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Full-Text Articles in Engineering

A Two-Component Aggregation Model, Thomas A. Chisholm Jr Jan 1999

A Two-Component Aggregation Model, Thomas A. Chisholm Jr

Dissertations, Theses, and Masters Projects

An aggregation model which allows specification of primary particle size, density, and fractal dimension for two different particle types was written. Three stickiness values are used, the stickiness of each particle type to itself and the stickiness between particle types. Aggregation mechanisms considered include differential settling and turbulent shear. The model is used in three forms. In its simplest form, it operates on a closed system with aggregates breaking up when their size approaches the Kolmogorov scale. If the system begins with two types of primary particles, larger aggregates have uniform composition. A second version of the model includes removal …


Nitrate Reduction At The Groundwater - Salt Marsh Interface, Craig -1967 Tobias Jan 1999

Nitrate Reduction At The Groundwater - Salt Marsh Interface, Craig -1967 Tobias

Dissertations, Theses, and Masters Projects

The influence of groundwater discharge on the hydrology and biogeochemical cycling of nitrogen in a fringing intertidal wetland was studied by characterizing groundwater discharge, determining N-cycling rates in cores, and examining nitrate reduction in situ using 15N enrichment and natural gradient tracer techniques. Groundwater discharge was estimated by three independent methods: Darcy's Law, a water/salt mass balance, and a subsurface tracer test. Seasonal patterns of discharge predicted by Darcy's Law and the mass balance were similar. Discharge maxima and minima occurred in April and September, respectively. The water/salt mass balance provided the more reasonable estimate of groundwater flux at high …


Fabrications And Characterizations Of Boron Containing Polyimides For Radiation Shielding, Christopher Scott Pugh Jan 1999

Fabrications And Characterizations Of Boron Containing Polyimides For Radiation Shielding, Christopher Scott Pugh

Dissertations, Theses, and Masters Projects

No abstract provided.


The Thermographic Nondestructive Evaluation Of Iron Aluminide Green Sheet, Michael L. Watkins Jan 1999

The Thermographic Nondestructive Evaluation Of Iron Aluminide Green Sheet, Michael L. Watkins

Dissertations, Theses, and Masters Projects

The recent development of manufacturing techniques for the fabrication of thin iron aluminide sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet by cold rolling FeAl powder mixed with organic binding agents. The green sheet composite has a bulk density, which is typically less than about 3.6 g/cc. The finished sheet, with a density of about 6.1 g/cc, …


Studies In Microwave And Rf Capacitively Coupled Excimer Lamp, Joseph Divine Ametepe Jan 1999

Studies In Microwave And Rf Capacitively Coupled Excimer Lamp, Joseph Divine Ametepe

Dissertations, Theses, and Masters Projects

A lamp that emits strongly in the 180--200 nm region is desirable because of the response of organic materials in this wavelength range. Therefore there is the demand for high-powered, efficient, and low-cost UV and VUV sources.;The purpose of this work is to construct and study two novel (low-cost) UV sources and to understand the (1) emission (180--200 nm) characteristics, (2) electron energy and (3) temperature distribution in the plasmas generated by these two novel excimer lamps.;We designed, constructed and studied (1) a probe-coupled 2.45 GHz microwave arrangement to drive Xe and KrI excimer lamps and (2) a 13.45 GHz …


Thermoelastic And Photoelastic Full-Field Stress Measurement, Deonna Faye Woolard Jan 1999

Thermoelastic And Photoelastic Full-Field Stress Measurement, Deonna Faye Woolard

Dissertations, Theses, and Masters Projects

Photoelasticity is an optical technique that measures the difference of the principal stresses plus the principal stress direction. A complementary technique is thermoelasticity which measures the sum of the principal stresses. Combining these two full-field, non-contact nondestructive evaluation techniques allows the individual stress components to be measured. One of the main difficulties in merging these two measurement systems is in identifying an appropriate surface coating. Thermoelasticity demands a highly emissive surface, while photoelasticity requires a thick, stress-birefringent, transparent coating with a retro-reflective backing. Two coatings have been identified that can be used for combined thermoelastic and photoelastic stress measurements: PMMA …