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Automated adaptive playback for encoder-adjudicated live sports
No full textIn low-latency live streaming, it is not easy to simultaneously avoid stalls and maintain low latency. The trade-off needs to be decided in real time. One of the best tools for controlling the buffer level (hence, the stalls) and live latency is adaptive playback speed control, which slows down the playback when the buffer level is critically low to reduce the risk of stalling and speeds up the playback when the buffer is sufficiently full to reduce the live latency. Adaptive playback generally works well. However, it may introduce artifacts depending on the content. Viewers may be more sensitive to playback speed changes at certain scenes. In this paper, we augment the state-of-the-art content-aware playback speed control (CAPSC) algorithm by developing a post-encoder add-on tool that analyzes the encoded live content and automatically tags each output chunk with a value indicating its suitability for playback speed changes. The source code for the CAPSC algorithm and the new post-encoder add-on (developed for the snooker games) is publicly available
Graphene as a piezoresistive material in strain sensing applications
No full textHigh accuracy measurement of mechanical strain is critical and broadly practiced in several application areas including structural health monitoring, industrial process control, manufacturing, avionics and the automotive industry, to name a few. Strain sensors, otherwise known as strain gauges, are fueled by various nanomaterials, among which graphene has attracted great interest in recent years, due to its unique electro-mechanical characteristics. Graphene shows not only exceptional physical properties but also has remarkable mechanical properties, such as piezoresistivity, which makes it a perfect candidate for strain sensing applications. In the present review, we provide an in-depth overview of the latest studies focusing on graphene and its strain sensing mechanism along with various applications. We start by providing a description of the fundamental properties, synthesis techniques and characterization methods of graphene, and then build forward to the discussion of numerous types of graphene-based strain sensors with side-by-side tabular comparison in terms of figures-of-merit, including strain range and sensitivity, otherwise referred to as the gauge factor. We demonstrate the material synthesis, device fabrication and integration challenges for researchers to achieve both wide strain range and high sensitivity in graphene-based strain sensors. Last of all, several applications of graphene-based strain sensors for different purposes are described. All in all, the evolutionary process of graphene-based strain sensors in recent years, as well as the upcoming challenges and future directions for emerging studies are highlighted.Sabanci University ; TÜBİTA
Use of natural minerals to immobilize bacterial cells for remediating cracks in cement-based materials
No full textCracks in cement-based materials are one of the main factors affecting the durability of structure. Recent research in the field of concrete materials showed that self-healing in cement-based systems can be achieved by triggering biogenic calcium carbonate (CaCO3) precipitation. The goal of this study is to establish a comparative evaluation of the use of sepiolite, bentonite, and diatomaceous earth (DE) as an immobilization barrier of Sporosarcina pasteurii (S. pasteurii) cells to trigger self-healing in cement-based systems. For the first time in the literature, this study will provide insight into the use of natural minerals, such as bentonite and sepiolite, as protective carriers for vegetative S. pasteurii cells in cement-based materials and present a comparative evaluation of factors influencing crack healing, such as the microstructure and composition of immobilization barriers. A two-phase self-healing bioadditive was obtained by immobilizing vegetative S. pasteurii cell samples on natural porous minerals with or without the use of required nutrients. Then the samples were cracked by a three-point bending test, and the healing process was screened via stereomicroscope imaging and ultrasonic pulse velocity (UPV) testing after subjecting the cracked samples to 28 days of moist curing. Flexural cracks induced in mortar samples were filled with biogenic precipitate. Relatedly, the water absorption capacity of the samples was decreased in mortar samples containing bacterial cells, the nutrients were added in the curing solution. Fourier transform infrared spectroscopy and scanning electron microscopy analyses showed that calcite was the predominant polymorph of CaCO3 sealant in cracks
Safety test setup installation for e-bike battery systems
No full textRecently, battery project studies have been increasing worldwide. Companies carrying out these projects must have their products checked for design safety and must obtain test approval reports in order to release their products on the market. IEC 62133-2 test approvals are required for lithium-ion rechargeable batteries, and EN 50604 test approvals are necessary for rechargeable li-ion batteries used in Light EV (electric vehicles). In addition, UN38.3(IEC 62281) battery transport tests must be applied for the transport of these batteries. These tests should be performed in an accredited laboratory, the safety of the design should be verified in this way, and then an accredited report should be issued to the product. There was no accredited laboratory in Turkey that performed tests in accordance with these standards. For this reason, companies were receiving services from overseas laboratories for the cell and battery approvals that they designed. There could be time and financial problems in overseas laboratories approvals. Due to these problems, an accredited laboratory was established at Vestel Electronics in Turkey, where tests can be carried out in accordance with IEC62133-2, EN50604, and UN38.3 (IEC62281) standards. Since batteries contain BMS cards, their tests are also carried out in this laboratory. Within the scope of this accredited laboratory established in Turkey, it will be stated how the test setups that meet the test requirements are set up. Test results with these devices will be evaluated. The test results will belong to an E-bike battery project.Vestel Electronic
Tv üretim son montaj hatlarında kapasite planlama için bir çok aşamalı senaryo optimizasyon yönetimi
No full textVestel Electronics is a large-scale TV producer that has an important share in the European television market. High End Factory, where Vestel assembles 20 different TVs in size, consists of 14 final assembly lines. High End Factory averagely produces more than a million products in 1000 orders of a monthly basis. Vestel aims to schedule 3 months' production plan before all the customer orders are not realized. Therefore, production planning becomes even more difficult when the amount of demands is unknown. To overcome this uncertain production planning problem, we demonstrate a multi-stage, multi-item capacitated stochastic lot sizing problem with an objective of minimizing total cost by taking worker group assignment, backlogging and stock into consideration. We propose 3 different mathematical models to overcome the planning problem. Model 1 and Model 2 have a similar stage structure. In Model 1, only backlogging and stock quantity decisions have wait-and-see structure whereas in Model 2, line status and worker group assignment decisions are converted from a here-and-now structure to a wait-and-see structure. In addition, an extra order option has been added. Model 3 has been proposed for the insolubility situation expected to occur with the increase in the number of stages. Stages are designed in a multi-period structure in Model 3. Although this change affects the demand structure, Model 3 makes it easier to solve the problem. It is observed that the problem solution time is shortened with Model 3.Vestel Elektronik, Avrupa pazarında önemli bir payı olan büyük ölçekli bir televizyon üreticisidir. Vestel High End Fabrikasında bulunan 14 adet son montaj hattı üzerinde 20 farklı boyutta televizyon modeli üretilmektedir. Şirket aylık olarak ortalama 1000 sipariş için bir milyondan fazla ürün üretmektedir. Vestel müşteri siparişleri kesinleşmeden önce 3 aylık üretim planını yapmayı amaçlar. Talebin miktarının bilinmemesinden dolayı üretim planı zor bir hâle gelmektedir. Bu belirsiz üretim planlama probleminin üstesinden gelebilmek için bir çok aşamalı çok ürünlü kapasiteli rassal parti büyüklüğü belirleme problemini; çalışma grubu atama, sipariş geciktirme ve stok durumları da göz önünde bulundurularak toplam maliyeti en aza indirmek amacıyla ortaya koyduk. Bu planlama probleminin üstesinden gelebilmek için üç farklı matematiksel model önerdik. Model 1 ve Model 2 benzer aşama yapısına sahiptir. Model 1'de sadece sipariş geciktirme ve stok miktarı kararları senaryo bağımlı yapıda iken Model 2'de hat durumları ve işçi grubu atama kararları senaryo bağımsız yapıdan senaryo bağımlı yapıya çevrilmiştir. Ayrıca sonradan üretim emri girişi seçeneği eklenmiştir. Aşama sayısındaki artışın oluşturması beklenen çözümsüzlük durumu için Model 3 önerilmiştir. Model 3'teki aşama yapısı çok dönemli olarak tasarlanmıştır. Bu değişiklik talep yapısını etkilemesine rağmen Model 3 problemin çözülmesini kolaylaştırmıştır. Böylelikle Model 3 ile problemin çözüm süresinin kısaldığı gözlemlenmiştir
Drone tabanlı FSO sistemlerinde hizalama hatalarının deneysel incelenmesi
No full textAirborne free-space optical (FSO) communication links can be efficiently used for backhaul/fronthaul needs of future cellular networks. Unlike terrestrial FSO links where a fixed connection between two buildings is considered, airborne FSO links bring unique challenges due to the mobility of the drone. In this thesis, an experimental study is carried out to demonstrate the effect of pointing errors in drone-based FSO systems. A supervised learning method is employed for tracking purpose of the FSO signal. Further, power measurements are taken, and the probability distribution of the received signal power is characterized. We further present comparisons between tracking and non-tracking cases and demonstrate the benefits of the tracking system. Motivated by these results, we then purse the second experimental campaign using a MEMS scanner. Furthermore, we investigate whether the studies in the literature match real-life situations. For this, quadcopter data taken from computer simulations are used, and after power measurements are taken by driving the MEMS scanner.Havadan serbest uzay optik haberleşme (FSO) bağlantıları, gelecekteki hücresel ağların arabağlanım ihtiyaçları için verimli bir şekilde kullanılabilir. İki bina arasında sabit bir bağlantı olarak düşünüldüğünde karasal FSO bağlantılarının aksine, havadan FSO bağlantıları dronun hareketliliği nedeniyle kendine özgü zorluklar getirir. Bu tezde, dron tabanlı FSO sistemlerinde hizalama hatalarının etkisini göstermek için deneysel bir çalışma gerçekleştiriyoruz. FSO sinyalinin izlenmesi amacıyla gözetimli bir öğrenme yöntemi kullanıyoruz. Güç ölçümleri alıyoruz ve alınan sinyal gücünün olasılık dağılımını karakterize ediyoruz. Ayrıca takipli ve takipsiz durumlar arasında karşılaştırmalar sunup takip sisteminin faydalarını gösteriyoruz. Bu sonuçlarla motive olarak, bir MEMS tarayıcı kullanarak ikinci deneysel süreci takip ediyoruz. Buna ek olarak, literatürdeki çalışmaların gerçek hayatta olan durumlarıyla uyuşup uyuşmadığını araştırıyoruz. Bunun için bilgisayar simülasyonlarından alınan dron verilerini kullanılıyor ve sonrasında MEMS tarayıcıyı sürerek güç ölçümleri yapıyoruz
Multi-criteria decision making for city-scale infrastructure of post-earthquake assembly areas: Case study of Istanbul
No full textAssembly areas are first gathering places after earthquakes, and provide temporary sheltering. However if these areas have greater risks after earthquakes, they become more deadly. Current studies commonly look for evacuation shelter and temporary housing location models but most of them are not suited to assembly areas. This study aims to determine safe post-earthquake assembly areas by using the multi-criteria decision-making approach through an analytical hierarchy process using a geographical information system. 15 criteria were defined to evaluate the suitability in terms of spatial, natural structure and accessibility of each potential open space for emergency gathering. Following these criteria, possible areas were mapped, evaluated and scored with thematic hazard maps by using geographic information system in a case study to demonstrate the model. Finally, suitability layers were superimposed to estimate the safe assembly areas index and produce the city-scale infrastructure map. As a result, 107 assembly areas were designated for seven neighborhoods in Istanbul. Study results show that not every open area is safe to be a post-earthquake assembly area. The proposed method can provide useful information that could assist in earthquake disaster mitigation, and help government decisionmakers support further location allocation optimization of safe assembly areas
Student and tutor perceptions of the pedagogical potential and challenges of design jury as an assessment method
No full textThis article examines the pedagogical potential and challenges of the design jury as an assessment method from the perceptions of the tutor/jury member and the design students. It aims to gain an understanding of the factors that create opportunities for, and barriers to, the promotion of learning in the design jury. It inquires the possible contributions of the jury into formative evaluation processes in design education. The results show that (1) the communication modalities, and (2) the evaluation criteria influence the way tutors and students perceive design jury as a pedagogical method. While the hierarchy between the jury member and the student creates a barrier to constructive feedback, a balance between formative and summative evaluations is essential in the design jury. Transparency of evaluation criteria decreases design students’ concern for grade. The design jury could also serve for formative evaluation. A student-centred approach to design jury engenders experiences of deep learning.TÜBİTAKPublisher versio
Transition dynamics in equilibrium search
No full textWe study a dynamic equilibrium search model where sellers differ in their urgency to liquidate an asset. Buyers strategically make price offers without knowing a given seller’s urgency. We study liquidity and price dynamics on the transition path after an unexpected shock. Generically, the transition includes a phase where all buyers offer the same price, causing a market collapse; however, price dispersion resumes in finite time, leading to a recovery where both types make sales. We show that prices and liquidity can overshoot before converging to the steady state. When relaxed sellers randomly become desperate, dampening oscillations can occur
Screen media exposure in early childhood and its relation to children's self-regulation
No full textSelf-regulation, the ability to control thoughts, emotions, and behavior for goal-directed activities, shows rapid development in infancy, toddlerhood, and preschool periods. Early self-regulatory skills predict later academic achievement and socioemotional adjustment. An increasing number of studies suggest that screen media use may have negative effects on children's developing self-regulatory skills. In this systematic review, we summarized and integrated the findings of the studies investigating the relationship between young children's screen media use and their self-regulation. We searched the ERIC, PsycINFO, PubMed, and Web of Science databases and identified 39 relevant articles with 45 studies. We found that screen time in infancy is negatively associated with self-regulation, but findings were more inconsistent for later ages suggesting that screen time does not adequately capture the extent of children's screen media use. The findings further indicated that background TV is negatively related to children's self-regulation, and watching fantastical content seems to have immediate negative effects on children's self-regulatory skills. We suggest that future studies should take the content and context of children's screen media use into account and also focus on parent- and home-related factors such as parental behaviors that foster the development of self-regulatory skills