Yazar "Rasheed, Omar" seçeneğine göre listele

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    Nano Groove and Prism-Structured Triboelectric Nanogenerators
    (Mdpi, 2023) Saritas, Resul; Al-Ghamdi, Majed; Das, Taylan Memik; Rasheed, Omar; Kocer, Samed; Gulsaran, Ahmet; Khan, Asif Abdullah
    Enhancing the output power of triboelectric nanogenerators (TENGs) requires the creation of micro or nano-features on polymeric triboelectric surfaces to increase the TENGs' effective contact area and, therefore, output power. We deploy a novel bench-top fabrication method called dynamic Scanning Probe Lithography (d-SPL) to fabricate massive arrays of uniform 1 cm long and 2.5 & mu;m wide nano-features comprising a 600 nm deep groove (NG) and a 600 nm high triangular prism (NTP). The method creates both features simultaneously in the polymeric surface, thereby doubling the structured surface area. Six thousand pairs of NGs and NTPs were patterned on a 6x5 cm2 PMMA substrate. It was then used as a mold to structure the surface of a 200 & mu;m thick Polydimethylsiloxane (PDMS) layer. We show that the output power of the nano-structured TENG is significantly more than that of a TENG using flat PDMS films, at 12.2 mW compared to 2.2 mW, under the same operating conditions (a base acceleration amplitude of 0.8 g).
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    Öğe
    Structural Health Monitoring via Phase Space Warping and Time-Delay Embedding
    (Asce-Amer Soc Civil Engineers, 2023) Saritas, Resul; Das, M. Taylan; Rasheed, Omar; AlHamaydeh, Mohammad; Yavuz, Mustafa; Abdel-Rahman, Eihab
    The state of a structure's health can be determined by investigating its vibration characteristics. Vibration-based structural health monitoring (SHM) enables early detection and diagnosis of damage as well as extension of service life. Herein, linear and nonlinear tracking metrics are proposed to track deterioration in the condition of multistory structures and assess their instantaneous health in real-time via measurement of floor accelerations. The linear metrics, the amplitude damage index ADIn(t over bar ) and the frequency damage index FDIn(t over bar ), are based on tracking the power spectra of floor accelerations. The nonlinear metric e(t over bar ) is based on a novel implementation of the phase-space warping method and obtained from the orbits representing the floors' motions in pseudo phase-space. A scaled-down model of a four-floor moment-resisting frame building is designed and fabricated to demonstrate and to compare the capabilities of the three damage indices. Structural damage is introduced to individual columns, to mimic damage initiation, by cutting two notches on opposite sides of a column cross-section at midheight. The ADIn(t over bar ) detected large damage events, fast deterioration beyond them, and the onset of failure using any of the four floor accelerations. The FDIn(t over bar ) proved insensitive to damage compared with the other two metrics. The nonlinear metric e(t over bar ) detected gradual (fatigue-induced) deterioration in the building's health before introduction of damage, large damage events, fast deterioration beyond them, and the onset of failure, using any of the four floor accelerations. The e(t over bar ) metric varied slowly and continuously with gradual deterioration and exhibited larger discontinuous jumps with discrete damage events. This was true for all three damage experiments undertaken on the model building. The nonlinear e(t over bar ) metric was also found to be more efficient, in terms of signal utilization, in comparison with the linear ADIn(t over bar ) metric. 1415.(c) 2022 American Society of Civil Engineers.