On the invertibility of mappings arising in 2D grid generation problems

In adapting a grid for a Computational Fluid Dynamics problem one uses a mapping from the unit square onto itself that is the solution of an elliptic partial differential equation with rapidly varying coefficients. For a regular discretization this mapping has to be invertible. We will show that such result holds for general elliptic operators (in two dimensions). The Carleman-Hartman-Wintner Theorem will be fundamental in our proof. We will also explain why such a general result cannot be expected to hold for the (three-dimensional) cube

On a Dirichlet problem related to the invertibility of mappings arising in 2D grid generation problems

this paper depends strongly on a theorem of Carleman-HartmanWintner. This theorem is only true in two dimensional domains. In fact a straightforward generalization to more than two dimensional domains cannot be true. A counterexample to the proof of [15]forthe three dimensional case can be found by using a special harmonic function due to Kellogg [12]. This function is shown in [2]. A direct counterexample can be found in [13]. 2 Main result on smooth domain

Quasiparticle Berry curvature and Chern numbers in spin-orbit coupled bosonic Mott insulators

We study the ground-state topology and quasiparticle properties in bosonic Mott insulators with two- dimensional spin-orbit couplings in cold atomic optical lattices. We show that the many-body Chern and spin-Chern number can be expressed as an integral of the quasihole Berry curvatures over the Brillouin zone. Using a strong-coupling perturbation theory, for an experimentally feasible spin-orbit coupling, we compute the Berry curvature and the spin Chern number and find that these quantities can be generated purely by interactions. We also compute the quasiparticle dispersions, spectral weights, and the quasimomentum space distribution of particle and spin density, which can be accessed in cold-atom experiments and used to deduce the Berry curvature and Chern numbers

Comments on a Note on Optimal Effort in the Maldivian Tuna Industry

Reasons are given why spatial differences in travel costs for tuna boats fishing in the same region may be of little significance in the Maldives. Claims are made that the fishing ground concept is of limited value in the case of a migratory species such as tuna and that there are practical difficulties in implementing the Campbell and Lindner tax/subsidy scheme, which in practice could give rise to a deadweight social loss. Furthermore, in the absence of empirical quantification, Campbell and Lindner give no real guide to optimal fishing effort policy in the Maldives.Environmental Economics and Policy, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,

A Low Cost and Labor Efficient Method for Rearing Black Cutworms (Lepidoptera: Noctuidae)

The black cutworm, Agrotis ipsilon (Hufnagel), has been and continues to be the subject of many biological and control studies in the north-central states. Interest in this insect can often be traced to its status as a major, but sporadic pest of field com in the region

ELECTRONIC MARKET USE BY OKLAHOMA LAMB PRODUCERS

Socioeconomic and production system characteristics of a sample of Oklahoma sheep producers were employed to examine the decision to use or not use an electronic market for slaughter lambs. Producer attributes that influence electronic market use were identified with qualitative choice models. The results help identify characteristics of electronic markets which influence their success. The findings also have implications about educational opportunities for cooperative extension.Livestock Production/Industries, Marketing,

Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer

International audienceWe report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer) was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976), but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection". We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL) to collapse our spectra. For the horizontal velocity spectra this scale is (zi ?o)2/3, where zi is inversion height and ?o is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z ?o)2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow. We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2). That is, the lengths of the thermal structures depend on both the lengths of the transporting eddies, ~9z, and the progressive aggregation of the plumes with height into the larger-scale structures of the CBL. This aggregation depends, in top-down fashion, on zi. The whole system is therefore highly organized, with even the smallest structures conforming to the overall requirements of the whole flow

Research on display scanning, sampling, and reconstruction using separate main and secondary tracking tasks

Dynamic model for effects of random scanning and sampling on human operator tracking performanc

A theory of human error

Human errors tend to be treated in terms of clinical and anecdotal descriptions, from which remedial measures are difficult to derive. Correction of the sources of human error requires an attempt to reconstruct underlying and contributing causes of error from the circumstantial causes cited in official investigative reports. A comprehensive analytical theory of the cause-effect relationships governing propagation of human error is indispensable to a reconstruction of the underlying and contributing causes. A validated analytical theory of the input-output behavior of human operators involving manual control, communication, supervisory, and monitoring tasks which are relevant to aviation, maritime, automotive, and process control operations is highlighted. This theory of behavior, both appropriate and inappropriate, provides an insightful basis for investigating, classifying, and quantifying the needed cause-effect relationships governing propagation of human error

Search for Variable Stars in the Globular Cluster M3

We describe here results of a photometric time-sequence survey of the globular cluster M3 (NGC 5272), in a search for contact and detached eclipsing binary stars. We have discovered only one likely eclipsing binary and one SX Phe type star in spite of monitoring 4077 stars with $V<20.0$ and observing 25 blue stragglers. The newly identified SX Phe star, V237, shows a light curve with a variable amplitude. Variable V238 shows variability either with a period of 0.49 d or with a period of 0.25 d. On the cluster colour-magnitude diagram, the variable occupies a position a few hundredths of magnitude to the blue of the base of the red giant branch. V238 is a likely descendent of a binary blue straggler. As a side result we obtained high quality data for 42 of the previously known RR Lyrae variables, including 33 of Bailey type ab, 7 type c and 2 double-mode pulsators. We used equations that relate the physical properties of RRc stars to their pulsation periods and Fourier parameters to derive masses, luminosities, temperatures and helium parameters for five of the RRc stars. One of the RRd stars (V79) has switched modes. In previous studies, it was classified as RRab, but our observations show that it is an RRd star with the first overtone mode dominating. This indicates blueward evolution on the horizontal branch.Comment: 21 pages including 14 figures, Latex, requires mn.sty, psfig.sty. Submitted, MNRA