1,721,229 research outputs found
The effect of Selenice Natural Bitumen on un-modified and polymer-modified bitumen rheological properties
No full textSelenice Natural Bitumen (SNB) is a natural bitumen with specific properties, which make it a valuable additive in asphalt mixtures in order to reduce the dosage of virgin bitumen, thus reducing the environmental footprint. The current state of the art validated its use in unmodified bituminous blends, highlighting the positive influence as an ageing inhibitor only at low dosages (≤ 10 %). In order to consider higher dosages of SNB in asphalt pavement materials, the objective of this study is to investigate the rheological properties of bituminous blends composed of SBS polymer-modified bitumen and SNB. The experimental program evaluated the addition of SNB in different dosages in an un-modified bitumen and an SBS polymer-modified bitumen. The analysis involved empirical and rheological properties at different ageing conditions. The main rheological characterization consisted in complex modulus tests, Multiple Stress-Creep Recovery (MSCR) tests and Linear Amplitude Sweep (LAS) tests. Overall, the results related to un-modified bituminous blends are consistent with findings reported in previous studies, confirming that a maximum SNB content of 10 % by weight is recommended to limit performance loss. Conversely, the experimental data did not support the feasibility of increasing the SNB dosage beyond 10 % when using SBS polymer-modified bitumen. The presence of SBS polymers in the modified blends did not mitigate the fatigue performance loss associated with SNB use. Therefore, the use of SNB at dosages exceeding 10 % by weight of the total bituminous blend is not ecommended, regardless of whether unmodified or SBS-modified bitumen is employed
A modular converter for converting the electric power produced by aerogenerators, and a wind-power plant that uses said converter
No full textA novel modular converter for high power aerogenerator
The Influence of Bitumen Nature and Production Conditions on the Mechanical and Chemical Properties of Asphalt Mixtures Containing Reclaimed Asphalt Pavement
No full text: Several variables influence the performance of hot asphalt mixtures including reclaimed asphalt pavement (RAP). Among these, the virgin bitumen's origin, the mix production temperature and the time the mix is kept at a high temperature between mixing and compaction play a fundamental role but are often neglected. This study aimed to quantify the negative effects associated with the improper choice of these variables. Therefore, their influence on the mechanical (indirect tensile stiffness modulus and strength, Cracking Tolerance Index) and chemical (Fourier Transform Infra-Red spectroscopy) characteristics of asphalt mixtures containing 50% RA were investigated. In particular, two rejuvenators, two types of virgin bitumen (visbreaker and straight-run), two production temperatures (140 °C and 170 °C) and three conditioning times in the oven (30 min, 90 min and 180 min) were analyzed. The results showed interesting findings that allow us to recommend selecting the virgin bitumen type carefully and to avoid excessively stressing the binder during the production of the mix
Convertitore modulare della potenza elettrica prodotta da generatori eolici e centrale eolica impiegante lo stesso
No full textDepositato il 30/04/200
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
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