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Processing Algorithms (processing + algorithms)
Kinds of Processing Algorithms Selected AbstractsNRC 3D imaging technology for museum and heritage applicationsCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3 2003J. Taylor Abstract The National Research Council of Canada (NRC) has developed and patented three high-resolution 3D imaging systems and processing algorithms which have been applied to a wide range of museum and heritage recording applications. The systems have been designed for different imaging applications and, in collaboration with a number of national and international museums and cultural agencies, have been used to scan a wide variety of objects and sites. The objective of this paper is to present a summary of the 3D technology and examples of its heritage applications. Copyright © 2003 John Wiley & Sons, Ltd. [source] Migration velocity analysis for tilted transversely isotropic mediaGEOPHYSICAL PROSPECTING, Issue 1 2009Laxmidhar Behera ABSTRACT Tilted transversely isotropic formations cause serious imaging distortions in active tectonic areas (e.g., fold-and-thrust belts) and in subsalt exploration. Here, we introduce a methodology for P-wave prestack depth imaging in tilted transversely isotropic media that properly accounts for the tilt of the symmetry axis as well as for spatial velocity variations. For purposes of migration velocity analysis, the model is divided into blocks with constant values of the anisotropy parameters , and , and linearly varying symmetry-direction velocity VP0 controlled by the vertical (kz) and lateral (kx) gradients. Since determination of tilt from P-wave data is generally unstable, the symmetry axis is kept orthogonal to the reflectors in all trial velocity models. It is also assumed that the velocity VP0 is either known at the top of each block or remains continuous in the vertical direction. The velocity analysis algorithm estimates the velocity gradients kz and kx and the anisotropy parameters , and , in the layer-stripping mode using a generalized version of the method introduced by Sarkar and Tsvankin for factorized transverse isotropy with a vertical symmetry axis. Synthetic tests for several models typical in exploration (a syncline, uptilted shale layers near a salt dome and a bending shale layer) confirm that if the symmetry-axis direction is fixed and VP0 is known, the parameters kz, kx, , and , can be resolved from reflection data. It should be emphasized that estimation of , in tilted transversely isotropic media requires using nonhyperbolic moveout for long offsets reaching at least twice the reflector depth. We also demonstrate that application of processing algorithms designed for a vertical symmetry axis to data from tilted transversely isotropic media may lead to significant misfocusing of reflectors and errors in parameter estimation, even when the tilt is moderate (30°). The ability of our velocity analysis algorithm to separate the anisotropy parameters from the velocity gradients can be also used in lithology discrimination and geologic interpretation of seismic data in complex areas. [source] Constrained total least-squares computations for high-resolution image reconstruction with multisensorsINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2002Michael K. Ng Multiple undersampled images of a scene are often obtained by using a charge-coupled device (CCD) detector array of sensors that are shifted relative to each other by subpixel displacements. This geometry of sensors, where each sensor has a subarray of sensing elements of suitable size, has been popular in the task of attaining spatial resolution enhancement from the acquired low-resolution degraded images that comprise the set of observations. With the objective of improving the performance of the signal processing algorithms in the presence of the ubiquitous perturbation errors of displacements around the ideal subpixel locations (because of imperfections in fabrication), in addition to noisy observation, the errors-in-variables or the total least-squares method is used in this paper. A regularized constrained total least-squares (RCTLS) solution to the problem is given, which requires the minimization of a nonconvex and nonlinear cost functional. Simulations indicate that the choice of the regularization parameter influences significantly the quality of the solution. The L-curve method is used to select the theoretically optimum value of the regularization parameter instead of the unsound but expedient trial-and-error approach. The expected superiority of this RCTLS approach over the conventional least-squares theory-based algorithm is substantiated by example. © 2002 John Wiley & Sons, Inc. Int J Imaging Syst Technol 12, 35,42, 2002 [source] Vision system for on-line characterization of paper slurry ,INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 4 2000Hamed Sari-Sarraf This paper presents a detailed description of a vision system that detects and localizes the nonuniformities that appear on the paper slurry (wood fiber and water mixture) at the wet end of a paper machine. Specifically, the system monitors the paper slurry as it exits the headbox and alerts the operators of any event (e.g., streaks) that disrupts the otherwise homogeneous background. These events affect crucial product properties such as formation. A poor formation results in thick and thin spots on the sheet and impacts its strength and printability. This paper describes the vision system in terms of its hardware modules, as well as the image processing algorithms that it utilizes to perform its function. The system acquires intensity and topographic information from the scene. It uses texture-based features for the detection and facet-based descriptors for the localization of the nonuniformities. In addition to being tested in a laboratory environment, a prototype of this system was constructed and deployed to a paper mill, where its performance was evaluated under realistic conditions. Installed on a fourdrinier paper machine, running at 480 m/min and producing linerboard material, the vision system monitored about a 1 m wide area and successfully detected and localized slurry streaks. Published 2001 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 11, 231,242, 2000 [source] An autonomous phase-boundary detection technique for colloidal hard sphere suspension experiments,MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2006Mark McDowell Abstract Colloidal suspensions of monodisperse spheres are used as physical models of thermodynamic phase transitions and as precursors to photonic band gap materials. Current techniques for identifying the phase boundaries involve manually identifying the phase transitions, which is very tedious and time-consuming. In addition, current image analysis techniques are not able to distinguish between densely packed phases within conventional microscope images, which are mainly characterized by degrees of randomness or order with similar grayscale value properties. We have developed an intelligent machine vision technique that automatically identifies colloidal phase boundaries. The technique utilizes intelligent image processing algorithms that accurately identify and track phase changes vertically or horizontally for a sequence of colloidal hard sphere suspension images. This technique is readily adaptable to any imaging application wherein regions of interest are distinguished from the background by differing patterns of motion over time. Microsc. Res. Tech. 69:236,245, 2006. Published 2006 Wiley-Liss, Inc. [source] Recent advances in breast MRI and MRSNMR IN BIOMEDICINE, Issue 1 2009S. Sinha Abstract Breast MRI is an area of intense research and is fast becoming an important tool for the diagnosis of breast cancer. This review covers recent advances in breast MRI, MRS, and image post-processing and analysis. Several studies have explored a multi-parametric approach to breast imaging that combines analysis of traditional contrast enhancement patterns and lesion architecture with novel methods such as diffusion, perfusion, and spectroscopy to increase the specificity of breast MRI studies. Diffusion-weighted MRI shows some potential for increasing the specificity of breast lesion diagnosis and is even more promise for monitoring early response to therapy. MRS also has great potential for increasing specificity and for therapeutic monitoring. A limited number of studies have evaluated perfusion imaging based on first-pass contrast bolus tracking, and these clearly identify that vascular indices have great potential to increase specificity. The review also covers the relatively new acquisition technique of MR elastography for breast lesion characterization. A brief survey of image processing algorithms tailored for breast MR, including registration of serial dynamic images, segmentation and extraction of morphological features of breast lesions, and contrast uptake modeling, is also included. Recent advances in MRI, MRS, and automated image analysis have increased the utility of breast MR in diagnosis, screening, management, and therapy monitoring of breast cancer. Copyright © 2008 John Wiley & Sons, Ltd. [source] Aircraft type-specific errors in AMDAR weather reports from commercial aircraftTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 630 2008C. Drüe Abstract AMDAR (Aircraft Meteorological DAta Relay) automated weather reports from commercial aircraft provide an increasing amount of input data for numerical weather prediction models. Previous studies have investigated the quality of AMDAR data. Few of these studies, however, have revealed indications of systematic errors dependent upon the aircraft type. Since different airlines use different algorithms to generate AMDAR reports, it has remained unclear whether a dependency on the aircraft type is caused by physical properties of the aircraft or by different data processing algorithms. In the present study, a special AMDAR dataset was used to investigate the physical type-dependent errors of AMDAR reports. This dataset consists of AMDAR measurements by Lufthansa aircraft performing over 300 landings overall at Frankfurt Rhein/Main (EDDF/FRA) on 22 days in 2004. All of this data has been processed by the same software, implying that influences from different processing algorithms should not be expected. From the comparison of single descents to hourly averaged vertical profiles, it is shown that temperature measurements by different aircraft types can have systematic differences of up to 1 K. In contrast, random temperature errors of most types are estimated to be less than 0.3 K. It is demonstrated that systematic deviations in AMDAR wind measurements can be regarded as an error vector, which is fixed to the aircraft reference system. The largest systematic deviations in wind measurements from different aircraft types (more than 0.5 m s,1) were found to exist in the longitudinal direction (i.e. parallel to the flight direction). Copyright © 2008 Royal Meteorological Society [source] Marginal Bone Level around Implants Assessed in Digital and Film Radiographs: In Vivo Study in the DogCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 1 2000Eva Borg DDS ABSTRACT Background: One of the objectives of postoperative radiographic examinations of implants is to evaluate the marginal bone height and its changes over time. Purpose: The purpose of this study was to assess the influence of digital image processing on measurements of the marginal bone level around implants. Material and Methods: Implants in beagle dogs, used to study the development of peri-implantitis and subsequent healing following treatment, were monitored with conventional radiography and a digital image plate system. Five observers measured the distance between a reference point and the bone level. Measurements in conventional radiographs were made with the use of an x-ray viewer (2X) and a magnifying lens (7X). For the digital images, the system's built-in measuring function was used together with five image processing techniques: edge enhancement (matrixes set on 5 and 25), inverted grey scale, single color highlight, and color intensity mapping together with the brightness and contrast control. From the time of maximum breakdown and the end of the experiment, histologic values were available. Results: Differences between techniques and observers increased toward the end of the healing period. Measurements made at maximum breakdown did not differ significantly from the histologic value. Measurements made after healing all methods, except that using edge enhancement and a 25 × 25 kernel, differed significantly from the histologic value by underestimating the bone level. Conclusions: Measurements of bone level around implants from digital radiographs are as accurate and precise as those from film images. In particular cases, the use of specific image processing algorithms may improve both accuracy and precision. After healing, the histologic specimens showed an incomplete bone fill in the crater with a remaining thin layer of connective tissue in contact with the fixture, and in such situations, the morphology of the bone will give a more complicated diagnostic task. [source] | |||||||||||||