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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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Department: search.filters.department.Department of Electrical and Electronics EngineeringSubject: search.filters.subject.Mechanical engineering

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Now showing 1 - 4 of 4
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    Measurement and characteristic analysis of ris-assisted wireless communication channels in sub-6 ghz outdoor scenarios
    (IEEE, 2023) Lan, Jifeng; Sang, Jian; Zhou, Mingyong; Gao, Boning; Meng, Shengguo; Li, Xiao; Tang, Wankai; Jin, Shi; Cheng, Qiang; Cuit, Tie Jun; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; College of Engineering
    Reconfigurable intelligent surface (RIS)-empowered communication has recently drawn significant attention due to its superior capability in manipulating the wireless propagation environment. However, the channel modeling and measurement of RIS-assisted wireless communication systems in real environment has not been adequately studied. In this paper, we construct a channel measurement system using vector network analyzer (VNA) is used to investigate RIS-assisted wireless communication channel in outdoor scenarios at 2.6 GHz. New path loss (PL) models including angle domain information are proposed by refining the traditional close-in (CI) and floating-intercept (FI) models. In the proposed models, both influences of the distance from transmitter (TX) to RIS and the distance from receiver (RX) to RIS on the PL, are taken into account. In addition, the value of root mean square (RMS) delay spread of RIS-assisted wireless communication is found to be much smaller than that of the traditional non line-of-sight (NLOS) case, implying that RIS provides a virtual line-of-sight (LOS) link.
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    Measurement-based characterization of physical layer security for ris-assisted wireless systems
    (IEEE, 2023) Kesir, Samed; Wikelek, Ibrahim; Pusane, Ali Emre; Gorcin, Ali; Department of Electrical and Electronics Engineering; Kayraklık, Sefa; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; CoreLab; Graduate School of Sciences and Engineering; College of Engineering
    There have been recently many studies demonstrating that the performance of wireless communication systems can be significantly improved by a reconfigurable intelligent surface (RIS), which is an attractive technology due to its low power requirement and low complexity. This paper presents a measurement-based characterization of RISs for providing physical layer security, where the transmitter (Alice), the intended user (Bob), and the eavesdropper (Eve) are deployed in an indoor environment. Each user is equipped with a software-defined radio connected to a horn antenna. The phase shifts of reflecting elements are software controlled to collaboratively determine the amount of received signal power at the locations of Bob and Eve in such a way that the secrecy capacity is aimed to be maximized. An iterative method is utilized to configure a Greenerwave RIS prototype consisting of 76 passive reflecting elements. Computer simulation and measurement results demonstrate that an RIS can be an effective tool to significantly increase the secrecy capacity between Bob and Eve.
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    Discrete and continuous mathematical models for torsional vibration of micromechanical scanners
    (Springer, 2007) Department of Electrical and Electronics Engineering; N/A; Ürey, Hakan; Faculty Member; N/A; Department of Electrical and Electronics Engineering; College of Engineering; N/A; 8579; N/A
    Micromechanical scanners are used in various industrial scanning applications like. display and imaging technologies. The desired vibration mode is often the torsional mode, so derivation of an accurate mathematical model for calculation of torsional mode frequency has great importance. In this work, discrete and continuous mathematical models are given for free torsional vibration of a box shaped scanner suspended with two beams. Numerical calculation of torsional rigidity using energy methods is shown. The derivations are extendible to scanners that have non-rectangular beam cross-sections, orthotropic material anisotropy, and different mirror geometries. Analytical formulas are compared with three-dimensional FEM simulations using ANSYS commercial software. The FEM simulations and analytical formulas are verified with experimental results. FEM simulations and experimental results showed that simple discrete models can be used for a wide range of beam dimensions except for the cases where beam inertia is comparable to mirror inertia.
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    Route to batch-compatible fabrication of nanotweezers by guided self-assembly
    (IEEE, 2007) Bøggild, Peter; Tang, P. Torben; Hansen, Ole; N/A; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Şardan, Özlem; Alaca, Burhanettin Erdem; Yalçınkaya, Arda Deniz; Master Student; Faculty Member; Researcher; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 115108; 144523
    Fabrication of integrated micro and nanoscale components in a single batch is one of the biggest challenges for nanosystems developement. A self-assembly technique that enables "batch-compatible" integration of micro electro mechanical systems with nanoribbons is presented by demonstrating electrostatically actuated combdrive microgrippers with nanoribbon end-effectors. Preliminary fabrication results demonstrate the possibility of obtaining well defined spatial density and orientation of nanoribbons matching the precision of top-down techniques and at the same time allowing complete alignment and registry with subsequent lithography steps.