Browsing by Author "Akin, J. E."

Now showing 1 - 4 of 4
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    A Raster scan visibility algorithm for parametric surfaces
    (1984) Montgomery, Jerome; Akin, J. E.; Wierum, Frederic A.; Wheeler, Mary F.
    A raster scan visibility algorithm is presented for contouring on parametric surfaces. The algorithm entails three-dimensional aspects of coloring, shading, and visibility of points. The approach uses parametric interpolation functions as the primary basis in computations. This technique along with a predictor-corrector method makes contour line tracing on each element more accurate. Continuous color variations on each surface are produced through the use of interpolation functions. The color at every display point can be assigned in proportion to the value of the quantity of interest at that pixel. Shading is included involving several possibilities of the shading rule. They may include ambient light, diffuse reflection, specular reflection, shadows, or transparency. A combination of these may also be included. All of the graphics generated using this algorithm can be displayed on color graphics, as well as, non-color graphics display terminals, and line printers. The algorithm could be used as a segment of a complete computer graphics package.
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    An orthogonal adaptive grid module to complement existing fluid dynamics and heat transfers codes
    (1985) Barry, Matthew Robert; Wierum, Frederic A.; Akin, J. E.; Chapman, Alan J.
    A versatile, orthogonal adaptive grid scheme for two-dimensional numerical fluid dynamics and heat transfer problems is presented. The scheme employs a one-dimensional adaptation sweep to define one family of physical grid lines. A second sweep then uses a technique called AOT, developed herein, to fit an orthogonal family of lines to the solution-adapted lines. These procedures are fast, require.little core storage, and do not change the original domain boundaries. Each subroutine developed performs a specific function and together they form the adaptive grid module. The versatility of these subroutines allows their usage in various combinations and in either grid direction. Modifications required to implement this scheme into existing fluid dynamics and heat transfer codes, therefore, are minimal. Code documentation and sample applications showing the implementation and versatility of the scheme are presented.
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    New generation valves and seats for reciprocating well servicing pumps
    (2008) Wago, Toshimichi; Akin, J. E.
    Valves and seats in well servicing reciprocating pumps have a short life as a result of the severe operating conditions. In this work, I present the development of valve and seats concepts that have the potential to last longer than the current industry average. The work performed discusses the failure analysis of valve and seats to facilitate identifying the development areas that can lead to life improvement. The concept of a seat with an embedded insert is presented, tested and evaluated. Finally, I suggest modifications that allow optimizing the design and manufacturing process in order to achieve a robust commercial product.
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    Use of hierarchical elements in isoparametric finite element procedures
    (1984) Kipp, Robert J.; Akin, J. E.; Wheeler, Mary F.; Walker, William F.
    This thesis reports on an initial study into how hierarchical elements can best be used to enhance existing isoparametric finite element routines. Hierarchical finite elements have been used to date primarily for self-adaptive solutions, but the architecture of these programs is significantly different than conventional finite element programs. The goal is to develop methods by which hierarchical elements can be easily adapted to the large number of existing conventional programs and provide additional output to assist the analyst. The investigation discussed in this thesis is carried out in one dimension. It is demonstrated that a lower-order formulation with a higher-order hierarchical term added results in a solution equivalent to the complete higher-order solution. A technique is demonstrated by which a correct higher-order solution can be iteratively calculated using the initial lower-order stiffness matrix and without assembly of the higher-order stiffness terms. Also shown is a method for calculating a useful element-level error indicator. The one-dimensional model problem used is of a form which yields non-zero off-diagonal hierarchical stiffness terms; a situation typical in cases of higher dimension. Consequently, this work provides a basis for extension of the concepts into higher dimensions, where the benefit of the hierarchical enhancement will be most significant.