369 research outputs found
Optimum filtering for optimum currency areas criteria
This study aims to analyze Turkey and the Economic and Monetary Union (EMU) countries in the light of criteria suggested by the optimum currency areas (OCA) theory and to compare the criteria obtained by an application of Hodrick-Prescott (H-P) and Baxter-King (B-K) filters. To this end, we follow a novel technique, fuzzy c-means (FCM) clustering with upper and lower levels of fuzziness. The results show that the application of the H-P filtering technique with appropriate smoothing parameter values produces sensible clusters.
Performance of using Mel-Frequency Cepstrum Based Features in Nonlinear Classifiers for Phonocardiography Recordings
Cardiovascular system diseases can be identified by using a specialized
diagnostic process utilizing a digital stethoscope. Digital stethoscopes
provide phonocardiography (PCG) recordings for further inspection, besides
filtering and amplification of heart sounds. In this paper, a framework that is
useful to develop feature extraction and classification of PCG recordings is
presented. This framework is built upon a previously proposed segmentation
algorithm that processes a feature vector produced by the agglutinate
application of Mel-frequency cepstrum and discrete wavelet transform (DWT). The
performance of the segmentation algorithm is also tested on a new data set and
compared to the previously reported results. After identifying the fundamental
heart sounds and segmenting the PCG recordings, five principal features are
extracted from the time domain signal and Mel-Frequency cepstral coefficients
(MFCC) of each cardiac cycle. Classification outcomes are reported for three
nonlinear models: k nearest neighbor (k-NN), support vector machine (SVM), and
multilayer perceptrons (MLP) classifiers in comparison with a linear approach,
namely Mahalanobis distance linear classifier. The results underline that
although neural networks and linear classifier show compatible performance in
basic classification problems, with the increase in the nonlinearity of the
classification problem their performance significantly vary.Comment: in 2023 31st European Signal Processing Conference (EUSIPCO
Inverse nodal problem for Dirac operator with integral type nonlocal boundary conditions
In this paper, Dirac operator with some integral type nonlocal boundary
conditions is studied. We show that the coefficients of the problem can be
uniquely determined by a dense set of nodal points. Moreover, we give an
algorithm for the reconstruction of some coefficients of the operator
Boundary Output Feedback Stabilization for a Novel Magnetizable Piezoelectric Beam Model
A magnetizable piezoelectric beam model, free at both ends, is considered.
Piezoelectric materials have a strong interaction of electromagnetic and
acoustic waves, whose wave propagation speeds differ substantially. The
corresponding strongly-coupled PDE model describes the longitudinal vibrations
and the total charge accumulation at the electrodes of the beam. It is known
that the PDE model with appropriately chosen collocated state feedback
controllers is known to have exponentially stable solutions. However, the
collocated controller design is not always feasible since the performance of
controllers may not be good enough, and moreover, a small increment of feedback
controller gains can easily make the closed-loop system unstable. Therefore, a
non-collocated controller and observer design is considered for the first time
for this model. In particular, two state feedback controllers are designed at
the right end to recover the states so that the boundary output feedback
controllers can be designed as a replacement of the states with the estimate
from the observers on the left end. By a carefully-constructed Lyapunov
function, it is proved that the both the observer and the observer error
dynamics have uniformly exponential stable solutions. This framework offers a
substantial foundation for the model reductions by Finite Differences.Comment: 2 figure
The Exponential Stabilization of a Heat and Piezoelectric Beam Interaction with Static or Hybrid Feedback Controllers
This study investigates a strongly-coupled system of partial differential
equations (PDE) governing heat transfer in a copper rod, longitudinal
vibrations, and total charge accumulation at electrodes within a magnetizable
piezoelectric beam. Conducted within the transmission line framework, the
analysis reveals profound interactions between traveling electromagnetic and
mechanical waves in magnetizable piezoelectric beams, despite disparities in
their velocities. Findings suggest that in the open-loop scenario, the
interaction of heat and beam dynamics lacks exponential stability solely
considering thermal effects. To confront this challenge, two types of
boundary-type state feedback controllers are proposed: (i) employing static
feedback controllers entirely and (ii) adopting a hybrid approach wherein the
electrical controller dynamically enhances system dynamics. In both cases,
solutions of the PDE systems demonstrate exponential stability through
meticulously formulated Lyapunov functions with diverse multipliers. The
proposed proof technique establishes a robust foundation for demonstrating the
exponential stability of Finite-Difference-based model reductions as the
discretization parameter approaches zero.Comment: 1 figur
Rare cause of intestinal obstruction, Ascaris lumbricoides infestation: two case reports
Ascaris lumbricoides is common resident of intestine especially low socioeconomic areas in the world. Complication of Ascaris lumbricoides has been reported include obstruction of the small intestine, intestinal volvulus and intussusception. We report two children with severe sequelae of intestinal obstruction
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