Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle ...Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle on the coatings were investigated by orthogonal experiment. It is found that the thickness of coatings increases with the increase of voltage and duty cycle, but decreases with the increase of frequency. The structure and morphology of the coatings also depend on voltage, frequency and duty cycle. The coatings become more porous and crack with increasing voltage and duty cycle. The coating is thin and transparent when the voltage is lower than 120 V. The corrosion resistances of different coatings were evaluated by polarization curves and electrochemical impedance spectroscopy （EIS） in 3.5% NaCl （mass fraction） solution. When the optimized values of voltage, frequency and duty cycle are 140 V, 2 000 Hz and 0.4, respectively, the anodic coating shows the best corrosion resistance.展开更多
O437 2000042574外加交变电场对光折变基频空间电荷场瞬态特性的影响=Effect of external applied alternating fieldon transients behaviour of fundamental harmonicof photorefractive space-charge field[刊,中]/周忠祥,冯玉文,姜...O437 2000042574外加交变电场对光折变基频空间电荷场瞬态特性的影响=Effect of external applied alternating fieldon transients behaviour of fundamental harmonicof photorefractive space-charge field[刊,中]/周忠祥,冯玉文,姜永远,孙秀冬,许克彬(哈尔滨工业大学应用物理系.黑龙江,哈尔滨(150001))//光学学报.—1999,19(12).—1608—1614利用"跳跃模型"讨论外加交变电场对光折变基频空间电荷场建立的影响,给出了空间电荷场基频分量时间、外加交流电场振幅频率等变化的通解表达式。发现基频空间电荷场虚部和实部的振荡频率分别是外加交流电场振荡频率的2倍和1倍。当外加交变电场频率较大时光折变光栅是相移型的。这和基于"带导模型"展开更多
The development status of the variable speed system of large power AC(alternating current)motor drive in China is introduced.The large power AC drive fed by AC-AC converters(cycloconverters)has developed greatly,and s...The development status of the variable speed system of large power AC(alternating current)motor drive in China is introduced.The large power AC drive fed by AC-AC converters(cycloconverters)has developed greatly,and some innovations on the theory and engineering technique have been realized.They have been applied to rolling mills,mine hoists,and so on,and remarkable economic and social benefit has been achieved.The development of AC drive fed by large power IGCT(integrated gate commutated thyristors)AC-DC-AC converter is also introduced.It has excellent performance and reliable operation,and has been used in traction.展开更多
基金Project (50801056) supported by the National Natural Science Foundation of ChinaProject (2005DKA10400-Z20) supported by the National R&D Infrastructure and Facility Development Program of ChinaProject supported by the Zijin Project of Zhejiang University, China
文摘Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle on the coatings were investigated by orthogonal experiment. It is found that the thickness of coatings increases with the increase of voltage and duty cycle, but decreases with the increase of frequency. The structure and morphology of the coatings also depend on voltage, frequency and duty cycle. The coatings become more porous and crack with increasing voltage and duty cycle. The coating is thin and transparent when the voltage is lower than 120 V. The corrosion resistances of different coatings were evaluated by polarization curves and electrochemical impedance spectroscopy （EIS） in 3.5% NaCl （mass fraction） solution. When the optimized values of voltage, frequency and duty cycle are 140 V, 2 000 Hz and 0.4, respectively, the anodic coating shows the best corrosion resistance.
文摘O437 2000042574外加交变电场对光折变基频空间电荷场瞬态特性的影响=Effect of external applied alternating fieldon transients behaviour of fundamental harmonicof photorefractive space-charge field[刊,中]/周忠祥,冯玉文,姜永远,孙秀冬,许克彬(哈尔滨工业大学应用物理系.黑龙江,哈尔滨(150001))//光学学报.—1999,19(12).—1608—1614利用"跳跃模型"讨论外加交变电场对光折变基频空间电荷场建立的影响,给出了空间电荷场基频分量时间、外加交流电场振幅频率等变化的通解表达式。发现基频空间电荷场虚部和实部的振荡频率分别是外加交流电场振荡频率的2倍和1倍。当外加交变电场频率较大时光折变光栅是相移型的。这和基于"带导模型"
文摘The development status of the variable speed system of large power AC(alternating current)motor drive in China is introduced.The large power AC drive fed by AC-AC converters(cycloconverters)has developed greatly,and some innovations on the theory and engineering technique have been realized.They have been applied to rolling mills,mine hoists,and so on,and remarkable economic and social benefit has been achieved.The development of AC drive fed by large power IGCT(integrated gate commutated thyristors)AC-DC-AC converter is also introduced.It has excellent performance and reliable operation,and has been used in traction.
