179,474 research outputs found
The Vehicle Routing Problem with Divisible Deliveries and Pickups
No full textThe vehicle routing problem with divisible deliveries and pickups is a new and interesting model within
reverse logistics. Each customer may have a pickup and delivery demand that have to be served with
capacitated vehicles. The pickup and the delivery quantities may be served, if beneficial, in two separate visits.
The model is placed in the context of other delivery and pickup problems and formulated as a mixed-integer
linear programming problem. In this paper, we study the savings that can be achieved by allowing the pickup
and delivery quantities to be served separately with respect to the case where the quantities have to be served
simultaneously. Both exact and heuristic results are analysed in depth for a better understanding of the problem
structure and an average estimation of the savings due to the possibility of serving pickup and delivery
quantities separately
A Metaheuristic for the Pickup and Delivery Problem with Split-Loads and its Extension
No full textIn this dissertation, we study improvements in the Pickup and Delivery Problem that can be achieved by allowing multiple vehicle trips to serve a common load. We explore how costs can be reduced through the elimination of the constraint that a load must be served by only one vehicle trip. Specifically, we investigate the problem of routing vehicles to serve loads that have distinct origins and destinations, with no constraint on the amount of a load that a vehicle may serve at a time. We develop a metaheuristic to solve large scale practical size problems in this form and apply the metaheuristic to randomly generated data sets. The metaheuristic is based on a predetermined fixed number of restarts of annealing-like procedure with tabu-lists to avoid cycling in the search process and the annealing-like procedure is to guide the local search in three neighborhoods defined to solve the problem. We test the algorithm on several sets of problem instances generated with different transportation requests and over different load size ranges. The experimental results on these problem sets have shown that benefits are common if split loads are adopted in designing practical sized transportation network for different load size configurations, and the most benefit is achieved when all the loads are just a little above half of the vehicle capacity and have small variations, and this most benefit is around 33% for all the three 75-, 100-, and 125-request problem sets, which overtakes the one reported in previous literature. In a more general setting when some load sizes are greater than the vehicle capacity and have to be split, there are also certain cost reduction if split loads are applied. We also generate numeral tests on different load size ranges and split the loads that are greater than the vehicle capacity using different ”splitting” strategy, in term of how much amount to split from the original load to form a new load, and find that there seem to be no optimal ”splitting” strategy, which can assure the best quality of solutions using the metaheuristic developed in the dissertation
Transport of Solar Wind Fluctuations: A Two-Component Model
No full textWe present a new model for the transport of solar wind fluctuations which treats them as two interacting incompressible components: quasi-two-dimensional turbulence and a wave-like piece. Quantities solved for include the energy, cross helicity, and characteristic transverse length scale of each component, plus the proton temperature. The development of the model is outlined and numerical solutions are compared with spacecraft observations. Compared to previous single-component models, this new model incorporates a more physically realistic treatment of fluctuations induced by pickup ions and yields improved agreement with observed values of the correlation length, while maintaining good observational accord with the energy, cross helicity, and temperature
Preliminary interpretation of Titan plasma interaction as observed by the Cassini Plasma Spectrometer: Comparisons with Voyager 1
No full textThe Cassini Plasma Spectrometer (CAPS) instrument observed the plasma environment at Titan during the Cassini orbiter's TA encounter on October 26, 2004. Titan was in Saturn's magnetosphere during the Voyager 1 flyby and also during the TA encounter. CAPS measurements from this encounter are compared with measurements made by the Voyager 1 Plasma Science Instrument (PLS). The comparisons focus on the composition and nature of ambient and pickup ions. They lead to: A) the major ion components of Saturn's magnetosphere in the vicinity of Titan are H+, H-2(+) and O+/CH4+ ions; B) finite gyroradius effects are apparent in ambient O+ ions as the result of their absorption by Titan's extended atmosphere; C) the principal pickup ions are composed of H+, H-2(+), N+/CH2+, CH4+, and N-2(+); D) the pickup ions are in narrow energy ranges; and E) there is clear evidence of the slowing down of background ions due to pickup ion mass loading
Finite Element Assisted Study of Magnetic Configurations of Flat Pickups for Inductively Coupled Power Transfer Systems
No full textThis publication describes the findings from a finite-element assisted study of an Inductively Coupled Power Transfer (ICPT) system with flat pickups. Results from the analysis of pickup elements are presented in a graphical form allowing comparison with a conventional (‘original’) pickup. The pickups were examined in unipolar and bipolar ICPT systems. Unlike the existing pickup, the proposed configurations utilize two components of the magnetic flux density, and are characterized by high-power transfer ability as well as much better response to the misalignment problem. Some recommendations and possible means for further improvements for higher power efficiency are also put forward
Heating of the low-latitude solar wind by dissipation of turbulent magnetic fluctuations
No full textWe test a theory presented previously to account for the turbulent transport of magnetic fluctuation energy in the solar wind and the related dissipation and heating of the ambient ion population. This theory accounts for the injection of magnetic energy through the damping of large-scale flow gradients, such as wind shear and compression, and incorporates the injection of magnetic energy due to wave excitation by interstellar pickup ions. The theory assumes quasi-two-dimensional spectral transport of the fluctuation energy and subsequent dissipation that heats the thermal protons. We compare the predictions of this theory with Voyager 2 and Pioneer 11 observations of magnetic fluctuation energy, magnetic correlation lengths, and ambient proton temperatures. Near-Earth Omnitape observations are used to adjust for solar variability, and the possibility that high-latitude effects could mask possible radial dependences is considered. We find abundant evidence for in situ heating of the protons, which we quantify, and show that the observed magnetic energy is consistent with the ion temperatures
Implementing PICKUP in LEA colleges under the Education Reform Act 1988 A guidance manual
No full textPICKUP - Professional, Industrial and Commercial UpdatingSIGLEAvailable from British Library Document Supply Centre- DSC:4059.5157(FEU-RP--300) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
An article on the emblematic Maine pickup truck and what it signifies about thos
No full textAn article on the emblematic Maine pickup truck and what it signifies about those who drive one. The image is one of working with your hands for a living or identifying with those who do. Pickup trucks are the most popular vehicle in Maine, and the Ford F-150, GMC Sierra, and Ford Ranger are the most numerous models. Maine law makes special provisions for both island vehicles and farm trucks. The author reminisces about his past pickup trucks
Turbulence transport throughout the heliosphere
No full textWe employ a turbulence transport model to compute distributions of turbulence throughout the heliosphere. The model determines the radial dependence of three (coupled) quantities that characterize interplanetary turbulence, the energy per unit mass, the cross helicity or Alfvénicity, and a similarity length scale. A fourth integrated quantity, the plasma temperature, is modified by heat deposition due to turbulent dissipation. The model includes advection, expansion, and reflection effects as well as the tendency toward dynamic alignment, and a von Kármán type dissipation function that represents decay of turbulence due to cascade to small scales. Two types of forcing are also featured, one a simple model of stream shear, and the other a driving in the outer heliosphere associated with wave energy injection due to pickup protons of interstellar origin. Parameters for the model have been tuned using observation data from Voyager and Ulysses. We analyze the constraining observations to provide boundary conditions and parameters that vary with heliocentric latitude, with some extrapolations. The fully assembled model permits the computation of the distribution of turbulence throughout the entire heliosphere, and we present solutions for several appropriate parameter sets
Pickup truck registrations
No full textTitle from Web page (viewed Aug. 30, 2001).; "August 15, 2000."; Discusses why pickup trucks are required to be registered as combination vehicles even though some are used by their owners only for private passenger transportation.; Harvested from the web on 3/11/0
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