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Operation altitude optimization of solar-powered rotary-wing UAVs for FSO backhauling
No full textFree space optical communication (FSO) has emerged as an alternative backhauling technology. It provides a line-of-sight (LOS) link with a capacity comparable to fiber optics and much higher than those that can be supported by radio counterparts. Rotary-wing unmanned aerial vehicles (UAVs) equipped with FSO terminals can be positioned as a complementary aerial solution to the terrestrial backhaul links in dense areas with high-peak traffic demands. In this paper, we consider a solar-powered rotary-wing UAV equipped with an FSO terminal that provides backhaul link to a ground base station in an urban area. We first quantity the energy consumption and energy harvesting of a rotary-wing solar-powered UAV. Then, we formulate an optimization problem to determine the optimal operation altitude with the goal of maximizing the net energy of UAV while satisfying the LOS requirements critical for the FSO link. Our results show that the selection of operation altitude is highly dependent on the weight of the UAV as well as the size and efficiency of the solar panel.European Union’s Horizon 2020 ; TÜBİTA
FSO-based backhauling for airborne THz base stations
No full textAirborne nodes in the form of high-altitude platform stations (HAPSs) or unmanned aerial vehicles (UAVs) can be used for backhauling and wireless access. In this paper, we investigate the cascaded free space optical (FSO)/terahertz (THz) link in which the FSO link serves as a backhaul between the gateway and the airborne node. In contrast, the THz link provides wireless communication between the airborne node and the user. We present channel models, including the atmospheric attenuation, geometrical loss, and fading effect. The FSO sub-system builds upon intensity-modulation direct-detection (IM/DD), while the THz sub-system employs coherent modulation and demodulation. Under the assumption of decode-and-forward relaying, we derive the end-to-end bit error rate (BER). We present numerical results to demonstrate the performance of cascaded airborne links.TÜBİTA
Tork kontrollü dört bacaklı robotun tasarımı, geliştirilmesi ve deneysel değerlendirilmesi
No full textThis thesis presents the design, development, and experimental test of a quadruped with high power-to-weight ratio. In this thesis, three design processes are studied, namely, actuator design, leg mechanism design and torso design.The robot is required to be lightweight and traverse relatively fast without payload. Initially, the dynamic model of the robot was built, and a design optimization study for weight minimization was conducted in accordance with the loading results obtained from simulation studies. In order to obtain enhanced locomotion capabilities, custom actuator units with a high power-to-weight ratio were developed and deployed at the robot joints. With these actuators, the position control method was applied to the robot to control the motion. Moreover, the FEM model of the robot was built, and a design optimization study for weight minimization was conducted in accordance with the loading results obtained from simulation studies. As the main result, two prototypes were built, and quadruped gait experiments were conducted.Bu tez, yüksek güç-ağırlık oranına sahip dört bacaklı robotun tasarımını, geliştirilmesini ve deneysel testini açıklamaktadır. Bu tezde, eyleyici tasarımı, bacak mekanizması tasarımı ve gövde tasarımı olmak üzere üç tasarım süreci incelenmiştir. Robotun hafif olması ve yük olmadan nispeten hızlı hareket etmesi gerekmektedir. Öncelikle robotun dinamik modeli oluşturulmuş ve buna bağlı simülasyon çalışmalarından elde edilen yükleme sonuçlarına göre ağırlık minimizasyonu için tasarım optimizasyon çalışması yapılmıştır. Gelişmiş hareket kabiliyeti elde etmek için, yüksek güç-ağırlık oranına sahip özel eyleyici üniteleri geliştirilmiştir ve robot eklemlerine yerleştirilmiştir. Bu eyleyiciler ile hareketin kontrol edilmesi için robota pozisyon kontrol yöntemi uygulanmıştır. Ayrıca robotun Sonlu Elemanlar modeli oluşturulmuş ve simülasyon çalışmalarından elde edilen yükleme sonuçlarına göre ağırlık minimizasyonu için tasarım optimizasyon çalışması yapılmıştır. Sonuç olarak, iki prototip inşa edilmiştir ve yürüyüş deneyleri yapılmıştır
Calcium sulfoaluminate cement and supplementary cementitious materials-containing binders in self-healing systems
No full textCreation of more durable concrete is one pathway to achieving improved sustainability and carbon footprint over a concrete structure's life. Microbially induced calcite precipitation has been shown to densify concrete microstructure and fill cracks, reducing moisture transport. One challenge associated with the longevity of bacterial-concrete systems is the high pH environment of the cement paste. Herein, two approaches to address this challenge were investigated: (i) sustainable binder systems, such as calcium sulfoaluminate (CSA) cement and fly ash substitutions of ordinary portland cement (OPC), which lead to lower pH systems, and (ii) non-axenic bacterial cultures, which may facilitate growth of more alkaline-resistant bacteria. Mechanical properties, water absorption, self-healing ability, and survivability of the bacterial systems were tracked, finding that incorporation of non-axenic bacteria did not result in increased bacteria survivability compared to axenic bacteria. However, both bacteria healed cracks [removed]Ohio Department of Transportatio
Collective co-design activities with children for designing classroom robots
No full textIn order to design classroom robots that meet children's expectations, it may be useful to involve children in the design process. In this paper, we propose a suite of activities that can be utilized collectively to help in co-designing classroom robots. We outline the details of a combination of activities including building a robot model using a dedicated robot toolkit, a placement activity, a story-telling activity, and an interview. We explore the use of these activities through a study with 31 children (8-15 years old), where we analyzed the data using a framework for the design of social robots extended to cover the classroom situation. Our study showed that the activities could help distinguish some clear group preferences regarding the embodiment of the robot, especially the head, arms, and legs, the role of the robot, and the personality. While we used these activities in a study to illustrate their use for an open-ended design process of a classroom robot, we argue that the proposed suite of activities complement each other and may help robot designers to involve children in the design process in a holistic way. This can allow designers to gain elaborate and in-depth insight from children who do not usually (and necessarily) have domain knowledge in classroom robot technologies, and can promote them to articulate ideas and views about the prospective attributes in terms of physical appearance, contextual behavior, and social interaction
Parenting culture(s): Ideal-parent beliefs across 37 countries
No full textWhat is it to be “an ideal parent”? Does the answer differ across countries and social classes? To answer these questions in a way that minimizes bias and ethnocentrism, we used open-ended questions to explore ideal-parent beliefs among 8,357 mothers and 3,517 fathers from 37 countries. Leximancer Semantic Network Analysis was utilized to first determine parenting culture zones (i.e., countries with shared ideal-parent beliefs) and then extract the predominant themes and concepts in each culture zone. The results yielded specific types of ideal-parent beliefs in five parenting culture zones: being “responsible and children/family-focused” for Asian parents, being “responsible and proper demeanor-focused” for African parents, and being “loving and responsible” for Hispanic-Italian parents. Although the most important themes and concepts were the same in the final two zones—being “loving and patient,” there were subtle differences: English-speaking, European Union, and Russian parents emphasized “being caring,” while French-speaking parents valued “listening” or being “present.” Ideal-parent beliefs also differed by education levels within culture zones, but no general pattern was discerned across culture zones. These findings suggest that the country in which parents were born cannot fully explain their differences in ideal-parent beliefs and that differences arising from social class or education level cannot be dismissed. Future research should consider how these differences affect the validity of the measurements in question and how they can be incorporated into parenting intervention research within and across cultures.Australian Research Council ; Fédération Wallonie-Bruxelle
Queueing systems with rationally inattentive customers
No full textProblem definition: Classical models of queueing systems with rational and strategic customers assume queues to be either fully visible or invisible, while service parameters are known with certainty. In practice, however, people only have "partial information" on the service environment, in the sense that they are not able to fully discern prevalent uncertainties. This is because assessing possible delays and rewards is costly, as it requires time, attention, and cognitive capacity, which are all limited. On the other hand, people are also adaptive and endogenously respond to information frictions. Methodology: We develop an equilibrium model for a single-server queueing system with customers having limited attention. Following the theory of rational inattention, we assume that customers optimize their learning strategies by deciding the type and amount of information to acquire and act accordingly while internalizing the associated costs. Results: We establish the existence and uniqueness of a customer equilibrium when customers allocate their attention to learn uncertain queue lengths and delineate the impact of service characteristics. We provide a complete spectrum of the impact of information costs on throughput and show numerically that throughput might be nonmonotone. This is also reflected in social welfare if the firm's profit margin is high enough, although customer welfare always suffers from information costs. Managerial implications: We identify service settings where service firms and social planners should be most cautious for customers' limited attention and translate our results to advisable strategies for information provision and service design. For example, we recommend firms to avoid partial hindrance of queue-length information when a low-demand service is not highly valued by customers. For a popular service that customers value reasonably highly, however, partial hindrance of information is particularly advisable. Academiclpractical relevance: We propose a microfounded framework for strategic customer behavior in queues that links beliefs, rewards, and information costs. It offers a holistic perspective on the impact of information prevalence (and information frictions) on operational performance and can be extended to analyze richer customer behavior and complex queue structures, rendering it a valuable tool for service design
Gözlenen deprem hızlanma kayıtlarına göre 1D ve 2D site müdahale analizleri arasında karşılaştırma çalışması
No full textDynamic site response analysis is a technique that uses site characteristics and dynamic movements to attempt to predict the response of the specific site to ground motions in the form of response spectra. The main objective of the present work is to evaluate the difference between the one-dimensional and two-dimensional site response analysis, based on the comparison among the peak ground and spectral accelerations recorded by Istanbul Rapid Response Network (IRRN) and three Istanbul vertical array stations (IGVA) including Ataköy, Fatih and Zeytinburnu stations, during the Mw=6.5, 24.5.2014 Gökçeada and Mw=5.9, 19.5.2011 Kütahya earthquakes with the calculated accelerations by the 1D and 2D site response analyses. In this study, shear wave velocity profiles were determined based on insitu geophysical, geotechnical measurements, and laboratory tests within the Istanbul Microzonation Project. The shear wave velocity values, which are subject to some uncertainties due to some measurement methods or environmental conditions, are re-evaluated using a revision scheme to obtain the best matches between the recorded and calculated spectral accelerations by 1D site response analysis. These modified shear wave velocity profiles are later used for 1D and 2D site response analyses which in North-South and East-West directions to model peak ground and spectral accelerations on the ground surface. The results show the improvement of the calculated PGA and SA values. Finally, as another focus of this study, by modelling different symmetric spacing around the main boreholes separately in two main directions of some IRRN stations, the influence of horizontal distance on site response was investigated for 2D analyses. The results show that, in general, no unique relationship can be defined between the horizontal distance and the site response. There is an optimal spacing for each soil profile to obtain the best agreement between the calculated SA and the recorded value.Dinamik site tepki analizi, belirli sitenin yer hareketlerine tepkisini tepki spektrumları biçiminde tahmin etmeye çalışmak için site özelliklerini ve dinamik hareketleri kullanan bir tekniktir. Bu çalışmanın temel amacı, İstanbul Acil Müdahale ve İstanbul düşey kayıt ağları (Ataköy, Fatih ve Zeytinburnu) ivme istasyonları tarafından, Mw=6.5, 24.5.2014 Gökçeada ve Mw=5.9, 19.5.2011 Kütahya depremlerinde kaydedilen en büyük yatay ve spektral ivmeler arasındaki karşılaştırmaya bağlı olarak tek-boyutlu ve iki-boyutlu saha davranış analizleri arasındaki farkı değerlendirmektir. Bu çalışmada, İstanbul Mikrobölgeleme Projesi kapsamında yerinde jeofizik, jeoteknik ölçümler ve laboratuvar deneylerine dayalı olarak kayma dalgası hız profilleri belirlenmiştir. . Ölçüm yöntemleri ve çevresel koşullar nedeniyle belirsizlikler içeren bulunmuş kayma dalgası hız değerleri, 1 boyutlu saha tepki analizi ile kaydedilen ve hesaplanan spektral ivmeler arasında en iyi eşleşmeleri elde etmek için bir iyileşyirme şeması kullanılarak yeniden değerlendirilmiştir. Bu yenilenmiş kayma dalgası hızı profilleri daha sonra Kuzey-Güney ve Doğu-Batı yönlerinde zemin yüzeyindeki en büyük ve spektral ivmeleri modellemek için 1B ve 2B saha tepki analizleri için kullanılmıştır. Sonuçlar, hesaplanan PGA ve SA değerleri modellenmesinde iyileşme olduğunu göstermektedir. Son olarak, bu çalışmanın bir diğer odak noktası olarak, bazı IRRN istasyonlarının iki ana yönünde ana sondaj kuyularının etrafındaki farklı simetrik boşluklar ayrı ayrı modellenerek, 2B analizler için yatay mesafenin saha tepkisi üzerindeki etkisi araştırılmıştır. Sonuçlar, genel olarak, yatay mesafe ile saha tepkisi arasında hiçbir ilişki tanımlanamayacağını göstermektedir. Hesaplanan SA ve kaydedilen değerler arasında en iyi anlaşmayı elde etmek için her kuyu için optimal bir ara mesafe bulunmaktadır