1,720,976 research outputs found
The long-term monitoring of suspended sediment transport with side-looking Acoustic Doppler Current Profilers: a graphical user interface for echo profiles interpretation.
No full textThe idea of a long-term and reliable monitoring of suspended sediment transport (SST) is attractive for a variety of applications in fluvial hydraulics, namely in hydropower projects that need to evaluate the impact of sediment erosion and deposition in a dam reservoir. This requires measuring both flow discharge and corresponding suspended sediment concentration (SSC) to determine the SST. Many devices and techniques have been proposed about these subjects: the acoustic Doppler current profiler (ADCP) is widely applied to evaluate river discharge whereas sediment samplers are often used to sample water-sediment mixture in the river channel. However, practical limitations of the physical samplers operation (e.g. no measurements in extreme cases such as flood events) and the need to displace human and technical resources to the field reduces the available data. Consequently, engineers usually correlate SST to water level, where the latter is much easier to be continuously monitored. Unfortunately, it is not trivial to obtain correlations between SSC, flow discharge and water level due to hysteresis processes. Therefore, scientific and practical questions remain about the actual possibility of continuously measuring the SST during long periods (i.e., years). Aiming to answer these questions, this work proposes the use of a side-looking ADCP for the monitoring of flow discharge and SSC, combined with an analytical method based on the sonar equation and written as function of the attenuation-backscatter ratio. An application of this method is presented with long-time measurements made in the Devoll river, Albania. For the application of this method, a Graphical User Interface (GUI) was developed to allow non-expert users to analyze the echoes profiles from a side-looking ADCP for the assessment of the SSC
River sediment transport monitoring by means of H-ADCP
No full textMonitoring stations in rivers and water courses are an important mean to obtain critical data about the different variables that play a role in the hydrodynamics and ecological processes. This is especially true during rough weather conditions when direct observations are not possible and even dangerous. A technique to determine the suspended sediment transport by means of fixed ADCPs at the side of a river channel (i.e., H-ADCP) is here presented. This technique relies on the Channel Master by Teledyne-RDI which continuously measures water velocity and echo intensity profiles along an horizontal alignment, these measurements are then transmitted to a remote server via GSM. In addition the proposed technique is based on an acoustic method to investigate poorly sorted sediment in the spectrum ranging from clay to fine sand. This combines the measurement of sound attenuation and backscatter to determine instrumental sensitivity to actual matter suspended in the horizontal alignment, thus relaxing the need of frequent calibrations to account for changes in the backscatter return not ascribable to a change in suspended sediment concentration, SSC. Last but not least a Matlab GUI was developed for the acoustic method implementation-validation and its coupling with discharge assessment using water velocity profiles from the Channel Master. The overall technique was applied in two very different case studies: i) the Devoll river in Albania that is a typical mountain stream with flow velocity and SSC larger than 5 m/s and 10 g/l during floods, respectively, in this case the monitoring serves hydropower industry; ii) the Secchia river where the observed peaks were close to 1.5 m/s and 2 g/l, this is the case of an embanked stream flowing in one of the most populous and heavily built areas of Italy where the monitoring station serves the prediction of sediments deposition and erosion close to existing infrastructures (e.g., bridge and levee). The proposed technique proved to work properly in both case studies eventually enlarging the Channel Master capabilities to river sediment transport monitoring
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
W.A.T.E.R. - a structured approach for training on advanced measurement and experimental research
Full text linkW.A.T.E.R. stands for Workshop on Advanced measurement Techniques and Experimental Research. It is an initiative started in 2016 in association with the Experimental Methods and Instrumentation (EMI) committee of the International Association for Hydro-Environment Engineering and Research (IAHR) aimed at advancing the use of experimental techniques in hydraulics and fluid mechanics research. It provides a structured approach for the learning and training workshop series to postgraduate students (aiming specifically at doctoral students), young researchers, and professionals with an experimental background in fluid mechanics. It offers an opportunity to learn about state-of-the-art instrumentation and measurement techniques and the latest developments in the field by partnering with manufacturers. W.A.T.E.R. brings together academics, instrumentation manufacturers and public sectors in a structured setting to share knowledge and to learn from good practices. It is about training people who already have a certain knowledge and skill level but who need to go deeper and/or wider in the field of measurement and experimental research
Gauging suspended sediment concentration in coastal waters by means of proxy acoustical methods
No full textApplying ADCPs for Long-Term Monitoring of SSC in Rivers
No full textThe flow rate and the suspended sediment concentration (SSC) of two different rivers draining into the Adriatic Sea basin, the Secchia in Italy and the Devoll in Albania, were analyzed by processing the data collected in a 245-day period at monitoring stations equipped with side-looking acoustic Doppler current profilers (H-ADCPs). SSC was determined as a by-product of the echo profiles along the horizontal aligned acoustic beams emitted by H-ADCPs. For the first time, the effect of organic matter other than a change of inorganic particles size distribution was evaluated as a possible reason for backscatter and attenuation variations during hydrological events. This reduced average deviations between acoustically inferred and sampled concentrations from 1 order of magnitude to 20% of actual values. The improvement required the measuring of attenuation to backscatter ratio (ABR) in addition to sound attenuation. The validation interval covered 3 orders of magnitude from 10−1 to 10 g L−1. In this paper the potential of the ABR method using H-ADCP to continuously monitor suspended sediment fluxes is tested in two different rivers, enabling single peak flood analysis and reliable assessment of sediment budget across a river cross section. The advantages and disadvantages of this method are presented and discussed
Bedload velocity and backscattering strength from mobile sediment bed: A laboratory investigation comparing bistatic versus monostatic acoustic configuration
Full text linkDespite the many advantages of using active ultrasound sonars, recent studies have shown that the specific acoustic geometry, signal-processing configuration, and complex surface-volume scattering process at the riverbed introduce several uncertainties in bedload estimation. This study presents a comparison of bedload velocity and bottom echo intensity measurements performed by monostatic and bistatic active ultrasound systems. The monostatic configuration is widely applied in the field to measure the apparent velocity at the riverbed with an acoustic current Doppler profiler (ADCP). Two laboratory investigations were conducted in two different hydraulic facilities deploying ADCP Stream Pro, monostatic and bistatic acoustic velocity profilers, manufactured by Ubertone. The bistatic instruments provided more accurate bedload velocity measurements and helped in understanding the acoustic sampling of the monastic systems. The bistatic profiles succeeded in measuring a profile over the active bedload layer, and the monostatic instruments resulted in different bedload velocity estimations depending on the acoustic resolution and sampling. The echo intensity increased in the cells measured within the active bedload layer with respect to the cell measuring the water column above. The cells that sampled the immobile bed surface beneath the bedload layer showed a reduction of the echo intensity compared with the cells above. The acoustic sampling, which combines the measurement volume geometry and internal processing, seems crucial for more accurate outputs. Future research about the use of monostatic instruments in the field should aim to define the best possible setting for the acoustic parameters at a given bedload condition that may be tuned by evaluating the backscattering at the river bottom together with the apparent bedload velocity
W.A.T.E.R. – a hands-on structured approach for training on advanced measurement and experimental research
No full textVariations on the Author
Full text link“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
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