A hypersonic vehicle is a key competitive equipment direction of world aerospace power, and its aerodynamic design faces multiple technical challenges. This paper focuses on three key technical issues related to the aerodynamic design of a hypersonic vehicle, such as high lift -to-drag ratio aerodynamic design, prediction of the complicated physical effects in hypersonic flow around a body, and the ground-to-flight correlation of aerodynamic characteristics. Research progress is reviewed from the perspectives of the design method, prediction method, flow mechanism, and engineering applications. The technical difficulties in the engineering realization of a high lift -to -drag ratio waverider configuration, such as loading space and longitudinal stability, are analyzed with respect to the aerodynamic design. For the complex flow physics and prediction method, this paper summarizes the significance of key issues, including the boundary-layer transition, surface ablation, high-temperature real gas effect, and rare gas
As the conductive channel, undoped channel hole polysilicon (poly-Si) plays a significant role in 3D NAND. Two important properties i.e. grain size and step coverage (S/C) of undoped channel hole poly-Si have attracted great attentions in practical manufacturing. The grain size affects the mobility of conductive poly-Si film and large grain size usually leads to high mobility. The step coverage influences the subthreshold swing (SS) and improved step coverage leads to small SS. In this paper, during the growth of poly-Si, the influence of different deposition conditions, such as temperature and gas source ratio between Si2H6 and SiH4, on the grain size and step coverage is investigated comprehensively. Grain size and step coverage are characterized using by Transmission Electron Microscope (TEM) and Precession Electron Diffraction (PED). It is found that as the decrease of deposition temperature, both the grain size and step coverage are improved. Compared to gas source SiH4, the employment of Si2H6 is beneficial in achieving large grain size to some degree and no further improvement can be obtained when the flow of Si2H6 is increased to a certain value. However, as-deposited poly-Si exhibits poorer step coverage using Si2H6 in contrast to SiH4.
Abstract-Multi-agent planning is a difficult, yet under investigated class of planning problems. In the cooperative assumption, agents plan to achieve their individual goals independently, communicate with each other by continually sending and receiving messages from other agents. However, finding a globally consistent plan requires agents to interact with each other, which is time-consuming. In this paper, we describe a general framework that extracts the graph structure from causal constraints between agents in solving multi-agent planning problems to reduce the effort of repeatedly searching agents' consistent local plans and we theoretical analytically show that our approach can efficiently solve multi-agent planning problems with very complicated coupling level.
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