Browsing by Subject "Reduction"
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Item An efficient hybrid model reduction for use with the AMLS method for frequency response problems(2010-05) Li, Qinqin, 1980-; Bennighof, Jeffrey Kent, 1960-; Sirohi, JayantA hybrid model reduction for use with the automated multilevel substructuring (AMLS) method is presented for frequency response analysis of complex structures. Structure responses to harmonic excitations and quasi-static responses to dominant damping forces are included in a reduced approximation subspace. Both types of responses greatly increase the efficiency of the subspace for solving the frequency response problem (FRP) for systems with high modal density and structural damping, and provide a good preparation for future frequency-dependent problems. A distilled subspace assumed to provide accurate frequency responses is generated from the finite element (FE) models by using the AMLS method. Then, the hybrid model reduction method is used to reduce the distilled subspace into a small new subspace. Three types of vectors are used to construct this subspace. The first type is distilled subspace dynamic response vectors (DRVs), which are exact solutions in the distilled subspace at certain chosen frequencies, called the DRV frequencies. The second type is modal DRVs, which are inexpensive approximate solutions calculated in an eigenspace. The third type is damping deformation vectors (DDVs), which provide information about response of the structure to damping effects. As exact responses, the distilled subspace DRVs eliminate frequency response errors at the DRV frequencies, and improve the accuracy at nearby frequencies as well. A small number of DRV frequencies are chosen carefully to offer maximum benefit with minimal computational cost. The modal DRVs are approximated very inexpensively from a suitable eigenspace. Only the diagonal entries in the modal coefficient matrices are used, along with low-rank updates that improve the accuracy of the modal DRVs and are applied using the Sherman-Morrison-Woodbury formula. Because of their low cost, a large number of modal DRVs constitute the major part of the reduced subspace. A small number of DDVs represent response to provide damping with minimal computational cost. The dimension of the final subspace is minimized by removing any redundancy through a special implementation of the QR factorization. This method results in a much smaller new subspace than the one from traditional modal truncation while achieving the same FRP accuracy. Such an efficiency also establishes a good foundation for future application in frequency-dependent problems.Item An evaluation of cost in government aircraft acquisition programs(2011-08) Reynolds, Robert Paul; McCann, Robert Bruce, 1948-; Nichols, Steven Parks, 1950-Aircraft system development has been steadily increasing in cost since the inception of human flight. Several factors have influenced this including economics, increasing complexity and increased customer expectations and requirements. In addition, the contractors which produce these systems have almost consistently been unable to complete them within the originally contracted budget and schedule. The factors which influence cost increase have been studied extensively by industry, government and private organizations and a study of those findings will be conducted in the following work with the intention of determining the factors which are primarily responsible for cost increase in aircraft acquisition programs. Following the discussion of data, recommendations for reducing cost will made with the goal of identifying the methods with which systems engineering can be used to improve the process at the system and program level. The intent will be to show how improved techniques for managing programs, meeting customer requirements and improving cost estimates can be implemented to manage cost growth. The ultimate goal of this study is to show that program risk can and should be managed more effectively and that high technology programs can be executed if they are properly managed.Item New work for non-reductive theories of consciousness(2019-08) Saad, Thomas Bradford; Montague, Michelle; Pautz, Adam; Dogramaci, Sinan; Juhl, Cory F; Sosa, Ernest D.; Strawson, GalenConscious states are ones that there is something it is like to undergo. There are three senses in which this dissertation delivers new work for non-reductive theories of consciousness. First, it supports non-reductive theorizing about consciousness by defending two new arguments against reductive physicalism about consciousness. Second, it introduces and argues in favor of three non-reductive theories of consciousness. Third, it motivates these theories by showing how they are distinctively well-suited to perform certain explanatory work. Each chapter of the dissertation is self-contained. Chapter 1 develops an empirically motivated argument against reductive physicalism. The argument distinguishes different interpretations of the special theory of relativity and argues that none provides a hospitable environment for reductive physicalism. Chapter 2 develops a new modal argument against reductive physicalism. The argument appeals to the possibility of aliens, i.e. (roughly) subjects of physically irreducible conscious states that are uninstantiated in the actual world. The argument has advantages and consequences that distinguish it from the more familiar anti-physicalist arguments that appeal to zombies and ghosts. I conclude the chapter by proposing quasi-reductive physicalism—a form of grounding physicalism—that retains some of reductive physicalism’s virtues but which is unthreatened by aliens. Chapter 3 introduces a second non-reductive theory of consciousness: tracking dualism. On tracking dualism, a fundamental psychophysical law fixes the distribution of conscious states by operating on facts about what features of the environment brain states “track”. I use a puzzle about spatial experience to argue that tracking dualism is an attractive theory for dualists. Chapter 4 motivates a stringent set of constraints on constructing a dualist theory of consciousness, explains why existing dualist theories satisfy only some of them, and constructs a dualist theory that satisfies all of them. On the resulting theory—which I call delegatory dualism—experiences uphold causal responsibilities “delegated” to them by physical statesItem Synthesis, metal complexes, reduction chemistry and antimicrobial applications of a novel bis(imino)acenaphthene (BIAN)-supported N-heterocyclic carbene(2012-12) Butorac, Rachel Renee; Cowley, Alan H; Jones, Richard A; Holliday, Bradley J; Anslyn, Eric V; Brown, Jr., R. MalcolmThe use of N-heterocyclic carbenes (NHCs) as ligands in catalysis is one of the most significant developments in modern catalysis and organometallic chemistry. One way to extend the scope of NHC ligand tuning is by means of annulation of carbocyclic and heterocyclic rings to the NHC backbone. The bis(imino)acenaphthene-supported N-heterocyclic carbene [IPr(BIAN)] has been synthesized and can be regarded as originating from the fusion of a naphthalene ring to an NHC. Several metal complexes of IPr(BIAN), including those incorporating copper(I), silver(I), gold(I), or iridium(I) have been synthesized and characterized, including single-crystal X-ray diffraction studies. The doncity of IPr(BIAN) was investigated using the Tolmen Electronic Parameter (TEP) method. A TEP value of 2042 cm-1 was calculated for the IPr(BIAN) ligand using the Ir(CO)2Cl complex which indicates that IPr(BIAN) is a relatively strong electron donating NHC ligand. The well-behaved redox chemistry of the BIAN ligand class rendered IPr(BIAN) an excellent candidate for exploration of the relationship between ligand charge and carbene donicity. The electrochemical reduction of IPr(BIAN) was studied by cyclic voltammetry (CV) in a THF solution and a reversible reduction wave was detected at - 1.79 V vs SCE. Spectroelectrochemical IR studies were also undertaken to further characterize the nature of the reduced state. IPr(BIAN) was found to be a stronger electron donating ligand in the reduced state in comparison with the neutral state of the ligand. IPr(BIAN) was also chemically reduced using potassium graphite and the resulting radical anion was studied by electron paramagnetic resonance (EPR) techniques. An isotropic EPR signal was observed at a g value of 2.0112. Due to the known antimicrobial activities of silver and gold NHCs, the activities of the silver and gold complexes of IPr(BIAN) and the imidazolium salts of several BIAN ligands were investigated using the minimum inhibitory concentration test. The silver(I) and gold(I) complexes of IPr(BIAN) were found to be moderately active. The most active compounds were found to be the imidazolium salts, with MIC values ranging between < 0.6 μg/mL and 78 μg/mL for the diisopropylphenyl(BIAN) and the mesityl(BIAN) imidazolium chlorides against S. aureas, B. subtilis, E. coli, and P. aeruginosa. The preparation of nanofibers impregnated with IPr(BIAN)AuCl by the process of electrospinning was also explored. The antimicrobial activities of the resulting nanofiber mats were determined on the basis of the inhibition zone test, and a localized antimicrobial activity was observed for the Gram-positive bacteria M. leuteus.