Literatura científica selecionada sobre o tema "Puits tubés"

Abstract. For decades, drop-freezing instruments have contributed to a better understanding of biological ice nucleation and its likely implications for cloud and precipitation development. Yet, current instruments have limitations. Drops analysed on a cold stage are subject to evaporation and potential contamination. The use of closed tubes provides a partial solution to these problems, but freezing events are still difficult to be clearly detected. Here, we present a new apparatus where freezing in closed tubes is detected automatically by a change in light transmission upon ice development, caused by the formation of air bubbles and crystal facets that scatter light. Risks of contamination and introduction of biases linked to detecting the freezing temperature of a sample are then minimized. To illustrate the performance of the new apparatus we show initial results of two assays with snow samples. In one, we repeatedly analysed the sample (208 tubes) over the course of a month with storage at +4 °C, during which evidence for biological ice nucleation activity emerged through an increase in the number of ice nucleators active around −4 °C. In the second assay, we indicate the possibility of increasingly isolating a single ice nucleator from a precipitation sample, potentially determining the nature of a particle responsible for a nucleation activity measured directly in the sample. These two seminal approaches highlight the relevance of this handy apparatus for providing new points of view in biological ice nucleation research.

Abstract. Since decades, drop-freezing instruments have contributed to a better understanding of biological ice nucleation and its likely implications on cloud and precipitation development. Yet, current instruments have limitations. Drops analysed on a cold stage are subject to evaporation and potential contamination. The use of closed tubes provides a partial solution to these problems, but freezing events are still difficult to be clearly detected. Here, we present a new apparatus where freezing in closed tubes is detected automatically by a change in light transmission upon ice development, caused by the formation of air bubbles and crystal facets that scatter light. Risks of contamination and introduction of biases linked to detecting the freezing temperature of a sample are then minimized. To illustrate the performance of the new apparatus we show initial results of two assays with snow samples. In one, we repeatedly analysed the sample (208 tubes) over the course of a month with storage at +4 °C, during which evidence for biological ice nucleation activity emerged through an increase in the number of ice nucleators active around −4 °C. In the second assay, we indicate the possibility to increasingly isolate a single ice nucleator from a precipitation sample, potentially determining the nature of a particle responsible for a nucleation activity measured directly in the sample. These two seminal approaches highlight the relevance of this handy apparatus to provide new points of view in biological ice nucleation research.

Le titrage des vaccins contre la péripneumonie contagieuse bovine se fait habituellement en tubes; on effectue tout d'abord une série de dilutions au dixième de la suspension à titrer puis on ensemence d'autres tubes à partir de chacune des dilutions. Cette méthode n'est pas très précise ou nécessite la manipulation d'une très grande quantité de tubes. La nouvelle technique proposée repose sur une première série de dilution au demi réalisées en parallèle dans une plaque de microtitration. La croissance des mycoplasmes peut être facilement appréciée, après 6 à 9 jours d'incubation, par le virage d'un indicateur coloré. Cette technique est plus rapide et précise et le résultat est alors obtenu par une moyenne, affectée d'une certaine précision, ce qui permet d'effectuer des comparaisons entre titrages qui soient statistiquement significatives.

Abstract The cracking failure accidents of austenitic stainless steel pipes of utility boilers often occur. The intergranular corrosion cracking caused by improper control of welding, heat treatment and cold working processes is an important reason for its failure. Through the analysis of typical cases, this paper expounds on the influence of welding, heat treatment and cold working processes on the service safety of austenitic stainless steel pipes and puts forward protective measures.

À la suite du décès par Ebola d’un parent, une famille accuse l’État guinéen d’être responsable de sa mort. Qu’est-ce qui a conduit à porter une telle accusation? À partir d’une enquête ethnographique en République de Guinée, cet article montre de quelle manière l’histoire politique guinéenne a influencé le déroulement de l’épidémie d’Ebola de 2014 à 2016 dans les pays du fleuve Mano. Pour comprendre comment les crises politiques du passé façonnent le rapport des Guinéens à la crise sanitaire provoquée par Ebola, je procéderai en trois temps. D’abord, je reviendrai sur les violences d’État qui ont jalonné l’histoire politique de la Guinée depuis son indépendance en 1958. Une des conséquences de ces violences se manifeste par un manque de confiance systémique vis-à-vis des élites et des actions gouvernementales. Puis, je montrerai comment les camps d’internement militaires de Sékou Touré réactivent un rapport à l’enfermement induisant des rumeurs et des comportements de peur face aux Centres de traitement d’Ebola (CTE). Enfin, pour me déprendre des approches fondées sur les « réticences » de la population guinéenne aux dispositifs sanitaires de lutte contre l’épidémie, j’analyserai des formes de résistance s’inscrivant plus largement dans l’histoire des contestations politiques en Guinée.

Reinforced concrete grid frame core-tube structure system is a new system. This article draws the conclusion that grid frame core-tube has high stiffness and obvious space affection, and that its basic mechanics properties is better than frame core-tube structure and similar to tube structure through the comparison of two tube structure systems, which the Inner tube is similar to grid frame core-tube and the outer tubes respectively are frame and high beam - column frame tube. It puts forward some reasonable suggestions for the future designation of this structural system.

In this paper, we study a kind of intelligent and high-accuracy flow measurement system, which is a type of venturi tube flowmeter that surpassed the international standard ISO5167. This paper analyzes the characteristics of the super-size flow measurement in the water transportation and industrial projects, and the choice for suitable flow meters. We study the practical compensation technology for discharging coefficient “C” of the international-standard-exceeding venturi tube, and puts forward water calibration method for venturi tube, and design the intelligent and high-accuracy flow metering system based on computer technology. Furthermore, this paper analyzes the calibration data of water flow, and propose the segment and compensation method for discharging coefficient “C” practically. We solved the limitations of the international-standard-exceeding venturi tubes, and effectively improved the accuracy and range of the flow measurement system.

The energy consumption in buildings for heating and cooling continues to increase from year to year, in order to meet people's increased demand for thermal comfort. A key energy issue for the buildings sector, the largest consumer of energy, requires the rational use of traditional resources and the application of non-polluting, inexhaustible renewable energy technologies that allow sustainable development. The public authorities are currently showing a clear desire to reduce energy consumption in the buildings sector through various legislated thermal regulations. In Algeria, law 99-09 and executive decree 2000-09, followed by other regulations, have as objectives the control of energy and the introduction of energy efficiency in buildings. In this paper, we focused on the effectiveness of the earth-to-air heat exchanger system for cooling buildings in three different climate regions in Algeria. The Earth to air heat exchanger device is a promising technology for reducing or avoiding the use of air conditioning systems. The Earth to air heat exchanger system which exploits the thermal inertia of the soil puts two different temperature sources in thermal contact, the air which circulates in the tubes, and the ground placed in contact with the tubes. This model was validated to show a good agreement between simulated results and other experimental data published. The simulation results confirmed that A maximum energy gain of 2221.15 kWh, 523.56 kWh and 300.27 kWh over a cooling season can be reached for Timimoun, Djelfa, and Jijel.

The spatial high-resolution synthetic aperture radar (SAR) for ocean exploration puts forward higher requirement for output power and amplitude-phase consistency of the pulsed TWT amplifier. The kW class pulsed TWT amplifier based on broadband power combining is the key technology for space SAR applications. In this paper, the factors affecting the amplitude and phase consistency of MPM are studied, and a phase consistency compensation circuit was designed to improve the phase consistency of multiple sets of products. A microwave power model (MPM) with dual TWTs output integrated architecture was proposed which consists of two short travelling wave tubes (TWT), two solid-state power amplifiers (SSPA), and an electronic power conditioner (EPC). More than 45% efficiency is achieved in 15% duty cycle within 600 MHz bandwidth, and the phase consistency was less than ± 5 degrees.With the improvement of synthesis efficiency, higher synthesis power and higher sensitivity of ocean wide scanning and detection can be obtained

Dans les puits pétroliers, de nombreux outils fonctionnant sur différents principes physiques sont couramment utilisés pour l’acquisition de données. Cette thèse se concentre sur les sondes de diagraphies nucléaires actives, faisant intervenir une source neutronique ou gamma. Elles sont utilisées dans l'industrie pétrolière pour caractériser la géologie des puits et ont été initialement développées pour réaliser des mesures quantitatives en conditions puits ouvert où la sonde est en contact direct avec la formation rocheuse. Une fois le puits pétrolier foré, un tube en acier est installé puis cimenté, les sondes ne sont alors plus en contact avec la formation rocheuse et les mesures sont considérées comme qualitatives en raison de la complexité de la géométrie et de l'atténuation du signal.Avec la raréfaction des ressources en hydrocarbures, le nombre de projets d’explorations diminue chaque année. Les compagnies pétrolières ont de plus en plus de puits dont il faut maintenir les capacités de production et d’autres en fin de vie qu’il faut abandonner, ce qui passe systématiquement par des mesures. La quantité de diagraphies en configuration puits tubé tend donc fortement à augmenter et il devient nécessaire d’améliorer leur interprétation.La problématique industrielle est de pouvoir caractériser de manière quantitative, dans un domaine à forte hétérogénéité radiale, l’ensemble de tous les éléments du puits (e.g. les fluides, le tubage, le ciment) et pas uniquement les paramètres du réservoir rocheux. L’approche développée dans la thèse se base sur le concept des fonctions de sensibilité des sondes diagraphiques nucléaires, qui représentent la dépendance en 3D de la mesure aux éléments du modèle et sont obtenues par simulation Monte-Carlo. Du fait du nombre important de variables, une inversion multiphysique prenant en compte l’ensemble des mesures des différentes sondes nucléaires (de porosité par diffusion neutronique, de densité par diffusion gamma, de lithologie par activation neutron-gamma) est indispensable.La première étape de la thèse a permis de comparer les codes Monte-Carlo de transport de particules GEANT4 et MCNP pour des applications de Géosciences. Les résultats montrent un très bon accord pour la physique gamma-gamma, un bon accord pour la physique neutron-neutron mais des écarts significatifs pour la physique neutron-gamma pour laquelle MCNP semble plus pertinent.La deuxième étape de la thèse a permis de valider expérimentalement les simulations Monte Carlo et de concevoir une méthode de calcul des fonctions de sensibilité numériques spécifique au domaine des puits tubés. La validation se traduit par une comparaison entre les fonctions de sensibilité expérimentales mesurées en centre d’étalonnage et les fonctions de sensibilité numériques calculées avec deux méthodes différentes, l’une basée sur des importances spatiales estimées par MCNP, l’autre sur les lieux d’interaction obtenus avec GEANT4. Les résultats montrent un bon accord expérimental entre les profils de sensibilité radial et axial mesurés et calculés, ce qui valide le concept de fonction de sensibilité avec une préférence pour la méthode des lieux d’interaction qui présente un contraste radial plus importante entre les différents constituants du puits.La troisième étape de la thèse a consisté à faire l’interprétation géologique d’une zone réservoir d’un puits tubé avec les fonctions de sensibilité. Les diagraphies neutron-gamma et de porosité prédites grâce aux fonctions de sensibilité sont comparées à celles mesurées en puits. Un modèle de terrain optimal est obtenu par itération, montrant une bonne capacité des algorithmes de prédiction à reproduire quantitativement en configuration puits tubé ce type de diagraphies à condition de choisir un étalonnage pertinent
In petroleum wells, many tools operating on different physical principles are commonly used for data acquisition. This thesis focuses on actives nuclear logging probes involving a neutron or a gamma source. They are used in the oil industry to characterize the well geology and have been initially developed to realize quantitative measurements in open hole conditions where the probe is directly in contact with the rock formation. Once the petroleum well is drilled, a steel casing is installed and cemented, the probes are then no longer in contact with the rock formation and the measurements are considered qualitative due to the complexity of the geometry and the signal attenuation.With the hydrocarbon resources rarefaction, the number of explorations projects decease each year. Petroleum companies have more and more mature wells whose production capacities must be maintained and others at the end of their life which must be abandoned. Those phases require systematically logging measurements. The quantity of logs in cased-hole configuration tends to increase a lot and it becomes necessary to improve their interpretation.The industrial problematic is to characterize quantitatively, in a filed with strong radial heterogeneity, all the components the well (e.g. the fluids, the casing, the cement) and not just the rock reservoir parameters. The approach developed in the thesis is based on the concept of sensitivity function of nuclear logging probes, which represents the 3D dependency of the measurement to the model elements and are obtained by Monte-Carlo simulation. Due to the large number of unknowns, a multiphysical inversion considering the all the measurements of the different nuclear probes (porosity by neutron diffusion, density by gamma diffusion, lithology by neutron-gamma activation) is essential.The first part of the thesis allowed to compare the Monte-Carlo particles transport codes GEANT4 and MCNP for Geosciences applications. Results show a very good agreement for the gamma-gamma physics and a good agreement for the neutron-neutron physics but significant discrepancies for the neutron-gamma physics where MCNP seems to be more relevant.The second part of the thesis allowed to experimental validate Monte-Carlo simulations and to design a sensitivity function computation method specific for the cased-hole configuration. The validation is a comparison between the experimental sensitivity functions measured in calibration center and the numerical sensitivity functions computed using two different methods, the first one based on spatial importances estimated with MCNP and the second one based on interaction locations obtained with GEANT4. The results show good experimental agreement between the measured and calculated radial and axial sensitivity profiles, which validates the concept of sensitivity function with a preference for the interaction locations method which presents greater radial contrast between the different components of the well.The third part of the thesis consisted of making the geological interpretation of a reservoir zone of a cased hole well with sensitivity functions. The neutron-gamma and porosity logs predicted using the sensitivity functions are compared to the measured logs. An optimal earth model is obtained by iteration, showing a good capacity of the fast forward modeling algorithums to quantitatively reproduce the logs in cased-hole configuration providing that a relevant calibration is apply

Ce chapitre décrit les caractéristiques des tubes absorbeurs utilisés dans les centrales solaires à concentration linéaire. Ensuite, les récepteurs solaires actuels puis les concepts émergents pour centrales à tour sont présentés. Enfin, les différentes pertes thermiques sont détaillées, le rendement thermique est exprimé et un modèle thermique simple et rapide de récepteur solaire est proposé.

Abstract Scientists have for long been attempting to put forth a mathematical model which could explain the flow of blood through arteries. The study of flow through rubes began as early as in 1839 with the volume flow rate equations put forth by Hagen. Another formulation was suggested by Poiseuille, which resulted in the Poiseuille’s law of Fluid Flow through circular tubes. Rubinow & Keller incorporated the elastic nature of the tubes in their paper of 1971 wherein an equation for the flow of a Newtonian fluid through an elastic tube was developed. Mazumdar generalized the model proposed by Rubinow & Keller for Non Newtonian flow. Though the above models can be made use of to study the flow of blood through arteries after several simplifying assumptions, a realistic mathematical model must necessarily account for various anomalous properties exhibited by blood. This paper puts forth a model, which incorporates experimentally observed, atypical behavior demonstrated by blood under special conditions of flow. The model is then shown to be a generalized case of the models put forth previously.

High and intermediate pressure feedwater heaters increase the thermal efficiency of a power plant. During their lifetime they are subject to many different failure, mechanisms. Some of these failures are attributed to flow induced vibration resulting from operation at high overload conditions and load cycling. No-Tubes-in-the-Window (NTIW) baffle designs have been used for many years in the design of power plant and process plant heat exchangers. This baffle design is typically used in larger units which have high flows are susceptible to failures attributable to flow induced vibration. The NTIW design allows for the inclusion of intermediate supports between baffles that allows the design engineer to “tune” the tubes by increasing their natural frequency to levels above any possible flow condition. Utilizing a NTIW baffle design, several of these operational failure mechanisms can be directly addressed in the design and fabrication stage of a new or replacement feedwater heater. In particular, the NTIW can be designed to have extremely short unsupported spans and excellent vibration characteristics even at the highest predicted loads. The design also incorporates a larger minimum bend radii which minimizes high U-Bend stresses as a result of differential leg expansion. The NTIW design puts the exhaust steam into the steam dome without the wet/dry conditions in the condensing zone area just outside the desuperheating zone. The ability to place intermediate tube supports in the baffle space allows the design engineer to have the flexibility to keep zone pressure drops low, even in high load situations.