| 1. |
- Asplund, Gustav, et al.
(författare)
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Rapport 11 från Taxonomikommittén
- 2020
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Ingår i: Vår Fågelvärld. - 0042-2649. ; :5, s. 38-42
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Här presenteras de senaste besluten av BirdLife Sveriges Taxonomi kommitté. Detta är en förkortad version, den fullständiga rapporten med mer detaljer, referenser och extralimitala förändringar finns på Tk:s hemsida under ”Rapporter”. I denna omgång utökas inte Sverigelistan med nya arter, dock urskiljs ett antal som mycket väl kan uppträda i Sverige i framtiden. Flera välkända svenska häckfåglar får vidare nya släktesnamn och svenska trivialnamn justeras på några amerikanska VPrariteter. Efter flera års diskuterande och remissande har slutligen listan med svenska namn på underarter fastställts.
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| 2. |
- Block, Jan, et al.
(författare)
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Changes in items' failure pattern during maintenance : an investigation of the perfect repair assumption
- 2008
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Ingår i: Annual Reliability and Maintainability Symposium, 2008. - Piscataway, NJ : IEEE Communications Society. - 9781424414604 ; , s. 117-122
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Konferensbidrag (refereegranskat)abstract
- It is clear that the simple ‘perfect repair' assumption is not immediately applicable to any of the studied types of hardware, i.e. Cooling Turbine, High-Voltage Generator, Hydraulic Accumulator, and Radar Transmitter. Hence, the assumption of ‘perfect repair' needs to be validated for each specific type of item. Assumptions based on the type of physical hardware (e.g. mechanical item or avionics item) are not always trustworthy.Strangely enough the ‘perfect repair' assumption fits best for the Cooling Turbine, which is a highly stressed mechanical item, while the fit is much poorer for the Radar Transmitter, which is an avionics item and for the Hydraulic Accumulator.For the Radar Transmitter the trend seems to be very scattered. For items with a large number of failures early in their life-cycle, repair is ‘better than perfect', i.e. the items become more reliable after repair, presumably by elimination of less reliable subcomponents. However, this effect is not seen for items with few failures early in their life-cycle. For these items ‘perfect repair' initially seems to be a valid model. However, in many cases repair becomes ‘less than perfect' later in the life-cycle. For the Hydraulic Accumulator this trend is even more accentuated and individual items seem to fall into two distinct subpopulations with opposite reliability trends.
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| 3. |
- Block, Jan, et al.
(författare)
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Fleet-Level Reliability Analysis of Repairable Units: A Non-Parametric Approach using the Mean Cumulative Function
- 2013
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Ingår i: International Journal of Performability Engineering. - 0973-1318. ; 9:3, s. 333-344
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Tidskriftsartikel (refereegranskat)abstract
- Complex technical systems are normally repaired rather than replaced when they fail. It is often desirable to analyze the reliability characteristics of these systems based on data generated in a customer use environment, in order to assess the reliability, frequency of failure or other parameters which may be influenced by the systems’ age and usage. Despite the advantages of continuously analyzing reliability data to be able to improve the maintenance programme continuously, methods such as parametric and non-parametric analysis are often ignored due to a belief that the mean time between failures (MTBF) is sufficient to describe the reliability pattern of repairable units. This paper describes the use of the mean cumulative function (MCF) and linear estimates based on the recurrence rate to predict the expected number of failures in the future. Reliability data from two repairable units are used to verify the procedure and comparison. The empirical data used in the paper is based on field data gathered during the operational life of the Swedish military aircraft system FPL 37 Viggen from 1977 to 2006, which essentially is the whole life cycle of the system.
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| 4. |
- Block, Jan, et al.
(författare)
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Fleet-level Reliability of Multiple Repairable Units: a Parametric Approach using the Power Law Process
- 2014
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Ingår i: International Journal of Performability Engineering. - 0973-1318. ; 10:3, s. 239-250
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Tidskriftsartikel (refereegranskat)abstract
- The application of parametric reliability analysis methods for repairable units, such as Power law process, is quite clear and straightforward for a single repairable unit. However, in practice, the analyst needs to know the reliability characteristics of units at a fleet level. The application of parametric reliability analysis methods at the fleet level, even if it is limited in scope, is quite complex. The aim of this paper is to describe the use of the power law process for multiple repairable units with differing reliability characteristics, to predict the expected number of failures at fleet level. The empirical data used in the paper are based on field data gathered during the operational life of two types of multi repairable units used in the Swedish military aircraft system FPL 37 Viggen from 1977 to 2006. The paper performs the trend test using TTT-based MIL-HDBK-189 and Laplace tests, and assesses the equality of shape-parameters for the intensity function of the power law process for multiple units. Estimation of the scale- and shape-parameters using maximum likelihood estimation is also performed. The parametric approach using power law process was found to yield relatively accurate estimations of number of failures, compared to empirical data
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| 5. |
- Block, Jan, et al.
(författare)
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Part-out-based spares provisioning management : A military aviation maintenance case study
- 2014
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Ingår i: Journal of Quality in Maintenance Engineering. - 1355-2511 .- 1758-7832. ; 20:1, s. 76-95
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Tidskriftsartikel (refereegranskat)abstract
- Purpose – The purpose of this paper is to present the prerequisites for a part-out-based spares provisioning (PBSP) programme during the phase-out of an aircraft fleet. Furthermore, associated key decision criteria are identified and a framework for the phase-out management process is presented. Design/methodology/approach – Once a decision has been taken to phase-out an aircraft fleet, a number of routines for operations, maintenance and storage are affected and new tasks and functions must be introduced before initiating the actual parting-out process. A decision-making system and a management framework is needed to manage spares planning during the end-of-life phase to ensure availability at minimum cost and to ensure a manageable risk of backorders. Findings – For PBSP programme during the phase-out of an aircraft fleet to succeed and be cost-effective, a number of linked processes, tasks and decisions are required, e.g., those included in the framework proposed in this paper (see Figure 3). A successful implementation of PBSP also requires that these processes and tasks are carried out in a timely manner and that the communications between the concerned parties are prompt, clear and direct. One experience from the studied case is that close and trustful contacts and cooperation between the operator and maintenance provider(s) will greatly facilitate the process. Originality/value – Although the PBSP method is fairly commonly applied within both the military and the civilian sector, somewhat surprisingly very literature has been published on the subject. Indeed, remarkably little has been published on any aspects of maintenance during the end-of-life period.
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| 6. |
- Block, Jan, et al.
(författare)
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Using Monte Carlo simulation as support for decision making while negotiating a PBL contract
- 2014
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Ingår i: IEEE Aerospace Conference. Proceedings. - 1095-323X.
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Tidskriftsartikel (refereegranskat)abstract
- In connection with performance-based logistics (PBL) contracts for aircraft fleets it is very important to carefully analyse both operations and maintenance before and during the contract negotiation phase. Monte Carlo Simulation is a valuable methodology in this context since it allows delimiting and exploring a complex parameter space in a transparent and relatively easily visualized manner. With timely analyses it is possible to identify both technical and economic risks and minimize the possible consequences, a process that benefits both parties in the negotiation process. This paper describes a part of this process in connection with the negotiation of a PBL contract for the Swedish Air Force SAAB 105 (SK 60) trainer fleet between Saab AB and the Swedish Defence Materiel Administration (FMV). The information used in the simulations was largely empirical data derived from previous operations of the aircraft system. The main factors that were simulated were operational requirements, fleet size, spares inventories, turn-around times, failure rates and influence of extraneous factors (e. g. weather). The simulations resulted in considerable savings due to reduction of the active fleet size, and increased reclamation of surplus spares and units from retired aircraft.
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| 9. |
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| 10. |
- Jirle, Erling, et al.
(författare)
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Förändringar i Tk:s lista : Rapport 12 från Taxonomikommittén
- 2022
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Ingår i: Vår Fågelvärld. - 0042-2649. ; 2022:1, s. 28-32
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Här presenteras några av de senaste besluten inom BirdLife Sveriges Taxonomikommitté. Den fullständiga rapporten, inklusive referenser, finns på birdlife.se/tk, liksom en uppdaterad Västpalearktislista (VP7).
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