Effects of irregular particle shapes on the sediment movement and transport rate in gravel-bed channels

2020 ◽  
pp. 294-301
Author(s):  
Takatoshi Atsumi ◽  
Shoji Fukuoka
Keyword(s):  
Transport Rate ◽  
Sediment Movement ◽  
Gravel Bed ◽  
Irregular Particle ◽  
Particle Shapes

scholarly journals Difficulties in Early Ice Detection with the Small Ice Detector-2 HIAPER (SID-2H) in Maritime Cumuli

2014 ◽  
Vol 31 (6) ◽  
pp. 1263-1275 ◽  
Author(s):  
Alexandria Johnson ◽  
Sonia Lasher-Trapp ◽  
Aaron Bansemer ◽  
Z. Ulanowski ◽  
Andrew J. Heymsfield
Keyword(s):  
High Performance ◽  
Water Environment ◽  
Ice Crystals ◽  
Environmental Research ◽  
Ice Formation ◽  
Cumulus Clouds ◽  
Irregular Particle ◽  
Water Drops ◽  
Ice Detection ◽  
Particle Shapes

Abstract The Small Ice Detector, version 2 (SID-2), High-performance Instrumented Airborne Platform for Environmental Research (HIAPER; SID-2H) was used to detect small ice particles in the early stages of ice formation in the high liquid water environment of tropical maritime cumulus clouds sampled during the Ice in Clouds Experiment—Tropical (ICE-T) field campaign. Its performance in comparison to other probes and the development of new corrections applied to the data are presented. The SID-2H detected small ice crystals among larger particles. It correctly identified water drops, and discriminated between round and irregular particle shapes in water-dominated clouds with errors less than 5%. Remaining uncertainties in the sensing volume and the volume over which coincidence of particles occurred, result in the data being used here in a qualitative manner to identify the presence of ice, and its habits and sizes.

scholarly journals Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

2021 ◽  
Author(s):  
Chenge An ◽  
Marwan A. Hassan ◽  
Carles Ferrer-Boix ◽  
Xudong Fu
Keyword(s):  
Sediment Transport ◽  
Critical Shear Stress ◽  
Transport Rate ◽  
Low Flow ◽  
Flood Event ◽  
Flume Experiments ◽  
Stress History ◽  
Gravel Bed ◽  
Sediment Transport Rate ◽  
Gravel Bed Rivers

<p>Recently, there has been an increasing attention on the environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers. More specifically, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Such an effect is often termed as “stress history” effect. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this study, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.</p>

scholarly journals Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

2020 ◽  
Author(s):  
Chenge An ◽  
Marwan A. Hassan ◽  
Carles Ferrer-Boix ◽  
Xudong Fu
Keyword(s):  
Sediment Transport ◽  
Critical Shear Stress ◽  
Transport Rate ◽  
Low Flow ◽  
Flood Event ◽  
Flume Experiments ◽  
Stress History ◽  
Gravel Bed ◽  
Sediment Transport Rate ◽  
Gravel Bed Rivers

Abstract. With the increasing attention on environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this paper, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.

scholarly journals Beyond Janus Geometry: Characterization of Flow Fields Around Nonspherical Photocatalytic Microswimmers

2021 ◽  
Author(s):  
Sandra Heckel ◽  
Clemens Bilsing ◽  
Martin Wittmann ◽  
Thomas Gemming ◽  
Lars Büttner ◽  
...  
Keyword(s):  
Surface Defects ◽  
High Spatial Resolution ◽  
Flow Fields ◽  
Chemical Gradient ◽  
Carrier Distribution ◽  
Motion Mechanism ◽  
Irregular Particle ◽  
Measured Flow ◽  
Particle Shapes

Catalytic microswimmers that move by a phoretic mechanism in response to a self-induced chemical gradient are often obtained by the design of spherical janus microparticles, which suffer from multi-step fabrication and low yields. Approaches such as irregular particle shapes, local excitation or intrinsic asymmetry are on the rise to facilitate manufacturing, but the effects on the generation of motion remain poorly understood. In this work, single crystalline BiVO4 microswimmers are presented that rely on a strict inherent asymmetry of charge-carrier distribution under illumination. The origin of the asymmetrical flow pattern is elucidated becauseof the high spatial resolution of measured flow fields around pinned BiVO4 colloids. As a result the flow from oxidative to reductive particle sides was confirmed. Distribution of oxidation and reduction reactions suggests a dominant self-electrophoretic motion mechanism with a source quadrupole as the origin of the induced flows. It is shown that the symmetry of the flow fields is broken by self-shadowing of the particles and synthetic surface defects that impact the photocatalytic activity of the microswimmers. The results demonstrate the complexity of symmetry breaking in nonspherical microswimmers and are leading the way towards understanding ofpropulsion mechanisms of phoretic colloids of various shapes.

scholarly journals A Super-Clustering Approach for Fully Automated Single Particle Picking in Cryo-EM

Genes ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 666 ◽  
Author(s):  
Al-Azzawi ◽  
Ouadou ◽  
Tanner ◽  
Cheng
Keyword(s):  
Structure Determination ◽  
Single Particle ◽  
Signal To Noise Ratio ◽  
Clustering Methods ◽  
Signal To Noise ◽  
Robust Detection ◽  
Irregular Particle ◽  
Clustering Approach ◽  
Noise Ratio ◽  
Particle Shapes

Structure determination of proteins and macromolecular complexes by single-particle cryo-electron microscopy (cryo-EM) is poised to revolutionize structural biology. An early challenging step in the cryo-EM pipeline is the detection and selection of particles from two-dimensional micrographs (particle picking). Most existing particle-picking methods require human intervention to deal with complex (irregular) particle shapes and extremely low signal-to-noise ratio (SNR) in cryo-EM images. Here, we design a fully automated super-clustering approach for single particle picking (SuperCryoEMPicker) in cryo-EM micrographs, which focuses on identifying, detecting, and picking particles of the complex and irregular shapes in micrographs with extremely low signal-to-noise ratio (SNR). Our method first applies advanced image processing procedures to improve the quality of the cryo-EM images. The binary mask image-highlighting protein particles are then generated from each individual cryo-EM image using the super-clustering (SP) method, which improves upon base clustering methods (i.e., k-means, fuzzy c-means (FCM), and intensity-based cluster (IBC) algorithm) via a super-pixel algorithm. SuperCryoEMPicker is tested and evaluated on micrographs of β-galactosidase and 80S ribosomes, which are examples of cryo-EM data exhibiting complex and irregular particle shapes. The results show that the super-particle clustering method provides a more robust detection of particles than the base clustering methods, such as k-means, FCM, and IBC. SuperCryoEMPicker automatically and effectively identifies very complex particles from cryo-EM images of extremely low SNR. As a fully automated particle detection method, it has the potential to relieve researchers from laborious, manual particle-labeling work and therefore is a useful tool for cryo-EM protein structure determination.

scholarly journals Prediction of sediment transport rates in gravel-bed rivers using Gaussian process regression

2019 ◽  
Vol 22 (2) ◽  
pp. 249-262 ◽  
Author(s):  
Kiyoumars Roushangar ◽  
Saman Shahnazi
Keyword(s):  
Sediment Transport ◽  
Gaussian Process ◽  
Gaussian Process Regression ◽  
The United States ◽  
Transport Rate ◽  
Support Vector ◽  
Sediment Properties ◽  
Gravel Bed ◽  
Sediment Transport Rate ◽  
Gravel Bed Rivers

Abstract Estimating sediment transport rate in rivers has high importance due to the difficulties and costs associated with its measurement, which has drawn the attention of experts in water engineering. In this study, Gaussian process regression (GPR) is applied to predict the sediment transport rate for 19 gravel-bed rivers in the United States. To compare the performance of GPR, the support vector machine (SVM) as a common type of kernel-based models was developed. Model inputs of sediment transport were prepared based on two scenarios: the first scenario considers only hydraulic characteristics and the second scenario was formed using hydraulic and sediment properties. Obtained results revealed that the GPR models present better performance compared to the SVM models and other empirical sediment transport formulas. Also, it was found that incorporating the second scenario as input led to better predictions. In addition, performing sensitivity analysis showed that the ratio of average velocity to shear flow velocity is the most effective parameter in predicting the sediment transport rate of gravel-bed rivers.

scholarly journals LONGSHORE WATER AND SEDIMENT MOVEMENT

1980 ◽  
Vol 1 (17) ◽  
pp. 76
Author(s):  
D.H. Swart ◽  
C.A. Fleming
Keyword(s):  
Sensitivity Analysis ◽  
Sediment Transport ◽  
Transport Rate ◽  
Sediment Movement ◽  
Sediment Transport Rate ◽  
Water And Sediment ◽  
Longshore Transport ◽  
Good Comparison ◽  
The Mean ◽  
Input Variables

The mean sediment transport rate obtained by using six known longshore transport formulae3 for which the input variables are determined consistently3 is used as best estimate of the transport. A good comparison is obtained when this package deal approach is compared with a prototype situation where the transport rates are inferred from quarterly bathymetric surveys over two years. The accuracy of the input variables is reviewed theoretically and the results are used to perform a sensitivity analysis.

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