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Öğe Adaptive neuro-fuzzy inference systems (ANFIS) application to investigate potential use of natural ventilation in new building designs in Turkey(Pergamon-Elsevier Science Ltd, 2007) Ayata, Tahir; Cam, Ertugrul; Yildiz, OsmanNatural ventilation in living and working places provides both circulation of clear air and a decrease of indoor temperature, especially during hot summer days. In addition to openings, the dimension ratio and position of buildings play a significant role to obtain a uniform indoor air velocity distribution. In this study, the potential use of natural ventilation as a passive cooling system in new building designs in Kayseri, a midsize city in Turkey, was investigated. First, indoor air velocity distributions with respect to changing wind direction and magnitude were simulated by the FLUENT package program, which employs finite element methods. Then, an adaptive neuro-fuzzy inference systems (ANFIS) model was employed to predict indoor average and maximum air velocities using the simulated data by FLUENT. The simulation results suggest that natural ventilation can be used to provide a thermally comfortable indoor environment during the summer season in the study area. Also, the ANFIS model can be proposed for estimation of indoor air velocity values in such studies. (C) 2007 Elsevier Ltd. All rights reserved.Öğe Application of ANN to explore the potential use of natural ventilation in buildings in Turkey(Pergamon-Elsevier Science Ltd, 2007) Ayata, Tahir; Arcaklioglu, Erol; Yildiz, OsmanIndoor natural ventilation provides both the circulation of clear air and the decrease of indoor temperature, especially, during hot summer days. In addition to openings, building dimensions and position play a significant role to obtain a uniform indoor air velocity distribution. In this study, the potential use of natural ventilation as a passive cooling system in new building designs in Kayseri, a mid-size city in Turkey, was investigated. First, indoor air velocity distributions with respect to changing wind direction, magnitude and door openings were simulated by the FLUENT package program, which employs finite element methods. Using the simulated data an artificial neural network (ANN) model was developed to predict indoor average and maximum air velocities. The simulations produced by FLUENT show that the average indoor air velocity is generally below 1.0 m/s for the local prevailing wind directions. The simulations results suggest that, in addition to the orientation of buildings in accordance with prevailing wind directions, a proper indoor design of buildings in the area can significantly increase the capability of air ventilation during warm summer days. It was found that a high correlation exists between the simulated and the ANN predicted data indicating a successful learning by the proposed ANN model. Overall, the evaluation of the network results indicated that the ANN approach can be utilized as an efficient tool for learning, training and predicting indoor air velocity distributions for natural ventilation. (C) 2006 Elsevier Ltd. All rights reserved.Öğe Assessing the Water Quality Parameters of the Munzur Spring, Tunceli, Turkey(Foundation Environmental Protection & Research-Fepr, 2014) Celiker, Murat; Yildiz, Osman; Sonmezer, Yetis BulentThis study presents an analysis of the temporal variations in the upstream water quality parameters of the Munzur Spring. For this purpose, the spring water quality was monitored from 2007 to 2009 at different time periods. There were 5 water samples taken from 2008 to 2009 for hydrochemical and biological analyses, while 6 water samples were gathered between 2007 and 2009 for heavy metal analysis. The analysis results reveal that the water quality parameters were found to be in good agreement with the drinking water standards of Anonymous (1993) and Anonymous (2005). It was seen that the upstream source of the Munzur spring is periodically characterized by Ca+2 - Mg+2 - HCO3- and Ca+2 - Cl- - HCO3- facies according to Anonymous (1978), and CaCO3 and CaCl2 facies according to Back (1960, 1966). The results of a tritium analysis indicated that the spring is recharged by daily precipitations. The spring water was also found suitable for irrigation purposes based on Wilcox and US salinity diagrams.Öğe Assessing winter-type PM10 pollution in the city of Kirikkale, Turkey: A case study(Parlar Scientific Publications (P S P), 2007) Akay, M. Ermin; Yildiz, OsmanIn this study, an emission inventory of winter-type PM10 was carried out for a 6-months period between October 2003 and March 2004 in the city of Kirikkale, Turkey. The monthly measurements of particulate matter concentrations were performed at 13 stations uniformly located across the city. Both temporal and spatial variations in PM10 concentrations within the city were evaluated. To identify the type of emission, the stations were classified into four different categories as urban, rural, urban-industrial and rural-industrial ones. The comparison of the measured PM10 concentrations against the Turkish and European Union limit values of 150 mu g/m(3) and 50 mu g/m(3), respectively, revealed that the city faces a serious winter-type air pollution problem caused by domestic heating, traffic load and industrial emissions, especially in the city centre and the regions close to heavy industrial plants. Overall, the study results suggest that in order to avoid possible health-related risks in the study area, there is an urgent need to reduce PM10 concentrations to an acceptable range during winter.Öğe Climate Variability, Water Resources, and Hydrologic Extremes - Modeling the Water and Energy Budgets(Blackwell Science Publ, 2005) Yildiz, Osman; Barros, Ana P.…Öğe Effects of Climate Change on Streamflow in the Ayazma River Basin in the Marmara Region of Turkey(Mdpi, 2023) Seddiqe, Khaja Haroon; Sediqi, Rahmatullah; Yildiz, Osman; Akturk, Gaye; Kostecki, Jakub; Gortych, MartaThis study investigates the effects of climate change on streamflow in the Ayazma river basin located in the Marmara region of Turkey using a hydrological model. Regional Climate Model (RCM) outputs from CNRM-CM5/RCA4, EC-EARTH/RACMO22E and NorESM1-M/HIRHAM5 with the RCP4.5 and RCP8.5 emission scenarios were utilized to drive the HBV-Light (Hydrologiska Byrans Vattenbalansavdelning) hydrological model. A trend analysis was performed with the Mann-Kendall trend test for precipitation and temperature projections. A meteorological drought assessment was presented using the Standardized Precipitation-Evapotranspiration Index (SPEI) method for the worst-case scenario (i.e., RCP8.5). The calibrated and validated hydrological model was used for streamflow simulations in the basin for the period 2022-2100. The selected climate models were found to produce high precipitation projections with positive anomalies ranging from 22 to 227 mm. The increase in annual mean temperatures reached up to 1.8 degrees C and 2.6 degrees C for the RCP4.5 and RCP8.5 scenarios, respectively. The trend results showed statistically insignificant upward and downward trends in precipitation and statistically significant upward trends in temperatures at 5% significance level for both RCP scenarios. It was shown that there is a significant increase in drought intensities and durations for SPEI greater than 6 months after mid- century. Streamflow simulations showed decreasing trends for both RCP scenarios due to upward trend in temperature and, hence, evapotranspiration. Streamflow peaks obtained with the RCP8.5 scenario were generally lower than those obtained with the RCP4.5 scenario. The mean values of the streamflow simulations from the CNRM-CM5/RCA4 and NorESM1-M/HIRHAM5 outputs were approximately 2 to 10% lower than the observation mean. On the other hand, the average value obtained from the EC-EARTH/RACMO 22E outputs was significantly higher than the observation average, up to 32%. The results of this study can be useful for evaluating the impact of climate change on streamflow and developing sustainable climate adaptation options in the Ayazma river basin.Öğe Evaluating solid waste landfill site selection using multi-criteria decision analysis and geographic information systems in the city of Elazig, Turkey(Pamukkale Univ, 2019) Celiker, Murat; Yildiz, Osman; Nacar Kocer, NiluferSolid waste landfill site selection is a relatively complex process and depends on several criteria and official regulations. In this study, the suitability of solid waste landfill site selection for the city of Elazig, Turkey, was determined by Multi-Criteria Decision Analysis (MCDA) and Geographic Information Systems (GIS). For this purpose, nine different criteria, namely distance from residential areas, distance from roads, distance from rivers, distance from spring wells, geology, slope, aspect, land capability classification and land use, were taken into consideration and their degrees of relative importance were defined via MCDA and the schematic maps for each criterion were prepared with GIS applications. The final landfill site suitability map for the study area was obtained by the overlay analysis tool of ArcGIS 9.3. The study results reveal that the landfill suitability index values for the selected site range between 2.64 and 6.10. The major part of the landfill site has relatively low index values implying that the selected site is suitable for solid waste landfill.Öğe Investigating the climate change effects on annual average streamflows in the Euphrates-Tigris basin using the climate elasticity method(Gazi Univ, Fac Engineering Architecture, 2021) Alivi, Abdulrezzak; Yildiz, Osman; Akturk, GayeThis study was conducted to investigate the response of streamflows (Q) to changes in precipitation (P), potential evapotranspiration (E-p) and drought index within the Euphrates-Tigris basin. For this purpose, 37 sub-basins that are not affected by dams were identified within the basin. Here, the sensitivity of annual average streamflows to precipitation, E-p and drought index was evaluated by the climate elasticity method proposed by Schaake [1]. With this method, the average values of the precipitation and E-p sensitivity coefficients of the streamflow (epsilon(P) and epsilon(Ep), respectively) throughout the basin were calculated as 1.50 and -0.50, respectively. Therefore, it is observed that a 10% increase (decrease) in precipitation would lead to an average increase (decrease) of 15% in streamflow, on the other hand, a 10% increase (decrease) in Ep would result in an average decrease (increase) of 5% in streamflow across the basin. Moreover, the average value of sensitivity coefficient of streamflow to drought index (epsilon((sic))) was determined as -0.47, which means that a 10% increase in the drought index will result in an average decrease of 4.7% in streamflow within the basin. Additionally, it is observed that there is a nonlinear inverse correlation between the climate change sensitivity coefficients (i.e., epsilon(P), |epsilon(Ep)| and |epsilon((sic))|) and the flow coefficient (Q/P) values of the sub-basins indicating that the decrease in streamflow would increase the sensitivity of streamflow to climatic changes. Finally, it was determined that there exist relative increases in epsilon(P), |epsilon(Ep)| and |epsilon((sic))| values from high to low elevations across the basin.Öğe Spatiotemporal Analysis of Historical Droughts in the Central Anatolia, Turkey(Gazi Univ, 2014) Yildiz, OsmanThe spatiotemporal characteristics of meteorological droughts in the Central Anatolia, a semiarid region in Turkey, are determined utilizing the Standardized Precipitation Index (SPI) as a measure for drought severity. Using the temporal and spatial characteristics of monthly SPI, drought intensity-areal extent-frequency curves for various return periods are constructed for the region, and then the spatiotemporal characteristics of selected historical droughts are evaluated. The results indicate that the region is usually under the influence of droughts with low return periods, in other words, high frequency droughts during the study period (from 1953 to 2004). However, the areal extent of drought may be significant because of its negative impact on the water resources in the region. The overall evaluation of study results reveal that this method can provide useful information for spatial and temporal variations of droughts and can be utilized for water resources management in this region.Öğe Unconfined propeller jet scour on clay/sand mixtures(Pergamon-Elsevier Science Ltd, 2022) Cihan, Kubilay; Dog, Ali; Yilmaz, Damla; Ozan, Ayse Yuksel; Yildiz, Osman; Sahin, CihanIn this study, scour due to an unconfined propeller water jet on homogeneous clay-sand mixtures was investigated experimentally. A total of 9 tests were conducted for the sand bed and 18 tests were carried out for the sand-clay mixture bed. Since clay contents (p) of 0, 5 and 10% by weight were used in the experiments, scour in poorly cohesive sand-clay mixture bed was taken into account. Propeller diameters (Dp) were 0.06 and 0.09 m. Dimensionless propeller heights (y0/Dp) were defined as 1.67, 1.11, 1.0. The increase in clay content causes a decrease in the scour depth and changes the formation of scour profiles. The parameters y0/Dp, F0 (densimetric Froude number), p were found to have significant effects on the behavior of clay-sand mixtures. Considering the test results, equations were proposed to estimate the maximum depth and length of the scour hole formed in the equilibrium condition. In addition, by modifying the equation proposed by Hong et al. (2013), a new equation is proposed for the estimation of temporal maximum scour depth due to the propeller water jet on the sand and weakly cohesive sand-clay mixture beds.
