在科学计算云服务环境中,出于安全和管理的角度考虑,客户端与计算节点间的数据传输需要经过多个中间服务器进行中转。为此,我们基于SFTP(Secure File Transfer Protocol)协议设计并实现了一个数据中转传输系统MCP,使用文件传输代理模式...在科学计算云服务环境中,出于安全和管理的角度考虑,客户端与计算节点间的数据传输需要经过多个中间服务器进行中转。为此,我们基于SFTP(Secure File Transfer Protocol)协议设计并实现了一个数据中转传输系统MCP,使用文件传输代理模式进行不落地式中转,实现经多个中间节点的数据中转传输,保证了数据访问的合法性和传输的安全性,数据传输进度可控,并且方便对外提供数据中转传输接口。理论分析和实际测试表明,MCP传输时间少于使用SFTP进行的落地式数据中转传输。展开更多
1国内首例终端到终端低轨卫星通信测试成功银河航天公司近日在灵犀03星上成功实现了国内首例终端到终端(Terminal to Terminal,T2T)低轨卫星通信测试。此项测试是指卫星地面终端之间直接通过卫星上的交换设备进行通信,无需经过地面信关...1国内首例终端到终端低轨卫星通信测试成功银河航天公司近日在灵犀03星上成功实现了国内首例终端到终端(Terminal to Terminal,T2T)低轨卫星通信测试。此项测试是指卫星地面终端之间直接通过卫星上的交换设备进行通信,无需经过地面信关站进行数据中转。在这样的工作模式中,由于省去了信关站中转的环节,通信时延可以降低50%,同时能提高整个系统的灵活性和可用性。展开更多
Joint loan guarantee contracts and mutual guarantee contracts among SMEs form the basis of SME guarantee networks. The expansion of these networks increases the fragility of a financial system as a result of the regio...Joint loan guarantee contracts and mutual guarantee contracts among SMEs form the basis of SME guarantee networks. The expansion of these networks increases the fragility of a financial system as a result of the regional and industrial risk contagion embedded within them. By providing a theoretical framework of a loan guarantee network, a method is proposed for calculating the amount of risk spillover caused by loan guarantees taking the perspective of the entire network. In addition,the route of risk contagion in guarantee networks is analyzed, revealing that when default risk shocks occur, risk contagion travels along the nodes not once but for several rounds and that the risk control of one firm cannot prevent these systemic risks. Therefore, a risk control scheme is designed based on the location and importance of firms in the network. Using data from a real guarantee network,we demonstrate that identifying the node locations of firms' in the guarantee network(including the coritivity and closeness of the firm) can help in understanding risk contagion mechanisms and preventing systemic credit risk before a crisis occurs.展开更多
The major source of loss in modem compressors is the secondary loss. Non-axisymmetric endwall profile contouring is now a well established design methodology in axial flow turbines. However, flow development in axial ...The major source of loss in modem compressors is the secondary loss. Non-axisymmetric endwall profile contouring is now a well established design methodology in axial flow turbines. However, flow development in axial compressors is differ from turbines, the effects of non-axisymmetric endwall to axial compressors requires flow analysis in detail. This paper presents both experimental and numerical data to deal with the application of a non-axisymmetric hub endwall in a high-subsonic axial-flow compressor. The aims of the experiment here were to make sure the numerically obtained flow fields is the physical mechanism responsible for the improvement in efficiency, due to the non-axisymmetric hub endwall. The computational results were first compared with avail- able measured data of axisymmetric hub endwall. The results agreed well with the experimental data for estima- tion of the global performance. The coupled flow of the compressor rotor with non-axisymmetric hub endwall was simulated by a state-of-the-art multi-block flow solver. The non-axisymmetric hub endwall was designed for a subsonic compressor rotor with the help of sine and cosine functions. This type of non-axisymmetric hub end- wall was found to have a significant improvement in efficiency of 0.45% approximately and a slightly increase for the total pressure ratio. The fundamental mechanisms of non-axisymmetric hub endwall and their effects on the subsonic axial-flow compressor endwall flow field were analyzed in detail. It is concluded that the non-axisymmetric endwall profiling, though not optimum, can mitigate the secondary flow in the vicinity of the hub endwall, resulting in the improvement of aerodynamic performance of the compressor rotor.展开更多
文摘在科学计算云服务环境中,出于安全和管理的角度考虑,客户端与计算节点间的数据传输需要经过多个中间服务器进行中转。为此,我们基于SFTP(Secure File Transfer Protocol)协议设计并实现了一个数据中转传输系统MCP,使用文件传输代理模式进行不落地式中转,实现经多个中间节点的数据中转传输,保证了数据访问的合法性和传输的安全性,数据传输进度可控,并且方便对外提供数据中转传输接口。理论分析和实际测试表明,MCP传输时间少于使用SFTP进行的落地式数据中转传输。
文摘1国内首例终端到终端低轨卫星通信测试成功银河航天公司近日在灵犀03星上成功实现了国内首例终端到终端(Terminal to Terminal,T2T)低轨卫星通信测试。此项测试是指卫星地面终端之间直接通过卫星上的交换设备进行通信,无需经过地面信关站进行数据中转。在这样的工作模式中,由于省去了信关站中转的环节,通信时延可以降低50%,同时能提高整个系统的灵活性和可用性。
基金supported by the National Nature Science Foundation of China under Grant Nos.71172186,71472148,71572144 and 71502138
文摘Joint loan guarantee contracts and mutual guarantee contracts among SMEs form the basis of SME guarantee networks. The expansion of these networks increases the fragility of a financial system as a result of the regional and industrial risk contagion embedded within them. By providing a theoretical framework of a loan guarantee network, a method is proposed for calculating the amount of risk spillover caused by loan guarantees taking the perspective of the entire network. In addition,the route of risk contagion in guarantee networks is analyzed, revealing that when default risk shocks occur, risk contagion travels along the nodes not once but for several rounds and that the risk control of one firm cannot prevent these systemic risks. Therefore, a risk control scheme is designed based on the location and importance of firms in the network. Using data from a real guarantee network,we demonstrate that identifying the node locations of firms' in the guarantee network(including the coritivity and closeness of the firm) can help in understanding risk contagion mechanisms and preventing systemic credit risk before a crisis occurs.
基金Financial supports for the work presented are provided by National Natural Science Foundation of China (Project No: 50806073)China Postdoctoral Science Foundation (Project No: 20070420068)K C Wong Education Foundation, these supports are greatly appreciated
文摘The major source of loss in modem compressors is the secondary loss. Non-axisymmetric endwall profile contouring is now a well established design methodology in axial flow turbines. However, flow development in axial compressors is differ from turbines, the effects of non-axisymmetric endwall to axial compressors requires flow analysis in detail. This paper presents both experimental and numerical data to deal with the application of a non-axisymmetric hub endwall in a high-subsonic axial-flow compressor. The aims of the experiment here were to make sure the numerically obtained flow fields is the physical mechanism responsible for the improvement in efficiency, due to the non-axisymmetric hub endwall. The computational results were first compared with avail- able measured data of axisymmetric hub endwall. The results agreed well with the experimental data for estima- tion of the global performance. The coupled flow of the compressor rotor with non-axisymmetric hub endwall was simulated by a state-of-the-art multi-block flow solver. The non-axisymmetric hub endwall was designed for a subsonic compressor rotor with the help of sine and cosine functions. This type of non-axisymmetric hub end- wall was found to have a significant improvement in efficiency of 0.45% approximately and a slightly increase for the total pressure ratio. The fundamental mechanisms of non-axisymmetric hub endwall and their effects on the subsonic axial-flow compressor endwall flow field were analyzed in detail. It is concluded that the non-axisymmetric endwall profiling, though not optimum, can mitigate the secondary flow in the vicinity of the hub endwall, resulting in the improvement of aerodynamic performance of the compressor rotor.
