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Simultaneous Measurements of Sound Attenuation and Backscatter for the Evaluation of Suspended Sediment Concentration
No full textThe use of acoustic techniques has become more and more common for estimating suspended sediment in water environments. An emitted beam propagates into water producing backscatter and attenuation, which depend on scattering particles concentration and size distribution. Unfortunately, the actual particles size distribution (PSD) may largely affect the accuracy of concentration quantification through the unknown coefficients of backscattering strength, ks2, and normalized attenuation, ζs. This issue was partially solved by applying the multi-frequency approach. Despite this possibility, a relevant scientific and practical question remains regarding the possibility of using acoustic methods to investigate poorly sorted sediment in the spectrum ranging from clay to fine sand. The aim of this study is to investigate the possibility of combining the measurement of sound attenuation and backscatter to determine ζs for the suspended particles and the corresponding concentration. The proposed method is moderately dependent from actual PSD, thus relaxing the need of frequent calibrations to account for changes in ks2 and ζs coefficients. Laboratory tests were conducted under controlled conditions to validate this measurement technique. With respect to existing approaches, the developed method more accurately estimates the concentration of suspended particles ranging from clay to fine sand and, at the same time, gives an indication on their actual PSD
Numerical simulations of 12-years evolution of the Po River morphodynamics
No full textMorphological variations of alluvial river beds, driven by the hydrological variability, are relatively slow if compared
with the hydraulic changes. Therefore, to evaluate the feedback of changing morphodynamics on hydraulic
infrastructures located along a watercourse, like bridge piers, it is necessary to perform long-term simulations,
combing CFD runs with field data and remote observations that can be used to calibrate the code. Moreover, given
the necessity to interact with water managers and final users, numerical models should also be integrated with GIS
environments, simplifying the interpretation of the modelling outcomes.
Within the Italian project INFRASAFE (infrasafe-project.com), the 12-years evolution of a 10-km reach of the Po
River close to Ostiglia, in Italy, is simulated by means of the numerical suite iRIC (i-ric.org) and its 2D solver
MFlow-02. The geometrical input refers to the 2005 bathymetry acquired with am multibeam having a resolution
of two meters, while the hydrological boundary conditions are the 2005-2016 monthly discharges and levels at
the upstream and downstream ends, respectively. To simulate the sediment transport, equilibrium conditions are
considered and the grainsize composition concerns samples taken along the reach in the past years. The overall
domain consists of a grid with triangular meshes having a maximum area of 3000 m2, while nested grids are
adopted in the middle part to better characterize the evolution of the reach between two bridges (1000 m2 and 250
m2) and close to three piers of the downstream bridge (50 m2) that deeply affect the local morphodynamics with
scour phenomena. Thanks to the model structure, the numerical results can be easily exported to be integrated in a
GIS environment, combining them with field observations and satellite maps, eventually improving the readability
for non-experts.
Preliminary simulations show a good agreement between the numerical outcomes and the field data on velocity and
erosion/deposition processes acquired during a campaign performed in October 2017. From such results, one can
observe that the Po riverbed morphology is principally driven by high flow conditions at the short-term, but also
that subsequent small but persistent floods can change it over long periods. Therefore, a better evaluation of the
long-term hydro-morphodynamics close to the bridge piers is necessary to address the local erosive phenomena,
possibly accounting for a 3D detailed description, which could be performed by means of a coupling approach
using the same suite iRIC, changing the solver and imposing the MFlow_02 results as boundary conditions
ASSESSING THE SUSPENDED SEDIMENT CONCENTRATION BY MEANS OF ACOUSTIC DOPPLER ECHO PROFILING
No full textTo obtain valuable information about rivers and water courses, scientists and engineers often rely on monitoring stations. These monitoring stations allow to measure several quantities that play a role in hydroenvironmental problems. One of these key variables is the suspended sediment concentration (SSC). In
this paper the application of an acoustic based method to determine the SSC in a river is presented. This method is founded on the sonar equation and uses the echo information from an Acoustic Doppler Current Profiler (ADCP) to assess the SSC.
The results from a monitoring station in the river Devoll in Albania are here presented and the method application is discussed. The advantages and disadvantages are highlighted and directions to improve the method are discussed
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
ASSESSING THE SUSPENDED SEDIMENT CONCENTRATION BY MEANS OF A SIDE LOOKING (HORIZONTAL) ADCP
No full textVariations 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
Measuring near-bed flow field in shallow quasi-uniform flow conditions with the use of an Ultrasonic Velocity Profiler
No full textIncipient motion of compact-shape microplastics: experimental design and expected results
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