5,081 research outputs found
Controlling the accuracy of unconditionally stable algorithms in Cahn-Hilliard Equation
Given an unconditionally stable algorithm for solving the Cahn-Hilliard
equation, we present a general calculation for an analytic time step \d \tau
in terms of an algorithmic time step \dt. By studying the accumulative
multi-step error in Fourier space and controlling the error with arbitrary
accuracy, we determine an improved driving scheme \dt=At^{2/3} and confirm
the numerical results observed in a previous study \cite{Cheng1}.Comment: 4 pages, late
Modeling Grain Boundaries using a Phase Field Technique
We propose a two dimensional frame-invariant phase field model of grain
impingement and coarsening. One dimensional analytical solutions for a stable
grain boundary in a bicrystal are obtained, and equilibrium energies are
computed. We are able to calculate the rotation rate for a free grain between
two grains of fixed orientation. For a particular choice of functional
dependencies in the model the grain boundary energy takes the same analytic
form as the microscopic (dislocation) model of Read and Shockley.Comment: 4 pages, 2 figure
Mathematical model of the evolution of polycrystalline structures : Manifold-valued equation with singular diffusivity (New Development of Numerical Analysis in the 21st Century)
A Mixed Methods Approach to Identifying Administration Issues Pertinent in Interscholastic Sports
The purpose of this study was to investigate three propositions: a) What are the administration issues most pertinent to interscholastic sport today, as well as the next five years?, b) How important are those administration issues to athletic administrators?, and c) What are the potential implications of those pertinent administration issues to practicing athletic administrators? The literature provides a general overview of relevant issues surrounding interscholastic athletics. However, the importance and implications of relevant issues to practicing high school athletic administrators are difficult to discern. To answer the first proposition, the Minnesota State High School League (MSHSL) provided 10 contemporary administration issues that were most pertinent to interscholastic sport today, as well as the next five years. To answer the second proposition, a Likert-Scale was created so that practicing athletic administrators could rate each issue on a scale of 5 = extremely important to 1 = very little importance. A national study was conducted with athletic directors from the National Interscholastic Athletic Administrators Association (N = 170) annual conference. A one-tailed ANOVA was executed to determine significant differences among the 10 administration issues identified by the MSHSL. Four issues were found to be significant; Athletic Facilities, Athletic Training, Health Issues and Travel Teams. A Games-Howell post hoc was executed to determine significant differences across geographical regions of the United States. For the third proposition, semi-structured interviews were completed to provide insight on the implications for practicing athletic administrators. The results offer insight from which further investigations could be conducted to continue building on policies that influence interscholastic athletic administrators’ day-to-day accountability when overseeing their athletic programs
Wind-Tunnel Investigation of the Low-Speed Characteristics of a 1/8-Scale Model of the Republic XP-91 Airplane with a Vee and a Conventional Tail. Addendum - Characteristics with a Revised Conventional Tail and Drooped Wing Tips
Additional wind-tunnel tests were made of a 1/8-scale model of the Republic XP-91 airplane to determine its characteristics with various modifications. The modifications included a revised conventional tail, revised rocket arrangement, drooped wing tips, and revised landing gear and doors. Tests were also made to determine the effectiveness of the control surfaces of the model with the conventional tail and the effect of changing wing incidence and tail length. The revised rocket arrangement provided a considerable increase in the static directional stability contributed by the vee tail at small angles of yaw. The conventional tail provided a greater static directional stability than the vee tail without increasing the rolling moment due to sideslip. The rolling moment die to sideslip was considerable reduced by either drooped wing tips or open main landing-gear doors. The reduction in rolling moment due to sideslip resulting from the drooped tips was less with the landing-gear doors open than with the doors closed. A change in wing incidence from 0 degrees to 6 degrees reduced the elevator angle required for balance by approximately 6 degrees
Stability of an electroweak string with a fermion condensate
A solution of the standard electroweak theory with a single lepton family is
constructed, consisting of a cosmic string and a fermion condensate within its
core. The stability of this system to small perturbations is examined, and it
is found that stability is not enhanced relative to the bare electroweak
string. The presence of quark zero modes is shown to violate the existence
criteria for embedded defects.Comment: 13 pages, preprint DAMTP 94-9, SWAT/2
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