External cooled exhaust gas recirculation (EGR) is drawing significant attention in downsized boosted spark ignition direct injection (SIDI) engines due to its potential to improve fuel economy. Meanwhile, worldwide emission standards pressure to reduce particle number (PN) emissions is generating great challenges for SIDI engine development. Thus it is necessary to examine the PN emission behaviors when implementing cooled EGR as a fuel-saving technology. In this study, the low-load with cold-engine (40 °C and 60 °C coolant temperature) and high-load with warm-engine (90 °C coolant temperature), representing high particle emission engine operating conditions over new European driving cycle, were chosen to understand the effects of cooled EGR on PN emissions in a downsized boosted SIDI gasoline engine using Horiba MEXA SPCS1000 PN measurement instrument. Measurements indicate that increasing cooled EGR levels provide higher PN emissions at low-load cold-engine operation, however, lower PN emissions at high-load warm-engine operation. This study, therefore, provides insight how cooled EGR impacts PN emissions under cold and warm engine operation.

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In a harsh environment, function aggregation of air–ground integrated network service function chaining (SFC) deployment can easily cause network load imbalance, which affects the network security and reliability. In this study, a task-similarity-based virtual network function (VNF) aggregation scheme was proposed. It considered air–ground network resource consumption and load balance before SFC mapping. A model for selecting VNFs to be aggregated based on task similarity was built. The tasks were classified based on their similarity. Furthermore, the VNFs to be aggregated were selected within the class under the constraints of the underlying physical resources. Load balancing was achieved by adjusting the similarity threshold. Moreover, an SFC mapping selection scheme based on network resource awareness was used to obtain the most suitable physical nodes for single-chain and multi-chain mapping according to various attributes of physical network nodes. The simulation results indicated that the proposed scheme with a better load balance design outperformed existing works on VNF aggregation. We also demonstrated that the task-similarity-based scheme was resource-consumption efficient and effective.

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