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Article Citation - WoS: 1Citation - Scopus: 1Flame Retarded Plasticized Poly(lactic Acid) Using Phosphorus-Based Additives(Sage Publications Ltd, 2024) Yesil, Sertan; Aytac, Ayse; Selim, FatmaIn this study, the synergistic effect of the flame-retardant additives on the properties of poly(lactic acid) (PLA) was investigated and at the same time, it was tried to increase the toughness of PLA by adding small amounts of phosphate-based additives to plasticized PLA as binary and ternary mixtures. Poly(ethylene glycol) (PEG) was used as a plasticizer. As flame retardant additives, ammonium polyphosphate (APP), tri-phenyl phosphate (TPP), and boron phosphate (BP) were used. Characterization of the composites was carried out by tensile test, impact test, differential scanning calorimetry (DSC), thermal gravimetric analyses (TGA), scanning electron microscopy (SEM), limiting oxygen index (LOI), and UL-94 horizontal burning tests. In addition, TGA-FTIR analyses were carried out to understand the thermal degradation mechanism of composites during combustion. According to the SEM micrographs of the burnt surfaces of the samples, a smooth and flat structure is observed in PLA/PEG/5TPP-5BP sample, while a porous structure and branching formations are observed in other composite samples. Among the composite samples, the best flame retardancy features were observed in the composite containing PLA/PEG/5APP-2.5TPP-2.5BP sample, and the highest impact strength and elongation at break values were obtained in the composite containing PLA/PEG/5APP-5TPP sample.Article Citation - WoS: 36Citation - Scopus: 42Modeling and Analysis of Weighted-k-out-of-n< G System Consisting of Two Different Types of Components(Sage Publications Ltd, 2014) Eryilmaz, Serkan; Sarikaya, KadirThis article is concerned with the reliability analysis of a weighted-k-out-of-n: G system consisting of two types of components. The system is assumed to have n components which are classified into two groups with respect to their weight and reliability, and it is assumed to operate if the total weight of all working components exceeds a prespecified threshold k. The reliability properties of such a system are studied. The optimal values of the number of components in each group are also determined under a minimum required reliability by minimizing the total acquisition cost.Article Citation - WoS: 10Citation - Scopus: 11Consecutive k-out-of-n< Lines With a Change Point(Sage Publications Ltd, 2016) Eryilmaz, SerkanReliability analysis of consecutive k-out-of-n systems and their generalizations has attracted a great deal of attention in the literature. Such systems have been used to model telecommunication networks, oil pipeline systems, vacuum systems in accelerators, spacecraft relay stations, etc. In this paper, nonrecursive closed form equations are presented for the reliability functions and mean time to failure values of consecutive k-out-of-n systems consisting of two types of nonidentical components. The results are illustrated for reliability evaluation of oil pipeline system.Article Citation - WoS: 6Citation - Scopus: 4Latent Dynamics of Movement Formation: the Kurdish Case in Turkey (1940s-1960s)(Sage Publications Ltd, 2015) Ozen, HayriyeThe attention of social movement studies has so far tended to focus on visible phases of movements, neglecting latent ones. This study argues that invisible mobilizations may be critical in preparing the groundwork of public mobilizations, particularly in authoritarian contexts. Using a process-oriented constructivist account of mobilization which incorporates insights from resistance studies, this article analyzes the Kurdish case in Turkey in the authoritarian 1940s and semi-authoritarian 1950s. Based on in-depth interviews, memoirs, newspaper reports, and official documents, it is demonstrated that a latent Kurdish dissent emerged in this period through the constitution of a sense of shared grievance and common identity both in hidden ways within the submerged networks of Kurdish students and professionals, and in public and visible, yet disguised, ways. Incubating the movement out of the gaze of the authorities within the authoritarian context, this latent dissent formed the groundwork of public acts of defiance and mobilization which emerged towards the end of the 1950s as the political changes encouraged Kurdish dissenters to publicly declare their opposition, and expanded in the more liberal context of the 1960s. Resume Les etudes des mouvements sociaux ont eu tendance jusqu'a present a privilegier les phases visibles de ces mouvements, negligeant les stades latents. Cette etude soutient que les mobilisations invisibles peuvent etre essentielles pour preparer le terrain des mobilisations publiques, en particulier dans un contexte autoritaire. En s'appuyant sur une interpretation constructiviste, axee sur le processus de mobilisation et reunissant des idees tirees des etudes des mouvements de resistance, cet article analyse le cas kurde dans la Turquie autoritaire des annees quarante et semi-autoritaire des annees cinquante. Fonde sur des entretiens approfondis, des biographies, des articles de journaux et des documents officiels, ce travail met en evidence l'apparition au cours de cette periode d'une dissidence kurde latente grace a la constitution d'un sentiment partage de mecontentement et d'identite commune au sein des reseaux secrets des etudiants et professionnels kurdes, de facon a la fois invisible et publique, mais dissimulee. Couvant a l'abri des regards des gouvernements autoritaires, cette dissidence latente a pose les bases des manifestations publiques de defiance et de mobilisation qui sont apparues a la fin des annees cinquante a l'occasion des changements politiques ayant encourage les dissidents kurdes a declarer publiquement leur opposition et favorise les mouvements sociaux dans le contexte plus liberal des annees soixante. Resumen La atencion de los estudios sobre movimientos sociales hasta ahora ha tendido a centrarse en las fases visibles de los movimientos, dejando de lado los latentes. Este estudio sostiene que las movilizaciones invisibles pueden ser centrales para la preparacion de las bases de movilizaciones publicas, en particular en contextos autoritarios. A partir de un relato constructivista orientado a los procesos de movilizacion que incorpora perspectivas de estudios de resistencia, este trabajo analiza el caso kurdo en Turquia en la decada autoritaria de 1940 y semi-autoritaria de 1950. Sobre la base de entrevistas en profundidad, memorias, informes de prensa y documentos oficiales, se demuestra que una disidencia kurda latente surgio en este periodo a traves de la constitucion de un sentimiento de agravio compartida y de identidad comun tanto en formas ocultas dentro de las redes sumergidas de estudiantes y profesionales kurdos, asi como de maneras publicos y visibles, aunque disfrazadas. Incubando el movimiento fuera de la mirada de las autoridades en el contexto autoritario, esta disidencia latente formo las bases del acto publico de rebeldia y movilizacion que surgio a finales de la decada de 1950 como los cambios politicos alentados disidentes kurdos para declarar publicamente su oposicion, y ampliado en el contexto mas liberal de la decada de 1960.Article Citation - WoS: 4Citation - Scopus: 6On Profust Reliability of Coherent Systems: Signature-Based Expressions(Sage Publications Ltd, 2013) Eryilmaz, Serkan; Rouyendegh, Babak DaneshvarIn this article we study profust reliability of non-repairable coherent systems through the concept of system signature. We obtain explicit expressions for the profust reliability and mean time to fuzzy failure of coherent systems. We compute and present mean time to failure and mean time to fuzzy failure of all coherent systems with three and four components. Finally, we illustrate the results for a well known class of coherent systems called m-consecutive-k-out-of-n:F.Article Citation - WoS: 7Citation - Scopus: 9Reliability-Based Evaluation of Hybrid Wind-Solar Energy System(Sage Publications Ltd, 2021) Devrim, Yilser; Eryilmaz, SerkanIn this article, a hybrid system that consists of a specified number of wind turbines and solar modules is considered. In particular, the system is modeled using weightedk-out-of-nsystem which is also known as a threshold system in reliability literature. The system under concern consists ofn1identical wind turbines andn2identical solar modules, and each turbine and module can be in one of two states as working or failed. The probability that the entire hybrid system withn=n1+n2components produces power at minimum levelkis computed and evaluated. The importance of single-wind turbine and solar module is also calculated to measure which renewable energy component is more critical and important. Extensive numerical results that are based on real data set are presented to illustrate the model.Article Citation - WoS: 1Citation - Scopus: 1PMMA-Based Electrospun Composite Fibers for Dye Adsorption From Water(Sage Publications Ltd, 2025) Cakar, Ilknur; Yesil, Sertan; Bayram, GoknurPoly (methyl methacrylate) (PMMA) and PMMA/poly (ethylene glycol) (PEG)-based composite fibers were produced using electrospinning technique with two different additives; halloysite nanotubes (HNTs) and boron phosphate (BPO4). The effect of the additives on the morphology, wettability and dye adsorption properties of electrospun fibers were investigated by Scanning Electron Microscopy (SEM), water contact angle measurement and UV-VIS spectrophotometry. The results of SEM analysis indicated that addition of PEG resulted in thinner average fiber diameter and beaded structure. Additionally, it was also observed that incorporating both HNT and BPO4 to the PMMA solution caused increased fiber diameter which might be due to increased solution viscosity. For PMMA fibers containing 3 wt% HNT, the highest average diameter and water contact angle were measured as 2204 +/- 302 nm and 110.29 +/- 3.9 degrees, respectively. The produced fibers were tested for the capability to adsorb methylene blue (MB) and methyl orange (MO) from aqueous solutions. Dye adsorption capacity of the samples increased by addition of HNT and BPO4. According to adsorption capacity results, PMMA/PEG/BPO4 composite sample containing 5 wt% BPO4, with an adsorption capacity of 0.76 mg/g, was determined as adsorbent for kinetic and isotherm studies. The adsorption kinetics were well described by the pseudo-second-order model, and equilibrium data were correlated with the Langmuir model.Article Citation - WoS: 22Citation - Scopus: 24Reliability Analysis of Weighted-K System Consisting of Three-State Components(Sage Publications Ltd, 2019) Eryilmaz, Serkan; Bozbulut, Ali RizaThe reliability of a weighted-k-out-of-n system that consists of three-state components is studied. The system is assumed to comprise n three-state components, namely, perfect functioning, partial working, and complete failure and functions if the total weight of all the working components is at least k. Reliability expressions are presented when the times spent by components in perfect functioning and partial working states are dependent with a given joint distribution. Sufficient conditions are also provided to compare the expected total weights of two systems.Article Citation - WoS: 7Citation - Scopus: 9Reliability of the Two-Unit Priority Standby System Revisited(Sage Publications Ltd, 2022) Eryilmaz, Serkan; Finkelstein, MaximThis paper deals with reliability assessment of the repairable two-unit cold standby system when the first, main unit has the better performance level than the second one. Therefore, after its repair, the main unit is always switched into operation. The new Laplace transform representation for the system's lifetime is obtained for arbitrary operation and repair time distributions of the units. For some particular cases, the Laplace transform of the system is shown to be rational, which enables the use of the matrix-exponential distributions for obtaining relevant reliability indices. The discrete setup of the model is also considered through the corresponding matrix-geometric distributions, which are the discrete analogs of the matrix-exponential distributions.Article Citation - WoS: 8Citation - Scopus: 10Computing Reliability Indices of a Wind Power System Via Markov Chain Modelling of Wind Speed(Sage Publications Ltd, 2024) Eryilmaz, Serkan; Bulanik, Irem; Devrim, YilserStatistical modelling of wind speed is of great importance in the evaluation of wind farm performance and power production. Various models have been proposed in the literature depending on the corresponding time scale. For hourly observed wind speed data, the dependence among successive wind speed values is inevitable. Such a dependence has been well modelled by Markov chains. In this paper, the use of Markov chains for modelling wind speed data is discussed in the context of the previously proposed likelihood ratio test. The main steps for Markov chain based modelling methodology of wind speed are presented and the limiting distribution of the Markov chain is utilized to compute wind speed probabilities. The computational formulas for reliability indices of a wind farm consisting of a specified number of wind turbines are presented through the limiting distribution of a Markov chain. A case study that is based on real data set is also presented.
