The role of the microalloying process in relaxation behavior and crystallization evolution of Zr_(20) Cu_(20) Ni_(20) Ti_(20) Hf_(20) high entropy bulk metallic glass(HEBMG) was investigated. We selected Al and Nb ele...The role of the microalloying process in relaxation behavior and crystallization evolution of Zr_(20) Cu_(20) Ni_(20) Ti_(20) Hf_(20) high entropy bulk metallic glass(HEBMG) was investigated. We selected Al and Nb elements as minor elements, which led to the negative and positive effects on the heat of mixing in the master HEBMG composition, respectively. According to the results, both elements intensified β relaxation in the structure;however, α relaxation remained stable. By using different frequencies in dynamic mechanical analysis, it was revealed that the activation energy of β relaxation for the Nb-added sample was much higher, which was due to the creation of significant structural heterogeneity under the microalloying process. Moreover, it was found that Nb addition led to a diversity in crystallization stages at the supercooled liquid region.It was suggested that the severe structural heterogeneity in the Nb-added sample provided multiple energy-level sites in the structure for enhancing the crystallization stages.展开更多
Noise Frequency Modulated (NFM) interference causes a disaster to almost all types of Radar systems. The echo signal and the interference are overlapped and because of strong energy of the NFM interference noth-ing co...Noise Frequency Modulated (NFM) interference causes a disaster to almost all types of Radar systems. The echo signal and the interference are overlapped and because of strong energy of the NFM interference noth-ing could be detected except the interference in the Radar receiver system. Up to now no good method against NFM has been declared, conventional methods are based on the passive Radar to track the interfer-ence source which are not applicable under most conditions. Here a novel anti-noise FM method is proposed to suppress the NFM interference, the method multiply the mixed signal two times by different reference signals. The principle and some key factors of the new method are analyzed in detail and some rules for pa-rameters designing are given. What’s more, results show that the method can eradicate NFM effectively.展开更多
文摘The role of the microalloying process in relaxation behavior and crystallization evolution of Zr_(20) Cu_(20) Ni_(20) Ti_(20) Hf_(20) high entropy bulk metallic glass(HEBMG) was investigated. We selected Al and Nb elements as minor elements, which led to the negative and positive effects on the heat of mixing in the master HEBMG composition, respectively. According to the results, both elements intensified β relaxation in the structure;however, α relaxation remained stable. By using different frequencies in dynamic mechanical analysis, it was revealed that the activation energy of β relaxation for the Nb-added sample was much higher, which was due to the creation of significant structural heterogeneity under the microalloying process. Moreover, it was found that Nb addition led to a diversity in crystallization stages at the supercooled liquid region.It was suggested that the severe structural heterogeneity in the Nb-added sample provided multiple energy-level sites in the structure for enhancing the crystallization stages.
文摘Noise Frequency Modulated (NFM) interference causes a disaster to almost all types of Radar systems. The echo signal and the interference are overlapped and because of strong energy of the NFM interference noth-ing could be detected except the interference in the Radar receiver system. Up to now no good method against NFM has been declared, conventional methods are based on the passive Radar to track the interfer-ence source which are not applicable under most conditions. Here a novel anti-noise FM method is proposed to suppress the NFM interference, the method multiply the mixed signal two times by different reference signals. The principle and some key factors of the new method are analyzed in detail and some rules for pa-rameters designing are given. What’s more, results show that the method can eradicate NFM effectively.
