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Johansson, Niklas
Publications (6 of 6) Show all publications
Holmberg, M., Dancila, D., Rydberg, A., Hjörvarsson, B., Jansson, U., Marattukalam, J. J., . . . Andersson, J. (2018). Direct metal laser sintering printed millimeter and submillimeter waveguides. In: : . Paper presented at GigaHertz Symposium, Lund, May 24-25 2018.
Open this publication in new window or tab >>Direct metal laser sintering printed millimeter and submillimeter waveguides
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2018 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Telecommunications
Identifiers
urn:nbn:se:uu:diva-369172 (URN)
Conference
GigaHertz Symposium, Lund, May 24-25 2018
Funder
Swedish Foundation for Strategic Research , GMT14-0048
Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Holmberg, M., Dancila, D., Rydberg, A., Hjörvarsson, B., Jansson, U., Marattukalam, J. J., . . . Andersson, J. (2018). On Surface Losses in Direct Metal Laser Sintering Printed Millimeter and Submillimeter Waveguides. Journal of Infrared, Millimeter and Terahertz Waves, 39(6), 535-545
Open this publication in new window or tab >>On Surface Losses in Direct Metal Laser Sintering Printed Millimeter and Submillimeter Waveguides
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2018 (English)In: Journal of Infrared, Millimeter and Terahertz Waves, ISSN 1866-6892, E-ISSN 1866-6906, Vol. 39, no 6, p. 535-545Article in journal (Refereed) Published
Abstract [en]

Different lengths of WR3 (220-330 GHz) and WR10 (75-110 GHz) waveguides are fabricated through direct metal laser sintering (DMLS). The losses in these waveguides are measured and modelled using the Huray surface roughness model. The losses in WR3 are around 0.3 dB/mm and in WR10 0.05 dB/mm. The Huray equation model is accounting relatively good for the attenuation in the WR10 waveguide but deviates more in the WR3 waveguide. The model is compared to finite element simulations of the losses assuming an approximate surface structure similar to the resulting one from the DMLS process.

Place, publisher, year, edition, pages
SPRINGER, 2018
Keywords
Millimeterwave, 3D-metal-printed, Waveguide loss
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-356385 (URN)10.1007/s10762-018-0470-x (DOI)000431255500005 ()
Funder
Swedish Foundation for Strategic Research
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-07-25Bibliographically approved
Jonsson, H., Gråsjö, J., Nordström, J., Johansson, N. & Frenning, G. (2015). An apparatus for confined triaxial testing of single particles. Powder Technology, 270, 121-127
Open this publication in new window or tab >>An apparatus for confined triaxial testing of single particles
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2015 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 270, p. 121-127Article in journal (Refereed) Published
Abstract [en]

A novel triaxial apparatus employing overlapping rigid boundaries has been designed and constructed for experimental measurement of contact forces under confined compression of single granules in the mm-scale. The performance of the apparatus was evaluated by performing uniaxial and triaxial compression experiments on ideal elastic-plastic materials. Compression curves were compared with the fully plastic Abbott-Firestone contact model and with results from FEM simulations. The increase in contact force associated with confined conditions was observed in the compression curves from triaxial compression experiments, as supported by predictions from simulations using single particle contact models. Hence, a new method for the assessment of mechanical behaviour of single particles under confined compression can be considered as established.

Keywords
Compression, Triaxial, Single particles, Confined conditions, Apparatus design, Contact mechanics
National Category
Pharmaceutical Sciences
Identifiers
urn:nbn:se:uu:diva-239203 (URN)10.1016/j.powtec.2014.10.016 (DOI)000347579300014 ()
Funder
Swedish Research Council, 621-2011-4049
Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2018-04-12Bibliographically approved
Englund, C.-J., Agåker, M., Fredriksson, P., Olsson, A., Johansson, N., Rubensson, J.-E. & Nordgren, J. (2015). An ultra-high vacuum chamber for scattering experiments featuring in-vacuum continuous in-plane variation of the angle between entrance and exit vacuum ports. Review of Scientific Instruments, 86(9), Article ID 095110.
Open this publication in new window or tab >>An ultra-high vacuum chamber for scattering experiments featuring in-vacuum continuous in-plane variation of the angle between entrance and exit vacuum ports
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2015 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 9, article id 095110Article in journal (Refereed) Published
Abstract [en]

A concept that enables in-vacuum continuous variation of the angle between two ports in one plane has been developed and implemented. The vacuum chamber allows for measuring scattering cross sections as a function of scattering angle and is intended for resonant inelastic X-ray scattering experiments. The angle between the ports can be varied in the range of 30 degrees-150 degrees, while the pressure change is less than 2 x 10(-10) mbars.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-265596 (URN)10.1063/1.4931041 (DOI)000362573300062 ()26429483 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2015-11-02 Created: 2015-11-02 Last updated: 2017-12-01
Goryashko, V., Dancila, D., Ekelöf, T., Gajewski, K., Hermansson, L., Johansson, N., . . . Ziemann, V. (2012). Proposal for Design and Test of a 352 MHz Spoke RF Source. Uppsala: Department of Physics and Astronomy, Uppsala University
Open this publication in new window or tab >>Proposal for Design and Test of a 352 MHz Spoke RF Source
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2012 (English)Report (Other academic)
Abstract [en]

More than a dozen of spoke resonators prototypes (SSR, DSR, TSR) have been constructed and tested worldwide. None have accelerated beam until now and the ESS LINAC will be the first accelerator to operate with spoke cavities. Experience with other types of superconducting cavities indicates that high-power test is vital for reliable operation of the cavity in an accelerator. Although characteristics of a bare cavity can be obtained in a low-power test some important features of a `dressed' cavity like the electroacoustic stability and tuning system can be studied only in a high-power test stand. The ESS LINAC is a pulsed machine and the Lorentz detuning originating from the electromagnetic pressure on the cavity walls is expected to be strong. The Lorentz force along with the cavity sensitivity to mechanical excitations at some resonant frequencies may lead to self-sustained mechanical vibrations which make cavity operation dicult. Practical experience shows that increasing the boundary stiness will decrease the static Lorentz force detuning but not necessarily the dynamic one. Therefore, the FREIA group at Uppsala University is building a high-power test stand able to study performance of the ESS spoke cavity at high power. The RF test stand will be able to drive the cavity not only in the self-excitation mode but also with closed RF loop and fixed frequency. The later technique will be used to reproduce the shape of the cavity voltage pulse as it is expected to be in the cavity operating in the ESS LINAC such that the cavity tuning compensation system will be tested under realistic conditions.

Place, publisher, year, edition, pages
Uppsala: Department of Physics and Astronomy, Uppsala University, 2012. p. 29
Series
FREIA Report ; 2012/04
National Category
Accelerator Physics and Instrumentation Engineering and Technology
Research subject
Engineering Science with specialization in Advanced Instrumentation and Measurements; Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-186802 (URN)
Projects
FREIA
Available from: 2012-11-30 Created: 2012-11-29 Last updated: 2017-01-25Bibliographically approved
Danielsson, U., Johansson, N. & Larfors, M. (2007). The world next door: Results in landscape topography. Journal of High Energy Physics (JHEP), 03, 080
Open this publication in new window or tab >>The world next door: Results in landscape topography
2007 (Swedish)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 03, p. 080-Article in journal (Refereed) Published
Abstract [en]

Recently, it has become clear that neighboring multiple vacua might have interesting consequences for the physics of the early universe. In this paper we investigate the topography of the string landscape corresponding to complex structure moduli of flux compactified type IIB string theory. We find that series of continuously connected vacua are common. The properties of these series are described, and we relate the existence of infinite series of minima to certain unresolved mathematical problems in group theory. Numerical studies of the mirror quintic serve as illustrating examples.

Keywords
Superstring Vacua, Flux compactifications, dS vacua in string theory
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-13761 (URN)10.1088/1126-6708/2007/03/080 (DOI)000245922000080 ()
Available from: 2008-01-25 Created: 2008-01-25 Last updated: 2017-12-11Bibliographically approved
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