1,720,971 research outputs found
Discussing the feasibility of improving fatigue performance of asphalt mixtures by incorporating high recycled asphalt pavement
No full textThe application of Recycled Asphalt Pavement (RAP) is one of the most accepted strategies in pavement communities due to instability in natural sources and environmental issues, however the performance of substitute materials is still the main concern of producers. Structural properties of produced mixtures such as rutting resistance, strength and fatigue life have the main role in the durability of asphalt mixtures which strongly depend on aggregate and bitumen contents. This paper presents a review of recent studies and results on fatigue performance of asphalt mixtures containing different percentages of Recycled Asphalt Pavement (RAP). The aim of this paper is to emphasize the role of RAP in fatigue performance— which is one of the main distresses of bituminous mixtures- of asphalt mixtures and also to highlight benefits and disadvantages (limitation) of using high RAP content in asphalt mixtures. In addition, the possibility of using a high portion of RAP is discussed. Based on literature review, it can be inferred that including RAP could affect the fatigue performance of asphalt mixtures. © 2019 Taylor & Francis Group, London
Improving runway strip performance to fulfill international requirements through eco-efficient soil treatments: Case study of a major italian airport
No full textThe paper presents a case study of a significant intervention conducted on a major Italian airport for improving the structural and functional properties of the runway safety STRIP in order to fulfill specific national and international standards. The STRIP had to accomplish strict requirements in terms of the maximum longitudinal and transversal terrain slope and minimum values of bearing capacity; in particular, soil bearing capacity was identified as the main lack and thus the most urgent action to be carried out in the airport. However, the STRIP itself is located in a very critical area due to its closeness to the runway and several constraints were therefore identified during the design stage. The optimal strategy was identified as the one that minimized the intervention timing and costs, reducing the handling of construction material to/from the airport, avoiding delays to the air traffic, and maximizing the performance of the treated soils in terms of bearing capacity. In this framework, an energy-controlled stabilization technique of in-situ soils was developed. Several measurements, in both laboratory and field environment, were also conducted at different stages: i) before the intervention took place, ii) during the construction stage, and iii) at the conclusion of the work to monitor and validate the expected results. The intervention was able to provide the STRIP areas with a smooth surface presenting terrain slopes and bearing capacity in accordance with the standards. The illustrated methodology could also be applied to other airports saving time, costs, materials, and limiting air traffic delays
Deterioration trends of asphalt pavement friction and roughness from medium-term surveys on major Italian roads
No full textDeterioration models are the key factor for effective Pavement Management Systems, helping out road agencies to assess the actual pavement condition and forecast future performance of the asset. Among pavement condition characteristics, friction should be taken into account due to its important effect on user safety, while roughness could be used to express user comfort. The purpose of this study was to provide a reasonable case study for future improvements of Italian road management, even if the length of the analyzed highways was not intended to be representative of the overall Italian network. This research studied the friction trend (Side Force Coefficient) depending on traffic levels (ESALs) and pavement aging for Italian highways, combining the data with roughness and macrotexture. Surface characteristics were monitored during a seven-year time span. A selection of different road sections with homogeneous traffic levels, similar environmental conditions and surface material was performed and high-speed/high-quality road surveys were used for distress data collection. Pavement deterioration models for Italian road sectors were developed at project level, as starting point to advance pavement management practices in Italy. Degradation curves showed the same trends for similar pavement structures, materials and traffic levels; on the other hand, differences in pavement characteristics, increased ESALs and various maintenance treatments significantly altered those trends
Application of rejuvenators and virgin bitumen to restore physical and rheological properties of RAP binder
No full textBoth chemical and rheological aspects of aged bitumen in reclaimed asphalt pavement ( RAP) material play an important role in the final performance of bituminous mixtures containing recycled asphalt material. This must be especially considered in the case of pavements containing high RAP content. The use of rejuvenators and/or virgin bitumen in recycled mixtures helps improving the properties of aged bitumen. This research study investigates RAP oxidised bitumen and its possible rejuvenation with virgin bitumen and addition of various additives as rejuvenator agents. Tests were conducted to analyse the chemical, rheological and physical behaviours of several binder mixes before and after laboratory ageing processes. Longterm ageing of rejuvenated binder mixes was also investigated to assess the effectiveness of rejuvenation over time. The results showed that the addition of virgin bitumen and rejuvenators could improve the performance of oxidised bitumen and increase its resistance to further ageing
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Probability contour map of landing overrun based on aircraft braking distance computation
No full textRunway excursions have formed the biggest share of runway-related accidents compare to all possible types of airport recorded events worldwide. Out of different possible event scenarios of excursions, runway overrun, which may occur in both landing and take-off phases of flight, is the most frequent one. Therefore many studies have been conducted focusing on determination of the contributing factors which have influence on the probability of runway overrun occurrence. This probability is directly related to the difference between aircraft Landing Distance Required (LDR) and real-time braking distance. In this regard, aircraft braking distance under certain circumstances should be computed. Runway surface condition as a result of previous studies is known to be one of the most contributing factors in runway overrun accidents. Existence of different water-film thicknesses on the pavement decreases the pavement skid resistance which leads to lower friction, for instance; consequently, longer aircraft braking distance is needed and greater risk for aircrafts to overrun is expected. Skid resistance strongly depends on the complex relationship between the aircraft operating conditions and pavement surface properties. Braking distances for a selected set of aircrafts were calculated and plotted in probability distribution format. Based on the probability distribution compared to LDR for the selected set of aircrafts, the landing overrun probability contour map and safety/risk probability distribution is presented
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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