A compact low noise single frequency linearly polarized distributed Bragg reflector(DBR)fiber laser based on a 1.4-cm-long homemade Er^(3+)/Yb^(3+)-codoped phosphate single mode glass fiber has been demonstrated.An ov...A compact low noise single frequency linearly polarized distributed Bragg reflector(DBR)fiber laser based on a 1.4-cm-long homemade Er^(3+)/Yb^(3+)-codoped phosphate single mode glass fiber has been demonstrated.An over 50 mW stable single frequency linearly polarized fiber laser was achieved.The measured slope efficiency is more than 21.6%,and the signal-to-noise ratio(SNR)is higher than 65 dB and the laser linewidth is less than 2.0 kHz.The laser RIN is measured to be less than-150 dB/Hz at the frequencies over 2.0 MHz,and the obtained linear polarization extinction ratio(LPER)is more than 30 dB.展开更多
With the impetus of the WTO and the further opening of China＇s international service trade in education, this paper is based on the background of China＇s national strategy ＂one belt ＆ one road＂, analyzing Guangzh...With the impetus of the WTO and the further opening of China＇s international service trade in education, this paper is based on the background of China＇s national strategy ＂one belt ＆ one road＂, analyzing Guangzhou higher education, its internationalization driving force and popularization value, ranging from the perspectives of higher education resources excess, the domestic university funding cuts, and the transnational education services output in developed countries to alleviate its school funds shortage to further introduction of foreign high-quality educational resources due to not fully meeting the requirements of domestic demand in developing and less developed countries, with expectation to promote the development of education internationalization healthily and orderly.展开更多
为探索脉冲爆轰水冲压发动机水下工作时导水器内燃气射流发展特性,利用可燃气体的爆轰在水下受限空间内产生脉动气泡,对爆轰管在圆筒形受限空间内的水下爆轰燃气射流进行了数值仿真与实验验证。基于雷诺时均基本方程组与k-ε两方程模型...为探索脉冲爆轰水冲压发动机水下工作时导水器内燃气射流发展特性,利用可燃气体的爆轰在水下受限空间内产生脉动气泡,对爆轰管在圆筒形受限空间内的水下爆轰燃气射流进行了数值仿真与实验验证。基于雷诺时均基本方程组与k-ε两方程模型耦合流体体积气液界面追踪方法的相输运方程建立受限空间中水下单次燃气射流流场流动模型,使用OpenFOAM中的Compressible Inter Foam求解器对受限空间中脉冲爆轰燃气射流进行数值求解。结果表明:受限空间对水下爆轰的前导激波的影响较小,前导激波幅值与自由空间相比变化不大,由爆轰燃气射流所引起的压力扰动大幅升高且持续时间明显增加,受限空间中各处压力显著高于受限空间之外;受限空间中燃气泡的脉动周期延长至60 ms左右,然而受限空间径向尺寸对燃气泡的脉动周期影响较小。可见,受限空间可提高水下爆轰管出口近场压力并延长燃气射流作用时间,研究结果对脉冲爆轰水冲压发动机推力性能提升方法研究具有重要指导作用。展开更多
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2011AA030203the National Natural Science Foundation of China under Grant Nos 11174085,U0934001 and 60977060+2 种基金the Guangdong Province and Hong Kong Invite Public Bidding Program(TC10BH07-1)the Science and Technology Project of Guangdong(2009A090100044,2009B091300127,cgzhzd0903,2011B090400055)the Fundamental Research Funds for the Central Universities(2012ZZ0002,2009ZG0005).
文摘A compact low noise single frequency linearly polarized distributed Bragg reflector(DBR)fiber laser based on a 1.4-cm-long homemade Er^(3+)/Yb^(3+)-codoped phosphate single mode glass fiber has been demonstrated.An over 50 mW stable single frequency linearly polarized fiber laser was achieved.The measured slope efficiency is more than 21.6%,and the signal-to-noise ratio(SNR)is higher than 65 dB and the laser linewidth is less than 2.0 kHz.The laser RIN is measured to be less than-150 dB/Hz at the frequencies over 2.0 MHz,and the obtained linear polarization extinction ratio(LPER)is more than 30 dB.
文摘With the impetus of the WTO and the further opening of China＇s international service trade in education, this paper is based on the background of China＇s national strategy ＂one belt ＆ one road＂, analyzing Guangzhou higher education, its internationalization driving force and popularization value, ranging from the perspectives of higher education resources excess, the domestic university funding cuts, and the transnational education services output in developed countries to alleviate its school funds shortage to further introduction of foreign high-quality educational resources due to not fully meeting the requirements of domestic demand in developing and less developed countries, with expectation to promote the development of education internationalization healthily and orderly.
文摘为探索脉冲爆轰水冲压发动机水下工作时导水器内燃气射流发展特性,利用可燃气体的爆轰在水下受限空间内产生脉动气泡,对爆轰管在圆筒形受限空间内的水下爆轰燃气射流进行了数值仿真与实验验证。基于雷诺时均基本方程组与k-ε两方程模型耦合流体体积气液界面追踪方法的相输运方程建立受限空间中水下单次燃气射流流场流动模型,使用OpenFOAM中的Compressible Inter Foam求解器对受限空间中脉冲爆轰燃气射流进行数值求解。结果表明:受限空间对水下爆轰的前导激波的影响较小,前导激波幅值与自由空间相比变化不大,由爆轰燃气射流所引起的压力扰动大幅升高且持续时间明显增加,受限空间中各处压力显著高于受限空间之外;受限空间中燃气泡的脉动周期延长至60 ms左右,然而受限空间径向尺寸对燃气泡的脉动周期影响较小。可见,受限空间可提高水下爆轰管出口近场压力并延长燃气射流作用时间,研究结果对脉冲爆轰水冲压发动机推力性能提升方法研究具有重要指导作用。
