Thesis (M.S. Ed.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 56-59). Also available via the Internet.

La nécessité de la montée en puissance, crête et moyenne, des chaines lasers hyper intenses a fait émerger un nouveau type d'architecture. Le principe consiste à combiner de manière cohérente un grand nombre de lasers élémentaires les plus simples et robustes possible. La difficulté de la montée en puissance est donc reportée essentiellement sur le système de recombinaison. Plusieurs laboratoires à travers le monde ont ainsi décidé de s'impliquer dans cette voie. S'il existe des concepts variés pour la boucle d'asservissement, il n'y a pas pour l'instant, à notre connaissance, de développement d'un moyen de métrologie absolue de la qualité du front d'onde final, et donc de la recombinaison. Or celui-ci est fondamental pour deux moments particuliers de la conception de ces nouvelles architectures.Dans un premier temps, il est nécessaire de connaître la nature, l'amplitude et la fréquence des défauts de phase en boucle ouverte afin de bien spécifier l'architecture de la tête optique et le système de contrôle/commande. Puis, lorsque la chaîne est pleinement opérationnelle, en boucle fermée, la qualité de la recombinaison doit être évaluée. L'objet de cette thèse est de proposer un nouvel interféromètre adapté à ces deux besoins, c'est-à-dire capable d'encaisser de fortes dynamiques et d'avoir en même temps des capacités de mesure absolue de très grandes précision et justesse, à haute cadence, afin de mesurer et d'analyser le front d'onde résultant de la combinaison des différents lasers sur toute la phase de conception de ces lasers, en boucle ouverte comme en boucle fermée. / The need for the rise in power, peak and medium, of hyper intense laser chains has led to the emergence of a new type of architecture. The principle is to consistently combine a large number of the simplest and most robust elementary lasers possible. The difficulty of ramping up is therefore mainly transferred to the recombination system. Several laboratories around the world have thus decided to get involved in this path. If there are various concepts for the servo loop, there is currently, to our knowledge, no development of a means of absolute metrology of the quality of the final wavefront, and therefore of recombination. This is fundamental for two particular moments in the design of these new architectures.First, it is necessary to know the nature, amplitude and frequency of open loop phase faults in order to properly specify the optical head architecture and the control/command system. Then, when the chain is fully operational, in closed loop, the quality of the recombination must be evaluated. The purpose of this thesis is to propose a new interferometer adapted to these two needs, i.e. capable of withstanding strong dynamics and at the same time having absolute measurement capabilities of very high precision and accuracy, at high cadence, in order to measure and analyze the wavefront resulting from the combination of the different lasers over the entire design phase of these lasers, in open loop as in closed loop.

One area of forest biometrics that continues to progress is the development of statistical models as tools to describe tree taper. Taper models allow for the prediction of multiple tree level attributes including: diameter at any height, total tree stem volume, merchantable volume and height to any upper stem diameter from any lower stem height, individual log volumes, and subsequently total tree value. In this work, we generalize segmented regression taper models to include multiple segments and compare it to the traditional 3-Segment (2-Knot) models commonly observed in the forestry literature. We then focus on predicting a future realization of diameter given previously observed data. This is accomplished by comparing a segmented taper model under both the Generalized Algebraic Difference Approach (GADA) and Nonlinear Mixed Effects Models (NLMM) methodologies. Both the GADA and NLMM allow for predictions at the individual tree level of a future realization diameter given a differing number of observed height-diameter pairs. Finally, we explore the prediction and cost/benefit of total tree volume obtained from an integrated taper equation with the incorporation of tree specific random effects given differing observed height-diameter pairs.

No description available.

Discussed is a numerical and experimental characterization of the response of small-scale fiber-reinforced composite cylinders constructed to represent a fuselage design whereby the crown and keel consist of one laminate stacking sequence and the two sides consist of another laminate stacking sequence. This construction is referred to as a segmented cylinder. The response to uniform axial endshortening is discussed. Numerical solutions for the nonlinear prebuckling, buckling, and postbuckling responses are compared to experimental results. Focus is directed at the investigation of two specific cylinder configurations, referred to as axially-stiff and circumferentially-stiff cylinders. Small-scale cylinders, each having a nominal radius of 5 in., were fabricated on a mandrel by splicing adjacent segments together to form 0.5 in. overlaps. Finite-element models of both cylinder configurations, including the overlap regions, are developed using the STAGS finite-element code. Perfectly circular cylinder models are considered, as are models which include the measured geometry of the specimens as an imperfection. Prebuckling predictions show that the segmented cylinder response is characterized by the existence of circumferential displacement, and an axial boundary layer accompanied by circumferential gradients in radial displacement. Experimental measurements, taken with strain gages and displacement transducers, confirm these numerical findings. As the endshortening approaches the critical, or buckling, values, the response of the cylinders is characterized by wrinkling in the axial direction. In the axially-stiff cylinder, the crown and keel segments wrinkle, while in the circumferentially-stiff cylinder the side segments wrinkle. Experimental images taken from Moire interferometry show this response in the circumferentially-stiff cylinder. Four methods are used to predict the buckling values of endshortening and load for both cylinders, and the four values are in good agreement. The experimentally-measured buckling conditions, however, show that the models overpredict buckling values. For the axially-stiff cylinder, the difference could be due to the fact material failure not included in the model plays a role in the cylinder response. For the circumferentially-stiff cylinder, the difference is definitely due to material failure characteristics not included in the model. The predicted postbuckling response of the segmented cylinders is shown to be dominated by the existence of inward dimples in some or all of the segments. For the axially-stiff cylinder, the as-predicted dimpled crown and keel configuration is observed in the experiment but at a load 12 percent below predicted values. For the circumferentially-stiff cylinder material failure in the linear prebuckling range of response triggered buckling that resembled the predicted circumferential rings of dimples, but at a load 31 percent below predictions. Finally, it is shown that the effect of including the measured imperfections in the model has little observable effect on the circumferentially-stiff cylinder. For the axially-stiff cylinder the inclusion of the imperfections is found to effect the transition from buckling to postbuckling, but ultimately has little effect on postbuckling deformations. / Ph. D.

This thesis is a numerical study of fields within ion traps having segmented electrodes1. The focus is on two cylindrical ion trap structures, two Orbit rap structures and one planar structure which mimics the field of the Orbit rap. In all these geometries, the segments which comprise the electrodes are easily Machin able rings and plates. By applying suitable potential to the different segments, the fields within these geometries are made to mimic the fields in the respective ideal structures. This thesis is divided into 6 chapters. Chapter 1 presents introduction and background information relevant to this work. A brief description of the Quadrupole Ion Trap (QIT) and the Orbit rap is given. The role of numerical simulations in the design of an ion trap geometry is briefly outlined. The motivation of this thesis is presented. The chapter ends by describing the scope of the thesis. Chapter 2 presents a general description of computational methods used throughout this work. The Boundary Element Methods (BEM) is first described. Both 2D and 3D BEM are used in this work. The software for 3D BEM is newly developed and hence 3D BEM is described in more detail. A verification of 3D BEM is presented with a few examples. The Runge-Kutta method used to compute the trajectory of ion is presented. A brief overview of the Nelder-Mead method of function minimization is given. The computational techniques specifically used to obtain the results in Chapter 3, 4 and 5 are presented in the respective chapters. Chapter 3 presents segmented electrode geometries of the Cylindrical Ion Trap (CIT). In these geometries, the electrodes of the CIT are split into number of mini-electrodes and different voltages are applied to these segmented electrodes to achieve the desired field. Two geometries of the segmented electrode CIT will be investigated. In the first, we retain the flat end cap electrodes of the CIT but split the ring electrode into five mini-rings. In the second configuration, we split the ring electrode of the CIT into three mini-rings and 1The term ‘segmented electrode’ used in this thesis has the same connotation as the term ‘split-electrode’ used in Sonalikar and Mohanty (2013). also divide the end caps into two mini-discs. By applying different potentials to the mini-rings and mini-discs of these geometries we will show that the field within the trap can be optimized to desired values. Two different types of fields will be targeted. In the first, potentials are adjusted to obtain a linear electric field and, in the second, a controlled higher order even multipole field are obtained by adjusting the potential. It will be shown that the different potentials to the segmented electrodes can be derived from a single RF generator by connecting appropriate capacitor terminations to segmented electrodes. The field within the trap can be modified by changing the value of the external capacitors. Chapter 4 presents segmented electrode geometries which are possible alternatives for the Orbitrap. Two segmented-electrode structures, ORB1 and ORB2, to mimic the electric field of the Orbitrap, will be investigated. In the ORB1, the inner spindle-like electrode and the outer barrel-like electrode of the Orbitrap are replaced by rings and discs of fixed radii, respectively. In this structure two segmented end cap electrodes are added. In this geometry, different potentials are applied to the different electrodes keeping top-bottom symmetry intact. In the second geometry, ORB2, the inner and outer electrodes of the Orbitrap are replaced by an approximate step structure which follows the profile of the Orbitrap electrodes. For the purpose of comparing the performance of ORB1 and ORB2 with that of the Orbitrap, the following studies will be undertaken: (1) variation of electric potential, (2) computation of ion trajectories, (3) measurement of image currents. These studies will be carried out using both 2D and 3D Boundary Element Method (BEM), the 3D BEM is developed specifically for this study. It will be seen in these investigations that ORB1 and ORB2 have performance similar to that of the Orbitrap, with the performance of the ORB1 being seen to be marginally superior to that of the ORB2. It will be shown that with proper optimization, geometries containing far fewer electrodes can be used as mass analysers. A novel technique of optimization of the electric field is proposed with the objective of minimizing the dependence of axial frequency of ion motion on the initial position of an ion. The results on the optimization of 9 and 15 segmented-electrode trap having the same design as ORB1 show that it can provide accurate mass analysis. Chapter 5 presents a segmented electrode planar geometry named as PORB used to mimic the electric field of the Orbit rap. This geometry has two planes, each plane consisting of 30 concentric ring electrodes. Although the geometry of PORB does not have conventional inner and outer electrodes of the Orbit rap, it will be shown that by selecting appropriate geometry parameters and suitable potentials for the ring electrodes, this geometry can trap the ions into an orbital motion similar to that in the Orbit rap. The performance of the planar geometry is studied by comparing the variation of potential, ion trajectories and image current in this geometry with that in the Orbit rap. The optimization of applied potentials is performed to correct the errors in the electric field so that the variation of axial frequency of ions with their initial position is minimized. Chapter 6 presents the summary and a few concluding remarks

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This study was carried out in order to analyze the performance of segmented and non-segmented taper models in terms of estimates for trees profiles with 1, 2 and 3 shape change points in stems; to test the accuracy of estimates of stem profiles and commercial height based on an adjusting taper model with non-stratified data, stratified in classes of DBH (diameter at breast height) and stratified in classes of shape quotient; and to examine the influence of the results on the formulation of a classification table for wood assortments. The data to this study were measured in Pinus taeda L. stands from Klabin S.A. in Telêmaco Borba-PR. The sample trees grew up in stands managed to sawmill, with two thinnings and coppicing, plantation of 1.600 trees/ha, spacing of 2,50 x 2,50 m. Forty trees were cut down and cubed by the Smalian method in the following positions: 0,10, 0,30, 0,80, 1,30, and in each meter until the total height. In these positions, stem transversal slices were obtained to study the reconstruction of growth using dendrocronology and it generated a database of 649 trees aged between 8 and 30 years, among which the samples to this research were selected. Aiming at the best model to estimate the stem profiles, for all kinds of trees the non-segmented models were superior, the 5th degree polynomial showed a better performance and the Garay model presented the second best result. Considering the best method to illustrate the data, the stratification by classes of shape quotient was more accurate, emphasizing K0,7h and K0,5h classes. The assortments table proved that the higher the trees dimensions, the higher the possibility of obtaining more products and, consequently, the better the performance, with a lower residual value. The validation also showed the accuracy of the models adopted in the assortments table. / Este trabalho foi realizado com os objetivos de verificar tanto o desempenho de modelos de afilamento segmentados e não segmentados quanto às estimativas dos perfis de árvores com 1, 2 e 3 pontos de mudanças de forma nos fustes, quanto a acurácia das estimativas dos perfis dos fustes e alturas comerciais a partir de um modelo de afilamento ajustado com os dados não estratificados, estratificados em classes de dap (diâmetro à altura do peito) e estratificados em classes de quociente de forma. Propôs ainda, a comparação entre de um modelo de afilamento ajustado com os dados sem estratificação e estratificado por uma classe de quociente de forma para estimativa do volume total e desenvolvimento dos resultados destes estudos na construção de uma tabela de classificação de sortimentos de madeira. Os dados para o presente trabalho foram mensurados em povoamentos de Pinus taeda L., da Klabin S.A., em Telêmaco Borba-PR. As árvores amostradas cresceram em povoamentos manejados para serraria, com dois desbastes e corte raso, plantio de 1.600 árvores/ha, em espaçamento de 2,50 x 2,50 m. Quarenta árvores foram abatidas e cubadas pelo Método de Smalian, nas posições de: 0,10, 0,30, 0,80, 1,30, e de 1 em 1 metro até a altura total. Nessas posições, foram retiradas fatias transversais do fuste para fins de estudos de reconstituição do crescimento por dendrocronologia, gerando um banco de dados de 649 árvores com idades entre 8 e 30 anos, de onde foram selecionadas aquelas que fizeram parte dos bancos de dados para os estudos propostos. Na busca do melhor modelo para estimativa dos perfis dos fustes, para todos os tipos de árvores, os modelos não segmentados foram superiores, tendo o Polinômio do 5º grau o melhor desempenho e o modelo de Garay o segundo melhor resultado. Em relação ao melhor método para dispor os dados, a estratificação por classe de quociente de forma mostrou o maior ganho de precisão, tendo as classes de K0,7h e K0,5h maiores destaques. A tabela de sortimentos mostrou que, à medida que as árvores têm aumento em suas dimensões, passam a apresentar a possibilidade de retirada de mais produtos e conseqüentemente maior aproveitamento, com pequeno valor residual. As validações mostraram as boas precisões dos modelos usados para construção da tabela de sortimentos.

Estudos para estabelecer níveis de nutrientes adequados em dietas de animais são bastante comuns no meio científico. Tais estudos são realizados utilizando a média da variável resposta nos diferentes níveis da variável independente e, geralmente, por meio de abordagem frequentista. Sendo assim, muita informação é perdida ou até mesmo as médias influenciadas por valores extremos nos resultados das repetições. O objetivo do presente trabalho foi realizar um estudo de simulação de modelos de regressão com platô de resposta, considerando diversos cenários de diferentes tamanhos amostrais, além da homogeneidade e heterogeneidade de variância entre níveis do fator dosagem levando em consideração as repetições em cada dosagem, por meio de abordagem bayesiana. Também foi realizado ajustes dos modelos de regressão quadrático com platô de resposta e do não linear com platô de resposta utilizando a metodologia bayesiana para estimar os parâmetros dos modelos. Os dados simulados representavam o teor de Zinco (Zn) depositado na tíbia de frangos, que receberam as dosagens 0, 15, 30, 45, 60, 75, 90, 105 e 120 ppm de Zn na ração. Nos cenários 1, 2 e 3 foi atribuído variância constante, com tamanhos amostrais de n=16, n=30 e n=100, respectivamente. Nos cenários 4, 5 e 6, foram considerados também os tamanhos amostrais n=16, n=30 e n=100, respectivamente, mas com diferentes variâncias ao longo do fator dose. Os dados utilizados para o estudo sobre os modelos de regressão com platô de resposta são referentes ao teor de Zinco (Zn), em ppm, na tíbia de frangos e frangas de corte como variável resposta. A análise de simulação mostrou que é adequada a utilização dos modelos com platô de resposta considerando a repetição das amostras em cada dose para estimar o nível adequado de um nutriente na ração animal. No ajuste dos modelos aos dados reais, o modelo de regressão quadrático com platô de resposta considerando a heterogeneidade de variâncias foi o que apresentou melhor ajuste, em que obteve-se uma estimativa de x̂0 = 73, 26 ppm para o nível de Zn aplicado na ração para uma deposição de Zn na tíbia dos frangos de P̂ = 290, 12 ppm. / Studies to establish adequate levels of nutrients in animal diets are quite common in the scientific world. Such studies are performed using the mean of the response variable in the different levels of the independent variable and, generally, through a frequentist approach. Thus, much information is lost or even the means influenced by extreme values in the results of the repetitions. The objective of the present work was to perform a simulation study of regression models with response plateau, where as different scenarios of different sample sizes, besides the homogeneity and heterogeneity of variance between levels of the dosage factor taking the repetitions in each dosage into account, through Bayesian approach. Fits were also made to the quadratic regression models with response plateau and nonlinear regression with response plateau using Bayesian methodology to estimate the parameters of the models. The simulated data represented the zinc content (Zn) deposited in the tibia of broilers, which received the dosages 0, 15, 30, 45, 60, 75, 90, 105 and 120 ppm of Zn in the feed. In the scenarios 1, 2 and 3 were attributed constant variance with sample sizes of n = 16, n = 30 and n = 100, respectively. In the scenarios 4, 5 and 6 the sample sizes were, respectively, n = 16, n = 30 and n = 100, but with different variances along the dose factor. The data used for the study on the regression models with response plateau refer to the Zn content, in ppm, in the tibia of male and female broilers as response variable. The simulation analysis showed that it is appropriate to use the models with response plateau considering the repetition of the samples at each dose to estimate the adequate level of a nutrient in the animal feed. In the fit of the models to the real data, the quadratic regression model with response plateau considering the heterogeneity of variances was the one that presented the best fit, which an estimate of x̂0 = 73.26 ppm for the level of Zn applied to the feed for a Zn deposition in the chicken tibia of P̂ = 290.12 ppm.

A avaliação do estado nutricional das culturas requer o uso de padrões para comparação, tais como os níveis críticos e as faixas de suficiência. Esses padrões de interesse agrícola geralmente são estimados a partir da curva de calibração da produção vegetal, que relaciona os rendimentos de uma cultura com a dose do adubo aplicada no solo ou com o teor de algum elemento nos tecidos. A curva de produção vegetal é fundamental para o desenvolvimento de pesquisas nas áreas de nutrição mineral de plantas e adubação, uma vez que o conhecimento a seu respeito possibilita o uso econômico de adubos e a elaboração de estratégias corretivas para o solo. No entanto, a curva de produção divide-se em diferentes regimes nutricionais, que lhe conferem uma forma peculiar e dificultam sua descrição matemática. O objetivo desse trabalho é a construção de modelos de regressão flexíveis, capazes de descrever adequadamente a curva de produção vegetal. Em uma primeira abordagem, modelos lineares segmentados com transições de fase suaves são usados para descrever a produção do trigo de inverno em função da adubação com nitrogênio. Por meio dos ajustes destes modelos, também são estimados os níveis críticos e as faixas de suficiência. Posteriormente, realiza-se a modelagem matemática da resposta vegetativa à adubação, desconsiderando doses tóxicas. Observa-se que cada tipo possível de resposta vegetativa é ligado de forma unívoca a uma função de produção agrícola. A técnica proposta, além de permitir a construção de novas funções de produção, fornece interpretações fisiológicas claras para parâmetros de alguns modelos de uso comum na agricultura. Com base na segunda abordagem, um novo enunciado para a lei de Mitscherlich é apresentado: quanto maior é o conteúdo total do nutriente limitante na planta, menor é o aproveitamento feito (a fim de lhe prover crescimento) de um incremento em sua disponibilidade - como consequência, os retornos da adubação são decrescentes. / The evaluation of the plant nutritional status requires standards for comparisons, such as the critical levels and sufficiency ranges. These standards are generally estimated by means of the yield curves in response to fertilizers, which relates production with doses applied or nutrient content in the plant tissues. The yield curve is essential for the development of researches on plant mineral nutrition and fertilization, since knowledge of this curve allows economic use of fertilizers and planning strategies for soil correction. However, the production curve is divided into different nutritional regimes, which give it a peculiar shape and hinders its mathematical description. In this work, the objective is to build flexible regression models, able to adequately describe the yield curves. In a first approach, linear piecewise models with smooth transitions between regimes are used to describe the winter-wheat yield in function of the nitrogen doses. By means of the fits of these models, the critical levels and sufficiency ranges are also estimated. In another approach, it is proposed a mathematical model for yield response (or returns) from fertilizers - toxic doses are neglected in this phase. It is verified that each possible yield response type is uniquely related with a production function. This approach allows to construct new production functions and, indeed, provides clear physiological interpretations for the parameters of some common models in agriculture. Based on the second approach, it is presented a new statement for the Mitscherlich law: the greater is the total content of the limiting nutrient in the plant, the lower is the exploited fraction (in order to provide growth) of an increment in its availability - as a consequence, the returns from fertilization are diminishing.

Devido ao processo de urbanização sem planejamento adequado, as cidades costeiras sofrem com as inundações e erosão das praias com a elevação do nível do mar e ação de ondas. Entre as estruturas mais utilizadas para proteção de praias destacam-se os quebra-mares segmentados. Para estudar e prever as respostas praiais à presença destas estruturas, podem ser empregados modelos numéricos, capazes de calcular os processos complexos deste ambiente. Este trabalho teve como objetivo o estudo da resposta hidrodinâmica e sedimentar de uma praia com a implantação de quebra-mares segmentados. O modelo hidrodinâmico utilizado é o MIKE21FM acoplado ao modelo de ondas SW e sedimentos ST e SM. Primeiramente, foram impostas condições hidrodinâmicas simplificadas e diferentes arranjos de quebra-mares segmentados. As áreas erodidas e acrescidas após a implantação da obra foram comparadas e priorizou-se minimizar a área erodida. Em seguida, foram considerados os cenários de condições hidrodinâmicas variadas com uma das estruturas. Os resultados são apresentados em termos de altura significativa e potência de onda para 18 casos de condições hidrodinâmicas constantes, as quais foram feitas variar em nível e características da onda. Para a condição hidrodinâmica mais crítica, obteve-se uma redução de 0,4m da altura significativa média e 2kW/m da potência média da onda. Através desses resultados é possível aquilatar a proteção da região da praia da ação das ondas após a implantação da estrutura. Além disso, foram feitas duas simulações com 3 a 4 meses de evolução do fundo em condições hidrodinâmicas reais, com o intuito de apresentar qualitativamente as áreas de erosão e acreção do fundo da praia. Resultados mostraram que a deriva litorânea local tem direção sudeste, para a Ponta da Praia. Foi observada sedimentação no tardoz dos segmentos e na região de sombra e erosão nas áreas entre segmentos e a frente destes. Com isso, este trabalho colabora com o gerenciamento costeiro na região de Santos, apresentando o início de uma pesquisa para uma possível solução para os problemas de inundação e erosão da região da Ponta da Praia. / Erosion and flooding are common problems faced by coastal cities as a consequence of urbanization process without previous planning, with the sea level rise and the wave action. In order to mitigate these problems, shoreline protection structures are constructed along the coastlines, such as segmented breakwaters. Numerical models are tools frequently used in these studies because of its capacity of calculating the complex processes on a coastal environment. This study aim is to present a study based on the hydrodynamic and sediment transport response of a curved beach to the presence of segmented emerged breakwaters. The numerical model used is the MIKE21FM coupled with wave spectral and sediment transport modules. Firstly, constant boundary conditions were applied for the period of one year in order to understand the response of the beach to five different designs of coastal breakwaters. One of these structures were chosen to continue the study based on the area and length of the beach eroded and accreted. Secondly, eighteen different scenarios of wave and water level were applied to the selected structure and the protection of wave action were compared and analyzed. To the most critical hydrodynamic condition, the structure reduced 0,4 m of the mean significant wave height and 2 kW/m of the mean wave power. Finally, two real hydrodynamic conditions were applied and the sediment transport was qualitatively analyzed. Results show that the littoral drift in the studied area is directed to the southeast end of the beach, straight to the Ponta da Praia, without the spur breakwater, the sediment would end inside the navigation channel. Besides that, it shows the sedimentation and erosion patterns at the beach generated by the presence of the breakwater. The sediment is accumulated at the shadow area and at the lee, whereas the erosion is located at the front of the breakwaters and between the segments, as expected. Therefore, this study collaborates with the management of Santos, by presenting herewith a possible solution for the inundation and erosion problems of this area.