482 research outputs found
Preliminary space mission design under uncertainty
This paper proposes a way to model uncertainties and to introduce them explicitly in the design process of a preliminary space mission. Traditionally, a system margin approach is used in order to take them into account. In this paper, Evidence Theory is proposed to crystallise the inherent uncertainties. The design process is then formulated as an Optimisation Under Uncertainties (OUU). Three techniques are proposed to solve the OUU problem: (a) an evolutionary multi-objective approach, (b) a step technique consisting of maximising the belief for different levels of performance, and (c) a clustering method that
firstly identifes feasible regions. The three methods are applied to the BepiColombo mission and their
effectiveness at solving the OUU problem are compared
MANAGEMENT OF COYOTES FOR PRONGHORN?
Coyotes (Canis latrans) and pronghorn (Antilocapra americana) have co-existed for thousands of years, but in today\u27s production-oriented society the Pronghorn may need some help periodically. Although pronghorn numbers have rebounded dramatically since the early 20th century, continued management of this species is necessary and may include management of its primarily predator, the coyote. Pronghorn defense mechanisms offer protection from predators, but the coyote\u27s hunting strategies overcome these mechanisms The Trans-Pecos region of Texas holds the greatest numbers of pronghorn In the state. Ranchers in the Trans-Pecos can use predators, such as rainfall; strategies, such as proper livestock stocking rates and pasture deferment; and tools, such as predator control, to help manage pronghorn populations in the presence of coyotes
MANAGEMENT OF COYOTES FOR PRONGHORN?
Coyotes (Canis latrans) and pronghorn (Antilocapra americana) have co-existed for thousands of years, but in today\u27s production-oriented society the Pronghorn may need some help periodically. Although pronghorn numbers have rebounded dramatically since the early 20th century, continued management of this species is necessary and may include management of its primarily predator, the coyote. Pronghorn defense mechanisms offer protection from predators, but the coyote\u27s hunting strategies overcome these mechanisms The Trans-Pecos region of Texas holds the greatest numbers of pronghorn In the state. Ranchers in the Trans-Pecos can use predators, such as rainfall; strategies, such as proper livestock stocking rates and pasture deferment; and tools, such as predator control, to help manage pronghorn populations in the presence of coyotes
Inquiry Into Use and Importance of R&D Tax Incentives in British Columbia
This is a report about the experiences of a sampling of BC companies with Federal R&D tax incentives. It is based on responses to a survey conducted during a workshop sponsored by the Science Council of British Columbia through its SPARK program on the topic of Venture Funding Alternatives: Financial Options for Funding Technology-Based Companies
FOOD HABITS OF MOUNTAIN LIONS IN THE TRANS-PECOS REGION OF TEXAS
Information regarding mountain lion (Felis concolor) food habits is relatively scarce overall, and this is particularly true in the Trans-Pecos region of Texas. Most information currently available is from Big Bend National Park where livestock are excluded and game animals are not actively managed. This study involved the analysis of 32 mountain lion stomachs collected throughout the Trans-Pecos over a 14 month period. Deer (Odocoileus spp.) and javelina (Tayassu tajacu) were the predominate prey species, each occurring in 39% of the stomachs analyzed. Domestic livestock was found in 9% of the total stomachs and non-game wildlife in 13%. Samples taken from areas with and without livestock differed significantly (P\u3c0.05). Samples from areas with livestock contained deer (50%), javelina (19%), small game (19%), and livestock (12%). Samples from areas without livestock contained javelina (86%) and deer (14%). No differences (P\u3e0.05) in food habits were found between sexes or among seasons of the year
Mission design for LISA Pathfinder
Here we describe the mission design for SMART-2/LISA Pathfinder. The best
trade-off between the requirements of a low-disturbance environment and
communications distance is found to be a free-insertion Lissajous orbit around
the first co-linear Lagrange point of the Sun-Earth system L1, 1.5x 10^6 km
from Earth. In order to transfer SMART-2/LISA Pathfinder from a low Earth
orbit, where it will be placed by a small launcher, the spacecraft carries out
a number of apogee-raise manoeuvres, which ultimatively place it to a parabolic
escape trajectory towards L1. The challenges of the design of a small mission
are met, fulfilling the very demanding technology demonstration requirements
without creating excessive requirements on the launch system or the ground
segment.Comment: 7 pages, 6 figures, 5th International LISA Symposium, see
http://www.landisoft.de/Markus-Landgra
FOOD HABITS OF MOUNTAIN LIONS IN THE TRANS-PECOS REGION OF TEXAS
Information regarding mountain lion (Felis concolor) food habits is relatively scarce overall, and this is particularly true in the Trans-Pecos region of Texas. Most information currently available is from Big Bend National Park where livestock are excluded and game animals are not actively managed. This study involved the analysis of 32 mountain lion stomachs collected throughout the Trans-Pecos over a 14 month period. Deer (Odocoileus spp.) and javelina (Tayassu tajacu) were the predominate prey species, each occurring in 39% of the stomachs analyzed. Domestic livestock was found in 9% of the total stomachs and non-game wildlife in 13%. Samples taken from areas with and without livestock differed significantly (P\u3c0.05). Samples from areas with livestock contained deer (50%), javelina (19%), small game (19%), and livestock (12%). Samples from areas without livestock contained javelina (86%) and deer (14%). No differences (P\u3e0.05) in food habits were found between sexes or among seasons of the year
Electrical expression of spin accumulation in ferromagnet/semiconductor structures
We treat the spin injection and extraction via a ferromagnetic
metal/semiconductor Schottky barrier as a quantum scattering problem. This
enables the theory to explain a number of phenomena involving spin-dependent
current through the Schottky barrier, especially the counter-intuitive spin
polarization direction in the semiconductor due to current extraction seen in
recent experiments. A possible explanation of this phenomenon involves taking
into account the spin-dependent inelastic scattering via the bound states in
the interface region. The quantum-mechanical treatment of spin transport
through the interface is coupled with the semiclassical description of
transport in the adjoining media, in which we take into account the in-plane
spin diffusion along the interface in the planar geometry used in experiments.
The theory forms the basis of the calculation of spin-dependent current flow in
multi-terminal systems, consisting of a semiconductor channel with many
ferromagnetic contacts attached, in which the spin accumulation created by spin
injection/extraction can be efficiently sensed by electrical means. A
three-terminal system can be used as a magnetic memory cell with the bit of
information encoded in the magnetization of one of the contacts. Using five
terminals we construct a reprogrammable logic gate, in which the logic inputs
and the functionality are encoded in magnetizations of the four terminals,
while the current out of the fifth one gives a result of the operation.Comment: A review to appear in Mod. Phys. Lett.
Low-thrust approach and gravitational capture at mercury
ABSTRACT BepiColombo, an ESA science mission, will reach Mercury in early 2017. The complex nearly 5-year long transfer consists of 6 flybys and many extended thrust arcs where the spacecraft is accelerated by solar electric propulsion. The thrust level is too low for a capture from a hyperbolic approach. To avoid a single point failure of a classical chemical orbit insertion burn, a trajectory is proposed where the gravity of the Sun is exploited to weakly capture the spacecraft in a Mercury orbit. The arrival conditions are optimised taking into account the interplanetary delta-V and low-cost recovery options in case of a failed orbit insertion. Finally, the navigation aspects for this unusual approach trajectory are studied
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