Global ETD Search

1	Defect and thickness inspection system for cast thin films using machine vision and full-field transmission densitometry Johnson, Jay Tillay 12 1900 (has links) Quick mass production of homogeneous thin film material is required in paper, plastic, fabric, and thin film industries. Due to the high feed rates and small thicknesses, machine vision and other nondestructive evaluation techniques are used to ensure consistent, defect-free material by continuously assessing post-production quality. One of the fastest growing inspection areas is for 0.5-500 micrometer thick thin films, which are used for semiconductor wafers, amorphous photovoltaics, optical films, plastics, and organic and inorganic membranes. As a demonstration application, a prototype roll-feed imaging system has been designed to inspect high-temperature polymer electrolyte membrane (PEM), used for fuel cells, after being die cast onto a moving transparent substrate. The inspection system continuously detects thin film defects and classifies them with a neural network into categories of holes, bubbles, thinning, and gels, with a 1.2% false alarm rate, 7.1% escape rate, and classification accuracy of 96.1%. In slot die casting processes, defect types are indicative of a misbalance in the mass flow rate and web speed; so, based on the classified defects, the inspection system informs the operator of corrective adjustments to these manufacturing parameters. Thickness uniformity is also critical to membrane functionality, so a real-time, full-field transmission densitometer has been created to measure the bi-directional thickness profile of the semi-transparent PEM between 25-400 micrometers. The local thickness of the 75 mm x 100 mm imaged area is determined by converting the optical density of the sample to thickness with the Beer-Lambert law. The PEM extinction coefficient is determined to be 1.4 D/mm and the average thickness error is found to be 4.7%. Finally, the defect inspection and thickness profilometry systems are compiled into a specially-designed graphical user interface for intuitive real-time operation and visualization. Nondestructive evaluation Nondestructive testing Beer's law Neural network classification Image processing
2	Integration and data acquisition of an optical spectroscopy and optical transmission properties of bulk GaNP material Lai, Chun-chen 09 September 2007 (has links) Our major work is to use LabVIEW as the platform to develop the instrument control programs for measuring the optical and electrical properties of semiconductor materials. To measure the optical properties of semiconductor materials, we developed an optical spectroscopy control program. The program can be modified to make it suitable for many kinds of optical spectroscopy systems. Here we use it to measure the transmission spectrum of GaNP bulk material. To measure the electrical properties of semiconductor materials, we developed a program to record the I-V characteristic curve of the device under test. We can use it to check the ohmic property of contact form between metal electrode and semiconductor material. Finally, we developed a program to record the photoconductivity build-up and decay transient curve. KEITHLEY Beer's law Triax Jobin Yvon ohmic photoconductivity optical spectroscopy LabVIEW I-V transmission Sequence Shift Registers
3	Mechanisms Causing Ferric Staining in the Secondary Water System of Brigham City, Utah Wallace, Robert Derring 26 May 2007 (has links) Water from Mantua reservoir has, during some years, exhibited reddish-brown staining when used by Brigham City for irrigation. I propose that seasonal fluctuations in the reservoir chemistry create an environment conducive to dissolving iron from the iron-rich sediments, which subsequently precipitate during irrigation, resulting in a staining event. These conditions are produced by chemical and biological decomposition of organic matter, coupled with isolation of the hypolimnetic waters, which results in seasonal low concentrations of dissolved oxygen in these waters. Under these specific circumstances, anaerobic conditions develop creating a geochemical environment that causes iron and manganese reduction from Fe(III) to Fe(II) and Mn(IV) to Mn(II), respectively. These reducing conditions facilitate reduction-oxidation (redox) chemical reactions that convert insoluble forms of iron and manganese found in the reservoir sediments into more soluble forms. Consequently, relatively high amounts of dissolved iron and manganese are generated in the bottom waters immediately adjacent to the benthic sediments of the reservoir. Water withdrawn from a bottom intake pipe during these periods introduces iron-rich water into the distribution system. When this water is exposed to oxygen, reoxidation shifts redox equilibrium causing precipitation of soluble Fe(II) and Mn(III) back to highly insoluble Fe(III) and Mn(IV). The precipitant appears on contact surfaces as the aforementioned ferric stain. This research focuses specifically on the iron chemistry involved and evaluates this hypothesis using various measurements and models including field data collection, computer simulations, and bench-scale testing to validate the processes proposed. anaerobic hypolimnion epilimnion stratification iron-staining reddish-brown staining hypereutrophic mesolimnion dissolved oxygen benchscale models iron reduction manganese redox potential Mantua Reservoir dissolved iron precipitate reoxidation aerobic PHREEQC benthic sediments seasonal fluctuations iron-rich sediments calibration curve spectrophotometer ICP Beer's Law EPA Methods thermal stratification Civil and Environmental Engineering

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