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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
461

The Coordination Dynamics of Multiple Agents

Unknown Date (has links)
A fundamental question in Complexity Science is how numerous dynamic processes coordinate with each other on multiple levels of description to form a complex whole - a multiscale coordinative structure (e.g. a community of interacting people, organs, cells, molecules etc.). This dissertation includes a series of empirical, theoretical and methodological studies of rhythmic coordination between multiple agents to uncover dynamic principles underlying multiscale coordinative structures. First, a new experimental paradigm was developed for studying coordination at multiple levels of description in intermediate-sized (N = 8) ensembles of humans. Based on this paradigm, coordination dynamics in 15 ensembles was examined experimentally, where the diversity of subjects movement frequency was manipulated to induce di erent grouping behavior. Phase coordination between subjects was found to be metastable with inphase and antiphase tendencies. Higher frequency diversity led to segregation between frequency groups, reduced intragroup coordination, and dispersion of dyadic phase relations (i.e. relations at di erent levels of description). Subsequently, a model was developed, successfully capturing these observations. The model reconciles the Kuramoto and the extended Haken-Kelso-Bunz model (for large- and small-scale coordination respectively) by adding the second-order coupling from the latter to the former. The second order coupling is indispensable in capturing experimental observations and connects behavioral complexity (i.e. multistability) of coordinative structures across scales. Both the experimental and theoretical studies revealed multiagent metastable coordination as a powerful mechanism for generating complex spatiotemporal patterns. Coexistence of multiple phase relations gives rise to many topologically distinct metastable patterns with di erent degrees of complexity. Finally, a new data-analytic tool was developed to quantify complex metastable patterns based on their topological features. The recurrence of topological features revealed important structures and transitions in high-dimensional dynamic patterns that eluded its non-topological counterparts. Taken together, the work has paved the way for a deeper understanding of multiscale coordinative structures. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
462

Choques monetários e cambiais sob regimes de câmbio flutuante nos países membros do Mercosul / Monetary and exchange rate shocks under floating exchange regimes in the Mercosur member countries

Pedro Raffy Vartanian 26 August 2008 (has links)
Esta tese analisa o comportamento das economias dos quatro países membros do Mercosul (Argentina, Brasil, Paraguai e Uruguai) sob o funcionamento de regimes de câmbio flutuante, que substituíram os regimes de câmbio mais rígidos a partir do final da década de 1990. O objetivo consiste em verificar se, sob regimes de câmbio flutuante, há sinais de convergência macroeconômica entre os países do Bloco, por meio da aplicação de um modelo VAR (vetores auto-regressivos) e de testes empíricos complementares. A simulação de choques com o uso de vetores auto-regressivos visou comparar o funcionamento e os efeitos das políticas monetária e cambial dos países por meio das elasticidades entre as variáveis, obtidas nas funções de resposta a impulso, e da participação de cada variável no sistema, analisada pela decomposição da variância dos erros de previsão. Complementarmente, foram executados testes de exogeneidade, com o intuito de se efetuar uma análise comparativa, e de estabilidade, para avaliar a ocorrência de eventuais choques simétricos na região. Os resultados da estimativa e dos testes permitiram demonstrar que não há qualquer indício de convergência macroeconômica entre os países do Mercosul, pois além da elasticidade distinta entre as variáveis estimadas para cada um dos países e das diferenças na classificação da exogeneidade das variáveis, os diferentes períodos de instabilidade indicam assimetria de choques entre os países da região. / This thesis examines the behavior of the economies of the four member countries of Mercosur (Argentina, Brazil, Paraguay and Uruguay) from the operation of floating exchange regimes, which replaced the strictest regimes since the end of the 90s. The goal is to determine if, under floating exchange rate, there are signs of macroeconomic convergence among countries of the bloc, through the application of a VAR (Vector Autoregression) model and complementary empirical tests. The simulation of shock with the use of vector autoregression model intended compare the operation and the effects of monetary and exchange rate policies of the countries through elasticities between variables, which has been obtained in the impulse response functions, and of the participation of each variable in the system, verified by the decomposition of the forecasting errors from the variance. In addition, exogeneity tests were performed, in order to make a comparative analysis, and stability, to evaluate the occurrence of symmetric shocks in the region. The results of estimation and testing enabled to demonstrate that there is no evidence of macroeconomic convergence among the Mercosur countries, because beyond the distinguished elasticity between variables estimated for each of the countries and the differences in classification of variables exogeneity, different periods of instability indicate asymmetry of shocks among countries of the region.
463

Investigation of Secondary Coordination Sphere Effects for Cyanohydrin Hydration with Transition Metal Catalysts

Knapp, Spring Melody, Knapp, Spring Melody January 2012 (has links)
The synthesis of high value acrylic monomers is currently done industrially via cyanohydrin hydration using concentrated acids, resulting in large quantities of useless byproducts. This current process is energy intensive and lacks atom economy; therefore, alternative cyanohydrin hydration strategies are under investigation. Ideally, cyanohydrin hydration would be done using organometallic nitrile hydration catalysts. Cyanohydrin hydration with these catalysts is challenging, because it needs to be done at low temperatures and under acidic conditions to reduce cyanohydrin degradation and catalyst poisoning with cyanide. This dissertation describes the reactivity of [Ru(#951; / 10000-01-01
464

Complexos de níquel (II) com sulfóxidos dialquílicos / Complexes of nickel(II) with dialkilsulfoxides

Oliveira, Denise de 16 August 1985 (has links)
Este trabalho consiste no estudo de complexos de Ni(II) com dialquilsulfóxidos. Os compostos foram sintetizados e caracterizados através de espectroscopia vibracional e eletrônica, medidas magnéticas e de condutância e determinação de ponto de fusão. Obtiveram-se os seguintes complexos: [Ni(R2SO)6](ClO4)2 (R = Me, n-Pr, n-Bu e i-Bu); [Ni (Me2SO)6] (NO3)2; [Ni (Me2SO)4 (NO3)](NO3); [Ni(R2SO)3 (NO3)2] (R = Me2SO, Me2SO-d6, n-Bu e i-Bu) e [Ni(R2SO)2 (N03)2] (R = n-Pr, i-Bu e t-Bu). O método de síntese é crítico para a obtenção de compostos bem definidos, principalmente no caso dos nitratos onde existe a possibilidade de formação de compostos de diferentes estequiometrias para o mesmo sulfóxido. Os complexos [Ni(Me2SO)6] (Cl04)2 e [Ni(Me2SO)4 NO3] NO3 não fundem até 245° C. Os demais fundem em temperaturas relativamente baixas. Alguns complexos de nitrato apresentam grandes intervalos de fusão, que podem ser devidos a perdas de ligante. Os complexos são octaédricos com os sulfôxidos coordenados ao Ni(II) através do átomo de oxigênio, conforme evidenciado por medidas magnéticas e espectroscopia vibracional e eletrônica. A influência doânion é marcante. O grupo perclorato não se coordena ao íon metálico, enquanto que o grupo nitrato pode não se coordenar ou, então, atuar como ligante monodentado ou bidentado, competindo com o sulfóxido na primeira esfera de coordenação do Ni(II). Os complexos contendo perclorato comportam-se como eletrólitos do tipo 1:2 em nitrometano. Os compostos contendo nitrato, ao contrário, comportam-se todos como nao condutores no mesmo solvente, embora os sólidos de Me2SO com proporção molar níquel-sulfóxido 1:6 e 1:4 apresentem nitrato iônico. Isto é uma evidência de que as espécies em solução não são as mesmas presentes nos sólidos. Os espectros eletrônicos confirmam este fato. As diferenças de basicidade e estereoquímica dos sulfóxidos afetam pouco os valores de Dq e B dos complexos contendo perclorato. Portanto, os sulfóxidos di-propílico e di-butílicos estudados ocupam a mesma posição do Me2SO na série espectroquímica e, também, na série nefelauxética. / This work consists on the study of Ni(II) complexes with dialquilsulfoxides. The compounds were synthesized and characterized by vibrational and electronic spectroscopies, magnetic and conductance measurements and melting point determination. The following complexes were obtained: [Ni(R2SO)6](ClO4)2 (R = Me, n-Pr, n-Bu and i-Bu); [Ni (Me2SO)6] (NO3)2; [Ni (Me2SO)4 (NO3)] NO3; [Ni(R2SO)3 (NO3)2] (R = Me2, Me2SO-d6, n-Bu and i-Bu) and [Ni(R2SO)2 (NO3)2] (R = n-Pr, i-Bu and t-Bu). The synthetic procedure is critical for the preparation of well defined compounds, mainly for the nitrates where the possibility of formation of compounds with different stoichiometry for the same sulfoxide exists. The complexes [Ni (Me2SO 6] (ClO4)2 and [Ni (Me2SO)4 NO3] NO3 do not melt up to 245°C, and the others melt at relatively low temperatures. Some nitrate complexes show broad melting point ranges, which may be due to ligand loss during the heating. The complexes are octahedral, and have the sulfoxides coordinated to the Ni(II) through the oxygen atom, as shown by magnetic measurements and the vibrational and electronic spectra. The anion influence is very important. The perchlorate group does not coordinate to the metal ion, while the nitrate group may either be non coordinating or behave as a monodentate or bidentate ligand, competing with the sulfoxide for the first coordination sphere of Ni(II). The perchlorate complexes are l:2 type electrolytes in nitromethane solution. The nitrate complexes, on the other hand, are non conducting in the same solvent, although the solid compounds of Me2SO which have molar Ni: sulfoxide ratios of l:6 and l:4 possess ionic nitrate in their molecules. This is an evidence of the existence of different species in the solid state and in solution in these cases. The electronic spectra confirm this fact. The differences in the basicity and in the stereochemistry of the sulfoxides affect little the Dq and B values in the perchlorate complexes. This implies the di-propyl and di-butylsulfoxide studied fall in the same position as the dimethylsulfoxide in the spectrochemical and nephelauxetic series.
465

Análise da perna dominante do chutar de crianças: condições de bola parada e em movimento / Analysis of the kick dominant leg of children: conditions of stationary and moving ball

Oliveira, Rodrigo Borghi de 04 April 2011 (has links)
A análise do chute através de técnicas biomecânicas pode auxiliar na compreensão do comportamento e organização do sistema motor. Ao identificar a predominância, emergência ou variabilidade de um padrão de movimento, deve-se considerar a interação de elementos internos e externos ao indivíduo, seja o ambiente onde está sendo executada a ação, as características que envolvem a tarefa ou as particularidades do organismo do executante. O objetivo deste trabalho foi analisar e comparar o padrão de movimento e o desempenho da habilidade motora chutar, a um alvo, em duas condições: bola parada e bola em movimento. Com o propósito de detectar a influência da faixa etária na execução desta tarefa, participaram deste estudo 10 crianças divididas em dois grupos: G1 (8 a 9 anos) e o G2 (12 a 13 anos). Cada criança realizou 10 chutes a um alvo em ambas as condições. As tentativas foram capturadas por duas câmeras de alta velocidade e foram obtidos dados referentes ao desempenho, variabilidade, coordenação e amplitude do movimento. A análise estatística detectou ajustes na coordenação e amplitude do movimento além de um aumento da variabilidade na condição da bola em movimento. Em relação à idade, foram encontradas diferenças estatisticamente significantes na velocidade do pé. Os resultados demonstraram que os grupos etários estudados apresentaram ajustes similares na coodenação do movimento. A condição da bola provocou adaptações no padrão de movimento, entretanto, apesar do aumento nos níveis de variabilidade, não exerceu influência no desempenho do chutar / The analysis of kicking through biomechanics techniques can help the comprehension of behavior and motor system organization. In order to identify the predominance, emergence, or variability of a moving pattern, is imperative to consider the interactions between internal and external elements to the individual, such as the environment where the action is executed, characteristics that are intrinsic to the task or any individual particularity. The aim of the present work was to analyze and compare the performance and movement pattern of the kick realized by children to a target, in two different conditions: stationary and moving ball. To enable us to detect the age influence on the execution of the given task, the experimental group comprised 10 children from different ages: group 1 (G1) children from 8 to 9 years old and group 2 (G2) children from 12 to 13 years old. Each participant performed 10 kicks to the target in both conditions. Attempts were captured by two high speed cameras and were obtained data to analyze performance, variability, coordination and range of motion. Statistical analysis showed adjustments in coordination and range of motion, besides an increase of variability in the condition of moving ball in relation to the stationary ball condition. Regarding the age, it was found differences statistically significant only in the foot velocity. The results showed that the age groups studied had similar adjustments in movement coordination. The moving ball condition led to adjustments in the movement pattern, however, despite the increase in the variability, the performance was not different in relation to the stationary ball condition
466

Multinuclear silver-ethynide supramolecular synthons for the construction of coordination networks. / CUHK electronic theses & dissertations collection

January 2007 (has links)
Incorporation of heteroaromatic rings (pyridyl, pyrazinyl, pyrimidyl and thienyl) in the silver-ethynide supramolecular synthon led to a series of silver(I) double salts of various heterocyclic ethynide ligands. Through variation of the relative orientations between the ethynide moiety and heteroatom as well as between heteroatoms, different coordination networks were generated. / Synthetic and structural studies were carried out on a series of silver(I) complexes of phenylethynide and phenylethynide derivatives with alkyl substituents (methyl, tert- butyl, trifluoromethyl) at variable positions (p-, m-, o-) on the aromatic ring. The invariable appearance of the mu4- and mu5-ligation modes of the ethynide moiety in ten silver(I) complexes reaffirms the general utility of the silver-arylethynide supramolecular synthon Ar-C≡C⊃Agn( n = 4, 5) in coordination network assembly. / Systematic investigation on silver(I) tert-butylethynide complexes resulted in the establishment of the general utility of the silver-ethynide supramolecular synthon with an alkyl tail. Upon the addition of nitrile ligands from CH3CN, CH3CH2CN to (CH3) 3CCN, adjacent silver ethynide moieties tBu-C≡C⊃Ag 5 approach closer to each other, and the resulting crystal structure transforms from a 2-D hydrogen bonding network, through a 2-D network held by hydrogen bonding and coordination, to a 2-D coordination network. Employment of the multidentate dicarboxylate ligand O2CCF2CF 2CO2 and the dinitrile ligand NC(CH2)4CN led to the formation of higher-dimensional networks. / The above-mentioned structural studies of silver-ethynide complexes of aromatic or heteroaromatic ligands indicate that pi-pi stacking plays a pivotal role in the self-assembly of corresponding silver-ethynide synthons. Investigation of the silver(I) complexes of phenylethynide and its derivatives with different substituents (methyl, tert- butyl) in variable positions (o-, m-, p-) on the aromatic ring shows the relative position and the bulk of substituents both affect the pi-pi stacking between adjacent phenyl rings. Furthermore, a comparative study of pi-pi stacking in the nitrate complexes Ag2(m-C≡CC 6H4C≡C)] · 5AgNO3 · 3H 2O (38), [(3-AgC≡C)-py] · 3AgNO3 (45), 2[(2-AgC≡C)-pyraz] · 6AgNO3 3H 2O (50) and 2[2,3-(AgC≡C)2-thienyl] · 10AgNO3 (56) suggests that the pi-electron deficiency of the aromatic ring also weakens this non-covalent interaction. (Abstract shortened by UMI.) / The ensuing study of silver(I) phenylenediethynide complexes led to the recognition of another kind of supramolecular synthon, Agn⊂ C2---R---C2⊃Agn (R= p-, m-, o-C6H4; n = 4, 5). / The reaction of Li-C≡C-Ca≡C-Li (generated in situ from hexachloro-1,3-butadiene and nBuLi) with AgNO3 led to the generation of a new silver carbide, silver 1,3-butadiynediide (Ag2C4). A series of fifteen double and multiple salts of Ag2C4 were synthesized by dissolving this polymeric starting material Ag2C4 in a concentrated aqueous solution of soluble silver salts (e.g. AgNO3, AgCF 3CO2, AgC2F5CO2). The silver-ethynide interaction may be conceived as a new kind of supramolecular synthon for the construction of 1-D, 2-D and 3-D coordination polymers. The terminal silver-ethynide interactions that are assigned in diverse configurations can be conveniently classified into three types: sigma, pi and mixed (sigma,pi), and tuned by variation of ancillary anionic ligands. In addition, the controlled hydrolysis of hexafluorophosphate led to the generation of the second silver quadruple salt Ag2C4 · 4AgNO3 · AgPF 2O2 · Ag3PO4 (4). The (F)2(H2O)18 fluoride-water tape in Ag 2C4 · 2AgF · 10AgC2F5CO 2 · CH3CN · 12H2O (10) and the (C4)3 Ag18 aggregate in 3Ag 2C4 · 12AgC2F5CO2 · 5[BzMe3N)C2F5CO2] · 4H 2O (15) are both unprecedented among silver(I)complexes. / This thesis describes our effort to explore, develop and utilize the silver-ethynide interaction in new kinds of metal-ligand supramolecular synthons for the construction of silver(I) coordination networks. / Zhao, Liang. / Adviser: Thomas C. W. Mak. / Includes supplementary digital materials. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1011. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 208-228). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
467

Group 4 transition-metal and lanthanide complexes supported by bulky amino ligands. / CUHK electronic theses & dissertations collection

January 2011 (has links)
Ku, Ka Wai. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
468

Synthesis and structural studies of some metal complexes of betaines.

January 1992 (has links)
by Xiao-Ming Chen. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 127-135). / Acknowledgements / Abstract --- p.i / Nomenclature --- p.ii / Table of Contents --- p.iii / List of Tables --- p.iv-v / List of Figures --- p.v-vii / Chapter 1. --- Introduction --- p.1-9 / Chapter 2. --- Results and Discussion --- p.10-104 / Chapter 1. --- Betaine derivatives --- p.10-19 / Chapter 2. --- "Complexes of manganese(II), cobalt(II), and nickel(II)" --- p.20-31 / Chapter 3. --- Complexes of zinc(II) --- p.32-40 / Chapter 4. --- Complexes of cadmium(II) and mercury(II) --- p.41-56 / Chapter 5. --- Complexes of silver(I) --- p.57-76 / Chapter 6. --- Complexes of copper(II) --- p.77-97 / Chapter 7. --- Mixed-metal complexes --- p.98-104 / Chapter 3. --- Conclusions --- p.105-106 / Chapter 4. --- Experimental --- p.107-126 / Chapter 5. --- References --- p.127-135 / Chapter 6. --- Appendix A --- p.136-151 / Chapter 1. --- Atomic coordinates and equivalent isotropic thermal parameters --- p.136-144 / Chapter 2. --- Anisotropic thermal parameters --- p.145-151 / Chapter 7. --- Appendix B (in a separated volume to be kept as Supplementary Data in the Department of Chemistry) Tables of structure factors
469

Síntese, caracterização e aplicação de polímeros de coordenação em fotocatálise heterogênea / Synthesis, characterization and application of coordination polymers in heterogeneous photocatalysis

Bruno Manduca 27 September 2018 (has links)
Este trabalho descreve a síntese e caracterização de polímeros de coordenação (PC) e sua aplicação como fotocatalisadores heterogêneos ativos sob a radiação visível, visando a degradação de compostos orgânicos em água. Problemas ambientais têm ocupado posição de destaque na sociedade contemporânea. Dentre eles, o uso de combustíveis fósseis e a remoção de compostos poluentes do meio ambiente têm merecido especial atenção. Uma das alternativas mais indicadas como substituinte dos combustíveis fósseis é a energia solar, por ser limpa, renovável e presente em todo o planeta. O estudo de materiais fotoativos é essencial para aproveitar ao máximo essa fonte. A fotocatálise é um processo que utiliza a energia luminosa para realizar reações químicas. Os PC têm mostrado ótimos resultados na área. Esses são compostos poliméricos cujos monômeros são unidades de coordenação. Neste trabalho foram sintetizados PC formados por diferentes metais de transição e ligantes orgânicos. Dentre eles destacam-se níquel e benzenodicarboxilato (Ni-BDC). Os materiais foram caracterizados por FTIR, DRX, adsorção-dessorção de N2, DRS, TGA, MEV e ICP-OES. Os resultados sugerem a formação de PC inéditos, dotados de sítios de coordenação insaturados, com boa estabilidade térmica, porém com estabilidade em meio aquoso inferior. O ensaio de degradação fotocatalítica de corante evidencia que os materiais são fotoativos na luz visível, apesar da descoloração não ser completa. Este resultado é interessante, pois polímeros de coordenação de níquel ainda são pouco estudados como fotocatalisadores, e esse é um metal barato e abundante. / This work describes the synthesis and characterization of coordination polymers (CP) and their application as heterogeneous photocatalysts, under visible radiation, in degradation of organic compounds in water. Environmental issues have taken prominent position in contemporary society. Among them, fossil fuel usage and removal of hazardous compounds deserve special attention. One of the best alternatives to replace fossil fuels is the solar power, which is clean, renewable and ubiquitous throughout the planet. Research on photoactive materials is essential to improve this energy source use. Heterogeneous photocatalysis process uses light energy to induce chemical reactions. CP are exhibiting remarkable results in the field. These are polymeric compounds with coordination units as monomers. In the present work, CP based on different transition metals and organic ligands were synthesized, such as nickel benzenedicarboxylate (Ni-BDC). The materials were characterized by FTIR, XRD, N2 adsorption-desorption, DRS, TGA, SEM and ICPOES. The results suggest the formation of novel CP, endowed with unsaturated metal sites and good thermal stability, however with low stability in aqueous medium. The photocatalytic dye degradation experiments indicate the materials are photoactive under visible light, although the discoloration was not complete. This is an interesting result, considering that the research on nickel coordination polymers as photocatalysts is still scarce.
470

Supramolecular assembly of multinuclear silver(I) complexes containing ethynediide, 1,3-butadiyne-1,4-diide or 1,5-hexadiyne-1,6-diide. / CUHK electronic theses & dissertations collection

January 2013 (has links)
Hu, Ting. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 185-198). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

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