No economic crisis in China in the near future, a possibility of a hard landing for China's economy, and non-performing assets in Chinese banks will continue to rise. These are the predictions of Ben Bernanke, Cha...No economic crisis in China in the near future, a possibility of a hard landing for China's economy, and non-performing assets in Chinese banks will continue to rise. These are the predictions of Ben Bernanke, Chairman of the U.S. Federal Reserve, as reported by Reuters on September 2. Whether his predictions are accurate or not remains to be seen. It is beneficial, however, to analyze the reasons why Bernanke made these remarks and examine the facts. Zuo Xiaolei, Chief Economist of China Galaxy Securities ...展开更多
In practical situations, large machinery is usually placed in an underwater vessel and changes the acoustic enclosure shape into an irregular one. The existence of machinery causes the difficulties in expressing sound...In practical situations, large machinery is usually placed in an underwater vessel and changes the acoustic enclosure shape into an irregular one. The existence of machinery causes the difficulties in expressing sound transmission and radiation analytically. In this study, the sound radiation of a cylindrical shell excited by an internal acoustic source is modeled and analyzed. The cylindrical shell contains a machine modeled as a rectangular object, which is attached to a shell with a spring-mass system. The acoustic field of the cavity is computed by the integro-modal approach. The effect of object size on the coupling between acoustic mode and structural mode is investigated. The relationship between object volume and sound radiation is also studied. Numerical results show that the existence of objects inside vessels leads to a more effective coupling between the structure and acoustic enclosure than the existence of no objects in a regular-shaped cavity（i.e. empty vessel）.展开更多
为降低变速箱的振动噪声,提高整车噪声、振动与声振粗糙度(noise vibration harshness,NVH)性能,通过变速箱下线台架(end of line,EOL)振动测试和整车NVH测试,对比分析正常齿廓齿轮、带S形齿廓的齿轮对整车NVH性能的影响。EOL测试结果表...为降低变速箱的振动噪声,提高整车噪声、振动与声振粗糙度(noise vibration harshness,NVH)性能,通过变速箱下线台架(end of line,EOL)振动测试和整车NVH测试,对比分析正常齿廓齿轮、带S形齿廓的齿轮对整车NVH性能的影响。EOL测试结果表明:装配S形齿廓齿轮的变速箱的振动加速度级明显高于正常齿廓齿轮变速箱,尤其在48阶次处增幅最大。整车NVH测试结果表明,S形齿廓齿轮在发动机舱及车内的声压级分别增大12、7 dB。实际加工制造验证结果表明,正确设定齿轮加工珩磨轮寿命可以有效消除齿廓的S形波动,改善变速箱及整车的NVH性能。展开更多
文摘No economic crisis in China in the near future, a possibility of a hard landing for China's economy, and non-performing assets in Chinese banks will continue to rise. These are the predictions of Ben Bernanke, Chairman of the U.S. Federal Reserve, as reported by Reuters on September 2. Whether his predictions are accurate or not remains to be seen. It is beneficial, however, to analyze the reasons why Bernanke made these remarks and examine the facts. Zuo Xiaolei, Chief Economist of China Galaxy Securities ...
基金Project supported by the National Natural Science Foundation of China(Grant No.61601149)the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China(Grant No.IRT 16R17)
文摘In practical situations, large machinery is usually placed in an underwater vessel and changes the acoustic enclosure shape into an irregular one. The existence of machinery causes the difficulties in expressing sound transmission and radiation analytically. In this study, the sound radiation of a cylindrical shell excited by an internal acoustic source is modeled and analyzed. The cylindrical shell contains a machine modeled as a rectangular object, which is attached to a shell with a spring-mass system. The acoustic field of the cavity is computed by the integro-modal approach. The effect of object size on the coupling between acoustic mode and structural mode is investigated. The relationship between object volume and sound radiation is also studied. Numerical results show that the existence of objects inside vessels leads to a more effective coupling between the structure and acoustic enclosure than the existence of no objects in a regular-shaped cavity（i.e. empty vessel）.
