Yazar "Dogan, Fatih" seçeneğine göre listele

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    Biosorption of Co(II), Cr(III), Cd(II), and Pb(II) Ions from Aqueous Solution Using Nonliving Neochloris Pseudoalveolaris Deason & Bold: Equilibrium, Thermodynamic, and Kinetic Study
    (Taylor & Francis Inc, 2012) Kizilkaya, Bayram; Dogan, Fatih; Akgul, Riza; Turker, Gulen
    In this study, biosorption of cobalt(II), chromium(III), cadmium(II), and lead(II) ions from aqueous solution was studied using the algae nonliving biomass (Neochloris pseudoalveolaris, Np) as natural and biological sorbents. The effect of pH, contact time, temperature, and metal concentration on the adsorption capacity of metal ions was investigated. The maximum adsorption capacities for Co(II), Cr(II), Cd(II), and Pb(II) were found to be 20.1, 9.73, 51.4 and 96.2 mg/g at the optimum conditions, respectively. The experiments showed that when pH increased, an increase in the adsorption capacity of the biomass was observed too. The kinetic results of adsorption obeyed a pseudo second-order model. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of metal ions adsorption and the value of R-L for Pb(II), Cb,(II), Co(II), and Cr(III) was found to be 0.376, 0271, 0872, and 096, respectively. The thermodynamic parameters related to the adsorption process such as E-a, Delta G(0), Delta H-0, and Delta S-0 were calculated. Delta H-0 values (positive) showed that the adsorption mechanism was endothermic. Weber-Morris and Urano-Tachikawa diffusion models were also applied to experimental equilibrium data. The algae biomass was effectively used as a sorbent for the removal of metal ions from aqueous solutions.
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    BIOSORPTION OF HEAVY METAL IONS FROM AQUEOUS SOLUTIONS BY NONLIVING Scenedesmus quadricauda BIOMASS
    (Parlar Scientific Publications (P S P), 2012) Akgul, Riza; Kizilkaya, Bayram; Akgul, Fusun; Dogan, Fatih
    In present study, biosorptions of lead (II), cadmium (II), cobalt (II) and chromium (III) ions from water were studied and dead algae biomass (Scenedesmus quadri-cauda Chodat) was used as natural and biological sorbents. The effects of pH, contact time and metal concentration on the biosorption capacity were investigated. The maximum biosorption capacities for Co (II), Cr (III), Cd (II) and Pb (II) were found to be 32.8, 20.3, 63.9 and 123.0 mg/g, respectively. The experiments showed that when pH increased, an increase in the biosorption capacity of the biomass was observed. Freundlich and Langmuir isotherm models were applied to experimental equilibrium data of metal ions adsorption and the value of R-L for Co (II), Cr (III), Cd (II) and Pb (II) was found to be 0.639, 0.580, 0.915 and 0.949, respectively. The algae biomass was effectively used as a sorbent for removal of metal ions from aqueous solutions.
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    Comparative Study of Biosorption of Heavy Metals Using Living Green Algae Scenedesmus quadricauda and Neochloris pseudoalveolaris: Equilibrium and Kinetics
    (Taylor & Francis Inc, 2012) Kizilkaya, Bayram; Turker, Gulen; Akgul, Riza; Dogan, Fatih
    The biosorption of several heavy metals such as cobalt(II), chromium(III), lead(II), cadmium(II), nickel(II), and manganese(II) from aqueous systems on living microalgae cultures, Scenedesmus quadricauda and Neochloris pseudoalveolaris were studied under laboratories conditions. The kinetic and statistical parameters were calculated by using the data obtained from batch cultivation and well fitted a pseudo-first-order rate equation. The initial metal concentrations in solution were about 5-40 mg . L-1. According to the pseudo-second-order model, the biosorption capacities of Scenedesmus quadricauda for Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions were found in the ranges of 2.14-52.48, 1.98-81.98, 8.05-4.26, 7.81-24.96, 2.17-55.71, and 3.54-75.20 mg g(-1), respectively. Kinetic studies revealed that the metal uptake capacity of each living green algae was rather fast. It was also observed that the biosorption kinetic rate decreased with increasing concentration for both microalgae. The application of diffusion-controlled models to the experimental results indicated that the contribution of intraparticle diffusion to the overall sorption kinetics was not very important. Results showed that Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions could effectively be absorbed by using living microalga cultures from aqueous solutions.
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    Developing Achievement Test on Cell Subject for 6th Grade: A Validity and Reliability Study
    (Cukurova Univ, 2019) Timur, Serkan; Dogan, Fatih; Cetin, Nagihan Imer; Timur, Betul; Isik, Ruveyda
    In this study, it is aimed to develop a valid and reliable achievement test for the subject of Cell belonging to the 6th grade Systems in our Body unit within the scope of Science course. The achievement test was prepared as a 25-item multiple-choice test, considering the cell-related objectives in the 6th grade Science curriculum. The pilot study of the test was carried out with 62 students attending 6th grade in 2017-2018 academic year. The comprehensibility and the consistency with the scientific knowledge of the test items were prepared by the opinions of various experts in the field of science education. The item analysis was performed according to the answers of the students in the achievement test, and the discriminant and difficulty indexes were calculated for each item. After the item analysis, 3 items were excluded from the test and a Cell Achievement Test (CAT) consisting of 22 questions was obtained. The mean item difficulty of CAT was 0.652 and the mean discrimination index was 0.507.
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    Digital literacy scale: Validity and reliability study with the rasch model
    (Springer, 2024) Avinc, Ece; Dogan, Fatih
    The study aimed to develop a Likert-type measurement tool (Digital Literacy Scale, DLS) to determine the digital literacy levels of secondary school students. The validity and reliability of the developed measurement tool were verified using the Rasch model. The Rasch Model can estimate missing data and allow for small study groups (Rasch, Rasch, Probabilistic models for some intelligence and attainment tests, Danish Institute for Educational Research, 1960). Additionally, this model can verify the expected pattern of the measurement tool by calibrating it across participants and items. The content validity of DLS was ensured by expert opinion, and the construct validity was ensured by using the Rach model. In the content validity study, a 25-item pool was created for the draft DLS, and 5 items were removed from the draft DLS at this stage. Construct validity studies were carried out with the remaining 20 items using the classical test theory and item response theory (Rasch model). Exploratory Factor Analysis (EFA) and first-level Confirmatory Factor Analysis (CFA) were used within the scope of classical test theory. Then some Rasch assumptions such as dimensionlessness, local independence, monotonicity, and bias were tested for DLS. In the validity and reliability analysis of DLS, no items were eliminated, and the quantitative theoretical results were statistically confirmed. The analysis results showed that the minimum statistical values required for a good measurement tool were met. Accordingly, 20 valid and reliable compatible items that can be used to determine the digital literacy status of secondary school students were produced.
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    Electrochemical polymer synthesis using thiophene and pyrrole/carbazole: Their electrochemical behaviours and capacitor performance
    (Elsevier Science Sa, 2024) Kocaeren, Aysel Aydin; Bahceci, Dilek Senol; Kizilkaya, Bayram; Dogan, Fatih
    In this study, carbazole-derived monomers were synthesized on ITO-coated PET via electrochemical reactions and conductivity measurements of the resulting polymeric films were performed by UV, FT-IR, NMR, TG-DTG, SEM and AFM analyses. Their spectroelectrochemical properties were investigated. The carbazole (C) based thiophene (Th) polymer abbreviated as pThC and its copolymer with pyrrole (Py), named as pThC-Py were obtained by electrochemical polymerization method. The surface stability of the resulting polymer films was good depending on time. The contact angle (CA) between the water and theco- polymer surface was determined by dropping 6.09 mu L of pure water and CA average was calculated as 68.19 degrees < 90 degrees. According to the thermal analysis data of the polymers, the thermal stability of the pThC-Py was better than pThC as it had higher thermal decomposition temperature. Comparisons of electrical conductivity measurements of the polymer films were made depending on the temperature (25, 50 and 90 degrees C). Due to increasing temperature, the electrical conductivity of pThC-Py film was read as 29.3 S/cm at 90 degrees C, and also the electrical conductivity values of the pThC-Py were determined as 1.92 x 10(-2) S/cm at 25 degrees C and 14.2 S/cm at 50 degrees C. Because of the high electrical conductivity of the pThC-Py, its capacitor performance was tried to be determined from cyclic voltammetric measurements. According to the voltammetric results, the power density (P) and the energy density (E) values of the synthesized substance were calculated as 290.532 W/g and 9.684 Wh/g, respectively. This indicates that the amount of energy the material storable is relatively high. Moreover, it is possible to say that it can be included in the classical capacitor class and in the supercapacitor category by improving its features. Moreover, since the electrical conductivity of pThC-Py is quite good, it is thought that it may be suitable for use in electronic devices.
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    Improving the Mechanical, Physical, Thermal, and Morphological Properties of Isotactic Polypropylene with Dialkylperoxide
    (Prints Publications Pvt Ltd, 2013) Sirin, Kamil; Yavuz, Mesut; Canli, Murat; Avci, Ali; Dogan, Fatih
    In this study, the influence of the visbreaking agent (DAP) on mechanical, physical, thermal and morphological properties of PP has been studied. For this reason, isotactic polypropylene (PP) matrices containing 0.01, 0.02, 0.04, 0.06, 0.08, and 0.1 wt% of dialkylperoxide [2, 5-dimethyl-2, 5-di (tert-butyl peroxy)-hexane, (DAP)] were prepared by using a single-screw extruder. As a result of DAP addition, the crystallinity ratio of the PP matrices has changed between 2.67-7.80%. Mechanical properties of the matrices have been improved. Particularly, the mechanical tests of PP have given interesting results when compounded with 0.02 wt.% dialkyl peroxide. The microstructure of isotactic polypropylene matrix was investigated by scanning electron microscopy (SEM). From SEM analysis, it was observed that the surface disorder increased by the increasing amount of DAP. Thermal analyses of the matrices were investigated using thermogravimetry in dynamic nitrogen atmosphere at different heating rates. The Flynn-Wall-Ozawa (FWO), Kissinger and master plots method were employed to determine the kinetic model and kinetic parameters of the decomposition processes under non-isothermal conditions. It was found that the thermal stability, activation energy and thermal decomposition processes were all changed by increasing amount of DAP in the matrix structure.
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    Mechanical properties of polypropylene (PP) plus high-density polyethylene (HDPE) binary blends: Non-isothermal degradation kinetics of PP+HDPE (80/20) Blends
    (Wiley-Blackwell, 2013) Sirin, Kamil; Dogan, Fatih; Canli, Murat; Yavuz, Mesut
    In this study, the mechanical properties and non-isothermal degradation kinetics of polypropylene (PP), high-density polyethylene (HDPE) with dilauroyl peroxide and their blends in different mixture ratios were investigated. The effects of adding dilauroyl peroxide (0-0.20 wt%) on the mechanical and thermal properties of PP + HDPE blends have been studied. On the other hand, the kinetics of the thermal degradation and thermal oxidative degradation of PP + HDPE (80/ 20 wt%) blends were studied in different atmospheres, to analyze their thermal stability. The kinetic and thermodynamic parameters such as the activation energy, Ea, the pre-exponential factor, A, the reaction order, n, the entropy change, the enthalpy change, and the free energies of activated complex related to PP, HDPE, and blend systems were calculated by means of the several methods on the basis of the single heating rate. A computer program was developed for automatically processing the data to estimate the reaction parameters by using different models. Most appropriate method was determined for each decomposition step according to the least-squares linear regression. Copyright (c) 2013 John Wiley & Sons, Ltd.
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    Modeling Development and Validation of Metaverse Attitude Scale
    (Int Soc Technology Education & Science-Istes, 2023) Kirbas, Omer; Dogan, Fatih
    This study is an attempt to develop a reliable and valid measurement tool to measure secondary school students' attitudes towards metaverse use. Therefore, the study reported the analyses related to metaverse attitude scale (MVAS). The content validity of the scale was ensured by an expert's view, and Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) designed according to the Technology Adaptation Model (TAM) were employed to ensure its construct validity.. The structural equation model was used to reveal the relationship across the variables. EFA was carried out with the data obtained from 251 5(th), 6(th,) 7(th), and 8(th)-grade secondary school students enrolled in public schools in a city in northwest Turkey. The results of EFA confirmed a 22-item three-factor model. Then, the three-factor model obtained from EFA was cross-validated through the use of CFA that proposed a 21-item 3-factor model. The fit indices for CFA were found as .05 for RMSEA, .049 for SRMR,.889 for GFI, .871 for AGFI, .9146 for NFI, .965 for CFI, and .916 for RFI. Besides, the results affirmed the proposed 21-item three-factor model theoretically and statistically. Structural equation modeling was used to determine the relationship across variables. Accordingly, secondary school students were identified to have positive responses towards cognitive and affective fields related to the metaverse. However, they could not transform these responses into behavioral field. As a result, the metaverse may be used in education since it is likely to observe the independent variables such as perceived usefulness, perceived ease of use and attitude towards use regarding the metaverse in secondary school students.
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    New equations for kinetic analysis of non-isothermal thermogravimetry
    (Asian Journal Of Chemistry, 2008) Dogan, Fatih; Yildirim, Ahmet; Yuerekli, Mehmet
    New equations have been proposed for the evaluation of the kinetic parameters from non-isothermal thermogravimetry. The Arrhenius temperature integral. In p(x), values were computed from the recently proposed series and approximations. The validity of the new equations has been confirmed by the analysis of theoretical and experimental thermogravimetric curves. The kinetic parameters computed using the proposed equations show better agreement for theoretical TG curves than the well-known methods.
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    Optical Sensor Applications of Carbazole Derivative Polymers Containing Different Aliphatic Groups Against Fe3+ Metal Ion
    (Maik Nauka/Interperiodica/Springer, 2022) Kocaeren, Aysel Aydin; Bahceci, Dilek Senol; Dogan, Fatih
    The carbazole derivatives containing aromatic rings with long alkyl groups such as C-6, C-8, C-10 and 3,4-bis(4-iodophenoxy) thiophene are synthesized. The products of carbazole derivatives and 3,4-bis(4-iodophenoxy) thiophene interaction were polymerized using FeCl3 oxidant. The structural characteristics of the synthesized compounds were obtained by FT-IR and NMR spectroscopy. UV measurements are performed to determine the optical changes of the copolymers in the presence of metal ions such as Ag+, Cd2+, Co2+, Cu2+, Fe2+, Fe3+, Hg2+, Li+, Ni2+, Pb2+, Zn2+. The selectivity of Fe3+ is investigated by recording of the absorbance changes of Fe3+ solutions prepared at different concentrations. The effect of pH is also investigated in optical sensor studies. According to UV measurements, the materials containing thiophene and carbazole units can be considered as candidates for sensor production due to their selectivity towards Fe3+ ions.
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    Thermal decomposition behavior of oligo(4-hydroxyquinoline)
    (Wiley, 2014) Dogan, Fatih
    In this study, the kinetic parameters and reaction mechanism of decomposition process of oligo(4-hydroxyquinoline) synthesized by oxidative polymerization were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA-derivative thermogravimetric analysis curves showed that the thermal decomposition occurred in two stages. The methods based on multiple heating rates such as Kissinger, Kim-Park, Tang, Flynn-Wall-Ozawa method (FWO), Friedman, and Kissinger-Akahira-Sunose (KAS) were used to calculate the kinetic parameters related to each decomposition stage of oligo(4-hydroxyquinoline). The activation energies obtained by Kissinger, Kim-Park, Tang, KAS, FWO, and Friedman methods were found to be 153.80, 153.89, 153.06, 152.62, 151.25, and 157.14 kJ mol(-1) for the dehydration stage, 124.7, 124.71, 126.14, 123.75, 126.19, and 124.05 kJ mol(-1) for the thermal decomposition stage, respectively, in the conversion range studied. The decomposition mechanism and pre-exponential factor of each decomposition stage were also determined using Coats-Redfern, van Krevelen, Horowitz-Metzger methods, and master plots. The analysis of the master plots and methods based on single heating rate showed that the mechanisms of dehydration and decomposition stage of oligo(4-hydroxyquinoline) were best described by kinetic equations of A(n) mechanism (nucleation and growth, n = 1) and D-n mechanism (dimensional diffusion, n = 6), respectively. POLYM. ENG. SCI., 54:992-1002, 2014. (c) 2013 Society of Plastics Engineers