Fakülteler / Faculties

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    Aligned Polyvinylpyrrolidone Nanofibers with Advanced Electrospinning for Biomedical Applications
    (2018) Karayegen, Gokay; Kocum, I. Cengiz; Serdaroglu, Dilek Cokeliler; Dogan, Mustafa; 0000-0001-5215-8887; 30400080; I-4296-2019
    BACKGROUND: Electrospinning is a highly effective method in order to generate nano-scaled fibers. In conventional electrospinning technique, geometry of nanofibers are mostly random due to the chaotic behavior of polymer jet. OBJECTIVE: Purpose of this study is to produce aligned nanofibers from PVP polymers with advanced electrospinning technique in order to be used in a potential novel sensor applications, tissue regeneration and engineering. METHODS: In this study, by using finite hollow cylinder focusing electrodes, an external electrostatic field is created. With these electrodes, it is aimed to decrease whipping instability of polymer jet. In addition, it is also investigated that the alignment ratio of nanofibers by using conductive parallel electrodes which placed through jet trajectory. RESULTS: In conclusion, with the effect of electrical field created by cylinder electrodes, radius of the fiber dispersion on the collector was able to be reduced and aligned nanofibers were successfully produced by using electrical field generated from the parallel plates. CONCLUSIONS: Radius of the fiber dispersion on the collector is 9.95 mm and fiber diameters varied between 800 nm and 3 mu m. Additionally, alignment ratio of the fibers is determined with ImageJ software. These alignment of nanofibers can be used in tissue engineering applications and sensor applications.
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    Design and Implementation of An Identifier System for Inter-Area Power Oscillations
    (2015) Atalika, Tevhid; Dogan, Mustafa; Demirci, Turan; 0000-0001-5215-8887; I-4296-2019
    Identifying inter-area oscillations can be a challenge for interconnected grids. Two identifier algorithms (FBMSWA and TBR-EMD) proposed to detect these oscillations are comparatively tested in this research. FBMSWA is implemented with T-STATCOM to damp out 0.15 Hz low-frequency inter-area oscillation after interconnection Turkey with ENTSO-E. Developed TBR-EMD algorithm has certain achievements, e.g. admissible for real time, handling intermittency problem of EMD, proved by real data. (C) 2015 Elsevier B.V. All rights reserved.
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    Efficient Energy Harvesting Systems for Vibration and Wireless Sensor Applications
    (2017) Dogan, Mustafa; Inam, Sitki Cagdas; Surel, O. Orkun; 0000-0001-5215-8887; 0000-0003-0820-9186; I-4296-2019
    In the first part of the research, we present the design of a vibration-based energy harvesting system. Robotic flexible arm having variable cross-section is investigated to overcome serious problems, e.g. insufficient bandwidth and model inaccuracies. Most of the energy harvesting systems are linear with unimodal characteristics. On the other hand, real vibrations can be modeled as random, multi-modal and time varying systems. Hence, unimodal linear systems can give highly unsatisfactory results under certain circumstances. However, non-linear systems can have multi-modal character with increased performance in real and practical situations. In this work, tapered links are preferred with nonlinear coupling setup to provide sufficient bandwidth and output power requirements for modern applications. Thus, the proposed scheme has been proven by simulated and experimental results successfully. In the second part of the research, we present design and experimental results of an electromagnetic harvester, energy source of which is single-phase household AC power with a nominal voltage of 220 V and a frequency of 50 Hz. In this case, energy harvesting is based on the induced electromotive force (EMF) as a result of the periodic variations of the magnetic field around the AC power cord. In this part, we also discuss basic principles of a wireless sensor network design powered by electromagnetically harvested energy obtained from household alternating current.