Considerations on Acoustic Mapping Velocimetry (AMV) Application for in-situ Measurement of Bedform Dynamics

Non-intrusive technologies for the in-situ measurement of river morphological features are increasingly popular in the scientific and practice communities due to their efficient and productive data acquisition. While the measurement of suspended load with optical and acoustic technologies is currently an active area of research, the measurement of bedform dynamics has not experienced similar progress. We have successfully demonstrated through laboratory experiments that, by combining acoustic mapping with image velocimetry concepts, we can characterize the planar dynamics of the bedform migration. The technique, labeled Acoustic Mapping Velocimetry (AMV), is currently transferred to field conditions using multiple-beam echo-sounders (MBES) for producing acoustic maps. During this transfer, new questions emerged because, in field conditions, many of the morphologic features targeted by AMV measurements are not a priori known. Moreover, the image velocimetry processing can be approached with several alternatives, each of them characterized by strength and limitations. This paper assembles guidelines for establishing optimal parameters for the acquisition of the acoustic maps based on analytical considerations, and for selecting essential features of the processing for image velocimetry. We test these guidelines using MBES data acquired in the Mississippi River

Acoustic mapping velocimetry

Knowledge of sediment dynamics in rivers is of great importance for various practical purposes. Despite its high relevance in riverine environment processes, the monitoring of sediment rates remains a major and challenging task for both suspended and bed load estimation. While the measurement of suspended load is currently an active area of testing with nonintrusive technologies (optical and acoustic), bed load measurement does not mark a similar progress. This paper describes an innovative combination of measurement techniques and analysis protocols that establishes the proof-of-concept for a promising technique, labeled herein Acoustic Mapping Velocimetry (AMV). The technique estimates bed load rates in rivers developing bed forms using a nonintrusive measurements approach. The raw information for AMV is collected with acoustic multibeam technology that in turn provides maps of the bathymetry over longitudinal swaths. As long as the acoustic maps can be acquired relatively quickly and the repetition rate for the mapping is commensurate with the movement of the bed forms, successive acoustic maps capture the progression of the bed form movement. Two-dimensional velocity maps associated with the bed form migration are obtained by implementing algorithms typically used in particle image velocimetry to acoustic maps converted in gray-level images. Furthermore, use of the obtained acoustic and velocity maps in conjunction with analytical formulations (e.g., Exner equation) enables estimation of multidirectional bed load rates over the whole imaged area. This paper presents a validation study of the AMV technique using a set of laboratory experiments

Union effectiveness: In Search of the Holy Grail

YesThis article revisits the concept of union effectiveness and proposes a conceptual model to inform its study and application. Previous conceptual and empirical work is examined to identify key strengths and weaknesses, and to relate the union effectiveness concept to union renewal and other key concepts. This leads to the proposal of a Goal-System framework that builds and improves on prior research

Sectional model of a prairie buffer strip in a laboratory flume for water quality research

Vegetative buffers have shown promising results in reducing runoff volume, sediment, nutrients, and manure‐borne contaminants in runoff from agricultural fields. Although these vegetative buffer systems have been extensively tested in field and plot‐scale studies that utilize either natural or simulated rainfall, studies of such systems under highly controlled conditions in the laboratory have been limited. Here, we present the development of a new system for laboratory testing of a full‐scale, sectional, physical model of a new practice under the Continuous Conservation Reserve Program (CRP) Clean Lakes, Estuaries, and Rivers (CLEAR) Initiative, CP‐43 Prairie Strips. This work includes the extraction of prairie strip sections from the field and their integration into an existing laboratory flume facility with specific auxiliary features to facilitate overland flow experimentation. As a proof of concept run, a potassium chloride (KCl) tracer study was conducted to verify system functionality and inform future work. The tracer pulse was injected under saturated conditions and the response was monitored through surface water (upstream and downstream of the prairie strip model) and subsurface water (infiltrated) sampling with continuous flow rate monitoring at the sampling locations. The tracer test provided highly resolved breakthrough curves (BTCs) with 93.5% of the injected tracer mass recovered, and provided useful information on flow partitioning, velocities, and dispersion characteristics along the surface and through the subsurface profile of the model. This model prairie strip system is expected to be useful in optimizing the performance of prairie strips under highly controlled flow and contaminant source conditions

Croce

Il libro propone una ricostruzione completa della filosofia dello spirito di Benedetto Croce, dai primi scritti sulla storia e il marxismo fino alle ultime meditazioni sulla vitalità. L’autore prende in particolare considerazione il rapporto tra la filosofia di Croce e la dialettica hegeliana, soffermandosi in maniera analitica sia sulla teoria della distinzione delle categorie dello spirito sia sul rapporto tra sfera dell’utile e sfera del concetto logico. The book proposes a complete reconstruction of Benedetto Croce’s philosophy of spirit, from the early writings on History and Marxism to the latest meditations on life and vitality. The author takes into particular consideration the relationship between Croce’s philosophy and the Hegelian dialectic, focusing on the theory of the distinction of the categories of spirit and the relationship between vitality and logical concept