A gate valve is one of the main elements of a circular pipeline, but the flow characteristics around the gate valve are hardly known. In this study, clarification of the flow field in front of the gate valve model in ...A gate valve is one of the main elements of a circular pipeline, but the flow characteristics around the gate valve are hardly known. In this study, clarification of the flow field in front of the gate valve model in a pipe flow via flow visualization and PIV analysis was attempted. As a result, four kinds of steady necklace-type vortex systems, 2-vortex, 4-vortex, 6-vortex and 8-vortex systems, were clearly observed in a Reynolds number between 290 and 2130. In addition, the main vortex was observed in the Reynolds number range between 2130 and 4870 with difficulty. On this account, both the center position and vorticity in the main vortex are presented against Reynolds number.展开更多
Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous rese...Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).展开更多
文摘A gate valve is one of the main elements of a circular pipeline, but the flow characteristics around the gate valve are hardly known. In this study, clarification of the flow field in front of the gate valve model in a pipe flow via flow visualization and PIV analysis was attempted. As a result, four kinds of steady necklace-type vortex systems, 2-vortex, 4-vortex, 6-vortex and 8-vortex systems, were clearly observed in a Reynolds number between 290 and 2130. In addition, the main vortex was observed in the Reynolds number range between 2130 and 4870 with difficulty. On this account, both the center position and vorticity in the main vortex are presented against Reynolds number.
基金Supported by the Support Program of the National 12th Five Year-Plan of China(2015BAK25B03)
文摘Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).
