| 5561. |
- Kruusmaa, Maarja, et al.
(författare)
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A low-risk approach to mobile robot path planning
- 1998
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Ingår i: Lecture Notes in Computer Science. - Heidelberg : Springer Berlin/Heidelberg. - 0302-9743 .- 1611-3349. ; 1416, s. 132-141
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a self-organizing approach for mobile robot path planning problems in dynamic environments by using case-based reasoning together with a more conventional method of grid-map based path planning. The map-based path planner is used to suggest new innovative solutions for a particular path planning problem. The case-base is used to store the paths and evaluate their traversability. While planning the route those paths are preferred which, according to former experience, are least risky. As the environment changes, the exploration as well as the evaluation of the paths will allow the system to self-organize by forming a set of low-risk paths that are safest to follow. The experiments in a simulated environment show that the robot is able to adapt in a dynamic environment and learns to use the least risky paths. © Springer-Verlag Berlin Heidelberg 1998.
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| 5562. |
- Kruusmaa, Maarja, et al.
(författare)
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Covering the path space : a casebase analysis for mobile robot path planning
- 2003
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Ingår i: Knowledge-Based Systems. - Guildford, Surrey : Elsevier. - 0950-7051 .- 1872-7409. ; 16:5-6, s. 235-242
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a theoretical analysis of a casebase used for mobile robot path planning in dynamic environments. Unlike other case-based path planning approaches, we use a grid map to represent the environment that permits the robot to operate in unstructured environments. The objective of the mobile robot is to learn to choose paths that are less risky to follow. Our experiments with real robots have shown the efficiency of our concept. In this paper, we replace a heuristic path planning algorithm of the mobile robot with a seed casebase and prove the upper and lower bounds for the cardinality of the casebase. The proofs indicate that it is realistic to seed the casebase with some solutions to a path-finding problem so that no possible solution differs too much from some path in the casebase. This guarantees that the robot would theoretically find all paths from start to goal. The proof of the upper bound of the casebase cardinality shows that the casebase would in a long run grow too large and all possible solutions cannot be stored. In order to keep only the most efficient solutions the casebase has to be revised at run-time or some other measure of path difference has to be considered.
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| 5563. |
- Kruusmaa, Maarja
(författare)
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Global level path planning for mobile robots in dynamic environments
- 2003
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Ingår i: Journal of Intelligent and Robotic Systems. - Dordrecht : Kluwer Academic Publishers. - 0921-0296 .- 1573-0409. ; 38:1, s. 55-83
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a self- adapting approach to global level path planning in dynamic environments. The aim of this work is to minimize risk and delays in possible applications of mobile robots ( e. g., in industrial processes). We introduce a hybrid system that uses case-based reasoning as well as grid-based maps for decision-making. Maps are used to suggest several alternative paths between specific start and goal point. The casebase stores these solutions and remembers their characteristics. Environment representation and casebase design are discussed. To solve the problem of exploration vs. exploitation, a decision-making strategy is proposed that is based on the irreversibility of decisions. Forgetting strategies are discussed and evaluated in the context of case-based maintenance. The adaptability of the system is evaluated in a domain based on real sensor data with simulated occupancy probabilities. Forgetting strategies and decision-making strategies are evaluated in simulated environments. Experiments show that a robot is able to adapt in dynamic environments and can learn to use paths that are less risky to follow.
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| 5564. |
- Kruusmaa, Maarja
(författare)
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Global Navigation in Dynamic Environments Using Case-Based Reasoning
- 2004
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Ingår i: Autonomous Robots. - : Springer Netherlands. - 0929-5593 .- 1573-7527. ; 14:1, s. 71-91
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a global navigation strategy for autonomous mobile robots in large-scale uncertain environments. The aim of this approach is to minimize collision risk and time delays by adapting to the changes in a dynamic environment. The issue of obstacle avoidance is addressed on the global level. It focuses on a navigation strategy that prevents the robot from facing the situations where it has to avoid obstacles. To model the partially known environment, a grid-based map is used. A modified wave-transform algorithm is described that finds several alternative paths from the start to the goal. Case-based reasoning is used to learn from past experiences and to adapt to the changes in the environment. Learning and adaptation by means of case-based reasoning permits the robot to choose routes that are less risky to follow and lead faster to the goal. The experimental results demonstrate that using case-based reasoning considerably increases the performance of the robot in a difficult uncertain environment. The robot learns to take actions that are more predictable, minimize collision risk and traversal time as well as traveled distances.
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| 5565. |
- Ku, Bih-Yuan, et al.
(författare)
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Report on Rail Conference and Wireless Communications : [VTS News]
- 2011
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Ingår i: IEEE Vehicular Technology Magazine. - New York : IEEE Press. - 1556-6072 .- 1556-6080. ; 6:3, s. 111-117
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The 2011 Joint Rail Conference (JRC) was held in Pueblo, Colorado, on March 16-18, 2011, immediately after the Association of American Railroads Research Review. The conference started with a technical tour of TTCi. The highlights of the technical tour were two on-site presentations on a full-scale train impact test and the field test of the positive train control (PTC) system. The tour attendees were given the opportunity to take a close look at the energy-absorption devices and sensors installed at various locations of the test car. The PTC presentation was held at the communications and train control (C&TC) test bed at the TTCi test track, which is the only CT&C test bed in North America. The 2012 Joint Rail Conference (JRC) will be held in Philadelphia in April 2012, and the IEEE Vehicular Technology Society (VTS) Land Transportation Division (LTD) will take the lead in the planning of the major technical forum onrail engineering in North America.
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| 5566. |
- Kudomi, Nobuyuki, et al.
(författare)
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Myocardial Blood Flow and Metabolic Rate of Oxygen Measurement in the Right and Left Ventricles at Rest and During Exercise Using 15O-Labeled Compounds and PET
- 2019
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Ingår i: Frontiers in Physiology. - Lausanne : Frontiers Media S.A.. - 1664-042X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Simultaneous measurement of right (RV) and left ventricle (LV) myocardial blood flow (MBF), oxygen extraction fraction (OEF), and oxygen consumption (MVO2) non-invasively in humans would provide new possibilities to understand cardiac physiology and different patho-physiological states. Methods: We developed and tested an optimized novel method to measure MBF, OEF, and MVO2 simultaneously both in the RV and LV free wall (FW) using positron emission tomography in healthy young men at rest and during supine bicycle exercise. Results: Resting MBF was not significantly different between the three myocardial regions. Exercise increased MBF in the LVFW and septum, but MBF was lower in the RV compared to septum and LVFW during exercise. Resting OEF was similar between the three different myocardial regions (similar to 70%) and increased in response to exercise similarly in all regions. MVO2 increased approximately two to three times from rest to exercise in all myocardial regions, but was significantly lower in the RV during exercise as compared to septum LVFW. Conclusion: MBF, OEF, and MVO2 can be assessed simultaneously in the RV and LV myocardia at rest and during exercise. Although there are no major differences in the MBF and OEF between LV and RV myocardial regions in the resting myocardium, MVO2 per gram of myocardium appears to be lower the RV in the exercising healthy human heart due to lower mean blood flow. The presented method may provide valuable insights for the assessment of MBF, OEF and MVO2 in hearts in different pathophysiological states.
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| 5567. |
- Kuiper, Pieter, 1960-, et al.
(författare)
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Polarization-dependent nickel 2p x-ray-absorption spectra of La2NiO4+δ
- 1998
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Ingår i: Physical Review B Condensed Matter. - College Park, MD : American Physical Society. - 0163-1829 .- 1095-3795. ; 57:3, s. 1552-1557
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Tidskriftsartikel (refereegranskat)abstract
- We present polarization dependent x-ray-absorption spectra at nickel L edges of well-characterized La2NiO4+δ single crystals. In the stoichiometric compound the splitting between the x2−y2 and the 3z2−r2 orbitals is 0.7 eV, according to a fit of the 2p53d9 multiplet to the spectra. This value is in agreement with an assignment of dd excitations of the optical spectrum. The Ni L edges of the doped compound are consistent with the isotropic prepeak observed at the oxygen 1s edge. Theory does not predict holes on the apex oxygens, but we argue that doping causes a polaronic deformation which reduces the tetragonal distortion of the NiO6 octahedra, and delocalizes the hole over all six ligands.
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| 5568. |
- Kuiper, Pieter, 1960-, et al.
(författare)
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Resonant X-Ray raman spectra of Cu dd excitations in Sr2CuO2Cl2
- 1998
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Ingår i: Physical Review Letters. - College Park, MD : American Physical Society. - 0031-9007 .- 1079-7114. ; 80:23, s. 5204-5207
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Tidskriftsartikel (refereegranskat)abstract
- We present resonant x-ray Raman scattering results on Sr2CuO2Cl2, a model compound for high- Tc superconductors. We demonstrate that the dd excitations can be observed and show that the polarization dependence can be used to identify the dd excitations. We find the transition from the dx2−y2 ground state to the dxy excited state at 1.35 eV and to the degenerate dxz and dyz excited states at 1.7 eV. From analysis of the polarization dependence we conclude that the d3z2−r2 orbital energy is at 1.5 eV and not in the midinfrared (0.5 eV) as recently suggested. We use recent theoretical arguments to show that the d3z2−r2 excitation is accompanied by a local spin flip resulting in a shift upwards of 0.2 eV due to the exchange interaction with the neighboring spins. ©1998 American Physical Society.
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| 5569. |
- Kullberg, Angelika, 1969, et al.
(författare)
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Teaching one thing at a time or several things together? : Teachers changing their way of handling the object of learning by being engaged in a theory-based professional learning community in mathematics and science
- 2016
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Ingår i: Teachers and Teaching. - Abingdon : Routledge. - 1354-0602 .- 1470-1278. ; 22:6
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Tidskriftsartikel (refereegranskat)abstract
- Twelve lower secondary schoolteachers in mathematics and science were asked to teach a topic of their choice during a lesson that was video-recorded. We were able to analyse 10 of the cases and we found that all of them were similar in one respect: concepts and principles were introduced one at a time, each one followed by examples of the concept or principle in question, apparently to highlight its essential meaning. All the teachers participated in three modified lesson studies with three cycles in four different groups during three semesters. The modified lesson studies were built on a theoretical idea supported by a large number of recent studies. The theory states that new meanings (of concepts and principles, for instance) are learned through engaging with instances of contrasting concepts and principles. The core idea is that new meanings derive from differences, not from sameness. After the three modified lesson studies, the teachers were asked to once again teach the same topic as in the recorded lessons before the lesson studies. The new lessons were also recorded and the analysis showed that there was one thing in common in all cases: all of the 10 teachers dealt with the relevant concepts and principles in relation to each other (i.e. simultaneously) and not one at a time. By thus bringing out the differences between them, their meaning was made possible to grasp for the students. The study lends support to the conjecture that the modified lesson study is a powerful tool for enabling teachers to structure the content of their teaching in accordance with a principle that is more powerful in making learning possible, even if this contradicts their taken-for-granted practice.
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| 5570. |
- Kullenberg, Tina, 1968-
(författare)
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Om bildning och ombildning i en föränderlig värld
- 2015. - 1
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Ingår i: Lärande ur ett livsvärldsperspektiv. - Malmö : Gleerups Utbildning AB. - 9789140687111 ; , s. 153-175
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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