5916 research outputs found
Sort by
A critical review on the junction temperature measurement of light emitting diodes
No full textIn the new age of illumination, light emitting diodes (LEDs) have been proven to be the most efficient alternative to conventional light sources. Yet, in comparison to other lighting systems, LEDs operate at low temperatures while junction temperature (Tj) is is among the main factors dictating their lifespan, reliability, and performance. This indicates that accurate measurement of LED temperature is of great importance to better understand the thermal effects over a system and improve performance. Over the years, various Tj measurement techniques have been developed, and existing methods have been improved in many ways with technological and scientific advancements. Correspondingly, in order to address the governing phenomena, benefits, drawbacks, possibilities, and applications, a wide range of measurement techniques and systems are covered. This paper comprises a large number of published studies on junction temperature measurement approaches for LEDs, and a summary of the experimental parameters employed in the literature are given as a reference. In addition, some of the corrections noted in non-ideal thermal calibration processes are discussed and presented. Finally, a comparison between methods will provide the readers a better insight into the topic and direction for future research.TÜBİTA
Interference management strategies for multiuser multicell MIMO VLC systems
No full textThis paper investigates different precoding strategies for rate splitting multiple access (RSMA) in the downlink of multi-cell visible light communication (VLC) networks. Since classical Shannon capacity formula does not hold for VLC, we first provide a lower bound on the channel capacity for RSMA in such interfering networks. Then, we formulate a spectral efficiency maximization problem to jointly find the optimal rate-splitting and transmit precoding. Beside that, since cell-edge users suffer from additional inter-cell interference, we propose to design the precoders of different RSMA signals utilizing coordinated beamforming (CB). Subsequently, aiming to improve the performance of the CB design for RSMA, while maintain a reduced complexity, we introduce two enhanced precoding strategies for RSMA. To the best of the authors' knowledge such a contribution has not been considered before in the open literature. It is shown in the paper that the formulated optimization problem is non-convex and a sub-optimal, yet, a low complexity solution can be obtained efficiently using semi-definite relaxation combined with successive convex approximation. Through analytical results, we illustrate the flexibility and superiority of the proposed precoding strategies for RSMA over conventional coordinated space division multiple access and non-orthogonal multiple access for different scenarios and network loads
Film tekniklerinin sinematik sanal gerçeklikteki hikaye anlatımına etkisinin incelenmesi
No full textThis thesis focuses on analyzing the usage of traditional film techniques and their effects on storytelling in cinematic virtual reality (CVR) or 360° films. Since virtual reality is an emerging technology, creating content for it is still an ongoing process and an open-ended discussion. Throughout this work, existing cinematic virtual reality contents are viewed and analyzed to seek answers for the following questions: "How does CVR function differently from traditional cinema?", "What is the essence of CVR?" and "Can we define the rules of production of a successful CVR film?". The chosen CVR films are analyzed by the following five main criteria to answer these questions: the first-person view vs. ghost view, still viewing or moving viewing position, the existence of a guiding content, space and time transitions, and vertical-horizontal movements. At the end of the study, a guideline is presented for virtual reality filmmakers and researchers about creating CVR content that would achieve a standardized storytelling approach.Bu çalışmanın odak noktası filmlerde kullanılan geleneksel anlatı tekniklerinin sinematik sanal gerçekliğe ya da 360° filmlere uygulanabilirliğini var olan örnekler üzerinden analiz ederek güçlü ve eksik yönlerini ortaya çıkarmaktır. Çalışma boyunca takip eden üç (3) soruya cevp aranmıştır: "Sinematik sanal gerçekliğin klasik sinemadan farkı nedir?", "Sinematik sanal gereçekliğin özü nedir?" ve "Başarılı bir sinematik sanal gerçeklik filminin üretim süreçlerinde kullanılmak üzere bir kılavuz hazırlanabilir mi?". Örnek içerikler incelenirken sırasıyla beş (5) temel kriter göz önünde bulundurulmuştur: birincil karakter bakış açısı ya da hayalet bakış açısı, sabit izleme ya da hareketli izleme konumu, izleyiciyi yönlendirme, zaman ve mekan geçişi ve yatay-dikey doğrultuda hareket etme. Bulgular sonucunda, bu alanda çalışan film yapımcılarına ve/veya araştırmacılara ideal bir anlatı diline sahip bir sinematik sanal gerçeklik filmine ulaşabilmeleri için yönergeler sunulmaktadır
NatiQ: An end-to-end text-to-speech system for arabic
No full textNatiQ is end-to-end text-to-speech system for Arabic. Our speech synthesizer uses an encoder-decoder architecture with attention. We used both tacotron-based models (tacotron-1 and tacotron-2) and the faster transformer model for generating mel-spectrograms from characters. We concatenated Tacotron1 with the WaveRNN vocoder, Tacotron2 with the WaveGlow vocoder and ESPnet transformer with the parallel wavegan vocoder to synthesize waveforms from the spectrograms. We used in-house speech data for two voices: 1) neutral male “Hamza”- narrating general content and news, and 2) expressive female “Amina”narrating children story books to train our models. Our best systems achieve an average Mean Opinion Score (MOS) of 4.21 and 4.40 for Amina and Hamza respectively.The objective evaluation of the systems using word and character error rate (WER and CER) as well as the response time measured by real-time factor favored the end-to-end architecture ESPnet.NatiQ demo is available online at https://tts.qcri.org
A newsvendor problem with markup pricing in the presence of within-period price fluctuations
No full textWe consider a single-item single-period joint inventory management and pricing problem of a retailer selling an item that has selling price uncertainties. Unlike most of the literature on the newsvendor problem, we assume that price-dependent demand arrives randomly according to a stochastic arrival process whose rate depends on the fluctuating market input price process. The retailer's problem is to choose the order quantity and a proportional price markup over the input price to maximize the expected profit. This setting is mostly encountered by retailers that trade in different currencies or have to purchase and convert commodities for seasonal sales. For this setting, we characterize both the optimal inventory and markup levels. We present monotonicity properties of the expected profit function with respect to each decision variable. We also show that more volatile input price processes lead to lower expected profits
Spatial configuration and passenger behavior at complex buildings İstanbul Sabiha Gökçen Airport
No full textThe behavior of the passengers in complex buildings may be affected by the spatial configuration of the building, also the functional demands of each individual. This research investigates complex buildings’spatial configuration and visibility characteristics’ impact on the choice of the service facilities that are related to the behavior of the passengers at an airport. The functional demands of an airport do not only rely on passenger activity and finding the gate. Passengers use the travel-related functions but also the retail facilities, and food/drink services at an airport according to their needs. The location of these facilities has the potential to attract people during their time until their flight. The optimized locations of these facilities may generate well-operated management by answering the functional demands and a time saver for the passengers. The general aim of the research is to point out the dependents of the choice of these facilities related to the syntax parameters such as some of the food services can locate in the highest visibility areas and some of them locate in very deep spaces and some of them lose customers because of the configuration of the airport. The method of the research involves the behavioral pattern of the passengers through the food/drink services and their relationship with the spatial structure of the airport. However, the whole wayfinding dynamics of the airport generally, is led by the arrows and signs through the destination, the random movement through the food/drink facilities will show the actual influence of the spatial structure on the behavioral patterns. The spatial characteristics will be discussed with visual connectivity, isovist measurements (e.g., circularity, occlusivity, isovist perimeter), and how they are related to the actual passenger populationat these facility zones at an airport. The common area of departures and domestic flights of the airport will be used for the research to investigate how people are using these spaces according to their locationand visibility potential. In the case study, the selected nodes will be counted in the gates, and the numeric data of the passengerswill be compared with the syntax measurements to achieve a correlation also detecting the ignored facilities because of the spatial structure that is meant to develop more optimized facility service to the passengers. The research includes a syntactic analysis at İstanbul Sabiha Gökçen Airport’s Domestic flights facility area to investigate the usage of these areas. The human movement through the airport leads the users to create a path regarding their activities, therefore the spatial configuration of the airport has a significant impact on the routes of the passengers and the choice of the facility within their functional needs
The development of social competence in children with disabilities
No full textChildren with disabilities experience unique challenges in developing social skills critical to achieve their social goals. In this chapter, the authors first introduce two theoretical frameworks that can guide research and practice relevant to social competence of children with disabilities. Second, they discuss personal and contextual factors that either facilitate or hinder social development of children with disabilities in everyday interactions. Third, the authors address cultural understandings of disability that influence children's socialization within family and community contexts. In addition to personal and developmental characteristics, various contextual factors influence how children with disabilities develop social competence. Discussion focuses on how external experiences and supports impact the development of social competence in children with disabilities. Three external factors are described: intervention programs, family-school partnerships, and technology supports. Finally, the authors conclude with the implications of using social intervention approaches for children with disabilities in home, school, and community-based contexts
Noise-tolerant object detection and ranging using quantum correlations
No full textImaging, detection and ranging of objects in the presence of significant background noise is a fundamental challenge in optical sensing. Overcoming the limitations imposed in conventional methods, quantum light sources show higher resistance against noise in a time-correlation-based quantum illumination. Here, we introduce the advantage of using not only time correlations but also polarization correlations in photon pairs in the detection of an object that is embedded in a noisy background. In this direction, a time- and polarization-correlated photon pair source using the spontaneous parametric down-conversion process is exploited. We found that the joint measurement of correlated pairs allows distinguishing the signal from the noise photons and that leads to an improved signal-to-noise ratio. Our comparative study revealed that using polarization correlations in addition to time correlations provides improved noise rejection. Furthermore, we show that polarization correlation allows undoing the detector limitation where high background often leads to detector saturation.TÜBİTA
Lezbiyen ve gey bireylerin ve ebeveynlerinin açılma sürecindeki deneyimleri: Türkiye'de kalitatif bir çalışma
No full textThis study is aimed to explore deeply the experiences of lesbian and gay youth in coming out process. Ten families from Turkey who participated included mothers and lesbian/gay youth ranging in ages of 21 to 33. In participants of youth, three of them define themselves as lesbian, and rest defines as gay. Thematic analysis using Family Systems Theory as a base is used to analyse 20 interviews. Seven themes (numbers) and 13 subthemes (letters) have emerged from thematic analysis of coming out experiences of gay youth and parents as following: 1) youth's acceptance of self as a process, 1a) experiencing confusion and isolation in coming out to oneself, 1b) motivation to come out: the burden of being closeted, 2) suspicion prior to coming out, 2a) youth suspicion of family's suspicion, 2b) suspicion of parents, 3) youth's worries about the anticipated negative reactions, 3a) using the opportunity of the context to come out, 4) family adjustment 4a) initial reactions, 4b) acceptance as a process, 5) positive effects of coming out, 5a) youth feeling free to be themselves after relieving the burden of being closeted, 5b) better relationships in family after coming out, 6) social & cultural effects, 6a) social cultural effects being a hump for both parents and youth, 6b) lack of reliable sources and being uninformed as barriers, 6c) social support easing the process for both youth and parents, 7) coming out being a difficult process, 7a) continuing negative effects. Further subthemes of subthemes are explained in the results section with quotes from participants. Themes and subthemes are discussed in the framework of Family Systems Theory. Themes overall highlight the characteristics of coming out as a process in the line with other studies in the field. Moreover, clinical implications of the study are discussed.Bu çalışma, kendini eşcinsel olarak tanımlayan gençlerin açılma sürecindeki deneyimlerini derinlemesine araştırmayı amaçlamaktadır. Türkiye'den 10 aile ile yapılan bu çalışmada anneler ve yaşları 21 ile 33 arasında değişen lezbiyen ve gey gençler yer almaktadır. Katılan gençlerin üçü kendini lezbiyen, geri kalanı ise gey olarak tanımlamaktadır. Aile Sistemleri Teorisini temel alan tematik analiz, 20 görüşmeyi analiz etmek için kullanmıştır. Eşcinsel gençlerin ve ebeveynlerin ortaya çıkan deneyimlerinin tematik analizinden aşağıdaki gibi yedi tema (sayı) ve 13 alt tema (harf) ortaya çıkmıştır: 1) kendini kabul süreci, 1a) kendine açılma sürecinde kafa karışıklığı ve yalnızlık, 1b) açılma motivasyonu: saklanmanın yükü, 2) açılma öncesi şüpheler, 2a) gencin ailenin şüphelendiğinden duyduğu şüphe, 2b) ebeveynlerin şüphesi, 3) gencin beklenen olumsuz tepkilerden endişe duyması, 3a) bağlamı açılma fırsatı olarak kullanma, 4) ailenin uyumlanma süreci 4a) ilk tepkiler, 4b) bir süreç olarak kabullenme, 5) açılmanın olumlu etkileri, 5a) gençlerin saklanmanın yükünü hafiflettikten sonra kendilerini özgür hissetmeleri, 5b) açıldıktan sonra ailede daha iyi ilişkiler, 6) sosyal ve kültürel etkiler, 6a) sosyal kültürel etkilerin hem ebeveynler hem de gençler için bir kambur olması, 6b) güvenilir kaynakların olmaması ve bilgi sahibi olmamanın engel teşkil etmesi, 6c) hem gençler hem de ebeveynler için süreci sosyal desteğin kolaylaştırması, 7) açılmanın zor bir süreç olması, 7a) açılmanın olumsuz etkilerinin devam etmesi. Alt temaların diğer alt temaları, katılımcılardan alınan alıntılarla sonuçlar bölümünde açıklanmıştır. Temalar ve alt temalar Aile Sistemleri Kuramı çerçevesinde ele alınmaktadır. Temalar genel olarak alandaki diğer çalışmalarla örtüşen şekilde açılma deneyimlerini süreç olma özelliğini vurgulamaktadır. Ayrıca, çalışmanın klinik sonuçları ve limitasyonları tartışılmıştır
Sütür atan cerrahi robot asistanlarının teleoperasyon ve kontrolü
No full textIn a robot-assisted surgical systems, optimizations in tele-operation can lower the surgeon's physical and mental exhaustion and cognitive load, as well as the operation's completion time. As a result, it can considerably boost the chances of an operation's success. This thesis investigates several tele-operation methods to enhance the quality of the manipulation which will enable the surgeon to perform sensitive tele-operation tasks in narrow spaces quickly while reducing their mental load. In the developed systems, it is ensured that the robot's end-effector configuration is automatically calculated among possible kinematic configurations in real-time. The presented methods have been tested in two highly redundant robotic surgical systems (DOF>=9) and benefits to the tele-operator have been demonstrated for each method by experiments that require dexterous manipulation. Experimental results show that using the developed methods in real-life operations will shorten the operation time and reduce the effort of the surgeon during the operation.Robotik destekli cerrahi sistemlerde, teleoperasyon üzerine yapılan iyileştirmeler, cerrahın fiziksel ve zihinsel yorgunluğunu, bilişsel yükünü ve operasyonun tamamlanma süresini azaltır. Sonuç olarak, bir operasyonun başarı şansı önemli ölçüde artırılır. Bu tez, manipülasyonun kalitesini artırarak, cerrahın zihinsel yüklerini azaltırken, dar alanlarda hassas teleoperasyon görevlerini hızlı bir şekilde gerçekleştirmesini sağlayacak çeşitli teleoperasyon yöntemleri önermektedir. Geliştirilen sistemlerde robotun uç eleman konfigürasyonunun olası kinematik konfigürasyonlar arasından gerçek zamanlı olarak otomatik olarak hesaplanması sağlanmıştır. Sunulan yöntemler, yüksek derecede indirgenebilir iki robotik cerrahi sistemde (DOF>=9) test edilmiş ve her bir yöntem için sistemlerin teleoperatöre faydaları, hünerli manipülasyon gerektiren deneylerle gösterilmiştir. Deneysel sonuçlar, geliştirilen yöntemlerin gerçek hayattaki operasyonlarda kullanılmasının operasyon süresini kısaltacağını ve operasyon sırasında cerrahın eforunu azaltacağını göstermektedir