5916 research outputs found
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Optical and radiative properties of individual and hybrid nanosuspensions: The effects of similar and dissimilar particle agglomerates on thermal radiation
No full textNanosuspensions are proposed for use in improving the thermal efficiency of different thermal systems; including solar thermal power plants. Because of their excellent and unique thermo-optical properties, which are the basis of thermal transfer phenomena, they are used as working fluids in solar thermal collectors for photothermal energy conversion. However, particle agglomeration in nanosuspensions remains one of the most important challenges faced in terms of their usage. The purpose of this study is to investigate the particle agglomeration behavior of water-based Al2O3 and TiO2 individual and hybrid nanosuspensions and observe their effects on spectral radiative properties. By carrying out number of experiments, the effects of similar and dissimilar particle agglomerations on radiative properties are clarified. The results show that pH have significant effect on the particle agglomeration which in turn affects the optical and radiative properties involving individual and hybrid nanosuspensions. Particle agglomerates (similar and dissimilar) plays an important role when specific radiative properties are required for specific applications. Different regimes of the dependent/independent scattering can be obtained from the effect of similar and dissimilar particle agglomerates of a particular nanosuspension.Center for Energy, Environment, and Economy (CEEE) at Ozyegin UniversityPublisher versio
First-principle diffraction simulations as a tool to solve the nanodiffraction problem
No full textN/APublisher versio
Vehicular VLC: A ray tracing study based on measured radiation patterns of commercial taillights
No full textIn this letter, we investigate the performance of vehicular visible light communications based on the radiation patterns of different commercial taillights (TLs) using non-sequential ray tracing simulations. Our simulation results indicate a significant variation in the path loss compared with Lambertian model. Based on the ray tracing results, we propose a new path loss model as a function of the propagation distance considering the asymmetrical radiation pattern of TLs. We use this model to derive the attainable transmission distance. We further present the delay spread for various vehicular communication scenarios to demonstrate the effect of neighboring vehicles.European Union's Horizon 2020 ; TÜBİTAK ; Optical Wireless Communication (OWC) Cost Actio
Designing an efficient gradient descent based heuristic for clusterwise linear regression for large datasets
No full textMultiple linear regression is the method of quantifying the effects of a set of independent variables on a dependent variable. In clusterwise linear regression problems, the data points with similar regression estimates are grouped into the same cluster either due to a business need or to increase the statistical significance of the resulting regression estimates. In this paper, we consider an extension of this problem where data points belonging to the same category should belong to the same partition. For large datasets, finding the exact solution is not possible and many heuristics requires an exponentially increasing amount of time in the number of categories. We propose variants of gradient descent based heuristic to provide high-quality solutions within a reasonable time. The performances of our heuristics are evaluated across 1014 simulated datasets. We find that the comparative performance of the base gradient descent based heuristic is quite good with an average percentage gap of 0.17 % when the number of categories is less than 60. However, starting with a fixed initial partition and restricting cluster assignment changes to be one-directional speed up heuristic dramatically with a moderate decrease in solution quality, especially for datasets with a multiple number of predictors and a large number of datasets. For example, one could generate solutions with an average percentage gap of 2.81 % in one-tenth of the time for datasets with 400 categories
Studies of charm and beauty hadron long-range correlations in pp and pPb collisions at LHC energies
No full textMeasurements of the second Fourier harmonic coefficient (v2) of the azimuthal distributions of prompt and nonprompt D0 mesons produced in pp and pPb collisions are presented. Nonprompt D0 mesons come from beauty hadron decays. The data samples are collected by the CMS experiment at nucleon-nucleon center-of-mass energies of 13 and 8.16 TeV, respectively. In high multiplicity pp collisions, v2 signals for prompt charm hadrons are reported for the first time, and are found to be comparable to those for light-flavor hadron species over a transverse momentum (pT) range of 2-6 GeV. Compared at similar event multiplicities, the prompt D0 meson v2 values in pp and pPb collisions are similar in magnitude. The v2 values for open beauty hadrons are extracted for the first time via nonprompt D0 mesons in pPb collisions. For pT in the range of 2-5 GeV, the results suggest that v2 for nonprompt D0 mesons is smaller than that for prompt D0 mesons. These new measurements indicate a positive charm hadron v2 in pp collisions and suggest a mass dependence in v2 between charm and beauty hadrons in the pPb system. These results provide insights into the origin of heavy-flavor quark collectivity in small systems.BMBWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, PUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (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); SEIDI, CPAN, PCTI, and FEDER (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 (USA). Individuals have received support from the Marie-Curie program and the European Research Council and Horizon 2020 Grant, contract Nos. 675440, 752730, and 765710 (European Union); the Leventis Foundation; the A.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; 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 HOMING PLUS program of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund, the Mobility Plus program of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/01406; the National Priorities Research Program by Qatar National Research Fund; the Ministry of Science and Higher Education of the Russian Federation, project no. 02.a03.21.
r 0005 (Russia); the Tomsk Polytechnic University Competitiveness Enhancement Program; the Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia Maria de Maeztu, grant MDM-2015-0509 and the Programa Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programs cofinanced by EU-ESF and the Greek NSRF; 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 (USA).Publisher versio
Synthetic jet cooling technology for electronics thermal management - A critical review
No full textEffective removal of excess heat from electronics equipment is the key to its intended functionality. A Defense Advanced Research Projects Agency (DARPA) hard problem is proposed in microtechnologies for the air-cooled heat exchangers (MACE) program that posed challenges to reduce the heat sink size fourfold while using only 50% of the current power budget. While numerous heat removal techniques have been proposed over the last several decades, synthetic jet actuator (SJA) is one of the leading candidates to create a game-changing cooling performance. This is due to its inherent advantages, such as size, low power consumption, ease of use, and affordability. This review article looks at different actuation methods (electromagnetic, piston cylinder, piezoelectric, and so on) to generate synthetic jet cooling. The performances of these approaches vary and need a procedure to unify the predictive capability. The performances are evaluated based on actuation (stroke length, operating frequency, and jet-to-heater spacing) and geometric parameters (shape and size of the cavity and the orifice). The flow characteristics and jet formation criterion are also discussed methods, and a critical commentary is added to normalize previous findings. Available correlations for predicting Nu numbers are evaluated and summarized through data sets for a possible unification. Finally, an empirical correlation is proposed based on available data using nonlinear regression via computational tools. To conclude, the challenges and research gaps are enumerated covering the fundamental and applied aspects of those jets for the implementation in electronics thermal management
A wireless power transfer method for electric vehicles by synchronization to secondary resonance
No full textIn this study, an alternative method and framework for a wireless power transfer system to a moving object such as an electric vehicle or a robot are presented. The well-known systems and their common series-connected/switched road embedded segment structures are discussed and challenged. Then, an alternative method of synchronization to the secondary resonance is presented. The suggested method eliminates switches between road-embedded coil units and makes the energy transition easy among units. This method shortens the length of the EMF radiative part of road embedded segments and the application is suitable for two-dimensional floor embedded structures for robot applications. The experimental setup and the simulation results are shared with the framework of further study
Coverage analysis of downlink MU-MIMO cellular networks
No full textIn this letter, we analyze the coverage performance of multi-user multiple-input multiple-output (MU-MIMO) downlink cellular networks. We model the locations of the base stations and mobile users using Poisson Point Processes and employ maximum ratio transmission precoding at the base station. Our analysis builds upon Prony's method to approximately calculate the coverage probability using the sum of exponentials which facilitates the computation of Laplace transform of both intra-cell and inter-cell interference. We demonstrate the accuracy of derived approximate coverage probability expressions through numerical simulations for different MU-MIMO configurations
Learning system dynamics via deep recurrent and conditional neural systems
No full textAlthough there are various mathematical methods for modeling system dynamics, more general solutions can be achieved using deep learning based on data. Alternative deep learning methods are presented in parallel with the improvements in artificial neural networks. In this study, both LSTM-based recurrent deep learning method and CNMP-based conditional deep learning method were used to learn the system dynamics of the selected system using time series data. The effects of the amount of time series data needed for training and the initial input length needed for predictions made using the learned system model on both methods were analyzed