Les travaux de recherche présentés dans ce manuscrit décrivent plusieurs apports au thème de l'évaluation de la qualité d'images de documents numérisés. Pour cela nous proposons de nouveaux descripteurs permettant de quantifier les dégradations les plus couramment rencontrées sur les images de documents numérisés. Nous proposons également une méthodologie s'appuyant sur le calcul de ces descripteurs et permettant de prédire les performances d'algorithmes de traitement et d'analyse d'images de documents. Les descripteurs sont définis en analysant l'influence des dégradations sur les performances de différents algorithmes, puis utilisés pour créer des modèles de prédiction à l'aide de régresseurs statistiques. La pertinence, des descripteurs proposés et de la méthodologie de prédiction, est validée de plusieurs façons. Premièrement, par la prédiction des performances de onze algorithmes de binarisation. Deuxièmement par la création d'un processus automatique de sélection de l'algorithme de binarisation le plus performant pour chaque image. Puis pour finir, par la prédiction des performances de deux OCRs en fonction de l'importance du défaut de transparence (diffusion de l'encre du recto sur le verso d'un document). Ce travail sur la prédiction des performances d'algorithmes est aussi l'occasion d'aborder les problèmes scientifiques liés à la création de vérités-terrains et d'évaluation de performances.

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Les oscillations paléoclimatiques au cours du Pléistocène et leur influence sur les bilans hydriques stationnels ont été considérées à Madagascar. La disponibilité en eau est l'élément majeur de la vie végétale et animale. À partir de travaux publiés en 2006, un modèle intégrant des aspects écologiques et géomorphologiques dans un contexte de changement climatique est considéré pour identifier les régions qui pouvaient présenter un bilan hydrique stationnel positif, indispensable à la survie de la faune et de la flore sylvicoles au cours des périodes les plus sèches, et l’évolution de ce bilan lorsque le climat redevenait chaud et humide. Le modèle a été appliqué à la biogéographie des lémuriens de Madagascar, et plus particulièrement à une région sédimentaire du versant occidental de l’île, pour expliquer le centre d’endémisme du Menabe Central, entre les bassins versants des fleuves Tsiribihina et Mangoky. / Pleistocene paleoclimatic oscillations have had a major influence on the hydrological balance in Madagascar, from the scale of individual sites to watersheds. Water availability is one of the major component for the life of plants and animals life. Based on previous research published in 2006, a model is considered which has been enriched, and encompasses ecological and geomorphological features in the context of changing climate to identify areas where water remained available during the driest periods, but also how availability increased again when climatic conditions become warmer and wetter. This model is applied to a portion of Western Madagascar encompassing the Tsiribihina and Mangoky watersheds and the Central Menabe center of endemism to describe the mechanism leading to landscape-Level evolution and especially the distribution patterns observed today of some of the island’s endemic animal species, comparing narrowly vs. broadly endemic taxa.

L'étude géologique du massif de fondation du futur barrage de Puylaurent (Massif Central français) a été menée en considérant que la connaissance de l'organisation structurale régionale est fondamentale pour l'interprétation des caractéristiques géotechniques du massif rocheux. Pour cela, les épisodes tectoniques qui ont faconné la région ont été analysés; ainsi ont été établis la genèse, la géométrie et les jeux des accidents résultants. Une étude structurale fine du massif rocheux cristallophyllien qui constitue la fondation du barrage a permis d'établir, outre la géométrie des déformations qu'il a subies, une filiation hiérarchique et chronologique avec les discontinuités régionales. L'existence éventuelle d'anisotropie de contraintes actuelles a été recherchée au moyen de mécanisme au foyer de séismes, de mesures de contraintes in situ et de mesures de vitesses sismisques. Celles-ci ont réussi à mettre en évidence une direction de sollicitation actuelle N*S à NNE-SSW. la confrontation des données géologiques et des résultats de travaux de reconnaissance (sondages, essais Lugeon, galeries) montre divers cas où une perméabilité élevée du massif de fondation est liée à l'orientation des sollicitations actuelles.

L'étude géochimique du volcanisme anté-orogénique de l'Equateur permet de mettre en évidence plusieurs unités magmatiques. La distinction de ces différentes formations conduit à la mise en évidence d'une zone de suture qui sépare le continent sur lequel s'est développée une série andésitique, de terrains allochtones constitués par un arc insulaire développé sur une croûte océanique. Les possibilités d'étendre le modèle d'accrétion des unités allochtones, proposé pour l'Equateur, à l'ensemble des Andes septentrionales sont également discutées,

Nous nous trouvons dans le prolongement ouest du Taurus, formant la liaison entre les Taurides ou les Iranides et les plis égéens. Stratigraphiquement, un net caractère mésogéen apparait dans la partie sud de la Turquie au Mésozoïque, mais l'orogène "alpin" individualise de façon extrême les domaines de sédimentation tertiaire . Nous retiendrons cependant deux traits caractérisant la Turquie; l'un concerne les structures, l'autre le volcanisme. Il y a un véritable enroulement des structures autour de noyaux de terrains "durs" cristallins et cristallophylliens, surtout dans la moltié ouest de la Turquie, avec le massif de Kir§ehir à l'E .d'Ankara et le massif du Menderes au SE d'Izmir . C'est à la bordure sud de ce massif que se rattachent les grandes lignes de la région étudiée. D'autre part un volcanisme basique et ultrabasique se répartit sur toute l'étendue de la Turquie et, semble-t-il, à différents niveaux . stratigraphiques. Nous retrouvons aussi ce deuxième caractère avec une importance particulière dans la région étudiée. Les formations quaternaires et néogènes mises à part, une coupe schématique donne de haut en bas: - des ultramafites ; - des écailles de terrains métamorphiques - des laves spilitiques et d es dia,bases ; - des terrains sédimentaires, avec: un ensemble supérieur nord, que nous appellerons ensem - ble de Koycegiz ;un ensemble inférieur nord que nous appellerons ensemble du Kepeztepe, auquel doit s'ajouter la coupe du Dalamau au Sud de la zone cartographiée, C'est cet ordre que nous suivrons dans le plan général, décri vant en plus, dans le chapitre des terrains sédimentaires, le Néogène et le Quaternaire .

Made available in DSpace on 2015-02-24T19:48:40Z (GMT). No. of bitstreams: 1 AnaCF_ate cap6.pdf: 4452178 bytes, checksum: 27b2ccb7e47f9a71ccabd7ab319267a6 (MD5) Previous issue date: 2002-09-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Hydrogeological prospecting in Northeast Brazil and in other crystalline terrains has been developed on the basis of structural and regional geology concepts that date back to the 50-60 decades and, as such, demand a natural re-evaluation and update. In this kind of terrain, the percolation and accumulation of ground water are controlled by fractures and other types of discontinuities, such as foliations and geological contacts that, through weathering, impart porosity and permeability to the rocks, allowing water flow and storage. Several factors should be considered in the process of locating water wells, as discussed in the literature. Among these, the kind of structures, fracture geometry (including aperture and connectivity) and their geological and chronological context. It is important to correlate fracture systems with the regional neotectonic framework. Fractures at low angle (sub parallel) with the principal stress axis (s1) are those which tend to open (actually they work as tension joints) and, in principle, would present major hydric potential; in the opposite side, fractures at high angle to s1 would behave as closed by a compressional component. Fractures diagonal to the compression and tension axes correspond to shear fractures and, due to their connectivity with second fractures, are also important in terms of hydric potential. Uplift followed by terrain denudation leads to decompression and a general tendency to open (aided by weathering processes) fractures and other rock discontinuities, at different orientations. Low angle fractures, formed in this context, are equally important to increase connectivity, collection of water and recharge of the aquifer systems. In a general way, an opening component (neotectonic or by terrain decompression) and several models to increase fracture connectivity correlate with a greater hydric potential of these structures. Together with parallel research, this thesis addresses models of ground water occurrence in crystalline terrains, either improving well established concepts like the (Riacho-Fenda model), but also stressing other possibilities, like the role of alluvium and paleo-regoliths (the Calha El?vio-Aluvionar model) and of strongly altered, permo-porous zones placed at variable depths below the present surface, flanking several types of discontinuities, especially interconnected fracture arrays (the Bols?es de Intemperismo model). Different methodological approaches are also discussed in order to improve success rates in the location of water wells in crystalline terrains. In this methodological review, a number of case studies were selected in the eastern domain of the State of Rio Grande do Norte, involving the localities of Santa Cruz, Santo Ant?nio, Serrinha, Nova Cruz, Montanhas, Lagoa de Pedras and Lagoa Salgada. Besides the neotectonic analysis of brittle structures, this Thesis addresses the validation of remote sensing as a tool for ground water prospecting. Several techniques were tested in order to detect and select areas with higher potential for ground water accumulation, using Landsat 5-TM and RADARSAT images, besides conventional aerial photos. A number of filters were tested to emphasize lineaments in the images, improving their discrimination, to identify areas with higher overburden humidity, which could reflect subsurface water accumulation, as well as alluvium and other sedimentary covers that might act as recharge zones. The work started with a regional analysis with the orbital images, followed by analysis of aerial photos, up to a detailed structural study of rock exposures in the terrain. This last step involved the analysis of outcrops surrounding wells (in a ray of approximately 10 to 100 m) with distinct productivities, including dry examples. At the level required for detail, it was not possible to accomplish a statistical approach using the available well data catalogs, which lack the desired specific information. The methodology worked out in this Thesis must undergo a testing phase through location of new water wells. An increase in the success rates as desired will led to a further consolidation step with wider divulgation of the methodology to private companies and governmental agencies involved in ground water prospecting in crystalline terrains / A prospec??o hidrogeol?gica no Nordeste do Brasil e em outros terrenos cristalinos tem sido baseada em conhecimentos de Geologia Estrutural e Regional que, pelo tempo decorrido, demandam uma natural reavalia??o. Neste tipo de terreno, a percola??o e ac?mulo de ?gua subterr?nea s?o controlados por fraturas e outros tipos de descontinuidades, tais como folia??es e contatos geol?gicos, que intemperizados adquirem certa porosidade e permeabilidade, permitindo o fluxo e/ou reten??o de ?gua. Diversos fatores devem ser considerados no processo de loca??o de um po?o para ?gua, conforme amplamente discutido na literatura. Dentre estes, o tipo de estrutura observada, a geometria do fraturamento (incluindo abertura e conectividade) e seu contexto geol?gico e cronol?gico. Neste ?ltimo sentido, ? importante correlacionar o fraturamento com o arcabou?o neotect?nico conhecido na regi?o. Fraturas orientadas em baixo ?ngulo (subparalelas) com o eixo de tens?o principal (s1) s?o aquelas que tendem a abrir (funcionam atualmente como juntas de distens?o) e apresentam, em princ?pio, maior potencial h?drico; em situa??o oposta situam-se as fraturas em forte ?ngulo com s1 (corresponderiam a fraturas fechadas , com um componente de compress?o). As fraturas diagonais ?s dire??es de compress?o e distens?o s?o equivalentes ?s fraturas de cisalhamento e, pela conectividade com planos de segunda ordem, s?o tamb?m importantes em termos de produtividade h?drica. A denuda??o do terreno tamb?m enseja descompress?o e uma tend?ncia geral de abertura (inclusive pelo efeito do intemperismo) de fraturas e outras descontinuidades, em orienta??es quaisquer. Fraturas de baixo ?ngulo, formadas nesse contexto, s?o igualmente importantes para definir a conectividade, coleta de ?gua e a recarga dos sistemas aq??feros. De um modo geral, um componente de abertura (neotect?nico ou pela descompress?o) e os v?rios modelos de interconex?o de fraturas resultam no aumento de sua potencialidade h?drica. Em conjunto com pesquisas em paralelo, a presente Tese aborda modelos de ocorr?ncia de ?gua subterr?nea no cristalino, procurando aperfei?oar conceitos j? estabelecidos (como o modelo Riacho-Fenda) e enfatizando outras possibilidades, a exemplo do papel de aluvi?es e paleo-regolitos (o modelo Calha El?vio-Aluvionar) e de zonas fortemente alteradas (permo-porosas) em subsuperf?cie, ladeando v?rios tipos de descontinuidades, em especial fraturas interconectadas (o modelo Bols?es de Intemperismo). S?o tamb?m discutidos diferentes aspectos metodol?gicos atualmente utilizados na loca??o de po?os, fazendo uma reavalia??o destes procedimentos com vistas a aumentar o ?ndice de acerto nas loca??es de po?os em terrenos cristalinos. Nessa metodologia, foram estudadas ?reas selecionadas, no interior do Rio Grande do Norte, envolvendo os munic?pios de Santa Cruz, Santo Ant?nio, Serrinha, Nova Cruz, Montanhas, Lagoa de Pedras e Lagoa Salgada, todos na regi?o oriental do Estado. Al?m de fazer uma an?lise neotect?nica do fraturamento, esta Tese aborda a validade da utiliza??o de sensoriamento remoto como ferramenta na prospec??o de ?gua subterr?nea. Foram testadas v?rias t?cnicas que pudessem facilitar a detec??o e sele??o de ?reas com maior potencial para o ac?mulo de ?gua subterr?nea, utilizando imagens Landsat 5-TM, RADARSAT e fotografias a?reas. Assim, foram utilizados filtros que melhor real?assem os lineamentos observados nas imagens, facilitando a sua discrimina??o, e destacassem ?reas com maior umidade no terreno, que pudessem refletir o ac?mulo de ?gua em subsuperf?cie, bem como coberturas sedimentares e aluvi?es que servem como zonas de recarga. O trabalho partiu de uma an?lise regional com as imagens orbitais, passando pela an?lise de fotografias a?reas, at? um estudo de detalhe, com estudo estrutural de afloramentos em campo. Esta ?ltima envolveu a an?lise de afloramentos pr?ximos a po?os pr?-existentes (em um raio de aproximadamente 10 a 100m), com produtividade distinta, inclusive secos. Ao n?vel de detalhamento requerido, n?o foi poss?vel realizar um trabalho estat?stico utilizando os dados (fichas) de po?os, pela falta das informa??es espec?ficas requeridas. Todo este acervo de conhecimentos gerados deve agora passar por uma fase de testes atrav?s de loca??es espec?ficas. O aumento no ?ndice de acertos, assim pretendido, pode ent?o conduzir a uma etapa posterior de consolida??o e divulga??o da metodologia, para empresas e ?rg?os envolvidos na prospec??o de ?gua subterr?nea em terrenos cristalinos

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / The Rhyacian Serra das Pipocas Greenstone Belt, is part of Archean/Proterozoic terrene of Cearà Central Domain, in the Setentrional portion of Borborema Province. It is located in Southwestern CearÃ, between the municipalities of Boa Viagem, IndependÃncia, Tauà and Pedra Branca. Geological mapping techniques, thin and polished sections petrography, mineral chemistry, lithogeochemistry, and geochronology have been useful in the distinction of the first Greenstone Belt sequence in CearÃ. The metavolcanic-sedimentary sequence is composed of metasedimentary rocks, marly psammite-pelite, containing alternation of mafic-ultramafic volcanic floods, tholeiitic and komatiitic, respectively, and meta-acidic rocks. The komatiitic meta-ultramafic floods are composed of chlorite-anthophyllite-actinolite-tremolite schist displaying acicular texture, or not, occuring discontinuously near the bottom of the sequence. The tholeiitic metamafic rocks are mainly represented by garnet amphibolites, which continuously extend 30km in length by 500m â 1km wide. Basic and acidic metatuffs, metacherts, and banded iron formation are alternated with amphibolites, which sometimes are deeply hydrotermalized. Metasedimentary rocks are mainly terrigenous, containing biotite, kyanite; however, occasional centimetric alternation of calc-silicatic rocks are observed. These lithotypes are cutted off by mafic-ultramafic intrusions, metagranodiorites and metabasic dykes. The lithological association has been developed in a extensional enviroment, probably a back-arc basin, where the komatiitic rocks Mg-Bearing schists display a transition from Munro-type to Barbeton-type, while the tholeiitic metabasalts (amphibolites) are iron-magnesium-rich. Regarding the structural geology, the area is caracterized by penetrative polyphasic strain, occurred during Brasiliano, with tight, isoclinal and recumbent folds, in addition to thrust faults and shear zones. The thrust faults are best recognized, especially, in the contact between the metavolcanic-sedimentary sequence and granite-gneiss-migmatite of Cruzeta Complex; also, between the mafic-ultramafic subunits. The metamorphic grade of the lithological association varies from high greenschist facies to high amphibolite facies, contrasting with Cruzeta Complex units, which are frequently migmatized. Besides, during the Brasiliano orogenesis, leucocratic granites have been intruded along the border zones of the oldest granites (2181,4Â4.4), near the Queimadas thrust fault, there are deeply hydrotemalized rocks, displaying silicification, potassification, chloritization, and carbonation, sulphidation is also present, and they may contain some mineralisation such as copper-gold Volcanic-hosted Massive Sulfide or auriferous lodes, because this association occurs near the silicified zones and also in shear zones. / O Greenstone Belt Serra das Pipocas, de idade riaciana, està inserido no NÃcleo Arqueano/Paleoproterozoico do DomÃnio Cearà Central, na porÃÃo Setentrional da ProvÃncia Borborema. Encontra-se na porÃÃo sudoeste do Estado do CearÃ, entre os municÃpios de Boa Viagem, IndependÃncia Tauà e Pedra Branca. TÃcnicas de mapeamento geolÃgico, anÃlise petrogrÃfica, atravÃs de estudos de seÃÃes delgadas e polidas, quÃmica mineral, litogeoquÃmica e geocronologia auxiliaram para a distinÃÃo desta primeira sequÃncia do tipo Greenstone Belt no CearÃ. A sequÃncia metavulcanossedimentar à composta por rochas metassedimentares psamo-pelito-margosos, contendo intercalaÃÃes de derrames vulcÃnicos metamÃfico-ultramÃficos de natureza toleÃtica e komatiÃtica, respectivamente, e meta-Ãcidas. Os derrames metaultramÃficos komatiÃticos sÃo constituÃdos por clorita-antofilita-actinolita/tremolita xisto, com texturas aciculares ou nÃo, ocorrendo de maneira descontÃnua prÃximo à base da sequÃncia. As rochas metamÃficas de natureza toleÃticas sÃo representadas principalmente por anfibolitos granadÃferos, que se estendem, de maneira descontÃnua, por uma faixa com comprimento da ordem de 30km e largura entre 500m e 1km. Metatufos bÃsicos a Ãcidos, metacherts e formaÃÃes ferrÃferas bandadas ocorrem intercaladas a estes anfibolitos, que se encontram por vezes, fortemente hidrotermalizados. As rochas metassedimentares sÃo principalmente de natureza terrÃgena, contendo biotita, cianita, mas podem apresentar ocasionais intercalaÃÃes centimÃtricas de calcissilicÃticas. Esses litotipos sÃo recortados por intrusÃes metamÃfica-ultramÃficas, metagranodioritos e dique metabÃsico. Toda a associaÃÃo litolÃgica desenvolveu-se ambiente extensional, provavelmente do tipo retro arco, cujas rochas komatiÃticas (xistos magnesianos) encontradas apresentam transiÃÃo entre os tipos Munro e Barbeton, enquanto os metabasaltos toleÃticos (anfibolitos) exibem alto teor de ferro e magnÃsio. Estruturalmente, a Ãrea à marcada por deformaÃÃes polifÃsicas penetrativas, ocorridas no Brasiliano, com dobras isoclinais apertadas, recumbentes, alÃm de falhamentos de empurrÃo e cisalhamento dÃctil. Esses falhamentos sÃo reconhecidos, sobretudo, no contato entre esta sequÃncia metavulcanossedimentar e as rochas granito-gnÃissico-migmatÃticas do Complexo Cruzeta e entre as subunidades dominadas pelas rochas ultramÃficas e mÃficas. O grau metamÃrfico das associaÃÃes litolÃgicas à variÃvel, indo da fÃcies xisto verde alto a anfibolito alto, o que contrasta com as unidades do Complexo Cruzeta que se encontra frequentemente migmatizadas. Durante o evento Brasiliano houve tambÃm a intrusÃo dos leucogranitos. Nas bordas dos corpos intrusivos riacianos, prÃximos à zona de empurrÃo Queimadas, hà presenÃas de rochas fortemente hidrotermalizadas, marcadas por silicificaÃÃo, potassificaÃÃo, cloritizaÃÃo e carbonataÃÃo. Estas sÃo acompanhadas de sulfetaÃÃo, sendo hospedeiras de possÃveis mineralizaÃÃes de cobre e ouro do tipo Sulfetos Massivos VulcanogÃnicos ou mesmo lodes aurÃferos, uma vez que esta associaÃÃo ocorre junto Ãs zonas silicificadas ao longo de cisalhamento.

L’altération chimique et l’érosion physique de la croûte continentale mobilisent de grandes quantités de matière sous formes solide et dissoute. Première productrice de sédiments sur le globe, la chaîne Himalayenne délivre ~1 Gt/a de sédiments aux océans. L'importance des différents facteurs qui contrôlent les flux érodés et celle des processus d’érosion (glaciers, glissements de terrain, sols) sont pourtant encore mal définies. Il en va ainsi des facteurs climatiques, en particulier de leur impact au cours des transitions climatiques. Afin de répondre à ces questions, ce travail s’attache à comparer la composition géochimique des produits de l’érosion à celles des sédiments actuels de rivière et des archives sédimentaires de la plaine du Gange. Un premier bilan des processus d’érosion a été établi petite échelle dans le bassin Haut-Himalayan de la Khudi. L’érosion actuelle conséquente de ce bassin de ~3mm/a se produit lors de la mousson, correspond pour l'essentiel à l’érosion des sols et surtout à l'intense activité d'une zone de glissement de terrain. Grâce au développement d'une nouvelle méthode de destruction de la matière organique, la mesure de l’hydratation des silicates a pu être utilisée comme traceur inédit des sols. Sur cette base, l’inversion des compositions des sédiments de la rivière démontre que l’érosion physique est dominée à ~80% par le glissement de terrain, l’érosion de sols étant mineure et comparable aux taux d’érosion des autres bassins alentours. L’érosion chimique qui conduit à un flux d'éléments dissous de 7.9 kt/a (soit une érosion équivalente de 0.02 mm/a) semble dériver de l’altération profonde du substrat rocheux. Néanmoins les flux d'éléments dissous dessinent également une relation marquée avec les flux particulaires durant la mousson, suggérant une altération additionnelle des sédiments au cours du transport fluvial. Une approche similaire a ensuite été menée à l’échelle plus vaste du bassin de la Narayani drainant l’ensemble du Népal central. Grâce à des mesures de courant par ADCP combinées à l’échantillonnage de sédiments en profondeur, un modèle de transport sédimentaire a été utilisé pour intégrer les flux sédimentaires en profondeur et ainsi réviser le taux d’érosion moyen sur le bassin versant à une valeur de ~1.7 mm/a, proche des taux d'érosion long-terme. Un système géochimique associant la mesure du δD des silicates associée aux concentrations en carbonate s’est révélé un traceur diagnostique de l’érosion glaciaire dans le Nord du bassin, tandis que la teneur en matière organique du sédiment a pu être utilisée comme traceur des sols. L’analyse temporelle des flux de sédiments, de leur composition et du signal granulométrique, a ainsi permis d’établir que seule une faible fraction des sédiments (<20%) provenait de l’érosion par les glaciers et les sols. À l'échelle du Népal central, l’érosion physique semble donc également dominée par les glissements déclenchés lors de la période de mousson. Le grand cône alluvial de la Narayani-Gandak, situé au débouché de cette rivière dans la plaine du Ganges, a enregistré l’histoire récente de l’érosion du Népal central. Trois forages réalisés dans ce méga-cône permettent ainsi d'étudier l'évolution de l'altération et de l'érosion en Himalaya au cours du tardi-Pléistocène. Ces dépôts sédimentaires révèlent une étonnante stabilité depuis ~45 ka de la géochimie, des provenances et du degré d’altération des sédiments. Seule l’intensité de l’érosion mesurée par isotopes cosmogéniques semble augmenter au cours de l’Holocène. Par contraste, l’évolution très récente de la distribution de l’érosion dans la chaîne est marquée par un accroissement (x3) de la proportion de matériel des régions basses et plus peuplées de l'Himalaya, montrant que les activités anthropiques, via notamment une forte croissance du réseau routier durant la dernière décennie, [...] / Chemical weathering and physical erosion of the continental crust mobilise huge amounts of both solid and dissolved material. As the first sediment generator on the Earth, the Himalayan range releases around 1 Gt/y of sediment into the ocean. The relative influence of the different factors that control the eroded fluxes and the importance of the erosion processes (such as landslides, glaciers, soils) are as yet poorly understood. The same is true of the climatic factors, especially regarding their impact during climatic transition periods. In order to address those questions, this work focuses on comparing the geochemical composition of erosion products to the composition of present river sediment and of sedimentary records in the Ganga Plain. A first budget of the erosion processes was done on a small scale in the Khudi catchment of Higher Himalaya. The total present-day erosion is considerable, at around 3 mm/y and takes place during the monsoon. It is mainly linked to the soils erosion and more importantly to the intense activity of a landsliding area. The development of a new method for the destruction of organic matter enabled the use of silicates hydration as a tracer for soils. Based on this method, a mathematical inversion of the sediment compositions was performed. It highlights that the landslide is responsible for ~80% of the overall physical erosion. The soil erosion is minor and is comparable to the erosion rates measured in the neighbouring catchments. The chemical erosion leads to a dissolved flux of 7.9 kt/y (corresponding to an erosion rate of 0.02mm/y) and seems to come from the bedrock deep weathering. Nevertheless, the dissolved fluxes also appear to be linked with the particles fluxes during the monsoon. This suggests an additional weathering of the sediment during the fluvial transport. A similar approach was used on a larger scale in the Narayani catchment that drains the whole of Central Nepal. Through ADCP-based current measurements combined with deep sediment sampling, a model for sedimentary transport was used to integrate the deep sediment fluxes. The average catchment-scale erosion rate was then corrected to a value of ~1.7 mm/y, close to the long-term erosion rates. A geochemical system that combines the measurement of the δD of silicates and the concentrations of carbonates was found to be a diagnosis tracer for glacial erosion in the northern part of the catchment. The organic matter ratio was used as a tracer for soils. The temporal analysis of sediment fluxes, as well as the sediment composition and granulometry showed that only a small fraction (< 20%) of the sediment comes from glacial and soils erosion. Over the whole Central Nepal, the physical erosion seems also to be dominated by the landslides that are triggered during the monsoon. The large Narayani-Gandak alluvial fan is located at the river mouth and can be used as a record of the recent history of Central Nepal erosion. Three drillings were done in this fan to enable the study of the evolution of Himalayan weathering and erosion during the Late Pleistocene. The sedimentary deposits display a surprising stability in their geochemistry, their sources and their weathering stage for the last ~45 ky. The erosion intensity derived from cosmogenic nuclides is the only feature that seems to have risen during Holocene. However, the very recent evolution of the erosion distribution in the range is characterised by an increase (x3) of the proportion of products coming from the lower, more densely populated areas. This shows that the anthropogenic activities have had a larger impact on the erosion than the last Pleistocene-Holocene transition, especially through the rapid growth of the road network during the last decade.

A wheeled mobile robot (WMR) will move on uneven terrain without slip if the length of the axle connecting two wheels can change or for a fixed length axle the wheels are allowed to tilt in a lateral direction. In this work, we consider a three-wheeled mobile robot with torus shaped wheels capable of lateral tilting. Due to the requirement of lateral tilting a two degree of freedom (DOF) suspension, one for maintaining contact with terrain and one for lateral tilting, is assumed to connect the wheels to the WMR body. Six concepts of two DOF suspension mechanisms are proposed. A WMR with these suspension mechanisms are modeled and two kinds of simulations, namely, direct kinematic analysis and inverse kinematic analysis are performed on several uneven terrains with and without suspension. Slip velocity, the path followed and the lateral tilt angle are estimated as a function of time. The force-angle stability measure is used to check the tip-over instability of the WMR on uneven terrain. It is shown that without the two DOF suspensions and with the wheels not allowed to tilt laterally, the WMR is not capable of traversing uneven terrains without large slip. When the wheels are allowed to tilt laterally with a two DOF suspension, the wheeled mobile robot slips very little. Based on least slip and less deviation from desired path, it is shown that the two best possible suspension mechanisms are the SFTA suspension and D4Bar suspension. Two prototype of three-wheeled mobile robot with these suspensions are fabricated using some components from a readily available commercial kit and with especially designed and manufactured wheels with the two degrees of freedom suspension. Simulations on an uneven terrain verify that the three-wheeled mobile robot can traverse uneven terrains with very little slip for three representative paths, namely a straight line, a circular arc and a path representing a lane change. Experiments with the two prototypes on physically constructed uneven terrain, very similar to the one used for simulation, confirm that the slip is significantly reduced with the two degree of freedom suspensions. The path of the centre of mass of the WMRs, projected on uneven surface, and the error from the desired path is presented for all the three representative paths. The simulation and experimental results clearly show that the three wheeled mobile robot with the novel two DOF suspension mechanisms can traverse uneven terrain with low slip.