<p> This thesis is concerned with the existence of cyclic block designs with parameters (b, v, r, k, λ) where λ = 1 , r = 2k and 3 ≤ k ≤ 6.</p> <p> It gives the proofs of the non-existence of cyclic block designs with k = 6, λ = 1 and r = 9, 10 and 12.</p> / Thesis / Master of Science (MSc)

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In this dissertation we present new results regarding optimality of block designs with limited resources. The dissertation is organized as follows. The first chapter outlines the theory of optimal block design. The second chapter shows new work in optimal minimally connected block designs with spatial correlation structure. The third chapter details the discovery of the optimal incomplete designs with two blocks. The fourth chapter does the same for the optimal binary incomplete designs with three blocks. The fifth chapter summarizes the techniques used and new results found and lists possible future research topics. / Ph. D.

Nitrile containing siloxane block copolymers were developed as stabilizers for siloxane magnetic fluids. The siloxane magnetic fluids have been recently proposed as internal tamponades for retinal detachment surgery. PDMS-b-PCPMS-b-PDMSs (PDMS = polydimethylsiloxane, PCPMS = poly(3-cyanopropylmethylsiloxane) were successfully prepared through kinetically controlled polymerization of hexamethylcyclotrisiloxane initiated by lithium silanolate endcapped PCPMS macroinitiators. The macroinitiators were prepared by equilibrating mixtures of 3- cyanopropylmethylcyclosiloxanes (DxCN) and dilithium diphenylsilanediolate (DLDPS). DxCNs were synthesized by hydrolysis of 3-cyanopropylmethyldichlorosilane, followed by cyclization and equilibration of the resultant hydrolysates. DLDPS was prepared by deprotonation of diphenylsilanediol with diphenylmethyllithium. It was found that mixtures of DxCN and DLDPS could be equilibrated at 100°C within 5-10 hours. By controlling the DxCN-to-DLDPS ratio, macroinitiators of different molecular weights could be obtained. The major cyclics in the macroinitiator equilibrate are tetramer (8.6 ± 0.7 wt%), pentamer (6.3 ± 0.8 wt%) and hexamer (2.1 ± 0.5 wt%). 2.5k-2.5k-2.5k, 4k-4k-4k, and 8k-8k-8k triblock copolymers were prepared and characterized. These triblock copolymers are transparent, microphase separated and highly viscous liquids. It was found that these triblock copolymers can stabilize nanometer gamma-Fe₂O₃ and cobalt particles in octamethylcyclotetrasiloxane or hexane. Hence PDMS-b-PCPMS -b-PDMSs represent a class of promising steric stabilizers for silicone magnetic fluids. / Master of Science

O presente trabalho é um estudo teórico e principalmente experimental sobre paredes de alvenaria de blocos cerâmicos. Inicialmente, estão apresentados alguns fatores que contribuem na resistência à compressão da alvenaria, mecanismos de ruína e prescrições para dimensionamento à compressão segundo algumas normas mais utilizadas. Em seguida, é apresentada uma compilação de vários resultados de ensaios à compressão de paredes de alvenaria estrutural de blocos cerâmicos realizados em diversos centros de pesquisa no Brasil. Depois, são apresentados procedimentos e resultados de diversos ensaios com unidades, prismas e paredes de alvenaria estrutural de blocos cerâmicos, com e sem graute. Todos esses ensaios foram realizados especialmente durante este trabalho de pesquisa com o intuito de confirmar e ampliar os conhecimentos adquiridos com a compilação de resultados anteriormente mencionada. Por fim, foram modeladas, numericamente, paredes com e sem graute visando, principalmente, obter-se informações sobre as melhores opções para a discretização de estruturas desse tipo. / This work deals with a theoretical and experimental study about clay masonry walls under compression. First, main factors that may cause influence on compressive capacity of walls, failure mechanisms and main codes used in Brazil are presented in order to discuss theoretical aspects of the phenomenon. After that, several experimental results obtained from many different researchers in Brazil, including results obtained for grouted walls by this work, are shown. These results are presented in order to obtain an overview about compressive strength of clay masonry walls with and without grout. So, important relationships among units, prisms and walls are established. Finally, the work presents some numerical models for walls with and without grout.

O presente trabalho é um estudo teórico e principalmente experimental sobre paredes de alvenaria de blocos cerâmicos. Inicialmente, estão apresentados alguns fatores que contribuem na resistência à compressão da alvenaria, mecanismos de ruína e prescrições para dimensionamento à compressão segundo algumas normas mais utilizadas. Em seguida, é apresentada uma compilação de vários resultados de ensaios à compressão de paredes de alvenaria estrutural de blocos cerâmicos realizados em diversos centros de pesquisa no Brasil. Depois, são apresentados procedimentos e resultados de diversos ensaios com unidades, prismas e paredes de alvenaria estrutural de blocos cerâmicos, com e sem graute. Todos esses ensaios foram realizados especialmente durante este trabalho de pesquisa com o intuito de confirmar e ampliar os conhecimentos adquiridos com a compilação de resultados anteriormente mencionada. Por fim, foram modeladas, numericamente, paredes com e sem graute visando, principalmente, obter-se informações sobre as melhores opções para a discretização de estruturas desse tipo. / This work deals with a theoretical and experimental study about clay masonry walls under compression. First, main factors that may cause influence on compressive capacity of walls, failure mechanisms and main codes used in Brazil are presented in order to discuss theoretical aspects of the phenomenon. After that, several experimental results obtained from many different researchers in Brazil, including results obtained for grouted walls by this work, are shown. These results are presented in order to obtain an overview about compressive strength of clay masonry walls with and without grout. So, important relationships among units, prisms and walls are established. Finally, the work presents some numerical models for walls with and without grout.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

When a vehicle enters an intersection with insufficient space to exit on the opposite side the result is often the obstruction of pedestrians and other vehicles, this phenomenon is usually referred to as "blocking the box." The purpose of this study was to determine different characteristics of blocking that might be considered in determining the installment of a "Don't Block the Box" (DBTB) campaign. This study identified potentially problematic intersections in Atlanta, Georgia and collected information, such as the number of vehicles that block the intersection (box junction), the amount of green time with blocking, and the percentages in which approaches were blocked. Based on the results it was found the characteristics of the number of blockers, percentage of green time with blocking, and the percentage of lost capacity are excellent indicators for a possible DBTB campaign. Organizations interested in potentially starting a DBTB should consider these characteristics part of the determination of suitability of DBTB for an intersection. Within this study is was found that the intersections of Peachtree Road & Highland Drive, Peachtree Road & Stratford Road, Peachtree Road & Lenox Mall Entrance, and 10th Street & Williams Street showed to be potential candidates for a DBTB campaign in Atlanta, Georgia. During the study period these intersections had high percentages of lost capacity, high number of blocks, and high percentages of green time with blocking. In conjunction with the DBTB data analysis a "DBTB survey" was developed. The objective of this survey was to help gain a better understanding of the current trends in DBTB campaigns around the United States. The "DBTB Survey" received 75 responses from 415 organizations around the nation, a 18.1% response rate. Six (60%) of the ten participants that currently have a DBTB campaign found a sufficient level of improvement in traffic operations and 46 of the total respondents (60%) proclaimed that if DBTB campaigns were shown to be an economical alternative for traffic management they would consider starting one to help congestion and safety.