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Article Citation - WoS: 19Citation - Scopus: 21Lyapunov Type Inequalities for Mixed Nonlinear Riemann-Liouville Fractional Differential Equations With a Forcing Term(Elsevier, 2017) Agarwal, Ravi P.; Ozbekler, AbdullahIn this paper, we present some new Lyapunov and Hartman type inequalities for Riemann-Liouville fractional differential equations of the form ((a)D(alpha)x)(t) + p(t) vertical bar x(t) vertical bar(mu-1) x(t) + q(t) vertical bar x(t) vertical bar(gamma-1) x(t) = f(t), where p, q, f are real-valued functions and 0 < gamma < 1 < mu < 2. No sign restrictions are imposed on the potential functions p, q and the forcing term f. The inequalities obtained generalize and compliment the existing results for the special cases of this equation in the literature. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 7Design of Novel Tellurium and Selenium Containing Semiconducting Polymers Using Quantum Mechanical Tools(Elsevier, 2017) Kaya, Birnur; Kayi, HakanStructural, optical and electronic properties of the two novel donor-acceptor-donor type conjugated polymers based on 4,7-di(selenophen-2-yl)benzo[c][1,2,5]selenadiazole (SeSeSe) and 4,7-di(tellurophen-2-yl)benzo[c][1,2,5]telluradiazole (TeTeTe) are investigated by means of quantum chemical calculations utilizing conventional and long-range corrected hybrid functionals. The lowest energy structures of the SeSeSe and TeTeTe monomers and oligomers are revealed through conformational analysis, while their electronic properties are obtained from density functional theory (DFT) molecular orbital calculations and optical properties are obtained from the time dependent DFT (TD-DFT) calculations for UV-vis absorption spectra. Electronic band gaps that directly affect the semiconducting properties of these novel polymers are calculated by using linear regression analysis of DFT data, and also periodic boundary conditions calculations (PBC-DFT). Our results indicate that SeSeSe and TeTeTe polymers have considerably lower band gap values than that of their furan-, thiophene-, benzooxadiazole- and benzothiadiazole-based analogs. The novel SeSeSe and TeTeTe polymers with improved optical and electronic properties may have an important role in the near future, especially for the optoelectronic and photovoltaic applications. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 11Low Temperature Thermoluminescence of Gd2o3< Nanoparticles Using Various Heating Rate and tmax< - texc< Methods(Elsevier, 2019) Delice, Serdar; Isik, Mehmet; Gasanly, Nizami M.Thermoluminescence (FL) measurements for Gd2O3 nanoparticles were carried out for various heating rates between 0.3 and 0.8 K/s at low temperatures (10-280 K). TL spectrum exhibited two observable and one faint peaks in the temperature region of 10-100 K, and four peaks in the temperature region of 160-280 K. Heating rate analysis was achieved to understand the behaviors of trap levels. It was seen that the peak maximum temperatures and TL intensities of all peaks increase with increasing heating rate. This behavior was ascribed to anomalous heating rate effect. T-max - T(exc )analysis was accomplished for TL, peaks at relatively higher temperature region to reveal the related traps depths. T-max - T-exc plot presented a staircase structure indicating that the TL glow curve is composed of well separated glow peaks. Mean activation energies of trapping centers corresponding to these separated peaks were found as 0.43, 0.50, 0.58 and 0.80 eV.Article Citation - WoS: 18Citation - Scopus: 18Quality Changes of Hazelnut Kernels Subjected To Different Cold Plasmas and Gamma Irradiation Treatments(Elsevier, 2019) Onal-Ulusoy, Baran; Sen, Yasin; Mutlu, MehmetIn this study, physicochemical parameters of hazelnuts after atmospheric-pressure (AP:air, 3000 L/h, 655 W, 25 kHz, 1.7 min) and low-pressure (LP:air, 25 Pa, 100 W, 13.56 MHz, 30 min) cold plasmas, and gamma irradiation (GMI:10 kGy, 10 min) treatments, and untreated and treated hazelnuts after accelerated storage for 30 days(60 degrees C) were investigated. All treatments significantly reduced moisture (26-47%), a(w) (16-48%), oil (13-15%), soluble phenolic content (SPC; 26-36%) and total tocopherols (TT; 8-38%) compared to untreated hazelnut (Control-1) while no significant changes determined between treatments and Control-1 in terms of L*a*b*, protein, total sugars (TS) and total phenolic compounds. However, TS of all treatments after storage were significantly increased (3.2-33%) while aw (7-27%) and TT (13-31%) of all treatments were significantly decreased compared to both Control-2 and before storage (p < 0.05). Among treatments, cold plasmas showed great potential for conservation of most tested parameters.Article Citation - WoS: 46Citation - Scopus: 51Multiscale modeling of tempering of AISI H13 hot-work tool steel - Part 1: Prediction of microstructure evolution and coupling with mechanical properties(Elsevier, 2016) Eser, A.; Broeckmann, C.; Simsir, C.In the first part of this two part study, the mechanical properties necessary for the simulation of tempering of an AISI H13 (DIN 1.2344, X40CrMoV5-1) tool steel was derived using physically based precipitation simulations and microstructure-property relationships. For this purpose, the precipitation of fine carbides were simulated using a thermo-kinetic software which allows prediction of the evolution of precipitation/dissolution reactions and the particle sizes. Then, those microstructural findings were coupled with physically based microstructure-property models to predict the yield stress, flow curve and creep properties. The predicted mechanical properties were verified with corresponding experiments and a good agreement was found. In the second part of this study, those properties were coupled with a Finite Element (FE) model in order to predict the relaxation of internal stresses and the evolution of deformations at the macroscopic scale. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 12Citation - Scopus: 11The Relationship Between Different Price Indices: Evidence From Turkey(Elsevier, 2006) Akdi, Y; Berument, H; Cilasun, SMA possible relationship between the Consumer Price Index and the Wholesale Price Index has been analyzed for long and short-run relationships. Conventional Engle and Granger [Estimation Test Econ. 55(1987) 2251-276] and Johansen's [J. Econ. Dyn. Control 12 (1988) 231-254] cointegration tests give mixed evidence for a possible long-run relationship between those two series. The model-free and seasonally robust peri odogram-based test fails to reject the null of no-cointegration relationship. However, these two series move together in the short run. (c) 2005 Elsevier B.V. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 5Absorption Edge and Optical Constants of Tl2ga2< Crystals From Reflection and Transmission, and Ellipsometric Measurements(Elsevier, 2012) Isik, M.; Gasanly, N. M.The optical properties of Tl2Ga2S3Se layered crystalline semiconductors were investigated from transmission, reflection and ellipsometric measurements. The experimental results of the room temperature transmission and reflection measurements performed in the wavelength range of 400-1100 nm showed the presence of both indirect and direct transitions in the band structure of the crystals with 2.38 and 2.62 eV band gap energies. Spectroscopic ellipsometry measurements on Tl2Ga2S3Se crystals were carried out on the layer-plane (0 0 1) surfaces with light polarization E perpendicular to c* in the 1.20-4.70 eV spectral range at room temperature. The real and imaginary parts of the dielectric function as well as refractive and absorption indices were found as a result of analysis of ellipsometric data. The Wemple-DiDomenico single-effective-oscillator model was used to study the dispersion of the refractive index in the below band gap energy range. The structures of critical points have been characterized from the second derivative spectra of the dielectric function. The analysis revealed four interband transition structures with 3.14, 3.40, 3.86 and 4.50 eV critical point energies. (C) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 10Citation - Scopus: 13Numerical Modeling of Visco-Elasto Hygro-Thermal Stresses and the Effects of Operating Conditions on the Mechanical Degradation of Pefc Membranes(Elsevier, 2018) Mehrtash, Mehdi; Tari, Ilker; Yesilyurt, SerhatDurability of membranes is one of the concerns for widespread commercialization of polymer electrolyte fuel cells. Effects of membrane swelling on the durability pose important challenges for the fabrication of the catalyst-coated membrane. This study provides insight into vulnerable locations of the membrane under hygrothermal loading, mechanical loading due to clamping and realistic conditions where a combination of both of these loadings are imposed. With a half rib-channel model, we simulate a polymer electrolyte fuel cell that operates under varying loads and clamping pressure. Model considers anisotropic diffusion in the gas diffusion layer as well as complex interactions of water transport dynamics between gas diffusion layers and the membrane. Mechanical responses of the membrane subject to conjugate hygro-thermo-mechanical loadings during typical scenarios of fuel cell operation reveal the effects of operating parameters as well as individual contributing factors on the development of local stresses in the membrane.Review Citation - WoS: 145Citation - Scopus: 189Challenges and Best Practices in Industry-Academia Collaborations in Software Engineering: a Systematic Literature Review(Elsevier, 2016) Garousi, Vahid; Petersen, Kai; Ozkan, BarisContext: The global software industry and the software engineering (SE) academia are two large communities. However, unfortunately, the level of joint industry-academia collaborations in SE is still relatively very low, compared to the amount of activity in each of the two communities. It seems that the two 'camps' show only limited interest/motivation to collaborate with one other. Many researchers and practitioners have written about the challenges, success patterns (what to do, i.e., how to collaborate) and anti-patterns (what not do do) for industry-academia collaborations. Objective: To identify (a) the challenges to avoid risks to the collaboration by being aware of the challenges, (b) the best practices to provide an inventory of practices (patterns) allowing for an informed choice of practices to use when planning and conducting collaborative projects. Method: A systematic review has been conducted. Synthesis has been done using grounded-theory based coding procedures. Results: Through thematic analysis we identified 10 challenge themes and 17 best practice themes. A key outcome was the inventory of best practices, the most common ones recommended in different contexts were to hold regular workshops and seminars with industry, assure continuous learning from industry and academic sides, ensure management engagement, the need for a champion, basing research on real world problems, showing explicit benefits to the industry partner, be agile during the collaboration, and the co-location of the researcher on the industry side. Conclusion: Given the importance of industry-academia collaboration to conduct research of high practical relevance we provide a synthesis of challenges and best practices, which can be used by researchers and practitioners to make informed decisions on how to structure their collaborations. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 5Forecasting Turkish Local Elections(Elsevier, 2012) Toros, EmreThe literature on political forecasting is large, although the main focus of this literature is limited to a number of countries. Nevertheless, and despite the major differences between political systems, scientific forecasting work has proved to be broadly possible, with noteworthy extensions to new countries. This article extends the literature further by developing a new forecasting model for local elections in Turkey. The basic motivation of this article is to test the usefulness of political forecasting in the contexts of alternative democratic settings. Turkey, in that sense, seems to be an interesting case for a number of reasons. First, the Turkish Republic has been a multi-party democracy since the mid-1940s. Although it has been interrupted by three military coups, the party and election system in Turkey has brought real alternations in the government starting from very early years of the multi-party system. So, it is plausible to argue that Turkish voters have the tradition of evaluating the performances of political parties, as in any other Western-type democracy. That is to say, the dynamics of evaluations of political parties in Turkey follow a similar pattern to other contemporary democracies, being driven by economic and political forces. The main contribution of this analysis is the introduction of an explicit model, which can forecast the impact of economic and political variables across local elections in Turkey by using reliable, public, and macro-level data. In particular, this study offers a new forecasting model which tries to forecast the Justice and Development Party's (Adalet ve Kalkinma Partisi, AKP) vote share in 81 cities. (C) 2012 International Institute of Forecasters. Published by Elsevier B.V. All rights reserved.
