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Effects of silt loading on turbulence and sand transport

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International Journal of Sediment Research 2012年第4期27卷 451-459页

作者： Daniel G.WREN roger A.kuhnle USDA-Agricultural Research Service-National Sedimentation Laboratory

The transport of bed material and fluid turbulence are affected by many factors,including the fine sediment load being carried in a *** research has focused on sand-sized particles introduced to gravel beds,while the effect of silt load on sand transport has received less attention. Experiments on the effects of silt load,in concentrations 0-26,900 mg l-1,on sand transport were performed with a recirculating laboratory flume using three different sand bed configurations:ripples （Fr=0.24）,dunes（Fr=0.34）,and dunes（Fr=0.48）.Three Acoustic Doppler Velocimeters were arranged to measure flow and turbulence quantities simultaneously in one *** transport did not change in a consistent manner with increasing silt load,increasing up to 4,000 mg l-1for dunes （Fr=0.48） and up to 2,000 mg l-1for dunes（Fr=0.34） and then declining to near the clear water case with increasing silt *** addition for the ripple case caused a relatively small change in sand transport,decreasing with added silt up to approximately 2,000 mg l-1and then increasing as silt went up to approximately 10,000 mg ***（Fr=0.48） decreased in length and height as silt increased,while dunes（Fr=0.34） did not show a consistent trend.A clear trend of decreasing Reynolds stress with increasing silt concentration was observed in the ripple case,with a 33% reduction in near-bed Reynolds stress caused by an 8,900 mg l-1concentration of silt.

关键词： Turbulence modulation Bedforms Dunes Sand transport Silt loading

Measurements of coupled fluid and sediment motion over mobile sand dunes in a laboratory flume

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International Journal of Sediment Research 2008年第4期23卷 329-337页

作者： Daniel G.WREN roger A.kuhnle Research Hydraulic Engineer USD A-ARS-National Sedimentation LaboratoryPh.D Research Hydraulic Engineer USD A-ARS-National Sedimentation Laboratory

The relationship between turbulent fluid motions and sediment particle motions over mobile sand dunes was investigated by using a laser Doppler velocimeter and an acoustic backscatter system in laboratory experiments performed at the USDA-ARS-National Sedimentation Laboratory. Profiles of acoustic backscatter from particles and at-a-point turbulence data were collected while translating both measurement devices downstream at the speed of mobile dune bedforms. The resulting data set was used to examine the frequency (recurrence frequency) at which the fluctuating backscatter and fluid velocity signals exceeded magnitude thresholds based on the standard deviation (σ) of the local velocity and the magnitude the acoustic signal resulting from backscatter from suspended particles. The slope of the downstream and vertical velocity recurrence frequencies generally indicated a gradually increasing recurrence time with increasing elevation. The recurrence frequency for acoustic backscatter data was not strongly variable with elevation. The closest correspondence between the recurrence frequencies of sediment backscatter and vertical velocities at the 1σ magnitude threshold was in a region defined by X/L<0.4 and y<6 cm. The downstream velocity was most closely related to backscatter in a small region at 0.4

关键词： Turbulence Suspended sediment Acoustic backscatter Dunes

Detailed bed topography and sediment load measurements for two stepdown flows in a laboratory flume

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International Journal of Sediment Research 2022年第3期37卷 287-298页

作者： Daniel Wren roger kuhnle Tate Mc Alpin David Abraham Keaton Jones United States Department of Agriculture Agricultural Research Service National Sedimentation Laboratory U.S.Army Research and Development Center Coastal and Hydraulics Laboratory

Streams and rivers, particularly smaller ones, often do not maintain steady flow rates for long enough to reach equilibrium conditions for sediment transport and bed topography. In particular, streams in small watersheds may be subject to rapidly changing hydrographs, and relict bedforms from previous high flows can cause further disequilibrium that complicates the prediction of sediment transport rates. In order to advance the understanding of how bedforms respond to rapid changes in flow rate, a series of flume experiments were performed where the flow was reduced rapidly from equilibrium *** transport rates and bed elevation data across the flume and over a 15-meter-long test section were collected during the experiments to allow detailed examination of evolving bedform dynamics. It was found that relict bedforms stopped moving completely after flow reductions, and the mode of sediment transport was shifted to small bedforms that arose rapidly over dune stoss sections throughout the test section. The changes in sediment transport with time as the sand bed adjusted to the new flow rate was found to agree with predictions based on the relations proposed in Wren et al.(2020). Wavelet analysis is used to visualize changes in length and amplitude scales during the bed transition process.

关键词： Sediment transport Bedforms Dunes Wavelets

SIMULTANEOUS SIDE BY SIDE VARIABILITY OF SEDIMENT CONCENTRATION OVER DUNES

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SIMULTANEOUS SIDE BY SIDE VARIABILITY OF SEDIMENT CONCENTRAT...

SEDIMENT TRANSPORT PROCESSES IN AGRICULTURAL WATERSHEDS

第九次河流泥沙国际学术大会

作者： roger Alan kuhnle ars.usda.gov Daniel Griffin WREN olemiss.edu National Sedimentation Laboratory USDA- Agricultural Research Service P. O. Box 1157 Oxford Mississippi U.S.A. rkuhnle National Center for Physical Acoustics University of Mississippi University Mississippi U.S.A. Email: dgwren

＜正＞A series of laboratory experiments were conducted in a laboratory flume to characterize the lateral variations of suspended sediment over dunes. Forty experimental runs were made using flow depths of 0.33m and 0.13 m in a 1.2 m wide flume channel. The Froude number was 0.5 and the median diameter of the bed material was 0.52 mm. Point samples and depth-integrated values calculated using acoustic backscatter data of suspended sediment were collected simultaneously at two lateral positions at spacings of 0.40m, 0.20m, 0.10m and 0.05 m. Mean absolute differences between the paired point samples were shown to increase and then level off to values of about 40 percent of the mean concentration as the lateral spacing between samples was increased. Mean absolute differences for paired depth-integrated samples had a similar pattern with values of 30% for the largest spacing. The information provided by this study has important implications for the testing of emerging techniques for measuring suspended sediment in fluvial environments.

关键词： Suspended sediment transport Lateral variation Dunes Sand

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International Journal of Sediment Research 2000年第2期 182-197页

作者： roger A. kuhnle Sean J. Bennett Carlos V. Alonso Ronald L. Bingner Eddy Langendoen(National Sedimentation Laboratory, U.S. Department of Agriculture, Agricultural Research Service, P.O. Box 1157,Oxford, Mississippi 38655, USA)

Determination of the total sediment load at selected points in agricultural Watersheds is important forevaltating the status of a land area. Total sediment load date allows the identification of problem areaswhere the land surface is eroding at rates too high to allow sustainable agriculture and/or is producingsediment at rales such that aquatic organisms in nearby streams will be adversely affected. Thedevelopment of effective sampling strategies and accurate computaional models requires accurateinformation on the processes by which sediment is transported. Researchers at the NationalSedimentation Laboratory are developing and testing new methods to measure and predict sedimentbospoft. These new methods are providing an improved understanding of the processes involved insediment transport and are leading to important advancements in the measurement and prediction ofsediment transport.

关键词： Total sediment load Sediment transport Sustainable agriculture Water quality Agricultural watershed

Heteronuclear Efimov resonances in ultracold quantum gases

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National Science Review 2016年第2期3卷 174-188页

作者： Juris Ulmanis Stephan Hfner Eva D.kuhnle Matthias Weidemller Physikalisches Institut Universitt Heidelberg Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics and CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum PhysicsUniversity of Science and Technology of China

The Efimov scenario is a universal three-body effect addressing many areas of modern quantum *** plays an important role in the transition between few- and many-body physics and has enabled important breakthroughs in the understanding of the universal few-body *** review the basic concepts of the Efimov scenario with specific emphasis on the similarities and differences between homonuclear and heteronuclear *** the latter scenario,the existence of a second,independently tunable interaction parameter enables novel few-body phenomena that are universal and have no counterexamples in the homonuclear *** discuss recent experimental approaches using ultracold atomic gases with magnetically tunable interactions and elucidate the role of short-range interactions in the emergence of universal and non-universal behavior.

关键词： Efimov resonances few-body physics Feshbach resonances ultracold atoms resonant scattering

PREDICTION OF THE GRAIN SIZE OF SUSPENDED SEDIMENT:IMPLICATIONS FOR CALCULATING SUSPENDED SEDIMENT CONCENTRATIONS USING SINGLE FREQUENCY ACOUSTIC BACKSCATTER

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International Journal of Sediment Research 2007年第1期22卷 1-15页

作者： R. A. kuhnle D. G. WREN J. P. CHAMBERS Dr.Research Hydraulic Engineer National Sedimentation Laboratory U. S. Department of Agriculture Agricultural Research Service Oxford Mississippi 38655 USA Senior Research Scientist National Center for Physical Acoustics University of Mississippi University Mississippi 38677 USA

Collection of samples of suspended sediment transported by streams and rivers is difficult and expensive. Emerging technologies, such as acoustic backscatter, have promise to decrease costs and allow more thorough sampling of transported sediment in streams and rivers. Acoustic backscatter information may be used to calculate the concentration of suspended sand-sized sediment given the vertical distribution of sediment size. Therefore, procedures to accurately compute suspended sediment size distributions from easily obtained river data are badly needed. In this study, techniques to predict the size of suspended sand are examined and their application to measuring concentrations using acoustic backscatter data are explored. Three methods to predict the size of sediment in suspension using bed sediment, flow criteria, and a modified form of the Rouse equation yielded mean suspended sediment sizes that differed from means of measured data by 7 to 50 percent. When one sample near the bed was used as a reference, mean error was reduced to about 5 percent. These errors in size determination translate into errors of 7 to 156 percent in the prediction of sediment concentration using backscatter data from 1 MHz single frequency acoustics.

关键词： Suspended sediment Grain size Acoustic backscatter Concentration errors

Tailoring molecular island shapes:influence of microscopic interaction on mesostructure

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Nano Research 2020年第3期13卷 843-852页

作者： Simon Aeschlimann Lu Lyu Benjamin Stadtmuller Martin Aeschlimann Angelika kuhnle Institute of Physical Chemistry Johannes Gutenberg University MainzDuesbergweg 10-14Mainz55099Germany Graduate School Materials Science in Mainz Staudingerweg 9Mainz55128Germany Department of Physics and Research Center OPTIMAS University of KaiserslauternErwin-Schrödinger-Straße 46Kaiserslautern67663Germany Graduate School Materials Science in Mainz Erwin-Schrodinger-Straße 46Kaiserslautern67663Germany Physical Chemistry I Faculty of ChemistryBielefeld UniversityUniversitätsstraße 25Bielefeld33615Germany

Controlling the structure formation of molecules on surfaces is fundamental for creating molecular nanostructures with tailored properties and functionalities and relies on tuning the subtle balance between intermolecular and molecule-surface *** far,however,reliable rules of design are largely lacking,preventing the controlled fabrication of self-assembled functional structures on *** addition,while so far many studies focused on varying the molecular building blocks,the impact of systematically adjusting the underlying substrate has been less frequently ***,we elucidate the potential of tailoring the mesoscopic island shape by tuning the interactions at the molecular *** a model system,we have selected the molecule dimolybdenum tetraacetate on three prototypical surfaces,Cu(111),Au(111)and CaF2(111).While providing the same hexagonal geometry,compared to Cu(111),the lattice constants of Au(111)and CaF2(111)differ by a factor of 1.1 and 1.5,*** high-resolution scanning probe microscopy images reveal molecular-level information on the resulting islands and elucidate the molecular-level design principles for the observed mesoscopic island *** study demonstrates the capability to tailor the mesoscopic island shape by exclusively tuning the substrate lattice constant,in spite of the very different electronic structure of the substrates *** work provides insights for developing general design strategies for controlling molecular mesostructures on surfaces.

关键词： scanning tunneling microscopy(STM) self-assembly island shape mesostmcture scanning probe microscopy(SPM) twodimensionBl structures

Fisheries statistics—— An importanttool for managers and scientists

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海洋水产研究 2001年第4期22卷 10-17页

作者： GretheAa.kuhnle DirectorateofFisheries Bergen

FISHERIES STATISTICS：AN IMPORTANT TOOL FORMANAGERSANDSCIENTISTS This presentation focuses on the type of information collected through fisheries statistics that could be useful to scientists and fisheries managers. In Norway the use of fisheries statistics as an analyzing tool for marine scientists can be dated back to around 1973. At that time the Directorate of Fisheries started to computerize information from logbooks of the trawl fleet. The fisheries managers started to use fisheries statistics as an analyzing tool by the late 1970's. Once again the computerization of sales notes information together with additional statistical information, enabled the manager to regroup the information according to new problems to be analyzed and new questions to be answered.

关键词：渔业统计渔业管理者科学家工具

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