1,379,128 research outputs found
Phase shifts from Gabor filters
No full textA technique is presented for extracting phase information from a pair of sinusoidal signals, with equal frequency, but different phase angle, by convolving each signal with a pair of quadrature Gabor filters.
It is shown that, under certain conditions, Gabor filters can be treated as linear functions. The applications of the Gabor filter are discussed with respect to both image processing, and extracting phase information from sinusoidal signals in minimum time
Geodetic datums of the Italian cadastral systems
No full textThe geodetic datum, and its possible descriptions, of the Italian cadastral networks are analyzed, in order to provide a solution to fit the cadastral sheets to modern map contents and grids, using just their corner crosshair data. Analyzing the extension of the Genova 1902 datum to the whole Italian territory, it occured that the transformation error is acceptable only in the original survey area of the respective triangulation net. For Souther Italy and Sicily (Sicilia), the errors exceed the 20 meters. The Molodensky-type transformation parameters of the Castanea della Furie 1910 and the Guardia Vecchia (Sardinia) datums are provided using only their fundamental point coordinates, without error estimation. While these datums are not correctly checked at their whole application are, we suggest to define local datums of the Bessel ellipsoid, using the Bessel and WGS84coordinates of the respective cadastral grid origins and use them for geo-reference as a basis of the local Cassini grids
Optimum Gabor filter design and local binary patterns for texture segmentation
No full textWe present a novel approach to multi-texture image segmentation based on the formation of an effective texture feature vector. Texture sub-features are derived from the output of an optimized Gabor filter. The filter's parameters are selected by an immune genetic algorithm, which aims at maximizing the discrimination between the multi-textured regions. Next the texture features are integrated with a local binary pattern, to form an effective texture descriptor with low computational cost, which overcomes the weakness of the single frequency output component of the filter. Finally, a K-nearest neighbor classifier is used to effect the multi-texture segmentation. The integration of the optimum Gabor filter and local binary pattern methods provide a novel solution to the task. Experimental results demonstrate the effectiveness of the proposed approach
Proposal of an abridged procedure to manage Cadastral maps in an open GIS package
No full textCadastral cartography, born after unification of Italy in 1870, is an important source of large scale geographic
information.
Cadastral maps represent the result of the largest scale survey of on the whole national territory. Because of
their large scale, their creation is extremely expensive and the updating of the cadastre claim considerable
funds from the state budgets. That’s why the coordinate system, the geodetic basis of a cadastral work, is
rarely changed.
Even if Gauss-Boaga grid system based on ROMA40 datum was introduced and applied at some smaller
parts of the country, the cartographic coordinates manly used in the cadastral maps are based on CassiniSoldner
projection and cadastral datum Bessel-Genova; Bessel_Monte Mario and Bessel Castanea delle
Furie.
In the Cassini-Soldner projection, the whole Italian territory is subdivided in 31 major ("grandi origini") and
more than 800 local ("piccole origini") cadastral systems.
Nowadays, it is fundamental the implementation of a fast and free procedure for the updating of cadastral
maps from Italian cadastral datum to modern WGS84.
The two main goals of this paper are: the identification of a suitable set of points with coordinates known in
both datums and the computation of Abridging Molodensky parameters from Cassini-Soldner cadastral
datum to WGS84. The test area selected is the district of Rome called “Città metropolitana di Roma
Capitale” .
The data set of points suitable for the least-square estimation is extracted from the information available on
the website www.globogis.it/fiduciali.it.
The "globogis" database includes a selection of trigonometric points, with coordinates expressed in the
WGS84 datum, and a selection of cadastral points ("punti fiduciali") with coordinates expressed in the
Bessel-Genova 1902 datum. The whole database is analysed in order to provide the correct association
between cadastral and trigonometric points.
Known the dataset of points, the Abridging Molodensky parameters are estimated with a least square
principle using a specific package developed by Prof. Timar.
The estimated parameters are implemented and tested in the open source software QGIS. The accuracy of
Abridging Molodensky parameters is tested using an independent set of point with respect to the estimation
points
Luminescence properties of natural muscovite relevant to optical dating of contaminated quartz samples
No full textMuscovite is a mineral commonly found along quartz in sediments, where the latter is the mineral of choice in numerous optically stimulated luminescence (OSL) dating studies. Since muscovite cannot be efficiently eliminated following standard laboratory treatments, it is important to assess its luminescence properties. This study is focused on the investigation of muscovite hand-picked from a quartz sample extracted from loess and of museum specimens of muscovite in order to evaluate their potential implication in the OSL dating of quartz samples contaminated with muscovite grains. The obtained results show that generally applicable luminescence characteristics cannot be described for muscovite. In terms of the thermoluminescence (TL) response, all samples investigated display the same wide peak at 200 °C. The blue light and infrared (IR) sensitivities differ between the samples: 3 out of 5 samples present no or negligible level of OSL and IRSL response, while the other 2 samples are characterised by both blue light (2000–3400 counts in 0.31 s of stimulation for 10 mg of muscovite after irradiation with a dose of 136 Gy) and IR sensitivity (265–320 counts in 0.31 s of stimulation for 10 mg of muscovite after irradiation with a dose of 136 Gy). Based on the samples analysed in this study, aliquots of quartz contaminated with optically (blue light) sensitive muscovite would also be IR sensitive. Hence, potentially problematic aliquots can be identified via the IRSL purity test usually used in the OSL dating of quartz samples for detection of feldspar contamination. The impact of muscovite on dose determination for quartz was also tested and it was concluded that at least in the case of bright quartz, muscovite minerals do not influence the OSL measurements.</p
Gabor frames with trigonometric spline dual windows
No full textA Gabor system is a collection of modulated and translated copies of a window function. If we have a signal in , it can be analyzed with a Gabor system generated by a certain window and then synthesized with a Gabor system generated by another window . If this leads us to a perfect reconstruction, we say that and are dual Gabor windows.
Few explicit examples of dual window pairs are known. This thesis constructs explicit examples of Gabor dual windows with trigonometric form. The windows have fixed support and have an arbitrary smoothness.
Also, in the discrete time domain, the trigonometric form allows us to evaluate the Gabor coefficients efficiently using the Discrete Fourier Transform.
For the higher dimensional cases, we find window examples for a large class of modulation parameter lattices, including shear lattices. Also, a sufficient condition on the norm of the modulation lattice to have explicit dual Gabor windows is presented, for every dimension.Item withdrawn by Mark Zulauf ([email protected]) on 2011-07-01T20:21:55Z
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University of Illinois Theses & Dissertations (ID: 1)
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Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror
No full textWe present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a Drosophila larvae. The focus adjustment is achieved by manipulating the curvature of the deformable mirror between two user-defined limits. Particularities of controlling the focus for Gabor filtering using the deformable mirror are presented. © 2015 Society of Photo-Optical Instrumentation Engineers
Dennis Gabor, "Father of Holography"
No full textDennis Gabor was born on June 5th, 1900 in Budapest, Hungary, a country that was then part of the Austro-Hungarian Dual Monarchy. Although physics fascinated him, he finally decided to study engineering. Later he wrote: «Physics was not yet a profession in Hungary, with a total of half-a-dozen university chairs – and who could have been presumptuous enough to aspire to one of these?». Throughout his entire life Gabor always said he was an engineer and inventor rather than a scientist, even though his work was almost always related to applied physics. But Gabor was also a humanist in the sense of the Renaissance: voracious reader, writer, essayist, man concerned about the technological society of the late twentieth century and member of the Club of Rome. Since 1958 he devoted much of his time to study the future of our industrial civilization on which he published, among others, the book Inventing the Future, published in 1963, and where he stated: «You cannot predict the future, but you can create it.
Dennis Gabor, “padre de la holografía”
No full textDennis Gabor (1900-1979) nació el 5 de junio de 1900 en Budapest, Hungría, un país que entonces formaba parte de la Monarquía Dual Austro-Húngara. Aunque la física le fascinaba, decidió estudiar ingeniería. Más tarde escribió, «ser físico no era todavía una profesión en Hungría y ¿con apenas media docena de cátedras de física en todo el país, quién podría haber sido tan presuntuoso para aspirar a una de ellas?». A lo largo de su vida Gabor siempre decía que él era ingeniero e inventor en vez de científico, a pesar de que su trabajo estaba casi siempre relacionado con la física aplicada. Pero Gabor, también fue un humanista en el más puro sentido del Renacimiento: lector voraz, escritor, ensayista, hombre preocupado por la sociedad tecnológica de finales del siglo XX y miembro del Club de Roma. Desde 1958 dedicó gran parte de su tiempo al estudio del futuro de nuestra civilización industrial. En 1971 fue galardonado con el Premio Nobel de Física «por su invención y desarrollo del método holográfico»
Limitations for change detection in multiple Gabor targets
No full textWe investigate the limitations on the ability to detect when a target has changed, using Gabor targets as simple quantifiable stimuli. Using a partial report technique to equalise response variables, we show that the log of the Weber fraction for detecting a spatial frequency change is proportional to the log of the number of targets, with a set-size effect that is greater than that reported for visual search. This is not a simple perceptual limitation, because pre-cueing a single target out of four restores performance to the level found when only one target is present. It is argued that the primary limitation on performance is the division of attention across multiple targets, rather than decay within visual memory. However in a simplified change detection experiment without cueing, where only one target of the set changed, not only was the set size effect still larger, but it was greater at 2000 msec ISI than at 250 msec ISI, indicating a possible memory component. The steepness of the set size effects obtained suggests that even moderate complexity of a stimulus in terms of number of component objects can overload attentional processes, suggesting a possible low-level mechanism for change blindness
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