unknown) nuisance parameter in the stable error distribution are derived. The methods proposed are applied to monthly returns on 12 portfolios of the New York Stock Exchange over the period 1926-1995 (5 year subperiods). We find that stable possibly skewed distributions provide statistically significant improvement in goodness-of-fit and lead to fewer rejections of the efficiency hypothesis.

On the behavior of EMD and MEMD in presence of symmetric alpha-stable noise

KOMATY, Ali; BOUDRAA, Abdel-Ouahab; NOLAN, John; DARE, Delphine
Fonte: IEEE Publicador: IEEE
Português
Relevância na Pesquisa
36.612021%
EmpiricalMode Decomposition (EMD) and its extended versions such as Multivariate EMD (MEMD) are data-driven techniques that represent nonlinear and non-stationary data as a sum of a finite zero-mean AM-FM components referred to as Intrinsic Mode Functions (IMFs). The aim of this work is to analyze the behavior of EMD and MEMD in stochastic situations involving non-Gaussian noise, more precisely, we examine the case of Symmetric Alpha-Stable noise. We report numerical experiments supporting the claim that both EMD and MEMD act, essentially, as filter banks on each channel of the input signal in the case of Symmetric Alpha Stable noise. Reported results show that, unlike EMD, MEMD has the ability to align common frequency modes across multiple channels in same index IMFs. Further, simulations show that, contrary to EMD, for MEMD the stability property is well satisfied for the modes of lower indices and this result is exploited for the estimation of the stability index of the Symmetric Alpha Stable input signal.

Estimating the mean of a heavy tailed distribution

Peng, L
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
46.521445%
For the estimation of the mean of a heavy tailed distribution with tail index -α<-1, the asymptotic distribution of the sample mean is not normal as α<2. In this paper we propose an alternative estimator whose limiting distribution, under a second order

Spatial distribution of annual grass weed populations in winter cereals

González-Andújar, José Luis; Saavedra, Milagros
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 77021 bytes; application/pdf
Português
Relevância na Pesquisa
36.591738%
5 pages; The spatial distribution of 12 annual weed species in 52 winter cereal fields was studied by applying frequency distribution and dispersion indices. Avena sterilis and Lolium rigidum were clearly the dominant species, infesting the 38% of the fields. The dispersion indices, viz. variance to media ratio, David and Moore’s index, and k of the negative binomial revealed that the studied weed species followed an aggregated or contagious distribution pattern. In 54 of the 68 cases (specie-site) and in 10 of the 12 fields with multiple infestation studied, the weed populations were well represented by fitting the negative binomial distribution to frequency distribution of weed counts. Estimated values of parameter k showed a great variability amongst fields and were, in most cases, small indicating a high degree of patchiness. There was no stable or common kc value across field sites for all the weed species populations. This makes management decisions on weed control less easy in these fields.; Ministerio de Educacion y Ciencia project (AGL 2002-3801) and FEDER; Peer reviewed

Fully Bayesian Inference for ?-Stable Distributions Using a Poisson Series Representation

Lemke, Tatjana; Riabiz, Marina; Godsill, Simon J.
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; accepted version
Português
Relevância na Pesquisa
36.801868%
This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.dsp.2015.08.018; In this paper we develop an approach to Bayesian Monte Carlo inference for skewed ?-stable distributions. Based on a series representation of the stable law in terms of infinite summations of random Poisson process arrival times, our framework leads to a simple representation in terms of conditionally Gaussian distributions for certain latent variables. Inference can therefore be carried out straightforwardly using techniques such as auxiliary variables versions of Markov chain Monte Carlo (MCMC) methods. The Poisson series representation (PSR) is further extended to practical application by introducing an approximation of the series residual terms based on exact moment calculations. Simulations illustrate the proposed framework applied to skewed ?-stable simulated and real-world data, successfully estimating the distribution parameter values and being consistent with other (non-Bayesian) approaches. The methods are highly suitable for incorporation into hierarchical Bayesian models, and in this case the conditionally Gaussian structure of our model will lead to very efficient computations compared to other approaches.; Godsill acknowledges partial funding for the work from the EPSRC BTaRoT project EP/K020153/1...

Beach dynamics and nest distribution of the leatherback turtle (Dermochelys coriacea )at Grande Riviere Beach,Trinidad &Tobago

Lee Lum,Lori
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2005 Português
Relevância na Pesquisa
36.836133%
Grande Riviere Beach in Trinidad and Tobago is an important nesting site in the Caribbean for the Critically Endangered leatherback sea turtle,Dermochelys coriacea .Community members were concerned that beach erosion and seasonal river flooding were destroying many of the nests deposited annually and thought that a hatchery was a possible solution.Over the 2001 turtle nesting season,the Institute of Marine Affairs (IMA) assessed the spatial and temporal distribution of nests using the Global Positioning System recorded to reference points,and beach dynamics using permanent bench mark profile stations,to determine areas of high risk and more stable areas for nesting.A total of 1449 leatherback nests were positioned.It was evident that at the start of the season in March,the majority of leatherback nests were deposited at the eastern section of the beach. After May,there was a continuing westward shift in nest distribution as the season progressed until August and beach erosion in the eastern section became predominant.The backshore remained relatively stable along the entire beach throughout the nesting season,and erosion was predominant in the foreshore at the eastern section of the beach,from the middle to the end of the season.Similar trends in accretion and erosion were observed in 2000.River flooding did not occur during the study period or in the previous year.With both high risk and more stable regions for turtle nesting available at Grande Riviere Beach...