1,720,966 research outputs found
Hyperspectral and multispectral studies of evaporite minerals at White Sands, New Mexico
No full textMost multispectral sensors such as Landsat 7 ETM+, ASTER, and ALI measure reflected energy in a few and separated wavelength bands and are thereby referred to as multispectral. In contrast, hyperspectral imaging spectrometers have a sufficient amount of continuous spectral channels to resolve the spectral variability of the earth\u27s surface. This study focuses on uncovering the spectral complexity of Alkali Flat and Lake Lucero, White Sands. They are remnants of Lake Otero and together form the primary source of gypsum that forms the dune field of the White Sands. One of the goals of this study was to compare the information dimensionality limits of Landsat 7 ETM+, ASTER and ALI data with high spectral resolution, low signal-to-noise Hyperion data, using AVIRIS data as a high spectral resolution, high signal-to-noise standard. Information dimensionality thresholds constrain the number of evaporite mineral and textural endmembers that can be detected, mapped, or unmixed using standard image processing methods. In this case, eigen analysis of the Minimum Noise Fraction (MNF) transformation and Principle Component Analysis (PCA) results were used to uncover the information dimensionality limits of all these datasets. The Pixel Purity Index (PPI), and n-D Visualization were used to identify spectrally distinct endmember classes, and along with ground truth and field spectra provide insights into the origin of the spectral variability uncovered in all of the datasets. The results confirm that AVIRIS and Hyperion data have higher information dimensionality thresholds exceeding the number of available bands of Landsat 7 ETM+, ASTER, and ALI data. AVIRIS has higher information dimensionality thresholds than Hyperion because of its 410x increase in signal-to-noise over Hyperion. Much of the information dimensionality uncovered by AVIRIS and Hyperion datasets can be due differences in vegetation landcover, grain size variations, and moisture contents as opposed to mineral compositional variations. These endmember components uncovered at Alkali Flat and Lake Lucero include: (1) dry gypsum, (2) wet gypsum, (3) water, (4) vegetation, and (5) clastic sediment dominated by ferric iron and calcite. The spectral signatures of these endmembers at the resolution of AVIRIS, Hyperion, ALI, ASTER, and Landsat 7 ETM+ agreed with field and laboratory spectral analysis. (Abstract shortened by UMI.
Reflectance spectroscopy and ASTER mapping of aeolian dunes of Shaqra and Tharmada Provinces, Saudi Arabia: Field validation and laboratory confirmation
No full textSpatial variability of grain sizes and mapping of aeolian dunes is important to study the sand erosion, transport, and dune movement and to understand the dune encroachment and land degradation. This study examines the grain size statistical parameters and mineralogical composition of 68 sand samples collected from 17 crescentic dunes and assesses the source and depositional environment of these dunes. The analyses of samples for grain sizes resulted that the sands are characteristics to fine with an average size of 2.28 Φ and classified as moderately well-sorted(0.59 Φ), mesokurtic (0.97 Φ), and fine to coarsely skewed (0.14 Φ). X-Ray Diffraction shows that the dunes are deposited mainly by quartz, calcite, and haematite. The occurrence of absorption features near 0.5, 0.9, and 2.22 μm confirm the presence of such iron and aluminosilicate minerals in the dunes. The dunes of the provinces were mapped using TIR bands of ASTER satellite data by Carbonate index (CI) and Quartz index (QI). A good agreement among the results of grain size analyses, spectral measurements, mineralogical studies, and mapping of dunes with the field observations suggests that the sand deposits in the study area have a diversity of sources in the aeolian environment.This project was supported by King Saud University, Deanship of Scientific Research, College of Science Research Center
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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