Search results for "CRAC"
showing 10 items of 1418 documents
Cracking Activity and Hydrothermal Stability of MCM-41 and Its Comparison with Amorphous Silica-Alumina and a USY Zeolite
1996
It has been found that the cracking activity of MCM-41 for a reaction catalyzed by strong acids site, such asn-heptane cracking, is much lower than that of a USY zeolite, and similar to that of amorphous silica-alumina. The higher activity of USY is due to the presence of stronger Bronsted acid sites in the zeolite. In the case of gas oil cracking, the greater accessibility of the large molecules to acid sites in MCM-41 relative to USY makes the difference in activity between these two catalysts much smaller than for the pure hydrocarbon. In the calcined state MCM-41 is more active and gives more gasoline and less gases and coke than amorphous silica-alumina. However, when the catalysts wer…
Mechanical Behavior of Concrete Columns Confined by Laterally Pre-Tensioned FRP
2011
This paper presents the results of an experimental investigation of concrete columns confined by a wound pre-tensioned carbon filament yarn. Yarn winding equipment was developed in the Institute of Polymer Mechanics with the ability to set the desired pre-tension force and thereby producing confined concrete specimens with different initial lateral pressure. It is shown that initial lateral pressure increases the axial stress at which intense internal cracking of the concrete develops.
Influence of the process variables on the product distribution and catalyst decay during cracking of paraffins
1986
Abstract The influence of the partial pressure of the hydrocarbon, reaction temperature, time on stream and the presence of olefins on the product distribution and the kinetics and decay during the cracking of n-heptane on an REHY zeolite were studied. It was found that the isomerization to cracking ratio depends on the hydrocarbon partial pressure. The active sites for cracking and isomerization are not the same and those for cracking decay faster, the selectivity changing with the degree of decay of the zeolite. The protolytic to β-cracking ratio, and therefore the paraffin to olefin ratio, are a function of the partial pressure of n-heptane. Both reactants and products have a marked infl…
Performance-based characterization of recycled polymer modified asphalt mixture
2021
Due to the introduction of secondary materials, the asphalt mixtures to be designed and tested in our laboratories are constantly becoming much more complex than traditional asphalt mixtures making difficult to use conventional laboratory procedure and/or predict expected results. This study proposes a comprehensive characterization of asphalt mixture modified with recycled polymer compound by using both wet and dry process proposing adjustments to laboratory mixing and sample compaction procedure. Accordingly, three AC20 Hot Asphalt Mixture (HMA) were designed and their conventional and performance related properties were assessed by looking at a) Indirect Tensile test (ITS) a) moisture da…
The influence of branching isomerization on the product distribution obtained during cracking of n-heptane on acidic zeolites
1985
Abstract The initial selectivities for the primary products occurring during the cracking of n-heptane on a rare-earth (RE)-HY ultrastable zeolite up to 470°C have been calculated. The activation energies for the cracking of n-heptane and its branched isomers in the fraction C4 + C3 have been obtained by molecular orbital calculations, and these values and the predicted product distribution have been compared with those obtained experimentally. It is concluded that the cracking of n-heptane on large-pore zeolites may take place by different parallel routes involving protolytic and β-cracking of n-heptane and β-cracking of the readily formed branched carbenium ions. The relative importance o…
Steel Fibres: Effective Way to Prevent Failure of the Concrete Bonded with FRP Sheets
2016
Although the efficiency of steel fibres for improving mechanical properties (cracking resistance and failure toughness) of the concrete has been broadly discussed in the literature, the number of studies dedicated to the fibre effect on structural behaviour of the externally bonded elements is limited. This experimental study investigates the influence of steel fibres on the failure character of concrete elements strengthened with external carbon fibre reinforced polymer sheets. The elements were subjected to different loading conditions. The test data of four ties and eight beams are presented. Different materials were used for the internal bar reinforcement: in addition to the conventiona…
La investigación crítica de las representaciones sociales de la ciencia: nanotecnologías, democratización del conocimiento científico y par
2013
El planteamiento del capítulo señala la importancia y centralidad de la investigación social de la cara oculta de la ciencia, de sus aplicaciones técnicas y de los procesos de participación ciudadana en la decisión sobre sus usos sociales. También que dicha reflexión es clave para entender el papel que los usos sociales de la ciencia pueden estar jugando para incrementar, no ya en el bienestar individual y colectivo, sino en las desigualdades sociales, económicas y ecológicas que comporta la actual globalización neoliberal. En términos de participación ciudadana, la tesis de fondo sostiene que en el actual sistema capitalista no se puede habla de sociedades democráticas, con rigor científic…
State, orders, and social distinction
2012
This essay seeks to compare different forms of the social distinction in Italy in the late Middle Ages, looking in particular at the specification of the hierarchical mechanisms and of the languages of aristocratic legitimation. In this perspective the framework of a ‘orders society’, whose issues are in part different from those of the previous centuries, correspond to the formation of the territorial states, as they emerge from the crisis of the communal cities and from the end of the unity of the “Regnum Siciliae”. The aim is to describe and analyse some of these forms in order to underscore both the common characters (beginning from those that can justify a ‘framework’, as the circulati…
Engaging Citizens in the Decision-Making Process
2019
The rapid development of internet and technologies in the 21th century is providing an opportunity for the development of digital democracy – citizen engagement in the decision-making process in an easier, faster and more contemporary way. The paper analysis Latvian public administration’s attitude to the development of digital democracy in Latvia, looking into digital engagement as a possible solution that could foster the low rates of civic and political participation in Latvia. Research methods of the paper consists of an analysis of academic publications on digital democracy and political engagement, and survey to the representatives of the public administration in Latvia. Conclusions o…