Comparison of heuristic approaches for the multiple depot vehicle scheduling problem

Given a set of timetabled tasks, the multi-depot vehicle scheduling problemis a well-known problem that consists of determining least-cost schedulesfor vehicles assigned to several depots such that each task is accomplishedexactly once by a vehicle. In this paper, we propose to compare theperformance of five different heuristic approaches for this problem,namely, a heuristic \\mip solver, a Lagrangian heuristic, a columngeneration heuristic, a large neighborhood search heuristic using columngeneration for neighborhood evaluation, and a tabu search heuristic. Thefirst three methods are adaptations of existing methods, while the last twoare novel approaches for this problem. Computational results on randomlygenerated instances show that the column generation heuristic performs thebest when enough computational time is available and stability is required,while the large neighborhood search method is the best alternative whenlooking for a compromise between computational time and solution quality.tabu search;column generation;vehicle scheduling;heuristics;Lagrangian heuristic;large neighborhood search;multiple depot

Which Investments Improve Student Performance? The Impact of Extracurricular Activities, Paid Classes, and At-Home Internet Use on Student Performance in Secondary School

The importance of education is acknowledged by modern society. As more and more people are willing to invest in education to improve students’ performance, the question of which areas of investment contribute most strongly to better academic performance arises. Parents can choose to involve their children in extracurricular activities, or they can choose to pay for additional classes outside of regular schooling. In addition, the use of technology, or, more specifically, access to the Internet at home, is becoming more and more common, and its influence on student performance is a popular topic of study. In this paper, we use two experiments to uncover the factors that influence students’ performance in Math and Portuguese Language and to support strategies for investment in education

Rabies Surveillance Identifies Potential Risk Corridors and Enables Management Evaluation

Intensive efforts are being made to eliminate the raccoon variant of rabies virus (RABV) from the eastern United States and Canada. The United States Department of Agriculture (USDA) Wildlife Services National Rabies Management Program has implemented enhanced rabies surveillance (ERS) to improve case detection across the extent of the raccoon oral rabies vaccination (ORV) management area. We evaluated ERS and public health surveillance data from 2006 to 2017 in three northeastern USA states using a dynamic occupancy modeling approach. Our objectives were to examine potential risk corridors for RABV incursion from the U.S. into Canada, evaluate the effectiveness of ORV management strategies, and identify surveillance gaps. ORV management has resulted in a decrease in RABV cases over time within vaccination zones (from occupancy (ψ) of 0.60 standard error (SE) = 0.03 in the spring of 2006 to ψ of 0.33 SE = 0.10 in the spring 2017). RABV cases also reduced in the enzootic area (from ψ of 0.60 SE = 0.03 in the spring of 2006 to ψ of 0.45 SE = 0.05 in the spring 2017). Although RABV occurrence was related to habitat type, greater impacts were associated with ORV and trap–vaccinate–release (TVR) campaigns, in addition to seasonal and yearly trends. Reductions in RABV occupancy were more pronounced in areas treated with Ontario Rabies Vaccine Bait (ONRAB) compared to RABORAL V-RG®. Our approach tracked changes in RABV occurrence across space and time, identified risk corridors for potential incursions into Canada, and highlighted surveillance gaps, while evaluating the impacts of management actions. Using this approach, we are able to provide guidance for future RABV management

Comparison of heuristic approaches for the multiple depot vehicle scheduling problem

Given a set of timetabled tasks, the multi-depot vehicle scheduling problem is a well-known problem that consists of determining least-cost schedules for vehicles assigned to several depots such that each task is accomplished exactly once by a vehicle. In this paper, we propose to compare the performance of five different heuristic approaches for this problem, namely, a heuristic \\mip solver, a Lagrangian heuristic, a column generation heuristic, a large neighborhood search heuristic using column generation for neighborhood evaluation, and a tabu search heuristic. The first three methods are adaptations of existing methods, while the last two are novel approaches for this problem. Computational results on randomly generated instances show that the column generation heuristic performs the best when enough computational time is available and stability is required, while the large neighborhood search method is the best alternative when looking for a compromise between computational time and solution quality

A Comparison of Solar Wind and Estimated Solar System Xenon Abundances: A Test for Solid/ Gas Fractionation in the Solar Nebula

Significant fractionation of dust/gas from the original interstellar cloud during the formation of the solar system is a distinct possibility. Identification of such an effect would provide important clues to nebular processes. Fractionation of volatiles is not constrained by CI abundances and only for the most abundant ones by photospheric observations. The solar Xe elemental abundance is determined here via solar wind measurements from lunar ilmenites and normalized to Si by spacecraft data. The results are compared with estimated abundances assuming no fractionation, which are relatively well constrained for Xe by s-process calculations, odd-mass abundance interpolations, and odd-even abundance systematics. When corrected for solar wind/photospheric fractionation, the ^(130)Xe abundance given by surface layer oxidation of ilmenite from soil 71501, exposed within the last - 200 m.y., is 0.24 ± 0.09 normalized to Si = 10^6. This is indistinguishable from the estimates made assuming no solid/gas fractionation. A similar result was obtained for Kr by Wiens et al (1991). Results from breccia 79035 ilmenite, exposed at least ~1 Gy ago, indicate that the solar wind Xe flux may have been significantly higher relative to other noble gases, perhaps due to more efficient Xe ionization. If this is true, fluxes of C and S, which have similar first ionization potentials to Xe, should also be higher in the ancient solar wind from the same time period, though such variations have not been observed

Antibody persistence and booster responses to split-virion H5N1 avian influenza vaccine in young and elderly adults

Avian influenza continues to circulate and remains a global health threat not least because of the associated high mortality. In this study antibody persistence, booster vaccine response and cross-clade immune response between two influenza A(H5N1) vaccines were compared. Participants aged over 18-years who had previously been immunized with a clade 1, A/Vietnam vaccine were re-immunized at 6-months with 7.5 mu g of the homologous strain or at 22-months with a clade 2, alum-adjuvanted, A/Indonesia vaccine. Blood sampled at 6, 15 and 22-months after the primary course was used to assess antibody persistence. Antibody concentrations 6-months after primary immunisation with either A/Vietnam vaccine 30 mu g alum-adjuvanted vaccine or 7.5 mu g dose vaccine were lower than 21days after the primary course and waned further with time. Re-immunization with the clade 2, 30 mu g alum-adjuvanted vaccine confirmed cross-clade reactogenicity. Antibody crossreactivity between A(H5N1) clades suggests that in principle a prime-boost vaccination strategy may provide both early protection at the start of a pandemic and improved antibody responses to specific vaccination once available