5916 research outputs found
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Ultraviolet communications for unmanned aerial vehicle networks
No full textDue to the strong scattering, ultraviolet (UV) communication links enable non-line-of-sight (NLOS) outdoor connectivity and relax the pointing, acquisition, and tracking requirements encountered in infrared links. This feature makes the UV communications attractive, in particular, for unmanned aerial vehicle (UAV) networks where link alignment is hard to realize. In this letter, we study the performance of the uplink of a ground sensor network where a UAV periodically visits the area to receive the data from serial sensor nodes. The transmission from the closest sensor to the flying UAV is the desired signal while the received signals from other nodes are treated as interference. We derive the bit error rate for the uplink airborne UV in the presence of interference. Numerical results are provided to validate our theoretical analysis and investigate the effect of interferers on the system performance
Search for charged-lepton flavor violation in top quark production and decay in pp collisions at s√ = 13 TeV
No full textResults are presented from a search for charged-lepton flavor violating (CLFV) interactions in top quark production and decay in pp collisions at a center-of-mass energy of 13 TeV. The events are required to contain one oppositely charged electron-muon pair in the final state, along with at least one jet identified as originating from a bottom quark. The data correspond to an integrated luminosity of 138 fb−1, collected by the CMS experiment at the LHC. This analysis includes both the production (q → eμt) and decay (t → eμq) modes of the top quark through CLFV interactions, with q referring to a u or c quark. These interactions are parametrized using an effective field theory approach. With no significant excess over the standard model expectation, the results are interpreted in terms of vector-, scalar-, and tensor-like CLFV four-fermion effective interactions. Finally, observed exclusion limits are set at 95% confidence levels on the respective branching fractions of a top quark to an eμ pair and an up (charm) quark of 0.13 × 10−6 (1.31 × 10−6), 0.07 × 10−6 (0.89 × 10−6), and 0.25 × 10−6 (2.59 × 10−6) for vector, scalar, and tensor CLFV interactions, respectively.BMBWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES and BNSF (Bulgaria); CERN; CAS, MoST, and NSFC (China); MINCIENCIAS (Colombia); MSES and CSF (Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC PUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRI (Greece); NKFIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); MES (Latvia); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MOS (Montenegro); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); MCIN/AEI and PCTI (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (U.S.A.).r Individuals have received support from the Marie-Curie program and the European Research Council and Horizon 2020 Grant, contract Nos. 675440, 724704, 752730, 758316, 765710, 824093, 884104, and COST Action CA16108 (European Union); the Leventis Foundation; the Alfred P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the "Excellence of Science -EOS" -be.h project n. 30820817; the Beijing Municipal Science & Technology Commission, No. Z191100007219010; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Deutsche Forschungsgemeinschaft (DFG), under Germany's Excellence Strategy -EXC 2121 "Quantum Universe" -390833306, and under project number 400140256 -GRK2497; the Lendulet ("Momentum") Program and the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences, the New National Excellence Program UNKP, the NKFIA research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, and 129058 (Hungary); the Council of Science and Industrial Research, India; the Latvian Council of Science; the Ministry of Science and Higher Education and the National Science Center, contracts Opus 2014/15/B/ST2/03998 and 2015/19/B/ST2/02861 (Poland); the Fundacao para a Ciencia e a Tecnologia, grant CEECIND/01334/2018 (Portugal); the National Priorities Research Program by Qatar National Research Fund; the Ministry of Science and Higher Education, projects no. 07232020-0041 and no. FSWW-2020-0008, and the Russian Foundation for Basic Research, project No.19-42-703014 (Russia); MCIN/AEI/10.
13039/501100011033, ERDF "a way of making Europe", and the Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia Maria de Maeztu, grant MDM-2017-0765 and Programa Severo Ochoa del Principado de Asturias (Spain); the Stavros Niarchos Foundation (Greece); the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Kavli Foundation; the Nvidia Corporation; the SuperMicro Corporation; the Welch Foundation, contract C-1845; and the Weston Havens Foundation (U.S.A.).Publisher versio
The effect of appearance of virtual agents in human-agent negotiation
No full textArtificial Intelligence (AI) changed our world in various ways. People start to interact with a variety of intelligent systems frequently. As the interaction between human and AI systems increases day by day, the factors influencing their communication have become more and more important, especially in the field of human-agent negotiation. In this study, our aim is to investigate the effect of knowing your negotiation partner (i.e., opponent) with limited knowledge, particularly the effect of familiarity with the opponent during human-agent negotiation so that we can design more effective negotiation systems. As far as we are aware, this is the first study investigating this research question in human-agent negotiation settings. Accordingly, we present a human-agent negotiation framework and conduct a user experiment in which participants negotiate with an avatar whose appearance and voice are a replica of a celebrity of their choice and with an avatar whose appearance and voice are not familiar. The results of the within-subject design experiment show that human participants tend to be more collaborative when their opponent is a celebrity avatar towards whom they have a positive feeling rather than a non-celebrity avatar.Vestel Elektronik Sanayi ve Ticaret A.ŞPublisher versio
BioCode: A data-driven procedure to learn the growth of biological networks
No full textProbabilistic biological network growth models have been utilized for many tasks including but not limited to capturing mechanism and dynamics of biological growth activities, null model representation, capturing anomalies, etc. Well-known examples of these probabilistic models are Kronecker model, preferential attachment model, and duplication-based model. However, we should frequently keep developing new models to better fit and explain the observed network features while new networks are being observed. Additionally, it is difficult to develop a growth model each time we study a new network. In this paper, we propose BioCode, a framework to automatically discover novel biological growth models matching user-specified graph attributes in directed and undirected biological graphs. BioCode designs a basic set of instructions which are common enough to model a number of well-known biological graph growth models. We combine such instruction-wise representation with a genetic algorithm based optimization procedure to encode models for various biological networks. We mainly evaluate the performance of BioCode in discovering models for biological collaboration networks, gene regulatory networks, and protein interaction networks which features such as assortativity, clustering coefficient, degree distribution closely match with the true ones in the corresponding real biological networks. As shown by the tests on the simulated graphs, the variance of the distributions of biological networks generated by BioCode is similar to the known models' variance for these biological network types
Su altında görünür ışık haberleşmesinde eş zamanlı ışık dalgaları bilgisi ve güç transferi
No full textIn this thesis, we investigate simultaneous lightwave information and power transfer (SLIPT) for underwater visible light communication systems. We consider four SLIPT methods namely AC-DC separation (ADS), time switching (TS), power splitting (PS) and time switching-power splitting (TS-PS) where the splitting/switching factors are defined as optimization parameters in TS, PS and TS-PS methods. For each of these methods, we derive closed-form expressions for the average harvested energy, bit error rate and spectral efficiency in the presence of underwater turbulence modeled by lognormal statistics. Using these expressions, we determine the optimal splitting factors to maximize the harvested energy while satisfying a given bit error rate value and a given threshold spectral efficiency value. Our results reveal that, if not optimized, SLIPT methods under consideration are outperformed by the simple AC-DC separation (ADS) method which provides the largest harvested energy versus spectral efficiency (HE-SE) region. Optimization of splitting/switching factors extends the HE-SE regions; hence, optimized versions of TS, PS and TS-PS methods are able to significantly outperform ADS for most cases. We further investigate the effect of various channel and system parameters such as water type, turbulence level, beam divergence, receiver aperture size on the harvested energy and quantify the improvements in battery lifetime through the use of SLIPT methods.Bu tezde, su altı görünür ışık iletişim sistemleri için eşzamanlı ışık dalgası bilgisi ve güç aktarımını (SLIPT) araştırıyoruz. Ayırma/anahtarlama faktörlerinin TS'de optimizasyon parametreleri olarak tanımlandığı AC-DC ayırma (ADS), zaman anahtarlama (TS), güç bölme (PS) ve zaman anahtarlama-güç bölme (TS-PS) olmak üzere dört SLIPT yöntemini ele alıyoruz, PS ve TS-PS yöntemleri. Bu yöntemlerin her biri için, lognormal istatistiklerle modellenen sualtı türbülansı varlığında ortalama hasat edilen enerji, bit hata oranı ve spektral verimlilik için kapalı biçimli ifadeler türetiyoruz. Bu ifadeleri kullanarak, belirli bir bit hata oranı değerini ve belirli bir eşik spektral verimlilik değerini karşılarken, hasat edilen enerjiyi en üst düzeye çıkarmak için en uygun bölme faktörlerini belirleriz. Sonuçlarımız, optimize edilmemişse, söz konusu SLIPT yöntemlerinin, en büyük hasat edilen enerjiye karşı spektral verimlilik (HE-SE) bölgesini sağlayan basit AC-DC ayırma (ADS) yönteminden daha iyi performans gösterdiğini ortaya koymaktadır. Ayırma/anahtarlama faktörlerinin optimizasyonu HE-SE bölgelerini genişletir; bu nedenle, TS, PS ve TS-PS yöntemlerinin optimize edilmiş sürümleri, çoğu durumda ADS'den önemli ölçüde daha iyi performans gösterebilir. Ayrıca su tipi, türbülans seviyesi, ışın sapması, alıcı açıklığı boyutu gibi çeşitli kanal ve sistem parametrelerinin hasat edilen enerji üzerindeki etkisini araştırıyor ve SLIPT yöntemlerini kullanarak pil ömründeki gelişmeleri nicelleştiriyoruz
Examining the effects of sequential polyhedron visibility on wayfinding and evacuation an online experiment in virtual reality environment
No full textThe paper presents the understanding the basics of the human wayfinding process that can be substantially illuminated by the correlations between space-syntactic variables and kinesthetic data of individuals roaming in a spatio-temporal environment. However, two-dimensional syntactic concepts offer a perception of place to some extent, they may neglect to capture the volumetric effects of space on human perception, especially during movement. Therefore, besides 2D syntactic variables, this paper essentially focuses on polyhedrons as 3D isovists to explore the impacts of the sequential volumetric visibility data on human behavior in terms of the spatial decision-making process in the wayfinding and evacuation issues. In this framework, the article discusses the results of a series of wayfinding and evacuation experiments implemented in a virtual building environment consisting of randomly arranged and dimensioned circulation areas. While evacuation experiments contained legal egress signages at properly designated doors and spots, wayfinding experiments had no signboards. On the other hand, the 3D building model is designed with a couple of architectural modeling software and transferred into a simulation environment. The experiments are conducted with forty four (44) respondents over an online meeting platform. Then, the respondents' trajectories and kinesthetic data are retrieved from the experiments, and the correlations between behavioral and syntactic data are investigated. The primary findings demonstrated that participants in the regular exit group tended to be around the zones with higher integration values. In contrast, the signages and volumetric visibility data are highly influential on the emergency exit group when evacuating the building
A comparative evaluation of sepiolite and nano-montmorillonite on the rheology of cementitious materials for 3D printing
No full textThrough the last decade, methods of digital manufacturing of concrete gained a significant interest compared to conventional concrete. The main challenge in additive manufacturing (3D printing) is to design a highly thixotropic cementitious system. This study aims to investigate the use of sepiolite as a rheology modifier as a novel approach to improve the thixotropic behavior and adapt cementitious systems to 3D printing. To understand the influence of sepiolite on rheological properties, a comparative evaluation with nano-montmorillonite was established. The effectiveness of clay addition was also investigated in fly-ash amended cement-based materials. The rheological analysis was done on cement-paste samples containing both clays in terms of their effects on thixotropy, structural build-up, and recovery. A preliminary printability assessment was done with a lab scale printer having a ram extruder. The results show that the incorporation of clays increased the dynamic yield stress and time-dependent evolution of static yield stress. Moreover, the addition of clays improved the thixotropic behavior of cement-based systems, particularly those containing fly-ash. Herein, the sepiolite was found to be more effective compared to nano-montmorillonite in terms of improving thixotropy, structural build-up and recovery. The results showed that use of fly-ash enhances the printability of the mix for the specified extruder and the samples containing 1% nano-montmorillonite or 0.5% sepiolite can be printed. The positive effects of sepiolite were attributed to opposing surface charges of the clay layers and its micro-fibrous microstructure. The findings in this study enabled an in-depth understanding of the rheology and printability of fly-ash amended clay containing printable cement-based mortars.TÜBİTA
Çok fazlı yüksek entropili alaşımların tasarımı ve işlenmesi
No full textThe multi-principal element alloys (MPEAs) known as high- and medium-entropy alloys possess promising properties due to their highly distorted atomic crystal structures. Employing multi-elements as principal elements has enabled a new platform for novel alloy designs and fabrications. Adding other phases as a heterogeneous phase in MPEAs structures can boost the mechanical behavior. Therefore, the heterogeneous MPEAs address the strength-strain trade-off in most of the conventional alloys. In this thesis, the microstructural evolution and mechanical behavior of two novel heterogeneous high-entropy alloys (HEA) are investigated through thermo-mechanical processing. Using the CALPHAD approach the compositions have been confirmed and subsequently cast. The homogenized samples for both compositions possessed a single-phase uniaxed face centered subic (FCC) structure with high ductility. Possessing high ductility levels in the homogenized condition enabled us to apply high thickness reductions via rolling at room temperature without crack propagation from edges. This study confirms that the sigma phase contribution becomes more significant in the microstructure at higher annealing temperatures. However, the body centered cubic (BCC) phase contribution as a suitable hard-domain becomes less with increasing the annealing temperature. As such, a systematic approach to investigate the effects of the sigma phase and degree of recrystallization on the microstructure and mechanical behavior of the HEAs is presented. In addition, samples subjected to annealing exhibit transformation-induced plasticity (TRIP) under plastic deformation. Results show that the sigma phase can limit the TRIP mechanism in the alloy system since the TRIP-assisted BCC phase is decreased with increased sigma phase present in the microstructure. As such, the designed TRIP-assisted multi-phase HEA enables a combination of 1 GPa yield strength and about 10% of strain at failure for the optimum condition of post-rolled annealed at 750 ℃ for 30 minutes samples. Moreover, this work introduces a novel high strength HEA with proposing a proper combination of homogenization, rolling, annealing, and aging sequences and details for this composition.Yüksek ve orta entropili alaşımlar (YEA) olarak bilinen çoklu element alaşımlar (MPEA), yüksek seviyede çarpılmaya uğramış kristal yapıları nedeniyle pratikte umut vadeden özelliklere sahiptir. Çoklu element yapılarının, ana elementler olarak kullanılması, yeni alaşım tasarımları ve bunların üretimi için yeni bir platform sağlamaktadır. MPEA bir yapıya eklenen başka bir heterojen faz, bu alaşımların mekanik özelliklerinin gelişmesini sağlamaktadır. Bu nedenle, heterojen MPEA'lar, geleneksel alaşımların çoğunda görülen mukavemet-gerinim takasını ele almaktadır. Bu tezde, iki yeni heterojen yüksek entropi alaşımının (HEA) mikro yapıdaki değişimleri ve mekanik özellikleri, termo-mekanik prosesler ile incelenmiştir. CALPHAD kullanılarak alaşımların bileşimi kontrol edilmiş ve doğrulanmıştır. Buna göre alaşımların döküm işlemi gerçekleştirilmiştir. Homojenize edilen numunelerin, yüksek sünekliğe sahip, tek fazlı ve eş eksenli yüzey merkezli kübik (YMK) yapıya sahip olduğu gözlemlenmiştir. Alaşımların sahip olduğu yüksek süneklik özelliği, oda sıcaklığında uygulanan haddeleme işlemi sırasında herhangi bir çatlak oluşumu meydana gelmeden malzeme kalınlığının daha fazla azaltılabilmesini sağlamıştır. Bu çalışma, daha yüksek tavlama sıcaklıklarında mikro yapıda bulunan sigma fazının etkisinin daha önemli hale geldiğini doğrulamaktadır. Ancak, daha sert yapıda olan hacim merkezli kübik (HMK) fazının katkısı, artan tavlama sıcaklığının ile ters orantılı olarak azalmıştır. Bu çalışmada, sigma fazının ve rekristalizasyon derecesinin YEA'nın mikroyapı gelişimi ve mekanik özellikleri üzerindeki etkileri incelenmiştir. Bunlara ek olarak, tavlama ısıl işlemi uygulanan numuneler, plastik deformasyon altında dönüşüm kaynaklı plastisite (TRIP) davranışı sergilemektedir. Sonuçlar incelendiğinde sigma fazının TRIP mekanizmasını sınırlandırdığı görülmüştür. Keza TRIP destekli HMK fazı sigma fazı arttıkça düşüş göstermektedir. Bu nedenle, bu çalışmada tasarlanan TRIP destekli, çok fazlı YEA, 30 dakika 750°C'de tavlanan numunelerde akma mukavemeti 1 GPa olarak gözlenmiş ve kopma noktasında yaklaşık %10 gerinim elde edilen bir alaşım kombinasyonu sağlanmıştır. Ayrıca, bu çalışma homojenleştirme, haddeleme, tavlama ve yaşlandırmanın uygun bir kombinasyonunu önererek yüksek mukavemete sahip yeni bir HEA sunar
Hospital service levels during drug shortages: Stocking and transshipment policies for pharmaceutical inventory
No full textIn this study, we consider a health network that faces uncertain supply disruptions in the form of regional, nationwide, or worldwide drug shortages. Each hospital observes stochastic demand and if the drug is unavailable, patients leave and receive care in another network. As these instances of unavailability diminish the brand value, health networks look for inventory sharing mechanisms among hospitals to mitigate the effect of uncertain supply disruptions. In line with this expectation, we propose a proactive inventory sharing approach for critical drugs to investigate the effect of the inventory-related parameters on service levels.TÜBİTA
Consumer, producer, and prosumer based mathematical models for optimal energy storage sizing
No full textEnergy storage technologies are getting more attention by the increased number of discussions on energy supply security, grid resiliency, and increased flexibility. While lots of studies showed the advantages and disadvantages of energy storage systems for various use cases, very few have studied the storage unit sizing for best results. This study aims to present mathematical models for three critical roles in the grid: consumer, producer, and prosumer. Moreover, the solutions of the models for the actual test cases are analyzed and discussed to further deliver the significance of such a study