Dissertations / Theses on the topic 'Multi-angular'

Thesis (M.S. in Astronautical Engineering and Aeronautical and Astronautical Engineer) Naval Postgraduate School, June 2001.
Thesis advisor(s): Agrawal, Brij N. "June 2001." Includes bibliographical references (p. 109-110). Also available in print.

Diffusion weighted magnetic resonance images offer unique insights into the neural networks of in vivo human brain. In this study, we investigate estimation and statistical analysis of multi-compartment models in high angular resolution diffusion imaging (HARDI) involving the Rician noise model. In particular, we address four important issues in multi-compartment diffusion model estimation, namely, the modelling of Rician noise in diffusion weighted (DW) images, the automatic determination of the number of compartments in the diffusion signal, the application of spatial prior on multi-compartment models, and the evaluation of parameter indeterminacy in diffusion models. We propose an expectation maximization (EM) algorithm to estimate the parameters of a multi-compartment model by maximizing the Rician likelihood of the diffusion signal. We introduce a novel scheme for automatically selecting the number of compartments, via a sparsity-inducing prior on the compartment weights. A non-local weighted maximum likelihood estimator is proposed to improve estimation accuracy utilizing repetitive patterns in the image. Experimental results show that the proposed algorithm improves estimation accuracy in low signal-to-noise-ratio scenarios, and it provides better model selection than several alternative strategies. In addition, we derive the Cram´er-Rao Lower Bound (CRLB) of the maximum Rician likelihood estimator for the balland-stick model and general differentiable diffusion models. The CRLB provides a general theoretical tool for comparing diffusion models and examining parameter indeterminacy in the maximum likelihood estimation problem.
published_or_final_version
Computer Science
Doctoral
Doctor of Philosophy

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 225-238).
Distributed Spacecraft Missions (DSMs) are gaining momentum in their application to Earth science missions owing to their ability to increase observation sampling in spatial, spectral and temporal dimensions. This thesis identifies a gap in the angular sampling abilities of monolithic spacecraft in Earth observation missions and proposes to use distributed spacecraft to address this gap. The science performance metric is chosen to be Bidirectional Reflectance-Distribution Function (BRDF), which describes the directional and spectral variation of reflectance of an optically thick surface element at any time instant. Airborne instruments are the gold standard for BRDF estimation (e.g. Cloud Absorption Radiometer/CAR). They can collect thousands of reflectance measurements at the same ground spot, but are localized in space and time. Spaceborne platforms estimate BRDF by combining angular measurements over time, made along-track, cross-track or by autonomous pointing. However, their plane of data acquisition is very restricted with respect to the sun and the target itself might change over time of acquisition. Formations with spectrometer payloads can make multi-spectral reflectance measurements of a ground target, at many zenith and azimuthal angles simultaneously and estimate the angular signature of the surface. Constellations with overlapping ground spots can capture the angular components of global and temporally varying science products. This work demonstrates the performance impact and feasibility of a BRDF estimation mission using a systems engineering tool (driven by model based systems engineering or MBSE), intricately coupled with a science evaluation tool (driven by observing system simulation experiments or OSSEs). Formations and payload pointing strategies are optimized to maximize angular spread and minimize estimation errors. The effect of angular spread on spatial, spectral and radiometric sampling dimensions is quantified for available spectrometer payloads that fit within the 6U CubeSat standard. Technical feasibility within 6U is verified for attitude determination and control, propulsion, communication and onboard processing modules. DSM architectures are generated and compared to each other and monoliths, in terms of BRDF, albedo, gross primary productivity and total outgoing radiation. Performance is benchmarked with respect to data from previous airborne campaigns (NASA CAR), tower measurements (AMSPEC II) and ideal values from radiative transfer or climate models (UMGLO, COART); and accepted BRDF models. A formation of 6 small satellites produces lesser average error (21.82%) than larger monoliths (23.2%) over extended time periods, purely in terms of angular sampling benefits. The monolithic albedo error of 3.6% is shown to be outperformed by a formation of 3 satellites (1.86%), when arranged optimally and by a formation of 5 satellites (3.36%) when arranged in any way. An 8-satellite formation pushes albedo errors to 0.67% and reduces gross primary productivity errors from 89.77% (monolithic) to 78.69%.
by Sreeja Nag.
Ph. D.

Imagens do sensor Multi-angle Imaging SpectroRadiometer (MISR), que está a bordo do satélite TERRA (EOS-AM1), foram utilizadas para investigar o uso potencial de dados multiangulares para a discriminação de cinco fitofisionomias do Cerrado (Floresta Estacional, Mata Seca, Mata Ciliar, Cerrado stricto sensu e Cerrado Ralo) em quatro datas distintas (novembro de 2003; abril, julho e outubro de 2004). Os dados multiangulares foram obtidos em nove câmeras de 0° (An), ±26,1° (Af, Aa), ±45,6° (Bf, Ba), ±60° (Cf, Ca), ±70,5° (Df, Da), relativas ao nadir, ambos para frente (+) e para trás (-) ao longo da trajetória orbital. Cada câmera fornece dados em quatro bandas espectrais (azul, verde, vermelho e infravermelho próximo). A área de estudo está localizada na porção noroeste do Estado de Minas Gerais. Para caracterizar o comportamento espectro-angular das fitofisionomias nas estações seca e chuvosa, uma Análise por Principais Componentes (APC) foi aplicada sobre 1800 espectros (10 pixels, 5 fitofisionomias, 9 ângulos de visada) em cada data, usando os valores do Fator de Reflectância Bidirecional (BRF) das 4 bandas MISR como variáveis de entrada. Perfis espectro-angulares de BRF e do Normalized Difference Vegetation Index (NDVI) foram analisados para cada fitofisionomia e para cada data. Para fins de classificação das fitofisionomias, o algorítmo da Máxima Verossimilhança (MAXVER) foi utilizado e os resultados de classificação foram comparados com um mapa de referência. Parâmetros dendrométricos destas fitofisionomias, coletados em campo, e dados auxiliares do sensor MISR (índice de área foliar, fração da vegetação fotossintenticamente ativa) foram usados para melhor entender a dinâmica espectro-angular-temporal destas classes de vegetação. Os resultados mostraram que: (a) a transição da região preferencial do espalhamento frontal para a de retroespalhamento foi caracterizada por um deslocamento dos escores da esquerda para a direita do eixo PC1, que representou a reflectância média dos componentes de cena. Isto ocorreu apenas para as imagens adquiridas no plano principal (PP) (abril, julho e outubro de 2004) devido a dominância de componentes iluminados do dossel vistos pelo sensor na direção de retroespalhamento; (b) os perfis das fitofisionomias fortemente afetadas pelos efeitos espectrais da sazonalidade, como a Mata Seca, ocuparam posições distintas ao longo da segunda componente (PC2), que refletiu principalmente variações na reflectância das bandas do infravermelho próximo e do vermelho; (c) para a imagem obtida no plano ortogonal (PO) (novembro de 2003), a resposta espectro-angular das fitofisionomias foi aproximadamente simétrica, em torno do nadir, em função de proporções similares de componentes iluminados e sombreados do dossel vistos pelo sensor. Para as demais imagens obtidas no PP, a resposta espectro-angular foi anisotrópica, especialmente para Cerrado Ralo; (d) o ângulo de visada que produziu o retroespalhamento máximo da radiação variou com o ângulo zenital solar nas imagens adquiridas no PP: abril-julho (câmera Bf ou visada de -45,6o) e outubro (câmera Af ou visada de -26,1o). Para a imagem adquirida no PO (novembro), o retroespalhamento máximo ocorreu ao nadir; (e) o cálculo do NDVI não removeu completamente os efeitos direcionais da vegetação, que foram mais fortes com a diminuição do índice de área foliar na estação chuvosa; (f) os melhores resultados de exatidão de classificação e do índice Kappa foram obtidos com as imagens da estação seca e na região preferencial do retroespalhamento (câmeras f). O ângulo de observação mais favorável para a discriminação das fitofisionomias compreendeu a visada de máximo retroespalhamento da radiação, que variou desde o nadir até a câmera Bf entre as datas analisadas. Estes resultados demonstram o potencial do uso de dados multiangulares para melhorar a discriminação e mapeamento de fitofisionomias do Cerrado com o advento da nova geração de sensores multiangulares.
Images collected by the Multi-angle Imaging SpectroRadiometer (MISR) sensor, onboard the Terra satellite (EOS-AM1), were used to investigate the potential use of multiangular data for the discrimination of five Brazilian savanna physiognomies (Floresta Estacional, Mata Seca, Mata Ciliar, Cerrado stricto sensu and Cerrado Ralo) in four different dates (November, 2003; April, July and October, 2004). The multiangular data were obtained in nine discrete view angles of 0° (An), ±26,1° (Af, Aa), ±45,6° (Bf, Ba), ±60° (Cf, Ca), ±70,5° (Df, Da), relative to nadir, both forward (+) and afterward (-) along the direction of flight. Each camera provides data in four spectral bands (blue, green, red and near-infrared). The study area is located in the northwestern portion of the Minas Gerais State. To characterize the spectral-angular behavior of the physiognomies in the dry and rainy seasons, the principal component analysis (PCA) was applied over 1800 spectra (10 pixels, 5 physiognomies, 9 view angles) in each date, using Bidirectional Reflectance Factor (BRF) values of the 4 MISR bands as an input data. Spectral-angular profiles of BRF and Normalized Difference Vegetation Index (NDVI) were analyzed for each physiognomy and date. For classification purposes, the maximum likelihood (MAXVER) algorithm was used and the classification results were compared with a reference map. Dendrometric parameters collected in field, and auxiliary MISR data (Leaf Area Index and Fraction of Photosynthetically Active Radiation) were used to understand better the spectral-angular-temporal dynamics of the vegetation types. The results showed that: (a) the transition from the forward to the backward scattering direction was characterized by a displacement of the scores from the left to the right side of the PC1 axis, which represented the mean reflectance of the scene components. This trend was observed only for the images acquired in the principal plane (PP) (April, July and October, 2004) due to the dominance of sunlit canopy components viewed by the sensor in the backward direction; (b) profiles of the physiognomies strongly affected by the spectral effects of the seasonallity, such as Mata Seca, were located at distinct positions along the second component (PC2), which was mainly related to variations in reflectance of the near-infrared and red bands; (c) for the image acquired in the orthogonal plane (OP) (November, 2003), the spectral-angular response of the physiognomies was approximately symmetrical to the nadir due to similar proportion of sunlit and shaded canopy components viewed by the sensor. For the remaining PP images, the spectral-angular response was anisotropic, especially for the Cerrado Ralo; (d) the view angle that produced the maximum backscattering varied according to the solar zenithal angle of the images acquired in the PP: April-July (camera Bf or view angle of -45.6o) and October (camera Af or view angle of -26.1o). For the OP image (November, 2003), the maximum backscattering was verified at nadir; (e) the NDVI determination did not remove the directional effects of vegetation, which were stronger with the decrease in the leaf area index values in the rainy season; (f) the best results of classification accuracy and Kappa index were obtained in the dry season and in the backward scattering direction (cameras f). The most favorable view angles for the discrimination of the physiognomies comprised the maximum backscattering viewing, which was observed from nadir to the camera Bf. Results demonstrated the potential use of multiangular data to improve discrimination and mapping of the savanna physiognomies.

[ES] La forma más exacta de conocer el desplazamiento de los neutrones a través de un medio material se consigue resolviendo la Ecuación del Transporte Neutrónico. Tres diferentes aproximaciones de esta ecuación se han investigado en esta tesis: Ecuación del transporte neutrónico resuelta por el método de Ordenadas Discretas, Ecuación de la Difusión y Ecuación de Armónicos Esféricos Simplificados. Para resolver estás ecuaciones se estudian diferentes esquemas del Método de Diferencias Finitas. La solución a estas ecuaciones describe la población de neutrones y las reacciones ocasionadas dentro de un reactor nuclear. A su vez, estas variables están relacionadas con el flujo y la potencia, parámetros fundamentales para el Análisis de Seguridad Nuclear. La tesis introduce la definición de las ecuaciones mencionadas y en particular se detallan para el estado estacionario. Se plantea el Método Modal como solución a los problemas de autovalores definidos por dichas ecuaciones. Primero se desarrollan varios algoritmos para la resolución del estado estacionario de la Ecuación del Transporte de Neutrones con el Método de Ordenadas Discretas para la discretización angular y el Método de Diferencias Finitas para la discretización espacial. Se ha implementado una formulación capaz de resolver el problema de autovalores para cualquier número de grupos energéticos con upscattering y anisotropía. Varias cuadraturas utilizadas por este método en su resolución angular han sido estudiadas e implementadas para cualquier orden de aproximación de Ordenadas Discretas. Además, otra formulación se desarrolla para la solución del problema fuente de la ecuación del transporte neutrónico. A continuación, se lleva a cabo un algoritmo que permite resolver la Ecuación de la Difusión de Neutrones con dos variantes del método de diferencias Finitas, una centrada en celda y otra en vértice o nodo. Se utiliza también el Método Modal calculando cualquier número de autovalores para varios grupos de energía y con upscattering. También se implementan los dos esquemas del Método de Diferencias Finitas anteriormente mencionados en el desarrollo de diferentes algoritmos para resolver las Ecuaciones de Armónicos Esféricos Simplificados. Además, se ha realizado un análisis de diferentes aproximaciones de las condiciones de contorno. Finalmente, se han realizado cálculos de la constante de multiplicación, los modos subcríticos, el flujo neutrónico y la potencia para diferentes tipos de reactores nucleares. Estas variables resultan esenciales en Análisis de Seguridad Nuclear. Además, se han realizado diferentes estudios de sensibilidad de parámetros como tamaño de malla, orden utilizado en cuadraturas o tipo de cuadraturas.
[CA] La forma més exacta de conèixer el desplaçament dels neutrons a través d'un mitjà material s'aconsegueix resolent l'Equació del Transport Neutrònic. Tres diferents aproximacions d'esta equació s'han investigat en aquesta tesi: Equació del Transport Neutrònic resolta pel mètode d'Ordenades Discretes, Equació de la Difusió i Equació d'Ármonics Esfèrics Simplificats. Per a resoldre estes equacions s'estudien diferents esquemes del Mètode de Diferències Finites. La solució a estes equacions descriu la població de neutrons i les reaccions ocasionades dins d'un reactor nuclear. Al seu torn, estes variables estan relacionades amb el flux i la potència, paràmetres fonamentals per a l'Anàlisi de Seguretat Nuclear. La tesi introduïx la definició de les equacions mencionades i en particular es detallen per a l'estat estacionari. Es planteja el Mètode Modal com a solució als problemes d'autovalors definits per les dites equacions. Primer es desenvolupen diversos algoritmes per a la resolució de l'estat estacionari de l'Equació del Transport de Neutrons amb el Mètode d'Ordenades Discretes per a la discretiztació angular i el Mètode de Diferències Finites per a la discretització espacial. S'ha implementat una formulació capaç de resoldre el problema d'autovalors per a qualsevol nombre de grups energètics amb upscattering i anisotropia. Diverses quadratures utilitzades per este mètode en la seua resolució angular han sigut estudiades i implementades per a qualsevol orde d'aproximació d'Ordenades Discretes. A més, una altra formulació es desenvolupa per a la solució del problema font de l'Equació del Transport Neutrònic. A continuació, es du a terme un algoritme que permet resoldre l'Equació de la Difusió de Neutrons amb dos variants del mètode de Diferències Finites, una centrada en cel·la i una altra en vèrtex o node. S'utilitza també el Mètode Modal calculant qualsevol nombre d'autovalors per a diversos grups d'energia i amb upscattering. També s'implementen els dos esquemes del Mètode de Diferències Finites anteriorment mencionats en el desenvolupament de diferents algoritmes per a resoldre les Equacions d'Harmònics Esfèrics Simplificats. A més, s'ha realitzat una anàlisi de diferents aproximacions de les condicions de contorn. Finalment, s'han realitzat càlculs de la constant de multiplicació, els modes subcrítics, el flux neutrònic i la potència per a diferents tipus de reactors nuclears. Estes variables resulten essencials en Anàlisi de Seguretat Nuclear. A més, s'han realitzat diferents estudis de sensibilitat de paràmetres com la grandària de malla, orde utilitzat en quadratures o tipus de quadratures.
[EN] The most accurate way to know the movement of the neutrons through matter is achieved by solving the Neutron Transport Equation. Three different approaches to solve this equation have been investigated in this thesis: Discrete Ordinates Neutron Transport Equation, Neutron Diffusion Equation and Simplified Spherical Harmonics Equations. In order to solve the equations, different schemes of the Finite Differences Method were studied. The solution of these equations describes the population of neutrons and the occurred reactions inside a nuclear system. These variables are related with the flux and power, fundamental parameters for the Nuclear Safety Analysis. The thesis introduces the definition of the mentioned equations. In particular, they are detailed for the steady state case. The Modal Method is proposed as a solution to the eigenvalue problems determined by the equations. First, several algorithms for the solution of the steady state of the Neutron Transport Equation with the Discrete Ordinates Method for the angular discretization and Finite Difference Method for spatial discretization are developed. A formulation able to solve eigenvalue problems for any number of energy groups, with scattering and anisotropy has been developed. Several quadratures used by this method for the angular discretization have been studied and implemented for any order of approach of the discrete ordinates. Furthermore, an adapted formulation has been developed as a solution of the source problem for the Neutron Transport Equation. Next, an algorithm is carried out that allows to solve the Neutron Diffusion Equation with two variants of the Finite Difference Method, one with cell centered scheme and another edge entered. The Modal method is also used for calculating any number of eigenvalues for several energy groups and upscattering. Both Finite Difference schemes mentioned before are also implemented to solve the Simplified Spherical Harmonics Equations. Moreover, an analysis of different approaches of the boundary conditions is performed. Finally, calculations of the multiplication factor, subcritical modes, neutron flux and the power for different nuclear reactors were carried out. These variables result essential in Nuclear Safety Analysis. In addition, several sensitivity studies of parameters like mesh size, quadrature order or quadrature type were performed.
Me gustaría dar las gracias al Ministerio de Economía, Industria y Competitividad y a la Agencia Estatal de Investigación de España por la concesión de mi contrato predoctoral de formación de personal investigador con referencia BES-2016-076782. La ayuda económica proporcionada por este contrato fue esencial para el desarrollo de esta tesis, así como para el financiamiento de una estancia.
Morato Rafet, S. (2020). Contributions to solve the Multi-group Neutron Transport equation with different Angular Approaches [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159271
TESIS

Global modeling of gross primary production (GPP) is a critical component of climate change research. On local scales, GPP can be assessed from measuring CO₂ exchange above the plant canopy using tower-based eddy covariance (EC) systems. The limited footprint inherent to this method however, restricts observations to relatively few discrete areas making continuous predictions of global CO₂ fluxes difficult. Recently, the advent of high resolution optical remote sensing devices has offered new possibilities to address some of the scaling issues related to GPP using remote sensing. One key component for inferring GPP spectrally is the efficiency (ε) with which plants can use absorbed photosynthetically active radiation to produce biomass. While recent years have seen progress in measuring ε using the photochemical reflectance index (PRI), little is known about the temporal and spatial requirements for up-scaling these findings continuously throughout the landscape. Satellite observations of canopy reflectance are subject to view and illumination effects induced by the bi-directional reflectance distribution function(BRDF) which can confound the desired PRI signal. Further uncertainties include dependencies of PRI on canopy structure, understorey, species composition and leaf pigment concentration. The objective of this research was to investigate the effects of these factors on PRI to facilitate the modeling of GPP in a continuous fashion. Canopy spectra were sampled over a one-year period using an automated tower-based, multi-angular spectroradiometer platform (AMSPEC), designed to sample high spectral resolution data. The wide range of illumination and viewing geometries seen by the instrument permitted comprehensive modeling of the BRDF. Isolation of physiologically induced changes in PRI yielded a high correlation (r²=0.82, p<0.05) to EC-measured ε, thereby demonstrating the capability of PRI to model ε throughout the year. The results were extrapolated to the landscape scale using airborne laser-scanning (light detection and ranging, LiDAR) and high correlations were found between remotely-sensed and EC-measured GPP (r²>0.79, p<0.05). Permanently established tower-based canopy reflectance measurements are helpful for ongoing research aimed at up-scaling ε to landscape and global scales and facilitate a better understanding of physiological cycles of vegetation and serve as a calibration tool for broader band satellite observations.

This research investigates the spectral reflectance characteristics of soil and vegetation using multi-angular and single view hyperspectral data. The question of the thesis is ???How much information can be obtained from multi-angular hyperspectral remote sensing in comparison with single view angle hyperspectral remote sensing of soil and vegetation???? This question is addressed by analysing multi-angular and single view angle hyperspectral remote sensing using data from the field, airborne and space borne hyperspectral sensors. Spectral mapping, spectral indices and Functional Data Analysis (FDA) are used to analyse the data. Spectral mapping has been successfully used to distinguish features of soil and cotton with hyperspectral data. Traditionally, spectral mapping is based on collecting endmembers of pure pixels and using these as training areas for supervised classification. There are, however, limitations in the use of these algorithms when applied to multi-angular images, as the reflectance of a single ground unit will differ at each angle. Classifications using six-class endmembers identified using single angle imagery were assessed using multi-angular Compact High Resolution Imaging Spectrometer (CHRIS) imagery, as well as a set of vegetation indices. The results showed no significant difference between the angles. Low nutrient content in the soil produced lower vegetation index values, and more nutrients increased the index values. This research introduces FDA as an image processing tool for multi-angular hyperspectral imagery of soil and cotton, using basis functions for functional principal component analysis (fPCA) and functional linear modelling. FDA has advantages over conventional statistical analysis because it does not assume the errors in the data are independent and uncorrelated. Investigations showed that B-splines with 20-basis functions was the best fit for multi-angular soil spectra collected using the spectroradiometer and the satellite mounted CHRIS. Cotton spectra collected from greenhouse plants using a spectrodiometer needed 30-basis functions to fit the model, while 20-basis functions were sufficient for cotton spectra extracted from CHRIS. Functional principal component analysis (fPCA) of multi-angular soil spectra show the first fPCA explained a minimum of 92.5% of the variance of field soil spectra for different azimuth and zenith angles and 93.2% from CHRIS for the same target. For cotton, more than 93.6% of greenhouse trial and 70.6% from the CHRIS data were explained by the first fPCA. Conventional analysis of multi-angular hyperspectral data showed significant differences exist between soil spectra acquired at different azimuth and zenith angles. Forward scan direction of zenith angle provides higher spectral reflectance than backward direction. However, most multi-angular hyperspectral data analysed as functional data show no significant difference from nadir, except for small parts of the wavelength of cotton spectra using CHRIS. There is also no significant difference for soil spectra analysed as functional data collected from the field, although there was some difference for soil spectra extracted from CHRIS. Overall, the results indicate that multi-angular hyperspectral data provides only a very small amount of additional information when used for conventional analyses.

The aim of this thesis is the modeling of surface directional thermal radiation and angular correction on the LST by using empirical and physical methods as well as the analysis of field validation. The work has conducted to some conclusions. The directional emissivity of natural surfaces was obtained from MODIS emissivity product and then used in the split-window algorithm for angular correction on LST. The parameterization models of directional emissivity and thermal radiation were developed. As for the non-isothermal pixels, the daytime-TISI method was proposed to retrieve directional emissivity and effective temperature from multi-angular middle and thermal infrared data. This was validated using an airborne dataset. The kernel-driven BRDF model was checked in the thermal infrared domain and its extension was used to make angular normalization on the LST. A new model, namely FovMod that concerns on the footprint of ground sensor, was developed to simulate directional brightness temperature of row crop canopy. Based on simulation result of the FovMod, an optimal footprintfor field validation of LST was obtained. This thesis has systematically investigated the topic of directional thermal radiation and angular correction on surface temperature and its findings will improve the retrieval accuracy of temperature and emissivity from remotely sensed data and will also provide suggestion for the future design of airborne or spaceborne multi-angular thermal infrared sensors and also for the ground measurement of surface parameters.

In this dissertation the results of the studies on the new readout electronics for the muon system of the LHCb experiment, and the perspectives for carrying out a full angular analysis in the rare decays D0 -> pi+ pi- mu+ mu- and D0 -> K+ K- mu+ mu- will be described. The LHCb experiment studies the heavy hadron physics, containing charm or bottom quarks, in particular searching for new Charge-Parity (CP ) symmetry violation sources, searching for rare decays and studying their properties. LHCb produced leading results in these fields so far. In order to obtain more precise measurements or be able to study new observables, many analyses need a considerable increase in statistics, thus the experiment is now being upgraded to run with an higher instantaneous luminosity of proton-proton collisions. For this reason the readout electronics has been completely replaced by a new optimised version. Several tests have been performed on the new readout electronics that will be here discussed, and that have allowed a comprehensive radiation hardness characterization of the UMC 130 nm technology, used to develop the main electronics device of the muon system readout electronics, the nSYNC chip. On the other hand, in the last two years of data taking, 2017 and 2018, an excellent performance of the LHCb experiment has been obtained and the significant increase in statistics allowed access to new observables, especially in the field of rare decays. In particular, it has been possible to increase the statistics of rare four-body charm decays, like D0 -> pi+ pi- mu+ mu- and D0 -> K+ K- mu+ mu- , of which LHCb already carried out the branching fractions measurement, as well as of angular and CP asymmetries. Since interesting results and flavour anomalies have already been obtained from angular analyses of rare B decays, it is important to study the possibility of these analyses in the complementary sector of rare charm decays. In this work the perspectives for performing a full angular analysis with D0 -> pi+ pi- mu+ mu- and D0 -> K+ K- mu+ mu- decays will be discussed. An angular analysis will allow to carry out several Standard Model tests in the field of rare D decays, allowing also to measure theoretically clean observables for probing effects of physics beyond Standard Model, that can occur at high energy scale.

La fotosintesi è il processo chiave che sostiene la vita sulla Terra. L'efficienza della fotosintesi in condizioni ambientali variabili è mantenuta da meccanismi di regolazione che rispondono velocemente, ovvero l'emissione della fluorescenza della clorofilla a (F) e il quenching non fotochimico (NPQ). F è una radiazione elettromagnetica emessa a lunghezze d'onda più lunghe (640-850 nm) rispetto a quelle di eccitazione. NPQ è un processo complesso che comprende la de-epossidazione dei pigmenti del ciclo della xantofilla con conseguente dissipazione dell'energia in eccesso sotto forma di calore. L'obiettivo del mio progetto di dottorato era quello di sfruttare i metodi di telerilevamento di prossimità della vegetazione per chiarire il collegamento tra misurazioni iperspettrali in continuo di indici ottici relazionati alla fisiologia delle piante (F e PRI) e la funzionalità della vegetazione. Sono state utilizzate misure multiangolari per caratterizzare la risposta anisotropa della fluorescenza nel rosso lontano (F760), nel rosso (F687) e del PRI. Presento un ampio dataset sperimentale di misurazioni multiangolari di F, PRI e riflettanza (R) raccolte durante cicli giornalieri su quattro diversi target di vegetazione. Le risposte direzionali di F760, F687 e PRI in canopy orizzontalmente omogenee sono caratterizzate da valori maggiori nella direzione di retrodiffusione con un massimo nell'hotspot e da valori minori nella direzione di diffusione in avanti. La forma della risposta angolare di F e PRI è per lo più controllata dalla funzione di distribuzione dell'inclinazione delle foglie (LIDF), mentre la grandezza e la forma del picco dell'hotspot sono sensibili ad una combinazione di fattori - l'indice di area fogliare (LAI) e il rapporto tra la larghezza delle foglie e l'altezza della canopy. La valutazione quantitativa dell'impatto dell'anisotropia sui rendimenti apparenti della fluorescenza (Fy*760 e Fy*687) ha mostrato che, in media, le osservazioni off-nadir sono sovrastimate del 20-67% in direzione della retrodiffusione e sottovalutate in altre direzioni del 10-45%. I risultati ottenuti corroborano l'importanza di mantenere una geometria di osservazione nadirale per le misure in continuo di F e PRI. Un ulteriore elemento di complessità per l'interpretazione delle serie temporali di segnali ottici risiede nella dipendenza temporale delle dinamiche della vegetazione. In tale contesto, questo lavoro verifica l'applicabilità di una tecnica di decomposizione delle serie temporali altamente flessibile chiamata Singular Spectrum Analysis (SSA) per disaccoppiare le componenti lente e veloci delle dinamiche della vegetazione nelle serie temporali di F760, Fy*760 e PRI. In primo luogo, è stata sviluppato un proof of concept sulla base di serie temporali spettrali e di flussi a intervalli di mezz’ora simulate realisticamente con il modello SCOPE. Le simulazioni comprendevano due output - considerando ed escludendo l'effetto del ciclo di de-epossidazione delle xantofille e il fattore di amplificazione dell’efficienza di fluorescenza rispettivamente su PRI e F760. Le componenti SSA lente decomposte di PRI, F760 e Fy*760 hanno mostrato una buona correlazione con la variabilità costitutiva di riferimento simulata escludendo l'effetto della modulazione fisiologica. L'accuratezza delle componenti SSA veloci è stata validata con variabili fisiologicamente indotte di riferimento (∆PRI, ∆F), e con il NPQ e l'efficienza di utilizzo della luce (LUE). Quindi, questa metodologia è stata applicata su un set di serie temporali spettrali e di flussi acquisite in campo su grano invernale, permettendo di migliorare significativamente la correlazione delle componenti veloci di F e PRI con LUE rispetto alle serie temporali originali. l'approccio basato su SSA è uno strumento promettente per disaccoppiare le informazioni fisiologiche a partire da misurazioni in continuo del segnale ottico.
Photosynthesis is the key process sustaining life on Earth. The efficiency of photosynthesis under varying environmental conditions is maintained by fast-responding regulatory mechanisms, namely chlorophyll a fluorescence emission (F) and non-photochemical quenching (NPQ). F is an electromagnetic radiation emitted at longer wavelengths (640-850 nm) than for excitation. NPQ is a complex process which includes the de-epoxidation of xanthophyll cycle pigments resulting in dissipation of excess energy as heat. This translates into changes in leaf absorbance at 531 nm, which can be detected with the photochemical reflectance index (PRI). Proximal sensing is a powerful tool for exploitation of subtle signals related to the downregulation of photosynthesis. However, F and PRI are also influenced by canopy structural and biochemical properties, illumination conditions and solar-view geometry, and its explicit interpretation is still challenging. The aim of my Ph.D. project was to exploit the methods of proximal sensing of vegetation to elucidate a link between continuous hyperspectral measurements of optical indicators related to plant physiology (F and PRI) and vegetation functioning. Multi-angular measurements were used to characterize the anisotropic response of far-red (F760), red (F687) fluorescence and PRI. I present an extensive experimental dataset of multi-angular measurements of F, PRI and R collected during a day over four different vegetation targets. Directional responses of F760, F687 and PRI in horizontally homogeneous canopies are characterized by increased values in the backward scattering direction with a maximum in the hotspot and decreased values in the forward scatter direction. The shape of F and PRI angular response is mostly controlled by leaf inclination distribution function (LIDF), while a magnitude and shape of the hotspot peak is sensitive to a combination of factors - leaf area index (LAI) and the ratio of leaf width to canopy height. Quantitative evaluation of the impact of anisotropy on fluorescence apparent yields (Fy*760 and Fy*687) showed, that, on average, off-nadir observations were overestimated by 20-67% in the backscatter direction and underestimated in other directions by 10-45%. The archived results reinforce the importance of maintaining nadir observation geometry for continuous measurements of F and PRI. Additional complexity for the interpretation of time series of optical signal lies in time-scale dependant vegetation dynamics. Here I test the applicability of highly-adaptive time series decomposition technique Singular Spectrum Analysis (SSA) for disentangling slow and fast varying components of vegetation dynamics in time series of F760, Fy*760 and PRI. First, the proof of concept was developed based on spectral and flux half-hourly time series realistically simulated with the SCOPE model. The simulations included two outputs - featuring and excluding the effect of the xanthophyll cycle de-epoxidation and fluorescence efficiency amplification factor on PRI and F760, respectively. The decomposed slow varying SSA-components of total PRI, F and Fy*760 showed a good correlation with reference constitutive variability simulated excluding the effect of physiological modulation (PRI0 , F0,760, Fy*0,760). The accuracy of disentangled fast varying SSA-components was validated with the reference physiologically induced variables (∆PRI, ∆F), and with non-photochemical quenching (NPQ) and light-use efficiency (LUE). Then, the application of this methodology on a field dataset of spectral and flux time series collected in winter wheat field allowed to significantly improve the correlation of fast components of F and PRI with the fast component of LUE in comparison with original time series. Therefore, SSA-based approach is a promising tool for decoupling physiological information from continuous measurements of optical signal which can foster the use of automated proximal sensing systems.

Ce travail porte sur l’étude des mécanismes de conversion de fréquences dans les cristaux photoniques non linéaires bidimensionnels. En particulier, nous avons étudié la génération paramétrique optique (GPO) dans les cristaux de LiTaO3 (PPLT- 2D) à réseau carré. Nous nous sommes d’abord intéressés à l’étude théorique et numérique de structures PPLT- 2D. Une étude numérique, nous a permis de comprendre la contribution des vecteurs de réseau réciproque (kmn) pour différents types de réseaux, en particulier les réseaux carrés et rectangulaires. Par simulations numériques, nous avons également étudié l’influence de l’angle incidence du faisceau de pompe sur l’efficacité de conversion paramétrique dans ses structures. Les mesures expérimentales nous ont permis de mettre en évidence, pour la première fois, l’existence de plusieurs singularités où le signal est partagé pour générer deux idlers et vice versa. En effet, en analysant les propriétés spectrales et angulaires des faisceaux à la sortie du cristal, nous avons, expérimentalement et numériquement, identifié les contributions impliquées dans ces processus communs de GPO. De plus, nous avons étudié le management du gain paramétrique optique dans un réseau carré de PPLT-2D. Les résultats montrent que l’exploitation de la direction non colinéaire permet d’augmenter le gain suivant deux angles d’incidences de la pompe : 0.8° et 1.6°. Cela implique, une meilleure efficacité de conversion en minimisant le walk-off entre la pompe et l’idler. Dans ces conditions, le gain pourrait être proche de celui de la direction colinéaire. Un bon accord a été constaté entre les résultats expérimentaux et ceux de la simulation
This work deals with the study of the mechanisms of frequency conversion in two-dimensional nonlinear photonic crystals. In particular, we have studied optical parametric (OPG) generation in square-lattice LiTaO3 crystals (PPLT-2D). We first focused on the theoretical and numerical study of PPLT-2D structures. A numerical study allowed us to understand the contribution of the reciprocal lattice vectors (kmn) for different types of gratting, in particular square and rectangular lattices. By numerical simulations, we also studied the influence of the incidence angle of the pump beam on the efficiency of the parametric conversion in these structures. Experimental measurements have allowed us to demonstrate, for the first time, the existence of several singularities where the signal is shared to generate two idlers and vice versa. Indeed, by analyzing the spectral and angular properties of the beams at the output of the crystal, we have experimentally and numerically identified the contributions involved in these common OPG processes. In addition, we studied the management of the optical parametric gain in a square lattice of PPLT-2D. The results show that the use of the non-collinear direction makes it possible to increase the gain according to two angles of incidence of the pump: 0.8 ° and 1.6 °. This implies, better conversion efficiency by minimizing the walk-off between the pump and the idler. Under these conditions, the gain could be close to that of the collinear direction. A good agreement was found between the experimental results and those of the simulation

La limite théorique de rendement des cellules photovoltaïques simple-jonction est de l’ordre de 33% d’après le modèle de Shockley-Queisser, ce qui reste éloigné de la limite de Carnot, prédisant une limite maximale de conversion énergie solaire → électricité de 93%. L’écart important entre ces deux limites découle des pertes intrinsèques, essentiellement liées à la conversion inefficace du spectre solaire et à la disparité entre les angles solides d’absorption et d’émission. Pour surmonter ces pertes et se rapprocher de la limite de Carnot, trois stratégies sont envisagées dans cette thèse : les cellules multi-jonction àconcentration, la combinaison de la concentration et de la restriction angulaire et les systèmes hybrides PV/CSP. Chacune de ces stratégies est limitée par des mécanismes qui dégradent leur performance.L’objectif de cette thèse est donc de comprendre dans quelle mesure les différents mécanismes limitants sont susceptibles d’affecter les performances des différentes stratégies étudiées, et d’optimiser l’architecture des cellules dans le but d’accroitre leur efficacité de conversion. Dans ce but, un modèle détaillé de cellule solaire tenant compte des principaux mécanismes limitant a été développé. Un outil d’optimisation par algorithme génétique a également été mis au point, afin d’explorer l’espace des différents paramètres étudiés pour identifier les conditions d’opération optimales. Nous démontrons l’importance majeure que revêt l’adaptation des propriétés optoélectroniques des matériaux utilisés aux conditions opératoires, que ce soit dans le cas des cellules solaires à concentration endurant des pertes résistives significatives, ou encore dans le cas de cellules solaires fonctionnant à des niveaux de températures très supérieurs à l’ambiante. Enfin, nous avons déterminé l’effet des principaux facteurs limitant que constituent les pertes résistives et les recombinaisons non-radiatives sur les cellules solairessimultanément soumises au flux solaire concentré et à la restriction angulaire du rayonnement émis
The maximum efficiency limit attainable with a single-junction PV cell is ~ 33% according to the detailed balance formalism (also known as Shockley-Queisser model), which remains far from the Carnot limit, predicting a solar to electricity efficiency upper value of 93%. The large gap between both limits is due to intrinsic loss mechanisms, including the inefficient conversion of the solar spectrum and the large discrepancy between the solid angles of absorption and emission. To overcome these losses and get closer to the Carnot limit, three different strategies are considered in this thesis: concentrated multi-junction solarcells, the combination of solar concentration and angular confinement, and hybrid PV/CSP systems. Each strategy is inherently limited by several loss mechanisms that degrade their performances. The objective of this thesis is, hence, to better understand the extent to which these strategies are likely to be penalized by these losses, and to tailor the cell properties toward maximizing their efficiencies. To address these questions, a detailed-balance model of PV cell accounting for the main loss mechanisms was developed. A genetic-algorithm optimization tool was also implemented, aiming at exploring the parameter space and identifying the optimal operation conditions. We demonstrate the uttermost importance of tailoring the electronic properties of the materials used with both multi-junction solar cells undergoing significant series resistance losses, and PV cells operating at temperature levels exceeding ambient temperature. We also investigate the extent to which series resistances losses and non-radiative recombination are likely to affect the ability of PV cells simultaneously submitted to concentrated sunlight and angular restriction of the light emitted by band-to-band recombination

Dans l'industrie de fabrication mécanique et notamment pour l'utilisation des centres d'usinage haute vitesse, la connaissance des propriétés dynamiques du système broche-outil-pièce en opération est d'une grande importance. L'accroissement des performances des machines-outils et des outils de coupe a œuvré au développement de ce procédé compétitif. D'innombrables travaux ont été menés pour accroître les performances et les remarquables avancées dans les matériaux, les revêtements des outils coupants et les lubrifiants ont permis d'accroître considérablement les vitesses de coupe tout en améliorant la qualité de la surface usinée. Cependant, l'utilisation rationnelle de cette technologie est encore fortement pénalisée par les lacunes dans la connaissance de la coupe, que ce soit au niveau microscopique des interactions fines entre l'outil et la matière coupée, aussi bien qu'au niveau macroscopique intégrant le comportement de la cellule élémentaire d'usinage, si bien que le comportement dynamique en coupe garde encore une grande part de questionnement et exige de l'utilisateur un bon niveau de savoir-faire et parfois d'empirisme pour exploiter au mieux les capacités des moyens de production. Le fonctionnement des machines d'usinage engendre des vibrations qui sont souvent la cause des dysfonctionnements et accélère l'usure des composantes mécaniques (roulements) et outils. Ces vibrations sont une image des efforts internes des systèmes, d'où l'intérêt d'analyser les grandeurs mécaniques vibratoires telle que la vitesse ou l'accélération vibratoire. Ces outils sont indispensables pour une maintenance moderne dont l'objectif est de réduire les coûts liés aux pannes

近年，IoTに基づく「つながる工場」に関する技術開発が着目され，日本の次世代の製造業を支えるために，新しい研究開発が求められている．特に機械加工の現場では，異常検知や適応制御のために加工現象を精確かつリアルタイムにモニタできる技術が必要とされている．そこで，マシニングセンタなどの工作機械において，回転工具の加工中に多チャンネルで各種の物理量を切削点近傍にてモニタ可能な無線多機能ホルダを開発し，様々な工具，加工方法を対象にその有効性を示した．
Currently, a smart monitoring technology has been attracting particular attention in the factory automation fields regarding the Internet of things (IoT). Particularly in the machining site, the technology of monitoring the processing phenomenon in precision and real-time is required for abnormality detection or adaptive control. Then, we developed a novel tool holder equipped with a wireless communication function to monitor the tool temperature and vibrating accelerations near the cutting point during a tool rotating operation, and we showed effectiveness for various tools and processing method.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University

碩士
國立臺灣大學
機械工程學研究所
98
Since variant reasons, linear moving stage has six degree-of-freedom errors during moving process. Especially the angular error influences the positioning precision significantly due to the Abbé principle. Therefore to improve the precision of the stage, the most important job is to measure its angular error information. In general, commercial high precision angular sensors are expensive so that cannot be installed on machine to do long-term monitoring. The purpose of this article is to develop small volume, low cost, and high-precision sensors based on commercialized DVD pick-up head, quadrant detector and self-made signal process circuits. In the application of DVD pick-up head, DVD autocollimator, 1-D and 2-D optoelectronic level are developed. Moreover, by employing two quadrant detector, optical system and laser source, a sensor which can measure 2-D straightness and roll angular error is fabricated. Finally, the DVD autocollimator and the roll sensor are integrated into one 5-DOFs measurement system, which can measure 2-D straightness , pitch, yaw and roll angular error simultaneously.

碩士
國立屏東科技大學
機械工程系所
101
It is recognized that, from clinical observations, current adapted locking bone plate system for fracture fixation of bone has good stability. Such system is characterized by the vertical angle locking of bone screws to the bone plate. However, it has a drawback of non-flexible angle locking design usually have problems particular in the area such as crushed bone or osteoporosis applications. The aim of this study is to design and develop an directional bone stabilization module for the fixture of long bone fractures via directional angular sleeve to improve the current clinical problem in the performing of angle screw replacement for bone fracture fixation. The system consists of three major parts: bone plates、bone screws and angle sleeve in this study. Based on the CAD software, we design and construct the module and evaluated the mechanical performance. Finally,the bone fracture fixation using finite elements analysis is compared to the bone plates available on the market. In this study, we complete the design and implement the prototype with the multi-directional and angular variable for bone stabilization module. Under the mechanical loading test, the prototype deformation is less than the market sold bone plate system and suitable for the use in adult body. From the finite element analysis results, our bone stabilization module has better fixation performance with the fracture face angle of 20°, around 47% less than the unit without face angle fixation.

碩士
國立交通大學
光電工程研究所
106
In this thesis, we use the multi-amplitude constraints to accelerate Computer Generated Hologram (CGH) and apply this into Iterative Fourier Transform Algorithm (IFTA) and Angular Spectrum Algorithm (ASA). For IFTA, we propose a model of Hybrid Iterative Fourier Transform Algorithm (HIFTA) to improve the defects of the IFTA and Symmetrical Iterative Fourier Transform Algorithm (SIFTA). Then, we focus on the targeted area with three different constraints to make a comparison between the results of the simulation and those of reconstruction in different images. For ASA, in order to reach the goal of multi-focal, we apply multi-amplitude constraints to the ASA and propose a method of Multi-amplitude constraints Angular Spectrum Algorithm (MASA). Later on, we compare the results of the images at 20cm, 30cm, 40cm, respectively. Finally, we successfully achieve the ideas that multi-amplitude constraints used in two algorithms accelerate CGH times, comparing to the previous algorithms. Obviously, the number of iterations and calculation time are reduced. Meanwhile, the quality of the images is more well-shaped and clearer.

碩士
國立虎尾科技大學
材料科學與綠色能源工程研究所
99
There are many advantages of using equal channel angular extrusion (ECAE) process for severe plastic deformation (SPD) of metallic materials. The texture structure of extruded bulk material can be controlled with changing the route during extrusion processing. The large plastic deformation can be accumulated and the cross-sectional area will not change in extruded bulk material through multi-pass extrusion process. Also it will obtain a homogenous and ultra-fine grain structure as the extruded materials were heat treated by recrytallizational annealing. Grain refinement plays an important role on strengthening mechanism of bulk metallic material. In this study, the heat-treatable 6061aluminum alloy bulk materials were extruded by equal channel angular extrusion with different passes. Microstructures with different grain sizes can be obtained by annealing the extruded bulk materials at recrytallizational temperature. The analysis of microstructures and measurement of mechanical properties on the extruded aluminum alloy specimens were conducted to reveal the effect of extrusion pass and annealing temperature on microstructures and mechanical properties. The extruded and grain refined aluminum alloy specimens were heat treated by T6 treatment (i.e. solution heat treatment, quenching and artificial aging).The correlation of the T6 treatment with mechanical properties of the extruded and the grain refined aluminum alloy specimens will be established. The results show that the specimens with structure of different grain sizes can be prepared by different extrusion pass and annealing temperature, the extrusion pass has a significant effect on mechanical properties of 6061 Al-Mg-Si aluminum alloy. The single pass can effectively enhance the tensile strength and hardness, and both will reach a maximum value at 4 passes. But both tensile strength and hardness will gradually decrease with the increasing pass as extrusion pass exceeds 8 passes. The extrusion pass also can significantly affect the grain size, the grain size can be refined to 80-100nm with 12 passes by ECAE process in 6061 Al-Mg-Si aluminum alloy. The extrusion pass only has a negligible effect on the tensile strength and hardness of the extruded aluminum alloy specimens that were heat treated by T6 treatment; but the % elongation will increase with the increasing pass. The extruded specimens with 8 passes can be completely recrystallized by annealing treatment at 500℃for 3 hours. But the hardness of the extruded specimens with 12 passes, which were heat treated by this annealing treatment, will decrease due to abnormal grain growth.

碩士
國立虎尾科技大學
材料科學與綠色能源工程研究所
103
Equal channel angular extrusion (ECAE) is a shear strain process of metal. ECAE mold has an equal cross-section channel with constant corner angle, an external force is applied to the metal through this channel to produce a homogenous and severe plastic deformation, extruded bulk metal will produce high flow stress due to metal flow at the corner, however the cross-section area of channel remains unchanged, the metal can be extruded continuously to accumulate large shear strain and causes grain refinement result, the hardness and the strength of metal can be increased, and elongation also can be improved. In this study, the pre-experiment was conducted to find a suitable extruded temperature for 7075 aluminum alloy. The multi-pass extrusion and T6 treatment were carried out at a fixed extrusion route to reveal the effect of extrusion parameters and process methods on mechanical properties and microstructures for extruded aluminum alloy samples by changing these parameters (temperature, passes) and process methods (solid solution treatment, quenching and extruded order); and also to compare the advantages and disadvantages of different process methods. The effect of strain on recrystallization and precipitation hardening was also revealed, and finally we demonstrated that the mechanical properties of the material can be improved through ECAE process. The experiment results show that annealed and solution-heat-treated 7075 aluminum alloy samples should be extruded at a minimum temperature of 165oC while they can be successfully carried out 12 passes ECAE process, and also achieve the result of strain hardening. The lower is the extrusion temperature, the higher will be the strengthening result obtained; the higher is the extrusion temperature, the better will be the elongation result. The samples which were conducted the ECAE (165oC or 205oC) process using extrusion route BC will obtain the highest elongation in 12 passes extrusion, and surface hardness of each side on extruded samples will achieve uniformity. Annealed samples were extruded by ECAE process at 165 oC and 205 oC, when the extrusion pass increases, both hardness and tensile strength of the samples present different variation tendency; but the elongation of the samples presents a minimum values at 4 passes extrusion and a maximum values at 12 passes extrusion. Annealed sample was extruded by ECAE process at 165 oC and T6 treatment, the higher is the extrusion pass, the shorter will be the aging time which gets peak hardness, but the higher the hardness value. The extruded sample with more extrusion passes gets the smaller grain size, the grains of sample with 12 extrusion passes show uniform equiaxed shape, ASTM grain size number is about 6. While solution-heat-treated 7075 aluminum alloy samples were extruded by ECAE process at 165 oC and subsequently artificially aged at 120 oC, the higher is the extrusion pass, the shorter will be the aging time which gets peak hardness, but the lower the hardness value; and vice versa. The solution-heat-treated samples which were extruded through 2 and 4 passes ECAE process at 165 oC and followed by peak artificial aging treatment can significantly improve the strength and hardness, the increment in strength and hardness for these samples is larger than that of samples which were solution-heat-treated and subsequently ECAE process at 165 oC and annealed then only through T6 (peak aging) treatment, and there is no loss on ductility. The strength and hardness of solution-heat-treated sample which was quenched and followed by 2 passes ECAE process at 165oC and peak artificially aged is almost equal to that of samples which was extruded through 12 passes ECAE process at 165oC and T6(peak artificially aged) treatment.

Deep-inelastic reactions between 6.2 MeV/A Xe-136 ions and a thick W-186 target have been used to investigate excited states in neutron-rich tantalum isotopes, establishing new structures in Ta-182 and Ta-183. Spins and parities were determined from angular correlations, internal conversion coefficients deduced from intensity balances, and consideration of transition strengths. The structure and configuration assignments have been established from the measured magnetic properties and alignments of the observed rotational bands, as well as comparison with multi- quasiparticle calculations. Multi-quasi particle calculations using adjusted Nilsson energies and Lipkin-Nogami pairing model were performed for the series of tantalum nuclei between A=181 and A=185.The previously known 1300 ns isomer in Ta-183 was fully characterised with its energy deduced as 1332 keV and a K = 19/2+ assignment. Several new multi-quasiparticle states, including two isomers with 41(5) ns mean-life, K = 29/2- and 70(4) ns (mean-life), K = 41/2-, have been further identified and found to be feeding the known 1300 ns isomer. From the multi-quasiparticle calculations, a three-quasiparticle configuration was assigned to both the K = 19/2+ and 29/2- isomers, while the upper-most isomer at 41/2- was established to have a five-quasiparticle nature.The out-of-beam gamma-ray coincidence data revealed a new level structure in coincidence with tantalum X-rays. Measurements of the magnetic properties of this structure from branching ratios, together with the yields from various data sets using W-186, Re-185, Re-187 and Os-192 targets, enabled an isotopic assignment of this structure to Ta-182. Three isomeric states were found to be feeding the known 10-> isomer in Ta-182. A rotational band built on the 10- isomer has been > observed and was found to be fed by a new 14+, 356 ns (mean-life) > isomer at 1950 keV. Several intrinsic states above this isomer are > also identified. Firm spins and parities have been established up to > the 14+ isomeric state. Due to limited spectroscopic information, the > spins and parities for the levels above this isomer are tentative.The structure of Ta-182 and Ta-183 are also investigated by comparing the measured transition strengths with similar transitions in the mass region. Most of the transition strengths measured are in good agreement with expectations in the region, except for a few cases of E1 decays that are anomalous. Possible explanations for some of these anomalous transition strengths have been discussed.Few cases has been observed where the predicted yrast states are not observed experimental in both Ta-182 and Ta-183. Possible explanations have been discussed as well.Both the calculations and experimental results suggest a high density of intrinsic states occurs along the yrast line at high excitation energy in both nuclei. This pattern seems to emerge in the more neutron-rich tantalums isotopes resulting in a more complex level scheme that is difficult to interpret.

This dissertation addresses novel techniques in determining gyroless micro-satellite attitude and attitude rate. The main objective of this thesis is to explore the possibility of using commercially available low cost micro-light star sensor as a stand-alone sensor for micro-satellite attitude as well as attitude rate determination. The objective is achieved by developing accurate and computationally efficient algorithms for the realization of onboard operation of a low fidelity star sensor. All the algorithms developed here are tested with the measurement noise presented in the catalog of the sensor array STAR-1000. A novel accurate second order sliding mode observer (SOSMO) is designed for discrete time uncertain linear multi-output system. Our design procedure is effective for both matched and unmatched bounded uncertain ties and/or disturbances. The bound on uncertainties and/or disturbances is assumed to be unknown. This problem is addressed in this work using the second order multiple sliding modes approach. Second order sliding manifold and corresponding sliding condition for discrete time system is defined similar on the lines of continuous counterpart. Our design is not restricted to a particular class of uncertain (matched) discrete time system. Moreover, it can handle multiple outputs unlike single out-put systems. The observer design is achieved by driving the state observation error and its first order finite difference to the vicinity of the equilibrium point (0,0) in a finite steps and maintaining them in the neighborhood thereafter. The estimation synthesis is based on Quasi Sliding Mode (QSM) design. The problem of designing sliding mode observer for a linear system subjected to unknown inputs requires observer matching condition. This condition is needed to ensure that the state estimation error is a asymptotically stable and is independent of the unknown input during the sliding motion. In the absence of a matching condition, asymptotic stability of the reduced order error dynamics on the sliding surface is not guaranteed. However, unknown bounded inputs guarantee bounded error on state estimation. The QSM design guarantees an ultimate error bound by incorporating Boundary Layer (BL) in its design procedure. The observer achieves one order of magnitude improvement in estimation accuracy than the conventional sliding mode observer (SMO) design for an unknown input. The observer estimation errors, satisfying the given stability conditions, converge to an ultimate finite bound (with in the specified BL) of O(T2), where T Is the sampling period. A relation between sliding mode gain and boundary layer is established for the existence of second order discrete sliding motion. The robustness of the proposed observer with respect to measurement noise is also analyzed. The design algorithm is very simple to apply and is implemented for two examples with different classes of disturbances (matched and unmatched) to show the effectiveness of the design. Simulation results show the robustness with respect to the measurement noise for SOSMO. Second order sliding mode observer gain can be calculated off-line and the same gain can work for large band of disturbance as long as the disturbance acting on the continuous time system is bounded and smooth. The SOSMO is simpler to implement on board compared to the other traditional nonlinear filters like Pseudo-Linear-Kalman-filter(PLKF); Extended Kalman Filter(EKF). Moreover, SMO possesses an automatic adaptation property same as optimal state estimator(like Kalman filter) with respect to the intensity of the measurement noise. The SMO rejects the noisy measurements automatically, in response to the increased noise intensity. The dynamic performance of the observer on the sliding surface can be altered and no knowledge of noise statistics is required. It is shown that the SOSMO performs more accurately than the PLKF in application to micro-satellite angular rate estimation since PLKF is not an optimal filter. A new method for estimation of satellite angular rates through derivative approach is proposed. The method is based on optic flow of star image patterns formed on a star sensor. The satellite angular rates are derived directly from the 2D-coordinates of star images. Our algorithm is computationally efficient and requires less memory allocation compared to the existing vector derivative approaches, where there is also no need for star identification. The angular rates are computed using least square solution method, based on the measurement equation obtained by optic flow of star images. These estimates are then fed into discrete time second order sliding mode observer (SOSMO). The performance of angular rate estimation by SOSMO is compared with the discrete time First order SMO and PLKF. The SOSMO gives the best estimates as compared to the other two schemes in estimating micro-satellite angular rates in all three axes. The improvement in accuracy is one order of magnitude (around1.7984 x 10−5 rad/ sec,8.9987 x 10−6 rad/ sec and1.4222 x 10−5 rad/ sec in three body axes respectively) in terms of standard deviation in steady state estimation error. A new method and algorithm is presented to determine star camera parameters along with satellite attitude with high precision even if these parameters change during long on-orbit operation. Star camera parameters and attitude need to be determined independent of each other as they both can change. An efficient, closed form solution method is developed to estimate star camera parameters (like focal length, principal point offset), lens distortions (like radial distortion) and attitude. The method is based on a two step procedure. In the first step, all parameters (except lens distortion) are estimated using a distortion free camera model. In the second step, lens distortion coefficient is estimated by linear least squares (LS) method. Here the derived camera parameters in first step are used in the camera model that incorporates distortion. However, this method requires identification of observed stars with the catalogue stars. But, on-orbit star identification is difficult as it utilizes the values of camera calibrating parameters that can change in orbit(detector and optical element alignment get change in orbit due to solar pressure or sudden temperature change) from the ground calibrated value. This difficulty is overcome by employing a camera self-calibration technique which only requires four observed stars in three consecutive image frames. Star camera parameters along with lens (radial and decentering) distortion coefficients are determined by camera self calibration technique. Finally Kalman filter is used to refine the estimated data obtained from the LS based method to improve the level of accuracy. We consider the true values of camera parameters as (u0,v0) = (512.75,511.25) pixel, f = 50.5mm; The ground calibrated values of those parameters are (u0,v0) =( 512,512) pixel, f = 50mm; Worst case radial distortion coefficient affecting the star camera lens is considered to be k1 =5 x 10−3 .Our proposed method of attitude determination achieves accuracy of the order of magnitude around 6.2288 x 10−5 rad,3.3712 x 10−5 radand5.8205 x 10−5 rad in attitude angles φ,θ and ψ. Attitude estimation by existing methods in the literature diverges from the true value since they utilize the ground calibrated values of camera parameters instead of true values. To summarize, we developed a formal theory of discrete time Second Order Sliding Mode Observer for uncertain multi-output system. Our methods achieve the desired accuracy while estimating satellite attitude and attitude rate using low fidelity star sensor data. Our methods require lower on-board processing requirement and less memory allocation; thus are suitable for micro-satellite applications. Thus, the objective of using low fidelity star sensor as stand-alone sensor in micro-satellite application is achieved.

Magnesium alloys have poor formability at room temperature, due to a limited number of slip systems owing to the hexagonal closed packed structure of magnesium. One possibility to increase the formability of magnesium alloys is to refine the grain size. A fine grain magnesium alloy shows high strength and high ductility at room temperature, hence an improved formability. In addition to grain refinement, the formability of Mg alloys can be improved by controlling crystallographic texture. Severe plastic deformation (SPD) processes namely, equal channel angular pressing (ECAP) and multi-axial forging (MAF) have led to improvement in room temperature mechanical property of magnesium alloys. Further, it has been reported that by adding rare earth elements, room temperature ductility is enhanced to nearly 30%. The increase in property is attributed to crystallographic texture. Many rare earth elements have been added to magnesium alloys and new alloy systems have been developed. Amongst these elements, Ce addition has been shown to enhance the tensile ductility in rolled sheets at room temperature by causing homogeneous deformation. It has been observed that processing of rare-earth containing alloys below 300°C is difficult. Processing at higher temperatures leads to grain growth which ultimately leads to low strength at room temperature. The present thesis is an attempt to combine the effect SPD and rare earth addition, and to examine the overall effect on microstructure and texture, hence on room temperature mechanical properties. In this thesis, Mg-0.2%Ce alloy has been studied with regard to the two SPD processes, namely, ECAP and MAF. The thesis has been divided into six chapters. Chapter 1 is dedicated to introduction and literature review pertaining to different severe plastic deformation processes as applied to different Mg alloys. Chapter 2 includes the details of experimental techniques and characterization procedures, which are commonly employed for the entire work. Chapter 3 addresses the effect of ECAP on the evolution of texture and microstructure in Mg-0.2%Ce alloy. ECAP has been carried out on two different initial microstructure and texture in the starting condition, namely forged and extruded. ECAP has been successfully carried out for the forged billets at 250°C while cracks get developed in the extruded billet when ECAP was done at 250°C. The difference in the deformation behaviour of the two alloys has been explained on the basis of the crystallographic texture of the initial materials. The microstructure of the ECAP materials indicates the occurrence of recrystallization. The recrystallization mechanism is identified as “continuous dynamic recovery and recrystallization” (CDRR) and is characterized by a rotation of the deformed grains by ~30⁰ along c-axis. The yield strengths and ductility of the two ECAP materials have been found quite close. However, there is a difference in the yield strength as well as ductility values when the materials were tested under compression. The extruded billet has the tension compression asymmetry ~1.7 while the forged material has the asymmetry as ~2.2. After ECAP, the yield asymmetry reduces to ~1 for initially extruded billet, while for the initially forged billet the yield asymmetry value reduces to ~1.9. In chapter 4, the evolution of microstructure and texture was examined using another severe plastic deformation technique, namely multi axial forging (MAF). In this process, the material was plastically deformed by plane strain compression subsequently along all three axes. In this case also two different initial microstructures and texture were studied, namely the material in as cast condition and the extruded material. The choice of initial materials in this case was done in order to examine the effect of different initial grain size in addition to different textures. By this method, the alloy Mg-0.2%Ce could be deformed without fracture at a minimum temperature of 350⁰C leading to fine grain size (~3.5 µm) and a weak texture. Grain refinement was more in the initial cast billets compared to the initial extruded billet after processing. The mechanism of grain refinement has been identified as twin assisted dynamic recrystallization (TDRX) and CDRR type. The mechanical properties under tension as well as under compression were also evaluated in the present case. The initially extruded billet has shown low tension compression asymmetry (~1.2) than cast billet (~1.9), after MAF. Chapter 5 addresses the exclusive effect of texture on room temperature tensile properties of the alloy. Different textures were the outcomes of ECAP and MAF processes. In this case, in order to obtain an exact role of texture, a third of deformation mode, rolling, was also introduced. All the processed materials were annealed to obtain similar grain size but different texture. A similar strength and ductility for ECAP and MAF, where the textures were qualitatively very different, was attributed to the fact that texture of both the ECAP and MAF processed materials, was away from the ideal end orientation for tensile tests. In chapter 7, the final outcomes of the thesis have been summarized and scope for the future work has been presented.

This thesis deals with design and implementation of personal data and consents to the processing of personal data management portal with multitenancy support. The work deals with theoretical basis for the portal design in the field of personal data protection and cloud software development. The final design is implemented and deployed in production environment.

The current trend towards mobility of individuals, together with the exponential growth of the number of mobile devices led the market to a boom in the demand for the development of mobile applications. Moreover, with the expansion and heterogeneity of the mobile devices and platforms, software companies need to search for faster and cheaper ways to develop applications that can span as many devices as possible to capture the market. Currently, the Android and iOS Operating Systems roughly share and dominate the mobile market, with timid expressions of other competitors. Each of these mobile operating systems were developed using their own languages, strategy and SDKs for development of applications using their libraries – known as Native apps. On the other hand, the evolution of HTML5, CSS and JavaScript created generic alternatives to create mobile apps that run on devices on all operating systems, although lacking the capability to access the device’s full potential. Alongside came the new Hybrid cross-platform development frameworks, which try to take the best of both worlds. This dissertation describes the evolution of the different mobile app development approaches and the state-of-the-art in their development techniques, and compares them with the Hybrid app approach, then highlighting the trends in mobile app development using Hybrid platforms and their advantages. This research includes the development of a mobile Hybrid application, CodeGT, which interacts with an Enterprise Resource Planning (ERP) to access the Transport Documents registered in this ERP and access to the code transmitted by the Portuguese Tax Authority (AT), therefore not requiring the printing of documents and meeting a need of the business market. This application does already have customer industry companies interested in it.
As tendências atuais em direção à grande mobilidade dos indivíduos, juntamente com o crescimento exponencial do número de dispositivos móveis, levaram ao enorme crescimento na procura do desenvolvimento de aplicações móveis. Além disso, com a expansão e heterogeneidade dos dispositivos e das plataformas móveis, as empresas de desenvolvimento de software necessitam de encontrar formas mais rápidas e baratas de desenvolver aplicações capazes de abranger o maior número de dispositivos para ir ao encontro da elevada procura do mercado. Atualmente, os sistemas operativos Android e iOS dividem e dominam o mercado de dispositivos móveis com expressões tímidas de outros concorrentes. Cada um desses sistemas operativos móveis foi desenvolvido especificamente para linguagens de programação e estratégias próprias e oferecem um conjunto de ferramentas de desenvolvimento com as suas bibliotecas, para a criação de aplicações nativas. Por outro lado, a evolução do HTML5, CSS e do JavaScript criaram oportunidades para o surgimento de alternativas genéricas para criação de aplicações multiplataforma que correm em todos os dispositivos e em todos os sistemas operativos, mas sem a capacidade de aceder todo o potencial nativo do dispositivo. Paralelamente surgiram as novas plataformas de desenvolvimento híbridas, que tentam tirar o melhor partido dos dois mundos. Esta dissertação descreve a evolução das diferentes abordagens no desenvolvimento de aplicações móveis mais concretamente na utilização de ferramentas multiplataformas para a criação de aplicações móveis híbridas e as suas vantagens. A pesquisa incluiu ainda o desenvolvimento de uma aplicação móvel, CodeGT, desenvolvido numa plataforma híbrida para interagir com um software ERP, acedendo aos Documentos de Transporte registados nesse ERP, assim como ao código transmitido pela Autoridade Tributária (AT), que assim dispensa a impressão de documentos e indo ao encontro de uma necessidade do mercado. Esta aplicação já tem empresas clientes interessadas nela.