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01 Mar 2008
TL;DR: In this article, the appropriateness of initial preventive maintenance task intervals and the improvement of changed intervals are evaluated based on logic found in the RCM (Reliability-Centered Maintenance) methodology.
Abstract: In this paper the appropriateness of initial preventive maintenance task intervals and the improvement of changed intervals are evaluated. The evaluation criteria are partly derived from logic found in the RCM (Reliability-Centered Maintenance) methodology. Empirical data is related to the whole life cycle of the Swedish military aircraft system FPL 37 Viggen, from 1977 to 2006. The analysis shows that the maintenance intervals are partly appropriate and that some performed changes are improvements. These conclusions are strengthened if the phase-out of the aircraft system is considered, where the preventive maintenance strategy has been replaced with a corrective one, in order to achieve cost-effectiveness. Considering the perfect repair assumption, it seems that the overhaul tasks essentially bring the items back to a state as good as new. The performed evaluation mostly considers when the failures are recognized, i.e. during operation or during maintenance. Hence, aspects such as item accessibility, personnel skill levels, and maintenance task intervals for other items are not included in the evaluation.
5 citations
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13 Aug 1997TL;DR: A multispectral imaging MWIR sensor developed by us utilizes the high frame rate made possible by modern FPA arrays and has the capability to perform two point correction in real time, thereby compensating for the different dynamic ranges in each spectral band.
Abstract: There is a trend today towards a reduction in target signatures, the signatures becoming increasingly adapted to the background in which the targets operate. In addition, new types of countermeasures are making the task for optical seekers increasingly difficult. One way to increase the capability of detecting low-signature targets in a countermeasure environment is to utilize not only the magnitude of the signature but also its distribution over the spectrum. For collection of information regarding the spectral signatures of targets, countermeasures and backgrounds, a multispectral imaging MWIR sensor has been developed by us. This device utilizes the high frame rate made possible by modern FPA arrays. Such an array has been combined with a rapidly rotating filter wheel, thereby producing images of 128 by 128 pixels in six wavelength bands in the 2 - 5 micrometer region at a frame rate exceeding 30 Hz in each band. The sensor has a field-of-view of 3.7 degrees and a pixel resolution of 0.5 mrad. The sensor has the capability to perform two point correction in real time, thereby compensating for the different dynamic ranges in each spectral band. An extensive measurement program is in progress for gathering data for targets, countermeasures and backgrounds. Selected results from this program are presented.
5 citations
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11 Feb 2011TL;DR: In this paper, the authors proposed a method for measuring isolation of an electrical system in a vehicle, the system comprising an AC/DC inverter (2), an AC motor (3), and an energy storage system (1), the ESS having a positive bus (16) and a negative bus (17) connectable to a first and second terminal (4, 5) of the DC-side of the inverter, respectively, a charging resistor (25), connectable in series with ESS during charging of a capacitance (30), and a discharge resistor (26
Abstract: A method for measuring isolation of an electrical system in a vehicle, the system comprising an AC/DC inverter (2), an AC motor (3), and an energy storage system (1), the ESS having a positive bus (16) and a negative bus (17) connectable to a first and second terminal (4, 5) of the DC-side of the inverter, respectively, a charging resistor (25), connectable in series with the ESS during charging of a capacitance (30) of the inverter, and a discharge resistor (26) connectable between said first and second terminals for discharge of said capacitance (30). The method comprises connecting said discharge resistor (26) between said first and second terminals (4, 5), connecting one bus (16 or 17) of said ESS to one of said first and second terminals (4, 5), and conducting an isolation measurement of said ESS. According to this method, an isolation measurement can be performed for the entire electrical system, i.e. the energy storage system, the motor, and the inverter, also before system start-up and post drive, i.e. when the inverter is deactivated and not in high voltage mode.
5 citations
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01 Oct 2008TL;DR: In this article, phase and amplitude controlling ICs realized in a low cost standard silicon process are demonstrated and the design of several ICs at S-, C- and X-band has shown that silicon germanium is a strong contender to gallium arsenide where lowest noise figure is not vital.
Abstract: Phase and amplitude controlling ICs realized in a low cost standard silicon process are demonstrated. The design of several ICs at S-, C- and X-band has shown that silicon germanium is a strong contender to gallium arsenide where lowest noise figure is not vital. This applies also to the T/R-modules suited for military AESA-radars. The circuits presented in this paper are manufactured by austriamicrosystems in their 0.35 mum SiGe-BiCMOS process with an fT of 70 GHz.
5 citations
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19 Jun 2013TL;DR: In this paper, a comparison of some fundamental parameters of active radars used nowadays widely as sources of information on situation in the air space used for air traffic control or defense systems with parameters achieved by passive radars (PCL) is presented.
Abstract: Passive radars have some renown advantages when used as sources of information for air surveillance and air space control systems. Their main advantage is a concealed operation due to the usage of signals of opportunity and especially signals emitted by commercial broadcasting stations. Many parameters of the passive radars and namely: resolution and estimation of air object coordinates depend on quality of captured signals. Some examples of range resolution achieved using UHF radio and TV broadcasting signals as given in the enclosed references are discussed.. The range uncertainty is explained and its influence on range estimation accuracy is indicated. The influence of air coverage volume on the number and localization of emitters has been explained. A comparison of some fundamental parameters of active radars used nowadays widely as sources of information on situation in the air space used for air traffic control or defense systems with parameters achieved by passive radars (PCL) is then presented. Conclusion resulting from the discussion of both active and passive radars features is that passive radars do not match several of temporary requirements obligatory for the ATC or air defense systems and presently they are not able to replace active radars but can be used only as a supporting sources of information, which can improve the active radar coverage for small RCS objects (“stealth”) and also improve low altitude detection.
5 citations
Authors
Showing all 760 results
Name | H-index | Papers | Citations |
---|---|---|---|
Christer Larsson | 64 | 272 | 12916 |
Björn Johansson | 62 | 637 | 16030 |
David C. Viano | 48 | 232 | 8283 |
Thomas Schiex | 47 | 138 | 11031 |
Robin Hanson | 28 | 114 | 3519 |
Per Lötstedt | 28 | 109 | 2960 |
Brigitte Mangin | 26 | 48 | 2652 |
Lars Hanson | 19 | 117 | 1138 |
Carl Gustafson | 17 | 34 | 1035 |
Magnus Carlsson | 16 | 37 | 808 |
Per-Johan Nordlund | 14 | 26 | 2738 |
David Allouche | 14 | 26 | 680 |
Mark A. Saab | 13 | 16 | 1153 |
Andreas Gällström | 13 | 34 | 402 |
Hans Hellsten | 12 | 37 | 549 |