Yazar "Yilmaz, Volkan" seçeneğine göre listele

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    Estimation of the Change in Lake Water Level by Artificial Intelligence Methods
    (SPRINGER, 2014) Buyukyildiz, Meral; Tezel, Gulay; Yilmaz, Volkan
    In this study, five different artificial intelligence methods, including Artificial Neural Networks based on Particle Swarm Optimization (PSO-ANN), Support Vector Regression (SVR), Multi- Layer Artificial Neural Networks (MLP), Radial Basis Neural Networks (RBNN) and Adaptive Network Based Fuzzy Inference System (ANFIS), were used to estimate monthly water level change in Lake Beysehir. By using different input combinations consisting of monthly Inflow - Lost flow (I), Precipitation (P), Evaporation (E) and Outflow (O), efforts were made to estimate the change in water level (L). Performance of models established was evaluated using root mean square error (RMSE), mean square error (MSE), mean absolute error (MAE) and coefficient of determination (R-2). According to the results of models, epsilon-SVR model was obtained as the most successful model to estimate monthly water level of Lake Beysehir.
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    FACTOR ANALYSIS OF SURFACE WATER QUALITY PARAMETERS FOR THE RIVERS OF TURKEY
    (PARLAR SCIENTIFIC PUBLICATIONS (P S P), 2015) Yilmaz, Volkan; Buyukyildiz, Meral
    In this study, the Factor Analysis, a multivariate statistical analysis, was applied on twelve different parameters [streamflow, temperature, pH, electrical conductivity (EC), Na+, K, (Ca+Mg)(2+), CO32-, Cl-, SO42-, sodium adsorption ratio (SAR) and boron (B) concentrations] measured at 67 streamflow gauging stations of Turkey's 19 water basins in terms of annual averages for a long period of time (1992-2008). First of all, the appropriateness of the data was confirmed using the Kaiser-Meyer-Olkin (KMO) Criteria and Bartlett's Test of Sphericity. As a result of the study, it was observed that 80% of the total variance was described by three factors, i.e. the first, second and third factors described the 50.25%, 19.04% and 10.52% of the total variance, respectively. Moreover, the characters described by each factor were determined and named as environmental effects (in the frame of high ion relation), alkaline and climatic effects. Finally, the score values of the stations were calculated, and the relationships between the stations and the factors were investigated. In this context, the stations giving extreme score values under each factor were considered as they should be carefully examined by the decision-makers.
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    GLOBAL CLIMATE CHANGE WITH ITS REFLECTIONS ON TURKEY
    (INT SCIENTIFIC CONFERENCE SGEM, 2009) Buyukyildiz, Meral; Marti, Ali Ihsan; Yilmaz, Volkan
    The climate change due to global warming is accepted among the greatest environmental problems resulted from the human effects of increasing energy consumption, urbanization and deforestation events threatening the healthy life of people and environment. Many results of the climate change due to global warming can be estimated as the melting of snow covers, terrestrial and sea icebergs, replacement of climate zones, frequent formation of severe weather events, floods that gain strength in time, severe droughts, formation of deserts, increasing epidemic cases and harmful agricultural insects, etc. all of which are very important events directly or indirectly affecting human life, socioeconomic sectors and ecological systems. Global warming is an effective change perceived by people from equator to poles, and from oceans to the highest lands. Since Turkey has a complex climatic structure, it is among the countries that will be mostly affected from the climate change especially due to global warming. Therefore, determining the dimensions of the effects of the global warming on Turkey's climate will provide to estimate and make projections about the climatic changes in the country, since it is necessary for the future plans of water supply, agriculture, flood control, ecology, etc. activities.