Development of methods for spatial modeling of sediments quality in Lake Okeechobee, Florida

The major objectives of this dissertation were to develop optimal spatial techniques to model the spatial-temporal changes of the lake sediments and their nutrients from 1988 to 2006, and evaluate the impacts of the hurricanes occurred during 1998–2006. Mud zone reduced about 10.5% from 1988 to 1998, and increased about 6.2% from 1998 to 2006. Mud areas, volumes and weight were calculated using validated Kriging models. From 1988 to 1998, mud thicknesses increased up to 26 cm in the central lake area. The mud area and volume decreased about 13.78% and 10.26%, respectively. From 1998 to 2006, mud depths declined by up to 41 cm in the central lake area, mud volume reduced about 27%. Mud weight increased up to 29.32% from 1988 to 1998, but reduced over 20% from 1998 to 2006. The reduction of mud sediments is likely due to re-suspension and redistribution by waves and currents produced by large storm events, particularly Hurricanes Frances and Jeanne in 2004 and Wilma in 2005. Regression, kriging, geographically weighted regression (GWR) and regression-kriging models have been calibrated and validated for the spatial analysis of the sediments TP and TN of the lake. GWR models provide the most accurate predictions for TP and TN based on model performance and error analysis. TP values declined from an average of 651 to 593 mg/kg from 1998 to 2006, especially in the lake’s western and southern regions. From 1988 to 1998, TP declined in the northern and southern areas, and increased in the central-western part of the lake. The TP weights increased about 37.99%–43.68% from 1988 to 1998 and decreased about 29.72%–34.42% from 1998 to 2006. From 1988 to 1998, TN decreased in most areas, especially in the northern and southern lake regions; western littoral zone had the biggest increase, up to 40,000 mg/kg. From 1998 to 2006, TN declined from an average of 9,363 to 8,926 mg/kg, especially in the central and southern regions. The biggest increases occurred in the northern lake and southern edge areas. TN weights increased about 15%–16.2% from 1988 to 1998, and decreased about 7%–11% from 1998 to 2006.

Current Status of Collectibility of Gaming-Related Credit Dollars

In her piece entitled - Current Status Of Collectability Of Gaming-Related Credit Dollars - Ruth Lisa Wenof, Graduate Student at Florida International University initially states: “Credit is an important part of incentives used to lure gamblers to gaming establishments. However, a collection problem exists in casinos retrieving gaming-related credit losses of individuals living in states where gambling is illegal. The author discusses the history of this question, citing recent cases related to Atlantic City.” This author’s article is substantially laden with legal cases associated with casinos in New Jersey; Atlantic City to be exact. The piece is specific to the segment of the gaming industry that the title suggests, and as such is written in a decidedly technical style. “Legalized casino gaming, which was approved by the citizens of New Jersey on November 8, 1976, has been used as a unique tool of urban redevelopment for Atlantic City,” Wenof says in providing some background on this ‘Jersey shore municipality. “Since Resorts International opened its casino…revenues from gambling have increased rapidly. Resorts' gross win in 1978 was $134 million,” Wenof says. “Since then, the combined gross win of the city's 11 casinos has been just shy of $7.5 billion.” The author points out that the competition for casino business is fierce and that credit dollars play an integral role in soliciting such business. “Credit plays a most important part in every casino hotel. This type of gambler is given every incentive to come to a particular hotel,” says the author. “Airplanes, limousines, suites, free meals, and beverages all become a package for the person who can sign a marker. The credit department of a casino is similar to that of a bank. A banker who loans money knows that it must be paid back or his bank will fail. This is indeed true of a casino,” Wenof warns in outlining the potential problem that this article is fundamentally designed around. In providing further background on credit essentials and possible pitfalls, Wenof affords: “…on the Casino Control Act the State Commission of Investigation recommended to the legislature that casinos should not be allowed to extend credit at all, by reason of a concern for illicit diversion of revenues, which is popularly called skimming within the industry…” Although skimming is an after-the-fact problem, and is parenthetic to loan returns, it is an important element of the collective [sic] credit scheme. “A collection problem of prime importance is if a casino can get back gaming-related credit dollars advanced by the casino to a gambler who lives in a state where gambling is illegal,” is a central factor to consider, Wenof reveals. This is a primary focus of this article. Wenof touches on the social/societal implications of gambling, and then continues the discussion by citing a host of legal cases pertaining to debt collection.

Eulerian-Lagrangian two phase debris flow model

The main objective of this work is to develop a quasi three-dimensional numerical model to simulate stony debris flows, considering a continuum fluid phase, composed by water and fine sediments, and a non-continuum phase including large particles, such as pebbles and boulders. Large particles are treated in a Lagrangian frame of reference using the Discrete Element Method, the fluid phase is based on the Eulerian approach, using the Finite Element Method to solve the depth-averaged Navier-Stokes equations in two horizontal dimensions. The particle’s equations of motion are in three dimensions. The model simulates particle-particle collisions and wall-particle collisions, taking into account that particles are immersed in a fluid. Bingham and Cross rheological models are used for the continuum phase. Both formulations provide very stable results, even in the range of very low shear rates. Bingham formulation is better able to simulate the stopping stage of the fluid when applied shear stresses are low. Results of numerical simulations have been compared with data from laboratory experiments on a flume-fan prototype. Results show that the model is capable of simulating the motion of big particles moving in the fluid flow, handling dense particulate flows and avoiding overlap among particles. An application to simulate debris flow events that occurred in Northern Venezuela in 1999 shows that the model could replicate the main boulder accumulation areas that were surveyed by the USGS. Uniqueness of this research is the integration of mud flow and stony debris movement in a single modeling tool that can be used for planning and management of debris flow prone areas.

Eulerian-Lagrangian Two Phase Debris Flow Model

The main objective of this work is to develop a quasi three-dimensional numerical model to simulate stony debris flows, considering a continuum fluid phase, composed by water and fine sediments, and a non-continuum phase including large particles, such as pebbles and boulders. Large particles are treated in a Lagrangian frame of reference using the Discrete Element Method, the fluid phase is based on the Eulerian approach, using the Finite Element Method to solve the depth-averaged Navier–Stokes equations in two horizontal dimensions. The particle’s equations of motion are in three dimensions. The model simulates particle-particle collisions and wall-particle collisions, taking into account that particles are immersed in a fluid. Bingham and Cross rheological models are used for the continuum phase. Both formulations provide very stable results, even in the range of very low shear rates. Bingham formulation is better able to simulate the stopping stage of the fluid when applied shear stresses are low. Results of numerical simulations have been compared with data from laboratory experiments on a flume-fan prototype. Results show that the model is capable of simulating the motion of big particles moving in the fluid flow, handling dense particulate flows and avoiding overlap among particles. An application to simulate debris flow events that occurred in Northern Venezuela in 1999 shows that the model could replicate the main boulder accumulation areas that were surveyed by the USGS. Uniqueness of this research is the integration of mud flow and stony debris movement in a single modeling tool that can be used for planning and management of debris flow prone areas.