High level exceedances in stationary sequences with extremal index

AbstractIn this paper we consider stationary sequences with extremal index θ, 0<θ⪕1, and verifying an extension of Leadbetter's D(un) condition. For these sequences we prove that the limit law for high level exceedances is of the Compound Poisson Type and specify the parameters. We also give the joint limit law for exceedances of multiple levels and consequently, for any r upper order statistics

Galactica, a digital planetarium that explores the solar system and the milky way

This paper describes a new Digital Planetarium system that allows interactive visualization of astrophysical data and phenomena in an immersive virtual reality (VR) setting. Taking advantage of the Cave Hollowspace at Lousal infrastructure, we have created a large-scale immersive VR experience, by adopting its Openscenegraph (OSG) based VR middleware, as a basis for our development. Since our goal was to create an underlying system that could scale to arbitrary large astrophysical datasets, we have splitted our architecture in offline and runtime subsystems, where the former is responsible for parsing the available data sources into a SQL database, which will then be used by the runtime system to generate the entire VR scene graph environment, for the interactive user experience. Real-time computer graphics requirements lead us to adopt some visualization optimization techniques, namely, GPU calculation of textured billboards representing stars, view-frustum culling with octree organization of scene objects and object occlusion culling, to keep the user experience within the interactivity limits. We have built a storyboard (the “Galatica” storyboard), which describes and narrates a visual and aural user experience, while navigating through the Solar System and the Milky Way, and which was used to measure and evaluate the performance of our visualization acceleration algorithms. The system was tested with an available dataset of the complete Milky Way (including the solar system), featuring 100.639 textured billboards representing stars and additional 104.328 polygons, representing constellations and planets of the solar system. We have computed the frame rate, GPU traverse time, Cull traverse time and Draw traverse time for three visualization conditions: (A) using standard OSG view frustum culling technique; (B) using view frustum culling with and our octree organizing the scene’s objects; (C) using view frustum culling with our octree organizing the scene’s objects and our occlusion culling algorithm. We have generally concluded that our octree organization and octree plus object culling techniques out-performs the standard OSG view frustum culling, when around half or less than half of the dataset is in view of the virtual camera.info:eu-repo/semantics/acceptedVersio

State Space Modelling to Increase the Accuracy of Weather Radar Estimation of Mean Area Precipitation

This work compares some state space models for correcting the bias of the weather radar in Cruz do Leão, at Coruche, Portugal. Particular attention was given to the statistical adjustment of models, because precipitation data clearly deviated from the normal distribution. This work is based on 17 storms occurred between September of 1998 and November of 2000, in an area that includes part of the Alenquer river hydrographical basin

Estimação dos parâmetros de modelos em espaço de estado com coeficientes variáveis

A estimação dos parâmetros é um processo importante em qualquer pro- cesso de modelação, em particular nos modelos em espaço de estados (MEE) com coe- ficientes variáveis, em tempo discreto. Este trabalho pretende contribuir para a especi- ficação de MEE univariados propondo estimadores que não dependem da distribuição dos erros (estimadores distribution-free) e comparando-os, via estudo de Monte Carlo, com a estimação pela máxima verosimilhança

Optimization of deposition parameters for thin silicon films on flexible substrates in a hot-wire chemical vapor deposition reactor

This paper studies the deposition of thin silicon films from silane on plastic substrates in a recently build hot-wire chemical vapor deposition reactor. Hydrogen dilution of silane was used to induce amorphous-to-nanocrystalline phase transition. Thin-film deposition rate, r(d), is roughly proportional to silane concentration during deposition but the proportionality factor depends on filament temperature, T-fil. At T-fil similar to 2500 degrees C (1900 degrees C), r(d) increases from 2.1 angstrom/s (1.2 angstrom/s) at 97% H-2 dilution to 14.5 angstrom/s (10.7 angstrom/s) for films deposited from pure silane. At T-fil similar to 2500 degrees C, films deposited under 80% H-2 dilution were amorphous, under 90% H-2 dilution the crystalline fraction was X-C = 49.4% and under 95% H-2 dilution, X-C = 52.8%. At T-fil similar to 1900 degrees C, samples were amorphous up to similar to 95% H-2 dilution where a crystalline fraction of 22.3% was measured. Films with amorphous structure have sigma(d) similar to 10(-10)-10(-9) Omega(-1.)cm(-1) while those with a measured crystalline fraction have sigma(d)similar to 10(-7)-10(-5) Omega(-1)cm(-1), depending on the amount of crystalline fraction and grain size. Films with lower sigma(d) have optical band gap in the range similar to 1.85-1.9 eV, typical of hydrogenated amorphous silicon, while those with higher sigma(d) have larger optical band gap (similar to 2 eV), typical of hydrogenated nanocrystalline silicon. Adhesion of the films to the plastic substrate was good, as they survived bending to small radius of curvature (< 1 mm) without peeling. Structural, optical and transport properties were similar on films deposited both on PEN and on glass under the same deposition conditions.Fundação para a Ciência e a Tecnologia (FCT

Effects of microcredit in fostering financial inclusion in Cape Verde

Banco de Cape Verde (BCV) is the Central Bank of the Republic of Cape Verde. Its mission is to ensure macro-financial stability for sustainable and inclusive economic growth and social development. Consequently, it supports micro, small, and medium enterprises (MSMEs) through microcredits disbursed through microfinance institutions. Interviews were conducted with microcredit stakeholders in the country and a qualitative analysis of the ecosystem was developed. A microcredit provision of one Cape Verdean institution and illustrated trends and evolution in fostering financial inclusion through microcredits disbursed in 2012 and 2019 were analysed. The result shows an increase in microcredits allocated to females and there is evidence of the diversification of the activities engaged by the recipients

Low substrate temperature deposition of amorphous and microcrystalline silicon films on plastic substrates by hot-wire chemical vapor deposition

Amorphous and microcrystalline silicon films were deposited by radio-frequency plasma enhanced chemical vapor deposition (rf-PECVD) and hot-wire chemical Vapor deposition (HW-CVD) on plastic (polyethylene terephthalate-PET) at 100 degrees C and 25 degrees C. Structural properties of these films were measured by Raman spectroscopy. Electronic properties were measured by dark conductivity and photoconductivity. For amorphous silicon films deposited by rf-PECVD on PET, photosensitivities > 10(5) were obtained at both 100 degrees C and 25 degrees C, For amorphous silicon films deposited by HW-CVD, a photosensitivity of > 10(5) was obtained at 100 degrees C. Microcrystalline silicon films deposited by HW-CVD at 95% hydrogen dilution had sigma(ph) similar to 10(-4) Omega(-1) cm(-1), while maintaining a photosensitivity of similar to 10(2) at both 100 degrees C and 15 degrees C. Microcrystalline silicon films with a large crystalline fraction (>50%) can be deposited by HW-CVD all the way down to room temperature. All the films had good adhesion and mechanical stability as neither adhesive nor cohesive failure was observed even when the substrates were bent elastically.Fundação para a Ciência e Tecnologia (FCT) Universidade do Minho (UM) Fundação Luso-Americana para o Desenvolvimento (FLAD

Promoção da saúde em Health Clubs: quem os frequenta e porquê

No presente estudo pretendeu-se saber o que leva os utentes a frequentarem um Health Club (HC), a partir da sua perspetiva e da dos professores do HC, relacionando as perceções entre os dois grupos. Aplicou-se um questionário a 129 utentes (94 mulheres; 35 homens), com idades entre 17-73 anos e outro questionário a 19 professores do HC. A motivação da entrada e contínua frequência dos utentes no HC em estudo é, sobretudo, pela melhoria e manutenção da sua saúde. Encontraram-se diferenças significativas entre géneros e entre faixas etárias relativamente às modalidades de atividade física escolhidas, mas não nas razões para utilização do HC.Fundação para a Ciência e a Tecnologia (FCT) - unidade de investigação 31

Doping of amorphous and microcrystalline silicon films deposited at low substrate temperatures by hot-wire chemical vapor deposition

The gas phase doping of amorphous (alpha -Si:H) and microcrystalline (muc-Si:H) silicon thin films deposited at substrate temperatures of 25 degreesC and 100 degreesC by hot-wire chemical vapor deposition is studied. Phosphine was used for n-type doping and diborane for p-type doping. The electronic and structural properties of the doped films are studied as functions of hydrogen dilution. Films were deposited on glass and polyethylene terephthalate. Similar dark conductivities, sigma (d), were obtained for the doped films deposited on either substrate. sigma (d) above 10(-6) Omega (-1) cm(-1) were obtained for a-Si:H films doped n-type at 25 degreesC and 100 degreesC (sigma (d)> 10(-4) Omega (-1) cm(-1)) and for alpha -Si:H doped p-type only at 100 degreesC. sigma (d), equal or above 10(-1) Omega (-1) cm(-1), were obtained for muc-Si:H doped p-type at 25 degreesC and 100 degreesC for Ac-Si:H doped n-type. only at 100 degreesC. Isochronal annealing at temperatures up to 200 degreesC reveals that, while the dopants are fully activated in microcrystalline samples, they are only partially activated in amorphous films deposited at a low substrate temperature.Fundação para a Ciência e Tecnologia (FCT) University of Minho (UM