Scopus
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Publication Implementation of DBSCAN Method in Star Trackers to Improve Image Segmentation in Heavy Noise Conditions(2023) Nevsan ŞENGİL; Şengil, Nevsan; Türk Hava Kurumu Üniversitesi, Uzay Mühendisliği Bölümü, Ankara, TürkiyeStar trackers are currently the most accurate sensors for determining the attitude of a spacecraft. These sensors comprise not only highly capable optical detectors and processor units but also complicated software solvers. One of the main solvers employed in star trackers is image segmentation. In this study, the aim is to develop a hybrid image segmentation method which is a combination of both global thresholding and density-based spatial clustering of applications with noise (DBSCAN) method to increase detection probability of the stars in heavy noise. Secondly, a sorting algorithm is added to list the detected stars in terms of their brightness to increase the efficiency of the star tracking algorithm. Then, this new approach and two different conventional segmentation methods are applied to the Orion star constellation image polluted with Gaussian, salt and pepper, and uneven background noises. The resulting images of these segmentation methods are compared in terms of denoising capabilities. Although computationally more expensive, the proposed DBSCAN-based hybrid method displays a background pixel recovery performance of 99.5%, compared to Otsu global thresholding and adaptive thresholding methods’ 73.5% and 79.9% recovery values, respectively. Additionally, it has been demonstrated that the sorting algorithm successfully listed the detected stars in accordance with their brightness.Publication Investigating on Environmental Effects of Different Combi Boilers Using LPG Fuel(2019) Halil İbrahim VARIYENLI Faraz AFSHARI Ataollah KHANLARI; Gazi Üniversitesi, Teknoloji Fakültesi, Enerji Sistemleri Mühendisliği, Teknikokullar, Ankara, Türkiye, Erzurum Teknik Üniversitesi, Makine Mühendisliği Bölümü, Erzurum, Türkiye Türk Hava Kurumu Üniversitesi, Makine Mühendisliği, Ankara, Türkiye.Space heating and hot water supplying are usually done by utilizing combi boilers. Various kinds of combi boilers are available. In the last years condensing type combi boilers have been introduced that have high efficiency in comparison to conventional one. In the present study the impact of combi boiler type on pollutant gas emissions was experimentally investigated. Three various combi boiler including condensing, full condensing and conventional type combi boilers have been utilized in the experiments. Moreover, the experiments have been conducted in various outlet hot water temperatures to determine the effect of temperature. The achieved findings indicated that in all temperatures utilizing condensing and full condensing combi boilers decreased NO, NOx and SO2, gas emissions considerably.Publication Probing molecular interactions on carbon nanotube surfaces using surface plasmon resonance sensors(AIP Publishing, 2012-11-26) Nurbek Kakenov; Osman Balci; Sinan Balci; Coskun KocabasIn this work, we present a method to probe molecular interactions on single-walled carbon nanotube (SWNT) surfaces using a surface plasmon sensor. SWNT networks were synthesized by chemical vapor deposition and transfer-printed on gold surfaces. We studied the excitation of surface plasmon-polaritons on nanotube coated gold surfaces with sub-monolayer, monolayer, and multilayer surface coverage. Integrating the fabricated sensor with a microfluidic device, we were able to obtain binding dynamics of a bovine serum albumin (BSA) protein on SWNT networks with various tube densities. The results reveal the kinetic parameters for nonspecific binding of BSA on SWNT coated surfaces having various tube densities.Publication 2D hybrid meshes for direct simulation Monte Carlo solvers(IOP Publishing, 2013-02-08) N Sengil; U SengilPublication Label-Free Nanometer-Resolution Imaging of Biological Architectures through Surface Enhanced Raman Scattering(Springer Science and Business Media LLC, 2013-09-11) Sencer Ayas; Goksu Cinar; Alper Devrim Ozkan; Zeliha Soran; Oner Ekiz; Deniz Kocaay; Aysel Tomak; Pelin Toren; Yasin Kaya; Ilknur Tunc; Hadi Zareie; Turgay Tekinay; Ayse Begum Tekinay; Mustafa Ozgur Guler; Aykutlu DanaPublication Compressive Response of Polycrystalline NiCoMnGa High-Temperature Meta-magnetic Shape Memory Alloys(Springer Science and Business Media LLC, 2013-05-29) H. E. Karaca; A. S. Turabi; B. Basaran; A. K. Pathak; I. Dubenko; N. Ali; Y. I. Chumlyakov; P. LiPublication Elasticity-Based Mechanism for the Collective Motion of Self-Propelled Particles with Springlike Interactions: A Model System for Natural and Artificial Swarms(American Physical Society (APS), 2013-12-26) Eliseo Ferrante; Ali Emre Turgut; Marco Dorigo; Cristián HuepePublication NREL VI rotor blade: numerical investigation and winglet design and optimization using CFD(Wiley, 2013-02-06) Monier A. Elfarra; Nilay Sezer‐Uzol; I. Sinan AkmandorABSTRACTThe main objectives of this study were to aerodynamically design and optimize a winglet for a wind turbine blade by using computational fluid dynamics (CFD) and to investigate its effect on the power production. For validation and as a baseline rotor, the National Renewable Energy Laboratory Phase VI wind turbine rotor blade is used. The Reynolds‐averaged Navier–Stokes equations are solved, and k–ε Launder–Sharma turbulence model was used. The numerical results have shown a considerable agreement with the experimental data. The genetic algorithm was used as the optimization technique with the help of artificial neural network to reduce the computational cost. In the winglet design, the variable parameters are the cant and twist angles of the winglet and the objective function the torque. Multipoint optimization is carried out for three different operating wind speeds, and a total of 24 CFD cases are run in the design. The final optimized winglet showed around 9% increase in the power production. Copyright © 2013 John Wiley & Sons, Ltd.Publication On Caputo modification of the Hadamard fractional derivatives(Springer Science and Business Media LLC, 2014-01-07) Yusuf Y. Gambo; Fahd Jarad; Dumitru Baleanu; Thabet AbdeljawadAbstract This paper is devoted to the study of Caputo modification of the Hadamard fractional derivatives. From here and after, by Caputo-Hadamard derivative, we refer to this modified fractional derivative (Jarad et al. in Adv. Differ. Equ. 2012:142, 2012, p.7). We present the generalization of the fundamental theorem of fractional calculus (FTFC) in the Caputo-Hadamard setting. Also, several new related results are presented.Publication Wide Operating Voltage Range Fuel Cell Battery Charger(Kaunas University of Technology (KTU), 2014-05-19) J. C. Hernandez; M. C. Mira; G. Sen; O. C. Thomsen; M. A. E. Andersen