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Full-Text Articles in Physical Sciences and Mathematics
Some Sampling Designs And Estimation Problems, Hassan Lakkis
Some Sampling Designs And Estimation Problems, Hassan Lakkis
Mathematics & Statistics Theses & Dissertations
In the first chapter we review some standard estimators in sampling from a finite population, and some design-based estimators in sampling from a continuous universe.
In concert with the theory initiated by professor Douglas Robson (personal communication) and later presented by Cordy (1993), we consider design-based variance estimation for probability sampling from a continuous and spatially distributed universe. Using this theory in chapter two, the sampling design of one random point from each cell of a translated grid is investigated and the problem of edge effects on estimation is illustrated with examples. Also in chapter four, standard systematic sampling methods …
Rational Cubic B-Spline Interpolation And Its Applications In Computer Aided Geometric Design, Kotien Wu
Rational Cubic B-Spline Interpolation And Its Applications In Computer Aided Geometric Design, Kotien Wu
Mathematics & Statistics Theses & Dissertations
Because of the flexibility that the weights and the control points provide, NURBS have recently become very popular tools for the design of curves and surfaces. If the weights are positive then the NURB will lie in the convex hull of its control points and will not possess singularities. Thus it is desirable to have positive weights.
In utilizing a NURB a designer may desire that it pass through a set of data points {xi} This interpolation problem is solved by the assigning of weights to each data point. Up to now little has been known regarding the …
Multigrid Acceleration Of Time-Dependent Solutions Of Navier-Stokes Equations, Sarafa Oladele Ibraheem
Multigrid Acceleration Of Time-Dependent Solutions Of Navier-Stokes Equations, Sarafa Oladele Ibraheem
Mechanical & Aerospace Engineering Theses & Dissertations
Recent progress in Computational Fluid Dynamics is encouraging scientists to look at fine details of flow physics of problems in which natural unsteady phenomena have hitherto been neglected. The acceleration methods that have proven very successful in steady state computations can be explored for time dependent computations. In this work, an efficient multigrid methods is developed to solve the time-dependent Euler and Navier-Stokes equations. The Beam-Warming ADI method is used as the base algorithm for time stepping calculations. Application of the developed algorithm proved very efficient in selected steady and unsteady test problems. For instance, the inherent unsteadiness present in …
Invariant Manifolds Of A Toy Climate Model, Michael Toner
Invariant Manifolds Of A Toy Climate Model, Michael Toner
Mathematics & Statistics Theses & Dissertations
According to astronomical theory, ice ages are caused by variations in the Earth's orbit. However, ice core data shows strong fluctuations in ice volume at a low frequency not significantly present in orbital variations. To understand how this might occur, the dynamics of a two dimensional nonlinear differential equation representing glacier/temperature interaction of an idealized climate was studied. Self sustained oscillation of the autonomous equation was used to model the internal mechanisms that could produce these fluctuations. Periodic parametric modulation of a damped internal oscillation was used to model periodic climate response at double the external modulation period. Both phenomena …