10,064 research outputs found
ECONOMIC THRESHOLDS: AN APPLICATION TO FLORICULTURE
This paper introduces conjunctive optimal pest management and production decision rules applied to the floriculture industry. A grower is faced with optimally controlling multiple pests and applying cultural controls to maximize the expected net present value of benefits within a discrete time framework, subject to biological and marketing constraints.Crop Production/Industries,
OPTIMAL PEST CONTROL IN FLORICULTURE PRODUCTION OF ORNAMENTAL CROPS
We develop a conceptual bioeconomic model of floriculture production, wherein optimal decision rules depend on an intertemporal economic objective to maximize profits subject to economic and biological processes. The necessary conditions highlight intertemporal tradeoffs between aesthetic benefits and expected future net benefits of insect stocks, which have important policy implications.Research Methods/ Statistical Methods,
Population inversion in optically pumped asymmetric quantum well terahertz lasers
Intersubband carrier lifetimes and population ratios are calculated for three- and four-level optically pumped terahertz laser structures. Laser operation is based on intersubband transitions between the conduction band states of asymmetric GaAs-Ga(1 – x)Al(x)As quantum wells. It is shown that the carrier lifetimes in three-level systems fulfill the necessary conditions for stimulated emission only at temperatures below 200 K. The addition of a fourth level, however, enables fast depopulation of the lower laser level by resonant longitudinal optical phonon emission and thus offers potential for room temperature laser operation. © 1997 American Institute of Physics
Spatially resolved ultrafast precessional magnetization reversal
Spatially resolved measurements of quasi-ballistic precessional magnetic
switching in a microstructure are presented. Crossing current wires allow
detailed study of the precessional switching induced by coincident longitudinal
and transverse magnetic field pulses. Though the response is initially
spatially uniform, dephasing occurs leading to nonuniformity and transient
demagnetization. This nonuniformity comes in spite of a novel method for
suppression of end domains in remanence. The results have implications for the
reliability of ballistic precessional switching in magnetic devices.Comment: 17 pages (including 4 figures), submitted to Phys. Rev. Let
Functionally dissociating ventro-dorsal components within the rostro-caudal hierarchical organization of the human prefrontal cortex
This work was supported by a grant of the BrainLinks-BrainTools Cluster of Excellence funded by the German Research Foundation (DFG, grant number EXC 1086).Peer reviewedPostprin
Stability and Hermitian-Einstein metrics for vector bundles on framed manifolds
We adapt the notions of stability of holomorphic vector bundles in the sense
of Mumford-Takemoto and Hermitian-Einstein metrics in holomorphic vector
bundles for canonically polarized framed manifolds, i.e. compact complex
manifolds X together with a smooth divisor D such that K_X \otimes [D] is
ample. It turns out that the degree of a torsion-free coherent sheaf on X with
respect to the polarization K_X \otimes [D] coincides with the degree with
respect to the complete K\"ahler-Einstein metric g_{X \setminus D} on X
\setminus D. For stable holomorphic vector bundles, we prove the existence of a
Hermitian-Einstein metric with respect to g_{X \setminus D} and also the
uniqueness in an adapted sense.Comment: 21 pages, International Journal of Mathematics (to appear
Derivative moments in turbulent shear flows
We propose a generalized perspective on the behavior of high-order derivative
moments in turbulent shear flows by taking account of the roles of small-scale
intermittency and mean shear, in addition to the Reynolds number. Two
asymptotic regimes are discussed with respect to shear effects. By these means,
some existing disagreements on the Reynolds number dependence of derivative
moments can be explained. That odd-order moments of transverse velocity
derivatives tend not vanish as expected from elementary scaling considerations
does not necessarily imply that small-scale anisotropy persists at all Reynolds
numbers.Comment: 11 pages, 7 Postscript figure
- …