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Full-Text Articles in Mechanical Engineering

Development Mems Acoustic Emission Sensors, Adrian Enrique Avila Gomez Nov 2017

Development Mems Acoustic Emission Sensors, Adrian Enrique Avila Gomez

Graduate Theses and Dissertations

The purpose of this research is to develop MEMS based acoustic emission sensors for structural health monitoring. Acoustic emission (AE) is a well-established nondestructive testing technique that is typically used to monitor for fatigue cracks in structures, leaks in pressurized systems, damages in composite materials or impacts. This technology can offer a precise evaluation of structural conditions and allow identification of imminent failures or minor failures that can be addressed by planned maintenances routines. AE causes a burst of ultrasonic energy that is measured as high frequency surface vibrations (30 kHz to 1 MHz) generated by transient elastic waves that ...


Design, Manufacturing, And Assembly Of A Flexible Thermoelectric Device, Christopher Anthony Martinez Jan 2013

Design, Manufacturing, And Assembly Of A Flexible Thermoelectric Device, Christopher Anthony Martinez

Graduate Theses and Dissertations

This thesis documents the design, manufacturing, and assembly of a flexible thermoelectric device. Such a device has immediate use in haptics, medical, and athletic applications. The governing theory behind the device is explained and a one dimensional heat transfer model is developed to estimate performance. This model and consideration for the manufacturing and assembly possibilities are the drivers behind the decisions made in design choices. Once the design was finalized, manufacturing methods for the various components were explored. The system was created by etching copper patterns on a copper/polyimide laminate and screen printing solder paste onto the circuits. Thermoelectric ...


Low Loss Vhf And Uhf Filters For Wireless Communications Based On Piezoelectrically-Transduced Micromechanical Resonators, Julio Mario Dewdney Jan 2012

Low Loss Vhf And Uhf Filters For Wireless Communications Based On Piezoelectrically-Transduced Micromechanical Resonators, Julio Mario Dewdney

Graduate Theses and Dissertations

For the past decade, a great deal of research has been focused towards developing a viable on-chip solution to replace the current state-of-the-art VHF and UHF filters based on SAW and FBAR technologies. Although filters based on SAW and FBAR devices are capable of fulfilling the basic requirements needed for IF and RF bandpass filtering and reference signal generation, an alternative solution that can enable the next generation of multi-frequency and multi-mode transceivers while enabling size and price reduction by allowing the manufacturing of single-chip monolithic RF transceivers is highly desired. In response to these new needs, piezoelectrically-transduced micromechanical filters ...


Model And Validation Of Static And Dynamic Behavior Of Passive Diamagnetic Levitation For Energy Harvesting, Chamila Shyamalee Siyambalapitiya Jan 2012

Model And Validation Of Static And Dynamic Behavior Of Passive Diamagnetic Levitation For Energy Harvesting, Chamila Shyamalee Siyambalapitiya

Graduate Theses and Dissertations

This dissertation reports the investigation conducted on the static and dynamic behavior of the passive diamagnetic levitation systems.

Attachment of a device to a substrate hinders the optimum performance ability of vibrating devices by altering the dynamic behavior of the moving part whilst introducing higher overall stiffness. The significance of this effect is prominent especially in vibration based energy harvesters as higher stiffness elevates the resonance frequency of the system, making it difficult to tune into ambient low frequencies. Other advantages of the proposed method are given by the removal of mechanical bending elements, which are often the source of ...


Diamond Based-Materials: Synthesis, Characterization And Applications, Qiang Hu Jan 2011

Diamond Based-Materials: Synthesis, Characterization And Applications, Qiang Hu

Graduate Theses and Dissertations

The studies covered in this dissertation concentrate on the various forms of diamond films synthesized by chemical vapor deposition (CVD) method, including microwave CVD and hot filament CVD. According to crystallinity and grain size, a variety of diamond forms primarily including microcrystalline (most commonly referred to as polycrystalline) and nanocrystalline diamond films, diamond-like carbon (DLC) films were successfully synthesized. The as-grown diamond films were optimized by changing deposition pressure, volume of reactant gas hydrogen (H2) and carrier gas argon (Ar) in order to get high-quality diamond films with a smooth surface, low roughness, preferred growth orientation and high sp3 bond ...