Civil and Environmental Engineering Faculty Publications

Spatio-temporal variability of daily and weekly precipitation extremes in South America

Shiraj Khan — Tue, 24 Jan 2012 12:54:12 PST

Spatial and temporal variability of precipitation extremes are investigated by utilizing daily observations available at 2.5° gridded fields in South America for the period 1940–2004. All 65 a of data from 1940–2004 are analyzed for spatial variability. The temporal variability is investigated at each spatial grid by utilizing 25-a moving windows from 1965–2004 and visualized through plots of the slope of the regression line in addition to its quality measure (R²). The Poisson-generalized Pareto (Poisson-GP) model, which is a peaks over threshold (POT) approach, is applied to weekly precipitation maxima residuals based on the 95%-quantile threshold, while daily data are...

Relative performance of mutual information estimation methods for quantifying the dependence among short and noisy data

Shiraj Khan — Tue, 24 Jan 2012 12:54:11 PST

Commonly used dependence measures, such as linear correlation, cross-correlogram, or Kendall's τ, cannot capture the complete dependence structure in data unless the structure is restricted to linear, periodic, or monotonic. Mutual information (MI) has been frequently utilized for capturing the complete dependence structure including nonlinear dependence. Recently, several methods have been proposed for the MI estimation, such as kernel density estimators (KDEs), k-nearest neighbors (KNNs), Edgeworth approximation of differential entropy, and adaptive partitioning of the XY plane. However, outstanding gaps in the current literature have precluded the ability to effectively automate these methods, which, in turn, have caused limited adoptions...

Oxidation of 2,4-dinitrotoluene using Fenton's reagent: reaction mechanisms and their practical applications

Nihar R. Moriarty — Mon, 29 Nov 2010 14:00:18 PST

With the strict regulations of present times, chemical oxidation holds tremendous potential for destructive treatment of hazardous wastes which are resistant to biological oxidation. Fenton's reagent has proved to be an inexpensive and powerful oxidant which has been shown to oxidize a wide variety of organics. In this paper, 2,4 dinitrotoluene (2,4 DNT) was chosen as a model compound following previous work where 2,4 DNT was subjected to oxidation by hydrogen peroxide in the presence of medium power UV source. Various factors that are important to optimize the oxidation of organics were studied. The effect of aeration, step dosing and...

Mechanism and kinetics of oxidation of 2,4,6-trichlorophenol by Fenton's reagent

Somnath Basu — Mon, 29 Nov 2010 14:00:16 PST

Fenton's reagent is an effective oxidant for pretreatment and toxicity reduction in wastewater contaminated with 2,4,6-trichlorophenol (TCP). The reaction, and its dependence on various parameters (e.g., molar ratios of the reacting chemicals, pH, temperature, etc.) have been reported elsewhere. In this paper a mechanistic interpretation of the reaction pathway, with identity of the intermediate reaction products, has been presented. An empirical expression for the rate of reaction has also been proposed in terms of the disappearance of TCP in water, as a function of the concentrations of the TCP itself and of the oxidant, hydrogen peroxide.

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