scholarly journals Water-Worked Gravel Bed: State-of-the-Art Review

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 694 ◽  
Author(s):  
Ellora Padhi ◽  
Subhasish Dey ◽  
Venkappayya R. Desai ◽  
Nadia Penna ◽  
Roberto Gaudio
Keyword(s):  
State Of The Art ◽  
Flow Characteristics ◽  
Streamwise Velocity ◽  
Secondary Currents ◽  
Gravel Bed ◽  
Natural Stream ◽  
Art Research ◽  
The Comparative Study ◽  
Water Work

In a natural gravel-bed stream, the bed that has an organized roughness structure created by the streamflow is called the water-worked gravel bed (WGB). Such a bed is entirely different from that created in a laboratory by depositing and spreading gravels in the experimental flume, called the screeded gravel bed (SGB). In this paper, a review on the state-of-the-art research on WGBs is presented, highlighting the role of water-work in determining the bed topographical structures and the turbulence characteristics in the flow. In doing so, various methods used to analyze the bed topographical structures are described. Besides, the effects of the water-work on the turbulent flow characteristics, such as streamwise velocity, Reynolds and form-induced stresses, conditional turbulent events and secondary currents in WGBs are discussed. Further, the results form WGBs and SGBs are compared critically. The comparative study infers that a WGB exhibits a higher roughness than an SGB. Consequently, the former has a higher magnitude of turbulence parameters than the latter. Finally, as a future scope of research, laboratory experiments should be conducted in WGBs rather than in SGBs to have an appropriate representation of the flow field close to a natural stream.

scholarly journals Block ramps for stream power attenuation in gravel-bed streams: a review

2020 ◽  
Author(s):  
Rakesh Kumar Chaudhary ◽  
Nayan Sharma ◽  
Zulfequar Ahmad
Keyword(s):  
Energy Dissipation ◽  
Flow Resistance ◽  
Simple Technique ◽  
State Of The Art ◽  
Flow Characteristics ◽  
Stream Power ◽  
Gravel Bed ◽  
The Past ◽  
Gravel Bed Streams ◽  
Block Ramp

Abstract Application of block ramp technique in steep gradient streams for energy dissipation as well as to maintain river stability finds increasing favor amongst researchers and practitioners in river engineering. This paper dwells on a comprehensive state-of-the-art review of flow resistance, energy dissipation,flow characteristics, stability, and drag force on block ramp by various investigators in the past. The forms and equations for each type are thoroughly discussed with the objective of finding the grey areas and gaps. While, more research is warranted further to improve the equations, essential for design analysis. Block ramps can be a promising simple technique to achieve reasonable attenuation of devastating fluvial forces unleashed in gravel-bed streams during cloud bursts.

scholarly journals On the role of turbulent large-scale streaks in generating sediment ridges

2021 ◽  
Vol 930 ◽  
Author(s):  
Markus Scherer ◽  
Markus Uhlmann ◽  
Aman G. Kidanemariam ◽  
Michael Krayer
Keyword(s):  
Large Scale ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Top Down ◽  
Outer Flow ◽  
Secondary Currents ◽  
Sediment Bed ◽  
Low Speed Streaks ◽  
O 10

The role of turbulent large-scale streaks or large-scale motions in forming subaqueous sediment ridges on an initially flat sediment bed is investigated with the aid of particle resolved direct numerical simulations of open channel flow at bulk Reynolds numbers up to 9500. The regular arrangement of quasi-streamwise ridges and troughs at a characteristic spanwise spacing between 1 and 1.5 times the mean fluid height is found to be a consequence of the spanwise organisation of turbulence in large-scale streamwise velocity streaks. Ridges predominantly appear in regions of weaker erosion below large-scale low-speed streaks and vice versa for troughs. The interaction between the dynamics of the large-scale streaks in the bulk flow and the evolution of sediment ridges on the sediment bed is best described as ‘top-down’ process, as the arrangement of the sediment bedforms is seen to adapt to changes in the outer flow with a time delay of several bulk time units. The observed ‘top-down’ interaction between the outer flow and the bed agrees fairly well with the conceptual model on causality in canonical channel flows proposed by Jiménez (J. Fluid Mech., vol. 842, 2018, P1, § 5.6). Mean secondary currents of Prandtl's second kind of comparable intensity and lateral spacing are found over developed sediment ridges and in single-phase smooth-wall channels alike in averages over ${O}(10)$ bulk time units. This indicates that the secondary flow commonly observed together with sediment ridges is the statistical footprint of the regularly organised large-scale streaks.

Environmental and Resource-Related Conflicts, Migration and Governance

2020 ◽  
pp. 1-16
Author(s):  
Tim Krieger ◽  
Diana Panke ◽  
Michael Pregernig
Keyword(s):  
State Of The Art ◽  
Analytical Framework ◽  
Global Migration ◽  
Resource Conflicts ◽  
Academic Literature ◽  
Interdisciplinary Perspective ◽  
Art Research

This introductory chapter provides the outline of the book and the analytical framework to explore the interlinkages and dynamics between environmental and resource-related conflicts, migration, and the role of governance in this context. It introduces how and under what conditions environmental and resource-related problems lead to conflicts and how this can induce migration. It also reflects on the role of governance in this respect. Based on state-of-the-art research, the chapter highlights the importance of understanding the interdependencies between migration, environmental and resource conflicts, as well as the development and roles of national, regional and global migration governance regimes. While extensive academic literature exists on each strand of research, little are the academic exercises that bring them together, particularly from an interdisciplinary perspective.

scholarly journals Oxytocin and the Neurobiology of Prosocial Behavior

2020 ◽  
pp. 107385842096011
Author(s):  
Nina Marsh ◽  
Abigail A. Marsh ◽  
Mary R. Lee ◽  
René Hurlemann
Keyword(s):  
Prosocial Behavior ◽  
State Of The Art ◽  
Behavioral Effects ◽  
Therapeutic Interventions ◽  
Social Brain ◽  
The Social ◽  
Neuropeptide Hormone ◽  
Art Research ◽  
Conceptual Overview

Humans are an unusually prosocial species, who engage in social behaviors that include altruism—whereby an individual engages in costly or risky acts to improve the welfare of another person—care, and cooperation. Current perspectives on the neurobiology of human prosociality suggest that it is deeply rooted in the neuroendocrine architecture of the social brain and emphasize the modulatory role of the neuropeptide hormone oxytocin. In this review, we provide a conceptual overview of the neurobiology of prosocial behavior with a focus on oxytocin’s modulatory role in human prosociality. Specifically, we aim to encourage a better understanding of the peptide’s susceptibility to diverse factors that produce heterogeneity in outcomes and the resulting methodological implications for measuring the behavioral effects of oxytocin in humans. After providing an overview of the state-of-the-art research on oxytocin’s exogenous use, we elaborate on the peptide’s modulatory role in the context of care-based altruism, cooperation, and conflict and discuss its potential for therapeutic interventions in psychiatric disorders characterized by social dysfunction.

State-of-the-Art: A Systematic Literature Review on Image Segmentation in Latent Fingerprint Forensics

2019 ◽  
Vol 12 ◽  
Author(s):  
Megha Chhabra ◽  
Manoj Kumar Shukla ◽  
Kiran Kumar Ravulakollu
Keyword(s):  
Image Segmentation ◽  
Background Noise ◽  
State Of The Art ◽  
Recognition Rate ◽  
Poor Quality ◽  
Latent Fingerprint ◽  
In The Beginning ◽  
The Comparative Study ◽  
Finger Skin

: Latent fingerprints are unintentional finger skin impressions left as ridge patterns at crime scenes. A major challenge in latent fingerprint forensics is the poor quality of the lifted image from the crime scene. Forensics investigators are in permanent search of novel outbreaks of the effective technologies to capture and process low quality image. The accuracy of the results depends upon the quality of the image captured in the beginning, metrics used to assess the quality and thereafter level of enhancement required. The low quality of the image collected by low quality scanners, unstructured background noise, poor ridge quality, overlapping structured noise result in detection of false minutiae and hence reduce the recognition rate. Traditionally, Image segmentation and enhancement is partially done manually using help of highly skilled experts. Using automated systems for this work, differently challenging quality of images can be investigated faster. This survey amplifies the comparative study of various segmentation techniques available for latent fingerprint forensics.

UNRAVELLING THE ROLE OF VEGETATION IN THE AVULSION HISTORY OF GRAVEL-BED RIVERS

2018 ◽  
Author(s):  
Daniel Donahue ◽  
◽  
José Antonio Constantine ◽  
Gregory B. Pasternack
Keyword(s):  
Gravel Bed ◽  
History Of ◽  
Gravel Bed Rivers
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