In natural systems, the solution concentration and hence, potential bioavailability of trace metals is primarily controlled by adsorption-desorption reactions at the mineral-water interface. While many studies have been conducted to understand the adsorption of trace metals to soil minerals, less is known about long-term adsorption/desorption processes. In this study, we examined the influence of mixing and sorption period on the desorption of lead from goethite. Lead sorption was rapid and essentially complete in 1 h, with no change in the quantity of lead adsorbed over the 6 month sorption period. Desorption of lead was slower than the adsorption reaction and was best modeled by two first order equations. At all sorption densities, the desorption of lead followed the order Short-term (24 h) > Long-term non-stirred (6 months) > Long-term stirred (6 months). However, statistical analysis indicated that these differences were not statistically significant. Furthermore, the desorption rate coefficients were very similar for all the experiments indicating that there was no significant residence time effect in this study. However, a sample from a previous study that was allowed to age 5 years and then analyzed by the desorption procedure did have statistically significant differences between the long-term (5 years) and the short-term (5 months). These results suggest that longer adsorption periods, perhaps a number of years, may be necessary to determine if residence time effects are an artifact of the experimental conditions or truly the length of the adsorption period. / Master of Science

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / his paper proposes a Lean Green model for increasing profitability in small and medium-sized businesses operating within the plastics sector. This model will use the 5S methodology, KanBan for inventory control and TPM to standardize new corrective and preventive maintenance processes. As an added contribution, a Circular Economy process will be included to reuse products, thus reducing consumption and generating less solid waste. In this way, companies will not only prevent damaging the environment but will also guarantee their compliance with regulatory standards. As a result, an 11% reduction was observed in the acquisition of supplies and spare parts for machine maintenance along with a 4% reduction in the number of machine breakdowns.

The research is a study on the microscopic scale of the immiscible displacement of oil by water in a porous medium such as sandstone. Of particular interest (with application to the oil industry) are the residual saturation of oil, the permeability to water at residual oil saturation and the maximum trapped blob size. Initially the effects of gravity, surface tension and distribution of pore sizes were studied in a computer simulation of a buoyancy driven, quasi-static invasion. The rock was modelled as a three-dimensional lattice of spherical pores connected by narrow cylindrical throats. With the rock water-wet, the tendency of the surface tension to favour the invasion of smaller pores led to a larger residual oil saturation by pore volume than by pore numbers. Also bourne out were some scaling arguments based on percolation theory for the maximum trapped blob size as a function of the relative strength of buoyancy and surface tension forces. The second part of the research investigated the interaction of viscous and surface tension forces. As this is a much more complicated problem, involving the solution of flow equations, the invasion process was first simulated with exact equations of motion on small networks (up to 10x10), where surface tension effects dominate. From these simulations a simplified set of rules was developed to determine which pore in a locality on the oil-water interface is invaded and how long the invasion takes. These rules include a viscous correction to the dominant surface tension forces. Finally, some theory has been developed for the inclusion of the small-scale analysis into a larger model, allowing a full simulation of the viscous dominated invasion to be performed.

No description available.

acase@tulane.edu / 1 / Nicole Katin

In this thesis I investigate the relationship between the gender distribution across industries and occupations and the incidence and consequences of displacement. First, I provide empirical evidence to support the idea that women self-select into less risky industries and occupations, that is industries and occupations with lower displacement rates and lower earnings growth. Using data from the Displaced Worker Survey (1984-2002), the corresponding Annual Demographic Supplement to the March Current Population Survey, and the Dictionary of Occupational Titles, I find that, even though women have a lower incidence of displacement in the aggregate, they are more likely to get displaced at the one-digit industry and occupation level than men. Displacement is also more costly for women, in terms of both employment and monetary consequences, which suggests that women’s choice of safer sectors could be an insurance mechanism against the risk of displacement and its costly consequences. I then construct a dynamic occupational choice model in the spirit of Keane and Wolpin (1997), in which occupation(industry) groups differ not only in terms of the rate of human capital accumulation, but also in the risk and associated cost of displacement, as well as in the value of the non-monetary utility component. I calibrate the model for men and perform a number of counterfactual experiments for women. Quantitative results suggest that differences in displacement probabilities, together with differences in re-employment probabilities, and in human capital penalty rates at displacement explain up to 15% of the gender occupational segregation, and up to 10% of the gender industry segregation. Allowing women to also have an extra preference for non-employment explains in a proportion of 60% why women avoid high risk occupations, that is occupations with higher displacement risk, higher earnings growth and higher human capital depreciation (or alternatively, lower human capital transferability).

In this thesis I investigate the relationship between the gender distribution across industries and occupations and the incidence and consequences of displacement. First, I provide empirical evidence to support the idea that women self-select into less risky industries and occupations, that is industries and occupations with lower displacement rates and lower earnings growth. Using data from the Displaced Worker Survey (1984-2002), the corresponding Annual Demographic Supplement to the March Current Population Survey, and the Dictionary of Occupational Titles, I find that, even though women have a lower incidence of displacement in the aggregate, they are more likely to get displaced at the one-digit industry and occupation level than men. Displacement is also more costly for women, in terms of both employment and monetary consequences, which suggests that women’s choice of safer sectors could be an insurance mechanism against the risk of displacement and its costly consequences. I then construct a dynamic occupational choice model in the spirit of Keane and Wolpin (1997), in which occupation(industry) groups differ not only in terms of the rate of human capital accumulation, but also in the risk and associated cost of displacement, as well as in the value of the non-monetary utility component. I calibrate the model for men and perform a number of counterfactual experiments for women. Quantitative results suggest that differences in displacement probabilities, together with differences in re-employment probabilities, and in human capital penalty rates at displacement explain up to 15% of the gender occupational segregation, and up to 10% of the gender industry segregation. Allowing women to also have an extra preference for non-employment explains in a proportion of 60% why women avoid high risk occupations, that is occupations with higher displacement risk, higher earnings growth and higher human capital depreciation (or alternatively, lower human capital transferability).

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

This document explores and questions notions of place, identity, and transformation caused by displacement.