| 1. |
- Özkahraman, Özer, 1992-
(författare)
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Multi-Agent Mission Planning and Execution for Small Autonomous Underwater Vehicles
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our planet is mostly covered in water, most of it still unexplored.In order to understand our environment better, oceanographers have been mapping and monitoring these waters using ship-mounted sensors and wired vehicles with limited range compared to the vastness of the oceans.The limited range and dependence on manned support vehicles has kept missions expensive and infrequent.To solve this problem, the sensors need to become independent of support vehicles, they need to venture into completely unexplored, unmapped regions of the seas by themselves and safely return with the data.This is where autonomous underwater vehicles (AUVs) have started to make a difference.In this thesis we investigate how multiple small AUVs can be utilized to efficiently and accurately sense very large volumes of water.Water absorbs electromagnetic radiation, meaning satellite-based global positioning systems (we will use GPS to refer to any such system), wide-angle cameras and radio communications are infeasible.These constraints ultimately result in uncertain localization of the vehicles.Furthermore, the vehicles are under constant disturbances from the water currents, fish and bio-fouling, which result in the dynamics of the vehicles being uncertain or even changing during the mission.In the first part of this thesis, we focus on the large-scale sensing problem under localization uncertainties by examining the caging and coverage problems.In the coverage problem, each AUV is uncertain about its exact position while tasked with sensing a stationary area.We show that we can still guarantee complete coverage and formulate the efficiency characteristics of different approaches.Furthermore, we show that when the vehicles are equipped with sensors and low-bandwidth communication methods, we can increase the effective range of a team of AUVs considerably by utilizing loop-closures over shared pose-graphs. In the caging problem, the localization uncertainty is focused on the entity that is being caged, its location is unknown but bounded.We show that through a combination of algorithms, the caging problem can be solved and a solution can be guaranteed, while simultaneously producing a list of specifications for the mission.In the second part, we focus on the individuals of the team and what they need to do in order for the team of AUVs to succeed.First, we identify that when there is a team of cooperative vehicles working together, conflicting goals rise.Each vehicle needs to pick between satisfying its own constraints and the constraints that come from being in a team. We propose a solution to this problem through a combination of Control Barrier Function (CBF) and Behavior Trees (BT).Secondly, we examine the possibility that a vehicle might undergo physical changes, like a broken thruster, that result in the vehicle being unable to complete the entire mission.Even in such a scenario, if the broken vehicle can still move to contact a normal one, the rest of the team can compensate through re-planning and the overall mission can still be completed.To do so, the broken vehicle must compensate for the change until a rendezvous.We propose a data-driven pipeline that can detect and plan around such a physical change within some bounds.
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| 2. |
- Aad, G, et al.
(författare)
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Measurements of fiducial cross-sections for [Formula: see text] production with one or two additional b-jets in pp collisions at [Formula: see text]=8 TeV using the ATLAS detector.
- 2016
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- Fiducial cross-sections for [Formula: see text] production with one or two additional b-jets are reported, using an integrated luminosity of 20.3 fb[Formula: see text] of proton-proton collisions at a centre-of-mass energy of 8 TeV at the Large Hadron Collider, collected with the ATLAS detector. The cross-section times branching ratio for [Formula: see text] events with at least one additional b-jet is measured to be 950 [Formula: see text] 70 (stat.) [Formula: see text] (syst.) fb in the lepton-plus-jets channel and 50 [Formula: see text] 10 (stat.) [Formula: see text] (syst.) fb in the [Formula: see text] channel. The cross-section times branching ratio for events with at least two additional b-jets is measured to be 19.3 [Formula: see text] 3.5 (stat.) [Formula: see text] 5.7 (syst.) fb in the dilepton channel ([Formula: see text], [Formula: see text], and ee) using a method based on tight selection criteria, and 13.5 [Formula: see text] 3.3 (stat.) [Formula: see text] 3.6 (syst.) fb using a looser selection that allows the background normalisation to be extracted from data. The latter method also measures a value of 1.30 [Formula: see text] 0.33 (stat.) [Formula: see text] 0.28 (syst.)% for the ratio of [Formula: see text] production with two additional b-jets to [Formula: see text] production with any two additional jets. All measurements are in good agreement with recent theory predictions.
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| 3. |
- Aad, G., et al.
(författare)
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Observation of WWW Production in pp Collisions at √s=13 TeV with the ATLAS Detector
- 2022
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Ingår i: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 129:6
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Tidskriftsartikel (refereegranskat)abstract
- This Letter reports the observation of WWW production and a measurement of its cross section using 139 fb−1 of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from WWW production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive WWW production cross section is measured to be 820±100 (stat)±80 (syst) fb, approximately 2.6 standard deviations from the predicted cross section of 511±18 fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy.
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| 4. |
- Özkale, M. Revan, et al.
(författare)
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The stochastic restricted ridge estimator in generalized linear models
- 2021
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Ingår i: Statistical papers. - : Springer Science and Business Media LLC. - 0932-5026 .- 1613-9798. ; 62, s. 1421-1460
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Tidskriftsartikel (refereegranskat)abstract
- Many researchers have studied restricted estimation in the context of exact and stochastic restrictions in linear regression. Some ideas in linear regression, where the ridge and restricted estimations are the well known, were carried to the generalized linear models which provide a wide range of models, including logistic regression, Poisson regression, etc. This study considers the estimation of generalized linear models under stochastic restrictions on the parameters. Furthermore, the sampling distribution of the estimators under the stochastic restriction, the compatibility test and choice of the biasing parameter are given. A real data set is analyzed and simulation studies concerning Binomial and Poisson distributions are conducted. The results show that when stochastic restrictions and ridge idea are simultaneously applied to the estimation methods, the new estimator gains efficiency in terms of having smaller variance and mean square error.
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| 5. |
- Godhe, Michael, 1964-
(författare)
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- 2001
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Ingår i: NT-ÖD. ; :28 december
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Recension (populärvet., debatt m.m.)
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| 6. |
- Sundgren, Mats, 1959, et al.
(författare)
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- 2005
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Ingår i: R &D Management. - : Wiley. - 0033-6807 .- 1467-9310. ; 35:4, s. 359-374
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Tidskriftsartikel (refereegranskat)abstract
- A path model of organizational creativity was presented; it conceptualized the influences of information sharing, learning culture, motivation, and networking on creative climate. A structural equation model was fitted to data from the pharmaceutical industry to test the proposed model. The model accounted for 86% of the variance in the creative climate-dependent variable. Information sharing had a positive effect on learning culture, which in turn had a positive effect on creative climate, while there were negative direct effects of information sharing on creative climate and on intrinsic motivation. This study suggests that information sharing and intrinsic motivation are important drivers for organizational creativity in a complex R&D environment in the pharmaceutical industry. Implications of the model are discussed.
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| 7. |
- Asplund, Matthias, et al.
(författare)
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- 2016
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Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 92, s. 19-27
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Tidskriftsartikel (refereegranskat)abstract
- Reliable data with less variation play a key role for acceptance of the usefulness of the measurement output of a wheel profile measurement system (WPMS) in a railway network. However, in practice, most studies are carried out without checking the reliability of data from such a system, which may lead to inappropriate maintenance strategies. To ensure the measurement capability of WPMS and to support robust maintenance in railway systems, this study has evaluated measurement data for the flange height, flange thickness, flange slope, and tread hollowing of rolling stock wheels by using gauge repeatability and reproducibility (GR&R). In this study, acceptance and rejection criteria for the precision-to-tolerance ratio (PTR), signal-to-noise ratio (SNR), and discrimination ratio (DR) have been employed to evaluate the measurement capabilities. For the purpose of illustration, we have implemented a new proposed approach. This approach involves both an analysis using graphs with four regions with a confidence interval (CI) of 95% and an analysis using a graph with three regions with only the predicted values; the latter type of graph represents an innovation made in this study. The results show that the measurements of the tread hollowing and flange slope are on an acceptable level, while those for the flange height and flange thickness have to be rejected as unacceptable. The action proposed to increase the quality of data on the flange height and flange thickness is to enhance the calibration of the WPMS. In conclusion, GR&R is a useful tool to evaluate the measurement capability of WPMS and to provide helpful support for maintenance decision making.
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| 8. |
- Aad, G., et al.
(författare)
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- 2014
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Aad, G., et al.
(författare)
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- 2011
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swepub:Mat__t (refereegranskat)
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| 10. |
- Aad, G., et al.
(författare)
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- 2013
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swepub:Mat__t (refereegranskat)
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