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Formulation of carbon black-ionomer dispersions for thin film formation in fuel cells

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Particuology 2019年第3期17卷 7-21页

作者： Eva hoffmann Su Zhang Martin Thoma Cornelia Damm Wolfgang Peukert Institute of Particle Technology (LFG) Friedrich-Alexander-Universitat Erlangen-Niimberg (FAU) CauerstraJSe 4 D-91058 Erlangen Germany

The performance of proton exchange membrane fuel cells (PEMFC) is strongly determined by the structure and composition of the electrode *** interactions between the ionomer,carbon black particles,and solvent affect the suspension properties and thus the layer *** analyze the effect of the ionomer-to-carbon (I/C) weight ratio for two different types of carbon black on the suspension and layer *** branched carbon blacks with a high surface area tend to form less cracked *** less branched carbons can pack together more closely,a smaller pore size results in a larger capillary pressure during drying and thus more *** added ionomer adsorbs on the carbon particles and improves the colloidal stability of the carbon black *** carbon black aggregates are thus smaller,resulting in closer packing and thinner ***,the addition of the ionomer increases the critical coating thickness (CCT) of the layers because drying stresses are dissipated by the deformation of the ionomer,preventing crack *** optimum I/C weight ratio is identified for optimal layer formation and minimized crack formation.

关键词： Perfluorosulfonic acid (PFSA) ionomer Carbon black Layer formation Cracking Porosity

Generation of Low Jitter Laser Diode Pulse With External Pulse Injection

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光学学报 2003年第S1期23卷 377-378页

作者： Olaf Reimann dieter Huhse dieter Bimberg Institute of Solid State Physics Technology University Berlin Germany Tel: 49-30-31322082Institute of Solid State Physics Technology University Berlin Germany Tel: 49-30-31322082Institute of Solid State Physics Technology University Berlin Germany Tel: 49-30-31322082

One gain-switched laser diode(LD) was used as external injection seeding source, to reduce the timing jitter of another gain-switched LD, This technique can generate low jitter, frequency-free and wavelength tunable l... 详细信息

关键词： were In of LD FP

High energy density physics with intense ion beams

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Matter and Radiation at Extremes 2016年第1期1卷 28-47页

作者： Boris Yu.Sharkov dieter H.H.hoffmann Alexander A.Golubev Yongtao Zhao FAIR GmbH:Facility for Antiproton and Ion Research in Europe GmbH PlanckstraBe 164291 DarmstadtGermany Institut fur Kernphysik Technische Universitat DarmstadtSchlossgartenstrasse 964289 DarmstadtGermany State Scientific Center Russian Federation e Institute for Theoretical and Experimental Physics of National Research Center“Kurchatov Institute”(SSC RF ITEP of NRC“Kurchatov Institute”) FSBI SSC RF ITEPBolshaya Cheremushkinskaya25117218 MoscowRussia School of Science Xi'an Jiaotong University and Institute of Modern PhysicsCASXianning West Road 28#Xi'an 710049PR China National Research Nuclear University MEPhI MoscowRussia National Research Nuclear University《MEPhI》Kashirskoe shosse31115409 MoscowRussia Institute of Modern Physics CASLanzhou 730000PR China

We review the development of High Energy Density Physics(HEDP)with intense heavy ion beams as a tool to induce extreme states of *** development of this field connects intimately to the advances in accelerator physics and *** will cover the generation of intense heavy ion beams starting from the ion source and follow the acceleration process and transport to the *** limitations and potential solutions to overcome these limitations are *** is exemplified by citing examples from existing machines at the Gesellschaft fur Schwerionenforschung(GSI-Darmstadt),the Institute of Theoretical and Experimental Physics in Moscow(ITEP-Moscow),and the Institute of Modern Physics(IMP-Lanzhou).Facilities under construction like the FAIR facility in Darmstadt and the High Intensity Accelerator Facility(HIAF),proposed for China will be *** elsewhere are covered where it seems appropriate along with a report of recent results and achievements.

关键词： High energy density physics Ion driven fusion Warm dense matter

Mortality of Australian alpine grasses (Poa spp.) after drought: species differences and ecological patterns

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Journal of Plant Ecology 2012年第2期5卷 121-133页

作者： Philippa C.Griffin Ary A.hoffmann Centre for Environmental Stress and Adaptation Research Department of GeneticsBio21 Institute30 Flemington RoadUniversity of MelbourneParkville 3010VictoriaAustralia

Aims Australian alpine ecosystems currently experience high precipitation in the snow-free season,but they are predicted to experience drier conditions under climate *** observed high mortality of the dominant alpine grasses following drought in *** aims were as follows:to test the involvement of plant-available water(PAW)and other environmental variables in grass mortality in the field;to detect possible species differences in drought response and to link soil moisture to precipitation using soil properties and climate *** The dominant tussock grasses of the Australian alpine zone,Poa hothamensis *** ***,Poa hiemata Vickery and Poa phillipsiana Vickery(Poaceae),all exhibited mortality following drought in the Bogong High Plains,Victoria,Australia in *** was calculated using soil water potential measurements,and past drought occurrence was modelled using climate *** then tested the effects of PAW and soil depth on grass survival both at a large spatial scale spanning the elevational range of the alpine zone and at a smaller *** hothamensis and *** were compared in a common-garden experiment to test drought *** Findings Poa hothamensis survival was predicted by dry-season PAW at the small spatial scale;at the large scale,soil depth and elevation were more important predictors of *** survival,but dry-season PAW predicted *** ***-garden experiments supported field observations that *** is more droughtsensitive than is *** also present a simple polynomial relationship between rainfall and field soil moisture,which predicts that the alpine soils dry below wilting point several times a *** suggest the timing of long rain-free periods may be more important than their duration.

关键词： climate change disturbance drought adaptation grassland

Genetic structure of the whitefly Bemisia tabaci populations in Colombia following a recent invasion

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Insect Science 2015年第4期22卷 483-494页

作者： Fernando Dfaz Nancy M. Endersby Ary A. hoffmann Department of Biology Universidad del Valle Cali Colombia Department of Genetics Pest and Disease Vector Group Bio 21 Institute University of Melboume Parkville Victoria 301 0 Australia

The whitefly Bemisia tabaci （Gennadius） is one of the most important pests causing economic losses in a variety of cropping systems around the world. This species was recently found in a coastal region of Colombia and has now spread inland. To investigate this invasive process, the genetic structure of B. tabaci was examined in 8 sampling locations from 2 infested regions （coastal, inland） using 9 microsatellite markers and the mitochondrial COI gene. The mitochondrial analysis indicated that only the invasive species of the B. tabaci complex Middle East-Asia Minor 1 （MEAM 1 known previously as biotype B） was present. The microsatellite data pointed to genetic differences among the regions and no isolation by distance within regions. The coastal region in the Caribbean appears to have been the initial point of invasion, while the inland region in the Southwest showed genetic variation among populations most likely reflecting founder events and ongoing changes associated with climatic and topographical heterogeneity. These findings have implications for tracking and managing B. tabaci.

关键词： Bemisia tabaci Colombia microsatellites Middle East-Asia Minor 1(MEAM 1) mtCOI population structure

Measurements of a 2-Stage Axial Turbine with Shrouded Rotor Cavities

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Journal of Thermal Science 2004年第4期13卷 310-314页

作者： dieter E. BOHN Franz KREITMEIER Michael SELL Institute of Steam and Gas Turbines Technical University of Aachen GermanyALSTOM Power CH-5401 Baden SwitzerlandALSTOM Power CH-5401 Baden Switzerland

This paper presents preliminary measurements of a 2-stage axial turbine with shrouded rotor cavities. The research facility and measurement techniques are reported. The flow field at both inlet and outlet was measured using 5-hole probes as well as temperature probes. The measurement results indicate that the inlet flow field is periodical in the tangential direction due to the influence of the first-stator leading-edge. The horse-shoe vortexes cause substantial flow blockage and turbulence near the endwall. Unsteady measurements of the rotor radial tip clearance show that one of the second-rotor blades has a little bigger clearance than the others.

关键词： axial turbine shrouded rotor measurement.

A note on circle packing

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Journal of Zhejiang University-Science C(Computers and Electronics) 2012年第8期13卷 559-564页

作者： Young Joon AHN Christoph M. hoffmann Paul ROSEN Department of Mathematics Education Chosun University Gwangju 501-759 Korea Department of Computer Science Purdue University West Lafayette IN 47907 USA Scientific Computing and Imaging Institute University of Utah Salt Lake City UT 84112 USA

The problem of packing circles into a domain of prescribed topology is considered. The circles need not have equal radii. The Collins-Stephenson algorithm computes such a circle packing. This algorithm is parMlelized in two different ways and its performance is reported for a triangular, planar domain test case. The implementation uses the highly parallel graphics processing unit （GPU） on commodity hardware. The speedups so achieved are discussed based on a number of experiments.

关键词： Circle packing Algorithm performance Parallel computation Graphics processing unit (GPU)

An Approximate Riemann Solver for Advection-Diffusion Based on the Generalized Riemann Problem

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Communications on Applied Mathematics and Computation 2020年第3期2卷 515-539页

作者： Steven Jöns Claus-dieter Munz Institute of Aerodynamics and Gas Dynamics University of StuttgartPfafenwaldring 2170569 StuttgartGermany

We construct an approximate Riemann solver for scalar advection-diffusion equations with piecewise polynomial initial *** objective is to handle advection and diffusion simultaneously to reduce the inherent numerical diffusion produced by the usual advection flux *** approximate solution is based on the weak formulation of the Riemann problem and is solved within a space-time discontinuous Galerkin approach with two *** novel generalized Riemann solver produces piecewise polynomial solutions of the Riemann *** conjunction with a recovery polynomial,the Riemann solver is then applied to define the numerical flux within a finite volume *** results for a piecewise linear and a piecewise parabolic approximation are *** results indicate a reduction in numerical dissipation compared with the conventional separated flux calculation of advection and ***,it is shown that using the proposed solver only in the vicinity of discontinuities gives way to an accurate and efficient finite volume scheme.

关键词： Generalized Riemann problem Advection-diffusion Discontinuous Galerkin Numerical flux ADER Diffusive generalized Riemann problem Space-time solution Recovery method

Tuning thermal release kinetics of soy oil from organic nanoparticles using variable synthesis conditions

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Particuology 2016年第3期14卷 54-65页

作者： Pieter Samyn dieter Van Nieuwkerke Vibhore Rastogi Dirk Stanssens University of Freiburg Freiburg Research Institute for Advances Studies (FRIAS) Faculty for Environment and Natural Resources Chair of Bio-based Materials Engineering Werthmannstrasse 6 D-79085 Freiburg Germany Ghent University Department of Textiles Technologiepark 907 B-9052 Zwijnaarde Belgium Topehim N.K Nijverheidsstraat 98 B-2160 Wommelgem Belgium

The thermal release properties of soy oil from poly（styrene-co-maleimide） nanoparticles containing 50 wt% encapsulated oil have been quantified as a function of temperature and time. The effects of dif- ferent synthesis conditions on the thermal stability of the nanoparticles and their oil release have been evaluated, i.e., by gradually increasing the amount of ammonium hydroxide used for the imidization of poly（styrene-co-maleic anhydride）. First, the intrinsic thermal properties of the oil-filled nanoparti- cles were analysed by differential scanning calorimetry, which revealed an exothermal reaction related to the oil release and a suppression of the glass transition that may be masked owing to the complex structure of the hybrid nanoparticles. The isothermal scans showed different rates of oil release after a post-imidization reaction. The oil release was better followed by dynamic mechanical analysis, which illustrated changes in visco-elastic properties expressed by the maximum in the loss factor that related to the amount of released oil. Depending on the amount of ammonium hydroxide, the oil started to release below the glass transition temperature at various rates. Thermal release profiles of the oil we re quantified by infrared and Raman spectrocopy after heating for 2 min to 6 h at 125 to 250 ℃, based on variations in oil-related and imide-related absorption bands. The oil release increased below and above the glass transition temperature, following a parabolic trend, and progressively decreased at higher ammonium hydroxide concentrations, in parallel with higher imide content and changes in imide conformation. The kinetics and mechanism of the oil release can be described by the Korsmeyer-Peppas model, suggesting a dominating diffusion mechanism that is influenced by further imidization of the polymer matrix during heating.

关键词： Soy oil Nanoparticle Encapsulation Release