Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item Moisture Transport through Housing Materials Enclosing Critical Automotive Electronics(2019) Roman, Artur; Han, Bongtae; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In automotive electronics, humidity-sensitive electronics are encapsulated by protective housings that are attached to the car body. Typical housing materials are comprised of polymer composites, through which moisture transport occurs. The objective of this paper is to provide a predictive capability for moisture transport through automotive housings enclosing a cavity with electronic modules. The temperature-dependent moisture properties including moisture diffusivity, solubility, and saturated concentration of three housing material candidates are characterized first. Then, the analogy between heat transfer and the mass transfer is implemented to model the moisture transport into the cavity enclosed by the housing materials. To cope with the transient boundary condition at the housing material and the cavity interface, the effective volume scheme is used, treating the cavity as an imaginary polymer with an extremely large diffusivity and “equivalent solubility.” The prediction is subsequently validated through an experimental setup designed to monitor the in-situ humidity condition inside the cavity sealed by the housing materials. The prediction and experimental results agree well with each other, which corroborates the validity of the FEA modeling and the measured moisture properties.Item RESPONSE OF FOUNDATIONS SUBJECTED TO VERTICAL DYNAMIC LOADING(2015) Sutaih, Ghassan Hassan; Aggour, Mohammed S; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Design of machine foundations that are subject to dynamic loading require that their amplified displacement is within certain limit so that such displacement doesn’t impede the operation of the machine they are supporting. For the design of such foundations, several methods are available that are based on a mathematical solution of the differential equation that represents dynamic loads on an elastic half space. When the soil conditions are not uniform, the response cannot be predicted accurately by these methods and hence numerical methods should be used to analyze the problem. This research presents a numerical solution to a foundation subject to dynamic loading considering: 1) the effect of soil layering on the dynamic response. Specifically, a footing rests on a finite soil layer over an elastic half space and 2) the effect of the depth of embedment of a foundation in a homogenous elastic half space on its dynamic responseItem Spatial Modeling using Triangular, Tetrahedral, and Pentatopic Decompositions(2006-04-28) Lee, Michael Thomas; Samet, Hanan; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Techniques are described for facilitating operations for spatial modeling using triangular, tetrahedral, and pentatopic decompositions of the underlying domain. In the case of terrain data, techniques are presented for navigating between adjacent triangles of a hierarchical triangle mesh where the triangles are obtained by a recursive quadtree-like subdivision of the underlying space into four equilateral triangles. We describe a labeling technique for the triangles which is useful in implementing the quadtree triangle mesh as a linear quadtree (i.e., a pointer-less quadtree). The navigation can then take place in this linear quadtree. This results in algorithms that have a worst-case constant time complexity, as they make use of a fixed number of bit manipulation operations. In the case of volumetric data, we consider a multi-resolution representation based on a decomposition of a field domain into nested tetrahedral cells generated by recursive tetrahedron bisection, that we call a Hierarchy of Tetrahedra (HT). We describe our implementation of an HT, and discuss how to extract conforming meshes from an HT so as to avoid discontinuities in the approximation of the associated scalar field. This is accomplished by using worst-case constant time neighbor finding algorithms. We also present experimental results in connection with a set of basic queries for performing analysis of volume data sets at different levels of detail. In the case of four-dimensional data which can include time as the fourth dimension, we present a multi-resolution representation of a four-dimensional scalar field based on a recursive decomposition of a hypercubic domain into a hierarchy of nested four-dimensional simplexes, that we call a Hierarchy of Pentatopes (HP). This structure allows us to generate conforming meshes that avoid discontinuities in the corresponding approximation of the associated scalar field. Neighbor finding is an important part of this process and using our structure, it is possible to find neighbors in worst-case constant time by using bit manipulation operations, thereby avoiding traversing the hierarchy.