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Article Citation - WoS: 30Citation - Scopus: 34Preparation and Testing of Nafion/Titanium Dioxide Nanocomposite Membrane Electrode Assembly by Ultrasonic Coating Technique(Wiley-blackwell, 2014) Devrim, Yilser; Alemdaroğlu Temel, Mine; Alemdaroğlu Temel, MineMembrane electrode assemblies with Nafion/nanosize titanium dioxide (TiO2) composite membranes were manufactured with a novel ultrasonic-spray technique (UST) and tested in proton exchange membrane fuel cell (PEMFC). The structures of the membranes were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis. The composite membranes gained good thermal resistance with insertion of TiO2. The SEM and XRD techniques have proved the uniform and homogeneous distribution of TiO2 and the consequent enhancement of crystalline character of these membranes. The existence of nanometer size TiO2 has improved the thermal resistance, water uptake, and proton conductivity of composite membranes. Gas diffusion electrodes were fabricated by UST. Catalyst loading was 0.4 (mg Pt) cm(-2) for both anode and cathode sides. The membranes were tested in a single cell with a 5 cm(2) active area operating at the temperature range of 70 degrees C to 110 degrees C and in humidified under 50% relative humidity (RH) conditions. Single PEMFC tests performed at different operating temperatures indicated that Nafion/TiO2 composite membrane is more stable and also performed better than Nafion membranes. The results show that Nafion/TiO2 is a promising membrane material for possible use in PEMFC at higher temperature. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40541.Article Citation - WoS: 1Citation - Scopus: 1Hole-Polar Phonon Interaction Scattering Mobility in Chain Structured Tlse0.75s0.25< Crystals(Wiley-blackwell, 2009) Qasrawi, A. F.; Gasanly, N. M.In this study, the electrical resistivity, charge carriers density and Hall mobility of chain structured TlSe0.75S0.25 crystal have been measured and analyzed to establish the dominant scattering mechanism in crystal. The data analyses have shown that this crystal exhibits an extrinsic p-type conduction. The temperature-dependent dark electrical resistivity analysis reflected the existence of three energy levels located at 280 meV, 68 meV and 48 meV. The temperature dependence of carrier density was analyzed by using the single donor-single acceptor model. The carrier concentration data were best reproduced assuming the existence of an acceptor impurity level being located at 68 meV consistent with that observed from resistivity measurement, The model allowed the determination of the hole effective mass and the acceptor-donor concentration difference as 0.44m(0) and 2.2 x 10(12) cm(-3), respectively. The Hall mobility of the TlSe0.75S0.25 crystal is found to be limited by the scattering of charged carriers over the (chain) boundaries and the scattering of hole-polar phonon interactions above and below 300 K, respectively. The value of the energy barrier height at the chain boundaries was found to be 261 meV. The polar phonon scattering mobility revealed the high-frequency and static dielectric constants of 13.6 and 15.0, respectively. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimArticle Citation - WoS: 9Citation - Scopus: 11Methodological Framework for the Allocation of Work Packages in Global Software Development(Wiley-blackwell, 2014) Ruano-Mayoral, Marcos; Casado-Lumbreras, Cristina; Garbarino-Alberti, Helena; Misra, SanjayGlobal software development in software development industry is a new aspect for many software project managers. In this scenario, the allocation of work packages among project participants is not a simple task. This allocation was traditionally determined by availability and competence but this new trend introduces complexity in an already complex process. Given the need to define new models to guide managers in these operations, this paper presents a framework to allocate work packages among project participants. Apart from the introduction of the framework itself, the results of its implementation are presented. These results show a notable output of the implementation in terms of accuracy of task execution to planning, effect introduction and overall satisfaction. Copyright (c) 2013 John Wiley & Sons, Ltd.Conference Object Ph-Dependent Conformational Changes and Thermal Stability of Outer Membrane Protein G Mutants by Fourier Transform Infrared Spectroscopy(Wiley-blackwell, 2016) Yilmaz, I.; Yildiz, O.; Korkmaz, F.[No Abstract Available]Article Citation - WoS: 22Citation - Scopus: 25Substituent and Heteroatom Effects on the Electrochromic Properties of Similar Systems(Wiley-blackwell, 2012) Icli-Ozkut, Merve; Cihaner, Atilla; Mersini, Jetmire; Onal, Ahmet M.; Cihaner, Atilla; Cihaner, Atilla; Chemical Engineering; Chemical EngineeringElectrochromic polymers called poly(3,4-dihydro-3,3-bis ((naphthalen-1-yl)methyl)-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT-Np-2), poly(3,3-dibenzyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxepine), and poly(3,3-dibenzyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) were synthesized electrochemically and the effect of substituents and heteroatoms on the electrochromic properties were investigated for the similar systems. All polymers show electrochromism from a colored state when neutralized to transmissive when oxidized. Although, increasing bulky size (PProDOT-Np-2) causes lower coloration efficiency (CE) as well as lower optical contrast, the replacement of S atom by Se atom resulted in a lower band gap polymer with a higher CE than its thiophene analog. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 615- 621, 2012Article Citation - WoS: 44Citation - Scopus: 52Signature Based Analysis of m-consecutive-k< f Systems With Exchangeable Components(Wiley-blackwell, 2011) Eryilmaz, Serkan; Koutras, Markos V.; Triantafyllou, Ioannis S.In this article, we study reliability properties of m-consecutive-k-out-of-n: F systems with exchangeable components. We deduce exact formulae and recurrence relations for the signature of the system. Closed form expressions for the survival function and the lifetime distribution as a mixture of the distribution of order statistics are established as well. These representations facilitate the computation of several reliability characteristics of the system for a given exchangeable joint distribution or survival function. Finally, we provide signature-based stochastic ordering results for the system's lifetime and investigate the IFR preservation property under the formulation of m-consecutive-k-out-of-n: F systems. (C) 2011 Wiley Periodicals, Inc. Naval Research Logistics 58: 344-354, 2011Article Citation - WoS: 23Citation - Scopus: 26Lifetime of Multistate k-out-of-n< Systems(Wiley-blackwell, 2014) Eryilmaz, SerkanA multistate k-out-of-n system model is an extension of binary k-out-of-n system model by allowing multiple performance levels for the system and its components. Various definitions of multistate k-out-of-n system model have been proposed in the literature. Previous studies on these systems mostly focus on reliability evaluation algorithms. The present paper investigates the lifetimes of multistate systems. In particular, the lifetimes of two different multistate k-out-of-n system models are represented in terms of order statistics, and bounds and approximations are presented using these representations. The results are illustrated for a multistate system whose components' degradation occurs according to a Markov process. Copyright (C) 2013 John Wiley & Sons, Ltd.Article Citation - WoS: 18Citation - Scopus: 21Component importance for linear consecutive-k-Out-of-n and m-Consecutive-k-Out-of-n systems with exchangeable components(Wiley-blackwell, 2013) Eryilmaz, SerkanMeasuring the relative importance of components in a mechanical system is useful for various purposes. In this article, we study Birnbaum and Barlow-Proschan importance measures for two frequently studied system designs: linear consecutive k -out-of- n and m -consecutive- k -out-of- n systems. We obtain explicit expressions for the component importance measures for systems consisting of exchangeable components. We illustrate the results for a system whose components have a Lomax type lifetime distribution. (c) 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013Article Citation - WoS: 3Citation - Scopus: 8Assessing Software Quality Using the Markov Decision Processes(Wiley-blackwell, 2014) Korkmaz, Omer; Akman, Ibrahim; Ostrovska, SofiyaQuality of software is one of the most critical concerns in software system development, and many products fail to meet the quality objectives when constructed initially. Software quality is highly affected by the development process's actual dynamics. This article proposes the use of the Markov decision process (MDP) for the assessment of software quality because MDP is a useful technique to abstract the model of dynamics of the development process and to test its impact on quality. Additionally, the MDP modeling of the dynamics leads to early prediction of the quality, from the design phases all the way through the different stages of development. The proposed approach is based on the stochastic nature of the software development process, including project architecture, construction strategy of Software Quality Assurance system, its qualification actions, and team assignment strategy. It accepts these factors as inputs, generating a relative quality degree as an output. The proposed approach has been demonstrated for the design phase with a case study taken from the literature. The results prove its robustness and capability to identify appropriate policies in terms of quality, cost, and time. (c) 2011 Wiley Periodicals, Inc.Article Citation - WoS: 3Citation - Scopus: 3Transport and Recombination Kinetics in Tlgate2 Crystals(Wiley-blackwell, 2009) Qasrawi, A. F.; Gasanly, N. M.In this work, the transport and recombination mechanisms as well as the average hole-relaxation time in TlGaTe2 have been investigated by means of temperature-dependent dark electrical conductivity, photoexcitation intensity-dependent photoconductivity, and Hall effect measurements, respectively. The experimental data analysis revealed the existence of a critical temperature of 150 K. At this temperature, the transport mechanism is disturbed. The dark conductivity data analysis allowed the determination of an energy state of 258 meV The hole-relaxation time that was determined from the Hall mobility data was observed to increase with decreasing temperature. The behavior was attributed to the hole-thermal lattice scattering interactions. At fixed photoexcitation intensity, the photocurrent I-ph decreases with decreasing temperature down to 150 K. Below this temperature it changes direction. The latter data allowed the determination of the recombination center energy as 1 10 meV On the other hand, at fixed temperature and variable illumination intensity, the photocurrent follows the relation I-ph alpha F-n (the value of the exponent, it, decreases with decreasing temperature). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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