Costs and Returns Analysis for South Carolina Shrimp Trawlers

This document provides an explanation on how shrimp trawler owners/operators can analyze the effects of changing costs and ex-vessel prices on the profitability of operating a shrimp trawler. An Excel spreadsheet is provided with sample boat costs and revenues. The spreadsheet allows the trawler owner/operator to enter costs and revenues data for their own vessel. This can be used to estimate average costs of landing a pound of shrimp by the vessel owner/operator and the profit (loss) per pound of landed shrimp. As input costs vary for key items like fuel, ice, BRDS, etc, the trawler owner can estimate the impact of these input costs on the total average cost of landing a pound of shrimp. Similarly, as the ex-vessel (landed) price for a pound of shrimp changes, the vessel owner/operator can estimate the impact of these price changes on the profitability of operating the trawler.Resource /Energy Economics and Policy,

Orbital Motion of Spiral Waves in Excitable Media

Spiral waves in active media react to small perturbations as particle-like objects. Here we apply the asymptotic theory to the interaction of spiral waves with a localized inhomogeneity, which leads to a novel prediction: drift of the spiral rotation centre along circular orbits around the inhomogeneity. The stationary orbits have alternating stability and fixed radii, determined by the properties of the bulk medium and the type of inhomogeneity, while the drift speed along an orbit depends on the strength of the inhomogeneity. Direct simulations confirm the validity and robustness of the theoretical predictions and show that these unexpected effects should be observable in experiment

The rise of fully turbulent flow

Over a century of research into the origin of turbulence in wallbounded shear flows has resulted in a puzzling picture in which turbulence appears in a variety of different states competing with laminar background flow. At slightly higher speeds the situation changes distinctly and the entire flow is turbulent. Neither the origin of the different states encountered during transition, nor their front dynamics, let alone the transformation to full turbulence could be explained to date. Combining experiments, theory and computer simulations here we uncover the bifurcation scenario organising the route to fully turbulent pipe flow and explain the front dynamics of the different states encountered in the process. Key to resolving this problem is the interpretation of the flow as a bistable system with nonlinear propagation (advection) of turbulent fronts. These findings bridge the gap between our understanding of the onset of turbulence and fully turbulent flows.Comment: 31 pages, 9 figure

The relationship between core symptoms of ADHD and the Cognitive Reflection Test in a non-clinical sample.

INTRODUCTION: Attention Deficit and Hyperactivity Disorder (ADHD) symptoms are frequently linked to executive function deficits. There is reason to believe that these deficits may give rise to problems with complex reasoning and problem solving. METHODS: Eighty-six men (N = 45) and women (N = 41) completed a self-report measure to assess ADHD symptoms, along with a complex reasoning task; the Cognitive Reflection Test (CRT). IQ was also tested due to its covariance with reasoning ability. RESULTS: Analysis suggested that all three symptoms of ADHD (inattention, hyperactivity, and impulsivity) are negatively related to performance on the CRT, however, only inattention significantly contributed to a model that predicted CRT performance. CONCLUSIONS: Of the three core symptoms of ADHD, inattention is the most important for reasoning ability. Results are discussed with reference to an executive function model of ADHD, with particular emphasis on the role of working memory in inattention

Computational Study of Turbulent-Laminar Patterns in Couette Flow

Turbulent-laminar patterns near transition are simulated in plane Couette flow using an extension of the minimal flow unit methodology. Computational domains are of minimal size in two directions but large in the third. The long direction can be tilted at any prescribed angle to the streamwise direction. Three types of patterned states are found and studied: periodic, localized, and intermittent. These correspond closely to observations in large aspect ratio experiments.Comment: 4 pages, 5 figure

Riding a Spiral Wave: Numerical Simulation of Spiral Waves in a Co-Moving Frame of Reference

We describe an approach to numerical simulation of spiral waves dynamics of large spatial extent, using small computational grids.Comment: 15 pages, 14 figures, as accepted by Phys Rev E 2010/03/2

Helicoidal instability of a scroll vortex in three-dimensional reaction-diffusion systems

We study the dynamics of scroll vortices in excitable reaction-diffusion systems analytically and numerically. We demonstrate that intrinsic three-dimensional instability of a straight scroll leads to the formation of helicoidal structures. This behavior originates from the competition between the scroll curvature and unstable core dynamics. We show that the obtained instability persists even beyond the meander core instability of two-dimensional spiral wave.Comment: 4 pages, 5 figures, revte