| 1. |
- Chen, XÍ, et al.
(författare)
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TDHQ Enabling Fine-granularity Adaptive Loading for SSB-DMT Systems
- 2018
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Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 1041-1135 .- 1941-0174. ; 30:19, s. 1687-1690
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we introduce time domain hybrid quadrature amplitude modulation (TDHQ) for the single sideband (SSB) discrete multi-tone (DMT) systems. Experimental results reveal that with a single precoding set and the proposed adaptive loading algorithm, the TDHQ scheme can achieve finer granularity and therefore smoother continuous growth of data rate than that with the conventional quadrature amplitude modulation (QAM). Besides, thanks to the frame construction and the tailored mapping rule, the scheme with TDHQ has an obviously better peak to average power ratio (PAPR).
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| 2. |
- Ingason, Haukur, et al.
(författare)
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Fire tests with automatic sprinklers in an intermediate scale tunnel
- 2022
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Ingår i: Fire safety journal. - : Elsevier Ltd. - 0379-7112 .- 1873-7226. ; 129
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Tidskriftsartikel (refereegranskat)abstract
- A series of 1:3 intermediate scale tunnel fire tests was performed to investigate the performance of a fully automatic sprinkler system in a road tunnel. The experiments were carried in a container tunnel with scaled geometry, using wood pallets as the fire source to simulate HGV fires. The activation of the sprinklers was simulated by using thermocouples that corresponded to a given Thermal Response Index (RTI) of a sprinkler bulb or a link. A total of 12 tests were carried out with varying longitudinal velocities (0.8–1.7 m/s), sprinkler activation temperatures (68–141 °C), water densities (2.9–8.7 mm/min) and types of arrangement of the fuel. The activation times, number of activated sprinklers, maximum heat release rates and other key parameters are presented and analyzed. The results show that the water density plays a key role in the performance of the automatic sprinkler systems tested. A high tunnel ventilation velocity, low water density and low sprinkler activation temperature are not recommended. © 2022 The Authors
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| 3. |
- Li, Kaiyuan, et al.
(författare)
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Inerting and dilution – nitrogen foam suppressions of air mixing effect and flame intensification
- 2024
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier Ltd. - 1540-7489 .- 1873-2704. ; 40:1-4
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Tidskriftsartikel (refereegranskat)abstract
- To reveal the flame intensification caused by foam agents extinguishing oil fires, inert gas foam generated by compressed nitrogen was used to extinguish oil pool fires, and the suppression mechanisms of the inert foaming gas on air mixing effect and flame intensification were investigated. The results show that nitrogen replaces the air in the foam, resulting in the inerting effect. At the same time, the released nitrogen dilutes the ambient oxygen concentration, producing the dilution effect. Due to the combined effects of inerting and dilution, the nitrogen foam reduced the extinguishment time by an average of 30.5 % and 32.1 % compared to compressed and aspirated air foams. For flame intensification, this work corrected the positive correlation between the dimensionless heat release rate increase and pool radius proposed by an existing study, and experimentally demonstrated that it is inversely proportional to 1/4 power of the pool radius. The dimensionless analysis shows that the flame intensification of nitrogen foam was reduced by approximately 30 % compared to air foam. Combining with experiments, it was found that the flame intensification of nitrogen foam was reduced by 25 %-36 % compared to air foam under the combined effects of inerting and dilution, of which the inerting and dilution effect accounted for approximately 20 % and 10 %, respectively. This study further corroborated the role of the air mixing effect in flame intensification and also found that the inerting effect remains generally stable with the change of experimental conditions because nitrogen replaces an equal volume of air. Therefore, the differences in the overall suppression effect of nitrogen foam on flame intensification mainly stem from the dilution effect.
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| 4. |
- Li, Ying Zhen, et al.
(författare)
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Influence of tunnel slope on smoke control
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The critical velocity and backlayering length in sloped tunnels are investigated by numerical simulations using FDS. Simulation in two full-scale tunnels, with negative slopes ranging up to -18 % and heat release rates from 5 to 100 MW were carried out.The results show that NFPA 502 equation significantly overestimates the effect of negative slopes.The equation proposed by Atkinson and Wu is found to be in closer agreement with the results. A simplified correlation, i.e. Eq. (12), is proposed and recommended for practical use.The previous correlation for dimensionless backlayering length, Eq. (3), is valid for tunnels of various slopes and aspect ratios, and can be used for prediction of backlayering length.
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