OpenMETU (Middle East Technical University)
Not a member yet
110280 research outputs found
Sort by
F VE Cl İÇEREN YENİ KİNOKSALİN TABANLI KONJÜGE POLİMERLERİN ORGANİK GÜNEŞ PİLİ İÇİN SENTEZİ
No full textIn this study, the benzodithiophene-based donor molecules and selenophene π-bridged quinoxaline-based novel acceptor molecules were polymerized by a Stille Cross-coupling reaction to produce nine donor-conjugated polymers. (P1F, P2F, PCL, P1FD2, P2FD2, PClD2, P2FS, PCLS). Six different polymers were synthesized (P1F, P2F, PCl, P1FD2, P2FD2, and PClD2) to produce organic solar cell devices. In addition, the other three polymers (P0F, P2FS, and PClS) were synthesized only to study and compare the optical and electrochemical properties of the polymers. Polymers were characterized by gel permeation chromatography (GPC), thermal gravimetric analysis (TGA), UV-Vis spectrometry, and differential pulse voltammetry (DPV). The optical bandgap (Egopt) values, calculated from the thin-film onset values of the polymers, were determined to be 1.62, 1.70, 1.72, 1.73, 1.76, 1.90, 1.72, 1.74, and 1.97 eV, respectively, in the order of P1F, P2F, PCl, P1FD2, P2FD2, PClD2, P0F, P2FS, and PClS. The HOMO/LUMO energy levels of the polymers were found to be -5.56/-3.87, -5.65/-3.87, -5.86/-3.82, -5.79/-3.91, -5.67/-3.63, -5.84/-3.76, -5.82/-3.78, -5.40/-3.66, and -5.64/-3.64 eV, respectively, in the same order. Devices were constructed using the structure ITO/PEDOT: PSS/Donor: Acceptor/PDINN/Ag, where the active layer consisted of polymers as donor materials blended with fullerene and non-fullerene acceptors. The current-voltage characteristics of the fabricated devices were evaluated using a solar simulator illuminated with AM 1.5G light. The performance of the best devices was recorded as 7.54%, 3.87%, 3.71%, 2.36%, 1.62%, and 1.57% respectively, in the order of polymers used in the active layer: P2F, PCl, P1F, P2FD2, PClD2, and P1FD2.Bu çalışmada, benzoditiyofen bazlı elekron verici moleküller ve selenofen π-köprülü kinoksalin bazlı yeni electron alıcı moleküller, Stille polikondensasyon tepkimesi ile polimerize edilerek dokuz elekron verici konjuge polimer (P1F, P2F, PCL, P1FD2, P2FD2, PClD2, P2FS, PCLS) üretildi. Organik güneş pili cihazlarının üretimi için altı farklı polimer (P1F, P2F, PCl, P1FD2, P2FD2 ve PClD2) sentezlendi. Ayrıca, diğer üç polimer (P0F, P2FS ve PClS) yalnızca polimerlerin optik ve elektrokimyasal özelliklerini incelemek ve karşılaştırmak amacıyla sentezlendi. Polimerler jel geçirgenlik kromatografisi (GPC), termal gravimetrik analiz (TGA), UV-Vis spektrometrisi ve diferansiyel darbe voltametrisi (DPV) ile karakterize edildi. Polimerlerin ince film başlangıç değerlerinden hesaplanan Egopt değerleri sırasıyla P1F, P2F, PCl, P1FD2, P2FD2, PClD2, P0F, P2FS ve PClS sırasıyla 1.62, 1.70, 1.72, 1.73, 1.76, 1.90, 1.72, 1.74 ve 1.97 eV olarak belirlendi. Polimerlerin aynı sırayla HOMO/LUMO enerji seviyeleri -5.56/-3.87, -5.65/-3.87, -5.86/-3.82, -5.79/-3.91, -5.67/-3.63, -5.84/-3.76, -5.82/-3.78, -5.40/-3.66 ve -5.64/-3.64 eV olarak tespit edildi. Cihaz, aktif katmanın fulleren ve fulleren olmayan alıcılarla harmanlanmış donör polimerlerden oluştuğu ITO/PEDOT: PSS/Donör:Akseptör/PDINN/Ag yapısı kullanılarak inşa edildi. Üretilen cihazların akım-gerilim özellikleri, AM 1.5G ışığıyla aydınlatılan bir güneş simülatörü kullanılarak değerlendirildi. Aktif tabakada P2F, PCl, P1F, P2FD2, PClD2 ve P1FD2 polimerleri içeren en iyi cihazların performansı sırasıyla %7,54, %3,87, %3,71, %2,36, %1,62 ve %1,57 olarak kaydedildi.M.S. - Master of ScienceTÜBİTA
Waterbased electrically conductive adhesive for PERC-type shingled solar cells
No full textThis study explores the development of innovative, environmentally friendly water-based electrically conductive adhesives (ECAs) designed specifically for interconnecting shingled passivated emitter rear cell (PERC) solar cells. Formulated with silver (Ag) microflakes and optimized polymeric additives, these adhesives aim to enhance electrical conductivity, adhesion strength, and reliability under real-world operating conditions of solar cells. By reducing reliance on conventional solvent-based adhesives, the water-based ECAs offer significant environmental benefits, including reduced volatile organic compound (VOC) emissions and improved handling safety, aligning with sustainable manufacturing practices. Through systematic experimental analysis and detailed characterization, the water-based adhesives demonstrated a yield stress of 4.8 MPa and a low volume resistivity of 22 μOhm-cm at a film thickness of 25 μm. A 0.4 % increase in power conversion efficiency is obtained compared to commercial counterparts. This efficiency improvement is attributed to the uniform dispersion and stabilization of Ag microflakes within the adhesive matrix, enabled by water-based dispersion techniques. These findings highlight the feasibility and effectiveness of water-based ECAs as a viable interconnection method, providing a balance of high conductivity and eco-friendliness. This research advances sustainable, cost-effective adhesive solutions in photovoltaic technology and beyond, aiding the industry's shift toward cleaner and more efficient solar cell production
Discontinuous Galerkin Solutions of Moving Boundary Problems Using Arbitrary Lagrangian-Eulerian Method on GPUs
No full textFlow problems with moving boundaries and interfaces appear
naturally in many applications, such as turbine flow, flapping flight,
etc. Numerical modeling of these flows poses additional challenges since
the numerical grid moves with time. The arbitrary Lagrangian-Eulerian
method (ALE) is one of the solution strategies for numerically dealing
with moving boundary problems. In this talk, we present an arbitrary
Lagrangian-Eulerian method on GPUs for moving boundary problems and its
implementation to an open-source discontinuous Galerkin library,
libParanumal
Long-term impacts of ocean acidification on the Mediterranean mussel Mytilus galloprovincialis
No full textThis study aims to elucidate the long-term physiological impacts of ocean acidification on a key seafood species. The Mediterranean mussel Mytilus galloprovincialis, was subjected to three pH conditions over a period of six months: two pH values within the present range of natural variability (pHT: 8.10 and 7.80) and a lower pH condition (pHT: 7.50) relevant in the context of near-future ocean acidification. A comprehensive assessment was conducted at the conclusion of the fourth and sixth months and encompassed a suite of physiological endpoints, including mortality, oxygen consumption, clearance rate, total haemocyte count (THC), nutritional content analysis, and polonium-210 (210Po) depuration rates. The findings revealed a marked decrease in survival rates at pH 7.50 compared with those at pH 8.10 and 7.80 after six months of exposure. This was associated with a significant increase in THC and a decrease in lipid content. No significant pH effects were observed for other endpoints (namely clearance rate, condition index, oxygen consumption rate, protein and carbohydrate contents, and 210Po). While the lack of response to low pH at some of these physiological endpoints may be a consequence of a lack of statistical power, our data clearly demonstrate the effects of low pH on the survival, THC, and lipid content of M. galloprovincialis. Such effects on a species’ overall fitness have the potential to negatively impact this key seafood species, associated ecosystems, and the socioeconomic dynamics of communities depending on this resource
Devlet Tiyatrosu Yapılarının Koruma Yönetimi : Ankara’daki Küçük Tiyatro Örneği
No full textToday, loss of many qualified twentieth century theater buildings and the scarcity of studies on their conservation indicates necessity for researches on this topic. Theater buildings as cultural icons, reflect various architectural, social and historical value that contribute to national identity and collective memory. However, many are under danger for function loss and destruction due to urban transformation, changing cultural habits, challenges as economic constraints, legal gaps, administrative complexities.
Preserving performing art buildings with conservation management plans(CMP) offers sustainable, long term and participatory approach for complex problems of these buildings. The Australia ICOMOS Burra Charter(2013) provide a recognized framework to management approaches, emphasizing conservation of cultural significance, stakeholder engagement and adaptability to change.
State Theaters of Türkiye, with its deep-roots, policies and widespread permanent stages, stands as a prominent art institution of Republic, while Ankara as capital city, has an important role in Türkiye’s cultural and artistic development and host significant theater space.Their cultural and historical significance makes them the study area together with Küçük Tiyatro in Ankara.On building scale, Küçük Tiyatro is selected as it is the first permanent stage of the State Theaters , representing pivotal role in modernization of culture and community and theater’s institutionalization.
In thesis it is aimed to develop a conservation management approach in building scale, over selected case - State Theaters building Küçük Tiyatro, that adhere the guidelines of Australia ICOMOS Burra Charter and propose a framework for national conservation laws and conservation of theatre buildings of State Theaters and performance&culture buildings inTürkiye context.Bugün, birçok nitelikli 20. yüzyıl tiyatro yapısının kaybı ve bu binaların korunması için yapılan çalışmaların azlığı, bu konuda yapılacak araştırmaların gerekliliğini göstermektedir. Bu kapsamda tiyatro yapıları, önemli kültürel simgeler olarak ulusal kimlik ve kollektif hafızaya katkıda bulunan birçok mimari, sosyal ve tarihi değeri yansıtmaktadır. Ancak bu yapılar, kentsel dönüşüm, değişen kültürel alışkanlıklar, ekonomik kısıtlar, yasal yetersizlikler ve yönetimsel zorluklar nedeniyle işlevini kaybetme veya yıkılma tehlikesiyle karşı karşıyadır.
Performans yapılarının koruma yönetim planlarıyla korunması, yapıların karşı karşıya olduğu kompleks sorunlara sürdürülebilir, uzun vadeli ve katılımcı bir koruma yaklaşımı sunmaktadır. Burra Tüzüğü (2013), yerin kültürel önemi, katılımcı koruma ve değişime adapte olma konusunda çizdiği çerçeve ile koruma yönetiminde kabul görmüş bir belge olarak karşımıza çıkar.
Devlet Tiyatroları, sahip olduğu derin kökler, sanat politikaları ve yaygın kalıcı sahneleri ile Cumhuriyetin en önemli sanat kurumlarından biri olarak öne çıkmaktadır. Ankara ise başkent olarak Türkiye’nin sanatsal ve kültürel gelişiminde kritik bir role sahip olup, önemli pek çok yapıya ev sahipliği yapmaktadır. Küçük Tiyatro, Türkiye’de Devlet Tiyatroları’nın ilk sürekli sahnesi olarak, tiyatronun kurumsallaşmasında, toplumun ve kültürün modernleşmesinde önemli bir yere sahiptir. Tez kapsamında Ankara, Devlet tiyatroları ve yapı ölçeğinde Küçük Tiyatro çalışma alanı olarak belirlenmiştir.
Bu çalışmayla, Burra Tüzüğü dikkate alınarak, Devlet Tiyatroları sahnelerinden Küçük Tiyatro örneği üzerinden tek yapı ölçeğinde bir koruma yönetimi yaklaşımı geliştirmek ve sonuç olarak ulusal koruma yasalarıyla, Devlet Tiyatrosu yapıları ile Türkiye’deki diğer performans ve kültür yapılarının korunması konusundaki yaklaşımların geliştirilmesi için bir çerçeve sunmak hedeflenmiştir.Ph.D. - Doctoral Progra
Marmara Denizi bentik foraminiferleri: dağılım, ekoloji ve biyotik indisler olarak önemi
No full textSea of Marmara (SoM), connecting the Black Sea and Mediterranean Sea, has a stratified water column with a strong pycnocline at ~25-40 m depth with limited mixing. As a result, the top layer is oxygenated, but in depth the dissolved oxygen values drop drastically and produce suboxic or anoxic conditions in bottom waters. This layered structure of the water column directly translates into the benthic foraminifera (BF) communities with Ammonia and Elphidium dominated shallow assemblages (<40 m), Cassidulina laevigata dominated deeper assemblages (40-150 m) and Bolivina spathulata, Bolivina vadescens and Paracassidulina minuta dominated deepest assemblages. This study quantitatively documented the BF assemblages from 18 stations (short sediment cores) from the SoM, presenting a comprehensive systematic taxonomy (of 172 identified taxa) and high-quality illustrations. With integration of the previously published quantitative BF data, this study generated the geographic distributions of BF assemblages and the relationship of BF communities with environmental variables. The changes in BF assemblages in the vertical dimension were investigated by the study of 15 sediment cores. Depositional history of the core from the Karamürsel Basin was documented in this way, and the establishment of sulfidic bottom water in the basin was linked to the 1999 earthquake with the abundance of Virgulinella fragilis. The quantitative data set was applied to assess the utility and applicability of four quantitative foraminiferal biotic indices: %P*, morphotype classification, BFOI and Foram-AMBI. In conclusion, this study forms a basis for future monitoring and taxonomic studies by documenting the present configuration in the SoM.Karadeniz ve Akdeniz’i birbirine bağlayan Marmara Denizi (MD) ~25-40 m derinlikteki piknoklin ile ayrılan, karışımın sınırlı olduğu bir tabakalı su kolonuna sahiptir. Sonuç olarak üst su tabakası oksijence zengin olmasına rağmen, alt su tabakasında oksijen bolluğu ciddi miktarda düşerek derin dip sularında suboksik veya anoksik ortamlar oluşturur. Su kolonunun bu tabakalı yapısı sayesinde sığ ortamlarda Ammonia ve Elphidium cinslerince zengin (<40 m), daha derinlerde Cassidulina laevigata türünce zengin (40-150 m), en derin ortamlarda ise Bolivina spathulata, Bolivina vadescens ve Paracassidulina minuta türlerince zengin olan bentik foraminifer (BF) toplulukları bulunur. Bu çalışma Marmara Denizinden alınmış 18 örnekteki (kısa sediman karotları) BF topluluklarını sayısal olarak belgelemekte, tanımlanmış 172 adet BF taksonu için kapsamlı bir sistematik taksonomi ve kaliteli görseller sunmaktadır. Daha önce Marmara Denizinden yayınlanmış sayısal BF verisi kullanılarak BF topluluklarının coğrafi dağılımları ve ortamsal değişkenlerle ilişkileri belirlenmiştir. 15 karotun çalışılması ile BF topluluklarının düşeydeki değişimleri de araştırılmıştır. Bu şekilde, Karamürsel Havzasındaki karotun çökelim geçmişi belirlenmiş, Virgulinella fragilis türünün bolluğu ile karakterize olan sülfidik dip suyu ortamının oluşumunun 1999 depremi ile ilişkisi ortaya konmuştur. Oluşturulan sayısal veri seti ile dört sayısal foraminiferal biyotik indisin, %P*, morfotip sınıflandırması, BFOI ve ForamAMBI, kullanışlılığı ve uygulanabilirliği test edilmiştir. Sonuç olarak bu çalışma, güncel durumu ortaya koyarak gelecek izleme ve taksonomik çalışmalarına zemin oluşturmaktadır.Ph.D. - Doctoral ProgramÇDAP-309-2021-1069
Fixated flue gas desulfurization scrubber sludge-ground granulated blast-furnace slag blends as one-part sustainable binders
No full textThis study investigates the performance of one-part sustainable binders composed of fixated flue gas desulfurization scrubber sludge (FSS) and medium-quality ground granulated blast furnace slag (BFS), both of which are underutilized industrial by-products. FSS, an inexpensive and sustainable sulfate source, enhances the reactivity of medium-quality BFS, enabling the development of 100 % waste-based binders without the need for chemical activators or thermal treatment. The inherent alkalinity and rich composition of calcium, silicon, aluminum, and sulfur in FSS effectively compensate for the shortcomings of medium-quality BFS, particularly its low early reactivity. Blending BFS with FSS yielded higher pH levels, shorter setting times, and significantly improved long-term compressive strengths. Blends with over 50 wt% FSS achieved 90-day compressive strengths of 50–55 MPa, compared to only 6 MPa for BFS-only mixes, although higher FSS contents reduced early age strength and water stability. Microstructural analysis using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) revealed ettringite and C-S-H/C-A-S-H as the primary hydration products. Thermal exposure tests revelated a decrease in strength due to the decomposition of these phases. The synergistic utilization of these underused waste materials enhanced their potential for reuse and supports a circular economy in the construction industry
A comprehensive mathematical modeling study for temperature evolution during radio frequency assisted honey decrystallization
No full textIn industrial settings, honey decrystallization is conducted by conventional thermal processing with hot water (12–18 h) or air (24–36 h) at around 60 °C. Considering the demands for a green and sustainable efficient process, a novel approach is needed. Radio frequency (RF) heating is a dielectric process where volumetric heat generation within the sample is expected. Designing such a process requires the knowledge of temperature evolution within the product. Hence, the objective of this study was to develop a mathematical model to determine the temperature evolution of crystallized honey during RF processing and compare the results with conventional approach to demonstrate the efficiency. For this purpose, a computational model was developed to determine the temperature evolution in a crystallized honey during RF and conventional hot water processing. Natural convection effects were also included within the model to see whether there will be any improving effect despite the higher viscosity. Decrystallization kinetics was also coupled with temperature evolution to observe the process efficiency. The results indicated the efficiency of RF heating as an innovative processing approach for decrystallization while the natural convection effects were not significant
Accretion, evaporation and superradiance phase diagram of (primordial) black holes and 10−21 − 1021 eV scalar, vector, tensor fields
No full textWe obtain the accretion, evaporation and superradiance phase diagram of astrophysical and primordial black holes in the mass range 10−33−1011M⊙. This black hole mass range corresponds to production of 10−21−1021 eV particles for superradiance (bosons) and evaporation (bosons and fermions). Only accretion and superradiance processes are relevant for heavy black holes, on the other hand for light black holes of primordial origin, all three processes can be relevant. We find that superradiance instability can happen even for black hole spin values as low as 10−9−10−2. Since light black holes are very unstable to these perturbations and sensitive probes of bosonic particles, a single moderately spinning BH can probe 2-9 orders of magnitude of mass parameter space depending on the nature of the perturbations that are scalar (axion), vector (dark photon and/or photon with effective mass) and spin-2. If spinning black holes are observed and superradiance is not observed, possibly due to self-interactions, we find limits on the axion/scalar decay constant and energy density. We generalize these bounds for vector and spin-2 fields
NEOLİBERAL ÖZNE VE KAMUSALLIK: TÜRKİYE’DE ORTA DÜZEY PROFESYONELLER ÖRNEĞİ
No full textThis thesis seeks to explore "neoliberal subjectivation" and barriers and possibilities toward the collective action and public engagement under neoliberal capitalism. The existing literature on the "neoliberal subject" often promotes the idea of "de-democratization," suggesting the emergence of economized individuals who behave and think as homo economicus in all areas of life. This kind of subject is argued to replaces the politically conscious citizens. This view is contested through a case study from Turkey, which has undergone neoliberal transformation in tandem with the West since the 1980s. The study focuses on forty professionals from Turkey’s two largest cities in terms of the private sector employment. They are selected for their relevance to the “human capital” theory. Through in-depth interviews, they were asked about their realities and strategies in the neoliberal context, as well as their attitudes toward collective action and public engagement. The research findings reveal that the economized behaviors of these individuals are not driven by the discourse of neoliberal subjectivity or human capital theory but by the imperatives of neoliberalism, which manifest in the production level, administration level, accumulation level, and political level. This thesis asserts that neoliberal subjectivity does not represent preferences or perspectives of individuals; instead, it reflects their limits. Therefore, subjects in the neoliberal period should not be degraded to being a mere functional component of neoliberalism, but should be addressed by taking into account the contradictions arising from their position within neoliberal capitalism and their public tendencies shaped by common material experiences.Bu tez, "neoliberal özneleşme"yi ve neoliberal kapitalizm koşullarında kolektif eylem ve kamusallığa dair engel ve olanakları incelemeyi amaçlamaktadır. "Neoliberal özne" üzerine mevcut literatür, "demokratiksizleşme" tezini savunmakta, tüm yaşam alanlarında homo economicus olarak davranan ve düşünen, ekonomikleşmiş bireylerin ortaya çıktığını, bu bireylerin siyasal bilince sahip vatandaşların yerini aldığını öne sürmektedir. Bu görüş, 1980'lerden bu yana Batı ile paralel bir neoliberal dönüşüm yaşayan Türkiye'den bir vaka çalışmasıyla sorgulanmaktadır. Çalışma, Türkiye’nin özel sektör istihdamı açısından en büyük iki şehrinden “insan sermayesi” teorisiyle ilişkili oldukları düşünülen kırk orta düzey profesyonel ile gerçekleştirilmiştir. Derinlemesine görüşmeler yoluyla, görüşmecilere neoliberal bağlamdaki gerçeklikleri, stratejileri ve kolektif eylem ile kamusallığa yönelik tutumları sorulmuştur. Araştırma bulguları, bu bireylerin ekonomikleşmiş davranışlarının neoliberal öznellik ya da beşerî sermaye teorisine dair söylem tarafından değil, neoliberalizmin üretim düzeyinde, yönetim düzeyinde, birikim düzeyinde ve siyasi düzeyde sebep olduğu zorunlulukları tarafından belirlendiğini ortaya koymaktadır. Bu tez, neoliberal öznelliğin bireylerin tercihlerini veya ufuklarını yansıtmadığını; daha ziyade, onların sınırlarını teşkil ettiğini savunmaktadır. Bu nedenle, neoliberal dönemde özneler yalnızca neoliberalizmin işlevsel bir parçası olmaya indirgenmemeli, neoliberal kapitalizm içindeki konumlarından kaynaklanan çelişkileri ve ortak maddi deneyimler üzerinden şekillenen kamusal eğilimleri de göz önünde bulundurularak ele alınmalıdır.Ph.D. - Doctoral Progra