Thesis (M.B.A.)--Boston University

This PhD project investigated the effects of a co-continuous phase structure on the ductility of poly(lactic acid) (PLA) blends. An empirical model was used to predict the phase inversion point of the blends. The co-continuous phase morphology was first observed in polybutylene succinate(PBS)/PLA blends. With as little as 10 wt% of PBS, PBS/PLA blends achieved a dramatic improvement in ductility, over 250% elongation-to-break. Clay additives were incorporated in PBS/PLA blends. Clay was found out to affect the compatibility and co-continuous phase morphology of PBS/PLA blends. The clay dispersion was found to have an intercalated and exfoliated structure at a PBS/PLA composition ratio of 20/80. The clay particles increased the mixing conditions between the polymers by producing a finer structure, but also destroyed the co-continuous phase morphology, resulting in a substantial decrease in elongation-at-break. PLA was then blended with Poly(butylene adipate-co-terephthalate) (PBAT) to examine whether the co-continuous phase model could also be applied to other PLA-polymer blends. From the melt viscosity ratio of PLA and PBAT in the processing regime used in the study, the predicted phase inversion value was 19 wt% of PBAT. This value was verified by the results of mechanical properties, where results for elongation-to-break show a dramatic rise from around 10% up to 300% in the composition range between 10 and 20wt% of PBAT. Polyhydroxyalkanoate (PHA) was also blended with PLA and this project investigated how co-continuous phase morphology affects the blends of two brittle polymers. It was found that when PHA content ranged from 10 to 20wt%, the brittle-brittle polymer blends showed ductile behaviour due to a plane stress effect.

In this paper, we show that a pointwise λ -symmetric λ -isotonic λ -closure function is uniquely determined by the pairs of sets it separates. We then show that when the λ -closure function of the domain is λ -isotonic and the λ -closure function of the codomain is λ -isotonic and pointwise- λ -symmetric, functions which separate only those pairs of sets which are already separated are λ -continuous.

Quick feedback in regards to build times is important in Continuous Integration. If builds become too long, it can hurt the rate of software development. There are multiple methods to reduce build times. One commonly suggested method is to parallelize builds. This thesis aims to investigate the effects of parallelizing builds in Continuous Integration software and provide support for whether parallelizing is a good way of reducing build times or not. We conducted an experiment consisting of running tests on different Continuous Integration software with different configurations. These configurations changed how many tests were executed and how many parallel build agents were used. The aspects that were observed and analyzed was how build time, average CPU usage and CPU time were affected. What we found was that parallelizing a Continuous Integration build drastically improves build time, while RAM usage and CPU time remains similar. This entails that there are no major consequences to parallelizing other than utilizing more threads and therefore using more of the available CPU resources.

Dans le but d’améliorer le rendement des propulseurs aérospatiaux, on s’intéresse à l’utilisation de ladétonation dans le cycle moteur. Cette thèse porte sur le développement et l’utilisation d’un codepour la compréhension du fonctionnement d’un moteur à détonation continue (CDWE). Le 1erchapitre place le cadre de l’étude, et positionne le CDWE par rapport à différents concepts demoteurs à détonation. Un état des lieux des simulations numériques concernant le fonctionnementd’un CDWE est établi afin de justifier l’approche numérique à utiliser. Cette approche numérique estdétaillée dans le 2e chapitre. Les équations d’Euler, les modèles thermochimiques, ainsi que lesschémas cinétiques utilisés dans cette étude y sont présentés. Le 3e chapitre décrit les méthodesnumériques implémentées dans le code. Le schéma WENO d’ordre 5 est utilisé pour l’évaluation desflux numériques. L’avancement temporel est assuré par le schéma semi-implicite d’ordre 2 ASIRK2Cou explicite d’ordre 3 RK3. Le 4e chapitre est consacré à la technique de raffinement adaptatif demaillage (AMR) et à la bibliothèque choisie. Le code est testé dans le 5e chapitre sur différents cas etappliqué à la simulation d’une onde de détonation afin de préparer les simulations présentées dans ledernier chapitre. Le 6e chapitre présente les résultats des simulations d’un CDWE. La structure 2Dd’une onde de détonation continue est présentée et comparée avec la structure 3D. L’influence durayon de courbure du canal et l’effet d’une injection par une fente sur la structure de l’écoulementsont étudiés. / In order to improve the performance of aerospace propulsion systems, it is interesting to use detonation in the engine cycle. This thesis focuses on the development and use of a code for understanding the operation of a continuous detonation wave engine (CDWE). The first chapter establishes the framework of the study and compares the CDWE with different concepts of detonation engines. An overview of numerical simulations concerning the operation of a CDWE is made to justify the numerical approach to use. This numerical approach is detailed in the second chapter. The Euler equations, thermochemical models and kinetic mechanisms used in this study are presented. The third chapter describes the numerical methods implemented in the code. The 5th order WENO scheme is used for the evaluation of numerical fluxes. The time-stepping is provided by the 2nd order semi-implicit ASIRK2C scheme or the 3rd order explicit RK3 scheme. The fourth chapter describes the technique of adaptive mesh refinement (AMR) and the selected library. The code is tested in the fifth chapter on different cases and applied to the simulation of a detonation wave in order to prepare the simulations presented in the last chapter. The sixth chapter presents the results of simulations of a CDWE. The 2D structure of a continuous detonation wave is presented and compared with the 3D structure. The influence of the radius of the curvature of the duct and the effect of a slot injection on the structure of the flowfield are discussed.

Esse trabalho tem dois objetivos principais: o primeiro deles consiste em apresentar o estado da arte sobre processos de otimização combinatorial dando uma ênfase especial ao método Simulated Annealing (SA). São apresentados seu histórico, funcionalidades, algoritmo genérico e propostas de paralelização presentes na literatura. Além disso, é apresentado o algoritmo de geração de redes aleatórias contínuas, algoritmo, esse, projetado por pesquisadores do Instituto de Física da UFRGS que utiliza o método SA para gerar redes que atendam certas restrições. O segundo objetivo consiste empropor a paralelização desse algoritmo visando diminuir significativamente o tempo de geração de cada rede, que com o algoritmo seqüencial chega a demorar mais de um mês. Nessa etapa foi utilizada uma adaptação de um dos métodos propostos pela literatura juntamente com a técnica de divisão de domínio. Os resultados obtidos mostraram-se satisfatórios tanto em relação à qualidade numérica quanto à diminuição do tempo de processamento. Além disso, discute-se no trabalho a genericidade da proposta de paralelização a outros problemas baseados em SA. / This work has two main goals: the first one is to present the state of the art on combinatorial optimization processes, with a special emphasis to the Simulated Annealing (SA) method. The work presents its history, features, generic algorithm and proposed parallelization present in the literature. Moreover, the algorithm to generate random networks continued is presented. This algorithm was designed by researchers of the UFRGS Physics Institute and it uses the SA method. The second goal of this work is to propose a parallelization for this algorithm in order to decrease significantly the generation time of each network, that with the sequential algorithm reaches more than months. To do that was used an adaptation of one of the methods proposed by literature together with the domain partitioning technical. The results were satisfactory in terms of the numerical quality and in the decrease of the processing time. In addition, this work discusses the genericity of the proposed parallelization to other problems based on SA.

The present thesis investigates the role of the prefrontal cortex and cholinergic modulation in attentional performance, and to a lesser extent, inhibitory response control, in rats. A greater understanding of these functions is important for the effective treatment of attentional and impulsive control deficits, present in a range of neuropsychiatric disorders. For this field to progress, the assessment of attentional performance in a similar manner across humans and animals is crucial. In the present thesis, attentional performance was assessed on the novel, touchscreen-based rodent continuous performance task (rCPT), which assesses sustained, focused attention in essentially an identical manner to CPTs commonly used in the clinic. Findings were compared to performance on the well-characterised 5-choice serial reaction time task (5-CSRTT), which assesses sustained, spatial divided attention and shares some, but not all characteristics of CPTs. The series of experiments described in this thesis contributes to the understanding of the role of the prefrontal cortex and cholinergic modulation in attentional performance; they also highlight differences between the two tasks in behaviour, brain functions and networks. Excitotoxic lesions of the medial prefrontal cortex (mPFC) and a range of cholinergic systemic pharmacology validated the role of the prefrontal cortex and cholinergic modulation in rCPT performance. A chemogenetic study also validated the role of the ascending cholinergic basal forebrain system in 5-CSRTT performance. These findings support 1. the idea of the relationship between cholinergic system activation and attentional performance to resemble an ‘inverted-U’ shaped function; 2. a double dissociation of mPFC sub-regions on attentional performance, in which the prelimbic cortex (PL) appears to play a role in rCPT performance, compared with a role of the anterior cingulate cortex (ACC) in 5-CSRTT performance; and 3. a role of ascending cholinergic projections from the basal forebrain to the ACC in 5-CSRTT performance. These findings also establish the development of a successful flanker distractor probe in rodents on the rCPT. This thesis concludes with an important comparison of the attentional and impulsivity measures in the rCPT compared to the 5-CSRTT, to help provide guidelines as to which task is most appropriate to use for particular research questions.

Made available in DSpace on 2014-06-11T19:25:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-09-30Bitstream added on 2014-06-13T20:53:51Z : No. of bitstreams: 1 yamashiro_crc_me_prud.pdf: 1060756 bytes, checksum: ed76459d0c9b7161520ddd1d87586b66 (MD5) / Secretaria Estadual de Educação / Este trabalho está vinculado à linha de pesquisa Políticas Públicas, Organização Escolar e Formação de Professores e tem como preocupação, investigar sobre as ações de formação contínua de professores e as necessidades formativas docentes, elementos importantes para a construção de uma identidade profissional crítica e reflexiva. O problema em pauta nesta pesquisa é como contemplar as necessidades formativas docentes nos projetos de formação contínua de professores, tendo em vista a importância da função docente na construção de uma sociedade mais justa e democrática. Esta pesquisa pretende, então, responder o seguinte questionamento: quais são as necessidades formativas dos professores estaduais, do ciclo I do Ensino Fundamental, do município de Presidente Prudente, quando levamos em consideração os outros aspectos envolvidos no desenvolvimento profissional docente, além da formação técnica-pedagógica, isto é: as suas condições sócio-econômicas, a sua formação profissional, as suas condições de trabalho e as suas expectativas sobre a função docente e a formação contínua... / This work is related to the research area “Public Policies, School Organization and Teachers’ Training”. Its aim is to perform research about teachers’ continuous training projects and teachers’ training needs. Those are very important elements in the construction of a critical and thoughtful teaching. The aim of this work is to study how to incorporate the teachers´ training needs in the projects of teachers´ continuous education taking into account the important role that teaching has in the construction of a fairer and democratic society. This research intends to answer the following question. Taking into account aspects, other than the technical-pedagogic, that take part in the teachers´ professional development, i.e., taking into account the teachers’ social-economic situation, their professional training and work conditions as well as their expectations about teaching and continuous training, what are the training needs of the teachers of the so-called “Ciclo I” (First Stage) of teaching in state schools in the city of Presidente Prudente, São Paulo state, Brazil. Therefore, this work has as its general aim. Therefore, this research has as its general aim to provide some contribution to the area of teachers’ continuous training through the analysis of the teachers’ training needs. As its more... (Complete abstract click electronic access below)

Esse trabalho tem dois objetivos principais: o primeiro deles consiste em apresentar o estado da arte sobre processos de otimização combinatorial dando uma ênfase especial ao método Simulated Annealing (SA). São apresentados seu histórico, funcionalidades, algoritmo genérico e propostas de paralelização presentes na literatura. Além disso, é apresentado o algoritmo de geração de redes aleatórias contínuas, algoritmo, esse, projetado por pesquisadores do Instituto de Física da UFRGS que utiliza o método SA para gerar redes que atendam certas restrições. O segundo objetivo consiste empropor a paralelização desse algoritmo visando diminuir significativamente o tempo de geração de cada rede, que com o algoritmo seqüencial chega a demorar mais de um mês. Nessa etapa foi utilizada uma adaptação de um dos métodos propostos pela literatura juntamente com a técnica de divisão de domínio. Os resultados obtidos mostraram-se satisfatórios tanto em relação à qualidade numérica quanto à diminuição do tempo de processamento. Além disso, discute-se no trabalho a genericidade da proposta de paralelização a outros problemas baseados em SA. / This work has two main goals: the first one is to present the state of the art on combinatorial optimization processes, with a special emphasis to the Simulated Annealing (SA) method. The work presents its history, features, generic algorithm and proposed parallelization present in the literature. Moreover, the algorithm to generate random networks continued is presented. This algorithm was designed by researchers of the UFRGS Physics Institute and it uses the SA method. The second goal of this work is to propose a parallelization for this algorithm in order to decrease significantly the generation time of each network, that with the sequential algorithm reaches more than months. To do that was used an adaptation of one of the methods proposed by literature together with the domain partitioning technical. The results were satisfactory in terms of the numerical quality and in the decrease of the processing time. In addition, this work discusses the genericity of the proposed parallelization to other problems based on SA.

abstract: In this thesis, the author described a new genetic algorithm based on the idea: the better design could be found at the neighbor of the current best design. The details of the new genetic algorithm are described, including the rebuilding process from Micro-genetic algorithm and the different crossover and mutation formation. Some popular examples, including two variable function optimization and simple truss models are used to test this algorithm. In these study, the new genetic algorithm is proved able to find the optimized results like other algorithms. Besides, the author also tried to build one more complex truss model. After tests, the new genetic algorithm can produce a good and reasonable optimized result. Form the results, the rebuilding, crossover and mutation can the jobs as designed. At last, the author also discussed two possible points to improve this new genetic algorithm: the population size and the algorithm flexibility. The simple result of 2D finite element optimization showed that the effectiveness could be better, with the improvement of these two points. / Dissertation/Thesis / Masters Thesis Civil and Environmental Engineering 2015