Underwater acoustic scattering echoes have time–space structures and are aliasing in time and frequency domains. Different series of echoes properties are not identified when incident angle is unknown. This article i...Underwater acoustic scattering echoes have time–space structures and are aliasing in time and frequency domains. Different series of echoes properties are not identified when incident angle is unknown. This article investigates variations in target echoes of monostatic sonar to address this problem. The mother wavelet with similar structures has been proposed on the basis of preprocessing signal waveform using matched filter, and the theoretical expressions between delay factor and incident angle are derived in the wavelet domain. Analysis of simulation data and experimental results in free-field pool show that this method can effectively separate geometrical scattering components of target echoes. The time delay estimation obtained from geometrical echoes at a single angle is consistent with target geometrical features, which provides a basis for object recognition without angle information. The findings provide valuable insights for analyzing elastic scattering echoes in actual ocean environment.展开更多
For the time-dependent harmonic oscillator and generalized harmonic oscillator with or without external forces in non-commutative space, wave functions, and geometric phases are derived using the Lewis-Riesenfeld inva...For the time-dependent harmonic oscillator and generalized harmonic oscillator with or without external forces in non-commutative space, wave functions, and geometric phases are derived using the Lewis-Riesenfeld invariant. Coherent states are obtedned as the ground state of the forced system. Quantum fluctuations are calculated too. It is seen that geometric phases and quantum fluctuations are greatly affected by the non-commutativity of the space.展开更多
Brian Swingle是斯坦福大学一名研究人员,当他还在MIT修读物质物理学专业研究生时,非常偶然的参加了几堂关于弦论的课程以丰富自己的学习经历。虽然开始时他很少留意课堂上碰到的一些概念,但随着学习的深入,他发觉自己的研究与黑洞物理...Brian Swingle是斯坦福大学一名研究人员,当他还在MIT修读物质物理学专业研究生时,非常偶然的参加了几堂关于弦论的课程以丰富自己的学习经历。虽然开始时他很少留意课堂上碰到的一些概念,但随着学习的深入,他发觉自己的研究与黑洞物理和量子引力的弦论方法之间竟然存在意外的高度相似。他的研究工作是使用张量网络来预测奇异材料的性质。＂我意识到它们之间有些深层的东西在起作用＂,他说道。张量出现在物理学的各个分支中,展开更多
基金Foundation item： Supported by the National Natural Science Foundation of China（Grant No.51279033） and Natural Science Foundation of Heilongjiang Province, China（Grant No.F201346 ）
文摘Underwater acoustic scattering echoes have time–space structures and are aliasing in time and frequency domains. Different series of echoes properties are not identified when incident angle is unknown. This article investigates variations in target echoes of monostatic sonar to address this problem. The mother wavelet with similar structures has been proposed on the basis of preprocessing signal waveform using matched filter, and the theoretical expressions between delay factor and incident angle are derived in the wavelet domain. Analysis of simulation data and experimental results in free-field pool show that this method can effectively separate geometrical scattering components of target echoes. The time delay estimation obtained from geometrical echoes at a single angle is consistent with target geometrical features, which provides a basis for object recognition without angle information. The findings provide valuable insights for analyzing elastic scattering echoes in actual ocean environment.
文摘For the time-dependent harmonic oscillator and generalized harmonic oscillator with or without external forces in non-commutative space, wave functions, and geometric phases are derived using the Lewis-Riesenfeld invariant. Coherent states are obtedned as the ground state of the forced system. Quantum fluctuations are calculated too. It is seen that geometric phases and quantum fluctuations are greatly affected by the non-commutativity of the space.
