Dissertations / Theses on the topic 'Ice jet'

This thesis presents a comprehensive study of the ice particle production process through experimentation and numerical methods using computational fluid dynamics (CFD) that can be used to produce ice particles with controlled temperature and hardness for use in ice jet (IJ) process for industrial applications. The analytical and numerical modeling for the heat exchanger system are developed that could predict the heat, mass and momentum exchange between the cold gas and water droplets. Further, the feasibility study of the deployment of ice particles produced from the ice jet system for possible cleaning and blasting applications are analyzed numerically. Although the use of Abrasive Water Jet (AWJ) technology in cutting, cleaning, machining and surface processing is a very successful industrial process, a considerable amount of secondary particle waste and contamination impingement by abrasive materials has been an important issue in AWJ process. Some alternate cryogenic jet methods involving vanishing abrasive materials, such as plain liquid nitrogen or carbon dioxide have been tried for these applications, but they also suffer from certain drawbacks relating to the quality, safety, process control and materials handling. The use of ice jet process involving minute ice particles has received relatively little attention in industrial applications. Some researches have concentrated on the studies of effects of Ice Jet outlet parameters of the nozzle and focus tube for machining soft and brittle materials. Most of the work in this area is qualitative and researchers have paid a cursory attention to the ice particles temperature and the efficiency of production of these particles. An extensive investigation to gain insight knowledge into the formulation of ice formation process parameters is required in arriving at a deeper understanding of the entire ice jet process for production application. Experimental investigations were focussed on the measurement of ice particle temperature, phase transitions, ice particle diameter, coalescence and hardness test. The change in ice particle diameter from the inlet conditions to the exit point of the heat exchanger wasinvestigated using the experimental results. These observations were extended to numerical analysis of temperature variations of ice particles at different planes inside the custom built heat exchanger. The numerical predictions were carried out with the aid of visualization studies and temperature measurement results from experiments. The numerical models were further analysed to find out the behaviour of ice particles in the transportation stage, the mixing chamber of the nozzle and focus tube. This was done to find out whether the methodology used in this research is feasible and if it can be used in applications such as cleaning, blasting, drilling and perhaps cutting. The results of the empirical studies show that ice particles of desired temperature and hardness could be produced successfully with the current novel design of the heat exchanger. At the optimum parameters, ice particles could be produced below -60�C, with hardness of particles comparable to gypsum (Moh�s hardness of 1.5 to 3). The visualization studies of the process assisted in observation of the phases of ice at various points along the heat exchanger. The results of numerical analysis were found to agree well with the experiments and were supported by the statistical model assessments. Numerical analyses also show the survival of ice particles at the nozzle exit even with high-pressure, high-velocity water/air mixture.

Mesoscale jet formation due to the Coriolis Effect is well understood over sharp changes in surface roughness such as coastlines. This sharp change in surface roughness is experienced by the atmosphere flowing over, and ocean flowing under, a compacted sea ice edge. Sea ice edge jets have been observed. This thesis presents a study of a dynamic sea ice edge responding to atmospheric and oceanic jet formation during various wind and ocean current conditions. An idealised analytical model of sea ice drift is created using a momentum balance and the viscous plastic rheology. This is compared to an ice edge in the Los Alamos sea ice climate model (CICE) run on an idealised domain. A scheme has been developed which analyses sea ice concentration and adds jets to the CICE model forcing data. The response of the model to jet formation is tested at various resolutions. The formation of atmospheric jets at the sea ice edge is shown to increase the wind speed parallel to the sea ice edge and results in the formation of a sea ice edge jet. The increase is dependent upon the angle between the ice and wind and results in an increase in ice transport along the sea ice edge of 40%. Observa- tions and climate model data of the polar oceans has been analysed to show areas of likely atmospheric jet formation with the Fram Strait being of particular interest. The possibility of oceanic jet formation and the resultant effect upon the sea ice edge is less conclusive. The coupling between the components of climate models is currently crude and does not allow for jet formation. Most climate model also misrepresent the ice drift through the Fram Strait leading to errors in the prediction of Arctic sea ice extent.

Processes at the air-water/ice interface are known to play a very important role in the release of reactive halogen species with atmospheric aerosols serving as catalysts. The ability to make different types of ice with various morphologies, hence, different adsorption and surface properties in vacuum, provide a useful way to probe the catalytic effect of ice in atmospheric reactions. Also, the use of the liquid jet technique provides the rare opportunity to probe liquid samples at the interface; hitherto impossible to investigate with traditional surface science techniques. Studies of reactions on both ice and liquid surfaces at ambient conditions are usually complicated by the rapid desorption and adsorption processes due to the high evaporation rates at the surface. To gain a better understanding and improve modeling of several atmospheric relevant reactions, it is therefore important to develop laboratory techniques that provide an opportunity to investigate non-thermal reactions on both ice and liquid surfaces. Detailed investigation of the interactions of atmospheric relevant molecules (methyl iodide and hydrogen chloride) on water ice at low temperature in UHV conditions has been carried out. These interactions were studied using different techniques such as temperature programmed desorption (TPD), electron stimulated desorption (ESD) and resonance enhanced multiphoton ionization (REMPI). Unlike probing reactions on ice surfaces, investigating air/liquid interfaces present several challenges. This is because traditional surface science techniques require an ultra high vacuum environment to prevent distortion of information due to interference from equilibrium vapor above the liquid surface during data acquisition. The liquid jet technique facilitates the direct study of continually renewed liquid surfaces in high vacuum, thereby preventing the constant changing of the properties and composition of the liquid surface due to the aging process (diffusion of impurities or liquid constituent). A linear time-of-flight mass spectrometer has been used to monitor ion ejection during laser irradiation of liquid jet containing aqueous solutions and pure water. Since these ions are ejected exclusively from the surface of the liquid and the cluster distributions observed are influenced by the local structure, these experiments provide a sensitive probe of the liquid vacuum interface of these solutions. Though the research is fundamental, the results obtained from these investigations indicate how the discontinuity of bulk properties on the surface of both ice and aqueous solutions affects interfacial reactions.

Electron-impact ionization of low-temperature water ice leads to H+, H2+, and H+(H2O)n=1-8 desorption. The threshold energy for ESD of H2+ from CI and H3O+ from PASW and ASW is 22 ± 3 eV. There is also a H2+ yield increase at 40 ± 3 eV and a 70 ± 3 eV threshold for ESD of H+(H2O)n=2-8 from PASW and ASW. H2+ production and desorption involves direct molecular elimination and reactive scattering of an energetic proton. Both of these channels likely involve localized two-hole one-electron and/or two-hole final states containing 4a1, 3a1 and/or 2a1 character. The 70 eV cluster ion threshold implicates either an initial (2a1-2) state localized on a monomer or the presence of at least two neighboring water molecules each containing a single hole. The resulting correlated two-hole or two-hole, one-electron configurations are localized within a complex and result in an intermolecular Coulomb repulsion and cluster ion ejection. The changes in the yields with phase and temperature are associated with structural and physical changes in the adsorbed water and longer lifetimes of excited state configurations containing a1 character. The dependence of the ESD cation yields on the local potential has been utilized to examine the details of HCl interactions on low temperature ice surfaces. The addition of HCl increases cluster ion yields from pure ice while decreasing H+ and H2+ yields. These changes reflect the changes in the local electronic potential due to the changing bond lengths at the surface of the ice as HCl ionizes and the surrounding water molecules reorient to solvate the ions. This work has been extended to ionic solutions at higher temperatures using a liquid jet and ultraviolet photoionization to interrogate the surface of aqueous ionic interfaces. Desorption of protonated water clusters and solvated sodium ion clusters were measured over a range of concentrations from NaCl, NaBr, and NaI solutions. The flux dependence indicated a multiple photon process and the proposed mechanism involves a Coulomb explosion resulting from the repulsion of nearby ions. The surface is investigated with regard to its importance in heterogeneous atmospheric chemistry.

This thesis investigates a novel combination of a jet-pump refrigeration cycle and a thermal (ice) storage (TIS) system that could substantially reduce the electrical energy requirements attributable to comfort cooling.Two methods of TIS were identified; spray ice TIS would use evaporative freezing to store ice on a vertical surface,and encapsulated ice TIS would freeze a bed of encapsulated elements by sublimation freezing.Thestudy also investigates jet-pump refrigeration at partload and a convergent-divergent design manufactured from a thermoset plastic to make recommendations for performance enhancement for a system that has a low COP. An experimental rig was built to investigate the novel concepts in the laboratory. Encapsulated ice TIS was superior to spray ice TIS because, for the same nominal secondary flow, sublimation freezing causes an increase in coolth storage rate of about 10 % compared to evaporative freezing. Encapsulated ice stores experience difficulties in fully discharging their coolth (approximately 6% in this case), but spray ice TIS can be used to produce an ice/brine slurry enabling all of the ice to be used, and so may be more suitable if the unmelted ice represents a large proportion of the cooling capacity. Approximately 85 % to 90 % of the ice formed on the vertical surface during spray ice TIS testing was formed by evaporative freezing from a falling film. At high saturation conditions, heat is transferred mainly by conduction across the falling film. Both the growth of an ice layer on a vertical surface and freezing of encapsulated elements were found to be successful, but a large data spread was observed during spray ice TIS testing. It was thought that a variation in the steady-state saturation conditions in the evaporator/ice store was caused by variability of droplet size distribution from the spray nozzle flow, which may make a full-scale system unreliable. The COP of the spray ice TIS system was approximately 0.15 compared to a COP of approximately 0.25 found during encapsulated ice TIS testing. The difference was because of the use of an over-expanded primary nozzle, which restricted secondary flow and increased momentum losses. A primary nozzle that expands close to the design evaporator saturation conditions should be used to maximise entrainment ratio. The COP of a jet-pump TIS is low, but a system designed to operate at off-peak periods could increase the COP to about 0.8 by taking advantage of the lower ambient conditions. The measurement of entrainment ratio was used successfully to determine ice storage rate and COP. This was valid because of the assumption that the saturation conditions in the evaporator/ice store approached steady-state. However, over longer periods that would be found in large-scale systems, the ice storage rate and entrainment ratio may fall substantially. The steady-state assumption could still be used to observe the change in evaporator conditions by sampling over short time intervals (30 minutes). At part-load, increases in evaporator saturation temperature could increase entrainment ratio substantially (50 % increase) for only a small reduction in critical pressure lift ratio Ns *(15 % reduction). A variation in chilled water temperature could be used to boost entrainment ratio at the peak demand. The variation in Ns* is too small to use this strategy to control the jet-pump with respect to condenser operating conditions. The entrainment ratio is approximately proportional to the diff-user to primary nozzle area ratio. A doubling of entrainment ratio was attained for only a 15% reduction in Ns*. The change in geometry from a constant area throat to a convergent-divergent design caused the flow through the jet-pump to vary with outlet conditions indicating that secondary flow was not choked. Higher entrainment ratios and pressure lift ratios were observed, but the entrainment ratio varied with outlet conditions in the form of peaks and troughs, making its operation unpredictable. This was thought to be caused by the restriction in secondary flow area due to the interaction of the primary jet and the curved wall. The convergent-divergent design manufactured from a thermoset plastic was successfully tested, showing that a plastic material can be used as a material of construction. In principle, a large number of jet-pump units could be manufactured from a single mould, reducing the first cost. The investigation proved the concept of jet-pump TIS. Waste-heat could be utilised over 24 hours and year round, increasing the efficiency of the process. The use of a convergent-divergent throat design, multiple geometry jet-pumps and operation at off-peak periods can maximise the performance over a cooling season, and be competitive with other TIS and chiller systems. The mass production of jet-pumps using injection moulding techniques could reduce substantially the capital cost of a system. All of these factors should encourage the development of such systems, so that the harmful emissions caused by the use of air conditioning systems can be minimised.

Dans le cadre de la construction du réacteur de fusion ITER, l’IRSN mène des travaux de recherche pour évaluer les conséquences de différents scénarios d'accidents pouvant conduire à l'endommagement de la chambre à vide du tokamak et induisant potentiellement un risque de dissémination de matières radioactives dans l’environnement. Le scénario considéré dans le cadre de cette étude est la perte de vide par entrée d’eau ou ICE (Ingress of Coolant Event) dont les conséquences sont susceptibles d’entrainer la formation d’hydrogène générant ainsi un risque d’explosion. Afin d'évaluer la quantité de poussières qui pourrait être mobilisée dans la chambre à vide du tokamak (dont dépend la quantité d’hydrogène produite) il est nécessaire d’identifier et de quantifier les mécanismes contribuant à la mise en suspension des particules à basse pression lors d’un scénario de perte de vide par entrée d’eau ou ICE. Lors d’un ICE, l’eau du circuit de refroidissement pénètre dans la chambre à vide à une température supérieure à son point d'ébullition en raison des conditions dites ITER like (basses pression et température) et subit une atomisation par effet thermodynamique dite flash. Le problème de l’atomisation flash dans le vide et de son impact sur la mise en suspension de poussières est particulièrement complexe. L’atomisation flash relève en effet du domaine des écoulements diphasiques en présence de phases métastables du point de vue de la thermodynamique et de changements de phase extrêmement rapides. De plus, l’atomisation en fines gouttelettes et la vaporisation intense qui ont lieu au niveau de la brèche peuvent donner lieu à des effets de compressibilité forts pouvant se traduire par l’apparition d’écoulements diphasiques supersoniques, de chocs et tout cela toujours à la limite des milieux raréfiés. Pour mener cette étude expérimentale, le développement d'un nouveau banc expérimental (FAAMUS, Flash Atomization and Aerosols Mobilization Under vacuum System) associé à une métrologie basée sur les techniques de PIV et d’ombroscopie haute cadence et adaptée à la caractérisation des écoulements diphasiques a fait l’objet de la première phase du travail de thèse. Des algorithmes de post-traitement ont également été développés pour extraire des données qualitatives et quantitatives sur la morphologie de l’écoulement diphasique et sur les vitesses des gouttes en sortie de brèche. Des expériences ont été réalisées afin d'étudier les phénomènes d'atomisation flash pour des conditions expérimentales représentatives de celles d’un ICE dans ITER ainsi que pour des conditions thermodynamiques élargies. Dans les conditions dites ITER like, nous avons pu mettre clairement en évidence et décrire la détente supersonique du jet diphasique en sortie de brèche. C’est un écoulement complexe pour lequel nous avons pu également quantifier sa sensibilité à la nature du régime d’écoulement diphasique développé dans le circuit en amont de la brèche. Les expérimentations effectuées ont permis d’obtenir l’évolution de la morphologie du spray ainsi que de la vitesse des gouttes produites sur une grande gamme de surchauffe. Ainsi, l’angle de spray atteint un angle de 150° tandis que la vitesse des gouttes dépasse les 60 m/s à forte surchauffe.L’évolution de ces caractéristiques n’est pas linéaire avec la surchauffe et dépend de nombreux paramètres géométriques et thermodynamiques. Des expériences préliminaires de mise en suspension aéraulique de particules à basse pression par flashage de jet liquide ont été réalisées et laissent entrevoir de nombreuses perspectives sur la problématique du comportement des poussières lors d’un scénario d’ICE dans ITER
As the ITER fusion reactor is being built, IRSN is conducting research to assess the consequences of various accident scenarios that could lead to damage to the vacuum chamber of the tokamak and potentially lead to a risk of radioactive materials being released into the environment. The scenario considered in this study is the loss of vacuum by water ingress or ICE (Ingress of Coolant Event), the consequences of which are likely to lead to the formation of hydrogen, thus generating a risk of explosion. In order to evaluate the quantity of dust that could be mobilized in the vacuum chamber of the tokamak (to which depends the quantity of hydrogen produced) it is necessary to identify and quantify the mechanisms contributing to the resuspension of particles at low pressure during a vacuum loss by ingress of coolant or ICE scenario. During an ICE, the water from the cooling circuit enters the vacuum chamber at a temperature above its boiling point due to the ITER like conditions (low pressure and high temperature) and undergoes atomization by thermodynamic effect known as flash boiling. The phenomenon of flash atomization in a vacuum and its impact on dust mobilisation is a particularly complex problem. Flash atomization falls under two-phase flow in the presence of thermodynamically metastable phases and extremely rapid phase changes. Moreover, the atomisation into fine droplets and the intense vaporization that takes place at the breach can give rise to strong compressibility effects that can result in the appearance of supersonic two-phase flows, shocks and this at the limit of rarefied environments. To conduct this experimental study, the development of a new experimental bench (FAAMUS, Flash Atomization and Aerosols Mobilization Under vacuum System) associated with metrology adapted to the characterization of two-phase flows based on high speed PIV and shadowgraphy techniques was the subject of the first part of the thesis work. Post-processing algorithms were also developed to extract qualitative and quantitative data on the morphology of the two-phase flow and on the velocities of the drops leaving the breach. Experiments have been carried out to study flash atomization phenomena for experimental conditions representative of those of an ICE in ITER as well as for extended thermodynamic conditions. Under ITER like conditions, we have been able to clearly demonstrate and describe the supersonic expansion of the two-phase jet as it exits the breach. This is a complex flow for which we were also able to quantify its sensitivity to the nature of the two-phase flow regime developed in the circuit upstream of the breach. The experiments carried out allowed us to obtain the evolution of the spray morphology as well as the velocity of the drops produced over a large range of overheat. Thus, the spray angle reaches an angle of 150° while the velocity of the drops exceeds 60 m/s at high overheat. The evolution of these characteristics is not linear with superheat and depends on many geometrical and thermodynamical parameters. Preliminary experiments on aeraulics resuspension of particles at low pressure by liquid-jet flashing have been carried out and provide many insights into the problem of dust behaviour under an ICE scenario inITER

La dernière période glaciaire est marquée par la présence de deux grandes calottes boréales recouvrant l’actuel Canada et le nord de l’Eurasie. Ces calottes constituent un élément actif du système climatique en interagissant avec les différentes composantes du système Terre. L’objectif de cette thèse est de déterminer par quels mécanismes les changements de circulation atmosphérique lors du dernier cycle glaciaire induisent potentiellement une téléconnexion entre les paléo-calottes de l’hémisphère nord. L’utilisation d’un modèle couplé climat-calotte simplifié m’a permis de tester séparément l’influence de la topographie et de l’albédo des calottes sur les champs de température et de précipitation lors du dernier cycle glaciaire, et de mettre en évidence le rôle de la circulation atmosphérique dans la synergie entre les paléo-calottes de l’hémisphère nord. Pour étudier plus en détail les mécanismes de cette interaction, l’utilisation d’un modèle de circulation générale s’est avérée nécessaire. J’ai tout d’abord effectué une inter-comparaison des modèles ayant participé à l’exercice PMIP3 pour le dernier maximum glaciaire (DMG). Cette inter-comparaison a permis d’illustrer l’impact des conditions glaciaires sur le décalage du courant-jet en Atlantique Nord et d’établir un lien entre ce décalage et les précipitations au sud de l’Europe. Enfin, à l’aide d’expériences idéalisées menées avec le modèle atmosphérique LMDZ, j’ai pu étudier le rôle de chacune des calottes dans les changements de circulation atmosphérique observés auDMG. Cette étude montre en particulier l’influence notable de la calotte nord-américaine sur le bilan de masse de surface de la calotte eurasienne
The last glacial period is characterized by the presence of two large ice sheets covering Canada and North Eurasia. These ice sheets are a key element of the climatic system by interacting with all the components of the Earth system. The aim of this thesis is to determine by which mechanisms changes in atmospheric circulation may have induced a teleconnexionbetween the Northern hemisphere paleo-ice sheets. The use of a simplified coupled climate-ice sheet model allowed to test separately the influence of the ice-sheet topography and albedo on temperature and precipitation fields throughout the last glacial cycle and to highlight the role of atmospheric circulation within the synergy of past boreal ice sheets.To investigate in more details the underlying mechanisms, the use of a general circulation model was necessary.I therefore carried out an inter-comparisonof the PMIP3 models to examine the GCM responsesto glacial conditions. This work allowed to determinethe role of glacial conditions on the shift of the NorthAtlantic jet stream position and to establish a relationshipbetween this shift and the amount of precipitationover southern Europe. The last part of this thesisis devoted to the respective role of each ice sheeton atmospheric circulation changes observed underglacial conditions. To achieve this, I performed idealizedexperiments with the atmospheric circulationmodel LMDZ. The results highlight the key influenceof the North American ice sheet on the Eurasian icesheet surface mass balance

This note proposes the continuous treatment approach as a valuable alternative to propensity score matching for evaluating economic effects of merger and acquisitions (M&As). This framework allows considering the variation in treatment intensities explicitly, and it does not call for an arbitrary definition of cutoff values in traded ownership shares to construct a binary treatment indicator. We demonstrate the usefulness of this approach using data from European M&As and by relying on the example of post-M&A employment effects. The empirical exercise reveals some heterogeneities over the whole distribution of acquired ownership shares and across different types of M&As and country groups.

We examine a model of social learning in networks following the lines of Bala and Goyal (1998, 2001). As a model of agents' behaviour we have chosen the model of informational cascades of Bikhchandani et al (1992). Similarly to Bala and Goyal we find that the higher the 'degree of integration' within the society is, the more likely it is that conformity of actions will arise. However, unlike their results our model suggests that in the presence of informational externalities globalisation of informational flows, expressed in the increasing density of communication channels in a network, may drive down the expected social welfare. (author's abstract)
Series: Working Papers Series "Growth and Employment in Europe: Sustainability and Competitiveness"

In 2012, plasma figuring was proven to be an alternative solution for the fabrication of large scale ultra-precise optical surfaces. Indeed, plasma figuring was successfully demonstrated on a metre class glass surface. The process was exceptionally rapid but residual errors were observed. This thesis addresses this issue by proposing an enhanced tool that provides a highly collimated plasma jet. The enhanced tool is characterized by a targeted material removal footprint in the range 1 to 5 mm FWHM. The energy beam is provided by an Inductively Coupled Plasma (ICP) torch equipped with a De-Laval nozzle. This thesis focuses on characterization and optimisation of the bespoke plasma torch and its plasma jet. Two research investigations were carried out using both numerical and experimental approaches. A novel CFD model was created to analyse and understand the behaviour of high temperature gas in the De-Laval nozzle. The numerical approach, that was based on appropriate profiles of temperature and velocity applied to the nozzle inlet, led to a significant reduction of computational resources. This model enabled to investigate the aerodynamic phenomena observed from the nozzle inlet up to the processed surface. Design rules and the effect of changing nozzle parameters were identified. Sensitivity analysis highlighted that the throat diameter is the most critical parameter. A challenging power dissipation analysis of the plasma torch was carried out. Temperature and flow rate in key components of the torch were measured. Experimental results enabled to calculate the power dissipation values for RF power up to 800 W and for the entire series of designed nozzles. This work enabled to scientifically understand the power dissipation mechanism in the bespoke ICP torches. In addition, by comparing the intensity of the power dissipation values, one nozzle was clearly identified as being more capable to provide a highly efficient plasma jet.

The following interdisciplinary study focuses on the poetic, prose and translation work of the Austrian Jewish writer Erich Fried. The present research concentrates on expressions of Fried’s identity or his sense of self in his work. Rather than being interpreted as a constant value, identity is perceived as fluid, expressed as a strategic positioning in one’s surroundings. It is postulated that various aspects of Fried’s identity appear in his work. Several traits coalesce to show one aspect or a combination of aspects, presenting an unexpected unity in disparity, as is shown throughout four core chapters. The kaleidoscopic blend of apparent inconsistencies and uncertainties becomes visible in the shape of different faces of Fried which shine through his work. This is indicated in the main proposition: the title of the thesis and the image of the ‘Vexierbild’ draw on Fried’s idea of ‘hidden faces’. The current thesis does not seek the author’s one ‘true face’ which possibly remains hidden under layers of traced and distorted circumlocutory accounts in his work, but rather captures the dynamic which drives the interchange between and metamorphosis of various components which contribute to the framework of Fried’s identity at different times of his life. The complexity of Fried’s identity in exile and its combined evidence in Fried’s literary and translation work is an aspect which has so far not been analysed. The findings reflect the main hypothesis—as suggested by the ‘Vexierbild’ image, aspects of Fried’s identity are complementary and opposing at times, dynamically and productively mirrored in his work.

This thesis describes the current state of the river Oslava in Oslavany design and reconstruction of the existing fixed weir in the affected location. As a best alternative reconstruction of the existing fixed weir reconstruction was chosen the hard threshold floating weir inflatable weirs. The next part of the thesis describes the proposed solution, and the last part of the thesis deals with the assessment of the proposed solutions.

La mise en œuvre de missions spatiales demande à développer de nombreuses technologies clés afin de surmonter certaines étapes cruciales. L’une d’entre elle concerne la rentrée atmosphérique : lorsque le véhicule pénètre dans la couche d’atmosphère, sa vitesse relative très grande par rapport au sol va engendrer des frottements importants ainsi qu’une augmentation de pression. L’énergie cinétique de l’objet va donc être transformée en énergie thermique et chauffer le gaz en formant une onde de choc. Les températures dépendent de la vitesse initiale, de la composition de l’atmosphère et de sa pression. Le gaz ainsi chauffé va s’ioniser et devenir un plasma, il va donc transférer sa chaleur au corps de la sonde non seulement par convection mais aussi par rayonnement. Afin de se protéger, le véhicule dispose d’un bouclier thermique pouvant résister aux phénomènes extrêmes rencontrés lors de la descente. Les contraintes supplémentaires vont imposer une géométrie particulière et un lourd bouclier. Ainsi l’objectif est d’avoir les protections les plus légères et efficaces possibles afin de permettre à la sonde de maximiser son emport en équipement scientifique. Pour cela, un des paramètres clés est de connaître le comportement et le rayonnement du plasma produit lors de la rentrée dans l’atmosphère. Cette thèse se positionne dans ce domaine d’étude: les expériences montées et réalisées ont pour objectif d’observer par moyens spectroscopiques un plasma correspondant à celui rencontré par les sondes spatiales
Many key technologies, to overcome some crucial steps, are needed for space missions. One of them concerns the re-entry: when the vehicle enters the atmosphere layer, its high velocity relative to the ground will generate significant friction and an increase in pressure. The kinetic energy of the object will be converted into heat energy and heat the gas forming a shock wave. Temperatures depend on the initial velocity, the atmosphere composition and its pressure. The gas is ionized and become plasma, it will therefore transfer its heat to the body of the probe not only by convection but also by radiation. To protect itself, the vehicle has a heat shield that can withstand extreme phenomena encountered during the descent. Additional constraints will impose a particular geometry and a heavy shield. So the goal is to have the lightest possible and effective protections to allow the probe to maximize its payload. For this, one of the key parameters is to know the behavior of the plasma and radiation produced during re-entry into the atmosphere. This thesis is positioned in this area of ​​study: experiments to create a re-entry plasma are intended to be observed by a spectrometer

Les tendances climatiques récentes montrent un réchauffement et un adoucissement des couches de surface dans la région du courant circumpolaire antarctique (ACC).Sur la même période, les vents d'ouest pilotant la circulation de l'océan Austral ont significativement augmentés. Cette augmentation est en partie liée à l'intensification du mode annulaire austral (SAM), principal mode de variabilité atmosphérique au sud de 20°S. Dans cette thèse, on s'intéresse à comprendre les effets de la tendance positive du SAM sur les propriétés des masses d'eau formées dans la région de l'ACC.A cette fin, on met en place une stratégie de simulations régionales couplées océan-glace de mer et forcées par une série de scénarios atmosphériques perturbés. Les scénarios atmosphériques sont construits à partir de réanalyses atmosphériques afin de décrire les différentes composantes (dynamiques et thermodynamiques) des changements liés au SAM.En réponse à l'intensification du SAM, les simulations montrent une forte salinisation de la couche de mélange océanique ainsi que des eaux modales (SAMW) et intermédiaires (AAIW).L'essentiel de ces changements peut être attribué aux composantes dynamiques du SAM. Dans les régions saisonnières englacées, les composantes thermodynamiques du SAM peuvent jouer un rôle important (en particulier en mer d'Amundsen et en mer de Weddell). Les simulations montrent également le rôle clef joué par la glacede mer dans la médiation des changements atmosphériques vers l'océan intérieur. Ces résultats de simulations suggèrent que le SAM ne serait pas le seul pilote des tendances climatiques récentes dans l'océan Austral
Recent climate trends show a warming and freshening of the surface layers in the region of the Antarctic Circumpolar Current (ACC). Over the same period, the westerlies driving the circulation of the Southern Ocean have significantly increased. This increase is partly due to the intensification of the Southern Annular Mode (SAM), the main mode of atmospheric variability south of 20°S. In this thesis, we are interested in understanding the effects of the positive trend of the SAM onto the properties of water masses formed in the region of the ACC. To do so, we implement a strategy of regional coupled ocean-sea ice simulations forced by a series of atmospheric disturbance scenarios.These scenarios are constructed from atmospheric reanalyses in order to describe the various components (dynamic and thermodynamic) of the changes related to the SAM. In response to the increase of the SAM, the simulations show a significant salinification of the ocean mixed layer and of the mode water (SAMW) and intermediate water (AAIW).Most of these changes can be attributed to the dynamic components of the SAM. In Seasonal Ice Zone, the thermodynamic components of the SAM can play an important part (especially in Amundsen Sea and Weddell Sea). The simulations also show the key role played by sea ice in mediating atmospheric changes toward the interior ocean.These simulation results suggest that SAM is not the only driver of recent climate trends in the Southern Ocean

Au cours de ce travail de thèse, un jet de plasma d’air subsonique crée par une torche ICP en configuration de jet libre et de couche limite de plaque plane a été étudié au moyen de diagnostics optiques. Les espèces moléculaires majoritaires ont été sondées sur leurs états fondamentaux via les méthodes de diffusion Raman spontanée - pour N2 et O2 - et de fluorescence induite par laser large-bande à 248 nm - pour NO. En outre, l’état excité (A2 ∑+) de cette dernière molécule a fait l’objet de mesures par spectroscopie d’émission. La détermination des températures de vibration et de rotation ainsi que de la densité a été effectuée par comparaison des spectres expérimentaux avec des spectres théoriques élaborés durant cette thèse. Toutes ces techniques ont clairement mis en évidence un déséquilibre entre les températures de vibration et de rotation dans le jet libre et dans la couche limite de plaque plane. Cependant, les diagnostics laser fournissent une température cinétique – identifiée à la température de rotation - bien inférieure aux valeurs usuelles trouvées par spectroscopie d’émission. D’autre part, au centre du jet, les densités des états fondamentaux sont très proches de l’équilibre chimique à la température cinétique de l’écoulement. Par contre, la densité des états excités est très supérieure - de plusieurs ordres de grandeurs. Il apparaît ainsi qu’un code d’écoulement ne permet pas d’estimer le rayonnement d’un plasma d’air hors-équilibre. En ce qui concerne la plaque plane, on observe que l’équilibre se conserve sur N2. Au contraire, la densité de NO augmente très nettement en proche paroi. Ce phénomène peut s’expliquer directement par la catalycité sur la paroi ou par les mécanismes d’échange dans l’air en proche paroi en supposant que de l’oxygène moléculaire est produit par catalyse hétérogène.

This diploma thesis deals with a design of the reconstruction of a smixed weir on the Oslava river in Oslavany town. The introduction describes the site of interest and the the occurrence of ice events. There are several types of fish ladders described theoretically. Further on in the thesis there is desribed the state of the objects on the flow and the state of the river basin in the area of interest of Oslava river. Next part of the thesis deals with the design of a movable baying structure (a hollow flap) and fish ladder type bypass channel. An impact assessment of the current and newly proposed weir on flow in the HEC-RAS program was carried out. The project also includes the basin adjustment in overweir and an evaluation of the stability of the newly designed construction.

In spite of their high abundance and importance, aqueous systems are enigmatic on the microscopic scale. In order to obtain information about their geometrical and electronic structure, simple aqueous solutions have been studied experimentally by photo- and Auger electron spectroscopy using the novel liquid micro-jet technique in conjunction with synchrotron radiation. The thesis is thematically divided into three parts. In the first part we utilize the surface sensitivity of photoelectron spectroscopy to probe the distributions of solutes near the water surface. In agreement with recent theoretical predictions we find that large polarizable anions, such as I- and ClO4-, display enhanced surface propensities compared to smaller rigid ions. Surface effects arising from ion-ion interactions at higher electrolyte concentrations and as function of pH are investigated. Studies of linear mono-carboxylic acids and benzoic acid show that the neutral molecular forms of such weak acids are better stabilized at the water surface than their respective conjugate base forms. The second part examines what type of information core-electron spectra can yield about the chemical state and hydration structure of small organic molecules in water. We demonstrate that the method is sensitive to the protonation state of titratable functional groups and that core-level lineshapes are dependent on local water hydration configurations. Using a combination of photoelectron and X-ray absorption spectroscopy we also show that the electronic re-arrangement upon hydrolysis of aldehydes yields characteristic fingerprints in core-level spectra. In the last part of this thesis we study ultrafast charge delocalization dynamics in aqueous solutions using resonant and off-resonant Auger spectroscopy. Intermolecular Coulombic decay (ICD) is found to occur in a number of core-excited solutions where excess energy is transferred between the solvent and the solute. The rate of ultrafast electron delocalization between hydrogen bonded water molecules upon oxygen 1s resonant core-excitation is found to decrease upon solvation of inorganic ions. The presented work is illustrative of how core-level photoelectron spectroscopy can be valuable in the study of fundamental phenomena in aqueous solutions.

In dieser Arbeit wurde eine neue Markierungsstrategie von Antikörpern mit dem Markierungsreagenz MeCAT (Metal Coded Tag) unter physiologischen Reaktionsbedingungen, sowie deren Anwendung in einem 8-fach Multiplex-Immunoassay von in Formalin-fixierten und in Paraffin-eingebetteten Gewebeschnitten entwickelt. Für eine aussagekräftige LA-ICP-MS Detektion von MeCAT-modifizierten Antikörpern, wurde eine Standardisierung für biologische Proben auf NC-Membranen, basierend auf einer homogenen Aufbringung eines internen Standards und Kalibrierstandards durch einen kommerziell verfügbaren Tintenstrahldrucker entwickelt und mit der ICP-MS Analyse von Lösungen evaluiert. Die LA-ICP-MS wurde in zwei 8-fach Multiplex-Immunoassays von Tissue Micro Arrays vom Prostatakarzinom und in Maushirngewebeschnitten zur Einschätzung von neurogenerative Erkrankungen erfolgreich eingesetzt werden. Es konnte hierbei gezeigt werden, dass das Nachweisvermögen, der hier entwickelten Methode bereits ausreicht, um die gängigen klinischen Biomarker mit guter Ortsauflösung nachzuweisen.
In this work a new tagging strategy of antibodies with the tagging reagent MeCAT (Metal Coded Tag) was developed under physiological reaction conditions. Their application was proved in an 8-fold multiplex immunoassay of formalin-fixed and paraffin-embedded tissue sections. For a significant LA-ICP-MS detection of MeCAT tagged antibodies standardization for biological samples owere developed. The standardization based on a homogeneous deposition onto the NC membrane via conventional CD-ink-jet printer was validated in addition with the ICP-MS analysis of solutions. The internal standardization of LA-ICP-MS was successfully applied in two 8-fold multiplex immunoassays for Tissue Micro Arrays (TMA) of prostate cancer and for detection of biomarkers for neurodegenerative diseases in mouse brain tissue sections. In both examples it could be shown that the detection capability of the new tagging strategy in combination with the printing standardization allows the detection of the clinical biomarker with good spatial resolutions.

Étant à la fois acteur de l’enseignement supérieur malgache et chercheur en SIC, nous nous sommes penchée sur le phénomène de faible utilisation des TIC chez les enseignants malgaches, en adoptant trois positionnements successifs.Nous avons débuté la recherche par l’interrogation : « Qu’est- ce qui ne va pas ? ». Elle comporte un postulat important : celui de l’existence d’un problème à résoudre dans le cadre de l’usage des TIC par les enseignants. Elle est également posée par un individu « acteur » de la situation, animé par une forte volonté de changement et non uniquement par un scientifique chercheur, dans une tentative de compréhension d’un phénomène. Au cours de l’étude, nous reformulons notre interrogation en : « comment ça fonctionne ? » puisque nous avons mis à jour le « mécanisme » qui sous-tend la construction des pratiques des technologies (logiques de valorisation et d’opportunisme) au travers de situations de mise en place et d’exploitation de dispositif dans le cadre universitaire. Nous avons adopté notre positionnement de chercheur.Au terme de la recherche, nous répondons à la question « comment composer avec ce fonctionnement ? ». Nous nous adressons à des acteurs du terrain (porteurs de projet et responsables) dans une optique d’accompagnement et de conseil. Nous endossons ici, la casquette d’intervenant. Après une revue du contexte de l’enseignement malgache et des recherches concernant le domaine des TIC en Sociologie et en Sciences de l’Education, nous avons tenté de proposer un modèle de compréhension supplémentaire de l’usage des TIC à travers l’application de l’analyse systémique qualitative des relations et la notion de « logique de jeu ». Nous avons ensuite déconstruit cette réflexion pour proposer des pistes d’actions pour mener les projets technologiques à l’université malgache
As an actor of malagasy higher education and researcher in Information and Communication Sciences, we analyzed the phenomenon of low usage of ICT among Malagasy teachers, by adopting three successive positionings. We started the research by asking ourselves : « what is wrong ?». This question includes an important postulate: the existence of a problem regarding the use of TIC by the teachers. It is also raised by an individual "actor" of a situation, with a strong will of change and not only by a scientist researcher, in an attempt to understanding a phenomenon. During the study, we reformulate our questioning : «How does it work? » since we have put in day the "mechanism" underlying the construction of practices of technologies (logic of promotion and opportunism) through situations of use of devices within the university. We adopted our positioning of researcher. At the end of research, we answer to the question « How to compose with this functioning? ». This part of the study is addressed to promoters and managers in a perspective of accompaniment and advising. We become an acting researcher . After a review of the context of malagasy education and researches concerning the domain of ICT in Sociology and in Education Sciences, we have attempted to offer an additional model of understanding for the usage of ICT through the application of the qualitative systemic analysis of relations and notion of « logic of the system». We have then proposed global actions for managing technological project among malagasy university

Presented work deals with heat transfer and its methods. At the beginning thesis describes the theory and the ways of heat transfer with connected quantities and equations. Then it explains the stack effect and impact of temperature on electro technical device. In work is also described ABB driver ACS line and calculation of heat transfer according to IEC 60890 standard. In the practical part there is the calculation of heat transfer in Flow Simulation simulating CFD program solved and finite element method is mentioned. Important part of work is devoted to setting and optimization of simulation. In conclusion are made some changes of construction of driver, dependence on heat transfer is inspected.

A rapidly melting ice sheet produces a distinctive geometry of sea level (SL) change. Thus, a network of SL observations may, in principle, be used to infer sources of meltwater flux. We outline a new method, based on a Kalman smoother, for using tide gauge observations to estimate the individual sources of global SL change. The Kalman smoother technique iteratively calculates the maximum likelihood estimate of Greenland and West Antarctic ice sheet melt rates at each time step, and it allows for data gaps while also permitting the estimation of non-linear trends. We have also implemented a fixed multi-model Kalman filter that allows us to rigorously account for additional contributions to SL changes, such as glacial isostatic adjustment and thermal expansion. We report on a series of detection experiments based on synthetic SL data that explore the feasibility of extracting source information from SL records before applying the new methodology to historical tide gauge records. In the historical tide gauge study we infer a global mean SL rise of ~1.5 ± 0.5 mm/yr up to 1970, followed by an acceleration to a rate of ~2.0 ± 0.5 mm/yr in 2008. In addition to its connection to SL, Greenland and its large ice sheet act as a barrier to storm systems traversing the North Atlantic. As a result of the interaction with Greenland, low-pressure systems located in the Irminger Sea, between Iceland and Greenland, often produce strong low-level winds. Through a combination of modeling and the analysis of rare in-situ observations, we explore the evolution of a lee cyclone that resulted in three high-speed-wind events in November 2004. Understanding Greenland’s role in these events is critical in our understanding of local weather in this region.

The main objective of this study was to describe the overflow of freshwater onto the sea ice surface in the Mackenzie Delta and to investigate the hydraulic behaviour of the upwelling and strudel events. This study was performed from the analysis of data collected during field investigations, from satellite images and from experimental laboratory studies. A forecasting method using the water level in the Mackenzie River was formulated to predict the overflow initiation about five days before its occurrence. The physical modelling of a strudel flow through a circular hole established a relation between the overflow depth and the discharge coefficient. Velocity measurements of the free-surface vortex using an Acoustic Doppler Velocimeter found that velocities at the vortexs core were influenced by its vorticity. Finally, predictions of maximum strudel scour, which are of great importance for the determination of burial depth of pipelines, were predicted from published impinging jet experiments.
Water Resources Engineering

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
Ao longo dos anos tem surgido vários desenvolvimentos e tentativas de criar tecnologias de arrefecimento baseadas na mudança de fase. A maior parte dos desenvolvimentos nesta área foram feitos com recurso à mudança de fase por vaporização, isto é, à mudança de fase entre líquido e vapor. No entanto, pouco tem sido explorado em relação à mudança de fase entre sólido e vapor, também conhecido por sublimação. A formação de partículas sólidas de dióxido de carbono, também conhecido por gelo seco, é feita com recurso ao efeito Joule-Thompson. Um fenómeno que permite o arrefecimento do dióxido de carbono, através da descida abrupta de pressão ao passar por um pequeno orifício e que consequentemente, devido à mudança de fase, resulta num jato de mistura bifásica sólido-gás a baixas temperaturas. Deste modo, formam-se partículas de gelo seco que, devido à baixa temperatura, irão mudar de fase sólida para vapor e contribuir para o arrefecimento em contacto com a superfície, aliado ao arrefecimento inerente da convecção das baixas temperaturas do jato.No âmbito desta dissertação, concebeu-se uma instalação experimental com o objetivo de estudar o arrefecimento provocado por um jato de partículas de dióxido de carbono, de modo mais preciso, tendo como variáveis independentes o ângulo de inclinação da placa e o tempo de incidência do jato.Os ensaios realizados revelaram a influência do ângulo de inclinação da placa em relação à horizontal, no processo de arrefecimento com jato de dióxido de carbono, onde se obteve fluxos de calor e coeficientes de convecção médios superiores para ângulos da placa nulos, havendo uma forte variação dos valores locais com a variação da distância ao centro da placa. Os resultados evidenciaram um processo de arrefecimento com eficiências a variar entre 6,39% e 11,59%.
Along the years there have been a significative amount of development and attempts to create cooling technologies based on the phase change. Most of the development in this area were made with the vaporization phase change, in other words, the phase change between liquid and vapor. However, little has been explored in relation to the phase change between solid and vapor, also known as sublimation.The formation of solid particles of carbon dioxide, also known as dry ice, is made using the Joule-Thompson effect. A phenomenon which allows the cooling of carbon dioxide through the abrupt drop of pressure as it passes through a small orifice and which consequently, due to the phase change, results in a solid-gas biphasic mixing jet at low temperatures. Thus, dry ice particles are formed which, due to the low temperatures, will change from solid to vapor phase and contribute to the cooling in contact with a surface, together with the inherent cooling of the convection of the low temperature jet.As part of this work, an experimental setup was designed aiming the study of the cooling caused by a jet of carbon dioxide particles with more accuracy, having as independent variables the angle and time of incidence of the jet.The tests showed the influence of the slab angle in relation to the horizontal in the cooling process with carbon dioxide jet blasting, where upper average heat fluxes and convection coefficients were obtained for null slab angles, with a strong variation of the local values with the variation of the distance to the center of the slab. The results showed a cooling process with efficiencies ranging from 6.39% to 11.59%.

The Diploma work deals with the explanation conceptions of the age and the parallel failures of the changes. Work defines closer specification of senior attitude, need and interests toward (ICT). To improve of senior lifelihood and lifestyle I am introducing the use of ICT. It can be helpful for senior citizens to inter-connect again in the social community. The contemporary trends of ICT are presented here which they are suitable for retired citizens and can be accessibled in the trade. I reclined my opinion during my own work experience as an assistant in project: ``Click by the right button, grandad!``