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ANALYSIS OF THE PHYSICAL FORCING MECHANISMS INFLUENCING SALINITY TRANSPORT FOR THE LOWER ST. JOHNS RIVER
Title
ANALYSIS OF THE PHYSICAL FORCING MECHANISMS INFLUENCING SALINITY TRANSPORT FOR THE LOWER ST. JOHNS RIVER.
Creator
Giardino, Derek, Hagen, Scott, University of Central Florida
Abstract / Description
The focus of this thesis is the forcing mechanisms incorporated with salinity transport for the Lower St. Johns River. There are two primary analyses performed: a historical data analysis of primary forcing mechanisms to determine the importance of each individual influence, and a tidal hydrodynamics analysis for the Lower St. Johns River to determine the required tidal constituents for an accurate resynthesis. This thesis is a preliminary effort in understanding salinity transport for the...
Show moreThe focus of this thesis is the forcing mechanisms incorporated with salinity transport for the Lower St. Johns River. There are two primary analyses performed: a historical data analysis of primary forcing mechanisms to determine the importance of each individual influence, and a tidal hydrodynamics analysis for the Lower St. Johns River to determine the required tidal constituents for an accurate resynthesis. This thesis is a preliminary effort in understanding salinity transport for the Lower St. Johns River for engineering projects such as the dredging of navigation canals and freshwater withdrawal from the river. The analysis of the physical forcing mechanisms is performed by examining the impact of precipitation, tides, and wind advection on historical salinity measurements. Three 30-day periods were selected for the analysis, to correspond with representative peak, most-variable, and low-salinity periods for 1999. The analysis displays that wind advection is the dominant forcing mechanism for the movement of salinity over a 30 day duration; however all mechanisms have an impact at some level. The dominant forcing mechanism is also dependent on the period of record examined where tidal influence is vital for durations of hours to a day, while freshwater inflow has more significance over a longer period due to climatological variation. A two-dimensional finite difference numerical model is utilized to generate a one month tidal elevations and velocities simulations that incorporates geometry, nonlinear advection and quadratic bottom friction. Several combinations of tidal constituents are extracted from this modeled tidal signal to investigate which combination of tidal constituents produces an accurate tidal resynthesis for the Lower St. Johns River. The analysis displays the need for 39 total tidal harmonic constituents to accurately resynthesize the original tidal signal. Additionally, due to the nonlinear nature of shallow water, the influence of the overtides for upstream or downstream locations in the Lower St. Johns River is shown to be spatially variable for different frequencies depending on the geometry. The combination of the constituent analysis and the historical analysis provides the basis information needed for the development of an accurate salinity transport model for the Lower St. Johns River.
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Date Issued
2009
Identifier
CFE0002665, ucf:48197
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002665
DERIVING THE DENSITY OF STATES FOR GRANULAR CONTACT FORCES
Title
DERIVING THE DENSITY OF STATES FOR GRANULAR CONTACT FORCES.
Creator
Metzger, Philip, Bhattacharya, Aniket, University of Central Florida
Abstract / Description
The density of single grain states in static granular packings is derived from first principles for an idealized yet fundamental case. This produces the distribution of contact forces P_f(f) in the packing. Because there has been some controversy in the published literature over the exact form of the distribution, this dissertation begins by reviewing the existing empirical observations to resolve those controversies. A method is then developed to analyze Edwards' granular contact force...
Show moreThe density of single grain states in static granular packings is derived from first principles for an idealized yet fundamental case. This produces the distribution of contact forces P_f(f) in the packing. Because there has been some controversy in the published literature over the exact form of the distribution, this dissertation begins by reviewing the existing empirical observations to resolve those controversies. A method is then developed to analyze Edwards' granular contact force probability functional from first principles. The derivation assumes Edwards' flat measure -- a density of states (DOS) that is uniform within the metastable regions of phase space. A further assumption, supported by physical arguments and empirical evidence, is that contact force correlations arising through the closure of loops of grains may be neglected. Then, maximizing a state-counting entropy results in a transport equation that can be solved numerically. For the present it has been solved using the "Mean Structure Approximation," projecting the DOS across all angular coordinates to more clearly identify its predominant features in the remaining stress coordinates. These features are: (1) the Grain Factor related to grain stability and strong correlation between the contact forces on the same grain, and (2) the Structure Factor related to Newton's third law and strong correlation between neighboring grains. Numerical simulations were then performed for idealized granular packings to permit a direct comparison with the theory, and the data including P_f(f) were found to be in excellent agreement. Where the simulations and theory disagree, it is primarily due to the coordination number Z because the theory assumes Z to be a constant whereas in disordered packings it is not. The form of the empirical DOS is discovered to have an elegant, underlying pattern related to Z. This pattern consists entirely of the functional forms correctly predicted by the theory, but with only slight parameter changes as a function of Z. This produces significant physical insight and suggests how the theory may be generalized in the future.
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Date Issued
2005
Identifier
CFE0000381, ucf:46325
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000381
Probing the Influence of Cx43 and Glucose on Endothelial Biomechanics
Title
Probing the Influence of Cx43 and Glucose on Endothelial Biomechanics.
Creator
Islam, Md Mydul, Steward, Robert, Kassab, Alain, Mansy, Hansen, Willenberg, Bradley, University of Central Florida
Abstract / Description
Endothelial cells (ECs) form the innermost layer of all vasculature and constantly receive both biochemical and biomechanical signals, yielding a plethora of biomechanical responses. In response to various biochemical or biomechanical cues, ECs have been documented to generate biomechanical responses such as tractions and intercellular stresses between the cell and substrate and between adjacent cells in a confluent monolayer, respectively. Thus far, the ability of endothelial tight junctions...
Show moreEndothelial cells (ECs) form the innermost layer of all vasculature and constantly receive both biochemical and biomechanical signals, yielding a plethora of biomechanical responses. In response to various biochemical or biomechanical cues, ECs have been documented to generate biomechanical responses such as tractions and intercellular stresses between the cell and substrate and between adjacent cells in a confluent monolayer, respectively. Thus far, the ability of endothelial tight junctions and adherens junctions to transmit intercellular stresses has been actively investigated, but the role of gap junctions is currently unknown. In addition, there is no report of the independent influence of hyperglycemia on endothelial biomechanics present in the literature. To fill these gaps, we conducted a two-fold study where we investigated the influence of endothelial gap junction Cx43 and hyperglycemia in endothelial tractions and intercellular stress generation. In the first study, we selectively disrupted and enhanced EC gap junction Cx43 by using 2',5'-dihydroxychalcone and retinoic acid, respectively and in the second study, we cultured ECs in both normal glucose and hyperglycemic condition for 10 days. In both studies, tractions and intercellular stresses were calculated using traction force microscopy (TFM) and monolayer stress microscopy (MSM), respectively. Our results reveal that Cx43 downregulation increased as well as decreased endothelial avg. normal intercellular stresses in response to a low (0.83 (&)#181;M) and a high dose (8.3 (&)#181;M) chalcone treatment, respectively, while Cx43 upregulation decreases avg. normal intercellular stresses in both treatment conditions (2.5 (&)#181;M and 25 (&)#181;M) compared to control. In addition, we observed a decrease in intercellular stresses with hyperglycemic condition compared to control. The results we present here represent, for the first time, detailed and comprehensive biomechanical analysis of endothelial cells under the influence of glucose and the gap junction Cx43. We believe our results will provide valuable insights into endothelial permeability, barrier strength as well as leading to a greater understanding of overall endothelial mechanics.
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Date Issued
2019
Identifier
CFE0007819, ucf:52805
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007819