A Neural Network Model of Spatio-Temporal Pattern Recognition, Recall and Timing

This paper describes the design of a self~organizing, hierarchical neural network model of unsupervised serial learning. The model learns to recognize, store, and recall sequences of unitized patterns, using either short-term memory (STM) or both STM and long-term memory (LTM) mechanisms. Timing information is learned and recall {both from STM and from LTM) is performed with a learned rhythmical structure. The network, bearing similarities with ART (Carpenter & Grossberg 1987a), learns to map temporal sequences to unitized patterns, which makes it suitable for hierarchical operation. It is therefore capable of self-organizing codes for sequences of sequences. The capacity is only limited by the number of nodes provided. Selected simulation results are reported to illustrate system properties.National Science Foundation (IRI-9024877

Self-Organizing Grammar Induction Using a Neural Network Model

This paper presents a self-organizing, real-time, hierarchical neural network model of sequential processing, and shows how it can be used to induce recognition codes corresponding to word categories and elementary grammatical structures. The model, first introduced in Mannes (1992), learns to recognize, store, and recall sequences of unitized patterns in a stable manner, either using short-term memory alone, or using long-term memory weights. Memory capacity is only limited by the number of nodes provided. Sequences are mapped to unitized patterns, making the model suitable for hierarchical operation. By using multiple modules arranged in a hierarchy and a simple mapping between output of lower levels and the input of higher levels, the induction of codes representing word category and simple phrase structures is an emergent property of the model. Simulation results are reported to illustrate this behavior.National Science Foundation (IRI-9024877

Slow Sphering to Suppress Non-Stationaries in the EEG

Non-stationary signals are ubiquitous in electroencephalogram (EEG) signals and pose a problem for robust application of brain-computer interfaces (BCIs). These non-stationarities can be caused by changes in neural background activity. We present a dynamic spatial filter based on time local whitening that significantly reduces the detrimental influence of covariance changes during event-related desynchronization classification of an imaginary movement task

A Neural Network Model for Cursive Script Production

This article describes a neural network model, called the VITEWRITE model, for generating handwriting movements. The model consists of a sequential controller, or motor program, that interacts with a trajectory generator to move a. hand with redundant degrees of freedom. The neural trajectory generator is the Vector Integration to Endpoint (VITE) model for synchronous variable-speed control of multijoint movements. VITE properties enable a simple control strategy to generate complex handwritten script if the hand model contains redundant degrees of freedom. The proposed controller launches transient directional commands to independent hand synergies at times when the hand begins to move, or when a velocity peak in a given synergy is achieved. The VITE model translates these temporally disjoint synergy commands into smooth curvilinear trajectories among temporally overlapping synergetic movements. The separate "score" of onset times used in most prior models is hereby replaced by a self-scaling activity-released "motor program" that uses few memory resources, enables each synergy to exhibit a unimodal velocity profile during any stroke, generates letters that are invariant under speed and size rescaling, and enables effortless. connection of letter shapes into words. Speed and size rescaling are achieved by scalar GO and GRO signals that express computationally simple volitional commands. Psychophysical data concerning band movements, such as the isochrony principle, asymmetric velocity profiles, and the two-thirds power law relating movement curvature and velocity arise as emergent properties of model interactions.National Science Foundation (IRI 90-24877, IRI 87-16960); Office of Naval Research (N00014-92-J-1309); Air Force Office of Scientific Research (F49620-92-J-0499); Defense Advanced Research Projects Agency (90-0083

Classifying motor imagery in presence of speech

In the near future, brain-computer interface (BCI) applications for non-disabled users will require multimodal interaction and tolerance to dynamic environment. However, this conflicts with the highly sensitive recording techniques used for BCIs, such as electroencephalography (EEG). Advanced machine learning and signal processing techniques are required to decorrelate desired brain signals from the rest. This paper proposes a signal processing pipeline and two classification methods suitable for multiclass EEG analysis. The methods were tested in an experiment on separating left/right hand imagery in presence/absence of speech. The analyses showed that the presence of speech during motor imagery did not affect the classification accuracy significantly and regardless of the presence of speech, the proposed methods were able to separate left and right hand imagery with an accuracy of 60%. The best overall accuracy achieved for the 5-class separation of all the tasks was 47% and both proposed methods performed equally well. In addition, the analysis of event-related spectral power changes revealed characteristics related to motor imagery and speech

The VITEWRITE Model of Handwriting Production

This article describes the VITEWRITE model for generating handwriting movements. The model consists of a sequential controller, or motor program, that interacts with a trajectory generator to move a hand with redundant degrees of freedom. The neural trajectory generator is the Vector Integration to Endpoint (VITE) model for synchronous variable-speed control of multijoint movements. VITE properties enable a simple control strategy to generate complex handwritten script if the hand model contains redundant degrees of freedom. The controller launches transient directional commands to independent hand synergies at times when the hand begins to move, or when a velocity peak in the outflow command to a given synergy occurs. The VITE model translates these temporally disjoint synergy commands into smooth curvilinear trajectories among temporally overlapping synergetic movements. Each synergy exhibits a unimodal velocity profile during any stroke, generates letters that are invariant under speed and size rescaling, and enables effortless connection of letter shapes into words. Speed and size rescaling are achieved by scalar GO and GRO signals that express computationally simple volitional commands. Psychophysical data such as the isochrony principle, asymmetric velocity profiles, and the two-thirds power law relating movement curvature and velocity arise as emergent properties of model interactions.Office of Naval Research (N00014-92-J-1309); National Science Foundation (IRI-90-24877, IRI-87-16960); Air Force Office of Scientific Research (F49620-92-J-0225); Defense Advanced Research Projects Agency (AFOSR 90-0083

Towards real-time body pose estimation for presenters in meeting environments

This paper describes a computer vision-based approach to body pose estimation.\ud The algorithm can be executed in real-time and processes low resolution,\ud monocular image sequences. A silhouette is extracted and matched against a\ud projection of a 16 DOF human body model. In addition, skin color is used to\ud locate hands and head. No detailed human body model is needed. We evaluate the\ud approach both quantitatively using synthetic image sequences and qualitatively\ud on video test data of short presentations. The algorithm is developed with the\ud aim of using it in the context of a meeting room where the poses of a presenter\ud have to be estimated. The results can be applied in the domain of virtual\ud environments

PVC pipes in gas distribution: still going strong!

In the Netherlands (impact-modified) PVC is the preferred material for low-pressure (30 and 100 mbar) gas distribution systems. More than 50% of the total length (about 122,000 km) of this system is rigid PVC or impact-modified PVC. The installation of rigid PVC (uPVC) pipelines started about 50 years ago. Presently, about 22,500 km of rigid PVC is still in operation. In this paper the good experiences with rigid PVC gas distribution systems in the Netherlands will be illustrated by results of regular leak surveys and test results on pipe samples taken from the gas grid. It will be shown that the leakage rate of uPVC pipe systems is very low and about equal to that of PE and steel pipe systems. Impact tests show no significant decrease in ductility with respect to time of use. Furthermore, the ductility of the PVC pipeline materials which have been in use for many years is shown to be mainly dependent on the (initial) quality (degree of gelation). The good performance of PVC gas pipeline systems is also proven by modelling studies. It will be shown that the long-term failure behaviour of uPVC is determined by the ability to yield. Failure will occur if a certain critical value of the plastic strain is surpassed. Using this model the long-term behaviour under internal pressure of rigid PVC pipes can be predicted quantitatively

Family Preservation: A Professional Reform Movement

Family Preservation is examined as a manifestation of collective professional activity intent on reforming various aspects of the social welfare system. George Smelser\u27s theoretical framework is used to analyze and interpret the emergence and development of the Family Preservation Movement. The article identifies societal problems which spawned the movement, the formation of a shared belief system, and the confirmation and sanctioning of those beliefs. Factors which mobilized increasing numbers of professionals to the cause, efforts which reflect collective action, and the conventionalization and standardization of the movement are discussed