944 resultados para Space analysis
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There is a recent trend to describe physical phenomena without the use of infinitesimals or infinites. This has been accomplished replacing differential calculus by the finite difference theory. Discrete function theory was first introduced in l94l. This theory is concerned with a study of functions defined on a discrete set of points in the complex plane. The theory was extensively developed for functions defined on a Gaussian lattice. In 1972 a very suitable lattice H: {Ci qmxO,I qnyo), X0) 0, X3) 0, O < q < l, m, n 5 Z} was found and discrete analytic function theory was developed. Very recently some work has been done in discrete monodiffric function theory for functions defined on H. The theory of pseudoanalytic functions is a generalisation of the theory of analytic functions. When the generator becomes the identity, ie., (l, i) the theory of pseudoanalytic functions reduces to the theory of analytic functions. Theugh the theory of pseudoanalytic functions plays an important role in analysis, no discrete theory is available in literature. This thesis is an attempt in that direction. A discrete pseudoanalytic theory is derived for functions defined on H.
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This paper presents the optimal design of a sur- face mounted permanent magnet Brushless DC mo- tor (PMBLDC) meant for spacecraft applications. The spacecraft applications requires the choice of a torques motor with high torque density, minimum cogging torque, better positional stability and high torque to inertia ratio. Performance of two types of machine con¯gurations viz Slotted PMBLDC and Slotless PMBLDC with halbach array are compared with the help of analytical and FE methods. It is found that unlike a Slotted PMBLDC motor, the Slotless type with halbach array develops zero cogging torque without reduction in the developed torque. Moreover, the machine being coreless provides high torque to inertia ratio and zero magnetic stiction
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This paper presents the design and analysis of a 400-step hybrid stepper motor for spacecraft applications. The design of the hybrid stepper motor for achieving a specific performance requires the choice of appropriate tooth geometry. In this paper, a detailed account of the results of two-dimensional finite-element (FE) analysis conducted with different tooth shapes such as square and trapezoidal, is presented. The use of % more corresponding increase in detent torque and distorted static torque profile. For the requirements of maximum torque density, less-detent torque, and better positional accuracy and smooth static torque profile, different pitch slotting with equal tooth width has to be provided. From the various FE models subjected to analysis trapezoidal teeth configuration with unequal tooth pitch on the stator and rotor is found to be the best configuration and is selected for fabrication. The designed motor is fabricated and the experimental results is compared with the FE results
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In the process of urbanization, natural and semi-natural landscapes are increasingly cherished as open space and recreational resource. Urban rivers are part of this kind of resource and thus play an important role in managing urban resilience and health. Employing the example of Tianjin, this doctoral dissertation research aims at learning to understand how to plan and design for the interface zones between urban water courses and for the land areas adjacent to such water courses. This research also aims at learning how to link waterfront space with other urban space in order to make a recreational space system for the benefit of people. Five questions of this dissertation are: 1) what is the role of rivers in spatial and open space planning? 2) What are the human needs regarding outdoor open space? 3) How do river and water front spatial structures affect people's recreational activities? 4) How to define the recreational service of urban river and waterfront open space? 5) How might answering these question change planning and design of urban open space? Quantitative and qualitative empirical approaches were combined in this study for which literature review and theoretical explorations provide the basis. Empirical investigations were conducted in the city of Tianjin. The quantitative approach includes conducting 267 quantitative interviews, and the qualitative approach includes carrying out field observations and mappings. GIS served to support analysis and visualization of empirical information that was generated through this study. By responding to the five research questions, findings and lessons include the following: 1) In the course of time rivers have gained importance in all levels and scales of spatial planning and decision making. Regarding the development of ecological networks, mainly at national scale, rivers are considered significant linear elements. Regarding regional and comprehensive development, river basins and watersheds are often considered as the structural link for strategic ecological, economic, social and recreational planning. For purposes of urban planning, particularly regarding recreational services in cities, the distribution of urban open spaces often follows the structure of river systems. 2) For the purpose of classifying human recreational needs that relate to outdoor open space Maslow's hierarchy of human needs serves as theoretical basis. The classes include geographical, safety, physiological, social and aesthetic need. These classes serve as references while analyzing river and waterfront open space and other kinds of open space. 3) Regarding the question how river and waterfront spatial structures might affect people's recreational activities, eight different landscape units were identified and compared in the case study area. Considering the thermal conditions of Tianjin, one of these landscape units was identified as affording the optimal spatial arrangement which mostly meets recreational needs. The size and the shape of open space, and the plants present in an open space have been observed as being most relevant regarding recreational activities. 4) Regarding the recreational service of urban river and waterfront open space the results of this research suggest that the recreational service is felt less intensively as the distances between water 183 front and open space user’s places of residence are increasing. As a method for estimating this ‘Service Distance Effect’ the following formula may be used: Y = a*ebx. In this equation Y means the ‘Service Distance’ between homes and open space, and X means the percentage of the people who live within this service distance. Coefficient "a" represents the distance of the residential area nearest to the water front. The coefficient "b" is a comprehensive capability index that refers to the size of the available and suitable recreational area. 5) Answers found to the questions above have implications for the planning and design of urban open space. The results from the quantitative study of recreational services of waterfront open space were applied to the assessment of river-based open space systems. It is recommended that such assessments might be done employing the network analysis function available with any GIS. In addition, several practical planning and designing suggestions are made that would help remedy any insufficient base for satisfying recreational needs. The understanding of recreational need is considered helpful for the proposing planning and designing ideas and for the changing of urban landscapes. In the course of time Tianjin's urban water system has shrunk considerably. At the same time rivers and water courses have shaped Tianjin's urban structure in noticeable ways. In the process of urbanization water has become increasingly important to the citizens and their everyday recreations. Much needs to be changed in order to improve recreational opportunities and to better provide for a livable city, most importantly when considering the increasing number of old people. Suggestions made that are based on results of this study, might be implemented in Tianjin. They are 1) to promote the quality of the waterfront open space and to make all linear waterfront area accessible recreational spaces. Then, 2), it is advisable to advocate the concept of green streets and to combine green streets with river open space in order to form an everyday recreational network. And 3) any sound urban everyday recreational service made cannot rely on only urban rivers; the whole urban structure needs to be improved, including adding small open space and optimize the form of urban communities, finally producing a multi-functional urban recreational network.
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A closed-form solution formula for the kinematic control of manipulators with redundancy is derived, using the Lagrangian multiplier method. Differential relationship equivalent to the Resolved Motion Method has been also derived. The proposed method is proved to provide with the exact equilibrium state for the Resolved Motion Method. This exactness in the proposed method fixes the repeatability problem in the Resolved Motion Method, and establishes a fixed transformation from workspace to the joint space. Also the method, owing to the exactness, is demonstrated to give more accurate trajectories than the Resolved Motion Method. In addition, a new performance measure for redundancy control has been developed. This measure, if used with kinematic control methods, helps achieve dexterous movements including singularity avoidance. Compared to other measures such as the manipulability measure and the condition number, this measure tends to give superior performances in terms of preserving the repeatability property and providing with smoother joint velocity trajectories. Using the fixed transformation property, Taylor's Bounded Deviation Paths Algorithm has been extended to the redundant manipulators.
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I present a novel design methodology for the synthesis of automatic controllers, together with a computational environment---the Control Engineer's Workbench---integrating a suite of programs that automatically analyze and design controllers for high-performance, global control of nonlinear systems. This work demonstrates that difficult control synthesis tasks can be automated, using programs that actively exploit and efficiently represent knowledge of nonlinear dynamics and phase space and effectively use the representation to guide and perform the control design. The Control Engineer's Workbench combines powerful numerical and symbolic computations with artificial intelligence reasoning techniques. As a demonstration, the Workbench automatically designed a high-quality maglev controller that outperforms a previous linear design by a factor of 20.
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Compositional data analysis motivated the introduction of a complete Euclidean structure in the simplex of D parts. This was based on the early work of J. Aitchison (1986) and completed recently when Aitchinson distance in the simplex was associated with an inner product and orthonormal bases were identified (Aitchison and others, 2002; Egozcue and others, 2003). A partition of the support of a random variable generates a composition by assigning the probability of each interval to a part of the composition. One can imagine that the partition can be refined and the probability density would represent a kind of continuous composition of probabilities in a simplex of infinitely many parts. This intuitive idea would lead to a Hilbert-space of probability densities by generalizing the Aitchison geometry for compositions in the simplex into the set probability densities
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One of the disadvantages of old age is that there is more past than future: this, however, may be turned into an advantage if the wealth of experience and, hopefully, wisdom gained in the past can be reflected upon and throw some light on possible future trends. To an extent, then, this talk is necessarily personal, certainly nostalgic, but also self critical and inquisitive about our understanding of the discipline of statistics. A number of almost philosophical themes will run through the talk: search for appropriate modelling in relation to the real problem envisaged, emphasis on sensible balances between simplicity and complexity, the relative roles of theory and practice, the nature of communication of inferential ideas to the statistical layman, the inter-related roles of teaching, consultation and research. A list of keywords might be: identification of sample space and its mathematical structure, choices between transform and stay, the role of parametric modelling, the role of a sample space metric, the underused hypothesis lattice, the nature of compositional change, particularly in relation to the modelling of processes. While the main theme will be relevance to compositional data analysis we shall point to substantial implications for general multivariate analysis arising from experience of the development of compositional data analysis…
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Examples of compositional data. The simplex, a suitable sample space for compositional data and Aitchison's geometry. R, a free language and environment for statistical computing and graphics
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Developments in the statistical analysis of compositional data over the last two decades have made possible a much deeper exploration of the nature of variability, and the possible processes associated with compositional data sets from many disciplines. In this paper we concentrate on geochemical data sets. First we explain how hypotheses of compositional variability may be formulated within the natural sample space, the unit simplex, including useful hypotheses of subcompositional discrimination and specific perturbational change. Then we develop through standard methodology, such as generalised likelihood ratio tests, statistical tools to allow the systematic investigation of a complete lattice of such hypotheses. Some of these tests are simple adaptations of existing multivariate tests but others require special construction. We comment on the use of graphical methods in compositional data analysis and on the ordination of specimens. The recent development of the concept of compositional processes is then explained together with the necessary tools for a staying- in-the-simplex approach, namely compositional singular value decompositions. All these statistical techniques are illustrated for a substantial compositional data set, consisting of 209 major-oxide and rare-element compositions of metamorphosed limestones from the Northeast and Central Highlands of Scotland. Finally we point out a number of unresolved problems in the statistical analysis of compositional processes
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The use of perturbation and power transformation operations permits the investigation of linear processes in the simplex as in a vectorial space. When the investigated geochemical processes can be constrained by the use of well-known starting point, the eigenvectors of the covariance matrix of a non-centred principal component analysis allow to model compositional changes compared with a reference point. The results obtained for the chemistry of water collected in River Arno (central-northern Italy) have open new perspectives for considering relative changes of the analysed variables and to hypothesise the relative effect of different acting physical-chemical processes, thus posing the basis for a quantitative modelling
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A novel metric comparison of the appendicular skeleton (fore and hind limb) of different vertebrates using the Compositional Data Analysis (CDA) methodological approach it’s presented. 355 specimens belonging in various taxa of Dinosauria (Sauropodomorpha, Theropoda, Ornithischia and Aves) and Mammalia (Prothotheria, Metatheria and Eutheria) were analyzed with CDA. A special focus has been put on Sauropodomorpha dinosaurs and the Aitchinson distance has been used as a measure of disparity in limb elements proportions to infer some aspects of functional morphology
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Factor analysis as frequent technique for multivariate data inspection is widely used also for compositional data analysis. The usual way is to use a centered logratio (clr) transformation to obtain the random vector y of dimension D. The factor model is then y = Λf + e (1) with the factors f of dimension k < D, the error term e, and the loadings matrix Λ. Using the usual model assumptions (see, e.g., Basilevsky, 1994), the factor analysis model (1) can be written as Cov(y) = ΛΛT + ψ (2) where ψ = Cov(e) has a diagonal form. The diagonal elements of ψ as well as the loadings matrix Λ are estimated from an estimation of Cov(y). Given observed clr transformed data Y as realizations of the random vector y. Outliers or deviations from the idealized model assumptions of factor analysis can severely effect the parameter estimation. As a way out, robust estimation of the covariance matrix of Y will lead to robust estimates of Λ and ψ in (2), see Pison et al. (2003). Well known robust covariance estimators with good statistical properties, like the MCD or the S-estimators (see, e.g. Maronna et al., 2006), rely on a full-rank data matrix Y which is not the case for clr transformed data (see, e.g., Aitchison, 1986). The isometric logratio (ilr) transformation (Egozcue et al., 2003) solves this singularity problem. The data matrix Y is transformed to a matrix Z by using an orthonormal basis of lower dimension. Using the ilr transformed data, a robust covariance matrix C(Z) can be estimated. The result can be back-transformed to the clr space by C(Y ) = V C(Z)V T where the matrix V with orthonormal columns comes from the relation between the clr and the ilr transformation. Now the parameters in the model (2) can be estimated (Basilevsky, 1994) and the results have a direct interpretation since the links to the original variables are still preserved. The above procedure will be applied to data from geochemistry. Our special interest is on comparing the results with those of Reimann et al. (2002) for the Kola project data
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This paper deals with fault detection and isolation problems for nonlinear dynamic systems. Both problems are stated as constraint satisfaction problems (CSP) and solved using consistency techniques. The main contribution is the isolation method based on consistency techniques and uncertainty space refining of interval parameters. The major advantage of this method is that the isolation speed is fast even taking into account uncertainty in parameters, measurements, and model errors. Interval calculations bring independence from the assumption of monotony considered by several approaches for fault isolation which are based on observers. An application to a well known alcoholic fermentation process model is presented
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This paper presents the assessment that inhabitants of some Colombian cities did on the conditions that contribute to the livability of public space. Seven hundred and forty people, inhabitants of Yopal, Villavicencio, Valledupar, Popayán, Pereira, Pasto, Neiva, Montería, Medellín, Fusagasugá, Cúcuta, Cartagena, Cali and Bogotá participated in the study. The assessment of the conditions that contribute to the livability of public space was carried out using an instrument composed of 48 items that inquired about the level of contribution that can have different conditions on the quality of public space, from a scale five points ranging from: Does not contribute at all (-2) to: Contribute significantly (+2). The results show the conditions that most affect the habitability of public space in Colombia, as well as the differences between cities according to the assessment made by participants about the general state of public space in cities. Multidimensional analysis (SSA) evidence a structure that reflects the function that public space plays in people’s assessment on Colombian cities. It is discussed the implications of the findings for urban planning and management and the designed instrument is proposed as a tool to assess the quality of urban public space.