This thesis introduces a new way to characterize the dynamic SEU cross section of an FPGA design in terms of its persistent and non-persistent components. An SEU in the persistent cross section results in a permanent interruption of service until reset. An SEU in the non-persistent cross section causes a temporary interruption of service, but in some cases this interruption may be tolerated. Techniques for measuring these cross sections are introduced. These cross sections can be measured and characterized for an arbitrary FPGA design. Furthermore, circuit components in the non-persistent and persistent cross section can statically be determined. Functional error mitigation techniques can leverage this identification to improve the reliability of some applications at lower costs by focusing mitigation on just the persistent cross section. The reliability of a practical signal processing application in use at Los Alamos National Laboratory was improved by nearly two orders of magnitude at a theoretical savings of over 53% over traditional comprehensive mitigation techniques such as full TMR.

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This study compares energy minimization with direct stiffness for linear structural analysis. The energy minimization approach locates the generalized displacement vector by minimizing the total potential energy of the structure being analyzed. From the survey of variable metric and conjugate gradient algorithms included in this study, the Davidon-Fletcher-Powell variable metric algorithm and the FletcherReeves conjugate gradient algorithm were chosen to minimize the total potential energy. A description of both algorithms is presented. The direct stiffness method assembles the equilibrium equations of the structure being analyzed. These equations are solved by Gaussian elimination to determine the generalized displacement vector. Computer codes have been written for the energy minimization and direct stiffness methods. The comparison was based on computational effort, in terms of computer time, required for analysis. The results of this study show energy minimization is not competitive with direct stiffness for linear structural analysis. As the problem size increases by degree of freedom the direct stiffness method rapidly increases in superiority over the energy minimization method. / Master of Science

Poisson's ratio for aluminum is estimated from velocity profile measurements of a free-free beam under dynamic loading conditions A weighted least-squares method is used to select a beam model which is subsequently used to determine the transverse and anticlastic radii of curvature. The model of the beam velocity profile is selected using forward regression with the possible regressor set formed by products of Legendre polynomials in x and y, the two-dimensional coordinates of the beam. The resulting model is manipulated to extract the transverse and anticlastic radii of curvature of the beam which are then used to find local and global estimates of Poisson's ratio. Estimates for Poisson's ratio are found for three different forcing frequencies and three force amplitudes at each frequency. The frequencies selected correspond to the frequencies of the operating shapes dominated by the first, second, and third bending modes. A statistical analysis is performed to assess the quality of the estimates of Poisson's ratio. Results show that the estimates of Poisson fs ratio are dependent on the forcing frequency and forcing amplitude. All estimates are below the accepted value of .33 for aluminum. Contributions of plate modes adversely affect the estimates. Estimates based on the first and third operating shapes exhibit a lower variance than the estimate based on the second operating shapes. / Master of Science

Composite diaphragm strength and behavior were studied using non-linear finite element analysis. A total of 57 three panel diaphragm models were analyzed to failure. Parameters studied included beam size and orientation, panel dimension, connector type and distance, slab opening, yield plateau, and beam connection flexibility. Shear connector, deck-to-concrete interface, and beam connection were the components modeled non-linearly. Orthotropic behavior was used for the deck elements. 2-D and 3-D contours of concrete slab, steel deck and deck-to-concrete interfacial stresses and connector forces are presented to clearly show the behavior of the diaphragm in relation with the component behavior. Complete and incomplete connector force redistributions were observed and an expression of yield plateau length required to develop a complete connector force redistribution was developed. Expressions for diaphragm strength based on beam, beam connection and connector strength for both the complete and incomplete connector force redistribution cases were presented. The diaphragm strength predicted by the expression compared favorably with the finite element results. / Master of Science

The main objective of this study is to develop an analytical model to explain the behavior of a hybrid structure under different loading conditions. The model developed for a simply supported beam on moment capacity, stiffness, and deflection can be generalized to deal with any type of material combination. The dependence of moment capacity of the hybrid beam on the thickness of the composite sheet was investigated. The inherent property of a high Young's modulus and strain-to-failure properties of the composite material increased the moment capacity of the RC beam dramatically. The moment model showed a percentage increase of 284% for KFRP while on the other hand the percentage increases for CFRP and GFRP were 191% and 174% respectively when using a FRP sheet of thickness 0.025 mm. KFRP showed the highest increase in moment capacity because of its high strain-to-failure. CFRP on the other hand has a high Young's modulus, but its strain to failure is low, causing it to lie in the middle range. The analytical model is that the ability of a beam to handle moment is strongly dependent on the strength characteristics and the thickness of the FRP sheet. / Master of Science

A numerical model was developed to analyze the effectiveness of active and passive secondary support systems on the stability of a retreating longwall tailgate opening. The range of loading conditions that any tailgate can be subjected to was identified to form the basis of numerical modeling. The tailgate entry was considered as a part of roof-pillar-floor system, whose behavior is controlled largely by the structural integrity of each member. Numerical modeling was then conducted on tailgate openings to determine roof, floor, and rib responses, including failure modes to a variety of loading conditions for wood cribs and roof trusses employed as active and passive means of secondary support. Trends were developed from numerical modeling to determine optimum load capacity and paints of application for reducing the potential for entry failure. / Master of Science

see document conclusions / Master of Science

The objective of this project is to develop a methodology to measure and predict the strength and the stiffness of red alder (Alnus rubra) nailed pallet connections subjected to repetitive loading. Joint tests were conducted to define the mechanical properties of bottom block pallet connections. The primary tests were conducted to define the strength and stiffness of joint specimens tested in cyclic lateral loading, using three different side member thicknesses and four types of nails. Also, the influence of other specific variables on joint performance was evaluated including friction, pattern, moisture content, number of nails per joint, specific gravity, and rate of loading. In total, 23 sets of nailed joint specimens, with 15 replications each, were constructed and tested. The use of a reversing cyclic lateral loading procedure permits documentation of the effect of dynamic loading on the load-slip response of the connection. Analysis of the data included the creation of two envelope curves, the initial and the final (stabilized) curve. The data obtained from the two curves was used to find the “best” model for predicting the strength and stiffness of the connections. Four models were identified but only one of these was found useful for prediction purposes. Finally, experimental capacity loads were found to be at least three times greater than the national design specification allowable design loads. / Master of Science

Experimental evaluations of impact damage resistance and residual compression strengths after impact are presented for nine laminated fiber reinforced composite material systems. The experiments employ a small scale specimen for assessing the impact damage resistance and impact damage tolerance of these materials. The damage area detected by C-scan is observed to develop linearly with the impact velocity for impact velocities higher than a threshold value. Brittle material systems have lower threshold velocities and higher damage area growth rates than toughened systems. The impact damage resistance of each material system can be characterized with threshold velocity V_c and damage area growth rate C. The residual compressive Strength after impact was observed to decrease linearly with the damage area equivalent diameter. The rate of compressive strength reduction, K_d, has been observed to be independent of the material properties. The impact damage can be simulated from quasi-static indentation test in which the damage due to these two loading conditions are quite similar. The residual compressive strength can also be simulated from specimens with similar damage size resulting from quasi-static indentation load. / Ph. D.