1,720,982 research outputs found
Performance and emissions of biodiesel in a boiler for residential heating
No full textThis paper presents the initial results of an experimental investigation of regulated and unregulated emissions of a boiler fueled with biodiesel and heating oil. In particular CO, SO2, NOx, particulate matter (PM), Polycyclic Aromatic Hydrocarbons (PAH), Volatile Organic Compounds (VOC) and aldehydes emissions were examined. When using biodiesel, a strong reduction in CO and PM emissions was recorded with respect to home heating oil. The PAHs contained in the PM in the case of biodiesel were nearly 13 times less toxic than in the oil case; the formaldehyde, on the contrary, is nearly double for biodiesel. The VOCs were very low for both fuels. The results indicate there may be benefits to using biodiesel in home heating or in industrial processes
Development of geosynthetic interface strength in landfill capping under seismic conditions.
No full textThe aim of this research is to carry out an analysis of the mobilisation of interface strength, in the geosynthetic liner system of a landfill capping, during seismic activity, since geosynthetics, widely-used for waterproofing, drainage and reinforcement, affect stability. Contact surfaces between geosynthetics and between geosynthetic and soil may become potential surfaces of slippage due to low available friction. The problem has been examined by means of a numerical Flac 2D model which, according to some simplifying hypotheses, could highlight the evolution of interface strength in the dynamic field. The analyses have shown that the seismic displacements may be large enough to mobilize dynamic friction at the level of the geosynthetic interface and thus that a dynamic characterisation of the interfaces is required in order to accurately predict stress in the liner and displacement of the capping
Geosynthetic Interface Friction at Low Normal Stress: Two Approaches with Increasing Shear Loading
Full text linkThe evaluation of geosynthetic interface friction is a key parameter for the stability of coupled geosynthetics, as in landfill capping liner. At the present time, few types of tests are suitable for measuring the interface friction at low normal stress: one of these is the inclined plane, usually carried out under a vertical stress of 5 kPa. This type of test is not without critical aspects, mainly due to the nonuniform normal stress state induced by the inclination of the plane, but, on the other hand, the most widespread direct shear test generally cannot be performed at such low values of normal stress. After a short discussion on the pros and cons of these two types of test, the paper presents a comparison of the interface friction angles obtained, for three interfaces, by means of an inclined plane and an unconventional direct shear apparatus, under the same low normal stress. The peculiarity of this latter device is of ensuring a gradual increase of the mobilized strength, in a way similar to what occurs during the inclined plane test. The good correspondence of the results of the two types of tests confirmed the validity of both the test approaches
The characterisation of geosynthetic interface friction by means of the inclined plane test.
No full textThe paper focuses on the evaluation of the shear strength in conditions of low normal stress of various
geosynthetic-geosynthetic interfaces, which are typical of landfill cover systems, by means of the inclined plane
test, with the aim of studying the friction mobilisation in relation to various kinematic behaviours. The results of
three different methods to evaluate the angle of friction were analysed, together with the sensitivity of the interfaces
in relation to the wear effect and the influence of the state of hydration. The results showed very
different responses of the interfaces to the shear stress, which involved three main types of sliding mechanisms,
referred to as sudden, gradual and uneven sliding. Another outcome observed was that the shear strength of
geosynthetic-geosynthetic interfaces cannot always be properly characterised following the procedure proposed
by the European standard for soil-geosynthetic interfaces (EN ISO 12957–2), since the actual mobilised kinematic
behaviour should be taken into consideration. In this regard, the paper provides some hints on the choice of the
more representative parameter of friction for each type of sliding. A particular focus was given to the case of
gradual sliding interfaces, for which the static friction is difficult to detect due to the very slow movements; for
practical purposes, the design friction of these interfaces should be evaluated by using an adequate safety factor
with respect to the friction evaluated at 1 mm of displacement
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Numerical analysis of stacked geo-tubes
No full textGeo-tubes and geo-containers are being increasingly used as marine structures for coastal protection and harbor construction. They represent an alternative solution compared to the traditional methods such as rock embankment and/or concrete units, with a significant reduction in cost and time. The tensile stress of stacked geo-tubes in immersed condition has been explored in this paper through numeri-cal modeling, considering that the main drawback for this kind of structures is the lack of definite design criteria. With the aim of increasing the knowledge of the shape of the tubes and of the tensile stress in the geotextiles after filling and load-ing, the analyses showed how these parameters may be influenced by many fac-tors, as the mutual distance of the geo-tubes, the interface friction and the level of filling of the geo-tubes
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