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 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.

Applying the mixing layer analogy for flow resistance evaluation in gravel-bed streams

2020 ◽  
Vol 589 ◽  
pp. 125119
Author(s):  
Ming Luo ◽  
XieKang Wang ◽  
XuFeng Yan ◽  
Er Huang
Keyword(s):  
Flow Resistance ◽  
Mixing Layer ◽  
Resistance Evaluation ◽  
Gravel Bed ◽  
Gravel Bed Streams

scholarly journals Reach-averaged flow resistance in gravel-bed streams

2020 ◽  
Author(s):  
Liguo Zhang ◽  
Wenguang Luo
Keyword(s):  
Shallow Water ◽  
Field Data ◽  
Flow Resistance ◽  
Roughness Parameter ◽  
Force Balance ◽  
Form Drag ◽  
Gravel Bed ◽  
River Reach ◽  
Gravel Bed Streams ◽  
Hydraulic Variables

Abstract Previous studies about flow resistance in gravel-bed streams mostly use the log-law form and establish the relationship between the friction factor and the relative flow depth based on field data. However, most established relations do not perform very well when applied to shallow water zones with relatively large roughness. In order to clarify the hydraulic variables defined in the single cross-section, and find the reasons that reflect the instability of flow and uneven boundaries of the river, the concepts of hydraulic variables, such as hydraulic radius, are re-defined in the river reach in the paper. The form drag in the river reach is solved based on a reach-averaged flow resistance model which is developed by force balance analyzing of the water body in the given river reach. The reach-averaged form drag relation is then formulated by incorporating the Einstein flow parameter and a newly derived roughness parameter defined in the river reach. A large number of field data (12 datasets, 780 field measurements) is applied to calibrate and validate the form drag relation. The relation is found to give better agreement with the field data in predicting flow velocity in comparison with existing flow resistance equations. A unique feature of the reach-averaged resistance relation is that it can apply to both deep and shallow water zones, which can be treated as a bridge to link the flow hydraulics in plain rivers and mountain streams.

scholarly journals An experimental investigation on the flow resistance over a porous gravel-bed surface and its non-porous counterpart

2018 ◽  
Vol 40 ◽  
pp. 05073
Author(s):  
Christy Ushanth Navaratnam ◽  
Jochen Aberle ◽  
Jie Qin ◽  
Pierre-Yves Henry
Keyword(s):  
Experimental Investigation ◽  
Surface Structure ◽  
Grain Orientation ◽  
Flow Resistance ◽  
Laboratory Experiments ◽  
Flow Characteristics ◽  
Experimental Setup ◽  
Preliminary Results ◽  
Gravel Bed ◽  
Bed Porosity

This paper presents preliminary results from laboratory experiments which were specifically designed to determine the flow resistance over a water-worked gravel-bed and its impermeable counterpart (cast-bed). The technique used to create the cast-bed is introduced, followed by the description of the experimental setup and the procedure to quantify flow resistance over both the water-worked and cast-bed. The influence of the grain orientation on flow resistance was investigated in an additional set of experiments by rotating the cast-bed through 180° in the flume. The main focus of the paper is on the comparison of the bulk flow characteristics for the three different cases for which the beds are characterized not only by the same characteristic grain-diameter but also by an identical surface structure. The obtained results show that the porous, non-porous bed and rotated bed result in different flow resistance and that both bed porosity and grain-orientation have a significant effect on flow resistance.

scholarly journals Application of various 'response surface' based algorithms in optimization of air manifolds for batch boilers

2019 ◽  
Vol 213 ◽  
pp. 02083
Author(s):  
Mateusz Szubel ◽  
Mariusz Filipowicz ◽  
Anna Mikrut
Keyword(s):  
Objective Function ◽  
Response Surface ◽  
Flow Resistance ◽  
State Of The Art ◽  
Flow Characteristics ◽  
Point Of View ◽  
Final Model ◽  
Operation Conditions ◽  
Optimal Values ◽  
Correct Design

Correct design of air manifolds applied in biomass-fired batch boilers allows to avoid excessive emissions and high flow resistance, as well as helps achieving the required parameters of the fan supplying air to the boiler. The paper describes the process and the results of the optimization performed using selected methods based on the response surface analysis. An experimentally validated CFD model of the state of the art air manifold has been geometrically parametrized, in order to find the shape that is optimal from the point of view of the objective function. In each analysis, the objective function was linked to air flow characteristics. Selected algorithms of the interpolation of design points that were obtained as the result of the numerical experiment have been compared and evaluated. Optimization using the response surface generated using various algorithms has been performed and verified by further direct CFD computations. The obtained optimal values of the input parameters were applied in the final model of the prototype. The flow characteristics of the prototype and the reference state have been compared and discussed. Significant improvement of the operation conditions has been achieved.

scholarly journals Bedload Sediment Transport in Connection with the Geomorphological Transition of Gravel-Bed Streams in the Moravskoslezské Beskydy Mountains

Geografie ◽  
2012 ◽  
Vol 117 (1) ◽  
pp. 95-109 ◽  
Author(s):  
Tomáš Galia ◽  
Václav Škarpich ◽  
Jan Hradecký
Keyword(s):  
Sediment Transport ◽  
Cross Sections ◽  
Bedload Transport ◽  
High Rate ◽  
Stream Power ◽  
Empirical Formulas ◽  
Fluvial Erosion ◽  
Gravel Bed ◽  
Bedload Sediment ◽  
Gravel Bed Streams

This paper summarizes the results of bedload transport research in the Morávka, Mohelnice and Ostravice basins, conducted using the BAGS (Bedload Assessment for Gravel-bed Streams) spreadsheet-based program and unit stream power empirical formulas. The presented results only show the potential rate of bedload transport, because sediment inputs and barriers were not included in the model. Trends in the potential bedload transport rate represent a good instrument for identifying the range of disconnected sediment transport along the longitudinal profile. Modelling on cross-sections with a high rate of fluvial erosion shows an increase in potential bedload transport and larger diameters of the largest possible transported particles, calculated using unit stream power empirical formulas. The results may be applied to improve local watershed management.

A Macintosh Interface for the Cameca Camebax-Micro Electron Microprobe

1990 ◽  
Vol 48 (1) ◽  
pp. 438-439
Author(s):  
Carl E. Henderson
Keyword(s):  
Electron Microprobe ◽  
Processing Speed ◽  
Word Processing ◽  
State Of The Art ◽  
Computer Control ◽  
Third Party ◽  
Disk Storage ◽  
The Past ◽  
User Facility ◽  
Instrument Control

Over the past few years it has become apparent in our multi-user facility that the computer system and software supplied in 1985 with our CAMECA CAMEBAX-MICRO electron microprobe analyzer has the greatest potential for improvement and updating of any component of the instrument. While the standard CAMECA software running on a DEC PDP-11/23+ computer under the RSX-11M operating system can perform almost any task required of the instrument, the commands are not always intuitive and can be difficult to remember for the casual user (of which our laboratory has many). Given the widespread and growing use of other microcomputers (such as PC’s and Macintoshes) by users of the microprobe, the PDP has become the “oddball” and has also fallen behind the state-of-the-art in terms of processing speed and disk storage capabilities. Upgrade paths within products available from DEC are considered to be too expensive for the benefits received. After using a Macintosh for other tasks in the laboratory, such as instrument use and billing records, word processing, and graphics display, its unique and “friendly” user interface suggested an easier-to-use system for computer control of the electron microprobe automation. Specifically a Macintosh IIx was chosen for its capacity for third-party add-on cards used in instrument control.

scholarly journals Inflammation, epigenetics, and metabolism converge to cell senescence and ageing: the regulation and intervention

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Xudong Zhu ◽  
Zhiyang Chen ◽  
Weiyan Shen ◽  
Gang Huang ◽  
John M. Sedivy ◽  
...  
Keyword(s):  
Cell Fate ◽  
Cellular Response ◽  
State Of The Art ◽  
Cell Senescence ◽  
Therapeutic Interventions ◽  
Cell Fate Decision ◽  
The Past ◽  
Fate Decision ◽  
The Individual ◽  
Remarkable Progress

AbstractRemarkable progress in ageing research has been achieved over the past decades. General perceptions and experimental evidence pinpoint that the decline of physical function often initiates by cell senescence and organ ageing. Epigenetic dynamics and immunometabolic reprogramming link to the alterations of cellular response to intrinsic and extrinsic stimuli, representing current hotspots as they not only (re-)shape the individual cell identity, but also involve in cell fate decision. This review focuses on the present findings and emerging concepts in epigenetic, inflammatory, and metabolic regulations and the consequences of the ageing process. Potential therapeutic interventions targeting cell senescence and regulatory mechanisms, using state-of-the-art techniques are also discussed.

scholarly journals Security assurance cases—state of the art of an emerging approach

2021 ◽  
Vol 26 (4) ◽  
Author(s):  
Mazen Mohamad ◽  
Jan-Philipp Steghöfer ◽  
Riccardo Scandariato
Keyword(s):  
State Of The Art ◽  
Tool Support ◽  
Security Assurance ◽  
The Past ◽  
Depth Analysis ◽  
Structured Argumentation ◽  
Security Properties ◽  
Standards And Regulations ◽  
Assurance Cases ◽  
Security Standards

AbstractSecurity Assurance Cases (SAC) are a form of structured argumentation used to reason about the security properties of a system. After the successful adoption of assurance cases for safety, SAC are getting significant traction in recent years, especially in safety-critical industries (e.g., automotive), where there is an increasing pressure to be compliant with several security standards and regulations. Accordingly, research in the field of SAC has flourished in the past decade, with different approaches being investigated. In an effort to systematize this active field of research, we conducted a systematic literature review (SLR) of the existing academic studies on SAC. Our review resulted in an in-depth analysis and comparison of 51 papers. Our results indicate that, while there are numerous papers discussing the importance of SAC and their usage scenarios, the literature is still immature with respect to concrete support for practitioners on how to build and maintain a SAC. More importantly, even though some methodologies are available, their validation and tool support is still lacking.

scholarly journals The state of the art in soybean transcriptomics resources and gene coexpression networks

2021 ◽  
Author(s):  
Fabricio Almeida-Silva ◽  
Kanhu C Moharana ◽  
Thiago M Venancio
Keyword(s):  
State Of The Art ◽  
The State ◽  
Gene Coexpression Network ◽  
Rna Seq ◽  
Transcriptomic Data ◽  
The Past ◽  
Gene Coexpression ◽  
Genomics Research ◽  
Public Repositories ◽  
Coexpression Networks

Abstract In the past decade, over 3000 samples of soybean transcriptomic data have accumulated in public repositories. Here, we review the state of the art in soybean transcriptomics, highlighting the major microarray and RNA-seq studies that investigated soybean transcriptional programs in different tissues and conditions. Further, we propose approaches for integrating such big data using gene coexpression network and outline important web resources that may facilitate soybean data acquisition and analysis, contributing to the acceleration of soybean breeding and functional genomics research.

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