18,523 research outputs found
The economic value of remote sensing of earth resources from space: An ERTS overview and the value of continuity of service. Volume 4: Forestry, wildlife and rangeland
The economic value of ERS information in the resource management area of extensive use of living resources, forestry, wildlife, and rangeland, is determined. Timber and forage resources are quantitatively evaluated. It is shown that these resources have economic value in the tens of billions of dollars, but the economic benefits of improved management of the forests and rangelands are not limited to efficiency in the production of these commercial resources. Multiple-use values including watershed, wildlife, and recreation are also involved
Morita theory and singularity categories
We propose an analogue of the bounded derived category for an augmented ring
spectrum, defined in terms of a notion of Noether normalization. In many cases
we show this category is independent of the chosen normalization. Based on
this, we define the singularity and cosingularity categories measuring the
failure of regularity and coregularity and prove they are Koszul dual in the
style of the BGG correspondence. Examples of interest include Koszul algebras
and Ginzburg DG-algebras, for finite groups (or for compact Lie
groups with orientable adjoint representation), cochains in rational homotopy
theory and various examples from chromatic homotopy theory.Comment: Final version, accepted for publication in Advances in Mathematics,
49 page
Extra-Curricular Activities: creating graduates with impact in education
Staff from the Carnegie Faculty’s Centre for Social and Educational Research across the Life-course (SERL) have completed a project for the Higher Education Academy subject group for education, ESCalate, into ‘Creating Graduates with Impact in Education’. Jacqueline Stevenson, Professor Sue Clegg and Paula Sealey undertook research with students and staff across a range of education-related courses as well as with employers from schools, local authorities and other education settings
Mass distributions in a variational model
The time-dependent Hartree-Fock approach may be derived from a variational
principle and a Slater Determinant wavefunction Ansatz. It gives a good
description of nuclear processes in which one-body collisions dominate and has
been applied with success to giant resonances and collisions around the
barrier. It is inherently unable to give a good description of two-body
observables. A variational principle, due to Balian and Veneroni has been
proposed which can be geared to good reproduction of two-body observables.
Keeping the Slater Determinant Ansatz, and restricting the two-body observables
to be the squares of one-body observables, the procedure can be implemented as
a modification of the time-dependent Hartree-Fock procedure. Applications,
using the Skyrme effective interaction, are presented for the mass
distributions of fragments following de-excitation of the giant dipole
resonance in S-32. An illustration of the method's use in collisions is given.Comment: 5 pages, proceedings of XXXII Symposium on Nuclear Physics, Cocoyoc,
Mexic
Volcanism by melt-driven Rayleigh-Taylor instabilities and possible consequences of melting for admittance ratios on Venus
A large number of volcanic features exist on Venus, ranging from tens of thousands of small domes to large shields and coronae. It is difficult to reconcile all these with an explanation involving deep mantle plumes, since a number of separate arguments lead to the conclusion that deep mantle plumes reaching the base of the lithosphere must exceed a certain size. In addition, the fraction of basal heating in Venus' mantle may be significantly lower than in Earth's mantle reducing the number of strong plumes from the core-mantle boundary. In three-dimensional convection simulations with mainly internal heating, weak, distributed upwellings are usually observed. We present an alternative mechanism for such volcanism, originally proposed for the Earth and for Venus, involving Rayleigh-Taylor instabilities driven by melt buoyancy, occurring spontaneously in partially or incipiently molten regions
Crucial Dependence of ``Precarious'' and ``Autonomous'' phi^4s Upon the Normal-ordering Mass
Using the Gaussian wave-functional approach with the normal-ordering
renormalization prescription, we show that for the (3+1)-dimensional massive
lambda phi^4 theory, ``precarious'' and ``autonomous'' phi^4s can exist if and
only if the normal-ordering mass is equal to the classical masses at the
symmetrc and asymmetric vacua, respectively.Comment: 6 pages, no figures, Revtex file, accepted for publication in Mod.
Phys. Lett.
Mind The Gap
We discuss an optimisation criterion for the exact renormalisation group
based on the inverse effective propagator, which displays a gap. We show that a
simple extremisation of the gap stabilises the flow, leading to better
convergence of approximate solutions towards the physical theory. This improves
the reliability of truncations, most relevant for any high precision
computation. These ideas are closely linked to the removal of a spurious scheme
dependence and a minimum sensitivity condition. The issue of predictive power
and a link to the Polchinski RG are discussed as well. We illustrate our
findings by computing critical exponents for the Ising universality class.Comment: 6 pages, Talk presented at 2nd Conference on Exact Renormalization
Group (ERG2000), Rome, Italy, 18-22 Sep 200
The unrestricted Skyrme-tensor time-dependent Hartree-Fock and its application to the nuclear response from spherical to triaxial nuclei
The nuclear time-dependent Hartree-Fock model formulated in the
three-dimensional space,based on the full Skyrme energy density functional and
complemented with the tensor force,is presented for the first time. Full
self-consistency is achieved by the model. The application to the isovector
giant dipole resonance is discussed in the linear limit, ranging from spherical
nuclei (16O, 120Sn) to systems displaying axial or triaxial deformation (24Mg,
28Si, 178Os, 190W, 238U).
Particular attention is paid to the spin-dependent terms from the central
sector of the functional, recently included together with the tensor. They turn
out to be capable of producing a qualitative change on the strength
distribution in this channel. The effect on the deformation properties is also
discussed. The quantitative effects on the linear response are small and,
overall, the giant dipole energy remains unaffected.
Calculations are compared to predictions from the (quasi)-particle random
phase approximation and experimental data where available, finding good
agreement
Aircraft control system
An aircraft control system is described which is particularly suited to rotary wing aircraft. Longitudinal acceleration and course rate commands are derived from a manual control stick to control translational velocity of the aircraft along a flight path. In the collective channel the manual controls provide vertical velocity commands. In the yaw channel the manual controls provide sideslip or heading rate commands at high or low airspeeds, respectively. The control system permits pilots to fly along prescribed flight paths in a precise manner with relatively low work load
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