Academic literature on the topic 'Etats compressés'

Carbon dioxide, as well as ammonia, are widely used in large-scale chemistry for the production of urea. Currently, the most common technology for producing carmabide is according to which liquid NH3 is pumped into the synthesis column by a pump at a pressure of 15 MPa, and gaseous CO2 is supplied by a compressor with the same pressure as ammonia. Gaseous CO2 is compressed in a multi-stage compressor to a pressure of 15 MPa before it enters the urea synthesis unit, in which it reacts with ammonia. The specific energy consumption for compressing carbon dioxide in a compressor unit is 0.13 kWh/kg. Reducing energy for producing CO2 and also urea can be achieved when it is possible to supply carbon dioxide in liquid form under a pressure of 15 MPa to the urea synthesis column. The analysis showed that to solve this problem it is necessary to implement two processes: compression to 1.8–3.0 MPa, and then cooling and liquefaction of gaseous CO2 due to the cold of liquid ammonia. Liquefied CO2 can then be pumped to the urea column. In order to introduce carbamide into production, a new carbon dioxide compressor and pumping unit has been created. The installation scheme for compressing CO2 to a pressure of 15 MPa and its subsequent supply to the production of urea is given. A cold liquid ammonia stream with an initial temperature of –30 °C is used as a source of cold in the installation. The performance and power consumption of the compressor unit depend on the compression pressure of CO2. After the CO2 is compressed to 1.8 MPa, it is possible to cool 2.3 t/h of carbon dioxide with cold liquid ammonia and then direct it to the synthesis of urea using a pump under a pressure of 15 MPa. The specific energy consumption in the installation will be 0.1 kWh/kg. When CO2 is compressed up to 3 MPa, the plant capacity is 8.78 t/h, and the unit costs are 0,108 kWh/kg. Urea production in this case may increase from 1400 to 1680 t/day. Ref. 5, Fig. 3, Tab. 3.

Electrolysis of water uses more energy to produce «green» hydrogen than can be obtained by using it. On 1 m3 of electrolytic hydrogen consumes from 4 to 5 kW·h of electricity, while it contains chemical energy of 3.0 kW·h. The calorific value of hydrogen is 3.3 times less than methane. Hydrogen dissolves in metals, causing their corrosion. Its transportation requires special materials for pipelines, as well as special design, compressors and control devices. Owing to wide borders of explosiveness, high speed of torch spreading its use is connected with risks and demands special safety measures. The use of hydrogen as a fuel for driving shunting capacities in the energy system of Ukraine or for substitution of liquid motor fuels requires for its production the amount of energy commensurate with the volume of its total consumption in Ukraine, significant amounts of water and solution of the problem of using surplus oxygen. Taking into account the cost of electricity from renewable energy sources in Ukraine, the economy of hydrogen production and its use is beyond reasonable limits. Transportation of hydrogen in compressed or liquefied state is energy and economically expensive. Mixtures of natural gas and hydrogen are allowed to be transported and used. The driver of hydrogen energy is the prevention of anthropogenic impacts on climate change, which in itself is problematic. The large number of projects on the hydrogen economy that have been introduced today in Europe and around the world can be explained by the significant funds allocated to the problem, in which major companies and scientists — hydrogen activists are interested. Bibl.16, Table 1.

Technological aspects of energy use of solid waste and their constituents and possibility of applying certain technologies in Ukraine are analyzed. Global trends in waste management technologies are identified. When organizing waste sorting, half of their energy potential can be used, which is estimated to be 1.5 billion m3 of natural gas equivalent in Ukraine. Share of food waste is close to 40 %. It is advisable to recycle them in biogas and biomethane mixtures with agricultural waste and energy plants. Biomethane production can be increased in several times. Electricity and heat production from biogas require government assistance in form of special tariffs. Biomethane is being used alongside natural gas in compressed and liquefied state as a motor fuel. Biogas complexes are used as balancing power of grids. The most common technology for utilizing the energy potential of municipal solid waste is incineration. Emissions systems for waste incineration plants have reached a level of perfection that allows them to be placed close to residential areas. Ref. 15, Fig. 6, Tab. 2.

Along with the growth of natural gas consumption in the world, small-scale production of liquefied natural gas (LNG) is developing at a faster pace. It opens up the possibility of LNG obtaining and transporting as a commodity product at remote from gas networks fields or wells, and also at low-production wells and alternative sources of methane-containing gas. The development of modern technologies for natural gas liquefaction has been studied and the liquefaction cycles used in the low-tonnage scale have been classified. In Ukraine, rather large reserves of natural gas are found in small as well as depleted fields, so the problem of energy efficient technologies for liquefaction and transportation of their hydrocarbon resources creating is of particular relevance. For the development of such low-resource fields, liquefaction units operating on the compression-throttle cycle are most suitable. Energy efficient technological schemes of natural gas liquefaction plants have been developed: in the high-pressure throttle-ejector cycle with pre-cooling using a propane refrigerating machine and in the middle-pressure throttle cycle with ethane refrigeration cycle and the recovery of part of the liquefied gas. Optimum parameters of the refrigeration cycle and the whole plant are obtained from the point of view of minimizing the specific energy costs. The advantages of the proposed throttle schemes are simplicity, reliability, that are results from the use of standard compressor and refrigeration equipment, and energy efficiency of 0.5 kWh/kg LNG, which is sufficiently high for low-tonnage LNG production. Ref. 20, Fig. 6, Tab.1.

One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.

Background The negative-pressure test using a self-inflating bulb (SIB) during emergency intubation was studied to determine its reliability and predictive value in this setting. Methods The endotracheal tube (ETT) position was tested in 300 consecutive patients undergoing in-hospital emergency endotracheal intubation. Immediately after intubation and before ETT cuff inflation, the following protocol was strictly followed: (1) an SIB was compressed, connected to the ETT, and released. A 10-s period was allowed for the bulb to inflate. (2) The ETT cuff was inflated, and the ETT position was confirmed using colorimetric or infrared carbon dioxide detection, or both, combined with clinical evaluation. Results There were 19 esophageal intubations (6% incidence). The SIB correctly identified all patients with esophageal intubation (sensitivity, 100%) and correctly identified all but three ETTs placed in the trachea (specificity, 99%). The three tracheally placed tubes that were misidentified by the bulb syringe occurred during one case each of chronic obstructive pulmonary disease, copious secretions, and obesity; of note were three tracheally placed tubes that were misidentified by the carbon dioxide analyzers during cardiopulmonary resuscitation. Conclusions The SIB proved to be a sensitive and specific test for esophageal intubation in the emergency setting when used according to the protocol described, and it is complementary to carbon dioxide detection. The predictive value of the bulb syringe appears to be improved when a prolonged period for reinflation is allowed. It holds particular promise because of its low cost and portability.

O crescimento da demanda por água potável tem implicado em um aumento da quantidade de resíduos nas estações de tratamento de água (ETA). Apesar destes terem sido gerados por processo erosivo do solo nos mananciais que antecedem as ETAs, o tratamento químico requerido para a sua remoção obriga a uma disposição correta para não impactar, negativamente, o meio ambiente. Até agora, o destino mais comum para o lodo de ETA são os cursos d'água, mesmo ele sendo considerado um resíduo sólido. Neste trabalho, é proposta alternativa de co-disposição deste resíduo, ainda úmido, em matrizes de concreto, substituindo-se parcialmente seus insumos: os agregados miúdos e o cimento, cuja extração e emprego também causam impacto ambiental. Inicialmente, caracterizaram-se os insumos do concreto (cimento Portland CPII-F 32, areia e brita), além do lodo extraído da ETA Passaúna, localizada na região metropolitana de Curitiba. Para os estudos de dosagem, utilizou-se um concreto-referência (sem adição de lodo) e traços de concreto com teores de 3, 5, 7 e 10% de lodo em relação ao peso de areia e em substituição à mesma. Nos concretos resultantes foram avaliadas propriedades tanto no estado fresco quanto no endurecido. O lodo é constituído, praticamente, de compostos de Si, Al e Fe, e do argilomineral do grupo caulinita, tendo teor de umidade em torno de 87%. Nos ensaios de resistência à compressão, as dosagens até 5% apresentaram um f c28 maior que 25 MPa. Para as dosagens com teores de lodo superiores a 5%, o f c28 foi menor, principalmente, para a dosagem de 10%. A análise dos dados permite concluir que os traços com até 5% de lodo podem ser aplicados em situações que vão desde a fabricação de artefatos e blocos até a construção de pavimentos em concreto de cimento Portland. Em relação às misturas com teores acima de 5%, a sua utilização é restrita a aplicações em que a trabalhabilidade não é um parâmetro primordial, como contrapisos, calçadas e pavimentos residenciais.

Cette thèse s'intéresse à la génération d'états atomiques compressés par la mesure. La mesure considérée est de type quantique non-destructive, et profite de la surtension d'un résonateur optique de grande finesse. L'interférométrie atomique a démontré des performances inégalées pour la mesure de rotations, d'accélérations et du temps. Mais la sensibilité de ces appareils est aujourd'hui limitée par le bruit de grenaille, qui ne pourra être dépassé que par l'utilisation d'états non-classiques. Dans ce contexte, nous avons développé un appareil contenant une cavité optique de haute-finesse résonante à 1560 nm et à 780 nm. La lumière laser à 1560 nm qui est injectée dans la cavité génère un piège dipolaire où des atomes de Rb 87 sont chargés à partir d'un piège magnéto-optique. Le temps de vie de ces atomes dans le piège dipolaire est limité par les collisions avec le gaz résiduel, ce qui donne bon espoir pour l'implémentation d'une évaporation. Les concepts de mesure QND sont ensuite mis en place et un formalisme de fonction d'onde décrivant la dynamique de compression d'états est discuté et appliqué à des situations concrètes. Expérimentalement, cette mesure non-destructive réalisée à 780 nm a été implémentée grâce à une technique de modulation de fréquence particulièrement insensible aux bruits classiques. L'influence de cette sonde sur le système a été quantifiée en simple passage et cet outil a permis de suivre en temps réel l'état d'un interféromètre atomique. En outre, nous avons réalisé un laser Raman de faible largeur de raie. Ce laser qui utilise les atomes froids comme milieu à gain serait particulièrement adapté pour réaliser des mesures spectroscopiques de précision
This thesis investigates the generation of atomic spin-squeezed states by quantum non-demolition (QND) measurements in a high-finesse optical cavity. Cold atom interferometry has demonstrated state of the art performance for the measurement of tiny rotations, accelerations and time. The sensitivity of atom interferometers has already reached the atomic shot noise level, a limit that could be overcome by the use of non-classical atomic states. In this context, we developed a crossed high-finesse cavity resonating both at 1560 nm and 780 nm. Laser light at 1560 nm injected in the cavity generates a far off resonance optical dipole trap where Rb 87 cold atoms are loaded from a magneto-optical trap. The lifetime of the atoms in this dipole trap is limited by the residual background collisions, indicating that further evaporation process should be effective. The concepts of QND measurement are introduced and a wavefunction formalism that describes the spin-squeezing dynamics of the atomic state is discussed. This formalism is applied to practical measurement apparatus that are the Mach-Zehnder interferometer and the heterodyne detection. Experimentally, this non-destructive measurement was implemented at 780 nm in a frequency modulation scheme strongly immune to noise. The influence of this non-demolition probe on the atomic sample has been characterized in single pass and this tool has been applied to follow in real time the state of atomic interferometers. In addition to this work, a narrow linewidth Raman laser suitable for high precision spectroscopy was implemented with cold atoms as the gain medium

Cette thèse s'intéresse à la génération d'états atomiques compressés par la mesure. La mesure considérée est de type quantique non-destructive, et profite de la surtension d'un résonateur optique de grande finesse. L'interférométrie atomique a démontré des performances inégalées pour la mesure de rotations, d'accélérations et du temps. Mais la sensibilité de ces appareils est aujourd'hui limitée par le bruit de grenaille, qui ne pourra être dépassé que par l'utilisation d'états non-classiques. Dans ce contexte, nous avons développé un appareil contenant une cavité optique de haute-finesse résonante à 1560 nm et à 780 nm. La lumière laser à 1560 nm qui est injectée dans la cavité génère un piège dipolaire où des atomes de Rb 87 sont chargés à partir d'un piège magnéto-optique. Le temps de vie de ces atomes dans le piège dipolaire est limité par les collisions avec le gaz résiduel, ce qui donne bon espoir pour l'implémentation d'une évaporation. Les concepts de mesure QND sont ensuite mis en place et un formalisme de fonction d'onde décrivant la dynamique de compression d'états est discuté et appliqué à des situations concrètes. Expérimentalement, cette mesure non-destructive réalisée à 780 nm a été implémentée grâce à une technique de modulation de fréquence particulièrement insensible aux bruits classiques. L'influence de cette sonde sur le système a été quantifiée en simple passage et cet outil a permis de suivre en temps réel l'état d'un interféromètre atomique. En outre, nous avons réalisé un laser Raman de faible largeur de raie. Ce laser qui utilise les atomes froids comme milieu à gain serait particulièrement adapté pour réaliser des mesures spectroscopiques de précision.

Resultats d'etude de la conduction electrique de liquides non polaires tres purs (cyclohexane, n-propane) en geometrie pointe-plan, en fonction du rayon de courbure de la pointe et de la pression hydrostatique (p<->10**(7)pa)