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  • 1.
    Acquaviva, Alessandro
    et al.
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Grunditz, Emma Arfa
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Lundmark, Sonja Tidblad
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Thiringer, Torbjorn
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Computationally Efficient Modeling of Electrical Machines With Cooling Jacket2019In: IEEE TRANSACTIONS ON TRANSPORTATION ELECTRIFICATION, ISSN 2332-7782, Vol. 5, no 3, p. 618-629Article in journal (Refereed)
    Abstract [en]

    Modeling of electrical machines is a multiphysics problem. Depending on the phenomena of interest and the computational time constraint, this can be done at different levels of detail. In this article, the main approaches to model the thermal behavior of electrical machines with a liquid cooled casing around the stator (often referred to as cooling jacket) are analyzed and a novel approach is presented. The proposed method aims at creating computationally efficient 3-D multiphysics models of electrical machines with liquid cooled jacket. This model is based on the assumption of a fully developed flow in the cooling jacket which allows to scale the computational fluid dynamics (CFD) simulation to 1-D. The slot with a two layer concentrated winding and potting material is modeled using a composite material comprising of both the conductors and slot filler. Similarly, a unified material is used to model the end-windings. Experimental results on a traction machine for vehicle applications are presented showing good agreement with the simulations. Also, a comparison with a 3-D CFD is presented to verify the pressure drop in the pipe bend. Finally, the model is used to simulate a dynamic load cycle, which would be computationally extremely demanding with combined 3-D CFD and thermal FEA of the machine and its cooling.

  • 2. Aguilera, M.
    et al.
    Vanfretti, L.
    Gómez, Francisco José
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Experiences in power system multi-domain modeling and simulation with modelica & FMI: The case of gas power turbines and power systems2018In: 2018 Workshop on Modeling and Simulation of Cyber-Physical Energy Systems, MSCPES 2018 - Held as part of CPS Week, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1-6, article id 8405397Conference paper (Refereed)
    Abstract [en]

    The turbine-governor models that are currently used in studies of power systems include over-simplifications of turbomachinery elements. Due to the growing need to support intermittent energy resources with other energy sources like gas turbines, more detailed models including an explicit representation of the physical dynamics are attractive. In this paper, the advantages of the Modelica language and the FMI standard are considered to carry out modeling and multi-domain simulation of gas turbines with power grids, which can be used to evaluate scenarios of power variability. The work gathers preliminary results of the potential that FMUs offer to promote the exchange of turbine models by manufacturers and to conduct multi-domain simulations in several tools.

  • 3.
    Albertsson, Dagur Ingi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Integrated devices and circuits.
    Zahedinejad, Mohammad
    Department of Physics, University of Gothenburg.
    Åkerman, Johan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. Department of Physics, University of Gothenburg.
    Rodriguez, Saul
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Integrated devices and circuits.
    Rusu, Ana
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Integrated devices and circuits.
    Compact Macrospin-Based Model of Three-Terminal Spin-Hall Nano Oscillators2019In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 55, no 10, article id 4003808Article in journal (Refereed)
    Abstract [en]

    Emerging spin-torque nano oscillators (STNOs) and spin-Hall nano oscillators (SHNOs) are potential candidates for microwave applications. Recent advances in three-terminal magnetic tunnel junction (MTJ)-based SHNOs opened the possibility to develop more reliable and well-controlled oscillators, thanks to individual spin Hall-driven precession excitation and read-out paths. To develop hybrid systems by integrating three-terminal SHNOs and CMOS circuits, an electrical model able to capture the analog characteristics of three-terminal SHNOs is needed. This model needs to be compatible with current electric design automation (EDA) tools. This work presents a comprehensive macrospin-based model of three-terminal SHNOs able to describe the dc operating point, frequency modulation, phase noise, and output power. Moreover, the effect of voltage-controlled magnetic anisotropy (VCMA) is included. The model shows good agreement with experimental measurements and could be used in developing hybrid three-terminal SHNO/CMOS systems.

  • 4.
    Aljure, Mauricio
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Karlsson, Mattias
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Erratum to: Aljure, M.; Becerra, M.; Karlsson, E.M. Streamer inception from ultra-sharp needles in mineral oil based nanofluids2018In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 11, article id 2900Article in journal (Refereed)
    Abstract [en]

    The authors wish to make the following corrections to their paper [1]: i. On pages 13 and 14, the numbering of references from 17 to 30 is incorrect. References 17 to 30 should be renumbered from the original order below: 17. Liu, Z.; Liu, Q.; Wang, Z.D.; Jarman, P.; Krause, C.; Smith, P.W.R.; Gyore, A. Partial discharge behaviour of transformer liquids and the influence of moisture content. In Proceedings of the 2014 IEEE 18th International Conference on Dielectric Liquids (ICDL), Bled, Slovenia, 29 June–3 July 2014. 18. Yamashita, H.; Yamazawa, K.; Wang, Y.S. The effect of tip curvature on the prebreakdown streamer structure in cyclohexane. IEEE Trans. Dielectr. Electr. Insul. 1998, 5, 396–401. 19. Dumitrescu, L.; Lesaint, O.; Bonifaci, N.; Denat, A.; Notingher, P. Study of streamer inception in cyclohexane with a sensitive charge measurement technique under impulse voltage. J. Electrostat. 2001, 53, 135–146. 20. Pourrahimi, A.M.; Hoang, T.A.; Liu, D.; Pallon, L.K.H.; Gubanski, S.; Olsson, R.T.; Gedde, U.W.; Hedenqvist, M.S. Highly efficient interfaces in nanocomposites based on polyethylene and ZnO nano/hierarchical particles: A novel approach toward ultralow electrical conductivity insulations. Adv. Mater. 2016, 28, 8651–8657. 21. Li, J.; Du, B.; Wang, F.; Yao, W.; Yao, S. The effect of nanoparticle surfactant polarization on trapping depth of vegetable insulating oil-based nanofluids. Phys. Lett. A 2016, 380, 604–608. 22. Aljure, M.; Becerra, M.; Pallon, L.K.H. Electrical conduction currents of a mineral oil-based nanofluid in needle-plane configuration. In Proceedings of the 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Toronto, ON, Canada, 16–19 October 2016; pp. 687–690. 23. Primo, V.A.; Garcia, B.; Albarracin, R. Improvement of transformer liquid insulation using nanodielectric fluids: A review. IEEE Electr. Insul. Mag. 2018, 34, 13–26. 24. Jin, H.; Andritsch, T.; Morshuis, P.H.F.; Smit, J.J. AC breakdown voltage and viscosity of mineral oil based SiO2 nanofluids. In Proceedings of the 2012 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Montreal, QC, Canada, 14–17 October 2012; pp. 902–905. 25. Jin, H.; Morshuis, P.; Mor, A.R.; Smit, J.J.; Andritsch, T. Partial discharge behavior of mineral oil based nanofluids. IEEE Trans. Dielectr. Electr. Insul. 2015, 22, 2747–2753. 26. Du, Y.; Lv, Y.; Li, C.; Chen, M.; Zhong, Y.; Zhou, J.; Li, X.; Zhou, Y. Effect of semiconductive nanoparticles on insulating performances of transformer oil. IEEE Trans. Dielectr. Electr. Insul. 2012, 19, 770–776. 27. Dung, N.V.; Høidalen, H.K.; Linhjell, D.; Lundgaard, L.E.; Unge, M. Effects of reduced pressure and additives on streamers in white oil in long point-plane gap. J. Phys. D Appl. Phys. 2013, 46, 255501. 28. McCool, J.I. Using the Weibull Distribution; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2012. 29. Lesaint, O.L.; Top, T.V. Streamer initiation in mineral oil. part I: Electrode surface effect under impulse voltage. IEEE Trans. Dielectr. Electr. Insul. 2002, 9, 84–91. 30. Becerra, M.; Frid, H.; Vázquez, P.A. Self-consistent modeling of laminar electrohydrodynamic plumes from ultra-sharp needles in cyclohexane. Phys. Fluids 2017, 29, 123605. to the following, corrected numbering: 17. Dumitrescu, L.; Lesaint, O.; Bonifaci, N.; Denat, A.; Notingher, P. Study of streamer inception in cyclohexane with a sensitive charge measurement technique under impulse voltage. J. Electrostat. 2001, 53, 135–146. 18. Liu, Z.; Liu, Q.; Wang, Z.D.; Jarman, P.; Krause, C.; Smith, P.W.R.; Gyore, A. Partial discharge behaviour of transformer liquids and the influence of moisture content. In Proceedings of the 2014 IEEE 18th International Conference on Dielectric Liquids (ICDL), Bled, Slovenia, 29 June–3 July 2014. 19. Yamashita, H.; Yamazawa, K.; Wang, Y.S. The effect of tip curvature on the prebreakdown streamer structure in cyclohexane. IEEE Trans. Dielectr. Electr. Insul. 1998, 5, 396–401. 20. Becerra, M.; Frid, H.; Vázquez, P.A. Self-consistent modeling of laminar electrohydrodynamic plumes from ultra-sharp needles in cyclohexane. Phys. Fluids 2017, 29, 123605. 21. Pourrahimi, A.M.; Hoang, T.A.; Liu, D.; Pallon, L.K.H.; Gubanski, S.; Olsson, R.T.; Gedde, U.W.; Hedenqvist, M.S. Highly efficient interfaces in nanocomposites based on polyethylene and ZnO nano/hierarchical particles: A novel approach toward ultralow electrical conductivity insulations. Adv. Mater. 2016, 28, 8651–8657. 22. Li, J.; Du, B.; Wang, F.; Yao, W.; Yao, S. The effect of nanoparticle surfactant polarization on trapping depth of vegetable insulating oil-based nanofluids. Phys. Lett. A 2016, 380, 604–608. 23. Aljure, M.; Becerra, M.; Pallon, L.K.H. Electrical conduction currents of a mineral oil-based nanofluid in needle-plane configuration. In Proceedings of the 2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Toronto, ON, Canada, 16–19 October 2016; pp. 687–690. 24. Primo, V.A.; Garcia, B.; Albarracin, R. Improvement of transformer liquid insulation using nanodielectric fluids: A review. IEEE Electr. Insul. Mag. 2018, 34, 13–26. 25. Jin, H.; Andritsch, T.; Morshuis, P.H.F.; Smit, J.J. AC breakdown voltage and viscosity of mineral oil based SiO2 nanofluids. In Proceedings of the 2012 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Montreal, QC, Canada, 14–17 October 2012; pp. 902–905. 26. Jin, H.; Morshuis, P.; Mor, A.R.; Smit, J.J.; Andritsch, T. Partial discharge behavior of mineral oil based nanofluids. IEEE Trans. Dielectr. Electr. Insul. 2015, 22, 2747–2753. 27. Du, Y.; Lv, Y.; Li, C.; Chen, M.; Zhong, Y.; Zhou, J.; Li, X.; Zhou, Y. Effect of semiconductive nanoparticles on insulating performances of transformer oil. IEEE Trans. Dielectr. Electr. Insul. 2012, 19, 770–776. 28. Dung, N.V.; Høidalen, H.K.; Linhjell, D.; Lundgaard, L.E.; Unge, M. Effects of reduced pressure and additives on streamers in white oil in long point-plane gap. J. Phys. D Appl. Phys. 2013, 46, 255501. 29. McCool, J.I. Using the Weibull Distribution; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2012. 30. Lesaint, O.L.; Top, T.V. Streamer initiation in mineral oil. part I: Electrode surface effect under impulse voltage. IEEE Trans. Dielectr. Electr. Insul. 2002, 9, 84–91. ii. On the last paragraph of page 9, the last sentence should be changed from: However, the results in [11] also show the consistent increase in the initiation voltage of prebreakdown phenomena in both polarities, as reported in Figure 11. to the following, corrected version: However, the results in [26] also show the consistent increase in the initiation voltage of prebreakdown phenomena in both polarities, as reported in Figure 11. iii. On the last paragraph of page 10, the third sentence should be changed from: Even though the existing hypotheses of the dielectric effect of NPs [8–10] were proposed for blunter electrodes (where charge generation before streamer initiation is less important [30]), they should still apply under the experimental conditions here reported. to the following, corrected version: Even though the existing hypotheses of the dielectric effect of NPs [5,6,16] were proposed for blunter electrodes (where charge generation before streamer initiation is less important [30]), they should still apply under the experimental conditions here reported. The authors would like to apologize for any inconvenience caused to the readers by these changes. The changes do not affect the scientific results. The manuscript will be updated and the original will remain online on the article webpage, with a reference to this Correction.

  • 5.
    Alm, Love
    et al.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Andre, Mats
    Swedish Inst Space Phys, Uppsala, Sweden..
    Graham, Daniel B.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Khotvaintsev, Yuri, V
    Swedish Inst Space Phys, Uppsala, Sweden..
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Chappell, Charles R.
    Vanderbilt Univ, Dept Phys & Astron, Vanderbilt Dyer Observ, Nashville, TN 37235 USA..
    Dargent, Jeremy
    Univ Pisa, Phys Dept Enrico Fermi, Pisa, Italy..
    Fuselier, Stephen A.
    Southwest Res Inst, San Antonio, TX USA.;Univ Texas San Antonio, Dept Phys & Astron, San Antonio, TX USA..
    Haaland, Stein
    Max Planck Inst Solar Syst Res, Gottingen, Germany.;Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway..
    Lavraud, Benoit
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France..
    Li, Wenya
    Chinese Acad Sci, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing, Peoples R China..
    Tenfjord, Paul
    Univ Bergen, Birkeland Ctr Space Sci, Bergen, Norway..
    Toledo-Redondo, Sergio
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France..
    Vines, Sarah K.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    MMS Observations of Multiscale Hall Physics in the Magnetotail2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007Article in journal (Refereed)
    Abstract [en]

    We present Magnetospheric Multiscale mission (MMS) observations of Hall physics in the magnetotail, which compared to dayside Hall physics is a relatively unexplored topic. The plasma consists of electrons, moderately cold ions (T similar to 1.5 keV) and hot ions (T similar to 20 keV). MMS can differentiate between the cold ion demagnetization region and hot ion demagnetization regions, which suggests that MMS was observing multiscale Hall physics. The observed Hall electric field is compared with a generalized Ohm's law, accounting for multiple ion populations. The cold ion population, despite its relatively high initial temperature, has a significant impact on the Hall electric field. These results show that multiscale Hall physics is relevant over a much larger temperature range than previously observed and is relevant for the whole magnetosphere as well as for other astrophysical plasma.

  • 6.
    Andersson, Kjell
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Hagnestål, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A Flexible Chain Proposal for Winch-Based Point Absorbers2019In: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001, Vol. 141, no 10, article id 102301Article in journal (Refereed)
    Abstract [en]

    Ocean wave power is a promising renewable energy source. It has, however, been difficult to find a cost-effective solution to convert wave energy into electricity. The harsh marine environment and the fact that wave power is delivered with large forces at low speed make design of durable mechanical structures and efficient energy conversion challenging. The dimensioning forces strongly depend on the wave power concept, the wave energy converter (WEC) implementation, and the actual power take-off (PTO) system. A WEC with a winch as a power take-off system, i.e., a winch-based point absorber (WBPA), could potentially enable a low levelized cost of energy (LCOE) if a low-cost, durable and efficient winch that can deal with peak loads can be developed. A key challenge for realizing such a winch is to find a force transmitting solution that can deal with these peak loads and that can handle up to 80 million cycles during its life. In this article, we propose a design solution for a force transmitting chain with elastomer bearings connecting the links of the chain. With this solution no sliding is present, and the angular motion is realized as elastic shear deformations in the elastomer bearings when the chain is wound onto the winch drum. The elastomer bearings were designed for low shear stiffness and high compression stiffness, and the links were designed primarily to minimize the number of joints in the chain. Thereby, the maximum allowed relative angle between the links when rolled up over the drum should be as large as possible within practical limits. Finite element-based topological optimization was performed with the aim to increase the link strength to weight ratio. A test rig for a first proof of concept testing has been developed, and preliminary test results indicate that this chain concept with elastomer bearings can be a potential solution for a durable chain and should be analyzed and tested further for fatigue and sea operations.

  • 7.
    Ariza Rocha, Oscar David
    et al.
    ABB Corporate Research, Västerås, Sweden. E.ON. Energidistribution AB, Malmö, Sweden.
    Morozovska, Kateryna
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Laneryd, Tor
    ABB Corporate Research.
    Ivarsson, Ola
    E.ON. Energidistribution AB, .
    Ahlrot, Claes
    E.ON. Energidistribution AB, .
    Hilber, Patrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Dynamic rating assists cost-effective expansion of wind farms byutilizing hidden capacity of transformersManuscript (preprint) (Other academic)
    Abstract [en]

    Dynamic rating of power transmission devices is a technology that allows better equipment utilization through real-time information about the system state. Dynamic rating of transformers is a fairly new technology if compared to dynamic rating of power lines, and has high potential for significantly improving component utilization while lowering investment costs on installing new transformers.

    Dynamic transformer rating increases the rating of the transformer considering load and temperature variations without affecting safe operation. Dynamic rating is highly suitable for being used in conjunction with renewable energy generation, specifically wind power. The following work investigates how to utilize existing transformers, which are under exploitation at wind farms, for expanding wind generation capacity. Also, this paper shows improvements that dynamic rating can bring to both power grid operators and wind farm owners by exploring the economic benefits of expanding wind parks while using dynamic rating. Connecting additional wind turbines with the same transformer at sites with high wind capacity after the wind park is already in exploitation can assist in lowering electricity price and provide a possibility of less risky investment in wind power.

    Five transformer locations and nine units are studied for finding the potential of dynamic transformer rating for network expansion applications. The analysis shows that the optimal expansion of wind power from a generator perspective is around 30 % to 50 %, although, it can be limited further by network restrictions. A possibility to use a large device, suchas power transformer, closer to its full potential can provide material and cost savings for building new devices and decrease investment costs on manufacturing, transportation and installation of new units. Dynamic rating of power transformers can also increase the socio-economic benefits of renewable energy by lowering electricity price from renewables and incentivize an increased share of green power in electricity markets.

    The full text will be freely available from 2021-01-31 22:22
  • 8.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH Stockholm.
    Becerra, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Magnusson, Jesper
    ABB Corporate Research, Västerås.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    System Design of Fast Actuator for Vacuum Interrupter in DC Applications2018In: 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV), Institute of Electrical and Electronics Engineers (IEEE), 2018, Vol. 2, p. 527-530Conference paper (Refereed)
    Abstract [en]

    One of the major challenges of DC circuit breakers is the required fast mechanical actuator. In this paper, a Thomson coil actuator system for a vacuum interrupter is designed. Active damping is used to decelerate the moving contacts. Challenges are discussed, especially concerning the power supply needed for the Thomson coil actuator. The design philosophy is explained and FEM simulation results are presented. The results indicate that a wide range of combinations of drive circuit capacitance and voltage fulfill the requirements for armature acceleration. However, active damping requires a very careful selection of drive circuit voltage and timing of applied damping.

  • 9.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH Stockholm.
    Becerra, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Advanced Test Circuit for DC Circuit Breakers2018In: 20th European Conference on Power Electronics and Applications (EPE'18 ECCE EUROPE), 2018Conference paper (Refereed)
    Abstract [en]

    In future HVDC systems, many DC circuit breakers (DCCBs) will be required. In this paper, an advanced test circuit for DCCBs is described. A DC source is combined with a capacitor bank. In contrast to other test circuits, the proposed test circuit allows to replicate constant DC and temporary faults. In addition to conventional faults, this enables testing of auto-reclosing, proactive commutation, and complex test sequences combining all of these modes. The test circuit is easy to setup and also suitable for smaller research facilities. Experimental results from a down-scaled mock-up are included to demonstrate the capabilities of the test circuit.

  • 10. Bakas, P.
    et al.
    Ilves, K.
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Harnefors, L.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hybrid alternate-common-arm converter with director thyristors - Impact of commutation time on the active-power capability2019In: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    This paper investigates the impact of the thyristor commutation time on the peak currents and the active-power capability of the hybrid alternate-common-arm converter (HACC). This converter employs director thyristors for the alternate connection of a common arm in parallel to the main arms. The parallel connection enables current sharing among the arms, which allows the HACC to transfer higher output power without increasing the peak arm current. It is shown that the active-power capability of the HACC is doubled for a certain current-sharing factor, which, however, is altered by the thyristor commutation time. Therefore, the impact of the commutation time on the active-power capability of the HACC is investigated theoretically. Finally, this analysis is verified by simulation results.

  • 11. Bakas, Panagiotis
    et al.
    Okazaki, Y.
    Ilves, K.
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Harnefors, L.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Design considerations and comparison of hybrid line-commutated and cascaded full-bridge converters with reactive-power compensation and active filtering capabilities2019In: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe, Institute of Electrical and Electronics Engineers Inc. , 2019Conference paper (Refereed)
    Abstract [en]

    This paper compares two hybrid topologies that combine the line-commutated converter (LCC) with cascaded full-bridge (FB) converters. The latter are utilized for compensating the reactive power and filtering the current harmonics of the LCC. The method that was developed for dimensioning these hybrid topologies is presented in detail. This method is utilized for calculating the arm voltage and current waveforms, which are used to estimate other important quantities, such as conduction losses and energy variations. Finally, the studied converters are compared in terms of voltage/current ratings, semiconductor requirements, conduction losses, and energy variations.

  • 12.
    Becker, Matthias
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Electronic and embedded systems.
    Lu, Zhonghai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Electronic and embedded systems.
    Chen, DeJiu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Towards QoS-Aware Service-Oriented Communication in E/E Automotive Architectures2018In: Proceedings of the 44th Annual Conference of the IEEE Industrial Electronics Society (IECON), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 4096-4101, article id 8591521Conference paper (Refereed)
    Abstract [en]

    With the raise of increasingly advanced driving assistance systems in modern cars, execution platforms that build on the principle of service-oriented architectures are being proposed. Alongside, service oriented communication is used to provide the required adaptive communication infrastructure on top of automotive Ethernet networks. A middleware is proposed that enables QoS aware service-oriented communication between software components, where the prescribed behavior of each software component is defined by Assume/Guarantee (A-G) contracts. To enable the use of COTS components, that are often not sufficiently verified for the use in automotive systems, the middleware monitors the communication behavior of components and verifies it against the components A/G contract. A violation of the allowed communication behavior then triggers adaption processes in the system while the impact on other communication is minimized. The applicability of the approach is demonstrated by a case study that utilizes a prototype implementation of the proposed approach.

  • 13.
    Becker, Matthias
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electronics, Electronic and embedded systems.
    Mubeen, Saad
    Mälardalen University.
    Timing Analysis Driven Design-Space Exploration of Cause-Effect Chains in Automotive Systems2018In: IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society, 2018Conference paper (Refereed)
    Abstract [en]

    Model-based development and component-based software engineering have emerged as a promising approach to deal with enormous software complexity in automotive systems. This approach supports the development of software architectures by interconnecting (and reusing) software components (SWCs) at various abstraction levels. Automotive software architectures are often modeled with chains of SWCs, also called cause-effect chains that are constrained by timing requirements. Based on the variations in activation patterns of SWCs, a single model of a cause-effect chain at a higher abstraction level can conform to several valid refined models of the chain at a lower abstraction level, which is closer to the system implementation. As a consequence, the total number of valid implementation-level models generated by the existing techniques increases exponentially, thereby significantly increasing the runtime of the timing analysis engines and liming the scalability of the existing techniques. This paper computes an upper bound on the activation pattern combinations that may result from a system of cause-effect chains in a given high-level model of the software architecture. An efficient algorithm is presented that traverses only a reduced number of possible combinations of the cause-effect chains, resulting in the timing analysis of a significantly lower number of implementation-level models of the software architecture. A proof of concept is provided by conducting a case study that shows significant reduction in the runtime of timing analysis engines, i.e., the timing behavior of the considered system is verified by performing the timing analysis of only 27% of all possible combinations of the cause-effect chains.

  • 14.
    Becker, T. M.
    et al.
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Retherford, K. D.
    Southwest Res Inst, San Antonio, TX 78228 USA..
    Roth, Lorenz
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Hendrix, A. R.
    Planetary Sci Inst, Tucson, AZ USA..
    McGrath, M. A.
    SETI Inst, Mountain View, CA USA..
    Saur, J.
    Univ Cologne, Inst Geophys & Meteorol, Cologne, Germany..
    The Far-UV Albedo of Europa From HST Observations2018In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 123, no 5, p. 1327-1342Article in journal (Refereed)
    Abstract [en]

    We present an analysis of Europa's far-UV spectral albedo using observations during the 1999-2015 time period made by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. Disk-integrated observations show that the far-UV spectrum in the similar to 130 to 170-nm range is relatively flat or slightly blue (increasing albedo with decreasing wavelength) for the studied hemispheres: the leading, trailing, and anti-Jovian hemispheres. At Lyman- (121.6nm), the albedo of the trailing hemisphere continues the blue trend, but it reddens for the leading hemisphere. Also at this wavelength, the albedo of the leading hemisphere, which is higher than the trailing hemisphere at near-UV and visible wavelengths, is lower than the trailing hemisphere, exhibiting spectral inversion. We find no evidence of a sharp water-ice absorption edge at 165nm on any hemisphere of Europa, which is intriguing since such an absorption feature has been observed on the icy Saturnian satellites. Plain Language Summary We used observations spanning from 1999 to 2015 obtained by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope to study the surface reflectance of Europa at far-ultraviolet (UV) wavelengths. We find that Europa has a low reflectance in the UV and that there is little variation in the surface brightness at most of the UV wavelengths. When observed at visible wavelengths, one of Europa's hemispheres is brighter than the other, but at the UV wavelength of 121.6nm, the hemisphere brightness is reversed. We also find that Europa looks different from the icy moons of Saturn at far-UV wavelengths.

  • 15.
    Bessegato, Luca
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Byes, Kalle
    ABB Corp Res, S-72178 Vasteras, Sweden..
    Harnefors, Lennart
    ABB Corp Res, S-72178 Vasteras, Sweden..
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies2020In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 35, no 3, p. 2411-2423Article in journal (Refereed)
    Abstract [en]

    Modular multilevel converters (MMCs) can be configured to perform ac/ac conversion, which makes them suitable as railway power supplies. In this paper, a hierarchical control scheme for ac/ac MMCs for railway power supplies is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. These models allow for analyzing the stability of the interconnected system using the impedance-based stability criterion and the passivity-based stability assessment. Finally, the findings presented in this paper are validated experimentally, using a down-scaled MMC.

  • 16.
    Bessegato, Luca
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Modeer, Tomas
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Modeling and control of a tapped-inductor buck converter with pulse frequency modulation2014In: Energy Conversion Congress and Exposition (ECCE), 2014 IEEE, IEEE, 2014, p. 3672-3678Conference paper (Refereed)
    Abstract [en]

    The tapped-inductor buck (TI-buck) converter has shown to be a suitable solution for auxiliary power supply for modular multilevel converter submodules. Such application features a large step-down voltage conversion, made at relatively low output power. This converter operates in discontinuous conduction mode with zero voltage switching of the high-voltage valve. This paper treats the dynamic behaviour of the aforementioned converter. First, an average output current model of the converter is developed and a small signal model is obtained. Then, a closed-loop output voltage control, which uses the switching frequency as control variable, is designed and implemented using a microcontroller. Measurements on a down-scaled prototype shows that the control system provides a well-controlled average output voltage, which is stable under significant load variation. Finally, a solution for implementing the start-up of the converter is presented and tested.

  • 17.
    Bitsi, Konstantina
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bosga, Sjoerd
    ABB Corporate Research.
    An Induction Machine with Wound Independently-Controlled Stator Coils2019In: Proceedings of the 22nd International Conference on Electrical Machines and Systems (ICEMS), IEEE, 2019Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel induction machine topology with wound, independently-controlled stator coils is presented. The introduced configuration of the stator-winding enables the individual energization and control of the coils in each stator slot. Therefore, the possibility of changing the number of poles and active phases in the stator winding during operation is explored in this study.

  • 18.
    Bitsi, Konstantina
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bosga, Sjoerd
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. 2ABB Corporate Research, Västerås, Sweden.
    Many-objective Optimization of IPM and Induction Motors for Automotive Application2019Conference paper (Refereed)
    Abstract [en]

    This paper presents a Pareto-optimality-based optimization methodology suitable for the design of electrical motors in automotive applications. The proposed many-objective evolutionary algorithm is utilized in this study case for the optimization of an interior permanent-magnet (IPM) synchronous motor and an induction motor (IM), considering as criteria the motors' torque capability, efficiency as well as torque density. Finite-element (FE) models of the investigated motor topologies are developed and incorporated in the optimization process in order to ensure an accurate estimation of their electromagnetic performance. The attainment of the targeted specifications by the final optimal designs validates the efficacy of the implemented optimization algorithm.

  • 19.
    Björkqvist, Oskar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Zetterström, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Additive manufactured dielectric Gutman lens2019In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 55, no 25, p. 1318-1320Article in journal (Refereed)
    Abstract [en]

    In this Letter, the design of a 3D printed fully dielectric Gutman lens is presented. The authors demonstrate the feasibility of using highly accessible and cheap additive manufacturing technology to produce a compact and high performing antenna lens. The lens is designed to operate at Ku band and utilises a flat feed surface that approximates the focal sphere. The flat feed surface allows for beam steering that requires only translational movement of the feed. The lens has a measured realised gain of 20 dBi with 3 dB scan loss at +45°. The lens finds applications in systems that require high gain antennas, such as the new generation of satellite and 5G communications and radar technology.

  • 20.
    Boričić, Aleksandar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Bhatt, Dhruv
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Westerlund, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Reliability and Cost-Effectiveness Analysis of Various HV Substation Configurations2019Conference paper (Refereed)
    Abstract [en]

    Reliable power supply is one of the crucial factors for the development of any industry. Different technologies as well as configurations are available when it comes to investing in new electrical assets. According to [1], the circuit configurations of high voltage substations are strongly influenced by many factors, such as operational requirements, security standards, availability, maintainability, etc. There is always a trade-off between the technical requirements and the cost of investment. This paper aims to quantify the availability of a switchyard with two lines and two transformer bays for various switching configurations. Once the overall availability is determined, the decision for the selection of a switching configuration is made based on the cost-benefit analysis.

    The voltage rating of a primary substation is decided based on the scale of an industry. Switching configuration is one of the major factors affecting the overall availability of the substation. Each switching configuration has its own pros and cons in terms of its operation, reliability and investment cost. It is impossible to achieve 100% availability of a substation with any kind of switching scheme. Availability and investment cost of a substation vary with the choice of the configuration and substation technology. There are mainly three available technologies - Air Insulated Switchgear (AIS), Gas Insulated Switchgear (GIS) and Mixed Technology Switchgear (MTS).

    This paper evaluates possible choices for an example of supply which is very often seen in practice, providing guidelines for decision-making process in order to optimize profit of an industry, from the supply-reliability point of view. In this paper, a 220/66kV AIS substation for an upcoming process plant is under consideration. The scope of this paper is limited to assess the availability of primary side of the substation. There are two-line bays and two transformer bays in the 220kV switchyard. Down-stream to the 66kV side is not taken into consideration for the analysis purpose.

  • 21.
    Breuillard, H.
    et al.
    Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France.;Univ Paris Sud, Sorbonne Univ, Ecole Polytech, UMR7648 CNRS,Lab Phys Plasmas, Paris, France..
    Henri, P.
    Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France..
    Bucciantini, L.
    Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France..
    Volwerk, M.
    Austrian Acad Sci, Space Res Inst, Graz, Austria..
    Karlsson, Tomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Eriksson, A.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Johansson, F.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Odelstad, E.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Richter, I
    Tech Univ Carolo Wilhelmina Braunschweig, Braunschweig, Germany..
    Goetz, C.
    Tech Univ Carolo Wilhelmina Braunschweig, Braunschweig, Germany..
    Vallieres, X.
    Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France..
    Hajra, R.
    Univ Orleans, CNES, CNRS, UMR7328,LPC2E, Orleans, France.;Natl Atmospher Res Lab, Tirupati, Andhra Pradesh, India..
    Properties of the singing comet waves in the 67P/Churyumov-Gerasimenko plasma environment as observed by the Rosetta mission2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 630, article id A39Article in journal (Refereed)
    Abstract [en]

    Using in situ measurements from different instruments on board the Rosetta spacecraft, we investigate the properties of the newly discovered low-frequency oscillations, known as singing comet waves, that sometimes dominate the close plasma environment of comet 67P/Churyumov-Gerasimenko. These waves are thought to be generated by a modified ion-Weibel instability that grows due to a beam of water ions created by water molecules that outgass from the comet. We take advantage of a cometary outburst event that occurred on 2016 February 19 to probe this generation mechanism. We analyze the 3D magnetic field waveforms to infer the properties of the magnetic oscillations of the cometary ion waves. They are observed in the typical frequency range (similar to 50 mHz) before the cometary outburst, but at similar to 20 mHz during the outburst. They are also observed to be elliptically right-hand polarized and to propagate rather closely (similar to 0-50 degrees) to the background magnetic field. We also construct a density dataset with a high enough time resolution that allows us to study the plasma contribution to the ion cometary waves. The correlation between plasma and magnetic field variations associated with the waves indicates that they are mostly in phase before and during the outburst, which means that they are compressional waves. We therefore show that the measurements from multiple instruments are consistent with the modified ion-Weibel instability as the source of the singing comet wave activity. We also argue that the observed frequency of the singing comet waves could be a way to indirectly probe the strength of neutral plasma coupling in the 67P environment.

  • 22.
    Brezinsek, S.
    et al.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Kirschner, A.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Mayer, M.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Baron-Wiechec, A.
    CCFE Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Borodkina, I
    Czech Acad Sci, Inst Plasma Phys, Prague 18200, Czech Republic..
    Borodin, D.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Coffey, I
    CCFE Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Coenen, J.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    den Harder, N.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Eksaeva, A.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Guillemaut, C.
    Univ Lisbon, Inst Super Tecn, Inst Plasmas & Fusao Nucl, Lisbon, Portugal..
    Heinola, K.
    IAEA, POB 100, A-1400 Vienna, Austria.;Univ Helsinki, Dept Phys, POB 64, FIN-00014 Helsinki, Finland..
    Huber, A.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Huber, V
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Imrisek, M.
    Czech Acad Sci, Inst Plasma Phys, Prague 18200, Czech Republic..
    Jachmich, S.
    Ecole Royale Mil, LPP, Koninkllijke Mil Sch, B-1000 Brussels, Belgium..
    Pawelec, E.
    Opole Univ, Inst Phys, Oleska 48, PL-45052 Opole, Poland..
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Krat, S.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Sergienko, G.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Matthews, G. F.
    CCFE Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Meigs, A. G.
    CCFE Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Wiesen, S.
    Forschungszentrum Julich, Inst Energie & Klimaforsch Plasmaphys, TEC, D-52425 Julich, Germany..
    Widdowson, A.
    CCFE Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Erosion, screening, and migration of tungsten in the JET divertor2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 9, article id 096035Article in journal (Refereed)
    Abstract [en]

    The erosion of tungsten (W), induced by the bombardment of plasma and impurity particles, determines the lifetime of plasma-facing components as well as impacting on plasma performance by the influx of W into the confined region. The screening of W by the divertor and the transport of W in the plasma determines largely the W content in the plasma core, but the W source strength itself has a vital impact on this process. The JET tokamak experiment provides access to a large set of W erosion-determining parameters and permits a detailed description of the W source in the divertor closest to the ITER one: (i) effective sputtering yields and fluxes as function of impact energy of intrinsic (Be, C) and extrinsic (Ne, N) impurities as well as hydrogenic isotopes (H, D) are determined and predictions for the tritium (T) isotope are made. This includes the quantification of intra- and inter-edge localised mode (ELM) contributions to the total W source in H-mode plasmas which vary owing to the complex flux compositions and energy distributions in the corresponding phases. The sputtering threshold behaviour and the spectroscopic composition analysis provides an insight in the dominating species and plasma phases causing W erosion. (ii) The interplay between the net and gross W erosion source is discussed considering (prompt) re-deposition, thus, the immediate return of W ions back to the surface due to their large Larmor radius, and surface roughness, thus, the difference between smooth bulk-W and rough W-coating components used in the JET divertor. Both effects impact on the balance equation of local W erosion and deposition. (iii) Post-mortem analysis reveals the net erosion/deposition pattern and the W migration paths over long periods of plasma operation identifying the net W transport to remote areas. This W transport is related to the divertor plasma regime, e.g. attached operation with high impact energies of impinging particles or detached operation, as well as to the applied magnetic configuration in the divertor, e.g. close divertor with good geometrical screening of W or open divertor configuration with poor screening. JET equipped with the ITER-like wall (ILW) provided unique access to the net W erosion rate within a series of 151 subsequent H-mode discharges (magnetic field: B-t = 2.0 T, plasma current: I-p = 2.0 MA, auxiliary power P-aux = 12 MW) in one magnetic configuration accumulating 900 s of plasma with particle fluences in the range of 5-6 x 10(26) D(+ )m(-2) in the semi-detached inner and attached outer divertor leg. The comparison of W spectroscopy in the intra-ELM and inter-ELM phases with post-mortem analysis of W marker tiles provides a set of gross and net W erosion values at the outer target plate. ERO code simulations are applied to both divertor leg conditions and reproduce the erosion/deposition pattern as well as confirm the high experimentally observed prompt W re-deposition factors of more than 95% in the intra- and inter-ELM phase of the unseeded deuterium H-mode plasma. Conclusions to the expected divertor conditions in ITER as well as to the JET operation in the DT plasma mixture are drawn on basis of this unique benchmark experiment.

  • 23.
    Chamorro Vera, Harold Rene
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Ordonez, C. A.
    Peng, J. C. -H
    Gonzalez-Longatt, F.
    Sood, V. K.
    Coherency Estimation in Power Systems: A Koopman Operator Approach2019In: Springer Optimization and Its Applications, Springer International Publishing , 2019, p. 201-225Chapter in book (Refereed)
    Abstract [en]

    Integrating a significant amount of non-synchronous generation into power systems creates new technical challenges for transmission systems. The research and understanding of the impact of the non-synchronous generation through back-to-back Full Rated Converters’ (FRCs) on power system’s coherency is a matter of importance. Coherency behavior under the presence of large inclusion of non-synchronous generation requires more research, in order to understand the forming groups, after a disturbance, when the inertia is decreasing due to the decoupling. This document presents the application of the so-called Koopman Operator for the identification of coherent groups in power systems with the influence of non-synchronous generation. The Koopman Analysis clusters the coherent groups based on the measurements obtained. The visualization of the coherent groups identified allows to observe their dynamic variations according to the penetration level or fault location. The applied method of coherency identification is evaluated in the Nordic test system through gradually increasing integration of non-synchronous generations and different fault scenarios.

  • 24. Chasapis, A.
    et al.
    Matthaeus, W. H.
    Parashar, T. N.
    Wan, M.
    Haggerty, C. C.
    Pollock, C. J.
    Giles, B. L.
    Paterson, W. R.
    Dorelli, J.
    Gershman, D. J.
    Torbert, R. B.
    Russell, C. T.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
    Khotyaintsev, Y.
    Moore, T. E.
    Ergun, R. E.
    Burch, J. L.
    In Situ Observation of Intermittent Dissipation at Kinetic Scales in the Earth's Magnetosheath2018In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 856, no 1, article id L19Article in journal (Refereed)
    Abstract [en]

    We present a study of signatures of energy dissipation at kinetic scales in plasma turbulence based on observations by the Magnetospheric Multiscale mission (MMS) in the Earth's magnetosheath. Using several intervals, and taking advantage of the high-resolution instrumentation on board MMS, we compute and discuss several statistical measures of coherent structures and heating associated with electrons, at previously unattainable scales in space and time. We use the multi-spacecraft Partial Variance of Increments (PVI) technique to study the intermittent structure of the magnetic field. Furthermore, we examine a measure of dissipation and its behavior with respect to the PVI as well as the current density. Additionally, we analyze the evolution of the anisotropic electron temperature and non-Maxwellian features of the particle distribution function. From these diagnostics emerges strong statistical evidence that electrons are preferentially heated in subproton-scale regions of strong electric current density, and this heating is preferentially in the parallel direction relative to the local magnetic field. Accordingly, the conversion of magnetic energy into electron kinetic energy occurs more strongly in regions of stronger current density, a finding consistent with several kinetic plasma simulation studies and hinted at by prior studies using lower resolution Cluster observations.

  • 25. Chen, Kun-Chih (Jimmy)
    et al.
    Ebrahimi, Masoumeh
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Wang, Ting-Yi
    Yang, Yuch-Chi
    NoC-based DNN Accelerator: A Future Design Paradigm2019Conference paper (Refereed)
    Abstract [en]

    Deep Neural Networks (DNN) have shown significant advantagesin many domains such as pattern recognition, prediction, and controloptimization. The edge computing demand in the Internet-of-Things era has motivated many kinds of computing platforms toaccelerate the DNN operations. The most common platforms areCPU, GPU, ASIC, and FPGA. However, these platforms suffer fromlow performance (i.e., CPU and GPU), large power consumption(i.e., CPU, GPU, ASIC, and FPGA), or low computational flexibilityat runtime (i.e., FPGA and ASIC). In this paper, we suggest theNoC-based DNN platform as a new accelerator design paradigm.The NoC-based designs can reduce the off-chip memory accessesthrough a flexible interconnect that facilitates data exchange betweenprocessing elements on the chip. We first comprehensivelyinvestigate conventional platforms and methodologies used in DNNcomputing. Then we study and analyze different design parametersto implement the NoC-based DNN accelerator. The presentedaccelerator is based on mesh topology, neuron clustering, randommapping, and XY-routing. The experimental results on LeNet, MobileNet,and VGG-16 models show the benefits of the NoC-basedDNN accelerator in reducing off-chip memory accesses and improvingruntime computational flexibility.

  • 26. Choopani, S.
    et al.
    Samavat, F.
    Kolobova, E. N.
    Grishin, Alexander M.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Ferromagnetic resonance and magnetic anisotropy in biocompatible Y3Fe5O12@Na0.5K0.5NbO3 core-shell nanofibers2019In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 46, no 2, p. 2072-2078Article in journal (Refereed)
    Abstract [en]

    Y3Fe5O12@Na0.5K0.5NbO3 (YIG@NKN) core-shell nanofibers were synthesized by the coaxial electrospinning technique. For comparison, samples of YIG and NKN nanofibers were prepared. Scanning Electron Microscopy (SEM) and 3D laser-scanning confocal microscopy (TDLM) of YIG@NKN nanofibers revealed long uniform size distributed fibers with the average diameter of 100–150 nm. X-Ray diffraction (XRD) examination shows the existence of the distinct peaks of orthorhombic NKN and cubic YIG. Magnetic force microscopy (MFM) of individual YIG@NKN nanofiber demonstrates a magnetic core that is extended in one half of the diameter of the fiber. These nanofibers show obvious Ferromagnetic resonance (FMR) with resonance near 2 KOe similar to YIG fibers but in such a way that it starts to increase linearly with applying magnetic field from zero up to near resonance field. Also they show a soft magnetic behavior with saturation magnetization of 10 emu/gr. Furthermore, we propose a model to explain line shape of randomly oriented fibers and extract all the magnetic anisotropy parameters from FMR data. The results rely the shape anisotropy as dominant effect, however the dipolar field among fibers should be considered. The highest degree of asymmetry observed in the case of core-shell fibers in hard direction that it can be originated from magneto electric effects. By taking into account the observed FMR, the ability of adequate control of microwave absorption by applying magnetic field and biocompatibility, the synthesized core-shell nanofibers are the most promising candidate for clinical application such as microwave cancer thermotherapy and adjustable microwave absorbers.

  • 27.
    Ciftci, Baris
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Gross, James
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Simple Distributed Control for Modular Multilevel Converters2019In: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe, Brussels: European Power Electronics and Drives Association, 2019, , p. 10article id 8915488Conference paper (Refereed)
    Abstract [en]

    The central control of MMC becomes demanding in computation power and communication bandwidth as the number of submodules increase. Distributed control methods can overcome these bottlenecks. In this paper, a simple distributed control method together with synchronization of modulation carriers in the submodules is presented. The proposal is implemented on a lab-scale MMC with asynchronous-serial communication on a star network between the central and local controllers. It is shown that the proposed control method works satisfactorily in the steady state. The method can be applied as is to MMCs with any number of submodules per arm.

  • 28.
    Cozzani, Giulia
    et al.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.;Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy..
    Retino, A.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France..
    Califano, F.
    Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy..
    Alexandrova, A.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France..
    Contel, O. Le
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France..
    Khotyaintsev, Y.
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Vaivads, Andris
    Swedish Inst Space Phys, SE-75121 Uppsala, Sweden..
    Fu, H. S.
    Beihang Univ, Sch Space & Environm, Beijing 100083, Peoples R China..
    Catapano, F.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.;Univ Calabria, Dipartimento Fis, I-87036 Arcavacata Di Rende, CS, Italy..
    Breuillard, H.
    Univ Paris Sud, Sorbonne Univ, Observ Paris, Lab Phys Plasmas,CNRS,Ecole Polytech, F-91128 Palaiseau, France.;Univ Orleans, UMR 7328, CNRS, Lab Phys & Chim Environm & Espace, F-45071 Orleans, France..
    Ahmadi, N.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Dept Earth & Space Sci, Los Angeles, CA 90095 USA..
    Nakamura, R.
    Austrian Acad Sci, Space Res Inst, A-8042 Graz, Austria..
    Fuseher, S.
    Southwest Res Inst, San Antonio, TX 78238 USA.;Univ Texas San Antonio, San Antonio, TX 78238 USA..
    Mauk, B. H.
    Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA..
    Moore, T.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX 78238 USA..
    In situ spacecraft observations of a structured electron diffusion region during magnetopause reconnection2019In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 99, no 4, article id 043204Article in journal (Refereed)
    Abstract [en]

    The electron diffusion region (EDR) is the region where magnetic reconnection is initiated and electrons are energized. Because of experimental difficulties, the structure of the EDR is still poorly understood. A key question is whether the EDR has a homogeneous or patchy structure. Here we report Magnetospheric Multiscale (MMS) spacecraft observations providing evidence of inhomogeneous current densities and energy conversion over a few electron inertial lengths within an EDR at the terrestrial magnetopause, suggesting that the EDR can be rather structured. These inhomogenenities are revealed through multipoint measurements because the spacecraft separation is comparable to a few electron inertial lengths, allowing the entire MMS tetrahedron to be within the EDR most of the time. These observations are consistent with recent high-resolution and low-noise kinetic simulations.

  • 29.
    Crosara, Alessandro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Tomasson, Egill
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Generation Adequacy in the Nordic and Baltic Area: The Potential of Flexible Residential Electric Heating2019In: Proceedings of 2019 IEEE PES Innovative Smart Grid Technologies Europe, ISGT-Europe 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, article id 8905720Conference paper (Refereed)
    Abstract [en]

    Generation adequacy is a concern in today's electricity market where intermittent renewable energy sources are rapidly becoming a greater share of the generation mix. This paper focuses on the North-European power system that is comprised of the system areas of the Nord Pool spot market. Sequential Monte Carlo Simulation is applied to assess the generation adequacy of this multi-area system for several future scenarios defined within the Nordic Flex4RES project. The paper gives insights into the characteristics of these adequacy problems that the system could face in a more sustainable future and quantifies their magnitude. Finally, some solutions based on the demand flexibility of residential electric heating are discussed.

  • 30.
    Dabar, Omar Assowe
    et al.
    CERD, Inst Sci Terre, Route Aeroport,BP 486, Ville, Djibouti..
    Awaleh, Mohamed Osman
    CERD, Inst Sci Terre, Route Aeroport,BP 486, Ville, Djibouti..
    Kirk-Davidoff, Daniel
    Univ Maryland, Dept Atmospher & Ocean Sci, College Pk, MD 20742 USA..
    Olauson, Jon
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Awaleh, Said Ismael
    CERD, Inst Sci Terre, Route Aeroport,BP 486, Ville, Djibouti..
    Wind resource assessment and economic analysis for electricity generation in three locations of the Republic of Djibouti2019In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 185, p. 884-894Article in journal (Refereed)
    Abstract [en]

    In the Republic of Djibouti, due to increasing electricity demands, the government has planned to increase power supply by using renewable resources such as geothermal, solar and wind energy. This work presents the first wind resource assessment in the Republic of Djibouti using measured wind speed data for the period of three years by meteorological stations at eight locations. The results confirmed that three of the eight locations (i.e. GaliMa-aba, Ghoubbet and Bada Wein) have the best resource, with mean annual wind speeds of more than 6.0 m/s. Wind simulations using NCEP-CFSR and ERA5 models reanalysis shows that the seasonal variations are stable between different years and are broadly consistent with the observed wind speed. The feasibility of three wind farms with total capacity of 275 MW at GaliMa-aba, Ghoubbet and Bada Wein is examined. Using the WindPRO program and two commercial wind turbines in according to IEC 61400-1 design criteria, the electricity generation were technically assessed. These wind farms can produce 1073 GWh of electricity per year, approximately equal to Djibouti's expected average annual electrical demand in 2030. The economic evaluation using the present value cost (PVC) method estimate that the generation cost per kWh at these locations varies from 7.03 US.$ cent/kWh to 9.67 US.$ cent/kWh. Elsevier Ltd. All rights reserved.

  • 31.
    Dahlberg, Oskar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Pucci, E.
    Wang, L.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Fully-metallic, Low-dispersive, Leaky-wave Fed Lens Antenna for 60 GHz Base Station Applications2018In: 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena, METAMATERIALS 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 90-92Conference paper (Refereed)
    Abstract [en]

    The guiding structure commonly employed in leaky-wave antennas is dispersive, resulting in beam-steering with frequency. This behavior reduces operational bandwidth in point-to-point communication applications. In this work, we present an approach that aims at increasing the operational bandwidth of leaky-wave antennas by the employment of a metasur-face lens.

  • 32.
    Du, Gaoming
    et al.
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Liu, Guanyu
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Li, Zhenmin
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Cao, Yifan
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Zhang, Duoli
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Ouyang, Yiming
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Gao, Minglun
    Hefei Univ Technol, 193 Tunxi Rd, Hefei, Anhui, Peoples R China..
    Lu, Zhonghai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    SSS: Self-aware System-on-chip Using a Static-dynamic Hybrid Method2019In: ACM JOURNAL ON EMERGING TECHNOLOGIES IN COMPUTING SYSTEMS, ISSN 1550-4832, Vol. 15, no 3, article id 28Article in journal (Refereed)
    Abstract [en]

    Network-on-Chip (NoC) has become the de facto communication standard for multi-core or many-core System-on-Chip (SoC) due to its scalability and flexibility. However, an important factor in NoC design is temperature, which affects the overall performance of SoC-decreasing circuit frequency, increasing energy consumption, and even shortening chip lifetime. In this article, we propose SSS, a self-aware SoC using a static-dynamic hybrid method that combines dynamic mapping and static mapping to reduce the hotspot temperature for NoC-based SoCs. First, we propose monitoring and thermal modeling for self-state sensoring. Then, in static mapping stage, we calculate the optimal mapping solutions under different temperature modes using the discrete firefly algorithm to help self-decisionmaking. Finally, in dynamic mapping stage, we achieve dynamic mapping through configuring NoC and SoC sentient units for self-optimizing. Experimental results show that SSS has substantially reduced the peak temperature by up to 37.52%. The FPGA prototype proves the effectiveness and smartness of SSS in reducing hotspot temperature.

  • 33.
    Dubrova, Elena
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Näslund, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Degen, Bernhard
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Gawell, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Yu, Yang
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    CRC-PUF: A Machine Learning Attack Resistant Lightweight PUF Construction2019In: 2019 IEEE European Symposium on Security and Privacy Workshops (EuroS&PW), IEEE conference proceedings, 2019, p. 264-271Conference paper (Refereed)
    Abstract [en]

    Adversarial machine learning is an emerging threat to security of Machine Learning (ML)-based systems. However, we can potentially use it as a weapon against ML-based attacks. In this paper, we focus on protecting Physical Unclonable Functions (PUFs) against ML-based modeling attacks. PUFs are an important cryptographic primitive for secret key generation and challenge-response authentication. However, none of the existing PUF constructions are both ML attack resistant and sufficiently lightweight to fit low-end embedded devices. We present a lightweight PUF construction, CRC-PUF, in which input challenges are de-synchronized from output responses to make a PUF model difficult to learn. The de-synchronization is done by an input transformation based on a Cyclic Redundancy Check (CRC). By changing the CRC generator polynomial for each new response, we assure that success probability of recovering the transformed

  • 34.
    Ebrahimi, Masoumeh
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Kelati, Amleset
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
    Nkonoki, Emma
    Kondoro, Aron
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Rwegasira, Diana
    KTH.
    Ben Dhaou, Imed
    Taajamaa, Ville
    Tenhunen, Hannu
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Creation of CERID: Challenge, Education, Research, Innovation, and Deployment in the context of smart MicroGrid2019In: IST-Africa 2019 Conference Proceedings / [ed] Paul Cunningham ; Miriam Cunningham, 2019Conference paper (Refereed)
    Abstract [en]

    The iGrid project deals with the design and implementation of a solar-powered smart microgrid to supply electric power to small rural communities. In this paper, we discuss the roadmap of the iGrid project, which forms by merging the roadmaps of KIC (knowledge and Innovation Community) and CDE (Challenge-Driven Education). We introduce and explain a five-gear chain as Challenge, Education, Research, Innovation, and Deployment, called CERID, to reach the main goals of this project. We investigate the full chain in the iGrid project, which is established between KTH Royal Institute of Technology (Sweden) and University of Dar es Salam (Tanzania). We introduce the key stakeholders and explain how CERID goals can be accomplished in higher educations and through scientific research. Challenges are discussed, some innovative ideas are introduced and deployment solutions are recommended.

  • 35.
    Ebrahimpouri, Mahsa
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    High Frequency Microwave and Antenna Devices based on Transformation Optics and Glide-Symmetric Metasurfaces2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The new generation of wireless communication networks intends to support data rate of Gbit/s. One solution to make it possible is to move upwards in frequency range to employ the unused spectrum in mm-wave frequencies. This brings new challenges in the design of hardware for the communication networks, namely high free space path loss and expensive manufacturing. In this thesis, transformation optics and glide symmetry are employed to address these new challenges for the design of high frequency microwave components and lens antennas.

    Transformation optics provides a systematic tool to manipulate electromagnetic waves in a desired way. In this thesis, this tool has been used to improve the radiation properties of conventional homogeneous three-dimensional lenses and compress the size of two-dimensional graded-index lenses.

    Glide symmetry is a subset of higher-order symmetries and is described by a translation followed by a reflection with respect to a defined plane. Periodic structures possessing glide symmetry exhibit interesting properties. In this thesis, four of these properties are explored and possible applications are discussed.

    First, it is demonstrated that the first mode in a glide-symmetric periodic structures is significantly less dispersive than the corresponding conventional non-glide structure. This property was employed to design fully metallic wideband metasurface-based antennas. The losses in this type of antennas are only ohmic which make them suitable for high frequency applications. Second, it is shown that anisotropic glide-symmetric periodic structures can provide higher levels of anisotropy compared to their conventional periodic counterparts. This property is employed to design compressed two-dimensional lenses. Third, it is demonstrated that glide symmetry can be used to match the impedance of two vastly different dielectric media in a parallel plate waveguide configuration by enhancing the magnetic properties. This property was used to match the profile of two-dimensional homogeneous lenses. Fourth it is shown that glide-symmetric holey metallic structures achieve a significantly wider stop-band compared to conventional non-glide periodic structures. This property is exploited to design cost-effective waveguiding structures and microwave components at mm-wave frequencies. Furthermore, using this property, a flange design that provides contact-less measurement at mm-wave frequencies is presented.

  • 36.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Brazalez, Astrid Algaba
    Ericsson AB, Ericsson Res, S-41756 Gothenburg, Sweden..
    Manholm, Lars
    Ericsson AB, Ericsson Res, S-41756 Gothenburg, Sweden..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Using Glide-Symmetric Holes to Reduce Leakage Between Waveguide Flanges2018In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 28, no 6, p. 473-475Article in journal (Refereed)
    Abstract [en]

    In this letter, a novel cost-effective flange is proposed to prevent the leakage created by undesired air gaps between flanges of two mating waveguides. The cause of an undesired gap can be surface curvature, dirt, human mistakes, or misalignment. Our proposal consists of machining glide-symmetric holes around the waveguide aperture on the flanges. Due to the glide symmetry properties, an identical pattern of the holes is possible at both sides, thus becoming glide-symmetric when they are mated together.

  • 37.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Quevedo-Teruel, L. F. Herran, O.
    Wide Angle Impedance Matching Using Glide-symmetric MetasurfacesManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    This letter demonstrates that glide symmetry can be used to match the impedance of highly dense dielectric profiles in wide angle and broad bandwidth. Using glidesymmetric metasurfaces permits tuning the magnetic properties of materials, so high values of permittivity can be matched to free space in wide band. This matching is achieved without disturbing the performance of the device since the refractive index remains fixed. The performance of the proposed matching method is validated through measurements for normal incidence. For oblique incidence, a hyperbolic dielectric lens is matched with glide-symmetric structures in simulations. These simulations demonstrate a smooth transmission of the fields manifesting a well-matched profile of the lens.

  • 38.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Contact-less Measurement by Using Glide-symmetric Holes on Flanges2018In: 2018 12TH INTERNATIONAL CONGRESS ON ARTIFICIAL MATERIALS FOR NOVEL WAVE PHENOMENA (METAMATERIALS), IEEE , 2018, p. 105-107Conference paper (Refereed)
    Abstract [en]

    We present a cost-effective solution for contact-less measurement of waveguiding structures at high frequencies. Drilling glide-symmetric holey EBG (electromagnetic band gap) on the flanges, the leakage caused by undesired air-gaps, by the result of human mistakes or instrumental errors, between the flanges can be minimized considerably and contact-less measurement becomes possible.

  • 39.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Ultrawideband Anisotropic Glide-Symmetric Metasurfaces2019In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 18, no 8, p. 1547-1551Article in journal (Refereed)
    Abstract [en]

    This letter presents a method to realize anisotropic two-dimensional designs with wideband operation. Glide symmetry has been proven to increase the bandwidth and equivalent refractive index of periodic structures. Here, two anisotropic glide-symmetric unit cells are proposed and characterized. Our simulated results prove that these unit cells follow the general behavior of periodic structures possessing glide symmetry. Moreover, we demonstrate that higher level of anisotropy can also be achieved by glide symmetry. Combining our proposed anisotropic glide-symmetric unit cell and transformation optics, a 30% compressed Luneburg lens is designed. The lens operates from 1 to 13 GHz.

  • 40.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ettorre, Mauro
    Grbic, Anthony
    Broadband Planar Leaky Wave Antenna Using Glide-symmetric Meandered Transmission LineManuscript (preprint) (Other (popular science, discussion, etc.))
  • 41.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Zetterström, Oskar
    Quevedo-Teruel, Oscar
    Experimental Validation of a Bespoke Lens for a Slot log-spiral FeedManuscript (preprint) (Other (popular science, discussion, etc.))
  • 42.
    El-Sayed, R.
    et al.
    Karolinska Inst, Dept Lab Med, Expt Canc Med, S-14186 Stockholm, Sweden..
    Waraky, A.
    Gothenburg Univ, Dept Lab Med, Gothenburg, Sweden..
    Ezzat, K.
    Stockholm Univ, Wenner Gren Inst, Dept Mol Biosci, Stockholm, Sweden..
    Albabtain, R.
    King Saud Univ, Coll Appl Med Sci, Riyadh, Saudi Arabia..
    Elgammal, Karim
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Shityakov, S.
    Univ Hosp Wilrzburg, Dept Anesthesia & Crit Care, Wurzburg, Germany..
    Muhammed, Mamoun
    KTH.
    Hassan, M.
    Karolinska Inst, Dept Lab Med, Expt Canc Med, S-14186 Stockholm, Sweden.;Karolinska Univ Hosp Huddinge, Clin Res Ctr, Stockholm, Sweden..
    Degradation of pristine and oxidized single wall carbon nanotubes by CYP3A42019In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 515, no 3, p. 487-492Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) are a class of carbon based nanomaterials which have attracted substantial attention in recent years as they exhibit outstanding physical, mechanical and optical properties. In the last decade many studies have emerged of the underlying mechanisms behind CNT toxicity including malignant transformation, the formation of granulomas, inflammatory responses, oxidative stress, DNA damage and mutation. In the present investigation, we studied the biodegradation of single-walled carbon nanotubes (SWCNTs) by Cytochrome P450 enzymes (CYP3A4) through using Raman spectroscopy. CYP3A4 is known isozyme accountable for metabolizing various endogenous and exogenous xenobiotics. CYP3A4 is expressed dominantly in the liver and other organs including the lungs. Our results suggest that CYP3A4 has a higher affinity for p-SWNTs compared to c-SWNTs. HEK293 cellular viability was not compromised when incubated with SWNT. However, CYP3A4 transfected HEK293 cell line showed no digestion of cSWNTs after incubation for 96 h. Cellular uptake of c-SWNTs was observed by electron microscopy and localization of c-SWNTs was confirmed in endosomal vesicles and in the cytoplasm. This is the first study CYP3A4 degrading both p-SWNTs and c-SWNTs in an in vitro setup. Interestingly, our results show that CYP3A4 is more proficient in degrading p-SWNTs than c-SWNTs. We also employed computational modeling and docking assessments to develop a further understanding of the molecular interaction mechanism. 

  • 43.
    Emadeddin, Ahmad
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    On direct matching and efficiency improvements for integrated array antennas2019In: Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 408-411, article id 8879178Conference paper (Refereed)
    Abstract [en]

    The goal of this design study is to determine the insertion-loss associated with a sequence of impedance-matching networks. These results are compared to the performance of direct integration of PA/antenna. In high-frequency, ≥ 20GHz, co-design of PA/antenna has as an important goal to remove any matching networks between the antenna and power amplifier by e.g. antenna shaping both to reduce the physical size and to improve the power added efficiency of the radio-front end. We determine the insertion-loss for matching a 2W GaN RF Transistor TGF2942 working in Class-A to a given real-valued load. This type of reference can serve as a benchmark to compare co-designed antenna performance. We also determine changes in power added efficiency and insertion-loss associated with changes in the physical size of a sequence of differently sized matching-network. The results are examined with respect to the electrical size, choice of material (dielectric attenuation), and given Z {mathbf{ant}} Z {mathbf{opt}}. In the reference case, we observe that direct matching may improve the power added efficiency by 10% for a 5% frequency bandwidth and by 6% at the center frequency.

  • 44.
    Fan, Xuge
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Micro and Nanosystems.
    Forsberg, Fredrik
    Scania Technical Centre.
    Smith, Anderson David
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Schröder, Stephan
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Micro and Nanosystems.
    Wagner, Stefan
    AMO GmbH.
    Östling, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Lemme, Max C.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits. RWTH Aachen University; AMO GmbH.
    Niklaus, Frank
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Micro and Nanosystems.
    Suspended Graphene Membranes with Attached Silicon Proof Masses as Piezoresistive Nanoelectromechanical Systems Accelerometers2019In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 19, no 10, p. 6788-6799Article in journal (Refereed)
    Abstract [en]

    Graphene is an atomically thin material that features unique electrical and mechanical properties, which makes it an extremely promising material for future nanoelectromechanical systems (NEMS). Recently, basic NEMS accelerometer functionality has been demonstrated by utilizing piezoresistive graphene ribbons with suspended silicon proof masses. However, the proposed graphene ribbons have limitations regarding mechanical robustness, manufacturing yield, and the maximum measurement current that can be applied across the ribbons. Here, we report on suspended graphene membranes that are fully clamped at their circumference and have attached silicon proof masses. We demonstrate their utility as piezoresistive NEMS accelerometers, and they are found to be more robust, have longer life span and higher manufacturing yield, can withstand higher measurement currents, and are able to suspend larger silicon proof masses, as compared to the previous graphene ribbon devices. These findings are an important step toward bringing ultraminiaturized piezoresistive graphene NEMS closer toward deployment in emerging applications such as in wearable electronics, biomedical implants, and internet of things (IoT) devices.

  • 45.
    Fan, Xuge
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Forsberg, Fredrik
    Scania Technical Centre.
    Smith, Anderson
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Schröder, Stephan
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Wagner, Stefan
    Faculty of Electrical Engineering and Information Technology, RWTH Aachen University.
    Rödjegård, Henrik
    Senseair AB .
    Fisher, Andreas
    Silex Microsystems AB.
    Östling, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Lemme, Max
    Faculty of Electrical Engineering and Information Technology, RWTH Aachen University.
    Niklaus, Frank
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Graphene beams with suspended masses as electromechanical transducers in ultra-small accelerometersIn: Article in journal (Refereed)
  • 46.
    Farrugia, C. J.
    et al.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Cohen, I. J.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Vasquez, B. J.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Lugaz, N.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Alm, L.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Torbert, R. B.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Argall, M. R.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Paulson, K.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Lavraud, B.
    UPMC Univ Paris 06, Univ Paris Sud, Ecole Polytech, LPP,UMR7648,CNRS,Observ Paris, Paris, France..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Gratton, F. T.
    Acad Nacl Ciencias Buenos Aires, Buenos Aires, DF, Argentina..
    Matsui, H.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Rogers, A.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Forbes, T. G.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Payne, D.
    Univ New Hampshire, Space Sci Ctr, Durham, NH 03824 USA..
    Ergun, R. E.
    Univ Colorado, Boulder, CO 80309 USA..
    Mauk, B.
    Johns Hopkins Univ, Appl Phys Lab, Laurel, MD USA..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Russell, C. T.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Strangeway, R. J.
    Univ Calif Los Angeles, Los Angeles, CA USA..
    Shuster, J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Nakamura, R.
    Space Res Inst, Graz, Austria..
    Fuselier, S. A.
    Southwest Res Inst, San Antonio, TX USA.;Univ Texas San Antonio, San Antonio, TX USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Khotyaintsev, Y. , V
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics. Swedish Inst Space Phys, Uppsala, Sweden..
    Marklund, G. T.
    Swedish Inst Space Phys, Uppsala, Sweden..
    Petrinec, S. M.
    Lockheed Martin Adv Technol Ctr, Palo Alto, CA USA..
    Pollock, C. J.
    West Virginia Univ, Morgantown, WV USA..
    Effects in the Near-Magnetopause Magnetosheath Elicited by Large-Amplitube Alfvenic Fluctuations Terminating in a Field and Flow Discontinuity2018In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 11, p. 8983-9004Article in journal (Refereed)
    Abstract [en]

    In this paper we report on a sequence of large-amplitude Alfvenic fluctuations terminating in a field and flow discontinuity and their effects on electromagnetic fields and plasmas in the near-magnetopause magnetosheath. An arc-polarized structure in the magnetic field was observed by the Time History of Events and Macroscale Interactions during Substorms-C in the solar wind, indicative of nonlinear Alfven waves. It ends with a combined tangential discontinuity/vortex sheet, which is strongly inclined to the ecliptic plane and at which there is a sharp rise in the density and a drop in temperature. Several effects resulting from this structure were observed by the Magnetospheric Multiscale spacecraft in the magnetosheath close to the subsolar point (11:30 magnetic local time) and somewhat south of the geomagnetic equator (-33 degrees magnetic latitude): (i) kinetic Alfven waves; (ii) a peaking of the electric and magnetic field strengths where E . J becomes strong and negative (-1 nW/m(3)) just prior to an abrupt dropout of the fields; (iii) evolution in the pitch angle distribution of energetic (a few tens of kilo-electron-volts) ions (H+, Hen+, and On+) and electrons inside a high-density region, which we attribute to gyrosounding of the tangential discontinuity/vortex sheet structure passing by the spacecraft; (iv) field-aligned acceleration of ions and electrons that could be associated with localized magnetosheath reconnection inside the high-density region; and (v) variable and strong flow changes, which we argue to be unrelated to reconnection at partial magnetopause crossings and likely result from deflections of magnetosheath flow by a locally deformed, oscillating magnetopause.

  • 47. Frid, Henrik
    et al.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Compensation of radome effects in small airborne monopulse arrays by convex optimization2018In: IET Conference Publications, Institution of Engineering and Technology , 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    The quality of small array antennas in airborne monopulse systems can be significantly reduced by the radome. We therefore present a convex optimization approach to minimize radome effects in monopulse arrays. This is achieved by using active element patterns in the optimization to determine the excitation weights. Simulation results for a BoR array with 48 elements and an extended hemispherical radome are presented. We demonstrate that it is possible to reduce the side-lobe level by 3.5 dB by taking radome effects into account in the optimization. This approach also results in an increased gain, particularly at large scan angles. Furthermore, the presented approach allows the monopulse slope to be indirectly specified as a design parameter. It is shown that the trade-off between the monopulse slope coefficient and the side-lobe level is approximately linear.

  • 48.
    Frid, Henrik
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Malmström, Johan
    Saab Surveillance, Stockholm, Sweden.
    Jonsson, B. Lars G.
    Determining Direction‐of‐Arrival Accuracy for Installed Antennas by Postprocessing of Far‐Field Data2019In: Radio Science, ISSN 0048-6604, E-ISSN 1944-799X, Vol. 54, no 12, p. 1204-1221Article in journal (Refereed)
    Abstract [en]

    Direction‐of‐arrival (DoA) estimation accuracy can be degraded due to installation effects, such as platform reflections, diffraction from metal edges, and reflections and refraction in the radome. To analyze these effects, this paper starts with a definition of the term installation error related to DoA estimation. Thereafter, we present a postprocessing method, which can be used to determine the DoA estimation accuracy for installed antennas. By computing synthetic signals from the installed far‐field data, it is possible to analyze the installation errors described above, in addition to analyzing array model errors. The method formulation is general, thus allowing generic array configurations, installation configurations, and direction‐finding algorithms to be studied. The use of the presented method is demonstrated by a case study of a wideband four‐quadrant array. In this case study, we investigate the installation errors due to a single‐shell radome. Thereafter, the effects of platform reflections are also analyzed, for an antenna placement in the tail of a fighter aircraft. Simulation results are presented for both the monopulse and the MUltiple SIgnal Classification direction‐finding algorithms.

  • 49.
    Fu, H. S.
    et al.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Cao, J. B.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Cao, D.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Wang, Z.
    Beihang Univ, Sch Space & Environm, Beijing, Peoples R China.
    Vaivads, Andris
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Khotyaintsev, Yuri V.
    Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen.
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA.
    Huang, S. Y.
    Wuhan Univ, Sch Elect & Informat, Wuhan, Hubei, Peoples R China.
    Evidence of Magnetic Nulls in Electron Diffusion Region2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 1, p. 48-54Article in journal (Refereed)
    Abstract [en]

    Theoretically, magnetic reconnection—the process responsible for solar flares and magnetospheric substorms—occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient techniques and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed First‐Order Taylor Expansion (FOTE) Expansion technique. We investigate 12 EDR candidates at the Earth's magnetopause and find radial nulls (X‐lines) in all of them. In some events, spacecraft are only 3 km (one electron inertial length) away from the null. We reconstruct the magnetic topology of these nulls and find it agrees well with theoretical models. These nulls, as reconstructed for the first time inside the EDR by the FOTE technique, indicate that the EDR is active and the reconnection process is ongoing.

    Plain Language Summary: Magnetic reconnection is a key process responsible for many explosive phenomena in nature such as solar flares and magnetospheric substorms. Theoretically, such process occurs at the X‐line or radial null in the electron diffusion region (EDR). However, whether this theory is correct is still unknown, because the radial null (X‐line) has never been observed inside the EDR due to the lack of efficient technique and the scarcity of EDR measurements. Here we report such evidence, using data from the recent MMS mission and the newly developed FOTE technique.

  • 50.
    Gingell, I
    et al.
    Imperial Coll London, Blackett Lab, London, England..
    Schwartz, S. J.
    Imperial Coll London, Blackett Lab, London, England.;Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Eastwood, J. P.
    Imperial Coll London, Blackett Lab, London, England..
    Burch, J. L.
    Southwest Res Inst, San Antonio, TX USA..
    Ergun, R. E.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Fuselier, S.
    Southwest Res Inst, San Antonio, TX USA..
    Gershman, D. J.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Giles, B. L.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Khotyaintsev, Y. , V
    Lavraud, B.
    Univ Toulouse, Inst Rech Astrophys & Planetol, CNRS, UPS,CNES, Toulouse, France..
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics. Swedish Inst Space Phys Uppsala, Uppsala, Sweden..
    Paterson, W. R.
    NASA, Goddard Space Flight Ctr, Greenbelt, MD USA..
    Phan, T. D.
    Univ Calif Berkeley, Space Sci Lab, Berkeley, CA 94720 USA..
    Russell, C. T.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Stawarz, J. E.
    Imperial Coll London, Blackett Lab, London, England..
    Strangeway, R. J.
    Univ Calif Los Angeles, Inst Geophys & Planetary Phys, Los Angeles, CA 90024 USA..
    Torbert, R. B.
    Univ New Hampshire, Dept Phys, Durham, NH 03824 USA..
    Wilder, F.
    Univ Colorado, Lab Atmospher & Space Phys, Boulder, CO 80309 USA..
    Observations of Magnetic Reconnection in the Transition Region of Quasi-Parallel Shocks2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 3, p. 1177-1184Article in journal (Refereed)
    Abstract [en]

    Using observations of Earth's bow shock by the Magnetospheric Multiscale mission, we show for the first time that active magnetic reconnection is occurring at current sheets embedded within the quasi-parallel shock's transition layer. We observe an electron jet and heating but no ion response, suggesting we have observed an electron-only mode. The lack of ion response is consistent with simulations showing reconnection onset on sub-ion time scales. We also discuss the impact of electron heating in shocks via reconnection.

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