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| 2. |
- Aksteiner, Steffen, et al.
(författare)
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All Local Gauge Invariants for Perturbations of the Kerr Spacetime
- 2018
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 121
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Tidskriftsartikel (refereegranskat)abstract
- We present two complex scalar gauge invariants for perturbations of the Kerr spacetime defined covariantly in terms of the Killing vectors and the conformal Killing-Yano tensor of the background together with the linearized curvature and its first derivatives. These invariants are, in particular, sensitive to variations of the Kerr parameters. Together with the Teukolsky scalars and the linearized Ricci tensor, they form a minimal set that generates all local gauge invariants. We also present curvature invariants that reduce to the gauge invariants in the linearized theory.
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| 3. |
- Alcolombri, Uria, et al.
(författare)
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Sinking enhances the degradation of organic particles by marine bacteria
- 2021
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Ingår i: Nature Geoscience. - : Springer Nature. - 1752-0894 .- 1752-0908. ; 14:10, s. 775-780
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Tidskriftsartikel (refereegranskat)abstract
- The sinking of organic particles in the ocean and their degradation by marine microorganisms is one of the main drivers of the biological pump. Yet, the mechanisms determining the magnitude of the pump remain poorly understood, limiting our ability to predict this carbon flux in future ocean scenarios. Current ocean models assume that the biological pump is governed by the competition between sinking speed and degradation rate, with the two processes independent from one another. Contrary to this paradigm, we show that sinking itself is a primary determinant of the rate at which bacteria degrade particles. Heterotrophic bacterial degradation rates were obtained from a laboratory study on model surface-colonized particles at atmospheric pressure under a range of flow speeds to mimic different sinking velocities. We find that even modest sinking speeds of 8 m day−1 enhance degradation rates more than 10-fold compared with degradation rates of non-sinking particles. We discovered that the molecular mechanism underlying this sinking-enhanced degradation is the flow-induced removal from the particles of the oligomeric breakdown products, which otherwise compete for enzymatic activity. This mechanism applies across several substrates and bacterial strains, suggesting its potentially broad occurrence under natural marine conditions. Integrating our findings into a mathematical model of particulate carbon flux, we propose that the coupling of sinking and degradation may contribute, in conjunction with other processes, to determining the magnitude of the vertical carbon flux in the ocean.
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| 4. |
- Chudoba, V., et al.
(författare)
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Detailed Study of External Correlations in the Low-Energy Spectrum of Beryllium-6
- 2019
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Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738 .- 1934-9432. ; 83:4, s. 392-398
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Tidskriftsartikel (refereegranskat)abstract
- Three-body continuum p-p-α for the charge exchange reaction 1H(6Li,6Be)n is studied in detail. The data are obtained with a high volume of statistics (approximately 4.7 million events), making it possible to analyze three-particle correlations. Detailed information about the structure of 6Ве and the reaction is obtained as a result.
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| 5. |
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| 6. |
- Diez-Olivan, Alberto, et al.
(författare)
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Adaptive Dendritic Cell-Deep Learning Approach for Industrial Prognosis Under Changing Conditions
- 2021
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Ingår i: IEEE Transactions on Industrial Informatics. - : IEEE. - 1551-3203 .- 1941-0050. ; 17:11, s. 7760-7770
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Tidskriftsartikel (refereegranskat)abstract
- Industrial prognosis refers to the prediction of failures of an industrial asset based on data collected by Internet of Things sensors. Prognostic models can experience the undesired effects of concept drift, namely, the presence of nonstationary phenomena that affects the data collected over time. Consequently, fault patterns learned from data become obsolete. To overcome this issue, contextual and operational changes must be detected and managed, triggering rapid model adaptation mechanisms. This article presents an adaptive learning approach based on a dendritic cell algorithm for drift detection and a deep neural network model that dynamically adapts to new operational conditions. A kernel density estimator with drift-based bandwidth is used to generate synthetic data for a faster adaptation, focusing on fine-tuning the lowest neural layers. Experimental results over a real-world industrial problem shed light on the outperforming behavior of the proposed approach when compared to other drift detectors and classification models.
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| 7. |
- Fuxin, Freddy
(författare)
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Evolution and communication of geometry based product information within an extended enterprise
- 2001
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The importance of conducting efficient product development is growing steadily as traditional market boundaries diminish and are replaced by global market conditions. Digital product development builds on the foundation that digital mock-ups replace physical mock-ups, and this has the potential for strongly improving the efficiency of the product development process. This is a rather drastic change compared to the conventional way of conducting product development, and it cannot be implemented overnight. It requires the extended enterprise to rely on geometry based product models. Business excellence is therefore partially synonymous with managing these models and making them available, and relevant, to different activities throughout the product development process. This thesis deals with the establishment of two key expressions, Geometry Management Process and Geometry Based Product Information. The objective is to improve the utilisation of Geometry Based Product Information by supporting the product development process with adequate methods, tools and processes for managing this type of information. This objective is partly realised by the elimination of rework in the downstream activities of traditional design departments. There are numerous influencing factors and the research approach has been to collect these factors into four separate but correlating domains. The consistency in the approach stems from the fact that all research work is conducted with a geometrical perspective on all types of activity, requirement and process. The methodology is elaborated through participation and surveys of real cases in ongoing projects and activities when developing heavy-duty trucks.
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| 8. |
- Fuxin, Freddy
(författare)
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Geometry users from a process perspective
- 2001
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Ingår i: 13th International Conference on Engineering Design - ICED 01. - Bury St. Edmunds : Professional Engineering Publishing Ltd.
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Konferensbidrag (refereegranskat)
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