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YARALIOĞLU, Göksen Göksenin

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Göksen Göksenin

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Now showing 1 - 10 of 25
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    Analysis of vibratory gyroscopes: drive and sense mode resonance shift by coriolis force
    (IEEE, 2017) Cetin, Hakan; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Cetin, Hakan
    In this paper, we demonstrate the analysis of coupling between drive and sense systems of vibratory gyroscopes. Vibratory gyroscopes have attracted a lot of interest recently with the development of MEMS gyroscopes. These gyroscopes made their way through portable devices and smart phones. Novel gyroscope architectures have been proposed and analyzed in detail. However, in most of these analyses, coupling between the sense and drive systems was ignored. We analytically show that drive and sense systems are coupled together via Coriolis and centrifugal force. As a result, system resonances shift as the rotation rate increase for linear and torsional gyroscope systems. Starting from a simple gyro system, we calculated the sense and drive resonant frequency shifts in various configurations. Then, for more complex systems where analytical solution is difficult to obtain, we used commercially available FEM tools to determine corresponding frequency shift. In general, we found that the shift is small and can be ignored for linear vibratory gyroscopes where Q of the sense system is less than 2500 for mode matched gyros. But for higher Q systems, the frequency shift may affect the linearity of these gyroscopes. This sets a fundamental limit for the linearity of vibratory gyroscopes. Based on our calculations the non-linearity is above 1% for linear 2-DOF mode-matched vibratory gyroscopes where Q is above 3000 and for torsional 2-DOF vibratory gyroscopes where Q is above 600. Multi-DOF and ring vibratory gyroscopes are also examined. We find that the effect is less pronounced for Multi-DOF gyros, whereas there is a large effect on the linearity of ring gyroscopes.
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    Coriolis Effect on elastic waves propagating in rods
    (Elsevier, 2020-10-27) Çetin, Hakan; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Çetin, Hakan
    Vibration analysis of rods that are subjected to rotation is presented. It is shown that flexural-flexural, longitudinal-flexural and torsional-flexural wave coupling occur due to the Coriolis Effect. First, we carried out our analysis for thin rods where the wavelength is much larger than the radius. It is shown that the wavenumbers change due to the Coriolis Effect. Then, we characterize the 3-D wave propagation in rotating rods by using the Finite Element Method (FEM) in order to determine the corresponding wavenumber shifts for each type of wave. We show that for different drive frequency (ω0) and rotation rate (Ω), wave couplings exhibit different characteristics. For flexural-flexural wave coupling, the wavenumber increases for the primary flexural wave whereas the wave number decreases for the coupled flexural wave where Ω < ω0. For the Coriolis coupling between flexural-longitudinal waves, the wavenumber increases for the flexural wave and decreases for the longitudinal wave where Ω < ω0. For the Coriolis coupling between flexural-torsional waves, the wavenumber increases for both flexural and torsional waves.
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    Optical fiber array based simultaneous parallel monitoring of resonant cantilever sensors in liquid
    (Elsevier, 2016-05-01) Mostafazadeh, A.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    This paper reports a novel method for simultaneous resonance monitoring of MEMS cantilevers using phase based dynamic measurements without any electrical connections to the sensor array. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. To our knowledge this is the first demonstration of simultaneous parallel optical monitoring of dynamic mode micro-cantilever array in liquid environment. Illumination is generated using a laser source and a diffractive pattern generator, which provides 500 μW laser power per channel. A compact fiber array based pick-up was built for optical readout. Its main advantages are easy customization to different size and pitch of sensor array, and good immunity to electrical noise and magnetic interference as the photo detectors are located away from the electro-coil. The resonant frequency of the cantilever is tracked with a custom multi-channel lock-in amplifier implemented in software. For demonstrating the stability and sensitivity of the system we performed measurements using glycerol solutions with different viscosities. Measured phase sensitivity was 0.9°/1% of Glycerol/DI-water solution and the standard deviation of measured phase was 0.025°. The resulting detection limit for Glycerol/DI-water solution was 280 ppm. The proposed method showed robust results with low laser power and very good noise immunity to interference signals and environmental vibrations. The sensor technology demonstrated here is very significant as it is scalable to larger arrays for simultaneous and real- time monitoring of multiple biological and chemical agents during fluid flow.
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    Precision density and viscosity measurement using two cantilevers with different widths
    (Elsevier, 2015) Cakmak, O.; Ermek, E.; Kilinc, N.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    We introduce a novel method for fast measurement of liquid viscosity and density using two cantilevers with different geometries. Our method can be used for real-time monitoring in lab on chip systems and offer high accuracy for a large range of densities and viscosities. The measurement principle is based on tracking the oscillation frequencies of two cantilevers with a phase-locked loop (PLL) and comparing with reference measurements with a known fluid. A set of equations and a simple algorithm is developed to relate the density and the viscosity to the frequency shifts of the cantilevers. We found that the effect of the density and the viscosity can be well separated if cantilevers have different widths. In the experiments, two Nickel microcantilevers (widths 25 μm and 100 μm, length: 200 μm, thickness: 1.75 μm) were fully immersed in the liquid and the temperature was controlled. The actuation was using an external electro-coil and the oscillations were monitored using laser Doppler vibrometer. Thus, electrical connections to the cantilevers are not required, enabling measurements also in conductive liquids. The PLL is used to set the phase difference to 90° between the actuator and the sensor. Calibration measurements were performed using glycerol and ethylene glycol solutions with known densities and viscosities. The measurement error with the new method was lower than 3% in density in the range 995–1150 kg/m3 and 4.6% in viscosity in the range 0.935–4 mPa.s. Based on the signal-to-noise ratio, the minimum detectable difference in the viscosity is 1 μPa.s and the density is 0.18 kg/m3. Further improvements in the range and the accuracy are possible using 3 or more cantilevers with different geometries.
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    Vertical cavity capacitive transducer
    (American Institute of Physics Inc., 2021-04-01) Yaralıoğlu, Göksen Göksenin; Ergun, A. S.; Bozkurt, A.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    The capacitive micromachined ultrasonic transducer (CMUT) has inherent advantages, such as larger bandwidth and monolithic integration capability with electronics, when compared to the piezoelectric transducer. The most significant shortcoming of the device is the trade-off between input and output sensitivities. Adequate receive sensitivity requires an electric field intensity on the order of 105 V/m, which can be achieved by sub-micron gap heights. However, a small gap limits the device stroke and, consequently, the maximum output pressure. This paper addresses this problem by proposing a CMUT with a vertical cavity. The membrane of the device has a piston part that is surrounded by the sidewalls of a vertical cylinder formed in the substrate. The fringing electric field pulls the piston in the vertical direction; hence, the gap height remains fixed, which alleviates the hard limit on device stroke. The performance of the proposed device is compared to that of the conventional CMUT by theoretical and analytical methods, and a micro-fabrication method is devised. Additionally, a millimeter-scale device has been manufactured and tested as a proof of concept.
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    Design of a quad element patch antenna at 5.8 GHz
    (IEEE, 2018) Majidi, Negar; Yaralıoğlu, Göksen Göksenin; Sobhani, M. R.; Imeci, T.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Majidi, Negar
    This paper presents simulation and experimental verification of a quad microstrip patch antenna that operates at 5.8 GHz. Sonnet antenna design software was used to simulate the performance of the antenna. To reduce the design's complexity and the computational load, the antenna and the feeding lines were simulated separately. An optimization was done for each subpart to get the optimum desired results. Finally, all the subparts were merged and the final structure was simulated to check the performance. A prototype of the antenna was fabricated on a double sided PCB substrate (relative permittivity=10.2, thickness=1.28 mm) using a PCB milling machine. The s 11 of -14 dB and -18.8 dB and maximum gain of 6.2 dB and 4.2 dB were obtained, from the simulation and experimental measurements, respectively.
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    Two cantilever based sytem for viscosity and density monitoring
    (IEEE, 2015) Cakmak, O.; Ermek, E.; Kilinc, N.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    Viscosity and density measurements in liquids in real-time is challenging. Previous MEMS based approaches use frequency sweeps for the purpose and those methods are slow and not real-time. We show that high precision viscosity and density measurements are possible using two cantilevers with different widths and by tracking their frequencies with a Phase-Locked-Loop in real-time.
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    Microcantilever based LoC system for coagulation measurements
    (Chemical and Biological Microsystems Society, 2014) Çakmak, O.; Ermek, E.; Kılınç, N.; Barış, I.; Kavaklı, I. H.; Yaralıoğlu, Göksen Göksenin; Urey, H.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    In this paper, a microcantilever-based system enabling multiple coagulation tests on the same disposable cartridge is demonstrated. The system consists of independent cartridge and reader unit. The actuation of the nickel cantilevers is conducted remotely with an external electro-coil and remote optical read-out is utilized for sensing. Both Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT) tests can be conducted on the same cartridge. The system’s repeatability and accuracy is investigated with standard control plasma samples. The results are concordant with the manufacturer’s datasheet. The architecture of the system and the repeatable results makes the system suitable for Point-of-Care applications.
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    MEMS based blood plasma viscosity sensor without electrical connections
    (IEEE, 2013) Çakmak, O.; Ermek, E.; Urey, H.; Yaralıoğlu, Göksen Göksenin; Kılınç, N.; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    A MEMS based viscometer is reported. The device has a disposable cartridge and a reader. The cartridge contains microfluidic channels and a MEMS cantilever sensor. The reader contains the actuator and the readout optics and electronics. A unique feature of the system is that both the actuation and the sensing are remote; therefore, no electrical connections are required between the reader and the cartridge. The reported sensor is capable of measuring viscosity with better than 0.01 cP resolution in a range of 0.8-14.1 cP, with less than 50 μl sample requirement. This range and sensitivity are sufficient for blood plasma viscosity measurements, which are in between 1.1-1.3 cP for healthy individuals and can be elevated to 3cP in certain diseases[1].
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    A pilot project for power quality improvements in distribution system by a Li-ion battery
    (IEEE, 2022) Çetin, A.; Ozen, C.; Bayatmakoo, A.; Kaya, K.; Poyrazoğlu, Göktürk; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin
    Power quality (PQ) metrics deterioration occurs in the distribution system by increasing the distributed generation plants, the existence of non-linear and harmonic loads. As a distribution system operator running under the Turkishelectricity regulation, a battery investment was made to improve PQ metrics to provide quality electricity service to customers by focusing on Volt/VAr optimization to obtain voltage stability parameters. The reverse power flow caused by the distributed generation can be eliminated and the power factor would be improved with the reactive support with this investment. This study includes the reasons for the battery pilot project, the engineering methodology, and post-solution improvements.