scholarly journals An improved coupling model for water flow, sediment transport and bed evolution (CASFE v.1)

2014 ◽  
Vol 7 (2) ◽  
pp. 2429-2454
Author(s):  
S. He ◽  
W. Liu ◽  
X. Li ◽  
C. Ouyang
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Morphological Evolution ◽  
Coupling Model ◽  
Chinese Academy Of Sciences ◽  
Bed Evolution ◽  
The One ◽  
Volume Method ◽  
Academy Of Sciences ◽  
Sediment Mixtures

Abstract. This paper presents a new coupling model to simulate water flow, sediment transport and bed evolution based on the shallow water assumption, depth-average integration as well as the morphological evolution (Chinese Academy of Sciences flow-erosion model, CASFE). The model takes account of the effects of rainfall, entrainment and deposition on the motion of water–sediment mixtures. Limitations and drawbacks of other authors' models are pointed out according to the comparison among these models. The finite volume method has been adopted to solve the one-dimensional dam-break problem considering an erodible bed. Numerical results indicate that the model can adequately describe the complex dynamic problems. Simulation results demonstrate that the entrainment and deposition significantly affects the flow dynamics and morphological evolution.

scholarly journals Two-dimension coupling model to simulate water flow, sediment transport and bed evolution

2016 ◽  
Vol 48 (6) ◽  
pp. 1537-1553
Author(s):  
Wei Liu ◽  
Siming He ◽  
Qiang Xu
Keyword(s):  
Sediment Transport ◽  
Velocity Profile ◽  
Water Flow ◽  
Morphological Evolution ◽  
Fixed Bed ◽  
Coupling Model ◽  
Momentum Conservation ◽  
Two Dimension ◽  
Bed Evolution ◽  
Flow Mobility

Abstract Catastrophic flood events worldwide have become increasingly more frequent and their dynamics mechanism has attracted much interest as how to predict them by numerical method. As the most common phenomenon occurs in the flowing process, entrainment and deposition can significantly influence flow mobility by increasing in mass and changing in flow character. In this paper, a two-dimension coupling model is presented to simulate water flow, sediment transport and bed evolution based on the shallow water assumption, depth-averaged integration as well as morphological evolution. A new term accounting for the sediment effect on the momentum conservation of water–sediment mixture is added to the model equations by assuming that the flow and the fixed bed is connected by an infinitesimally thin boundary layer, in which the erodible material gains the necessary velocity to enter the flow above. Comparison of numerical results and experimental data indicate the presented model can adequately describe the complex dynamic process, sediment transport and bed evolution. The velocity profile of flow can influence the momentum transfer between the water column and the erodible bottom boundary due to sediment exchange, further influencing flow mobility. Moreover, the velocity profile of flow changes with variations of sediment concentration, bed surface and friction resistance.

scholarly journals The New Evolution for SIA Rotorcraft UAV Project

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Juntong Qi ◽  
Dalei Song ◽  
Lei Dai ◽  
Jianda Han ◽  
Yuechao Wang
Keyword(s):  
Control Method ◽  
Test Bed ◽  
Advanced Control ◽  
Autonomous Mode ◽  
Chinese Academy Of Sciences ◽  
Aerial Vehicle ◽  
Active Modeling ◽  
Rotorcraft Uav ◽  
The One ◽  
Academy Of Sciences

This paper describes recent research on the design, implement, and testing of a new small-scaled rotorcraft Unmanned Aerial Vehicle (RUAV) system—ServoHeli-40. A turbine-powered UAV weighted less than 15 kg was designed, and its major components were tested at the Shenyang Institute of Automation, Chinese Academy of Sciences in Shenyang, China. The aircraft was designed to reach a top speed of more than 20 mps, flying a distance of more than 10 kilometers, and it is going to be used as a test-bed for experimentally evaluating advanced control methodologies dedicated on improving the maneuverability, reliability, as well as autonomy of RUAV. Sensors and controller are all onboard. The full system has been tested successfully in the autonomous mode using the multichannel active modeling controller. The results show that in a real windy environment the rotorcraft UAV can follow the trajectory which was assigned by the ground control station exactly, and the new control method is obviously more effective than the one in the past year's research.

Beach-face evolution in the swash zone

2010 ◽  
Vol 661 ◽  
pp. 316-340 ◽  
Author(s):  
DAVID MATTHEW KELLY ◽  
NICK DODD
Keyword(s):  
Sediment Transport ◽  
Swash Zone ◽  
Full Coupling ◽  
Bed Evolution ◽  
Run Up ◽  
The One ◽  
Offshore Transport ◽  
Bed Mobility ◽  
Upper Third ◽  
Fully Coupled

We investigate swash on an erodible beach using the one-dimensional shallow-water equations fully coupled to a bed-evolution (Exner) equation. In particular, the dam-break/bore-collapse initial condition of Shen & Meyer (J. Fluid Mech., vol. 16, 1963, pp. 113–125) and Peregrine & Williams (J. Fluid Mech., vol. 440, 2001, pp. 391–399) is investigated using a numerical model based on the method of characteristics. A sediment-transport formula (cubic in velocity u: Au3) is used here; this belongs to a family of sediment-transport formulae for which Pritchard & Hogg (Coastal Engng, vol. 52, 2005, pp. 1–23) showed that net sediment transport under the Shen & Meyer (1963) bore collapse is offshore throughout the swash zone when a non-erodible bed is considered. It is found that full coupling with the beach, although still resulting in the net offshore transport of sediment throughout the swash zone, leads to a large reduction in the net offshore transport of sediment from the beach face. This is particularly true for the upper third of the swash zone. Moreover, in contradistinction to swash flows over non-erodible beds, flows over erodible beaches are unique to the bed mobility and porosity under consideration; this has very important implications for run-up predictions. The conclusion is that it is essential to consider full coupling of water and bed motions (i.e. full morphodynamics) in order to understand and predict sediment transport in the swash, regardless of other physical effects (e.g. turbulence, infiltration, pre-suspended sediment, etc.).

Construction of Alkylated Stereocenters

2017 ◽  
Author(s):  
Zara M. Seibel ◽  
Tristan H. Lambert
Keyword(s):  
Cross Coupling ◽  
Israel Institute ◽  
University Of Utah ◽  
Chinese Academy Of Sciences ◽  
Palladium Catalyzed ◽  
Institute Of Technology ◽  
Quaternary Stereocenters ◽  
The One ◽  
The University ◽  
Academy Of Sciences

Hirohisa Ohmiya and Masaya Sawamura at Hokkaido University reported (Angew. Chem. Int. Ed. 2013, 52, 5350) the copper-catalyzed, γ-selective allylation of terminal alkyne 1 to produce the chiral skipped enyne 3 with high ee. A method to synthe­size asymmetric skipped diene 6 via copper-catalyzed allylic allylation of diene 4 was developed (Chem. Commun. 2013, 49, 3309) by Ben L. Feringa at the University of Groningen. Prof. Feringa also disclosed (J. Am. Chem. Soc. 2013, 135, 2140) the regi­oselective and enantioselective allyl–allyl coupling of bromide 7 with allyl Grignard under Cu catalysis in the presence of phosphoramidite 8. James P. Morken of Boston College reported (Org. Lett. 2013, 15, 1432) the cross-coupling of allylboronate 11 with a mixture of alkenes 10a,b under palladium catalysis to produce diene 13 with high ee. Jian Liao at the Chengdu Institute of Biology Chinese Academy of Sciences and the University of Chinese Academy of Sciences reported (Angew. Chem. Int. Ed. 2013, 52, 4207) the palladium-catalyzed allylic alkylation of indole using the chi­ral bis(sulfoxide) phosphine ligand 15. Yi-Xia Jia at the Zhejiang University of Technology reported (J. Am. Chem. Soc. 2013, 135, 2983) the enantioselective alkyl­ation of indole to produce the trifluoromethyl adduct 19 using nickel catalysis in the presence of bisoxazoline ligand 18. Sarah E. Reisman at the California Institute of Technology disclosed (J. Am. Chem. Soc. 2013, 135, 7442) the reductive cross-coupling of acid chloride 20 and benzyl chloride 21 using a nickel complex with bisoxazoline ligand 22 and manganese(0) as reductant. Ilan Marek at the Technion-Israel Institute of Technology reported (Angew. Chem. Int. Ed. 2013, 52, 5333) a method for the construction of all-carbon quaternary stereocenters, such as the one present in aldehyde 25, using a diastereoselective car­bometallation of cyclopropene 24 followed by oxidation and ring opening. Switching from methyl Grignard and copper iodide to MeCuCNLi reverses the diastereoselec­tivity of the carbometallation and allows access to the opposite enantiomer. Matthew S. Sigman at the University of Utah reported (J. Am. Chem. Soc. 2013, 135, 6830) the redox–relay oxidative Heck arylation of alkenyl alcohol 27 with boronic acid 26 using a palladium catalyst and pyridine oxazole ligand 28 to produce the γ-substituted aldehyde 29.

scholarly journals The Design of Terahertz Monolithic Integrated Frequency Multipliers Based on Gallium Arsenide Material

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 336
Author(s):  
Jin Meng ◽  
Luwei Qi ◽  
Xiaoyu Liu ◽  
Jingtao Zhou ◽  
Dehai Zhang ◽  
...  
Keyword(s):  
Gallium Arsenide ◽  
Circuit Design ◽  
Design Method ◽  
Schottky Diodes ◽  
Frequency Multiplier ◽  
Frequency Multipliers ◽  
Chinese Academy Of Sciences ◽  
The One ◽  
Academy Of Sciences ◽  
Independent Design

A global design method for a terahertz monolithic integrated frequency multiplier is proposed. Compared with a traditional independent design, the method in this paper adopts overall optimization and combines the device with the circuit design. The advantage is that it provides a customized design for frequency multipliers according to specifications. On the basis of the gallium arsenide process of the Institute of Microelectronics, Chinese Academy of Sciences, two types of Schottky diodes have been developed to meet the needs of different designs. On the one hand, a Schottky diode with a 3 μm junction’s diameter was used in the design of the 200 GHz balanced doubler and, on the other hand, a diode with a 5 μm diameter was used in the 215 GHz unbalanced tripler. The measured results indicated that the output power of the doubler was more than 250 μW at 180~218 GHz, and the maximum was 950 μW at 198 GHz when driven with 12.3 mW, whereas that of the tripler was above 5 mW at 210~218 GHz and the maximum exceeded 10 mW. Such frequency multiplier sources could be widely used in terahertz imaging, radiometers, and so on.

Analysis and Evaluation of One-Way Time Service by Beidou Dual-Frequency Multichannel Receiver

2013 ◽  
Vol 718-720 ◽  
pp. 1234-1239
Author(s):  
Fan Yang ◽  
Hai Bo Yuan ◽  
Shao Wu Dong
Keyword(s):  
Dual Frequency ◽  
Time Service ◽  
Analysis And Evaluation ◽  
Chinese Academy Of Sciences ◽  
Geo Satellites ◽  
Precision Time ◽  
The One ◽  
Technology And Economy ◽  
Academy Of Sciences ◽  
Service Theory

High precision time plays a key role in technology and economy domain. as the time transmitting carrier, time service restricts timing precision of users. Combined with the characteristics of Beidou navigation system, the paper describes the one-way time service theory, accomplishes Beidou one-way timing algorithm and the software design. Finally, using the satellite data of Beidou dual-frequency multichannel receiver at the National Time Service Center (NTSC), the Chinese Academy of Sciences, the precision of Beidou one-way time service by the different types of satellites-GEO satellites, IGSO satellites, GEO combined with IGSO satellites-is analyzed and evaluated. The experiment result will provide important reference for optimizing the function of Beidou one-way time service.

Sign in / Sign up

Export Citation Format

Share Document