Tailoring explicit time-marching schemes to improve convergence characteristics

Multi-stage time-stepping schemes, tailored to chosen spatial-differencing operators, are derived and tested. The schemes are constructed to give optimal damping of the high-frequency waves. They are ideal for use with multi-grid acceleration. The concept of characteristic time-stepping, necessary for the extension of the scalar analysis to systems of equations, is presented. The schemes show a marked improvement over Runge-Kutta schemes

Tolerance of Plant Monoterpenes and Diterpene Acids by Four Species of Lymantriidae (Lepidoptera) Exhibiting a Range of Feeding Specificities

Lymantriidae (Lepidoptera) is a family of leaf-feeding insects that includes some of the most damaging forest pests worldwide. Species within this family vary widely in feeding specificity. We evaluated the ability of four species, Douglas fir tussock moth (Orgyia pseudotsugata McDunnough), nun moth (Lymantria monacha L. ), rusty tussock moth (Orgyia antiqua (L.)), and white- marked tussock moth (Orgyia leucostigma (J. E. Smith)), to contend with one of the most ubiquitous and effective groups of plant defense compounds, terpenoids. We selected these species to provide a range of feeding specificities on conifer hosts, from obligate to occasional. We evaluated the effects of three monoterpenes (bornyl acetate, limonene, and myrcene) and two diterpene acids (isopimaric acid and neoabietic acid) on larval performance. Although these four species differ in their feeding ranges, utilization of conifers as hosts, and other life history processes, each shows a relatively high tolerance for conifer terpenes. The mean relative growth rates, relative consumption rates, and development times were not affected by these monoterpenes and diterpene acids when administered at concentrations present in the foliage of conifers in which they are most abundant. The most likely explanation seems to be metabolism, as a) no limonene or myrcene were recovered from frass or larvae, and b) borneol, an apparent metabolite of bornyl acetate, was recovered from frass of Douglas fir tussock moth, rusty tussock moth, and white-marked tussock moth, and from tissues of Douglas fir tussock moth and white-marked tussock moth

An embedded mesh procedure for leading-edge vortex flows

A cell-vertex scheme is outlined for solving the flow about a delta wing with M (sub infinity) is greater than 1. Embedded regions of mesh refinement allow solutions to be obtained which have much higher resolution than those achieved to date. Effects of mesh refinement and artificial viscosity on the solutions are studied, to determine at what point leading-edge vortex solutions are grid-converged. A macroscale and a microscale for the size of the vortex are defined, and it is shown that the macroscale (which includes the wing surface properties) is converged on a moderately refined grid, while the microscale is very sensitive to grid spacing. The level of numerical diffusion in the core of the vortex is found to be substantial. Comparisons with the experiment are made for two cases which have transonic cross-flow velocities

Remembering Nina R. Kestin

There are many people whose lives are different because Ricki Kestin was in it. I am one of those people. You will understand when I tell you that I did not want to speak today; that I did not want to tell you what I knew or thought or felt about Ricki

Remembering Nina R. Kestin

There are many people whose lives are different because Ricki Kestin was in it. I am one of those people. You will understand when I tell you that I did not want to speak today; that I did not want to tell you what I knew or thought or felt about Ricki

Factors That Prospective Teachers at Utah State University Considered Important in Their Decision to Enter Teacher Preparation

A critical shortage of teachers became an acute threat to society following World War II according to Jantzen (1959). Because of the shortage of teachers, many institutions of higher learning and a number of interested groups have discussed and made studies on means of recruiting prospective teachers, as brought out by Riccio(1961). The studies that have been made on prospective teachers expounded mainly on the age students decided to become teachers and influences from parents, relative-teachers, teachers, guidance counselors, and teaching experience

Towards a genuinely multi-dimensional upwind scheme

Methods of incorporating multi-dimensional ideas into algorithms for the solution of Euler equations are presented. Three schemes are developed and tested: a scheme based on a downwind distribution, a scheme based on a rotated Riemann solver and a scheme based on a generalized Riemann solver. The schemes show an improvement over first-order, grid-aligned upwind schemes, but the higher-order performance is less impressive. An outlook for the future of multi-dimensional upwind schemes is given