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1.
Broadband topological valley-projected edge-states transport in composite structure phononic crystal 下载免费PDF全文
Hong-Yong Mao 《中国物理 B》2021,30(8):84302-084302
The topological valley transport, realized in phononic crystals, has aroused tremendous interest in these years. Many previous researches have further promoted the development of this transport phenomenon. Crucially, the bandwidth of the valley-projected edge mode has been an essential research topic. As is well known, the broadband will improve the adaptability of the acoustic edge-states, which will be more conducive to the transmission of information. Therefore, in this paper, we present a composite structure, composed of the atoms with different shapes forming a hexagonal lattice, which can achieve larger bandwidth than a single structure. Meanwhile, the results demonstrate that the topological protected edge states are also observed in our structure. Furthermore, the backscattering suppressions from associated valley-protected edge states under certain perturbations have also been investigated and demonstrated. Our work can provide a new idea for designing acoustic devices based on valley degree of freedom. 相似文献
2.
<正>We present a novel method for realizing double-image encryption algorithm by combining the images in different transform domains.Two original images are encrypted into two interim images by fractional Fourier transform and gyrator transform,respectively.The two encrypted images can be obtained by means of the addition and subtraction of the two interim images.This is defined as a double-image sharing scheme,in which the original images are encrypted into two parts.The original images cannot be recovered only with any one of the two interim images.Numerical simulation experiments demonstrate the validity of the algorithm. 相似文献
3.
Excitation of defect modes from the extended photonicband-gap structures of 1D photonic lattices 下载免费PDF全文
This paper stuides numerically the model equation in a one dimensional defective photonic lattice by modifying the potential function to a periodic function. It is found that defect modes (DMs) can be regarded as Bloch modes which are excited from the extended photonic band-gap structure at Bloch wave-numbers with k x = 0. The DMs for both positive and negative defects are considered in this method. 相似文献
4.
Detection accuracy of target accelerations based on vortex electromagnetic wave in keyhole space 下载免费PDF全文
The influence of the longitudinal acceleration and the angular acceleration of detecting target based on vortex electromagnetic waves in keyhole space are analyzed. The spectrum spreads of different orbital angular momentum(OAM)modes in different non-line-of-sight situations are simulated. The errors of target accelerations in detection are calculated and compared based on the OAM spectra spreading by using two combinations of composite OAM modes in the keyhole space. According to the research, ... 相似文献
5.
This paper investigates the generation of self-organized
surface structures on amorphous alloys by vortex femtosecond laser
pulses. The scanning electron microscope characterizations show that
the as-formed structures are periodic ripples, aperiodic ripples,
and `coral-like' structures. Optimal conditions for forming these
surface structures are determined in terms of pulses number at a
given pulse energy. The applicable mechanism is suggested to
interpret the formation and evolution of the `coral-like'
structures. 相似文献
6.
7.
Size-dependent nonlinear absorption and refraction of Ag nanoparticles excited by femtosecond lasers 下载免费PDF全文
Silver (Ag) nanoparticles with different average sizes are prepared, and the nonlinear absorption and refraction of these nanoparticles are investigated with femtosecond laser pulses at 800 nm. The smallest Ag nanoparticles show insignificant nonlinear absorption, whereas the larger ones show saturable absorption. By considering the previously reported positive nonlinear absorption of 9 nm Ag nanoparticles, the nonlinear absorptions of Ag nanoparticles are found to be size-dependent. All these nonlinear absorptions can be compatibly explained from the viewpoints of electronic transitions, energy bands and electronic structures in the conduction band of Ag nanoparticles. The nonlinear refraction is attributed to the effect of hot electrons arising from the intraband transition in the s–p conduction band of Ag nanoparticles. 相似文献
8.
We investigate the dynamics of strongly localized solitons trapped in remote troughs of radially periodic lattices with Kerr-type self-focusing nonlinearity. The rotary motion of solitons is found to be more stable for larger nonlinear wavenumbers, lower rotating velocity, and shorter radius of the trapping troughs. When the lattice is shrunk or expanded upon propagation, the solitons can be trapped in the original trough and move outward or inward, with their rotating linear velocity inversely proportional to the radius of the trapping troughs. 相似文献
9.
Superposition of orbital angular momentum of photons by a combined computer-generated hologram fabricated in silica glass with femtosecond laser pulses 下载免费PDF全文
This paper introduces a novel method to realize the superposition of orbital angular momentum of photons by combined computer-generated hologram (CCGH) fabricated in silica glass with femtosecond laser pulses. Firstly, the two computer-generated holograms (CGH) of optical vortex were obtained and combined as a CCGH according to the design. Then the CCGH was directly written inside glass by femtosecond laser pulses induced microexplosion without any preor post-treatment of the material. The vortex beams with different vortex topological charges (including new topological charges) have been restructured using a collimated He-Ne laser beam incidence to the CCGH normally. A theoretical and experimental explanation has been presented for the generations of the new topological charges. 相似文献
10.
战场电磁环境日益复杂、多变,对武器装备的正常使用带来很大影响。针对其中影响最剧烈的有源干扰,分别联系时域、频域和能量域三个方面对其进行分析,提出定量描述干扰的方法。通过能谱图结合能量计算公式的方式完成了对压制干扰的表征,通过相关性算法以及提出的频谱重叠度概念完成了对欺骗干扰的表征。同时,基于Simulink/Matlab仿真的结果分别验证了所提出的几种表征方法具有一定的有效性与可行性,该定量描述方法对于战场电磁环境的评估具有参考意义。 相似文献