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‣ Análise de ocorrência de metamerismo em revestimentos cerâmicos

Maccari Neto, Alfredo
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
Português
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Um dos problemas técnicos que ocorrem nos revestimentos cerâmicos é a possibilidade de duas peças serem da mesma cor sob a luz do dia, mas de cores diferentes sob outra iluminação. Tal fenômeno é chamado metamerismo. O presente trabalho teve como objetivo realizar um estudo sobre a influência de variáveis do processo de fabricação de revestimentos cerâmicos na ocorrência do fenômeno de metamerismo, tendo como objeto de estudo uma peça monoporosa de esmalte branco-brilhante, e um porcelanato mate. Para tanto, avaliou-se o efeito da variação de iluminante, correlacionado com as seguintes características dos revestimentos cerâmicos investigados: i) tipologia de esmalte; ii) base, engobe esmaltes; iii) variação de camada; iv) utilização de quartzo, caulim e zirconita; v) variação de corantes. Os resultados mostraram que esmaltes, como o branco-brilhante, se destacam no aparecimento da característica metamérica, tanto mais quanto mais espessa a camada. Já, quando se aumenta a camada do mate, este fenômeno ameniza. A zirconita, por ser um opacificante, ameniza a reflexão da luz, gerando uma diminuição do metamerismo. O quartzo promove o metamerismo, já que influencia no aparecimento do brilho. Quanto aos corantes...

‣ Correspondência de cor de diferentes marcas e sistemas de resina c omposta em relação à escala vita classical

Dantas, Andréa Abi Rached; Florez, Fernando Luis Esteban; Campos, Edson Alves de; Andrade, Marcelo Ferrazi de; Saad, José Roberto Cury; Oliveira Júnior, Osmir Batista de
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 45-51
Português
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The objective of this study was to compare different resins and determine their matching color with Vita shade, also investigating the possibility of substitution among them and the correlation between the visual and spectrophotometry methods of color selection. The composite resin Tetric N-Ceram® shade A1 was used as light-control and color A4 as dark-control. For each material were prepared five 10 x 2 mm disks. Analyses were performed in a metamerism box by volunteers who ordered the specimens from the lightest to the darkest. The spectrophotometry was carried out using the spectrophotometer Vita Easyshade®. ∆E values were subjected to analysis of variance with 5% significance level. The Fisher exact test showed that there was no color match among the materials and the reference Vita shade. The possibility of substitution among the composites could not be established. The two methods are able to correctly differentiate the control resin A4 as distinct from the other resins shade A2.; O objetivo desse estudo foi identificar dentre as resinas compostas: (1) quais apresentam maior correspondência de cor com a escala Vita Classical; (2) quais poderiam ser utilizadas como substitutas umas das outras; (3) qual é a correlação existente entre os métodos de seleção de cor visual e por espectrometria. Para tal...

‣ Calibração de dispositivos a cores utilizando uma camera digital

Leite, Frederico Nogueira
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Dissertação
Português
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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2006.; Em ambientes que possuem uma grande quantidade de monitores e impressoras, onde a coerência de representação de cor é requerida, a calibração de dispositivo é fundamental. Calibração é em geral executada utilizando ferramentas colorimétricas, usualmente requerendo dispositivos sofisticados como colorímetros ou espectrofotômetros. Nesta tese propomos um método mais barato de executar a calibração de maneira não colorimétrica utilizando uma câmera digital como substituta do colorímetro. Para isto, utilizamos a câmera como um simples dispositivo de mapeamento. A calibração é feita a partir de referencias, isto é, um dispositivo é calibrado tendo como referência outro dispositivo. Desenvolvemos um método de evitar ou minimizar a adaptação da câmera e a lidar com metamerismo. Ambos podem prejudicar a medição feita com a câmera. Obtivemos resultados para a calibração WYSIWYG entre monitores e monitor e impressora com uma média de Eab menor que 6. Os resultados são mostrados e discutidos ao longo da dissertação, bem como um modelo de erros. _________________________________________________________________________________ ABSTRACT; In environments with a multitude of monitors and printers...

‣ Imagens hiperespetrais aplicadas ao estudo e conservação de obras pictóricas

Pereira, Luís Emanuel Bravo de Abreu Santos
Fonte: Universidade Católica Portuguesa Publicador: Universidade Católica Portuguesa
Tipo: Tese de Doutorado
Publicado em 12/07/2013 Português
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A ampla difusão presenciada, durante a última década, das câmaras fotográficas digitais do tipo Reflex (D-SLRs), veio abrir aos investigadores na área das Artes novas possibilidades, pois têm agora ao seu dispor uma ferramenta não apenas para documentar o estado de conservação de uma obra de arte, mas também para a examinar no espetro invisível (como por exemplo no infravermelho ou ultravioleta) ou para recolher e analisar informação no espetro visível, mas de uma forma inovadora e com novas aplicações. É neste âmbito que se enquadra a presente tese, que apresenta os resultados obtidos na construção, calibração e validação de um sistema hiperespetral baseado numa câmara digital comercial (uma Nikon D300 D-SLR) e que mostrou ser possível, operando inteiramente dentro da região visível do espetro eletromagnético, capturar imagens hiperespetrais compostas por 28 bandas, entre os 420 nm e os 690 nm, em passos de 10 nm (22 bandas são capturadas diretamente com o sistema e 6 são interpoladas), um número de bandas em alguns casos superior ao que é possível de obter com outros sistemas de imagiografia multiespetral ou hiperespetral, equipamentos por vezes mais complexos e dispendiosos que o aqui apresentado. Em comparação com o espetroradiómetro de referência (Photoresearch PR650)...

‣ Polychaeta, Annelida, and Articulata are not monophyletic: articulating the Metameria (Metazoa, Coelomata)

Almeida,Waltécio de Oliveira; Christoffersen,Martin Lindsey; Amorim,Dalton de Souza; Garraffoni,André Rinaldo Senna; Silva,Gustavo Sene
Fonte: Sociedade Brasileira de Zoologia Publicador: Sociedade Brasileira de Zoologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2003 Português
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Polychaetes are metameric worms recognized for having parapodia, chaetae, and nuchal organs. Some authors have extended the Annelida to include Pogonophora, Echiura, and Clitellata. These suggestions are insufficient to generate a monophyletic group. They do not take into account two very large and important clades that in a cladistic analysis at a higher level are shown to be nested within the Annelida: the Ecdysozoa (arthropods and related taxa) and Enterocoela (deuterostomes and related taxa). Evolutionary histories of most characters across metazoan phyla are still very poorly known. Metameres and coeloms have been considered homoplastic in the literature, and yet the homeobox genes responsible for the expression of metamerism and of paired appendages, at least, are very largely distributed among the Metazoa. A phylogenetic analysis was performed for the ingroups of Polychaeta, including Clitellata, Enterocoela, and Ecdysozoa as terminal taxa. The remaining non-metameric phyla Platyhelminthes, Nemertea, Mollusca, and Sipuncula were included to root the tree within the Bilateria. Empirical data was obtained from the literature and run with the software Hennig86 with two comparative interpretations of a priori hypotheses of primary homology: one with negative characters (coding losses) and another considering only positive characters (without assumptions about losses). The most relevant conclusions are: (1) Annelida and Polychaeta are non-monophyletic...

‣ Theory and practice of colour vision testing: A review. Part 2

Lakowski, R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1969 Português
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Lakowski, R. (1969).Brit. J. industr. Med.,26, 265-288. Theory and practice of colour vision testing: A review. Part 2. The more modern tests of colour confusion, hue discrimination, metamerism, and special aptitudes measure a wide variety of attributes. Norms, including variations among normal as well as among defective observers, are given for each test, along with any other information we require to understand them. Finally there is the problem of choice, and factors influencing it, of which tests should be used in different circumstances. Some advice is given on the most useful combinations of tests.

‣ The role of the notochord in vertebral column formation

FLEMING, ANGELEEN; KEYNES, ROGER J. ; TANNAHILL, DAVID
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2001 Português
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The backbone or vertebral column is the defining feature of vertebrates and is clearly metameric. Given that vertebrae arise from segmented paraxial mesoderm in the embryo, this metamerism is not surprising. Fate mapping studies in a variety of species have shown that ventromedial sclerotome cells of the differentiated somite contribute to the developing vertebrae and ribs. Nevertheless, extensive studies in amniote embryos have produced conflicting data on exactly how embryonic segments relate to those of the adult. To date, much attention has focused on the derivatives of the somites, while relatively little is known about the contribution of other tissues to the formation of the vertebral column. In particular, while it is clear that signals from the notochord induce and maintain proliferation of the sclerotome, and later promote chondrogenesis, the role of the notochord in vertebral segmentation has been largely overlooked. Here, we review the established role of the notochord in vertebral development, and suggest an additional role for the notochord in the segmental patterning of the vertebral column.

‣ Frequency of Metamerism in Natural Scenes

Foster, David H.; Amano, Kinjiro; Nascimento, Sérgio M. C.; Foster, Michael J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2006 Português
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Estimates of the frequency of metameric surfaces, which appear the same to the eye under one illuminant but different under another, were obtained from 50 hyperspectral images of natural scenes. The degree of metamerism was specified with respect to a color-difference measure after allowing for full chromatic adaptation. The relative frequency of metameric pairs of surfaces, expressed as a proportion of all pairs of surfaces in a scene, was very low. Depending on the criterion degree of metamerism, it ranged from about 10−6 to 10−4 for the largest illuminant change tested, which was from a daylight of correlated color temperature 25,000 K to one of 4000 K. But, given pairs of surfaces that were indistinguishable under one of these illuminants, the conditional relative frequency of metamerism was much higher, from about 10−2 to 10−1, sufficiently large to affect visual inferences about material identity.

‣ Neuropilin receptors guide distinct phases of sensory and motor neuronal segmentation

Roffers-Agarwal, Julaine; Gammill, Laura S.
Fonte: Company of Biologists Publicador: Company of Biologists
Tipo: Artigo de Revista Científica
Português
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The segmented trunk peripheral nervous system is generated by ventrally migrating neural crest cells that exclusively invade the anterior sclerotome and differentiate into metameric dorsal root and sympathetic ganglia. Meanwhile, ventral spinal motor axons also project through the somites in a segmental fashion. How peripheral nervous system segmentation is generated is unknown. We previously showed that neuropilin 2 (Nrp2)/semaphorin 3F (Sema3F) signaling is required for segmental neural crest migration, but not for metameric dorsal root gangliogenesis. We now expand these results to show that Nrp2 patterns initial motor axon outgrowth as well. Later, Nrp1/Sema3A signaling is essential for segmental dorsal root gangliogenesis and motor axonal fasciculation into ventral roots. Strikingly, Nrp/Sema signaling is not required for sympathetic ganglia segmentation. These data show that Nrp2 and Nrp1 work together to produce segmentation of sensory and motor nerves, and that dorsal peripheral nervous system metamerism is generated in a stepwise, Nrp-dependent process.

‣ METAMERISM IN MULTISPECTRAL IMAGING OF HISTOPATHOLOGY SPECIMENS

Cukierski, William J.; Foran, David J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 14/04/2010 Português
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A multispectral camera is capable of imaging a histologic slide at narrow bandwidths over the range of the visible spectrum. There is currently no clear consensus over the circumstances in which this added spectral data may improve computer-aided interpretation and diagnosis of imaged pathology specimens [1, 2, 3]. Two spectra which are perceived as the same color are called metamers, and the collection of all such spectra are referred to as the metamer set. Highly metameric colors are amenable to separation through multispectral imaging (MSI).

‣ Dynamic CREB family activity drives segmentation and posterior polarity specification in mammalian somitogenesis

Lopez, T. Peter; Fan, Chen-Ming
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
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The segmented axial skeleton of vertebrates is composed of an interlinked framework of vertebrae and ribs. During embryogenesis, vertebral precursors known as somites form sequentially from a progenitor tissue known as the presomitic mesoderm to foreshadow the metamerism of the axial skeleton. We have discovered that the cAMP responsive element binding protein (CREB) family of transcription factors operates in combination with Notch and Wnt signaling to instruct the timely scission of presomitic mesoderm into somites with proper anterior/posterior polarities. Thus, the CREB family represents a new and important molecular integrator in axial skeleton development. Our work has potential implications to spinal disorders such as scoliosis.

‣ Detecting near-UV and near-IR wavelengths with the FOVEON image sensor

Cheak, Seck Fai
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xvi, 61 p. : ill. (some col.) ;
Português
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Approved for public release; distribution in unlimited.; Traditionally, digital imaging systems rely on the use of dedicated photodetectors to capture specific wavelengths in the visible spectrum. These photodetectors, which are commonly made of silicon, are arranged as arrays to capture the red, green and blue wavelengths. The signal captured by the individual photodetectors must then be interpolated and integrated to obtain the closest color match and the finest possible resolution with reference to the actual object. The use of spatially separated detectors to sense primary colors reduces the resolution by a factor of three compared to black and white imaging. The FOVEON detector technology greatly improves the color and resolution of the image through its vertically arranged, triple well photodetector. This is achieved by exploiting the variation of absorption coefficient of silicon with wavelength in the visible spectrum. Hence, in a silicon detector, the shorter wavelength (e.g. blue) would be mainly absorbed at a shallow depth. A longer wavelength (e.g. red) would penetrate the material deeper than the shorter wavelengths and be primarily absorbed at a greater depth. By producing a layered silicon detector, all three primary colour wavelengths of red...

‣ Illumination inconsistency sleuthing for exposing fauxtography and uncovering composition telltales in digital images; Investigando inconsistências de iluminação para detectar fotos fraudulentas e descobrir traços de composições em imagens digitais

Tiago José de Carvalho
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/03/2014 Português
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Antes tomadas como naturalmente genuínas, fotografias não mais podem ser consideradas como sinônimo de verdade. Com os avanços nas técnicas de processamento de imagens e computação gráfica, manipular imagens tornou-se mais fácil do que nunca, permitindo que pessoas sejam capazes de criar novas realidades em minutos. Infelizmente, tais modificações, na maioria das vezes, têm como objetivo enganar os observadores, mudar opiniões ou ainda, afetar como as pessoas enxergam a realidade. Assim, torna-se imprescindível o desenvolvimento de técnicas de detecção de falsificações eficientes e eficazes. De todos os tipos de falsificações de imagens, composições são de especial interesse. Esse tipo de falsificação usa partes de duas ou mais imagens para construir uma nova realidade exibindo para o observador situações que nunca aconteceram. Entre todos os diferentes tipos de pistas investigadas para detecção de composições, as abordagens baseadas em inconsistências de iluminação são consideradas as mais promissoras uma vez que um ajuste perfeito de iluminação em uma imagem falsificada é extremamente difícil de ser alcançado. Neste contexto, esta tese, a qual é fundamentada na hipótese de que inconsistências de iluminação encontradas em uma imagem são fortes evidências de que a mesma é produto de uma composição...

‣ Adaptation in the vertebral column: a comparative study of patterns of metameric variation in mice and men

O'HIGGINS, P.; MILNE, N.; JOHNSON, D. R.; RUNNION, C. K.; OXNARD, C. E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1997 Português
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In this paper we examine metamerism in the vertebral column of certain mammals from the perspectives of development and adaptation. To this end we examine the patterns of metameric variation of dimensions of the neural (vertebral) canal, vertebral body and spinous process in man and inbred strains of mice. The data from inbred strains of mice indicate that variability in dimensions within a strain reflects the temporal ordering and nature of developmental influences on vertebral morphogenesis. Differences between strains parallel the within-strain findings. These findings are attributed to somatic and neural influences on morphogenesis. Comparisons between mice and man indicate that these same influences can be invoked to explain and interpret the mosaic nature of vertebral column evolution. These findings lead us to conclude that different vertebral elements and levels are subject to different interactions of evolutionary and morphogenetic influences. The study of these influences and their interactions should prove fruitful in developing an understanding of the relationship between adaptation, development, growth and function in the skeleton generally.

‣ A Study of Metamerism

Morgan, T. H.
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /05/1895 Português
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That there were occasionally to be found in the Annelids irregularities in the serial repetition of the rings seems to have been known to several of the earlier writers on descriptive and systematic zoology. The fact did not attract more than a passing attention, and such irregularities were relegated to that waste-heap of abnormalities from which subsequent investigation has often drawn valuable material. Simultaneously in 1892 two articles appeared dealing with these abnormal conditions, one by C. J. Cori (13), and the other by the present writer (33). Both writers pointed out the general interest attached to these modifications, and their importance for an interpretation of the general problem of metamerism. Subsequently a third paper appeared (10), recording the presence of similar abnormalities in many groups of Annelids, but without making any attempt to solve the problem itself. My own paper was only a preliminary notice, and until the present time I have not had an opportunity of fully describing the material that I had at that time already accumulated, studied, and drawn. The present paper attempts to give a full consideration of the facts only touched on before, and to extend over a wider field the conclusions reached.

‣ Modeling observer metamerism through Monte Carlo simulation

Fairchild, Mark
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Conferência ou Objeto de Conferência
Português
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Metameric color matches depend on the observer’s color matching functions. Data were collected on observer variability in typical metameric matches. A Monte Carlo simulation, using a model of color matching functions and physiological data, was performed to derive a complete colorimetric system capable of predicting inter-observer variability in addition to mean color matches.; Location: Rochester, NY Event: OSA Annual Meeting

‣ Computer synthesis of Spectroradiometric images for color imaging systems analysis

Johnson, Garrett; Fairchild, Mark
Fonte: Society for Imaging Science and Technology Publicador: Society for Imaging Science and Technology
Tipo: Proceedings
Português
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A technique to perform full spectral based color calculations through an extension of OpenGL has been created. This method of color computations is more accurate than the standard RGB model that most computer graphics algorithms utilize. By maintaining full wavelength information in color calculations, it is also possible to interactively simulate and display many important color phenomena such as metamerism and fluorescence. This technique is not limited to creating simple images suitable for interactive display, however. Using this extension, it is also possible to synthesize spectroradiometric images of arbitrary spatial and spectral resolution, for use in color imaging system analysis.; Location: Scottsdale, Arizona Publishers version can be found here: http://www.imaging.org/store/physpub.cfm?seriesid=4&pubid=3

‣ A Study to evaluate current color matching procedures

McDonough, Brian
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
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The primary objective of this study was to determine if current color matching procedures produce the desired color on the final printed package. A problem with printed items is that multiple departments and companies are involved with the choosing, specifying and approving of colors. This study evaluated one part of this procedure - the printed color standard. The printed color standard is used by the printer and packaging buyer to assure color consistency. However, there is often little understanding of light sources, color perception, chromatic adaptation, metamerism and ink dry-back. Color reference systems, like Pantone, recommend updating their color standards every six months to assure color consistency. Yet, printed color standards that are produced with less inert inks and a more reactive surface, are often used for years. This study evaluated the drying and ageing characteristics of ink both visually and spectrophotometrically, and showed that the current color matching procedures need to be improved to reduce the chance of off colors.

‣ Spectral-based color separation algorithm development for multiple-ink color reproduction

Tzeng, Di-Yuan
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
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Conventional four-color printing systems are limited by an insufficient number of degrees of freedom for tuning the visible region of the spectrum; as a consequence, they are often limited to metameric color reproductions. That is, color matches defined for a single observer and illuminant (usually CIE illuminant D50 and the 1931 standard observer) are often unstable when viewed under other illuminants or by other observers. For critical color-matching applications, such as catalog sales and artwork reproductions, the results are usually disappointing due to typical uncontrolled lighting and viewing. Furthermore, the existing multiple-ink printing systems, which all focus on expanding color gamut, do not alleviate metamerism since their separation algorithms are trichromatic in nature. The advantage of an increased number of degrees of freedom is not exploited. A research and development program has been initiated at the Rochester Institute of Technology's Munsell Color Science Laboratory to develop a spectral-based color reproduction system Research has included multi-spectral acquisition systems and spectral-based printing. The current research is concerned with bridging these analysis and synthesis stages of color reproduction. The goal of the doctoral research was to minimize IV metamerism between originals and their corresponding reproductions...

‣ A Computational analysis of observer metamerism in cross-media color matching

Alfvin, Richard
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
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Standard color-matching functions are designed to represent the mean color-matching response of the population of human observers with normal color vision. When using these functions, two questions arise. Are they an accurate representation of the population? And what is the uncertainty in color-match predictions? To address these questions in the dual context of human visual performance and cross-media reproduction, a color-matching experiment was undertaken in which twenty observers made matches between seven different colors presented in reflective and transmissive color reproduction media and a CRT display viewed through an optical apparatus that produced a simple split field stimulus. In addition, a single observer repeated the experiment 20 times to quantify intra-observer variability. The results are used to evaluate the accuracy of three sets of color-matching functions, to quantify the magnitude of observer variability, and to compare intra- and inter-observer variability in color matching. These results are compared with current CIE recommendations on observer metamerism. The magnitude of observer variability in this experiment also provides a quantitative estimate of the limit of cross-media color reproduction accuracy that need not be exceeded.