| 471. |
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| 472. |
- Liu, Zhendong, et al.
(författare)
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Implications of the operation of multiple pantographs on the soft catenary systems in Sweden
- 2015
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : Sage Publications. - 0954-4097 .- 2041-3017. ; 53:3, s. 341-346
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Tidskriftsartikel (refereegranskat)abstract
- Trains operating with several pantographs are used in Sweden and other countries. The more complex operational conditions, however, cause additional difficulties, i.e. low quality of current collection, increased mechanical wear and electromagnetic interference, due to the poor dynamic behaviour of the system. In order to address these problems, a three-dimensional model for the computational analysis of the interaction between catenary and pantograph is presented and validated in this paper, and the dynamic behaviour of the multi-pantograph system, based on Swedish soft pantograph/catenary systems, is analysed. Parametric studies are performed to investigate cases with different distances between pantographs and with up to three pantographs in use. The relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, is studied. The results show that an appropriate distance between pantographs and a given type of catenary allow operation on the existing infrastructure with up to three pantographs while maintaining an acceptable dynamic performance at the desired speed.
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| 473. |
- Liu, Zhendong, et al.
(författare)
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Possible speed increase on soft catenary system with help of auxiliary pantograph
- 2016
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Ingår i: The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015. - : CRC Press. ; , s. 927-936
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Konferensbidrag (refereegranskat)abstract
- Stiffness variations and wave propagation in the catenary system cause high dynamic variations in the contact force between pantograph and catenary at high operating speeds. In order to increase the operational speed on an existing catenary system, especially on soft catenary systems, technical upgrading is usually required to keep the current collection quality within an acceptable range. Therefore, it is desirable to explore a more practical and costsaving method to achieve higher operational speed. With the help of a 3D pantograph-catenary finite element (FE) model, a parametric study on two-pantograph operation at short spacing distances is carried out. Results show that although the leading pantograph suffers from deterioration of dynamic performance, the trailing pantograph achieves a better dynamic behaviour by using a proper spacing distance between pantographs. To avoid the additional wear caused by poor dynamic performance on the leading pantograph, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current. In this way, the operational speed of the existing system can be increased while still sustaining a good dynamic performance without large modifications on the existing catenary system.
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| 474. |
- Lundblad, Thomas, et al.
(författare)
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Dialogic manifestation of an augmented reality simulation
- 2013
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Ingår i: EDUCARE. - Malmö : Fakulteten för lärande och samhälle, Malmö högskola. - 1653-1868 .- 2004-5190. ; 2, s. 45-63
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we focus on the use of a combination of socio-scientific issues (SSI) and simulations. We have developed an augmented reality (AR) simulation called Transformer. The SSI narrative in Transformer concerns an electric transformer station situated in an area close to a planned new campus. Students’ task is the issue if it is advisable to build a campus area. The simulation is organized as a role-play. The students take part in groups, playing one of five different roles.The aim of this study is to explore students’ ways of using knowledge in relation to the AR simulation. We investigate how students integrate science and other knowledge in the debate constituting the final part of the role-play. The study is a part of a research process, guiding the researchers to further develop Transformer.The study showed that students justified their positions using scientific evidence and information collected through their own efforts outdoors in the real and actual environment where the AR simulation was situated. Students kept the controversy that existed between the different roles alive throughout the debate and stayed focused on the issue in question. We argue that this is due to the situated context achieved through the simulation.
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| 475. |
- Lundblad, Thomas, et al.
(författare)
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Simulating real life problems in secondary science class : a socio scientific issue carried through by an augmented reality simulation
- 2012
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Ingår i: HUMANIT: Tidskrift för studier av ur ett humanvetenskapligt perspektiv. - Borås : ITH - Centrum för studier av IT ur ett humanvetenskapligt perspektiv och Center for Collaborative Innovation vid Högskolan i Borås. ; 12:2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- With the purpose of developing new methods in science education, the authors combine a socio-scientific issue and game-based technologies from augmented reality games into an intervention activity called Transformer. The authors design the intervention, collect and analyze data, and present results using the three elements from the theory of transformational play (Barab, Gresalfi & Ingram-Goble 2010) namely: engaging and stimulating roles, scientifically relevant content and complex and societally significant context. In Transformer, 20 upper-secondary students engage in a role-play concerning the project of building a school campus area close to a transformer station. The students explore the actual area using simulation-based mobile technologies to collect information through interviews with virtual characters, virtual measurements, and own observations. Collected information is synthesized into arguments concerning the appropriateness of building the campus area. The Transformer activity is based on SSI (socio-scientific issue), a pedagogical model aiming at developing students’ competences to make well-informed decisions through engaging them in complex societal issues.Data from the intervention are collected with multiple methods using questionnaires and interviews. The analysis illustrates expressions of immersive role play and active and engaged students who enjoy the opportunity of working in groups with a challenging task outside the class room. For some roles, however, there is room for improvement in the outdoor part of the intervention. We argue that this design perspective makes it feasible for a teacher or team of teachers to stage a multi-disciplinary engaging intervention that is constructively aligned with the students’ and teachers’ own practices and that addresses curricular goals.
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| 476. |
- Lundblad, Thomas
(författare)
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Simulerad verklighet i gymnasieskolans fysik : En designstudie om en augmented reality simulering med socio-naturvetenskapligt innehåll
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis takes its standpoint in the declining interest for science studies in Sweden and abroad. According to Dillon and Oshorne (2009), science education is not conceived as an education for the lllajority of students. It is targeted at supplying the society with future scientists, ignoring the need for a science education for all students. One way to include more students in science activities can be to let them investigate the world outside school and make connections between these investigations and their own personal life (Aikenhead, 2007). Socio-scientific issues (SSJ) arc brought forward by many ,,'Searchers as a pedagogical model to engage students in developing scientific knowledge while dealing with prohlelTIs situated in their society.The thesis describe the design and use of an Augmented Reality (AR) simulation (Klopfer, 200S) called Transformer where students engage in a role play concerning a socio-scientific dilemma situated in their local environment. Students use smartphones equipped with the AR-simulation to collect information and take measurements in their local environment. The different roles use their collected information in a concluding debate where they argue for their standpoint in the dilemma.The design and use of Transformer was investigated in two studies. The first study describes the design of Transformer and investigates in how the silTIulation influenced the students. In the second study students actions in a debate was investigated concerning which sources if information students use, how the socio-scientific nature of the issue was expressed, and how the roles influenced the use of information. Results from the studies give evidence of engaged students that experienced the dilemma as actual and relevant.Their argumentation in the debate was focused around the dilemma and meets the criteria for socioscicntific reasoning stated by Sadlcr, ]larab and Scott (2007). The results also points at parts of the design vvhere there is room for improvements. These experiences will infonn the next step in a design based research cycle.The thesis shows that a combination of AR and SS! is a feasible way for practitioners to situate pedagogicaUy relevant content in an enVlrOlllnent outside school.
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| 477. |
- Ly, John, et al.
(författare)
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Semi-automatic analysis of standard uptake values in serial PET/CT studies in patients with lung cancer and lymphoma
- 2012
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Ingår i: BMC Medical Imaging. - : Springer Science and Business Media LLC. - 1471-2342. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Background: Changes in maximum standardised uptake values (SUVmax) between serial PET/CT studies are used to determine disease progression or regression in oncologic patients. To measure these changes manually can be time consuming in a clinical routine. A semi-automatic method for calculation of SUVmaxin serial PET/CT studies was developed and compared to a conventional manual method. The semi-automatic method first aligns the serial PET/CT studies based on the CT images. Thereafter, the reader selects an abnormal lesion in one of the PET studies. After this manual step, the program automatically detects the corresponding lesion in the other PET study, segments the two lesions and calculates the SUVmaxin both studies as well as the difference between the SUVmaxvalues. The results of the semi-automatic analysis were compared to that of a manual SUVmaxanalysis using a Philips PET/CT workstation. Three readers did the SUVmaxreadings in both methods. Sixteen patients with lung cancer or lymphoma who had undergone two PET/CT studies were included. There were a total of 26 lesions.Results: Linear regression analysis of changes in SUVmaxshow that intercepts and slopes are close to the line of identity for all readers (reader 1: intercept = 1.02, R2= 0.96; reader 2: intercept = 0.97, R2= 0.98; reader 3: intercept = 0.99, R2= 0.98). Manual and semi-automatic method agreed in all cases whether SUVmaxhad increased or decreased between the serial studies. The average time to measure SUVmaxchanges in two serial PET/CT examinations was four to five times longer for the manual method compared to the semi-automatic method for all readers (reader 1: 53.7 vs. 10.5 s; reader 2: 27.3 vs. 6.9 s; reader 3: 47.5 vs. 9.5 s; p < 0.001 for all).Conclusions: Good agreement was shown in assessment of SUVmaxchanges between manual and semi-automatic method. The semi-automatic analysis was four to five times faster to perform than the manual analysis. These findings show the feasibility of using semi-automatic methods for calculation of SUVmaxin clinical routine and encourage further development of programs using this type of methods. © 2012 Ly et al; licensee BioMed Central Ltd.
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| 478. |
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| 479. |
- Ma, Mingxuan, et al.
(författare)
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Natural Orbitals and Targeted Non-Orthogonal Orbital Sets for Atomic Hyperfine Structure Multiconfiguration Calculations
- 2024
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Ingår i: Atoms. - : MDPI. - 2218-2004. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Hyperfine structure constants have many applications, but are often hard to calculate accurately due to large and canceling contributions from different terms of the hyperfine interaction operator, and also from different closed and spherically symmetric core subshells that break up due to electron correlation effects. In multiconfiguration calculations, the wave functions are expanded in terms of configuration state functions (CSFs) built from sets of one-electron orbitals. The orbital sets are typically enlarged within the layer-by-layer approach. The calculations are energy-driven, and orbitals in each new layer of correlation orbitals are spatially localized in regions where the weighted total energy decreases the most, overlapping and breaking up different closed core subshells in an irregular pattern. As a result, hyperfine structure constants, computed as expectation values of the hyperfine operators, often show irregular or oscillating convergence patterns. Large orbital sets, and associated large CSF expansions, are needed to obtain converged values of the hyperfine structure constants. We analyze the situation for the states of the {2s22p3,2s22p23p,2s22p24p} odd and {2s22p23s,2s2p4,2s22p24s,2s22p23d} even configurations in N I, and show that the convergence with respect to the increasing sets of orbitals is radically improved by introducing separately optimized orbital sets targeted for describing the spin- and orbital-polarization effects of the 1s and 2s core subshells that are merged with, and orthogonalized against, the ordinary energy-optimized orbitals. In the layer-by-layer approach, the spectroscopic orbitals are kept frozen from the initial calculation and are not allowed to relax in response to the introduced layers of correlation orbitals. To compensate for this lack of variational freedom, the orbitals are transformed to natural orbitals prior to the final calculation based on single and double substitutions from an increased multireference set. The use of natural orbitals has an important impact on the states of the 2s22p23s configuration, bringing the corresponding hyperfine interaction constants in closer agreement with experiment. Relying on recent progress in methodology, the multiconfiguration calculations are based on configuration state function generators, cutting down the time for spin-angular integration by factors of up to 50, compared to ordinary calculations.
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| 480. |
- Magnusson, Marie V, et al.
(författare)
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Pentoxifylline and vitamin E treatment for prevention of radiation-induced side-effects in women with breast cancer : a phase two, double-blind, placebo-controlled randomised clinical trial (Ptx-5)
- 2009
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Ingår i: European Journal of Cancer. - Oxford : Elsevier. - 0959-8049 .- 1879-0852. ; 69:24, s. 740-740
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Tidskriftsartikel (refereegranskat)abstract
- Background: A previous study has shown that pentoxifylline in combination with vitamin E can reverse radiation-induced fibrosis. The aim of the present study is to investigate if the same drugs could prevent radiation-induced side-effects in women with breast cancer.Patients and methods: A randomised, placebo-controlled, double-blind, parallel group trial was performed. Women with breast cancer were treated for 12 months with 400 mg pentoxifylline t.i.d. or placebo, in combination with 100 mg vitamin E t.i.d,, starting 1-3 months after the completion of radiotherapy. The primary end-point was passive abduction of the shoulder, and the secondary end-point was difference in arm volumes. The trial is registered on the ISRCTN.org website, number ISRCTN39143623.Results: 83 patients were included in the study; 42 in the pentoxifylline + vitamin E group and 41 in the placebo + vitamin E group. Both treatments were generally well tolerated. Seven patients were withdrawn from the treatment due to disease progression; four in the pentoxifylline group and three in the placebo group. At inclusion, patients had impaired passive abduction of the shoulder. During treatment, both the groups improved significantly. Median improvement from baseline was 3.7 degrees (p = 0.0035) on pentoxifylline and was 9.4 degrees (p = 0.0041) in the placebo group, but no difference between the groups was detected (p = 0.20). Arm volumes increased over time in the placebo group (1.04%), but not on pentoxifylline (0.50%), and differed significantly between the groups (p = 0.0172).Conclusions: The combination of pentoxifylline and vitamin E was safe and may be used for the prevention of some radiation-induced side-effects. (C) 2009 Elsevier Ltd. All rights reserved.
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