Huseyin Koçak

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The electroencephalogram (EEG), like many other biological phenomena, is quite likely governed by nonlinear dynamics. Certain characteristics of the underlying dynamics have recently been quantified by computing the correlation dimensions (D2) of EEG time series data. In this paper, D2 of the unbiased autocovariance function of the scalp EEG data was used(More)
The term "Lagrangian coherent structure" (LCS) is normally used to describe numerically detected structures whose properties are similar to those of stable and unstable manifolds of hyperbolic trajectories. The latter structures are invariant curves, i.e., material curves of fluid that serve as transport barriers. In this paper we use the term LCS to(More)
Motivated by observations of surface drifters in the Adriatic Sea, transport in a three-gyre system is studied with the aid of dynamical systems techniques. Particular attention is paid to the issue of intergyre transport. The velocity field is assumed to be two-dimensional and incompressible, and composed of a steady three-gyre background flow on which a(More)
Despite many advances, still image storage and transfer, particularly in low-cost devices, remain to be important problems. For example, some wireless phone displays do not have the capacity to handle true colors. To remedy this problem, a color quantization (color palette) technique is often applied to images in order to reduce the number of colors.(More)
Pseudo-color images are widely used on World-Wide-Web (WWW) to reduce file storage, RAM, video memory buffer space, and to speed up data transfers. A pseudo-color image consists of indices and indices are stored in a file with raster scan order. The investigations on different scanning patterns in filing of indices showed that further improvements on(More)
The pseudo-distance technique (PDT) in lossless compression of color-mapped images has proved to be effective. We showed previously that by utilizing the PDT along with the Burrows-Wheeler transformation and an entropy coder, we obtained better compression gain than other well-known generic image compressors e.g. Portable Network Graphics (PNG). Most of(More)
In this work, we study the lossless compression of EEG (electroencephalograph) signals using linear prediction and arithmetic coder. We show that, when we separate the less significant bits of each signal, linear prediction techniques yield better prediction, and with a structured arithmetic coder not only our technique achieves better compression rates(More)
  • SEMINARIO MATEMATICO, A. Collino, +11 authors Gaetano Zampieri
  • 2009
Turin guested a " WORKSHOP ON DYNAMICS ". We invited six among the speakers to write a survey for this special issue of the Journal. Zanolin wrote a paper with coauthors, moreover Matteo Franca's survey is based on the seminar delivered by Russell Johnson at the Workshop. Some of the articles present new results in a more general framework, so they also(More)
We empirically study power consumptions of two linear transformations and lossless data compression algorithms on a TI MSP432 microcontroller. We developed a custom circuit using a TI INA219 breakout board and an Arduino Uno R3 board and programmed it to record power usage automatically. We validated the accuracy of our measurements with that obtained from(More)
Shadowing deals with the existence of true orbits of dynamical systems near approximate orbits with sufficiently small local errors. Although it has roots in abstract dynamical systems, recent developments have made shadowing into a new effective tool for rigorous computer-assisted analysis of specific dynamical systems, especially chaotic ones. For(More)
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