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Influence of water evaporation on elastohydrodynamic lubrication with water-containing polyalkylene glycols

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Friction 2024年第10期12卷 2370-2388页

作者： stefan HOFMANN Thomas LOHNER Karsten STAHL Technical University of Munich School of Engineering and DesignDepartment of Mechanical EngineeringGear Research Center(FZG)Boltzmannstraße 1585748 Garching near MunichGermany

The reduction of frictional power losses in power transmitting gears takes a crucial role in the design of energy-and resource-efficient ***-containing lubricants like glycerol and polyalkylene glycols have shown great potential in achieving friction within the superlubricity regime with coefficients of friction lower than 0.01 under elastohydrodynamic ***,a bio-based production of the base stocks can lead to the development of green ***,one challenge associated with the application of water-containing lubricants to gearboxes is the evaporation of water and its impact on the lubricant *** this study,the influence of water evaporation on elastohydrodynamic friction and film thickness was investigated for three water-containing polyalkylene *** nominal water contents of 20 wt%and 40 wt%and two viscosities were *** results show that the friction increases continuously with higher evaporated water content,while the overall friction level remains low in nearly water-free states.A similar trend is observed for film thickness,where the strong increase in viscosity results in a notable increase in film ***,the sensitivity of friction and film thickness to water evaporation is low for small amounts of evaporated *** allows generous thresholds for permissible variations in water content.

关键词： friction superlubricity aqueous lubrication elastohydrodynamic lubrication(EHL) evaporation polyalkylene glycol

Support elements in conventional tunneling–Focus on long-term behavior

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Underground Space 2018年第4期3卷 277-287页

作者： Robert Galler stefan Lorenz Chair of Subsurface Engineering Department of Mineral Resources EngineeringMontanuniversita¨t LeobenP.O.Box 8700Erzherzog Johann Str.3LeobenAustria

Owing to increasing traffic and the need for constructing second tunnel tubes including corresponding cross-passages,where only one tube existed thus far,sampling of tunnel-lining materials with an age of 30–40 years has been made *** and in situ tests were carried out to evaluate the long-term effects of the tunnel *** paper presents the outcomes regarding the long-term behav-ior of support elements and membranes after performing strength tests on inner and outer lining concrete samples,flat jack tests,rock bolt tests,and tests on re-extracted sheet membranes,as well as ***,the interface connection mechanical behavior in a double-shell-lined tunnel was investigated with laboratory *** aim of this research was to determine the characteristics of sheet membranes and geotextiles in the case of reduced load-bearing capacity caused by degradation of the primary *** results provide information on the load-sharing effects of the interaction between the primary and secondary lining,depending on the waterproofing sheet membrane and geotextile *** on the results,conclusions for new design approaches for underground infrastructure construction can be formulated.

关键词： Tunnel lining Long-term behavior Concrete Sheet membrane Rock bolt Flat jack test In situ tests

Supercritical angle Raman microscopy: a surfacesensitive nanoscale technique without field enhancement

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Light(Science & Applications) 2017年第1期6卷 482-489页

作者： Diana Serrano stefan Seeger Department of Chemistry University of ZurichWintherthurerstrasse 190CH-8057 ZurichSwitzerland

Raman scattering microscopy is a versatile tool for label-free imaging and molecular fingerprint ***,we provide the first demonstration that the selective collection of scattered signals exceeding the critical angle for total internal reflection enables surface-confined spontaneous Raman investigations at nanometre *** high-axial selectivity leads to improved signal-to-background ratios,thus making this technique an excellent probe for surface-related molecular *** richness of the spectroscopic information obtained through the supercritical angle Raman(SAR)collection path was proven by comparing its output with that of a parallel far-field collection ***,we demonstrated that the proposed SAR technique is a versatile microscopy approach that can be used alone or in combination with amplified Raman modalities such as surfaceenhanced resonance Raman scattering.

关键词： near-field optics Raman scattering supercritical microscopy surface science

Exploring Content Popularity in Information-Centric Networks

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China Communications 2015年第7期12卷 13-22页

作者： Andriana Ioannou stefan Weber School of Computer Science and Statistics Trinity College

Information-Centric Networking(ICN), an alternative architecture to the current Internet infrastructure, focuses on the distribution and retrieval of content by employing caches in a network to reduce network traffic. The employment of caches may be accomplished using graph-based and content-based criteria such as the position of a node in a network and content popularity. The contribution of this paper lies on the characterization of content popularity for on-path in-network caching. To this end, four dynamic approaches for identifying content popularity are evaluated via simulations. Content popularity may be determined per chunk or per object, calculated by the number of requests for a content against the sum of requests or the maximum number of requests. Based on the results, chunk-based approaches provide 23% more accurate content popularity calculations than object-based approaches. In addition, approaches that are based on the comparison of a content against the maximum number of requests have been shown to be more accurate than the alternatives.

关键词： network distributed architectures future internet information-centric networks caching technologies on-path caching content popularity

Urbanization between compactness and dispersion:designing a spatial model for measuring 2D binary settlement landscape configurations

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International Journal of Digital Earth 2019年第6期12卷 679-698页

作者： Hannes Taubenbock Michael Wurm Christian GeiB stefan Dech stefan Siedentop German Aerospace Center(DLR) German Remote Sensing Data Center(DFD)OberpfaffenhofenGermany ILS-Research Institute for Regional and Urban Development DortmundGermany

Measuring spatial patterns is a crucial task in spatial *** indicators have been developed to measure patterns in a quantitative ***,most comparative studies rely on relative comparisons,limiting their explanatory power to specific case *** by advancements in earth observation providing unprecedented resolutions of settlement patterns,this paper suggests a measurement technique for spatial patterns to overcome the limits of relative *** design a model spanning a feature space based on two metrics-largest patch index and number of *** feature space is defined as‘dispersion index’and covers the entire spectrum of possible two-dimensional binary(settlement)*** model configuration allows for an unambiguous ranking of each possible pattern with respect to spatial *** spatial resolutions of input data as well as selected areas of interest influence measurement results,we test dependencies within the ***,common other spatial metrics are selected for testing whether they allow unambiguous *** scenarios,we apply the model to artificially generated patterns representing all possible configurations as well as to real-world settlement classifications differing in growth dynamics and patterns.

关键词： Land cover spatial patterns landscape metrics dispersion index sensitivity analysis urban settlements remote sensing comparative spatial analysis

Scaling granular material with polygonal particles in discrete element modeling

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Particuology 2023年第4期75卷 151-164页

作者： Alireza Ahmadi stefan Larsson Carl Wersall KTH Royal Institute of Technology Division of Soil and Rock MechanicsBrinellvagen 2310044StockholmSweden

Despite advancements in computational resources,the discrete element method(DEM)still requires considerable computational time to solve detailed problems,especially when it comes to the large-scale *** addition to the geometry scale of the problem,the particle shape has a dramatic effect on the computational cost of ***,many studies have been performed with simplified spherical particles or *** scaling is an approach to increase the particle size to reduce the number of particles in the *** several particle scaling methods have been introduced,there are still some disagreements regarding their applicability to certain aspects of *** this study,the effect of particle scalping on the shear behavior of granular material is *** granular particles were scanned and imported as polygonal particles in the direct shear *** effect of particle size distri-bution,particle angularity,and the amount of scalping were *** results show that particle scalping can simulate the correct shear behavior of the model with significant improvement in computational ***,the accuracy of the scalping method depends on the particle angularity and particle size range.

关键词： Particle scaling Direct shear test Discrete element method PFC Polygonal shape Granular material

Predictions of the P1 approximation for radiative heat transfer in heterogeneous granular media

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Particuology 2023年第11期82卷 25-47页

作者： Jelena Macak Christoph Goniva stefan Radl DCS Computing GmbH 4020LinzAustria Graz University of Technology Institute of Process and Particle Engineering8010GrazAustria

The P1 approximation is a computationally efficient model for thermal ***,we present a P1 formulation in the context of the combined computational fluid dynamics and discrete element method(CFD-DEM),including closures for dependent scattering and *** available analytical and semi-analytical solutions,we find agreement for steady-state and transient quantities in sizedisperse *** flux is identified as the most sensitive quantity to predict,displaying unphysical spatial *** oscillations are due to a temperature slip at the locations of abrupt change in solid *** propose two techniques that mitigate this effect:smoothing of the radiative properties,and ***,using up to a million times enlarged particles,we demonstrate practically limitless compatibility with ***,we compare predictions made with our code to experimental data for a pebble bed under vacuum conditions,and in presence of *** find that a carefully calibrated simulation can replicate trends observed in experiments,with relative temperature error of less than 10%.

关键词： CFD-DEM Thermal radiation Coarse-graining P1 Pebble bed nuclear reactor

Carbon Footprint of Transitional Shelters

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International Journal of Disaster Risk Science 2015年第3期6卷 226-237页

作者： Matti Kuittinen stefan Winter Department of Architecture School of Arts Design and Architecture Aalto University Faculty of Civil Geo and Environmental EngineeringTechnische Universitt München

Extreme weather events, sea level rise, and political disputes linked to climate change are driving masses to leave their homes. Their transitional settlements should be produced in a manner that causes minimum greenhouse gas(GHG) emissions to prevent any further acceleration of climate change and the humanitarian crises it causes. This article presents a study of the carbon footprint and primary energy demand of the construction materials of eight different transitional shelters. The lowest carbon footprints were found from shelter models made from bamboo or timber. The highest emissions were caused by shelters that have either a short service life or that are made from metal-intensive structures. The choice of cladding materials was surprisingly important. The findings were further compared to the overall impacts of each construction project, to national per capita GHG emissions,and to construction costs. Some shelter projects had notable total energy consumption even compared to the annual energy use of industrialized countries. The study concludes that construction materials have an important impact on the carbon footprint of shelters. Comparisons should however be made only between similar functional units. Furthermore, benchmark values and more background data are urgently needed in order to give humanitarian nongovernmental organizations tools for lowering the carbon footprint of their construction operations.

关键词： Carbon footprint Humanitarian construction Lifecycle assessment Primary energy

A review on the aging phenomena of organic components and their mass transfer through the NAPL interfacial phase

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Chinese Journal Of Geochemistry 2013年第3期32卷 252-260页

作者： LIU Lihua stefan Haderlein Key Laboratory of Renewable Energy and Gas Hydrate Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Eberhard-Karls-University of Tuebingen Center for Applied Geoscience (ZAG)

It occurs worldwide that the organic components of non-aqueous phase liquid (NAPL) enter the porous medium and become the source of contaminants in the subsurface. The transport of the organic components through NAPL interphase into the aqueous phase and the subsurface determines the extent of contamination, the persistence of residual NAPL phases and the techniques of remediation. During the transport process the NAPL interphase may experience "aging", a physical and chemical change when NAPL is exposed to aqueous and or gaseous phases. This aging process alters vice versa the mass transfer behaviour of the organic contaminants in the porous medium.

关键词：老化现象有机组成传质界面相部分和非水相液体评论污染物源