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Full-Text Articles in Engineering
Synthesis And Characterization Of Hydrogen-Rich Polyimide Materials For Radiation Shielding, Sha Yang
Synthesis And Characterization Of Hydrogen-Rich Polyimide Materials For Radiation Shielding, Sha Yang
Dissertations, Theses, and Masters Projects
No abstract provided.
Photochemical Modification Of Polyethylene Terephthalate Surface, Zhengmao Zhu
Photochemical Modification Of Polyethylene Terephthalate Surface, Zhengmao Zhu
Dissertations, Theses, and Masters Projects
The prospect of obtaining desired surface-mediated characteristics while retaining bulk-mediated physical properties and avoiding potential environmental issues with wet chemical technology lends considerable appeal to photochemical approaches to surface modification.;We undertook a combined experimental and computational approach to investigate the effect of deep UV irradiation on the polyethylene terephthalate (PET) surface. its response to 172 nm UV from a xenon examiner lamp in the absence of oxygen was characterized with X-ray Photoelectron Spectroscopy (XPS), Time of Flight/Secondary Ion Mass Spectrometry (ToF/SIMS), transmission infrared spectroscopy (IR), and Atomic Force Microscopy (AFM). The surface chemistry details suggested that the primary photochemical reactions …
Simulation Of Turbidity Maximums In The York River, Virginia, Jae-Il Kwon
Simulation Of Turbidity Maximums In The York River, Virginia, Jae-Il Kwon
Dissertations, Theses, and Masters Projects
Two of the most important processes in cohesive sediment transport, erosion rate and settling velocity, were the focus of this study. Settling velocities were estimated by the Owen tube method and the acoustic Doppler velocimeter (ADV) method. A novel erosion model, namely a constant erosion rate model, was implemented in a three-dimensional hydrodynamic eutrophication model (HEM-3D) to simulate the turbidity maximums in the York River system, Virginia. Two one-month periods of model simulations were conducted to mimic typical dry (November--December, 2001) and wet (March--April, 2002) seasons. In order to have enough data to verify the model, four slack water surveys …
Vibrational Lifetimes Of Hydrogen And Oxygen Defects In Semiconductors, Baozhou Sun
Vibrational Lifetimes Of Hydrogen And Oxygen Defects In Semiconductors, Baozhou Sun
Dissertations, Theses, and Masters Projects
Characterization of defect and impurity reactions, dissociation, and migration in semiconductors requires a detailed understanding of the rates and pathways of vibrational energy flow and of the coupling mechanisms between local modes and the phonon bath of the host material. Information on the inelastic microscopic interaction can be obtained by measuring the lifetime of local vibrational modes. This dissertation presents lifetime measurements of hydrogen and oxygen defects in semiconductors by means of time-resolved infrared pump-probe spectroscopy.;First, we measured the vibrational lifetime of H- and D-related bending modes in Si and other semiconductors. Time-resolved pump-probe and linewidth measurements reveal that the …
Sonar Sensor Interpretation For Ectogeneous Robots, Wen Gao
Sonar Sensor Interpretation For Ectogeneous Robots, Wen Gao
Dissertations, Theses, and Masters Projects
We have developed four generations of sonar scanning systems to automatically interpret surrounding environment. The first two are stationary 3D air-coupled ultrasound scanning systems and the last two are packaged as sensor heads for mobile robots. Template matching analysis is applied to distinguish simple indoor objects. It is conducted by comparing the tested echo with the reference echoes. Important features are then extracted and drawn in the phase plane. The computer then analyzes them and gives the best choices of the tested echoes automatically. For cylindrical objects outside, an algorithm has been presented to distinguish trees from smooth circular poles …
Characterization Of Ionic, Dipolar And Molecular Mobility In Polymer Systems, Zhenrong Guo
Characterization Of Ionic, Dipolar And Molecular Mobility In Polymer Systems, Zhenrong Guo
Dissertations, Theses, and Masters Projects
Changes in the ionic and dipolar molecular mobility in a polymer system are the basis for the changes in the dielectric mechanical properties of polymer materials. Frequency Dependent Dielectric Measurements (FDEMS) and Ion Time-of-Flight (ITOF) are two important techniques to investigate ionic and dipolar molecular mobility in polymer systems. The results can be related to the macro- and molecular dielectric, electrical and dynamic properties of polymeric materials. The combination of these two methods provides a full view of electric, dielectric and dynamic behavior for the systems as they undergo chemical and/or physical changes during polymerization crystallization, vitrification, and/or phase separation.;The …