| 11. |
- Bondestam Malmberg, John, 1988, et al.
(författare)
-
Iterative regularization and adaptivity for an electromagnetic coefficient inverse problem
- 2017
-
Ingår i: AIP Conference Proceedings. 1863, nr. 370002. - : Author(s). - 0094-243X .- 1551-7616. - 9780735415386
-
Konferensbidrag (refereegranskat)abstract
- We study how the choice of the regularization parameter affects the quality of the reconstruction of the dielectric permittivity for an inhomogeneous medium, with data consisting of boundary observations of the electric field. Our method is based on the minimization of a Tikhonov functional and uses a finite element method for computations of the electric field. We conclude that the choice of the regularization parameter does not affect the quality of the reconstruction significantly in the studied cases, and can even be removed with results not significantly different from those with regularization.
|
|
| 12. |
- Bonora, Nicola, et al.
(författare)
-
Validating material modelling for OFHC copper using Dynamic Tensile Extrusion (DTE) test at different velocity impact
- 2017
-
Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. ; 1793, s. 100019-
-
Konferensbidrag (refereegranskat)abstract
- In the Dynamic Tensile Extrusion (DTE) test, the material is subjected to very large strain, high strain rate and elevated temperature. Numerical simulation, validated comparing with measurements obtained on soft-recovered extruded fragments, can be used to probe material response under such extreme conditions and to assess constitutive models. In this work, the results of a parametric investigation on the simulation of DTE test of annealed OFHC copper -at impact velocity ranging from 350 up to 420 m/s -using the modified Rusinek-Klepaczko model, are presented. Simulation of microstructure evolution was performed using the visco-plastic self consistent model (VPSC), providing, as input, the velocity gradient history obtained with FEM at selected locations along the axis of the fragment trapped in the extrusion die. Finally, results are compared with EBSD analysis.
|
|
| 13. |
- Bulanov, S. S., et al.
(författare)
-
Depletion of intense fields
- 2017
-
Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. - 9780735414808 ; 1812:1, s. Article no. UNSP 100006 -
-
Konferensbidrag (refereegranskat)abstract
- The problem of backreaction of quantum processes on the properties of the background field still remains on the list of outstanding questions of high intensity particle physics. Usually, photon emission by an electron or positron, photon decay into electron-positron pairs in strong electromagnetic fields, or electron-positron pair production by such fields are described in the framework of the external field approximation. It is assumed that the external field has infinite energy and is not affected by these processes. However, the above-mentioned processes have a multi-photon nature, i.e., they occur with the absorption of a significant number of field photons. As a result, the interaction of an intense electromagnetic field with either a highly charged electron bunch or a fast growing population of electrons, positrons, and gamma photons (as in the case of an electromagnetic cascade) may lead to a depletion of the field energy, thus making the external field approximation invalid. Taking the multi-photon Compton process as an example, we estimate the threshold of depletion and find it to become significant at field strengths (a0∼103) and electron bunch charge of about tens of nC. © 2017 Author(s).
|
|
| 14. |
- Burtseva, Evgeniya, 1988-, et al.
(författare)
-
Potential type operators in PDEs and their applications
- 2017
-
Ingår i: AIP Conference Proceedings. - : AIP Publishing. - 0094-243X .- 1551-7616. ; 1798
-
Tidskriftsartikel (refereegranskat)abstract
- We prove the boundedness of Potential operator in weighted generalized Morrey space in terms of Matuszewska-Orlicz indices of weights and apply this result to the Hemholtz equation in r3 with a free term in such a space. We also give a short overview of some typical situations when Potential type operators arise when solving PDEs.
|
|
| 15. |
- Christoph, Richter, et al.
(författare)
-
Identification of optimum molten salts for use as heat transfer fluids in parabolic trough CSP plants. A techno-economic comparative optimization
- 2017
-
Ingår i: AIP Conference Proceedings. - : American Institute of Physics (AIP). - 0094-243X .- 1551-7616. - 9780735417571
-
Tidskriftsartikel (refereegranskat)abstract
- Parabolic trough power plants using thermal oil as heat transfer fluid are the most mature concentrating solar power technology and state of the art. To further increase their efficiency and lower costs, molten salts can be used as heat transfer fluid. This results in higher operating temperature differences for improved cycle efficiencies and enables direct thermal energy storage at lower costs due to omission of the oil-to-salt heat exchanger and the need for smaller storage sizes. As a variety of salts are available to choose from, this study uses a multi-objective optimization to identify the most suitable heat transfer fluid for three locations in South Africa, Spain and Chile. The lowest values for the levelized costs of electricity (LCOE) can be found in Chile using Solar Salt as heat transfer fluid (75.0 $/MWhe). Generally, Solar Salt offers the lowest LCOE values followed by thermal oil and Hitec. The results also suggest that the choice of the heat transfer fluid is dependent on the direct normal irradiance (DNI) at each location. Thermal oil is competitive with Solar Salt in small systems at locations with low DNI values, whereas Hitec can be cheaper than thermal oil in large systems at locations with high DNI. Furthermore, it is also investigated at which freeze alert temperature set point the activation of the freeze protection system is optimal. The results indicate that this temperature should be chosen close to the solar field inlet temperature for small systems, while it can be lowered significantly for large systems to reduce electricity consumption from the freeze protection system.
|
|
| 16. |
- Cohen, David, 1977-
(författare)
-
Numerical discretisations of stochastic wave equations
- 2018
-
Ingår i: International conference of numerical analysis and applied mathematics (ICNAAM 2017). - : American Institute of Physics (AIP). - 9780735416901 ; 1978:1, s. 1-5
-
Konferensbidrag (refereegranskat)abstract
- This extended abstract starts with a brief introduction to stochastic partial differential equations with a particular focus on stochastic wave equations. Various numerical experiments for this stochastic partial differential equation are presented. Finally, we point out results from the literature on the numerical analysis of stochastic wave equations.
|
|
| 17. |
|
|
| 18. |
- Forsgren, Christer, 1955
(författare)
-
Recycling experiences from Scandinavia, focus on ash from waste incineration and plastics
- 2019
-
Ingår i: AIP Conference Proceedings. - : AIP Publishing. - 1551-7616 .- 0094-243X. ; 2124
-
Konferensbidrag (refereegranskat)abstract
- Ash from waste incineration generated when cleaning flue gases contain about 40 w% of water soluble salts, most containing heavy metals like Pb. A method to use the acid scrubber liquid from the air pollution control system to neutralize the alkaline ash has been developed and a full scale demonstration plant is presently being built in Copenhagen, Denmark. The project has partly been financed by EU LIFE. The plant includes steps for metal recycling, mainly Cu and Zn, and removal of chlorides from the washed solid fraction that could be used for construction purposes. Stena Recycling International finance a Professorship in Industrial Material Recycling at Chalmers Technical University in Gothenburg Sweden since more than 10 years back, where most of the research in this area takes place. Not all thermoplastic waste fractions are clean enough to be mechanically recycled. Feed stock recycling, substitutional fuel and energy recovery are possible alternatives that have been evaluated and tested in Europe. Halogens are in general the biggest challenge since they produce corrosive acids when decomposing due to increased temperature. In a more Circular Economy materials are material recycled more often than today. No sorting equipment is 100 % correct why low concentrations of contaminants will be able to detect in many recycled materials. Bio test is one efficient method to prove that even though contaminants can be detected the bio availability could be very low. Gene response monitoring has successfully been applied.
|
|
| 19. |
- Gaska, Karolina, 1986, et al.
(författare)
-
Evidence of percolated network at the linear - Nonlinear transition in oscillatory shear
- 2019
-
Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. ; 2107
-
Konferensbidrag (refereegranskat)abstract
- In this publication we review evidence for the detection of a percolated network in polymer nanocomposites at the linear - nonlinear transition in oscillatory shear tests. Two types of nanocomposites based on branched polymers as matrix are compared: a low density polyethylene (LDPE) and graphite nanoplatelets (GnP) as filler and a poly(ethylene- butyl acrylate) (EBA) containing graphite nanoplatelets and carbon black (CB). Oscillatory shear tests were analyzed in the framework of Fourier-transform rheology and Tschebyshev polynomial decomposition. For both nanocomposites, in the vicinity of the electrical percolation threshold, i.e. the formation of a continuous filler network, a distinct region is evidence at the transition linear - nonlinear transition in the strain dependent third relative higher harmonics of the shear stress Fourier spectra. The region can be characterized by different strain amplitude dependence that could be related to the specific filler morphologies, however, further investigations are required to assess the factors that influence the linear - nonlinear transition region in polymer nanocomposites.
|
|
| 20. |
- Gaska, Karolina, 1986, et al.
(författare)
-
Highly structured graphene polyethylene nanocomposites
- 2019
-
Ingår i: AIP Conference Proceedings. - : Author(s). - 1551-7616 .- 0094-243X. ; 2065
-
Konferensbidrag (refereegranskat)abstract
- This research presents an overview of the properties of highly structured, low density polyethylene-graphene nanoplatelets (LDPE-GnP). The influence of nanofiller content, size and processing conditions on the material properties have been investigated. Therefore, rheological and thermal nanocomposite properties were investigated. So-called dry-coating method has been used in order to prepare masterbatches which were thereafter extruded by means of single screw extruder resulting in a strong anisotropy in the extruded samples. Graphene nanoplatelets were oriented in the extrusion direction for all shear rates and flow histories investigated, as confirmed by scanning electron microscopy. The rheological percolation was determined via nonlinear parameters to be around 11wt%. Thermal conductivity measurements revealed strong anisotropy with in-plane conductivity increasing with GnP content.
|
|
