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 On- and off-optical-resonance dynamics of dielectric microcylinders under plane wave illumination(OPTICAL SOC AMER, 2015) Mahariq, I.; Kurt, H.; TOBB Ekonomi ve Teknoloji University; Turkish Aeronautical Association; Turk Hava Kurumu UniversityWe explore the on-resonance and off-resonance optical response of dielectric cylinders excited by normal incident plane waves. Both the analytical method, based on Mie theory, and the numerical method, implemented with the spectral element method, are undertaken in the study. We demonstrate that the whispering gallery mode characteristic of resonance behavior is strongly dependent on the refractive index and radius changes. Detuning of either parameter deteriorates the resonance action and creates yet another exciting phenomenon known as photonic nanojets. The subwavelength light focusing property can be associated with nanojets, and engineering the parameters yields strong field confinement and slowly diffracting beam propagation. The current work investigates the optical properties of the dielectric microcylinders at close proximity to the resonance condition. Both strong field focusing associated with photonic nanojets and enhanced field localization linked with the resonance condition are desired for photon manipulation scenarios in nanophotonics. (C) 2015 Optical Society of AmericaPublication Characterizations of self-assembly of peptides and self-assembled peptide nanonetworks(AMER CHEMICAL SOC, 2014) Cinar, Goksu; Tekin, Emine Deniz; Guler, Mustafa Ozgur; Tekin, Emine Deniz; Ihsan Dogramaci Bilkent University; Turk Hava Kurumu University; Turkish Aeronautical AssociationPublication 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 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 Reduce Power Losses and Improve Voltage Level by Using Distributed Generation in Radial Distributed Grid(IEEE, 2017) Sajir, Husham; Rahebi, Javad; Abed, Amir; Farzamnia, Ali; Turkish Aeronautical Association; Turk Hava Kurumu University; Universiti Malaysia SabahServices provided by distributed generation (DG) to power generation and transmission systems have become an urgent necessity due to increase in load demand in recent years. These services include bridging the lack of central generation, increase the reliability of the network, reduce the inactive power in the system, and improve the margin of voltage for the network. On the other hand, the use of energy sources and diversification in the production of electric power. The voltage fluctuation on the end of consumer requires fast-paced strategic solutions and one of these solutions is the distributed generation. They contribute to the control of the voltage fluctuation to have a positive role in the work of the on-load tap changer (OLTC) which is sometimes unable to compensate for the lack of value of the voltages supplied from the source. The main contribution of this work is the introduction particle swarm optimization (PSO) algorithm to simulate a power system using the MATPOWER 6.0 as a tool box and one distributed generation to support the voltage profile. The results were positive as the system was simulated before the generator was entered into the network and the voltage measurement results were Low and after the input of the generator to the distribution network recorded a clear improvement in the voltage profile.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 Peak to Average Power Ratio (PAPR) Reduction in OFDM for Optic Communications based on Conventional Selected Mapping(INT JOURNAL COMPUTER SCIENCE & NETWORK SECURITY-IJCSNS, 2019) Awad, Ousama M. Abdulwanes; Kilicaslan, Muhammed Fatih; Rahebi, Javad; Kastamonu University; Turkish Aeronautical Association; Turk Hava Kurumu UniversityOFDM is a modulation technique that utilizes the optic communication band efficiently by dividing the high-speed information sequence into parallel arms and lifting the frequency selectivity of the multi-carrier channel at the same time and using vertically selected carriers at the same time. Selected mapping is an accurate method for reducing peak to average power ratio from orthogonal frequency division multiplexing. A fundamental weakness of selected mapping is the high computational complexity. To reduce the complexity of the selected mapping, the real and imaginary part of the orthogonal frequency division multiplexing signals is treated separately. Numerical sequences and even real and imaginary elements are obtained using Fourier transform properties. More candidates are produced with a different combination of all the following sequences. The proposed scheme produces less computational complexity using the IFFT algorithm for M4 equations only. The simulation results show that the proposed design reduces the good performance of peak to average power ratio and also reduces computational complexity compared with the selected mapping design.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 Strong field enhancement of resonance modes in dielectric microcylinders(OPTICAL SOC AMER, 2016) Mahariq, Ibrahim; Kurt, Hamza; Turk Hava Kurumu University; Turkish Aeronautical Association; TOBB Ekonomi ve Teknoloji UniversityA loss-free compact dielectric microcylinder acting as an optical resonator is studied in the present work by means of the spectral element method. A specific whispering gallery mode (WGM) supported by the structure is constantly tracked under the same type of illumination while varying the diameter of the resonator between similar to 5 lambda and 8 lambda (lambda = wavelength of light). The parameter space of the optical resonator informs us that it is possible to have either a larger radius of microcylinder with a smaller refractive index or a smaller radius of microcylinder with a larger refractive index value. Two different scenarios are also considered in the current study in order to verify the strong field confinement; one is under Bessel beam illumination conditions and the other is the introduction of nonhomogeneity in the material forming the cylinder. Strong power enhancement up to 3 orders of magnitude is attainable with small microcylinders. While the refractive index changes from 1.50 to 2.25, the corresponding radius utilizing the same type of WGM has to be carefully captured with fine tuning. It is imperative to increase the number of significant digits from 3.9380 lambda to 2.6600939 lambda in order not to miss such huge field enhancement phenomena. Standard resonance condition for constructive interference does not give us targeted parameters. The study may pave the way toward a new technique to detect nanoscale objects below the diffraction limit and may contribute to a new ultramicroscopy technique for detecting single molecules by low-threshold microcavity lasers. Additionally there are nonlinear optics applications. (C) 2016 Optical Society of America