Monitoring the working environment of laboratories and industries for pollutants is of primary concern to ensure the healthiness of working personnel. Semiconducting metal oxides (SMOs) are sensitive to the gas ambience and can be tuned for sensing purpose. As SMOs are not selective, an array of sensors with differential selectivity may resolve to great extent. The objective of the thesis is to understand the physicochemical properties and gas sensing characteristics of Cr1-xFexNbO4. Applying principal component analysis to the sensor response data either for selection of features or for differentiation of analysts is also of concern. Preparation of Cr1-xFexNbO4, phase characterization, lattice parameters estimation, morphological and micro chemical analysis (SEM & EDX), electrical characterization by direct current (DC & AC) in the temperature range of 423 K to 573 K, weighted magnetic moment of iron and chromium deduced from susceptibility measurements, spin nature of iron and surface compositions of different valences of chromium and iron deduced from X-ray photoelectron spectroscopy of are presented. The wide dynamic range hydrogen sensing characteristics of CrNbO4 bulk pellets at different temperatures along with the cross-sensitivity towards NH3, NOx(NO+NO2) and PG (petroleum gas) are investigated. The preparation of Cr1-xFexNbO4 thick and thin films by screen-printing and PLD are also presented. The thick films are tested at different temperatures towards hydrogen. The n-type or p-type nature of thick films towards hydrogen with varying iron concentration in Cr1-xFexNbO4 is reported. The thin films are characterized for phase formation, morphology by XRD, SEM and AFM. XPS performed surface characterization. Electrical resistance measurements at different temperatures and preliminary experiments on hydrogen sensing are presented. The probable hydrogen sensing mechanism of CrNbO4 was revealed by X-ray photoelectron spectroscopy. The experimentally observed reduction in metal ion oxidation states upon interacting with hydrogen is best illustrated by Kröger Vink notation. Principal component analysis was applied for three different types of studies: i) The fit parameters of the transient response of CrNbO4 thick films towards hydrogen are analyzed for finding out the better feature for calibration, ii) Different thick films of CrNbO4, Cr0.5Fe0.5NbO4 and FeNbO4 operated at various temperatures for testing H2 and VOCs are analyzed for redundancy in sensor behaviour and iii) Cr0.8Fe0.2NbO4 thick films are studied for sensing H2, NH3 and their mixtures and usefulness of PCA in resolving them in PC-space. In addition, H2 and VOCs are tested at different temperatures and redundancy in temperature is deduced to construct a sensor array with a minimum number of sensors. Finally, a sensor array consisting of Cr0.8Fe0.2NbO4 thick films, operating at different temperatures is built, and qualitative discrimination of analysts in PC-space is demonstrated. Finally, the major findings of the present investigations and suggestions for future aspects of experimentation are provided

[pt] Esta pesquisa discutiu a produção de liderança, nas práticas relacionais de uma organização do movimento estudantil brasileiro, na qual foi realizada uma etnometodologia situada em múltiplas localidades onde a organização atua. Desde o retorno do movimento de pós-graduação à cena pública brasileira, em 2019, nas manifestações que ficaram conhecidas como tsunami da educação, contra os cortes orçamentários das universidades federais, o sistema nacional de pós-graduação brasileiro enfrenta o contingenciamento constante de recursos e cortes orçamentários de programas e projetos, que incidem direta e imediatamente sobre a realidade de seus atores. Nesse contexto, organizações representativas de pós-graduação protagonizam um papel importante na produção de práticas de organização, que oferecem às ações de seus participantes um tipo de direcionalidade favorável ao atendimento de suas demandas: liderança. No entanto, pensar a liderança para além das organizações clássicas comuns aos setores privados da sociedade civil empresarial, de modo a conceber suas práticas em estruturas organizacionais informais e descentralizadas, onde a figura de líderes heroicos e individuais desvanece, ainda é um desafio para o campo de pesquisa do fenômeno. Também é desafiador pensar as práticas de liderança fora do pressuposto de alcance de objetivos instrumentais definidos para o bom funcionamento das organizações. Esses desafios, entretanto, não apontam para inexistência da liderança, mas para existência de práticas não empresariais/gerenciais de organização relacionadas ao fenômeno ainda pouco compreendidas em organizações de resistência e luta social. A análise etnometodológica destaca duas práticas de liderança produzidas nas interações entre os participantes da organização estudada. / [en] This research discussed the leadership production in the relational practices of a Brazilian student movement organization in which an ethnomethodology located in multiple locations where the organization operates was carried out. Since the return of the postgraduate movement to the Brazilian public scene in 2019 during the manifestations known as tsunami da educação, against the federal universities budget cuts, Brazilian national postgraduate system face the constant contingency of resources and budget cuts for programs and projects which direct and immediately affect the reality of their actors. In this scenario, postgraduate representative organizations play an important role in producing organizing practices that offer to the actions of their participants a type of directionality favorable to the resolution of their demands: leadership. However, it is still a challenge for the field to think about leadership beyond the classic organizations usually found in private sectors of business-civil society, so as to conceive their practices in informal and decentralized organizational structures, where the figure of heroic and individual leaders fades. It is also challenging to think about leadership practices outside the assumption of achieving instrumental goals defined for the proper functioning of organizations. These challenges, nonetheless, do not indicate the non-existence of leadership, but the existence of non business/managerial organizing practices related to the phenomenon that are still poorly understood in resistance and social struggle organizations. The ethnomethodological analysis highlights two leadership practices produced in the interactions between the participants of the studied organization.

Dans le cadre de la mission spatiale SMOS (Soil Moisture and Ocean Salinity), nous présentons dans cette thèse une nouvelle approche numérique de modélisation du calcul de l'émissivité et du coefficient bi-statique de systèmes forestiers sol-litière en Bande L. Le système sol-litière est représenté par deux couches diélectriques 3D comportant des interfaces rugueuses, une démarche qui n'apparait pas actuellement dans la littérature. Nous validons notre approche pour une seule couche en comparant les simulations de l'émissivité avec celles produites par la méthode des moments et des données expérimentales. A partir de ce nouveau modèle, nous évaluons la sensibilité de l'émissivité du système sol-litière en fonction de l'humidité et de la rugosité de la litière. Ce nouveau modèle permettra de créer une base de données synthétiques d'émissivités calculées en fonction de nombreux paramètres qui contribuera à améliorer la prise en compte de la litière dans l'algorithme d'inversion des données de la mission spatiale SMOS.

Un regain d'intérêt pour la télédétection de la salinité de surface de l'océan (SSS) par radiométrie en bande-L (21cm) est apparu dans les années 1990 et a conduit au lancement des missions spatiales SMOS (nov. 2009) et Aquarius (juin 2011). Cependant, en raison du faible rapport signal sur bruit, l'inversion de la SSS à partir des mesures radiométriques en bande-L est très difficile. Ce travail porte sur l'étude de la signature radiométrique en bande-L des propriétés de la surface de l'océan (en particulier SSS et rugosité) à partir des mesures du radiomètre aéroporté en bande-L CAROLS, acquises dans le golfe de Gascogne en 2009 et 2010. Une première étude a montré que la SSS déduite des mesures du radiomètre CAROLS était précise à mieux que 0.3 pss dans une zone de forte variabilité spatio-temporelle avec une meilleure précision que les modèles océanographiques côtiers. La seconde étude qui combine les mesures passives (CAROLS) et active (diffusiomètre en bande-C STORM) a mis en évidence l'amélioration des nouveaux modèles de rugosité par rapport aux modèles pré-lancement satellitaires. Par ailleurs, l'étude a montré l'importance de la prise en compte des moyennes et grandes échelles de rugosité (> 20 cm) pour l'interprétation des mesures radiomé- triques loin du nadir.