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Article Citation - WoS: 12Citation - Scopus: 14Numerical 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: 152Citation - Scopus: 194Challenges 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 Robust Divergence-Based Tests of Hypotheses for Simple Step-Stress Accelerated Life-Testing Under Gamma Lifetime Distributions(Elsevier, 2026) Balakrishnan, Narayanaswamy; Jaenada, Maria; Pardo, LeandroMany modern devices are highly reliable, with long lifetimes before their failure. Conducting reliability tests under actual use conditions may require therefore impractically long experimental times to gather sufficient data for developing accurate inference. To address this, Accelerated Life Tests (ALTs) are often used in industrial experiments to induce product degradation and eventual failure more quickly by increasing certain environmental stress factors. Data collected under such increased stress conditions are analyzed, and results are then extrapolated to normal operating conditions. These tests typically involve a small number of devices and so pose significant challenges, such as interval-censoring. As a result, the outcomes are particularly sensitive to outliers in the data. Additionally, a comprehensive analysis requires more than just point estimation; inferential methods such as confidence intervals and hypothesis testing are essential to fully assess the reliability behaviour of the product. This paper presents robust statistical methods based on minimum divergence estimators for analyzing ALT data of highly reliable devices under step-stress conditions and Gamma lifetime distributions. Robust test statistics generalizing the Rao test and divergence-based tests for testing linear null hypothesis are then developed. These hypotheses include in particular tests for the significance of the identified stress factors and for the validity of the assumption of exponential lifetimes.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.Article Citation - WoS: 25Citation - Scopus: 39Optimization and Thermal Analysis of Radial Ventilated Brake Disc To Enhance the Cooling Performance(Elsevier, 2022) Jafari, Rahim; Akyuz, RecepVentilated brake discs are preferable to automobile application because of their higher heat dissipation ability than solid discs. The shape, geometry and number of the cooling fins are interested parameters to be investigated to improve the cooling performance of the discs. In the present study, the optimum design of the brake disc with radial vanes is investigated numerically using the Taguchi design of experiments with taking into account nine design parameters. Finite element method is employed to simulate the detailed airflow and temperature distribution in the disc considering adjoined components as pads, rim, tire and dust shield. It has been found that the ventilation gap width has the highest impact on the brake disc cooling. The cooling time of the disc decreases 21% as the ventilation gap increases from 8 mm to 14 mm. In addition, it reduces about 10% with the increment of the channel width between two adjacent vanes (inverse of vane numbers from 43 to 30) and the twist point from 225 mm to 266 mm. In a decreasing order of importance, fin angle, inner and outer diameters of fin, dust shield, bell link and disc material affect the cooling performance of the ventilated disc.Article Citation - WoS: 20Citation - Scopus: 23A Novel Comfort Temperature Determination Model Based on Psychology of the Participants for Educational Buildings in a Temperate Climate Zone(Elsevier, 2023) Ozbey, Mehmet Furkan; Turhan, CihanMaintaining thermal comfort in the educational buildings is vital due to the impacts on learning effectiveness of students. Therefore, development of a proper comfort temperature in educational buildings is a must. In naturally ventilated and mixed-mode buildings, the adaptive thermal comfort model, which considers additively psychological, and behavioural factors to the Fanger's PMV/PPD model, is commonly applied based on regression analyses. However, the psychological adjustments based on current mood state are very limited in these adaptive thermal comfort models. Therefore, this study focuses on the psychological adjustments in terms of Profile of Mood States in order to predict comfort temperature of students in a case building. The experiments are conducted in a university on a temperate climate zone for a long period-data including both heating and cooling seasons. In this study, the comfort temperatures for each student are determined via Griffith method for the case building. Moreover, the current mood states of students are assessed utilizing the Profile of Mood States survey, which are collected via a developed mobile application. As a conclusion, the relation between the current mood state of the students and comfort temperature are statistically investigated. The results show that a Griffith constant are found as 0.332/K and mean annual comfort temperature is found as 21.32 degrees C in the case building. Additionally, a significant difference is found in the comfort temperatures among the students who have more, or fewer concerns than typically reported. The novelty of the study is to present a comfort temperature determination model which considers human psychology as a starter study in the literature.Article Citation - WoS: 136Citation - Scopus: 148Palladium(0) Nanoparticles Supported on Silica-Coated Cobalt Ferrite: a Highly Active, Magnetically Isolable and Reusable Catalyst for Hydrolytic Dehydrogenation of Ammonia Borane(Elsevier, 2014) Akbayrak, Serdar; Kaya, Murat; Volkan, Murvet; Ozkar, SaimPalladium(0) nanoparticles supported on silica-coated cobalt ferrite (Pd(0)/SiO2-CoFe2O4) were in situ generated during the hydrolysis of ammonia borane, isolated from the reaction solution by using a permanent magnet and characterized by ICP-OES, XRD, TEM, TEM-EDX, XPS and the N-2 adsorption-desorption techniques. All the results reveal that well dispersed palladium(0) nanoparticles were successfully supported on silica coated cobalt ferrite and the resulting Pd(0)/SiO2-CoFe2O4 are highly active, magnetically isolable, and recyclable catalysts in hydrogen generation from the hydrolysis of ammonia borane with an unprecedented turnover frequency (TOF, calculated on the basis of the total amount of Pd) of 254 mol H-2 (mol Pd min)(-1) at 25 +/- 0.1 degrees C. The reusability tests reveal that Pd(0)/SiO2-CoFe2O4 are still active in the subsequent runs of hydrolysis of ammonia borane providing 100% conversion. Pd(0)/SiO2-CoFe2O4 provide the highest catalytic activity with a TOF value of 198 mol H-2 (mol Pd min)(-1) in the 10th use in hydrogen generation from the hydrolysis of ammonia borane as compared to the other palladium catalysts. The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy of the reaction (E-a = 52 +/- 2 kJ/mol) and the effect of catalyst concentration on the rate of hydrolytic dehydrogenation of ammonia borane, respectively. (C) 2013 Elsevier B.V. All rights reserved.Article Regular AdS3 Black Holes From a Regularized Gauss-Bonnet Coupling(Elsevier, 2026) Alkac, Gokhan; Mesta, Murat; Unal, GonulWe obtain a three-dimensional bi-vector-tensor theory of the generalized Proca class by regularizing the Gauss-Bonnet invariant within the Weyl geometry. We show that the theory admits a regular AdS3 black hole solution with primary hairs. Introducing a deformation in the theory, a different regular AdS3 black hole solution is obtained. Charged generalizations of these solutions are given by coupling to Born-Infeld electrodynamics.Article Citation - WoS: 10Citation - Scopus: 9Structural and temperature-tuned band gap energy characteristics of PbMoO4 single crystals(Elsevier, 2022) Isik, M.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.PbMoO4 is one of the member of the molybdate materials and has been a significant research interest due to its photocatalytic and optoelectronic applications. In the present paper, the structural and optical properties of PbMoO4 single crystals grown by Czochralski technique were investigated. X-ray diffraction pattern presented well-defined and intensive peaks associated with tetragonal scheelite structure. Energy dispersive spectroscopy analyses presented the atomic compositional ratio of constituent elements as consistent with chemical formula of PbMoO4. Raman and infrared transmittance spectra were reported to give information about the vibrational characteristics of the compound. Room temperature transmission spectrum was analyzed by derivative spectroscopy technique and band gap energy was found as 3.07 eV. Temperature-tuned band gap energy characteristics of the single crystal were investigated by performing transmission measurements at different temperatures between 10 and 300 K. The analyses indicated that band gap energy of the PbMoO4 single crystal increases to 3.24 eV when the temperature was decreased to 10 K. Temperature-band gap energy dependency was studied considering Varshni and Bose-Einstein models. The successful fitting processes under the light of applied models presented various optical parameters like absolute zero band gap energy, variation rate of band gap with temperature and Debye temperature.Article Citation - WoS: 10Citation - Scopus: 19Effectiveness of Smart Toy Applications in Teaching Children With Intellectual Disability(Elsevier, 2018) Ekin, Cansu C.; Cagiltay, Kursat; Karasu, NecdetPlay is an important element in a child's social and intellectual development and toys are indispensable play tools. This study investigates the effectiveness of smart toys in teaching social studies concepts to children with intellectual disability (ID). A single-subject design is used to identify such effects on teaching social studies concepts to children with ID with the help of smart toys developed within this study. The smart toys are also developed within the scope of present work. Three special education teachers and three children with moderate ID participated in the study, which was carried out in two schools in Turkey. According to the results, smart toys have a positive effect in teaching social studies concepts to children with moderate ID which is significant in development of academic and social skills for individuals with ID.
