441 research outputs found
Valores del potencial de corrosión y de a resistencia de polarización de armaduras galvanizadas embebidas en hormigón
[ES]Muchas de las estructuras de hormigón armado se muestran exentas de corrosión aun después
de períodos muy prolongados de servicio. Ello es debidq a que en el hormigón el electrolito
está constituido por la fase líquida que rellena sus poros y que es, fundamentalmente,
una disolución saturada de Ca(OH)2, con un pH alrededor de 13. A este elevado pH
y a los potenciales de corrosión, E,corr» ^^^ presentan las armaduras, el acero se encuentra
en la zona de pasividad descrita por Pouorbaix (1), fig. 1, permaneciendo protegido indefinidamente
mientras no cambien las condiciones del medio.
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inmunidad {
I 1 j I I I' I
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1
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-6 1
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-2 0 2 4 6 8 1 0 12 14 16-2 0 2 4 6 8 10 12 14 16
o) pH b) PH
Fig. 1—Condiciones teóricas de corrosión, inmunidad y pasivación.
(a) Del sistema hierro-agua a 25oC.
(b) Del sistema zinc-agua a 25»C en presencia de CO2.
Este cambio en las condiciones de servicio del hormigón capaz de introducir en la zona
de corrosión al acero de las armaduras, se puede producir con relativa frecuencia. Así,
(*) Texto integro del trabajo presentado al simposio de Electroquímica, celebrado en Madrid en octubre de
1978, dentro del Congreso del 75.o Aniversario de la Real Sociedad Española de Física y Química.
(**) C. Andrade. Dra. en Química Industrial. Dpto. de Química del lETCC.
J. A. González. Dr. en Química Industrial. Investigador Científico en el Dpto. de Corrosión y Protección
del CENIM.
71
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la carbonatación del cemento disminuye el pH del hormigón y provoca una corrosión generalizada,
la presencia de iones despasivantes o de fisuras conduce a corrosión localizada
y, ñnalmente, la acción simultánea de tensiones mecánicas y factores agresivos puede
ser la causa de corrosión bajo tensiones.
Así pues, es aconsejable recurrir a una protección suplementaria de los aceros cuando
se prevean situaciones que puedan provocar la corrosión de las armaduras. Entre los varios
métodos de protección que se utilizan se viene ensayando desde hace varios lustros,
con resultados muy contradictorios, la galvanización en caliente de los redondos (2) (3).Peer reviewe
Chocolat noir ou chocolat blanc? Le cacao et la santé cardiovasculaire
Epidemiological data show that a regular dietary intake of plant-derived foods reduces the risk of cardiovascular disease. Recent research indeed demonstrates interesting data about cocoa consumption, with high concentrations of polyphenols, and beneficial effects on blood pressure, insulin resistance and platelet function. Although still debated, a range of potential mechanisms through which cocoa might exert their benefits on cardiovascular health have been suggested: activation of nitric oxide, antioxidant, anti-inflammatory, anti-platelet effects, which might in turn improve endothelial function, lipid levels, blood pressure and insulin resistance. This article reviews available data about the effects of the consumption of cocoa and different types of chocolate on cardiovascular health, and outlines potential mechanisms involved on the basis of recent studies
Generalized Flow and Determinism in Measurement-based Quantum Computation
We extend the notion of quantum information flow defined by Danos and Kashefi
for the one-way model and present a necessary and sufficient condition for the
deterministic computation in this model. The generalized flow also applied in
the extended model with measurements in the X-Y, X-Z and Y-Z planes. We apply
both measurement calculus and the stabiliser formalism to derive our main
theorem which for the first time gives a full characterization of the
deterministic computation in the one-way model. We present several examples to
show how our result improves over the traditional notion of flow, such as
geometries (entanglement graph with input and output) with no flow but having
generalized flow and we discuss how they lead to an optimal implementation of
the unitaries. More importantly one can also obtain a better quantum
computation depth with the generalized flow rather than with flow. We believe
our characterization result is particularly essential for the study of the
algorithms and complexity in the one-way model.Comment: 16 pages, 10 figure
Generalized Flow and Determinism in Measurement-based Quantum Computation
We extend the notion of quantum information flow defined by Danos and Kashefi
for the one-way model and present a necessary and sufficient condition for the
deterministic computation in this model. The generalized flow also applied in
the extended model with measurements in the X-Y, X-Z and Y-Z planes. We apply
both measurement calculus and the stabiliser formalism to derive our main
theorem which for the first time gives a full characterization of the
deterministic computation in the one-way model. We present several examples to
show how our result improves over the traditional notion of flow, such as
geometries (entanglement graph with input and output) with no flow but having
generalized flow and we discuss how they lead to an optimal implementation of
the unitaries. More importantly one can also obtain a better quantum
computation depth with the generalized flow rather than with flow. We believe
our characterization result is particularly essential for the study of the
algorithms and complexity in the one-way model.Comment: 16 pages, 10 figure
Hydrothermal monitoring using embedded sensors of the actual roof system of the prado museum
El Prado Museum in Madrid has been recently submitted to a refurbishment of its roof which from been made with the traditional tiles has been changed to the use of modern waterproofing layers covered with a metallic lead finishing. Due to an unexpected damp patch that produced leaking in the hall in which Las Meninas by Velázquez was exhibited, the authors were commissioned by the Ministry of Education and Culture to study the suitability of the roof and its waterproofing properties. The study led to suggestions of modifications in the design of the roof layers, which are out of the scope of present paper. In present paper are given the behaviour of the sensors embedded in two specific areas of the roof. The sensors installed were of: temperature, relative humidity, measurement of local strain and detection of liquid water. The liquid water sensors reveal that some water is withheld in the layer just below the thermal insulation material, although it is standing. The results of over four years of readings show that the temperature attenuates over distance away from the outermost layer, where the readings are very high in summer, due to it consists of lead. During the colder seasons, in turn, the temperature in the inner layers of the roof is higher than in the outer layers. The strain recorded follows the logical evolution of temperature with no abnormal behaviour being detected. Some of relative humidity sensors had measuring problems due to water condensing on them. In summary however, if the behaviour in this area is extrapolated to the rest of the roof, it can be considered to perform correctly as intended. No more leaking events have been detected from the design modifications were incorporated to the existing roof
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