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Signal Detection of Large Volume Airgun Source Excitation in the Fixed Field of the Yangtze River 被引量:4
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作者 Xu Jiajun Cai Huiteng +3 位作者 Jin Xing Wang Shanxiong Xia Ji Li Pei 《Earthquake Research in China》 CSCD 2016年第3期418-429,共12页
As this is the first time a large volume airgun has been excited in the "Yangtse River Geoscience Project",it is necessary to study the time-frequency characteristic based on the linear stacked seismic data ... As this is the first time a large volume airgun has been excited in the "Yangtse River Geoscience Project",it is necessary to study the time-frequency characteristic based on the linear stacked seismic data from records from portable stations near the fixed fields and seismic stations. Airgun signal propagation distances were detected using stacked seismic data to analyze the environmental impact on signal propagation distance. The results showed that:( 1) the airgun signal produced by bubble pulses,pressure pulses and the surface wave can be received by a portable station near the fixed field;( 2) the dominant frequency of a bubble at 5Hz or so can be received by both near-field stations and far-field stations,pressure pulses rapidly weaken and the dominant frequency bands get narrower as epicentral distance increases;( 3) the longest spread distance of signal is 260 km,the nearest is 180 km,and the signal can travel further in the evening. 展开更多
关键词 Large volume airgun Excited in fixed field Time-frequency characteristics Signal detection
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Coupled extension and thickness-twist vibrations of lateral field excited AT-cut quartz plates 被引量:1
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作者 Ting-Feng Ma Rong-Xing Wu +4 位作者 Ji Wang Jian-Ke Du Li-Li Yuan Fa-Peng Yu Chao Xie 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2014年第1期67-72,共6页
In this paper, the coupled extension and thickness- twist vibrations are studied for AT-cut quartz plates under Lateral Field Excitation (LFE) with variations along the x1- direction. Mindlin's two-dimensional equa... In this paper, the coupled extension and thickness- twist vibrations are studied for AT-cut quartz plates under Lateral Field Excitation (LFE) with variations along the x1- direction. Mindlin's two-dimensional equations are used for anisotropic crystal plates. Both free and electrically forced vibrations are considered. Important vibration characteristics are obtained, including dispersion relations, frequency spectra, and motional capacitances. It is shown that, to avoid the effects of the couplings between extension and thickness-twist vibrations, a series of discrete values of the length/thickness ratio of the crystal plate need to be excluded. The results are of fundamental significance for the design of LFE resonators and sensors. 展开更多
关键词 Lateral field excitation - Resonators QUARTZ Thickness-twist vibrations
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Lateral field excitation properties of langasite single crystal
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作者 马廷锋 张超 +1 位作者 冯冠平 江小宁 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第8期597-603,共7页
In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational... In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation (LFE) on langasite substrate, namely the (yxl)65° (pure-LFE mode), (yxl)45° (quasi-LFE mode), and (yxl)0° (pseudo-LFE mode). Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the (yxl)65° langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, (yxl)0° langasite LFE device is also found suitable for liquid phase sensing applications. 展开更多
关键词 lateral field excitation LANGASITE bulk acoustic wave
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Properties study of LiNbO_3 lateral field excited device working on thickness extension mode
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作者 张志甜 张超 +3 位作者 王文炎 马廷锋 刘岩 冯冠平 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第9期584-589,共6页
This paper investigates the properties of thickness extension mode excited by lateral electric field on LiNbO3 by using the extended Christoffel-Bechmann method. It finds that the lateral field excitation coupling fac... This paper investigates the properties of thickness extension mode excited by lateral electric field on LiNbO3 by using the extended Christoffel-Bechmann method. It finds that the lateral field excitation coupling factor for amode (quasi-extensional mode) reaches its maximum value of 28% on Xmcut LiNbO3. The characteristics of a lateral field excitation device made of X-cut LiNbO3 have been investigated and the lateral field excitation device is used for the design of a high frequency ultrasonic transducer. The time and frequency domain pulse/echo response of the LiNbO3 lateral field excitation ultrasonic transducer is analysed with the modified Krimholtz-Leedom-Matthae model and tested using traditional pulse/echo method. A LiNbO3 lateral field excitation ultrasonic transducer with the centre frequency of 33.44 MHz and the -6 dB bandwidth of 33.8% is acquired, which is in good agreement with the results of the Krimholtz-Leedom-Matthae model. Further analysis suggests that the LiNbO3 lateral field excitation device has great potential in the design of broadband high frequency ultrasonic transducers. 展开更多
关键词 lateral field excitation high frequency ultrasonic transducer LiNb03 thickness extension mode
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Gravitational Field Excitation from the First Term of Quantum Wilson Loop
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作者 SHAO Liang SHAO Dan +2 位作者 SHAO Chang-Gui H. Noda CHEN Yi-Han 《Communications in Theoretical Physics》 SCIE CAS CSCD 2006年第1X期77-86,共10页
In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation (order k^4) of gravitational field, which is giv... In 4-dimensional R-gravity, using the linear and square terms of the expanding expression of the space-time connection, we calculate the possible curvature excitation (order k^4) of gravitational field, which is given by the first term of quantum Wilson loop (w) through two-point Green's function of the connection. At the same time using the tree diagram propagators of gravitons, the lowest order (k^4) correction to (w) is also calculated through the graviton self-energy in the term. Under the accuracy condition up to order k^4, we have obtained a complete expression of the excitation contributed from the leading term (w^(2))of (w). 展开更多
关键词 excitation of gravitational field graviton self-energy correction complete expression of excitation of order k^4 in (w^(2))
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IMPROVEMENT OF EXPRESSION FOR EXCITATION BY AN ELECTRIC DIPOLE IN GTEM CELL
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作者 Ren Liehui Chen Zhiyu (institute of Electronics, Chinese Academy of Sciences, Beijing 100080) 《Journal of Electronics(China)》 2002年第1期94-98,共5页
On the basis of Wilson's work in which the vertical electric dipole is centrally located in GHz Transverse ElectroMagnetic (GTEM) cell, we deduce the expression for the field distribution excited by an electric di... On the basis of Wilson's work in which the vertical electric dipole is centrally located in GHz Transverse ElectroMagnetic (GTEM) cell, we deduce the expression for the field distribution excited by an electric dipole in the case that the dipole is not centrally located. It will be useful for EMC measurements using GTEM cell. 展开更多
关键词 Excitation field Electric dipole GTEM cell
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Design of Braunbeck Coil for Nuclear Magnetic Resonance Gyro Magnetic Field Excitation 被引量:1
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作者 WANG Pei LIU Hua +3 位作者 CHENG Xiang ZHAO Wanliang LI Shaoliang CHENG Yuxiang 《Journal of Shanghai Jiaotong university(Science)》 EI 2018年第6期740-745,共6页
For generating a uniform and steady magnetic field, Helmholtz coil is extensively used in nuclear magnetic resonance gyro(NMRG). Unfortunately, the volume of Helmholtz coil makes it inconvenient to miniaturize NMRG. T... For generating a uniform and steady magnetic field, Helmholtz coil is extensively used in nuclear magnetic resonance gyro(NMRG). Unfortunately, the volume of Helmholtz coil makes it inconvenient to miniaturize NMRG. This study introduces Braunbeck coil that can be used in magnetic field excitation system. Braunbeck coil can produce homogeneous magnetic field within a limit space, and occupy a small volume. In addition, this study presents mathematical expressions that can be used to calculate the area of uniform magnetic field. Experimental test verifies the effectiveness of the proposed design, and the results accord closely with the actual simulation. 展开更多
关键词 Braunbeck coil finite element simulation Helmholtz coil magnetic field excitation magnetic uniform area nuclear magnetic resonance gyro(NMRG)
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Interior noise field of a viscoelastic cylindrical shell excited by TBL pressure fluctuations:Ⅰ.Production mechanisms of the noise
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作者 TANG Weilin and WU Yi (Harbin Engineering University Harbin 150001) 《Chinese Journal of Acoustics》 1997年第4期289-300,共12页
Applying the wavenumber frequency transfer function to describe the whole system including tht elastic cylindrical shell and the fluid loading, a general expression of the cross spectrum of the interior noise induced ... Applying the wavenumber frequency transfer function to describe the whole system including tht elastic cylindrical shell and the fluid loading, a general expression of the cross spectrum of the interior noise induced by the TBL (turbulent boundary layer) pressure fiuctuations is derived. There are two production mechanisms of the noise: one is direct transfer of the convective ridge of the pressure fluctuations through the shell, the other is the reradiation of resonance modes excited by the pressure fluctuations. At low frequencies the noise produced by the latter mechanism is dominant. Solving the frequency equation of the cylindrical shell with liquid loading, the two Stoneley-type poles in the complex K plane are presented. They are the major sources of the reradiation of shell at low frequencies. Finally, effects of the shell radius, shell thickness, absorption of material and the flow speeds on the noise reduction are computed by numerical iniegration. 展开更多
关键词 Production mechanisms of the noise Am Interior noise field of a viscoelastic cylindrical shell excited by TBL pressure fluctuations TBL
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Interior noise field of a viscoelastic cylindrical shell excited by TBL pressure fluctuations:Ⅱ. finite hydrophone and array
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作者 WU Yi TANG Weilin(Harbin Engineering University Harbin 150001) 《Chinese Journal of Acoustics》 1998年第1期14-23,共10页
Finite hydrophone and hydrophone array are the wave vector filter and can re-duce the flow noise. In this paper the responses of the cylindrical area hydrophone and two-circular area hydrophone within viscoelastic cyl... Finite hydrophone and hydrophone array are the wave vector filter and can re-duce the flow noise. In this paper the responses of the cylindrical area hydrophone and two-circular area hydrophone within viscoelastic cylindrical shell to the TBL (turbulent boundary layer) pressure fluctuations are investigated. Applying the method based on the wavenumber frequency spectrum analysis, the expressions of 1) the noise power spectrum of a single hy-drophone; 2) the space correlation of two hydrophones; 3) the noise power spectrum of array are derived. The dependencies of the noise reduction on hydrophone shape, dimension, element amount and separation of hydrophones of array are calculated by numerical integration. The wide-band and narrow-band correlation for two hydrophones is also calculated. The numerical results show that hydrophone array can effectively reduce the interior noise. 展开更多
关键词 Interior noise field of a viscoelastic cylindrical shell excited by TBL pressure fluctuations finite hydrophone and array TBL
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