In order to use electron beam as a movable welding heat source and whose energy distribution along its moving trace can be controlled, a method of electron beam scanning track and scanning mode control was put forward...In order to use electron beam as a movable welding heat source and whose energy distribution along its moving trace can be controlled, a method of electron beam scanning track and scanning mode control was put forward. Based on it, the electron beam scanning track and scanning mode can be edited at will according to actual requirements, and the energy input of each point of the scanning track can be controlled. In addition, the scanning frequency and points control, real time adjusting of the scanning track etc. were explained. This method can be used in electron beam brazing, surface modification, surface heat treatment etc.展开更多
The emergence of Zhang Heng's seismoscope has a profound historical background. This paper intends to explore the formation and material basis of Zhang Heng's scientific thought. It appears that the simple int...The emergence of Zhang Heng's seismoscope has a profound historical background. This paper intends to explore the formation and material basis of Zhang Heng's scientific thought. It appears that the simple intention of "observing visions and distinguishing good fortune or misfortune"was his motivation to develop the seismoscope. Tracing its historical background,the authors proposed in this paper that the development of this seismoscope started around 128 A. D., and based on perceptual knowledge, two ideas about earthquakes came into being,i. e.,earthquake location could be judged according to the instrument shaking direction, and the earthquake and earth split were essentially different. In the instrument manufacture,Zhang Heng advocated a principle of "making utensils to imitate cosmos". By this principle,the following three problems were readily solved: the seismoscope imitated the response of the suspension system to earthquakes( i. e. natural seismoscope). Technically,the trigger mechanism of the latch was used for reference,and it recorded the physical evidence of earthquake occurrence by an ingenious way of a ball dropping from a dragon's mouth. The solution of these three key problems lead to the emergence of the seismoscope in 132 A. D. and the successful detection of an earthquake in 134 A. D. His invention deepened humanity's knowledge of natural laws, and promoted the development of science and technology in that time and later.展开更多
Using the photon closed orbit theory, the spontaneous emission rate of a polarized atom in a medium between two parallel mirrors is derived and calculated. It is found that the spontaneous emission rate of a polarized...Using the photon closed orbit theory, the spontaneous emission rate of a polarized atom in a medium between two parallel mirrors is derived and calculated. It is found that the spontaneous emission rate of a polarized atom between the mirrors is related to the atomic position and the polarization direction. The results show that in the vicinity of the mirror, the variation of the spontaneous emission rate depends crucially on the atomic polarization direction. With the increase of the polarization angle, the oscillation in the spontaneous emission rate becomes decreased. For the polarization direction parallel to the mirror plane, the oscillation is the greatest; while for the perpendicular polarization direction, the oscillation is nearly vanished. The agreement between our result and the quantum electrodynamics result suggests the correctness of our calculation. This study further verifies that the atomic spontaneous emission process can be effectively controlled by changing the polarization orientation of the atom.展开更多
This paper presents a statistically refined Bouc-Wen model of tri-axial interactions for the identification of structural systems under tri-directional seismic excitations. Through limited vibration measurements in th...This paper presents a statistically refined Bouc-Wen model of tri-axial interactions for the identification of structural systems under tri-directional seismic excitations. Through limited vibration measurements in the National Center for Research on Earthquake Engineering in Taiwan conducting model-based experiments, the 3-D Bouc-Wen model has been statistically and repetitively refined using the 95% confidence interval of the estimated structural parameters to determine their statistical significance in a multiple regression setting. When the parameters＇ confidence interval covers the ＂null＂ value, it is statistically sustainable to truncate such parameters. The remaining parameters will repetitively undergo such parameter sifting process for model refinement until all the parameters＇ statistical significance cannot be further improved. The effectiveness of the refined model has been shown considering the effects of sampling errors, of coupled restoring forces in tri-directions, and of the under-over-parameterization of structural systems. Sifted and estimated parameters such as the stiffness, and its corresponding natural frequency, resulting from the identification methodology developed in this study are carefully observed for system vibration control.展开更多
基金Commission of Science Technology and In-dustry for National Defense Project:Electron beam brazing tech-nology research ( 4 13 183 2 3 )
文摘In order to use electron beam as a movable welding heat source and whose energy distribution along its moving trace can be controlled, a method of electron beam scanning track and scanning mode control was put forward. Based on it, the electron beam scanning track and scanning mode can be edited at will according to actual requirements, and the energy input of each point of the scanning track can be controlled. In addition, the scanning frequency and points control, real time adjusting of the scanning track etc. were explained. This method can be used in electron beam brazing, surface modification, surface heat treatment etc.
基金sponsored by the National Natural Science Foundation of China(40644019)the Special Found of Scientific Research Program for "The Optimization and Design for Reconstruction Models of Seismoscope",China Earthquake Administration
文摘The emergence of Zhang Heng's seismoscope has a profound historical background. This paper intends to explore the formation and material basis of Zhang Heng's scientific thought. It appears that the simple intention of "observing visions and distinguishing good fortune or misfortune"was his motivation to develop the seismoscope. Tracing its historical background,the authors proposed in this paper that the development of this seismoscope started around 128 A. D., and based on perceptual knowledge, two ideas about earthquakes came into being,i. e.,earthquake location could be judged according to the instrument shaking direction, and the earthquake and earth split were essentially different. In the instrument manufacture,Zhang Heng advocated a principle of "making utensils to imitate cosmos". By this principle,the following three problems were readily solved: the seismoscope imitated the response of the suspension system to earthquakes( i. e. natural seismoscope). Technically,the trigger mechanism of the latch was used for reference,and it recorded the physical evidence of earthquake occurrence by an ingenious way of a ball dropping from a dragon's mouth. The solution of these three key problems lead to the emergence of the seismoscope in 132 A. D. and the successful detection of an earthquake in 134 A. D. His invention deepened humanity's knowledge of natural laws, and promoted the development of science and technology in that time and later.
基金Supported by National Natural Science Foundation of China under Grant No. 10604045the University Science & Technology Planning Program of Shandong Province under Grant No. J09LA02the Discipline Construction Fund of Ludong University
文摘Using the photon closed orbit theory, the spontaneous emission rate of a polarized atom in a medium between two parallel mirrors is derived and calculated. It is found that the spontaneous emission rate of a polarized atom between the mirrors is related to the atomic position and the polarization direction. The results show that in the vicinity of the mirror, the variation of the spontaneous emission rate depends crucially on the atomic polarization direction. With the increase of the polarization angle, the oscillation in the spontaneous emission rate becomes decreased. For the polarization direction parallel to the mirror plane, the oscillation is the greatest; while for the perpendicular polarization direction, the oscillation is nearly vanished. The agreement between our result and the quantum electrodynamics result suggests the correctness of our calculation. This study further verifies that the atomic spontaneous emission process can be effectively controlled by changing the polarization orientation of the atom.
文摘This paper presents a statistically refined Bouc-Wen model of tri-axial interactions for the identification of structural systems under tri-directional seismic excitations. Through limited vibration measurements in the National Center for Research on Earthquake Engineering in Taiwan conducting model-based experiments, the 3-D Bouc-Wen model has been statistically and repetitively refined using the 95% confidence interval of the estimated structural parameters to determine their statistical significance in a multiple regression setting. When the parameters＇ confidence interval covers the ＂null＂ value, it is statistically sustainable to truncate such parameters. The remaining parameters will repetitively undergo such parameter sifting process for model refinement until all the parameters＇ statistical significance cannot be further improved. The effectiveness of the refined model has been shown considering the effects of sampling errors, of coupled restoring forces in tri-directions, and of the under-over-parameterization of structural systems. Sifted and estimated parameters such as the stiffness, and its corresponding natural frequency, resulting from the identification methodology developed in this study are carefully observed for system vibration control.
