scholarly journals What sets river width?

2020 ◽  
Vol 6 (41) ◽  
pp. eabc1505 ◽  
Author(s):  
Kieran B. J. Dunne ◽  
Douglas J. Jerolmack
Keyword(s):  
Channel Model ◽  
Planetary Science ◽  
Resistant Material ◽  
Threshold Channel ◽  
Wide Range ◽  
Geological Factors ◽  
Strong Control ◽  
Bank Strength ◽  
Channel Theory ◽  
Natural Rivers

One of the simplest questions in riverine science remains unanswered: “What determines the width of rivers?” While myriad environmental and geological factors have been proposed to control alluvial river size, no accepted theory exists to explain this fundamental characteristic of river systems. We combine analysis of a global dataset with a field study to support a simple hypothesis: River geometry adjusts to the threshold fluid entrainment stress of the most resistant material lining the channel. In addition, we demonstrate how changes in bank strength dictate planform morphology by exerting strong control on channel width. Our findings greatly extend the applicability of threshold channel theory, which was originally developed to explain straight gravel-bedded rivers with uniform grain size and stable banks. The parsimonious threshold-limiting channel model describes the average hydraulic state of natural rivers across a wide range of conditions and may find use in river management, stratigraphy, and planetary science.

scholarly journals Laboratory rivers: Lacey's law, threshold theory, and channel stability

2017 ◽  
Vol 5 (1) ◽  
pp. 187-198 ◽  
Author(s):  
François Métivier ◽  
Eric Lajeunesse ◽  
Olivier Devauchelle
Keyword(s):  
Laboratory Experiments ◽  
Braided River ◽  
Channel Stability ◽  
Typical Size ◽  
Single Thread ◽  
Threshold Theory ◽  
Threshold Channel ◽  
Natural Counterpart ◽  
Channel Theory ◽  
Natural Rivers

Abstract. More than a century of experiments have demonstrated that many features of natural rivers can be reproduced in the laboratory. Here, we revisit some of these experiments to cast their results into the framework of the threshold-channel theory developed by Glover and Florey (1951). In all the experiments we analyze, the typical size of the channel conforms to this theory, regardless of the river's planform (single-thread or braiding). In that respect, laboratory rivers behave exactly like their natural counterpart. Using this finding, we reinterpret experiments by Stebbings (1963). We suggest that sediment transport widens the channel until it reaches a limit width, beyond which it destabilizes into a braided river. If confirmed, this observation would explain the remarkable scarcity of single-thread channels in laboratory experiments.

scholarly journals Laboratory rivers: Lacey's law, threshold theory and channel stability

2016 ◽  
Author(s):  
François Métivier ◽  
Eric Lajeunesse ◽  
Olivier Devauchelle
Keyword(s):  
Laboratory Experiments ◽  
Braided River ◽  
Channel Stability ◽  
Typical Size ◽  
Single Thread ◽  
Threshold Theory ◽  
Threshold Channel ◽  
Natural Counterpart ◽  
Channel Theory ◽  
Natural Rivers

Abstract. More than a century of experiments have demonstrated that many features of natural rivers can be reproduced in the laboratory. Here, we revisit some of these experiments to cast their results into the framework of the threshold-channel theory developed by Glover and Florey (1951). In all the experiments we analyze, the typical size of the channel conforms to this theory, regardless of the river's planform (single-thread or braiding). In that respect, laboratory rivers behave exactly like their natural counterpart. Using this finding to reinterpret experiments by Stebbings (1963), we suggest that sediment transport widens the channel until it reaches a limit width, beyond which it destabilizes into a braided river. If confirmed, this observation would explain the remarkable scarcity of single-thread channels in laboratory experiments.

An intelligent algorithm for autonomous scientific sampling with the VALKYRIE cryobot

2017 ◽  
Vol 17 (3) ◽  
pp. 247-257 ◽  
Author(s):  
Evan B. Clark ◽  
Nathan E. Bramall ◽  
Brent Christner ◽  
Chris Flesher ◽  
John Harman ◽  
...  
Keyword(s):  
Human Performance ◽  
Autonomous Underwater Vehicles ◽  
Field Performance ◽  
Planetary Science ◽  
Operating Environment ◽  
Intelligent Algorithm ◽  
Future State ◽  
Science Operations ◽  
Wide Range ◽  
Matanuska Glacier

AbstractThe development of algorithms for agile science and autonomous exploration has been pursued in contexts ranging from spacecraft to planetary rovers to unmanned aerial vehicles to autonomous underwater vehicles. In situations where time, mission resources and communications are limited and the future state of the operating environment is unknown, the capability of a vehicle to dynamically respond to changing circumstances without human guidance can substantially improve science return. Such capabilities are difficult to achieve in practice, however, because they require intelligent reasoning to utilize limited resources in an inherently uncertain environment. Here we discuss the development, characterization and field performance of two algorithms for autonomously collecting water samples on VALKYRIE (Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice Explorer), a glacier-penetrating cryobot deployed to the Matanuska Glacier, Alaska (Mission Control location: 61°42′09.3″N 147°37′23.2″W). We show performance on par with human performance across a wide range of mission morphologies using simulated mission data, and demonstrate the effectiveness of the algorithms at autonomously collecting samples with high relative cell concentration during field operation. The development of such algorithms will help enable autonomous science operations in environments where constant real-time human supervision is impractical, such as penetration of ice sheets on Earth and high-priority planetary science targets like Europa.

MOSCOW INTERNATIONAL SYMPOSIA ON SOLAR SYSTEM RESEARCH (10M-S3 AND 11M-S3) REPORTS REVIEW. Part 1. Mars exploration

2021 ◽  
pp. 114-136
Author(s):  
Roman A. EVDOKIMOV
Keyword(s):  
Solar System ◽  
Solar System Research ◽  
New Technologies ◽  
Interplanetary Space ◽  
Planetary Science ◽  
Subsurface Water ◽  
System Research ◽  
Deep Space ◽  
Wide Range ◽  
Scientific Results

A review of the reports of the last two Moscow International Symposia on Solar System Research has been completed. In the first part of the review, 43 reports of the main session of the "Mars" section are considered. The works of leading experts in the field of planetary science cover a wide range of scientific and applied problems - from the study of the geological history and climate of Mars, the search for traces of life and subsurface water reserves, to new technologies in planetary research, mission planning, as well as monitoring solar activity and radiation conditions in the interplanetary space, orbit and the surface of Mars. The data obtained in the last two decades has made it possible to significantly advance in understanding the nature of Mars, but many unresolved questions remain regarding the climate in the early era, the existence of the Martian oceans in the past, biological and geological activity. The scientific results obtained by unmanned spacecraft should be fully taken into account in the development of manned deep space exploration programs. Key words: Solar system, planetology, international symposium, deep space, automatic interplanetary stations, Mars, Moon, reports review

Innovative visualization and analysis capabilities to advance scientific discovery

2020 ◽  
Author(s):  
Emily Law ◽  
Brian Day ◽  
Keyword(s):  
Solar System ◽  
Data Science ◽  
Scientific Discovery ◽  
Scientific Research ◽  
Value Added ◽  
Planetary Science ◽  
Analysis Tools ◽  
Wide Range ◽  
Data Products ◽  
Advanced Analysis

<p>NASA’s Solar System Treks program produces a suite of interactive visualization and AI/data science analysis tools. These tools enable mission planners, planetary scientists, and engineers to access geospatial data products derived from big data returned from a wide range of instruments aboard a variety of past and current missions, for a growing number of planetary bodies.</p><p>The portals provide easy-to-use tools for browse, search and the ability to overlay a growing range and large amount of value added data products. Data products can be viewed in 2D and 3D, in VR and can be easily integrated by stacking and blending together rendering optimal visualization. Data sets can be plotted and compared against each other. Standard gaming and 3D mouse controllers allow users to maneuver first-person visualizations of flying across planetary surfaces.</p><p>The portals provide a set of advanced analysis tools that employed AI and data science methods. The tools facilitate measurement and study of terrain including distance, height, and depth of surface features. They allow users to perform analyses such as lighting and local hazard assessments including slope, surface roughness and crater/boulder distribution, rockfall distribution, and surface electrostatic potential. These tools faciliate a wide range of activities including the planning, design, development, test and operations associated with lunar sortie missions; robotic (and potentially crewed) operations on the surface; planning tasks in the areas of landing site evaluation and selection; design and placement of landers and other stationary assets; design of rovers and other mobile assets; developing terrain-relative navigation (TRN) capabilities; deorbit/impact site visualization; and assessment and planning of science traverses. Additional tools useful scientific research are under development such as line of sight calculation.</p><p>Seven portals are publicly available to explore the Moon, Mars, Vesta, Ceres, Titan, IcyMoons, and Mercury with more portals in development and planning stages.</p><p>This presentation will provide an overview of the Solar System Treks and highlight its innovative visualization and analysis capabilities that advance scientific discovery.  The information system and science communities are invited to provide suggestions and requests as the development team continues to expand the portals’ tool suite to maximize scientific research.</p><p>Lastly, the authors would like to thank the Planetary Science Division of NASA’s Science Mission Directorate, NASA’s SMD Science Engagement and Partnerships, the Advanced Explorations Systems Program of NASA’s Human Exploration Operations Directorate, and the Moons to Mars Mission Directorate for their support and guidance in the development of the Solar System Treks.</p>

Typologies and touchpoints: designing multi-channel digital strategies

2015 ◽  
Vol 9 (2) ◽  
pp. 110-128 ◽  
Author(s):  
Karla Straker ◽  
Cara Wrigley ◽  
Michael Rosemann
Keyword(s):  
Content Analysis ◽  
New Technologies ◽  
Channel Model ◽  
Research Question ◽  
Channel Design ◽  
Content Type ◽  
Customer Needs ◽  
Starting Point ◽  
Wide Range ◽  
Digital Channels

Purpose – This study aims to gain a clearer understanding of digital channel design. The emergence of new technologies has revolutionised the way companies interact and engage with customers. The driver for this research was the suggestion that practitioners feel they do not possess the skills to understand and exploit new digital channel opportunities. To gain a clearer understanding of digital channel design, this paper addresses the research question: What digital channels do companies from a wide range of industries and sectors use? Design/methodology/approach – A content analysis of 100 international companies was conducted with multiple data sources to form a typology of digital “touchpoints”. The appropriateness of a digital channel typology for this study was for developing rigorous and useful concepts for clarifying and refining the meaning of digital channels. Findings – This study identifies what digital channels companies globally currently employ and explores the related needs across industries. A total of 34 digital touchpoints and 4 typologies of digital channels were identified across 16 industries. This research helps to identify the relationship between digital channels and enabling the connections with industry. Research limitations/implications – The findings contribute to the growing research area of digital channels. The typology of digital channels is a useful starting point for developing a systematic, theory-based study for enabling the development of broader, comprehensive theories of digital channels. Practical implications – Typologies and touchpoints are outlined in relation to industry, company objectives and customer needs to allow businesses to seize opportunities and optimise performance through individual touchpoints. A digital channel model as a key outcome of this research guides practitioners on what touchpoint to implement through an interrelated understanding of industry, company and customer needs. Originality/value – This is the first paper to explore a range of industries in relation to their use of digital channels using a unique content analysis. Contributions include clarifying and refining digital channel meaning; identifying and refining the hierarchical relations among digital channels (typologies); and establishing typology and industry relationship model.

scholarly journals Preprint-Word order patterns in gesture are sensitive to modality-specific production constraints

2017 ◽  
Author(s):  
Melissa Kline ◽  
Miguel Angel Salinas ◽  
Eunice Lim ◽  
Evelina Fedorenko ◽  
Edward Gibson
Keyword(s):  
Word Order ◽  
Ad Hoc ◽  
Channel Model ◽  
Noisy Channel ◽  
Production Studies ◽  
Task Instructions ◽  
Communication Task ◽  
Physical Form ◽  
Wide Range ◽  
Communication Dynamics

A fundamental typological variation in the world’s languages is their basic word order; around 80% of spoken languages are either Subject-Object-Verb (SOV) or Subject-Verb-Object (SVO). Previous work has related this typological pattern to a striking finding in ad-hoc gesture production: across a wide range of languages, people tend to use the order SOV to gesture events with inanimate patients, and SVO orders for those with animate patients (Gibson, Piantadosi, et al., 2013; Hall, Mayberry, & Ferreira, 2013, i.a.). Gibson et al. (2013) interpret this evidence as support for a noisy channel model of communication, under which producers attempt to reduce ambiguity for comprehenders. On the other hand, this pattern might also result from the particular kinds of gestures that people tend to use for different kinds of events (Hall et al. 2013). We conducted two production studies – one in gesture, one using non-iconic written symbols– designed to modify the communication task in different ways. Two main findings emerged from these tests: first, simple modifications to the gesture paradigm can have a profound effect on the orders used: the instructions given in Experiment 1 (gesture) dramatically affected the use of SVO orders, even though participants were gesturing about the same events under the same communicative contexts. Second, there is an apparent association between the physical form of the gestures used to communicate and word order: we found that participants were most likely to use SVO orders in Experiment 1 for animate-animate events when using body-based gestures (avoiding role conflict, as described by Hall et al. 2013); furthermore in Experiment 2 (written symbols), there was no association between SVO ordering and animate-animate scenes (contrary to predictions of the noisy channel model). We conclude that gesturing paradigms, while a striking and naturalistic example of ad-hoc communication dynamics, are also sensitive to the particular modality and task instructions, and as such do not provide straightforward evidence for noisy channel theories of word order typology.

scholarly journals Morphology of the Kosi megafan channels

2014 ◽  
Vol 2 (2) ◽  
pp. 1023-1046 ◽  
Author(s):  
K. Gaurav ◽  
F. Métivier ◽  
O. Devauchelle ◽  
R. Sinha ◽  
H. Chauvet ◽  
...  
Keyword(s):  
Water Discharge ◽  
Morphological Characteristics ◽  
Acoustic Doppler Current Profiler ◽  
Sandy Sediment ◽  
Strongly Correlated ◽  
Data Set ◽  
Threshold Channel ◽  
Average Slope ◽  
Current Profiler ◽  
Channel Theory

Abstract. We study the morphology of streams flowing on the alluvial megafan of the Kosi River in north Bihar, India. All streams develop on a uniform sandy sediment and under a similar climate, allowing for statistically significant comparisons. Our data set includes both channels from the braid of the Kosi River and channels from isolated single-thread rivers. Using an Acoustic Doppler Current Profiler, we measure the width, depth and water discharge of the channels. Their average slope is also acquired with a kinematic GPS. These morphological characteristics are strongly correlated with the discharge. However, rescaling the data according to the threshold channel theory removes most of this dependency. The rescaled data suggest that the threads of the Kosi River braid are morphologically similar to isolated channels.

A Mathematical Model Development for Simulating Nitrate Pollutant Transport along a River

2021 ◽  
Vol 57 ◽  
pp. 149-168
Author(s):  
Kayode O. Olowe ◽  
Muthukrishnavellaisamy Kumarasamy
Keyword(s):  
Mathematical Model ◽  
Water Quality ◽  
Surface Water ◽  
Analytical Solutions ◽  
Numerical Solutions ◽  
Nitrate Concentration ◽  
Pollutant Transport ◽  
Spatial And Temporal Variation ◽  
Wide Range ◽  
Natural Rivers

Contamination of surface water bodies by a wide range of organic and inorganic pollutants has been a serious problem in the recent time, these have an effect on human and aquatic animals. The water quality deterioration calls for regular monitoring of the water quality in order to maintain the health and sustainability of the aquatic ecosystems. Accurate monitoring of discharged pollutants into the rivers may be time taking and labour intensive. Water quality models are significant tools for simulating water quality and controlling the surface water pollution. The purpose of this study is to develop a simplified mathematical model which is hybrid cells in series model (HCIS) to simulate the spatial and temporal variation of nitrate concentration in natural rivers. The HCIS model was formulated to serve as an alternative method to the Fickian based models. Analytical solutions for the first order reaction kinetics of nitrate with the advection and dispersion process were derived using Laplace transformation technique. The model considered the effect of nitrate concentration at several points along the river downstream by considering the transformation of nitrite to nitrate through nitrification process. In addition, the uptake of nitrate by algae for its growth and conversion of nitrate to nitrogen gas due to denitrification process were considered. The HCIS-NO3 model was applied to uMgeni River, South Africa to investigate the nitrate concentration along the river. Furthermore, the quantitative measures based on the coefficient of determination (R2) and standard errors (SE) were used to evaluate the performance of the model. The result shows that the simulated values agreed with the measured values of nitrate concentration in the river which resulted in a R2 value of 0.72 and a low standard error. Analytical solutions of HCIS - NO3 model were compared with the numerical solutions of the Fickian based ADE model for hypothetical problems. Comparison of the responses indicates that the HCIS - NO3 and ADE- NO3 models were in good agreement. The study shows that the hybrid model is a simple and effective tool for simulating pollutant transport in natural rivers.

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