| 21. |
- Berg, Mikael, Universitetslektor, 1970-, et al.
(författare)
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Graderande granskning och förklarade glapp : Svensk historie- och samhällskunskapsdidaktisk forskning om lärares bedömningspraktik 2009–2019
- 2020
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Ingår i: Nordidactica. - Karlstad : CSD Karlstad. - 2000-9879. ; :1, s. 18-44
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade there has been an increasing interest in the Swedish research field concerning assessment in schools, especially with focus on the school subject’s history and social science. The aim of this article is therefore to explore what perspectives that have being used by researchers in the Swedish field of history and social science subject didactic, when investigating teacher’s assessment practice. The method used in the article is a text analysis of 13 Swedish thesis and articles that deal with teacher’s assessment practice within the Swedish field of history and social science subject didactics between 2009 and 2019. The result shows that there an overwhelming part of the studies deals with examine teacher’s assessment practice. Another dominant trend is to explain the variations in teacher’s assessment practice. Overall the result shows that there is a lack of studies which begin with teachers subject specific experiences and also a lack of studies with a policy critical approach. To try to capture the complexity in assessment we therefore argue in the light of the result that there is a need of both a theoretical and cumulative broadening of the Swedish research field concerning teacher’s assessment with focus on the school subject’s history and social science.
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| 22. |
- Berg, Mikael, Universitetslektor, 1970-, et al.
(författare)
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The Didactic Function of Narratives : Teacher discussions on the use of challenging, engaging, unifying, and complementing narratives in the history classroom
- 2023
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Ingår i: Historical Encounters. - : HERMES History Education Research Network. - 2203-7543. ; 10:1, s. 44-59
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Tidskriftsartikel (refereegranskat)abstract
- At a time when society is characterised by a polarised social climate, it is teachers who need to contribute to a nuanced orientation of the world. This article looks at the ways historical narratives can be used as a collective didactic resource in the historical-cultural context of contemporary society. Its purpose is to analyse the didactic function that underlies historical narratives in relation to students’ understanding of society. Our study builds on three focus group interviews with six upper-secondary-school teachers of history and social studies. The method used is the stimulated-recall interview whereby teachers talk about various teaching situations. Four uses of historical narratives were identified, each with its own didactic function. The first is the use of the “challenging” narrative, the function of which is to disrupt and realign students’ understanding of society. The second is the use of the “engaging” narrative: its function is to involve and activate students in their present understanding of society. The third is the use of the “unifying” narrative, the function of which is to bridge contradictions within society. The fourth and final narrative is the “complementing” narrative, whose function it is to broaden and open students’ understanding of society. To address students in terms of their present understanding of society, teachers employ these four narratives as didactic resources. In such a way, these uses of historical narratives tie in with the teachers’ overall aim to contribute an alternative perspective to students’ current understanding of society.As such, the results reveal the general theoretical knowledge teachers have relating to their profession.
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| 23. |
- Berglund, Martin, 1985-, et al.
(författare)
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Evaluation of a microplasma source based on a stripline split-ring resonator
- 2013
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Ingår i: Plasma sources science & technology. - : Institute of Physics (IOP). - 0963-0252 .- 1361-6595. ; 22:5, s. 055017-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a stripline split-ring resonator microwave-induced plasma source, aimed for integration in complex systems, is presented and compared with a traditional microstrip design. Devices based on the two designs are evaluated using a plasma breakdown test setup for measuring the power required to ignite plasmas at different pressures. Moreover, the radiation efficiency of the devices is investigated with a Wheeler cap, and their electromagnetic compatibility is investigated in a variable electrical environment emulating an application. Finally, the basic properties of the plasma in the two designs are investigated in terms of electron temperature, plasma potential and ion density. The study shows that, with a minor increase in plasma ignition power, the stripline design provides a more isolated and easy-to-integrate alternative to the conventional microstrip design. Moreover, the stripline devices showed a decreased antenna efficiency as compared with their microstrip counterparts, which is beneficial for plasma sources. Furthermore, the investigated stripline devices exhibited virtually no frequency shift in a varying electromagnetic environment, whereas the resonance frequency of their microstrip counterparts shifted up to 17.5%. With regard to the plasma parameters, the different designs showed only minor differences in electron temperature, whereas the ion density was higher with the stripline design.
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| 24. |
- Berglund, Martin, 1985-, et al.
(författare)
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Evaluation of dielectric properties of HTCC alumina for realization of plasma sources
- 2015
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 44:10, s. 3654-3660
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Tidskriftsartikel (refereegranskat)abstract
- As the sensitivity of optogalvanic spectroscopy based on prototype microplasma sources increases, contamination from composite materials in the printed circuit board used starts to become a concern. In this paper, a transfer to high-temperature cofired alumina and platinum is made and evaluated. The high-purity alumina provides an inert plasma environment, and allows for temperatures above 1000A degrees C, which is beneficial for future integration of a combustor. To facilitate the design of high-end plasma sources, characterization of the radio frequency (RF) parameters of the materials around 2.6 GHz is carried out. A RF resonator structure was fabricated in both microstrip and stripline configurations. These resonators were geometrically and electrically characterized, and epsilon (r) and tan were calculated using the RF waveguide design tool Wcalc. The resulting epsilon (r) for the microstrip and stripline was found to be 10.68 (+/- 0.12) and 9.65 (+/- 0.14), respectively. The average tan of all devices was found to be 0.0011 (+/- 0.0007). With these parameters, a series of proof-of-concept plasma sources were fabricated and evaluated. Some problems in the fabrication stemmed from the lamination and difficulties with the screen-printing, but a functioning plasma source was demonstrated.
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| 25. |
- Berglund, Martin, 1985-, et al.
(författare)
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Extreme-temperature lab on a chip for optogalvanic spectroscopy of ultra small samples – key components and a first integration attempt
- 2016
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Ingår i: 27th Micromechanics And Microsystems Europe Workshop (MME 2016). - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- This is a short summary of the authors’ recent R&D on valves, combustors, plasma sources, and pressure and temperature sensors, realized in high-temperature co-fired ceramics, and an account for the first attempt to monolithically integrate them to form a lab on a chip for sample administration, preparation and analysis, as a stage in optogalvanic spectroscopy.
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| 26. |
- Berglund, Martin, 1985-, et al.
(författare)
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Manufacturing Miniature Langmuir probes by Fusing Platinum Bond Wires
- 2015
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Ingår i: Journal of Micromechanics and Microengineering. - Bristol : Institute of Physics Publishing (IOPP). - 0960-1317 .- 1361-6439. ; 25:10
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a novel method for manufacturing microscopic Langmuir probes with spherical tips from platinum bond wires by fusing for plasma characterization in microplasma sources. Here, the resulting endpoints, formed by droplets on the ends of a fused wire, are intended to act as spherical Langmuir probes. For studying the fusing behavior, bond wires were wedge bonded over a 2 mm wide slit, to emulate the final application, and fused with different voltages and currents. For electrical isolation, a set of wires were coated with a 4 μm thick layer of Parylene before they were fused. After fusing, the gap size, as well as the shape and area of the ends of the remaining stubs were measured. The yield of the process was also investigated, and the fusing event was studied using a high-speed camera for analyzing its dynamics. Four characteristic tip shapes were observed: spherical, folded, serpentine shaped and semi-spherical. The stub length leveled out at ~400 μm as the fusing power increased. The fusing of the coated wires required a higher power to yield a spherical shape. Finally, a Parylene coated bond wire was integrated into a stripline split-ring resonator (SSRR) microplasma source, and was fused to form two Langmuir probes with spherical endpoints. These probes were used for measuring the I–V characteristics of a plasma generated by the SSRR. In a voltage range between −60 V and 60 V, the fused stubs exhibited the expected behavior of spherical Langmuir probes, and will be considered for further integration.
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| 27. |
- Berglund, Martin, 1985-, et al.
(författare)
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Microplasma source for optogalvanic spectroscopy of nanogram samples
- 2013
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 114:3, s. 033302-
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Tidskriftsartikel (refereegranskat)abstract
- The demand for analysis of smaller samples in isotopic ratio measurements of rare isotopes is continuously rising with the development of new applications, particularly in biomedicine. Interesting in this aspect are methods based on optogalvanic spectroscopy, which have been reported to facilitate both 13C-to-12C and 14C-to-12C ratio measurements with high sensitivity. These methods also facilitate analysis of very small samples, down to the microgram range, which makes them very competitive to other technologies, e.g., accelerator mass spectroscopy. However, there exists a demand for moving beyond the microgram range, especially from regenerative medicine, where samples consist of, e.g., DNA, and, hence, the total sample amount is extremely small. Making optogalvanic spectroscopy of carbon isotopes applicable to such small samples, requires miniaturization of the key component of the system, namely the plasma source, in which the sample is ionized before analysis. In this paper, a novel design of such a microplasma source based on a stripline split-ring resonator is presented and evaluated in a basic optogalvanic spectrometer. The investigations focus on the capability of the plasma source to measure the optogalvanic signal in general, and the effect of different system and device specific parameters on the amplitude and stability of the optogalvanic signal in particular. Different sources of noise and instabilities are identified, and methods of mitigating these issues are discussed. Finally, the ability of the cell to handle analysis of samples down to the nanogram range is investigated, pinpointing the great prospects of stripline split-ring resonators in optogalvanic spectroscopy.
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| 28. |
- Berglund, Martin, et al.
(författare)
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Operation characteristics and optical emission distribution of a miniaturized silicon through-substrate split-ring resonator microplasma source
- 2014
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Ingår i: Journal of microelectromechanical systems. - 1057-7157 .- 1941-0158. ; 23:6, s. 1340-1345
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Tidskriftsartikel (refereegranskat)abstract
- There are many new microplasma sources being developed for a wide variety of applications, each with different properties tailored to its specific use. Microplasma sources enable portable instruments for, e.g., chemical analysis, sterilization, or activation of substances. A novel microplasma source, based on a microstrip split-ring resonator design with electrodes integrated in its silicon substrate, was designed, manufactured, and evaluated. This device has a plasma discharge gap with a controlled volume and geometry, and offers straightforward integration with other microelectromechancial systems (MEMS) components, e.g., microfluidics. The realized device was resonant at around 2.9 GHz with a quality factor of 18.7. Two different operational modes were observed with the plasma at high pressure being confined in the gap between the electrodes, whereas the plasma at low pressures appeared between the ends of the electrodes on the backside. Measurement of the angular distribution of light emitted from the device with through-substrate electrodes showed narrow emission lobes compared with a reference plasma source with on-substrate electrodes.
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| 29. |
- Bergman, Eva, et al.
(författare)
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Synthesis of theoretical and empirical experineces from nutrient and cyprinid reductions in Lake Ringsjön
- 1999
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Ingår i: Hydrobiologia. - 0018-8158. ; 404, s. 145-156
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Tidskriftsartikel (refereegranskat)abstract
- The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
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| 30. |
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