Boolean Satisfiability (SAT) is a fundamental NP-complete problem of determining whether there exists an assignment of variables which makes a Boolean formula evaluate to True. SAT is a convenient representation for many naturally occurring optimization and decisions problems such as planning and circuit verification. SAT is most commonly solved by a form of backtracking search which systematically explores the space of possible variable assignments. We show that the order in which variable polarities are assigned can have a significant impact on the performance of backtracking algorithms. We present several ways of transforming SAT instances into non-linear objective functions and describe three value-ordering methods based on iterative optimization techniques. We implement and test these heuristics in the widely-recognized MiniSAT framework. The first approach determines polarities by applying Newton's Method to a sparse system of non-linear objective functions whose roots correspond to the satisfying assignments of the propositional formula. The second approach determines polarities by minimizing an objective function corresponding to the number of clauses conflicting with each assignment. The third approach determines preferred polarities by performing stochastic gradient descent on objective functions sampled from a family of continuous potentials. The heuristics are evaluated on a set of standard benchmarks including random, crafted and industrial problems. We compare our results to five existing heuristics, and show that MiniSAT equipped with our heuristics often outperforms state-of-the-art SAT solvers.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references (leaves 157-175). Also available in an electronic version.

Thesis (Master of library science)--University of Texas. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Master of library science)--University of Texas. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 29-31.

In this thesis a high order finite difference scheme is derived and implemented solving the shallow water equations using the SBP-SAT method. This method was tested against various benchmark problems were convergence was verified. The shallow water equations were also solved on a multi-block setup representing a tsunami approaching a shoreline from the ocean. Experiments show that a bottom topography with many spikes provides a dispersing effect on the incoming tsunami wave. Higher order convergence is not guaranteed for the multi-block simulations and could be investigated further in a future study.

This project, elaborated in terms of Master’s studies in domain 2303T005 presents an analysis comparing conventional method of welding MAG and welding technology ESAB SAT^TM. ESAB SAT^TM is the new innovative method based on the principle of welding by the method MAG. The experimental part of the project is aimed to assessing the quality of welded joints, produced by ESAB SAT^TM, which part is performing selected destructive tests. Afterwards economic analysis by comparative method evaluates the measured and calculated parameters of welding.

The study examines the Projection method and the simultaneousapproximation-term (SAT) method as boundary treatment for the dynamic beam equation using summation-by-parts (SBP) operators for handling the inner domain. The methods are examined for both the homogeneous constant coefficient case, and the inhomogeneous piecewise constant coefficient case with a coupled interface. The outer boundaries are handled by SAT or Projection, the coupled interfaced is handled by Projection or a mix between Projection and SAT. Solutions are integrated in time with finite central difference schemes and compared to analytical solutions. A convergence study is conducted with respect to the spatial discretization to measure the accuracy, and the stability is examined by numerical simulations of the CFL-condition. The study shows that Projection has the same accuracy as SAT for most boundary conditions while allowing for a larger timestep. A discontinuity in the medium is found to be handled equally accurate by Projection and the Projection and SAT mixture for all but one case studied, where the mixture was slightly more accurate.

There has been in recent years a marked decline in college entrance examination test scores. Declines have been documented both on the Scholastic Aptitude Test (SAT) and the American College Testing Program (ACT). In turn there has been an increasing interest concerning the test score declines as well as possible sources of influence on test scores. These sources or factors seem to be functions of three main "contexts." These contexts are: (a) school-related factors, (b) student-related factors and (c) family-structure related factors. It was of interest to attempt to explain the relative association of each variable to composite ACT scores and of each "context" to composite ACT scores. In turn, it was of interest to attempt to assess the extent to which combinations of two, or all three sets of variables aid in explaining the variance on composite ACT scores. The sample population consisted of entering college freshmen at Utah State University for the fall quarter of 1976. All Ss were from one of the six major feeder high schools to Utah State University. Information was gathered through the use of a questionnaire distributed at freshmen registration and by mail. Other sources of information included school principals and official student ACT transcripts and school records. Using composite ACT scores as the dependent variable both stepwise and hierarchical multiple regression analyses were done. As a result of stepwise multiple regression using all ten factors, it was found that academic course taking had the greatest partial regression coefficient. Next -in predictive power was the level of educational aspiration of the student. Size of school entered the prediction equation on Step 3 and was negatively associated with composite ACT scores. Student-related factors helped to explain 38 percent of the total variance on composite ACT scores and as such comprises the most significant "context" of association. More modest support has been demonstrated for school-related factors. Family-structure factors do not appear significantly related to composite ACT scores. Recommendations were made for a larger sample sjze from a more diverse geographic region.