| 1. |
- Telldahl, Ylva
(author)
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Skeletal changes in lower limb bones in domestic cattle from Eketorp ringfort on the Öland island in Sweden
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In: International Journal of Paleopathology. - 1879-9817 .- 1879-9825.
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Journal article (peer-reviewed)abstract
- Abstract: In this paper the occurrence of skeletal changes in joints has been investigated in cattleextremities. The bone elements derive from the archaeological site Eketorp ringfort on the Ölandisland in Sweden dated between Iron Age - Middle Age (ca 300 - 1200/50 A.D.). The analysis wasconducted in order to examine skeletal lesions and their connection to traction work. Different skeletallesions were recorded and the joint surface on metapodia and phalanges was divided in 4-7 sites toexamine if different types of lesions were located on particular sites of the articular facets or ifdifferent types of lesions were noted in bone elements from fore- and hindlimbs. The results show thatmetatarsals exhibited a higher frequency of pathologies in both phases compared to metacarpals whileanterior phalanges 1 and 2 had a higher occurrence of lesions than the posterior elements. The studyalso demonstrates that the type and location of depressions on joint surfaces are unevenly distributedbetween bone elements. Furthermore the results show that the occurrence of skeletal lesions weremore common in robust animals.
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| 2. |
- Afzal, Mohammad, 1987-, et al.
(author)
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Numerical analysis of multiple friction contacts in bladed disks
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In: International Journal of Mechanical Sciences. - 0020-7403 .- 1879-2162.
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Journal article (other academic/artistic)abstract
- The damping potential of multiple friction contacts in a bladed disk, tip shroud and strip damper is investigated, showing that friction damping effectiveness can be potentially increased by using multiple friction contact interfaces. Friction damping depends on many parameters such as rotational speed, engine excitation order and mode family and therefore it is not possible to damp all the critical resonances using a single friction contact interface. For example, a strip damper is more effective for the low nodal diameters, where blade/disk coupling is strong. The equations of motion of the bladed disk with multiple friction contacts are derived in the frequency domain for a cyclic structure with rotating excitations and a highly accurate method is used to generate the frequency response function (FRF) matrix. Furthermore, a finite element contact analysis is performed to compute the normal contact load and the contact area of the shroud interface at operating rotational speed. The multiharmonic balance method is employed in combination with the alternate frequency time domain method to find the approximate steady state periodic solution. A low-pressure turbine bladed disk is considered and the effect of the engine excitation level, strip mass, thickness and the accuracy of FRF matrix on the nonlinear response curve are investigated in detail.
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| 3. |
- Ahlström, Anders
(author)
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Aeroelastic FE modelling of wind turbine dynamics
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In: Computers & structures. - 0045-7949 .- 1879-2243.
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Journal article (peer-reviewed)abstract
- By designing wind turbines with very flexible components it is possible toreduce loads and consequently the associated cost. As a result, the increased flexibilitywill introduce geometrical nonlinearities. Design tools that can cope with those nonlinearitieswill therefore be necessary at some stage of the design process. The developedmodel uses the commercial finite element system MSC.Marc, which is an advanced finiteelement system focused on nonlinear design and analysis, to predict the structuralresponse. The aerodynamic model named AERFORCE, used to transform the wind toloads on the blades, is a Blade-Element/Momentum model, developed by The SwedishDefence Research Agency (FOI, previously named FFA). The paper describes the developedmodel with focus on component modelling to allow for geometrical nonlinearities.Verification results are presented and discussed for an extensively tested Danwin 180 kWstall-controlled wind turbine. Code predictions of mechanical loads, fatigue and spectralproperties, obtained at normal operational conditions, have been compared with measurements.The simulated results correspond well with measurements. Results from a bladeloss simulation are presented to exemplify the versatility of the developed code.
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| 4. |
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| 5. |
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| 6. |
- Atasoy, Merve, PhD Candidate, 1990-, et al.
(author)
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Bioaugmented mixed culture fermentation by Clostridium aceticum to enhance acetic acid dominant volatile fatty acids production from dairy industry wastewater
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In: Chemosphere. - 0045-6535 .- 1879-1298.
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Journal article (other academic/artistic)abstract
- By increasing volatile fatty acids (VFA) production efficiency via fermentation can lead to shifting from industrial wastewater treatment plants to biorefineries. In the current paper, acetic acid dominant VFA mixture production by bioaugmentation of mixed culture with Clostridium aceticum was aimed. The maximum acetic acid concentration was increased 10 times in the bioaugmented reactor (1170±18 mgCOD/L) than the control reactor (122±9 mgCOD/L). Additionally, the highest total VFA production was 5 times higher in bioaugmented reactor than the control reactor. Nevertheless, the bioaugmentation did not affect the propionic acid dominancy in the VFA mixture. The correlation analysis stated that the copy gene number of C. aceticum was highly correlated with acetic acid (p<0.05) and iso-valeric acid (p<0.01). The cycle analysis stated that 6 hours was adequate retention time to have the same acetic acid and total VFA production efficiency instead of 24 hours.
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| 7. |
- Bagherbandi, Mohammad, et al.
(author)
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A study on the relationship between isostatic equilibrium and seismicity : A case study in Africa
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In: Journal of Geodynamics. - 0264-3707 .- 1879-1670.
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Journal article (other academic/artistic)abstract
- The principle of isostasy plays an important role in understanding the relationship between the geodynamic processes. It is difficult to find an exact method that delivers a complete image of the Earth structure, gravimetric and seismic methods can provide images of the interior of the Earth. The Earth’s crust parameters, i.e. crustal depth and crust-mantle density contrast, can reveal information about the solid Earth system e.g. earthquakes and continental rifting processes. In this study, a combined Moho model using seismic and gravity data is determined to investigate the relationship between the isostatic state of the crust and seismic activities in our study area in Africa. To do this we determine the isostatic gravity disturbance and the density contrast. Our results show that isostatic equilibrium and compensation states are closely correlated to the seismicity patterns in the study area. This paper presents a method to determine the crustal thickness and crust-mantle density contrast and consequently one can detect low-density contrasts (about 200 kg/m3) and thin crust (about 30 km) near the Afar Triangle, which confirms the state of over-compensation. Furthermore, the density structure of the mantle lithosphere shows a large correlation with the earthquake activity, sub-crustal stress and volcanic distribution.
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| 8. |
- Bekele, Getachew, et al.
(author)
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Solar-wind-based village electrification in Ethiopia : a comparision of technologies
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In: Renewable energy. - 0960-1481 .- 1879-0682.
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Journal article (peer-reviewed)abstract
- The aim of this paper is to investigate the possibility of supplying electriclight and potable water from a solar-wind based hybrid system. The main target is a remotely resettled community in Ethiopia out of reach of the electric grid. The wind energy potential of the location has been assessed in a previous article. The solar potential has also been investigated in an accompanying article awaiting publication. Based on the findings of the potential, a feasibility study has been carried out on how to supply electricity to the community, modeled as having 200 families, comprising of approximately 1000 to 1200 people in total. A community school and a health post is also considered for the community. The electric load considered is of both primary and deferrable types consisting of lighting ,water pumps, radio receivers, and some clinical equipment. In theattempt of finding the most economical solution, a system with less energy efficient, and less expensive components have been compared to a more expensive system with the latest, most energy efficient ,technology on both the supply and load sides. A system solution on individual basis (solution per house hold) has also been considered and the net present cost (NPC) is compared against the aggregate solution. A software tool, Hybrid Optimization Model for Electric Renewables (HOMER) is used for the analysis. The result of the analysis is a list of feasible power supply systems, sorted according to their net present cost. Furthermore, sensitivity diagrams, showing the influence of wind speeds, PV costs, and diesel prices on the optimum solutions are also provided.
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| 9. |
- Bergstedt, Edwin, 1986-, et al.
(author)
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Gear Micropitting Initiation of Ground and Superfinished Gears: Wrought versus Pressed and Sintered Steel
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In: Tribology International. - 0301-679X .- 1879-2464.
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Journal article (peer-reviewed)abstract
- This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with C-PT gears. The materials are wrought steel (16MnCr5) and a commercialpowder metallurgical material (AstaloyTM Mo). Two finishing methods were studied: grinding andsuperfinishing. Experimental results show that the superfinishing prevented micropitting, but ledto premature failure due to cracks in the root caused by tip-to-root interference. Micropitting wasinitiated at load stage 8, and 9 for the ground wrought, and powder metallurgical steel respectively.The failure mechanisms were similar between materials with the same surface finish. The powdermetallurgical steel showed subsurface initiated fatigue compared to the wrought groundsteel having surface-initiated fatigue. Testing new finishing methods and materials, onehas to be aware of the influence of the gear micro geometry.
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| 10. |
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| 11. |
- Burman, Magnus, 1966-, et al.
(author)
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Comparative Life Cycle Assessment (LCA) of theHull of a High Speed Craft
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In: Composite structures. - 0263-8223 .- 1879-1085.
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Journal article (other academic/artistic)abstract
- A comparative Life Cycle Assessment (LCA) has been performed on the hull of a 24 meter long high speed patrol craft. The aim of the study is to compare different structural materials concepts to determine differences and sensitivities in environmental impact, especially in relation to the total impact including fuel burn. The material concepts studied are aluminium and various composite combinations consisting of glass fibre and carbon fibre with vinyl ester resin both as single skins and as sandwich with a Divinycell foam core. For each material concept a unique and weight optimized structural design was employed fulfilling the DNV high speed craft design code [1]. All identical systems and components for the five hull concepts are omitted in the LCA and hence a comparative study is performed focused on the hull structure. The commercial software SimaPro have been utilized for the LCA calculations and the impact assessment method chosen is the CML Baseline 2000. The structural optimization carried out in [1] show that a weight reduction by to up to 50% (on the hull) could be achieved by switching from aluminium to a carbon fibre sandwich concept. The weight reduction switching from glass fibre single skin to a carbon fibre sandwich concept is roughly 20%. The LCA study performed herein shows that, regardless of hull material concept, the environmental impact is by large dominated by the usage phase due to relatively large fuel consumption. A lower structural weight will reduce the fuel consumption and hence the environmental impact. This is illustrated in fig. 1 for the aluminum hull. All different phases of the life cycle are plotted for all environmental impact categories assessed herein. The green color is related to the operation phase and the red is the manufacturing phase. As observed the operation phase is dominating. In fig. 2 are the results from the LCA presented for all hull concepts and for all environmental impact factors. The Al-hull is the concept with highest structural weight (red bars) and hence was found to have the highest environmental impact. The carbon fibre sandwich hull (green bars) had the lowest weight of the five and consequently the lowest environmental impact. In the normalization analysis performed, in which different impact factors are assessed using a common impact unit, three impact factors stand out as dominating, independent of hull concept; Abiotic depletion, Global warming and Acidification. All these impact factors are herein associated with the usage phase and diesel consumption. If the operation phase is omitted and only the manufacturing phase (including the material extraction/manufacturing) is studied the observation is that the aluminium concept still will have the largest environmental impact for all categories. The most significant environmental impact is now on the marine and the fresh water aquatic ecotoxicity which is associated with the aluminium raw material excavation and manufacturing processes.
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| 12. |
- Crialesi-Esposito, Marco, et al.
(author)
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FluTAS: A GPU-accelerated finite difference code for multiphase flows
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In: Computer Physics Communications. - 0010-4655 .- 1879-2944.
-
Journal article (peer-reviewed)abstract
- We present the Fluid Transport Accelerated Solver, FluTAS, a scalable GPU code for multiphase flows with thermal effects. The code solves the incompressible Navier-Stokes equation for two-fluid systems, with a direct FFT-based Poisson solver for the pressure equation. The interface between the two fluids is represented with the Volume of Fluid (VoF) method, which is mass conserving and well suited for complex flows thanks to its capacity of handling topological changes. The energy equation is explicitly solved and coupled with the momentum equation through the Boussinesq approximation. The code is conceived in a modular fashion so that different numerical methods can be used independently, the existing routines can be modified, and new ones can be included in a straightforward and sustainable manner. FluTAS is written in modern Fortran and parallelized using hybrid MPI/OpenMP in the CPU-only version and accelerated with OpenACC directives in the GPU implementation. We present different benchmarks to validate the code, and two large-scale simulations of fundamental interest in turbulent multiphase flows: isothermal emulsions in HIT and two-layer Rayleigh-Bénard convection. FluTAS is distributed through a MIT license and arises from a collaborative effort of several scientists, aiming to become a flexible tool to study complex multiphase flows.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Graham, Robert M., et al.
(author)
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Identifying sources and transport pathways of iron in the Southern Ocean
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In: Deep Sea Research Part I. - 0967-0637 .- 1879-0119.
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Journal article (peer-reviewed)abstract
- Over large regions of the global ocean primary productivity is limited by the availability of dissolved iron. Changes in the supply of iron to these regions could have major impacts on primary productivity and the carbon cycle. One of the largest sources of dissolved iron to the ocean is thought to be from shelf sediments, and this source is often parameterized in biogeochemical models as a depth dependent iron flux through the seafloor. Using the knowledge that Southern Ocean surface waters are iron limited, we infer source regions of iron to the Southern Ocean by identifying where the most intense chlorophyll blooms develop. We further derive surface current patterns from satellite sea surface height fields to assess the role of the ocean circulation in transporting iron away from these source regions. We find a tight relationship between satellite chlorophyll concentrations and sea surface height. Large chlorophyll blooms develop on the shelf and where the western boundary currents detach from the continental shelves and turn eastward into the Southern Ocean. This is likely due to shelf supplied iron becoming entrained into western boundary currents and advected into the Southern Ocean along the Dynamical Subtropical Front. The most intense chlorophyll blooms are located along coastal margins of islands and continents. Blooms do not develop over submerged seamounts or plateaus in the open ocean. This suggests that shelf sediments in coastal regions act as large bioavailable iron sources to the Southern Ocean. We recommend that a more accurate method of parameterizing the shelf sediment iron flux could be to prescribe this flux only through grid cells neighboring coastlines. Finally, we hypothesize how changes in sea level during glacial-interglacial cycles may have altered the distribution of shelf sediment iron sources in the Southern Ocean and helped to drive export production anomalies in the Sub-Antarctic Zone.
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| 19. |
- Hedlund, Magnus, 1986-, et al.
(author)
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Fast Optimization Methodology for Press-fitted Composite Hollow Cylinder Flywheel Energy Storage
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In: Composite structures. - 0263-8223 .- 1879-1085.
-
Journal article (peer-reviewed)abstract
- An optimization strategy for a hollow flywheel energy storage is presented. Several press-fitted shells of anisotropic materials (such as carbon composites) are studied by an analytical model based on a plane stress assumption. The optimization target is stored energy. The optimizer constraints (which were evaluated at full and zero charge level, respectively) were based on strain-based models for fatigue life of composites, and stress-based fatigue life models for high-strength aluminum. A compiled library was built within the scope of this work, and used to run a robust global grid-search optimizing method. The analytical model was compared against a finite element method solution, and the (single-core) library was seen to be at least 5 orders of magnitude faster.
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| 20. |
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Jonsson, Andreas, 1977-, et al.
(author)
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The effect on transparency and light scattering of dip coated antireflection coatings on window glass and plastics
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In: Solar Energy Materials and Solar Cells. - 0927-0248 .- 1879-3398.
-
Journal article (peer-reviewed)abstract
- High visible transmittance values are interesting for windows in general and for the bleached state of smart windows in particular. For smart windows it is always possible to darken them and therefore the transparency of the bleached state can never become too high. One way of achieving a higher transmittance could be the use of antireflective coatings on the surfaces of the smart window. In this project the use of dip coating for putting antireflective coatings on window surfaces has been studied. The effect on transmittance and surface light scattering has been investigated and the results show that antireflective coatings on windows can have a positive impact on both.
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| 26. |
- Joyce, Peter James, et al.
(author)
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Identifying hotspots of environmental impact in the development of novel inorganic polymer paving blocks from bauxite residue
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In: Resources, Conservation and Recycling. - 0921-3449 .- 1879-0658.
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Journal article (peer-reviewed)abstract
- High bauxite residue content inorganic polymer paving blocks have the potential not only to provide a solution to the ongoing waste management issues faced by the alumina sector, but to simultaneously provide low environmental impact building materials to the construction sector. In order to realise the potential of this emerging technology, it is important to understand where the hotspots of environmental impact are likely to occur, and identify routes to reduce this impact, at an early stage of development. In this study we use anticipatory Life Cycle Assessment (LCA) to identify hotspots of environmental impact in the production of paving blocks made from inorganic polymers derived from bauxite residue. This technology has only been demonstrated at laboratory scale; however, production was modelled at industrial scale. The bauxite residue is fired in a rotary kiln in the presence of a carbon and silica source, in order to create a reactive precursor. When mixed with an alkali the precursor forms a solid block. Our results identify the firing process as the major hotspot of environmental impact, primarily due to the combustion of fossil fuels in the rotary kiln. Steps to reduce the impact of the firing step or to reduce the amount of fired precursor used in the final paving block are suggested as routes for future impact reduction. Optimisation of the environmental aspects of these building materials at an early stage in their development could lead to a promising future for high-volume bauxite residue valorisation at low environmental cost.
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| 27. |
- Kamf, Tobias, 1987-
(author)
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A Method for Calibrating Work-Piece Orientation : Using a Dual-Axis MEMS Inclinometer
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In: Robotics and Computer-Integrated Manufacturing. - 0736-5845 .- 1879-2537.
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Journal article (peer-reviewed)abstract
- An accelerometer based alignment system designed to align robotic tools and work-pieces in a Cartesian coordinate system is presented, with potential applications within the automated production industry. An overview of the underlying theory, used hardware, micro-controller implementation and performed experiments is presented. The developed theoretical model and prototype hardware is veried against both simulations and experiments, evaluating their performance and practical limitations. For a set of 2000 random initial misalignments with an amplitude in the range of 0° to 10°, the system achieved an alignment accuracy with a 3-sigma bound of 0.023° in the XY plane and 0.14° along the Z-axis. On average the used robot needed 20.86 s to align the used tool to stated accuracy.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Lövqvist, Lisa, 1992-, et al.
(author)
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Evaluation of the standard test method for resistance of bituminous materials to de-icing fluids
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In: Construction and Building Materials. - 0950-0618 .- 1879-0526.
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Journal article (peer-reviewed)abstract
- As an important maintenance measure, de-icing agents are commonly used to ensure safe surface conditions of highways and airport runways during winter. There are however issues related to their use, such as deteriorating effects on road materials, causing particle loss and a decreased low-temperature stiffness of asphalt pavements. To avoid this, it is therefore important to be able to evaluate the effect of the deicer on the asphalt mixture with reliable results. The European standard method for this, EN12697-41, is however associated with several issues such as a high variability of the results and a lack of consistency with the field. Using both experimental testing and numerical simulations, this paper aims to explain the cause of these and to identify the main dominant parameters which can potentially be modified for an improvement. The experimental testing evaluated both the diffusive properties of de-icing fluid and water in mastic and the standard method itself, and the numerical simulations evaluated the effect of different parameters related to the set-up of the test. From the evaluations, it was concluded that both the set-up of the test and the geometryof the test sample contribute to the high variability of the test method and its lack of consistency with the field. Recommendations are therefore made regarding the potential for improvement and further evaluation of the method.
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| 36. |
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| 37. |
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| 38. |
- Metere, Alfredo, et al.
(author)
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A new computer program for topological, visual analysis of 3D particle configurations based on visual representation of radial distribution function peaks as bonds
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In: Computer Physics Communications. - 0010-4655 .- 1879-2944.
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Journal article (peer-reviewed)abstract
- We present a new program able to perform unique visual analysis on generic particle systems: PASYVAT (PArticle SYstem Visual Analysis Tool). More specifically, it can perform a selection of multiple interparticle distance ranges from a radial distribution function (RDF) plot and display them in 3D as bonds. This software can be used with any data set representing a system of particles in 3D. In this manuscript the reader will find a description of the program and its internal structure, with emphasis on its applicability in the study of certain particle configurations, obtained from classical molecular dynamics simulation in condensed matter physics.
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| 39. |
- Mvungi, Esther F., et al.
(author)
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When Zostera marina is intermixed with Ulva, its photosynthesis is reduced by increased pH and lower light, but not by changes in light quality
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In: Aquatic Botany. - 0304-3770 .- 1879-1522.
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Journal article (peer-reviewed)abstract
- In eutrophic coastal waters, seagrasses often become intermixed with opportunistic algae, such as different species of Ulva that grow on top of, or between shoots in Zostera marina beds. When this occurs, the algae can both reduce the amount of light reaching the seagrasses and also alter the quality of that light so that it becomes dominated by the green part of the spectrum. Since Ulva has an efficient photosynthetic carbon uptake, its photosynthesis can drastically increase the pH of the surrounding seawater, and thus create conditions where Zostera marina is unable to acquire inorganic carbon (Ci). To evaluate the effects of Ulva on the photosynthetic capacities of the temperate seagrass Zostera marina, we compared it in the laboratory under normal light and light filtered through layers of Ulva intestinalis, and repeated the experiments with the addition of pH-induced changes in carbon speciation and availability. One thallus of Ulva reduced photosynthetically available irradiance to underlying seagrass by about 50% and shifted the quality of remaining light towards the green part of the spectrum. Interestingly, there was no significant difference in photosynthetic performance between Zostera marina under normal light and under Ulva-filtered green light when adjusted to the same irradiance as for the control plants, indicating that the green spectrum transmitted through Ulva layers may be efficient in driving photosynthesis in the seagrass bed. On the other hand, algae-generated pH shifts had drastic negative effects on the photosynthesis of the seagrass.
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| 40. |
- Nakagawa, Kei, et al.
(author)
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Relationship between nitrate, heavy metal, and sterols contents in Japanese agricultural soils with risk of groundwater pollution
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In: Chemosphere. - 1879-1298. ; , s. 142335-142335
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Journal article (peer-reviewed)abstract
- In Japanese agricultural lands, nitrate-nitrogen contamination of soil and groundwater often occurs due to the application of livestock excrements and compost. Therefore, rural soils in Japan were sampled and analyzed for nitrate-nitrogen leaching, heavy metal content, and sterols associated with livestock excrement and compost to calculate contamination risk indicators. The results were analyzed using self-organizing maps and cluster analysis. Nitrate-nitrogen content using water extraction was detected in most of the sampled soils. In addition, many samples from areas that were already severely contaminated with nitrate-nitrogen showed particularly high concentrations. Coprostanol, an indicator of fecal contamination, was detected in more than half of the samples. The main source of nitrate-nitrogen contamination in these areas is livestock excrement and compost. Self-organization maps showed that areas with high nitrate-nitrogen contamination also corresponded to areas with high copper and zinc soil contents. The self-organization maps and cluster analysis resulted in five clusters: a nitrate-contaminated group mainly originating from livestock excrement and compost, a heavy metal-contaminated group, a general group, a nitrate-contaminated group mainly originating from chemical fertilizers, and a contaminated group with potentially hazardous substances requiring attention. Authorities and decision-makers can use the results to prioritize areas requiring remediation.
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| 41. |
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| 42. |
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| 43. |
- Noréus, Olof, 1970-, et al.
(author)
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Comparison of measured and simulated drawbar pull forsix wheeled vehicle with radial pneumatic tyres on sand
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In: Journal of terramechanics. - 0022-4898 .- 1879-1204.
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Journal article (other academic/artistic)abstract
- To enable improved cross country characteristics of wheeled vehicles with individually controlled transmission on soft ground,suitable tyre/terrain models are needed. Here tyre/terrain models for simulating driving with both rigid and pneumatic wheels onsoft ground have been developed. A method to measure terrain parameters and drawbar pull for a six-wheeled vehicle on sand isproposed, tested and evaluated. The method is developed in order to be able to validate the proposed tyre/terrain models includingboth rigid and pneumatic wheels that are developed to simulate the behaviour of a six-wheeled vehicle with electric transmissionon soft ground. Tests were performed at different tyre pressures, and it is shown that the drawbar pull is vastly improved atlower tyre pressures. Since the tyre/terrain model uses terrain parameters such as pressure–sinkage and shear stress–displacementrelationships, the sand properties are measured with a Bevameter. Parameters in the pressure–sinkage relationship are estimated tofit the measured data. Both external and internal shearing properties of the sand are measured using a rubber coated shear ring anda shear ring with grousers, respectively. Shear curves of simple exponential form from the developed tyre/terrain models are shownto agree reasonably well with the measured shear behaviour. This will be the base in the development of a strategy to get improvedcross country characteristics of six-wheeled vehicles.
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| 44. |
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| 45. |
- Obregon, Evanny, et al.
(author)
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Is Spectrum Sharing in the Radar Bands Commercially Attractive? : A Regulatory and Business Overview
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In: Telecommunications Policy. - 0308-5961 .- 1879-3258.
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Journal article (other academic/artistic)abstract
- The need to meet users’ expectations in the ”mobile data avalanche” represents a significant challenge for mobile networks operators (MNOs). More spectrum is a natural way to meet these requirements in a cost and time-efficient way; but new, exclusively licensed, spectrum is increasingly hard to come by. Instead, vertical spectrum sharing has been discussed as a potential solution for finding additional spectrum for mobile communications. In this paper, we focus on vertical spectrum sharing in the radar bands for providing short-range wireless access, e.g. indoors and in ”hotspots” that ”offload” mobile traffic demand. We propose a methodology for dealing with the technical, regulatory and business aspects of deploying large-scale wireless networks. Moreover, we identify the following criteria for achieving business success: spectrum availability, availability of low-cost end user devices, system scalability in terms of number of concurrently used devices and finally, the ability to guarantee a quality of service for the users.Our technical availability assessment has identified geo-location database support as necessary technical enabler and detect-and-avoid mechanism as a beneficial technical enabler for improving sharing conditions. Therefore, we propose a sharing mechanism based on three components: a central spectrum manager witha geo-location database controlling the aggregate interference, a spectrum sensing mechanism and a fast feedback between the radars and the central spectrum manager. Moreover, Licensed Shared Access (LSA) was found to be the suitable regulatory framework to support the proposed sharing mechanism and regulatory policies in real-life implementation. Our business feasibility assessment concludes that there is enough spectrum available for indoor and hotspots communication in urban areas in the radar bandsto make a large scale system commercially viable. Service quality can be guaranteedand there is a strong potential to construct low-cost devices. Uncertainties do, however, remain regarding the spectrum access cost.
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| 46. |
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| 47. |
- Onifade, Ibrahim, 1983-
(author)
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Continuum Plasticity Mechanics (CPM) - An energy-based plasticity model - Application to asphalt concrete mixtures.
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In: International Journal of Solids and Structures. - 0020-7683 .- 1879-2146.
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Journal article (peer-reviewed)abstract
- A new generalized energy-based elasto-plastic constitutive model for both pressure-sensitive and pressure insensitive materials is developed and presented in this paper. The model is developed with the energy formulation which inherently captures the rate-sensitivity and can be used to model a wide range of materials ranging from rate-dependent materials such as polymers and asphalt concrete to rate-independent materials such as steel. No additional rate-dependency parameters is required to model rate dependent behaviour at different strain-rates. The new energy-based plasticity formulation takes a similar form as the conceptsused in continuum damage mechanics with the plastic strain transformed into a plasticity variable whichenters into the formulation to obtain the corresponding stress and strain due to the applied or subjected load conditions. The new energy-based plasticity formulation fits nicely into the thermodynamics framework thereby providing a true unifying framework for coupling damage and plasticity
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| 48. |
- Onifade, Ibrahim, 1983-
(author)
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Damage and Fracture Characterization of Asphalt Concrete Mixtures using the Equivalent Micro-crack Stress Approac
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In: Construction and Building Materials. - 0950-0618 .- 1879-0526.
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Journal article (peer-reviewed)abstract
- In this paper, a new parameter termed ”equivalent micro-crack stress” (σmc) is proposed for characterizingthe cracking performance of asphalt mixtures. The ”equivalent micro-crack stress” (σmc) is a function ofthe material stiffness and a critical micro-crack initiation threshold (MCIT). The ”equivalent micro-crackstress” (σmc) takes a similar form as the failure stress obtained from the Griffith energy balance equation.The MCIT incorporates the influence of the fracture work and the size and spatial distribution of the airvoids in the determination of the material cracking performance. Experimental tests are carried out toobtain the (σmc) to characterize the cracking performance of unmodified and wax modified mixtures usingthe Superpave IDT tests at low temperature range (i.e. -20oC, -10oC and 0oC). The result shows that the ”equivalent micro-crack stress” (σmc) gives a good indication of the material cracking performance ofthe unmodified and wax modified mixtures. The result of numerical simulations of the fatigue behaviouralso shows that the relationship between the number of cycles to micro-crack formation (Nmc) and σmc can be used to distinguish the wax modified mixtures from the unmodified mixture.
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| 49. |
- Persson Ridell, Oscar, 1983-, et al.
(author)
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Facilitating knowledge sharing between consumer communities and hosting firms : Expanding the solution space to a virtual innovation platform
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In: Technovation. - 0166-4972 .- 1879-2383.
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Journal article (peer-reviewed)abstract
- Consumer communities, such as in the video game industry, are settings where knowledge sharing and innovation abound as consumers dedicate their own resources to innovate upon firm-developed solutions. Researchers have focused extensively on investigating how toolkits facilitate knowledge sharing for innovation between firms and consumer communities. However, we suggest that toolkits are only one such means to achieve knowledge sharing. As such, we investigate in this article how knowledge sharing vis-à-vis innovation is facilitated between a consumer community and its hosting firm. Applying concepts from the communities of practice literature to an in-depth study of a video game developer and its global gaming community, our findings suggest that the boundary process between the consumer community and the hosting firm envelops a complete virtual innovation platform – a sequence of innovation practices each accompanied by a tailored yet emergent combination of brokers and boundary objects, which is further supported by moderators.
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- Petersen, Tom
(author)
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Estimation of accessibility elasticities in connection with the Öresund fixed link using a panel of micro-data
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In: Regional Science and Urban Economics. - 0166-0462 .- 1879-2308.
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Journal article (other academic/artistic)abstract
- The productivity of public infrastructure has been the subject of numerous studies during the last two decades, often with vastly differing results. Matters of concern for these estimates have been the level of aggregation of the data, the measurement of the infrastructure stock, and endogeneitybias. In an attempt to estimate the wider economic impacts of the Öresund fi…xed link, these issues are addressed by estimating production functions from fi…rm data in Scania——the Swedish part of the Öresund region——using a novel method due to Olley and Pakes (1996), that takes endogenous inputchoices and self-selection into account. As a measure of the service provided by the infrastructure, accessibility to the workforce is used on a fi…ne-grained geographic level. The sign and signi…ficance of the two sources of bias are tested, as well as the robustness of the accessibility parameter with respect to the speci…cation of the barrier of trips across Öresund.
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