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Article Citation - WoS: 2Citation - Scopus: 2Analysis of Optical Constants and Temperature-Dependent Absorption Edge of Gas0.75se0.25< Layered Crystals(Pergamon-elsevier Science Ltd, 2017) Isik, Mehmet; Gasanly, NizamiGaS0.75Se0.25 single crystals were optically characterized through transmission and reflection measurements in the wavelength range of 450-1000 nm. Derivative spectrophotometry analyses on temperature dependent transmittance spectra showed that band gap energies of the crystal increase from 239 eV (T=300 K) to 2.53 eV (T=10 K). Band gap at zero temperature, average phonon energy, electron phonon coupling parameter and rates of change of band gap energy with temperature were found from the temperature dependences of band gap energies under the light of different models reported in literature. Furthermore, the dispersion of room temperature refractive index was discussed in terms of single effective oscillator model. The refractive index dispersion parameters, namely oscillator and dispersion energies, zero-frequency refractive index, were determined as a result of analyses. (C) 2017 Elsevier Ltd. All rights reserved.Article Citation - WoS: 209Citation - Scopus: 259Impact of Cyclic Wetting-Drying on Swelling Behavior of Lime-Stabilized Soil(Pergamon-elsevier Science Ltd, 2007) Guney, Yucel; Sari, Dursun; Cetin, Murat; Tuncan, MustafaIn this study, the impact of cyclic wetting and drying on swelling behavior of lime-stabilized clayey soils has been investigated. Swelling potential and swelling pressure tests have been carried out on soil mixtures with various amounts of kaolinite-bentonite clays, and on a high plasticity clayey soil sample. The tests have been repeated after the addition of lime to the lime-treated samples in different preparation. In each cycle the tested samples were allowed air dry to their initial water content thus shrinking to their initial height, which is called 'partial shrinkage' method. The results showed that the initial beneficiary effect of lime stabilization was lost after the first cycle and the swelling potential increased at the subsequent cycles. On the other hand, the swelling potential and the swelling pressure of the untreated soil samples started decreasing after the first cycle and they reached equilibrium after the fourth cycle. (c) 2005 Elsevier Ltd. All rights reserved.Article Citation - WoS: 199Citation - Scopus: 195Existence and uniqueness of a common fixed point on partial metric spaces(Pergamon-elsevier Science Ltd, 2011) Abdeljawad, T.; Karapinar, E.; Tas, K.In this work, a general form of the weak phi-contraction is considered on partial metric spaces, to get a common fixed point. It is shown that self-mappings S, T on a complete partial metric space X have a common fixed point if it is a generalized weak phi-contraction. (C) 2011 Elsevier Ltd. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 8Some Remarks on Global Asymptotic Stability of Neural Networks With Constant Time Delay(Pergamon-elsevier Science Ltd, 2007) Singh, VimalAn elegant proof of a previously reported criterion for the uniqueness and global asymptotic stability of the equilibrium point of a class of neural networks with constant time delay is presented. The present proof yields some interesting observations. (c) 2005 Elsevier Ltd. All rights reserved.Article Citation - WoS: 11Citation - Scopus: 12A Low Band Gap Polymer Based on Selenophene and Benzobis (thiadiazole)(Pergamon-elsevier Science Ltd, 2017) Abdulrazzaq, Mohammed; Ozkut, Merve Icli; Gokce, Gurcan; Ertan, Salih; Tutuncu, Esra; Cihaner, AtillaA new derivative of benzobis(thiadiazole) based donor-acceptor-donor type monomers, namely 4,7-di (selenophen-2-yl)benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole (SeBTSe), was synthesized and its polymerization was carried out successfully via electrochemical polymerization in an electrolyte solution of 0.1 M tetrabutylammonium hexafluorophosphate dissolved in dichloromethane. The monomer SeBTSe is a deep red chromophore and it has four redox states: one oxidation, one neutral and two reduction states. The electrochemical behaviour of the corresponding polymer called PSeBTSe was studied by cyclic and differential pulse voltammetry. There is a good agreement between electrochemical (0.62-0.66 eV) and optical (0.63 eV) bandgaps of the polymer. Like the monomer, the ambipolar polymer has four redox states and electrochromic properties: gray beige at neutral state, smoky azurite at oxidized state, beige at first reduced state and dark beige at second reduced state. (C) 2017 Elsevier Ltd. All rights reserved.Article Citation - WoS: 42Citation - Scopus: 41Synthesis and Characterization of Mg2b2<(Pergamon-elsevier Science Ltd, 2005) Qasrawi, AF; Kayed, TS; Mergen, A; Gürü, MMagnesium borate of the form Mg2B2O5 has been prepared and its structural and thermal properties were studied using X-ray diffraction and differential thermal analysis. An investigation of the electrical and optical properties of Mg2B2O5 system has been carried out. The electrical resistivity of the sample was measured in the temperature range of 170-400 K. The data analysis revealed an extrinsic nature of the conductivity with two impurity levels located at 0.13 and 0.71 eV in the temperature ranges of 170-230 K and 240-400 K, respectively. The optical transmission and reflection was recorded at 300 K in the incident photon energy range of 3.0-6.0 eV. The absorption coefficient data analysis revealed an indirect optical energy band gap of 4.73 eV. In addition, two impurity levels located at 3.43, and 4.49 eV were observed in the absorption spectra. (c) 2005 Elsevier Ltd. All rights reserved.Article Citation - WoS: 45Citation - Scopus: 47An Electroactive Polymeric Material and Its Voltammetric Response Towards Alkali Metal Cations in Neat Water(Pergamon-elsevier Science Ltd, 2008) Algi, Fatih; Cihaner, AtillaThe syntheses and characterization of a unique system based on thiophene, pyrrole and benzo-15-crown-5 (SNS-Crown) and its corresponding polymer (PSNS-Crown) are reported. Furthermore, selective, clear and reversible voltammetric responses of the conjugated polymer (PSNS-Crown) film towards the alkali series Li+, Na+ and K+ in both neat water and organic media (ethanol) are described. (c) 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 29Citation - Scopus: 30The Temporal Communication Behaviors of Global Software Student Teams(Pergamon-elsevier Science Ltd, 2012) Swigger, Kathleen; Hoyt, Matthew; Serce, Fatma Cemile; Lopez, Victor; Alpaslan, Ferda NurThis paper examines the global software development process by using content analysis techniques, as described in an earlier study (Serce et al., 2011), to determine time-variant patterns of communication behaviors among student teams engaged in a global software development project. Data gathered from two software development projects involving students in the US, Panama, and Turkey were used to determine how globally distributed team behavior is temporally patterned in complex ways. A formal, quantitative methodology for time variant analysis of the transcripts of global software student teams based on content analysis is established. Results from the analysis suggest a positive correlation between a team's temporal communication patterns and project outcomes as well as a relationship between variations in communication behaviors and different phases of the software development cycle. The research also found that the temporal variations in communication behaviors between software phases were similar for the two projects. Such findings are intended to strengthen the case for developing new temporal measures for analyzing groups and teams. (C) 2011 Elsevier Ltd. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Trap Distribution in Agin5s8< Single Crystals: Thermoluminescence Study(Pergamon-elsevier Science Ltd, 2018) Delice, S.; Işık, Mehmet; Isik, M.; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringDistribution of shallow trap levels in AgIn5S8 crystals has been investigated by thermoluminescence (TL) measurements performed below room temperature (10-300 K). One broad TL peak centered at 33 K was observed as constant heating rate of 0.2 K/s was employed for measurement. The peak shape analysis showed that the TL curve could consist of several individual overlapping TL peaks or existence of quasi-continuous distributed traps. Therefore, TL experiments were repeated for different stopping temperatures (T-stop) between 10 and 34 K with constant heating rate of 0.2 K/s to separate the overlapping TL peaks. The E-t vs T-stop indicated that crystal has quasi-continuously distributed traps having activation energies increasing from 13 to 41 meV. Heating rate effect on trapped charge carriers was also investigated by carrying out the TL. experiments with various heating rates between 0.2 and 0.6 K/s for better comprehension of characteristics of existed trap levels. Analyses indicated that the trap levels exhibited the properties of anomalous heating rate behavior which means the TL intensity and area under the TL peak increase with increasing heating rate.Article Citation - WoS: 155Citation - Scopus: 190An Eye-Tracking Study of How Color Coding Affects Multimedia Learning(Pergamon-elsevier Science Ltd, 2009) Ozcelik, Erol; Karakus, Turkan; Kursun, Engin; Cagiltay, KursatColor coding has been proposed to promote more effective learning. However, insufficient evidence currently exists to show how color coding leads to better learning. The goal of this study was to investigate the underlying cause of the color coding effect by utilizing eye movement data. Fifty-two participants studied either a color-coded or conventional format of multimedia instruction. Eye movement data were collected during the study. The results indicate that color coding increased retention and transfer performance. Enhancement of learning by color coding was due to efficiency of locating corresponding information between illustration and text. Color coding also attracted attention of learners to perceptually salient information. (C) 2009 Elsevier Ltd. All rights reserved.
