507 resultados para REFLECTIVITY
Resumo:
Este trabalho analisou 10 anos de distribuição espacial e temporal dos raios, dos sistemas precipitantes e suas características, como refletividade, temperatura de brilho e altura dos sistemas precipitantes amostrados pelo satélite Tropical Rainfall Measuring Mission (TRMM) através dos sensores Lightning Imaging Sensor (LIS), Precipitation Radar (PR) e TRMM Microwave Imager (TMI). Estes dados foram organizados e armazenados pelo grupo de pesquisa da convecção tropical da University of Utah no período de dezembro de 1997 a fevereiro de 2009. Também foram analisados dados de focos de queimadas detectadas pelo Instituto Nacional de Pesquisas Espaciais (INPE), no período de 1998 a 2008. Foi selecionada uma área delimitada entre 60ºW a 45ºW de longitude e 10ºS a 5ºN de latitude, a qual, posteriormente, foi dividida em nove sub-áreas para um melhor detalhamento dasinformações. Para verificar a possível influência das queimadas no número de raios, selecionaram-se oito áreas, sendo 4 com o maior número de focos de queimadas e 4 com o menor número de focos de queimadas. Os sistemas precipitantes foram classificados seguindo a metodologia de Nesbitt et. al. 2000 e obedecendo a nova definição dos dados realizado por Liu (2007). Os sistemas precipitantes amostrados pelo satélite TRMM utilizados neste trabalho são denominados ALLPFS e são definidos como aqueles que apresentam pixel de chuva estimado pelo algoritmo 2A25. Estes são classificados em PFS e OTHPFS, que respectivamente, são aqueles que apresentam e não apresentam informação de temperatura de brilho. Os PFS são sub-classificados em sistemas sem assinatura de gelo (NOICE), com assinatura de gelo (WICE) e sistemas convectivos de mesoescala (MCS), sendo que os sistemas mais intensos, dentre estes últimos, são sistemas que recebem a denominação de IMCS. Os resultados mostram que as regiões do sul do Estado do Pará, município de Belém e Ilha do Marajó foram as que apresentaram as maiores ocorrências de raios na Amazônia Oriental, com valores superiores a 20 a 35 raios/km²/ano. Os NOICEs foram os sistemas mais frequentes em todas as regiões e os sistemas precipitantes da categoria WICE e MCS são aqueles que mais contribuem com a produção de raios sobre essas regiões. Os sistemas eletrificados apresentam grande contribuição no volume de chuva estimada sobre as áreas CENTRO e SUL, com percentuais superiores a 50% nas áreas SUL. A variação mensal dos raios na área de estudo mostrou que as maiores ocorrências de raios sobre o município de Belém são nos meses de janeiro a junho, com um pico no mês de janeiro. As maiores ocorrências no setor SUL da Amazônia Oriental concentram-se nos meses de setembro a dezembro. Nas análises sobre a interação entre os raios e as queimadas não se observou coerência, dentro das áreas de maior número de queimadas, na correlação mensal entre os raios e as queimadas, evidenciando que, apesar do grande número de queimadas observado sobre essas áreas, outros fatores interferem na produção de raios.
Resumo:
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Resumo:
Pós-graduação em Ciência dos Materiais - FEIS
Resumo:
Within the Wittgensteinian approach, the ideal of exactness, disconnected from concrete situations of language use, does not make any sense. Such an approach takes into account every and any kind of intersubjective communication, inasmuch as it is based on a previous agreement concerning the use of language and the interpretation of the world linked to it. This paper, throughout its three parts, seeks to understand this agreement, and evaluates whether or not philosophy plays a role in relation to it. To start with, the obstacles to such an agreement will be considered, namely, solipsism and private, subjective language. In the following stage, the intention is to indicate that the rupture from the subjectivist conception of language allows Wittgenstein to visualize another subject, the one incorporated by the community. From then on, the question is to verify whether reflectivity is possible in the ambit of a linguistic community or not, since the objectivity of concepts is not sought within knowledge, but within forms of life. In the third and last part, we will point to the language game metaphor
Resumo:
In addition to the comments summarized herein, regarding the difficulties in understanding scientific phenomena by the human mind (epistemological obstacles), this paper presents and proposes a methodological framework for transdisciplinarity and reflectivity as an interactive method through critical reflection to be used as an antidote against prejudice and a lack of transparency of researcher that are often seen as impeding proper understanding of the true, specifically in the human processes that occur with people living in rural areas. Then, three examples of research are presented, which – in different time periods – a polyocular view was applied to conduct investigations outlined by guidelines in the framework related to the proposal summarized within this work.
Resumo:
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Resumo:
Pós-graduação em Ciências Ambientais - Sorocaba
Resumo:
A climatological characterization of storm properties during two summer seasons, viz. 1998-1999 and 1999-2000, based on observations from the Bauru S-band Doppler radar, was obtained from the TITAN Software of the National Center for Atmospheric Research (Boulder, Co), implemented at IPMet. Parameters, such as mean volume, mean area, mean and maximum echo tops, mean and maximum reflectivity, as well as speed and direction of precipitating systems were determined using the reflectivity >25, 30 and 40 dBZ and a volume >30 km3 as thresholds for storm identification. For the first time, the spatial distributions of these parameters were determined in the central State of São Paulo, based on radar observations. It was found that some preferential areas, where most of the convective activity was concentrated during the study period, were located along the Tietê River. The mean maximum reflectivity field has highlighted preferential regions for convection to develop over the metropolitan area of Campinas, which in turn was reinforced by the distribution of the echo tops and reflectivity >40 dBZ.
Resumo:
A new method for analysis of scattering data from lamellar bilayer systems is presented. The method employs a form-free description of the cross-section structure of the bilayer and the fit is performed directly to the scattering data, introducing also a structure factor when required. The cross-section structure (electron density profile in the case of X-ray scattering) is described by a set of Gaussian functions and the technique is termed Gaussian deconvolution. The coefficients of the Gaussians are optimized using a constrained least-squares routine that induces smoothness of the electron density profile. The optimization is coupled with the point-of-inflection method for determining the optimal weight of the smoothness. With the new approach, it is possible to optimize simultaneously the form factor, structure factor and several other parameters in the model. The applicability of this method is demonstrated by using it in a study of a multilamellar system composed of lecithin bilayers, where the form factor and structure factor are obtained simultaneously, and the obtained results provided new insight into this very well known system.
Resumo:
A polarimetric X-band radar has been deployed during one month (April 2011) for a field campaign in Fortaleza, Brazil, together with three additional laser disdrometers. The disdrometers are capable of measuring the raindrop size distributions (DSDs), hence making it possible to forward-model theoretical polarimetric X-band radar observables at the point where the instruments are located. This setup allows to thoroughly test the accuracy of the X-band radar measurements as well as the algorithms that are used to correct the radar data for radome and rain attenuation. For the campaign in Fortaleza it was found that radome attenuation dominantly affects the measurements. With an algorithm that is based on the self-consistency of the polarimetric observables, the radome induced reflectivity offset was estimated. Offset corrected measurements were then further corrected for rain attenuation with two different schemes. The performance of the post-processing steps was analyzed by comparing the data with disdrometer-inferred polarimetric variables that were measured at a distance of 20 km from the radar. Radome attenuation reached values up to 14 dB which was found to be consistent with an empirical radome attenuation vs. rain intensity relation that was previously developed for the same radar type. In contrast to previous work, our results suggest that radome attenuation should be estimated individually for every view direction of the radar in order to obtain homogenous reflectivity fields.
Resumo:
Recently high spectral resolution sensors have been developed, which allow new and more advanced applications in agriculture. Motivated by the increasing importance of hyperspectral remote sensing data, the need for research is important to define optimal wavebands to estimate biophysical parameters of crop. The use of narrow band vegetation indices (VI) derived from hyperspectral measurements acquired by a field spectrometer was evaluated to estimate bean (Phaseolus vulgaris L.) grain yield, plant height and leaf area index (LAI). Field canopy reflectance measurements were acquired at six bean growth stages over 48 plots with four water levels (179.5; 256.5; 357.5 and 406.2 mm) and tree nitrogen rates (0; 80 and 160 kg ha-1) and four replicates. The following VI was analyzed: OSNBR (optimum simple narrow-band reflectivity); NB_NDVI (narrow-band normalized difference vegetation index) and NDVI (normalized difference index). The vegetation indices investigated (OSNBR, NB_NDVI and NDVI) were efficient to estimate LAI, plant height and grain yield. During all crop development, the best correlations between biophysical variables and spectral variables were observed on V4 (the third trifoliolate leaves were unfolded in 50 % of plants) and R6 (plants developed first flowers in 50 % of plants) stages, according to the variable analyzed.
Resumo:
Die vorliegende Arbeit beschäftigt sich mit der Synthese und Charakterisierung von nematischen und smektischen LC-Polyestern, die mit ionischen Gruppen funktionalisiert wurden. Als ionische Gruppen wurden Phosphonsäure-salze und Phosphonium- oder Ammoniumgruppen verwendet. Je nach Polymerrückgrat erhält man LC-Ionomere, bei denen die ionischen Gruppen entweder an das Mesogen oder an den Hauptkettenspacer gebunden sind. Diese LC-Ionomere können zusammen mit amorphen Polyelektrolyten oder anorganischen Schichtmineralien für den Multischichtaufbau durch alternierende Adsorption von Polykation und Polyanion aus der Lösung verwendet werden (Methode von G. Decher). Die Multischichtbildung konnte mittels UV-Spektroskopie, IR-Spektroskopie, Kontaktwinkel-Messungen, Röntgenreflexionsmessungen und Oberflächen Plasmonen-Spektroskopie verfolgt werden. Die Subschichten sind zwischen 25 und 55 Å dick und hängen z.B. von der Polarität des Lösungsmittels ab. Erste cis-trans Isomerisierungen und Photoorientierungs-Versuche wurden durchgeführt.
Resumo:
Chalcogenides are chemical compounds with at least one of the following three chemical elements: Sulfur (S), Selenium (Sn), and Tellurium (Te). As opposed to other materials, chalcogenide atomic arrangement can quickly and reversibly inter-change between crystalline, amorphous and liquid phases. Therefore they are also called phase change materials. As a results, chalcogenide thermal, optical, structural, electronic, electrical properties change pronouncedly and significantly with the phase they are in, leading to a host of different applications in different areas. The noticeable optical reflectivity difference between crystalline and amorphous phases has allowed optical storage devices to be made. Their very high thermal conductivity and heat fusion provided remarkable benefits in the frame of thermal energy storage for heating and cooling in residential and commercial buildings. The outstanding resistivity difference between crystalline and amorphous phases led to a significant improvement of solid state storage devices from the power consumption to the re-writability to say nothing of the shrinkability. This work focuses on a better understanding from a simulative stand point of the electronic, vibrational and optical properties for the crystalline phases (hexagonal and faced-centered cubic). The electronic properties are calculated implementing the density functional theory combined with pseudo-potentials, plane waves and the local density approximation. The phonon properties are computed using the density functional perturbation theory. The phonon dispersion and spectrum are calculated using the density functional perturbation theory. As it relates to the optical constants, the real part dielectric function is calculated through the Drude-Lorentz expression. The imaginary part results from the real part through the Kramers-Kronig transformation. The refractive index, the extinctive and absorption coefficients are analytically calculated from the dielectric function. The transmission and reflection coefficients are calculated using the Fresnel equations. All calculated optical constants compare well the experimental ones.
Resumo:
Im ersten Teil der Arbeit wurden Ionomere durch aufeinanderfolgende polymeranaloge Reaktionen eines Reaktivesterpolymers mit verschiedenen primären bzw. sekundären Aminen synthetisiert. Polarisationsmikroskopische Untersuchungen zeigten, dass diese Ionomere sowohl über thermotrope als auch über lyotrope flüssigkristalline Eigenschaften verfügen. Anschließend wurden mit der 'self-assembly'-Methode Multischichtfilme aus den Ionomeren und hochgeladenen Polyelektrolyten sowie aus entgegengesetzt geladenen Ionomeren aufgebaut. Bei Röntgen-reflexionsmessungen an den Multischichtfilmen konnten winkelabhängige Modulationen der Strahlungsintensität beobachtet werden. Es ist zu vermuten, dass es sich bei diesen Modulationen um Überlagerungen von Kiessig-Ringen und Bragg-Peaks handelt, was ein Indiz dafür ist, dass regel-mäßige Subschichten in den Filmen existieren. Das Konzept der polymeranalogen Reaktionen eines Reaktivesterpolymers mit verschiedenen primären Aminen wurde außerdem dazu benutzt, Polymere zur Modifikation von Cadmiumselenid-Nanokristallen herzustellen. Hierbei konnte zum einen gezeigt werden, dass Nanokristalle direkt mit aminogruppenhaltigen Polymeren modifiziert werden können, zum anderen ist es auch möglich kationische Ionomere auf Nanokristallen mit Mercaptoessigsäure-Liganden zu adsorbieren. Im letzten Teil der Arbeit wurden ionische triazinhaltige Polymere hergestellt und elektrochemisch charakterisiert. Die hergestellten Polymere sind sehr leicht reduzierbar. Anschließend wurden aus den triazinhaltigen Polymeren und entgegengesetzt geladenen Polyelektrolyten ebenfalls Multischichtfilme hergestellt.
Resumo:
In this thesis two major topics inherent with medical ultrasound images are addressed: deconvolution and segmentation. In the first case a deconvolution algorithm is described allowing statistically consistent maximum a posteriori estimates of the tissue reflectivity to be restored. These estimates are proven to provide a reliable source of information for achieving an accurate characterization of biological tissues through the ultrasound echo. The second topic involves the definition of a semi automatic algorithm for myocardium segmentation in 2D echocardiographic images. The results show that the proposed method can reduce inter- and intra observer variability in myocardial contours delineation and is feasible and accurate even on clinical data.