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Conference Object Citation - WoS: 137Citation - Scopus: 149Polybenzimidazole/Sio2< Hybrid Membranes for High Temperature Proton Exchange Membrane Fuel Cells(Pergamon-elsevier Science Ltd, 2016) Devrim, Yilser; Devrim, Huseyin; Eroglu, InciPolybenzimidazole/Silicon dioxide (PBI/SiO2) hybrid membranes were prepared and characterized as alternative materials for high temperature proton exchange membrane fuel cell (HT-PEMFC). The PBI/SiO2 membranes were cast from a PBI polymer synthesized in the laboratory and contained 5 wt. % SiO2 as inorganic filler. Scanning electron microscopy (SEM) analysis showed that the uniform and homogeneous distribution of SiO2 particles in the hybrid membrane. The existence SiO2 has improved the acid retention and proton conductivity properties. A maximum conductivity of 0.1027 S/cm at 180 degrees C was obtained for the PBI/SiO2 hybrid membrane. Gas diffusion electrodes (GDE) were fabricated by ultrasonic coating technique with 1 mg Pt/cm(2) catalyst loading for both anode and cathode. The membranes were tested in a single HT-PEMFC with a 5 cm(2) active area operating at the temperature range of 140 degrees C-180 degrees C. Single HT-PEMFC tests indicated that PBI/SiO2 hybrid membrane was more stable and also performed better than pristine PBI membrane. Maximum current density was observed for PBI/SiO2 membrane at 165 degrees C and cell voltage of 0.6 V as 0.24 A/cm(2). The results suggested that PBI/SiO2 hybrid membrane is promising electrolytes for HT-PEMFC with improved fuel cell performance. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 11Citation - Scopus: 12A Standard Benchmarking Suite for Structural Optimization Algorithms: Iscso 2016-2022(Elsevier Science inc, 2023) Azad, Saeid Kazemzadeh; Azad, Saeıd Kazemzadeh; Azad, Sina Kazemzadeh; Azad, Saeıd Kazemzadeh; Kazemzadeh Azad, Saeid; Department of Civil Engineering; Department of Civil EngineeringBenchmarking is an essential part of developing efficient structural optimization techniques. Despite the advent of numerous metaheuristic techniques for solving truss optimization problems, benchmarking new algorithms is often carried out using a selection of classic test examples which are indeed unchallenging for contemporary sophisticated optimization algorithms. Furthermore, the limited optimization results available in the literature on new test examples are usually not accurately comparable. This is typically due to the lack of infromation about the performance of the investigated algorithms and the inconsistencies between the studies in terms of adopted test examples for benchmarking, optimization problem formulation, maximum number of objective function evaluations and other similar issues. Accordingly, there exists a need for developing new standard test suites composed of easily reproducible challenging test examples with rigorous and comparable performance evaluation results of algorithms on these test suites. To this end, the present work aims to propose a new baseline for benchmarking structural optimization algorithms, using a set of challenging sizing and shape optimization problems of truss structures selected from the international student competition in structural optimization (ISCSO) instances. The most recent six structural optimization examples from the ISCSO are tackled using a representative metaheuristic structural optimization algorithm. The statistical results of all the optimization runs using the proposed benchmarking suite are provided to pave the way for more rigorous benchmarking of structural optimization algorithms.Article Citation - WoS: 22Citation - Scopus: 41Argumentation To Foster Pre-Service Science Teachers' Knowledge, Competency, and Attitude on the Domains of Chemical Literacy of Acids and Bases(Royal Soc Chemistry, 2017) Cigdemoglu, C.; Arslan, H. O.; Cam, A.Argumentative practices have the potential to contribute to scientific literacy. However, these practices are not widely incorporated in science classrooms and so their effect on the domains of literacy is still not revealed. Therefore, this study proposes to reveal the effect of argumentation on the three domains of chemical literacy related to the concepts of acids and bases. The study participants comprised 29 freshman pre-service science teachers' enrolled in a General Chemistry-II course. Argumentation practices were implemented over six weeks. Open-ended contextual chemical literacy items were developed to assess the differences in the chemical literacy domains and the items were administered before and right after the intervention. The responses to the chemical literacy items were scored with a rubric and three scores were calculated: knowledge, competency, and attitudes. Paired sample t-tests were used to compare the mean scores. All the intervention sessions were video recorded, and three of them were analyzed according to three criteria: the presence of arguments, the frequency of arguments, and the levels of the arguments. The findings revealed that the argumentation practices contributed to the pre-service teachers' chemical literacy skills, mostly to their knowledge and competencies when compared to their attitudes. Moreover, distinct differences in the quality of argumentation levels were observed over the six weeks.Article Citation - WoS: 11Citation - Scopus: 11Design and Applications of Al/Inse Hybrid Device(Ieee-inst Electrical Electronics Engineers inc, 2015) Qasrawi, Atef F.; Khanfar, Hazem K.In this paper, a hybrid device made of Ag/BN Schottky barrier and anisotype InSe/BN heterojunction is designed and characterized. The design of the energy band diagram of the device revealed a valance band splitting at the InSe/BN interface and a barrier height at the Ag/BN junction of 3.04 and 6.49 eV, respectively. These parameters which were designed to force current conduction by tunneling were experimentally confirmed by the dark I-V characteristics which revealed an electric field assisted tunneling process. The hybrid device exhibited high/low current switching property at Vs = 2.60 V when forward biased. When the device was exposed to 850-nm lasers light, Vs regularly increased with increasing light power indicating the applicability of these devices as IR photodetectors. In addition, when it was used as capacitor and depleted with signal of frequency of 0.1 GHz and varying amplitude it showed good energy storing property with a quality factor of similar to 200. On the other hand, when the hybrid device was used as microwave resonator it behaves like bandstop filter that blocks signals of various notch frequencies in the range of 1.58-2.30 GHz. The features of the device are promising as they indicate the applicability of the Al/InSe/BN/Ag in communication technology.Article Citation - WoS: 14Citation - Scopus: 17NEW EDOT CONTAINING POLYMERS: EFFECT OF RING SIZE ON THE BENZIMIDAZOLE ACCEPTOR(Pergamon-elsevier Science Ltd, 2016) Cansu-Ergun, E. G.; Onal, A. M.; Cihaner, A.In this study, three different benzimidazole (BIm) based acceptor groups bearing cyclohexane, cycloheptane and cyclooctane rings at 2-C position of benzimidazole were synthesized and coupled with ethylenedioxythiophene (EDOT) donor units via Stille cross-coupling reaction. The resulting donor acceptor-donor (DAD) type monomers were examined in terms of their electrochemical and optical behaviors. All three monomers exhibited dual absorption bands due to their donor-acceptor pattern and exhibited one irreversible oxidation peak at about 0.80 V. The monomers were electrochemically polymerized via both potentiostatic and potentiodynamic methods and electro-optical properties of obtained conjugated polymer films were investigated in monomer free electrolytic solution. It was found that the polymer films exhibited quasi-reversible redox behavior due to the doping/dedoping process of the polymers, which was accompanied by a reversible electrochromic behavior. Electrochromic investigations showed that all three polymer films showed similar multichromic behaviors: green in the neutral state, gray in the oxidized state, and brick-red in the reduced state. Their band gap (Eg) values were elucidated utilizing spectroelectrochemical data and it was found to be around 1.18 eV. Furthermore, one of the polymer film was utilized for the construction of transmissive type electrochromic device (ECD) with poly(3,4-ethylenedioxythiophene) (PEDOT). (C) 2015 Elsevier Ltd. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 5Performance Analysis of a Gas-To System Based on Protonic-Ceramic Electrochemical Compressor(Pergamon-elsevier Science Ltd, 2023) Baniasadi, Ehsan; Ghojavand, Fateme; Colpan, Can Ozgur; Devrim, YilserIn this study, two scenarios are considered to evaluate the performance of a protonic ceramic electrochemical hydrogen compressor (EHC) and reformer integrated with a pro-ton exchange membrane fuel cell (PEMFC). First scenario includes integration of an EHC with PEMFC and in the second scenario, steam methane reforming (SMR) is replaced by an EHC. Results show that the highest energy and exergy efficiencies of the system in the first scenario is achieved when the area-specific resistance (ASR) in EHC is 1.5 Ucm2. An in-crease in the working temperature of EHC causes a considerable rise in the exergy destruction and an increase of energy efficiency by 7% in the first scenario, while the temperature of the reformer affects the exergy destruction, negligibly. The parametric study indicates that the best value of the current density of PEMFC is 0.8481 A/cm2 and 0.8324 A/cm2 and the best current density of PEM-EHC value is 0.4468 A/cm2 and 0.11 A/cm2 in the 1st and 2nd scenarios, respectively. Under the same conditions, energy and exergy efficiencies for the first scenario are 61.63% and 54.9% and for the second scenario are 42.48% and 14.61%, respectively.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Lyapunov type inequalities for second-order forced dynamic equations with mixed nonlinearities on time scales(Springer-verlag Italia Srl, 2017) Agarwal, Ravi P.; Cetin, Erbil; Ozbekler, AbdullahIn this paper, we present some newHartman and Lyapunov inequalities for second-order forced dynamic equations on time scales T with mixed nonlinearities: x(Delta Delta)(t) + Sigma(n)(k=1) qk (t)vertical bar x(sigma) (t)vertical bar (alpha k-1) x(sigma) (t) = f (t); t is an element of [t(0), infinity)(T), where the nonlinearities satisfy 0 < alpha(1) < ... < alpha(m) < 1 < alpha(m+1) < ... < alpha(n) < 2. No sign restrictions are imposed on the potentials qk, k = 1, 2, ... , n, and the forcing term f. The inequalities obtained generalize and compliment the existing results for the special cases of this equation in the literature.Article Citation - WoS: 65Citation - Scopus: 67An Electrochromic and Fluorescent Polymer Based on 1-(1(Elsevier Science Sa, 2008) Cihaner, Atilla; Algi, FatihA novel polymer was synthesized by electrochemical polymerization of 1-(1-naphthyl)-2,5-di-2-thienyl-1H-pyrrole (SNS-1-NAPH). The corresponding polymer (PSNS-1-NAPH) was characterized by cyclic voltammetry, FT-IR and UV-vis spectroscopy. The polymer has a very well-defined and reversible redox process in both organic and aqueous solutions. Furthermore, it shows stable electrochromic behavior; yellow in the neutral state, green in the intermediate state and violet in the oxidized state. PSNS-1-NAPH is soluble in common solvents. Although SNS-1-NAPH is almost nonfluorescent, its polymer is a yellow and/or green light emitter. (c) 2007 Elsevier B.V. All rights reserved.Letter Discussion of the Article "approximate Solution of Limit Angular Speed for Externally Loaded Rotating Solid Disk" by S. Bhowmick, D. Misra and Nk Saha [int J Mech Sci 2008;50:163-74](Pergamon-elsevier Science Ltd, 2008) Eraslan, Ahmet N.; Akis, Tolga[No Abstract Available]Article Citation - WoS: 16Citation - Scopus: 16q-bernstein Polynomials of the Cauchy Kernel(Elsevier Science inc, 2008) Ostrovska, SofiyaDue to the fact that in the case q > 1, q-Bernstein polynomials are not positive linear operators on C[0, 1], the study of their approximation properties is essentially more difficult than that for 0 < q < 1. Despite the intensive research conducted in the area lately, the problem of describing the class of functions in C[0, 1] uniformly approximated by their q-Bernstein polynomials (q > 1) is still open. In this paper, the q-Bernstein polynomials B-n,B-q(f(a); z) of the Cauchy kernel f(a) = 1/(z - a), a is an element of C \ [0, 1] are found explicitly and their properties are investigated. In particular, it is proved that if q > 1, then polynomials B-n,B-q(f(a); z) converge to f(a) uniformly on any compact set K subset of {z : vertical bar z vertical bar < vertical bar a vertical bar}. This result is sharp in the following sense: on any set with an accumulation point in {z : vertical bar z vertical bar > vertical bar a vertical bar}, the sequence {B-n,B-q(f(a); z) is not even uniformly bounded. (C) 2007 Elsevier Inc. All rights reserved.
