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High-order Bragg forward scattering and frequency shift of low-frequency underwater acoustic field by moving rough sea surface

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Chinese Physics B 2024年第3期33卷 459-470页

作者：莫亚枭张朝金鹿力成孙启航马力 Key Laboratory of Underwater Acoustic Environment Institute of AcousticsChinese Academy of Sciences (CAS)Beijing 100190China China State Shipbuilding Corporation Systems Engineering Research Institute Beijing 100094China Little Bird Co. LtdBeijing 100089China

Acoustic scattering modulation caused by an undulating sea surface on the space-time dimension seriously affects underwater detection and target ***,underwater acoustic scattering modulation from a moving rough sea surface is studied based on integral equation and parabolic *** with the principles of grating and constructive interference,the mechanism of this acoustic scattering modulation is *** periodicity of the interference of moving rough sea surface will lead to the interference of the scattering field at a series of discrete angles,which will form comb-like and frequency-shift characteristics on the intensity and the frequency spectrum of the acoustic scattering field,respectively,which is a high-order Bragg scattering *** the conventional Doppler effect,the frequency shifts of the Bragg scattering phenomenon are multiples of the undulating sea surface frequency and are independent of the incident sound wave ***,even if a low-frequency underwater acoustic field is incident,it will produce obvious frequency ***,under the action of ideal sinusoidal waves,swells,fully grown wind waves,unsteady wind waves,or mixed waves,different moving rough sea surfaces create different acoustic scattering processes and possess different frequency shift *** the swell wave,which tends to be a single harmonic wave,the moving rough sea surface produces more obvious high-order scattering and frequency *** same phenomena are observed on the sea surface under fully grown wind waves,however,the frequency shift slightly offsets the multiple peak frequencies of the wind wave *** with the swell and fully-grown wind waves,the acoustic scattering and frequency shift are not obvious for the sea surface under unsteady wind waves.

关键词： high-order Bragg scattering frequency shift low-frequency acoustic field moving rough sea surface

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Coupled vibrations and frequency shift of compound system consisting of quartz crystal resonator in thickness-shear motions and micro-beam array immersed in liquid

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Applied Mathematics and Mechanics(English Edition) 2015年第2期36卷 225-232页

作者： Xuan XIE Lingcheng KONG Yuxi WANG Jun ZHANG Yuantai HU Department of Mechanics Huazhong University of Science and Technology

The dynamic characteristics of a quartz crystal resonator（QCR） in thicknessshear modes（TSM） with the upper surface covered by an array of micro-beams immersed in liquid are studied. The liquid is assumed to be inviscid and incompressible for simplicity. Dynamic equations of the coupled system are established. The added mass effect of liquid on micro-beams is discussed in detail. Characteristics of frequency shift are clarified for different liquid depths. Modal analysis shows that a drag effect of liquid has resulted in the change of phase of interaction（surface shear force）, thus changing the system resonant frequency. The obtained results are useful in resonator design and applications.

关键词： quartz crystal resonator(QCR) micro-beam modal analysis frequency shift added mass of liquid

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Measurement of ^(129)Xe frequency shift due to Cs–^(129)Xe collisions

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Chinese Physics B 2014年第6期23卷 170-176页

作者：房建成万双爱陈瑶 School of Instrument Science and Opto-Electronics Engineering Beihang University

Enhancement factor K0, which characterizes NMR and EPR frequency shifts for Cs-129Xe, is measured for the first time. The enhancement factor r-o was measured to be （702±41） at 80 ℃ and （653±20） at 90 ℃, using the NMR frequency shift, detected by atomic magnetometer at a low magnetic field of 100 nT. This result is useful for predicting the EPR frequency shifts for Cs and the NMR frequency shifts for 129Xe in spin-exchange cells.

关键词： Cs-129Xe frequency shift atomic magnetometer

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Type WYZ-97 Eighteen information Noninsulate frequency shift Automatic Blocking System

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High Technology Letters 2000年第3期6卷 38-39页

作者：陈志龙 Harbin Inst of Technology Harbin China

Type WYZ 97 eighteen information noninsulate frequency shift automatic blocking system is the most advanced railroad signaling system in China *** article introduced its principles,technical targets,features and the a... 详细信息

关键词： frequency shift Automatic blocking Noninsulate Eighteen information

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TWO COMPONENT LDV SYSTEM WITH DUAL-DIFFERENTIAL ACOUSTO-OPTICAL frequency shift AND ITS APPLICATIONS

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Acta Mechanica Sinica 1986年第1期2卷 81-92页

作者： Shen Xiong Zhang Jingyi Wang Zongsen Yu Hesheng (Department of Engineering Mechanics,Tsinghua University) Department of Engineering Mechanics Tsinghua University Beijing China

This paper describes the main properties of the two component LDV systemdeveloped with the dual-differential frequency shift *** has the advantages ofmultiple functions,better *** high utilization of *** it offers as a completetechnique and method for measuring 2-D complex *** applying this system,2-D turbulentseparated flow measurements have been made in a duct with an asymmetrical suddenexpansion and in a wind tunnel flow over a 2-D *** Reynolds numbers were at 5900 and 4500respectively.

关键词： laser doppler velocimetry frequency shift two component

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frequency shift and pulse compression of an ultrashort pulse in a large-amplitude plasma wave

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Chinese Journal of Lasers 1992年第4期 27-33页

作者： Zhengming Sheng, Zhizhan Xu, Jinxiu Ma, Wei Yu(Shanghai Institute of Optics and Fine Mechanics,Academia sinica, Shanghai 201800, China)

By calculating the momenta of a coupled set of nonlinear equations of laserpulse-plasma wave interaction in the weak relativistic approximation,the conditions for fre-quency up-shift have been *** the energy change of the pulse due to frequency shiftis compensated by the change of plasma wave energy results in photon number *** factors that affect the frequency up-shift are *** is also found that the laser pulsecan be compressed when it is located near the valley of plasma density perturbation and ifsome threshold value of the plasma wave field is exceeded.

关键词： frequency shift pulse compression ultrashort laser pulse plasma wave

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Effect of strain-gradients of surface micro-beams on frequency-shift of a quartz crystal resonator under thickness-shear vibrations

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Acta Mechanica Sinica 2015年第5期31卷 647-652页

作者： Ling-Cheng Kong Yuan-Tai Hu Department of Mechanics Huazhong University of Science and Technology

With introduction of the first-order strain-gradient of surface micro-beams into the energy density function,we developed a two-dimensional dynamic model for a compound quartz crystal resonator（QCR） system,consisting of a QCR and surface micro-beam *** frequency shift that was induced by micro-beams with consideration of strain-gradients is discussed in detail and some useful results are obtained,which have important significance in resonator design and applications.

关键词： Micro-beams Strain-gradient Quartz crystal resonator frequency shift

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Measurement of frequency shift Characteristics Based on LiNbO_3 Waveguide Electro-Optic Intensity Modulator

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Journal of Electronic Science and Technology of China 2008年第4期6卷 449-452页

作者： Zhou Meng Hui-Juan Zhou Yi Liao Qiong Yao College ofOptoelectronic Science and Engineering National University of DefenseTechnology Changsha Hunan 410073 China

High-speed and wide-band LiNbO3 waveguide electro-optic intensity modulator has drawn great attention in the field of optical fiber communication and sensor. This paper reports the research results on the measurement of frequency shift characteristics of Mach-Zehnder electro-optic intensity modulator. Two measurement methods of frequency shift characteristics for high and low frequency modulations are studied in theory and experiment and demonstrate different results. The realization of a multi-wavelength optical source based on Mach-Zehnder electro-optic intensity modulator has been introduced. The technique to reach the maximum intensity for interesting shift frequency, particularly for heterodyne detection of Brillouin distributed optical fiber sensing, has been given.

关键词： Brillouin electro-optic intensity modulator frequency shift LiNbO3.

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Modulation Depth Based on frequency-shift Characteristic of LiNbO3 Waveguide Electro-optic Intensity Modulator

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Journal of Measurement Science and Instrumentation 2010年第2期1卷 125-128页

作者：周会娟孟洲廖毅 College of Optoelectronic Science and Engineering National University of Defense Technology

The modulation depth, defined according to practical modulation results, which changes with the microwave power and its frequency, is significant for systems utilizing the frequency-shift characteristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator （EOIM）. By analyzing the impedance mismatch between the microwave source and the EOIM, the effective voltage applied to the RF port of the EOIM is deprived from the microwave power and its frequency. Associating with analyses of the phase velocity mismatch between the microwave and the optical wave, the theoretical modulation depth has been obtained, which is verified by experimental results. We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias for the system based on the frequency-shift characteristic of the EOIM.

关键词： waveguide electro-optic intensity modulator modulation depth frequency shift distributedBriiouin optical fiber sensing

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Development of Raman acousto-optic frequency shifter based on SAW

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Journal of Semiconductors 2014年第8期35卷 104-109页

作者：王春梅温志渝张祖伟张颖异 Key Laboratory of Fundamental Science on Micro/Nano-Device and System Technology Chongqing University National Center for International Research of Micro/Nano-System and New Material Technology Chongqing University Microsystem Research Center of Chongqing University

A Raman acousto-optic frequency shifter （AOFS） based on surface acoustic wave （SAW） is presented. It consists of a double-ended SAW resonator and optical waveguide system. The structure parameters of the SAW resonator are optimized using COM software and the optical waveguide system is designed using an effective index method. The AOFS prototype fabricated using MEMS technology is detected. The optical beat signals su- perimposed by ± 1st-order and ±2nd-order diffracted beams are detected. The frequency shift of 78.2201 MHz related to the 1 st-order diffracted beams and 156.2306 MHz related to the 2nd-order diffracted beams are obtained respectively.

关键词： SAW Raman AOFS frequency shift

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