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Influence of rolling friction on single spout fluidized bed simulation

Particuology 2012年第5期10卷 582-591页

作者： Christoph goniva Christoph Kloss Niels g. Deen johannes A.M.Kuipers stefan Pirker Christian-Doppler Laboratory on Particulate Flow Modelling Johannes Kepler UniversityLinz Austria DCS Computing gmbH Linz Austria Christian-Doppler Laboratory on Particulate Flow Modelling Johannes Kepler UniversityLinz Austria Department of Chemical Engineering and Chemistry Eindhoven University of TechnologyEindhovenThe Netherlands Department of Chemical Engineering and Chemistry Eindhoven University of TechnologyEindhovenThe Netherlands Christian-Doppler Laboratory on Particulate Flow Modelling Johannes Kepler UniversityLinzAustria Institute of Fluid Mechanics and Heat Transfer Johannes Kepler UniversityLinzAustria

In this paper we study the effect of rolling friction on the dynamics in a single spout fluidized bed using Discrete Element Method （DEM） coupled to Computational Fluid Dynamics （CFD）. In a first step we neglect rolling friction and show that the results delivered by the open source CFD-DEM framework applied in this study agree with previous simulations documented in literature. In a second step we include a rolling friction sub-model in order to investigate the effect of particle non-sphericity. The influence of particle-particle as well as particle-wall rolling friction on the flow in single spout fluidized bed is studied separately. Adequate rolling friction model parameters are obtained using first principle DEM simulations and data from literature. Finally, we demonstrate the importance of correct modelling of rolling friction for coupled CFD-DEM simulations of spout fluidized beds. We show that simulation results can be improved significantly when applying a rolling friction model, and that experimental data from literature obtained with Positron Emission Particle Trackin~ fPEPT） technique can be satisfactorily reoroduced.

关键词： CFD-DEMOpen sourceRolling frictionSpout fluidized bedNon-sphericity

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Actuation of Liquid Flow by guided Acoustic Waves on Punched Steel Tapes with Protruding Loops

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Journal of Bionic Engineering 2021年第3期18卷 534-547页

作者： Alexander Backer johannes Landskron Klaus stefan Drese gerhard Lindner Institute of Sensor and Actuator Technology Coburg University of Applied Sciences and Arts96450 CoburgGermany

In a biomimetic approach the feasibility of liquid flow actuation by vibrating protruding structures excited via guided acoustic waves is *** by periodically beating cilia the loop part of a punched metallic hook-and-loop tape with tilted protruding loops was used as a waveguide for plate waves in *** waves were excited in the frequency range of 110 Hz to 220 Hz by directly coupling the tape to a loudspeaker membrane.A flow generated in the tilt direction of the loops with velocities up to 60 mm s 1 was visualized by ink droplets deposited on the *** phenomenon persisted,when the protruding length of the loops was reduced by decreasing the protrusion ***,after closing the punch holes near the loops with sticking tape streaming could not be observed any *** same happened with open punch holes when the ink was replaced by ***-frequency acoustic streaming around vibrating sharp edges is proposed as an explanation for the observed *** are expected with respect to the modification of flow profiles and the enhancement of transport processes along and across liquid-solid boundaries.

关键词： bio-inspired guided acoustic waves metallic hook-and-loop tape artificial cilia liquid propulsion Copyright

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Routing through open spaces-A performance comparison of algorithms

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geo-Spatial Information Science 2018年第3期21卷 247-256页

作者： stefan Hahmann Jakob Miksch Bernd Resch johannes Lauer Alexander Zipf gIScience Research group Institute of GeographyHeidelberg UniversityHeidelbergGermany Fraunhofer IVI Fraunhofer Institute for Transportation and Infrastructure SystemsDresdenGermany Department of geoinformatics-Z_gIS University of SalzburgAustria Center for geographic Analysis Harvard UniversityCambridgeMAUSA HERE gmbH&Co Kg Schwalbach am TaunusGermany

Finding the shortest path through open spaces is a well-known challenge for pedestrian routing engines.A common solution is routing on the open space boundary,which causes in most cases an unnecessarily long route.A possible alternative is to create a subgraph within the open *** paper assesses this approach and investigates its implications for routing engines.A number of algorithms(grid,Spider-grid,Visibility,Delaunay,Voronoi,Skeleton)have been evaluated by four different criteria:(i)Number of additional created graph edges,(ii)additional graph creation time,(iii)route computation time,(iv)routing *** show that each algorithm has advantages and disadvantages depending on the use *** identify the algorithms Visibility with a reduced number of edges in the subgraph and Spider-grid with a large grid size to be a good compromise in many scenarios.

关键词： OpenStreetMap routing open space navigation pedestrian polygon

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Pneumothorax in a Thiel cadaver model of cardiopulmonary resuscitation

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World Journal of Emergency Medicine 2023年第2期14卷 143-147页

作者： Daniel Auinger Simon Orlob johannes Wittig gabriel Honnef stefan Heschl georg Feigl gerhard Prause Division of Anaesthesiology and Intensive Care Medicine 1 Department of Anaesthesiology and Intensive Care MedicineMedical University of GrazGraz 8036Austria Division of Anaesthesiology and Intensive Care Medicine 2 Department of Anaesthesiology and Intensive Care MedicineMedical University of GrazGraz 8036Austria Medical University of graz Graz 8036Austria Research Center for Emergency Medicine Aarhus University HospitalAarhus 8200Denmark Department of Medicine Randers Regional HospitalRanders 8930Denmark Chair of Macroscopic and Clinical Anatomy Gottfried Schatz Research CenterMedical University of GrazGraz 8036Austria Institute of Morphology and Clinical Anatomy Faculty of Health/School of MedicineWitten/Herdecke UniversityWitten 58448Germany

INTRODUCTION There has been some previous research in the field of cardiopulmonary resuscitation (CPR) using cadaver models.[1]The Thiel method was developed by Professor Walter Thiel (graz, Austria) and described in 1992 and 2002. It consists of both an intravascular injection of the embalming solution and submersion of the bodies in a tank with the same solution for a determined period.[2,3]

关键词： Walter cardiopulmonary bal

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Exposing the urban continuum:implications and crosscomparison from an interdisciplinary perspective

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International Journal of Digital Earth 2020年第1期13卷 22-44页

作者： johannes H.Uhl Hamidreza Zoraghein stefan Leyk Deborah Balk Christina Corbane Vasileios Syrris Aneta JFlorczyk Department of geography University of Colorado BoulderBoulderCOUSA National Center for Atmospheric Research(NCAR) BoulderCOUSA CUNY Institute for Demographic Research and Baruch College City University of New YorkNew York CityNYUSA European Commission Joint Research Centre(JRC)IspraItaly

There is an increasing availability of geospatial data describing patterns of human settlement and population such as various global remote-sensing based built-up land layers,fine-grained census-based population estimates,and publicly available cadastral and building footprint *** development constitutes new integrative modeling opportunities to characterize the continuum of urban,peri-urban,and rural settlements and ***,little research has been done regarding the agreement between such data products in measuring human presence which is measured by different proxy variables(*** of built-up structures derived from different remote sensors,census-derived population counts,or cadastral land parcels).In this work,we quantitatively evaluate and cross-compare the ability of such data to model the urban continuum,using a unique,integrated validation database of cadastral and building footprint data,*** data,and three different versions of the global Human Settlement Layer(gHSL)derived from remotely sensed *** identify advantages and shortcomings of these data types across different geographic settings in the U.S.,which will inform future data users on implications of data accuracy and suitability for a given application,even in data-poor regions of the world.

关键词： Built-up surfaces global Human Settlement Layer(gHSL) Sentinel-1 Landsat agreement assessment urban modeling cadastral parcel data U.S.census data

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Assessment of agri-spillways as a soil erosion protection measure in Mediterranean sloping vineyards

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Journal of Mountain Science 2017年第6期14卷 1009-1022页

作者： Jesus RODRIgO-COMINO stefan WIRTZ Eric C. BREVIK Jose D.RUIZ-SINOgA johannes B.BIES Instituto de geomorfologfa y Suelos Department of Geography University of Malaga 29071 Malaga Spain Physical geography Trier University 542-85 Trier Germany Department of Natural Sciences 291 Campus Drive Dickinson State University Dickinson ND 58601 USA

Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to protect the soil in Mediterranean sloping vineyards(>25° of slope inclination). In the vineyards of the Montes de Málaga(southern Spain), a sustainable land management practice that controls soil erosion is actually achieved by tilling rills in the down-slope direction to canalize water and sediments. Because of their design and use, we call them agri-spillways. In this research, we assessed two agri-spillways(between 10 m and 15 m length, and slopes between 25.8° and 35°) by performing runoff experiments under extreme conditions(a motor driven pump that discharged water flows up to 1.33 l s^(-1) for 12 to 15 minutes: ≈1000 l). The final results showed: i) a great capacity by these rills to canalize large amounts of water and sediments; and, ii) higher water flow speeds(between 0.16 m s-1 and 0.28 m s^(-1)) and sediment concentrationrates(up to 1538.6 g l^(-1)) than typically found in other Mediterranean areas and land uses(such as badlands, rangelands or extensive crops of olives and almonds). The speed of water flow and the sediment concentration were much higher in the shorter and steeper rill. We concluded that agri-spillways, given correct planning and maintenance, can be a potential solution as an inexpensive method to protect the soil in sloping Mediterranean vineyards.

关键词： Agri-spillway Vineyards Runoff experiment Soil erosion Water discharge

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Transport in graphene nanostructures

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Frontiers of physics 2011年第3期6卷 271-293页

作者： Christoph Stampfer stefan Fringes johannes gfittinger Francoise Molitor Christian Yolk Bernat Terrds Jan Dauber Stephan Engels stefan Schnez Arnhild Jacobsen Susanne Droscher Thomas Ihn Klaus Ensslin JARA-FIT and II. Institute of Physics B RWTH Aachen University 52074 Aachen and Peter Griinberg Institute （PCI-9） Forschungszentrum Jiilich 52425 Jiilich Germany Solid State Physics Laboratory ETH Zurich 8093 Zurich Switzerland

graphene nanostructures are promising candidates for future nanoelectronics and solid-state quan- tum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching ＂paper-cutting＂ technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including dou- ble quantum dots. These quasi-one-dimensional （nanoribbons） and quasi-zero-dimensional （quantum dots） graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, wo emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperflne interaction in graphene.

关键词： graphene nanostructures electron transport quantum dots

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Hopf algebras and Dyson-Schwinger equations

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Frontiers of physics 2016年第3期11卷 161-177页

作者： stefan Weinzierl PRISMA Cluster of Excellence Institut fiir Physik Johannes Gutenberg- Universitiit Mainz D - 55099 Mainz Germany

In this paper I discuss Hopf algebras and Dyson-Schwinger equations. This paper starts with an introduction to Hopf algebras, followed by a review of the contribution and application of Hopf algebras to particle physi... 详细信息

关键词： Feynman integrals Hopf algebras Dyson-Schwinger equations

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geomorphologic and Hydrogeologic Characteristics of Populated Rockslide Deposits (Sagarmatha National Park, Khumbu Himal, Nepal)

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Journal of Water Resource and Protection 2015年第13期7卷 1038-1048页

作者： Joachim gö tz johannes Thomas Weidinger stefan Kraxberger Anne-Lise Hennecke johannes Buckel Basanta Raj Adhikari Department of geography and geology University of Salzburg Salzburg Austria Erkudok-Institute K-Hof-Museums of Gmunden Gmunden Austria Department of Civil Engineering Tribhuvan University Kathmandu Nepal

Surface morphology and internal composition of large rockslide deposits have been frequently studied, but their hydrogeologic conditions and consequences for (drinking) water quality and quantity on such deposits are largely unknown. In this study we provide first information on this critical relationship for two large rockslide deposits in the Khumbu Himal (Nepal), which are at the same time the main settlement areas in the region. In the first step, we investigated the Lukla and the Namche-Khumjung rockslides with respect to their dimensions and internal composition based on orthophotos and digital elevation models, geomorphologic field mapping, and the analysis of rockslide outcrops. Secondly, we studied their hydrogeologic characteristics by means of spring water mapping, sampling and analyses. As a consequence of the fragmented and highly shattered rockslide material, both deposits are characterized by 1) effective infiltration, 2) short residence times of percolating water and 3) by only small amounts of available spring water and surface runoff at all. Human activity on the studied rockslide deposits can therefore be described as an ambivalent relationship: On the one hand, the rockslide deposits provide a gentle topography and the only available areas for extensive settlements and agriculture in the steep upper DudhKosi catchment;On the other hand, their internal composition accounts for water scarcity—a critical issue for the local population demanding for adaptation strategies, especially in the light of the ever—increasing trekking and expedition tourism in the region.

关键词： Khumbu Himal geomorphologic and Hydrogeologic Mapping Rockslide Morphology Rockslide Hydrology Water Scarcity

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Simulation of spray coating in a spouted bed using recurrence CFD

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Particuology 2019年第1期17卷 92-103页

作者： Paul Kieckhefena Thomas Lichtenegger Swantje Pietsch stefan Pirker stefan Heinrich Institute of Solids Process Engineering and Particle Technology Hamburg University of Technology. HamburgGermany Department for Particulate Flow Modelling. johannes Kepler University LinzAustria Linz Institute of Technology (LIT) Johannes Kepler UniversityLinzAustria

Although numerical models such as the computational fluid dynamics–discrete element method (CFD–DEM) have enabled the accurate simulation of laboratory-scale apparatuses, the application of these methods to large-scale apparatuses with many particles and time scales ranging from minutes to hours remains a challenge. The recently developed recurrence CFD (rCFD) method seeks to overcome these issues in pseudo-periodic processes by extrapolating globally recurring patterns in a physically meaningful way and describing the transport and interaction of passive scalars using Lagrangian tracers. Spouted beds represent an interesting target because of the associated variety of flow regimes. They can be effectively described by CFD–DEM on the time scale of tens of seconds, whereas industrially relevant processes typically take hours. In this contribution, we established the validity of applying the Lagrangian rCFD method to spouted beds by demonstrating the accurate reproduction of the particle residence time distribution in a fictitious spray zone. The deposition of spray droplets onto tracer particles was simulated for 1 h, and the particle surface coverage distribution was estimated using a statistical approach for both an unstabilized prismatic spouted bed and one stabilized by draft plates.

关键词： CFD–DEM Recurrence CFD Spray coating Time-scale decoupling Spouted bed Draft plate

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