The task of inferring a set of classes and class descriptions most likely to explain a given data set can be placed on a firm theoretical foundation using Bayesian statistics. Within this framework, and using various mathematical and algorithmic approximations, the AutoClass system searches for the most probable classifications, automatically choosing the number of classes and complexity of class descriptions. A simpler version of AutoClass has been applied to many large real data sets, have discovered new independently-verified phenomena, and have been released as a robust software package. Recent extensions allow attributes to be selectively correlated within particular classes, and allow classes to inherit, or share, model parameters though a class hierarchy. In this paper we summarize the mathematical foundations of Autoclass. 1 Introduction The task of supervised classification - i.e., learning to predict class memberships of test cases given labeled training cases - is a familia...

The task of inferring a set of classes and class descriptions most likely to explain a given data set can be placed on a firm theoretical foundation using Bayesian statistics. Within this framework, and using various mathematical and algorithmic approximations, the AutoClass system searches for the most probable classifications, automatically choosing the number of classes and complexity of class descriptions. Simpler versions of AutoClass have been applied to many large real data sets, have discovered new independently-verified phenomena, and have been released as a robust software package. Recent extensions allow attributes to be selectively correlated within particular classes, and allow classes to inherit, or share, model parameters though a class hierarchy. 1

Relaxation oscillations exhibiting more than one time scale arise naturally from many physical systems. This paper proposes a method to numerically integrate large systems of relaxation oscillators. The numerical technique, called the singular limit method, is derived from analysis of relaxation oscillations in the singular limit. In such limit, system evolution gives rise to time instants at which fast dynamics takes place and intervals between them during which slow dynamics takes place. A full description of the method is given for LEGION (locally excitatory globally inhibitory oscillator networks), where fast dynamics, characterized by jumping which leads to dramatic phase shifts, is captured in this method by iterative operation and slow dynamics is entirely solved. The singular limit method is evaluated by computer experiments, and it produces remarkable speedup compared to other methods of integrating these systems. The speedup makes it possible to simulate large-scale oscillato...

This paper presents analysis and design results for control systems subject to oscillatory inputs, i.e., inputs of large amplitude and high frequency. The key analysis results are a series expansion characterizing the averaged system and various Lie-algebraic conditions that guarantee the series can be summed. Various example systems provide insight into the results. With regards to design, we recover and extend a variety of point stabilization and trajectory tracking results using oscillatory controls. We present novel developments on stabilization of systems with positive trace and on tracking for second order underactuated systems.

Abstract. Linear instantaneous independent component analysis (ICA) is a well-known problem, for which efficient algorithms like FastICA and JADE have been developed. Nevertheless, the development of new contrasts and optimization procedures is still needed, e.g. to improve the separation performances in specific cases. For example, algorithms may exploit prior information, such as the sparseness or the non-negativity of the sources. In this paper, we show that support-width minimizationbased ICA algorithms may outperform other well-known ICA methods when extracting bounded sources. The output supports are estimated using symmetric differences of order statistics. 1

Personal information agents monitor ongoing user information accesses in order to provide users with context-relevant information. Providing the needed information requires effective methods for identifying the user’s task context, based on available information. For user browsing tasks, one approach to context identification is to extract context-determining terms from the documents that the user consults. The thesis of this article is (1) that term extraction for personal information agents can be done by learning terms whose occurrence frequencies have a large variance over time, (2) that indexing and retrieval based on these terms can be at least as effective as standard information retrieval techniques, and (3) that this information can be learned without comprehensive corpus analysis, making it suitable for use in personal information retrieval. We have developed an unsupervised term extraction algorithm, WordSieve, that learns individualized context-differentiating terms for document indexing and retrieval. This article presents a new version of WordSieve, compares its design and performance to our initial approach, and assesses its effectiveness for a controlled personal information retrieval task, compared to three common indexing techniques requiring statistics about the global corpus. In the experiments, the new version of WordSieve generates task-relevant indices of comparable or better quality to common indexing techniques, using only local information. 1

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A new procedure for the calculation of spatial impulse responses for linear sound fields is introduced. This calculation procedure uses the well known technique of calculating the spatial impulse response from the intersection of a circle emanating from the projected spherical wave with the boundary of the emitting aperture. This general result holds for all aperture boundaries for a flat transducer surface, and this is used in the procedure to yield the response for all types of flat transducers. An arbitrary apodization function over the aperture can be incorporated through a simple one-dimensional integration. The case of a soft baffle mounting of the aperture is also included. Specific solutions for transducer boundaries made from lines are given, so that any polygon transducer can be handled. Specific solutions for circles are also given. Finally, a solution for a general boundary is stated, and all these boundary elements can be combined to, e.g., handle annular arrays ...

We establish the asymptotic equivalence, up to complex conjugation, of two problems: 1) determining the nearfield performance of a farfield beampattern specification and 2) determining the equivalent farfield beampattern corresponding to a nearfield beampattern specification. Using this reciprocity relationship, we develop a computationally simple procedure to design a beamforming array to achieve a desired nearfield beampattern response. The superiority of this approach to existing methods, both in ease of design implementation and performance obtained, is analyzed and then illustrated by a design example.

This paper (Part II), which is the second in a series of two papers, presents new closed-form solutions for net-section-collapse (NSC) analysis of circumferentially cracked pipes for several idealized crack shapes subjected to combined bending and tension (pressure-induced) loads. They are based on further simplications of generalized NSC equations developed in a parallel study. Analytical solutions were developed for cracks with constant-depth, parabolic, and elliptical shapes. For all three crack shapes, separate equations were developed when the entire crack is subjected to tension and when part of the crack is subjected to compression. For part of the crack subjected to compression, the proposed equations can handle both tight (with crack-closure) and blunt (without crack-closure) cracks. Currently, of the three crack shapes examined in this paper, previous analytical solutions exist only for the constant-depth crack. Hence, they should be useful for pipe fracture analysis involving other crack shapes, such as the elliptical and parabolic cracks. The analytical solutions were validated by numerical analysis based on the generalized NSC equations.