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Öğe Application of Artificial Neural Network-Based Approach for Calculating Dissolved Oxygen Profiles in Kapulukaya Dam Reservoir(Centre Environment Social & Economic Research Publ-Ceser, 2007) Tüzün, İlhami; Soyupak, Selçuk; İnce, Özlem; Başaran, GökbenAn Artificial Neural Network (ANN) modelling approach has been shown to be successful in calculating time and space dependent dissolved oxygen (DO) concentration profiles in Kapulukaya Dam Reservoir using limited number of input variables. The variation of inflow to the reservoir with respect to time was significantly high. The reservoir operational levels were relatively stable. The Levenberg-Marquardt algorithm was adopted during training. Preprocessing before training and post processing after simulation steps were the treatments applied to raw data and predictions respectively. Different configurations of Multilayer perceptron neural networks were designed by selecting different combinations of number of hidden layers (single and double) and number of neurons within each of the hidden layers. Generalisation was improved and over-fitting problems were eliminated: Early stopping method was applied for improving generalisation. The conventional model criteria of correlation coefficient (R) and mean square errors (MSE) were adopted to compare model performances. The correlation coefficients between neural network estimates and field measurements were as high as 0.96 for daily and monthly data respectively with experiments that involve double layer neural network structure with 31 neurons within each hidden layer. The study results revealed that the data sizes effect model performances up to a certain level.Öğe An automata networks based preprocessing technique for artificial neural network modelling of primary production levels in reservoirs(Elsevier, 2007) Kılıç, Hürevren; Soyupak, Selçuk; Tüzün, İlhami; İnce, Özlem; Başaran, GökbenPrimary production in lakes and reservoirs develops as a result of complex reactions and interactions. Artificial neural networks (ANN) emerges as an approach in quantification of primary productivity in reservoirs. Almost all of the past ANN applications employed input data matrices whose vectors represent either water quality parameters or environmental characteristics. Most of the time, the components of input matrices are determined using expert opinion that implies possible factors that affect output vector. Major disadvantage of this approach is the possibility of ending-up with an input matrix that may have high correlations between some of its components. In this paper, an automata networks (AN) based preprocessing technique was developed to select suitable and appropriate constituents of input matrix to eliminate redundancy and to enhance calculation efficiency. The proposed technique specifically provides an apriori rough behavioral modeling through identification of minimal AN interaction topology. Predictive ANN models of primary production levels were developed for a reservoir following AN based pre-modeling step. The achieved levels of model precisions and performances were acceptable: the calculated root mean square error values (RMSE) were low; a correlation coefficient (R) as high as 0.83 was achieved with an ANN model of a specific structure. (c) 2006 Elsevier B.V. All rights reserved.Öğe Biosorption of mercury(II), cadmium(II) and lead(II) ions from aqueous system by microalgae Chlamydomonas reinhardtii immobilized in alginate beads(Elsevier, 2006) Bayramoğlu, Gülay; Tüzün, İlhami; Çelik, Gökçe; Yilmaz, Meltem; Arica, M. YakupThe potential use of the immobilized microalgae (in Ca-alginate) of Chlamydomonas reinhardtii to remove Hg(II), Cd(II) and Pb(II) ions from aqueous solutions was evaluated using bare Ca-alginate bead as a control system. Ca-alginate beads containing immobilized microalgae were incubated for the uniform growth at 22 degrees C for 5 days. Effects of pH, temperature, initial concentration of metal ions and biosorbent dosages on the adsorption of Hg(II), Cd(II) and Pb(II) ions were studied. Adsorption of Hg(II), Cd(II) and Pb(II) ions on the immobilized microalgae showed highest values at around pH 5.0 to 6.0. The adsorption equilibrium was represented with Langnmir and Freundlich adsorption isotherms. The adsorption of these ions on the immobilized microalgae followed second-order kinetics and equilibrium was established in about 60 min. The temperature change in the range of 5-40 degrees C did not affect the adsorption capacities of the immobilized microalgae. The immobilized-algal systems can be regenerated using 2 M NaCl for Hg(II), Cd(II) and Pb(II) ions. (c) 2006 Elsevier B.V. All rights reserved.Öğe The effect of disturbances to habitat quality on Otter (Lutra lutra) activity in the River Kızılırmak (Turkey): A case study(2005) Tüzün, İlhami; Albayrak, İrfanHabitat restriction for otters living in a small part of the K?z?l?rmak River occurred due Mainly to 3 causes: dam construction at the upper end, heavy pollution by oil refinery effluent at the lower end and man-made activities such as housing and angling in-between. Sprainting activity was measured to assess habitat use by otters within the area and differences were shown between the sites. Compared to site II, higher sprainting activity was found at the site below the dam (site 1), where habitat quality was poorer, as indicated by the water quality index (BMWP), diversity indices (Simpson's and Shannon-Wiever) and riparian quality index (QBR). This was due to the relatively more stable standing water formed at the foot of the dam, offering sufficient food availability at this site throughout the year. A site further downstream (site II) had higher river water and riparian habitat quality but flow variations caused by dam operations led to the occurrence of less suitable food conditions for otters at various times of the year. The food items found in spraints from the 2 sites revealed that otters fed on more fish at site 1. No spraints were found in the lowest part of the study area (site III). where heavy pollution occurred due to oil refinery discharge. Incorporation of the previously developed habitat quality indices into otter activity for habitat use was attempted in this study and these indices appeared to be promising tools for the establishment of management strategies for otters. © TÜBİTAK.Öğe Equilibrium and kinetic studies on biosorption of Hg(II), Cd(II) and Pb(II) ions onto microalgae Chlamydomonas reinhardtii(Academic Press Ltd- Elsevier Science Ltd, 2005) Tüzün, İlhami; Bayramoğlu, Gülay; Yalçın, Emine; Başaran, Gökben; Çelik, Gökçe; Arıca, M. YakupThe microalgae Chlamydomonas reinhardtii was used for the biosorption of Hg(II), Cd(II) and Pb(II) ions. The maximum adsorption of Hg(II) and Cd(II) ions on Chlamydomonas reinhardtii biomass was observed at pH 6.0 and the corresponding value for Pb(II) ions was 5.0. The biosorption of Hg(II), Cd(II) and Pb(II) ions by microalgae biomass increased as the initial concentration of Hg(II), Cd(II) and Pb(II) ions increased in the biosorption medium. The maximum biosorption capacities of microalgae for Hg(II), Cd(II) and Pb(II) ions were 72.2 +/- 0.67, 42.6 +/- 0.54 and 96.3 +/- 0.86 mg/g dry biomass, respectively. The affinity order for algal biomass was Pb(II) > Hg(II) > Cd(II). FT-IR analysis of algal biomass revealed the presence of amino, carboxyl, hydroxyl and carbonyl groups, which were responsible for biosorption of metal ions. Biosorption equilibrium was established in about 60 min and the equilibrium was well described by the Freundlich biosorption isotherms. Temperature change in the range of 5 - 35 degrees C did not affect the biosorption capacity. The microalgae could be regenerated using 0.1 M HCl, with up to 98% recovery, which allowed the reuse of the biomass in six biosorption-desorption cycles without any considerable loss of biosorption capacity. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Relationship between water flow volume and in-lake total phosphorus concentrations via dissolved oxygen concentrations and temperature in a warm temperate reservoir: Implications by path analysis(2006) Tüzün, İlhami; İnce, ÖzlemThe effects of water inflow-outflow volumes on the in-lake total phosphorus (TP) concentrations was investigated for the deep, stratified Çubuk II Dam Lake. The fluctuations in the TP concentrations followed a seasonal pattern, with lower values found during the summer, and peak values during wet seasons. Both the seasonal pattern and the horizontal/vertical heterogeneities in the TP concentrations were usually found to be in accordance with those of the water flow parameters. The vertical differences in the TP concentrations provided evidence that an interflow formed at the 5 m and 10 m depths by the water inflow resulted in higher mean TP concentrations at these depths. In contrast, the water outflows had a reducing effect on the TP concentrations, particularly at the 15 m depth, by promoting net TP export. Although the horizontal distribution of the TP concentrations differed slightly between the riverine, transition and lacustrine zones, the differences did not indicate any statistical significance (P>0.05, multivariate analysis of variance). The path analysis performed on the vertical data proved to be a promising tool in estimating the direct correlations between water flow dynamics and TP concentrations when the decomposition of indirect correlations via dissolved oxygen concentrations and temperature was accounted for in these mutual associations. © 2006 Blackwell Publishing Asia Pty Ltd.Öğe Utilisation of native, heat and acid-treated microalgae Chlamydomonas reinhardtii preparations for biosorption of Cr(VI) ions(Elsevier Sci Ltd, 2005) Arica, M. Yakup; Tüzün, İlhami; Yalçın, Emine; İnce, Özlem; Bayramoğlu, GülayThe hexavalent chromium biosorption onto native, heat- and acid-treated Chlamydomonas reinhardtii was studied from aqueous solutions. Biosorption equilibrium was established in about 120 min. The surface properties of the microalgae preparations varied with pH, and the maximum absorption of chromium ions on the microalgae preparations was obtained at pH 2.0. The biosorption of chromium ions by the microalgae preparations increased as the initial concentration of chromium ions increased in the medium. The maximum biosorption capacities of the native, heat- and acid-treated algal preparations were 18.2, 25.6 and 21.2 mg Cr(VI) per g of dry biosorbents, respectively. Equilibrium concentration (q(m)) and dissociation constant (K-d) were calculated by fitting the experimental data with the Langmuir isotherms. The chromium adsorption data were analysed using the first- and the second-order kinetic models. The experimental results suggest that the second-order equation is the most appropriate equation to predict the biosorption capacities of all the biosorbents. All the tested algal preparations could be regenerated using 0.1 M NaOH solution, with up to 96% recovery. (c) 2004 Elsevier Ltd. All rights reserved.
