| 1. |
- Hansson, Jörgen, et al.
(författare)
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Clearance of Flight Control Laws for Time-Varying Parameters
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this article exponential stability of the closed loop for the Saab AB VEGAS model controlled by a gain-scheduled linear fractional transformation controller is investigated for time-varying Mach-number. The analysis is based on parameter-dependent Lyapunov-functions which are obtained by investigating feasibility of linear matrix inequalities.
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| 2. |
- Hansson, Lars Jörgen, et al.
(författare)
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Vitrectomy for retained lens fragments in the vitreous after phacoemulsification.
- 2002
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Ingår i: Journal of Cataract and Refractive Surgery. - 1873-4502. ; 28:6, s. 1007-1011
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To assess the visual results, retinal detachment (RD) rate, incidence of glaucoma, and intraocular lens (IOL) placement after vitrectomy for removal of retained lens fragments in the vitreous after phacoemulsification. SETTING: Department of Ophthalmology, University Hospital of Lund, Lund, Sweden. METHODS: This retrospective noncomparative interventional case series included all cases of pars plana vitrectomy for removal of retained lens fragments from January 1997 through January 2000. RESULTS: Sixty-six eyes of 65 patients had pars plana vitrectomy with removal of the lens material over the 3-year period. Visual acuity on presentation was 0.1 or worse in 36 eyes (54%). Visual acuity after vitrectomy was 0.5 or better in 35 eyes (53%). The postoperative visual acuity was worse than 0.1 in 14 eyes (21%). Twenty-seven (56%) of the 48 eyes operated on within 1 week and 8 (44%) of the 18 eyes operated on later achieved a visual acuity of 0.5 or better. Twelve eyes (80%) that had secondary posterior chamber IOL implantation achieved an acuity of 0.5 or better. An RD occurred in 7 eyes (11%). CONCLUSIONS: There was no statistically significant difference in outcomes between those having vitrectomy the first few days after cataract surgery and those having it later, although there was a trend toward better results when the vitrectomy was done sooner. Secondary IOL implantation resulted in a good visual outcome. Retinal detachment was the most severe complication.
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| 3. |
- Lindgren, Markus, 1975-
(författare)
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Measurement and Simulation Based Techniques for Real-Time Systems Analysis
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Rigorous methods for design and implementation of safety critical real-time systems are vital to avoid loss of human lives and/or severe economic losses. Unfortunately, many of these systems are designed and evaluated using ad-hoc techniques. There are, on the other hand, relatively well developed theories for modeling and analysis of timing and reliability. These theories are, however, seldom applied in industry for system development, mainly because of the simplifying model assumptions and lack of appropriate tool support.This thesis presents two new methods aimed to narrow the gap between research results and industrial practice in evaluation and design of real-time systems.The first contribution is a technique that can be used to derive worst-case execution time estimates for real-time software by measurments on the target system. Such estimates are essential when verifying if a system fulfills its timing requirements. The second contribution is a simulation based technique that can be used to evaluate timing aspects of distributed real-time systems, as well as calculating reliability estimates of these systems. Such estimates are essential in determining if a system meets its requirements sufficiently well. Compared to existing analytical methods for execution time analysis and schedulability analysis, which analyze models of the hardware, the starting point for both these methods are real target systems, rather than an abstract model with limited correspondance to reality.The presented initial case-studies give clear evidence that the proposed methods have potential of being both applicable and useful.
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| 4. |
- Ståhl Gunnarsson, Karin, et al.
(författare)
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Clearance of Flight Control Laws using Linear Fractional Transformations
- 2004
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Ingår i: Proceedings of the 2004 AIAA Guidance, Navigation and Control Conference and Exhibit. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781624100734
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Konferensbidrag (refereegranskat)abstract
- The problem of flight clearance of linear stability requirements in the complete flight evelope is studied. The approach is to use mu-analysis of linear fractional transformations description of the system dynamics augmented with an uncertainty model of the clearance criteria. Two methods to derive the linear fractional transformations are used and compared: the Trends and Bands method and rational approximations. The two approaches are applied to a UAV demostrator model. The resulting models are analyzed by mu-sensitivites in order to demonstrate how this can be used to reduce the order of the linear fractional transformations description. A number of algorithms to compute upper and lower bounds on mu are also compared. Results from applying the clearance criteria to the UAV demonstrator model are given.
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| 5. |
- Aad, G., et al.
(författare)
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Commissioning of the ATLAS Muon Spectrometer with cosmic rays
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 875-916
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Tidskriftsartikel (refereegranskat)abstract
- The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions.
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| 6. |
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| 7. |
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| 8. |
- Aad, G., et al.
(författare)
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Readiness of the ATLAS Tile Calorimeter for LHC collisions
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:4, s. 1193-1236
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Tidskriftsartikel (refereegranskat)abstract
- The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.
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| 9. |
- Aad, G., et al.
(författare)
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Studies of the performance of the ATLAS detector using cosmic-ray muons
- 2011
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 71:3
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Tidskriftsartikel (refereegranskat)abstract
- Muons from cosmic-ray interactions in the atmosphere provide a high-statistics source of particles that can be used to study the performance and calibration of the ATLAS detector. Cosmic-ray muons can penetrate to the cavern and deposit energy in all detector subsystems. Such events have played an important role in the commissioning of the detector since the start of the installation phase in 2005 and were particularly important for understanding the detector performance in the time prior to the arrival of the first LHC beams. Global cosmic-ray runs were undertaken in both 2008 and 2009 and these data have been used through to the early phases of collision data-taking as a tool for calibration, alignment and detector monitoring. These large datasets have also been used for detector performance studies, including investigations that rely on the combined performance of different subsystems. This paper presents the results of performance studies related to combined tracking, lepton identification and the reconstruction of jets and missing transverse energy. Results are compared to expectations based on a cosmic-ray event generator and a full simulation of the detector response.
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| 10. |
- Aad, G., et al.
(författare)
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The ATLAS Inner Detector commissioning and calibration
- 2010
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 70:3, s. 787-821
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Tidskriftsartikel (refereegranskat)abstract
- The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 +/- 0.9 mu m and a relative momentum resolution sigma (p) /p=(4.83 +/- 0.16)x10(-4) GeV(-1)xp (T) have been measured for high momentum tracks.
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