Leak identification in saturated unsteady flow via a Cauchy problem

This work is an initial study of a numerical method for identifying multiple leak zones in saturated unsteady flow. Using the conventional saturated groundwater flow equation, the leak identification problem is modelled as a Cauchy problem for the heat equation and the aim is to find the regions on the boundary of the solution domain where the solution vanishes, since leak zones correspond to null pressure values. This problem is ill-posed and to reconstruct the solution in a stable way, we therefore modify and employ an iterative regularizing method proposed in [1] and [2]. In this method, mixed well-posed problems obtained by changing the boundary conditions are solved for the heat operator as well as for its adjoint, to get a sequence of approximations to the original Cauchy problem. The mixed problems are solved using a Finite element method (FEM), and the numerical results indicate that the leak zones can be identified with the proposed method

Evolution of domestic traffic and fares at the top 200 US airports between 1990 and 2008

Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 167-170).The main objective of this thesis is to analyze the evolution of domestic Origin- Destination (O-D) traffic and fares at the Top 200 airports in the United States between 1990 and 2008. The impetus behind this research is to shed light on the differences in trends between the largest and smallest, primary and secondary, hub and non-hub airports, and to measure the impact of Low Cost carriers (LCC) on traffic, fares and competition. Furthermore, case studies of five multi-airport systems located within major US metropolitan areas were performed to identify the trends shaping multi-airport systems. We find that domestic O-D passenger traffic at the Top 200 commercial airports in the United States increased by more than 52% between 1990 and 2005, but dropped by 2% from 2005 to 2008 because of the global economic downturn. Average fares at the Top 200 airports increased by 14% during the "golden 90s", decreased by 13% between 2000 and 2005, but rebounded by 16% between 2005 and 2008, as a result of soaring jet fuel prices and reduced capacity. Low Cost carriers' share of the total domestic O-D traffic in the US is still growing, although leveling off, reaching 34% in 2008. LCC entry focused initially on largest airports, then grew rapidly in second and third airport tiers. As a result, in 2008, 95 of the Top 200 airports had an LCC aggregated market share greater than 20%, up from 27 airports in 1990. We show that LCC's effective entrance or substantial growth at a particular airport had a significant impact lowering average fares and stimulating passenger volumes. However in recent years, this market stimulation effect has been leveling off, as the gap in average fares between LCC and Network Legacy carriers (NLC) has narrowed. Secondary airports played a critical role in accommodating the increase in demand for air traffic in the nation's largest metropolitan areas: They served 19.8% of the total domestic O-D passenger traffic in the 15 studied multi-airport systems in 2008, compared to 16.9% in 1990, highlighting their increasing importance. Finally, the airport concentration levels, as measured by the average weighted Herfindahl-Hirschman Index, increased by 8% during the studied period, demonstrating that the Top 200-airport sample is more concentrated in 2008 compared to 1990.by Mehdi Ben Abda.S.M.in Transportatio

Identification of 2D Cracks by Elastic Boundary Measurements

The purpose of this work is to identify 2D cracks by the mean of elastic boundary measurements. A uniqueness result is first proved in the general case, as well as the local lipschitzian stability in the case of line segment emergent cracks. In this last case, the search of the unique zero of the reciprocity gap functional related to the singular solution of the elasticity problem provides a fast algorithm to determine the unknown crack tip

Tunisian Toxoplasma gondii strains genotyping by the use of AK69 marker

<p>Abstract</p> <p>Background</p> <p>Clinical manifestation due to infection by <it>Toxoplasma gondii </it>is closely linked to the infecting strain of the parasite. Several genetic markers are available to determinate its genotype but few of them are able to discriminate between the three predominant lineages, namely types I, II and III. The number of markers decreases when atypical, recombinant/mixed genotypes need to be identified.</p> <p>Findings</p> <p>In our study, the contribution of sequence polymorphisms in the AK69 gene as typing markers for <it>T. gondii </it>was investigated for the first time in an epidemiological study. The coding region of the marker was amplified, sequenced and aligned for different <it>Toxoplasma </it>strains. The identified nucleotide polymorphism at 12 positions was able to highly discriminate between the different congenital toxoplasmosis Tunisian strains. Moreover the high detection sensitivity level of the marker enabled unambiguous identification of mixed/recombinant genotypes directly.</p> <p>Conclusion</p> <p>It can be, thus, very useful for direct typing in areas where such genotypes are frequently encountered, mainly in the African continent.</p

Effect of Date (Phoenix dactylifera L.) Pits on the Shelf Life of Beef Burgers

Anew ingredient from date palm coproducts (pits) was obtained and tested as a preservative in burgers. Di erent concentrations of date pit (0%, 1.5%, 3%, and 6%) were added to beef burgers, and its e ect on the safety and quality was evaluated during 10 days of storage. The incorporation of date pit was able to improve the shelf life and the cooking properties of the burgers. The date pit stabilized the color, lipid oxidation, and microbial growth of the burgers during the storage time due to the antioxidant activity and the phytochemical content of the date pits. For the consumer panel, the color and the o -odors were improved, and the addition of 1.5% and 3% date pit in cooked burgers obtained similar scores. Based on the obtained results, the new ingredient from date pit may have potential preservative properties for enhancing stability during shelf life and could improve the composition of bioactive compounds (fiber and phenolic content) of beef burger