Le catalyseur quatre voies est destiné à diminuer simultanément les émissions d’hydrocarbures, de monoxyde de carbone, d’oxydes d’azote et de suies par l’intermédiaire d’un seul monolithe ...catalytique. Plusieurs études sur ce type de catalyseur ont montré que la présence d’oxydes d’azote entraîne une diminution de la température d’oxydation des suies. Cependant, l’effet de la présence d’eau sur l’adsorption des oxydes d’azote n’est pas encore clair, surtout en présence de suies. Les travaux présentés dans ce manuscrit ont pour but de mettre en évidence l’influence de la présence d’eau et/ou de suies sur le fonctionnement de catalyseur «piège à NOx». Les résultats obtenus montrent que la présence d’eau entraîne une inhibition de la fonction oxydante du catalyseur, une diminution de la quantité de stockage des oxydes d’azote, et une inhibition de la formation des espèces adsorbées de surface. Ces phénomènes ont été attribués à la voix réactionnelle spécifique en présence d’eau associée à l’adsorption des oxydes d’azote. Les résultats obtenus sur le mélange noir de carbone et catalyseur montrent que la présence de noir de carbone induit une diminution de stockage des oxydes d’azote. De plus, cet effet se trouve plus important en contact fort. Les expériences réalisées sur l’adsorption des oxydes d’azote en présence simultanée de noir de carbone et d’eau ont montré un effet non cumulé de l’eau et du noir de carbone. Ce phénomène a été attribué à une compétition entre l’action de l’eau qui favorise la formation de nitrate de cœur à partir des nitrates faiblement liés et l’action du noir de carbone qui tend à déstabiliser les nitrates faiblement liés pour former les carbonates.
The four ways catalyst is used to decrease the emissions of hydrocarbon, carbon monoxide, nitrogen oxides and soot by a monolithic catalyst. Several researches on this type of catalyst have shown that the presence of nitrogen oxides involves a decrease of the soot oxidation temperature. However, the effect of the presence of water on the nitrogen oxides adsorption is not clear yet, especially with the presence of soot. The works presented in this manuscript are intended to study the influence of the presence of water or/and soot on the performance of the catalyst NOx trap. The results showed that the presence of water involves an inhibition of the oxidation function of catalyst, a decrease of the capacity of the NOx storage, and an inhibition of the formation of the surface adsorbed species. It is attributed to a special reactive way in the presence of water linked to the adsorption of nitrogen oxides. The results obtained on the mix of carbon black and catalyst showed that the presence of carbon black induce a decrease of the NOx storage capacity of catalyst. Besides, this effect was more important with a tight contact between carbon black and catalyst. The experiments realized on the adsorption of nitrogen oxides with the presence of carbon black and water simultaneously showed an effect not accumulated of the water and the carbon black. This phenomenon is attributed to a competition between the action of water which favors the formation of the bulk nitrate from the weak-linked nitrates and the action of carbon black which tend to destabilize the weak-linked nitrates to form the carbonates.
In an attempt to evaluate the influence of water on the mechanical properties of composite resin, the transverse strengths of 15 commercially available composites were determined in water at 37°C and ...compared with the strength measured in air after storage in water for periods of 1 day to 3 months. Some of the composites, including two which contained a blend filler, showed remarkable reduction of transverse strength when measured in air, according to the procedures specified in ISO 4049, in comparison with transverse strength measured in water. The change of water content in the material can predominantly affect the mechanical behavior of composite resin.
Chapter III - Fracturing Fluids
Water-Based Chemicals and Technology For Drilling, Completion, and Workover Fluids,
2015
Book Chapter
This chapter deals with general issues of fracturing fluids. The desirable functions of fracturing fluids are reviewed. In particular, the advantages of water-based fracturing fluids are explained. ...Further, the special chemicals used for water-based fracturing fluids are explained and summarized. Special compositions are reviewed.
An investigation has been carried out concerning the effects of water absorption on the mechanical properties and fatigue strength of two types of unidirectionally reinforced carbon/epoxy composites, ...i. e., 130°C cure-type composite T-1/347 and 180°C cure-type MM-1/982 X. T-1/347 composites absorb more water than MM-1/982X composites. After long immersion of about seven months, however, MM-1/982X composites absorb water rapidly, and the fatigue strength is considerably decrease. In the case of wet specimens of T-/347 composites preconditioned in water for two months, high amount of water absorption degrades the matrix and decreases the strength of the fiber/matrix interface, thereby decreasing the mechanical properties. For MM-1/982X composites, small amount of water absorption moderately decreases the interfacial strength and increases the ductility of the matrix, thereby increasing the mechanical properties. However, fatigue life of wet specimens of both T-1/347 and MM-1/982X composites is decreased in water, but the one of dry specimens proconditioned in laboratory air is increased in water. In these tests, the synthesized evaluation of acoustic emission (AE) signals using several AE parameters and AE signal location have been done, and the fracture mechanisms are discussed in terms of the observations of internal damages by a scanning acoustic microscope (SAM) and of fracture surfaces by a scanning electron microscope (SEM).
Kao cilj istraživanja na terenu postavljena je determinacija anomalnih stanja u vodi Parka prirode Vransko jezero koja bi mogla biti posljedica pritisaka na okoliš. Očekuje se da pritisci na kakvoću ...vode Vranskog jezera dolaze od poljoprivrede u slivnom području, ali i utjecajem mora i klime. Metode uključuju analizu dinamike temperatura i oborina i dinamika razine morske i jezerske vode za razdoblje promatranja od siječnja 2000. do prosinca 2009. Dinamika razina mora i jezerske vode praćena je na vodokazima postavljenim na dvije lokacije. Uzorkovanje vode provedeno je na dvije mjerne točke u sklopu državnog praćenja stanja voda. Usporedbom dinamike razine vode u jezeru i razine mora s dinamikom koncentracije iona kalcija, magnezija, klora, te sulfatnog iona, vidljivo je da odnos razine vode u jezeru i razine mora ima direktan i snažan utjecaj na kemizam jezerske vode. Lužnatost i njena visoka električna vodljivost posljedica su miješanja s morskom vodom. Činjenica da se promjenom odnosa razine jezerske vode i razine mora mijenja i koncentracija soli u jezeru pokazuje da je morska voda izvor soli u jezeru. Prodor morske vode u jezero korespondira s dugotrajnošću i izraženošću sušnih razdoblja. Podatci o tvrdoći jezerske vode na Prosiki prate isti trend kao i podatci o ionima i električnoj vodljivosti. Činjenica da se promjenom odnosa razine jezerske vode i razine mora mijenja i koncentracija soli u jezeru pokazuje da je morska voda izvor soli u jezeru.
An investigation has been carried out concerning the effect of water absorption on the mechanical properties and fatigue strength of ±45° angle-ply carbon/epoxy composites, i.e., 130°C cure-type ...composites T-1/347, and 180°C cure-type MM-1/982X. In both composites, water absorption lowers the strength of the interface, resulting in a decrease in the tensile strength, an elongation at the break, and besides, fatigue strength. In a higher stress region in laboratory air, cyclic loads make the temperature of a T-1/347 composite so high that plastic deformation of the matrix is enhanced and the fatigue life is shortened. In water, however, cooling effects by water circulation around specimens become predominant, so that the fatigue life increases in a higher stress region. We also pointed out the usefulness of a scanning acoustic microscope to examine the internal damage of the composites.
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