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Layer path updating algorithm based on Voronoi diagrams for material extrusion additive manufacturing
No full textIn Material Extrusion (MEX) types of Additive Manufacturing (AM) technologies, the continuity of the trajectories affects the surface quality of the artifacts manufactured and the time of fabrication. Continuous paths result in lower surface roughness values and lower fabrication times. AM machines employing MEX technologies have the flexibility to fill the interior of objects with regular or irregular patterns to serve various applications. Any of these infill patterns can be modelled with 3D Voronoi diagrams. Therefore, developing a continuous path planning algorithm based on Voronoi diagrams would increase the flexibility of the approach. Accompanied with an encryption method, the proposed approach can represent the motion trajectories of the extruder head in a compact manner, decreasing file sizes representing them. Based on the results of various test cases, the proposed approach improves surface quality, decreases fabrication time and the size of the manufacturing files
Development of the Middle Devonian-Mississippian carbonate platform in Zonguldak Terrane (NW Anatolia, Türkiye) with special emphasis on the Devonian-Carboniferous Boundary
No full textThe Zonguldak Terrane in the northwestern Türkiye is one of the continental micro-plates representing the eastern prolongation of the Variscan belt in Eastern Europe. Its distinguishing feature from the neighboring Variscan terranes (e.g. Istanbul Terrane) is the presence of a well-developed Middle Devonian–Mississippian carbonate platform. This platform carbonate succession, named as Yılanlı Formation, was sampled in detail for conodonts and foraminifera along six measured sections for a better understanding of its geological evolution. In the studied sections, the lowermost limestone bands alternating with green-yellow shales and marls are dated by conodonts to latest Emsian–late Eifelian. This interval is interpreted as the onset of the carbonate platform deposition. The following limestone-shale intercalations yielded an Eifelian–lower Givetian succession, conformably overlain by upper Givetian–? lower middle Frasnian strata. This series is covered by shallow marine, medium to thick-bedded grey limestones with five to twenty cm thick K-bentonite bands. Scarce foraminifera findings only suggest a Late Devonian age. The upper part of this thick-bedded carbonate package with cm-thick black chert bands, which are named as the “transitional D-C beds” as they yielded foraminifera (including the new taxon: Laxoendothyra parakosvensis gracilis subsp. nov.) ranging from latest Famennian to earliest Tournaisian. Upwards the cherty limestones are replaced by cherts and nodular limestones with conodonts of the Siphonodella mehli Zone indicating a change from platform to slope conditions during the early Tournaisian. The following package of dark grey, thick-bedded to massive limestone with conodonts of the Si. isosticha Zone marks the restoration back to shallow platform conditions during the middle Tournaisian, frequently observed in Variscan terranes. The uppermost part of the Yılanlı Formation comprises a thick package of grey to pink nodular limestones alternating with shales and mudstones. The Yılanlı Formation is transitional to the Alacaağzı Formation, which comprises siltstones and plant-bearing sandstones with calcarenite nodules including early Serpukhovian conodonts. This change from carbonate platform to deltaic and fluvial conditions is typical along the Variscan belt and ascribed to the drowning of the Middle Devonian–Mississippian carbonate platform. Biostratigraphic data recovered from the studied sections of the Yılanlı Formation from the Zonguldak Terrane in NW Anatolia suggest that the Yılanlı Formation was deposited during latest Emsian-late Eifelian to late Viséan
Global trends and regime state shifts of lacustrine aquatic vegetation
Get PDFAquatic vegetation (AV) is vital for maintaining the health of lake ecosystems, with submerged aquatic vegetation (SAV) and floating/emergent aquatic vegetation (FEAV) representing clear and shaded states, respectively. However, global SAV and FEAV dynamics are poorly understood due to data scarcity. To address this gap, we developed an innovative AV mapping algorithm and workflow using satellite imagery (1.4 million Landsat images) from 1989 to 2021 and created a global database of AV across 5,587 shallow lakes. Our findings suggest that AV covers 108,186 km2 on average globally, accounting for 28.9% (FEAV, 15.8%; SAV, 13.1%) of the total lake area. Over two decades, we observed a notable transition: SAV decreased by 30.4%, while FEAV increased by 15.6%, leading to a substantial net loss of AV. This global trend indicates a shift from clear to shaded conditions, increasingly progressing toward turbid states dominated by phytoplankton. We found that human-induced eutrophication was the primary driver of change until the early 2010s, after which global warming and rising lake temperatures became the dominant drivers. These trends serve as a warning sign of deteriorating lake health worldwide. With future climate warming and intensified eutrophication, these ongoing trends pose a significant risk of disrupting lake ecosystems
ARDIŞIK DEPREMLER ALTINDA BETONARME ÇERÇEVELİ BİNALARIN DURUMA BAĞLI DEPREM DAVRANIŞLARI
No full textThis study focuses on the seismic damage evolution for reinforced concrete (RC) frame buildings which are subjected to sequential earthquakes. In this study, the most significant sequential earthquakes from different parts of the world are collected from the available strong motion databases. This dataset also includes ground motion records from the recent Kahramanmaraş, Türkiye earthquake sequence that took place in February 2023. The structural modeling is carried out at two different levels of idealization. The first level belongs to a single degree of freedom idealization of RC frame buildings whereas planar frame models have been utilized for the second level. In both cases, the response statistics are obtained through dynamic analyses by employing the developed sequential ground motion dataset, and the evolution of seismic damage is monitored when building models are subjected to multiple earthquakes. The results of this study reveal that sequential earthquakes may create excessive demands on the seismic behavior of RC frame buildings and this issue should be explicitly considered in the seismic design and analysis of structures in the near future.Bu çalışma, ardışık depremlere maruz kalan betonarme çerçeveli binaların yapısal hasar değişimine odaklanmaktadır. Bu tezde, dünyanın farklı bölgelerinde meydana gelmiş olan en etkili ardışık depremler, mevcut yer hareketi veri tabanlarından alınarak bir araya getirilmiştir. Bu veri tabanı, Şubat 2023’te Türkiye Kahramanmaraş’ta meydana gelmiş olan ardışık depremler sırasında elde edilmiş kuvvetli yer hareketi kayıtlarını da içermektedir. Yapısal modelleme iki farklı detaylandırma seviyesinde gerçekleştirilmiştir. İlk seviyede betonarme binalar tek serbestlik dereceli yapılar olarak ele alınırken ikinci seviyede ise 2 boyutlu çerçeve modelleri olarak dikkate alınmıştır. Her iki durumda da, çalışma için derlenmiş olan ardışık deprem veri tabanı ile dinamik analizler gerçekleştirilerek tepki istatistikleri oluşturulmuş ve ardışık depremlere maruz kalan yapılarda görülen hasar değişimi irdelenmiştir. Bu çalışmanın sonuçları, ardışık depremlerin betonarme binalar üzerinde ek talepler oluşturabileceğini ve bu durumun kısa vadede yapıların deprem tasarımı ve analizi açısından kesin olarak değerlendirilmesi gerektiğini ortaya çıkarmaktadır.Ph.D. - Doctoral Progra
PbS çekirdek ve CdSxSe1-x/ZnSe çekirdek/kabuk kuantum noktalarinin yüzey mühendisliğinin optoelektronik özellikleri üzerindeki etkileri
No full textQuantum dots (QDs) are extraordinary materials due to their ease of tuning optical&electronic properties. However, surface defects together with their high surface-to-volume ratio limit their performance in optoelectronics. This study explores defect mitigation strategies for QDs such as PbS, CdS, CdSe, and CdSxSe1−x to enhance their performance parameters in fields such as solar cells and detectors. Additionally, the effects of surface passivation (SP) and heterojunction type on the charge decay characteristics of polymers were investigated. In this study, CdS/PbS bilayer solar cells, where PbS QDs were synthesized and ligand exchanged using conventional techniques, were fabricated. Utilizing electrodeposited CdS as the electron transport layer and doping with carbon QDs resulted in enhanced morphology and reduced defects, achieving an efficiency of 6.79%. In addition, a new direct synthesis-DS protocol was developed for the PbS QDs and photodetectors fabricated with the developed new protocol, achieved detectivities in the range of 11×1012 Jones. Furthermore, a novel in-situ metal halide SP strategy was developed for DS-PbS QDs, and treatment with CdI2 resulted in a promising PCE of 7.92%. Additionally, defect control was achieved by overcoating core QDs with a high bandgap shell material. This approach led to profound effects on the excited state dynamics and antistatic behavior of polymers. Later, alloying approach was used to control composition dependent defects in core and tune the heterojunction type. Finally, the heterojunction type was validated further by studying the charge decay mechanisms of the polymers embedded with alloy core-shell QDs. These advancements highlight the promise of innovative QD architectures and surface passivation in enhancing the efficiency of next-generation optoelectronic devices.Kuantum noktalar (KN), optik ve elektronik özelliklerinin ayarlanabilirliğiyle dikkat çeken malzemelerdir. Ancak bu malzemeler, yüksek alan-hacim oranları nedeniyle yüzey kusurları içerir ve KN´lerin optoelektronik uygulamalarını sınırlandırır. Bu çalışmada, PbS, CdS, CdSe ve CdSxSe1−x KN´lerinin yüzey kusurlarını gidermek ve güneş hücreleri ve fotodedektörler gibi alanlarda verimliliği artırmak hedeflenmiştir. Bu çalışmada, PbS KN´lerinin geleneksel teknikler kullanılarak sentezlenmesiyle CdS/PbS çift katmanlı güneş pilleri üretilmiştir. Elektron iletim tabakası olarak elektrokaplama yöntemiyle elde edilen CdS kullanılması ve bu tabakanın karbon KN´leri ile katkılanması, gelişmiş morfoloji ve azaltılmış kusurlarla sonuçlanmış ve %6,79´luk bir verimlilik elde edilmiştir. Ayrıca, bu çalışma kapsamında PbS KN´leri için yeni bir direkt sentez (DS) protokolü geliştirilmiş olup, bu KN´lerin kullanılmasıyla üretilen fotodedektörler 11×1012 Jones mertebesinde çalışmaktadır. Ek olarak, DS PbS KN'ler için sentez esnasında metal halojenür eklenmesine dayanan yeni bir yüzey pasivasyonu yöntemi geliştirilmiştir ve CdI2 eklenmesiyle edilen KN'ler ile üretilen hücrelerinin %7,92 verime ulaştığı görülmüştür. Ayrıca, yüzey kusurları çekirdek KN'lere yüksek bant aralıklı kabuk malzemeler kaplanmasıyla da kontrol edilmiştir. Bu yaklaşımın, polimer yüzeylerin antistatik davranışları üzerinde belirgin etkilere yol açtığı gözlemlenmiştir. Daha sonra, alaşımlama yaklaşımı çekirdekteki bileşime bağlı kusurları kontrol etmek ve heteroeklem tipini ayarlamak için kullanılmıştır ve alaşım çekirdek-kabuk KN´lerinin heteroeklem tipi, polimer yüzeylerinde oluşan yüklerin davranım mekanizmalarının incelenmesiyle doğrulanmıştır. Bu sonuçlar, yeni nesil optoelektronik cihazlar için yenilikçi KN yüzey pasivasyon yöntemlerinin önemini vurgulamaktadır.M.S. - Master of Scienc
Wage effects of educational mismatch in public and private sectors: evidence from Türkiye
No full textPurpose: Significant changes have been observed in Türkiye labor market over the last two decades, driven by the substantial increase in the number of universities and students and by factors such as economic crises and unemployment. This phenomenon has also affected the number of overeducated (undereducated) wage earners in the labor market. In this study, we first consider compulsory education policy to calculate the educational mismatch. Our aim is to analyze the wage returns of overeducated (undereducated) workers employed in the public and private sectors. The pooled data from the TurkStat Household Labour Force Survey for 2021 and 2022 are used. Design/methodology/approach: Unconditional quantile regression (UQR) was introduced by Firpo et al. (2009). The UQR method has become very popular and is used in several areas, such as labor economics, health economics and public policy, to examine income inequality, discrimination by gender and discrimination by race and others (Agyire et al., 2018; Gaeta et al., 2023). Firpo et al. (2009) used the recentered influence function (RIF) to estimate the outcome equation (wage equation in our case) to obtain UQR estimates. The RIF regresses the influence function (IF) which is developed by Hampel (1974) (Rios-Avila, 2020). Findings: We find that overeducated workers in the Turkish labor market received a wage penalty relative to required educated workers. The returns to years of required education are positive, which means that the returns to each year of required education have higher wages than each year of their overeducated counterparts employed in the same occupation. In the private sector, the effect of the increase in one year of education on wages in the lower percentile is lower than in the public sector for both overeducation, undereducation and required education. Originality/value: An important contribution of our study is the inclusion of the compulsory education policy in the calculation of the educational mismatch in Türkiye. The study uses data from the Household Labour Force Survey (HLFS) covering the period 2021–2022. Previous studies on the wage effects of educational mismatch in Türkiye have typically addressed this issue in the context of conditional wage distribution. However, wages can vary significantly at different points in the distribution. An important advantage of the UQR is its ability to provide comparable coefficient estimates across the wage distribution
Investigation of Variable Taper Angle Design in Highly Tapered Laminates for Delaying Delamination
No full textSpecific requirements in aircraft components may necessitate the use of high taper angles in the thickness transition region of composite laminates, leading to early delamination initiation at the thin side of the taper region. This study demonstrates that nonlinear taper geometries could significantly delay delamination in highly tapered laminates. A method is proposed to define the taper geometry with a single design parameter, and the effectiveness of the proposed variable taper angle design, a nonlinear taper geometry, on delamination is demonstrated. Delamination analysis is performed utilizing cohesive elements by incorporating the compression-induced shear enhancement effect. Finite element model is validated through a comparison of the numerical results with the experimental results of single-stage ply drop-off specimens. This study revealed that by utilizing the variable taper angle design, the thin section delamination can be delayed by reducing the stress concentrations in the taper region. For tapered laminates with the particular multi-stage ply drop-off configuration investigated, the proposed concept provided a 35% increase for GFRP laminates and an 81% increase for CFRP laminates in the delamination onset load with the proper choice of the taper angle increment
Soil amendment leads to shifts in the rhizosphere microbial community and promotes Myriophyllum spicatum growth: a salinized aquatic system mesocosm experiment
No full textThe escalating salinization of lakes and wetlands is reducing the ecological functions of these ecosystems and undermines the survival and diversity of aquatic macrophytes. Although the application of amendments has been shown to efficiently alleviate the salinization of terrestrial ecosystems, their improvement effects on saline aquatic ecosystems are yet to be fully understood. We conducted mesocosms experiment to investigate the effects of three soil amendment treatments—biochar, desulfurized gypsum, and zeolite powder—on saline sediment and the submerged macrophyte Myriophyllum spicatum. The results showed that all three amendments effectively reduced salinity and pH in both the sediment and water column, thereby alleviating salt stress on M. spicatum, decreased the levels of antioxidant enzymes and significantly enhanced the growth of M. spicatum. The biochar treatment showed the most pronounced improvements, with a 34% reduction in sediment salinity and a 46% increase in macrophyte root length. High-throughput sequencing results revealed that the rhizosphere microorganisms in the biochar-amended group had a higher OTU diversity compared to the other groups. LEfSe analysis further revealed that biochar increased the abundance of the key functional microbial groups responsible for organic matter decomposition and the nitrogen and phosphorus cycles, such as Microscillaceae, Promicromonospora, and Arthrobacter. Structural equation modeling analysis suggested that desulfurized gypsum and zeolite powder primarily improved sediment physical properties, while biochar had both a direct effect by promoting macrophyte growth and an indirect effect through water and sediment quality amelioration. Our study provides information on the effectiveness of various soil amendments for habitat improvement in brackish wetlands and offers valuable insights for macrophyte restoration in specific habitats
SIVI KRİSTAL BAZLI NANOPARÇACIK SENSÖRLERİNİN GELİŞTİRİLMESİ
No full textLiquid crystal (LC) exhibits both the flow properties of liquids and long-range orientational ordering of crystalline solids. Since the ordering of LCs can be controlled by the fine scale of energetics, they have remarkable sensitivity. In this study, we used LC to be able to get response to nanomaterials. Firstly, we aimed to examine the interparticle interactions and self-assemblies of nanoparticles by using the confined systems. We used LC droplet as a confined medium and analyzed the interparticle and LC-nanoparticle interactions at LC-aqueous interface by using gold nanoparticles. Then, we developed a method to determine LC configuration within the microwells with shape of circle, square, triangle, rectangle and star. Lastly, we prepared stable, three-dimensional and water insoluble platform for analyzing LC-aqueous interface by using soft-lithography. The LC configuration within microwells was examined under polarized optical microscope, revealing interfacial tilting and defect formation. Sodium dodecyl sulfate (SDS) molecules were used as a model analyte, demonstrating that change in interfacial tilting due to surfactant adsorption. Depending on the interfacial anchoring, metastable configurations having defect structures which were point defects and disclination lines were formed. Also, the response of LC to the adsorption of silica nanoparticles functionalized with silane and dye molecules were studied and found that concentration of dye molecules on the nanoparticle surface, in the range of ppb, could be detected via changes in the tilting at the LC-aqueous interface. These findings suggest a potential for sensor applications, a stable platform was developed for detecting various analytes like molecules or colloids.Sıvı kristaller, hem sıvıların akış özelliklerini ve kristal katıların uzun mesafeli yönsel düzenlerini sergileyen duyarlı malzemelerdir. Sıvı kristallerin oryantasyonu, enerji seviyelerinin kolaylıkla kontrol edilebilmesi sayesinde son derece hassas duyarlılık gösterirler. Bu tez çalışmasında, nanomalzemelere karşı tepki almak amacıyla sıvı kristal kullanılmıştır. Sınırlı sistemler içerisine hapsedilmiş sıvı kristalin konfigürasyonunun tespit edilmesi üzerine yöntem geliştirilerek nanopartiküllerin arasındaki etkileşimlerin ve kendiliğinden oluşturdukları yapıların incelenmesi amaçlanmıştır. Sıvı kristal damlacıkları sınırlama olarak kullanarak, altın nanopartikülleriyle sıvı kristal-su arayüzünde nanopartikül ve sıvı kristal arasındaki etkileşimler analiz edilmiştir. Ardından, daire, kare, üçgen, dikdörtgen ve yıldız şekillerinde mikrokuyularda sıvı kristal konfigürasyonlarını belirlemek için bir yöntem geliştirdik. Son olarak, yumuşak litografi kullanarak sıvı kristal-su arayüzünü analiz etmek için stabil, üç boyutlu ve suya çözünmeyen bir platform hazırlanmıştır. Mikrokuyulardaki sıvı kristal konfigürasyonları polarize optik mikroskop altında incelenerek arayüzdeki eğilme ve defekt oluşumu gözlemlenmiştir. Sodyum dodesil sülfat (SDS) molekülleri, yüzey aktif madde adsorpsiyonuna bağlı olarak arayüzdeki eğilmedeki değişiklikleri gösteren bir model analizörü olarak kullanılmıştır. Arayüz bağlanmasına bağlı olarak, nokta defektleri ve disklinkasyon hatları gibi defekt yapıları içeren metastabil (kararsız) konfigürasyonlar oluşmuştur. Ayrıca, silan ve boya molekülleri ile işlevsel hale getirilmiş silika nanopartiküllerinin adsorpsiyonuna karşı sıvı kristalin tepkisi incelenmiştir ve nanopartikül yüzeyindeki boya moleküllerinin konsantrasyonunun (ppb seviyesinde) sıvı kristal-su arayüzündeki eğilme değişiklikleri ile tespit edilebileceği bulunmuştur. Bu bulgular, sensör uygulamaları için bir potansiyel sunduğunu ve molekül veya kolloidlerin tespiti için stabil bir platform geliştirildiğini göstermektedir.Ph.D. - Doctoral ProgramTÜBİTA
Developmental Bioelectricity as an Explanatory Framework for Cognition and Meaning
Get PDFWe critically examine the intersection of developmental bioelectricity within the context of the Peircean philosophy of science. We address the criticism of Peirce’s objective idealism and synechism, contest the conflation of semiotic and physical laws, and scrutinise Peirce’s recovery of physical from psychological laws. The upshot is a nonmechanistic, nonreductive interpretation of the evolution of cognition in the bioengineering realm. The work of Kull and others is leveraged to demarcate semiotics and physics, emphasising the irreducibility of bioelectric phenomena to mechanistic explanations. Our paper advocates for methodological synechism in evolutionary biology, highlighting the heightened roles of bioelectricity in morphogenesis and basal cognition. We propose the free-energy principle as a unifying arbiter that sets an explanatory pathway toward integrated cognition and meaning in developmental bioelectricity