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Articles 271 - 287 of 287
Full-Text Articles in Physical Sciences and Mathematics
Adaptive Boundary Detection Using “Live-Wire” Two-Dimensional Dynamic Programming, William A. Barrett, Bryan S. Morse, Eric N. Mortensen, Jayaram Udupa
Adaptive Boundary Detection Using “Live-Wire” Two-Dimensional Dynamic Programming, William A. Barrett, Bryan S. Morse, Eric N. Mortensen, Jayaram Udupa
Faculty Publications
An adaptive boundary detection algorithm that uses two-dimensional dynamic programming is presented. The algorithm is less constrained than previous one-dimensional dynamic programming algorithms and allows the user to interactively determine the mathematically optimal boundary between a user-selected seed point and any other dynamically selected "free” point in the image. Interactive movement of the free point by the cursor causes the boundary to behave like a “live wire” as it adapts to the new minimum cost path between the seed point and the currently selected free point. The algorithm can also be adapted or customized to learn boundary-defining features for a …
Approximation By Interval Bezier Curves, Thomas W. Sederberg, Rida T. Farouki
Approximation By Interval Bezier Curves, Thomas W. Sederberg, Rida T. Farouki
Faculty Publications
The interval Bezier curve, which, unlike other curve and surface approximation schemes, can transfer a complete description of approximation errors between diverse CAD/CAM systems that impose fundamentally incompatible constraints on their canonical representation schemes, is described. Interval arithmetic, which offers an essentially infallible way to monitor error propagation in numerical algorithms that use floating-point arithmetic is reviewed. Affine maps, the computations of which are key operations in the de Casteljau subdivision and degree-elevation algorithms for Bezier curves, the floating-point error propagation in such computations, approximation by interval polynomials, and approximation by interval Bezier curves are discussed.
A Self-Organizing Binary Decision Tree For Incrementally Defined Rule-Based Systems, Douglas M. Campbell, Tony R. Martinez
A Self-Organizing Binary Decision Tree For Incrementally Defined Rule-Based Systems, Douglas M. Campbell, Tony R. Martinez
Faculty Publications
This paper presents an adaptive self-organizing concurrent system (ASOCS) model for massively parallel processing of incrementally defined rule systems in such areas as adaptive logic, robotics, logical inference, and dynamic control. An ASOCS is an adaptive network composed of many simple computing elements operating asynchronously and in parallel. This paper focuses on adaptive algorithm 3 (AA3) and details its architecture and learning algorithm. It has advantages over previous ASOCS models in simplicity, implementability, and cost. An ASOCS can operate in either a data processing mode or a learning mode. During the data processing mode, an ASOCS acts as a parallel …
Techniques For Cubic Algebraic Surfaces Ii, Thomas W. Sederberg
Techniques For Cubic Algebraic Surfaces Ii, Thomas W. Sederberg
Faculty Publications
A survey of some techniques that may have potential for free-form modeling with algebraic surfaces is continued. Classical results as well as several recent innovations are included. Specific attention is paid to cubic algebraic surfaces, although many of the ideas presented have application to algebraic surfaces of any degree. Topics addressed include piecewise constructions, interpolation to points and space curves, and parameterization.
Techniques For Cubic Algebraic Surfaces I, Thomas W. Sederberg
Techniques For Cubic Algebraic Surfaces I, Thomas W. Sederberg
Faculty Publications
The tutorial presents some tools for free-form modeling with algebraic surfaces, that is, surfaces that can be defined using an implicit polynomial equation f(x, y, z )=0. Cubic algebraic surfaces (defined by an implicit equation of degree 3) are emphasized. While much of this material applies only to cubic surfaces, some applies to algebraic surfaces of any degree. This area of the tutorial introduces terminology, presents different methods for defining and modeling with cubic surfaces, and examines the power basis representation of algebraic surfaces. Methods of forcing an algebraic surface to interpolate a set of points or a space curve …
Consistency And Generalization In Incrementally Trained Connectionist Networks, Tony R. Martinez
Consistency And Generalization In Incrementally Trained Connectionist Networks, Tony R. Martinez
Faculty Publications
This paper discusses aspects of consistency and generalization in connectionist networks which learn through incremental training by examples or rules. Differences between training set learning and incremental rule or example learning are presented. Generalization, the ability to output reasonable mappings when presented with novel input patterns, is discussed in light of the above learning methods. In particular, the contrast between humming distance generalization and generalizing by high order combinations of critical variables is overviewed. Examples of detailed rules for an incremental learning model are presented for both consistency and generalization constraints.
Interactive Morphometrics From Three-Dimensional Surface Images, William A. Barrett, Shawn C. Becker
Interactive Morphometrics From Three-Dimensional Surface Images, William A. Barrett, Shawn C. Becker
Faculty Publications
Techniques have been developed for extracting three-dimensional (3D) measurements directly and interactively from 3D representations of surface anatomy. In order to obtain 3D measurements the anatomical surface is interrogated directly through the use of morphometric tools. Morphometric tools include points, 3D graphical "probes", and logical sectioning functions which interact with the surface through depth buffer compositing operations. Tools are interactively positioned on or through the surface to measure surface dimensions and partial volumes, or to define intersecting functions which allow surface anatomy to be visualized in the context of surrounding anatomy. Visualization is also enhanced because tools reveal much pertaining …
A Relaxation Algorithm For Segmentation Of The Endocardial Surface From Cine Ct, William A. Barrett, Bryan S. Morse
A Relaxation Algorithm For Segmentation Of The Endocardial Surface From Cine Ct, William A. Barrett, Bryan S. Morse
Faculty Publications
A relaxation algorithm has been developed for automated segmentation of the endocardial surface from contrast Cine CT images. The image is contoured at an initial density threshold and a one-dimensional edge operator is applied orthogonally to each point of the contour. Output from the operator is used to generate a histogram, the mode of which identifies a new threshold. The image is contoured again at the new threshold and the process is repeated. Iteration continues with successive threshold estimates converging to a stable value in the region of the endocardial surface. Computer-determined thresholds compare favorably with manual segmentation while reducing …
Interactive Measurement Of Three-Dimensional Cardiac Morphology, William A. Barrett, Shawn C. Becker
Interactive Measurement Of Three-Dimensional Cardiac Morphology, William A. Barrett, Shawn C. Becker
Faculty Publications
Techniques have been developed for extracting three-dimensional (3D) measurements directly and interactively from 3D representations of Cine CT images. In order to obtain 3D measurements the anatomical surface is interrogated directly through the use of a 3D graphical "probe" (line). The probe is interactively positioned and stretched between any visible surface points to allow direct capture of 3D (linear) distance. Distance measurements are updated in real time as the probe dynamically "penetrates" any intervening anatomy while providing valuable depth cuing for visual feedback and probe placement. Curvilinear distance is obtained by stretching the probe over multiple surface points. The probe …
Probabilistic Segmentation Of Myocardial Tissue By Deterministic Relaxation, William A. Barrett, Shawn C. Becker, Jerome A. Broekhuijsen
Probabilistic Segmentation Of Myocardial Tissue By Deterministic Relaxation, William A. Barrett, Shawn C. Becker, Jerome A. Broekhuijsen
Faculty Publications
A recently-developed probabilistic model for automatically segmenting regions of interest in abdominal CT scans has been adapted to the challenging task of segmenting myocardial tissue in Cine CT scans. A system has been implemented on relatively low-cost hardware which performs such segmentations. Special techniques have been developed to improve consistency and accuracy. Early results of testing this new modality are encouraging and promising. Based on observations from experimentation, new directions for future work have been identified.
A Parallel-Processing Subsystem For Rapid 3-D Interpolation Of Ct Images, William A. Barrett, Stephen J. Allan, Scott R. Cannon
A Parallel-Processing Subsystem For Rapid 3-D Interpolation Of Ct Images, William A. Barrett, Stephen J. Allan, Scott R. Cannon
Faculty Publications
An inexpensive parallel-processing subsystem for the rapid interpolation of CT image planes is demonstrated with a variety of node topologies. The subsystem is based on a tree network of INMOS T414 Transputer processors and is hosted by an AT-based image workstation. The subsystem accepts a stack of eight arbitrarily-spaced 256 x 256 image planes from the host. Subsystem output to the host consists of a stack of 32 scaled and evenly-spaced image planes (256 x 256 x 32 with cubic voxels). Benchmark execution times ranged from 12.3 seconds for three nodes to 5.8 seconds for eight nodes.
Dynamic Display And Quantitative Analysis Of Three-Dimensional Left Ventricular Pathology, William A. Barrett, Jayaram K. Udupa
Dynamic Display And Quantitative Analysis Of Three-Dimensional Left Ventricular Pathology, William A. Barrett, Jayaram K. Udupa
Faculty Publications
Techniques have been developed for automated extraction and dynamic interactive display of three-dimensional (3D) left ventricular (LV) surface anatomy from Cine CT images using a PC-based image display architecture. Images of both endocardial and myocardial surface anatomy are generated from multiple views at multiple time instances to demonstrate various LV pathologies including apical akinesis, apical and posterior aneurysms, LV Failure, IHSS, and a left atrial myxoma. Surface generation requires interpolation between scans, surface tracking, and rendering. Generation of 60 views corresponding to a single time instance requires approximately 15 minutes. LV dimensions are measured between two or more surface points …
Digital Neural Networks, Tony R. Martinez
Digital Neural Networks, Tony R. Martinez
Faculty Publications
Demands for applications requiring massive parallelism in symbolic environments have given rebirth to research in models labeled as neural networks. These models are made up of many simple nodes which are highly interconnected such that computation takes place as data flows amongst the nodes of the network. To present, most models have proposed nodes based on simple analog functions, where inputs are multiplied by weights and summed, the total then optionally being transformed by an arbitrary function at the node. Learning in these systems is accomplished by adjusting the weights on the input lines. This paper discusses the use of …
Can Programmers Reuse Software?, Scott N. Woodfield, David W. Embley, Del T. Scott
Can Programmers Reuse Software?, Scott N. Woodfield, David W. Embley, Del T. Scott
Faculty Publications
An experiment asked programmers untrained in reuse to evaluate component reusability. They did poorly. Are reusability's promises hollow? Or are there some answers?
Algebraic Geometry For Computer-Aided Geometric Design, Thomas W. Sederberg, Ronald N. Goldman
Algebraic Geometry For Computer-Aided Geometric Design, Thomas W. Sederberg, Ronald N. Goldman
Faculty Publications
Classical algebraic geometry has been virtually ignored in computer-aided geometric design. However, because it deals strictly with algorithms, it is really more suited to this field than is modern algebraic geometry, which introduces abstractions far removed from the algorithmic nature of computer-aided design. This tutorial examines resultants, curve implicitization, curve inversion, and curve intersection. Discussion follows a series of examples simple enough for those with only a modest algebra background to follow.
Computing As A Part Of A P.H.D Students Education: A Position Paper, Andrew D. Bailey, Rayman D. Meservy
Computing As A Part Of A P.H.D Students Education: A Position Paper, Andrew D. Bailey, Rayman D. Meservy
Faculty Publications
The skills and abilities associated with computer literacy are becoming required tools for accounting Ph.D. students. Not only are new doctoral students entering Ph.D. programs with better skills, they are also applying these skills more on a day to day basis. This paper presents a brief discussion of a number of issues associated with computer use and computer literacy in general. The paper also presents several aspects of the Ph.D. program at the University of Minnesota and how computers are affecting the program.
A Hidden-Line Algorithm For Hyperspace, Robert P. Burton, David R. Smith
A Hidden-Line Algorithm For Hyperspace, Robert P. Burton, David R. Smith
Faculty Publications
An object-space hidden-line algorithm for higher-dimensional scenes has been designed and implemented. Scenes consist of convex hulls of any dimension, each of which is compared against the edges of all convex hulls not eliminated by a hyperdimensional clipper, a depth test after sorting and a minimax text. Hidden and visible elements are determined in accordance with the dimensionality of the selected viewing hyperspace. When shape alone is the attribute of interest, hidden-line elimination need be performed only in that hyperspace. The algorithm is of value in the production of shadows of hyperdimensional models, including but not limited to four-dimensional space-time …