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Mega: An Energy Aware Algorithm For Self-Powered Wireless Sensor Networks In Sustainable Smart Infrastructure, Dong Qi, Yu Chen, Shahrzad Towfighian

Mechanical Engineering Faculty Scholarship

Smart infrastructure is attractive for possessing many desirable features, such as uninterrupted monitoring of health conditions, timely response to damages, and human-infrastructure interactions. Embedded sensors that collectinformation are critical for decision making. However, the lifetime of electronic sensors is a constraint to infrastructure lifetime if sensors are physically embedded in the infrastructure at construction time. In this paper, we studied a self-powered wireless sensor network that harvests energy from mechan-ical vibration in the environment. A dynamic, hierarchical algorithm called MEGA is proposed that constructs clusters and elects the cluster head based on residue energy and energy harvest rate. Taking a …

Theoretical Prediction Of Experimental Jump And Pull-In Dynamics In A Mems Sensor, Laura Ruzziconi, Abdallah H. Ramini, Mohammad I. Younis, Stefano Lenci

Mechanical Engineering Faculty Scholarship

The present research study deals with an electrically actuated MEMS device. An experimental investigation is performed, via frequency sweeps in a neighbourhood of the first natural frequency. Resonant behavior is explored, with special attention devoted to jump and pull-in dynamics. A theoretical single degree-of-freedom spring-mass model is derived. Classical numerical simulations are observed to properly predict the main nonlinear features. Nevertheless, some discrepancies arise, which are particularly visible in the resonant branch. They mainly concern the practical range of existence of each attractor and the final outcome after its disappearance. These differences are likely due to disturbances, which are unavoidable …

Simple Fall Criteria For Mems Sensors: Data Analysis And Sensor Concept, Alwathiqbellah Ibrahim, Mohammad I. Younis

Mechanical Engineering Faculty Scholarship

This paper presents a new and simple fall detection concept based on detailed experimental data of human falling and the activities of daily living (ADLs). Establishing appropriate fall algorithms compatible with MEMS sensors requires detailed data on falls and ADLs that indicate clearly the variations of the kinematics at the possible sensor node location on the human body, such as hip, head, and chest. Currently, there is a lack of data on the exact direction and magnitude of each acceleration component associated with these node locations. This is crucial for MEMS structures, which have inertia elements very close to the …

Jump And Pull-In Dynamics Of An Electrically Actuated Bistable Mems Device, Laura Ruzziconi, Stefano Lenci, Mohammad I. Younis

Mechanical Engineering Faculty Scholarship

This study analyzes a theoretical bistable MEMS device, which exhibits a considerable versatility of behavior. After exploring the coexistence of attractors, we focus on each rest position, and investigate the final outcome, when the electrodynamic voltage is suddenly applied. Our aim is to describe the parameter range where each attractor may practically be observed under realistic conditions, when an electric load is suddenly applied. Since disturbances are inevitably encountered in experiments and practice, a dynamical integrity analysis is performed in order to take them into account. We build the integrity charts, which examine the practical vulnerability of each attractor. A …

Modeling The Structural-Thermal-Electrical Coupling In An Electrostatically Actuated Mems Switch And Its Impact On The Switch Stability, Hassen M. Ouakad, Mohammad I. Younis

Mechanical Engineering Faculty Scholarship

Modeling and analysis for the static behavior and collapse instabilities of a MEMS cantilever switch subjected to both electrical and thermal loadings are presented. The thermal loading forces can be as a result of a huge amount of switching contact of the microswitch. The model considers the microbeam as a continuous medium and the electric force as a nonlinear function of displacement and accounts for its fringing-field effect. The electric force is assumed to be distributed over specific lengths underneath the microbeam. A boundary-value solver is used to study the collapse instability, which brings the microbeam from its unstuck configuration …

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

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

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

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.

A Large-Stroke Electrostatic Micro-Actuator, Shahrzad Towfighian, Abdulrahman Seleim, Eihab Abdel-Rahman, Glenn Heppler

Mechanical Engineering Faculty Scholarship

Voltage-driven parallel-plate electrostatic actuators suffer from an operation range limit of 30% of the electrostatic gap; this has restrained their application in microelectromechanical systems. In this paper, the travel range of an electrostatic actuator made of a micro-cantilever beam above a fixed electrode is extended quasi-statically to 90% of the capacitor gap by introducing a voltage regulator (controller) circuit designed for low-frequency actuation. The voltage regulator reduces the actuator input voltage, and therefore the electrostatic force, as the beam approaches the fixed electrode so that balance is maintained between the mechanical restoring force and the electrostatic force. The low-frequency actuator …

Recent Advances In Solid Hydrogen Storage Systems, B. S. Chao, R. C. Young, V. Myasnikov, Y. Li, F. Gingl, Patrick D. Ferro, V. Sobolev, S. R. Ovshinsky

Mechanical Engineering Faculty Scholarship

Hydrogen energy offers great promise as an energy alternative. Hydrogen technologies can reduce and eliminate the release of carbon dioxide from fossil-fuel combustion, the main cause of global warming. One of the main challenges is hydrogen storage. Storing hydrogen in the solid-state hydride form holds a volumetric advantage over compressed and liquid hydrogen states. Solid hydrogen storage systems also have features of low-pressure operation, compactness, safety, tailorable delivery pressure, excellent absorption /desorption kinetics, modular design for easy scalability, and long cycle life.

In this paper, solid hydrogen storage systems (such as portable power canisters, lightweight fiber wrapped vessels, and aluminum …