Mehmet Ozger - Academia.edu (original) (raw)

Papers by Mehmet Ozger

Research paper thumbnail of Disaggregation of Future Regional Climate Model Data to Generate Future Rainfall Intensity-Duration-Frequency Curves to Assess Climate Change Impacts

Heavy increase in urbanization, industrialization and population is causing an increase in emissi... more Heavy increase in urbanization, industrialization and population is causing an increase in emissions of greenhouse gases (GHG) and this causes variations in atmosphere. Climate change causes extreme rainfall events and these events are expected to be enhanced in the future. Since flooding is influencing urban areas, controlling and management of flooding is a major necessity. Intensity-Duration-Frequency (IDF) curves play a huge role in representing rainfall characteristics by linking intensity, duration, and frequency of rainfall. Analysing short-duration rainfall is crucial for urban areas due to fast responses of drainage systems against heavy rainfall events. IDF curves were generated via the Gumbel method for rainfalls from 5-min to 24-h in this study. However, providing short-duration rainfall data is challenging due to the low capacity, costs and geographic conditions. Therefore, the HYETOS disaggregation model was applied to obtain sub-hourly data. IDF curves are stationary ...

Research paper thumbnail of Drought Analysis with Machine Learning Methods

Pamukkale University Journal of Engineering Sciences, 2019

Research paper thumbnail of Comparison of Discrete and Continuous Wavelet Transforms

Computational Complexity, 2012

Article Outline Glossary 1 1. Definition 8 2. Introduction 8 3. The discrete vs continuous wavele... more Article Outline Glossary 1 1. Definition 8 2. Introduction 8 3. The discrete vs continuous wavelet Algorithms 9 3.1. The Discrete Wavelet Transform 9 3.2. The Continuous Wavelet Transform 11 3.3. Some background on Hilbert space 11 3.4. Connections to group theory 15 4. List of names and discoveries 16 5. History 18 6. Tools from Mathematics 19 7. A Transfer Operator 20 8. Future Directions 20 9. Literature 21 10. Bibliography 21 21 Glossary This glossary consists of a list of terms used inside the paper: In mathematics, in probability, in engineering, and on occasion in physics. To clarify the seemingly confusing use of up to four different names for the same idea or concept, we have further added informal explanations spelling out the reasons behind the differences in current terminology from neighboring fields. Disclaimer: This glossary has the structure of four columns. A number of terms are listed line by line, and each line is followed by explanation. Some "terms" have up to four separate (yet commonly accepted) names. mathematics probability engineering physics function (measurable) random variable signal state Mathematically, functions may map between any two sets, say, from X to Y ; but if X is a probability space (typically called Ω),

Research paper thumbnail of Total Sediment Discharge Estimation by Adaptive Neuro-Fuzzy and Neural Network Approaches

ABSTRACT With regard to the importance of sediment transportation in Hydraulic and Water Resource... more ABSTRACT With regard to the importance of sediment transportation in Hydraulic and Water Resources Engineering, it is essential to focus on the topic with details and it is a matter of paramount importance. Recently, sediment and its transportation has become a trouble to experts and scientists of this field. Since 1950s, a plethora of studies have been conducted and many scientists have spent their time in laboratories to evaluate the behavior of sediment transportation. Nowadays, improvement of the computer-aided programs such as MATLAB has paved the way for researchers to explore the unknowns, easily. In sediment transportation, ANN and ANFIS may be intensely used for evaluate the laboratory data or a definite river's data. Researches of Yang (1983) have been offered in six diagrams. The mentioned diagrams are about relationship between water discharge, average velocity, water surface slope, shear stress, stream power and unit stream power with total sediment discharge (TSD). The parameter of unit stream power has been neglected due to the fact that it is a repetitive manner of other parameters. For getting the input data values, Get Data Graph Digitizer program has been used. 79 set of data has been considered. For each one, the mean of their Y values have been extracted and used as observed output data for evaluation. Feed Forward Back Propagation (FFBP) type of ANN and Hybrid, Back Propagation (BP) types of ANFIS have been utilized in analyzing the data and giving the results in two classifications, train and test. Subsequently, the relationship between predicted and observed values have been obtained and depicted in diagrams. Correlation (R 2) of higher than 0.98 proves the compatibility and capability of ANN and ANFIS for predicting (TSD).

Research paper thumbnail of Performance evaluation of parametric models in the hindcasting of wave parameters along the south coast of Black Sea

Research paper thumbnail of Wet and dry spell analysis of Global Climate Model-generated precipitation using power laws and wavelet transforms

Stochastic Environmental Research and Risk Assessment, 2010

Abstract Climate model simulations for the twenty-first century point toward changing characteris... more Abstract Climate model simulations for the twenty-first century point toward changing characteristics of precipi-tation. This paper investigates the impact of climate change on precipitation in the Kansabati River basin in India. A downscaling method, based on Bayesian Neural ...

Research paper thumbnail of Stochastic wave energy calculation formulation

Renewable Energy, 2004

The wave energy potential is directly proportional to the wave period and second power of wave he... more The wave energy potential is directly proportional to the wave period and second power of wave height averaged over a suitable time period. The wave height and period have temporal and spatial stochastic variations. It is the main purpose of this paper to derive the most general ...

Research paper thumbnail of Space-time Interpolation by Combining Air Pollution and Meteorologic Variables

Pure and Applied Geophysics, 2006

Research paper thumbnail of Scaling characteristics of ocean wave height time series

Physica A: Statistical Mechanics and its Applications, 2011

Research paper thumbnail of Triple diagram method for the prediction of wave height and period

Research paper thumbnail of Temporal significant wave height estimation from wind speed by perceptron Kalman filtering

Research paper thumbnail of Prediction of wave parameters by using fuzzy logic approach

Ocean Engineering, 2007

The purpose of this study is to investigate the relationship between wind speed, previous and cur... more The purpose of this study is to investigate the relationship between wind speed, previous and current wave characteristics. It is expected that such a non-linear relationship includes some uncertainties. A fuzzy inference system employing fuzzy IF-THEN rules has an ability to deal with ill-defined and uncertain systems. Compared with traditional approaches, fuzzy logic is more efficient in linking the multiple inputs to a single output in a non-linear domain. In this paper, a sophisticated intelligent model, based on Takagi-Sugeno (TS) fuzzy modeling principles, was developed to predict the changes in wave characteristics such as significant wave height and zero up-crossing period due to the wind speed. Past measurements of significant wave height values and wind speed variables are used for training the adaptive model and it is then employed to predict the significant wave height amounts for future time intervals such as 1, 3, 6 and 12 h. The verification of the proposed model is achieved through the wave characteristics time series plots and various numerical error criterias. Also the model results were compared with classical Auto Regressive Moving Average with exogenous input (ARMAX) models. For the application of the proposed approach the offshore station located in the Pacific Ocean was used.

Research paper thumbnail of Return period and risk calculations for ocean wave energy applications

Research paper thumbnail of Investigating the Multifractal Properties of Significant Wave Height Time Series Using a Wavelet-Based Approach

Journal of Waterway, Port, Coastal, and Ocean Engineering, 2011

Singularities play a significant role in the characterization of time series. The temporal charac... more Singularities play a significant role in the characterization of time series. The temporal characteristics of fluctuating significant wave height time series are investigated in this study. The hourly time series from 24 stations located off the west coast of the United States are used for the ...

Research paper thumbnail of Increasing Water Supply by Mixing of Fresh and Saline Ground Waters

Journal of the American Water Resources Association, 2003

Research paper thumbnail of Long Lead Time Drought Forecasting Using a Wavelet and Fuzzy Logic Combination Model: A Case Study in Texas

Journal of Hydrometeorology, 2012

Drought forecasting is important for drought risk management. Considering the El Niño–Southern Os... more Drought forecasting is important for drought risk management. Considering the El Niño–Southern Oscillation (ENSO) variability and persistence in drought characteristics, this study developed a wavelet and fuzzy logic (WFL) combination model for long lead time drought forecasting. The idea of WFL is to separate each predictor and predictand into their frequency bands and then reconstruct the predictand series by using its predicted bands. The strongest-frequency bands of predictors and predictand were determined from the average wavelet spectra. Applying this combination model to the state of Texas, it was found that WFL had a significant improvement over the fuzzy logic model that did not use wavelet banding. Comparison with an artificial neural network (ANN) model and a coupled wavelet and ANN (WANN) model showed that WFL was more accurate for drought forecasting. Also, it should be noted that the ENSO variability is not a global precursor of drought. For this reason, prior to an a...

Research paper thumbnail of An entropy-based investigation into the variability of precipitation

Journal of Hydrology, 2009

Employing the entropy concept spatial and temporal variability of precipitation time series were ... more Employing the entropy concept spatial and temporal variability of precipitation time series were investigated for the State of Texas, USA. Marginal entropy was used to investigate the variability associated with monthly, seasonal and annual time series. Also, apportionment entropy ...

Research paper thumbnail of Association between Uncertainties in Meteorological Variables and Water-Resources Planning for the State of Texas

Journal of Hydrologic Engineering, 2011

Due to the complexity and rapidly occurring changes in the dynamics of human demography and water... more Due to the complexity and rapidly occurring changes in the dynamics of human demography and water demands it is difficult to assess the future adequacy of limited freshwater resources. The planning of water resources largely depends on the meteorological ...

Research paper thumbnail of Scaling Characteristics of Precipitation Data over Texas

Journal of Hydrologic Engineering, 2011

Research paper thumbnail of Autorun Persistence of Hydrologic Design

Journal of Hydrologic Engineering, 2003

Persistence is the most important property in any hydrologic design concerning the storage capaci... more Persistence is the most important property in any hydrologic design concerning the storage capacity of reservoirs, average return periods, failure risks, and drought properties. Its consideration in analytical derivations of design criteria presents difficulties, especially in autocorrelated ...

Research paper thumbnail of Disaggregation of Future Regional Climate Model Data to Generate Future Rainfall Intensity-Duration-Frequency Curves to Assess Climate Change Impacts

Heavy increase in urbanization, industrialization and population is causing an increase in emissi... more Heavy increase in urbanization, industrialization and population is causing an increase in emissions of greenhouse gases (GHG) and this causes variations in atmosphere. Climate change causes extreme rainfall events and these events are expected to be enhanced in the future. Since flooding is influencing urban areas, controlling and management of flooding is a major necessity. Intensity-Duration-Frequency (IDF) curves play a huge role in representing rainfall characteristics by linking intensity, duration, and frequency of rainfall. Analysing short-duration rainfall is crucial for urban areas due to fast responses of drainage systems against heavy rainfall events. IDF curves were generated via the Gumbel method for rainfalls from 5-min to 24-h in this study. However, providing short-duration rainfall data is challenging due to the low capacity, costs and geographic conditions. Therefore, the HYETOS disaggregation model was applied to obtain sub-hourly data. IDF curves are stationary ...

Research paper thumbnail of Drought Analysis with Machine Learning Methods

Pamukkale University Journal of Engineering Sciences, 2019

Research paper thumbnail of Comparison of Discrete and Continuous Wavelet Transforms

Computational Complexity, 2012

Article Outline Glossary 1 1. Definition 8 2. Introduction 8 3. The discrete vs continuous wavele... more Article Outline Glossary 1 1. Definition 8 2. Introduction 8 3. The discrete vs continuous wavelet Algorithms 9 3.1. The Discrete Wavelet Transform 9 3.2. The Continuous Wavelet Transform 11 3.3. Some background on Hilbert space 11 3.4. Connections to group theory 15 4. List of names and discoveries 16 5. History 18 6. Tools from Mathematics 19 7. A Transfer Operator 20 8. Future Directions 20 9. Literature 21 10. Bibliography 21 21 Glossary This glossary consists of a list of terms used inside the paper: In mathematics, in probability, in engineering, and on occasion in physics. To clarify the seemingly confusing use of up to four different names for the same idea or concept, we have further added informal explanations spelling out the reasons behind the differences in current terminology from neighboring fields. Disclaimer: This glossary has the structure of four columns. A number of terms are listed line by line, and each line is followed by explanation. Some "terms" have up to four separate (yet commonly accepted) names. mathematics probability engineering physics function (measurable) random variable signal state Mathematically, functions may map between any two sets, say, from X to Y ; but if X is a probability space (typically called Ω),

Research paper thumbnail of Total Sediment Discharge Estimation by Adaptive Neuro-Fuzzy and Neural Network Approaches

ABSTRACT With regard to the importance of sediment transportation in Hydraulic and Water Resource... more ABSTRACT With regard to the importance of sediment transportation in Hydraulic and Water Resources Engineering, it is essential to focus on the topic with details and it is a matter of paramount importance. Recently, sediment and its transportation has become a trouble to experts and scientists of this field. Since 1950s, a plethora of studies have been conducted and many scientists have spent their time in laboratories to evaluate the behavior of sediment transportation. Nowadays, improvement of the computer-aided programs such as MATLAB has paved the way for researchers to explore the unknowns, easily. In sediment transportation, ANN and ANFIS may be intensely used for evaluate the laboratory data or a definite river's data. Researches of Yang (1983) have been offered in six diagrams. The mentioned diagrams are about relationship between water discharge, average velocity, water surface slope, shear stress, stream power and unit stream power with total sediment discharge (TSD). The parameter of unit stream power has been neglected due to the fact that it is a repetitive manner of other parameters. For getting the input data values, Get Data Graph Digitizer program has been used. 79 set of data has been considered. For each one, the mean of their Y values have been extracted and used as observed output data for evaluation. Feed Forward Back Propagation (FFBP) type of ANN and Hybrid, Back Propagation (BP) types of ANFIS have been utilized in analyzing the data and giving the results in two classifications, train and test. Subsequently, the relationship between predicted and observed values have been obtained and depicted in diagrams. Correlation (R 2) of higher than 0.98 proves the compatibility and capability of ANN and ANFIS for predicting (TSD).

Research paper thumbnail of Performance evaluation of parametric models in the hindcasting of wave parameters along the south coast of Black Sea

Research paper thumbnail of Wet and dry spell analysis of Global Climate Model-generated precipitation using power laws and wavelet transforms

Stochastic Environmental Research and Risk Assessment, 2010

Abstract Climate model simulations for the twenty-first century point toward changing characteris... more Abstract Climate model simulations for the twenty-first century point toward changing characteristics of precipi-tation. This paper investigates the impact of climate change on precipitation in the Kansabati River basin in India. A downscaling method, based on Bayesian Neural ...

Research paper thumbnail of Stochastic wave energy calculation formulation

Renewable Energy, 2004

The wave energy potential is directly proportional to the wave period and second power of wave he... more The wave energy potential is directly proportional to the wave period and second power of wave height averaged over a suitable time period. The wave height and period have temporal and spatial stochastic variations. It is the main purpose of this paper to derive the most general ...

Research paper thumbnail of Space-time Interpolation by Combining Air Pollution and Meteorologic Variables

Pure and Applied Geophysics, 2006

Research paper thumbnail of Scaling characteristics of ocean wave height time series

Physica A: Statistical Mechanics and its Applications, 2011

Research paper thumbnail of Triple diagram method for the prediction of wave height and period

Research paper thumbnail of Temporal significant wave height estimation from wind speed by perceptron Kalman filtering

Research paper thumbnail of Prediction of wave parameters by using fuzzy logic approach

Ocean Engineering, 2007

The purpose of this study is to investigate the relationship between wind speed, previous and cur... more The purpose of this study is to investigate the relationship between wind speed, previous and current wave characteristics. It is expected that such a non-linear relationship includes some uncertainties. A fuzzy inference system employing fuzzy IF-THEN rules has an ability to deal with ill-defined and uncertain systems. Compared with traditional approaches, fuzzy logic is more efficient in linking the multiple inputs to a single output in a non-linear domain. In this paper, a sophisticated intelligent model, based on Takagi-Sugeno (TS) fuzzy modeling principles, was developed to predict the changes in wave characteristics such as significant wave height and zero up-crossing period due to the wind speed. Past measurements of significant wave height values and wind speed variables are used for training the adaptive model and it is then employed to predict the significant wave height amounts for future time intervals such as 1, 3, 6 and 12 h. The verification of the proposed model is achieved through the wave characteristics time series plots and various numerical error criterias. Also the model results were compared with classical Auto Regressive Moving Average with exogenous input (ARMAX) models. For the application of the proposed approach the offshore station located in the Pacific Ocean was used.

Research paper thumbnail of Return period and risk calculations for ocean wave energy applications

Research paper thumbnail of Investigating the Multifractal Properties of Significant Wave Height Time Series Using a Wavelet-Based Approach

Journal of Waterway, Port, Coastal, and Ocean Engineering, 2011

Singularities play a significant role in the characterization of time series. The temporal charac... more Singularities play a significant role in the characterization of time series. The temporal characteristics of fluctuating significant wave height time series are investigated in this study. The hourly time series from 24 stations located off the west coast of the United States are used for the ...

Research paper thumbnail of Increasing Water Supply by Mixing of Fresh and Saline Ground Waters

Journal of the American Water Resources Association, 2003

Research paper thumbnail of Long Lead Time Drought Forecasting Using a Wavelet and Fuzzy Logic Combination Model: A Case Study in Texas

Journal of Hydrometeorology, 2012

Drought forecasting is important for drought risk management. Considering the El Niño–Southern Os... more Drought forecasting is important for drought risk management. Considering the El Niño–Southern Oscillation (ENSO) variability and persistence in drought characteristics, this study developed a wavelet and fuzzy logic (WFL) combination model for long lead time drought forecasting. The idea of WFL is to separate each predictor and predictand into their frequency bands and then reconstruct the predictand series by using its predicted bands. The strongest-frequency bands of predictors and predictand were determined from the average wavelet spectra. Applying this combination model to the state of Texas, it was found that WFL had a significant improvement over the fuzzy logic model that did not use wavelet banding. Comparison with an artificial neural network (ANN) model and a coupled wavelet and ANN (WANN) model showed that WFL was more accurate for drought forecasting. Also, it should be noted that the ENSO variability is not a global precursor of drought. For this reason, prior to an a...

Research paper thumbnail of An entropy-based investigation into the variability of precipitation

Journal of Hydrology, 2009

Employing the entropy concept spatial and temporal variability of precipitation time series were ... more Employing the entropy concept spatial and temporal variability of precipitation time series were investigated for the State of Texas, USA. Marginal entropy was used to investigate the variability associated with monthly, seasonal and annual time series. Also, apportionment entropy ...

Research paper thumbnail of Association between Uncertainties in Meteorological Variables and Water-Resources Planning for the State of Texas

Journal of Hydrologic Engineering, 2011

Due to the complexity and rapidly occurring changes in the dynamics of human demography and water... more Due to the complexity and rapidly occurring changes in the dynamics of human demography and water demands it is difficult to assess the future adequacy of limited freshwater resources. The planning of water resources largely depends on the meteorological ...

Research paper thumbnail of Scaling Characteristics of Precipitation Data over Texas

Journal of Hydrologic Engineering, 2011

Research paper thumbnail of Autorun Persistence of Hydrologic Design

Journal of Hydrologic Engineering, 2003

Persistence is the most important property in any hydrologic design concerning the storage capaci... more Persistence is the most important property in any hydrologic design concerning the storage capacity of reservoirs, average return periods, failure risks, and drought properties. Its consideration in analytical derivations of design criteria presents difficulties, especially in autocorrelated ...