| 1. |
- Li, Yajie, et al.
(författare)
-
Flexible RAN : Combining Dynamic Baseband Split Selection and Reconfigurable Optical Transport to Optimize RAN Performance
- 2020
-
Ingår i: IEEE Network. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0890-8044 .- 1558-156X. ; 34:4, s. 180-187
-
Tidskriftsartikel (refereegranskat)abstract
- The introduction of functional splits in C-RANs brings a tradeoff between radio performance and transport capacity. Higher-layer splits relax transport capacity requirements, whereas radio performance is not guaranteed. Lower-layer splits are beneficial for the radio performance, but they may require a more expensive and high capacity transport network. Facing the challenge of how to deploy 5G RANs in the short-term future, network operators need to find the best functional split options able to accommodate radio performance requirements without incurring excessive transport network costs. This article presents an architecture referred to as F-RAN able to choose the most appropriate split option while considering time-varying radio performance and the availability of transport resources. F-RAN can accommodate these needs by means of an SDN-based orchestration layer and a programmable optical transport network. The performance of F-RAN is benchmarked against a conventional C-RAN architecture in terms of the number of wavelengths and transponders to be deployed. Simulation results confirm the overall benefits of F-RAN in terms of better utilization of transport resources.
|
|
| 2. |
- Zhao, Shengzhong, et al.
(författare)
-
A theoretical and experimental study on the buoyancy-driven smoke flow in a tunnel with vertical shafts
- 2019
-
Ingår i: International journal of thermal sciences. - : Elsevier BV. - 1290-0729 .- 1778-4166. ; 141, s. 33-46
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a series of small-scale experiments was carried out in a model scale tunnel with dimensions of 20 m (Length) × 2 m (Width) × 1 m (Height) to investigate the characteristics of buoyancy-driven smoke flow in a tunnel with vertical shafts. Different shaft settings and four different longitudinal ventilation velocities were tested in the experiments. A theoretical model for the mass flow rate of buoyancy-driven smoke flow in the shaft was developed and validated. The gas temperature along the tunnel ceiling and smoke stratification were subsequently analyzed and discussed. The results showed that more shafts, greater shaft heights and greater shaft cross sectional areas can significantly increase the smoke extraction rate, and the total smoke mass flow rate in the shafts increases with the increasing ventilation velocity. The local pressure loss coefficient at the shaft inlet may not be a fixed value. An average value of 1.0 for this coefficient was recommended for engineering estimation and design of rectangular-shaped natural shafts. The presence of vertical shaft is beneficial to the smoke stratification and could increase the height of the smoke layer interface, especially for the downstream of the shaft.
|
|
| 3. |
|
|
| 4. |
- Zhao, Z., et al.
(författare)
-
CFD simulation of soot generation during biomass gasification in a cyclone gasifier
- 2024
-
Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 364
-
Tidskriftsartikel (refereegranskat)abstract
- Soot generation is a challenging issue in high-temperature biomass gasification, which reduces the biomass conversion rate and leads to contamination of the reactor. To provide new means and insights to optimize gasification processes, the soot generation during biomass gasification in a cyclone reactor is studied here by establishing a novel biomass gasification and soot formation model to improve the accuracy attainable in numerical predictions of spatio-temporal soot evolution. The new method is validated by comparing it with gasification experiments in two reactor configurations. A good performance in capturing the overall soot generation and light gas yield of the current model is obtained in the simulations of an entrained flow reactor compared with experimental data. Besides, the biomass gasification behavior in this entrained flow reactor is systematically studied by reviewing the tar, precursor, and soot mass fraction evolution in the reactor under different steam/carbon ratios, gasification temperatures, and air excess ratios with the new model. Furthermore, the influence of varying air equivalence ratios, the operation temperature and the fuel moisture on the soot generation in a cyclone gasifier, as well as the ability of the proposed model to reflect such influences, are also discussed. Numerical simulations demonstrate the existence of an optimal operation condition for the cyclone gasifier in terms of the soot generation. The current work thus provides a useful tool for analyzing the mechanism of soot formation at the reactor scale.
|
|
