Hyperspectral reflectance data are utilised in many applications, where measured data are processed and converted into physical, chemical and/or biological properties of the target objects and/or processes being studied. It has been proven that crop reflectance data can be used to detect, characterise and quantify disease severity and plant density. In this thesis, various methods were proposed and used for detection, characterisation and quantification of disease severity and plant density utilising data acquired by hand-held spectrometers. Following this direction, hyperspectral images provide both spatial and spectral information opening for more efficient analysis. Hence, in this thesis, various surface water quality parameters of inland waters have been monitored using hyperspectral images acquired by airborne systems. After processing the images to obtain ground reflectance data, the analysis was performed using similar methods to those of the previous case. Hence, these methods may also find application in future satellite based hyperspectral imaging systems. However, the large size of these images raises the need for efficient data reduction. Self organising and learning neural networks, that can follow and preserve the topology of the data, have been shown to be efficient for data reduction. More advanced variants of these neural networks, referred to as the weighted neural networks (WNN), were proposed in this thesis, such as the weighted incremental neural network (WINN), which can be used for efficient reduction, mapping and clustering of large high-dimensional data sets, such as hyperspectral images. Finally, the analysis can be reversed to generate spectra from simpler measurements using multiple colour-filter mosaics, as suggested in the thesis. The acquired instantaneous single image, including the mosaic effects, is demosaicked to generate a multi-band image that can finally be transformed into a hyperspectral image.

Les États latins d’Orient ont vu la création d’une société en Terre sainte développant un art syncrétique au carrefour des mondes latin, byzantin et arabe. Outre l’architecture religieuse et militaire, les manuscrits sont également les témoignages d’une culture levantine aux multiples influences. L’étude des œuvres croisées nous a montré une très nette augmentation de la production de manuscrits après le séjour de Louis IX au Proche Orient, ainsi qu’un changement dans la nature même des textes copiés. Les manuscrits liturgiques sont ainsi délaissés au profit de la littérature historique, telle l’Histoire Ancienne jusqu’à César. À partir d’un texte venu de Flandre, les nobles francs de Terre sainte et les enlumineurs à leur service ont recréé un cycle de miniatures pour inscrire leurs images dans la tradition multiculturelle croisée. Des partis-pris artistiques ont ainsi été mis au jour et définis comme des choix conscients visant à personnaliser les copies levantines et les inscrire dans une tradition de près de deux siècles : l’emprunt à différentes traditions artistiques, occidentales et orientales, pour la création des miniatures, la mise en lumière de héros liés à la Terre sainte ou aux Francs, et parfois la figuration de leur environnement oriental. Ces processus de personnalisation des images, replacés dans le contexte de la vie culturelle de Saint Jean d’Acre de la fin du XIIIe siècle, nous amènent à dépasser la constatation de phénomènes d’acculturation à leur milieu oriental pour évoquer, de la part des nobles francs de Terre sainte, une volonté d’affirmer visiblement leur identité sociale collective et leur double culture, entre Orient et Occident. / The Crusader States have created a society in the Holy Land developing a syncretic art at the crossroads of Latin, Byzantine and Arabic worlds. In addition to religious and military architecture, manuscripts are also evidences of a cosmopolitan Levantine culture. The study of Crusader Art has shown that the painting of manuscripts was revived at Acre in the early 1250’s, after Louis XI’s stay in the Middle East. Secular manuscripts written mostly in Old French became popular, as well as new historical literature. The most popular examples were the Histoire d’Outremer by William of Tyre and the Histoire Ancienne jusqu’à César. This illustrated text was first composed in France for Roger de Lille and brought to the Crusader East in the mid-thirteenth century. Frankish aristocracy and crusader illuminators have created a cycle of miniatures in order to integrate their images in the cosmopolitan Crusader Art. Artistic choices have then come to light and been defined as conscious choices to offer works that represent the best of the Frankish culture of Acre and integrate them in an almost two centuries old artistic tradition : the borrowing from Western and Oriental artistic traditions in order to create their miniatures, the revelation of heroes linked to the Holy Land and the Franks, and sometimes the representation of their Oriental environment. This process of personalization and multicultural content, set within the context of the cultural society of Saint Jean d’Acre at the end of the thirteenth century, are the evidences of the remarkable artistic acculturation of Frankish society in the Holy Land, at the crossroads of the West and the Near East.

Data acquisition from multiple analog channels is an important function in many embedded devices used in avionics, medical electronics, robotics and space applications. It is desirable to engineer these systems to reduce their size, power consumption, heat dissipation and cost. The goal of this research is to explore designs that exploit a priori knowledge of the input signals in order to achieve these objectives. Sparsity is a commonly observed property in signals that facilitates sub-Nyquist sampling and reconstruction through compressed sensing, thereby reducing the number of A to D conversions. New architectures are proposed for the real-time, compressed acquisition of streaming signals. A. It is demonstrated that by sampling a collection of signals in a multiplexed fashion, it is possible to efficiently utilize all the available sampling cycles of the analogue-to-digital converters (ADCs), facilitating the acquisition of multiple signals using fewer ADCs. The proposed method is modified to accommodate more general signals, for which spectral leakage, due to the occurrence of non-integral number of cycles in the reconstruction window, violates the sparsity assumption. When the objective is to only detect the constituent frequencies in the signals, as against exact reconstruction, it can be achieved surprisingly well even in the presence of severe noise (SNR ~ 5 dB) and considerable undersampling. This has been applied to the detection of the carrier frequency in a noisy FM signal. Information redundancy due to inter-signal correlation gives scope for compressed acquisition of a set of signals that may not be individually sparse. A scheme has been proposed in which the correlation structure in a set of signals is progressively learnt within a small fraction of the duration of acquisition, because of which only a few ADCs are adequate for capturing the signals. Signals from the different channels of EEG possess significant correlation. Employing signals taken from the Physionet database, the correlation structure of nearby EEG electrodes was captured. Subsequent to this training phase, the learnt KLT matrix has been used to reconstruct signals of all the electrodes with reasonably good accuracy from the recordings of a subset of electrodes. Average error is below 10% between the original and reconstructed signals with respect to the power in delta, theta and alpha bands: and below 15% in the beta band. It was also possible to reconstruct all the channels in the 10-10 system of electrode placement with an average error less than 8% using recordings on the sparser 10-20 system. In another design, a set of signals are collectively sampled on a finer sampling grid using ADCs driven by phase-shifted clocks. Thus, each signal is sampled at an effective rate that is a multiple of the ADC sampling rate. So, it is possible to have a less steep transition between the pass band and the stop band, thereby reducing the order of the anti-aliasing filter from 30 to 8. This scheme has been applied to the acquisition of voltages proportional to the deflection of the control surfaces in an aerospace vehicle. The idle sampling cycles of an ADC that performs compressive sub-sampling of a sparse signal, can be used to acquire the residue left after a coarse low-resolution sample is taken in the preceding cycle, like in a pipelined ADC. Using a general purpose, low resolution ADC, a DAC and a summer, one can acquire a sparse signal with double the resolution of the ADC, without having to use a dedicated pipelined ADC. It has also been demonstrated as to how this idea can be applied to achieve a higher dynamic range in the acquisition of fetal electrocardiogram signals. Finally, it is possible to combine more than one of the proposed schemes, to handle acquisition of diverse signals with di_erent kinds of sparsity. The implementation of the proposed schemes in such an integrated design can share common hardware components so as to achieve a compact design.

In der vorliegenden Arbeit wurde mit Hilfe eines Photon-STM die Korrelation zwischen optischen Eigenschaften und der lokalen Morphologie an zwei unterschiedlichen Systemen untersucht. Hierfür wurden zum einem oxidgetragene Ensemble von Silber-Partikeln präpariert, wobei sowohl die Partikelform (Kuppel- und Scheibenform) als auch die deponierte Partikeldichte variiert werden konnte. Neben der Präparation solcher Partikel auf Al10O13/NiAl, konnten sphärische Silber-Kolloide geordnet, als auch ungeordnet auf HOPG aufgebracht und untersucht werden. Dabei zeigte sich, dass das Verhältnis von Höhen zu Breiten nicht nur einen signifikanten Einfluss auf die Mie-Resonanz des einzelnen Partikels hat, sondern auch die elektromagnetische Kopplung der Partikel in einem Ensemble stark kontrolliert. Die energetische Lage der Mie-Resonanz zeigt im Fall der kuppelförmigen Ag-Partikel eine starke Abhängigkeit vom Intepartikel-Abstand, was sich in einer Verschiebung zu höheren Energien für eine steigende Partikeldichte äußert. Eine solche Abhängigkeit konnte bei den Ensembles der scheibenförmigen Partikel nicht beobachtet werden. Des weiteren zeigte sich, dass, verglichen mit den ungeordneten Ensembles, die selbstorganisierte langreichweitige Ordnung der Silber-Kolloide auf HOPG nur einen schwachen Einfluss auf die energetische Position der Mie Resonanz hat.Das zweite hier untersuchte System sind dünne MgO Filme unterschiedlicher Dicken auf einem Mo(001) Substrat. Diese zeigen ein reichhaltiges Wachstumsverhalten, welches durch eine Differenz in den Gitterkonstanten von 5.3% begründet ist und erst ab etwa 25 ML zu einem flachen und defektarmen Film führt. Die so induzierte Spannung relaxiert bis zu einer Dicke von etwa 7 ML in einer periodischen Überstruktur die aus abwechselnd flachen und verkippten Ebenen an der MgO-Mo Grenzschicht hervorgeht. Für MgO Filme mit einer Dicke von etwa 12 ML werden dann Schraubenversetzungen, ausgedehnte verkippte Ebenen und Stufenkanten mit einer Orientierung entlang der Richtung beobachtet. Die optische Charakterisierung durch Feldemission von Elektronen aus der STM-Spitze in den MgO-Film wird dominiert von zwei Emissionsmaxima bei Energien von 3.1 eV und 4.4 eV. Die kontrollierte Nukleation von Gold Partikeln und die Erzeugung von Farbzentren im MgO Film erlaubten eine Zuordnung dieser Emissionen zu strahlenden Zerfällen von Exitonen an Ecken, Kinken bzw. Stufen des Magnesiumoxids. Solche Emissionsprozesse konnten allerdings nur unter Einstellungen beobachtet werden, bei denen ein gleichzeitiges Rastern der Oberfläche unmöglich ist. Bei moderaten Einstellungen war auch eine ortsaufgelösten Spektroskopie möglich, wobei dann neue Emissionsmechanismen beobachtet wurden. Dabei sind zwei Prozesse wesentlich; zum einen die Ausbildung von sog. Spitzen-induzierten Plasmonen im Bereich zwischen Spitze und dem Mo-Substrat, zum anderen strahlende Elektronenübergänge zwischen sog. Feldemissionsresonanzen, die sich im Spitze/MgO-Film System ausbilden. / In this thesis, the correlation between the optical properties and the local morphology of supported silver nanoparticle ensembles and MgO thin films deposited on Mo(001) systems is explored by means of Photon-STM. In the first section, dome and disk shaped Ag nanoparticle ensembles with increasing density on an alumina film on NiAl(110) were analyzed as well as ordered and disordered ensembles of Ag nanocolloids on HOPG. The aspect ratio of the Ag nanoparticles was found to have a significant influence not only on the Mie plasmon resonance of a single particle, but also on the electromagnetic coupling within the nanoparticle ensembles. The Mie resonance in the ensemble of dome shaped Ag nanoparticles shows a strong dependence on the interparticle distance, where it shifts to higher energies with increasing particle density, due to destructive interference effects. In the disk-like Ag ensembles, however, the plasmon energy is independent of particle-particle separation. The long-range lateral ordering of size-selected Ag nanocolloids is found to induce a high dipole-dipole coupling within the ensemble. This is mainly reflected by the enhancement of the spectral intensity of the in-plane Mie mode, due to constructive coupling. However, ensembles with either well-ordered or disordered arrangements reveal no important difference in their optical properties, reflecting the weak influence of the long-range order in the particle ensemble. Thin MgO films with different thicknesses were grown on a Mo(001) surface. The stress resulting from the 5.3% lattice mismatch between the MgO(001) and the Mo(001) lattice parameters is found to control the surface morphology of the MgO film until thicknesses of around 25ML at which flat and defect-poor films are obtained. The relaxation of the stress induces a periodic network in the first 7ML of the MgO film, consisting of alternated flat and tilted mosaics. The presence of screw dislocations, steps oriented along the MgO directions, and tilted planes is observed when the MgO films are approximately 12ML thick. In addition, an increase of the MgO work function around these new surface features is revealed from STM spectroscopy. The photon emission induced by field-emitted electron injection from the STM tip into the MgO films is dominated by two emission bands located at 3.1eV and 4.4eV. To check the origin of these bands, further experiments, namely, nucleation of Au particles and creation of F-centers on the MgO surface, have been performed. The nucleation of Au particles at the low coordinated sites is found to quench the MgO optical signal, while the creation or annihilation of F-centers does not alter the MgO emission bands. The 3.1eV and the 4.4eV bands are therefore assigned to the radiative decay of MgO excitons at corner and kink sites, and step sites, respectively. Besides, spatially resolved optical measurements in the tunneling mode of the STM revealed different light emission mechanisms. These radiative processes are mainly related to tip-induced plasmons that form between the tip and the Mo support and to electron transitions between field-emission-resonance states in the STM tip-MgO film junction. The signal from exciton decays at corners and kinks of the MgO surface is however only observed at excitation conditions where the spatial resolution is already strongly reduced.