Person: ÇİFTÇİOĞLU, GÖKÇEN ALEV
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ÇİFTÇİOĞLU
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GÖKÇEN ALEV
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Publication Open Access A bibliometric analysis on ircular economy of packaging(2023-08-01) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Tunçok-Çeşme B., Yıldız-Geyhan E., Çiftçioğlu G. A.Publication Metadata only Life cycle assessment of power generation alternatives for a stand-alone mobile house(PERGAMON-ELSEVIER SCIENCE LTD, 2013) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Sevencan, Suat; Ciftcioglu, Gokcen A.This paper presents comparative life cycle assessment of nine different hybrid power generation solutions that meet the energy demand of a prototypical mobile home. In these nine solutions, photovoltaic panels and a wind turbine are used as the main energy source. Fuel cell and diesel generator are utilized as backup systems. Batteries, compressed H-2, and H-2 in metal hydrides are employed as backup energy storage. The findings of the study shows that renewable energy sources, although they are carbon-free, are not as environmentally friendly as may generally be thought. The comparative findings of this study indicate that a hybrid system with a wind turbine as a main power source and a diesel engine as backup power system is the most environmentally sound solution among the alternatives. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only Environmental analysis of different packaging waste collection systems for Istanbul - Turkey case study(ELSEVIER, 2016) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yildiz-Geyhan, Eren; Yilcan-Ciftci, Gulsah; Altun-Ciftcioglu, Gokcen Alev; Kadirgan, Mehmet Arif NesetSource-separated collection of recyclable packaging wastes has been a huge issue for cities such as Istanbul considering their socially, economically, culturally and environmentally cosmopolite structure. In order to apply an environmentally effective separation and collection, system has to be analyzed with a holistic approach including whole recycled packaging material amounts, source consumptions and related emissions. In this context, the aim of this study is to determine the environmentally optimum source-separated packaging waste collection system applicable in Istanbul, Turkey for the first time in literature. Eight scenarios for separated collection system were defined and all of them were compared with each other and with the existing system. To measure the efficiency of the system, some efficiency indicators were chosen and effectiveness related variables were determined to predict the participation rate. Calculations of the efficiency indicators for alternative scenarios were based on the existing system. The environmental analysis was conducted by using Life Cycle Assessment methodology. The results of this study showed that existing system was still one of the environmentally most promising scenarios. Following advantageous scenarios were Scenarios 5 and 6 which were two and three fractionated curbside collection systems, respectively. It is also seen that more fractionated scenarios were less beneficial than two fractionated scenarios. And finally, it can be concluded that with an increment on participation rate and changing collection material type, collection efficiency of curbside system would increase and be environmentally more beneficial. (C) 2015 Elsevier B.V. All rights reserved.Publication Metadata only Stochastic Modeling and Simulation of Photopolymerization Process(WILEY-BLACKWELL, 2011) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Altun-Ciftcioglu, Gokcen A.; Ersoy-Mericboyu, Aysegul; Henderson, Clifford L.In this study, the effect of photoinitiator concentration on the gelation time of different resins were studied in the absence of oxygen in the reaction volume by using passive microrheology technique. Four different monomers which are ethoxylated pentaerythritol tetraacrylate (SR494), trimethylolpropane triacrylate (SR351), Methylene glycol diacrylate (SR272), and 2(2-ethoxyetoxy) ethyl acrylate (SR256) were used in these experiments. Resins were prepared from these four different monomers by mixing them with various amount of 2,2-dimethoxy 1,2-diphenylethanone photoinitiator molecule with high absorption coefficient at the frequency of UV light used in these experiment. The simulations of the results obtained from microrheology experiments were carried out with the new model based on the stochastic Monte Carlo approach in order to account for the inherently random and discrete nature of the photopolymerization reactions. The model captures the nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer. POLYM. ENG. SCI., 51:1710-1719, 2011. (C) 2011 Society of Plastics EngineersPublication Metadata only Focal point analysis of torsional isomers of acrylic acid(TAYLOR & FRANCIS LTD, 2010) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Ciftcioglu, Gokcen Alev; Trindle, Carl; Yavuz, IlhanThe thermochemistry of acrylic acid has presented challenges owing to its high reactivity, tendency to dimerize in the gas phase, and the existence of two very nearly equal energy conformational isomers. Well-tested thermochemical schemes including G2, G3, G4, and CBS-QB3 agree in the prediction that the s-cis syn structure is the most stable of the torsional isomers, with the s-cis anti form lying 3 kJ mol-1 or less higher in energy. Microwave spectra suggest a value of 0.63 kJ mol-1. The energy barrier between these forms is in the neighbourhood of 25 kJ mol-1 according to a MP2/cc-pVDZ calculation. We present estimates of the relative energies of all four torsional isomers and the rotational barrier based on a variant of the Focal Point Analysis developed by Csaszar and co-workers. These calculations, extending to the CCSD(T)/cc-pV5Z level, predict that the s-cis anti torsional isomer is the most stable form, in contrast to prior estimates. The s-cis syn form lies about 2.9 kJ mol-1 higher, while the s-trans syn and anti forms lie at about 21.7 and 23.3 kJ mol-1, respectively. We estimate the rotational barrier between the s-cis trans and s-cis anti structures to be about 23.9 kJ mol-1. Error ranges derived from the fit to extrapolation forms suggest that our estimates have an uncertainty of about 0.1 kJ mol-1.Publication Open Access Smart agriculture through using cost-effective and high-efficiency solar drying(ELSEVIER SCI LTD, 2020-02) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Ciftcioglu, G. A.; Kadirgan, F.; Kadirgan, M. A. N.; Kaynak, G.Background: Challenges must be handled in an integrated manner when addressing food security and climate change. More efficient designs for food production systems, as well as their logistics, are needed in order to increase food production and to reduce emissions intensity. Specifically, any enhancements done on this purpose would contribute to mitigating climate change. Five important dimensions are being considered in smart agriculture: food security, availability, accessibility, utilization, and stability. Scope and approach: Food supply-demand chain can seriously be effected by uncontrolled population growth. Thus, any perspective to solve these uncontrolled conditions can have a positive impact. Especially giving emphasis on reduction of food losses via expoloring various ways of production, or increasing productivity, or ensuring food security are effective ways for solutions. For example, the use of solar drying for agricultural, marine or meat products is very important for preservation, thus minimizing food losses. However, traditional sun drying is a relatively slow process. Also, the product quality worsens due to several factors: microorganism growth, enzymatic reactions, insect infestations. It is known that utilizing solar energy involves several factors that need attention. Thus, a lot of effort is directed toward improving solar energy technology for drying processes. Key findings and conclusion: This study presents a smart agriculture design for drying using low cost and highly-efficient solar selective absorber. The system is based on an air heating flat plate solar absorber. Levelized cost of heat (LCOH) for the prototype using solar renewable energy is calculated and compared with the fossil fuel energy sources; natural gas, electricity, and liquified petroleum gas (LPG). In addition; a comparison of the costs for air collectors using various selective absorbers; unglazed or glazed, is presented. It is shown that solar energy, in the long run, will be more advantageous compared to fossil fuels.Publication Open Access Human factors analysis by classifying chemical accidents into operations(2023-05-01) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yalçın E., Çiftçioğlu G. A., Güzel D. H. B.In the chemical industry, organizational and operational human factors significantly contribute to accidents. Chemical accidents occur in various operations of the industry due to a range of factors. Understanding the relationship between these factors and the accidents that happen is crucial in preventing similar accidents from happening repeatedly and promoting sustainability. Therefore, this study was divided into five operations: maintenance repair, process, loading unloading, storage, and shutdown startup of the chemical industry, to provide a more concrete, intuitive explanation of the interplay between causes and illustrate the routes to failure. The data were collected from 251 accident reports from various online data. The study was analyzed using the Human Factors Analysis and Classification System (HFACS) method as a conceptual framework. Each level’s frequency variables were obtained to define nominal and ordinal data. The chi-square test and Fisher’s exact test were used in the difference analysis of data in the model. The results show that the high-frequency accidents caused under the HFACS framework were organizational processes in the process (63.73%), in the storage (70.58%), and in the shutdown startup (91.66%), and skill-based errors in the maintenance repair (81.81%) and in the loading unloading (66.03%). Furthermore, resource management, technological environment, and personal readiness were significantly correlated with the operations. Human factors have differences in different operations in the chemical industry.Publication Metadata only Simulation of Models for Multifunctional Photopolymerization Kinetics(WILEY-BLACKWELL, 2014) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Altun-Ciftcioglu, Gokcen A.; Ersoy-Mericboyu, Aysegul; Henderson, Clifford L.In this study, two different models of photopolymerization of multifunctional monomers are developed. The first is a kinetic model and is based on first order nonlinear ordinary differential equations describing the rates of photoinitiator, monomer, and live and dead radicals of different chain lengths. In the second model, a stochastic Monte Carlo approach is used to predict the time evolution of the photopolymerization process. In this model the chain affects are incorporated both in the propagation and termination rate constants. The simulations of these models for the predictions of gelation times are compared with the experimental values measured in the absence of oxygen in the reaction volume by using passive microrheology technique. The nonlinear decrease of gelation time with increasing photoinitator concentration and number of acrylate fragments on each monomer is best captured with the second model. Furthermore, the second model is successfully verified with kinetic data generated from FTIR and DSC experiments. (C) 2013 Society of Plastics EngineersPublication Open Access Comparison of Conventional and Modified Burners in Performance with Different Fuels using a Linear and a Non-linear Eddy-viscosity Turbulence Model(ISFAHAN UNIV TECHNOLOGY, 2019-11-01) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yangaz, M. U.; Ciftcioglu, G. A.; Kadirgan, M. A. N.Energy sources must be used efficiently to provide the sufficient amount of energy for the still-growing population in the world, already threatened by the effects of global warming. The significant increase in the use of natural resources causes serious problems due to its unsustainable situation. Therefore, exhaust gases/emissions must be reduced to prevent more damage on the environment. This study aims to provide solutions for a sustainable ecosystem by lowering emissions such as CO, unburnt HC, NOx, and enhancing the combustion efficiency in a certain type/scale industrial burner. In that way, some geometric modifications (on furnace design and the connected burner) have been applied on the conventional type burners to benefit the effects of preheating of combustion air. Modified geometries have been analyzed numerically and compared with the conventional design's results. Moreover, the comparison between a linear and non-linear turbulence model has been given in terms of simulation results. Major findings indicate that Burner-1 has significantly lower emissions compared to the others. Preheating effect coupled with the flue gas recirculation (FGR) seems to work well in terms of performance and emissions. Also, a significant difference between linear and non-linear turbulence model appeared on the emission characteristics for the same simulations.Publication Open Access Kimya Endüstrilerinde Patlama ve Yangınların Önlenmesi ve İlgili Vaka Çalışması(2019-03-31) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Ufuk MEVLEVİOĞLU;M.A. Neşet KADIRGAN;GÖKÇEN ALEV ÇİFTÇİOĞLUBu çalışmada, iş yerlerinde karşılaşılabilen patlama ve yangın risklerini değerlendirmek ve bu risklere karşı alınabilecek önlemleri belirlemek için Türkiye’nin ulusal mevzuatı ve TSE standartlarında belirtilen yöntemler incelenmekte ve hayali bir kimya tesisine uygulanmaktadır. Hayali tesisteki solvent tankı ve solvent pompası için yapılan değerlendirmede, tank içerisinin “Bölge 0” patlayıcı ortam olarak sınıflandırılabileceği, pompa etrafında ise çeşitli mühendislik yaklaşımlarıyla farklı patlayıcı ortam değerlendirmeleri yapılabileceği sonuçlarına varılmıştır. Ayrıca hayali tesisteki polimer toz besleme hunisi için yapılan değerlendirmede, huni içerisinin “Bölge 20” patlayıcı ortam olarak sınıflandırılabileceği, huni etrafında oluşabilecek patlayıcı ortamın tehlike mesafesinin ise, ilgili standartta verilen nitel yöntemlere dayanarak tahmini olarak yapılabileceği gösterilmiştir. Sınıflandırılmış olan bu tehlikeli bölgelerin dahilinde kullanılabilecek cihazların kategorileri ve diğer özellikleri belirlenmiş, bu bölgelerde patlama ve yangınlara karşı alınabilecek önlemlere çeşitli örnekler verilmiştir. Sonuç olarak kimya endüstrisinde sıkça rastlanabilecek tanklar, pompalar, solventler vb. etkenlerle ilgili deneysel veriler üretilmesine ve yanıcı tozlarla ilgili standart testleri yapabilecek akredite laboratuvarlara ihtiyaç duyulduğu vurgulanmıştır.
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