Energy dissipation and ion heating at the heliospheric termination shock

The Los Alamos hybrid simulation code is used to examine heating and the partition of dissipation energy at the perpendicular heliospheric termination shock in the presence of pickup ions. The simulations are one-dimensional in space but three-dimensional in field and velocity components, and are carried out for a range of values of pickup ion relative density. Results from the simulations show that because the solar wind ions are relatively cold upstream, the temperature of these ions is raised by a relatively larger factor than the temperature of the pickup ions. An analytic model for energy partition is developed on the basis of the Rankine-Hugoniot relations and a polytropic energy equation. The polytropic index gamma used in the Rankine-Hugoniot relations is varied to improve agreement between the model and the simulations concerning the fraction of downstream heating in the pickup ions as well as the compression ratio at the shock. When the pickup ion density is less than 20%, the polytropic index is about 5/3, whereas for pickup ion densities greater than 20%, the polytropic index tends toward 2.2, suggesting a fundamental change in the character of the shock, as seen in the simulations, when the pickup ion density is large. The model and the simulations both indicate for the upstream parameters chosen for Voyager 2 conditions that the pickup ion density is about 25% and the pickup ions gain the larger share ( approximately 90%) of the downstream thermal pressure, consistent with Voyager 2 observations near the shock

Pick-up ion dynamics at the structured quasi-perpendicular shock

We study the pickup ion dynamics and mechanism of multiple reflection and acceleration at the structured quasi-perpendicular supercritical shock. The motion of the pickup ions in the shock is studied analytically and numerically using the test particle analysis in the model shock front. The analysis shows that slow pickup ions may be accelerated at the shock ramp to high energies. The maximum ion energy is determined by the fine structure of the electro-magnetic field at the shock ramp and decreases when the angle between magnetic field and shock normal decreases. Evolution of pickup ion distribution across the nearly-perpendicular shock and pickup ion spectrum is also studied by direct numerical analysis.Comment: LaTeX (elsart.cls), packages: times,amsmath,amssymb; 15 pages + 13 figures (GIF). To appear in Planetary and Space Science

Isotopic and velocity distributions of Bi produced in charge-pickup reactions of 208Pb at 1 A GeV

Isotopically resolved cross sections and velocity distributions have been measured in charge-pickup reactions of 1 A GeV 208Pb with proton, deuterium and titanium target. The total and partial charge-pickup cross sections in the reactions 208Pb + 1H and 208Pb + 2H are measured to be the same in the limits of the error bars. A weak increase in the total charge-pickup cross section is seen in the reaction of 208Pb with the titanium target. The measured velocity distributions show different contributions - quasi-elastic scattering and Delta-resonance excitation - to the charge-pickup production. Data on total and partial charge-pickup cross sections from these three reactions are compared with other existing data and also with model calculations based on the coupling of different intra-nuclear cascade codes and an evaporation code.Comment: 20 pages, 12 figures, background information on http://www-w2k.gsi.de/kschmidt

The Vehicle Routing Problem with Divisible Deliveries and Pickups

The 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

Development of a Straw Tube Chamber with Pickup-Pad Readout

We have developed a straw tube chamber with pickup-pad readout. The mechanism for signal pickup, the size of the pickup signal, and the distribution of signals among neighboring pads are discussed. We have tested a prototype chamber in a beamtest at Brookhaven National laboratory and have measured chamber efficiencies in excess of 99%.Comment: 7 pages, 8 figures, 2 tables. Talk presented at DPF '99 Meeting, UCL

Apparatus for sequentially transporting containers

Apparatus for transferring and manipulating a plurality of containers in a sequence is disclosed including a mechanical manipulator arm having a gripping device which automatically picks up a container at a fixed pickup position P and transfers it to a processing station. At a processing station X, the container is loaded with silicon wafers and thereafter returned by the arm to the fixed position P at the pickup and return station Y. A plurality of the containers may be processed in sequence from the fixed pickup position by providing a movable carriage upon which container pedestal platforms are supported, at least one of which is an elevator platform. The platforms include abutments for properly positioning the containers for accurate pickup by the manipulator arm

A mathematical model for the sequestering of chemical contaminants by magnetic particles

A mathematical model is developed and implemented to characterize the pickup of various liquid chemical contaminants by polyethylene-coated magnetic particles. The model and its associated experimental and analytical protocols were applied to a wide range of liquid chemicals in order to gain insights into the physical basis for the pickup phenomenon. The characteristics of the pickup isotherms range between “ideal” and “nonideal” behaviors that are reflected in the mathematical model by a single parameter, �0, where �0=1 corresponds to ideal behavior and �0�1 corresponds to a departure from idealized behavior that is directly quantified by the magnitude of �0. The parameter �0 is also related to the efficiency of pickup, and since most isotherms observed in the study deviate from ideality, the high efficiency of pickup observed in these systems has been attributed in part to this deviation. The proposed model and its associated experimental and analytical protocols demonstrate great potential for the systematic evaluation of the uptake of chemical contaminants using magnetic particle technology

An ant colony algorithm for the mixed vehicle routing problem with backhauls

The Vehicle Routing Problem with Pickup and Delivery (VRPPD) is a variant of the Vehicle Routing Problem where the vehicles are not only required to deliver goods but also to pick up some goods from the customers. The Mixed Vehicle Routing Problem with Backhauls (MVRPB) is a special case of VRPPD where each customer has either a delivery or a pickup demand to be satisfied and the customers can be visited in any order along the route. Given a fleet of vehicles and a set of customers with known pickup or delivery demands MVRPB determines a set of vehicle routes originating and ending at a single depot and visiting all customers exactly once. The objective is to minimize the total distance traversed with the least number of vehicles. For this problem, we propose an Ant Colony Optimization algorithm with a new visibility function which attempts to capture the “delivery” and “pickup” nature of the problem. Our numerical tests to compare the performance of the proposed approach with those of the well-known benchmark problems reveal that the proposed approach provides encouraging results