Browsing by Author "Kaya, A."

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Open Access
Continuous processing of images through user sketched functional blocks
(Wiley-Blackwell, 1988) Kaya, A.; Ozguc, B.
Our aim is to implement an image processing system with previously defined algorithms through the use of functional blocks connected together to form a diagram that we call a schematic. A functional block means the representation of a routine or function by a visual object in our intent. The arc connecting two blocks is the path and direction through which an image is transferred. In the development of the system we relied on the usage of new developments in software providing for the construction of better interfaces. Most important of these are the object oriented style of programming, iconic interfacing, multiple window and multi-tasking operating systems.
Open Access
The effect of GaN thickness inserted between two AlN layers on the transport properties of a lattice matched AlInN/AlN/GaN/AlN/GaN double channel heterostructure
(Elsevier BV, 2014-01-31) Tülek, R.; Arslan, E.; Bayraklı, A.; Turhan, S.; Gökden, S.; Duygulu, Ö.; Kaya, A.; Fırat, T.; Teke, A.; Özbay, Ekmel
One AlInN/AlN/GaN single channel heterostructure sample and four AlInN/AlN/GaN/AlN/GaN double channel heterostructure samples with different values of the second GaN layer were studied. The interface profiles, crystalline qualities, surface morphologies, and dislocation densities of the samples were investigated using high resolution transmission electron microscopy, atomic force microscopy, and high-resolution X-ray diffraction. Some of the data provided by these measurements were used as input parameters in the calculation of the scattering mechanisms that govern the transport properties of the studied samples. Experimental transport data were obtained using temperature dependent Hall effect measurements (10-300 K) at low (0.5 T) and high (8 T) magnetic fields to exclude the bulk transport from the two-dimensional one. The effect of the thickness of the second GaN layer inserted between two AlN barrier layers on mobility and carrier concentrations was analyzed and the dominant scattering mechanisms in the low and high temperature regimes were determined. It was found that Hall mobility increases as the thickness of GaN increases until 5 nm at a low temperature where interface roughness scattering is observed as one of the dominant scattering mechanisms. When GaN thicknesses exceed 5 nm, Hall mobility tends to decrease again due to the population of the second channel in which the interface becomes worse compared to the other one. From these analyses, 5 nm GaN layer thicknesses were found to be the optimum thicknesses required for high electron mobility. (C) 2013 Published by Elsevier B.V.
Open Access
Isolated subcutaneous abscess: A rare presentation of extrapulmonary tuberculosis
(Lippincott Williams & Wilkins, 2023-08-01) Sahin, A.; Kara-Aksay, A.; Bicmen, C.; Belkaya, Serkan; Kaya, A.; Yilmaz, D.
Open Access
Looking for timing variations in the transits of 16 exoplanets
(Oxford University Press, 2024-04-05) Yalcinkaya, S.; Esmer, E. M.; Basturk, O.; Muhaymin, A.; Kutluay, A. C.; Silistre, D. I.; Akar, F.; Southworth, J.; Mancini, L.; Davoudi, F.; Karamanli, E.; Tezcan, F.; Demir, E.; Yilmaz, D.; Guleroglu, E.; Tekin, M.; Taskin, I.; Aladag, Y.; Sertkan, E.; Kurt, U. Y.; Fisek, S.; Kaptan, S.; Alis, S.; Aksaker, N.; Yelkenci, F. K.; Tezcan, C. T.; Kaya, A.; Oglakkaya, D.; Aydin, Z. S.; Yesilyaprak, C.
We update the ephemerides of 16 transiting exoplanets using our ground-based observations, new Transiting Exoplanet Survey Satellite data, and previously published observations including those of amateur astronomers. All these light curves were modelled by making use of a set of quantitative criteria with the exofast code to obtain mid-transit times. We searched for statistically significant secular and/or periodic trends in the mid-transit times. We found that the timing data are well modelled by a linear ephemeris for all systems except for XO-2 b, for which we detect an orbital decay with the rate of -12.95 +/- 1.85 ms yr(-1) that can be confirmed with future observations. We also detect a hint of potential periodic variations in the transit timing variation data of HAT-P-13 b, which also requires confirmation with further precise observations.
Open Access
A maintanence policy for a system with multi-state components: an approximate solution
(Elsevier, 2002) Gürler, Ü.; Kaya, A.
For maintenance and quality assessment purposes, various performance levels for both systems and components are identified, usually as a function of the deterioration. In this study, we consider a multicomponent system where the lifetime of each component is described by several stages, (0,…,S), which are further classified as good, doubtful, preventive maintenance due (PM due) and down. A control policy is suggested where the system is replaced when a component enters a PM due or a down state and the number of components in the doubtful states (K,…,S−2) is at least N. All maintenance activities are assumed to take negligible time. The exact description of the underlying stochastic model under the policy is very complicated. We therefore propose some approximations, which allow an explicit expression for the long run average cost function, which is minimized w.r.t. (K,N) by numerical methods. Sensitivity of the model to system parameters and the performance of the approximation are investigated through several examples.