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Статті в журналах з теми "Spectral distances"
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Navarro, Silvana G., Romano L. M. Corradi, and Antonio Mampaso. "Distance determination to PNe using the extinction-distance method." Proceedings of the International Astronomical Union 7, S283 (July 2011): 460–61. http://dx.doi.org/10.1017/s1743921312011921.
Повний текст джерелаАнотація:
AbstractWe present individual distances to three PNe: NGC 6537, NGC 6781 and NGC 7027, determined by the extinction-distance method. These objects are part of a larger sample (35) of PNe that we observed at ORM. In order to apply this method, and to obtain accurate distances, we determined the spectral type of 40 to 60 stars in the line of sight of each PNe. This implied the necessity of classifying few thousands of stellar spectra with S/N ratio between 10 and 60. To solve such need we developed an ANN system to perform automatic spectral classification which could classify spectra with S/N ratio as low as 20 with an accuracy better than 2 spectral subtypes. In this poster we compare the accuracy of such distances with previous distance determinations using other methods. We conclude that it is possible to use this method to obtain the distance of a large number of PNe with better precision.
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Jovanović, Irena, and Zoran Stanić. "Spectral distances of graphs." Linear Algebra and its Applications 436, no. 5 (March 2012): 1425–35. http://dx.doi.org/10.1016/j.laa.2011.08.019.
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Gu, Jiao, Bobo Hua, and Shiping Liu. "Spectral distances on graphs." Discrete Applied Mathematics 190-191 (August 2015): 56–74. http://dx.doi.org/10.1016/j.dam.2015.04.011.
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Chelli, A., and G. Duvert. "Pseudo-photometric distances of 30 open clusters." Astronomy & Astrophysics 619 (November 2018): A132. http://dx.doi.org/10.1051/0004-6361/201833082.
Повний текст джерелаАнотація:
Aims. We demonstrate that reliable photometric distances of stellar clusters, and more generally of stars, can be obtained using pseudomagnitudes and rough spectral type without having to correct for visual absorption. Methods. We determine the mean absolute pseudomagnitude of all spectral (sub)types between B and K. Distances are computed from the difference between the star’s observed pseudomagnitude and its spectral type’s absolute pseudomagnitude. We compare the distances of 30 open clusters thus derived against the distances derived from TGAS parallaxes. Results. Our computed distances, up to distance modulus 12, agree within 0.1 mag rms with those obtained from TGAS parallaxes, proving excellent distance estimates. We show additionally that there are actually two markedly different distances in the cluster NGC 2264. Conclusions. We suggest that the pseudomagnitude distance estimation method, which is easy to perform, can be routinely used in all large-scale surveys where statistical distances on a set of stars, such as an open cluster, are required.
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Pollacco, D. L., and G. Ramsay. "Reddening Distances for Planetary Nebulae from Broad Band BVIc CCD Imaging." Symposium - International Astronomical Union 155 (1993): 180. http://dx.doi.org/10.1017/s0074180900170421.
Повний текст джерелаАнотація:
If the zero age main sequence is expressed in the (V–I) versus (B–V)–(V–I) plane the reddening lines are found to lie at a great enough angle to allow reasonably accurate spectral type classification for stars later than ∼ F5. Earlier spectral types can also be identified but with lower accuracy. Comparison with the Q method of UBV photometry and with spectra of some of the program stars shows that the BVIc technique produces reliable results. As late–type stars constitute the most numerous spectral types and are plentiful in all galactic plane directions BVIc reddening distances can be derived close to the desired direction (although to smaller distances than techniques that utilize early type stars). The applicability of the technique is further enhanced by the use of CCDs which generally have a spectral response well suited for BVIc imaging observations. Using the new technique the distance to the PN NGC2440 was found to be (3100 ± 320)pc.
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Cvetkovic, Dragos. "Spectral recognition of graphs." Yugoslav Journal of Operations Research 22, no. 2 (2012): 145–61. http://dx.doi.org/10.2298/yjor120925025c.
Повний текст джерелаАнотація:
At some time, in the childhood of spectral graph theory, it was conjectured that non-isomorphic graphs have different spectra, i.e. that graphs are characterized by their spectra. Very quickly this conjecture was refuted and numerous examples and families of non-isomorphic graphs with the same spectrum (cospectral graphs) were found. Still some graphs are characterized by their spectra and several mathematical papers are devoted to this topic. In applications to computer sciences, spectral graph theory is considered as very strong. The benefit of using graph spectra in treating graphs is that eigenvalues and eigenvectors of several graph matrices can be quickly computed. Spectral graph parameters contain a lot of information on the graph structure (both global and local) including some information on graph parameters that, in general, are computed by exponential algorithms. Moreover, in some applications in data mining, graph spectra are used to encode graphs themselves. The Euclidean distance between the eigenvalue sequences of two graphs on the same number of vertices is called the spectral distance of graphs. Some other spectral distances (also based on various graph matrices) have been considered as well. Two graphs are considered as similar if their spectral distance is small. If two graphs are at zero distance, they are cospectral. In this sense, cospectral graphs are similar. Other spectrally based measures of similarity between networks (not necessarily having the same number of vertices) have been used in Internet topology analysis, and in other areas. The notion of spectral distance enables the design of various meta-heuristic (e.g., tabu search, variable neighbourhood search) algorithms for constructing graphs with a given spectrum (spectral graph reconstruction). Several spectrally based pattern recognition problems appear in many areas (e.g., image segmentation in computer vision, alignment of protein-protein interaction networks in bio-informatics, recognizing hard instances for combinatorial optimization problems such as the travelling salesman problem). We give a survey of such and other graph spectral recognition techniques used in computer sciences.
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Bronstein, Michael M., and Alexander M. Bronstein. "Shape Recognition with Spectral Distances." IEEE Transactions on Pattern Analysis and Machine Intelligence 33, no. 5 (May 2011): 1065–71. http://dx.doi.org/10.1109/tpami.2010.210.
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da Cunha Lima, A. T., I. C. da Cunha Lima, and M. P. de Almeida. "Analysis of turbulence power spectra and velocity correlations in a pipeline with obstructions." International Journal of Modern Physics C 28, no. 02 (February 2017): 1750019. http://dx.doi.org/10.1142/s012918311750019x.
Повний текст джерелаАнотація:
We calculate the power spectral density and velocity correlations for a turbulent flow of a fluid inside a duct. Turbulence is induced by obstructions placed near the entrance of the flow. The power spectral density is obtained for several points at cross-sections along the duct axis, and an analysis is made on the way the spectra changes according to the distance to the obstruction. We show that the differences on the power spectral density are important in the lower frequency range, while in the higher frequency range, the spectra are very similar to each other. Our results suggest the use of the changes on the low frequency power spectral density to identify the occurrence of obstructions in pipelines. Our results show some frequency regions where the power spectral density behaves according to the Kolmogorov hypothesis. At the same time, the calculation of the power spectral densities at increasing distances from the obstructions indicates an energy cascade where the spectra evolves in frequency space by spreading the frequency amplitude.
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Jovanovic, Irena, and Zoran Stanic. "Spectral distances of graphs based on their different matrix representations." Filomat 28, no. 4 (2014): 723–34. http://dx.doi.org/10.2298/fil1404723j.
Повний текст джерелаАнотація:
The investigation of the spectral distances of graphs that started in [3] (I. Jovanovic, Z. Stanic, Spectral distances of graphs, Linear Algebra Appl., 436 (2012) 1425-1435.) is continued by defining Laplacian and signless Laplacian spectral distances and considering their relations to the spectral distances based on the adjacency matrix of graph. Some separate results concerning the defined distances are given, and the initial spectral distances in certain sets of graphs are investigated. Computational data on Laplacian and signless Laplacian spectral distances are provided.
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Baggio, Giacomo, Augusto Ferrante, and Rodolphe Sepulchre. "Conal Distances Between Rational Spectral Densities." IEEE Transactions on Automatic Control 64, no. 5 (May 2019): 1848–57. http://dx.doi.org/10.1109/tac.2018.2855114.
Повний текст джерелаДисертації з теми "Spectral distances"
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Godbout, Martin. "Mesures de distances et de spectres résolus en distance en utilisant les battements hétérodynes entre peignes de fréquences." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27451/27451.pdf.
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Imran, Hafiz Ali. "Remote Sensing Tools for Monitoring Grassland Plant Leaf Traits and Biodiversity." Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/329592.
Повний текст джерелаАнотація:
Grasslands are one of the most important ecosystems on Earth, covering approximately one-third of the Earth’s surface. Grassland biodiversity is important as many services provided by such ecosystems are crucial for the human economy and well-being. Given the importance of grasslands ecosystems, in recent years research has been carried out on the potential to monitor them with novel remote sensing techniques. Improved detectors technology and novel sensors providing fine-scale hyperspectral imagery have been enabling new methods to monitor plant traits (PTs) and biodiversity.
The aims of the work were to study different approaches to monitor key grassland PTs such as Leaf Area Index (LAI) and biodiversity-related traits. The thesis consists of 3 parts: 1) Evaluating the performance of remote sensing methods to estimate LAI in grassland ecosystems, 2) Estimating plant biodiversity by using the optical diversity approach in grassland ecosystems, and 3) Investigating the relationship between PTs variability with alpha and beta diversity for the applicability of the optical diversity approach in a subalpine grassland of the Italian Alps
To evaluate the performance of remote sensing methods to estimate LAI, temporal and spatial observations of hyperspectral reflectance and LAI were analyzed at a grassland site in Monte Bondone, Italy (IT-MBo). In 2018, ground temporal observations of hyperspectral reflectance and LAI were carried out at a grassland site in Neustift, Austria (AT-NEU). To estimate biodiversity, in 2018 and 2019 a floristics survey was conducted to determine species composition and hyperspectral data were acquired at two grassland sites: IT-MBo and University of Padova’s Experimental Farm, Legnaro, Padua, Italy (IT-PD) respectively. Furthermore, in 2018, biochemistry analysis of the biomass samples collected from the grassland site IT-MBo was carried out to determine the foliar biochemical PTs variability.
The results of the thesis demonstrated that the grassland spectral response across different spectral regions (Visible: VIS, red-edge: RE, Near-infrared: NIR) showed to be both site-specific and scale-dependent. In the first part of the thesis, the performance of spectral vegetation indices (SVIs) based on visible, red-edge (RE), and NIR bands alongside SVIs solely based or NIR-shoulder bands (wavelengths 750 - 900 nm) was evaluated. A strong correlation (R2 > 0.8) was observed between grassland LAI and both RE and NIR-shoulder SVIs on a temporal basis, but not on a spatial basis. Using the PROSAIL Radiative Transfer Model (RTM), it was demonstrated that grassland structural heterogeneity strongly affects the ability to retrieve LAI, with high uncertainties due to structural and biochemical PTs co-variation.
In the second part, the applicability of the spectral variability hypothesis (SVH) was questioned and highlighted the challenges to use high-resolution hyperspectral images to estimate biodiversity in complex grassland ecosystems. It was reported that the relationship between biodiversity (Shannon, Richness, Simpson, and Evenness) and optical diversity metrics (Coefficient of variation (CV) and Standard deviation (SD)) is not consistent across plant communities. The results of the second part suggested that biodiversity in terms of species richness could be estimated by optical diversity metrics with an R2 = 0.4 at the IT-PD site where the grassland plots were artificially established and are showing a lower structure and complexity from the natural grassland plant communities. On the other hand, in the natural ecosystems at IT-MBo, it was more difficult to estimate biodiversity indices, probably due to structural and biochemical PTs co-variation. The effects of canopy non-vegetative elements (flowers and dead material), shadow pixels, and overexposed pixels on the relationship between optical diversity metrics and biodiversity indices were highlighted.
In the third part, we examined the relationship between PTs variability (at both local and community scales, measured by standard deviation and by the Euclidean distances of the biochemical and biophysical PTs respectively) and taxonomic diversity (both α-diversity and β-diversity, measured by Shannon’s index and by Jaccard dissimilarity index of the species, families, and functional groups percent cover respectively) in Monte Bondone, Trentino province, Italy. The results of the study showed that the PTs variability metrics at alpha scale were not correlated with α-diversity. However, the results at the community scale (β-diversity) showed that some of the investigated biochemical and biophysical PTs variations metrics were associated with β-diversity. The SVH approach was also tested to estimate β-diversity and we found that spectral diversity calculated by spectral angular mapper (SAM) showed to be a better proxy of biodiversity in the same ecosystem where the spectral diversity failed to estimate alpha diversity, this leading to the conclusion that the link between functional and species diversity may be an indicator of the applicability of optical sampling methods to estimate biodiversity.
The findings of the thesis highlighted that grassland structural heterogeneity strongly affects the ability to retrieve both LAI and biodiversity, with high uncertainties due to structural and biochemical PTs co-variation at complex grassland ecosystems. In this context, the uncertainties of satellite-based products (e.g., LAI) in monitoring grassland canopies characterized by either spatially or temporally varying structure need to be carefully taken into account. The results of the study highlighted that the poor performance of optical diversity proxies in estimating biodiversity in structurally heterogeneous grasslands might be due to the complex relationships between functional diversity and biodiversity, rather than the impossibility to detect functional diversity with spectral proxies.
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Deborah, Hilda. "Towards spectral mathematical morphology." Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2328/document.
Повний текст джерелаАнотація:
En fournissant en plus de l'information spatiale une mesure spectrale en fonction des longueurs d'ondes, l'imagerie hyperspectrale s'enorgueillie d'atteindre une précision bien plus importante que l'imagerie couleur. Grâce à cela, elle a été utilisée en contrôle qualité, inspection de matériaux,… Cependant, pour exploiter pleinement ce potentiel, il est important de traiter la donnée spectrale comme une mesure, d'où la nécessité de la métrologie, pour laquelle exactitude, incertitude et biais doivent être maitrisés à tous les niveaux de traitement.Face à cet objectif, nous avons choisi de développer une approche non-linéaire, basée sur la morphologie mathématique et de l'étendre au domaine spectral par le biais d'une relation d'ordre spectral basée sur les fonctions de distance. Une nouvelle fonction de distance spectrale et une nouvelle relation d'ordonnancement sont ainsi proposées. De plus, un nouvel outil d'analyse du basé sur les histogrammes de différences spectrales a été développé.Afin d'assurer la validité des opérateurs, une validation théorique rigoureuse et une évaluation métrologique ont été mises en œuvre à chaque étage de développement. Des protocoles d'évaluation de la qualité des traitements morphologiques sont proposés, exploitant des jeux de données artificielles pour la validation théorique, des ensembles de données dont certaines caractéristiques sont connues pour évaluer la robustesse et la stabilité et des jeux de données de cas réel pour prouver l'intérêt des approches en contexte applicatif. Les applications sont développées dans le contexte du patrimoine culturel pour l'analyse de peintures et pigmentsProviding not only spatial information but also spectral measure as a function of wavelength, hyperspectral imaging boasts a much greater gain in accuracy than the traditional color imaging. And for this capability, hyperspectral imaging has been employed for quality control, inspection of materials in various fields. However, to fully exploit this potential, it is important to process the spectral data as a measure. This induces the need of metrology where accuracy, uncertainty, and bias are managed at every level of processing.Aiming at developing a metrological image processing framework for spectral data, we select to develop a nonlinear approach using the mathematical morphology framework and extended it to the spectral domain by means of a distance-based ordering relation. A novel spectral distance function and spectral ordering relation are proposed, in addition of a new analysis tools based on spectral differences. To ensure the validity of the spectral mathematical morphology framework, rigorous theoretical validation and metrological assessment are carried out at each development stages. So, protocols for quality assessment of spectral image processing tools are developed. These protocols consist of artificial datasets to validate completely the theoretical requirements, datasets with known characteristics to assess the robustness and stability, and datasets from real cases to proof the usefulness of the framework on applicative context. The application tasks themselves are within the cultural heritage domain, where the target images come from pigments and paintings
Hyperspektral avbildning muliggjør mye mer nøyaktige målinger enn tradisjonelle gråskala og fargebilder, gjennom både høy romlig og spektral oppløsning (funksjon av bølgelengde). På grunn av dette har hyperspektral avbildning blitt anvendt i økende grad ulike applikasjoner som kvalitetskontroll og inspeksjon av materialer. Men for å fullt ut utnytte sitt potensiale, er det viktig å være i stand til å behandle spektrale bildedata som målinger på en gyldig måte. Dette induserer behovet for metrologi, der nøyaktighet, usikkerhet og skjevhet blir adressert og kontrollert på alle nivå av bildebehandlingen.Med sikte på å utvikle et metrologisk rammeverk for spektral bildebehandling valgte vi en ikke-lineær metodikk basert på det etablerte matematisk morfologi-rammeverket. Vi har utvidet dette rammeverket til det spektrale domenet ved hjelp av en avstandsbasert sorteringsrelasjon. En ny spektral avstandsfunksjon og nye spektrale sorteringsrelasjoner ble foreslått, samt nye verktøy for spektral bildeanalyse basert på histogrammer av spektrale forskjeller.For å sikre gyldigheten av det nye spektrale rammeverket for matematisk morfologi, har vi utført en grundig teoretisk validering og metrologisk vurde-ring på hvert trinn i utviklingen. Dermed er og-så nye protokoller for kvalitetsvurdering av spektrale bildebehandlingsverktøy utviklet. Disse protokollene består av kunstige datasett for å validere de teoretiske måletekniske kravene, bildedatasett med kjente egenskaper for å vurdere robustheten og stabiliteten, og datasett fra reelle anvendelser for å bevise nytten av rammeverket i en anvendt sammenheng. De valgte anvendelsene er innenfor kulturminnefeltet, hvor de analyserte bildene er av pigmenter og malerier
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Bertrand, Jérôme. "Pincement spectral en courbure positive." Paris 11, 2003. https://tel.archives-ouvertes.fr/tel-00008705.
Повний текст джерелаАнотація:
Sur l'ensemble des variétés Riemanniennes compactes à courbure de Ricci positive (on normalise par Ric ≥ (n -1)g), la première valeur propre du Laplacien agissant sur les fonctions atteint son minimum uniquement pour la sphère canonique. Dans cette thèse, nous caractérisons, à l'aide de la distance de Gromov-Hausdorff, les variétés Riemanniennes à courbure positive dont les premières valeurs propres du Laplacien sont proches de celles de la sphère canonique. Cette propriété de minimimalité du spectre de la sphère s'étend par un procédé de symétrisation, au spectre de Dirichlet des boules géodésiques de la sphère parmi les domaines de variétés à courbure de Ricci positive. Nous étudions les domaines de variétés à courbure de Ricci positive dont la première valeur propre de Dirichlet est presque minimale. En particulier, nous montrons qu'un domaine dont la première valeur propre de Dirichlet est proche de celle d'un hémisphère est Gromov-Hausdorff proche d'un hémisphère d'un sinus produit torduOn the set of compact Riemannian manifolds with positive Ricci curvature (normalized by Ric ≥ (n-1)g), the first eigenvalue of the Laplacian acting on functions reaches its minimum only for the round sphere. In this thesis, we characterize, using the Gromov-Hausdorff distance, Riemannian manifolds with positive Ricci curvature whose first eigenvalues are close to those of the round sphere. This property of minimality of the spectrum of the round sphere has been extended by a symmetrization principle, to the Dirichlet spectrum of the geodesic balls of the round sphere among the domains of Riemannian manifolds with positive curvature. We study the domains of Riemannian manifolds with positive Ricci curvature whose first Dirichlet eigenvalue is almost minimal. In particular, we show that a domain whose first Dirichlet eigenvalue is close to the one of a hemisphere is Gromov-Hausdorff close to a hemisphere of a sine warped product
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Diego, Víctor. "On some spectral and combinatorial properties of distance-regular graphs and their generalizations." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461632.
Повний текст джерелаАнотація:
In this work we present the study we did in Graph Theory. In the firsts chapteres of the tesis we study the pieces of information that can be obtained from a graph: the spectrum of the adjacency matrix, the preintersection numbers, the predistance polynomials and the average number of closed walks. Some of this pieces of information are direct generalizations of the intersection numbers or the predistance polynomials defined in the distance-regular graphs. We prove that the multiple properties that these pieces of information have in distance-regular graphs hold also in their generalizations, and these properties can be applied to any other graph.
We also prove that the distinct pieces of information (even if their nature is algebraic or combinatorial) are equivalent. That is, we can obtain each one of the pieces in terms of each other; proving in this way that the properties of the graph derived from each one of the pieces can be also obtained in terms of each one of the other. We dedicate a chapter of the tesis to describe completly the especific procedures with which obtain each piece of inforation in terms of the others.
In this tesis we introduce the "distance mean-regular" graphs. These graphs are a generalization of the distance-regular graphs. In this occasion, we demand to the graph combinatorial properties and we generalizate the algebraic properties of the distance-regular graphs. We generalizate the spectrum of a graph to introduce the "pseudo-spectrum" and we generalizate the Bose-Mesner algebra in distinct matrix algebras. The study of these generalizations, as well as the study of the relation between them, give us combinatorial and algebraic properties.
In the final part of the tesis we study the vertex-isoperimetric problem in the Johnson Graph J(n,m). We solve completly the problem for some particular cases: J(n,1), J(n,2), J(2m-2,m), as well as their symetrics J(n,n-2) and J(2m+2,m). The solution for these cases are the initial segments of the colexicographic order. This order is also the solution for small cardinals in every graph of this family, as well as for the asymptotic behaviour of the parameters n and m.
However, this solution is not the optimal solution for every cardinal in every graph J(n,m). We prove and give an infinity family of counterexamples for which the initial segment of the colexicographic order is not optimal in terms of the vertex-isoperimetric problem.En este documento presentamos el estudio realizado en Teoría de Grafos. En los primeros capítulos de la tesis estudiamos las distinetas piezas de información que se pueden obtener de un grafo: el espectro de su matriz de adyacencia, los números de preintersección, los polinomios predistancia o la cantidad media de caminos cerrados. Algunos de estas piezas de información son generalizaciones directas de los números de intersección o los pollinomios distancia definidos en los grafos distancia-regulares. Demostramos que las múltiples propiedades que tienen estas piezas de información en los grafos distancia-regulares se mantienen también en sus generalizaciones, pudiendo aplicar estas propiedades a todo tipo de grafos. Demostramos también que las ditintas piezas de información (ya sean de naturaleza algebraica o combinatoria) son equivalentes. Es decir, podemos obtener cada una de estas piezas en términos de cada una de las otras; probando así que las propiedades del grafo derivadas de cada una de estas piezas puede ser obtenida en términos de cada una de las otras. Dedicamos uno de los capítulos de la tesis a describir cuáles son los procesos específicos completos mediante los cuales obtener cada pieza de información en función de las otras. En esta tesis introducimos también los grafos distance mean-regular. Estos grafos son una generalización de los grafos distancia-regulares. En esta ocasión, al grafo se le exigen propiedades combinatorias y generalizamos las propiedades algebraicas de los grafos distancia-regulares. Generalizamos el espectro de un grafo para introducir el "pseudo-espectro" y generalizamos el álgebra de Bose-Mesner en distintas álgebras de matrices. El estudio de estas generalizaciones, así cómo su relación entre ellas nos proporciona propiedades combinatorias y algebraicas del grafo. En la parte final de la tesis estudiamos el problema isoperimétrico de vértices en el Grafo de Johnson J(n,m). Solucionamos el problema completamente para varios casos particulares: J(n,1), J(n,2) y J(2m-2,m), así como sus simétricos J(n,n-2) y J(2m+2,m). La solución para estos casos son los segmentos iniciales del orden colexicográfico. Este orden es también la solución para cardinales pequeños en todos los grafos de esta familia, así como para el comportamiento asimptótico de los parámetros n y m. Sin embargo, esta solución no es la solución óptima en todos cardinales de todos los grafos J(n,m). Demostramos y damos una familia infinita de contraejemplos para los cuales el segmento inicial de orden colexicográfico no es óptimo en términos del problema isoperimétrico de vértices
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Taylor, Melinda Marie. "Analysis of Cepheid Spectra." Thesis, The University of Sydney, 1998. http://hdl.handle.net/2123/388.
Повний текст джерелаАнотація:
Using high resolution optical spectra from Mount John University Observatory, Mount Stromlo Observatory and the Anglo-Australian Observatory, new, high accuracy radial velocity curves have been obtained for the two bright southern Cepheids l carinae (HR 3884) and beta doradus (HR 1922). An indepth investigation into period variations, cycle-to-cycle and long-term variations in the velocity curves and the reliability of the combination of velocity data from different observatories is carried out. Evidence for shock waves in the atmosphere of l car and resonance in beta dor is discussed. A grid of static model atmospheres incorporating plane-parallel geometry is compared with the observational spectra of both Cepheids, using line depth ratios, to determine the variation in effective temperature, surface gravity and microturbulence with phase. This information is used to determine the phase dependence of the surface-brightness for both Cepheids. The surface brightness variation with phase was found to follow an almost linear relationship. The distance to and radius of the Cepheids are determined using both a near-infrared version of the Barnes-Evans method and the Fourier Baade-Wesselink (BW) method. The derived radii and distances agree within the limits of the errors for both methods. The Fourier BW method was found to be very sensitive to phase shifts between the photometric and spectroscopic data and the derived distance highly dependent on the assumed reddening. An investigation into line profile variations in l car and beta dor has revealed the magnitude of these phenomena increase as the pulsational period of the Cepheid increases. It is estimated that line level variations introduce an additional uncertainty into derived radii of approximately 4 per cent for beta dor and 10 per cent in lcar. The uncertainty introduced into derived distances and radii by line profile asymmetries was estimated to be of the order of 6 per cent in beta dor and 10 per cent in l car. A comparative analysis is made of the hydrogen line radial velocity curves of l car and beta dor. A trend in the properties of these radial velocity curves with period has been revealed. In longer period Cepheids, the Halpha line seems to be forming in a region that does not partake in the pulsation as a whole, probably in a chromospheric shell. A quantitative analysis of the asymmetries in these lines reveal large redward asymmetries near maximum infall velocity. The magnitude of these asymmetries and the period for which they are present are larger in l Car than in beta dor. The blueward asymmetries in the Halpha line in l Car are comparable in magnitude to the redward asymmetries while the other lines exhibit only small blueward asymmetries. A qualitative analysis of these line profiles with phase reveal no conclusive evidence for line doubling in these Cepheids. Evidence of emission is found in the Halpha and H Beta lines of beta dor and l car. The strength and duration of the emission is found to be greater in the longer period Cepheid. Although it is likely that this emission is shock-related, theoretical work is needed to determine the exact origin of the emission. A non-LTE radiative hydrodynamic model for l Car has been created. This atmosphere will be used in further work to calculate synthetic spectral line profiles which will aid the interpretation of our observational results.
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Taylor, Melinda Marie. "Analysis of Cepheid Spectra." University of Sydney, Physics, 1998. http://hdl.handle.net/2123/388.
Повний текст джерелаАнотація:
Using high resolution optical spectra from Mount John University Observatory, Mount Stromlo Observatory and the Anglo-Australian Observatory, new, high accuracy radial velocity curves have been obtained for the two bright southern Cepheids l carinae (HR 3884) and beta doradus (HR 1922). An indepth investigation into period variations, cycle-to-cycle and long-term variations in the velocity curves and the reliability of the combination of velocity data from different observatories is carried out. Evidence for shock waves in the atmosphere of l car and resonance in beta dor is discussed. A grid of static model atmospheres incorporating plane-parallel geometry is compared with the observational spectra of both Cepheids, using line depth ratios, to determine the variation in effective temperature, surface gravity and microturbulence with phase. This information is used to determine the phase dependence of the surface-brightness for both Cepheids. The surface brightness variation with phase was found to follow an almost linear relationship. The distance to and radius of the Cepheids are determined using both a near-infrared version of the Barnes-Evans method and the Fourier Baade-Wesselink (BW) method. The derived radii and distances agree within the limits of the errors for both methods. The Fourier BW method was found to be very sensitive to phase shifts between the photometric and spectroscopic data and the derived distance highly dependent on the assumed reddening. An investigation into line profile variations in l car and beta dor has revealed the magnitude of these phenomena increase as the pulsational period of the Cepheid increases. It is estimated that line level variations introduce an additional uncertainty into derived radii of approximately 4 per cent for beta dor and 10 per cent in lcar. The uncertainty introduced into derived distances and radii by line profile asymmetries was estimated to be of the order of 6 per cent in beta dor and 10 per cent in l car. A comparative analysis is made of the hydrogen line radial velocity curves of l car and beta dor. A trend in the properties of these radial velocity curves with period has been revealed. In longer period Cepheids, the Halpha line seems to be forming in a region that does not partake in the pulsation as a whole, probably in a chromospheric shell. A quantitative analysis of the asymmetries in these lines reveal large redward asymmetries near maximum infall velocity. The magnitude of these asymmetries and the period for which they are present are larger in l Car than in beta dor. The blueward asymmetries in the Halpha line in l Car are comparable in magnitude to the redward asymmetries while the other lines exhibit only small blueward asymmetries. A qualitative analysis of these line profiles with phase reveal no conclusive evidence for line doubling in these Cepheids. Evidence of emission is found in the Halpha and H Beta lines of beta dor and l car. The strength and duration of the emission is found to be greater in the longer period Cepheid. Although it is likely that this emission is shock-related, theoretical work is needed to determine the exact origin of the emission. A non-LTE radiative hydrodynamic model for l Car has been created. This atmosphere will be used in further work to calculate synthetic spectral line profiles which will aid the interpretation of our observational results.
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Bertrand, Jerome. "Pincement spectral en courbure positive." Phd thesis, Université Paris Sud - Paris XI, 2003. http://tel.archives-ouvertes.fr/tel-00008705.
Повний текст джерелаАнотація:
Sur l'ensemble des variétés riemanniennes compactes à courbure de Ricci positive (on normalise par $Ric \geq (n-1)g$), la première valeur propre non nulle du laplacien agissant sur les fonctions atteint son minimum uniquement pour la sphère canonique. Dans cette thèse, nous caractérisons, à l'aide de la distance de Gromov-Hausdorff, les variétés riemanniennes à courbure positive dont les premières valeurs propres du laplacien sont proches de celles de la sphère canonique. Cette propriété de minimimalité du spectre de la sphère s'étend par un procédé de symétrisation, au spectre de Dirichlet des boules géodésiques de la sphère parmi les domaines de variétés à courbure de Ricci positive. Nous étudions les domaines de variétés à courbure de Ricci positive dont la première valeur propre de Dirichlet est presque minimimale. En particulier, nous montrons qu'un domaine convexe dont la première valeur propre de Dirichlet est proche de celle d'un hémisphèere est Gromov-Hausdorff proche d'un hémisphère d'un sinus produit tordu.
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Harrell, Dameon C. (Dameon Cartíer) 1976. "Effects of microphone type and distance upon the spectra of speech sounds." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80067.
Повний текст джерелаАнотація:
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaf 71).
by Dameon C. Harrell.
S.B.and M.Eng.
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Cerocchi, Filippo. "Dynamical and Spectral applications of Gromov-Hausdorff Theory." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENM077/document.
Повний текст джерелаАнотація:
Cette thèse est divisée en deux parties. La première est consacrée à la méthode du barycentre, introduite en 1995 par G. Besson, G. Courtois et S. Gallot pour résoudre la conjecture de l'Entropie Minimale. Dans le Chapitre 1 nous décrivons ses développements les plus récents, notamment l'extension de cette méthode au cadre des variétés dont la courbure sectionnelle est de signe quelconque (voir les énoncés 1.2.1 et 1.4.1). Dans le Chapitre 2 et 3 nous présentons des résultats dans lesquels la méthode du barycentre joue un rôle important. Le problème “deux variétés dont les flots géodésiques sont conjugués sont-elles isométriques ?” (problème de la rigidité par conjugaison des flots) est le thème du Chapitre 2. Après avoir montré que deux telles variétés ont la même géométrie à grande échelle, on montre comment on peut utiliser ce résultat et la méthode du barycentre pour donner une nouvelle preuve de la rigidité (par conjugaison des flots) des variétés plates. Dans le Chapitre 3 nous utilisons la méthode du barycentre (en courbure de signe quelconque) et des inégalités de Sobolev itérées pour démontrer un théorème de comparaison entre les spectres de deux variétés riemanniennes (Y , g) et (X , g') de volumes proches, sachant qu'il existe une approximation de Gromov-Hausdorff de degré non nul entre ces deux variétés. Il s'agit d'un résultat d'approximation avec majoration de l'erreur d'approximation (et pas seulement d'un résultat de convergence). Remarquons qu'il n'est fait aucune autre hypothèse géométrique (et en particulier aucune hypothèse de courbure) sur la variété (Y , g), ce qui autorise un grand nombre de contre-exemples prouvant que le résultat est optimal. Dans la deuxième partie de la thèse (chapitre 4), on démontre un Lemme de Margulis sans hypothèse sur la courbure, qui s'applique aux variétés dont les groupes fondamentaux sont des produits libres (et qui ne possèdent pas d'élément de torsion d'ordre 2). Nous donnons également une borne inférieure de la systole des variétés dont le diamètre et l'entropie volumique sont majorés et dont le groupe fondamental est isomorphe à un produit libre sans torsion. Comme conséquences de ce dernier résultat nous obtenons des résultats de précompacité et de finitude topologique ou différentiable pour les variétés riemanniennes et une minoration de leur volume, tout ceci sans faire d'hypothèse de courbureThis Ph.D. Thesis is divided into two parts. In the first part we present the barycenter method, a technique which has been introduced by G. Besson, G. Courtois and S. Gallot in 1995, in order to solve the Minimal Entropy conjecture. In Chapter 1 we are interested in the more recent developments of this method, more precisely in the recent extension of the method to the case of manifolds having sectional curvature of variable sign. In Chapters 2 and 3 we shall present some new results whose proofs make use of the barycenter method. The Conjugacy Rigidity problem is the theme of Chapter 2. First we show a general result which provide a comparison between the large scale geometry of the Riemannian universal coverings of two compact manifolds whose geodesic flows are conjugates. Then we shall show how we can apply the latter result and the barycenter method in curvature of variable sign in order to give a new proof of the conjugacy rigidity of flat manifolds. In Chapter 3 we shall give a proof of a spectra comparison theorem for a compact Riemannian manifold which admits a Gromov-Hausdorff-approximation of non zero absolute degree on a fixed compact manifold (X,g') and which has volume almost smaller than the one of the reference manifold. The proof relies on the barycenter method in curvature of variable sign and on iterated Sobolev inequalities. We underline that it is an approximation result (and not just a convergence result) and that no curvature assumptions are made or inferred on (Y,g). The second part of the Thesis consists of a single chapter. In this chapter we prove a Margulis Lemma without curvature assumptions for Riemannian manifolds having decomposable 2-torsionless fundamental group. We shall give also a proof of a universal lower bound for the homotopy systole of compact Riemannian manifolds having bounded volume entropy and diameter, and decomposable torsionless fundamental group. As a consequence of the latter result we shall deduce a Precompactness and Finiteness theorem and a Volume estimate without curvature assumptions
Книги з теми "Spectral distances"
1
Patanè, Giuseppe. An Introduction to Laplacian Spectral Distances and Kernels. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8.
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2
Hunt, M. J. Distance measures for speech recognition =: Les distances spectrales pour la reconnaissance de la parole. Ottawa: National Research Council Canada, 1989.
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3
Elliott, James L. New mysteries at Chiron: Final technical report. [Washington, DC: National Aeronautics and Space Administration, 1998.
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4
Patane, Giuseppe. Introduction to Laplacian Spectral Distances and Kernels: Theory, Computation, and Applications. Morgan & Claypool Publishers, 2017.
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5
Patanè, Giuseppe. Introduction to Laplacian Spectral Distances and Kernels: Theory, Computation, and Applications. Springer International Publishing AG, 2017.
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6
Patanè, Giuseppe, and Brian A. Barsky. Introduction to Laplacian Spectral Distances and Kernels: Theory, Computation, and Applications. Morgan & Claypool Publishers, 2017.
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7
Distance Education: Spectrum of Case Studies. Kogan Page Ltd, 1991.
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8
Edmunds, D. E., and W. D. Evans. Essential Spectra of General Second-Order Differential Operators. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198812050.003.0010.
Повний текст джерелаАнотація:
In this chapter, the operators considered are those m-sectorial operators discussed in Chapter VII, and the essential spectra are the sets defined in Chapter IX that remain invariant under compact perturbation. A generalization of a result of Persson is used to determine the least point of the essential spectrum. Davies’ mean distance function is introduced and consequences investigated.
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Greyser, Naomi. “Spectres of Liberty” and the Archive. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190460983.003.0007.
Повний текст джерелаАнотація:
This epilogue considers the legacy of nineteenth-century sentimentalism, turning to contemporary civic statuary that memorializes nineteenth-century sentimentalists. Juxtaposing this statuary with the hauntingly ephemeral installation The Ghost of Liberty Street Church, the chapter offers postpresentist inquiry as a method that regards the archive as an urgent and poignantly incomplete political project. Where historicist approaches emphasize distance and difference from history through periodization, and charges of presentism name historians’ overidentification with the past, postpresentism holds in view intimacy and distance between past and the present. The epilogue lays out postpresentist readings of sculptures of Harriet E. Wilson in Milford, New Hampshire; Winnemucca Hopkins and Sojourner Truth in the United States Capitol Rotunda; and Elizabeth Cady Stanton, Amelia Bloomer, and Susan B. Anthony in Seneca Falls, New York. These statues’ site-specific installations bring into relief the raced, gendered, and colonial legacies of the grounds beneath their podia and feet.
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Eland, John H. D., and Raimund Feifel. Mainly aliphatic molecules. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198788980.003.0007.
Повний текст джерелаАнотація:
Double photoionisation spectra of homologous iodides and alcohols, acetonitrile, methyl mercaptan, acetaldehyde, acetone, norbornane, cyclooctatetraene, and TMMD are presented. Effects on the spectra of these molecules from electronic state congestion and geometry changes on ionisation mean that only the lowest dication states can be identified. As little detailed analysis of the individual spectra is possible, this chapter presents the molecules in groups rather than individually. In this chapter, molecules are ordered more thematically than strictly by size. The chapter starts with four homologous iodides and three homologous alcohols. Then this chapter takes some individual molecules with different substituent groups and proceed to a few larger molecules. The chapter demonstrates the dominant effect of the distance to which charges can separate in the dication on the double ionisation threshold.
Частини книг з теми "Spectral distances"
1
Patanè, Giuseppe. "Discrete Spectral Distances." In An Introduction to Laplacian Spectral Distances and Kernels, 53–69. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8_4.
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Bavaud, François. "Euclidean Distances, Soft and Spectral Clustering on Weighted Graphs." In Machine Learning and Knowledge Discovery in Databases, 103–18. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-15880-3_13.
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Patanè, Giuseppe. "Conclusions." In An Introduction to Laplacian Spectral Distances and Kernels, 91. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8_6.
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Patanè, Giuseppe. "Laplace-Beltrami Operator." In An Introduction to Laplacian Spectral Distances and Kernels, 1–10. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8_1.
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Patanè, Giuseppe. "Heat and Wave Equations." In An Introduction to Laplacian Spectral Distances and Kernels, 11–29. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-031-02593-8_2.
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Liu, Rong, Hao Zhang, and Oliver van Kaick. "Spectral Sequencing Based on Graph Distance." In Geometric Modeling and Processing - GMP 2006, 630–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11802914_50.
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Wang, Nian, Jun Tang, Jiang Zhang, Yi-Zheng Fan, and Dong Liang. "Spectral Edit Distance Method for Image Clustering." In Advances in Data and Web Management, 350–57. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-72524-4_37.
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Civril, Ali, Malik Magdon-Ismail, and Eli Bocek-Rivele. "SDE: Graph Drawing Using Spectral Distance Embedding." In Graph Drawing, 512–13. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/11618058_48.
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Reames, Donald V. "High Energies and Radiation Effects." In Solar Energetic Particles, 135–49. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66402-2_6.
Повний текст джерелаАнотація:
AbstractIn this chapter we characterize the high-energy spectra of protons that can penetrate shielding and determine the radiation dose to humans and equipment in space. High-energy spectral breaks or “knees”, seen in all large SEP events, determine the contribution of highly penetrating protons. The streaming limit, discussed earlier, places an upper bound on particle fluences early in events and the radial variation of intensities is important for near-solar and deep-space missions. The streaming limit is a strong function of radial distance from the Sun. We also consider requirements for a radiation storm shelter for deep space, a mission to Mars, suitability of exoplanets for life, and radiation-induced chemistry of the upper atmosphere of Earth.
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Maeng, Hyunju, Shengcai Liao, Dongoh Kang, Seong-Whan Lee, and Anil K. Jain. "Nighttime Face Recognition at Long Distance: Cross-Distance and Cross-Spectral Matching." In Computer Vision – ACCV 2012, 708–21. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-37444-9_55.
Повний текст джерелаТези доповідей конференцій з теми "Spectral distances"
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Memoli, Facundo. "Spectral Gromov-Wasserstein distances for shape matching." In 2009 IEEE 12th International Conference on Computer Vision Workshops, ICCV Workshops. IEEE, 2009. http://dx.doi.org/10.1109/iccvw.2009.5457690.
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McKechnie, T. S., and Charles K. Carniglia. "Propagation of the spectral correlation function in a homogeneous medium." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.wp7.
Повний текст джерелаАнотація:
When two infinitely extensive electromagnetic waves of wavelengths λ1, and λ2propagate in the Fresnel region of a homogeneous medium, the spectral correlation function, 〈 A ( x ′ , y ′ ; λ 1 ) A * ( x , y ; λ 2 ) 〉 , gradually changes with increasing propagation distance. An exact expression is developed which describes these changes. The changes are exhibited in terms of both modulus and phase. In the special case where the two wavelengths are identical, the spectral correlation function reduces to the autocorrelation function. In this case, the function, as expected, is found to conserve during propagation. The paper considers two spectrally well-separated plane waves from the visible part of the spectrum at 450 and 650 nm. Numerical evaluations are given for a typical spectral correlation function that might arise from these waves in conditions of good seeing. It is shown that this spectral correlation function is capable of propagating with a high degree of conservation over distances of the order of the atmospheric depth. It is inferred from this that the spectral correlation function that arises when visible waves pass through the atmosphere is determined only by the accumulated effect of the local atmospheric turbulence; the propagation distance itself makes no significant contribution to the final value attained by the function. This result simplifies the task of describing the statistical properties of polychromatic images formed by large astronomical telescopes. It also offers insights and tools for dealing with the problems associated with laser beam propagation through the atmosphere.
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Patané, Giuseppe. "An introduction to laplacian spectral distances and kernels." In SIGGRAPH '17: Special Interest Group on Computer Graphics and Interactive Techniques Conference. New York, NY, USA: ACM, 2017. http://dx.doi.org/10.1145/3084873.3084919.
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Scragg, Carl A. "Spectral Analysis of Ship-Generated Waves in Finite-Depth Water." In ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28510.
Повний текст джерелаАнотація:
Recent efforts to compare the waves generated by different vessels traveling in finite-depth water have struggled with difficulties presented by various data sets of wave elevations (either measurements or predictions) corresponding to different lateral distances from the ship. Some of the attempts to shift the data to a common reference location have relied upon crude and potentially misleading approximations. The use of free-wave spectral-methods not only overcomes such difficulties, but it also provides us the means to accurately extend CFD results into the far field. As in the deep-water case, one can define a free-wave spectrum that is valid for all lateral positions and distances astern of the vessel. The free-wave spectrum contains a complete description of the Kelvin wake, and wave elevations at any far-field position can be readily calculated once the spectrum is known. For the case of infinitely deep water, Eggers, Sharma, and Ward [1967] presented a method by which free-wave spectra can be determined from appropriate measurements of the far-field wave elevations. The current paper discusses the use of free-wave spectra for finite-depth problems and presents a method for the determination of free-wave spectra based upon fitting predicted wave elevations to a corresponding data set. The predicted wave elevations can be calculated from an unknown distribution of finite-depth Havelock singularities. The unknown singularities are determined by minimizing the mean-square-difference between predicted and measured wave fields. The method appears to be quite general and can be used to calculate either finite or infinite-depth free-wave spectra from experimental data or from local CFD predictions.
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Gamliel, Avshalom, and Govind P. Agrawal. "Correlation-induced spectral changes in homogeneous and inhomogeneous media." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.tuv5.
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It was recently shown that the spectrum of partially coherent light can change on propagation.1 So far most of the work has applied to propagation in free space and has been limited to far-zone observation points. In this paper we consider the propagation of partially coherent light through homogeneous and inhomogeneous media. Our formulation is based on the analysis of Agrawal et al.,2 which applies to graded-index fibers whose index of refraction changes quadratically as a function of the radial distance from the core center. With this formulation we derive expressions by using the paraxial approximation for the spectrum of the field for arbitrary propagation distances. This allows us to examine the evolution of spectral changes as a function of the propagation distance and the state of coherence of the source. The results for propagation in free space and in homogeneous media are derived by using the appropriate limits. The effects of chromatic dispersion are also investigated by allowing the refractive index to be frequency-dependent.
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Hlubina, Petr. "Measuring distances and displacements using dispersive white-light spectral interferometry." In Optical Metrology, edited by Wolfgang Osten, Malgorzata Kujawinska, and Katherine Creath. SPIE, 2003. http://dx.doi.org/10.1117/12.488763.
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Rahman, Hala Abdul, Guy Carrault, Di Ge, Hassan Amoud, Jacques Prioux, Alexis Le Faucheur, and Remy Dumond. "Ambulatory physical activity representation and classification using spectral distances approach." In 2015 International Conference on Advances in Biomedical Engineering (ICABME). IEEE, 2015. http://dx.doi.org/10.1109/icabme.2015.7323253.
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Mohs, Georg. "Ultra High Spectral Efficiency and Ultra High Capacity Transmission over Transoceanic Distances Using Nyquist Spectral Shaping." In Asia Communications and Photonics Conference. Washington, D.C.: OSA, 2013. http://dx.doi.org/10.1364/acp.2013.af3e.5.
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Mohs, Georg. "Ultra High Spectral Efficiency and Ultra High Capacity Transmission over Transoceanic Distances Using Nyquist Spectral Shaping." In Asia Communications and Photonics Conference. Washington, D.C.: OSA, 2013. http://dx.doi.org/10.1364/acpc.2013.af3e.5.
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Nicolalde, Daniel Patricio, and Jose Antonio Apolinario. "Evaluating digital audio authenticity with spectral distances and ENF phase change." In ICASSP 2009 - 2009 IEEE International Conference on Acoustics, Speech and Signal Processing. IEEE, 2009. http://dx.doi.org/10.1109/icassp.2009.4959859.
Повний текст джерелаЗвіти організацій з теми "Spectral distances"
1
White, H. P., W. Chen, and S G Leblanc. Satellite observations for detection of dust from mining activities in a caribou habitat, Northwest Territories and Nunavut. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330548.
Повний текст джерелаАнотація:
Diamond mining via open pit mining has been ongoing within the Tlicho region of the Northwest Territories for several decades, which includes the habitat range of the Bathurst Caribou Herd. This has led to the importance of quantitative characterization of the Zone Of Influence (ZOI), where resource development activities may be influencing the natural behaviour of the caribou herd in the tundra environment. As part of better defining and understanding the ZOI in this region, an initiative to evaluate the potential of detecting and mapping mine waste rock dust in the surrounding environment is explored. This dust has been shown to coat foliage near roads, influencing the acidity levels of the surficial soil layer and impacting the foliage distribution. To this end, field spectrometry was acquired at various distances from road ways. Satellite imagery from the Proba-1 CHRIS hyperspectral sensor and the multi-spectral Sentinel-2a system were also acquired of the region. This presentation presents the initial spectral analysis pursued to evaluate the potential to remotely spectrally detect waste rock dust material used in road construction in the surrounding tundra vegetation. Initial analysis of the Proba-1 CHRIS hyperspectral imagery shows spectral indicators of fugitive dust and waste rock easily detects the road and suggests detectable dust concentration above ambient up to a distance of under 1km from the road.
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Si, Hongjun, Saburoh Midorikawa, and Tadahiro Kishida. Development of NGA-Sub Ground-Motion Model of 5%-Damped Pseudo-Spectral Acceleration Based on Database for Subduction Earthquakes in Japan. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, December 2020. http://dx.doi.org/10.55461/lien3652.
Повний текст джерелаАнотація:
Presented within is an empirical ground-motion model (GMM) for subduction-zone earthquakesin Japan. The model is based on the extensive and comprehensive subduction database of Japanese earthquakes by the Pacific Engineering Research Center (PEER). It considers RotD50 horizontal components of peak ground acceleration (PGA), peak ground velocity (PGV), and 5%-damped elastic pseudo-absolute acceleration response spectral ordinates (PSA) at the selected periods ranging from 0.01 to 10 sec. The model includes terms and predictor variables considering tectonic setting (i.e., interplate and intraslab), hypocentral depths (D), magnitude scaling, distance attenuation, and site response. The magnitude scaling derived in this study is well constrained by the data observed during the large-magnitude interface events in Japan (i.e., the 2003 Tokachi-Oki and 2011 Tohoku earthquakes) for different periods. The developed ground-motion prediction equation (GMPE) covers subduction-zone earthquakes that have occurred in Japan for magnitudes ranging from 5.5 to as large as 9.1, with distances less than 300 km from the source.
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Zilberman, Mark. Shouldn’t Doppler 'De-boosting' be accounted for in calculations of intrinsic luminosity of Standard Candles? Intellectual Archive, September 2021. http://dx.doi.org/10.32370/iaj.2569.
Повний текст джерелаАнотація:
"Doppler boosting / de-boosting" is a well-known relativistic effect that alters the apparent luminosity of approaching/receding radiation sources. "Doppler boosting" alters the apparent luminosity of approaching light sources to appear brighter, while "Doppler de-boosting" alters the apparent luminosity of receding light sources to appear fainter. While "Doppler boosting / de-boosting" has been successfully accounted for and observed in relativistic jets of AGN, double white dwarfs, in search of exoplanets and stars in binary systems it was ignored in the establishment of Standard Candles for cosmological distances. A Standard Candle adjustment appears necessary for "Doppler de-boosting" for high Z, otherwise we would incorrectly assume that Standard Candles appear dimmer, not because of "Doppler de-boosting" but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of redshift Z and spectral index α is given by the formula ℳ(Z) = L/Lo=(Z+1)^(α-3) and for Type Ia supernova as ℳ(Z) = L/Lo=(Z+1)^(-2). These formulas are obtained within the framework of Special Relativity and may require adjustments within the General Relativity framework.
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Zilberman, Mark. “Doppler de-boosting” and the observation of “Standard candles” in cosmology. Intellectual Archive, July 2021. http://dx.doi.org/10.32370/iaj.2549.
Повний текст джерелаАнотація:
“Doppler boosting” is a well-known relativistic effect that alters the apparent luminosity of approaching radiation sources. “Doppler de-boosting” is the name of relativistic effect observed for receding light sources (e.g. relativistic jets of active galactic nuclei and gamma-ray bursts). “Doppler boosting” changes the apparent luminosity of approaching light sources to appear brighter, while “Doppler de-boosting” causes the apparent luminosity of receding light sources to appear fainter. While “Doppler de-boosting” has been successfully accounted for and observed in relativistic jets of AGN, it was ignored in the establishment of Standard candles for cosmological distances. A Standard candle adjustment of an Z>0.1 is necessary for “Doppler de-boosting”, otherwise we would incorrectly assume that Standard Candles appear dimmer not because of “Doppler de-boosting” but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of the redshift Z and spectral index α is given by the formula ℳ(Z) = L/Lo=(Z+1)α -3 and for Type Ia supernova appears as ℳ(Z) = L/Lo=(Z+1)-2. “Doppler de-boosting” may also explain the anomalously low luminosity of objects with a high Z without the introduction of an accelerated expansion of the Universe and Dark Energy.
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Zilberman, Mark. PREPRINT. “Doppler de-boosting” and the observation of “Standard candles” in cosmology. Intellectual Archive, June 2021. http://dx.doi.org/10.32370/ia_2021_06_23.
Повний текст джерелаАнотація:
PREPRINT. “Doppler boosting” is a well-known relativistic effect that alters the apparent luminosity of approaching radiation sources. “Doppler de-boosting” is the term of the same relativistic effect observed for receding light sources (e.g.relativistic jets of active galactic nuclei and gamma-ray bursts). “Doppler boosting” alters the apparent luminosity of approaching light sources to appear brighter, while “Doppler de-boosting” alters the apparent luminosity of receding light sources to appear fainter. While “Doppler de-boosting” has been successfully accounted for and observed in relativistic jets of AGN, it was ignored in the establishment of Standard candles for cosmological distances. A Standard candle adjustment of Z>0.1 is necessary for “Doppler de-boosting”, otherwise we would incorrectly assume that Standard Candles appear dimmer, not because of “Doppler de-boosting” but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of the redshift Z and spectral index α is given by the formula ℳ(Z) =L/Lo=(Z+1)^(α-3) and for Type Ia supernova appears as ℳ(Z)=L/Lo=(Z+1)^(-2). “Doppler de-boosting” may also explain the anomalously low luminosity of objects with a high Z without the introduction of an accelerated expansion of the Universe and Dark Energy.
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Zilberman, Mark. "Doppler De-boosting" and the Observation of "Standard Candles" in Cosmology. Intellectual Archive, July 2021. http://dx.doi.org/10.32370/iaj.2552.
Повний текст джерелаАнотація:
“Doppler boosting” is a well-known relativistic effect that alters the apparent luminosity of approaching radiation sources. “Doppler de-boosting” is the same relativistic effect observed but for receding light sources (e.g. relativistic jets of AGN and GRB). “Doppler boosting” alters the apparent luminosity of approaching light sources to appear brighter, while “Doppler de-boosting” alters the apparent luminosity of receding light sources to appear fainter. While “Doppler de-boosting” has been successfully accounted for and observed in relativistic jets of AGN, it was ignored in the establishment of Standard candles for cosmological distances. A Standard Candle adjustment of Z>0.1 is necessary for “Doppler de-boosting”, otherwise we would incorrectly assume that Standard Candles appear dimmer, not because of “Doppler de-boosting” but because of the excessive distance, which would affect the entire Standard Candles ladder at cosmological distances. The ratio between apparent (L) and intrinsic (Lo) luminosities as a function of the redshift Z and spectral index α is given by the formula ℳ(Z) = L/Lo=(Z+1)α -3 and for Type Ia supernova appears as ℳ(Z) = L/Lo=(Z+1)-2. “Doppler de-boosting” may also explain the anomalously low luminosity of objects with a high Z without the introduction of an accelerated expansion of the Universe and Dark Energy.
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Alchanatis, Victor, Stephen W. Searcy, Moshe Meron, W. Lee, G. Y. Li, and A. Ben Porath. Prediction of Nitrogen Stress Using Reflectance Techniques. United States Department of Agriculture, November 2001. http://dx.doi.org/10.32747/2001.7580664.bard.
Повний текст джерелаАнотація:
Commercial agriculture has come under increasing pressure to reduce nitrogen fertilizer inputs in order to minimize potential nonpoint source pollution of ground and surface waters. This has resulted in increased interest in site specific fertilizer management. One way to solve pollution problems would be to determine crop nutrient needs in real time, using remote detection, and regulating fertilizer dispensed by an applicator. By detecting actual plant needs, only the additional nitrogen necessary to optimize production would be supplied. This research aimed to develop techniques for real time assessment of nitrogen status of corn using a mobile sensor with the potential to regulate nitrogen application based on data from that sensor. Specifically, the research first attempted to determine the system parameters necessary to optimize reflectance spectra of corn plants as a function of growth stage, chlorophyll and nitrogen status. In addition to that, an adaptable, multispectral sensor and the signal processing algorithm to provide real time, in-field assessment of corn nitrogen status was developed. Spectral characteristics of corn leaves reflectance were investigated in order to estimate the nitrogen status of the plants, using a commercial laboratory spectrometer. Statistical models relating leaf N and reflectance spectra were developed for both greenhouse and field plots. A basis was established for assessing nitrogen status using spectral reflectance from plant canopies. The combined effect of variety and N treatment was studied by measuring the reflectance of three varieties of different leaf characteristic color and five different N treatments. The variety effect on the reflectance at 552 nm was not significant (a = 0.01), while canonical discriminant analysis showed promising results for distinguishing different variety and N treatment, using spectral reflectance. Ambient illumination was found inappropriate for reliable, one-beam spectral reflectance measurement of the plants canopy due to the strong spectral lines of sunlight. Therefore, artificial light was consequently used. For in-field N status measurement, a dark chamber was constructed, to include the sensor, along with artificial illumination. Two different approaches were tested (i) use of spatially scattered artificial light, and (ii) use of collimated artificial light beam. It was found that the collimated beam along with a proper design of the sensor-beam geometry yielded the best results in terms of reducing the noise due to variable background, and maintaining the same distance from the sensor to the sample point of the canopy. A multispectral sensor assembly, based on a linear variable filter was designed, constructed and tested. The sensor assembly combined two sensors to cover the range of 400 to 1100 nm, a mounting frame, and a field data acquisition system. Using the mobile dark chamber and the developed sensor, as well as an off-the-shelf sensor, in- field nitrogen status of the plants canopy was measured. Statistical analysis of the acquired in-field data showed that the nitrogen status of the com leaves can be predicted with a SEP (Standard Error of Prediction) of 0.27%. The stage of maturity of the crop affected the relationship between the reflectance spectrum and the nitrogen status of the leaves. Specifically, the best prediction results were obtained when a separate model was used for each maturity stage. In-field assessment of the nitrogen status of corn leaves was successfully carried out by non contact measurement of the reflectance spectrum. This technology is now mature to be incorporated in field implements for on-line control of fertilizer application.
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Chapman, Martin C., G. A. Bollinger, and Matthew S. Sibol. Modeling Delay-Fired Explosion Spectra and Source Function Deconvolution at Regional Distances. Fort Belvoir, VA: Defense Technical Information Center, September 1992. http://dx.doi.org/10.21236/ada260232.
Повний текст джерела
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Keahava, N. Distance Metrics and Band Selection in Hyperspectral Processing with Applications to Material Identification and Spectral Libraries. Fort Belvoir, VA: Defense Technical Information Center, December 2002. http://dx.doi.org/10.21236/ada409023.
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Anderson, Gerald L., and Kalman Peleg. Precision Cropping by Remotely Sensed Prorotype Plots and Calibration in the Complex Domain. United States Department of Agriculture, December 2002. http://dx.doi.org/10.32747/2002.7585193.bard.
Повний текст джерелаАнотація:
This research report describes a methodology whereby multi-spectral and hyperspectral imagery from remote sensing, is used for deriving predicted field maps of selected plant growth attributes which are required for precision cropping. A major task in precision cropping is to establish areas of the field that differ from the rest of the field and share a common characteristic. Yield distribution f maps can be prepared by yield monitors, which are available for some harvester types. Other field attributes of interest in precision cropping, e.g. soil properties, leaf Nitrate, biomass etc. are obtained by manual sampling of the filed in a grid pattern. Maps of various field attributes are then prepared from these samples by the "Inverse Distance" interpolation method or by Kriging. An improved interpolation method was developed which is based on minimizing the overall curvature of the resulting map. Such maps are the ground truth reference, used for training the algorithm that generates the predicted field maps from remote sensing imagery. Both the reference and the predicted maps are stratified into "Prototype Plots", e.g. 15xl5 blocks of 2m pixels whereby the block size is 30x30m. This averaging reduces the datasets to manageable size and significantly improves the typically poor repeatability of remote sensing imaging systems. In the first two years of the project we used the Normalized Difference Vegetation Index (NDVI), for generating predicted yield maps of sugar beets and com. The NDVI was computed from image cubes of three spectral bands, generated by an optically filtered three camera video imaging system. A two dimensional FFT based regression model Y=f(X), was used wherein Y was the reference map and X=NDVI was the predictor. The FFT regression method applies the "Wavelet Based", "Pixel Block" and "Image Rotation" transforms to the reference and remote images, prior to the Fast - Fourier Transform (FFT) Regression method with the "Phase Lock" option. A complex domain based map Yfft is derived by least squares minimization between the amplitude matrices of X and Y, via the 2D FFT. For one time predictions, the phase matrix of Y is combined with the amplitude matrix ofYfft, whereby an improved predicted map Yplock is formed. Usually, the residuals of Y plock versus Y are about half of the values of Yfft versus Y. For long term predictions, the phase matrix of a "field mask" is combined with the amplitude matrices of the reference image Y and the predicted image Yfft. The field mask is a binary image of a pre-selected region of interest in X and Y. The resultant maps Ypref and Ypred aremodified versions of Y and Yfft respectively. The residuals of Ypred versus Ypref are even lower than the residuals of Yplock versus Y. The maps, Ypref and Ypred represent a close consensus of two independent imaging methods which "view" the same target. In the last two years of the project our remote sensing capability was expanded by addition of a CASI II airborne hyperspectral imaging system and an ASD hyperspectral radiometer. Unfortunately, the cross-noice and poor repeatability problem we had in multi-spectral imaging was exasperated in hyperspectral imaging. We have been able to overcome this problem by over-flying each field twice in rapid succession and developing the Repeatability Index (RI). The RI quantifies the repeatability of each spectral band in the hyperspectral image cube. Thereby, it is possible to select the bands of higher repeatability for inclusion in the prediction model while bands of low repeatability are excluded. Further segregation of high and low repeatability bands takes place in the prediction model algorithm, which is based on a combination of a "Genetic Algorithm" and Partial Least Squares", (PLS-GA). In summary, modus operandi was developed, for deriving important plant growth attribute maps (yield, leaf nitrate, biomass and sugar percent in beets), from remote sensing imagery, with sufficient accuracy for precision cropping applications. This achievement is remarkable, given the inherently high cross-noice between the reference and remote imagery as well as the highly non-repeatable nature of remote sensing systems. The above methodologies may be readily adopted by commercial companies, which specialize in proving remotely sensed data to farmers.