AIS系统是一种工作在海上甚高频的船舶自动识别系统,ASM是包含在VDES下的特殊应用报文的通道,二者被用于实现海上船舶通信、船舶航行避碰等。针对AIS和ASM通信设备对实时处理能力的需求,采用FPGA和DSP共同合作的方法,实现了AIS与ASM的...AIS系统是一种工作在海上甚高频的船舶自动识别系统,ASM是包含在VDES下的特殊应用报文的通道,二者被用于实现海上船舶通信、船舶航行避碰等。针对AIS和ASM通信设备对实时处理能力的需求,采用FPGA和DSP共同合作的方法,实现了AIS与ASM的多信道实时接收解调,通过信号源进行地面测试,测试结果证明,该解调系统可以同时解调四个AIS信道和两个ASM信道的信息,且AIS的灵敏度为-119 d Bm,ASM的灵敏度为-116 d Bm。展开更多
The stability of the flow in the vaneless diffuser of a centrifugal compressor is studied with the linear theory. The characteristics of direct and adjoint perturbation modes are investigated,and the receptivity of th...The stability of the flow in the vaneless diffuser of a centrifugal compressor is studied with the linear theory. The characteristics of direct and adjoint perturbation modes are investigated,and the receptivity of the instability mode to momentum forcing or mass injection is identified based on the adjoint modes. Analysis shows that the perturbation with the largest amplitude is located at the outlet of the vaneless diffuser, while the highest-receptivity region is located in the middle of the vaneless diffuser along the radial direction. The large difference between the direct and adjoint modes indicates that the instability mechanism cannot be identified from a study of either eigenmode separately. Therefore, the structural sensitivity analysis is adopted to study the feedback of the instability mode. The structural sensitivity of the eigenvalue which is proportional to the perturbation pressure and velocity is used to explain the mechanism of flow control for the vaneless diffuser.展开更多
文摘AIS系统是一种工作在海上甚高频的船舶自动识别系统,ASM是包含在VDES下的特殊应用报文的通道,二者被用于实现海上船舶通信、船舶航行避碰等。针对AIS和ASM通信设备对实时处理能力的需求,采用FPGA和DSP共同合作的方法,实现了AIS与ASM的多信道实时接收解调,通过信号源进行地面测试,测试结果证明,该解调系统可以同时解调四个AIS信道和两个ASM信道的信息,且AIS的灵敏度为-119 d Bm,ASM的灵敏度为-116 d Bm。
文摘The stability of the flow in the vaneless diffuser of a centrifugal compressor is studied with the linear theory. The characteristics of direct and adjoint perturbation modes are investigated,and the receptivity of the instability mode to momentum forcing or mass injection is identified based on the adjoint modes. Analysis shows that the perturbation with the largest amplitude is located at the outlet of the vaneless diffuser, while the highest-receptivity region is located in the middle of the vaneless diffuser along the radial direction. The large difference between the direct and adjoint modes indicates that the instability mechanism cannot be identified from a study of either eigenmode separately. Therefore, the structural sensitivity analysis is adopted to study the feedback of the instability mode. The structural sensitivity of the eigenvalue which is proportional to the perturbation pressure and velocity is used to explain the mechanism of flow control for the vaneless diffuser.
