Digital Commons Network^™

The Effect Of Freeze /Thaw Temperature Fluctuations On Microbial Metabolism Of Petroleum Hydrocarbon Contaminated Antarctic Soil, Conrad George Leszkiewicz

Doctoral Dissertations

Petroleum contaminated soil exists at McMurdo Station in Antarctica. These soils were contaminated with historic releases of JP-8 jet fuel. Over time, there does not appear to have been significant reduction in the petroleum concentrations in these soils. This lack of reduction has been attributed to the extremely cold Antarctic environment and the lack of available moisture.

Cold temperatures and/or lack of moisture may not be the factors inhibiting biodegradation. Soil temperatures can exceed 20 degrees centigrade (°C) during the austral summer and melt water becomes available. However, the soil temperatures have also been reported to fluctuate rapidly. Swings of …

Discrete Modeling Of Sculptured Surface Machining For Robust Automatic Feedrate Selection, Jeffrey Gordon Hemmett

Doctoral Dissertations

Traditional feedrate selection techniques currently used in three and five-axis CNC machining reduces milling efficiency. Manually estimated feedrates tend to be conservative and constant, greatly increasing mill time. The goal of this research is to develop robust techniques and software tools for automatically generating optimized feedrates for use on three and five-axis CNC mills, to both simplify the feed selection process and to increase the safety and efficiency of the milling operation through milling process simulation.

The simulation software estimates milling force vectors for each tool move, and identifies a feedrate that maintains a desired peak force. The desired cutting …

An Experimental And Finite Element Investigation Of Thermally Induced Inelastic Deformation Of Single-Level Damascene Copper High Density Interconnect Structures, Nazri B. Kamsah

Doctoral Dissertations

An atomic force microscope was used to investigate thermally induced deformation mechanisms in the areas of copper and polyimide vias in copper-polyimide interconnect structure, as a result of a thermal cycle to 350°C. The copper films exhibited evidence of copper grain boundary sliding, Coble creep, and voids formation. Cu-Ta interfacial sliding was observed in the Cu and polyimide via areas. The direction of the Cu-Ta sliding changes as the polyimide via size decreases. The polyimide experienced a residual deformation attributed to the Cu-Ta sliding and in-plane deformation of the copper vias.

A finite element method was used to simulate the …

Open Ocean Fish Cage And Mooring System Dynamics, David Wayne Fredriksson

Doctoral Dissertations

To satisfy the global need for seafood, marine aquaculture is expected to play an increasing role as wild fish stocks decline. The expansion of near-shore aquaculture is becoming more difficult because of multi-use issues and environmental impact concerns. As a result, a national objective has been initiated to establish an open ocean aquaculture industry. To design and evaluate fish cages and moorings for the energetic open ocean requires a systematic approach utilizing physical and numerical modeling techniques. Using these methods, two robust fish cage and mooring systems were designed, deployed and have survived two New England winters. Prior to the …

E -Commerce For The Metal Removal Industry, Okhyun Ryou

Doctoral Dissertations

The popularity of outsourcing fabrication introduces a problem, namely an inevitable loss of data as information is translated from design to fabrication or from one system to another. Unsatisfactory information, delivered to the outsourcing facility, and inefficient communications between design and fabrication certainly cause enormous economic losses from late product delivery or bad product quality. To overcome these data transferring problems and to improve communications between the design and fabrication sides, a design and manufacturing methodology for custom machined parts in E-Commerce is suggested and implemented in this dissertation. This methodology is based on the idea of a "Clean Interface" …

A Model For Backscattering Angular Response Of Gassy Sediments: Applications To Petroleum Exploration And Development Programs, Luciano Emidio Neves Da. Fonseca

Doctoral Dissertations

The location and distribution of near-surface gas in continental margins is of particular interest for oil exploration and development programs. The presence of gas seepages can be evidence of the possible existence of subsurface hydrocarbon reservoirs. Gas is also a potential hazard for offshore facilities, as it decreases the strength of unconsolidated sediments increasing the risk of seafloor failures and slumps.

Acoustic remote sensing systems such as multibeam and sidescan sonars can be used for mapping and detection of near-surface gas in marine sediments. These systems provide a realistic depiction of the seafloor by means of the simultaneous acquisition of …

Regulation Of Mammalian Photoreceptor Phosphodiesterase (Pde) By Its Noncatalytic Gaf Domains And Its Two Small Subunits, Gamma And Delta, Hongmei Mou

Doctoral Dissertations

cGMP phosphodiesterase (PDE) is the central effector of visual transduction in retinal rod photoreceptors. The overall goal of this work was to investigate the possible regulatory mechanisms of PDE in mammalian rod photoreceptors by its noncatalytic cGMP binding sites on the PDE catalytic dimer (Palphabeta), and by the interactions between the inhibitory Pgamma subunit and Palphabeta in their phosphorylated and non-phosphorylated states.

First, the binding of cGMP to the noncatalytic sites on membrane-associated PDE (PDE-M) and soluble PDE (PDE-S) was characterized. We found that PDE-M holoenzyme contains 2 non-identical high-affinity cGMP binding sites; one of the cGMP binding sites is …

Numerical Simulation Of Acoustic Waves In A Rectangular Chamber, Normah Mohd. Ghazali

Doctoral Dissertations

Numerical simulation of acoustic waves in a closed two-dimensional rectangular chamber is considered. The waves are generated by a membrane or piston boundary condition on one wall. The simulations are performed through many acoustic cycles. A stack of heat exchanger plates are sometimes included. The study is motivated by thermoacoustic refrigeration, a phenomena which uses soundwaves in a chamber to achieve a cooling effect.

The present study treats the flow numerically. The governing equations are the viscous compressible Navier-Stokes system, assuming a perfect gas. The numerical method employs a finite difference spatial discretization and semi-implicit time-marching procedure. Verification is accomplished …

Estimating The Environmental Costs Of The Hydro Fuel Cycle Using Life Cycle Assessment Techniques And Economic Valuation, Benjamin Harwood Ellis

Doctoral Dissertations

A Life Cycle Assessment model, with an integrated impact assessment, is used to estimate average external economic damages from the hydro fuel cycle. Aggregated average damage assessments of the hydro fuel cycle are complementary to marginal and site specific assessments, and are useful for general energy policy planning. For the upstream inventory assessment, detailed material input data from the Morrow Point Dam is used to estimate material inputs at 174 New England, and 4 Quebec, concrete hydroelectric projects. LCNetBase input-output life cycle assessment software, developed by Dr. Gregory Norris at Sylvatica, is used to estimate upstream emissions associated with material …