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Choon-Young Lee

Publications and source records attributed to Choon-Young Lee.

2 recordsLinked to original sources

Adaptive control for uncertain nonlinear systems based on multiple neural networks.

A new adaptive multiple neural network controller (AMNNC) with a supervisory controller for a class of uncertain nonlinear dynamic systems was developed in this paper. The AMNNC is a kind of adaptive feedback linearizing controller where nonlinearity terms are approximated with multiple neural networks. The weighted sum of the multiple neural networks was used to approximate system nonlinearity for the given task. Each neural network represents the system dynamics for each task. For a job where some tasks are repeated but information on the load is not defined and unknown or varying, the proposed controller is effective because of its capability to memorize control skill for each task with each neural network. For a new task, most similar existing control skills may be used as a starting point of adaptation. With the help of a supervisory controller, the resulting closed-loop system is globally stable in the sense that all signals involved are uniformly bounded. Simulation results on a cartpole system for the changing mass of the pole were illustrated to show the effectiveness of the proposed control scheme for the comparison with the conventional adaptive neural network controller (ANNC).

Journal Article↗

Stress-induced cardiomyopathy presenting as acute myocardial infarction.

Stress-induced cardiomyopathy is described as an acute cardiomyopathy that occurs under the influence of an excessive level of catecholamine related to intense emotional stress. A 64-year-old woman presented with symptoms of acute myocardial infarction after emotional upset, but her coronary angiographic findings were revealed to be normal. Diffuse T wave inversions were observed in her electrocardiograms with akinetic wall motions sparing the basal segments in her left ventriculography. After four months, her electrocardiogram and echocardiogram findings had completely returned to normal. The precise diagnosis of this acute cardiomyopathy must be emphasized because it can initially be misdiagnosed as acute coronary syndromes. However in complete contrast to acute myocardial infarction, it has a rapid and favorable recovery with hardly any sequelae after a few months.

Cardiomyopathies↗