Proefschrift Universiteit Maastricht. / Auteursnaam op omslag: Bert Starmans. Met lit. opg. - Met samenvatting in het Nederlands.

A general eigen-value buckling solution is developed for the buckling of long thick pipes subjected to internal and external hydrostatic pressure. The principle of stationary potential energy is used to formulate the conditions of equilibrium, neutral stability conditions, and associated boundary conditions using polar coordinates. The formulation accounts for shear deformation effects and is suited for composite pipe systems with thick cores. It involves destabilizing terms: one is due to the external hydrostatic pressure and incorporates the follower effects, and the other, is due to the pre-bucking stresses undergoing the nonlinear components of strains. The formulation adopts a work conjugate triplet consisting the Cauchy stress tensor, the Green Lagrange strain tensor, and constant constitutive relations. A Fourier series expansion of the displacement fields is adopted to transform the 2D problem into a series of independent 1D problems, thus keeping the computational effort to a minimum while preserving the accuracy of the solution. Two numerical solutions were developed and implemented under MATLAB; the first one is based on the finite difference technique and the second one is based on the finite element solution. Both solutions were shown to converge to the same solution, the finite difference from below, while the finite element converges from above. The finite element solution is then applied to predict the buckling capacity of sandwich pipes consisting of two steel pipes with a soft core. A comprehensive verification study is conducted and the validity of the formulation was established through comparison with other solutions. A parametric study is then conducted to investigate the effect of hydrostatic internal pressure, core material, core thickness, and internal and external pipe thicknesses, on the external buckling pressure of sandwich pipes.

In this thesis, I present my study on the impact of multi-group network structure on the performance of consensus building strategies, and the preliminary mathematical formulation of the problem on improving the performance of the National Airspace system (NAS) through long-term investment. The first part of the thesis is concerned with a structural approach to the consensus building problem in multi-group distributed sensor networks (DSNs) that can be represented by bipartite graph. Direct inference of the convergence behavior of consensus strategies from multi-group DSN structure is one of the contributions of this thesis. The insights gained from the analysis facilitate the design and development of DSNs that meet specific performance criteria. The other part of the thesis is concerned with long-term planning and development of the NAS at a network level, by formulating the planning problem as a resource allocation problem for a flow network. The network-level model viewpoint on NAS planning and development will give insight to the structure of future NAS and will allow evaluation of various paradigms for the planning problem.

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No / Eigenvalue based spectrum sensing schemes such as Maximum Minimum Eigenvalue (MME), Maximum Energy Detection (MED) and Energy with Minimum Eigenvalue (EME) have higher spectrum sensing performance without requiring any prior knowledge of Primary User (PU) signal but the decision hypothesis used in these eigenvalue based sensing schemes depends on the calculation of maximum eigenvalue from covariance matrix of measured signal. Calculation of the covariance matrix followed by eigenspace analysis of the covariance matrix is a resource intensive operation and takes overhead time during critical process of spectrum sensing. In this paper we propose a new blind spectrum sensing scheme based on the approximation of the maximum eigenvalue using state of the art results from Random Matrix Theory (RMT). The proposed sensing scheme has been evaluated through extensive simulations on wireless microphone signals and the proposed scheme shows higher probability of detection (Pd) performance. The proposed spectrum sensing also shows higher detection performance as compared to energy detection scheme and RMT based sensing schemes such as MME and EME.

Biometrics includes the study of automatic methods for distinguishing human beings based on physical or behavioral traits. The problem of finding good biometric features and recognition methods has been researched extensively in recent years. Our research considers the use of ears as a biometric for human recognition. Researchers have not considered this biometric as much as others, which include fingerprints, irises, and faces. This thesis presents a novel approach to recognize individuals based on their outer ear images through spatial segmentation. This approach to recognizing is also good for dealing with occlusions. The study will present several feature extraction techniques based on spatial segmentation of the ear image. The study will also present a method for classifier fusion. Principal components analysis (PCA) is used in this research for feature extraction and dimensionality reduction. For classification, nearest neighbor classifiers are used. The research also investigates the use of ear images as a supplement to face images in a multimodal biometric system. Our base eigen-ear experiment results in an 84% rank one recognition rate, and the segmentation method yielded improvements up to 94%. Face recognition by itself, using the same approach, gave a 63% rank one recognition rate, but when complimented with ear images in a multimodal system improved to 94% rank one recognition rate. / Master of Science

The plumage colour and patterns of birds have interested biologists for a long time.Why are some bird species all black while others have a multitude of colours? Does ithave anything to do with sexual selection, predator avoidance or social signalling?Many questions such as these have been asked and as many hypotheses about thefunctional role of the plumage have been formed. The problem, however, has been toprove any of these. To test these hypotheses you need to analyse the bird plumagesand today such analyses are still rather subjective. Meaning the results could varydepending on the individual performing the analysis. Another problem that stemsfrom this subjectiveness is that it is difficult to make quantitative measurements of theplumage colours. Quantitative measurements would be very useful since they couldbe related to other statistical data like speciation rates, sexual selection and ecologicaldata. This thesis aims to assist biologists with the analysis and measurement of birdplumages by developing a MATLAB toolbox for this purpose. The result is a wellstructured and user friendly toolbox that contains functions for segmenting, resizing,filtering and warping, all used to prepare the images for analysis. It also containsfunctions for the actual analysis such as basic statistical measurements, principalcomponent analysis and eigenvector projection.

Baigiamajame magistro darbe pirmame skyriuje nagrinėjama precizinių mechatroninių sistemų veikimo principai, medžiagų savybės, aliekama konstrukcijų analizė, tyrimų analizė. Antrame skyriuje apžvelgtas precizinių mechatroninių sistemų modeliavimas, pateikti skaitiniai modeliai, ištirta precizinių mechatroninių sistemų geometrinių parametrų įtaka, pateikta dominavimo koeficientų nauda. Trečiame skyriuje pateikti praktinio tyrimo rezultatai. Atlikus teorinės medžiagos ir praktines užduoties analizę, pateikiamos baigiamojo darbo išvados. Darbą sudaro 6 dalys: įvadas, precizinių mechatroninių sistemų veikimo principai, precizinių mechatroninių sistemų modeliavimas, precizinių mechatroninių sistemų tyrimas, išvados, literatūros sąrašas. Darbo apimtis – 54 p. teksto be priedų, 19 iliustr., 8 lent. Atskirai pridedami darbo priedai. / In the first section of the final master thesis precision mechatronic system‘s operating principles, characteristics of materials are analyzed, analysis of constructions and research are accomplished. In the second section precision mechatronic system‘s simulation is reviewed, numerical models are given, precision mechatronic system‘s influence of geometrical parameters is studied, advantage of the dominance coefficients is represented. In the third section practical results are presented. After the theoretical material and practical task analysis accomplishment, the conclusions of final thesis are presented. The work contains 6 sections: introduction, precision mechatronic system‘s operating principles, precision mechatronic system‘s simulation, precision mechatronic system‘s research, conclusions, references. The volume of the thesis – 54 p. of text without supplements, 19 ill., 8 tab. Separately are attached thesis supplements.

[pt] A modelagem de fenômenos climatológicos constitui um dos maiores desafios enfrentados pela humanidade, impactando toda a vida do planeta. Muitos modelos têm sido propostos e muitas ferramentas têm sido construídas na tentativa de explicar a dinâmica destes processos e sua evolução espacial e temporal. Este trabalho visa oferecer uma contribuição para a modelagem, análise e compreensão dos fenômenos climatológicos com base no conceito da Inovação. Ao invés de procurar, como os modelos clássicos, a representação de comportamentos e relações com base em técnicas estatísticas, esta pesquisa apóiase em um novo conceito: a Inovação, que busca o novo, e não o padrão, identificando a diferença e modelando o fenômeno a ela associado O conceito da Inovação é capaz de caracterizar o fenômeno climatológico, reconhecendo seu surgimento, localização, intensidade e duração. A aplicação do Conceito da Inovação leva à identificação das conexões globais, definindo propagações espaciais e temporais, além de delinear caminhos que explicam as teleconexões entre regiões e sua variação ao longo do tempo. Os resultados obtidos são bastante promissores, uma vez que conseguem caracterizar os processos e sua evolução com uma precisão e eficiência até agora não obtidas pelos métodos disponíveis. Além disso, a descoberta e a individualização dos caminhos que explicam as teleconexões globais iniciam uma nova classe de ferramentas para um conhecimento mais profundo e abrangente de todo o processo climatológico. / [en] Modeling climatological phenomena is one of the most intriguing challenges faced by mankind; the results impact on the whole planet life. Most existing models and tools search for the explanation of these process dynamics and associated spatial and temporal evolution. This work targets a contribution to the modeling, analysis and understanding of climatological phenomena based on the Innovation concept. Instead of following the classical search for statistical behaviors, the aim is searching for the transient and the associated impacts. The Innovation concept is initially applied to the climatological phenomena, identifying its birth, location, duration and intensity. Next, global connections are identified, defining spatial and temporal propagations. Finally, global paths and corresponding variations in time are highlighted and used to explain global teleconnections between regions. The obtained results are promising, characterizing processes and corresponding evolution within a precision and efficiency not offered by existing models. Furthermore, uncovering the roots of global teleconnections permits a new class of tools for a more complete and deep understanding of the whole climatological environment.

USFKAD is an encoded expert system for the eigenfunction expansion of solutions to the wave, diffusion, and Laplace equations: both homogeneous and nonhomogenous; one, two, or three dimensions; Cartesian, cylindrical, or spherical coordinates; Dirichlet, Neumann, Robin, or singular boundary conditions; in time, frequency, or Laplace domain. The user follows a menu to enter his/her choices and the output is a LaTeX file containing the formula for the solution together with the transcendental equation for the eigenvalues (if necessary) and the projection formulas for the coefficients. The file is suitable for insertion into a book or journal article, and as a teaching aid. Virtually all cases are covered, including the Mellin, spherical harmonic, Bessel, modified Bessel, spherical Bessel, Dini, Hankel, Weber, MacDonald, and Kantorovich-Lebedev expansions, mixed spectrum, and rigid body modes.