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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.
471

A influência da ventilação no molde da prótese auditiva retro-auricular para o controle do zumbido: ensaio clínico randomizado cego crossover / The influence of the BTE hearing aid earmold ventilation on tinnitus control: randomized crossover blind clinical trial

Santos, Gisele Munhoes dos 10 August 2005 (has links)
Introdução: Muitos pacientes com zumbido também apresentam algum grau de perda auditiva associada e o uso de próteses auditivas pode ser uma boa opção para melhorar ambos os sintomas. Porém, na prática clínica, a oclusão do meato acústico externo pelo molde da prótese auditiva pode até piorar o zumbido em alguns casos. A literatura apresenta poucos estudos sobre a real influência da ventilação do molde da prótese auditiva na percepção do zumbido. Objetivo: avaliar a resposta do zumbido à prótese auditiva retro-auricular com dois tipos de ventilação no molde (molde aberto e ventilação de alívio) em pacientes com perda auditiva neurossensorial simétrica após um mês de uso. Métodos: 50 pacientes atendidos no Grupo de Pesquisa em Zumbido com zumbido bilateral e perda auditiva neurossensorial simétrica de grau leve a severo foram submetidos a um ensaio clínico randomizado cego crossover. Destes, 26 pacientes iniciaram o ensaio utilizando próteses auditivas com molde aberto (ventilação de 4mm) e 24 iniciaram usando molde com ventilação de alívio (ventilação de 1mm). Após 30 dias de teste com o primeiro tipo de molde e um período de wash-out (15 dias), o tipo de molde foi trocado e o segundo molde foi usado por mais 30 dias. O zumbido foi avaliado de modo qualitativo (classificado em melhora, inalterado e piora) e quantitativo (variação de 0 a 10 de uma escala numérica). Resultados: A melhora do zumbido foi observada em 82% dos casos com pelo menos um tipo de molde e não houve diferença significante na diminuição do incômodo com o zumbido nas avaliações qualitativa e quantitativa com ambos os moldes. Apesar disto, 66% dos pacientes preferiram o molde aberto. Conclusão: A curto prazo, a melhora do zumbido por meio da prótese auditiva em pacientes com perda auditiva neurossensorial simétrica de grau leve a severo não depende do tamanho da ventilação do molde auricular / Introduction: Most tinnitus patients also have some degree of associated hearing loss, and the use of hearing aids is an option to improve both symptoms. In daily practice, the occlusion of the external meatus by the earmold during hearing aids fitting may enhance the tinnitus perception. However, the literature lacks studies about the real influence of the earmold ventilation on tinnitus perception. Objective: to evaluate the tinnitus response to the BTE hearing aids using two types of ventilation (open mold and relief ventilation) in patients with symmetric sensorineural hearing loss after one month usage. Methods: 50 patients attended in our Tinnitus Clinic who presented bilateral tinnitus and mild to severe symmetric sensorineural hearing loss underwent a randomized blind crossover clinical trial. Among them, 26 first used BTE hearing aids with open molds (4mm ventilation) and 24 first used hearing aids with relief ventilation mold (1mm ventilation). After 30 days using the first mold and a 15-day wash-out period, the type of earmold was changed in a crossover way and the second mold was used for another 30-day-period. Tinnitus evaluation was performed by a qualitative way (classified in improvement, unchanged and worsening) and by a quantitative way (variation of a numeric scale from 0 to 10). Results: Tinnitus improvement was observed by 82% of the patients with at least one type of earmold and there was no significant difference in the decrease of tinnitus discomfort by both, quantitative and qualitative evaluation. Despite the similar tinnitus control, 66% of the patients preferred to acquire the hearing aids with open mold. Conclusion: In a short-term evaluation, the tinnitus improvement by the use of hearing aids in patients with mild to severe symmetric sensorineural hearing loss does not depend on the size of earmold ventilation
472

Nanoestruturas bimetálicas e ocas: controlando forma, composição, e estrutura para aplicações em catálise / Bimetalli and hollew nanostructures: controlling shape, composition, and structure for catalytic applications

Wendler, Alexandra Macedo 09 September 2016 (has links)
Essa tese visa o desenvolvimento de metodologias simples, eficazes, versáteis e ambientalmente amigáveis para se obter nanomateriais metálicos com controle fino sobre sua forma, composição e estrutura (interior sólido ou vazio) para aplicações em catálise. Em especial, temos interesse no desenvolvimento de nanoestruturas ocas esféricas (nanocascas) compostas por prata-ouro (AgAu), prata-paládio (AgPd) e prata platina (AgPt). Essas nanocascas foram obtidas através da reação de substituição galvânica entre esferas de Ag e íons AuCl4-, PdCl42- ou PtCl62-, respectivamente. Como a reação de substituição galvânica permite não apenas o controle sobre a composição destes sistemas, mas também a obtenção de interiores vazios, esta estratégia representa uma alternativa promissora para a obtenção de nanomateriais apresentando características controláveis e atrativas para aplicações catalíticas. Diante dessas qualidades, esse projeto focou em aplicações para reações orgânicas de redução e acoplamento. Foi realizada uma investigação, de maneira sistemática, como a estrutura e composição dos nanomateriais metálicos produzidos influenciam a sua atividade catalítica, mostando que as atividades foram fortemente dependentes da composição e estrutura, abrindo a possibilidade para o planejamento de nanocatalisadores com atividades catalíticas controladas para uma transformação de interesse. / This thesis aims at developing facile, efficient, versatile, and environmentally friendly methodologies to obtain metallic nanomaterials with controlled shapes, compositions and structure (solid or hollow interiors) for applications in catalysis. In particular, we focused on hollow nanospheres (nanoshells) composed of silver-gold (AgAu), silver-palladium (AgPd), and silver-platinum (AgPt). These nanoshells were obtained by galvanic replacement reaction between Ag nanosphere and AuCl4-, PdCl42- or PtCl62-, respectively. The galvanic replacement reaction not only allows control over the composition of these systems, but also to obtain hollow interiors. Therefore, this strategy is a very promising alternative for obtaining nanomaterials with controllable features attractive for catalytic applications. In this case, we investigated applications towards reduction and coupling transformations. A systematic investigation was carried out regarding how the structures and compositions of the produced nanoshells influenced their catalytic performance. Our results showed that the activities were strongly dependent on the composition and structure, opening a range of possibility for designing nanocatalysts with desired catalytic activities for a target transformation.
473

Efeito do conhecimento de performance autocontrolado na aquisição de uma habilidade motora em idosos / Effect of self-controlled knowledge performance in the acquisition of a motor skill in the elderly

Nunes, Marcelo Eduardo de Souza 20 March 2015 (has links)
O uso do feedback extrínseco ao longo do processo de aquisição de uma habilidade motora tem sido objeto de estudo e, mais recentemente, tem se investigado se o aprendiz é capaz de gerenciar o fornecimento dessas informações. Contudo, a literatura sobre os efeitos do conhecimento de performance (CP) com populações idosas é incipiente e os resultados não são esclarecedores. Nesse sentido, o objetivo geral desse estudo foi investigar o efeito de um regime de fornecimento de CP autocontrolado na aprendizagem motora de idosos. Foram planejados dois experimentos. O objetivo do Experimento 1 foi investigar o efeito do fornecimento de diferentes tipos de CP (CP descritivo/vídeo-replay e CP prescritivo/verbal) na aprendizagem de uma habilidade motora em idosos. A tarefa utilizada foi a tacada curta do golfe. Participaram deste experimento 36 idosos com média de idade de 65 anos, distribuídos em três grupos experimentais: Presc; Vídeo+Presc; e Vídeo. Os idosos praticaram 120 tacadas a 2,20m do alvo em duas sessões de prática e foram realizados testes de retenção e transferência. A ANOVA encontrou diferenças significantes entre os grupos no desempenho (escore), na amplitude do backswing e forwardswing. O post hoc de Bonferroni mostrou que os grupos Presc e Video+Presc foram superiores ao grupo Vídeo (p<=0,05). Portanto, o CP prescritivo foi responsável pela mudança no padrão de movimento, bem como, na diminuição dos erros. O objetivo do Experimento 2 foi investigar o efeito do fornecimento de CP autocontrolado no processo de aprendizagem de uma habilidade motora em indivíduos idosos. Participaram desse estudo 40 indivíduos com idade entre 60 e 80 anos, divididos em dois grupos: Auto e Yoked. A tarefa utilizada foi a mesma do Experimento 1 e o delineamento experimental contou com testes de retenção (R5 e R24) e transferência (T1 e T2). O desempenho foi avaliado pela pontuação obtida na tacada (escore) e foi realizada a análise cinemática. A ANOVA não detectou diferenças significantes entre os grupos Auto e Yoked nas medidas realizadas (p<=0,05). Além disso, a análise da variabilidade intraindividual mostrou que o grupo Auto variou mais comparado ao grupo Yoked nas medidas de tempo e amplitude do backswing, tempo de preparação e tempo de movimento. Portanto, não houve efeito do regime de CP autocontrolado na aquisição da tacada curta do golfe. A partir do reagrupamento realizado com base na frequência de recebimento de CP, os idosos foram organizados em dois grupos G9 e G55, que receberam CP em 9% e 55% das tentativas, respectivamente. Com a formação dos novos grupos, foram refeitas todas as análises. A análise inferencial encontrou diferenças significantes em praticamente todas as medidas (p<=0,05), mostrando que o G55 apresentou um comportamento qualitativamente superior quando comparado ao G9. Em suma, os resultados corroboram com as pesquisas que investigaram idosos sob uma condição autocontrolada, confirmando que idosos não foram influenciados ao serem inseridos num regime autocontrolado de fornecimento de CP. Além disso, a frequência de fornecimento de CP elevada, ou 55%, parece ser um fator que incrementa o desempenho de idosos / The use of extrinsic feedback throughout the process of acquisition of a motor skill has been a topic of study and, more recently, has investigated if the learner is able to manage the provision of this information. However, the literature on the effects of knowledge of performance (CP) with elderly populations is incipient and the results are not clear. In this sense, the general objective of this study was to investigate the effect of a system for providing self-controlled CP of motor learning in the elderly. Two experiments were planned. The goal of the Experiment 1 was to investigate the effect of the providing of different types of CP (descriptive/video-replay CP and prescriptive/verbal CP) in learning a motor skill in the elderly. The task used was the golf putting. Thirty six elderlies, average age of 65 years, participated in this experiment and were divided into three experimental groups: Presc; Video+Presc; and Video. The elderly practiced 120 strokes to 2.20 m from the target in two practice sessions and tests of retention and transfer were conducted. ANOVA found significant differences between the groups on performance (score), the amplitude of the backswing and forwardswing. Post hoc Bonferroni test showed that Presc and Video+Presc were superior to Video (p <= 0.05). Therefore, CP prescriptive was responsible for the change in the pattern of movement, as well as in the reduction of errors. The goal of the Experiment 2 was to investigate the effect of providing selfcontrolled CP in the acquisition of a motor skill in elderly individuals. Forty 40 individuals aged between 60 and 80 years, participated of this study and were divided into two groups: Auto and Yoked. The task used was the same as that of Experiment 1 and there was retention (R5 and R24) and transfer (T1 and T2) tests. The performance was evaluated by the score obtained in the shot and kinematic analysis was performed. ANOVA did not detect significant differences between groups in the all measures undertaken (p <= 0.05). Furthermore, the analysis showed that intraindividual variability of the Auto group varied more than Yoked in the time and amplitude of the backswing, preparation time and movement time. Therefore, there was no effect of the self-regulated CP in the acquisition of short putt golf. Participants reorganization was carried out based on the frequency of the CP given, and elderly were divided into two groups G9 and G55, who received CP in 9% and 55% in the attempts, respectively. All the analyses were redone. The inferential analysis found significant differences in virtually all measures (p <= 0.05), showing that the G55 presented a qualitatively superior behavior when compared to the G9. In short, the results corroborate with the research that investigated elderly under a selfregulated condition, confirming that the elderly were not influenced by being inserted in a self-controlled system of CP delivery. In addition, the high frequency of providing CP, or 55%, seems to be a factor that increases the performance of the elderly
474

Fertilizantes nitrogenados de liberação gradual: longevidade e volatilização em ambiente controlado / Gradual release of nitrogen fertilizers: longevity and volatilization under controlled environment

Mota, Edson Pereira da 12 November 2012 (has links)
O aumento populacional verificado em escala mundial remete a necessidade do aumento da produção de alimentos, fibras e energia e, neste cenário, a prática da adubação como aporte de nutrientes ao solo ganha destaque para atender essas necessidades. Nesse contexto, a adubação nitrogenada, por fornecer nitrogênio, elemento fundamental ao desenvolvimento das plantas e à manutenção e aumento da produtividade, destaca-se com o uso da ureia. A ureia é o principal fertilizante sólido em âmbito mundial, ocupando metade da matriz dos nitrogenados tanto no Brasil como no mundo, possui alta concentração de N e preço mais atrativo por unidade do nutriente, porém esta sujeita a perdas, das quais a volatilização de amônia é o principal fator da baixa eficiência nas adubações. Como alternativa a minimização dessas perdas, tem-se hoje o desenvolvimento de produtos denominados fertilizantes de eficiência aumentada. Dentre esses, uma opção é o recobrimento da ureia com polímeros, resultando em proteção física do insumo. O objetivo foi estudar a dinâmica de fertilizante nitrogenado de liberação gradual avaliando a longevidade e suas perdas por volatilização de amônia. O experimento foi conduzido no município de Batatais- SP, de Novembro de 2011 a Fevereiro de 2012, utilizando Latossolo Vermelho-Amarelo. Foram utilizados 5 tratamentos de ureia recoberta com diferentes porcentagens de resina de poliuretano, mais um tratamento de ureia sem recobrimento para fins de comparação. As porcentagens de recobrimento utilizadas correspondem ao número de dias esperado para a liberação do nutriente sendo: 3,70% (30 dias), 4,55% (60 dias), 5,40% (90 dias), 7,10% (150 dias) e 8,80% (250 dias). Experimentos semelhantes foram instalados em condições laboratoriais de ambiente controlado (25 ± 2°C), e em casa de vegetação, simulando condições de aplicação em superfície e enterrada. Para o experimento de volatilização, foi utilizado o sistema fechado dinâmico, capturando a amônia volatilizada em coletores contendo solução ácida e, esta solução foi analisada em sistema FIA determinando a quantidade de N perdida. Em relação ao experimento de longevidade, foi desenvolvido sistema de análise destrutiva, colocando os tratamentos em sachês porosos e alocando-os em superfície e enterrados a 5 cm no solo. Para ambos os experimentos foram realizadas coletas periódicas, analisando as amostras e traçando gráficos relativos à volatilização da amônia, a faixas de liberação e potencial de longevidade dos tratamentos. O recobrimento da ureia com polímero de poliuretano apresentou redução na volatilização com porcentagens acima de 7%, além de causar atraso nos picos de volatilização. Quanto à longevidade, o recobrimento do fertilizante resultou em liberação gradual do nutriente com dinâmica exponencial, podendo ser traçadas faixas de liberação e potenciais de longevidade dos tratamentos. A aplicação superficial dos tratamentos obteve melhores resultados de liberação/longevidade. Os fatores temperatura e umidade interferem diretamente na volatilização da amônia, na velocidade de liberação e na longevidade dos fertilizantes recobertos com poliuretano. Pesquisas envolvendo este tipo de tecnologia são necessárias, pois além do estabelecimento de metodologias padrão, aplicáveis a estes produtos ou grupos dos mesmos, em rotinas de laboratório, pode-se obter melhor caracterização, entendimento e classificação desses novos materiais. / The worldwide population increase leads to necessity to increase food, fiber and energy production and, under this scenario, fertilizer applications like supply of nutrients to the soil, is highlighted to meet those needs. In this context, nitrogen fertilization, to provide nitrogen, essential element for plant development and maintenance and increased productivity, stands out with the urea use. Urea is the main solid fertilizer worldwide, occupying half of the matrix of nitrogen both in Brazil and in the world, has a high concentration of N and an attractive price per unit of nutrient, but is subject to losses, which the volatilization ammonia is the main factor in the low efficiency of fertilization. As alternative to minimize these losses, currently we have the development of products denominated increased efficiency fertilizer, which focus on urea coatings using polymers resulting in physical protection of the material. The objective was to study the dynamics of nitrogen fertilizer gradual release bu means of evaluating their longevity and losses by volatilization. The experiment was conducted in the municipality of Batatais-SP, extending from November 2011 to February 2012, using a Oxisol. Five treatments of coated urea with different percentages of a polyurethane resin were used, aswell a urea treatment without coating for comparison purposes was used too, the percentages used remitted expected number of days for the release of the nutrient was: 3.70% (30 days) 4.55% (60 days) 5.40% (90 days) 7.10% (150 days) and 8.80% (250 days). Similar experiments were assembled in a controlled environment (25 ± 2 ° C) and under greenhouse conditions simulating application in surface and buried. For the volatilization experiment, we used the closed system dynamic, capturing the volatilized ammonia in collectors containing acidic solution, and this solution was analyzed in FIA system in order to determine the amount of N lost. In relation to the longevity experiment, a destructive analysis system was used, placing the treatments in porous sachets and placing them on the surface and buried 5 cm into the soil. For both experiments samples were collected and analyzed periodically allowing plotting graphs for ammonia volatilization, release bands and potential longevity of the treatments. The urea coating with polyurethane polymer decreased the volatilization with percentages above 7%, besides causing a delay in the peak of volatilization. As for longevity, the fertilizer coating resulted in a gradual release of the nutrient presenting a release dynamic exponential and can be traced release bands and potential longevity treatments. Surface application of the treatments resulted in better results of release / longevity. The factors temperature and humidity affects directly ammonia volatilization, speed and longevity of release fertilizer coated with polyurethane. Additional research in this field is required, in addition to establishing standard methodologies to be used in routine laboratory in order to obtain a better characterization, classification and understanding of these new materials.
475

Processing of polymer-based systems for improved performance and controlled release

Ma, Jia January 2011 (has links)
This thesis focuses on improved processing methods for enhanced mechanical properties in polymer nanocomposites, and controlled drug release in polymer based delivery systems. Supercritical carbon dioxide assisted mixing was successfully used in preparation of polypropylene/sepiolite and polypropylene/multiwall carbon nanotube nanocomposites. Relatively homogeneous dispersed and well separated nanofillers were obtained throughout the PP matrix. A better preservation of nanofiller lengths was observed in the scCO 2 assisted mixing. Mechanical property studies showed a marked increase in Young's modulus and tensile strength with the addition of nanofillers. More interestingly, techniques usually designed to achieve high quality PP nanocomposites, such as the use of masterbatches, maleic anhydride grafted polypropylene compatibilizers or polymer coated MWNTs are not needed to achieve equivalent mechanical properties with scCO2 assisted mixing. ScCO2 was also used as a foaming technique to modify the traditional cured poly(ethyl methacrylate/tetrahydrofurfuryl methacrylate) system for a controlled release of chlorhexidine. Highly porous structures were produced and chlorhexidine released from scCO2 foamed samples was more than 3 times higher than traditionally cured samples. By altering the processing conditions, such as CO2 saturation time and depressurization time the CX release rate was altered. Finally, the electrospinning method was combined with the layering encapsulation technique in order to enable the incorporation of water-soluble drugs in poly(lactic-co-glycolic acid) fibres for biomedical applications. Water-soluble drug, Rhodamine 6G or protein bovine serum albumin, loaded calcium carbonate microparticles were successfully incorporated in PLGA fibres and a bead and string structured composite fibres.
476

Nanoestruturas bimetálicas e ocas: controlando forma, composição, e estrutura para aplicações em catálise / Bimetalli and hollew nanostructures: controlling shape, composition, and structure for catalytic applications

Alexandra Macedo Wendler 09 September 2016 (has links)
Essa tese visa o desenvolvimento de metodologias simples, eficazes, versáteis e ambientalmente amigáveis para se obter nanomateriais metálicos com controle fino sobre sua forma, composição e estrutura (interior sólido ou vazio) para aplicações em catálise. Em especial, temos interesse no desenvolvimento de nanoestruturas ocas esféricas (nanocascas) compostas por prata-ouro (AgAu), prata-paládio (AgPd) e prata platina (AgPt). Essas nanocascas foram obtidas através da reação de substituição galvânica entre esferas de Ag e íons AuCl4-, PdCl42- ou PtCl62-, respectivamente. Como a reação de substituição galvânica permite não apenas o controle sobre a composição destes sistemas, mas também a obtenção de interiores vazios, esta estratégia representa uma alternativa promissora para a obtenção de nanomateriais apresentando características controláveis e atrativas para aplicações catalíticas. Diante dessas qualidades, esse projeto focou em aplicações para reações orgânicas de redução e acoplamento. Foi realizada uma investigação, de maneira sistemática, como a estrutura e composição dos nanomateriais metálicos produzidos influenciam a sua atividade catalítica, mostando que as atividades foram fortemente dependentes da composição e estrutura, abrindo a possibilidade para o planejamento de nanocatalisadores com atividades catalíticas controladas para uma transformação de interesse. / This thesis aims at developing facile, efficient, versatile, and environmentally friendly methodologies to obtain metallic nanomaterials with controlled shapes, compositions and structure (solid or hollow interiors) for applications in catalysis. In particular, we focused on hollow nanospheres (nanoshells) composed of silver-gold (AgAu), silver-palladium (AgPd), and silver-platinum (AgPt). These nanoshells were obtained by galvanic replacement reaction between Ag nanosphere and AuCl4-, PdCl42- or PtCl62-, respectively. The galvanic replacement reaction not only allows control over the composition of these systems, but also to obtain hollow interiors. Therefore, this strategy is a very promising alternative for obtaining nanomaterials with controllable features attractive for catalytic applications. In this case, we investigated applications towards reduction and coupling transformations. A systematic investigation was carried out regarding how the structures and compositions of the produced nanoshells influenced their catalytic performance. Our results showed that the activities were strongly dependent on the composition and structure, opening a range of possibility for designing nanocatalysts with desired catalytic activities for a target transformation.
477

Refining Prerequisite Skill Structure Graphs Using Randomized Controlled Trials

Adjei, Seth Akonor 25 April 2018 (has links)
Prerequisite skill structure graphs represent the relationships between knowledge components. Prerequisite structure graphs also propose the order in which students in a given curriculum need to be taught specific knowledge components in order to assist them build on previous knowledge and improve achievement in those subject domains. The importance of accurate prerequisite skill structure graphs can therefore not be overemphasized. In view of this, many approaches have been employed by domain experts to design and implement these prerequisite structures. A number of data mining techniques have also been proposed to infer these knowledge structures from learner performance data. These methods have achieved varied degrees of success. Moreover, to the best of our knowledge, none of the methods have employed extensive randomized controlled trials to learn about prerequisite skill relationships among skills. In this dissertation, we motivate the need for using randomized controlled trials to refine prerequisite skill structure graphs. Additionally, we present PLACEments, an adaptive testing system that uses a prerequisite skill structure graph to identify gaps in students’ knowledge. Students with identified gaps are assisted with more practice assignments to ensure that the gaps are closed. PLACEments additionally allows for randomized controlled experiments to be performed on the underlying prerequisite skill structure graph for the purpose of refining the structure. We present some of the different experiment categories which are possible in PLACEments and report the results of one of these experiment categories. The ultimate goal is to inform domain experts and curriculum designers as they create policies that govern the sequencing and pacing of contents in learning domains whose content lend themselves to sequencing. By extension students and teachers who apply these policies benefit from the findings of these experiments.
478

Investigating Learning in an Intelligent Tutoring System through Randomized Controlled Experiments

Razzaq, Leena 28 August 2009 (has links)
"In the United States, many students are doing poorly on new high-stakes standards-based tests that are required by the No Child Left Behind Act of 2002. Teachers are expected to cover more material to address all of the topics covered in standardized tests, and instructional time is more precious than ever. Educators want to know that the interventions that they are using in their classrooms are effective for students of varying abilities. Many educational technologies rely on tutored problem solving, which requires students to work through problems step-by-step while the system provides hints and feedback, to improve student learning. Intelligent tutoring researchers, education scientists and cognitive scientists are interested in knowing whether tutored problem solving is effective and for whom. Intelligent tutoring systems have the ability to adapt to individual students but need to know what types of feedback to present to individual students for the best and most efficient learning results. This dissertation presents an evaluation of the ASSISTment System, an intelligent tutoring system for the domain of middle school mathematics. In general, students were found to learn when engaging in tutored problem solving in the ASSISTment System. Students using the ASSISTment System also learned more when compared to paper-and-pencil problem-solving. This dissertation puts together a series of randomized controlled studies to build a comprehensive theory about when different types of tutoring feedback are more appropriate in an intelligent tutoring system. Data from these studies were used to analyze whether interactive tutored problem solving in an intelligent tutoring system is more effective than less interactive methods of allowing students to solve problems. This dissertation is novel in that it presents a theory that designers of intelligent tutoring systems could use to better adapt their software to the needs of students. One of the interesting results showed is that the effectiveness of tutored problem solving in an intelligent tutoring system is dependent on the math proficiency of the students. Students with low math proficiency learned more when they engaged in interactive tutoring sessions where they worked on one step at a time, and students with high math proficiency learned more when they were given the whole solution at once. More interactive methods of tutoring take more time versus less interactive methods. The data showed that it is worth the extra time it takes for students with low math proficiency. The main contribution of this dissertation is the development of a comprehensive theory of when educational technologies should use tutored problem solving to help students learn compared to other feedback mechanisms such as hints on demand, worked out solutions, worked examples and educational web pages. "
479

Design of a High Speed Hydraulic On/Off Valve

Katz, Allan A 29 May 2009 (has links)
"On-off control of hydraulic circuits enables significant improvements in efficiency compared with throttling valve control. A key enabling technology to on-off control is an efficient high speed on-off valve. This project aims to design an on-off hydraulic valve that minimizes input power requirements and increases operating frequency over existing technology by utilizing a continuously rotating valve design. This is accomplished through use of spinning port discs which chop the flow into pulses, with the relative phase between these discs determining the pulse duration. A mathematical model for determining system efficiency is developed with a focus on the throttling, leakage, compressibility, and viscous friction power losses of the valve. Parameters affecting these losses were optimized to produce the most efficient design under the chosen disc-style architecture. Using these optimum parameter values, a first generation prototype valve was developed and experimental data collected. The experimental valve matched predicted output pressure and flows well, but suffered from larger than expected torque requirements and leakage, resulting in a maximum efficiency of 38% at 1.0 duty ratio. Also, due to motor limitations, the valve was only able to achieve a 64Hz switching frequency versus the designed 100Hz frequency. Future design iterations will need to focus on controlling leakage, hydrodynamically balancing the spinning port disc axially to reduce torque requirements, developing a computational fluid dynamics model to gain further insight into the workings of the valve, and creating a control methodology for single and multiple high speed valves."
480

Analysis of long-term opioid prescribing practices in cancer patients at a pediatric tertiary institution

Jan, Jenny Lin 08 April 2016 (has links)
INTRODUCTION: Pain is common in cancer. Pain can present at the time of diagnosis or it can develop during treatment. Cancer-related chronic pain is often treated with long-term (3 or more consecutive refills) opioid prescriptions. Opioids are a controlled substance and are thus regulated at the federal, state, and local levels. OBJECTIVES: The first goal of this study is to examine Boston Children's Hospital's general compliance with federal, state, and local opioid prescribing policies. The second goal of this study is to distinguish cancer patients requiring long-term opioids from non-cancer patients requiring long-term opioids. METHODS: This study was a retrospective chart review using summative qualitative content analysis. This is the process where content is grouped into themes and then is further quantified within each theme. RESULTS: Documents required to ensure compliance with opioid prescribing regulations at the local level are not always well documented. These include the Long-Term Opioid Agreement and the risk evaluation of opioid misuse and abuse using one of several tools annually. At Boston Children's Hospital (BCH), the CRAFFT (car, relax, alone, forget, friends, trouble) questionnaires are used for this purpose. State policies require that, if a patient is not seen at least once every 6 months, physicians must document explicitly why a clinic visit was not possible. These reasons are never clearly listed within the medical record. Additionally, data shows that cancer patients using long-term opioids tend to be younger (mean age 14.4) than non-cancer patients (mean age 26.7). Cancer pain can present either at diagnosis, during treatment, or be present during both. Where n=16 cancer patients, 62.53% experienced pain both at diagnosis and during treatment, 25% experienced pain only during treatment, and 12.5% experience pain only at diagnosis. Finally, data also show that anxiety and comorbidity are common, 34.6% of n=29 patients in both cancer and non-cancer patients using long-term opioids. 34.6% of patients experienced comorbidities of either anxiety or depression. CONCLUSIONS: Despite these discrepancies with documentation, review of patients on long-term opioids revealed those with complex and painful medical conditions generally had valid reasons to require long-term opioids. Therefore, there is no evidence that BCH prescribers are involved in any sort of inappropriate opioid prescribing. Finally, no meaningful conclusions were drawn from data regarding pain score and weight because of inconsistencies in electronic medical record documentation in these areas.

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