Teknik Bilimler Meslek Yüksekokulu / Vocational School of Technical Sciences
Permanent URI for this collectionhttps://hdl.handle.net/11727/2031
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Item Investigation Of The Frequency Effect On Electrical Modulus And Dielectric Properties Of Al/P-Si Structure With %0.5 Bi:Zno Interfacial Layer(Başkent Üniversitesi Teknik Bilimler Meslek Yüksekokulu, 2024-05-01) Bengi, S.; Cetinkaya, H. G.; Altindal, S.; Durmus, P.Capacitance and conductance measurements were made to evaluate the effects of voltage and frequency on the dielectric properties, ac electrical conductivity (sigma(ac)), and electric-modulus of the Al/%0.5 Bi:ZnO/p-Si structures. The measurements were taken in a voltage range of (- 4 V)-(+ 4 V) and frequency range of 0.1-1 MHz, respectively. All parameters were discovered to have substantial relationships to voltage and frequency at accumulation and depletion regions due to relaxation mechanisms and interface traps positioned between %0.5 Bi:ZnO interlayer and p-Si with energies in the Si bandgap. The e'-V, M''-V, and Z''-V plots all demonstrate a peak, and because of electronic charges being reordering and restructuring at surfaces, traps, and dipole-polarization under the external electric field, the peak's position and magnitude vary with frequency. The double logarithmic sigma ac-w curve shows linear behaviour, its slope was found as 0.699, and this value of the Al/%0.5 Bi:ZnO/p-Si/Au structure has high ac conductivity or low resistivity. The observed high changes in the dielectric constant and dielectric loss (e', e'') were explained by Maxwell-Wagner type polarization as well as interface traps.Item Esra (Elevator Simulation, Research & Analysis): An Open-Source Software Tool For Elevator Traffic Simulation, Research, And Analysis(Başkent Üniversitesi Teknik Bilimler Meslek Yüksekokulu, 2024-04-05) Tartan, Emre Oner; Ciflikli, CebrailToday, although elevator companies typically have their own elevator simulation and analysis tools, these remain inaccessible to the public due to commercial concerns and rivalry in the sector. Consequently, due to the lack of modular open-source software tools, interest in the design and development of elevator systems in academia is quite limited, contrary to the vast potential of the field. This paper addresses this gap introducing an open-source software tool, the Elevator Simulator for Research and Analysis (ESRA), developed using the MATLAB programming language and an object-oriented approach. ESRA features built-in control methods, and visualization options with the capability to save and reuse traffic data, facilitating in-depth comparative analysis. Moreover, its modular architecture allows a design and development basis for further research in the field. The proposed software aims to enable developers to design, implement, analyse, and compare their control algorithms with other methods.Item The Frequency Dependent of Main Electrical Parameters, Conductivity and Surface States in the Al/ (%0.5 Bi:ZnO)/p-Si/Au (MIS) Structures(Başkent Üniversitesi Teknik Bilimler Meslek Yüksek Okulu, 2024-03-09) Cetinkaya, H. G.; Bengi, S.; Durmus, P.; Demirezen, S.; Altindal, S.The capacitance/conductance-voltage-frequency (C/G-V-f) features of the Au/p-Si structures with (%0.5 Bi-doped ZnO) interlayer grown by spin-coating technique was investigated between 100 kHz and 1 MHz. The C-2-V curves that depend on frequency were used to determine the electrical-parameters like diffusion-potential (V-D), Fermi-energy level (E-F), barrier-height (Phi(B)), and depletion-layer (W-D) thickness. The value of Phi(B) was found to increase with increasing frequency due to the decrease in surface-states (N-ss) effects on the C-V characteristics. Voltage dependent series-resistance (R-s) was obtained by using Nicollian-Brews method for each frequency and it decreased with increasing frequency. Both the low-high frequency capacitance (C-LF-C-HF) and Hill-Coleman techniques were used to determine the voltage-dependent profile of N-ss. While N-ss decreases with increasing frequency, voltage-dependent on them give two distinctive peaks due to a special distribution of them at interlayer/semiconductor interface in the bandgap depending on their relaxation time. All these experimental results indicate that the existence of R-s, N-ss, and interlayers considerably influence the impedance measurements.Item Sequential Decision Making for Elevator Control(2023) Tartan, Emre Oner; Ciflikli, Cebrail; 0000-0002-5688-4226; JVD-9650-2023In the last decade Reinforcement Learning (RL) has significantly changed the conventional control paradigm in many fields. RL approach is spreading with many applications such as autonomous driving and industry automation. Markov Decision Process (MDP) forms a mathematical idealized basis for RL if the explicit model is available. Dynamic programming allows to find an optimal policy for sequential decision making in a MDP. In this study we consider the elevator control as a sequential decision making problem, describe it as a MDP with finite state space and solve it using dynamic programming. At each decision making time step we aim to take the optimal action to minimize the total of hall call waiting times in the episodic task. We consider a sample 6-floor building and simulate the proposed method in comparison with the conventional Nearest Car Method (NCM).Item A viable snore detection system: hardware and software implementations(2020) Tuncer, Ahmet Turgut; Bilgen, MehmetA stand-alone, custom-made biomedical system was introduced for long-term monitoring of sleep and detection of snoring events. Commercially available electronic components were assembled for recording audio, pulse, and respiration signals. Its software was implemented for off-line processing of the acquired signals in C++ and MATLAB environments. The linear and nonlinear features of the signals were extracted and characterized using spectral energy distribution, entropy, and largest Lyapunov exponent (LLE). The performance of the system was evaluated with real physiological data gathered from 14 chronic snorers. Analysis of the cases indicated that the system identified the snoring events with an accuracy of 88.22%, sensitivity of 94.91%, and positive predictive value of 90.95%. This high level of validation confirmed the reliability and utility of the system in detecting snoring.Item Timing studies of X Persei and the discovery of its transient quasi-periodic oscillation feature(2014) Acuner, Z.; Inam, S.C.; Sahiner, S.; Serim, M.M.; Baykal, A.; Swank, J.We present a timing analysis of X Persei (X Per) using observations made between 1998 and 2010 with the Proportional Counter Array (PCA) onboard the Rossi X-ray Timing Explorer (RXTE) and with the INTEGRAL Soft Gamma-Ray Imager (ISGRI). All pulse arrival times obtained from the RXTE-PCA observations are phase-connected and a timing solution is obtained using these arrival times. We update the long-term pulse frequency history of the source by measuring its pulse frequencies using RXTE-PCA and ISGRI data. From the RXTE-PCA data, the relation between the frequency derivative and X-ray flux suggests accretion via the companion's stellar wind. However, the detection of a transient quasi-periodic oscillation feature, peaking at similar to 0.2 Hz, suggests the existence of an accretion disc. We find that double-break models fit the average power spectra well, which suggests that the source has at least two different accretion flow components dominating the overall flow. From the power spectrum of frequency derivatives, we measure a power-law index of similar to-1, which implies that, on short time-scales, disc accretion dominates over noise, while on time-scales longer than the viscous time-scales, the noise dominates. From pulse profiles, we find a correlation between the pulse fraction and the count rate of the source.Item An OFDM throughput analysis for cognitive radio application in contiguous or noncontiguous TV white spaces(2015) Ciftlikli, Cebrail; Tuncer, Ahmet Turgut; Ozturk, YusufRadio frequency spectrum is a finite and scarce resource. Efficient use of the radio frequency spectrum is a fundamental research issue. Since a large portion of the assigned radio frequency spectrum is used only sporadically, the bands currently allocated to TV services can be opportunistically reassigned to support broadband networking services while continuing to provide broadcast TV. The fragmented and unused TV channels named white spaces have a considerable amount of bandwidth potential and long transmission ranges. Bandwidth scalability can be supported by bonding multiple contiguous or noncontiguous consecutive channels using orthogonal frequency division multiplexing (OFDM)-based cognitive radio. In this paper, an in-depth throughput analysis of OFDM fixed carrier spacing and fixed carrier number approaches has been done for various modulation schemes in TV white spaces. Signal propagation delay is studied under various channel conditions. An analytical model-based estimation of the throughput by taking into account channel bonding is presented.Item Slot Parameter Optimization for Multiband Antenna Performance Improvement Using Intelligent Systems(2015) Demircioglu, Erdem; Yagli, Ahmet Fazil; Gulgonul, Senol; Ankishan, Haydar; Tartan, Emre Oner; Sazli, Murat H.; Imeci, TahaThis paper discusses bandwidth enhancement for multiband microstrip patch antennas (MMPAs) using symmetrical rectangular/square slots etched on the patch and the substrate properties. The slot parameters on MMPA are modeled using soft computing technique of artificial neural networks (ANN). To achieve the best ANN performance, Particle Swarm Optimization (PSO) and Differential Evolution (DE) are applied with ANN's conventional training algorithm in optimization of the modeling performance. In this study, the slot parameters are assumed as slot distance to the radiating patch edge, slot width, and length. Bandwidth enhancement is applied to a formerly designed MMPA fed by a microstrip transmission line attached to the center pin of 50 ohm SMA connecter. The simulated antennas are fabricated and measured. Measurement results are utilized for training the artificial intelligence models. The ANN provides 98% model accuracy for rectangular slots and 97% for square slots; however, ANFIS offer 90% accuracy with lack of resonance frequency tracking.Item The LOFT mission concept - A status update(2016) Inam, S.C.The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, > 8m(2) effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e. g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.Item Reduced Graphene Oxide-GelMA Hybrid Hydrogels as Scaffolds for Cardiac Tissue Engineering(2016) Shin, Su Ryon; Zihlmann, Claudio; Akbari, Mohsen; Assawes, Pribpandao; Cheung, Louis; Zhang, Kaizhen; Manoharan, Vijayan; Zhang, Yu Shrike; Yuksekkaya, Mehmet; Wan, Kai-tak; Nikkhah, Mehdi; Dokmeci, Mehmet R.; Tang, Xiaowu (Shirley); Khademhosseini, Ali; 0000-0002-2665-5799; 27254107; P-1760-2016Biomaterials currently used in cardiac tissue engineering have certain limitations, such as lack of electrical conductivity and appropriate mechanical properties, which are two parameters playing a key role in regulating cardiac cell behavior. Here, the myocardial tissue constructs are engineered based on reduced graphene oxide (rGO)-incorporated gelatin methacryloyl (GelMA) hybrid hydrogels. The incorporation of rGO into the GelMA matrix significantly enhances the electrical conductivity and mechanical properties of the material. Moreover, cells cultured on composite rGO-GelMA scaffolds exhibit better biological activities such as cell viability, proliferation, and maturation compared to ones cultured on GelMA hydrogels. Cardiomyocytes show stronger contractility and faster spontaneous beating rate on rGO-GelMA hydrogel sheets compared to those on pristine GelMA hydrogels, as well as GO-GelMA hydrogel sheets with similar mechanical property and particle concentration. Our strategy of integrating rGO within a biocompatible hydrogel is expected to be broadly applicable for future biomaterial designs to improve tissue engineering outcomes. The engineered cardiac tissue constructs using rGO incorporated hybrid hydrogels can potentially provide high-fidelity tissue models for drug studies and the investigations of cardiac tissue development and/or disease processes in vitro.