Meslek Yüksek Okulu

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Citation - WoS: 1
Citation - Scopus: 3
Comparative Performance Analysis of Filtering Methods for Removing Baseline Wander Noise From an Ecg Signal
(World Scientific Publ Co Pte Ltd, 2024) Ozaydin, Selma; Ahmad, Imteyaz; 253019; 01. Çankaya Üniversitesi; 08. Meslek Yüksekokulları; 08.02. Çankaya Meslek Yüksekokulu
ECG signals play a vital role in the diagnosis of cardiovascular conditions. However, they often suffer from the effects of various noise sources, including baseline wandering, respiratory artifact noise, power line interference and electrode motion artifacts. To overcome these challenges, it is imperative to implement low-frequency signal noise reduction strategies. Such strategies aim to significantly improve the quality of ECG signals, thus promoting more accurate and reliable diagnosis of cardiovascular disorders. This paper conducts a comparative analysis to assess the effectiveness of commonly used filtering and wavelet techniques in reducing Baseline Wander (BW) noise within ECG signals generated by the influence of breathing or electrode movements. It is common to observe the selection and evaluation of only one particular technique in the existing literature. In contrast, this study aims to provide a comprehensive comparative analysis, providing insight into the performance and relative merits of different techniques. Our research uses both filtering and Discrete Wavelet Transform (DWT) techniques in baseline noise removal. In this context, a reference point is established utilizing noise-free signals and a meticulous investigation of the wavelet-based approach that most effectively eliminates the resulting noise is provided. Subsequently, we assess the reference input and output signal via Signal-to-Noise Ratio (SNR) and Kolmogorov-Smirnov statistical test measurements. The most important contribution of this work to the scientific community resides in the comprehensive examination of IIR/FIR-based and wavelet method-based filtering methods capable of yielding the highest SNR levels across various ECG signals with various types of BW noise. Additionally, the effectiveness of the Chebychev-II filter in BW noise removal is highlighted. Our study was conducted using the MATLAB platform and code command lines were shared to facilitate the reproduction of our study by other researchers. It is considered that this study will be an important reference in the selection of effective techniques for removing BW noise within ECG signals.
Citation - WoS: 12
Citation - Scopus: 12
The Effects of Inflation Uncertainty on Interest Rates: a Nonlinear Approach
(Routledge Journals, Taylor & Francis Ltd, 2010) Hasanov, Muebariz; Omay, Tolga; 08.02. Çankaya Meslek Yüksekokulu; 08. Meslek Yüksekokulları; 01. Çankaya Üniversitesi
In this article, we investigate the effects of inflation variability on short-term interest rates within a nonlinear smooth transition regression framework. The test results suggest that only the conditional mean of the inflation is a nonlinear process whereas the conditional variance is time variant but linear. Using the square root of conditional variance as a proxy for inflation risk, we estimate Fisher equation augmented with inflation risk. Although the estimated Fisher equations suggest that inflation risk reduces short-term interest rates, we find that the effects of inflation risk on interest rates are regime-dependent. Particularly, we find that the negative effects of inflation variability on nominal rates are greater in low-inflationary regimes when compared to high-inflationary regimes. On the other hand, it is found that both inflation and inflation uncertainty raise the expected inflation effect.
Citation - WoS: 31
Citation - Scopus: 36
The Endogenous and Non-Linear Relationship Between Terrorism and Economic Performance: Turkish Evidence
(Taylor & Francis Ltd, 2009) Arin, K. Peren; Omay, Tolga; Araz-Takay, Bahar; 177438; 08.02. Çankaya Meslek Yüksekokulu; 08. Meslek Yüksekokulları; 01. Çankaya Üniversitesi
This paper investigates the macroeconomic effects of terror by using a novel data set from Turkey for the period of 1987:1 to 2004:4. This research contributes to the literature by controlling for the possible non-linear and endogenous relationship between political conflict and economic activity. Empirical evidence from both linear and non-linear models confirms that terrorism has a large significant negative impact on economic activity. Finally, the results from the non-linear model show that the impact of terrorism on the aggregate economy is more severe during expansionary periods, and that the impact of economic activity on terrorism is significant only in recessionary periods.
Citation - WoS: 20
Citation - Scopus: 23
Nonlinearities in Emerging Stock Markets: Evidence From Europe's Two Largest Emerging Markets
(Routledge Journals, Taylor & Francis Ltd, 2008) Omay, Tolga; Hasanov, Muebariz; 08.02. Çankaya Meslek Yüksekokulu; 08. Meslek Yüksekokulları; 01. Çankaya Üniversitesi
Recent developments in time series analysis allow proper modelling of nonlinearities in economic and financial variables. A growing body of research was dedicated to investigation of potential nonlinearities in conditional mean of many economic and financial variables, mainly concentrating in developed economies. However, nonlinearities in financial variables in developing economies have not been fully examined yet. In this article we investigate potential nonlinearity and cyclical behaviour of stock returns in Europe's two largest emerging stock markets, mainly in the Greek and Turkish stock markets. Specifically, we use STAR family models, which allow to model nonlinearities in the conditional mean, for modelling monthly returns on stock exchange indices of the Athens Stock Exchange and Istanbul Stock Exchange. Although we find no nonlinearity in conditional variance, we do find strong evidence in favour of nonlinear adjustment of stock returns. It is found that allowing for nonlinearity in conditional mean results in a superior model and provides good out-of-sample forecasts, which contradicts to efficient market hypothesis.
Citation - Scopus: 28
The Relationship Between Energy Consumption and Economic Growth: Evidence From Different Income Country Groups
(Econjournals, 2017) Yaşar, N.; 230528; 01. Çankaya Üniversitesi
This study analyses the relationship between energy consumption and economic growth for 119 countries during the period of 1970-2015, classified into four groups regarding to the World Bank income ranking. The main motivation of this study is to analyze whether the causal relationship differs between different income groups of countries. For this purpose, panel auto regressive distributed lag boundary approach and Granger causality test were used. The results of the study indicate that the causal relationship between energy use and economic growth differs depending on which income group country belongs to. We conclude that the feedback hypothesis is supported for upper-middle income group in the long run and high-income group, while conservation hypothesis is supported for upper-middle income group in the short run and lower-middle income group in the long run. Finally, neutrality hypothesis is supported for low and lower middle-income groups in the short run. © 2017, Econjournals. All rights reserved.
Citation - Scopus: 1
Stationarity Properties of Renewable Energy Consumption in the Commonwealth of Independent States
(Econjournals, 2020) Yasar, N.; 230528; 01. Çankaya Üniversitesi
This study investigates the stochastic properties of renewable energy consumption series across 11 Commonwealth of Independent States countries through the period of 1990-2015. For this purpose, along with traditional stationarity analysis recently improved unit root techniques which allows for nonlinear adjustments in the data generating process are used in this paper. Based on our findings we may conclude that, consideration of nonlinearity in regression process causes to more frequent non rejection of the null hypothesis of stationarity. It implies that ignoring possible nonlinearities in time series regression process may lead to some misleading results. Hereby, fluctuations in global energy supply and trade systems influence renewable energy consumption in nonlinear pattern and policy-makers should take it into consideration in terms of proper energy policy implication. © 2019, Econjournals. All rights reserved.
Citation - WoS: 150
Citation - Scopus: 160
Testing for Unit Root in Nonlinear Heterogeneous Panels
(Elsevier Science Sa, 2009) Ucar, Nuri; Omay, Tolga; 189073; 08.02. Çankaya Meslek Yüksekokulu; 08. Meslek Yüksekokulları; 01. Çankaya Üniversitesi; 03.01. Bankacılık ve Finans; 03. İktisadi ve İdari Birimler Fakültesi
We develop unit root tests for nonlinear heterogeneous panels where the alternative hypothesis is an exponential smooth transition (ESTAR) model, and provide their small sample properties. We apply our tests for investigating the income convergence hypothesis in the OECD sample. (C) 2009 Published by Elsevier B.V.

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