| 1. |
- Almgren, Magnus, 1972, et al.
(författare)
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RICS-el : Building a national testbed for research and training on SCADA security (short paper)
- 2019
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Ingår i: Lect. Notes Comput. Sci.. - Cham : Springer Nature. ; 11260 LNCS, s. 219-225, s. 219-225
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Konferensbidrag (refereegranskat)abstract
- Trends show that cyber attacks targeting critical infrastructures are increasing, but security research for protecting such systems are challenging. There is a gap between the somewhat simplified models researchers at universities can sustain contra the complex systems at infrastructure owners that seldom can be used for direct research. There is also a lack of common datasets for research benchmarking. This paper presents a national experimental testbed for security research within supervisory control and data acquisition systems (SCADA), accessible for both research training and experiments. The virtualized testbed has been designed and implemented with both vendor experts and security researchers to balance the goals of realism with specific research needs. It includes a real SCADA product for energy management, a number of network zones, substation nodes, and a simulated power system. This environment enables creation of scenarios similar to real world utility scenarios, attack generation, development of defence mechanisms, and perhaps just as important: generating open datasets for comparative research evaluation.
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| 2. |
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| 3. |
- Fransson, J.E.S., et al.
(författare)
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Mapping of Wind-Thrown Forests Using VHF/UHF SAR Images
- 2007
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Ingår i: IEEE 2007 International Geoscience and Remote Sensing Symposium (IGARSS 2007), Barcelona, Spain, July 23-27 2007. ; DOI: 10.1109/IGARSS.2007.4423313, s. 2350-2353
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- SAR images from the Swedish airborne CARABAS-II and LORA systems have been visually analyzed over simulated wind-thrown forest at both single tree and stand level. In ideal conditions, the results show that LORA is more accurate than CARABAS-II at detecting wind-thrown trees, regardless of tree size and direction of the fallen trees relative to flight heading. Furthermore, the visible single trees in the LORA images appeared more distinct than in the CARABAS-II images, which could be explained by the high resolution in the LORA images. Based on visual interpretation, it is likely that the detection of wind-thrown forests could be improved using VHF/UHF SAR images acquired both prior to and after a storm event.
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| 4. |
- Smith Jonforsen, Gary, 1972, et al.
(författare)
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Forest stem volume estimation using high-resolution lidar and SAR data
- 2002
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Ingår i: IEEE Geoscience and Remote Sensing Symposium (IGARSS), Toronto, Canada, 24-28 June. - 078037536X ; IV, s. 2084-6
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Presents a comparison of remote sensing of forests using two complementary, high-resolution sensors; namely the TopEye lidar and CARABAS VHF SAR systems. The lidar data are from a small footprint configuration, allowing discrimination between pulses reflected from the tree crowns, and those penetrating through gaps in the canopy. From these data, measurements of tree height and crown size can be made for individual trees, and the tree volume calculated through empirical relationships. The CARABAS VHF SAR provides a more direct measurement of tree volume, since the long wavelengths penetrate the forest canopy and are scattered by the trunk-ground dihedral. Results of stem volume retrieval for individual trees using data from the two systems are presented, and the possibility of using the complementary measurements discussed
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| 5. |
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| 6. |
- Eriksson, Leif, 1970, et al.
(författare)
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ALOS PALSAR Calibration and Validation Results from Sweden
- 2007
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Ingår i: IEEE Geoscience and Remote Sensing Symposium (IGARSS 2007), Barcelona, Spain, July 23-27, 2007. ; DOI: 10.1109/IGARSS.2007.4423115, s. 1589-1592
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In 2006 calibration activities for ALOS PALSAR wereconducted in Sweden. Four five-metre trihedral corner reflectorsand three smaller dihedral reflectors were deployed and operatedduring eight months. 23 PALSAR scenes were acquired over thecalibration site allowing an evaluation of the quality and temporalstability of the data. Results show that the co-polarized datahave been stable during the whole calibration period with variationsin the trihedral responses lower than 0.7 dB. The measuredresolution in azimuth was 4.4 m and in slant range 4.7 m forsingle polarization images and 9.5 m for polarimetric data. Forthe cross-polarized data large variations in the dihedral responseswere found. It is assumed that this is caused by a larger sensitivityto pointing errors. For the polarimetric data, estimation ofFaraday rotation gave values ranging from 0.1º to 3º.
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| 7. |
- Hallberg, Robert T., et al.
(författare)
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Palladium seeded GaAs nanowires
- 2016
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Ingår i: Journal of Materials Research. - : Springer Science and Business Media LLC. - 0884-2914 .- 2044-5326. ; 31:2, s. 175-185
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a detailed investigation of the growth of palladium-seeded GaAs nanowires. Nanowires grown on GaAs (111)B substrates consist of three different morphologies, denoted as curly (containing multiple kinks), inclined (relative to the substrate, such as 〈001〉), and vertical. We show that the relative yield of the different types is controllable by a combination of V/III ratio and temperature, where vertical and inclined nanowires are promoted by a high temperature and low V/III ratio. These growth conditions are expected to promote a higher Ga incorporation into the Pd particle, which is confirmed by energy dispersive x-ray analysis. We propose that the observed relationship between particle composition and nanowire morphology may be related to the particle phase, with liquid particles promoting straight nanowire growth. In addition, particles at the tips of nanowires are sometimes observed to be smaller than the initial particle size, suggesting that Pd has been lost during the growth process. Finally, we demonstrate the importance of initial particle size-control to interpret diameter changes after growth.
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| 8. |
- Hallberg, R. T., et al.
(författare)
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Hydrogen-assisted spark discharge generated metal nanoparticles to prevent oxide formation
- 2018
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 52:3, s. 347-358
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Tidskriftsartikel (refereegranskat)abstract
- There exists a demand for production of metal nanoparticles for today's emerging nanotechnology. Aerosol-generated metal nanoparticles can oxidize during particle formation due to impurities in the carrier gas. One method to produce unoxidized metal nanoparticles is to first generate metal oxides and then reduce them during sintering. Here, we propose to instead prevent oxidation by introducing the reducing agent already at particle formation. We show that by mixing 5% hydrogen into the nitrogen carrier gas, we can generate single crystalline metal nanoparticles by spark discharge from gold, cobalt, bismuth, and tin electrodes. The non-noble nanoparticles exhibit signs of surface oxidation likely formed post-deposition when exposed to air. Nanoparticles generated without hydrogen are found to be primarily polycrystalline and oxidized. To demonstrate the advantages of supplying the reducing agent at generation, we compare to nanoparticles that are generated in nitrogen and sintered in a hydrogen mixture. For bismuth and tin, the crystal quality of the particles after sintering is considerably higher when hydrogen is introduced at particle generation compared to at sintering, whereas for cobalt it is equally effective to only add hydrogen at sintering. We propose that hydrogen present at particle generation prevents the formation of oxide primary particles, thus improving the ability to sinter the nanoparticles to compact and single crystals of metal. This method is general and can be applied to other aerosol generation systems, to improve the generation of size-controlled nanoparticles of non-noble metals with a suitable reducing agent.
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| 9. |
- Hallberg, Robert T., et al.
(författare)
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Nanowire morphology and particle phase control by tuning the in concentration of the foreign metal nanoparticle
- 2018
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 30:5
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Tidskriftsartikel (refereegranskat)abstract
- Controllable particle assisted growth (PAG) of III-V nanowires is today almost exclusively done with Au, Ga or In nanoparticles, whereas other metals often yield nanowires with uncontrolled growth directions. To improve the control of the initial growth direction in PAG, independent of choice of metal, we propose to initiate nanowire growth from a group-III-rich foreign metal particle. For III-V nanowire growth, the group III concentration of the particle can be made to increase or decrease with the relative supply of group III and group V material, which can be used to promote the liquid phase that is necessary for vapor-liquid-solid growth. In this paper, 30 nm Pd nanoparticles are used to develop growth conditions for In-rich PAG of InAs nanowires. The particle size evolution for different growth times and V/III ratios is correlated with changes in nanowire density and morphology. In addition, we demonstrate In-rich Co, Pd, Pt and Rh nanoparticles and optimized In-rich PAG from Au and Pd seeds. The Au and Pd seeded nanowires are remarkably similar and by tuning the particle composition we trigger a morphological change. The vertical nanowire morphology is associated with In-rich nanoparticles that contain a liquid phase. The curly nanowire morphology, with random growth directions have an In concentration less than or equal to that of the most In rich compound of the seed metal-In system.
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| 10. |
- Lindahl, O A, et al.
(författare)
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Tactile resonance sensors in medicine.
- 2009
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Ingår i: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 33:4, s. 263-273
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Tidskriftsartikel (refereegranskat)abstract
- Tactile sensors in general are used for measuring the physical parameters associated with contact between sensor and object. Tactile resonance sensors in particular are based on the principle of measuring the frequency shift, Deltaf, defined as the difference between a freely vibrating sensor resonance frequency and the resonance frequency measured when the sensor makes contact to an object. Deltaf is therefore related to the acoustic impedance of the object and can be used to characterize its material properties. In medicine, tactile resonance sensor systems have been developed for the detection of cancer, human ovum fertility, eye pressure and oedema. In 1992 a Japanese research group published a paper presenting a unique phase shift circuit to facilitate resonance measurements. In this review we summarize the current state-of-the-art of tactile resonance sensors in medicine based on the phase shift circuit and discuss the relevance of the measured parameters for clinical diagnosis. Future trends and applications enabled by this technology are also predicted.
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