Browsing by Author "Orhan, E."

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    Optimization of piezoresistive motion detection for ambient NEMS applications
    (Institute of Electrical and Electronics Engineers, 2020) Ti, C.; Arı, A.; Orhan, E.; Gonzalez, M.; Yanık, C.; Kaya, İ. İ.; Hanay, Mehmet Selim; Ekinci, K. L.
    Electrical readout of nanomechanical motion in ambient pressure and temperature imposes an important challenge for emerging applications of nanoelectromechanical systems (NEMS). Here, we optimize a metallic piezoresistive motion transducer for NEMS resonators in air. The nanomechanical motion of the NEMS resonator serves as a signal down-mixer and enables the detection of the motional signal by a low-frequency circuit. A balanced circuit in the detection loop reduces some of the unwanted background and allows for detection without significant losses. We explore the detection parameter space and use an optimized parameter set to detect the fundamental, second and third harmonic resonances of a NEMS doubly-clamped beam resonator. Our simple circuit model agrees with experimental observations and points the way for further optimization.
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    Performance evaluation of fiber-based ballistic composites against laser threats
    (Elsevier, 2019) Candan, C.; Seymen, A. Aytaç; Karatutlu, Ali; Tiken, M.; Midilli, Yakup; Orhan, E.; Berberoğlu, H.; Ortaç, Bülend
    The interaction between a laser and a composite material has been an intense subject within the past decade and become an emerging field for the defense and manufacturing industry since high-power lasers were initiated to be utilized for the directed-beam applications. In this study, a specially developed composite material for the ballistic applications was shined to a continuous wave (CW) laser beam at 915 nm. The ballistic material was composed of 77 layers of the single sheet of the SR-3136 by Spectra Shield® from Honeywell consisting of ultra-high molecular weight polyethylene (UHMW-PE) fibers reinforced with low-density PE (LD-PE) fibers and a polyurethane-based thermoplastic resin. At the instant of the exposure, the region of interest was completely evaporated and punctured with a slight swelling around the hole where the temperature was over 450 °C. The composite material was drilled completely upon exceeding 20 kJ of laser energy. The chemical and physical changes on the composite material after the laser exposure were extensively studied by a combination of techniques including High-Resolution Scanning Electron Microscopy (HR-SEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). The physical properties of a single layer of the SR-3136 were also studied using HR-SEM, UV-VIS-NIR Absorption Spectroscopy, Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and XPS. The research presented here reveals the first study on the effects of the high-power laser beam irradiance on the fiber-reinforced composite materials utilized for the ballistic protection.