Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8651

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Now showing 1 - 10 of 32
  • Article
    Citation - WoS: 20
    Citation - Scopus: 22
    Analysis of Optical Wireless Mimo Communication in Underwater Medium
    (Ieee-inst Electrical Electronics Engineers inc, 2024) Ata, Yalcin; Baykal, Yahya; Gokce, Muhsin Caner
    Leveraging on the multiple-input-multiple-output (MIMO) application for enabling high data rates and ensuring reliable communication between underwater platforms connected to underwater sensor network, this article presents a comprehensive analysis of the performance of optical wireless MIMO communication systems depending on the various phenomena. The outage performance of an underwater optical wireless communication (UOWC) is obtained in analytical form using the Meijer-G function. Aysmptotic expression of outage probability is also derived for high signal-to-noise ratio (SNR) regime. Results show that the destructive combined effect of the underwater turbulence, pointing error, attenuation, and angle of arrival (AOA) on the outage performance can be reduced by applying the MIMO spatial diversity technique.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 15
    Intelligent Reflecting Surface Aided Vehicular Optical Wireless Communication Systems Using Higher-Order Mode in Underwater Channel
    (Ieee-inst Electrical Electronics Engineers inc, 2024) Ata, Yalcin; Gokce, Muhsin Caner; Baykal, Yahya
    Instead of traditional acoustic communication, optical wireless communication (OWC) remains as a prominent solution in terms of ensuring high data rates for underwater sensor network (USN) including autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs), submarines, and other underwater platforms. This study is devoted to the performance analysis of underwater optical wireless communication (UOWC) systems using higher-order mode optical beam source and performance improvement with the application of intelligent reflecting surface (IRS) by using realistic parameters. To make the study as comprehensive as possible, the effects of beam misalignment, attenuation (absorption- and scattering-induced), and underwater turbulence are included. The analytical expressions are obtained for probability density function (PDF), cumulative distribution function (CDF) and outage probability (OP) of UOWC channel. The benefit of IRS application is observed to attain at significant levels for UOWC.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 10
    Transformerless Single-Phase Buck-Boost Inverter Decoupled From the Midpoint of the Input Dc Capacitors
    (Ieee-inst Electrical Electronics Engineers inc, 2024) Demirkutlu, Eyyup; Iskender, Ires
    A transformerless, single-phase, buck-boost inverter is proposed in this study. Unlike similar topologies, the proposed inverter does not need to have a mid-point of dc sources or dc-bus capacitors at the input side of the inverter. The proposed inverter can suppress the leakage current drawn from the input power source and provide a long-lasting solution for applications with a wide input voltage range and/or unregulated input voltage. This article presents the controller and modulation design details, and a comparative evaluation conducted for the proposed inverter. A single-phase, buck-boost inverter for realizing the power stage with 110 V-rms output ac voltage and a range of 100-200 V input dc voltage is investigated in this study. The proposed inverter has been proven through theory, computer simulations, and experimental studies with SiC MOSFETS-based prototype of a 300 VA power supply. Theory, computer simulation, and experimental results are all correlated.
  • Article
    Citation - WoS: 65
    Citation - Scopus: 70
    Feedforward Strategies for Cooperative Adaptive Cruise Control in Heterogeneous Vehicle Strings
    (Ieee-inst Electrical Electronics Engineers inc, 2018) Al-Jhayyish, Ahmed M. H.; Schmidt, Klaus Werner
    String stability is an essential property to ensure that the fluctuations are attenuated along vehicle strings. This paper focuses on the fulfillment of string stability in the practical case of heterogeneous vehicle strings that comprise vehicles with different dynamic properties. Using the idea of predecessor following, acceleration feedforward, predicted acceleration feedforward, and input signal feedforward are considered as different possible feedforward strategies. For all strategies, the parameter ranges of predecessor vehicles that ensure string stability of a given vehicle are characterized, computed, and validated by simulation.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 6
    Scintillation of Laser Beams in Weak Atmospheric Turbulence for Aerial Vehicle in the Use of Lidar
    (Ieee-inst Electrical Electronics Engineers inc, 2022) Baykal, Yahya; Gercekcioglu, Hamza
    Formulation of on-axis scintillation of laser beams is found in weak atmospheric turbulence for aerial vehicle in the use of light detection and ranging (LIDAR) systems by employing the Rytov method. The formulation derived for collimated Gaussian, plane and spherical beams is evaluated in vertical link involving up/down link. In this medium, the behavior of these beams in terms of deterioration is examined. In this context, the on-axis scintillation index values are plotted versus normalized target size parameter, target size, source size, propagation distance and zenith angle, and the results are obtained for LIDAR systems operating for aerial vehicle in vertical atmospheric link by using ground/space transceiver. The degradation is greater in operating with ground transceiver than in operating with space transceiver. Additionally, while the on-axis scintillation index is minimized in the smaller target size in use of ground transceiver than in use of space transceiver, that is, it can also be minimized in the larger target size in use of space transceiver. The values of source size and the normalized target size parameter minimizing the obtained scintillation index, are 1.2 cm, 10, and 6 cm and 5 for ground transceiver and space transceiver, respectively.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    String Stability Under Actuator Saturation on Straight Level Roads: Sufficient Conditions and Optimal Trajectory Generation
    (Ieee-inst Electrical Electronics Engineers inc, 2022) Bingol, Hilal; Schmidt, Klaus Werner
    The heterogeneity of vehicles is an important factor when realizing cooperative adaptive cruise control (CACC) in practice. Specifically, it has to be considered that platoons generally consist of vehicles with both different dynamic properties and actuator limits on the engine and braking force, which is expected to have a negative impact on important properties such as string stability. Accordingly, the subject of this paper is the preservation of string stability for CACC in heterogeneous vehicle strings with potential actuator saturation. To this end, the paper formulates a velocity-dependent force bound that enables the derivation of sufficient conditions for preserving string stability during velocity changes of heterogeneous platoons. These conditions are then used for the analytical computation of trajectories for time-optimal velocity changes. The formal results of the paper are supported by an illustrative simulation study.
  • Article
    Citation - WoS: 9
    Citation - Scopus: 13
    Fiber-Coupling Efficiency of Laser Array Beam From Turbulent Atmosphere To Fiber Link
    (Ieee-inst Electrical Electronics Engineers inc, 2023) Baykal, Yahya; Ata, Yalcin; Gokce, Muhsin Caner
    Free-space optical communication (FSOC) systems are nowadays integrated with fiber optical components developed for fiber-optic communications. In such integrated systems, the collected portion of the incident beam on the receiver lens is coupled into a single-mode fiber. The process of coupling, however, is mostly affected by the atmospheric turbulence which distorts the coherency of the propagating beam i.e., it results in speckle over the coupling lens causing a reduction in the coupling efficiency. In this article, we aimed at investigating the fiber coupling efficiency of laser array beams propagating in a turbulent atmosphere. For this purpose, using the Huygens-Fresnel principle, mutual coherence function (MCF) for a laser array beam incidence is formulated. In this way, the average power coupled into the fiber and the average received power on the coupling lens are derived for a laser array beam incidence. It is found that the fiber coupling efficiency clearly increases with the increase in ring radius and the number of Gaussian beams in the array and rapidly decreases with increasing structure constant of atmosphere, link distance, and the number of speckles over the receiver aperture. We also demonstrate the effect of various FSOC system parameters on the coupling efficiency.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 17
    Entanglement Sustainability Improvement Using Optoelectronic Converter in Quantum Radar (Interferometric Object-Sensing)
    (Ieee-inst Electrical Electronics Engineers inc, 2021) Salmanogli, Ahmad; Gokcen, Dincer
    In this study, the main focus is laid on the design of an optoelectronic converter as a part of the quantum radar to enhance the entanglement between retained and returned modes at high temperatures. The electro-opto-mechanical converter has been widely studied, and the results showed that the operation at high temperature is so crucial to generate and preserve the entanglement between modes. The main problem arises because the mechanical part operating at a low frequency leads to a large number of thermally excited photons, and eventually, the entanglement between modes becomes lost. To solve the problem, we replace the mechanical part with the optoelectronic components. The optical cavity is coupled to the microwave cavity in the newly designed system through a Varactor diode excited by a photodetector. As the main goal, to improve the entanglement sustainability, the effect of the coupling factor of the microwave cavity to photodetector is investigated. The results show that the mentioned factor creates some degrees of freedom to enhance the entanglement at high temperatures compared to the electro-opto-mechanical converter. At some specific values of the coupling factor, the retained and returned fields remained completely entangled up to 5.5 K and partially entangled around 50 K.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 7
    Optical and Microcavity Modes Entanglement by Means of Plasmonic Opto-Mechanical System
    (Ieee-inst Electrical Electronics Engineers inc, 2020) Salmanogli, Ahmad; Gecim, H. Selcuk
    In this study, plasmonic opto-mechanical tripartite system is proposed to improve the performance of the traditional tripartite opto-mechanical system. In the new design, significantly, optical cavity and microwave cavity modes are directly coupled to each other. The originality of this work consists in embedding a microsphere in the optical cavity where the plasmon-plasmon interaction between the metal plates generates a plasmon mode inside the optical cavity and changes the electric field distribution. The plasmonic property influences the microsphere electrical properties and interacts with the photonic mode inside the optical cavity by which the microwave cavity properties are also affected through coupling to the optical cavity. Microsphere introduces a capacitor as a function of plasmonic properties that can strongly influence the microwave cavity resonance frequency. That is the feature that we want to utilize to enhance the performance of the system at high temperature. The results show that the optical cavity and microwave cavity modes remain entangled at high temperature. It is contributed to the plasmonic-based capacitor induced by the microsphere which is not affected by the thermally induced photons (noise). It is worth mentioning that the induced noise strongly restricts the traditional tripartite system operated with a wide bandwidth.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Plasmonic Effect on Quantum-Dot Photodetector Responsivity
    (Ieee-inst Electrical Electronics Engineers inc, 2019) Salmanogli, Ahmad; Gokcen, Dincer; Gecim, H. Selcuk; Selcuk Gecim, H.
    In this paper, we analyze and simulate the plasmonic effect on the quantum-dot photodetector responsivity. For this purpose, a plasmonic-based quantum-dot photodetector is designed in which a few quantum dots are embedded in the hot-spot regions of the plasmonic nanoparticles, wherein a high-intensity localized field is created. Notably, due to the maximum overlapping of the plasmonic field with the quantum dots at the hot spot, some of the optical characteristics of the quantum dot, particularly the spontaneous emission decay rate, are changed. This paper focuses on the engineering of the decay rate, through which we found that the quantum-dot photodetector responsivity is strongly enhanced with the order of 100 times at the visible range. For analyzing the proposed system, we first work on the plasmonic effect of the nanoparticle on the quantum-dot lifetime using the Heisenberg-Langevin equations. It is shown that by embedding the quantum dots at the hot spot of the nanoparticle, the decay rate of the quantum dot is dramatically influenced. In the following, plasmonic-quantum dot system responsivity is theoretically examined using a time-varying perturbation theory. Using this approach is necessary because the spontaneous emission cannot be analyzed with the classical methods. Consequently, it is proved that using plasmonic effect leads to enhanced photodetector responsivity, suggesting that even very small incoming signals are detectable.