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The influence of reflections from the train body and the ground on the sound radiation from a railway rail

Railway Sciences 2024年第1期3卷 1-17页

作者： David J.Thompson Dong Zhao Evangelos Ntotsios Giacomo Squicciarini Ester Cierco Erwin Jansen Institute of Sound and Vibration Research University of SouthamptonSouthamptonUK Ingenierıa para el Control del Ruido SL BarcelonaSpain TNO Acoustics and Sonar Den HaagThe Netherlands

Purpose – The vibration of the rails is a significant source of railway rolling noise, often forming the dominantcomponent of noise in the important frequency region between 400 and 2000 Hz. The purpose of the paper is toinvestigate the influence of the ground profile and the presence of the train body on the sound radiation fromthe rail.Design/methodology/approach – Two-dimensional boundary element calculations are used, in which therail vibration is the source. The ground profile and various different shapes of train body are introduced in themodel, and results are observed in terms of sound power and sound pressure. Comparisons are also made withvibro-acoustic measurements performed with and without a train present.Findings – The sound radiated by the rail in the absence of the train body is strongly attenuated by shieldingdue to the ballast shoulder. When the train body is present, the sound from the vertical rail motion is reflectedback down toward the track where it is partly absorbed by the ballast. Nevertheless, the sound pressure at thetrackside is increased by typically 0–5 dB. For the lateral vibration of the rail, the effects are much smaller. Oncethe sound power is known, the sound pressure with the train present can be approximated reasonably well withsimple line source directivities.Originality/value – Numerical models used to predict the sound radiation from railway rails have generallyneglected the influence of the ground profile and reflections from the underside of the train body on the soundpower and directivity of the rail. These effects are studied in a systematic way including comparisons with measurements.

关键词： Rolling noise Sound radiation Railway track Boundary elements Ground reflections directivity

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Superdirective Circular Arrays of Electric and Huygens Dipole Elements

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Electromagnetic Science 2024年第1期2卷 38-62页

作者： Richard W Ziokowski TheUniversityofArizona TucsonAZ85721USA

Uniform circular arrays(UCAs)provide both omnidirectional(360°)and directive(sector)coverage of the azimuthal plane.Superdirective versions with unidirectional,high front-to-back ratio(FTBR)properties could provide the radiated field char-acteristics being pursued for NextG wireless networks and their perceived applications.Typical UCA configurations–full,semi-circular,and sector–that radiate vertically-polarized(VP)fields and are composed of either omnidirectional electric dipole ele-ments or unidirectional Huygens dipole elements are analyzed first with conventional methods as reference cases.These omni-and uni-directional element configurations are then treated with several optimization techniques:the classic Rayleigh-quotient(RQ)method and its unidirectional-constrained version;the eigenbeam decomposition and synthesis(EBDS)technique used to design su-perdirective acoustic receiving arrays;and the Bessel-azimuthal multipole(BEAM)approach developed herein.Several arrays are identified as being superdirective with extremely high FTBR values.The performance characteristics of the arrays of unidirectional elements are demonstrated to be superior in general.Moreover,it is shown that larger radius arrays with RQ-specified excitation amplitudes are robust to changes in them whereas the outcomes of the corresponding small radius versions are not.On the other hand,the BEAM-optimized densely-packed small-radius superdirective arrays are quite tolerant to those variations while generating unidirectional pseudo-needle beams.

关键词： directivity Huygens dipole antennas Multipoles Needle radiation Optimization Superdirective arrays Uniform circular arrays.

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Reproducing fling-step and forward directivity at near source site using of multi-objective particle swarm optimization and multi taper

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Earthquake Engineering and Engineering Vibration 2013年第4期12卷 529-540页

作者： A.Nicknam A.Hosseini H.Hamidi Jamnani M.A.Barkhordari School of Civil Engineering Iran University of Science & Technology

This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.

关键词： near-fault simulation fling step directivity multi-taper multi-objective algorithm MO-PSO

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Effect of seismic super-shear rupture on the directivity of ground motion acceleration

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Earthquake Engineering and Engineering Vibration 2013年第4期12卷 519-527页

作者： Hu Jinjun Xie Lili Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake Administration School of Civil Engineering and Architecture Harbin Institute of Technology

The effect of seismic super-shear rupture on the directivity of ground motions using simulated accelerations of a vertical strike-slip fault model is the topic of this study. The discrete wave number/finite element method was adopted to calculate the ground motion in the horizontal layered half space. An analysis of peak ground acceleration （PGA） indicates that similar to the sub-shear situation, directivity also exists in the super-shear situation. However, there are some differences as tbllows：（1） The PGA of the fault-normal component decreases with super-shear velocity, and the areas that were significantly affected by directivity in the PGA field changed from a cone-shaped region in the forward direction in a sub-shear situation to a limited near-fault region in a super-shear situation. （2） The PGA of the fault-parallel and vertical component is not as sensitive as the fault-normal component to the increasing super-shear velocity. （3） The PGA of the fault-normal component is not always greater than the fault-parallel component when the rupture velocity exceeds the shear wave velocity.

关键词： ground motion directivity rupture velocity super-shear rupture peak ground acceleration

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Response spectra for nuclear structures on rock sites considering the near-fault directivity effect

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Earthquake Engineering and Engineering Vibration 2010年第3期9卷 357-365页

作者： Xu Longjun Yang Shengchao Xie Lili Department of Civil Engineering Harbin Institute of Technology at Weihai Weihai 264209 China CCCC Highway and Bridge Consultants Co. Ltd. Beijing 100029 China

Near-fault ground motions, potentially with large amplitude and typical velocity pulses, may significantly impact the performance of a wide range of structures. The current study is aimed at evaluating the safety implications of the near-fault effect on nuclear power plant facilities designed according to the Chinese code. To this end, a set of near- fault ground motions at rock sites with typical forward-directivity effect is examined with special emphasis on several key parameters and response spectra. Spectral comparison of the selected records with the Chinese and other code design spectra was conducted. The bi-normalized response spectra in terms of different comer periods are utilized to derive nuclear design spectra. It is concluded that nuclear design spectra on rock sites derived from typical rupture directivity records are significantly influenced both by the earthquake magnitude and the rupture distance. The nuclear design spectra specified in the code needs to be adjusted to reflect the near-fault directivity effect of large earthquakes.

关键词： near-fault ground motion directivity response spectrum rock site nuclear design

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Influences of prolate spheroidal baffle of sound diffraction on spatial directivity of acoustic vector sensor

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Science China(Technological Sciences) 2010年第10期53卷 2846-2852页

作者： JI JianFei, LIANG GuoLong, WANG Yan & LIN WangSheng National Laboratory of Underwater Acoustic Technology, Harbin Engineering University, Harbin 150001, China National Laboratory of Underwater Acoustic Technology Harbin Engineering University Harbin China

The directivity of acoustic vector sensor (AVS) will be distorted by the sound diffraction of the AVS carrier. In this paper,the scattering of a plane acoustic wave from a prolate spheroid baffle is considered. At first,the sound diffraction of prolate spheroidal baffle is established,then the mathematical expressions of sound pressure field and particle vibration velocity field of sound diffraction are derived and the characteristic of the directivity of pressure and velocity of sound diffraction field at different frequencies and distances is analyzed. The directivity of AVS is determined by the amplitude and phase difference of diffraction wave and incident wave,which possesses a close relationship with frequency and incident angle. Finally,the calculated results are compared with the experimental results.

关键词： prolate spheroidal baffle sound diffraction field spatial directivity vector sensor

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Design of a High Power Directional Coupler with High directivity Used in the LHCD Launcher for EAST

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Plasma Science and Technology 2009年第6期11卷 739-743页

作者：张长虹刘甫坤杨津甫赵洪亮 Institute of Plasma Physics Chinese Academy of Sciences

A high power waveguide directional coupler was designed to measure the transmitted power and reflected power in the 4.6 GHz LHCD （lower hybrid current drive） launcher for the EAST tokamak. The design principle of the coupler is assessed. Further analysis is performed by CST （computer simulating test） and Ansoft HFSS （high frequency structure simulator） software and the optimal structural parameter is obtained. In addition, finite element code ANSYS is used to determine the temperature distribution in the coupler conductively cooled by forced water. The test results of a directional coupler manufactured according to the design are close to what is expected.

关键词： directional coupler directivity thermal analysis test

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directivity OPTIMIZATION OF CURVED SURFACE DIPOLE ANTENNAS

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Journal of Electronics(China) 1994年第4期11卷 322-331页

作者：王均宏任朗 Institute of EM Theory and Microwave Tech. Southwest Jiaotong University Chengdu 610031

Based on the calculation of the characteristic parameters by moment method, the curved surface dipoles are optimized by an optimization method, the maximum directivities of some V-curved and Gauss-curved surface dipol... 详细信息

关键词： Antennas Curved surface dipoles directivity Optimization Moment method

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Influences on the Spatial directivity of Acoustic Vector Sensor by Finite Cylinder Baffle and Future Prospects About Eliminating the Effects

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Journal of Shanghai Jiaotong university(Science) 2012年第4期17卷 436-446页

作者：嵇建飞梁国龙庞福滨张光普 National Laboratory of Underwater Acoustic Technology Harbin Engineering University

The directivity of acoustic vector sensor can be distorted by the sound diffraction wave of baffle.According to Helmholtz integral equation,the directivity of acoustic vector sensor under the condition of finite cylinder baffle is calculated by using boundary element method(BEM).Considering the problem of nearly singular integrals of BEM,the exponent parts of fundamental solutions are expanded in trigonometric functions.The singular and the nonsingular parts are separated:the nonsingular parts are calculated by Gaussian integral method;the singular parts are regularized by subsection integral method.Then the surface integrals are reduced into line integrals along the elements' contour which can be calculated by Gaussian integral method.The sound diffraction field of a plane wave under the condition of finite cylinder baffle at different frequencies and incident angles is calculated,and the characteristics of directivity of pressure and vibration velocity at different frequencies are analyzed.The experimental data are treated and the errors between the experimental and theoretical results are analyzed.Finally,according to the research results about the influences on the directivity of acoustic vector sensor by baffle at present,some future prospects about eliminating the effects of sound diffraction field by baffle are presented.

关键词： acoustic vector sensor boundary element method(BEM) spatial directivity regularization

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Low-radioactivity ultrasonic hydrophone used in positioning system for Jiangmen Underground Neutrino Observatory

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Nuclear Science and Techniques 2022年第6期33卷 102-113页

作者： Duo Teng Jiang-Lai Liu Guo-Lei Zhu Yue Meng Yuan-yuan Zhang Tao Zhang Kai Luo Rui Li Jia-Qi Hui School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an 710072China National Key Laboratory for Underwater Information Processing and Control Northwestern Polytechnical UniversityXi’an 710072China School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Tsung-Dao Lee Institute Shanghai Jiao Tong UniversityShanghai 200240China

To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The radioactivity of the proposed hydrophone is strictly controlled by selecting pure raw materials, especially active piezoelectric ceramics. The electroacoustic performance of the hydrophone is improved by making structural optimization. High sensitivity and aimed directivity are achieved using 33-mode piezoelectric ceramic rings arranged in series and improvement in the radiating head of the Tonpilz hydrophone, respectively. All electroacoustic performances are studied through finite element analyses.The simulations indicate that the electroacoustic performances of the hydrophones in linear alkylbenzene-based liquid scintillator can be approximately predicted according to the results in water because their differences caused by two types of acoustic media, water and liquid scintillator, are known. The tests show that the hydrophone prototype can achieve a maximum sensitivity of-209.3dB and a beamwidth of 132.2° at a frequency of 143 kHz.In addition, eight hydrophones only contributed to a background radioactivity level of 26 ± 4 mHz in the neutrino analysis.

关键词： JUNO Liquid scintillator Tonpilz hydrophone Low radioactivity Sensitivity directivity Finite element

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