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Pattern Analysis and Machine Intelligence, IEEE Transactions on

Issue 12 • Date Dec 1991

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Displaying Results 1 - 8 of 8
  • A computationally compact divergence measure for speech processing

    Publication Year: 1991 , Page(s): 1255 - 1260
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The directed divergence, which is a measure based on the discrimination information between two signal classes, is investigated. A simplified expression for computing the directed divergence is derived for comparing two Gaussian autoregressive processes such as those found in speech. This expression alleviates both the computational cost (reduced by two thirds) and the numerical problems encountered in computing the directed divergence. In addition, the simplified expression is compared with the Itakura-Saito distance (which asymptotically approaches the directed divergence). Although the expressions for these two distances closely resemble each other, only moderate correlations between the two were found on a set of actual speech data View full abstract»

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  • Synthesis and recognition of sequences

    Publication Year: 1991 , Page(s): 1245 - 1255
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    A string or sequence is a linear array of symbols that come from an alphabet. Due to unknown substitutions, insertions, and deletions of symbols, a sequence cannot be treated like a vector or a tuple of a fixed number of variables. The synthesis of an ensemble of sequences is a sequence of random elements that specify the probabilities of occurrence of the different symbols at the corresponding sites of the sequences. The synthesis is determined by a hierarchical sequence synthesis procedure (HSSP), which returns not only the taxonomic hierarchy of the whole ensemble of sequences but also the alignment and the synthesis of a group (a subset of the ensemble) of the sequences at each level of the hierarchy. The HSSP does not require the ensemble of sequences to be presented in the form of a tabulated array of data, the hierarchical information of the data, or the assumption of a stochastic process. The authors present the concept of sequence synthesis and the applicability of the HSSP as a supervised classification procedure as well as an unsupervised classification procedure View full abstract»

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  • On the verification of hypothesized matches in model-based recognition

    Publication Year: 1991 , Page(s): 1201 - 1213
    Cited by:  Papers (47)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1156 KB)  

    Model-based recognition methods generally use ad hoc techniques to decide whether or not a model of an object matches a given scene. The most common such technique is to set an empirically determined threshold on the fraction of model features that must be matched to data features. Conditions under which to accept a match as correct are rigorously derived. The analysis is based on modeling the recognition process as a statistical occupancy problem. This model makes the assumption that pairings of object and data features can be characterized as a random process with a uniform distribution. The authors present a number of examples illustrating that real image data are well approximated by such a random process. Using a statistical occupancy model, they derive an expression for the probability that a randomly occurring match will account for a given fraction of the features of a particular object. This expression is a function of the number of model features, the number of data features, and bounds on the degree of sensor noise. It provides a means of setting a threshold such that the probability of a random match is very small View full abstract»

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  • The geometry of basis sets for morphologic closing

    Publication Year: 1991 , Page(s): 1214 - 1224
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    P. Maragos (1989) provided a framework for the decomposition of many morphologic operations into orthogonal components or basis sets. Using this framework, a method to find the minimal basis set for the important operation of closing in two dimensions is described. The closing basis sets are special because their elements are members of an ordered, global set of closing shapes or primitives. The selection or design of appropriate individual or multiple structuring elements for image filtering can be better understood, and sometimes implemented more easily, through consideration of the orthogonal closing decomposition. Partial closing of images using ordered fractions of a closing basis set may give a finer texture or roughness measure than that obtained from the conventional use of scaled sets of shapes such as the disc. The connection between elements of the basis set for closing and the complete, minimal representation of arbitrary logic functions is analyzed from a geometric viewpoint View full abstract»

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  • Direct computation of qualitative 3-D shape and motion invariants

    Publication Year: 1991 , Page(s): 1236 - 1240
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    Structure from motion often refers to the computation of three-dimensional structure from a matched sequence of images. However, a depth map of a surface is difficult to compute and may not be a good representation for storage and recognition. Given matched images it is shown that the sign of the normal curvature in a given direction at a given point in the image can be computed from a simple difference of slopes of line segments in one image. Using this result, local surface patches can be classified as convex, concave, cylindrical, hyperbolic (saddle point), or planar. At the same time, the translational component of the optical flow, from which the focus of expansion can be computed, is obtained View full abstract»

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  • Minimax search algorithms with and without aspiration windows

    Publication Year: 1991 , Page(s): 1225 - 1235
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1020 KB)  

    Investigation of several algorithms for computing exact minimax values of game trees (utilizing backward pruning) are discussed. The focus is on trees with an ordering similar to that actually found in game playing practice. The authors compare the algorithms using two different distributions of the static values, the uniform distribution and a distribution estimated from practical data. A systematic comparison of using aspiration windows for all of the usual minimax algorithms is presented. The effects of aspiration windows of varying size and position are analyzed. Increasing the ordering of moves to near the optimum results in unexpectedly high savings. Algorithms with linear space complexity benefit most. Although the ordering of the first move is of predominant importance, that of the remainder has only second-order effects. The use of an aspiration window not only makes alpha-beta search competitive, but there also exist dependencies of its effects on certain properties of the trees View full abstract»

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  • Camera calibration: a quick and easy way to determine the scale factor

    Publication Year: 1991 , Page(s): 1240 - 1245
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    The author presents a quick and easy solution to the camera calibration problem of finding the scale factor that arises because of a difference between the scanning frequency of the camera sensor plane and the scanning frequency of the image capture board frame buffer. The method presented is based on the observation that the scale factor is related to the distortion in an image of a circle: this is a distortion that can easily be measured by considering the occluding boundary of a precisely fabricated sphere, such as a ball bearing. Implementation results are presented View full abstract»

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  • Building a sonar map in a specular environment using a single mobile sensor

    Publication Year: 1991 , Page(s): 1260 - 1269
    Cited by:  Papers (54)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB)  

    The physical properties of acoustic sensors are exploited to obtain information about the environment for sonar map building. A theoretical formulation for interpreting the sensor databases on the physical principles of acoustic propagation and reflection is presented. A characterization of the sonar scan that allows the differentiation of planes, corners, and edges in a specular environment is described. A single sensor mounted on an autonomous vehicle in a laboratory verifies the technique. The implications for sonar map building and the limitations of differentiating elements with one sensor are discussed View full abstract»

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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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David A. Forsyth
University of Illinois