Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 15 of 15 for “"Electret"”.
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Study of the use of Electret Ion chambers as radom dosimeters in South Africa
… In this thesis, commercially available electret ion chambers (EICs) are studied, with a view to use them as personal monitors. These detectors were developed to measure radon activity concentrations in houses. Their use in the harsh underground mining environments has shown some …
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Experimental study of electrostatic aerosol filtration at moderate filter face velocity
Electrostatic filtration media (electret) has been used in many applications due to its ability to efficiently collect submicron particles while maintaining a low pressure drop. Filter face velocities have ranged from 0.01-0.5 m/s in previous studies. However, in this study, measurements were …
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Towards in-situ device fabrication : electrostatic lithography and nanowire field effect devices
… were used to deposit fine line-width charge in electret materials. The electrets were exposed to charged or polarizable nanoparticle precursors. These nanoparticles decorate the charge pattern. Electret materials including Mylar, Polyamide and Teflon were used for this process. Nanoparticles …
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Functional Materials and Device Concepts for Magnetic Sensing, Gas Detection and Energy Harvesting
… magnetostrictive polymer composites with an electret to form a scalable capacitive sensor for low-field detection. The second avoids magnetostrictive materials by using permanent magnets to induce mechanical strain and piezoelectric transduction to generate the electrical signal. A third …
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A Re-Evaluation of the US EPA Radon Risk Categorization for Unicoi County, Tennessee.
… concentrations were measured in 69 homes using Electret Passive Environmental Radon Monitors (E-PERM’s), following standard methods. Radon concentrations determined in this study (avg. 4.03 ± 3.04) were significantly higher than those measured in the USEPA study (avg. 1.96 ± 1.08). Using this …
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Charging and discharging of Lichtenberg electrets
… a thin dielectric sheet to create a Lichtenberg electret that can be discharged elsewhere to form spectacular Lichtenberg figures. This study examines how the amount of charge deposited onto the surface, the geometry of the probes, and the type of material used can all impact the formation of the …
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Charge-Storage mechanisms in polymer electrets
… of the importance of charge storage in polymer electrets for electromechanical transducer applications, the aim of this work is to contribute to the understanding of the charge-retention mechanisms. Furthermore, we will try to explain how the long-term storage of charge carriers in polymeric …
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A Fully-Implantable Low-Noise Emi-Resistant Piezoelectric-Polymer Microphone and Amplifier for the Middle Ear
… microphone design is competitive with commercial electret microphones used for cochlear implants, especially since our design is fully implantable and interfaces with the existing middle ear structures.
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Development of a Multiple Microphone Probe Calibrator
… The probe microphones are 0.006 m diameter electret microphones which typically do not have an ideal “flat" response over a wide range of frequencies as compared to precision condenser microphones. The probe microphone characteristics prompted the need for simultaneous, multi-microphone …
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Feedback Applications in Active Noise Control for Small Axial Cooling Fans
… loudspeakers as control sources and four small electret microphones as error sensors. A feasibility study was conducted with a single channel of analog feedback control. However, for the majority of this research, the ANC algorithm was executed on a digital signal processor. Several electronic …
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Bearing failure detection in farm machinery using low-cost acoustic techniques
… constructed to test the feasibility of using a electret microphone as a sensor for monitoring bearing condition through vibration signature analysis. Laboratory experiments designed to evaluate the sensors with test bearings at both an advanced and an early stage of wear were developed. A …
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Carbon nanotube based carbon dioxide gas sensors for respiratory monitoring.
… sensing transducer is developed using an electret microphone. This stiffness measurement technique is based on the extreme sensitivity of an electret microphone's capacitance to the stiffness of its membrane. A CO2 sensor is obtained by coating such a microphone with SWNTs. This embodiment …
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Ingeniería avanzada para sistemas de control de ruido acústico mediante técnicas adaptativas
… (del mismo ordenador) y un simple micrófono electret. En ruidos aleatorios la atenuación es sensiblemente inferior (< 5 dB) y apenas se percibe acústicamente.
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Modelling the effect of ventilation on the concentration and distribution of radon in closed environments
… using a combination of the RAD7, Airthings, and Electret Ion Chambers (EICs). The exhalation rates in the tunnel were measured with EIC flux monitors, and in the mine, it was measured using the accumulator method. Additionally, the wind speed and direction in both environments were measured with …
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CMOS Readout Interfaces for MEMS Capacitive Microphones
… systems by leveraging the MEMS technology. Electret-Condenser-Microphones (ECM) are the current market solution for acoustic applications; however, MCMs are being considered as the future microphone-of-choice for mobile phones in consumer electronics and for hearing aids in medical …