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Pattern Analysis and Machine Intelligence, IEEE Transactions on

Issue 4 • Date July 1985

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Displaying Results 1 - 20 of 20
  • [Front cover]

    Page(s): c1
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  • List of Contributors

    Page(s): nil1
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  • [Breaker page]

    Page(s): nil1
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  • In Memoriam: King-sun Fu

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  • Dynamic Occlusion Analysis in Optical Flow Fields

    Page(s): 374 - 383
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    Optical flow can be used to locate dynamic occlusion boundaries in an image sequence. We derive an edge detection algorithm sensitive to changes in flow fields likely to be associated with occlusion. The algorithm is patterned after the Marr-Hildreth zero-crossing detectors currently used to locate boundaries in scalar fields. Zero-crossing detectors are extended to identify changes in direction and/or magnitude in a vector-valued flow field. As a result, the detector works for flow boundaries generated due to the relative motion of two overlapping surfaces, as well as the simpler case of motion parallax due to a sensor moving through an otherwise stationary environment. We then show how the approach can be extended to identify which side of a dynamic occlusion boundary corresponds to the occluding surface. The fundamental principal involved is that at an occlusion boundary, the image of the surface boundary moves with the image of the occluding surface. Such information is important in interpreting dynamic scenes. Results are demonstrated on optical flow fields automatically computed from real image sequences. View full abstract»

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  • Determining Three-Dimensional Motion and Structure from Optical Flow Generated by Several Moving Objects

    Page(s): 384 - 401
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    A new approach for the interpretation of optical flow fields is presented. The flow field, which can be produced by a sensor moving through an environment with several independently moving, rigid objects, is allowed to be sparse, noisy, and partially incorrect. The approach is based on two main stages. In the first stage, the flow field is partitioned into connected segments of flow vectors, where each segment is consistent with a rigid motion of a roughly planar surface. In the second stage, segments are grouped under the hypothesis that they are induced by a single, rigidly moving object. Each hypothesis is tested by searching for three-dimensional (3-D) motion parameters which are compatible with all the segments in the corresponding group. Once the motion parameters are recovered, the relative environmental depth can be estimated as well. Experiments based on real and simulated data are presented. View full abstract»

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  • Local Determination of a Moving Contrast Edge

    Page(s): 402 - 409
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    This paper proposes an intensity-based method for determining the spatial orientation and observed velocity of a continuously moving edge. Space-time relations arise from the translation of a straight edge across a fixed detector array; a tesselation unit comprised of three equidistant detectors is used to exploit these relationships. The time ordering of cells within this unit can estimate edge direction and velocity. More precise edge determination is possible when intercell times are available and constant edge velocity is assumed; a sensitivity analysis examines the effect of relaxing the velocity constraint. The simulation of a translating synthetic image over an array of detectors is presented in order to demonstrate the method. View full abstract»

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  • Recognizing Partially Occluded Parts

    Page(s): 410 - 421
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    The problem of recognizing an object from a partially occluded boundary image is considered, and the concept of saliency of a boundary segment is introduced. Saliency measures the extent to which the boundary segment distinguishes the object to which it belongs from other objects which might be present. An algorithm is presented which optimally determines the saliency of boundary segments of one object with respect to those of a set of other objects. An efficient template matching algorithm using templates weighted by boundary segment saliency is then presented and employed to recognize partially occluded parts. The results of these experiments illustrate the effectiveness of the new technique. View full abstract»

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  • Connected Line Drawing Extraction from a Perspective View of a Polyhedron

    Page(s): 422 - 430
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    To extract line drawings with positional information from perspective veiws of three-dimensional objects is essential in image analysis and understanding. A new heuristic-search algorithm driven by a priori knowledge contained in a world model is presented which extracts a connected line drawing from a perspective view of a polyhedron. A main feature of our algorithm is that the search is concentrated on local areas centered at corners found with a corner finder. Therefore, the search time is significantly reduced and so are the positional errors in the extracted line drawing. An iterative process removes the false corners and lines and thus guarantees that our algorithm will work stably and reliably even in a noisy environment. Experimental results are presented. View full abstract»

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  • Knowledge-Driven Ultrasonic Three-Dimensional Organ Modeling

    Page(s): 431 - 441
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    A representation is described for nonstructured biologic objects which are single-valued distortions of a sphere. The representation is implemented in a model-driven system for extracting three-dimensional (3-D) organ reconstructions from a series of arbitrarily oriented ultrasound slices. A training set of ultrasonic reconstructions of similarly shaped objects is used to give the computer generic knowledge of a given shape class. This knowledge is in the form of local slope constraints defined on an object coordinate system. The combination of constraints, interacting together via a relaxation process on continuous label sets, attempts to capture the essential shape and range of variation for an organ class. An initial tolerance region and ``bestguess'' organ surface are established by the interaction of the learned shape knowledge with manually input organ landmarks. A hypothesize-verify paradigm is employed to alternately request new data and to update the tolerance region and bestguess surface. Examples from runs on two balloon classes are presented. These examples show: 1) the local constraints interact to produce a reasonable global depiction of the essential shape and range of variation, 2) the use of shape knowledge permits accurate results from only one third of the available data, and 3) the 3-D shape knowledge provides a two-dimensional (2-D) tolerance region for plan-guided edge detection. View full abstract»

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  • Parallel Game-Tree Search

    Page(s): 442 - 452
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    The design issues affecting a parallel implementation of the alpha-beta search algorithm are discussed with emphasis on a tree decomposition scheme that is intended for use on well ordered trees. In particular, the principal variation splitting method has been implemented, and experimental results are presented which show how such refinements as progressive deepening, narrow window searching, and the use of memory tables affect the performance of multiprocessor based chess playing programs. When dealing with parallel processing systems, communication delays are perhaps the greatest source of lost time. Therefore, an implementation of our tree decomposition based algorithm is presented, one that operates with a modest amount of message passing within a network of processors. Since our system has low search overhead, the principal basis for comparison is the communication overhead, which in turn is shown to have two components. View full abstract»

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  • Attributed String Matching with Merging for Shape Recognition

    Page(s): 453 - 462
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    A new structural approach to shape recognition using attributed string matching with merging is proposed. After illustrating the disadvantages of conventional symbolic string matching using changes, deletions, and insertions, attributed strings are suggested for matching. Each attributed string is an ordered sequence of shape boundary primitives, each representing a basic boundary structural unit, line segment, with two types of numerical attributes, length and direction. A new type of primitive edit operation, called merge, is then introduced, which can be used to combine and then match any number of consecutive boundary primitives in one shape with those in another. The resulting attributed string matching with merging approach is shown useful for recognizing distorted shapes. Experimental results prove the feasibility of the proposed approach for general shape recognition. Some possible extensions of the approach are also included. View full abstract»

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  • A Width-Independent Fast Thinning Algorithm

    Page(s): 463 - 474
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    The skeleton of a digital figure can often be regarded as a convenient alternative to the figure itself. It is useful both to diminish drastically the amount of data to be handled, and to simplify the computational procedures required for description and classification purposes. Thinning a digital figure down to its skeleton is a time-consuming process when conventional sequential computers are employed. The procedure we propose allows one to speed up the thinning transformation, and to get a well-shaped skeleton. After cleaning of the input picture has been performed, the pixels of the figure are labeled according to their distance from the background, and a set, whose pixels are symmetrically placed with respect to distinct contour parts of the figure, is found. This set is then given a linear structure by applying topology preserving removal operations. Finally, a pruning step, regarding branches not relevant in the framework of the problem domain, completes the process. The resulting skeleton is a labeled set of pixels which is shown to possess all the required properties, particularly those concerning connectedness, topology, and shape. Moreover, the original figure can almost completely be recovered by means of a reverse distance transformation. Only a fixed and small number of sequential passes through the picture is necessary to achieve the goal. The computational effort is rather modest, and the use of the proposed algorithm turns out to be more advantageous the greater the width of the figure to be thinned. View full abstract»

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  • Restoration of Multichannel Microwave Radiometric Images

    Page(s): 475 - 484
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    A constrained iterative image restoration method is applied to multichannel diffraction-limited imagery. This method is based on the Gerchberg-Papoulis algorithm utilizing incomplete information and partial constraints. The procedure is described using the orthogonal projection operators which project onto two prescribed subspaces iteratively. Its properties and limitations are presented. The effect of noise was investigated and a better understanding of the performance of the algorithm with noisy data has been achieved. The restoration scheme with the selection of appropriate constraints was applied to a practical problem. The 6.6, 10.7, 18, and 21 GHz satellite images obtained by the scanning multichannel microwave radiometer (SMMR), each having different spatial resolution, were restored to a common, high resolution (that of the 37 GHz channels) to demonstrate the effectiveness of the method. Both simulated data and real data were used in this study. The restored multichannel images may be utilized to retrieve rainfall distributions. View full abstract»

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  • Sensing Error for a Mobile Robot Using Line Navigation

    Page(s): 485 - 490
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    The use of a contrasting line for the visual navigation of autonomous mobile robots in a factory environment is developed. Minimum and maximum linewidths are determined analytically by considering sensor geometry, field of view, and error conditions present in the system. The effects of these error conditions on the width of the line, as seen in the image plane, determines the optimal linewidth. Numerical examples using typical sensor parameters are given. View full abstract»

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  • Reliability and Speed of Recall in an Associative Network

    Page(s): 490 - 498
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    Previous investigations of the storage capacity of associative nets have not explicitly considered quantitative aspects of the tradeoff between storage capacity and reconstructive power in these systems. Furthermore, few comparisons have been made between theoretical estimates and experimental results (simulations). In this correspondence, we describe some results recently obtained and relevant to these issues. It is shown that a high storage capacity is possible, without sacrificing reliability in the recall process. Furthermore, an efficient algorithm for retrieval of the information stored is presented, and the speed of recall employing various degrees of parallelism is discussed. View full abstract»

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  • The AI Business: The Commercial Uses of Artificial Intelligence

    Page(s): 499
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  • List of Reviewers

    Page(s): 500
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  • List of Contributors

    Page(s): nil2
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  • [Front cover]

    Page(s): c2
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Aims & Scope

The IEEE Transactions on Pattern Analysis and Machine Intelligence (TPAMI) is published monthly. Its editorial board strives to present most important research results in areas within TPAMI's scope.

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Meet Our Editors

Editor-in-Chief
David A. Forsyth
University of Illinois