| 1. |
- Abdullaev, Fatkhulla, et al.
(författare)
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Faraday waves in quasi-one-dimensional superfluid Fermi-Bose mixtures
- 2013
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 87:2
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Tidskriftsartikel (refereegranskat)abstract
- The generation of Faraday waves in superfluid Fermi-Bose mixtures in elongated traps is investigated. The generation of waves is achieved by periodically changing a parameter of the system in time. Two types of modulations of parameters are considered: a variation of the fermion-boson scattering length and the boson-boson scattering length. We predict the properties of the generated Faraday patterns and study the parameter regions where they can be excited.
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| 2. |
- Abdullaev, Farakhulla, et al.
(författare)
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Zeno effect and switching of solitons in nonlinear couplers
- 2011
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 36:23, s. 4566-4568
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Tidskriftsartikel (refereegranskat)abstract
- The Zeno effect is investigated for soliton type pulses in a nonlinear directional coupler with dissipation. The effect consists in increase of the coupler transparency with increase of the dissipative losses in one of the arms. It is shown that localized dissipation can lead to switching of solitons between the arms. Power losses accompanying the switching can be fully compensated by using a combination of dissipative and active (in particular, parity-time-symmetric) segments.
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| 3. |
- Abrahamsson, Johan, 1977-, et al.
(författare)
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A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:9
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Tidskriftsartikel (refereegranskat)abstract
- Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.
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| 4. |
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| 5. |
- Corboz, Philippe, et al.
(författare)
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Phase-space methods for fermions
- 2013
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Ingår i: Quantum Gases. - London : Imperial College Press. - 1848168101 ; , s. 407-416
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We review phase-space simulation techniques for fermions, showing how a Gaussian operator basis leads to exact calculations of the evolution of a many-body quantum system in both real and imaginary time. We apply such techniques to the Hubbard model and to the problem of molecular dissociation of bosonic molecules into pairs of fermionic atoms.
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| 6. |
- Jarodzka, Halszka, et al.
(författare)
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There's more to multimedia than meets the eye : is seeing pictures believing?
- 2013
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Ingår i: 17th European Conference on Eye Movements. - : European Group for Eye Movement Research. ; , s. 211-211
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cognitive theories on learning with multimedia recommend combining different presentation formats (e.g., text and pictures) in teaching. However, recent research showed that pictures lurk people into trusting the accompanying text, instead of critically studying it. To investigate this we asked 36 physics students to solve mathematical problems, which consisted of a text describing the problem and a statement about the problem that had to be confirmed or rejected (control). The multimedia condition additionally received graphs displaying the same information as the text. Results revealed a bias to confirm statements that were accompanied by a graph irrespective of their correctness. Eye tracking showed that students looked less at the text and the problem statement when a graph was present. The more students looked at the statement and the more transitions they made between the statement and the graph, the better they performed. Verbal data showed that students heavily relied on the graphs: when the graph itself was correct, but the statement was not, students judged the statement as correct referring to the graph. Thus, the mere presence of pictures is not sufficient. Instead, they need to be carefully integrated with the problem statement to improve performance.
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| 7. |
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| 8. |
- Nyström, Marcus, et al.
(författare)
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How illustrations influence performance and eye movement behaviour when solving problems in vector calculus
- 2012
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Ingår i: Conference on Teaching and Learning 2012. - : Lund University.
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Konferensbidrag (refereegranskat)abstract
- Mathematical formulas in vector calculus often have direct visual representations, which in form of illustrations are used extensively during teaching and when assessing students’ levels of understanding. However, there is very little, if any, empirical evidence of how the illustrations are utilized during problem solving and whether they are beneficial to comprehension. In this paper we collect eye movements and performance scores (true or false answers) from students while solving eight problems in vector calculus; 20 students solve illustrated problems whereas 16 students solve the same problems, but without the illustrations. Results show no overall performance benefit for illustrated problems even though they are clearly visually attended. Surprisingly, we found a significant effect of whether the answer to the problem was true of false; students were more likely to answer that the question was true given an illustrated problem. We interpret this finding as if the illustrations persuade the students that the answer is true, irrespective of whether or not it in fact is. These results may question the tacit consensus among teachers of vector calculus that illustrations are generally beneficial for comprehending a problem.
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| 9. |
- Ögren, Magnus, 1977-, et al.
(författare)
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An exact lower energy bound for the infinite square well potential
- 2011
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Ingår i: European journal of physics. - : Institute of Physics (IOP). - 0143-0807 .- 1361-6404. ; 32:2, s. L3-L6
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Tidskriftsartikel (refereegranskat)abstract
- We give a lower bound for the energy of a quantum particle in the infinite square well. We show that the bound is exact and identify the well-known element that fulfils the equality. Our approach is not directly dependent on the Schrödinger equation and illustrates an example where the wavefunction is obtained directly by energy minimization. The derivation presented can serve as an example of a variational method in an undergraduate level university course in quantum mechanics.
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| 10. |
- Ögren, Magnus, 1977-, et al.
(författare)
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Blick för bättre läromedel?
- 2012
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Ingår i: Manus. - Stockholm : Läromedelsförfattarnas förening. - 2000-4028. ; :2, s. 6-6
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Forskningsöversikt (populärvet., debatt m.m.)
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