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CFD-DEM simulation of turbulence modulation in horizontal pneumatic conveying

Particuology 2017年第2期15卷 15-24页

作者： Mohammadreza Ebrahimi martin Crapper Institute for Infrastructure and Environment School of Engineering The University of Edinburgh The King's Buildings Edinburgh EH9 3JL UK Department of Mechanical and Construction Engineering Northumbria University Ellison Place Newcastle-upon-Tyne NE1 8ST UK

A study is presented to evaluate the capabilities of the standard k–ε turbulence model and the k–ε turbulence model with added source terms in predicting the experimentally measured turbulence modulation due to the presence of particles in horizontal pneumatic conveying, in the context of a CFD–DEM Eulerian–Lagrangian simulation. Experiments were performed using a 6.5-m long, 0.075-m diameter horizontal pipe in conjunction with a laser Doppler anemometry （LDA） system. Spherical glass beads with two sizes, 1.5 and 2 mm, were used. Simulations were performed using the commercial discrete element method software EDEM, coupled with the computational fluid dynamics package FLUENT. Hybrid source terms were added to the conventional k–ε turbulence model to take into account the influence of the dispersed phase on the carrier phase turbulence intensity. The simulation results showed that the turbulence modulation depends strongly on the model parameter Cε3. Both the standard k–ε turbulence model and the k–ε turbulence model with the hybrid source terms could predict the gas phase turbulence intensity trend only generally. A noticeable discrepancy in all cases between simulation and experimental results was observed, particularly for the regions close to the pipe wall. It was also observed that in some cases the addition of the source terms to the k–ε turbulence model did not improve the simulation results when compared with those of the standard k–ε turbulence model. Nonetheless, in the lower part of the pipe where particle loading was greater due to gravitational effects, the model with added source terms performed somewhat better.

关键词： Turbulence modulation Pneumatic conveying Eulerian-Lagrangian approach Laser Doppler anemometry

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A force-compensated compliant MEMS-amplifier with electrostatic anti-springs

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Microsystems & Nanoengineering 2023年第3期9卷 235-244页

作者： Philip Schmitt martin Hoffmann Microsystems Technology Ruhr-Universität BochumUniversitätsstr.15044801 BochumGermany

In this paper,an electrostatic compliant mechanical amplifier intended for force-compensated displacement amplification in MEMS sensor applications is ***,mechanical transformers that enhance a small input displacement into a large output displacement generate large forces at the input of the *** microsystem proposed here allows for the reduction and compensation of the input stiffness of the amplifier and any mechanical components connected to it while providing a constant amplification ratio at the same *** amplifying mechanism features bidirectional electrostatic anti-springs enabling the control of the stiffness by applying a constant DC *** electrode design of the anti-springs and its influence on the force-displacement characteristic,the side instability and the maximal displacement are studied through analytical approaches and supported by FEA and by *** on the derived models,a compliant electromechanical amplifier is developed,featuring an amplification ratio of *** this amplifier the initial input stiffness of 422 N/m could be reduced to 6.8 N/m by applying a voltage of 100 *** an additional application,we show how the amplifier can be used as a mechanical force sensor with tuneable sensitivity,where the forces at the input are transformed into large output *** experiments,we show how the sensitivity can be adjusted and increased by a factor of 25 by applying a voltage at the anti-springs.

关键词： amplifier electrostatic spring

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Froth flotation of scheelite – A review

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International Journal of Mining Science and Technology 2018年第3期28卷 373-384页

作者： Nathalie Kupka martin Rudolph Helmholtz Zentrum Dresden Rossendorf (HZDR) Helmholtz Institute Freiberg for Resource Technology (HIF)

Froth flotation of scheelite has regained new focus since the 2010s and research regarding floatability and reagents has made great progress over the years. The main objective was and remains the selective flotation of scheelite from other calcium-bearing minerals, in particular calcite, fluorite and apatite. Due to similar properties, most attempts have limited success or only specific application(linked to a type of ore or a location). This article aims at reviewing all general physical-chemical information on froth flotation of scheelite, including electrokinetic properties, influence of p H and already existing reagents as well as ones still under examination. It appears that chelating or mixed collectors and modified versions of sodium silicate and quebracho hold great promise for scheelite flotation, while the use of said depressants and/or promoters seems inevitable.

关键词： Scheelite Froth flotation Calcium-bearing minerals Selectivity challenges Promising reagents

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MODELING SOCCER BY MEANS OF RELATIVE PHASE

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Journal of Systems Science & Complexity 2013年第1期26卷 14-20页

作者： SIEGLE Malte LAMES martin TU Munchen Department for Training and Computer Science in Sports

Soccer is a complex ***,appropriate(nontrivial) models have to be applied to be able to analyze the behavior of the teams on the *** study analyzed the World Cup Final 2006 between France and Italy by means of relative *** longitudinal and lateral positions of all 20 outfield players were used to calculate relative phase by Hilbert *** team-,group-,and attacker-fullbacks couplings showed that soccer is clearly an in-phase *** of the relative phase structure helped to identify scoring opportunities of the attacking ***,analyses of the relative phase structure can help to understand the complexity of soccer.

关键词： Perturbations relative phase soccer.

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Using the DEM-CFD method to predict Brownian particle deposition in a constricted tube

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Particuology 2014年第4期12卷 94-106页

作者： Florian Chaumeil martin Crapper School of Engineering The University of EdinburghEdinburgh EH9 3JLUnited Kingdom

Modelling of the agglomeration and deposition on a constricted tube collector of colloidal size particles immersed in a liquid is investigated using the discrete element method （DEM）. The ability of this method to represent surface interactions allows the simulation of agglomeration and deposition at the particle scale. The numerical model adopts a mechanistic approach to represent the forces involved in colloidal suspensions by including near-wall drag retardation, surface interaction and Brownian forces. The model is implemented using the commercially available DEM package EDEM 2.3~, so that results can be repli- cated in a standard and user-friendly framework. The effects of various particle-to-collector size ratios, inlet fluid flow-rates and particle concentrations are examined and it is found that deposition efficiency is strongly dependent on the inter-relation of these parameters. Particle deposition and re-suspension mechanisms have been identified and analyzed thanks to EDEM＇s post processing capability. One-way coupling with computational fluid dynamics （CFD） is considered and results are compared with a two- way coupling between EDEM 2.3 and FLUENT 12.1. It is found that two-way coupling requires circa 500% more time than one-way coupling for similar results.

关键词： Discrete element method DEM Colloids Agglomeration Deposition Simulation

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Enhanced nitric oxide production is a universal response to hypoxic stress

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National Science Review 2018年第4期5卷 532-533页

作者： martin Feelisch Clinical & Experimental Sciences and Integrative Physiology and Critical Illness Group Faculty of Medicine Southampton General Hospital and Institute for Life Sciences University of Southampton NSR

Life at high altitude poses a formidable challenge to human physiology because every breath of thin air inhaled contains less oxygen(O2)per volume than air at sea level,causing the resultant drop in O2 pressure in blood to limit performance and threaten *** short-term adjustments to hypoxia(acclimatization)including increased erythropoiesis ensure total

关键词： Enhanced nitric oxide production is a universal response to hypoxic stress

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Artificial versus Natural Reuse of CO2 for DME Production：Are We Any Closer？

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Engineering 2017年第2期3卷 166-170页

作者： Mariano martin Department of Chemical Engineering University of Salamanca Salamanca 37008 Spain

This work uses a mathematical optimization approach to analyze and compare facilities that either capturecarbon dioxide （CO2） artificially or use naturally captured COs in the form of lignocellulosic biomass towardthe production of the same product, dimethyl ether （DME）. In nature, plants capture COs via photosynthesisin order to grow. The design of the first process discussed here is based on a superstructure optimizationapproach in order to select technologies that transform lignocellulosic biomass into DME. Biomass is gas-ified; next, the raw syngas must be purified using reforming, scrubbing, and carbon capture technologiesbefore it can be used to directly produce DME. Alternatively, CO2 can be captured and used to produce DMEvia hydrogenation. Hydrogen （H2） is produced by splitting water using solar energy. Facilities based on bothphotovoltaic （PV） solar or concentrated solar power （CSP） technologies have been designed; their monthlyoperation, which is based on solar availability, is determined using a multi-period approach. The currentlevel of technological development gives biomass an advantage as a carbon capture technology, since bothwater consumption and economic parameters are in its favor. However, due to the area required for growingbiomass and the total amount of water consumed （if plant growing is also accounted for）, the decision to use biomass is not a straightforward one.

关键词： Solar energy Photovoltaic Concentrated solar power Biomass Water electrolysis Dimethyl ether

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Stable analysis on speed-adaptive observer in regenerating mode

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Science China(Technological Sciences) 2012年第1期55卷 213-222页

作者： OUYANGYi MAERZ martin Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China Institute for Integrated Systems and Device Technology ofFraunhofer Erlangen 91058 Germany

Speed-adaptive full-order flux observer is the most promising flux estimator among all the sensorless control ***,conventional speed-adaptive flux observer becomes unstable during regenerating operation at low speed since induction motor is an observable system except dc ***,the instability problem is caused by inappropriate designing of *** on the eigenvalues of extended observer,this paper interprets unstable situation,that the eigenvalues of extended ob-server have a positive real ***,the observer cannot *** the two different solutions for unstable prob-lem-positive real maintaining and current error augment,the proposed method based on the eigenvalue could unify these two solutions,which gives the complete stability condition for speed-adaptive full-order *** does a lot help in observer *** observer configured by this proposed method was verified in the torque controlling of 20 kW induction *** to the experiment result,with appropriate designing of observer,the unstable situation during regeneration mode could be completely overcome.

关键词： sensorless control field orientation induction motor drives instability regenerating mode

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The pH of the Apoplast： Dynamic Factor with =unctional Impact Under Stress

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Molecular Plant 2017年第11期10卷 1371-1386页

作者： Christoph-martin Geilfus Division of Controlled Environment Horticulture Faculty of Life Sciences Albrecht Daniel Thaer-Institute of Agricultural and Horticultural Sciences Humboldt-University of Berlin Albrecht-Thaer-Weg 1 14195 Berlin Germany

The apoplast is an interconnected compartment with a thin water-film that alkalinizes under stress. This systemic pH increase may be a secondary effect without functional implications, arising from ion movements or proton-pump regulations. On the other hand, there are increasing indications that it is part of a mechanism to withstand stress. Regardless of this controversy, alkalinization of the apoplast has received little attention. The apoplastic pH （PHapo） increases not only during plant-pathogen interactions but also in response to salinity or drought. Not much is known about the mechanisms that cause the leaf apoplast to alkalinize, nor whether, and if so, how functional impact is conveyed. Controversial explanations have been given, and the unusual complexity of pHapo regulation is considered as the primary reason behind this lack of knowledge. A gathering of scattered information revealed that changes in PHapo convey functionality by regulating stomatal aperture via the effects exerted on abscisic acid. Moreover, apoplastic alkalinization may regulate growth under stress, whereas this needs to be verified. In this review, a comprehensive survey about several physiological mechanisms that alkalize the apoplast under stress is given, and the suitability of apoplastic alkalinization as transducing element for the transmission of sensory information is discussed.

关键词： apoplastic fluid alkalinization abscisic acid PM-H^+-ATPase S-Type anion channel malate

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Adaptive optical microscopy: the ongoing quest for a perfect image

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Light(Science & Applications) 2014年第1期3卷 243-249页

作者： martin J Booth Department of Engineering Science University of OxfordOxford OX13PJUK Centre for Neural Circuits and Behaviour University of OxfordOxford OX13SRUnited Kingdom School in Advanced Optical Technologies Friedrich-Alexander Universita¨t Erlangen-Nu¨rnberg91052 ErlangenGermany

Adaptive optics is becoming a valuable tool for high resolution microscopy,providing correction for aberrations introduced by the refractive index structure of *** is proving particularly promising for applications that require images from deep within biological tissue *** review recent developments in adaptive microscopy,including methods and applications.A range of advances in different microscope modalities is covered and prospects for the future are discussed.

关键词： aberrations adaptive optics microscopy

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