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- Mader, P., et al.
(författare)
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Experimental validation of fringing field effects for the multipactor phenomenon
- 2012
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Ingår i: 15th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2012, Toulouse, 25-28 June 2012. - 9781467302913
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Konferensbidrag (refereegranskat)abstract
- The multipactor effect is a constraining phenomenon in the design of RF components. Due to an increasing number of channels and power levels for multicarrier signals, specific requirements of design must be taken into account in order to prevent the multipactor effect. The current methods of analysis are based on the Hatch and Williams diagrams, which provide the multipaction threshold voltage for a parallel plate geometry as a function of the frequency gap product. However, whereas experimental results have shown good correlation with the theoretical charts for the parallel plate geometry, discrepancies have been found for complex geometries such as irises.
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| 2. |
- Jarvis, M.J., et al.
(författare)
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The discovery of a z = 0.7092 OH megamaser with the MIGHTEE survey
- 2024
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 529:4, s. 3484-3494
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Tidskriftsartikel (refereegranskat)abstract
- We present the discovery of the most distant OH megamaser (OHM) to be observed in the main lines, using data from the MeerKAT International Giga-Hertz Tiered Extragalactic Exploration (MIGHTEE) survey. At a newly measured redshift of z = 0.7092, the system has strong emission in both the 1665 MHz (L ≈ 2500 L-) and 1667 MHz (L ≈ 4.5 × 104 L-) transitions, with both narrow and broad components. We interpret the broad line as a high-velocity-dispersion component of the 1667 MHz transition, with velocity v ∼330 km s-1 with respect to the systemic velocity. The host galaxy has a stellar mass of M = 2.95 × 1010 M- and a star formation rate of SFR = 371 M- yr-1, placing it ∼1.5 dex above the main sequence for star-forming galaxies at this redshift, and can be classified as an ultraluminous infrared galaxy. Alongside the optical imaging data, which exhibit evidence for a tidal tail, this suggests that the OHM arises from a system that is currently undergoing a merger, which is stimulating star formation and providing the necessary conditions for pumping the OH molecule to saturation. The OHM is likely to be lensed, with a magnification factor of ∼2.5, and perhaps more if the maser emitting region is compact and suitably offset relative to the centroid of its host galaxy's optical light. This discovery demonstrates that spectral line mapping with the new generation of radio interferometers may provide important information on the cosmic merger history of galaxies.
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| 3. |
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| 4. |
- Sinigaglia, Andrea, et al.
(författare)
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Coordination of motion actuators in heavy vehicles using Model Predictive Control Allocation
- 2016
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Ingår i: IEEE Intelligent Vehicles Symposium, Proceedings. - 9781509018215 ; 2016-August, s. 590-596
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Konferensbidrag (refereegranskat)abstract
- The paper presents a Model Predictive Control Allocation (MPCA) method in order to coordinate the motion actuators of a heavy vehicle. The presented method merges the strong points of two different control theories: Model Predictive Control (MPC) and Control Allocation (CA); MPC explicitly considers the motion actuators dynamics before deciding on a suitable input for the actuators while CA dynamically decides how to use the motion actuators in order to modify the vehicle behaviour. The designed MPCA formulation belongs to the class of Quadratic Programming (QP) problems so that the solution is optimization based, i.e. at every step a quadratic cost function has to be minimized while fulfilling a set of linear constraints. Three scenarios were set up to evaluate the effectiveness of the controller: split-μ braking, split-μ acceleration and brake blending. Split-μ means that the wheels on one side of the vehicle are in contact with a slippery surface (e.g. ice) while the wheels of the other side lay on a normal surface (e.g. dry asphalt). The split-μ scenarios aim to combine three different types of motion actuators, disc brakes, powertrain and rear active steering (RAS), in order to brake/accelerate the vehicle while keeping it on course. The third scenario is a mild braking event on a normal road and its purpose is to combine the use of the engine brake with the disc brakes. Simulation results of the scenarios have shown promising vehicle performance when using MPCA to coordinate the motion actuators. Tests on a real vehicle have then confirmed the expected vehicle behaviour in a slit-μ braking scenario. MPCA has also been compared to a simpler CA formulation, in all scenarios. The performance of the two is comparable in steady state, but MPCA shows advantages in transients, whereas CA is less computationally demanding.
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