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- Nordebo, Sven, et al.
(författare)
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Wave modeling and fault localization for underwater power cables
- 2011
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Ingår i: 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC). - : IEEE Press. - 9781457700460 ; , s. 698-701
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Konferensbidrag (refereegranskat)abstract
- This paper describes some preliminary results regarding Time-Domain pulse Reflection (TDR) measurements and modeling performed on the Baltic Cable submarine HVDC link between southern Sweden and northern Germany. The measurements were conducted in collaboration between the Linnaeus University, Lund University, Baltic Cable AB and ABB High Voltage Cables AB, and is part of the research project: “Fundamental wave modeling for signal estimation on lossy transmission lines”. Preliminary results on measurements and modeling are included here, as well as a first numerical study regarding the low-frequency dispersion characteristics of power cables. The numerical study shows that the finite conductivity of the cable lead shield has a great impact on the losses at low frequencies (0-1 kHz), and that the low-frequency asymptotics of the propagation constant is consistent with common propagation models based on the skin-effect.
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- Alatalo, Tarja, 1961-, et al.
(författare)
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Characteristics of Teacher Competence : Trends over Time and Between Student Groups in the Swedish Compulsory School
- 2018
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Konferensbidrag (refereegranskat)abstract
- BackgroundAchievement differences across schools have increased in Sweden during the past two decades, at the same time as average achievement levels have declined, for example in mathematics (Holmlund et al., 2014; SOU 2014:05) and reading (Skolverket, 2013). These negative trends may be related to schools’ demographic, organizational and resource prerequisites. The organizational basis for the Swedish compulsory school has undergone significant changes since the late 1980s, with free school choice, an increasing number of private schools and a larger autonomy for school leaders. The increased school segregation with respect to migration background since the implementation of these reforms (Yang Hansen & Gustafsson, 2016), could possibly be caused by the continuing decline in inclusion of migrant students and a related educational inequality in instructional quality and teacher competence. Inclusion is defined as a structure of organizing integration according to particular rules and regulations.The results of research on effects of teacher competence are, however, somewhat fragmented and unclear, at least with respect to effects on different student groups. This can partly be explained by uncertainties in the determination of crucial teacher characteristics. Making comparisons between for example authorized and unauthorized teachers has been shown to be problematic. There is vast research in this field which is characterized by severe methodological problems, e.g. with respect to drawing causal conclusions from cross-sectional observational data. For example, no correlation between student achievement and various resource factors has been found in some studies (e.g. Hanushek, 1997), whereas others found a positive correlation (e.g. Greenwald, Hedges & Laine, 1996).A teacher effect on student achievement is, however, well manifested (e.g., Gustafsson, 2003; Gustafsson & Myrberg, 2002; Johansson, Myrberg, & Rosén, 2015; Nye, Konstantopoulus, & Hedges, 2004; Rockoff, 2004), and the results also suggest that lower achieving students, as for example immigrants, are the more likely to benefit from increases in teacher effectiveness (e.g., Sanders, 1998). Teacher quality is, furthermore, one of the resource factors that explains most of the increase in performance differences between schools in Sweden (Björklund, Fredriksson, Gustafsson, & Öckert, 2010, Ch 7; Gustafsson & Myrberg, 2002). The general reduction in teacher quality in Sweden the last decades (SOU 2014:05), and the decreased equality of allocation of teacher competence between schools (Hansson & Gustafsson, 2016; OECD, 2013), supports these results. However, the variation between student outcomes that different teachers are achieving (Hanushek, 2003) needs to be further problematized and discussed. Teacher knowledge and skills, teacher training and teaching experience are examples of characteristics highlighted in different meta-studies (e.g., Greenwald, Hedges & Laine, 1996), that should be subject of such an investigation.This study intends to develop a precise and differentiated description of teacher quality for use in future analyses of relations between teacher competence and educational results, with focus on interactions with student composition of schools due to students’ socio-economic and migration backgrounds. The description is among other factors focusing on teacher’s basic knowledge, subject-related and pedagogical training, and type of teacher training program. One aim is to investigate the variation over time in access to qualified teachers and the variation in teacher qualifications between schools. In further analyses, the significance of the teacher characteristics for literacy and mathematics in grades 1 to 6 will be focused.Overall, the project, which this study is a part of, is expected to generate insights about essential conditions for effective and equitable teaching in Swedish and mathematics in primary school, and about distributions of teacher competence across schools with different student composition.
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| 5. |
- Bengtsson, Peter, et al.
(författare)
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Energy structure and transition rates in the Ne-like sequence from relativistic CI calculations
- 2012
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Ingår i: Europhysics Conference Abstracts;36C. - : European Physical Society. ; , s. 128-128
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Atomic data are important in astrophysical applications and transition rates can be used in the determination of element abundances and plasma diagnostics. To provide for the extensive data needs a number of general computer codes such as SUPERSTRUCTURE, CIV3, and ATSP2K have been developed. As an alternative to these codes, which all rely on the Breit-Pauli approximation, the fully relativistic GRASP2K code can be used. GRASP2K is based on the multiconfiguration Dirac-Hartree-Fock method and implements a bi-orthogonal transformation method that permits initial and final states in a transition array to be optimized separately, which, in many cases, leads to more accurate values of the resulting rates. The GRASP2K package also contains modules to compute diagonal and off-diagonal hyperfine interaction constants, isotope shifts, Land´e gJ factors, and splittings of magnetic sub-state in intermediate and strong magnetic fields. In this work, GRASP2K has been applied to provide highly accurate spectroscopic data for ions in the Ne-like sequence between Mg III and Kr XXVII. Valence, core-valence, and core-core correlation effects were accounted for through SD-MR expansions to increasing sets of active orbitals. In Mg III, Al IV, Si V, P VI, S VII, and Ar IX, for which experimental energies are known to high accuracy, the mean error in the calculated energies is only 0.011%. For ions with no available experimental energy levels the calculated values should be most valuable in various applications. The high accuracy of the calculated energies makes it possible, in some cases, to to point out experimental values that are in error. Babushkin (length) and Coulomb (velocity) forms of transition rates are computed and agree to within a few percent for the majority of the allowed transitions. Computed lifetimes for states belonging to the 2p33s and 2p53d configurations are in good agreement with values from beam-foil measurements as well as from accurate MCHF Breit-Pauli calculations.
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| 9. |
- de Blanche, Andreas, 1975, et al.
(författare)
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Dual Core Efficiency for Engineering Simulation Applications
- 2008
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Ingår i: International Conference on Parallel and Distributed Processing Techniques and Applications, Las Vegas, NV, USA, 14-17 July 2008. ; , s. 888-894
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Konferensbidrag (refereegranskat)abstract
- With the event of multi-core processors the parallel execution of simulation applications has resulted in new problems and possibilities in resource usage in high performance computing (HPC). In this paper we have investigated the impact of execution of engineering applications utilizing one and two cores in an Intel Core 2 Duo based Linux cluster. In engineering industry the number of licenses puts practical and economical constraints on the maximum number of processes. Consequently the issue of how to distribute a given number of processes over the compute nodes in a HPC resource becomes very important. When distributing the application over multiple nodes we found that having N processes on N computer nodes, only using one core on each node, is significantly faster than running N processes on N cores in N/2 computer nodes. Only in one case out of 32 it was beneficial to use both cores. The “one compute node – one simulation process” approach gave an average cost efficiency increase of 16.5%, and for several sub-cases it is actually costbeneficial to run on more nodes than fewer, which decreases the overall run time.
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