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- Engström, Klas, 1973
(författare)
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Interactions and Interference in Mesoscopic Systems: Josephson Current through Quantum Dots and Josephson Junction Arrays
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of the thesis is on the interplay between interactions and interference effects in mesoscopic systems. More specifically, the two main projects included deal with Coulomb interactions and Josephson effect in two superconductor-normal metal systems: (i) a Josephson junction array and (ii) a superconductor-normal metal-superconductor (SNS) system in which the normal part is a quantum dot. Theoretical treatments of Josephson junction arrays (JJA) are numerous and cover a range of regimes. Our analysis is based on the simplest model of a one-dimensional JJA, which is known to exhibit a superconductor-insulator transition at zero temperature as the Josephson coupling is varied, in the limit of an infinitely long array. We consider the experimentally more realistic case in which the temperature, as well as the array length, is finite. The key approach is the well-known mapping onto a classical two-dimensional XY-model, which we proceed to analyze with both analytic and numerical methods. SNS systems also exhibit Josephson effects. In short junctions, the supercurrent is supported exclusively by discrete so-called Andreev states, which are localized near the junction due to the presence of the superconducting gap in the leads. In a density functional approach, we investigate the effects of Coulomb interactions on the transport of charge through the normal part of the system, which we take to be a quantum dot-like structure. States confined by the dot potential interact with charge associated with the Andreev state, hence producing an extra contribution to the total energy of the system, which is manifested as a strongly modified supercurrent--phase relationship. Our first paper on this system treats a quasi-one-dimensional case. The second paper in the series is a generalization to two dimensions, with somewhat greater emphasis on computational issues. In the final paper we take into account the influence of states with continuous energies outside the superconducting gap.
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- Mark, Andreas, 1980, et al.
(författare)
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Simulation of Electrostatic Rotary Bell Spray Painting in Automotive PAint Shops
- 2013
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Ingår i: Atomization and Sprays. - 1044-5110 .- 1936-2684. ; 23:1, s. 25-45
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Tidskriftsartikel (refereegranskat)abstract
- A new framework for simulation of electrostatic spray painting is proposed based on novel algorithms for coupled simulations of air flow, electromagnetic fields, and paint droplets. Particularly important for the computational efficiency is the Navier-Stokes solver. The incompressible solver is based on a finite volume discretization on a dynamic Cartesian octree grid and unique immersed boundary methods are used to model the presence of objects in the fluid. This enables modeling of moving objects at virtually no additional computational cost and greatly simplifies preprocessing by avoiding the cumbersome generation of a body-conforming mesh. To validate the simulation framework an extensive measurement campaign has been performed. Several test plates and car fenders were painted with different process conditions and robot paths. The same cases were then simulated and overall the agreement between simulations and experiments are remarkably good. The very efficient implementation gives a major improvement of computational speed compared to other approaches and makes it possible to simulate spray painting of a full car in just a few hours on a standard computer.
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- Mark, Andreas, 1980, et al.
(författare)
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Simulation of Electrostatic Rotary Bell Spray Painting in Automotive Paint Shops
- 2012
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Ingår i: Proceedings of 12th International Conference on Liquid Atomization and Spray Systems.
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Konferensbidrag (refereegranskat)abstract
- A new framework for simulation of electrostatic spray painting is proposed based on novel algorithms for coupled simulations of air flow, electromagnetic fields and paint droplets. Particularly important for the computational efficiency is the Navier-Stokes solver. The incompressible solver is based on a finite volume discretization on a dynamic Cartesian octree grid and unique immersed boundary methods are used to model the presence of objects in the fluid. This enables modeling of moving objects at virtually no additional computational cost, and greatly simplifies preprocessing by avoiding the cumbersome generation of a body conforming mesh. To validate the simulation framework an extensive measurement campaign has been performed. Several test plates and car fenders were painted with different process conditions and robot paths. The same cases were then simulated and overall the agreement between simulations and experiments are remarkably good. The very efficient implementation gives a major improvement of computational speed compared to other approaches and makes it possible to simulate spray painting of a full car in just a few hours on a standard computer.
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- Mårdberg, Peter, 1980, et al.
(författare)
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A novel tool for optimization and verification of layout and human logistics in digital factories
- 2018
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 72, s. 545-550
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Konferensbidrag (refereegranskat)abstract
- We introduce a novel digital factory layout tool that optimizes both the layout of machines and the corresponding ergonomic logistics considering space constraints. A model is constructed by tangible properties on machines and environment, regions on the floor and by ranking their mutual relations. An optimized layout is then computed based on the model, the relations and an ergonomic score for the human work tasks, which are automatically computed by digital manikins. The result is an optimized layout, visualized in 3D, with improved logistic routes. The layout tool has been implemented and successfully tested on a relevant industrial case.
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