Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic ...Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.展开更多
Hawking radiation of the stationary Kerr–de Sitter black hole is investigated using the relativistic Hamilton–Jacobi method. Meanwhile, extending this work to a non-stationary black hole using Dirac equations and ge...Hawking radiation of the stationary Kerr–de Sitter black hole is investigated using the relativistic Hamilton–Jacobi method. Meanwhile, extending this work to a non-stationary black hole using Dirac equations and generalized tortoise coordinate transformation, we derived the locations, the temperature of the thermal radiation as well as the maximum energy of the non-thermal radiation. It is found that the surface gravity and the Hawking temperature depend on both time and different angles. An extra coupling effect is obtained in the thermal radiation spectrum of Dirac particles which is absent from thermal radiation of scalar particles. Further, the chemical potential derived from the thermal radiation spectrum of scalar particle has been found to be equal to the highest energy of the negative energy state of the scalar particle in the non-thermal radiation for the Kerr–de Sitter black hole. It is also shown that for stationary black hole space time, these two different methods give the same Hawking radiation temperature.展开更多
针对当光伏板处于不均匀的太阳光照射时,产生发电效率低的问题,提出一种混沌哈里斯鹰算法与电导增量法结合的算法。哈里斯鹰算法引入Levy飞行函数和Henon混沌映射,在跟踪早期,扩大算法的搜索范围。再引入最优个体策略,可进一步减少算法...针对当光伏板处于不均匀的太阳光照射时,产生发电效率低的问题,提出一种混沌哈里斯鹰算法与电导增量法结合的算法。哈里斯鹰算法引入Levy飞行函数和Henon混沌映射,在跟踪早期,扩大算法的搜索范围。再引入最优个体策略,可进一步减少算法的迭代次数。该算法使系统更易跳出局部最大功率点,而在跟踪后期,算法精确运行在小范围内,提高了局部搜索能力。实验结果表明,电导增量法的加入缓解了系统位于全局最大功率点(GMPP:Global Maximum Power Point)附近时的功率振荡,稳定输出。展开更多
文摘Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.
文摘Hawking radiation of the stationary Kerr–de Sitter black hole is investigated using the relativistic Hamilton–Jacobi method. Meanwhile, extending this work to a non-stationary black hole using Dirac equations and generalized tortoise coordinate transformation, we derived the locations, the temperature of the thermal radiation as well as the maximum energy of the non-thermal radiation. It is found that the surface gravity and the Hawking temperature depend on both time and different angles. An extra coupling effect is obtained in the thermal radiation spectrum of Dirac particles which is absent from thermal radiation of scalar particles. Further, the chemical potential derived from the thermal radiation spectrum of scalar particle has been found to be equal to the highest energy of the negative energy state of the scalar particle in the non-thermal radiation for the Kerr–de Sitter black hole. It is also shown that for stationary black hole space time, these two different methods give the same Hawking radiation temperature.
文摘针对当光伏板处于不均匀的太阳光照射时,产生发电效率低的问题,提出一种混沌哈里斯鹰算法与电导增量法结合的算法。哈里斯鹰算法引入Levy飞行函数和Henon混沌映射,在跟踪早期,扩大算法的搜索范围。再引入最优个体策略,可进一步减少算法的迭代次数。该算法使系统更易跳出局部最大功率点,而在跟踪后期,算法精确运行在小范围内,提高了局部搜索能力。实验结果表明,电导增量法的加入缓解了系统位于全局最大功率点(GMPP:Global Maximum Power Point)附近时的功率振荡,稳定输出。
