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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
Distribuzioni statistiche delle proprietà meccaniche di elementi strutturali in acciaio
No full textAssessing light non-aqueous phase liquids in the subsurface using the soil gas Rn deficit technique: a literature overview of field studies
Full text link(222)Radon (Rn) was proposed in the late 1990s as a naturally occurring tracer for light non-aqueous phase liquids (LNAPLs) in the subsurface, due to its preferential partitioning behavior in the non-aqueous phase, resulting in a reduction in Rn activities in areas with LNAPLs in the subsurface compared to unimpacted areas (Rn deficit). The Rn deficit technique emerged as a cost-effective, non-invasive, and sustainable method to rapidly identify and quantify LNAPLs, for the characterization and monitoring of contaminated sites. This paper presents an overview of the technique and its field applications, with a specific focus on the use of the method in the vadose zone based on soil gas Rn measurements. Although various configurations have shown favorable outcomes, limitations persist in the application of the soil gas Rn deficit technique. Deep LNAPL contamination, soil matrix heterogeneity, and temporal variations in Rn emissions pose challenges to quantitative evaluations of LNAPL contamination. Recognizing these factors is crucial for site-specific assessments. This review aims to highlight both the strengths and limitations of the method, providing insights into potential areas for future research while acknowledging the positive outcomes achieved in different configurations over the past decades
Examining the applicability of the soil gas radon deficit tecnique for quantifying residual LNAPL contamination
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Modeling of soil gas radon as an in situ partitioning tracer for quantifying LNAPL contamination
No full textIn the last decades radon (Rn) has been widely proposed as a naturally occurring tracer for non-aqueous phase liquids (NAPL) in the soil. This work examines the feasibility of using soil gas data collected at some distance from the source zone for the application of the Rn deficit technique for the identification and quantification of NAPL contamination. To this end, we used a steady-state 1-D analytical solution that is based on a 3-layer model that allows to simulate the transport and distribution of Rn in the source zone, capillary fringe and overlying unsaturated soil. The analytical solution was first validated against a more detailed numerical model available in the literature. Then, a series of simulations were carried out to evaluate the vertical concentration profiles of Rn in soil gas above the source zone and in background location not impacted by NAPL. Simulation results showed that the parameters that most influence the migration and distribution of Rn in the subsurface are the distance of the soil gas probe from the source zone and, to a lower extent, the type of contamination (e.g. diesel or gasoline) and the soil type. On the basis of these results, we developed some easy-to-use nomographs to estimate the residual NAPL phase based on the observed radon deficit in soil gas and on the probe to source distance and soil and NAPL characteristics. According to the obtained results, the radon deficit technique results a feasible method for a qualitative identification of residual NAPL when radon in soil gas is measured at distances lower than 2 m from the contaminated zone. However, for an accurate quantitative estimation of the NAPL phase content, soil gas probes should be preferably located at distances lower than 1 m from the source zone
Examining the applicability of the soil gas radon deficit technique for quantifying residual LNAPL contamination
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