Semiconductor-based heterogeneous photocatalysis, as one of the advanced oxidation processes that makes use of semiconductors and inexhaustible solar light, has recently been extensively studied and applied to water decontamination. However, due to low light absorption efficiencies and severe electron-hole recombination, modifications on semiconductor structures are required in order to enhance their photocatalytic performance. Heterogeneous photocatalyst composites, taking advantage of the improved light absorption efficiency as well as the facilitated electron-hole separation at the interface between different semiconductors, have been proven to be a promising strategy. In this study, novel NaNbO3/Bi2WO6 photocatalyst composites with a type-II heterogeneous alignment were successfully prepared via a facile wet impregnation method. The as-prepared photocatalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-Vis spectroscopy (DRS), photocurrent (PC) and electrochemical impedance spectroscopy (EIS) analyses. The 30 wt% NaNbO3/Bi2WO6 composite exhibited the best performance for degrading an RhB (rhodamine B) aqueous solution under visible light irradiation (λ > 410 nm), which was ca. 40 times and ca. 2.5 times that of the pristine NaNbO3 and Bi2WO6, respectively. The improved photocatalytic activity may be attributed to the enhanced electron-hole separation efficiency in Bi2WO6 with the assistance of NaNbO_3, as well as the dye-sensitization effect of RhB itself. Radical quenching experiments revealed that h+ played the predominant role, and O2•- functioned as well to some degree. The produced intermediates during the reaction and RhB degradation pathway were speculated and investigated as well. The excellent stability and reusability were verified by repetitively running for five times. Based on experimental results, a plausible functioning mechanism was proposed. Effects of several operation parameters on the catalyst performance including initial RhB concentration, catalyst dosage, reaction temperature and initial pH were also discussed. This study provides solid evidence for NaNbO3 to be a promising candidate for photocatalysis and gives out a novel photocatalytic mechanism of Bi2WO6-based type-II heterostructures.

Cooperative operation of multiple manipulators has been increasingly used in industrial automation, outer space and hazardous terrestrial applications. Moreover, the requirement for increased speeds of operation and light-weight design of robot manipulators has made structural flexibility a dominant factor in the design and control of cooperating manipulator systems. When multiple manipulators act cooperatively on an object, a closed-loop chain structure is formed. Redundant actuation is one of the inherent characteristics of such systems. Determining actuator torques necessary to achieve a prescribed object motion is known as the inverse dynamics process. Due to the presence of the redundant actuators, inverse dynamics torques for cooperating manipulator systems admit an infinite number of solutions. Consideration of flexibility in the links of manipulators, particularly relevant in space applications, not only complicates the dynamics modeling of the system, but also introduces instability in the inverse dynamics solution. In this study, a dynamics model is derived for a flexible-link cooperating manipulator system and the inverse dynamics procedure for such a system is investigated. In particular, the latter is divided into two subproblems--the force distribution problem and the inverse dynamics problem for serial flexible-link manipulators. The approach chosen to the force distribution problem is to formulate it as a linearly constrained local optimization problem. Several objectives particularly relevant to flexible-link cooperating manipulators are proposed. These include minimum strain energy, minimum weighted norm of elastic accelerations and optimal load sharing schemes. The resulting algorithms are shown to be effective in reducing the vibration of the system and stabilizing the inverse dynamics solution. A stability analysis of the internal dynamics of the inverse dynamics system is also performed by using linearization. Agreement in the behavior of the inverse dynamics system is demonstrated between directly solving the nonlinear dynamics equations with optimal force distribution and calculating the eigenvalues of the plant matrix of the linearized system. A stability approach to the force distribution problem is then proposed which ensures stable behavior of the internal dynamics system under the condition that the number of elastic coordinates of the system is less than or equal to the total number of redundant actuators. / Graduate

Doctor of Philosophy / Department of Agronomy / Mithila Jugulam / Kochia (Kochia scoparia (L.) Schrad), one of the most troublesome weeds in the North American Great Plains, including Kansas (KS), has become a significant concern in croplands ever since the evolution and spread of glyphosate resistance in this weed. Dicamba, an important synthetic auxin herbicide, is a useful substitute for managing glyphosate-resistant (GR) broadleaf weeds. As a result of extensive and intensive use, kochia populations have also developed resistance to dicamba. However, the precise mechanism(s) of dicamba resistance in kochia is still unknown. In the first part of this dissertation, the physiological, biochemical and genetic basis of dicamba resistance in dicamba-resistant (DR) kochia from KS was investigated. The results suggest that the mechanism of dicamba resistance in this kochia is not due to decreased absorption, reduced translocation or enhanced detoxification of dicamba. In contrary, reduced translocation of dicamba was found to contribute to the dicamba resistance in DR kochia from Colorado (CO). Further investigation of DR kochia from KS revealed a possible role of single nucleotide polymorphism (SNP) in TIR1 (the receptor gene of auxin) in the dicamba resistance evolution. Genetic analyses of data from inheritance studies demonstrated that an incomplete dominant nuclear gene controls the dicamba resistance in kochia from KS. Also, it was found that the genes controlling dicamba resistance in kochia from KS and CO are not linked. Similarly, although, GR and DR traits were found to be controlled by two distinct single dominant genes, they appear to co-exist in many kochia populations from KS. Nonetheless, these two genes were also found not to be linked. The second part of this dissertation focused on the development of reliable tools for the management of DR and/or GR kochia. The following experiments were conducted under greenhouse and field conditions in KS: a) the effect of temperature stress on the efficacy of dicamba or glyphosate; b) efficacy of dicamba and glyphosate when applied in combination; and c) efficacy of dicamba when used as pre-emergence (PRE) herbicide. The results suggest that the efficacy of both dicamba and glyphosate on kochia can be improved when applied at cooler temperature conditions. Also, it was found that the dicamba and glyphosate tank-mix should not be recommended to manage kochia, especially DR kochia, due to significant antagonistic interaction when applied in combination. On the other hand, application of dicamba as PRE compared to the postemergence application, was found to improve kochia control including DR kochia. Overall, this dissertation provided several novel outcomes both in basic and applied aspects of dicamba resistance in kochia.

The first objective of this investigation was to conduct a systematic study into the reactions of chloroketenes with ketene acetals. The second objective was to explore the synthetic utility of these reaction products and offer a rational explanation for these reaction products.

Neste trabalho foi realizado um estudo das interações entre o corante catiônico azul de metileno com partículas de argilas em suspensão aquosa, visando detectar processos de migração de moléculas de corante entre partículas de argila. Até o momento as interações entre moléculas de corante e partículas de argila vem sendo descritas tendo-se em conta dois processos, um deles devido a adsorção de moléculas de corante nas superfícies externas e migração do corante para a região interlamelar, e outro devido as interações partícula-partícula, onde as interações entre as partículas de argila levam a formação de aglomerados de partículas, com o corante aprisionado nas regiões internas formadas. Há fortes indícios da ocorrência da migração de moléculas de corante entre partículas de argila, porém não houve detecção direta deste processo. No presente trabalho, foi idealizada uma metodologia que permitiu detectar variações espectrais, as quais podem ser atribuídas ao processo de migração de corante entre partículas de argila. A metodologia empregada consistiu na adição de suspensão de argila à suspensão argila-corante. Foram realizadas medidas espectrofotométricas na região do visível, em função do tempo, a partir do instante em que as suspensões são misturadas. Os espectros determinados para as amostras foram comparadas com os espectros determinados para a amostra de referência, a qual foi preparada pela adição de água a suspensão corante argila. Os resultados mostraram que as amostras e a referência apresentam comportamento espectral distinto, este comportamento pode ser atribuídos a migração de moléculas de corante entre partículas de argila. De forma geral, verificou-se que a migração do corante entre partículas ocorre preferencialmente para as partículas da argila SWy-1, pois esta argila apresenta a região interlamelar disponível para a adsorção das moléculas de AM, onde ocorre a protonação da molécula do corante, tornado-a mais estável. Os experimentos utilizando membrana de diálise mostraram que quando as suspensões estão isoladas pela membrana a migração das moléculas de corante entre partículas de argila não ocorre, é necessário uma interação ou contato entre as partículas para que a migração ocorra. / In the present work, studies on the interaction between the cationic dye methylene blue and clay particles in aqueous suspension are presented, aiming to detect migration processes of dyes molecules between clay particles. Up to now, the interaction between dye molecules and clay particles is described considering mainly two processes, one due to the adsorption of the dye molecules onto the outer surfaces of the clay particles, and subsequent migration toward the inner surfaces of the clay tactoids. The other process involves particle-particle interaction; the interaction between clay particles promotes particle agglomeration, with dye molecules being trapped in the internal sites formed between particles. There are strong evidences that dye molecules can exchange between dye coated particles, and in the present study a methodology was idealized to detect spectral changes, which could be attributed to migration of dye molecules between clay particles. According to the methodology used, clay particles were added to a dye-clay suspension and spectrophotometric measurements in the visible region was taken after different time intervals. The results were compared with reference spectra, determined for samples prepared adding water to the clay-dye suspension. The results showed that the spectral behavior of the samples and the reference were different, and this behavior can be attributed to the migration of adsorbed dye molecules between clay particles. It was observed that migration occurs preferentially in a direction towards the SWy-1 clay particles. The clay SWy-1 has interlamellar surfaces available to the dye adsorption. In the interlamellar region there are acids sites, where the dyes molecules are protonated. The protonation of dye molecules stabilize the adsorbed molecules. The experiments using dialysis membrane showed that when the particles are isolated by a membrane, the migration between clay particles do not occur, indicating that a close contact or interaction between the clay particles is necessary to the migration occur.

As interações entre as moléculas de corante e as partículas de argila em suspensão podem envolver diferentes processos dependendo da argila e da maneira pela qual as suspensões corante/argila são preparadas. Os processos que ocorrem são: a adsorção de moléculas de nas superfícies externas das partículas de argila seguidas de migração para as regiões interlamelares, outro processo é devido a interações partícula-partícula, onde as moléculas de corante ficam envoltas em aglomerados de partículas de argila e um terceiro processo é devido a migração das moléculas de corante entre partículas de argila. No presente trabalho foi estudada a influência de diferentes metodologias nos processos de migração de moléculas do corante azul de metileno (AM) entre partículas de argilas em suspensão aquosa. Experimentos adicionando-se partículas de argila nas suspensões corante/argila foram realizados com acompanhamento das variações espectrais em função do tempo. Foi possível detectar variações espectrais nas suspensões corante/argila atribuídas a processos de migração de moléculas de corante adsorvidas em partículas de argila para outras partículas na suspensão. Os resultados indicaram que o processo de migração entre diferentes partículas de argila depende da razão corante/argila. Em outro tipo de experimento, utilizando diferentes formas de adição do corante à suspensão de argila (lenta, rápida e diálise) constatou-se que o modo de adição do corante pode afetar os processos de adsorção, para alguns sistemas corante/argila é muito importante considerar a forma de adição do corante à suspensão de argila, para que se tenham suspensões corante/argila com propriedades desejáveis. / Interactions between dye molecules and suspended clay particles may follow different processes depending on how the dye/clay suspensions are prepared. The processes that occur are: adsorption of molecules on the external surfaces of clay followed by migration to the interlamelar areas, another process is due to particle-particle interactions, in which the dye molecules are wrapped in clay particle agglomerates and a third process due to the migration of the dye molecules between clay particles. In the presente work the influence of different metodologies on the migration processes for the methylene blue dye between clay particles in aqueous suspension was studied. Experiments adding clay particles to the system dye/clay were done monitoring following the spectral changes in function of time. It was possible to detect spectral variations in the dye/clay suspensions attributed to the migration of adsorbed dye molecules to other particles in the suspension dye molecules adsorbed in clay particles migration process. The results indicated that the migration process between different clay particles depend on the nature of the clay and on the dye/clay ratio. In another type of experiment, using different forms for adding dye to the clay suspension (slow, fast and dialysis) it was seen that the adding way for the dye can affect the adsorption processes, for some dye/clay systems it is very important to consider the adding way of the dye to the clay suspension, so that dye/clay suspensions with desirable properties are obtained.

Using complexing-agent assisted sol-gel routes, mixed Pd/ceria-alumina and Pd/terbia-ceria-alumina catalysts were prepared. The materials have been characterised by means of ICP-MS, TEM, EDX, XPS, XRD, BET, TPR, TPO and TPD. Catalytic testing was carried out in a temperature programmed mode as well as isothermally, using synthetic exhaust gas mixtures with different air-to-fuel ratios. The obtained results were compared with those of traditionally impregnated Pd/ceria-alumina and PtRh/ceria-alumina. Evaluating the catalysts potential as three-way converters, it has been shown that as a result of the sol-gel preparation chosen, highly homogeneous materials were produced. These had (i) much higher oxygen storage potential (especially at low temperatures, T ≈ 400 - 500K), (ii) improved metal support interactions and (iii) lower CO and propane light-off temperatures (T50%(CO) ≈ 423K, T50%(C3H8) ≈ 593K for R ≥ 1). Under fuel-rich conditions an improved low temperature NO activity was shown for the ceria-containing materials. This was attributed to a ceria-mediated redox mechanism and an improved Pd-ceria interaction for these sol-gel-derived samples. The addition of terbia was found to promote the catalysts propane activity, especially under fuel-rich conditions. The application of the different catalysts as three-way converters has been discussed, with special emphasis on their potential during the cold-start period. In a further set of catalytic experiments, using less complex gas mixtures, a more comprehensive view of the detailed Pd chemistry involved in these new three-way catalysts was obtained.

No description available.

This paper is a critical essay on the question "Can machines think?", with particular attention paid to the articles appearing in an anthology Minds and Machines, A. R. Anderson editor. The general conclusion of this paper is that those arguments which have been advanced to show that machines can think are inconclusive. I begin by examining rather closely a paper by Hilary Putnam called "Minds and Machines" in which he argues that the traditional mind-body problem can arise with a complex cybernetic machine. My argument against Putnam's is that either there are no problems with computers which are analogous to the ones raised by mental states, or where there are problems with machines, these problems do not have at bottom the same difficulties that human experiences raises. I then continue by showing that a cybernetic machine is an instantiation of a formal system. This leads to a discussion of the relationship between formality and predictability in which I try to show that some types of machine are in principle predictable. In the next section I attempt to prove that any discussion of outward signs of imitative behavior presupposes that some linguistic theory, such as a type reduction, has been substantiated. The force of this argument is that such a theory has not in fact been substantiated. I offer some general theory about the complexity of concept-property relations. Finally I give a demonstration that no test or set of tests can be found that will be logically sufficient for the ascription of the concept "capable of thought." If this is successful, then I have shown that no test can be found, which when a machine is built to pass it, is logically adequate for saying that that .machine can think. This argument is offered as further criticism of the Imitation Game which A. M. Turing proposed as an adequate test for thinking subjects. Besides the specific conclusion that insufficient evidence, has been offered to say that machines can think, this paper offers a more general conclusion that most standard problems have at bottom a linguistic difficulty. However, this general conclusion is a broad speculative one to which the work in this paper, is only a small exemplification and as such reflects mainly the further ambitions of the author. / Arts, Faculty of / Philosophy, Department of / Graduate

A complete solution to the inverse kinematics problem for a large class of practical manipulators, which includes manipulators with no closed form inverse kinematics equations, is presented in this thesis. A complete solution to the inverse kinematics problem of a manipulator is defined as a method for obtaining the required joint variable values to establish the desired endpoint position, endpoint orientation, and manipulator configuration; the only requirement being that the desired solution exists. For all manipulator geometries that satisfy a set of conditions (THEOREM I), an algorithm is presented that is theoretically guaranteed to always converge to the desired solution (if it exists). The algorithm is extensively tested on two complex 6 degree of freedom manipulators which have no known closed form inverse kinematics equations. It is shown that the algorithm can be used in real time manipulator control. Applications of the method to other 6 DOF manipulator geometries and to redundant manipulators are discussed. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate