| 1. |
- Amouzgar, Kaveh, 1980-, et al.
(författare)
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An approach towards generating surrogate models by using RBFN with a priori bias
- 2014
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Ingår i: Proceedings of the ASME International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, 2014, Vol. 2B. - New York, USA : ASME Press. - 9780791846322
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Konferensbidrag (refereegranskat)abstract
- In this paper, an approach to generate surrogate modelsconstructed by radial basis function networks (RBFN) with a prioribias is presented. RBFN as a weighted combination of radialbasis functions only, might become singular and no interpolationis found. The standard approach to avoid this is to add a polynomialbias, where the bias is defined by imposing orthogonalityconditions between the weights of the radial basis functionsand the polynomial basis functions. Here, in the proposed a prioriapproach, the regression coefficients of the polynomial biasare simply calculated by using the normal equation without anyneed of the extra orthogonality prerequisite. In addition to thesimplicity of this approach, the method has also proven to predictthe actual functions more accurately compared to the RBFNwith a posteriori bias. Several test functions, including Rosenbrock,Branin-Hoo, Goldstein-Price functions and two mathematicalfunctions (one large scale), are used to evaluate the performanceof the proposed method by conducting a comparisonstudy and error analysis between the RBFN with a priori and aposteriori known biases. Furthermore, the aforementioned approachesare applied to an engineering design problem, that ismodeling of the material properties of a three phase sphericalgraphite iron (SGI) . The corresponding surrogate models arepresented and compared
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| 2. |
- Chatzigiannakou, Maria Angeliki, et al.
(författare)
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Numerical analysis of an Uppsala University WEC deployment by a barge for different sea states
- 2020
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 205
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Tidskriftsartikel (refereegranskat)abstract
- Wave energy converters (WECs) have been deployed onshore, nearshore, and offshore to convert ocean wave movement into electricity. The exploitation of renewable energy sources has restrictions; in the case of wave energy, high installation, maintenance, and decommissioning costs have limited their commercial use. Moreover, these offshore operations can be compromised by safety issues. This paper draws attention to offshore operation safety of a WEC developed by Uppsala University. Specifically, this paper investigates what sea states are suitable for the safe deployment of a WEC from a barge. This study follows recommendations in DNV-RP-H103 for analysis of offshore operations, namely lifting through the wave zone. ANSYS Aqwa is used to find hydrodynamic forces acting on a typical barge, using frequency domain analysis. Based on these hydrodynamic simulation results and methodology given in DNV-RP-H103, tables are created to show the sea states that would allow for the safe installation of a WEC using a typical barge. Considered sea states have significant wave heights varying between 0 m and 3 m and the wave zero crossing periods varying between 3 s and 13 s. The WEC submersions are considered between 0 m and 7 m, i.e. when the WEC is in the air until it is fully submerged. © 2020 Elsevier Ltd
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| 3. |
- Goel, Sneha, 1993-, et al.
(författare)
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Axial suspension plasma spraying of Al2O3 coatings for superior tribological properties
- 2017
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 315, s. 80-87
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Tidskriftsartikel (refereegranskat)abstract
- Suspension plasma spray is a relatively new thermal spray technique which enables feeding of fine powder to produce advanced coatings for varied applications. This work investigates the difference in structure and performance of Al2O3 coatings manufactured using conventional micron-sized powder feedstock and a suspension of sub-micron to few micron sized powder. Axial injection was implemented for deposition in both cases. The effect of feedstock size and processing on the tribological performance of the two coatings was of specific interest. The coatings were characterized by Optical and Scanning Electron Microscopy, micro-hardness and scratch resistance testing, and their dry sliding wear performance evaluated. The suspension sprayed coatings yielded significantly higher scratch resistance, lower friction coefficient and reduced wear rate compared to conventional coatings. The improved tribological behaviour of the former is attributable to finer porosity, smaller splat sizes, and improved interlamellar bonding.
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| 4. |
- Ekergård, Boel, 1985-, et al.
(författare)
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Longitudinal end effects in a linear wave power generator
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- Even though the magnetic circuit of a linear electric machine is very similar to a rotating electric machine, they diverge in one fundamental property. The linear generator is open in both ends, i.e., the magnetic circuit is non-symmetric. This paper investigates and discusses the drawbacks of this non-symmetric design in a linear permanent magnet generator, installed in a wave energy conversion system. A two-dimensional geometry has been utilized for the numerical calculations in a finite element method simulation tool. The results present an increased cogging force and significant core losses in the translator as consequences of the longitudinal ends in the machine.
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| 5. |
- Frost, Robert J. W., et al.
(författare)
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Preliminary results from a study of luminescent materials : For application in the beam imaging system at the ESS
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 540, s. 227-233
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Tidskriftsartikel (refereegranskat)abstract
- As part of the development of the beam imaging system at the European Spallation Source, luminescent screens have been fabricated by the flame spraying of scintillating materials onto stainless steel backings. A total of seven screens were produced, three of chromia alumina (Al2O3:Cr), two of YAG (Y3Al5O12:Ce) and two of a 50/50 mix of these. The properties of these screens under proton irradiation were evaluated using a2.55 MeV proton beam at currents of up to 10 μA. Irradiation times were up to 25 h per sample, during which luminescence-, spectrographic-, thermal- and current-data was sampled at a rate of 1 Hz. Preliminary results of these measurements are reported here; with a quantitative analysis presented for one of the chromia alumina screens and a qualitative comparison of all three material types. The luminescent yield for chromia alumina was determined to be around 2000 photons/MeV for a virgin screen, and was found to drop to 1.5% after 167 mC of proton irradiation. A recovery of the luminescence of chromia alumina to >60% was observed after beam current was reduced for an 8 h period. Observations indicate that the YAG and mixed composition screens retain higher luminescence than the chromia alumina even at temperatures of over 200 ◦C. It is indicated that the luminescence from YAG feeds the R-lines of chromia alumina in the mixed composition screens.
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| 6. |
- Abrahamsson, Sten, 1953-, et al.
(författare)
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Integrated Management Systems : testing a model for integration
- 2011
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Ingår i: 14th Toulon-Verona Conference. - Alicante : University of Alicante. - 9788890432712 ; , s. 22-35
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Konferensbidrag (refereegranskat)abstract
- Management systems are widely used for creating order, minimising risks and for assuring performance. Management systems are in many occasions integrated since this has been found to be beneficial. In this paper a model for a fully integrated management system (IMS) based on the three axes of level, extent and scope of integration is tested for relevance. The studied system permits the integration of all relevant process dimensions. The research is only in a pilot stage, but the initial results are promising and indicate that there are advantages in using the process view as a base for identifying critical aspects to be managed. A review of the current situation for system integration is studied and the model is subjected to some tests using Sweden as a case. The background study shows that system integration still is limited, especially when comparing with a fully integrated IMS. The feedback from the organisations interviewed is positive and supports continued work with development of the model.
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| 7. |
- Abrahamsson, Sten, 1953-, et al.
(författare)
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Integrated Management Systems : advantages, problems and possibilities
- 2010
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Ingår i: 13th Toulon-Verona Conference. - 9789729344046 ; , s. 1-12
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Konferensbidrag (refereegranskat)abstract
- Effective management in the globalized world requires an effective, efficient and flexible management system. Effective could be interpreted as addressing all relevant stakeholder concerns in a context of Corporate Social Responsibility (CSR). Efficient would mean that it does the job with low resource use. Flexibility requires that changed conditions and new requirements easily can be included. Many organizations are already working with Integrated Management Systems (IMS). Interesting questions are to what extent current integration covers the above mentioned needs and if not what changes are needed. This conceptual paper looks at the advantages and problems of integration. Possibilities for development of fully integrated management systems are studied from the perspective of managing stakeholder needs, with the forthcoming ISO 26000 – “Guidance on social responsibility”, as inspiration. Results show that there are advantages in integration, but that the scope and level of integration often is limited. A conceptual model for integrating all stakeholder needs in value networks is presented.
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| 8. |
- Goel, Sneha, 1993-, et al.
(författare)
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Axial Plasma Spraying of Mixed Suspensions : A Case Study on Processing, Characteristics, and Tribological Behavior of Al2O3-YSZ Coatings
- 2020
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 10:15
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Tidskriftsartikel (refereegranskat)abstract
- Thermal spraying deploying liquid feedstock offers an exciting opportunity to obtain coatings with characteristics vastly different from those produced using conventional spray-grade powders. The most extensively investigated variant of this technique is Suspension Plasma Spraying (SPS), which utilizes a suspension of fine powders in an appropriate medium. The relatively recent advent of axial feed capable plasma spray systems can enable higher throughputs during SPS, provides the possibility for spraying with longer stand-off distances, and also permit the use of suspensions with higher solid loading. The present work investigates axial plasma sprayed coatings produced using a mixed suspension of fine (submicron or nano-sized) powders of Al(2)O(3)and YSZ as a case study. Deposition of the mixed suspension using axial injection plasma spraying, comprehensive evaluation of characteristics of the resulting coatings, and assessment of their tribological behavior were of particular interest. Evaluation of surface morphology, microstructure, and hardness of the coatings reveals that axial SPS of mixed suspensions provides an exciting pathway to realize finely structured multi-constituent coatings using suspensions with as high as 40 wt.% solid loading. The study of scratch, dry sliding wear, and erosion behavior also specifically shows that the addition of YSZ in the Al(2)O(3)matrix can improve the tribological properties of the coating.
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