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Full-Text Articles in Engineering
Chemical Vapor-Deposited Carbon Nanofibers On Carbon Fabric For Supercapacitor Electrode Applications, Yang Gao, Gaind P. Pandey, James Turner, Charles R. Westgate, Bahgat Sammakia
Chemical Vapor-Deposited Carbon Nanofibers On Carbon Fabric For Supercapacitor Electrode Applications, Yang Gao, Gaind P. Pandey, James Turner, Charles R. Westgate, Bahgat Sammakia
Mechanical Engineering Faculty Scholarship
Entangled carbon nanofibers (CNFs) were synthesized on a flexible carbon fabric (CF) via water-assisted chemical vapor deposition at 800A degrees C at atmospheric pressure utilizing iron (Fe) nanoparticles as catalysts, ethylene (C2H4) as the precursor gas, and argon (Ar) and hydrogen (H-2) as the carrier gases. Scanning electron microscopy, transmission electron microscopy, and electron dispersive spectroscopy were employed to characterize the morphology and structure of the CNFs. It has been found that the catalyst (Fe) thickness affected the morphology of the CNFs on the CF, resulting in different capacitive behaviors of the CNF/CF electrodes. Two different Fe thicknesses (5 and …
The Effect Of Time-Delay Feedback Controller On An Electrically Actuated Resonator, S. Shao, K. M. Masri, Mohammad I. Younis
The Effect Of Time-Delay Feedback Controller On An Electrically Actuated Resonator, S. Shao, K. M. Masri, Mohammad I. Younis
Mechanical Engineering Faculty Scholarship
This paper presents a study of the effect of a time-delay feedback controller on the dynamics of a Microelectromechanical systems (MEMS) capacitor actuated by DC and AC voltages. It is shown that negative time-delay feedback control gain can lead to an unstable system, even if AC voltage is relatively small compared to DC voltage. Perturbation method is utilized to present analytically the nonlinear dynamic characteristics of the MEMS capacitor. Agreements among the results of a shooting technique, long-time integration, basin of attraction analysis with the perturbation method are achieved.
Dynamics Of A Close-Loop Controlled Mems Resonator, Abdulrahman Seleim, Shahrzad Towfighian, Emmanuel Delande, Eihab Abdel-Rahman, Glenn Heppler
Dynamics Of A Close-Loop Controlled Mems Resonator, Abdulrahman Seleim, Shahrzad Towfighian, Emmanuel Delande, Eihab Abdel-Rahman, Glenn Heppler
Mechanical Engineering Faculty Scholarship
The dynamics of a close-loop electrostatic MEMS resonator, proposed as a platform for ultra sensitive mass sensors, is investigated. The parameter space of the resonator actuation voltage is investigated to determine the optimal operating regions. Bifurcation diagrams of the resonator response are obtained at five different actuation voltage levels. The resonator exhibits bi-stability with two coexisting stable equilibrium points located inside a lower and an upper potential wells. Steady-state chaotic attractors develop inside each of the potential wells and around both wells. The optimal region in the parameter space for mass sensing purposes is determined. In that region, steady-state chaotic …
Low-Voltage Closed Loop Mems Actuators, Shahrzad Towfighian, Glenn Heppler, Eihab Abdel-Rahman
Low-Voltage Closed Loop Mems Actuators, Shahrzad Towfighian, Glenn Heppler, Eihab Abdel-Rahman
Mechanical Engineering Faculty Scholarship
An efficient electrostatic resonator is designed by adding a low voltage controller to an electrostatic actuator. The closedloop actuator shows stable, and bi-sable behaviors with bounded chaotic oscillations as large as 117% of the capacitor gap. The controller voltage is decreased from a previously designed resonator to less than 9 V thereby reducing the load on the controller circuit components. Bifurcation diagrams are obtained showing the frequency and magnitude of AC voltage required for chaotic oscillations to develop. The information entropy, a measure of chaotic characteristic, is calculated for the micro-resonator and is found to be 0.732.