| 1. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Mantzouki, Evanthia, et al.
(författare)
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Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins
- 2018
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Ingår i: Toxins. - : MDPI. - 2072-6651. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.
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| 3. |
- Fang, Yurui, 1983, et al.
(författare)
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Plasmon Enhanced Internal Photoemission in Antenna-Spacer-Mirror Based Au/TiO2 Nanostructures
- 2015
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:6, s. 4059-4065
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Tidskriftsartikel (refereegranskat)abstract
- Emission of photoexcited hot electrons from plasmonic metal nanostructures to semiconductors is key to a number of proposed nanophotonics technologies for Solar harvesting, water splitting, photocatalysis, and a variety of optical sensing and photodetector applications. Favorable materials and catalytic properties make systems based on gold and TiO2 particularly interesting, but the internal photo emission efficiency for visible light is low because of the wide bandgap of the semiconductor. We investigated the incident photon-to-electron conversion efficiency of thin TiO2 films decorated with Au nanodisk antennas in an electrochemical circuit and found that incorporation of a Au mirror beneath the semiconductor amplified the photoresponse for light with wavelength lambda = 500-950 nm by a factor 2-10 compared to identical structures lacking the mirror component. Classical electrodynamics simulations showed that the enhancement effect is caused by a favorable interplay between localized surface plasmon excitations and cavity modes that together amplify the light absorption in the Au/TiO2 interface. The experimentally determined internal quantum efficiency for hot electron transfer decreases monotonically with wavelength, similar to the probability for interband excitations with energy higher than the Schottky barrier obtained from a density functional theory band structure simulation of a thin Au/TiO2 slab.
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| 4. |
- Mehta, Ankit Nalin, et al.
(författare)
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Understanding noninvasive charge transfer doping of graphene: a comparative study
- 2018
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Ingår i: Journal of Materials Science: Materials in Electronics. - : Springer Science and Business Media LLC. - 1573-482X .- 0957-4522. ; 29:7, s. 5239-5252
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we systematically investigate and compare noninvasive doping of chemical vapor deposition graphene with three molecule dopants through spectroscopy and electrical conductivity techniques. Thionyl chloride shows the smallest improvement in conductivity with poor temporal and thermal stability and nitric acid induces the biggest sheet resistance reduction with modified stability. Molybdenum trioxide doping stands out, after thermal annealing, with both causing a significant sheet-resistance reduction and having superior temporal and thermal stability. These properties make it ideal for applications in advanced electronics. Theoretical studies based on the van der Waals density functional method suggest that cluster formation of molybdenum trioxide underpins the significant reduction in sheet resistance, and the stability, that arises after thermal annealing. Our comparative study clarifies charge transfer doping of graphene and brings understanding of the weak-interaction nature of such non-destructive doping of graphene. Our work also shows that we can use weak chemisorption to tailor the electronic properties of graphene, for example, to improve conductivity. This ability open up possibilities for further use of graphene in electronic interconnects, field effect transistors and other systems.
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| 5. |
- Meyer, H.F., et al.
(författare)
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Overview of physics studies on ASDEX Upgrade
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation (q 95 = 5.5, ) at low density. Higher installed electron cyclotron resonance heating power 6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with MW m-1 with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently . This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of and E r allow for inter ELM transport analysis confirming that E r is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the ELM crash and are in good agreement with nonlinear MHD modelling. The observation of accelerated ions during the ELM crash can be seen as evidence for the reconnection during the ELM. As type-I ELMs (even mitigated) are likely not a viable operational regime in DEMO studies of 'natural' no ELM regimes have been extended. Stable I-modes up to have been characterised using -feedback. Core physics has been advanced by more detailed characterisation of the turbulence with new measurements such as the eddy tilt angle - measured for the first time - or the cross-phase angle of and fluctuations. These new data put strong constraints on gyro-kinetic turbulence modelling. In addition, carefully executed studies in different main species (H, D and He) and with different heating mixes highlight the importance of the collisional energy exchange for interpreting energy confinement. A new regime with a hollow profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvénic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO.
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| 6. |
- Tao, Jianmin, et al.
(författare)
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First-principles study of the binding energy between nanostructures and its scaling with system size
- 2018
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 97:15
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium van der Waals binding energy is an important factor in the design of materials and devices. However, it presents great computational challenges for materials built up from nanostructures. Here we investigate the binding-energy scaling behavior from first-principles calculations. We show that the equilibrium binding energy per atom between identical nanostructures can scale up or down with nanostructure size, but can be parametrized for large N with an analytical formula (in meV/atom), Eb/N=a+b/N+c/N2+d/N3, where N is the number of atoms in a nanostructure and a, b, c, and d are fitting parameters, depending on the properties of a nanostructure. The formula is consistent with a finite large-size limit of binding energy per atom. We find that there are two competing factors in the determination of the binding energy: Nonadditivities of van der Waals coefficients and center-to-center distance between nanostructures. To decode the detail, the nonadditivity of the static multipole polarizability is investigated from an accurate spherical-shell model. We find that the higher-order multipole polarizability displays ultrastrong intrinsic nonadditivity, no matter if the dipole polarizability is additive or not.
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| 7. |
- Yang, Hengyan, et al.
(författare)
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New Understanding on Photocatalytic Mechanism of Nitrogen-Doped Graphene Quantum Dots-Decorated BiVO4 Nanojunction Photocatalysts
- 2017
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 2:7, s. 3766-3773
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Tidskriftsartikel (refereegranskat)abstract
- Bismuth vanadate (BiVO4) is a promising candidate as a visible-light-driven photocatalyst in the aspect of practical applications. To investigate the origin of active species from BiVO4 and understand the influence of the variations of the photocatalytic process, comparative studies on zero-dimensional nitrogen-doped graphene quantum dot (NGQD)-decorated BiVO4 have been carried out for methylene blue photodegradation. It was found that the hydroxyl group-rich NGQD surface and the established heterojunction structure between NGQDs and BiVO4 were greatly beneficial for the conversion of the MOH radical. With NGQD decoration, the dominant oxidant species for NGQDs/BiVO4 were confirmed to be MOH and H2O2, rather than holes originating from the valence band of unmodified BiVO4. The synergistic photocatalytic mechanism with respect to the interfacial charge transport and the conversion of active species was proposed. The achievement of the controllable active species significantly altering the activity may be applied for different photocatalytic reactions.
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| 8. |
- Yang, Yang, 1985-
(författare)
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Phytoplankton and Physical Disturbance : Seasonal dynamics in temperate Lake Erken, Sweden
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phytoplankton mirrors changes in the environment and plays an important role in biogeochemical processes. Phytoplankton dynamics is the outcome of both autogenic succession and external disturbances. This thesis focused on the seasonal variation of water column stability and its effects on phytoplankton, particularly considering the influence of mixing events on phytoplankton development. Lake Erken is a dimictic lake with weak and often interrupted summer stratification, which represents an intermediate case between a polymictic lake and a lake with strong summer stratification.There are two diatom phases annually. The spring bloom is caused by pioneer centric diatoms, and the autumn diatom phase is dominated by meroplanktonic diatoms induced by turnover. A summer Cyanobacteria bloom – mainly Gloeotrichia echinulata, depended on the length and stability of stratification.Winter and spring air temperature is found to play an important role in the annual succession of phytoplankton by initiating changes in ice/snow-cover and lake thermal stability and setting the basic status. Instead of starting from zero, the vernal phytoplankton piles up on the overwintering community, this trans-annual ecological memory influences both the composition and diversity and taxonomic distinctness of spring phytoplankton.Water column stability during summer in Lake Erken is mainly influenced by wind-induced turbulence and internal seiches. As thermal stratification develops from early until late summer, variations in stability and gradual deepening of the thermocline depth influence phytoplankton dynamics directly by changing its distribution, and also indirectly by altering the nutrient and light availability. A new disturbance index (DI) was defined to quantify environmental stability/disturbance and tested well to indicate phytoplankton equilibrium status in two summer stratification periods. The concept of species and functional groups was generally used in this study. However, a next generation sequencing based approach was also tested and proved to provide an excellent candidate for revealing distribution patterns of phytoplankton in inland waters.
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| 9. |
- Yang, Yang, 1985-, et al.
(författare)
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Repetitive baselines of phytoplankton succession in an unstably stratified temperate lake (Lake Erken, Sweden) : a long-term analysis
- 2016
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 764:1, s. 211-227
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Tidskriftsartikel (refereegranskat)abstract
- The seasonal development of phytoplankton is a sequence of consecutive events with waxes and wanes of biomass and compositional shifts. This study analyzed 16 years data in Lake Erken, Sweden and revealed four baselines of phytoplankton succession with their underlying drivers. Results showed that there were two diatom-dominated phases annually. The vernal community was dominated by centric diatoms larger than 15 A mu m (functional groups B and C) which were fast-growing diatoms being highly efficient in the use of nutrients. The autumn community was comprised mainly meroplanktonic mixing-dependent Aulacoseira granulata and Fragilaria sp. (MP and P) or/and large centric diatoms (B). Between the two mixing-phases with diatoms, a Gloeotrichia echinulata (H 2) bloom occurred due to its preference for a stratified water column with elevated water temperatures and high light availability. The summer stratification in Lake Erken was weak and short, thus, favoring meroplanktonic diatoms to peak once the lake turned over in early autumn. Lake Erken represents an intermediate case between a highly mixed polymictic lake and a lake with strong summer stratification, where the observed stratification patterns allowed the development of an autumn diatom phase similar, by extent, to the vernal one and mainly dominated by meroplanktonic diatoms.
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| 10. |
- Yang, Yang, 1985-, et al.
(författare)
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Water column stability and summer phytoplankton dynamics in a temperate lake (Lake Erken, Sweden)
- 2016
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Ingår i: Inland Waters. - 2044-2041 .- 2044-205X. ; 6:4, s. 499-508
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton development in aquatic ecosystems is caused by interactions among multiple environmental factors. Physical processes, particularly development of thermal stratification, have been proposed to be important factors for regulating phytoplankton composition and abundance during summer. This study examined the temporal pattern of thermal stratification during summer in Lake Erken, Sweden, based on 21 years of historical data spanning 23 years and investigated the role played by water stability on phytoplankton development. Water column stability indexes were calculated from high frequency measurements during periods of summer thermal stratification. Clustering and ordination analyzed the dissimilarities between communities during different periods and extracted the significant environmental gradients controlling phytoplankton succession. Wind introduced the major external disturbance to Lake Erken during summer and played an important role for the progression of thermocline depth. Species-specific thermal stability preference or tolerance determined the response of individual species to the stratification and constitutes a mechanism of species selection in phytoplankton dynamics. Lake Erken is an unstably stratified lake during summer, caused by wind-induced turbulence and internal seiches. Adaptation to these unstable conditions is the major determinant of phytoplankton dynamics. Hydrodynamic variability, characterized by different stability indexes in early, mid, and late summer, was the key factor regulating phytoplankton dynamics, directly by changing phytoplankton distribution and indirectly by altering both the light and nutrient availability in the epilimnion.
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| 11. |
- Ajdari, Sima, 1985, et al.
(författare)
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Formation and Control of NOx and SOx in Pressurized Oxy-Combustion Systems
- 2015
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Ingår i: The Proceedings of the 40th International Technical Conference on Clean Coal & Fuel Systems, 31 May-4 June 2015, Clearwater, Florida, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation and control of NOx and SOx in pressurized oxy-fuel combustion systems is discussed in the present work. The chemistry of nitrogen and sulfur species under pressurized conditions and the experiences gained from operating atmospheric oxy-fuel combustion pilot plants are reviewed in brief. In a conventional combustion and gas cleaning process, SO2 and NO are the principle NOx and SOx species. However, the oxidation of NO to NO2 and SO2 to SO3 is favored by low temperature and high pressure. In the present paper we will make a first modelling based of the altered oxidation conditions during both high and low temperature conditions in pressurized oxy-combustion. Besides the gas-phase oxidation, the liquid-phase N-S interactions will further enhance the formation of acids in the flue gas condensate. Thus, these low and high temperature processes will be discussed in the present work due to their relevance for the design of the flue gas compression and gas cleaning system in pressurized oxy-combustion.
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| 12. |
- Alkadir Abdulahi, Birhan, 1985, et al.
(författare)
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Structural engineering of pyrrolo[3,4-: F] benzotriazole-5,7(2 H,6 H)-dione-based polymers for non-fullerene organic solar cells with an efficiency over 12%
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 7:33, s. 19522-19530
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have synthesized two wide band gap donor polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) and pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione (TzBI), namely, PBDT-TzBI and PBDT-F-TzBI and studied their photovoltaic properties by blending them with ITIC as an acceptor. Polymer solar cell devices made from PBDT-TzBI:ITIC and PBDT-F-TzBI:ITIC exhibited power conversion efficiencies (PCEs) of 9.22% and 11.02% and while annealing at 160 °C, improved the device performances to 10.24% and 11.98%, respectively. Upon solvent annealing with diphenyl ether (DPE) (0.5%) and chlorobenzene (CB), the PCE of the PBDT-F-TzBI-based device increased to 12.12%. The introduction of the fluorinated benzodithiophene (BDT-F) moiety on the backbone of PBDT-F-TzBI improved the open circuit voltage, short circuit current and fill factor simultaneously. The high PCEs of the PBDT-F-TzBI:ITIC-based devices were supported by comparison and analysis of the optical and electronic properties, the charge carrier mobilities, exciton dissociation probabilities, and charge recombination behaviors of the devices.
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| 13. |
- Arikere, Adithya, 1987, et al.
(författare)
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Experimental Verification of Evasive Manoeuvre Assist Controller for Collision Mitigation with Oncoming Vehicles
- 2018
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Ingår i: Proceedings of the 14th International Symposium on Advanced Vehicle Control (AVEC’ 18), Beijing, China.
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Konferensbidrag (refereegranskat)abstract
- An evasive manoeuvre assist controller to mitigate the risk of collision with oncoming vehicles while performing evasive manoeuvres has previously been formulated and tested in simulation. In this work, a real-time application of this controller is implemented and used in experiments with a Volvo XC90 hybrid test vehicle. For comparison, manoeuvres are also carried out without the controller but with the driver adopting different speed control strategies. Analysis of the results show that the controller can consistently mitigate collision risk with the oncoming vehicle and while driver control of speed can perform better, it is far less robust and is heavily dependant on the driver skill and performance.
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| 14. |
- Arikere, Adithya, 1987, et al.
(författare)
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Integrated evasive manoeuvre assist for collision mitigation with oncoming vehicles
- 2018
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 56:10, s. 1577-1603
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Tidskriftsartikel (refereegranskat)abstract
- Development and deployment of steering based collision avoidance systems are made difficult due to the complexity of dealing with oncoming vehicles during the evasive manoeuvre. A method to mitigate the collision risk with oncoming vehicles during such manoeuvres is presented in this work. A point mass analysis of such a scenario is first done to determine the importance of speed for mitigating the collision risk with the oncoming vehicle. A characteristic parameter was identified, which correlates well with the need to increase or decrease speed, in order to reduce the collision risk. This finding was then verified in experiments using a Volvo XC90 test vehicle. A closed-loop longitudinal acceleration controller for collision mitigation with oncoming vehicles is then presented. The longitudinal control is combined with yaw stability control using control allocation to form an integrated controller. Simulations in CarMaker using a validated XC90 vehicle model and the proposed controller showed consistent reductions in the collision risk with the oncoming vehicle.
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| 15. |
- Arikere, Adithya, 1987, et al.
(författare)
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Optimal motion control for collision avoidance at Left Turn Across Path/Opposite Direction intersection scenarios using electric propulsion
- 2019
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Ingår i: Vehicle System Dynamics. - : Informa UK Limited. - 1744-5159 .- 0042-3114. ; 57:5, s. 637-664
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Tidskriftsartikel (refereegranskat)abstract
- Collision avoidance at intersections involving a host vehicle turning left across the path of an oncoming vehicle (Left Turn Across Path/Opposite Direction or LTAP/OD) have been studied in the past, but mostly using simplified interventions and rarely considering the possibility of crossing the intersection ahead of a bullet vehicle. Such a scenario where the driver preference is to avoid a collision by crossing the intersection ahead of a bullet vehicle is considered in this work. The optimal vehicle motion for collision avoidance in this scenario is determined analytically using a particle model within an optimal control framework. The optimal manoeuvres are then verified through numerical optimisations using a two-track vehicle model, where it was seen that the wheel forces followed the analytical global force angle result independently of the other wheels. A Modified Hamiltonian Algorithm (MHA) controller for collision avoidance that uses the analytical optimal control solution is then implemented and tested in CarMaker simulations using a validated Volvo XC90 vehicle model. Simulation results showed that collision risk can be significantly reduced in this scenario using the proposed controller, and that more benefit can be expected in scenarios that require larger speed changes.
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| 16. |
- Berland, Kristian, 1983, et al.
(författare)
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Assessment of two hybrid van der Waals density functionals for covalent and non-covalent binding of molecules
- 2017
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 146:23
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Tidskriftsartikel (refereegranskat)abstract
- Two hybrid van der Waals density functionals (vdW-DFs) are developed using 25% Fock exchange with (i) the consistent-exchange vdW-DF-cx functional [K. Berland and P. Hyldgaard, Phys. Rev. B89, 035412 (2014)] and (ii) with the vdW-DF2 functional [K. Lee et al., Phys. Rev. B 82, 081101 (2010)]. The ability to describe covalent and non-covalent binding properties of molecules is assessed. For properties related to covalent binding, atomization energies (G2-1 set), molecular reaction energies (G2RC set), and ionization energies (G21IP set) are benchmarked against experimental reference values. We find that hybrid-vdW-DF-cx yields results that are rather similar to those of the standard non-empirical hybrid PBE0 [C. Adamo and V. Barone, J. Chem. Phys. 110, 6158 (1999)], with mean average deviations (MADs) of 4.9 and 5.0 kcal/mol for the G2-1 set, respectively. In this comparison, experimental reference values are used, back corrected by wavefunction-based quantum-chemistry calculations of zero-point energies. Hybrid vdW-DF2 follows somewhat different trends, showing on average significantly larger deviations from the reference energies, with a MAD of 14.5 kcal/mol for the G2-1 set. Non-covalent binding properties of molecules are assessed using the S22 benchmark set of non-covalently bonded dimers and the X40 set of dimers of small halogenated molecules, using wavefunction-based quantum chemistry results as references. For the S22 set, hybrid-vdW-DF-cx performs better than standard vdW-DF-cx for the mostly hydrogen-bonded systems, with MAD dropping from 0.6 to 0.3 kcal/mol, but worse for purely dispersion-bonded systems, with MAD increasing from 0.2 to 0.6 kcal/mol. Hybrid-vdW-DF2 offers a slight improvement over standard vdW-DF2. Similar trends are found for the X40 set, with hybrid-vdW-DF-cx performing particularly well for binding energies involving the strongly polar hydrogen halides, but poorly for systems with tiny binding energies. Our study of the X40 set reveals the potential of mixing Fock exchange with vdW-DF, but also highlights shortcomings of the hybrids constructed here. The solid performance of hybrid-vdW-DF-cx for covalent-bonded systems, as well as the strengths and issues uncovered for non-covalently bonded systems, makes this study a good starting point for developing even more accurate hybrid vdW-DFs.
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| 17. |
- Blessing, Sebastian, et al.
(författare)
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Run, Actor, Run : Towards Cross-Actor Language Benchmarking
- 2019
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Ingår i: AGERE 2019 Proceedings of the 9th ACM SIGPLAN International Workshop on Programming Based on Actors, Agents, and Decentralized Control. - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450369824 ; , s. 41-50
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Konferensbidrag (refereegranskat)abstract
- The actor paradigm supports the natural expression of concurrency. It has inspired the development of several actor-based languages, whose adoption depends, to a large extent, on the runtime characteristics ( the performance and scaling behaviour) of programs written in these languages.This paper investigates the relative runtime characteristics of Akka, CAF and Pony, based on the Savina benchmarks. We observe that the scaling of many of the Savina benchmarks does not reflect their categorization (into essentially sequential, concurrent and parallel), that many programs have similar runtime characteristics, and that their runtime behaviour may drastically change nature ( go from essentially sequential to parallel) by tweaking some parameters.These observations lead to our proposal of a single benchmark program which we designed so that through tweaking of some knobs (we hope) we can simulate most of the programs of the Savina suite.
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| 18. |
- Despeisse, Mélanie, 1985, et al.
(författare)
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Sustainable Value Roadmapping Framework for Additive Manufacturing
- 2017
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 61, s. 594-599
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Konferensbidrag (refereegranskat)abstract
- Recent developments around the use of additive manufacturing (AM) for making components and end-products is radically changing the way manufacturing activities are organized. Many researchers are now turning their attention to AM technology and its potential benefits for boosting economic, social, and environmental sustainability. However, there is still much uncertainty on the full impact from a life cycle perspective. Previous work has reviewed the implications of AM from a sustainability and life cycle point of view, but it is unclear whether the technology can fully realize the potential benefits identified, and whether it will lead to unintended consequences such as increased material consumption, thereby further straining the planet's carrying capacity and pushing society towards unsustainable, more materialistic values. This research builds on previous work to customize a tool, the Sustainable Value Roadmapping Tool (SVRT), which combines the strategic roadmapping technique with the sustainable value analysis tool. Roadmapping is a well-established approach for businesses to strategically plan activities for the short-, medium- and long-term; combined with the value analysis tools, it can identify opportunities for sustainable value creation for all stakeholders, including society and the planet. While SVRT has been developed and tested in a more generic context (i.e. not technology-specific), it also has good promises to help companies to explore the potential benefits and challenges of AM adoption across products’ life cycle and the associated business model implications. This paper will present the prototype version of SVRT for AM. The findings consolidate and expand the opportunities and challenges already identified in the literature. Further work will conduct case studies to use the SVRT with companies adopting AM technology and better understand the sustainability impacts from a business perspective.
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| 19. |
- Devassy, Rahul, 1985, et al.
(författare)
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Finite-SNR Bounds on the Sum-Rate Capacity of Rayleigh Block-Fading Multiple-Access Channels with no a Priori CSI
- 2015
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:10, s. 3621-3632
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Tidskriftsartikel (refereegranskat)abstract
- We provide nonasymptotic upper and lower bounds on the sum-rate capacity of Rayleigh block-fading multiple-access channels for the set up where a priori channel state information is not available. The upper bound relies on a dual formula for chan- nel capacity and on the assumption that the users can cooperate perfectly. The lower bound is derived assuming a noncooperative scenario where each user employs unitary space-time modulation (independently from the other users). Numerical results show that the gap between the upper and the lower bound is small already at moderate SNR values. This suggests that the sum-rate capac- ity gains obtainable through user cooperation are minimal for the scenarios considered in the paper.
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| 20. |
- Devassy, Rahul, 1985, et al.
(författare)
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Nonasymptotic coding-rate bounds for binary erasure channels with feedback
- 2016
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Ingår i: IEEE Information Theory Workshop (ITW), Cambridge, ENGLAND, SEP 11-14, 2016. - 9781509010912 ; , s. 86-90
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Konferensbidrag (refereegranskat)abstract
- We present nonasymptotic achievability and converse bounds on the maximum coding rate (for a fixed average error probability and a fixed average blocklength) of variable-length full-feedback (VLF) and variable-length stop-feedback (VLSF) codes operating over a binary erasure channel (BEC). For the VLF setup, the achievability bound relies on a scheme that maps each message onto a variable-length Huffman codeword and then repeats each bit of the codeword until it is received correctly. The converse bound is inspired by the meta-converse framework by Polyanskiy, Poor, and Verdú (2010) and relies on binary sequential hypothesis testing. For the case of zero error probability, our achievability and converse bounds match. For the VLSF case, we provide achievability bounds that exploit the following feature of BEC: the decoder can assess the correctness of its estimate by verifying whether the chosen codeword is the only one that is compatible with the erasure pattern. One of these bounds is obtained by analyzing the performance of a variable-length extension of random linear fountain codes. The gap between the VLSF achievability and the VLF converse bound, when number of messages is small, is significant: 23% for 8 messages on a BEC with erasure probability 0.5. The absence of a tight VLSF converse bound does not allow us to assess whether this gap is fundamental.
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| 21. |
- Fan, Jin, et al.
(författare)
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Design of Novel Flat Bend Crossed Dipole for Wideband Phased Array Feed Applications
- 2019
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Ingår i: 2019 International Symposium on Antennas and Propagation, ISAP 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- This paper presents a novel Phased Array Feed (PAF) element based on flat bend crossed dipole fed by 50-Ohm coaxial line. The PAF element is dual-polarized and made from all-metal to minimize Ohmic losses and simplify cryogenic integration. It is optimized for 4- 8 GHz band aiming to possible later integration in the SKA pathfinder PHAROS2. The proposed design can also be a good element candidate of PAF for the Five hundred meter Aperture Spherical Telescope (FAST) and Qi Tai Telescope (QTT) as well as other large radio telescopes.
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| 22. |
- Gordon, Timothy James, 1953, et al.
(författare)
-
Robust Implementation of Automated Collision Avoidance Using an Updating Particle Reference
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In recent work, an autonomous collision avoidance system was described, targeting speed and path changes based on optimal control theory applied to a friction-limited particle. This avoids artificial separation of the control problem into path-planning and path following, fully integrates speed control and stability criteria with the lateral motion control, and provides a modular framework for motion control at the limits of friction. The present paper extends the previous work by providing an updating reference aimed at improving the robustness and real-world applicability of the controller. The controller is tested and evaluated under conditions of uncertain geometry and surface friction, using a high-fidelity simulation model as well as physical testing on the track.
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| 23. |
- Guan, Ke, et al.
(författare)
-
Towards realistic high-speed train channels at 5G millimeter-wave band - Part I: Paradigm, significance analysis, and scenario reconstruction
- 2018
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 67:10, s. 9112-9128
-
Tidskriftsartikel (refereegranskat)abstract
- The upcoming fifth-generation (5G) mobile communication system is expected to support high mobility up to 500 km/h, which is envisioned in particular for high-speed trains. Millimeter wave (mmWave) spectrum is considered as a key enabler for offering the 'best experience' to highly mobile users. Despite that channel characterization is necessary for the mmWave system design and validation, it is still not feasible to directly do extensive mmWave mobile channel measurements on moving high-speed trains (HST) at a speed up to 500 km/h in the present. Thus, rather than conducting mmWave HST channel sounding directly with high mobility, this study proposes a viable paradigm for realizing the realistic HST channels at the 5G mmWave band. We first propose the whole paradigm. Then, we define the scenario of interest and select the main objects and materials. Afterwards, the electromagnetic and scattering parameters of the materials are measured and estimated between 26.5 GHz and 40 GHz. With this information, the most influential materials are determined through significance analysis. Correspondingly, we reconstruct the three-dimensional mmWave outdoor HST and tunnel scenario models. Through extensive ray-tracing simulations, we determine the main propagation mechanisms in these two scenarios, the channel models based on that are validated by measurements. This verifies the whole paradigm proposed in this paper.
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| 24. |
- Guan, Ke, et al.
(författare)
-
Towards realistic high-speed train channels at 5G millimeter-wave band - Part II: Case study for paradigm implementation
- 2018
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 67:10, s. 9129-9144
-
Tidskriftsartikel (refereegranskat)abstract
- © 1967-2012 IEEE. In this paper, we present two case studies for generating realistic high-speed train (HST) channels at fifth-generation (5G) millimeter-wave (mmWave) band. The first one is the tunnel environment at relatively low 5G mmWave band, 30 GHz band, whereas the second one is the outdoor HST environment at relatively high 5G mmWave band, 90 GHz band. Both case studies include the following steps: ray-tracing simulations, stochastic channel modeling and realization, verification with ray-tracing simulations, and validation with a reduced set of measurements. A profound and insightful conclusion is reached that by employing the proposed paradigm, realistic channels can be realized for the design and evaluation of 5G mmWave communication systems in high-speed railways, even without the support of sufficient channel sounding data.
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| 25. |
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| 26. |
- Hakonen, Aron, 1970, et al.
(författare)
-
Dimer-on-mirror SERS substrates with attogram sensitivity fabricated by colloidal lithography.
- 2015
-
Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 7:21
-
Tidskriftsartikel (refereegranskat)abstract
- Nanoplasmonic substrates with optimized field-enhancement properties are a key component in the continued development of surface-enhanced Raman scattering (SERS) molecular analysis but are challenging to produce inexpensively in large scale. We used a facile and cost-effective bottom-up technique, colloidal hole-mask lithography, to produce macroscopic dimer-on-mirror gold nanostructures. The optimized structures exhibit excellent SERS performance, as exemplified by detection of 2.5 and 50 attograms of BPE, a common SERS probe, using Raman microscopy and a simple handheld device, respectively. The corresponding Raman enhancement factor is of the order 10(11), which compares favourably to previously reported record performance values.
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| 27. |
- Huang, Yang, 1985-
(författare)
-
Analysis of NMR Spin-lattice Relaxation Dispersion on Complex Systems
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focus on the analysis of spin-lattice NMRD relaxation profilesmeasured in various complex systems such as proteins, zeolites and ionicliquids. Proton, deuterium and fluoride T1-NMRD relaxation profiles wereobtained from a fast-field cycling (FFC) instrument. It is found that alsopossible to obtain NMRD profiles from the molecular dynamics (MD)simulation trajectories. NMRD Profiles were analyzed by using differentrelaxation models, such as the Solomon-Bloembergen-Morgan (SBM) theoryand the Stochastic Liouville (SL) theory.Paper I described the hydration of protein PrxV obtained from a MDsimulation, and compared with the picture emerges from an analysis byusing a generally accepted relaxation model [appendix C]. The result showsthat the information from NMRD analysis is an averaged picture of watermolecules with similar relaxation times; and the MD simulations containsinformation of all types of interested water molecules with differentresidence times.In paper II NMRD profiles have been used to characterize the hydration ofthe oxygen-evolving complex in state S1 of photosystem II. NMRDexperiments were performed on both intact protein samples and Mndepletedsamples, and characteristic dispersion difference were foundbetween 0.03 MHz to 1 MHz; approximately. Both the SBM theory and theSL theory have been used to explain this dispersion difference, and it isfound that this is due to a paramagnetic enhancement of 1-2 water moleculesnearby ~10 Å from the spin center of the Mn4CaO5 cluster. The result showsthe reorientation of the molecular cluster is in μs time interval. Whencompare these two theories, the SL theory presented a better interpretationbecause parameters obtained from the SBM theory shows they didn’t fulfilthe presupposed perturbation criterion (the Kubo term).Paper III deals with the water dynamics in the restricted/confined spaces inthe zeolite samples (H-ZSM-5 and NH4-ZSM-5) and obtained by proton anddeuterium spin-lattice NMRD profiles. The results show that the spin-latticeNMRD can be used to characterize various zeolites. The temperature has aweak effect on the relaxation rate R1, but the change of different counter ionsmay change the hydration and the translational diffusion pores and givedifferent R1.Proton and fluoride NMRD profiles and MD simulations were both used tostudy the dynamics of BMIM[PF6] in paper IV. Results indicate the reorientation of the molecules are in the ns time regime, and the effectivecorrelation time obtained from 1H and 19F are the same. From the MDsimulation it is found the reorientation of [PF6]- ions is much faster (in ps)compare with BMIM+ ion which moves in the ns time range.With previous results, the FFC NMRD profiles are indeed very informativetools to study the molecular dynamics of complex systems. The MDsimulation can be used as a complementary method to obtain detailedinformation. By combine these two methods, it provide a more colorfulpicture in the study of protein hydration and liquid molecular dynamics.
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| 28. |
- Huang, Yang, 1985-, et al.
(författare)
-
Analysis of proton/fluoride spin-lattice NMR dispersion experiment of an ionic liquid, BMIM[PF6] by using molecular dynamics simulations and relaxation theory
- 2015
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Proton/Fluoride spin-lattice nuclear magnetic relaxation dispersion(NMRD) measurements of 1-Butyl-3-methylimidazolium-hexa fluorophosphate (BMIM[PF6])have been carried out using a 1T Stelar FFC2000 fast-field-cycling instrument at proton Larmor frequencies ranging from 10 kHz to 40 MHz and at different temperatures. The NMRD profiles are interpreted by means of a simple relaxation modelbased on the inter- and intra-molecular dipole dipole relaxation mechanims. Using an atomic and a coarse-grained (CG)Molecular Dynamics (MD) simulations at temperature 323 K the relevant dipole-dipole correlation functions are calculated. The result indicate that the NMRD profiles can be rationalized using a combination of intra and inter molecular dipole-dipole couplings. However, both are mainly modulated by molecular reorientation whereas translation diffusion plays a minor role. The molecular reorientation dynamics of BMIM[PF6] ,BMIM+ ion are in the nano secondtime regime whereas the reorientation of [PF6]- is much faster and loses its correlation in the ps regime. The relaxation mechanism for [PF6]- is H-F inter-molecular dipole-dipole coupling which is modulated by the reorientation of the H-containing molecule.
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| 29. |
- Huang, Yang, 1985-, et al.
(författare)
-
Water proton and deuterium spin-lattice relaxation in Zeolite ZSM-5 by fast field-cycling NMR relaxometry
- 2015
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The water dynamics in the confined space of the zeolite ZSM-5 has bee ninvestigated by means of the field dependence of 1H- and 2H- spin-lattice relaxation rates using a 1T Stelar FFC2000 fast field-cycling instrument. The NMRD analysis of the experimental results indicates that the characteristic time dependence ( 50 ns to 1-2.4 μs) is due to water translational diffusion in narrow pores. The temperature dependence of the spin-lattice relaxation rates is weak.Zeolites with different counter ions( H+, NH4+ change the water hydration and the water translational diffusion in the pores drastically. The Zeolite-NH4+ slow down the water motion with a factor of 2.The NMRD profiles show somewhat stretched character and is described by two Lorenzian which indicates that the distribution of pore sizes is broaden.The water 1H and 2H spin lattice relaxation profiles give qualitatively information about water hydration in zeolites with different counter ions and is expected also to indicate structural changes of the zeolites.
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| 30. |
- Insulander Björk, Klara L, 1982, et al.
(författare)
-
Irradiation testing of enhanced uranium oxide fuels
- 2019
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 125, s. 99-106
-
Tidskriftsartikel (refereegranskat)abstract
- Enhanced uranium oxide fuel types are being tested in the Halden Research Reactor in Norway with the aim is to assess the effect that these enhancements have on fuel performance. Fuel temperatures, rod pressures and dimensional changes are being monitored online and an extensive post-irradiation examination programme is planned. Preliminary data show that fuel centerline temperatures can be lowered by addition of ThO2 to the fuel matrix, or by incorporating Cr or SiO2-TiO2 as a network structure within the fuel. In parallel, two types of cladding coatings are tested in order to investigate their in-core properties. No abnormal behaviour has been noted during the first 100 days of irradiation.
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| 31. |
- Jacobson, Bengt J H, 1962, et al.
(författare)
-
Vehicle tyre to road friction value estimation arrangement
- 2018
-
Patent (övrigt vetenskapligt/konstnärligt)abstract
- A vehicle tyre to road friction value estimation arrangement (1) is provided comprising a vehicle impact detecting unit (3), a vehicle wheel axle lateral acceleration estimation unit (5.1, 5.2, 5.3, 5.4), and a processing unit (7). The vehicle impact detecting unit (3) is arranged to detect occurrence of an impact. The vehicle wheel axle lateral acceleration estimation unit (5.1, 5.2, 5.3, 5.4) is arranged to, upon a detected occurrence of an impact, estimate or measure a lateral acceleration of at least one vehicle wheel axle (13.1, 13.2) of the host vehicle (9). The processing unit (7) is arranged to determine an occurrence of a shift in direction of the lateral acceleration, and obtain a subsequent peak lateral acceleration estimate and to calculate an estimate of a host vehicle tyre to road friction value based on the thus obtained peak lateral acceleration estimate. The present invention also relates to a post impact vehicle control system (2), a vehicle (9) comprising a post impact vehicle control system (2) and a method (100) of estimating a vehicle tyre to road friction value. The present invention relates to a vehicle tyre to road friction value estimation arrangement. The present invention also relates to post impact vehicle control system comprising a vehicle tyre to road friction value estimation arrangement and a vehicle comprising a post impact vehicle control system and a method of estimating a vehicle tyre to road friction value. https://encrypted.google.com/patents/EP2883771A1?cl=un
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| 32. |
- Jiao, Yang, 1985, et al.
(författare)
-
Extent of Fock-exchange mixing for a hybrid van der Waals density functional?
- 2018
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 148:19
-
Tidskriftsartikel (refereegranskat)abstract
- The vdW-DF-cx0 exchange-correlation hybrid design [K. Berland et al., J. Chem. Phys. 146, 234106 (2017)] has a truly nonlocal correlation component and aims to facilitate concurrent descriptions of both covalent and non-covalent molecular interactions. The vdW-DF-cx0 design mixes a fixed ratio, a, of the Fock exchange into the consistent-exchange van der Waals density functional, vdW-DF-cx [K. Berland and P. Hyldgaard, Phys. Rev. B 89, 035412 (2014)]. The mixing value a is sometimes taken as a semi-empirical parameter in hybrid formulations. Here, instead, we assert a plausible optimum average a value for the vdW-DF-cx0 design from a formal analysis; A new, independent determination of the mixing a is necessary since the Becke fit [A. D. Becke, J. Chem. Phys. 98, 5648 (1993)], yielding a 0 = 0.2, is restricted to semilocal correlation and does not reflect non-covalent interactions. To proceed, we adapt the so-called two-legged hybrid construction [K. Burke et al., Chem. Phys. Lett. 265, 115 (1997)] to a starting point in the vdW-DF-cx functional. For our approach, termed vdW-DF-tlh, we estimate the properties of the adiabatic-connection specification of the exact exchange-correlation functional, by combining calculations of the Fock exchange and of the coupling-constant variation in vdW-DF-cx. We find that such vdW-DF-tlh hybrid constructions yield accurate characterizations of molecular interactions (even if they lack self-consistency). The accuracy motivates trust in the vdW-DF-tlh determination of system-specific values of the Fock-exchange mixing. We find that an average value a 0 = 0.2 best characterizes the vdW-DF-tlh description of covalent and non-covalent interactions, although there exists some scatter. This finding suggests that the original Becke value, a 0 = 0.2, also represents an optimal average Fock-exchange mixing for the new, truly nonlocal-correlation hybrids. To enable self-consistent calculations, we furthermore define and test a zero-parameter hybrid functional vdW-DF-cx0p (having fixed mixing a 0 = 0.2) and document that this truly nonlocal correlation hybrid works for general molecular interactions (at reference and at relaxed geometries). It is encouraging that the vdW-DF-cx0p functional remains useful also for descriptions of some extended systems. Published by AIP Publishing.
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| 33. |
- Jiao, Yang, 1985, et al.
(författare)
-
Schottky barrier formation and band bending revealed by first- principles calculations
- 2015
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 5, s. Art. no. 11374-
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures.
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| 34. |
- Jiao, Yang, 1985, et al.
(författare)
-
Signatures of van der Waals binding: A coupling-constant scaling analysis
- 2018
-
Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 97:8
-
Tidskriftsartikel (refereegranskat)abstract
- The van der Waals (vdW) density functional (vdW-DF) method [Rep. Prog. Phys. 78, 066501 (2015)RPPHAG0034-488510.1088/0034-4885/78/6/066501] describes dispersion or vdW binding by tracking the effects of an electrodynamic coupling among pairs of electrons and their associated exchange-correlation holes. This is done in a nonlocal-correlation energy term Ecnl, which permits density functional theory calculation in the Kohn-Sham scheme. However, to map the nature of vdW forces in a fully interacting materials system, it is necessary to also account for associated kinetic-correlation energy effects. Here, we present a coupling-constant scaling analysis, which permits us to compute the kinetic-correlation energy Tcnl that is specific to the vdW-DF account of nonlocal correlations. We thus provide a more complete spatially resolved analysis of the electrodynamical-coupling nature of nonlocal-correlation binding, including vdW attraction, in both covalently and noncovalently bonded systems. We find that kinetic-correlation energy effects play a significant role in the account of vdW or dispersion interactions among molecules. Furthermore, our mapping shows that the total nonlocal-correlation binding is concentrated to pockets in the sparse electron distribution located between the material fragments.
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| 35. |
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| 36. |
- Jonasson, Mats, 1969, et al.
(författare)
-
Method and system for providing an intervening steering action for a host vehicle to avoid collision
- 2018
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This function assists the driver with steering when needed, by following an escape safe zone to avoid threats around the host vehicle. The proposed idea is an add-on to an existing evasive steering function to solve the collision by steering problem. It can however be used alone also. The function will apply a steering torque request when a collision threat is present, but doesn’t require that the driver has initiated the steering manoeuvre. The function is thereby a step towards automated steering avoidance manoeuvres. The steering torque amplitude should be low and smooth. The applied torque will pretension the steering system so it will respond quicker when driver applies steering. Another effect is that vehicle slowly will drift laterally in the intended direction. The torque amplitude should not exceed a level where the driver has difficulties to notice and override the torque; and should not result in an over-reaction of panic driver steering against the opposite direction. The total yaw angle from the funcytion is typically low.
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| 37. |
- Kang, Naixin, et al.
(författare)
-
Antischistosomal Properties of Hederacolchiside A1 Isolated from Pulsatilla chinensis
- 2018
-
Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 23:6
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Schistosomiasis is a major neglected disease for which the current control strategy involves mass treatment with praziquantel, the only available drug. Hence, there is an urgent need to develop new antischistosomal compounds.Methods: The antischistosomal activity of hederacolchiside A1 (HSA) were determined by total or female worm burden reductions in mice harboring Schistosoma japonicum or S. mansoni. Pathology parameters were detected on HSA against 1-day-old S. japonicum-harboring mice. Moreover, we confirmed the antischistosomal effect of HSA on newly transformed schistosomula (NTS) of S. japonicum in vitro.Results: HSA, a natural product isolated from Pulsatilla chinensis (Bunge) Regel, was initially corroborated to possess promising antischistosomal properties. We demonstrated that HSA had high activity against S. japonicum and S. mansoni less in 11 days old parasites harbored in mice. The antischistosomal effect was even more than the currently used drugs, praziquantel, and artesunate. Furthermore, HSA could ameliorate the pathology parameters in mice harboring 1-day-old juvenile S. japonicum. We also confirmed that HSA-mediated antischistosomal activity is partly due to the morphological changes in the tegument system when NTS are exposed to HSA.Conclusions: HSA may have great potential to be an antischistosomal agent for further research.
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| 38. |
- Korol, Sergiy V, et al.
(författare)
-
Functional Characterization of Native, High-Affinity GABAA Receptors in Human Pancreatic β Cells
- 2018
-
Ingår i: EBioMedicine. - : Elsevier BV. - 2352-3964. ; 30
-
Tidskriftsartikel (refereegranskat)abstract
- In human pancreatic islets, the neurotransmitter γ-aminobutyric acid (GABA) is an extracellular signaling molecule synthesized by and released from the insulin-secreting β cells. The effective, physiological GABA concentration range within human islets is unknown. Here we use native GABAA receptors in human islet β cells as biological sensors and reveal that 100-1000nM GABA elicit the maximal opening frequency of the single-channels. In saturating GABA, the channels desensitized and stopped working. GABA modulated insulin exocytosis and glucose-stimulated insulin secretion. GABAA receptor currents were enhanced by the benzodiazepine diazepam, the anesthetic propofol and the incretin glucagon-like peptide-1 (GLP-1) but not affected by the hypnotic zolpidem. In type 2 diabetes (T2D) islets, single-channel analysis revealed higher GABA affinity of the receptors. The findings reveal unique GABAA receptors signaling in human islets β cells that is GABA concentration-dependent, differentially regulated by drugs, modulates insulin secretion and is altered in T2D.
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| 39. |
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| 40. |
- Koskela, Salla, et al.
(författare)
-
Lytic polysaccharide monooxygenase (LPMO) mediated production of ultra-fine cellulose nanofibres from delignified softwood fibres
- 2019
-
Ingår i: Green Chemistry. - : Royal Society of Chemistry. - 1463-9262 .- 1463-9270. ; 21:21, s. 5924-5933
-
Tidskriftsartikel (refereegranskat)abstract
- The production of cellulose nanofibres (CNFs) typically requires harsh chemistry and strong mechanical fibrillation, both of which have negative environmental impacts. A possible solution is offered by lytic polysaccharide monooxygenases (LPMOs), oxidative enzymes that boost cellulose fibrillation. Although the role of LPMOs in oxidative modification of cellulosic substrates is rather well established, their use in the production of cellulose nanomaterials is not fully explored, and the effect of the carbohydrate-binding module (CBM) on nanofibrillation has not yet been reported. Herein, we studied the activity of two LPMOs, one of which was appended to a CBM, on delignified softwood fibres for green and energy-efficient production of CNFs. The CNFs were used to prepare cellulose nanopapers, and the structure and properties of both nanofibres and nanopapers were determined. Both enzymes were able to facilitate nanocellulose fibrillation and increase colloidal stability of the produced CNFs. However, the CBM-lacking LPMO was more efficient in introducing carboxyl groups (0.53 mmol/g) on the cellulose fibre surfaces and releasing CNFs with thinner width (4.3 ± 1.5 nm) from delignified spruce fibres than the modular LPMO (carboxylate content of 0.38 mmol/g and nanofibre width of 6.7± 2.5 nm through LPMO pretreatment followed by mild homogenisation. The prepared nanopapers showed improved mechanical properties (tensile strength of 262 MPa, and modulus of 16.2 GPa) compared to conventional CNFs preparation methods, demonstrating the potential of LPMOs as green alternatives for cellulose nanomaterials preparation.
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| 41. |
- Liang, Xi, et al.
(författare)
-
Assimilating Copernicus SST Data into a Pan-Arctic Ice–Ocean Coupled Model with a Local SEIK Filter
- 2017
-
Ingår i: Journal of Atmospheric and Oceanic Technology. - : American Meteorological Society. - 0739-0572 .- 1520-0426. ; 34:9, s. 1985-1999
-
Tidskriftsartikel (refereegranskat)abstract
- Sea surface temperature (SST) data from the Copernicus Marine Environment Monitoring Service are assimilated into a pan-Arctic ice–ocean coupled model using the ensemble-based local singular evolutive interpolated Kalman (LSEIK) filter. This study found that the SST deviation between model hindcasts and independent SST observations is reduced by the assimilation. Compared with model results without data assimilation, the deviation between the model hindcasts and independent SST observations has decreased by up to 0.2°C at the end of summer. The strongest SST improvements are located in the Greenland Sea, the Beaufort Sea, and the Canadian Arctic Archipelago. The SST assimilation also changes the sea ice concentration (SIC). Improvements of the ice concentrations are found in the Canadian Arctic Archipelago, the Beaufort Sea, and the central Arctic basin, while negative effects occur in the west area of the eastern Siberian Sea and the Laptev Sea. Also, sea ice thickness (SIT) benefits from ensemble SST assimilation. A comparison with upward-looking sonar observations reveals that hindcasts of SIT are improved in the Beaufort Sea by assimilating reliable SST observations into light ice areas. This study illustrates the advantages of assimilating SST observations into an ice–ocean coupled model system and suggests that SST assimilation can improve SIT hindcasts regionally during the melting season.
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| 42. |
- Lin, Changgui, 1985, et al.
(författare)
-
Impact of model resolution on simulating the water vapor transport through the central Himalayas: implication for models’ wet bias over the Tibetan Plateau
- 2018
-
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 51:9-10, s. 3195-3207
-
Tidskriftsartikel (refereegranskat)abstract
- © 2018 The Author(s) Current climate models commonly overestimate precipitation over the Tibetan Plateau (TP), which limits our understanding of past and future water balance in the region. Identifying sources of such models’ wet bias is therefore crucial. The Himalayas is considered a major pathway of water vapor transport (WVT) towards the TP. Their steep terrain, together with associated small-scale processes, cannot be resolved by coarse-resolution models, which may result in excessive WVT towards the TP. This paper, therefore, investigated the resolution dependency of simulated WVT through the central Himalayas and its further impact on precipitation bias over the TP. According to a summer monsoon season of simulations conducted using the weather research forecasting (WRF) model with resolutions of 30, 10, and 2 km, the study found that finer resolutions (especially 2 km) diminish the positive precipitation bias over the TP. The higher-resolution simulations produce more precipitation over the southern Himalayan slopes and weaker WVT towards the TP, explaining the reduced wet bias. The decreased WVT is reflected mostly in the weakened wind speed, which is due to the fact that the high resolution can improve resolving orographic drag over a complex terrain and other processes associated with heterogeneous surface forcing. A significant difference was particularly found when the model resolution is changed from 30 to 10 km, suggesting that a resolution of approximately 10 km represents a good compromise between a more spatially detailed simulation of WVT and computational cost for a domain covering the whole TP.
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| 43. |
- Liu, Sichao, et al.
(författare)
-
An ‘Internet of Things’ enabled dynamic optimization method for smart vehicles and logistics tasks
- 2019
-
Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 215, s. 806-820
-
Tidskriftsartikel (refereegranskat)abstract
- Centralized and one-way logistics services and the lack of real-time information of logistics resources are common in the logistics industry. This has resulted in the increased logistics cost, energy consumption, logistics resources consumption, and the decreased loading rate. Therefore, it is difficult to achieve efficient, sustainable, and green logistics services with dramatically increasing logistics demands. To deal with such challenges, a real-time information-driven dynamic optimization strategy for smart vehicles and logistics tasks towards green logistics is proposed. Firstly, an ‘Internet of Things’-enabled real-time status sensing model of logistics vehicles is developed. It enables the vehicles to obtain and transmit real-time information to the dynamic distribution center, which manages value-added logistics information. Then, such information can be shared among logistics companies. A dynamic optimization method for smart vehicles and logistics tasks is developed to optimize logistics resources, and achieve a sustainable balance between economic, environmental, and social objectives. Finally, a case study is carried out to demonstrate the effectiveness of the proposed optimization method. The results show that it contributes to reducing logistics cost and fuel consumption, improving vehicles’ utilization rate, and achieving real-time logistics services with high efficiency.
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| 44. |
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| 45. |
- Luo, Xin, 1983, et al.
(författare)
-
Unusual tensile behaviour of fibre-reinforced indium matrix composite and its in-situ TEM straining observation
- 2016
-
Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454. ; 104, s. 109-118
-
Tidskriftsartikel (refereegranskat)abstract
- Indium-based thermal interface materials are superior in thermal management applications of electronic packaging compared to their polymer-based counterparts. However, pure indium has rather low tensile strength resulting in poor reliability. To enhance the mechanical properties of such a material, a new composite consisting of electrospun randomly oriented continuous polyimide fibres and indium was fabricated. The composite has been characterised by tensile tests and in-situ transmission electron microscopy straining observations. It is shown that the composite's ultimate tensile strength at 20 degrees C is five times higher than that of pure indium, and the strength of the composite exceeds the summation of strengths of the individual components. Furthermore, contrary to most metallic matrix materials, the ultimate tensile strength of the composite decreases with the increased strain rate in a certain range. The chemical composition and tensile fracture of the novel composite have been analysed comprehensively by means of scanning transmission electron microscopy and scanning electron microscopy. A strengthening mechanism based on mutually reinforcing structures formed by the indium and surrounding fibres is also presented, underlining the effect of compressing at the fibre/indium interfaces by dislocation pileups and slip pinning.
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| 46. |
- Mellin, Pelle, 1985-, et al.
(författare)
-
Influence of Reaction Atmosphere (H2O, N2, H2, CO2, CO) on Fluidized-Bed Fast Pyrolysis of Biomass Using Detailed Tar Vapor Chemistry in Computational Fluid Dynamics
- 2015
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 54:33, s. 8344-8355
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Tidskriftsartikel (refereegranskat)abstract
- Secondary pyrolysis in fluidized bed fast pyrolysis of biomass is the focus of this work. A novel computational fluid dynamics (CFD) model coupled with a comprehensive chemistry scheme (134 species and 4169 reactions, in CHEMKIN format) has been developed to investigate this complex phenomenon. Previous results from a transient three-dimensional model of primary pyrolysis were used for the source terms of primary products in this model. A parametric study of reaction atmospheres (H2O, N2, H2, CO2, CO) has been performed. For the N2 and H2O atmosphere, results of the model compared favorably to experimentally obtained yields after the temperature was adjusted to a value higher than that used in experiments. One notable deviation versus experiments is pyrolytic water yield and yield of higher hydrocarbons. The model suggests a not overly strong impact of the reaction atmosphere. However, both chemical and physical effects were observed. Most notably, effects could be seen on the yield of various compounds, temperature profile throughout the reactor system, residence time, radical concentration, and turbulent intensity. At the investigated temperature (873 K), turbulent intensity appeared to have the strongest influence on liquid yield. With the aid of acceleration techniques, most importantly dimension reduction, chemistry agglomeration, and in-situ tabulation, a converged solution could be obtained within a reasonable time (∼30 h). As such, a new potentially useful method has been suggested for numerical analysis of fast pyrolysis.
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| 47. |
- Mellin, Pelle, 1985-
(författare)
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Pyrolysis of biomass in fluidized-beds: in-situ formation of products and their applications for ironmaking
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The iron and steel industry emitted 8 % of all CO2 emissions in Sweden, 2011. Investigating alternative energy carriers is the purpose of this thesis. By pyrolyzing biomass, an energetic solid, gaseous and liquid (bio oil) fraction is obtained. If pyrolyzing biomass in a fluidized-bed reactor, the highest value may be added to the combined products. Additional understanding of pyrolysis in fluidized beds is pursued, using Computational Fluid Dynamics (CFD) and comprehensive kinetic schemes. The obtained solid product is investigated as a bio-injectant in blast furnaces for ironmaking.A new approach of separately modeling, the primary and secondary pyrolysis, is developed in this thesis. A biomass particle devolatilizes during pyrolysis. Primary pyrolysis is the solid decomposition which results in the volatiles that can leave the particle. Secondary pyrolysis is the decompositions of these volatiles, primarily in the gas phase.The primary pyrolysis (35 species, 15 reactions) mainly occurs in the bed-zone and as such, the model needs to take into account the complex physical interaction of biomass-particles with the fluidizing media (sand) and the fluidizing agent (gas). This is accomplished by representing the components by Eulerian phases and implementing interaction terms, as well as using a Stiff Chemistry Solver for the implemented reactions. The secondary pyrolysis (not considering heterogeneous reactions), mainly occurs outside the bed zone in one phase. The fluid flow is simpler but the chemistry is more complex, with a larger variety of molecules emerging. Carrying out the simulations time-effectively, for the secondary pyrolysis (134 species, 4169 reactions) is accomplished by using Dimension Reduction, Chemistry Agglomeration and In-situ Tabulation (ISAT); in a Probability Density Functional (PDF) framework.An analysis of the numerical results suggest that they can be matched adequately with experimental measurements, considering pressure profiles, temperature profiles and the overall yield of gas, solid and liquid products. Also, with some exceptions, the yield of major and minor gaseous species can be matched to some extent. Hence, the complex physics and chemistry of the integrated process can be considered fairly well-considered but improvements are possible. A parametric study of reaction atmospheres (or fluidizing agents), is pursued as means of understanding the process better. The models revealed significant effects of the atmosphere, both physically (during the primary and secondary pyrolysis) and chemically (during secondary pyrolysis).During primary pyrolysis, the physical influence of reaction atmospheres (N2, H2O) is investigated. When comparing steam to nitrogen, heat flux to the biomass particles, using steam, is better distributed on a bed level and on a particle level.During secondary pyrolysis, results suggest that turbulence interaction plays an important role in accelerating unwanted decomposition of the liquid-forming volatiles. Steam, which is one of the investigated atmospheres (N2, H2O, H2, CO, CO2), resulted in a lower extent of unwanted secondary pyrolysis. Altough, steam neither resulted in the shortest vapor residence time, nor the lowest peak temperature, nor the lowest peak radical concentration; all factors known to disfavor secondary pyrolysis. A repeated case, using a high degree of turbulence at the inlet, resulted in extensive decompositions. The attractiveness of the approach is apparent but more testing and development is required; also with regards to the kinetic schemes, which have been called for by several other researchers.The solid fraction after pyrolysis is known as charcoal. Regarding its use in blast furnaces; modelling results indicate that full substitution of fossil coal is possible. Substantial reductions in CO2 emissions are hence possible. Energy savings are furthermore possible due to the higher oxygen content of charcoal (and bio-injectants in general), which leads to larger volumes of blast furnace gas containing more latent energy (and less non-recoverable sensible energy). Energy savings are possible, even considering additional electricity consumption for oxygen enrichment and a higher injection-rate on energy basis.A survey of biomass availability and existing technology suppliers in Sweden, suggest that all injection into Blast furnace M3 in Luleå, can be covered by biomass. Based on statistics from 2008, replacement of coal-by-charcoal from pyrolysis could reduce the on-site carbon dioxide emissions by 28.1 % (or 17.3 % of the emissions from the whole industry). For reference, torrefied material and raw biomass can reduce the on-site emissions by 6.4 % and 5.7 % respectively.
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| 48. |
- Meyer-Jacob, Carsten, 1984-, et al.
(författare)
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Early land use and centennial scale changes in lake-water organic carbon prior to contemporary monitoring
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:21, s. 6579-6584
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Tidskriftsartikel (refereegranskat)abstract
- Organic carbon concentrations have increased in surface waters across parts of Europe and North America during the past decades, but the main drivers causing this phenomenon are still debated. A lack of observations beyond the last few decades inhibits a better mechanistic understanding of this process and thus a reliable prediction of future changes. Here we present past lake-water organic carbon trends inferred from sediment records across central Sweden that allow us to assess the observed increase on a centennial to millennial time scale. Our data show the recent increase in lake-water carbon but also that this increase was preceded by a landscape-wide, long-term decrease beginning already A. D. 1450-1600. Geochemical and biological proxies reveal that these dynamics coincided with an intensification of human catchment disturbance that decreased over the past century. Catchment disturbance was driven by the expansion and later cessation of widespread summer forest grazing and farming across central Scandinavia. Our findings demonstrate that early land use strongly affected past organic carbon dynamics and suggest that the influence of historical landscape utilization on contemporary changes in lake-water carbon levels has thus far been underestimated. We propose that past changes in land use are also a strong contributing factor in ongoing organic carbon trends in other regions that underwent similar comprehensive changes due to early cultivation and grazing over centuries to millennia.
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| 49. |
- Nie, Xuefang, et al.
(författare)
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Modeling and Analysis of FeICIC in OFDMA HetNets with Limited Backhaul Capacity
- 2018
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Ingår i: 2018 10th International Conference on Wireless Communications and Signal Processing, WCSP 2018. - 9781538661208
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Konferensbidrag (refereegranskat)abstract
- Heterogeneous networks (HetNets) with dense deployment of small cells in co-channel manner are recognized as a key solution to boost network capacity. However, in addition to the severe inter-Tier interference, the non-ideal backhaul is also a bottleneck in improving the performance of HetNets. This paper proposes an analytical model of further-enhanced intercell interference coordination (FeICIC) in orthogonal frequency division multiple access (OFDMA) HetNets with limited backhaul capacity, and further evaluates the performance of HetNets. Stochastic geometry is applied to derive the expression of rate coverage in two-Tier HetNets, while modeling the BS interference in the context of OFDMA. The accuracy of analytical results is validated by Monte Carlo simulation. The superiority of FeICIC for rate coverage of HetNets is demonstrated, and the proper parameter settings are further investigated to provide design guidelines for future dense networks.
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| 50. |
- Nilsson, Rickard, et al.
(författare)
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Method and system for providing a steering guidance to a driver of a host vehicle
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The idea is to guide the driver by giving a short autonomous change of yaw angle. The host vehicle should be controlled to reach the left limit of the lane, rather than avoid the threat itself. Thereby the envisioned function inspire the driver to avoid a collision by steering. The yawangle directly after the control intervention, will help driver to understand where to go and that there is a free space that admits the manoeuvre without departure the road or collide with oncoming traffic.
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