WOS - Web of Science
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Publication A Novel Current-Controlled Oscillator-Based Low-Supply-Voltage Microbolometer Readout Architecture(World Scientific Pub Co Pte Lt, 2020-01-06) Mehmet Ali Gülden; Enver Çavuş; Zencir, ErtanIn this paper, we present a novel, almost-digital approach for bolometer readout circuits to overcome the area and power dissipation bottlenecks of analog-based classical microbolometer circuits. A current-controlled oscillator (CCO)-based analog-to-digital converter (ADC) is utilized instead of a capacitive transimpedance amplifier (CTIA) in the classical readout circuits. This approach, which has not been reported before, both produces the required gain in the bolometer input circuit and directly digitizes the bolometer signal. With the proposed architecture, the need for large capacitances (of the order of 10–15[Formula: see text]pF for each column) at which the current is accumulated in the bolometer circuits and the voltage headroom limitation of classical microbolometer circuits are eliminated. Therefore, the proposed architecture permits to design readout circuits with reduced pixel pitch and lower power supply, both of which in turn lead to higher-resolution Focal Plane Arrays (FPAs) with lower power dissipation. The new architecture is modeled and simulated using a 180-nm CMOS process for sensitivity, noise performance, and power dissipation. Unlike the 3.3-V power supply usage of classical readout circuits, the proposed design utilizes 1.2-V analog and 0.9-V digital supply voltages with a power dissipation of almost half of the classical approach.Publication Spectroscopic and DFT study on molecular structure of 1-(o-tolyl) thiourea molecule(ELSEVIER, 2020) Bahceli, Semiha; Sarikaya, Ebru Karakas; Dereli, Omer; Ozturan, Feride Pinar; Turk Hava Kurumu University; Turkish Aeronautical Association; Necmettin Erbakan UniversityThe molecule 1-(o-Tolyl)thiourea, (C-8 H-10 N-2 S), which is biologically active, was investigated experimentally using the infrared and Raman spectroscopies and theoretically by performing at the B3LYP/6-311++G (d,p) level of theory. In this framework, the geometrical conformational analysis of the title molecule pointed out the most stable conformation with the energy of -818.732369 Hartree and the dipole moment of 5.431104 Debye. Additionally, the vibrational frequencies were calculated and compared with experimental values and a good agreement between the measured and calculated values for the molecule 1-(o-Tolyl)thiourea were obtained. Furthermore, some thermodynamic parameters of the title molecule were calculated at the mention level of the theory. (C) 2020 Elsevier B.V. All rights reserved.Publication A 120 MHz fast automatic tuning CMOS active-RC lowpass filter(ELSEVIER SCI LTD, 2023) Yesil, Ercem; Zencir, Ertan; Zencir, Ertan; Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK); Turk Hava Kurumu University; Turkish Aeronautical AssociationIn this paper, a fast automatic cutoff frequency calibrating, CMOS lowpass filter with linear-in-dB tunable gain and constant in-band group delay is presented. The automatic frequency tuning (AFT) circuit can successfully tune the cutoff frequency to 120 MHz with less than 4.7% error. In-band group delay variation is handled using a capacitor process variation detection circuit (CPVD), and the overall tuning time is less than 700 ns. The design is done using STM PD-SOI 130 nm CMOS process, and the supply voltage is 1.2 V with a total power consumption of 21.7 mW. The overall filter provides a programmable linear-in-dB gain of 0.5 dB to 17.6 dB range with a cutoff tuning range of 80 to 180 MHz. The in-band group delay variation is below 500 ps with an adjacent channel ratio (ACR) of 85 dB. The spurious free dynamic range (SFDR) is over 66.6 dBc. The active area of the filter with tuning is 0.171 mm2.Publication Smart prospects for solar-based cooling and heating systems in the Middle East and Turkey(IEEE, 2022) Baba, Abdullatif; Al Shehabi, Shadi; Bonny, M. Talal; Baba, Abdullatif; Turkish Aeronautical Association; Turk Hava Kurumu University; University of SharjahSolar-based systems represent the focal interest field for most of the newest studies of renewable energy. Solar heating and cooling systems convert thermal energy coming from the sun into electricity or heat to provide residential, commercial, and industrial areas with hot water, or to retain a specific required temperature. These technologies replace the classical fossil energy sources that are characterized by their damaging environmental impacts as well as their expensive costs. In this paper, we look at the ambitious solar projects that are already established or will be constructed in different countries of the ME and Turkey. Then, we discuss in brief most of the available technologies that rely on solar-based approaches for heating and cooling purposes. To overcome some challenges that may affect the performance of solar plants like cloudy or night environments, smart management techniques for interconnected units, or the cross-border power units of neighbored countries, are presented here and clarified by a case study. Finally, we conclude with a summary describing the most important features of our paper.Publication On Modified Mellin-Gauss-Weierstrass Convolution Operators(SPRINGER BASEL AG, 2022) Aral, A.; Erbay, H.; Yilmaz, B.; Kirikkale University; Turk Hava Kurumu University; Turkish Aeronautical AssociationMellin transform has various applications to real-life problems in function approximation, signal processing, and image recognition, thus, it has been the main ingredient of many studies in diverse fields. This study is devoted to Mellin operators and their variants to improve approximation accuracy and approximate ratio. Two Mellin type operators are reconstructed by using two sequences of functions to enable lower pointwise approximation error as well as higher pointwise convergence rate. Keeping the idea of Mellin convolution, these classes aim to be associated with functions defined on the semi-real axis, and the affine and quadratic functions pairs are fixed points. It has been shown, both theoretically and numerically, that operators can be used to approximate functions pointwise. Indeed the approximation accuracy can be adjusted by tuning the parameters. Moreover, weighted approximation, as well as Voronovskaya type results, are studied throughout the paper. The advantages of each operator over the other in terms of both approximation errors and convergence rates are presented.Publication Parallel Multiobjective Feature Selection for Binary Classificatio(IEEE, 2020) Deniz, Ayca; Kiziloz, Hakan Ezgi; Middle East Technical University; Turkish Aeronautical Association; Turk Hava Kurumu UniversityFeature selection has become a prominent step for many research studies as available data increases continuously with the advances in technology. The objective of feature selection is two-fold: minimizing the number of features and maximizing learning performance. Therefore, it requires a multi-objective optimization. In this study, we utilize the multi-core nature of a regular PC in the feature selection domain. For this purpose, we build three models that exploit the parallel processing capability of a modern CPU. We execute the feature selection task on a single processor in the first model as a baseline. In other models, we execute the feature selection task in four cores of the CPU, in parallel. Specifically, in the second model, we decrease the population size per processor and explore whether we can achieve comparable solution sets in less amount of time. The third model preserves the population size and explores a more extensive search space. We compare the results of these models in terms of accuracy, number of features and execution time. Experiment results show that parallel processing in the feature selection domain leads to faster execution and better feature subsets.Publication Investigation of Vibration, Sound Intensity, Machine Current and Surface Roughness Values of AISI 4140 During Machining on the Lathe(SPRINGER HEIDELBERG, 2020) Sahinoglu, Abidin; Rafighi, Mohammad; Cankiri Karatekin University; Turk Hava Kurumu University; Turkish Aeronautical AssociationThe AISI 4140 steel is one of the most widely used alloys in various applications due to its good formability, high-strength, weldability and excellent corrosion resistance properties. In this study, the effects of cutting parameters (feed rate, depth of cut and cutting speed) were investigated on surface roughness, vibration, sound intensity and machine current during turning of AISI 4140 using coated carbide cutting tools under dry test condition. The response surface methodology, analysis of variance and statistical methods of main effect plot were applied to investigate the effects of input parameters on the response variables. Mathematical models for surface roughness, vibration, sound intensity and machine current were developed using multiple linear regression methods. In addition, the confirmation test was carried out in order to validate reasonable degree of approximation between predicted and experimental results. The results of this study showed that feed rate has the most significant impact on output parameters followed by depth of cut. Therefore, according to the experimental data, vibration, sound intensity, surface roughness and current values increase as the amount of feed rate and the depth of cut increases.Publication What's going on in my mind? The effects of cognitive differences on buying impulsiveness, cognitive dissonance, and price consciousness(WILEY, 2022) Ozyoruk, Huseyin Erbil; Turkish Aeronautical Association; Turk Hava Kurumu UniversityBuying impulsiveness, tendency for cognitive dissonance, and price consciousness may differ among consumers, primarily because of differences in individuals' time orientation, thinking style, risk perception, and cognitive flexibility. This exploratory hypothesis-testing study aims to examine whether the cognitive differences in future orientation, holistic thinking, risk perception, and cognitive flexibility of consumers affect buying impulsiveness, tendency for cognitive dissonance, and price consciousness, through hypothesis testing and structural equation modelling. Data were collected face-to-face from 414 participants across the two largest cities of Turkey (Istanbul and Ankara) using the convenience sampling method. The findings demonstrate that future orientation, holistic thinking, and risk perception negatively affect buying impulsiveness. The tendency for post-purchase cognitive dissonance is negatively affected by future orientation and holistic thinking and is positively affected by risk perception. Price consciousness, however, is affected positively by future orientation and negatively by risk perception. In addition, cognitive flexibility, which is also shaped by future orientation and holistic thinking, increases price consciousness and plays a mediating role in the relationship between future orientation and price consciousness.Publication An Analysis of the Impact of the Syrian Crisis on Turkey's Politic-Military, Social and Economic Security(HALE SIVGIN, 2020) Demir, Sertif; Yilmaz, Muzaffer Ercan; Demir, Sertif; Turk Hava Kurumu University; Turkish Aeronautical Association; Uludag UniversityThis study analyzes how the ongoing Syrian Crisis has affected Turkey's security. It starts with an overview of recent developments in the Middle East in general and in Syria specifically. It then examines the political, military, social, and economic effects of the Syrian Crisis for Turkey's security. It concludes that the Syrian Crisis represents Turkey's most challenging security problem since the end of the Second World War as it has had many profound impacts on the country.Publication Experimental and analytical investigation of the tensile behavior of 3D-printed composites based on micro-CT analysis(SAGE PUBLICATIONS LTD, 2023) Sik, Alp; Tanabi, Hamed; Cubukcu, H. Evren; Sabuncuoglu, Baris; Hacettepe University; Hacettepe University; Turk Hava Kurumu University; Turkish Aeronautical Association; Hacettepe University; Hacettepe UniversityMechanical properties of short fiber reinforced composites manufactured with fused deposition modeling is affected by variables such as printing properties and internal structure of the composite. In this study, the relation between the tensile properties of 3D-printed short fiber reinforced composites, printing orientation and internal structure is inspected. Samples of different printing orientations are manufactured. These samples are inspected under X-ray micro computed tomography (micro-CT) and their fiber orientation distributions and fiber properties are determined. Then, these internal structure properties are applied to analytical material models to estimate the tensile properties of composites. Estimated material properties are compared with tensile test results. It turns out that analytical models that consider internal structure properties provide more accurate estimations than other analytical models that does not take these into account.