It has been believed for about one hundred years that the cavitation directly induces the cavitation erosion. It is proposed in this research that cavitation is only the necessary condition but not the sufficient cond...It has been believed for about one hundred years that the cavitation directly induces the cavitation erosion. It is proposed in this research that cavitation is only the necessary condition but not the sufficient condition of the cavitation erosion. The experiment performed on the rotary disk cavitation system shows that the micro-particles in the fluid play indispensable roles in the cavitation erosion process, and the generation of the erosion pits on the steel surface is also affected by the particles' size. These cracks and deformations on the sample surface indicate that the erosion is the result of the mechanical behavior. Numerical calculations are also provided to support this mechanism.展开更多
La0.8Ba0.2MnO3 nano-particles were synthesized by sol-gel process, and the crystal structure and morphology were characterized by XRD and SEM, respectively. The complex permittivity and permeability were determined by...La0.8Ba0.2MnO3 nano-particles were synthesized by sol-gel process, and the crystal structure and morphology were characterized by XRD and SEM, respectively. The complex permittivity and permeability were determined by microwave vector network analyzer in the frequency range of 2-18 GHz. The relationship between reflection coefficient and microwave frequency of La0.8Ba0.2 MnO3 was calculated based on measured data. The results show that the average diameter of La0.8Ba0.2MnO3 crystal powders is about 80 nm and the crystal structure is perovskite when being calcined at 800 ℃ for 2 h. The microwave absorbing peak is 13 dB at 6.7 GHz and the effective absorbing bandwidth above 10 dB reaches 1.8 GHz for the sample with the thickness of 2.6 mm. The microwave absorption can be attributed to both the dielectric loss and the magnetic loss from the loss tangents of the sample, but the former is greater than the latter.展开更多
Indoor Air Quality(IAQ)“室内空气质量”这一概念,盛行于90年代。对于“空气污染”一词,一般人直觉认为只是室外空气污染问题,但是,一个您长期忽略的问题:室内空气的污染正严重地影响我们的健康。 事实上,我们无法完全避免来自住家环...Indoor Air Quality(IAQ)“室内空气质量”这一概念,盛行于90年代。对于“空气污染”一词,一般人直觉认为只是室外空气污染问题,但是,一个您长期忽略的问题:室内空气的污染正严重地影响我们的健康。 事实上,我们无法完全避免来自住家环境及工作场合中污染源的侵袭。科学家和空气净化专家正努力研究如何以最有效的方式,净化室内空气污染。展开更多
基金the National Natural Science Foundation of China (Grant Nos. 50675112, 50475018 and 50505020)
文摘It has been believed for about one hundred years that the cavitation directly induces the cavitation erosion. It is proposed in this research that cavitation is only the necessary condition but not the sufficient condition of the cavitation erosion. The experiment performed on the rotary disk cavitation system shows that the micro-particles in the fluid play indispensable roles in the cavitation erosion process, and the generation of the erosion pits on the steel surface is also affected by the particles' size. These cracks and deformations on the sample surface indicate that the erosion is the result of the mechanical behavior. Numerical calculations are also provided to support this mechanism.
基金Project(05JT1034) supported by the Planned Item of Science and Technology of Hunan Province, China
文摘La0.8Ba0.2MnO3 nano-particles were synthesized by sol-gel process, and the crystal structure and morphology were characterized by XRD and SEM, respectively. The complex permittivity and permeability were determined by microwave vector network analyzer in the frequency range of 2-18 GHz. The relationship between reflection coefficient and microwave frequency of La0.8Ba0.2 MnO3 was calculated based on measured data. The results show that the average diameter of La0.8Ba0.2MnO3 crystal powders is about 80 nm and the crystal structure is perovskite when being calcined at 800 ℃ for 2 h. The microwave absorbing peak is 13 dB at 6.7 GHz and the effective absorbing bandwidth above 10 dB reaches 1.8 GHz for the sample with the thickness of 2.6 mm. The microwave absorption can be attributed to both the dielectric loss and the magnetic loss from the loss tangents of the sample, but the former is greater than the latter.
文摘Indoor Air Quality(IAQ)“室内空气质量”这一概念,盛行于90年代。对于“空气污染”一词,一般人直觉认为只是室外空气污染问题,但是,一个您长期忽略的问题:室内空气的污染正严重地影响我们的健康。 事实上,我们无法完全避免来自住家环境及工作场合中污染源的侵袭。科学家和空气净化专家正努力研究如何以最有效的方式,净化室内空气污染。
