Stochastic and Dynamic Shipper Carrier Network Design Problem

The focus of this work is to determine the optimal storage capacity to be installed on transhipment nodes by shippers in a dynamic shipper carrier network under stochastic demand. A two stage linear program with recourse formulation is developed where in the first stage, the shipper decides the optimal capacity to be installed on transhipment nodes. In the second stage, the shipper chooses a routing strategy based on the realized demand. The performance of the following solution methods: Stochastic L Shaped Method, Regularized Decomposition and L Shaped Method with preliminary cuts were compared for various network sizes and numerous demand scenarios. A novel capacity shifting heuristic was introduced to generate a feasible implementable solution which significantly improves the performance of Regularized Decomposition and provides the best performance in the cases tested. Various ways of generating analytical bounds on the objective function value was discussed. The new capacity shifting heuristic was found to be efficient in generating tight upper bounds. Even though the formulation considered in this paper is for a single commodity, the model can be easily extended to account for multiple commodities.     

Chemical and microbiological parameters in New Orleans floodwater following Hurricane Katrina

Hurricane Katrina, rated as a Category 4 hurricane on the Saffir-Simpson scale, made landfall on the U.S. Gulf Coast near New Orleans, Louisiana on Monday, August 29, 2005. The storm brought heavy winds and rain to the city, and several levees intended to protect New Orleans from the water of Lake Pontchartrain were breached. Consequently, up to 80% of the city was flooded with water reaching depths in excess of three meters in some locations. Research described in this paper was conducted to provide an initial assessment of contaminants present in floodwaters shortly after the storm and to characterize water pumped out of the city into Lake Pontchartrain once dewatering operations began several days after the storm. Data are presented which demonstrate that during the weeks following the storm, floodwater was brackish and well-buffered with very low concentrations of volatile and semivolatile organic pollutants. Dissolved oxygen was depleted in surface floodwater, averaging 1.6 mg/L in the Lakeview district and 4.8 mg/L in the Mid-City district. Dissolved oxygen was absent (< 0.02 mg/L) at the bottom of the floodwater column in the Mid-City district 9 days afterthe storm. Chemical oxygen demand (Mid-City average = 79.9 mg/L) and fecal coliform bacteria (Mid-City average = 1.4 x 10(5) MPN/100 mL) were elevated in surface floodwater but typical of stormwater runoff in the region. Lead, arsenic, and in some cases, chromium, exceeded drinking water standards but with the exception of some elevated Pb concentrations generally were typical of stormwater. Data suggest that what distinguishes Hurricane Katrina floodwater is the large volume and the human exposure to these pollutants that accompanied the flood, rather than very elevated concentrations of toxic pollutants.     

Transport of chemical vapors through soil: A landfill cover simulation experiment

Experimental simulation studies of the transport of volatile organic chemical vapors by both diffusion and convection through soil covers, as in landfi     

High-performance composite from epoxy and glass fibers: Morphology,mechanical, dynamic mechanical,and thermal analysis

Diglycidyl ether of bisphenol-A type epoxy resin cured with diamino diphenyl sulfone was used as the matrix for fiber-reinforced composites to get improved mechanical and thermal properties for the resulting composites. E-glass fiber was used for fiber reinforcement. The morphology, tensile, flexural, impact, dynamic mechanical, and thermal properties of the composites were analyzed. The tensile, flexural, and impact properties showed dramatic improvement with the addition of glass fibers. Dynamic mechanical analysis was performed to obtain the T_g of the cured matrix as well as the composites. The improved thermal stability of the composites was clear from the thermogravimetric analysis. Scanning electron micrographs were taken to understand the interfacial adhesion between the fiber and the matrix. The values of mechanical properties were compared with modified epoxy resin composite system. Predictive models were applied using various equations to compare the mechanical data obtained theoretically and experimentally. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Cascade crossflow air stripping of moderately volatile compounds using high air-to-water ratios

The cascade crossflow air stripper provides the capability at the design stage of independently varying the cross-sectional areas for air and water flow. This flexibility results in a greatly reduced gas-phase pressure drop and permits stable operation at air and water flow rates which would cause flooding in a countercurrent column. Experimental results from a laboratory-scale cascade crossflow packed column have been coupled with design calculations to show the feasibility of stripping compounds such as 1,2-dichloroethane and methyl ethyl ketone which are not easily amenable to countercurrent air stripping. For 1,2-dichloroethane, comparable experimental stripping efficiency in countercurrent and cascade cross-flow modes was achieved with a pressure drop reduction in the cascade crossflow mode of approximately two orders of magnitude. High efficiency stripping of less volatile methyl ethyl ketone requires large G/L ratios which would flood a countercurrent column. In contrast, the large G/L ratios can be achieved in the cascade crossflow mode, and design calculations based upon the experimental results suggest that 95% efficiency can be achieved using a column of reasonable size.     

In-situ control of DNAPL density using polyaphrons

Once spilled into soils, dense nonaqueous phase liquids (DNAPLs) such as chlorinated solvents migrate deep into the subsurface because of their high density. Their downward migration typically continues until capillary forces balance gravitational forces or until essentially impermeable strata are reached. Efforts to mobilize the DNAPL for remediation purposes risks driving the contaminants deeper, which has spurred research for modifying buoyancy forces in situ. In this paper, a novel means of controlling the density of a DNAPL phase using polyaphrons is presented. Polyaphrons are a class of high internal phase ratio emulsions (HIPREs) that have unusual properties such as indefinite stability and flow properties through porous media. They provide a means of selectively delivering a light organic phase liquid to the vicinity of the DNAPL phase. Upon destabilization of the polyaphron by a polyvalent cation, the light internal phase mixes with the DNAPL to produce a nonaqueous phase of lower density than the original contaminant. The negative buoyancy of the DNAPL can thus be reversed. This approach holds great promise for manipulating DNAPL densities prior to or during remediation treatments.     

Influence of bromide,chloride and thiourea additions on the reduction of Pb(II) from molten Ca(NO)3)2.4H2O at the mercury electrode

Electrochemical reduction of Pb(II) ion in the presence and absence of bromide, chloride and thiourea(TU) have been studied in molten Ca(NO₃)₂.4H₂O at 60°C. The overall and step-wise stability constants of the bromo, chloro and thiourea complexes have been evaluated from polarographic parameters using a computer analysis.Adsorption of complexes of Pb(II) in the melt induced by coadsorption of ligands (Br^? and TU) is also inferred and surface excesses are calculated from the results of lsv and chronopotentiometry are discussed.