TOBB ETU GCRIS Database
Not a member yet
9778 research outputs found
Sort by
Effects of Nonunique Residual Traction on the Non-Repeatability of the Dynamics of Jointed Structures
No full textThe tangential friction force of a permanently sticking contact (referred to as residual traction) can have an arbitrary (nonunique) value within the limits defined by the Coulomb cone. However, the actual value of residual traction is unknown due to its dependence on the load history. This uncertainty can introduce significant variability, ranging from 20 to 300 percent, in the level of resonant vibration, as observed in experiments of structures with friction dampers. In this study, we systematically investigate, for the first time, the influence of nonunique residual traction on the vibration response variability of a system with bolted joints. The selected benchmark consists of an L-shaped beam and a cross beam (stiffener) connected by two joints. The joints are aligned under 90-degree angle, establishing a structural coupling between the tangential and normal directions of the contacts. Both experimental and numerical analyses are conducted to assess the effects in detail. In the experimental phase, phase-locked-loop testing is employed to measure the amplitude-dependent modal parameters. On the computational side, the structure is modelled using commercial finite element software, and quasi-static modal analysis is employed. The results show to what extent the nonuniqueness of residual traction contributes to the non-repeatability of the vibration response and the accuracy of the correlation between experiments and numerical analyses
Heat Treatment Conditions for High-Performance High-Pressure Die-Cast Al–si–cu–mg Alloy
No full textRandom porosity in high-pressure die castings of aluminum alloys poses additional challenges in the form of blistering during follow-on heat treatment process. To avoid blisters, the current industrial practice is to lower solution temperature, but this compromises the strength. Herein, kinetics of eutectic Si spheroidization and coarsening during various solution treatment conditions and maximizing the dissolution of much needed Al2Cu and Al5Cu2Mg8Si6 phases, followed by formation of their precipitates in the aging stage with higher particle number densities, are studied and then higher tensile strength of 435 MPa in most commonly used high-pressure die-cast Al–Si–Cu–Mg alloy without causing blisters is demonstrated. © 2023 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH.The Future Liquid Metal Engineering Research Hub, (EP/N007638/1); Engineering and Physical Sciences Research Council, EPSRC; Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, TÜBİTAK, (2219
Seri Üretim Termal Görüntüleme Sistemlerinde Kalibrasyon–tabanlı Düzensizlik Giderme Metotlarının Elektro–optik Performansa Etkisi
No full textPlanck'in siyah cisim ışıması kanununa göre, mutlak sıcaklığı 0 Kelvin üzerinde olan tüm cisimler elektromanyetik ışıma yapmaktadır. Termal görüntüleme sistemleri, cisimlerin sıcaklıklarından dolayı kızılötesi dalga boyunda yaptıkları ışımaların anlamlandırılabildiği ve günümüzde askeri, medikal, sivil vb. birçok alanlarda çeşitli uygulamalarda yaygın olarak kullanılan sistemlerdir. Kızılötesi odak düzlem dizileri, çok sayıda kızılötesi dedektörün iki boyutlu bir dizgi halinde oluşturduğu ve termal görüntüleme sistemlerinde sahneden gelen kızılötesi ışımanın kuyudolum seviyesi adı verilen dijital sinyallere dönüştürüldüğü görüntüleme sensörüdür. Kızılötesi odak düzlem dizilerinden elde edilen ham kuyudolum seviyeleri üzerinde; kızılötesi dedektörlerin tam anlamıyla özdeş olmaması, optik birimlerdeki kusurlar, ışımanın odak düzleminde homojen dağılmayışı ve çevresel koşulların etkisi gibi nedenlerden kaynaklı bir takım istenmeyen etkiler bulunmaktadır. Bu etkilerden bir veya birkaçı bir araya gelerek dedektörlerin tepkiselliklerinin kızılötesi ışıma karşısında değişkenlik göstermesine yol açmakta ve kızılötesi odak düzlem dizisinden elde edilen ham kuyudolum seviyelerinde düzensizlik etkisi oluşturmaktadır. İdeal şartlarda kızılötesi odak düzlem dizisi tekdüze bir ışıma kaynağı karşısında vi konumlandırıldığında yine tekdüze kuyudolum seviyeleri elde edilmesi beklenirken, elde edilen ham kuyudolum seviyeleri düzensizlik etkisinden dolayı direkt olarak kullanıma uygun değildir. Termal görüntüleme sistemlerinin fonksiyonlarını düzgün bir şekilde yerine getirebilmesi için kızılötesi dedektörlerin tepkisellikleri, dinamik aralık üzerinde belirli noktalarda düzensizlik giderme metotları ile tekdüze tepkiselliğe kalibre edilebilmektedir. Düzensizlik giderme sonrası termal görüntüleme sisteminin tekdüze ışıma kaynağı karşısındaki elektro–optik performansı, kuyudolum seviyelerinin tekdüzelikten ne derece değişkenlik gösterdiğinin ölçütü olan kalıntı düzensizlik ile ifade edilmektedir. Termal görüntüleme sistemleri geliştirilirken uygulanacak olan düzensizlik giderme yöntemi, sınırlı sayıda prototipin tekdüze ışıma sağlayan siyah cisim ışıyıcı karşısındaki tepkisellik karakteristiği göz önünde bulundurularak belirlenir. Ne var ki, seri üretim aşamasında üretilen prototip sayısı arttıkça prototiplerin siyah cisim ışıyıcı karşısındaki tepkisellik ve hassasiyetleri birbirlerinden farklılık göstermeye başlamaktadır. Oluşan bu farklılık, tek bir sebepten kaynaklanmayıp birden çok etkinin bir araya gelmesiyle oluşabilmekle birlikte; optik, elektro–optik ve elektronik birimlerin üretim toleransları ve daha birçok etkiden dolayı gerçek anlamda özdeş olmamaları bu farklılığa sebep olabilecek sebeplerinden sadece bir tanesidir. Seri üretim prototipleri arasında oluşan bu tepkisellik ve hassasiyet farklılıkları, düzensizlik gidermenin uygulanma yöntemine bağlı olarak prototiplerin dinamik aralıkta farklı noktalarda kalibre edilmesine ve kızılötesi ışıma karşısında aynı karakterde olmamasına yol açabilmektedir. Bu tezde, 2018 yılından bu yana seri üretimi devam eden bir termal görüntüleme sisteminin, 123 adet seri üretim prototipinden elde edilen ham kuyudolum seviyelerinin dinamik aralık boyunca ne derece değişkenlik gösterdiği incelenecek ve bu ham kuyudolum seviyeleri kullanılarak farklı düzensizlik giderme metotlarının farklı uygulama yöntemleri elektro–optik performanslarına göre kıyaslanacaktır. Elde edilen sonuçlar göz önünde bulundurularak seri üretim prototiplerinde tepkisellik ve hassasiyet değişkenliğine rağmen dinamik aralıkta aynı noktalarda düzensizlik giderme uygulayarak prototiplerin elektro–optik karakteristiğinin aynı olmasını sağlayacak ve üretilebilirliği arttıracak otomatik bir karakterizasyon ve kalibrasyon düzeneği sunulacaktır.According to Planck's law of black body radiation, all objects with absolute temperature above 0 Kelvin emit electromagnetic radiation. Radiations emitted from objects in infrared wavelength can be interpreted by thermal imaging systems. Thus, thermal imaging systems are widely used in various applications across many fields such as military, medical, civilian, etc. Infrared focal plane arrays are the imaging sensors in thermal imaging systems that consists of a large number of infrared detectors arranged in a two–dimensional array and they convert the infrared radiation coming from scene into digital signals also known as wellfill levels. Due to several factors —including bot not limited to infrared detectors not being identical, defects in the coatings and alignment of optical units, the inhomogeneous distribution of incoming radiation onto the focal plane, environmental conditions— there exist some unwanted effects on the raw well–fill levels obtained by infrared focal plane arrays. When one or several of these effects are combined, they lead to a variance in the detectors' responsivity against infrared radiation, causing a non–uniformity effect on the raw well–fill levels obtained by the infrared focal plane array. Ideally, when an infrared focal plane array is positioned against a uniform radiation source, uniform viii well–fill levels would be expected across the detector array. However, the raw well–fill levels are not directly usable due to the non–uniformity effect. The responsivities of infrared detectors can be calibrated to uniform responsivities at specific points across the dynamic range using non–uniformity correction methods, in order for thermal imaging systems to function properly. The electro–optical performance of a thermal imaging system, with non–uniformity correction applied, can be indicated by residual non–uniformity. This measures the variance of well–fill levels from a uniform response when exposed to a uniform radiation source. The way of applying a non–uniformity correction method in thermal imaging systems is determined during the development phase, by taking into account the responsivity characteristics of a limited number of prototypes against a black body radiator that provides uniform radiation. Nevertheless, as the number of prototypes increases during the serial production phase, the responsivity and sensitivity of the prototypes against the black body radiator start to vary from one another. This variation may be caused by not just a single isolated source, but by multiple combined effects. These include, but are not limited to, the fact that subsystems such as optical, electro–optical, and electronic units are not exactly identical, due to manufacturing tolerances among many other reasons. The variance in responsivity and sensitivity among serial production prototypes may lead to them being calibrated at different points across the dynamic range and exhibiting different characteristics against infrared radiation, depending on the application procedure of non–uniformity correction methods. In this thesis, the raw well–fill data taken from 123 prototypes of a thermal imaging system that is in serial production since 2018 will be examined in terms of how they differs from one another across dynamic range and by using these well–fill data, different applications of different non–uniformity methods will be compared in terms of electro–optical performances. As a result, an automatic characterization and calibration setup that increases manufacturability will be presented which will apply non–uniformity correction on same points across dynamic range to thermal imaging system prototypes despite the responsivity and the sensitivity variances
Push and Pull Factors of Why Medical Students Want to Leave Turkiye: A Countrywide Multicenter Study
No full textSunter, Ahmet TeVfik/0000-0002-7264-9760; Picakciefe, Metin/0000-0002-2877-7714; Yavuz, Melike/0000-0001-9037-6770; Erdal, Deniz/0000-0001-7721-0653; Yildirim Ozturk, Elif Nur/0000-0003-1447-9756; Thomas, David Terence/0000-0002-8278-5934; Uygun, Tunahan/0000-0003-3560-2514; Yilmaz, Sinan/0000-0001-7784-3274; Dogan, Edanur/0000-0002-0728-3408; Citil, Riza/0000-0002-7198-0195; Durmus, Hasan/0000-0001-5719-1475; Torun, Sebahat Dilek/0000-0001-9139-9325; Eser, Erhan/0000-0002-2514-0056; Bulut, Irem/0000-0002-6954-7886; Sen Gundogan, Efruz/0000-0003-0308-0256; Kurt, Burak/0000-0002-8185-2146; Dede, Bahadir/0000-0003-3985-5973;Phenomenon: Physician immigration from other countries is increasing as developed countries continue to be desirable destinations for physicians; however, the determinants of Turkish physicians' migration decisions are still unclear. Despite its wide coverage in the media and among physicians in T ; uuml;rkiye, and being the subject of much debate, there is insufficient data to justify this attention. With this study, we aimed to investigate the tendency of senior medical students in T ; uuml;rkiye to pursue their professional careers abroad and its related factors. Approach: This cross-sectional study involved 9881 senior medical students from 39 different medical schools in T ; uuml;rkiye in 2022. Besides participants' migration decision, we evaluated the push and pull factors related to working, social environment and lifestyle in T ; uuml;rkiye and abroad, medical school education inadequacy, and personal insufficiencies, as well as the socioeconomic variables that may affect the decision to migrate abroad. The analyses were carried out with a participation rate of at least 50%. Findings: Of the medical students, 70.7% had emigration intentions. Approximately 60% of those want to stay abroad permanently, and 61.5% of them took initiatives such as learning a foreign language abroad (54.5%) and taking relevant exams (18.9%). Those who wanted to work in the field of Research ; Development were 1.37 (95% CI: 1.22-1.54) times more likely to emigrate. The push factor that was related to emigration intention was the "working conditions in the country" (OR: 1.89, 95% CI: 1.56-2.28) whereas the "social environment/lifestyle abroad" was the mere pull factor for the tendency of emigration (OR: 1.73, 95% CI: 1.45-2.06). In addition, the quality problem in medical schools also had a significant impact on students' decisions (OR: 2.20, 95% CI: 1.83-2.65). Insights: Although the percentage of those who want to emigrate "definitely" was at the same level as in the other developing countries, the tendency to migrate "permanently" was higher in T ; uuml;rkiye. Improving working conditions in the country and increasing the quality of medical faculties seem vital in preventing the migration of physicians
A Nonlinear Filbert-Like Matrix With Three Free Parameters: From Linearity To Nonlinearity
No full textFilbert and Lilbert matrices are defined by terms of linear Fibonacci-like sequences. By considering terms of such linear recurrences and additional free parameters, we define a nonlinear variant of these matrices via ratios of q-forms of terms of Fibonacci-like sequences whose indices are in nonlinear forms. We derive explicit formulae for the matrices L and U come from LU-decomposition, their inverses, inverse of the main matrices and their determinants
Iıı. Selim Döneminde Nizam Kavramının Dönüşümü
No full textBu çalışma ile III. Selim döneminde nizam kavramının dönüşümü incelenmiştir. Böylelikle, nizam kavramı üzerinden III. Selim döneminin siyasi düşünce yapısı anlaşılmaya çalışılmıştır. Bu amaçla öncelikle III. Selim'den önce kavramın hangi anlamlarda kullanıldığına değinilmiş ve Nizam-ı Cedid programını tanıtmak, savunmak veya programın eksik yönlerine işaret etmek üzere yazılan metinlerden yararlanılmıştır. Yeniliğin nasıl meşrulaştırıldığı ve nizam kavramının dönüşümünün neyi gösterdiği sorgulanmaktadır. Bu amaçla kavram tarihi metodundan faydalanılmıştır.This study examines the transformation of the concept of nizam (order) in the period of Selim III. As such, it seeks to understand the political thought of the the period of Selim III through the concept of nizam. For this purpose, first of all, it refers to the connotations of the concept Selim III, and makes use of the texts written to introduce, defend, or point out the shortcomings of the Nizam-ı Cedid program. The thesis questions how innovation is legitimized and what the transformation of the concept of order indicates. For this purpose, it benefits from the conceptual history method
Infrastructure for Exploring SIMT Architecture in General-Purpose Processors
No full textSingle-Instruction Multiple-Thread (SIMT) computing has enabled a revolution in graphics, high-performance computing, and artificial intelligence. However, despite its benefits in these domains, SIMT processing has been relegated to accelerators rather than becoming a feature of general-purpose computing. Although a number of recent works have explored the potential benefits of "GPSIMT," current research infrastructures to study high performance general-purpose CPUs provide no support for the SIMT architecture and its programming model. This work presents our initial efforts toward developing a full-system GPSIMT research infrastructure. We first describe how we extend the QEMU emulator with SIMT features, enabling ISA pathfinding for GPSIMT hardware and providing a platform for the rapid development of system software for GPSIMT. We then present our approach to leveraging the Chipyard hardware generation framework to develop a full-system GPSIMT exploration platform on an FPGA by extending the RISC-V Rocket Core
The Crime Effect of Refugees
No full textWe analyze the impact on crime of millions of refugees who entered and stayed in Turkey as a result of the civil war in Syria. Using a novel administrative data source on the flow of offense records to prosecutors’ offices in 81 provinces of the country each year, and utilizing the staggered movement of refugees across provinces over time, we estimate instrumental variables models that address potential endogeneity of the number of refugees and their location and find that an increase in the number of refugees leads to more crime. We estimate that the influx of refugees between 2012 and 2016 generated additional 75,000 to 150,000 crimes per year, although it is not possible to identify the distribution of these crimes between refugees and natives. Additional analyses reveal that a low-educated native population has a separate, but smaller, effect on crime. Our results underline the need to quickly strengthen the social safety systems, to take actions to dampen the impact on the labor market, and to provide support to the criminal justice system for mitigating the repercussions of massive influx of individuals into a country, and to counter the social and political backlash that typically emerges in the wake of such large-scale population movements. © 2023 by the Association for Public Policy Analysis and Management
Measurement of the Centrality Dependence of the Dijet Yield in Formula Presented Collisions at Formula Presented With the Atlas Detector
No full textATLAS measured the centrality dependence of the dijet yield using Formula Presented of Formula Presented data collected at Formula Presented in 2016. The event centrality, which reflects the Formula Presented impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, Formula Presented, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The Formula Presented shows a scaling with the Bjorken Formula Presented of the parton originating from the proton, Formula Presented, while no such trend is observed as a function of Formula Presented. This analysis provides unique input to understanding the role of small proton spatial configurations in Formula Presented collisions by covering parton momentum fractions from the valence region down to Formula Presented and Formula Presented. © 2024 CERN, for the ATLAS Collaboration.Göran Gustafssons Stiftelser; Australian Research Council, ARC; Fundação para a Ciência e a Tecnologia, FCT; Narodowa Agencja Wymiany Akademickiej, NAWA; Royal Society of South Australia, RSSA; British Columbia Knowledge Development Fund, BCKDF; Minerva Foundation; Agencia Nacional de Investigación y Desarrollo, ANID; Ministry of Science and Technology, Taiwan, MOST; Deutsche Forschungsgemeinschaft, DFG; Institutul de Fizică Atomică, IFA; Neurosurgical Research Foundation, NRF; Defence Science Institute, DSI; Israel Science Foundation, ISF; Nella and Leon Benoziyo Center for Neurological Diseases, Weizmann Institute of Science; U.S. Department of Energy, USDOE; Javna Agencija za Raziskovalno Dejavnost RS, ARRS; Japan Society for the Promotion of Science, JSPS; National Research Council Canada, NRC; European Research Council, ERC; National Stroke Foundation, NSF; European Cooperation in Science and Technology, COST; 2014-2021; Science and Technology Facilities Council, STFC; Helmholtz-Gemeinschaft, HGF; Canada Foundation for Innovation, CFI; Austrian Science Fund, FWF; Alexander von Humboldt-Stiftung, AvH; Fundação de Amparo à Pesquisa do Estado de São Paulo, FAPESP; Generalitat de Catalunya; Narodowe Centrum Nauki, NCN; Bundesministerium für Wissenschaft, Forschung und Wirtschaft, BMWFW; Bundesministerium für Bildung und Forschung, BMBF; National Natural Science Foundation of China, NSFC; Ministerio de Ciencia e Innovación, MCIN; Natural Sciences and Engineering Research Council of Canada, NSERC; Irish Rugby Football Union, IRFU; Instituto Nazionale di Fisica Nucleare, INFN; Nederlandse Organisatie voor Wetenschappelijk Onderzoek, NWO; Danmarks Grundforskningsfond, DNRF; Leverhulme Trust; Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq; Agence Nationale de la Recherche, ANR; Chinese Academy of Sciences, CAS; CERN; European Regional Development Fund, ERDF; Canarie; Multiple Sclerosis Scientific Research Foundation, MSSRF; Ministarstvo Prosvete, Nauke i Tehnološkog Razvoja, MPNTR; H2020 Marie Skłodowska-Curie Actions, MSCA; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, SNF; Staatssekretariat für Bildung, Forschung und Innovation, SBFI; IN2P3-CNRS; Ministry of Education, Culture, Sports, Science and Technology, MEXT; SCI/013; Compute Canada: 21/SCI/017; Compute Canada; Agencia Nacional de Promoción Científica y Tecnológica, ANPCyT; Centre National pour la Recherche Scientifique et Technique, CNRS