Abstract A piano is called ¡§the king of instruments¡¨. Almost every great musician writes good compositions for piano, and they are also good pianoists. Piano almost appears in every concert. Bartolomeo Cristofori made the first instrument that we recognize as a piano today in 1709.It is an important invention in music history. The basic structure of a modern piano was approximately decided in 19 century. Many patents were designed to improve the performance of piano in these years, but they didn¡¦t change the basic structure of piano. The research adopts the method of structure synthesis to design new piano and brings up a new idea ¡§linkage controls a hammer¡¨ to improve the performance of a piano.

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The protection zone of the Franklin Rod is widely used in practice due to its effectiveness and the wide usage. The theories are based on the mathematical approaches, regardless of physical inherence of lightning strokes. The study of this thesis is based on computer analysis of the field distribution in pre-breakdown stage, laboratory experiments of various test configurations and mathematical modeling. The impact of the Franklin Rod¡¯s height and the polarity of impulse are considered. New equations are developed to calculate the striking distance to Franklin Rod both under negative and positive polarity lightning strokes. The lightning protection zone of the Franklin Rod can be predicted by a proposed elliptical model. The experimental data coincides to the calculated protection zone by proposed equations. Finally, the dual-rod lightning protection system is studied. The protection zone of the dual-rod protection system can be evaluated by a combination of Rolling Sphere Circular Model and elliptical model.

In this dissertation, experimental data was used to investigate the influence of a nearby mast structure on the striking distance to a lightning rod. The results of this research helped identify and understand the impact of different factors such as stroke polarity, lightning rod height, striking distance to the ground, lateral distance from the lightning stroke to an adjacent mast, and height of the adjacent mast on the striking distance of a lightning rod. Moreover, a system identification methodology was employed for the development and validation of striking distance models from experimental work performed at the Mississippi State University High Voltage Laboratory. Striking distance models were obtained to represent the striking distance to the ground, striking distance to an isolated lightning rod, and striking distance to a lightning rod in the presence of an adjacent mast. In the case of the striking distance to the ground the system identification approach was used for the extraction of the parameters of the black-box model proposed. From the results the relationship between the striking distance to ground and the leader voltage were obtained for both polarities of the lightning stroke. The system identification approach was then expanded to obtain the models for the striking distance to the lightning rod. The system identification approach was used to evaluate different mathematical models based on the ones found in the literature. The models were trained on experimental data, their quality evaluated, and the best model was selected for both positive and negative polarity. Furthermore, the model for negative polarity was evaluated against data from real lightning conditions in order to corroborate the model extrapolation capability. Building on the success obtained on the cases of the striking distance to the ground and to an isolated lightning rod the focus was turned to expanding the models to incorporate the influence of an adjacent mast. Models for positive and negative polarity were obtained and the quality of the equations was evaluated.

Snakes represent an impressive evolutionary radiation of over 3,500 widely-distributed species, categorized into 515 genera, encompassing a diverse range of morphologies and ecologies. This diversity is likely attributable to their distinctive morphology, which has allowed them to populate a wide range of habitat types within most major ecosystems. In my first chapter, I provide the largest-yet estimate of the snake tree of life using maximum likelihood on a supermatrix of 1745 taxa (1652 snake species + 7 outgroup taxa) and 9,523 base pairs from 10 loci (5 nuclear, 5 mitochondrial), including previously unsequenced genera (2) and species (61). I then use this phylogeny to test hypotheses regarding heterogeneity in diversification rates and how this shaped overall patterns of snake diversity in Chapter 2. I also used the species-level phylogeny to test the evolution of habitat use in snakes, morphological variation, and whether distantly-related species exhibit morphological convergence in Chapter 3. Finally, in Chapter 4 I investigate how prehensile tails effect striking performance in arboreal snakes.

O propósito desse estudo foi investigar a influência da prática sistemática no desempenho e na estrutura do movimento em crianças de diferentes estados de desenvolvimento na habilidade motora básica rebater. Seqüências de desenvolvimento geralmente são utilizadas para definir mudanças de um estágio para outro, entretanto, essas mudanças não se relacionam exclusivamente a fatores internos. Restrições do organismo, do ambiente e da tarefa são responsáveis por mudanças. Nesse contexto, surge uma indagação: será que com a prática sistemática o indivíduo mudaria de um estágio para outro? Para responder a essa questão, um estudo foi realizado compreendendo um delineamento de duas fases nas quais as crianças deveriam praticar o rebater ao alvo uma bola de tênis de mesa lançada por um robô: a primeira fase foi denominada de aquisição e a bola foi lançada formando uma trajetória parabólica, sendo que as crianças deveriam atingir a meta critério de três acertos consecutivos na pontuação 50 do alvo, em até no máximo 120 tentativas; na segunda fase, denominada transferência, a bola foi lançada numa trajetória semi-retilínea e foram executadas 30 tentativas. Participaram dessa investigação 70 crianças com média de 11,6 anos de idade. Vinte e nove crianças atingiram a meta critério, as quais foram classificadas em grupos (inicial e avançado). As tentativas analisadas foram divididas em quatro blocos com três execuções cada. Dezenove variáveis foram estudadas envolvendo análise cinemática e medidas qualitativas a partir do checklist proposto por LANGENDORFER (1987a). Os resultados mostraram que a prática influencia a aquisição da habilidade, e foi revelada diferença estatisticamente significante (p< 0,05) na análise coletiva dos componentes, na ação da raquete, na aceleração e velocidade da raquete. Os resultados também mostraram que o controle dos graus de liberdade passa a ser feito nas articulações ou segmentos distais a medida que se congela e domina os graus de liberdade das grandes articulações ou segmentos corporais durante a ação motora. / The purpose of this study was to investigate the effect of systematic practice on the performance and movement structure of children in different development stages in the basic motor skill of striking. Developmental sequences are often used to define changes from one stage to another, but these changes are not exclusively related to internal factors. Organismic, environmental and task constraints are responsible for them. In this context, a question arises: can a systematic practice change the developmental stage? Based on this question, a study was carried out having an experimental design of two phases, on which children practiced striking a table tennis ball thrown by a robot to a target. The first phase was denominated acquisition and the ball was thrown in a parabolic trajectory. Children were asked to reach a performance criterion of three consecutive hits on the target (50 points), allowed a maximum of 120 trials. In the second phase, called transfer, 30 trials were performed with the ball thrown in a straight trajectory. Seventy children (±11,6= years old) participated in this study and 29 of them reached the defined criterion, who were divided into two groups (initial and advanced). The trials were divided in four blocks with three trials each. Nineteen variables envolving kinematic and qualitative measures belonging to a checklist (LANGENDORFER, 1987a) were analysed. Results showed that practice affects skill acquisition and a statistic differences (p<0.05) on collective component analysis, racquet action, and racquet acceleration and velocity were observed. The results also showed that the control to degrees of freedom is transferred to distal joints or body segments as the degrees of freedom of major joints and body segments are frozen during the action.