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Shear Strength Prediction of Fiber Reinforced Concrete Beam-Column Joints
No full textIn this analytical study, an experimental database of 184 FRC beam-column joints that underwent joint shear failure with or without yielding of longitudinal beam or column reinforcement is compiled. Pearson Correlation Analyses are performed to determine the key parameters affecting joint shear strength. Composite tensile strength, column axial load ratio, joint shear reinforcement ratio, fiber reinforcing index, and geometric dimensions are observed to be the most influential parameters. A parametric joint shear strength prediction equation is then developed by nonlinear regression analyses. Comparison of predicted strengths with experimental results and existing equations demonstrates the improved accuracy of the proposed equation
Mikro şekillendirmenin kristal plastisiteye dayalı bünye modeli geliştirilerek incelenmesi
No full textThe deformation behavior of materials changes significantly when their size is reduced to the micro-scale. Therefore, the traditional knowledge obtained from macroscale forming may no longer be sufficient for accurate analysis of microforming processes. To address this, a dislocation density based crystal plasticity constitutive model is proposed to investigate size effects on micro-scale deformation. The proposed model can also predict the effects of slip-rate gradients using a simplified approach that does not require higher-order stresses or additional balance equations, unlike conventional gradient theories. To incorporate the slip-rate gradient effect, the minimal gradient-enhanced hardening law is employed. A distinct approach for calculating geometrically necessary dislocation (GND) and statistically stored dislocation (SSD) densities is developed and incorporated into the hardening law. The constitutive model is implemented into a commercial finite element code through user subroutines. Electron Backscatter Diffraction (EBSD) data is obtained before and after the tensile test of
a copper sample. In this way, it is possible to identify the grain orientations before and after experiments in terms of Euler angles. Furthermore, GND density analysis is conducted based on the EBSD data. The copper sample is analyzed using the developed constitutive model and the predictions are found to be in good agreement with the experimental data. Moreover, the developed approach is applied to investigate the effects of the thickness-to-grain diameter ratio (t/d) and grain orientation on deformation behavior by using two copper foils with different t/d ratios. Consequently, the proposed size-dependent model accurately captures the effect of microstructural characteristics.Malzemelerin deformasyon altında davranışı, boyutları mikron ölçeğine indirildiğinde önemli ölçüde değişmektedir. Bu nedenle, makro ölçekli şekillendirme süreçlerinden elde edilen geleneksel bilgi birikimi, mikro ölçekli şekillendirme işlemlerinin doğru bir şekilde analiz edilmesi için yetersiz kalabilmektedir. Bu sorunu ele almak amacıyla, mikro ölçekli deformasyon üzerindeki boyut etkisini incelemek üzere, dislokasyon yoğunluğuna dayalı bir kristal plastisite bünye modeli önerilmiştir. Önerilen model, geleneksel gradyan teorilerinin aksine, daha yüksek dereceli gerilmeler veya ek denge denklemleri gerektirmeyen basitleştirilmiş bir yaklaşım kullanarak kayma hızı gradyanlarının etkilerini de tahmin edebilmektedir. Kayma hızı gradyan etkisini dahil etmek için minimum gradyanla geliştirilmiş sertleşme yasası kullanılmıştır. Geometrik olarak gerekli dislokasyon (GND) ve istatistiksel olarak depolanmış dislokasyon (SSD) yoğunluklarını hesaplamak için farklı bir yaklaşım geliştirilmiş ve sertleşme yasasına dahil edilmiştir. Geliştirilen model, kullanıcı alt programları aracılığıyla ticari bir sonlu elemanlar yazılımına entegre edilmiş. Bakır numunenin çekme testi öncesinde ve sonrasında Elektron Geri Saçılım Kırınımı (EBSD) verileri elde edilmiştir. Bu sayede, deneyler öncesi ve sonrası tanelerin yönelimleri Euler açıları cinsinden belirlenebilmektedir. Ayrıca, EBSD verilerine dayalı olarak GND yoğunluğu analizi gerçekleştirilmiştir. Bakır numune geliştirilen model ile analiz edilmiş ve elde edilen tahminlerin deneysel verilerle iyi bir uyum sağladığı görülmüştür. Ek olarak, geliştirilen model, iki bakır folyo kullanılarak t/d oranının ve tane yöneliminin deformasyon davranışı üzerindeki etkisini incelemek için kullanılmıştır. Sonuç olarak, önerilen boyuta bağlı model, mikro yapısal özelliklerin etkisini doğru bir şekilde yakalamıştır.Ph.D. - Doctoral Progra
Damage detection in aircraft engine borescope inspection using deep learning
No full textAircraft engine inspection is a key pillar of aviation safety as it helps to maintain adequate performance standards to ensure engine airworthiness. In addition, it is also vital for asset value retention. Borescope inspection is currently the most widely used visual inspection method for aircraft engines. However, borescope inspection is a time-consuming, subjective, and complex process that heavily depends on the experience and attention level of the inspector. Moreover, the cost savings of airlines and the maintenance, repair, and overhaul (MRO) centers expose pressure and workload on inspectors. These factors make an automated system to support damage detection during borescope inspection necessary in order to mitigate potential risks. In this paper, we propose a deep learning-based automated damage detection framework that employs aircraft engine borescope inspection images. Faster R-CNN-based deep learning model with Inception v2 feature extractor is utilized for the present architecture. Due to the limited number of images, data augmentation and other overfitting methods are also employed. The framework supports crack, burn, nick, and dent damage types across all modules of turbofan engines. It is trained and validated with moderate to complex borescope images obtained from the field. The framework achieves 92.64% accuracy for crack, 92.05% for nick or dent, and 81.14% for burn damage classes, with an overall 88.61% average accuracy
Kentsel dönüşümün iklimsel eş-faydaları: Ankara’da üç örnek alan incelemesi
No full textClimate change, one of the most significant global crises of the 21st century, impacts cities through cause-and-effect relationships. Since a large share of the world’s population lives in cities, dense urban development, high levels of energy and resource consumption, as well as transportation and infrastructure systems, both contribute to climate change and are among the primary areas affected by it. Therefore, cities must address climate change mitigation and adaptation holistically. In this context, the climate co-benefits approach allows cities to simultaneously adapt to climate crises and reduce greenhouse gas emissions, creating mutually reinforcing effects. However, in global literature, these two strategies are often addressed separately, and the co-benefits approach is not sufficiently implemented. Specifically, urban regeneration in Türkiye is driven by a construction-based economic development approach that remains disconnected from sustainability and environmental goals. To close this gap, this study assesses the capacity of regeneration to generate climate co-benefits at different spatial scales and through various applications, aiming to establish this approach within a solid theoretical, methodological, and practical framework. The study selected a sample of urban regeneration practices that accelerated after 2000 and analyzed their potential to produce co-benefits, evaluating both direct and indirect climate advantages. Accordingly, indicator sets and assessment tools for co-benefit-oriented interventions are proposed. Ultimately, the study seeks to reevaluate Türkiye 's urban regeneration practices through the lens of climate co-benefits and to provide both theoretical and practical recommendations that support integrating spatial interventions at various scales into climate policies. In this way, the thesis makes a meaningful contribution to the literature on urban climate policies in developing countries.21. yüzyılın en önemli küresel krizlerinden biri olan iklim değişikliği hem sebep hem de sonuç ilişkileri açısından kentleri etkilemektedir. Dünya nüfusunun büyük bir bölümünün kentlerde yaşaması nedeniyle yoğun kentsel yapılaşma, yüksek enerji ve kaynak tüketimi, ulaşım ve altyapı sistemleri iklim değişikliğine katkıda bulunmakta ve iklim değişikliğinden etkilenen alanların başında gelmektedir. Bu nedenle kentlerin rolü, iklim değişikliğini azaltan ve uyum sağlayan hedefleri bütüncül olarak ele almaktır. Bu bağlamda, iklim eş-faydaları yaklaşımı, kentlerde eş zamanlı iklim krizlerine uyum ve sera gazı emisyonlarının azaltımı stratejilerini ve bu stratejilerin birbirini destekleyici etkiler yaratmasını sağlamaktadır. Ancak küresel literatürde, bu iki stratejinin çoğunlukla ayrı ele alındığı, eş-fayda yaklaşımının yeterince hayata geçirilmediği görülmektedir. Özellikle, Türkiye’deki kentsel dönüşüm uygulamaları inşaat sektörüne dayalı ekonomik kalkınma anlayışıyla yürütülmekte ve sürdürülebilirlik ve çevresel hedeflerden uzak kalmaktadır. Bu çalışma, söz konusu boşluğu doldurmak amacıyla dönüşüm projelerinin iklim eş-fayda üretme kapasitesini farklı mekânsal ölçeklerde, çeşitlenen uygulamalarla değerlendirmekte ve bu yaklaşımı kuramsal, yöntemsel ve uygulamalı bir çerçeveye oturmayı hedeflemektedir. Çalışmada, 2000 sonrası hızlanan kentsel dönüşüm pratiklerinden örneklem seçilmiş; bu projeler üzerinden eş-fayda potansiyelleri analiz edilerek doğrudan ve dolaylı iklim faydaları değerlendirilmiştir. Böylece, eş-fayda odaklı müdahale türleri için gösterge setleri ve değerlendirme araçları önerilmektedir. Sonuç olarak çalışma, iklim eş-fayda konsepti üzerinden Türkiye’nin kentsel dönüşüm pratiklerini yeniden düşünmeyi ve farklı ölçeklerdeki mekânsal müdahaleleri iklim politikalarıyla bütünleştirme hedeflerine katkı sağlayacak kuramsal ve uygulamaya dönük öneriler sunmayı amaçlamaktadır. Bu yönüyle tez, gelişmekte olan ülkelerdeki kentsel iklim politikaları literatürüne teorik, yöntemsel ve pratik düzeyde önemli bir katkı sunmaktadır.Ph.D. - Doctoral Progra
Instability and information production around Kerr black holes: effects on entropy and the shadow
No full textMassless or massive particles in unstable orbits around a Kerr black hole exhibit exponentially unstable motion when perturbed. They either plunge into the black hole or escape to infinity after making some oscillations around the equatorial plane. This exponentially unstable motion causes information production. In the case of the photons that escape to infinity, it was recently suggested that this information can be used to resolve the subring structure of the shadow image and obtain more precise data about the black hole mass and spin (Johnson et al. in Sci Adv 6(12):eaaz1310, 2020). Here, we extend this method to obtain more precise results by including the non-equatorial contributions to the Lyapunov exponents. For massive particles plunging into the Kerr black hole, we show that the associated Kolmogorov-Sinai entropy derived from the Lyapunov exponents can be interpreted in the context of black hole thermodynamics and obeys Bekenstein's bound on the entropy of a physical system. Thus, the perturbed unstable orbits, either ending inside the black hole or at the observer's screen, have physical consequences
Sally Rooney's Inclusiveness in Beautiful World Where Are You?
No full textSally Rooney is engaged in an inclusive worldmaking by creating a textual space for diversecharacters and genres. Contemporary Irish women’s writing yields a direct interest in the post-millennial global agenda in the post-Celtic Tiger period steering its attention to post-millennialconcerns like people’s well-being, the soul-destroying effects of consumerism, capitalism, andthe planet's future. In Rooney’s tertiary novel Beautiful World the four characters, thoughhaving different backgrounds, lifestyles, and beliefs, are in pursuit of making sense of life intheir unique ways. The ability to devise a genuine way of holding onto life, being one of theoldest issues raised on the planet, is of interest to Alice disfiguring the importance of fame andwealth as a writer, of Eileen a language editor of a magazine seeking alternative ways to attachherself to a meaningful life by gauging giving birth to a baby, of Simon taking refuge in theperformativity of religion and of Felix a worker at a warehouse trying his hand in singing andbisexual affairs. The novel achieves inclusiveness not only with these various characters’experiences but also by conflating the zeitgeist of the post-millennial spirit with social mediaapps like Tinder or WhatsApp. The experience of these flawed characters is variegated andRooney’s novel promotes inclusiveness by building inextricable generic relations. Taxonomicalways of handling genres might be disaffecting. Still, the book can be seen in the light of a genrefiction due to following some common tropes, an auto-fiction due to Alice and Rooney’s similarconcerns about being a well-known aut
