Efeito da concentração de sólidos e de variáveis operacionais no desempenho de um hidrociclone concentrador

The hydrocycloning operation has a goal to separate solid-liquid suspensions and liquid-liquid emulsions through the centrifugal force action. Hydrocyclones are equipment with reduced size and used in both clarification and thickening. This device is used in many areas, like petrochemical and minerals process, and accumulate advantages like versatility and low cost of maintenance. However, the demand to improve the process and to reduce the costs has motivated several studies of equipment optimization. The filtering hydrocyclone is a non-conventional equipment developed at FEQUI/UFU with objective to improve the hydrocycloning separation efficiency. The purpose of this study is to evaluate the operating conditions of feed concentration and underflow diameter on the performance of a filtering geometry optimized to minimization of energy costs. The filtration effect was investigated through the comparison between the performance of the Optimized Filtering Hydrocyclone (HCOF) and the Optimized Concentrator Hydrocyclone (HCO). Because of the resemblance of hydrocyclones performance, the filtration did not represent significant effect on the performance of the HCOF. It was found that in this geometry the decrease of the variable underflow diameter was very favorable to thickening operation. The suspension concentration of quartzite at 1.0% of solids in volume was increased about 42 times when the 3 mm underflow diameter was used. The increase on the feed solid percentage was good for decreasing the energy spent, so that a minimum number of Euler of 730 was achieved at CVA = 10.0%v. However, a greater amount of solids in suspension leads to a lower efficiency of the equipment. Therefore, to minimize the underflow-to-throughput ratio and keep a high efficiency level, it is indicated to work with dilute suspension (CVA = 1.0%) and 3 mm underflow diameter (η = 67%). But if it is necessary to work with high feed concentration, the use of 5 mm underflow diameter provides a rise in the efficiency. The HCO hydrocyclone was compared to the traditional family of hydrocyclones Rietema and presented advantages like higher efficiency (34% higher in average) and lower energy costs (20% lower in average). Finally, the efficiency curves and project equation have been raised for the HCO hydrocyclone each with satisfactory adjust.

Fatores que influenciam o uso do marketing de guerrilha nas empresas em Portugal

Atualmente vivemos numa era em que a publicidade nos rodeia através de várias formas e onde as empresas esforçam-se cada vez mais para tornar eficaz a mensagem que pretendem passar. O uso de métodos convencionais, como a televisão, rádio, ou até outdoors, está a tornar-se pouco eficaz. Em muito pouco tempo, nos últimos vinte anos, a Internet mudou a nossa forma de viver, sendo até comparado ao Renascimento e à Revolução Industrial. As gerações mais recentes nasceram rodeadas deste “boom” publicitário, o que as tornou imunes. De forma a contornar este problema, surge Levinson em 1989 onde apresenta uma forma de minimizar este efeito e ao mesmo tempo proporcionar a que pequenas empresas tenham capacidade de competir com as maiores (Levinson, 2007). Assim, o marketing de guerrilha caracteriza-se por estar normalmente associado a implementações de baixo custo, que por vezes são irrepetíveis, pois conseguem alcançar um impacto “wow” significativo junto do grande público (Oliveira & Ferreira, 2013). O presente estudo contribui para a literatura do marketing de guerrilha existente, realizando assim uma compilação acerca do desenvolvimento desta temática até aos dias de hoje. De forma a perceber quais são os fatores que influenciam o uso do marketing de guerrilha pelas empresas portuguesas, foram inquiridas 140 empresas de todo o país, através de um questionário com base no estudo desenvolvido por Overbeek (2012). Através desta investigação exploratória, numa área ainda pouco explorada em Portugal, até à data, em especial a nível académico, “verificou-se que existe uma grande procura por este tipo de ferramentas não convencionais, tanto que, verificou-se que 86,4% da amostra já presenciou uma ação de guerrilha, no entanto apenas 36,4% admite já ter implementado na sua empresa, o que levanta a questão do porquê de uma taxa tão reduzida de utilização deste tipo de abordagem não convencional (Almeida & Au-Yong-Oliveira, 2015, p.1). A explicação poderá estar ligada à grande aversão à incerteza que existe em Portugal (Hofstede, 2001), e ao receio da mudança e da experimentação de novos produtos em Portugal (Steenkamp et al., 1999). Fatores que não irão mudar durante décadas, dado o tempo que demora a mudar culturas nacionais (Hofstede, 2001). Verifica-se também que na amostra das 140 empresas se destacam pessoas formadas (ao grau de licenciatura e mestrado) em Marketing (18,7% da amostra), Design (15,7%), Gestão (10,4%) e Tecnologias da Informação e Comunicação (7,9%). Pode-se concluir que são as quatro áreas fundamentais, ou pelo menos a necessidade existe em ter conhecimento nestas quatro áreas atualmente. Devido à [pequena] dimensão das empresas, um colaborador que tenha estas quatro competências tem uma vantagem competitiva face aos restantes, no que toca a hard skills.

Métabolomique et spectrométrie de masse : de nouvelles perspectives en analyse biomédicale

International audience

Oxidative stress and its haemodynamic consequences in chronic kidney disease

Chronic kidney disease (CKD) is associated with increased cardiovascular risk in comparison with the general population. This can be observed even in the early stages of CKD, and rises in proportion to the degree of renal impairment. Not only is cardiovascular disease (CVD) more prevalent in CKD, but its nature differs too, with an excess of morbidity and mortality associated with congestive cardiac failure, arrhythmia and sudden death, as well as the accelerated atherosclerosis which is also observed. Conventional cardiovascular risk factors such as hypertension, dyslipidaemia, obesity, glycaemia and smoking, are highly prevalent amongst patients with CKD, although in many of these examples the interaction between risk factor and disease differs from that which exists in normal renal function. Nevertheless, the extent of CVD cannot be fully explained by these conventional risk factors, and non-conventional factors specific to CKD are now recognised to contribute to the burden of CVD. Oxidative stress is a state characterised by excessive production of reactive oxygen species (ROS) and other radical species, a reduction in the capacity of antioxidant systems, and disturbance in normal redox homeostasis with depletion of protective vascular signalling molecules such as nitric oxide (NO). This results in oxidative damage to macromolecules such as lipids, proteins and DNA which can alter their functionality. Moreover, many enzymes are sensitive to redox regulation such that oxidative modification to cysteine thiol groups results in activation of signalling cascades which result in adverse cardiovascular effects such as vascular and endothelial dysfunction. Endothelial dysfunction and oxidative stress are present in association with many conventional cardiovascular risk factors, and can be observed even prior to the development of overt, clinical, vascular pathology, suggesting that these phenomena represent the earliest stages of CVD. In the presence of CKD, there is increased ROS production due to upregulated NADPH oxidase (NOX), increase in a circulating asymmetric dimethylarginine (ADMA), uncoupling of endothelial nitric oxide synthase (eNOS) as well as other mechanisms. There is also depletion in exogenous antioxidants such as ascorbic acid and tocopherol, and a reduction in activity of endogenous antioxidant systems regulated by the master gene regulator Nrf-2. In previous studies, circulating markers of oxidative stress have been shown to be increased in CKD, together with a reduction in endothelial function in a stepwise fashion relating to the severity of renal impairment. Not only is CVD linked to oxidative stress, but the progression of CKD itself is also in part dependent on redox sensitive mechanisms. For example, administration of the ROS scavenger tempol attenuates renal injury and reduces renal fibrosis seen on biopsy in a mouse model of CKD, whilst conversely, supplementation with the NOS inhibitor L-NAME causes proteinuria and renal impairment. Previous human studies examining the effect of antioxidant administration on vascular and renal function have been conflicting however. The work contained in this thesis therefore examines the effect of antioxidant administration on vascular and endothelial function in CKD. Firstly, 30 patients with CKD stages 3 – 5, and 20 matched hypertensive controls were recruited. Participants with CKD had lower ascorbic acid, higher TAP and ADMA, together with higher augmentation index and pulse wave velocity. There was no difference in baseline flow mediated dilatation (FMD) between groups. Intravenous ascorbic acid increased TAP and O2-, and reduced central BP and augmentation index in both groups, and lowered ADMA in the CKD group only. No effect on FMD was observed. The effects of ascorbic acid on kidney function was then investigated, however this was hindered by the inherent drawbacks of existing methods of non-invasively measuring kidney function. Arterial spin labelling MRI is an emerging imaging technique which allows measurement of renal perfusion without administration of an exogenous contrast agent. The technique relies upon application of an inversion pulse to blood within the vasculature proximal to the kidneys, which magnetically labels protons allowing measurement upon transit to the kidney. At the outset of this project local experience using ASL MRI was limited and there ensued a prolonged pre-clinical phase of testing with the aim of optimising imaging strategy. A study was then designed to investigate the repeatability of ASL MRI in a group of 12 healthy volunteers with normal renal function. The measured T1 longitudinal relaxation times and ASL MRI perfusion values were in keeping with those found in the literature; T1 time was 1376 ms in the cortex and 1491 ms in the whole kidney ROI, whilst perfusion was 321 mL/min/100g in the cortex, and 228 mL/min/100g in the whole kidney ROI. There was good reproducibility demonstrated on Bland Altman analysis, with a CVws was 9.2% for cortical perfusion and 7.1% for whole kidney perfusion. Subsequently, in a study of 17 patients with CKD and 24 healthy volunteers, the effects of ascorbic acid on renal perfusion was investigated. Although no change in renal perfusion was found following ascorbic acid, it was found that ASL MRI demonstrated significant differences between those with normal renal function and participants with CKD stages 3 – 5, with increased cortical and whole kidney T1, and reduced cortical and whole kidney perfusion. Interestingly, absolute perfusion showed a weak but significant correlation with progression of kidney disease over the preceding year. Ascorbic acid was therefore shown to have a significant effect on vascular biology both in CKD and in those with normal renal function, and to reduce ADMA only in patients with CKD. ASL MRI has shown promise as a non-invasive investigation of renal function and as a biomarker to identify individuals at high risk of progressive renal impairment.

Exploring redox-driven self-assembly of mixed metal polyoxometalates

How can we control the experimental conditions towards the isolation of specific structures? Why do particular architectures form? These are some challenging questions that synthetic chemists try to answer, specifically within polyoxometalate (POM) chemistry, where there is still much unknown regarding the synthesis of novel molecular structures in a controlled and predictive manner. This work covers a wide range of POM chemistry, exploring the redox self-assembly of polyoxometalate clusters, using both “one-pot”, flow and hydrothermal conditions. For this purpose, different vanadium, molybdenum and tungsten reagents, heteroatoms, inorganic salts and reducing agents have been used. The template effect of lone-pair containing pyramidal heteroatoms has been investigated. Efforts to synthesize new POM clusters displaying pyramidal heteroanions (XO32-, where X= S, Se, Te, P) are reported. The reaction of molybdenum with vanadium in the presence of XO32- heteroatoms is explored, showing how via the cation and experimental control it is possible to direct the self-assembly process and to isolate isostructural compounds. A series of four isostructural (two new, namely {Mo11V7P} and {Mo11V7Te} and two already known, namely {Mo11V7Se} and {Mo11V7S} disordered egg-shaped Polyoxometalates have been reported. The compounds were characterized by X-ray structural analysis, TGA, UV-Vis, FT-IR, Elemental and Flame Atomic Absorption Spectroscopy (FAAS) analysis and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Cyclic Voltammetry measurements have been carried out in all four compounds showing the effect of the ionic density of the heteroatom on the potential. High-Resolution ESI-MS studies have revealed that the structures retain their integrity in solution. Efforts to synthesize new mixed-metal compounds led to isolation, structural, and electronic characterization of the theoretically predicted, but experimentally elusive δ-isomer of the Keggin polyoxometalate cluster anion, {H2W4V9O33(C6H13NO3)}, by the reaction of tungstate(VI) and vanadium(V) with triethanolammonium ions (TEAH), acting as a tripodal ligand grafted to the surface of the cluster. Control experiments (in the absence of the organic compound) have proven that the tripodal ligand plays crucial role on the formation of the isomer. The six vanadium metal centres, which consist the upper part of the cluster, are bonded to the “capping” TEA tripodal ligand. This metal-ligand bonding directs and stabilises the formation of the final product. The δ-Keggin species was characterized by single-crystal X-ray diffraction, FT-IR, UV-vis, NMR and ESI-MS spectrometry. Electronic structure and structure-stability correlations were evaluated by means of DFT calculations. The compounds exhibited photochromic properties by undergoing single-crystal-to-single-crystal (SC-SC) transformations and changing colour under light. Non-conventional synthetic approaches are also used for the synthesis of the POM clusters comparing the classical “one-pot” reaction conditions and exploring the synthetic parameters of the synthesis of POM compounds. Reactions under hydrothermal and flow conditions, where single crystals that depend on the solubility of the minerals under hot water and high pressure can be synthesized, resulted in the isolation of two isostructural compounds, namely, {Mo12V3Te5}. The compound isolated from a continuous processing method, crystallizes in a hexagonal crystal system, forming a 2D porous plane net, while the compound isolated using hard experimental conditions (high temperature and pressure) crystallizes in monoclinic system, resulting in a different packing configuration. Utilizing these alternative synthetic approaches, the most kinetically and thermodynamically compounds would possibly be isolated. These compounds were characterised by single-crystal X-ray diffraction, FT-IR and UV-vis spectroscopy. Finally, the redox-controlled driven oscillatory template exchange between phosphate (P) and vanadate (V) anions enclosed in an {M18O54(XO4)2} cluster is further investigated using UV-vis spectroscopy as a function of reaction time, showed that more than six complete oscillations interconverting the capsule species present in solution from {P2M18} to {V2M18} were possible, provided that a sufficient concentration of the TEA reducing agent was present in solution. In an effort to investigate the periodicity of the exchange of the phosphate and vanadate anions, time dependent Uv-vis measurements were performed for a period at a range of 170-550 hours. Different experimental conditions were also applied in order to investigate the role of the reducing agent, as well as the effect of other experimental variables on the oscillatory system.

Production and characterization of an alcoholic fermented beverage from grape must and beer wort

Mestrado Vinifera Euromaster - Instituto Superior de Agronomia - UL

Estudo de inibidores de corrosão em concreto armado, visando a melhoria na sua durabilidade

This thesis has as objective presents a methodology to evaluate the behavior of the corrosion inhibitors sodium nitrite, sodium dichromate and sodium molybdate, as well as your mixture, the corrosion process for the built-in steel in the reinforced concrete, through different techniques electrochemical, as well as the mechanical properties of that concrete non conventional. The addition of the inhibitors was studied in the concrete in the proportions from 0.5 to 3.5 % regarding the cement mass, isolated or in the mixture, with concrete mixture proportions of 1.0:1.5:2.5 (cement, fine aggregate and coarse aggregate), superplasticizers 2.0 % and 0.40 water/cement ratio. In the modified concrete resistance rehearsals they were accomplished to the compression, consistence and the absorption of water, while to analyze the built-in steel in the concrete the rehearsals of polarization curves they were made. They were also execute, rehearsals of corrosion potential and polarization resistance with intention of diagnose the beginning of the corrosion of the armors inserted in body-of-proof submitted to an accelerated exhibition in immersion cycle and drying to the air. It was concluded, that among the studied inhibitors sodium nitrite , in the proportion of 2.0 % in relation to the mass of the cement, presented the best capacity of protection of the steel through all the studied techniques and that the methodology and the monitoring techniques used in this work, they were shown appropriate to evaluate the behavior and the efficiency of the inhibitors

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

In this review, we consider the main processes for the asymmetric transfer hydrogenation of ketones from 2008 up today. The most effective organometallic compounds (derived from Ru, Rh, Ir, Fe, Os, Ni, Co, and Re) and chiral ligands (derived from amino alcohols, diamines, sulfur- and phosphorus-containing compounds, as well as heterocyclic systems) will be shown paying special attention to functionalized substrates, tandem reactions, processes under non-conventional conditions, supported catalysts, dynamic kinetic resolutions, the use of water as a green solvent, theoretical and experimental studies on reaction mechanisms, enzymatic processes, and finally applications to the total synthesis of biologically active organic molecules.

El papel de los Estados Unidos en la reforma energética mexicana del 2013. Estudio de caso: el fin del monopolio petrolero de Pemex

Este estudio de caso analiza las razones por las cuales México adelantó una reforma constitucional en materia energética en 2013, y el interés que tuvo Estados Unidos en esta, puesto que se destaca la intención del gobierno estadounidense de convertir a América del Norte en una región más sólida. Es así como se exponen las razones por las cuales México decide reformar su constitución y por esa vía tener un impacto directo en Petróleos Mexicanos (Pemex), la cual es la mayor compañía del país, encargada de adelantar los procesos de exploración y explotación de hidrocarburos. Asimismo, se explica el interés de Estados Unidos en el tema del intercambio de hidrocarburos, ya que es primordial para lograr la seguridad energética en Norteamérica, una región donde se está realizando extracción de gas y petróleo a través del fracking, un método no convencional, que ha propiciado un nuevo panorama en los recursos energéticos.

La exploración y producción de hidrocarburos en yacimientos no convencionales, frente a los principios de prevención, precaución y desarrollo sostenible

El presente trabajo de grado busca exponer el panorama actual de la exploración y producción de hidrocarburos en Yacimientos No Convencionales, realizada utilizando el fracturamiento hidráulico – Fracking – cómo método para lograr mejores condiciones físicas en el reservorio que permitan la extracción del recurso. El método mencionado es estudiado a la luz de los principios de prevención, precaución y desarrollo sostenible, que rigen la política ambiental en Colombia, con el objetivo de analizar los posibles impactos ambientales y sociales que se puedan generar por el desarrollo de la actividad extractiva de hidrocarburos en Yacimientos No Convencionales. Para finalmente mostrar que el Fracking como actividad está legalmente permitida en Colombia, y la legislación vigente responde a los principios mencionados previamente.

Embedded systems and advanced signal processing for Acousto- Ultrasonic Inspections

Non Destructive Testing (NDT) and Structural Health Monitoring (SHM) are becoming essential in many application contexts, e.g. civil, industrial, aerospace etc., to reduce structures maintenance costs and improve safety. Conventional inspection methods typically exploit bulky and expensive instruments and rely on highly demanding signal processing techniques. The pressing need to overcome these limitations is the common thread that guided the work presented in this Thesis. In the first part, a scalable, low-cost and multi-sensors smart sensor network is introduced. The capability of this technology to carry out accurate modal analysis on structures undergoing flexural vibrations has been validated by means of two experimental campaigns. Then, the suitability of low-cost piezoelectric disks in modal analysis has been demonstrated. To enable the use of this kind of sensing technology in such non conventional applications, ad hoc data merging algorithms have been developed. In the second part, instead, imaging algorithms for Lamb waves inspection (namely DMAS and DS-DMAS) have been implemented and validated. Results show that DMAS outperforms the canonical Delay and Sum (DAS) approach in terms of image resolution and contrast. Similarly, DS-DMAS can achieve better results than both DMAS and DAS by suppressing artefacts and noise. To exploit the full potential of these procedures, accurate group velocity estimations are required. Thus, novel wavefield analysis tools that can address the estimation of the dispersion curves from SLDV acquisitions have been investigated. An image segmentation technique (called DRLSE) was exploited in the k-space to draw out the wavenumber profile. The DRLSE method was compared with compressive sensing methods to extract the group and phase velocity information. The validation, performed on three different carbon fibre plates, showed that the proposed solutions can accurately determine the wavenumber and velocities in polar coordinates at multiple excitation frequencies.

Radical chemistry of the catechol/quinone system and its role in the control of lipid peroxidation and melanin biosynthesis

The catechol (1,2-dihydroxybenzene) is a privileged structural motif among natural antioxidants like flavonoids, owing to its reactivity with alkylperoxyl radicals due to the stability of the semiquinone radical. The exploration of the relevance and mechanism of this non-conventional antioxidant chemistry in heterogenous biomimetic systems (aqueous micelles and unilamellar liposomes) is explored for the first time in Chapter 1. Results show antioxidant behaviour that surpasses that of nature’s premiere antioxidant α-tocopherol and relies on the cross-dismutation of alkylperoxyl and hydroperoxyl radicals at the water-lipid interface with regeneration of the catechol function from the oxidized quinone. The design and synthesis of new biomimetic catechol-type antioxidants by conjugation of thiols (e.g. cysteine) with quinones highlighted an unusual 1,6-type regioselectivity, which had been previously reported but never fully rationalized. Owing to its importance both in nature and in the development of new antioxidants, we investigated it in detail in Chapter 2. We could prove the onsetting of a radical-chain mechanism intermediated by thiyl and thiosemiquinone radicals at the basis of the “anomalous nucleophilic addition” of thiols to ortho-quinones, which paves the way to better understanding of the chemistry of such systems. The oxidation of catechols to the corresponding quinones is also a key reaction in the biosynthesis of melanins, mediated by enzyme Tyrosinase.

New methodologies in organocatalysis: from discovery to application and mechanistic

This PhD thesis deals with three different topics: i) sulfoxonium ylides, ii) donor-acceptor cyclopropanes, and iii) desymmetrization reactions. Catalysis, and in more detail organocatalysis, is the fil rouge linking the three subjects of study. The main focus treated during this doctorate period is the reactivity of sulfoxonium ylides, and in particular stabilized sulfoxonium ylides. Special attention has been dedicated to the behavior of these particular substrates under asymmetric and non-asymmetric reaction conditions. Moreover, also similarities and differences with the related, less stable, sulfonium ylides were fully analyzed, both experimentally and from a theoretical point of view. Two different reactions were developed in full. One conducted under acidic reaction conditions and the second one exploiting the asymmetric aminocatalysis. Subsequently, the reactivity of donor-acceptor cyclopropanes was studied. After different attempts in the development of a new catalytic methodology based on these substrates, a non-conventional reactivity conducted under phase transfer catalysis was discovered and optimized. In particular, a chemodivergent reaction depending on the reaction conditions was developed. Finally, during the period spent abroad, a preliminary study of a desymmetrization reaction was carried out. The studied reaction is based on an asymmetric elimination reaction conducted under asymmetric phosphoric acid catalysis. In summary, this PhD thesis shows the versatility of different organocatalytic methodologies when applied to different reactions and substrates.

Development of a 3D very high-resolution seismic reflection system for lacustrine settings - a case study over a thrust fault zone in Lake Geneva

Un système efficace de sismique tridimensionnelle (3-D) haute-résolution adapté à des cibles lacustres de petite échelle a été développé. Dans le Lac Léman, près de la ville de Lausanne, en Suisse, des investigations récentes en deux dimension (2-D) ont mis en évidence une zone de faille complexe qui a été choisie pour tester notre système. Les structures observées incluent une couche mince (<40 m) de sédiments quaternaires sub-horizontaux, discordants sur des couches tertiaires de molasse pentées vers le sud-est. On observe aussi la zone de faille de « La Paudèze » qui sépare les unités de la Molasse du Plateau de la Molasse Subalpine. Deux campagnes 3-D complètes, d?environ d?un kilomètre carré, ont été réalisées sur ce site de test. La campagne pilote (campagne I), effectuée en 1999 pendant 8 jours, a couvert 80 profils en utilisant une seule flûte. Pendant la campagne II (9 jours en 2001), le nouveau système trois-flûtes, bien paramétrés pour notre objectif, a permis l?acquisition de données de très haute qualité sur 180 lignes CMP. Les améliorations principales incluent un système de navigation et de déclenchement de tirs grâce à un nouveau logiciel. Celui-ci comprend un contrôle qualité de la navigation du bateau en temps réel utilisant un GPS différentiel (dGPS) à bord et une station de référence près du bord du lac. De cette façon, les tirs peuvent être déclenchés tous les 5 mètres avec une erreur maximale non-cumulative de 25 centimètres. Tandis que pour la campagne I la position des récepteurs de la flûte 48-traces a dû être déduite à partir des positions du bateau, pour la campagne II elle ont pu être calculées précisément (erreur <20 cm) grâce aux trois antennes dGPS supplémentaires placées sur des flotteurs attachés à l?extrémité de chaque flûte 24-traces. Il est maintenant possible de déterminer la dérive éventuelle de l?extrémité des flûtes (75 m) causée par des courants latéraux ou de petites variations de trajet du bateau. De plus, la construction de deux bras télescopiques maintenant les trois flûtes à une distance de 7.5 m les uns des autres, qui est la même distance que celle entre les lignes naviguées de la campagne II. En combinaison avec un espacement de récepteurs de 2.5 m, la dimension de chaque «bin» de données 3-D de la campagne II est de 1.25 m en ligne et 3.75 m latéralement. L?espacement plus grand en direction « in-line » par rapport à la direction «cross-line» est justifié par l?orientation structurale de la zone de faille perpendiculaire à la direction «in-line». L?incertitude sur la navigation et le positionnement pendant la campagne I et le «binning» imprécis qui en résulte, se retrouve dans les données sous forme d?une certaine discontinuité des réflecteurs. L?utilisation d?un canon à air à doublechambre (qui permet d?atténuer l?effet bulle) a pu réduire l?aliasing observé dans les sections migrées en 3-D. Celui-ci était dû à la combinaison du contenu relativement haute fréquence (<2000 Hz) du canon à eau (utilisé à 140 bars et à 0.3 m de profondeur) et d?un pas d?échantillonnage latéral insuffisant. Le Mini G.I 15/15 a été utilisé à 80 bars et à 1 m de profondeur, est mieux adapté à la complexité de la cible, une zone faillée ayant des réflecteurs pentés jusqu?à 30°. Bien que ses fréquences ne dépassent pas les 650 Hz, cette source combine une pénétration du signal non-aliasé jusqu?à 300 m dans le sol (par rapport au 145 m pour le canon à eau) pour une résolution verticale maximale de 1.1 m. Tandis que la campagne I a été acquise par groupes de plusieurs lignes de directions alternées, l?optimisation du temps d?acquisition du nouveau système à trois flûtes permet l?acquisition en géométrie parallèle, ce qui est préférable lorsqu?on utilise une configuration asymétrique (une source et un dispositif de récepteurs). Si on ne procède pas ainsi, les stacks sont différents selon la direction. Toutefois, la configuration de flûtes, plus courtes que pour la compagne I, a réduit la couverture nominale, la ramenant de 12 à 6. Une séquence classique de traitement 3-D a été adaptée à l?échantillonnage à haute fréquence et elle a été complétée par deux programmes qui transforment le format non-conventionnel de nos données de navigation en un format standard de l?industrie. Dans l?ordre, le traitement comprend l?incorporation de la géométrie, suivi de l?édition des traces, de l?harmonisation des «bins» (pour compenser l?inhomogénéité de la couverture due à la dérive du bateau et de la flûte), de la correction de la divergence sphérique, du filtrage passe-bande, de l?analyse de vitesse, de la correction DMO en 3-D, du stack et enfin de la migration 3-D en temps. D?analyses de vitesse détaillées ont été effectuées sur les données de couverture 12, une ligne sur deux et tous les 50 CMP, soit un nombre total de 600 spectres de semblance. Selon cette analyse, les vitesses d?intervalles varient de 1450-1650 m/s dans les sédiments non-consolidés et de 1650-3000 m/s dans les sédiments consolidés. Le fait que l?on puisse interpréter plusieurs horizons et surfaces de faille dans le cube, montre le potentiel de cette technique pour une interprétation tectonique et géologique à petite échelle en trois dimensions. On distingue cinq faciès sismiques principaux et leurs géométries 3-D détaillées sur des sections verticales et horizontales: les sédiments lacustres (Holocène), les sédiments glacio-lacustres (Pléistocène), la Molasse du Plateau, la Molasse Subalpine de la zone de faille (chevauchement) et la Molasse Subalpine au sud de cette zone. Les couches de la Molasse du Plateau et de la Molasse Subalpine ont respectivement un pendage de ~8° et ~20°. La zone de faille comprend de nombreuses structures très déformées de pendage d?environ 30°. Des tests préliminaires avec un algorithme de migration 3-D en profondeur avant sommation et à amplitudes préservées démontrent que la qualité excellente des données de la campagne II permet l?application de telles techniques à des campagnes haute-résolution. La méthode de sismique marine 3-D était utilisée jusqu?à présent quasi-exclusivement par l?industrie pétrolière. Son adaptation à une échelle plus petite géographiquement mais aussi financièrement a ouvert la voie d?appliquer cette technique à des objectifs d?environnement et du génie civil.<br/><br/>An efficient high-resolution three-dimensional (3-D) seismic reflection system for small-scale targets in lacustrine settings was developed. In Lake Geneva, near the city of Lausanne, Switzerland, past high-resolution two-dimensional (2-D) investigations revealed a complex fault zone (the Paudèze thrust zone), which was subsequently chosen for testing our system. Observed structures include a thin (<40 m) layer of subhorizontal Quaternary sediments that unconformably overlie southeast-dipping Tertiary Molasse beds and the Paudèze thrust zone, which separates Plateau and Subalpine Molasse units. Two complete 3-D surveys have been conducted over this same test site, covering an area of about 1 km2. In 1999, a pilot survey (Survey I), comprising 80 profiles, was carried out in 8 days with a single-streamer configuration. In 2001, a second survey (Survey II) used a newly developed three-streamer system with optimized design parameters, which provided an exceptionally high-quality data set of 180 common midpoint (CMP) lines in 9 days. The main improvements include a navigation and shot-triggering system with in-house navigation software that automatically fires the gun in combination with real-time control on navigation quality using differential GPS (dGPS) onboard and a reference base near the lake shore. Shots were triggered at 5-m intervals with a maximum non-cumulative error of 25 cm. Whereas the single 48-channel streamer system of Survey I requires extrapolation of receiver positions from the boat position, for Survey II they could be accurately calculated (error <20 cm) with the aid of three additional dGPS antennas mounted on rafts attached to the end of each of the 24- channel streamers. Towed at a distance of 75 m behind the vessel, they allow the determination of feathering due to cross-line currents or small course variations. Furthermore, two retractable booms hold the three streamers at a distance of 7.5 m from each other, which is the same distance as the sail line interval for Survey I. With a receiver spacing of 2.5 m, the bin dimension of the 3-D data of Survey II is 1.25 m in in-line direction and 3.75 m in cross-line direction. The greater cross-line versus in-line spacing is justified by the known structural trend of the fault zone perpendicular to the in-line direction. The data from Survey I showed some reflection discontinuity as a result of insufficiently accurate navigation and positioning and subsequent binning errors. Observed aliasing in the 3-D migration was due to insufficient lateral sampling combined with the relatively high frequency (<2000 Hz) content of the water gun source (operated at 140 bars and 0.3 m depth). These results motivated the use of a double-chamber bubble-canceling air gun for Survey II. A 15 / 15 Mini G.I air gun operated at 80 bars and 1 m depth, proved to be better adapted for imaging the complexly faulted target area, which has reflectors dipping up to 30°. Although its frequencies do not exceed 650 Hz, this air gun combines a penetration of non-aliased signal to depths of 300 m below the water bottom (versus 145 m for the water gun) with a maximum vertical resolution of 1.1 m. While Survey I was shot in patches of alternating directions, the optimized surveying time of the new threestreamer system allowed acquisition in parallel geometry, which is preferable when using an asymmetric configuration (single source and receiver array). Otherwise, resulting stacks are different for the opposite directions. However, the shorter streamer configuration of Survey II reduced the nominal fold from 12 to 6. A 3-D conventional processing flow was adapted to the high sampling rates and was complemented by two computer programs that format the unconventional navigation data to industry standards. Processing included trace editing, geometry assignment, bin harmonization (to compensate for uneven fold due to boat/streamer drift), spherical divergence correction, bandpass filtering, velocity analysis, 3-D DMO correction, stack and 3-D time migration. A detailed semblance velocity analysis was performed on the 12-fold data set for every second in-line and every 50th CMP, i.e. on a total of 600 spectra. According to this velocity analysis, interval velocities range from 1450-1650 m/s for the unconsolidated sediments and from 1650-3000 m/s for the consolidated sediments. Delineation of several horizons and fault surfaces reveal the potential for small-scale geologic and tectonic interpretation in three dimensions. Five major seismic facies and their detailed 3-D geometries can be distinguished in vertical and horizontal sections: lacustrine sediments (Holocene) , glaciolacustrine sediments (Pleistocene), Plateau Molasse, Subalpine Molasse and its thrust fault zone. Dips of beds within Plateau and Subalpine Molasse are ~8° and ~20°, respectively. Within the fault zone, many highly deformed structures with dips around 30° are visible. Preliminary tests with 3-D preserved-amplitude prestack depth migration demonstrate that the excellent data quality of Survey II allows application of such sophisticated techniques even to high-resolution seismic surveys. In general, the adaptation of the 3-D marine seismic reflection method, which to date has almost exclusively been used by the oil exploration industry, to a smaller geographical as well as financial scale has helped pave the way for applying this technique to environmental and engineering purposes.<br/><br/>La sismique réflexion est une méthode d?investigation du sous-sol avec un très grand pouvoir de résolution. Elle consiste à envoyer des vibrations dans le sol et à recueillir les ondes qui se réfléchissent sur les discontinuités géologiques à différentes profondeurs et remontent ensuite à la surface où elles sont enregistrées. Les signaux ainsi recueillis donnent non seulement des informations sur la nature des couches en présence et leur géométrie, mais ils permettent aussi de faire une interprétation géologique du sous-sol. Par exemple, dans le cas de roches sédimentaires, les profils de sismique réflexion permettent de déterminer leur mode de dépôt, leurs éventuelles déformations ou cassures et donc leur histoire tectonique. La sismique réflexion est la méthode principale de l?exploration pétrolière. Pendant longtemps on a réalisé des profils de sismique réflexion le long de profils qui fournissent une image du sous-sol en deux dimensions. Les images ainsi obtenues ne sont que partiellement exactes, puisqu?elles ne tiennent pas compte de l?aspect tridimensionnel des structures géologiques. Depuis quelques dizaines d?années, la sismique en trois dimensions (3-D) a apporté un souffle nouveau à l?étude du sous-sol. Si elle est aujourd?hui parfaitement maîtrisée pour l?imagerie des grandes structures géologiques tant dans le domaine terrestre que le domaine océanique, son adaptation à l?échelle lacustre ou fluviale n?a encore fait l?objet que de rares études. Ce travail de thèse a consisté à développer un système d?acquisition sismique similaire à celui utilisé pour la prospection pétrolière en mer, mais adapté aux lacs. Il est donc de dimension moindre, de mise en oeuvre plus légère et surtout d?une résolution des images finales beaucoup plus élevée. Alors que l?industrie pétrolière se limite souvent à une résolution de l?ordre de la dizaine de mètres, l?instrument qui a été mis au point dans le cadre de ce travail permet de voir des détails de l?ordre du mètre. Le nouveau système repose sur la possibilité d?enregistrer simultanément les réflexions sismiques sur trois câbles sismiques (ou flûtes) de 24 traces chacun. Pour obtenir des données 3-D, il est essentiel de positionner les instruments sur l?eau (source et récepteurs des ondes sismiques) avec une grande précision. Un logiciel a été spécialement développé pour le contrôle de la navigation et le déclenchement des tirs de la source sismique en utilisant des récepteurs GPS différentiel (dGPS) sur le bateau et à l?extrémité de chaque flûte. Ceci permet de positionner les instruments avec une précision de l?ordre de 20 cm. Pour tester notre système, nous avons choisi une zone sur le Lac Léman, près de la ville de Lausanne, où passe la faille de « La Paudèze » qui sépare les unités de la Molasse du Plateau et de la Molasse Subalpine. Deux campagnes de mesures de sismique 3-D y ont été réalisées sur une zone d?environ 1 km2. Les enregistrements sismiques ont ensuite été traités pour les transformer en images interprétables. Nous avons appliqué une séquence de traitement 3-D spécialement adaptée à nos données, notamment en ce qui concerne le positionnement. Après traitement, les données font apparaître différents faciès sismiques principaux correspondant notamment aux sédiments lacustres (Holocène), aux sédiments glacio-lacustres (Pléistocène), à la Molasse du Plateau, à la Molasse Subalpine de la zone de faille et la Molasse Subalpine au sud de cette zone. La géométrie 3-D détaillée des failles est visible sur les sections sismiques verticales et horizontales. L?excellente qualité des données et l?interprétation de plusieurs horizons et surfaces de faille montrent le potentiel de cette technique pour les investigations à petite échelle en trois dimensions ce qui ouvre des voies à son application dans les domaines de l?environnement et du génie civil.

Développement et validation d'un instrument non-invasifde caractérisation du comportement musculaire respiratoire

Réalisé en cotutelle avec l'Université Joseph Fourier École Doctorale Ingénierie pour la Santé,la Cognition et l'Environnement (France)