Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 3Citation - Scopus: 3Reconstructions of Effective Parameters for a Metamaterial Antenna Via 3d-Printed Components(Taylor & Francis, 2022) Yılmaz, Hasan Önder; Yaman, FatihThis study presents the reconstruction of effective medium parameters for a double negative metamaterial slab from the knowledge of the measured/simulated S-matrix. The structure initially has been designed to embed into a patch antenna for a radar application. To observe the medium characteristics, we locate the slab in a rectangular waveguide for various orientations. The waveguide-based retrieval method is applied to find parameters regarding the biaxial anisotropic medium. Fundamental mode is used for the excitation. Additive printing technology is employed to manufacture a rectangular waveguide and its adapters for the experiments. The metallization is achieved by coating the printed structures with conductive thin layers. Experimental setups for each orientation are simulated as well. We illustrate good agreements between simulation and measurements under the fabrication tolerances. The feasibility and applicability of the additive printing technology for the investigations of the metamaterial anisotropic/bianisotropic nature is reported.Article Citation - WoS: 4Citation - Scopus: 4A Symmetrical Self-Diplexing Microstrip Antenna With Eight-Shaped Defects(Taylor & Francis, 2022) Karatay, AnılThis article aims to demonstrate the simulation and measurement results of a two-port and symmetrical microstrip antenna operating at 6.6 and 7 GHz frequencies. The essential advantages of the antenna in terms of numerical electromagnetism are that the geometry has a small electrical length at both frequencies, does not use a structure that requires extra computational load such as substrate integrated waveguide, and is symmetrical, thus reducing the mesh requirement by half. The proposed antenna was manufactured with the chemical etching method and the measurement results were presented. In addition, varying operating frequencies are shown with the aid of liquid metal to experimentally demonstrate the independent redesign/reconfigurability feature of the antenna. To further reduce the fabrication cost, the manufacturing process of the proposed antenna with the help of a 3D printer is explained, and the performance parameters are compared. Good agreement between simulations and measurements has been reported.Article Citation - WoS: 6Citation - Scopus: 7Human-Robot Interfaces of the Neuroboscope: a Minimally Invasive Endoscopic Pituitary Tumor Surgery Robotic Assistance System(ASME, 2021) Dede, Mehmet İsmet Can; Kiper, Gökhan; Ayav, Tolga; Özdemirel, Barbaros; Tatlıcıoğlu, Enver; Hanalioğlu, Şahin; Işıkay, İlkayEndoscopic endonasal surgery is a commonly practiced minimally invasive neurosurgical operation for the treatment of a wide range of skull base pathologies including pituitary tumors. A common shortcoming of this surgery is the necessity of a third hand when the endoscope has to be handled to allow active use of both hands of the main surgeon. The robot surgery assistant NeuRoboScope system has been developed to take over the endoscope from the main surgeon's hand while providing the surgeon with the necessary means of controlling the location and direction of the endoscope. One of the main novelties of the NeuRoboScope system is its human-robot interface designs which regulate and facilitate the interaction between the surgeon and the robot assistant. The human-robot interaction design of the NeuRoboScope system is investigated in two domains: direct physical interaction (DPI) and master-slave teleoperation (MST). The user study indicating the learning curve and ease of use of the MST is given and this paper is concluded via providing the reader with an outlook of possible new human-robot interfaces for the robot assisted surgery systems.Article Citation - WoS: 2Citation - Scopus: 2Electromagnetic Effects of Equatorially Misaligned Rf Cavities(IOP Publishing, 2021) Karatay, Anıl; Yaman, FatihOne of the most challenging problems in modern particle accelerator systems is the manufacture of RF cavities within the desired tolerance limits. In this study experimental and computational investigations to quantify the effects of transversal half-cell misalignments on the fundamental accelerator cavity parameters and beam dynamics are presented. Equivalent circuit components of an equatorially misaligned single-cell aluminum elliptical cavity are obtained from the measured data and are employed to calculate longitudinal impedance and modal wake function. Critical coupling and bead-pull measurements are performed at the TM010-like mode frequency, 2.45 GHz for the quality factor and shunt impedance of the high-beta cavity. We report equivalent circuit analysis for higher-order modes and variations of the equivalent circuit components with respect to considered misalignment errors for the MICE experiment's muon cooling cavity. It is shown that using the equivalent circuit model decreases the computational load significantly for the wake field simulations of resonator cavities. Good agreement between simulations and measurements in terms of accelerating cavity parameters and impedances is illustrated.Article Citation - WoS: 10Citation - Scopus: 10The Effect of Additional Telerounding on Postoperative Outcomes, Patient and Surgeon Satisfaction Rates in the Patients Who Underwent Percutaneous Nephrolithotomy(Iniestares, S.A., 2019) Aydoğdu, Özgü; Şen, Volkan; Yarımoğlu, Serkan; Aydoğdu, Canan; Bozkurt, İbrahim H.; Yonguç, TarıkINTRODUCTION: We wanted to investigate the potential effect of additional telerounding system on postoperative outcomes, patient and surgeon satisfaction rates in the patients who underwent percutaneous nephrolithotomy (PNL). METHODS: Eighty patients who underwent PNL were included in the study. The patients were randomly divided to two groups. Group 1 included 40 patients who were followed-up with standard rounds and group 2 included 40 patients who were followed-up with telerounding in addition to standard rounds. Patient and surgeon satisfaction rates were assessed with a visual analog scale (VAS) where 0 point represents very dissatisfied and 100 points very satisfied. RESULTS: Mean time of preoperative telerounding visit was 3.65 +/- 0.59 (2-4) minutes. Mean time of telerounding visits on the postoperative 1st and 2nd days was 3.80 +/- 0.62 and 2.9 +/- 0.91 minutes respectively. The VAS score evaluating the surgeon's satisfaction rate for telerounding was 91 +/- 11.2 and patients expressed a high level of satisfaction with 72.5%. CONCLUSION: The use of additional telerounding in urological patient care provides high satisfaction rates for both the patients and the surgeon. However the findings of the present study don't underestimate the importance of personal surgeon-patient interaction.Article Citation - WoS: 6Citation - Scopus: 6Structure and Performance Evaluation of Fractional Lower-Order Covariance Method in Alpha-Stable Noise Environments(Bentham Science Publishers B.V., 2019) Ahmed, Areeb; Savacı, Ferit AcarBackground: All existing time delay estimation methods, i.e. correlation and covariance, depend on second or higher-order statistics which are inapplicable for the correlation of alpha-stable noise signals. Therefore, fractional lower order covariance is the most appropriate method to measure the similarity between the alpha-stable noise signals. Methods: In this paper, the effects of skewness and impulsiveness parameters of alpha-stable distributed noise on fractional lower order covariance method have been analyzed. Results: It has been found that auto-correlation, i.e. auto fractional lower order covariance, \ of non delayed alpha-stable noise signals follows a specific trend for specific ranges of impulsiveness and skewness parameters of alpha-stable distributed noise. The results also depict that, by maintaining the skewness and impulsiveness parameters of alpha-stable noise signals in a certain suggested range, better auto-correlation can be obtained between the transmitted and the received alpha-stable noise signals in the absence and presence of additive white Gaussian noise. Conclusion: The obtained results would improve signal processing in alpha-stable noise environment which is used extensively to model impulsive noise in many noise-based systems. Mainly, it would optimize the performance of random noise-based covert communication, i.e. random communication.Article Citation - WoS: 7Citation - Scopus: 8Compact Wideband Tapered-Fed Printed Bow-Tie Antenna With Rectangular Edge Extension(John Wiley and Sons Inc., 2019) Bozdağ, Göksenin; Seçmen, MustafaIn this article, a wideband printed bow-tie antenna is designed entire band of GPS (L5), PCS, IMT-2000, Bluetooth, Wi-Fi, WiMAX bands, and the most of frequency range of UWB. Apart from the traditional designs, the proposed antenna includes tapered printed line with a feeding point patch and triangular bows with rectangular edge extensions, which makes the antenna more compact. The antenna realized at the frequency band of 1.49-9.5 GHz (more than 6.3:1 ratio bandwidth) has the dimensions of 122mmx56mm (0.61(0)x0.28(0)). According to measurement results, the realized gain varies between almost 1 and 6.5 dBi with 4.44dBi average, which are in good agreement with simulation results. Radiation patterns at the lower frequencies of operating band show dipole like radiation pattern with higher cross-pol discrimination levels while they degrade at the higher frequencies due to increase in gain.Article Numerical Investigations of Resistive Wall Wake Potentials(Institution of Engineering and Technology, 2020) Yaman, FatihThe aim of this Letter is to examine and identify longitudinal resistive wall wake potential behaviours of medium-beta long bunches and ultra-relativistic short bunches using different beam and pipe properties for particle accelerator applications. The lack of detailed analysis in current literature for the chosen set of parameters ignites this work. Since computations of wake potentials for the considered beam parameters by particle-in-cell codes are extremely difficult the author uses an analytical approach. Numerical integrations are evaluated for large domains with fine discretisations. The author observes that conductivity of beam pipe has a larger impact on medium-beta long bunches, variation of beam velocity effects wakes of short bunches more significantly, beam radii changes may have a contribution to instability for low energy short bunches. Interesting numerical results are presented and their physical explanations are discussed in this Letter.Article Citation - WoS: 5Citation - Scopus: 8Covert Electromagnetic Nanoscale Communication System in the Terahertz Channel(World Scientific Publishing, 2020) Ahmed, Areeb; Savacı, Ferit AcarIn this paper, an electromagnetic nano random communication system (EM-nRCS) has been proposed which ensures covert communication in the terahertz (THz) band. In the proposed system, the skewed alpha-stable noise shift keying method has been used to transmit random noise signals (RNSs) from the nano-transmitter (NT) by utilizing single-walled/carbon nanotubes-based true random number generator (SWCNTs-TRNG) and a graphene-based nano-antenna. A line-of-sight THz transparency window between 0.1 THz and 0.5 THz in the THz channel with spreading loss, molecular absorption loss and molecular absorption noise has been considered. Due to the broadband nature of the RNSs, the proposed EM-nRCS provides efficient transmission by overcoming the high path loss and intense channel noise arising from random fluctuations in the THz band. Non-coherent nano-receiver (NR) consisting of the modified extreme value method (MEVM) estimator has been proposed to extract the hidden binary information in the received RNSs. The bit error rate performance shows that the proposed EM-nRCS ensures high performance and covertness for future EM nanoscale communication devices.Article Citation - WoS: 1Citation - Scopus: 1Spatial Signature for Secure Miso-Ofdm Systems(Institution of Engineering and Technology, 2018) Özbek, Berna; Karabulut Kurt, GüneşPhysical layer security is a promising approach to establish secure communications based on the characteristics of wireless channels. A spatial signature based secure multiple-input single-output (MISO) orthogonal frequency division multiplexing (OFDM) system is proposed to disrupt the reception of a passive eavesdropper by holding two practically relevant assumptions: a limited feedback link for legitimate node and the unavailability of channel state information of eavesdropper. The proposed algorithm achieves a higher average secrecy rate than the conventional secure MISO-OFDM systems in presence of a limited feedback link.
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