Digital Commons Network^™

Time And Frequency Domain Analyses Of Hydrologic And Stream Water Quality Data, Shesh Raj Koirala

Doctoral Dissertations

The issue of scaling of deterministic properties at various domain levels has become an area of interest for active research. Interpretation of observational data, and similarly hydrologic simulation, require an understanding of how certain deterministic modeling parameters scale from the smaller to larger domains spatially and temporally. Novel approaches to better understand scaling behavior in hydrologic systems and that will result in improved deterministic modeling are necessary to advance the state-of-the-science in hydrologic transport processes, particularly in the areas of microbial concentration and inorganic chemical constituent dynamics. Two primary objectives of this research were i) to determine the statistical relationship …

Evaluation Of Impacts On Delay, Cycle-Length Optimization, Control Types, And Peak-Hour Factor With The Randomness Of Traffic, Jan-Mou Li

Doctoral Dissertations

Some basic concepts about traffic which are correct in theory may be misinterpreted in practice. Such misinterpretations may lead to a different direction from the ideal operation. This four-part dissertation is designated to examine fundamental concepts in traffic operation, and to validate the impact of randomness on control delays, cycle-length optimization, control types, and the peak-hour factor.

Control delays experienced by drivers is a critical performance measure on interrupted-flow traffic which involves movements at slower speeds and stops on intersection approaches, as vehicles move up in the queue or slow down upstream of an intersection. Since the basic term of …

Application Of Particulate-Filled Composite (Pfc) Theory To Hot-Mix Asphalt (Hma) Mixtures, Xiang Shu

Doctoral Dissertations

Dynamic modulus (|E*|) of HMA mixtures is one of the fundamental engineering properties measured by the Simple Performance Tester (SPT) and has been incorporated as a basic input parameter in the American Association of State Highway and Transportation Officials (AASHTO) 2002 Mechanistic-Empirical (M-E) Design Guide for flexible pavement design. Although direct laboratory testing and empirical equations (such as the Witczak model and the Hirsch model) provide two ways to obtain the values of dynamic modulus of HMA mixtures, a predictive model based on the microstructure of HMA mixtures is more desirable.

HMA mixtures consist of three phases: aggregate, …

Study On Infrastructure Materials Using Neutron Radiography And Diffraction, Xin Luo

Doctoral Dissertations

Advanced nondestructive neutron technology has been utilized to study fundamental issues in the Lost Foam Casting (LFC) process and in the mechanical behavior of infrastructure materials.

Time lapsed neutron radiography combined with digital image processing was used to investigate the real-time LFC process. Behavior and characteristics of the pyrolysis front in the LFC processes were discussed. Evidence shows that neutron radiography offers new insights into the pyrolysis front and the dynamics of the processes involved with the casting. Behavior and characteristics of the pyrolysis front and the molten metal interface in the LFC processes were revealed. The proposed approach will …

Modeling The Quorum Sensing Signaling Regulatory Network In Vibrio Fischeri, Ling Yan

Doctoral Dissertations

Quorum sensing is a mechanism by which bacteria can sense the levels of signaling molecules and respond by controlling the expression of target genes. The marine bacterium, Vibrio fischeri, has been extensively studied as a model for the quorum sensing mechanism in Gram-negative bacteria. In order to systematically investigate the quorum sensing regulatory network in V. fischeri, a conceptual model was first established based on the existing knowledge. Next, molecular microbiology and bioinformatics techniques were employed to both qualitatively and quantitatively characterize the system. These techniques included the quantification of the 3-oxo-C6-HSL concentrations in the cell culture supernatant …