| 1. |
- Ask, Maria, et al.
(författare)
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The Innovative Exploration Drilling and Data Acquisition Research School
- 2021
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Ingår i: NSG2021 27th European Meeting of Environmental and Engineering Geophysics. - : European Association of Geoscientists and Engineers.
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Konferensbidrag (refereegranskat)abstract
- The Innovative Exploration Drilling and Data Acquisition Research School (I-EDDA-RS) is aimed at educating emerging scientists and engineers in on-site drilling and geoscientific investigation technology for mining. I-EDDA-RS consists if a consortium of scientists and specialists from six universities and research institutes in Germany and Sweden. A central component of the research school is that the courses have hands-on components at drill sites, boreholes and repositories. In addition, a course on entrepreneurial skills required in the exploration industry is also included in I-EDDA-RS. The arrival of the Covid-19 pandemic resulted in altered plans. Instead of offering ten courses with strong field work, practical, and entrepreneurial components during 2020, four courses via distant learning were offered. While this was disappointing in many aspects, two of the courses attracted a larger group of students from a wider part of the world than original envisioned. Outreach via on-line and open webinars is also a route to explore, as a complement to meetings and conferences in real life. The I-EDDA-RS courses in 2021 welcomes students at MSc & PhD level, as well as experienced professionals for lifelong learning (c.f. https://www.iedda.eu/rs). The form and type of teaching is to be determined.
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| 2. |
- Vakis, A.I., et al.
(författare)
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Modeling and simulation in tribology across scales : An overview
- 2018
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Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 125, s. 169-199
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Tidskriftsartikel (refereegranskat)abstract
- This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and micro-scales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions.
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| 3. |
- Almqvist, Andreas, et al.
(författare)
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A Scientific Perspective on Reducing Ski-Snow Friction to Improve Performance in Olympic Cross-Country Skiing, the Biathlon and Nordic Combined
- 2022
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Ingår i: Frontiers in Sports and Active Living. - : Frontiers Media S.A.. - 2624-9367. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Of the medals awarded at the 2022 Winter Olympics in Beijing, 24% were for events involving cross-country skiing, the biathlon and Nordic combined. Although much research has focused on physiological and biomechanical characteristics that determine success in these sports, considerably less is yet known about the resistive forces. Here, we specifically describe what is presently known about ski-snow friction, one of the major resistive forces. Today, elite ski races take place on natural and/or machine-made snow. Prior to each race, several pairs of skis with different grinding and waxing of the base are tested against one another with respect to key parameters, such as how rapidly and for how long the ski glides, which is dependent on ski-snow friction. This friction arises from a combination of factors, including compaction, plowing, adhesion, viscous drag, and water bridging, as well as contaminants and dirt on the surface of and within the snow. In this context the stiffness of the ski, shape of its camber, and material composition and topography of the base exert a major influence. An understanding of the interactions between these factors, in combination with information concerning the temperature and humidity of both the air and snow, as well as the nature of the snow, provides a basis for designing specific strategies to minimize ski-snow friction. In conclusion, although performance on “narrow skis” has improved considerably in recent decades, future insights into how best to reduce ski-snow friction offer great promise for even further advances.
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| 4. |
- Almqvist, Andreas, et al.
(författare)
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Interfacial separation between elastic solids with randomly rough surfaces : Comparison between theory and numerical techniques
- 2011
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Ingår i: Journal of the mechanics and physics of solids. - : Elsevier BV. - 0022-5096 .- 1873-4782. ; 59:11, s. 2355-2369
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Tidskriftsartikel (refereegranskat)abstract
- We study the distribution of interfacial separations at the contact region between two elastic solids with randomly rough surfaces. An analytical expression is derived for the distribution of interfacial separations using Persson's theory of contact mechanics, and is compared to numerical solutions obtained using (a) a half-space method based on the Boussinesq equation, (b) a Green's function molecular dynamics technique and (c) smart-block classical molecular dynamics. Overall, we find good agreement between all the different approaches.
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| 5. |
- Almqvist, Nils, et al.
(författare)
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Scanning probe microscopy and thermo-mechanical characterization of silicon carbide composites
- 1995
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Ingår i: Fourth Euro-Ceramics. - : Gruppo Ed. Faenza Ed.. - 8881380072 ; , s. 361-368
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Konferensbidrag (refereegranskat)abstract
- series of SiC-based composites was obtained by sintering. Since such materials are considered for fusion applications, their thermal shock resistance and behaviour under deuterium irradiation are of primary interest. Extensive bulk and surface characterisation of pure and doped (AlN, TiB2, graphite) silicon carbides treated by a deuterium plasma was carried out. The change in surface structure following irradiation is addressed, and major factors influencing deuterium retention are discussed.
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| 6. |
- De Melo, C., et al.
(författare)
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Local Structure and Point-Defect-Dependent Area-Selective Atomic Layer Deposition Approach for Facile Synthesis of p-Cu2O/n-ZnO Segmented Nanojunctions
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:43, s. 37671-37678
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Tidskriftsartikel (refereegranskat)abstract
- Area-selective atomic layer deposition (AS-ALD) has attracted much attention in recent years due to the possibility of achieving accurate patterns in nanoscale features, which render this technique compatible with the continuous downscaling in nanoelectronic devices. The growth selectivity is achieved by starting from different materials and results (ideally) in localized growth of a single material. We propose here a new concept, more subtle and general, in which a property of the substrate is modulated to achieve localized growth of different materials. This concept is demonstrated by selective growth of high-quality metallic Cu and semiconducting Cu2O thin films, achieved by changing the type of majority point defects in the ZnO underneath film exposed to the reactive species using a patterned bilayer structure composed of highly conductive and highly resistive areas, as confirmed by transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The selective growth of these materials in a patterned ZnO/Al-doped ZnO substrate allows the fabrication of p-Cu2O/n-ZnO nanojunctions showing a nonlinear rectifying behavior typical of a p-n junction, as confirmed by conductive atomic force microscopy (C-AFM). This process expands the spectra of materials that can be grown in a selective manner by ALD and opens up the possibility of fabricating different architectures, taking advantage of the area-selective deposition. This offers a variety of opportunities in the field of transparent electronics, catalysis, and photovoltaics.
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| 7. |
- Furustig, Joel, et al.
(författare)
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A two scale mixed lubrication wearing-in model, applied to hydraulic motors
- 2015
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Ingår i: Tribology International. - : Elsevier BV. - 0301-679X .- 1879-2464. ; 90, s. 248-256
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Tidskriftsartikel (refereegranskat)abstract
- Wearing-in of a machine component can increase the conformity between contacting pairs and smoothen the surface topography. A two scale model, combining the wearing-in effects, resulting in changes in the surface topography, with the wear that occurs on the component, is presented. The geometry of the components are represented with measured coordinates. Wear leads to changes of the geometry, which has an effect on several tribological conditions, such as contact forces, relative velocities and conformity. Due to the wear on the topography scale, the load sharing is also affected. The model is applied to orbital hydraulic motors. The wear depth predicted with the model, is qualitatively in good agreement with the wear depth recorded in experiments.
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| 8. |
- Furustig, Joel, et al.
(författare)
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A wear model for EHL contacts in gerotor type hydraulic motors
- 2015
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Ingår i: Proceedings of the Institution of mechanical engineers. Part C, journal of mechanical engineering science. - : SAGE Publications. - 0954-4062 .- 2041-2983. ; 229:2, s. 254-264
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Tidskriftsartikel (refereegranskat)abstract
- The heart of gerotor motors is a gear-set. The gear-set consists of an inner gear which is rotating and orbiting in contact with an outer gear. Wear in these contacts is investigated experimentally and with a numerical implementation of an Archard based wear model in combination with a load sharing concept. The model utilizes the symmetry of the motor and is based on a three-scale approach to estimate the wear on the gears. The global model calculates contact forces, relative surface velocities and contact radii in the contacts between inner and outer gear. The calculations performed on the local scale are used to collect information about the influence of the surface roughness on lubricant film thickness. The wear depth is calculated on a semi-local scale, involving only one tooth on the outer gear. In partial elastohydrodynamic lubrication, load is carried by the part of the conjunction where there is direct contact between the mating surfaces and by the lubricant pressure. In the wear model, wear only occurs as a direct consequence of contact between the mating surfaces. Experimental results are compared with the model predictions for equivalent running conditions. The wear predicted by the model agrees with the experimental results. For this reason, it is concluded that wear in the gerotor motor is dominated by the wear mechanisms which are considered in the tribological model.
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| 9. |
- Rubel, M., et al.
(författare)
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Behaviour of Si and Ti doped carbon composites under exposure to the deuterium plasma
- 1998
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Ingår i: Journal of Nuclear Materials. - 0022-3115 .- 1873-4820. ; 258-263:1, s. 787-792
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Tidskriftsartikel (refereegranskat)abstract
- Studies of the deuterium interaction with carbon-based substrates were performed for graphite doped either with SiC or with TiC (5% or 10% of Si or Ti) and carbon fibre composites doped with SiC (2.5; 8; 40% of carbide). Non-doped CFC and graphite were used as reference materials. The materials were exposed to the deuterium plasma in a tokamak or in simulators of plasma-surface interactions. The main emphasis was on the determination of the deuterium retention in the near surface region and in the bulk of the composites. Characterisation of the non-exposed and deuterium irradiated substrates was accomplished by means of RBS, NRA, EDS, laser profilometry and ultra-high resolution microscopies. The most important observations are connected with the penetration of the deposited deuterium into the bulk of composites - even a few millimetres beneath the surface. The rate of the process was found to be related to the structure of materials and, to a certain extent, to the content of dopants.
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| 10. |
- Rubel, M., et al.
(författare)
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Deuterium interaction with silicon-graphite materials exposed to the tokamak plasma
- 1994
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 45:4, s. 429-434
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Tidskriftsartikel (refereegranskat)abstract
- Silicon-containing composites are considered as plasma facing materials in controlled fusion devices. Comparative studies of deuterium interaction with carbon based substrates were performed for graphite-silicon mixtures (5-50 wt% of Si), carbon fibres and isotropic graphite. Both virgin and deuterium treated surfaces were characterized by means of several surface sensitive techniques. The substrates were exposed to the deuterium plasma in the TEXTOR tokamak, in a magnetron or in a hollow cathode. The uptake, retention and release of deuterium were investigated. Migration of deuterium from the plasma deposited layer to the bulk of the substrates was found for the graphite-silicon mixtures. The structure of the deuterium-containing deposits was studied using atomic force microscopy. The initial stage of bubble formation was observed on the surfaces exposed to the tokamak plasma
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