225,755 research outputs found
System converts slow-scan to standard fast-scan TV signals
Signal conversion system converts slow-scan video signals into standard fast-scan television signals that are required for reproduction of television pictures on American TV sets. This system permits conversion of TV pictures produced in accordance with the standards of one country into the standards of another country
Television signal scan rate conversion system Patent
Conversion system for transforming slow scan rate of Apollo TV camera on moon to fast scan of commercial T
Improved Transverse Crack Detection in Composites
A modified ultrasonic C-scan technique was implemented for improving the detection of a certain type of damage in composite specimens. The type of damage being studied is transverse (through the thickness) cracking of unidirectional off-axis graphite-epoxy specimens. These cracks are difficult to detect using standard through-transmission C-scan techniques. The modification is based on mode conversion to produce transmitted shear waves from incident longitudinal waves. While mode conversion is used extensively with isotropic materials, its use with composites is more limited. This is largely because the computation of wave propagation parameters is significantly more complicated with highly anisotropic materials than with isotropic materials. The appropriate incident angles to produce the desired mode conversion were computed based on the mechanical properties of the composite. Once the angles were computed the technique was simple to implement and resulted in marked improvement in detection of the transverse cracks being studied
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Assessment of visual quality and spatial accuracy of fast anisotropic diffusion and scan conversion algorithms for real-time three-dimensional spherical ultrasound
Three-dimensional ultrasound machines based on matrix phased-array transducers are gaining predominance for real-time dynamic screening in cardiac and obstetric practice. These transducers array acquire three-dimensional data in spherical coordinates along lines tiled in azimuth and elevation angles at incremental depth. This study aims at evaluating fast filtering and scan conversion algorithms applied in the spherical domain prior to visualization into Cartesian coordinates for visual quality and spatial measurement accuracy. Fast 3d scan conversion algorithms were implemented and with different order interpolation kernels. Downsizing and smoothing of sampling artifacts were integrated in the scan conversion process. In addition, a denoising scheme for spherical coordinate data with 3d anisotropic diffusion was implemented and applied prior to scan conversion to improve image quality. Reconstruction results under different parameter settings, such as different interpolation kernels, scaling factor, smoothing options, and denoising, are reported. Image quality was evaluated on several data sets via visual inspections and measurements of cylinder objects dimensions. Error measurements of the cylinder's radius, reported in this paper, show that the proposed fast scan conversion algorithm can correctly reconstruct three-dimensional ultrasound in Cartesian coordinates under tuned parameter settings. Denoising via three-dimensional anisotropic diffusion was able to greatly improve the quality of resampled data without affecting the accuracy of spatial information after the modification of the introduction of a variable gradient threshold parameter
An MRI-Derived Definition of MCI-to-AD Conversion for Long-Term, Automati c Prognosis of MCI Patients
Alzheimer's disease (AD) and mild cognitive impairment (MCI), continue to be
widely studied. While there is no consensus on whether MCIs actually "convert"
to AD, the more important question is not whether MCIs convert, but what is the
best such definition. We focus on automatic prognostication, nominally using
only a baseline image brain scan, of whether an MCI individual will convert to
AD within a multi-year period following the initial clinical visit. This is in
fact not a traditional supervised learning problem since, in ADNI, there are no
definitive labeled examples of MCI conversion. Prior works have defined MCI
subclasses based on whether or not clinical/cognitive scores such as CDR
significantly change from baseline. There are concerns with these definitions,
however, since e.g. most MCIs (and ADs) do not change from a baseline CDR=0.5,
even while physiological changes may be occurring. These works ignore rich
phenotypical information in an MCI patient's brain scan and labeled AD and
Control examples, in defining conversion. We propose an innovative conversion
definition, wherein an MCI patient is declared to be a converter if any of the
patient's brain scans (at follow-up visits) are classified "AD" by an
(accurately-designed) Control-AD classifier. This novel definition bootstraps
the design of a second classifier, specifically trained to predict whether or
not MCIs will convert. This second classifier thus predicts whether an
AD-Control classifier will predict that a patient has AD. Our results
demonstrate this new definition leads not only to much higher prognostic
accuracy than by-CDR conversion, but also to subpopulations much more
consistent with known AD brain region biomarkers. We also identify key
prognostic region biomarkers, essential for accurately discriminating the
converter and nonconverter groups
Hybrid shear-warp rendering
Shear-warp rendering is a fast and efficient method for visualizing a volume of sampled data based on a factorization of the viewing transformation into a shear and a warp. In shear-warp rendering, the volume is resampled, composited and warped to obtain the final image. Many applications, however, require a mixture of polygonal and volumetric data to be rendered together in a single image. This paper describes a new approach for extending the shear-warp rendering to simultaneously handle polygonal objects. A data structure, the zlist-buffe, is presented. It is basically a multilayered z-buffer. With the zlist-buffer, an object-based scan conversion of polygons requires only a simple modification of the standard polygon scan-conversion algorithm. This paper shows how the scan conversion can be integrated with shear-warp rendering of run-length encoded volume data to obtain quality images in real time. The utility and performance of the approach using a number of test renderings is also discussed
A Spinning Mirror for Fast Angular Scans of EBW Emission for Magnetic Pitch Profile Measurement
A tilted spinning mirror rapidly steers the line of sight of the electron
Bernstein wave (EBW) emission radiometer at the Mega Amp Spherical Tokamak
(MAST). In order to resist high mechanical stresses at rotation speeds of up to
12,000 rpm and to avoid eddy current induced magnetic braking, the mirror
consists of a glass-reinforced nylon substrate of a special self-balanced
design, coated with a reflecting layer. By completing an angular scan every
2.5-10ms, it allows one to characterize with good time resolution the
Bernstein-extraordinary-ordinary mode-conversion efficiency as a function of
the view angles. Angular maps of conversion efficiency are directly related to
the magnetic pitch angle at the cutoff layer for the ordinary mode. Hence,
measurements at various frequencies provide the safety factor profile at the
plasma edge. Initial measurements and indications of the feasibility of the
diagnostic are presented. Moreover, angular scans indicate the best launch
conditions for EBW heating.Comment: 4 pages, 7 figures. Presented at High Temperature Plasma Diagnostics
(HTPD) Conference. Accepted on June 15, 2010 for publication on
Rev.Sci.Instru
Stochastic Rounding for Image Interpolation and Scan Conversion
The stochastic rounding (SR) function is proposed to evaluate and demonstrate
the effects of stochastically rounding row and column subscripts in image
interpolation and scan conversion. The proposed SR function is based on a
pseudorandom number, enabling the pseudorandom rounding up or down any
non-integer row and column subscripts. Also, the SR function exceptionally
enables rounding up any possible cases of subscript inputs that are inferior to
a pseudorandom number. The algorithm of interest is the nearest-neighbor
interpolation (NNI) which is traditionally based on the deterministic rounding
(DR) function. Experimental simulation results are provided to demonstrate the
performance of NNI-SR and NNI-DR algorithms before and after applying smoothing
and sharpening filters of interest. Additional results are also provided to
demonstrate the performance of NNI-SR and NNI-DR interpolated scan conversion
algorithms in cardiac ultrasound videos.Comment: 10 pages, 17 figures, 3 tables. International Journal of Advanced
Computer Science and Applications, 202
Vertical Scan-Conversion for Filling Purposes
Conventional scan-conversion algorithms were developed independently of filling algorithms. They cause many problems, when used for filling purposes. However, today's raster printers and plotters require extended use of filling, especially for the generation of typographic characters and graphic line art. A new scan-conversion algorithm, called vertical scan-conversion has been specifically designed to meet the requirements of parity scan line fill algorithms. Vertical scan-conversion ensures the selection of exactly one pixel per intersecting scan live between a local minimum and a local maximum of the shape outline. Pairs of selected pixels define horizontal spans. All horizontal spans contain the full set of pixels interior to the original shape. Vertical scan-conversion greatly simplifies traditional edge-tracking filling algorithms, such as ordered edge fill, flag fill and descriptive contour fill, removing the need for testinf and processing special cases
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