| 11. |
- Heshmati Alamdari, Shahab, et al.
(författare)
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Robust trajectory tracking control for underactuated autonomous underwater vehicles
- 2019
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Ingår i: Proceedings 2019 IEEE Conference on Decision and Control (CDC).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Motion control of underwater robotic vehicles isa demanding task with great challenges imposed by external disturbances, model uncertainties and constraints of the operating workspace. Thus, robust motion control is still an open issue for the underwater robotics community. In that sense, this paper addresses the tracking control problem of 3D trajectories for underactuated underwater robotic vehicles operating in a constrained workspace including obstacles. In particular, a robust Nonlinear Model Predictive Control (NMPC) scheme is presented for the case of underactuated Autonomous Underwater Vehicles (AUVs) (i.e., vehicles actuated only in surge, heave and yaw). The purpose of the controller is to steer the underactuated AUV to a desired trajectory with guaranteed input and state constraints inside a partially known and dynamic environment where the knowledge of the operating workspace is constantly updated on–line via the vehicle’s on–board sensors. In particular, by considering a ball which covers the volume oft he system, obstacle avoidance with any of the detected obstacles is guaranteed, despite the model dynamic uncertainties and the presence of external disturbances representing ocean currents and waves. The proposed feedback control law consists of two parts: an online law which is the outcome of a Finite Horizon Optimal Control Problem (FHOCP) solved for the nominal dynamics; and a state feedback law which is tuned off-line and guarantees that the real trajectories remain bounded in a hyper-tube centered along the nominal trajectories for all times. Finally, a simulation study verifies the performance and efficiency of the proposed approach.
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| 12. |
- Heyman, Viveka
(författare)
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Ett par Stagneliusfragment
- 1945
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Ingår i: Samlaren. - Uppsala : Svenska Litteratursällskapet. - 0348-6133 .- 2002-3871. ; N.F. 26, s. 51-62
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 13. |
- Langlet, David, 1977, et al.
(författare)
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Ocean Governance Podcast Episode 2 - Analysing Law And Policy: A Matter Of Method?
- 2018
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Ingår i: Ocean Governance Podcast.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this second episode of the Ocean Governance Podcast, we discuss two articles which can both be said to assess or analyse a legal or governance framework – in one case relating to high seas fisheries management and in the other to the regulation of GHG emissions from international shipping. However, they do so in strikingly different ways and take very different approaches overall to the use and account of scientific method.
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| 14. |
- Pham, Tuan D
(författare)
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Fractal characteristics of mass spectrometry based cancer data
- 2007
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Ingår i: WSEAS Transactions on Mathematics. - : World Scientific and Engineering Academy and Society. - 1109-2769 .- 2224-2880. ; , s. 30-35
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the fractal analysis of mass spectrometry data for the prediction of complex diseases. We studied ovarian and prostate cancers as examples of the analysis. Experimental results show that the fractal dimensions of cancer states distinctively tend to have higher values than those of the control states. High values of the Hurst exponent of the mass spectrometry data under study suggest the persistent behavior of the datasets and the reliability of the fractal dimensions.
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| 15. |
- Sasic, Srdjan, 1968, et al.
(författare)
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Fuel mixing in bubbling fluidized beds: an experimental and numerical study
- 2015
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Ingår i: The 16th International Conference on Fluid Flow Technologies (CMFF15), Budapest, Hungary.
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Konferensbidrag (refereegranskat)abstract
- In this paper we study experimentally and numerically the behaviour of inert and fuel particles in a bubbling gas-solid fluidized bed. We use the Particle Image Velocimetry (PIV) technique to obtain detailed information on the dynamics of the inert particles. Furthermore, a digital image analysis technique is applied to track an illuminated tracer particle in the bed, in an attempt to reproduce the behaviour of the fuel particles. The results of the experimental work are presented in the form of the averaged velocity vectors of the inert and tracer particles. In addition, a numerical investigation is carried out where the inert bulk phase is modelled within the Eulerian-Eulerian framework and large fuel particles are tracked in a Lagrangian frame of reference. The stresses in an inert phase are modelled using the visco-plastic constitutive law (the so-called µ-rheology approach). The assumption that the inert particulate phase behaves as a visco-plastic fluid leads to a correct prediction of the movement of the fuel particles in the bed.
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| 16. |
- Zamani, Neda, et al.
(författare)
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Unsupervised genome-wide recognition of local relationship patterns
- 2013
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 14, s. 347-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUNDPhenomena such as incomplete lineage sorting, horizontal gene transfer, gene duplication and subsequent sub- and neo-functionalisation can result in distinct local phylogenetic relationships that are discordant with species phylogeny. In order to assess the possible biological roles for these subdivisions, they must first be identified and characterised, preferably on a large scale and in an automated fashion.RESULTSWe developed Saguaro, a combination of a Hidden Markov Model (HMM) and a Self Organising Map (SOM), to characterise local phylogenetic relationships among aligned sequences using cacti, matrices of pair-wise distance measures. While the HMM determines the genomic boundaries from aligned sequences, the SOM hypothesises new cacti in an unsupervised and iterative fashion based on the regions that were modelled least well by existing cacti. After testing the software on simulated data, we demonstrate the utility of Saguaro by testing two different data sets: (i) 181 Dengue virus strains, and (ii) 5 primate genomes. Saguaro identifies regions under lineage-specific constraint for the first set, and genomic segments that we attribute to incomplete lineage sorting in the second dataset. Intriguingly for the primate data, Saguaro also classified an additional ~3% of the genome as most incompatible with the expected species phylogeny. A substantial fraction of these regions was found to overlap genes associated with both the innate and adaptive immune systems.CONCLUSIONSSaguaro detects distinct cacti describing local phylogenetic relationships without requiring any a priori hypotheses. We have successfully demonstrated Saguaro's utility with two contrasting data sets, one containing many members with short sequences (Dengue viral strains: n = 181, genome size = 10,700 nt), and the other with few members but complex genomes (related primate species: n = 5, genome size = 3 Gb), suggesting that the software is applicable to a wide variety of experimental populations. Saguaro is written in C++, runs on the Linux operating system, and can be downloaded from http://saguarogw.sourceforge.net/.
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| 17. |
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| 18. |
- Abbasi, R., et al.
(författare)
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IceCube Search for Neutrinos Coincident with Gravitational Wave Events from LIGO/Virgo Run O3
- 2023
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 944:1
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Tidskriftsartikel (refereegranskat)abstract
- Using data from the IceCube Neutrino Observatory, we searched for high-energy neutrino emission from the gravitational-wave events detected by the advanced LIGO and Virgo detectors during their third observing run. We did a low-latency follow-up on the public candidate events released during the detectors' third observing run and an archival search on the 80 confident events reported in the GWTC-2.1 and GWTC-3 catalogs. An extended search was also conducted for neutrino emission on longer timescales from neutron star containing mergers. Follow-up searches on the candidate optical counterpart of GW190521 were also conducted. We used two methods; an unbinned maximum likelihood analysis and a Bayesian analysis using astrophysical priors, both of which were previously used to search for high-energy neutrino emission from gravitational-wave events. No significant neutrino emission was observed by any analysis, and upper limits were placed on the time-integrated neutrino flux as well as the total isotropic equivalent energy emitted in high-energy neutrinos.
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| 19. |
- Abel, Ian, 1985, et al.
(författare)
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Multiscale modelling for tokamak pedestals
- 2018
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 84:2
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Tidskriftsartikel (refereegranskat)abstract
- Pedestal modelling is crucial to predict the performance of future fusion devices. Current modelling efforts suffer either from a lack of kinetic physics, or an excess of computational complexity. To ameliorate these problems, we take a first-principles multiscale approach to the pedestal. We will present three separate sets of equations, covering the dynamics of edge localised modes (ELMs), the inter-ELM pedestal and pedestal turbulence, respectively. Precisely how these equations should be coupled to each other is covered in detail. This framework is completely self-consistent; it is derived from first principles by means of an asymptotic expansion of the fundamental Vlasov-Landau-Maxwell system in appropriate small parameters. The derivation exploits the narrowness of the pedestal region, the smallness of the thermal gyroradius and the low plasma beta (the ratio of thermal to magnetic pressures) typical of current pedestal operation to achieve its simplifications. The relationship between this framework and gyrokinetics is analysed, and possibilities to directly match our systems of equations onto multiscale gyrokinetics are explored. A detailed comparison between our model and other models in the literature is performed. Finally, the potential for matching this framework onto an open-field-line region is briefly discussed.
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| 20. |
- Afan, Haitham Abdulmohsin, et al.
(författare)
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Thermal and Hydraulic Performances of Carbon and Metallic Oxides-Based Nanomaterials
- 2022
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- For companies, notably in the realms of energy and power supply, the essential requirement for highly efficient thermal transport solutions has become a serious concern. Current research highlighted the use of metallic oxides and carbon-based nanofluids as heat transfer fluids. This work examined two carbon forms (PEG@GNPs & PEG@TGr) and two types of metallic oxides (Al2O3 & SiO2) in a square heated pipe in the mass fraction of 0.1 wt.%. Laboratory conditions were as follows: 6401 ≤ Re ≤ 11,907 and wall heat flux = 11,205 W/m2. The effective thermal–physical and heat transfer properties were assessed for fully developed turbulent fluid flow at 20–60 °C. The thermal and hydraulic performances of nanofluids were rated in terms of pumping power, performance index (PI), and performance evaluation criteria (PEC). The heat transfer coefficients of the nanofluids improved the most: PEG@GNPs = 44.4%, PEG@TGr = 41.2%, Al2O3 = 22.5%, and SiO2 = 24%. Meanwhile, the highest augmentation in the Nu of the nanofluids was as follows: PEG@GNPs = 35%, PEG@TGr = 30.1%, Al2O3 = 20.6%, and SiO2 = 21.9%. The pressure loss and friction factor increased the highest, by 20.8–23.7% and 3.57–3.85%, respectively. In the end, the general performance of nanofluids has shown that they would be a good alternative to the traditional working fluids in heat transfer requests.
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