18,609 research outputs found
Algorithms to solve the Sutherland model
We give a self-contained presentation and comparison of two different
algorithms to explicitly solve quantum many body models of indistinguishable
particles moving on a circle and interacting with two-body potentials of
-type. The first algorithm is due to Sutherland and well-known; the
second one is a limiting case of a novel algorithm to solve the elliptic
generalization of the Sutherland model. These two algorithms are different in
several details. We show that they are equivalent, i.e., they yield the same
solution and are equally simple.Comment: 15 pages, LaTe
Remote sensing applied to the evaluation of crop freeze protection devices
Thermal images from an aircraft-mounted scanner are used to evaluate the effectiveness of crop freeze protection devices. Fuel oil heaters, wind machines and irrigation systems are evaluated from flights at an altitude of 450 m over an experimental citrus grove of 1.5 hectares
Comparative jet wake structure and swimming performance of salps
Salps are barrel-shaped marine invertebrates that swim by jet propulsion. Morphological variations among species and life-cycle
stages are accompanied by differences in swimming mode. The goal of this investigation was to compare propulsive jet wakes
and swimming performance variables among morphologically distinct salp species (Pegea confoederata, Weelia (Salpa)
cylindrica, Cyclosalpa sp.) and relate swimming patterns to ecological function. Using a combination of in situ dye visualization
and particle image velocimetry (PIV) measurements, we describe properties of the jet wake and swimming performance variables
including thrust, drag and propulsive efficiency. Locomotion by all species investigated was achieved via vortex ring propulsion.
The slow-swimming P. confoederata produced the highest weight-specific thrust (T =53 N kg^(–1)) and swam with the highest wholecycle
propulsive efficiency (η_wc= 55%). The fast-swimming W. cylindrica had the most streamlined body shape but produced an
intermediate weight-specific thrust (T=30 N kg^(–1)) and swam with an intermediate whole-cycle propulsive efficiency (η_wc =52%).
Weak swimming performance variables in the slow-swimming C. affinis, including the lowest weight-specific thrust (T=25 N kg^(–1))
and lowest whole-cycle propulsive efficiency (η_wc=47%), may be compensated by low energetic requirements. Swimming
performance variables are considered in the context of ecological roles and evolutionary relationships
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