TOBB ETU GCRIS Database
Not a member yet
9778 research outputs found
Sort by
Dark Ecology in Industrial Areas: the Case of Turkish Sugar Factories
No full textThe sugar industry is one of the most important representatives of industrialization and modernization in Turkey. Sugar Factories have become the tools of urban and social transformation and developed the regions where they are established. But, over time, the ideologies that formed sugar factories decayed. Such a decay could be caused by reasons such as the lack of adaptation to the changing economic and technological conditions in a short time, the restriction of sugar production with the amendments made to the law, the inability to maintain the continuity of the modern daily life in the campus areas. In this respect, this study is to discuss the dark-depression faced by the sugar industry theoretically within the framework of Timothy Morton’s con- cept of Dark Ecology. This phenomenon is developed from ecological awareness and is dark-depressing. This concept is a way of thinking about future coexistence called Dark Ecology. Sugar factories will become inactive and turn into brownfields as an inevitable end of all industrial areas such as the Ruhr region in Germany and Dock- lands in England. When the day of this inactivity comes, methods of accepting the dark sides of these areas and living with them have to be found. With this discussion, the uncertain future of sugar factories, which are the places of industrialization and modernization, will be approached with the new-dark perspective created by Timo- thy Morton. Thus, it will be possible to contribute to the infrastructure for the future of the areas theoretically
The Number of Diametral Paths in Fibonacci Cubes
No full text[No Abstract Available]This work is partially supported by TUBİTAK under grant no. 120F125 and is a joint work with Elif Saygı and Ömer Eğecioğlu
Classification of Electronic Devices Using a Frequency-Swept Harmonic Radar Approach
No full textA new method to classify electronic devices using a Frequency-Swept Harmonic Radar (FSHR) approach is proposed in this paper. The FSHR approach enables us to utilize the frequency diversity of the harmonic responses of the electronic circuits. Unlike previous studies, a frequency-swept signal with a constant power is transmitted to Electronic Circuits Under Test (ECUTs). The harmonic response to a frequency-swept transmitted signal is found to be distinguishable for different types of ECUTs. Statistical and Fourier features of the harmonic responses are derived for classification. Later, the harmonic characteristics of the ECUTs are depicted in 3D harmonic and feature spaces for classification. Three-dimensional harmonic and feature spaces are composed of the first three harmonics of the re-radiated signal and the statistical or Fourier features, respectively. We extensively evaluate the performance of our novel method through Monte Carlo simulations in the presence of noise
Nanostructured Coatings for Anisotropy and Fano-Like Resonances
No full textOptical Interference Coatings, OIC 2022 -- 19 June 2022 through 24 June 2022 -- -- 182861In this study two topics are presented: i) anisotropic coatings for phase and polarization control and ii) dielectric structures with periodic modulation of optical constants together with the application of angular filtering of light. © 2022 TheAuthor(s)This work received funding from Horizon 2020 ERA.NET-COFUND program project MiLaCo (Project No.S-M-ERA.NET-20–2) under grant agreement with the Research Council of Lithuania (LMTLT), as well as from the European Social Fund (Project No. 09.3.3-LMT-K712–17-0016) under grant agreement with LMTLT
Rediscovering the Teacher’s Voice in Higher Education in the Middle of the Covid-19 Pandemic
No full text[No abstract available
Combined Effects of Bone Morphogenetic Protein-7 and Mineral Trioxide Aggregate on the Proliferation, Migration, and Differentiation of Human Dental Pulp Stem Cells
No full textBioactive molecules present the potential to be used along with biomaterials in vital pulp therapy and regenerative endodontic treatment. Objective: The aim of this study was to assess the effects of the combined use of bone morphogenetic protein-7 (BMP-7) and mineral trioxide aggregate (MTA) on the proliferation, migration, and differentiation of human dental pulp stem cells (DPSCs). Methodology: For the proliferation analysis, DPSCs were incubated with a growth medium and treated with MTA and/or BMP-7 at different concentrations. For the following analyses, DPSCs were incubated with a differentiation medium and treated with MTA and/ or BMP-7. Moreover, there were groups in which DPSCs were incubated with the growth medium (control), the differentiation medium, or DMEM/F12 containing fetal bovine serum, and not treated with MTA or BMP-7. Cell proliferation was analyzed using the WST-1 assay. The odontogenic/osteogenic differentiation was evaluated by immunocytochemistry, alkaline phosphatase (ALP) activity assay, alizarin red staining, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cell migration was evaluated using a wound-healing assay. Data were analyzed using analysis of variance and Tukey test (p=0.05). Results: The use of BMP-7 with MTA presented no significant effect on cell proliferation in comparison with the treatment with MTA alone (p>0.05), but showed higher ALP activity, increased mineralization, and higher expression of DMP1 and DSPP when compared with other groups (p0.05). Nestin expression was higher in the control group than in groups treated with MTA and/or BMP-7 (p0.05). The cell migration rate increased after treatment with MTA when compared with other groups in all periods of time (p0.05). At 72 hours, the wound area was smaller in groups treated with MTA and/ or BMP-7 than in the control group (p0.05). Conclusion: The use of BMP-7 with MTA increased odontogenic/osteogenic differentiation without adversely affecting proliferation and migration of DPSCs. The use of BMP-7 with MTA may improve treatment outcomes by increasing repair and regeneration capacity of DPSCs.Hacettepe University Scientific Research Projects Coordination Unit [THD-2020-18625]The authors declare no conflict of interest related to this study. This study was supported by the Hacettepe University Scientific Research Projects Coordination Unit (THD-2020-18625)
Optimizing the Performance of the Cpw-To Surface Plasmon Polariton Waveguides for 0.3 Thz Band
No full textConference on Terahertz Photonics II Part of SPIE Photonics Europe Conference -- APR 03-MAY 20, 2022 -- ELECTR NETWORKThe competition to suggest high performance solutions for terahertz communication targets 0.22-0.32 THz band because of its bandwidth and attenuation advantages over other terahertz frequencies. However, the state-of-the-art suffers from conventional terahertz waveguide performance. Alternatively, the spoof surface plasmon polariton waveguides (SSPP WGs) measurements achieve the record-low insertion loss per unit length at 0.3 THz. On the other hand, the SSPP WGs require high performance transitions to interface with terahertz active devices such as transistors and diodes. In this paper, we present design, optimization, and experimental verification of high-performance coplanar waveguide-to-SSPP WG (CPW-to-SSPP WG) transitions at 0.25-0.3 THz band. The measurements show that the insertion loss of a CPW to SSPP WG transition can be suppressed up to -0.5 dB at the proposed frequency band.We acknowledge TUBITAK 119E489 for their financial support. We also acknowledge TeraProbes, Inc. and Prof. Kubilay Sertel for their support during measurements.SPIE,IdEx Univ Strasbourg,CNRS,ICube,Univ StrasbourgTUBITAK [119E489
Balistik Çarpmaya Maruz Kalan Seramik ve Kompozit Yapilarin Sonlu Elemanlar Yöntemi Kullanilarak Modellenmesi ve Tasarim Eniyilemesi
No full textArmors are used to protect aircrafts, vehicles, space crafts, structures, and the human body. The main purpose of the armors is to absorb the kinetic energy of the threat by spreading the impact power to wide areas to reduce the damage. The armors are expected to be lightweight while providing a high level of protection. In addition to their high hardness, ceramic and composite materials are lighter than traditional armor materials. Within the scope of this thesis, ceramic body armors and composite aircraft armors are investigated numerically. The finite element models are developed using LS-DYNA software. Then, the developed models are validated with the literature data. Finally, the validated models are used for design optimization to reduce the weight of the armors without sacrificing from safety. In body armors, ceramic materials are used as a front layer to erode and tear up the threat. Alumina is the most widely used ceramic body armor material. To increase the ballistic protection of the alumina ceramic, there are many options, and one of these options is to create surface profiling on the armor plate. By surface profiling, the penetration power of the threat can be reduced by changing the fly direction. In this thesis, the effect of hemispherical surface profiling on alumina ceramic plates with different diameters is investigated numerically. The effect of surface profiling is investigated through the kinetic energy absorption capacity per unit mass. The alumina plate is modeled by the Johnson Holmquist material model and the Smooth Particle Hydrodynamics (SPH) methods. With the SPH method, the cracks and debris formed by ballistic impact can be modeled without any erosion algorithm. To validate the established finite element model, the flat alumina ceramic plate is modeled and compared with the experimental data obtained from the literature. Then, the ballistic performance of the surface profiled ceramic plate is investigated numerically. With the hemisphere surface profiling, the specific kinetic energy absorption capacity is increased by 56%. Composite materials are preferred especially in the field of aviation. The most widely used composite in the aviation industry is carbon fiber/epoxy composite. The epoxy resin is reinforced with unidirectional carbon fibers so that lightweight but high-strength layers are obtained, and the layers are brought together to form a composite plate. In the design of the composite armor, the thicknesses of plies affect the ballistic performance of the plate. It is therefore important to find the optimum layer thickness with a given ply angle. Carbon fiber/epoxy composite is modeled with the enhanced composite damage material model with a medium-scale modeling method, thin shell elements. To validate the carbon fiber/epoxy composite, low-speed impact analyses are performed and the literature data are verified. Then, the optimum carbon fiber/epoxy armor thickness value is found for the composite armor to withstand the ballistic impact of a threat, which is determined by the standards. By using the support vector machining and genetic algorithm, the optimum thickness values are determined for each ply with different ply angles, and a 6.3% reduction in weight is achived.Zırhlar; hava, kara, deniz ve uzay araçlarını, yapıları ve insan vücudunu korumak amacıyla kullanılmaktadır. Zırhların temel amacı, tehdidin kinetik enerjisini soğurmak ve çarpışmanın etkisini geniş bir alana yayarak hasarın azaltılmasını sağlamaktır. Zırhların koruyuculuk seviyelerinin yüksek olmasının yanı sıra hafif olmaları da beklenmektedir. Seramik ve kompozit malzemeler yüksek sertliklerinin yanı sıra geleneksel zırh malzemelerine göre daha hafiftirler, bu sebeple yaygın olarak tercih edilirler. Bu tez kapsamında seramik vücut zırhları ve kompozit uçak zırhları numerik olarak LS-DYNA yazılımı kullanılarak incelenmiştir. Tez kapsamında geliştirilen sonlu elemanlar modellerinin literatür verileri ile doğrulandıktan sonra tasarım eniyilemesi yapılarak zırhların ağırlığının azaltılması hedeflenmiştir. Seramik malzemeler vücut zırhlarında tehdidi aşındırmak, parçalara ayırmak ve ilerleyişini durdurmak amacıyla ön katman olarak kullanılırlar. Seramik vücut zırhı olarak sıklıkla alümina seramiği kullanılmaktadır. Alümina seramiğinin balistik performansını yükseltmek amacıyla yüzey şekillendirmesi yapılabilir. Yüzey şekillendirmesi sayesinde, tehdidin doğrultusu değiştirilerek, tehdidin delme gücü azaltılabilir. Bu tez kapsamında alümina seramik plaka üzerinde farklı çaplara sahip yarım küre yüzey şekillendirmenin etkisi numerik olarak incelenmiştir. Yüzey şekillendirmenin etkisi birim kütle başına kinetik enerji soğurulma kapasitesi karşılaştırılarak yapılmıştır. Alümina plaka Johnson Holmquist malzeme modeli kullanılarak modellenmiştir. Çarpışma anında alümina plakada oluşan çatlak ve molozun modellenebilmesi için interpolasyonlu parçacık hidrodinamiği (İng. smooth particle hydrodynamics (SPH)) yöntemi kullanılmıştır. Kurulan sonlu elemanlar modelinin doğrulanabilmesi için öncelikle düz alümina seramik plaka literatürden elde edilen deneysel veriler ile doğrulanmıştır. Ardından doğrulanmış alümina plakanın yüzeyi şekillendirilerek, yeni tasarımın balistik performansı numerik olarak incelenmiştir. Yarım küre, yüzey şekillendirmesi sayesinde özgül kinetik enerji soğurma kapasitesi %56 oranında artmaktadır. Kompozit malzemeler ise özellikle havacılık alanında tercih edilmektedir. Havacılık alanında en yaygın kullanılan kompozit karbon fiber/epoksi kompozitidir. Epoksi reçinesi tek yönlü karbon fiberleri ile güçlendirilmekte, böylece hafif ancak mukavemeti yüksek katmanlar elde edilmekte ve katmanlar bir araya getirilerek kompozit plaka oluşturulmaktadır. Plaka oluşumu sırasında katmanların fiber açısı plakanın balistik dayanımını etkilemektedir. Bu sebeple her katman açısı için doğru katman kalınlığının bulunması önemlidir. Karbon fiber/epoksi kompoziti LS-DYNA programında, gelişmiş kompozit hasar (İng. enhanced composite damage) malzeme modeli kullanılarak, orta ölçekli bir modelleme yöntemi olan ince kabuk elemanlar ile modellenmiştir. Karbon fiber/epoksi kompozitinin doğrulanabilmesi için öncelikle düşük hızlı çarpışma analizleri yapılarak literatür verileri doğrulanmıştır. Ardından standartlara uygun çarpışma hızına dayanabilecek karbon fiber/epoksi zırh kalınlığı belirlenmiştir. Destek vektör makinesi ve genetik algoritma kullanılarak farklı açılara sahip katmanlar için uygun kalınlık belirlenmiş ve kütlede %6.3 oranında azalma elde edilmiştir
Evaluation of Deep Learning Networks for Predicting Truss Topology Optimization Results
No full textASME 2022 International Mechanical Engineering Congress and Exposition, IMECE 2022 -- 30 October 2022 through 3 November 2022 -- 186577The applicability of artificial neural networks (ANNs) on the prediction of the structural optimization results of a truss structure is investigated. Two different ANN architectures are employed and the effect of using various optimizers and activation functions on their prediction performance is evaluated. Unlike the traditional machine learning network strategies where usually a physical response of the truss optimization (such as compliance, stress, etc.) is predicted, in this study, a new way of prediction is utilized for the truss-like structures; particularly predicting the optimized thickness values of the strut members by the ANNs. Thus, the input data used in these networks are the thickness values of the strut members at a certain initial iteration while the optimized thickness values are predicted as the outputs. A cantilever beam example is presented for the truss optimization to show the efficacy of the presented ANNs. The results indicate that using the thickness values at a certain initial iteration as inputs and final iteration thicknesses as outputs in ANNs are promising for the structural optimization prediction of the presented truss problem with the appropriate selection of the architecture, optimizer, activation function, and the input-output data formation. Copyright © 2022 by ASME
İspanya'da Vatansızlık Sorunu: Romanyalı ve Batı Sahralı Vatansız Çocuklar Vakalarının Analizi
No full textIn a context where the state is the sole provider of individual rights, not being member of any state brings along fundamental human rights violations. It has been studied in social sciences within the concept of statelessness. This thesis conducts a study on Spain which is evaluated very positively in Statelessness Index on the prevention and reduction of the problem. Nevertheless, the study demonstrates that there is actually no holistic resolutionary effort in Spain regarding statelessness. To clarify the ambuigity and its causes, stateless children from Romania and Western Sahara origin were chosen for a within case analysis. Statelessness is directly linked to the regulation of citizenship policies, which necessitates to analyze the citizenship policy-making process. The case comparison gives an opportunity to understand how and why these two policy processes related to the statelessness problem end up with different outcomes. The study shows that two vital components of the Multiple Stream Framework that we use to compare the policy change processes, which known as "Policy Entrepreneur" and "Policy Window" are effective in the formation of different policy outcomes. While in case of Romanian children, these two factors were effective and led the process to success, for Sahrawis the status quo persists due to the lack of people or institutions who will be the advocator of policy-change.Devletin birey haklarının sağlayıcısı olduğu bir ortamda herhangi bir devlete mensup olmamak, temel insan hakları ihlallerini de beraberinde getirir. Bu durum sosyal bilimlerce vatansızlık kavramı ile incelenir. Bu tezde, sorunun önlenmesi ve azaltılması konusunda Vatansızlık Endeksinde yapılan olumlu değerlendirmeler nedeniyle İspanya özelinde bir çalışma yapılmıştır. Çalışmada, İspanya'da aslında vatansızlığa ilişkin kuşatıcı bir çözüm sürecinin işlememiş olduğu tespit edilmiştir. Bu ikilemli durumu anlamak ve açıklamak için, vatansızlık sorunu yaşayan Romanyalı ve Batı Sahralı göçmen çocuklar karşılaştırmalı olarak ele alınmıştır. Vatansızlık, vatandaşlık politikalarında yapılacak düzenlemelerle doğrudan doğruya bağlantılıdır ve vatandaşlık politika yapımı süreçlerini incelemeyi gerekli kılmaktadır. İspanya özelinde karşılaştırmalı olarak incelenen iki vaka, vatansızlık sorununa ilişkin çözüm süreçlerinin nasıl ve neden farklılık gösterdiğini ve farklı sonuçlar ürettiğini anlama imkânı sunmaktadır. Çalışma, vakaların politika değişim süreçlerini karşılaştırmada esas aldığımız Çoklu Akış Teorisinin önemli iki bileşeni olan "Politika Girişimcisi" ve "Politika Penceresi" unsurlarının farklı politika çıktıları oluşmasında etkili olduğunu ortaya koyar. Özetle, Romanyalı çocuklar vakasında iki unsurun etkin olup süreci başarıya götürdüğü; Batı Sahralı göçmen vatansızlar vakasında ise bu iki kavramdan birinin yüklenicisi olacak kişi ya da kurumların eksikliği nedeniyle çözümsüzlüğün devam ettiği görülür