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Tunable acoustic radiation pattern assisted by effective impedance boundary 被引量:1
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作者 钱枫 全力 +2 位作者 王力维 刘晓宙 龚秀芬 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第2期215-220,共6页
The acoustic wave propagation from a two-dimensional subwavelength slit surrounded by metal plates decorated with Helmholtz resonators (HRs) is investigated both numerically and experimentally in this work. Owing to... The acoustic wave propagation from a two-dimensional subwavelength slit surrounded by metal plates decorated with Helmholtz resonators (HRs) is investigated both numerically and experimentally in this work. Owing to the presence of HRs, the effective impedance of metal surface boundary can be manipulated. By optimizing the distribution of HRs, the asymmetric effective impedance boundary will be obtained, which contributes to generating tunable acoustic radiation pattern such as directional acoustic beaming. These dipole-like radiation patterns have high radiation efficiency, no finger- print of sidelobes, and a wide tunable range of the radiation pattern directivity angle which can be steered by the spatial displacements of HRs. 展开更多
关键词 effective impedance boundary acoustic radiation pattern Helmholtz resonator
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SOME PROPERTIES OF FAR FIELD PATTERNS OF ACOUSTIC WAVES IN AN INHOMOGENEOUS MEDIUM
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作者 程晋 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1990年第8期787-793,共7页
In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inver... In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method. 展开更多
关键词 SOME PROPERTIES OF FAR FIELD patternS OF acoustic WAVES IN AN INHOMOGENEOUS MEDIUM
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Multi-scale morphology analysis of acoustic emission signal and quantitative diagnosis for bearing fault 被引量:3
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作者 Wen-Jing Wang Ling-Li Cui Dao-Yun Chen 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2016年第2期265-272,共8页
Monitoring of potential bearing faults in operation is of critical importance to safe operation of high speed trains.One of the major challenges is how to differentiate relevant signals to operational conditions of be... Monitoring of potential bearing faults in operation is of critical importance to safe operation of high speed trains.One of the major challenges is how to differentiate relevant signals to operational conditions of bearings from noises emitted from the surrounding environment.In this work,we report a procedure for analyzing acoustic emission signals collected from rolling bearings for diagnosis of bearing health conditions by examining their morphological pattern spectrum(MPS) through a multi-scale morphology analysis procedure.The results show that acoustic emission signals resulted from a given type of bearing faults share rather similar MPS curves.Further examinations in terms of sample entropy and Lempel-Ziv complexity of MPS curves suggest that these two parameters can be utilized to determine damage modes. 展开更多
关键词 Bearing fault acoustic emission Morphological pattern spectrum(MPS) Sample entropy Lempel-Ziv complexity
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Pattern recognition of the acoustic Sea-bed Profiling——Records and sea-bed geological classification 被引量:1
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作者 JI Wenyun, LIN Yijun, ZHANG Shuying (Shanghai Acoustics Laboratory, Academia Sinica Shanghai 200032) (Marine Geology Laboratory, Tongji University Shanghai 200092) 《Chinese Journal of Acoustics》 2001年第3期213-223,共11页
The physical properties of pattern characteristics for typical Acoustic Sea-bed Profiling Records (ASPRs) in the area of Changjiang Estuary and the East China Sea are analyzed in this paper. Nine pattern characterist... The physical properties of pattern characteristics for typical Acoustic Sea-bed Profiling Records (ASPRs) in the area of Changjiang Estuary and the East China Sea are analyzed in this paper. Nine pattern characteristics are summarized and it was shown that 9 geological categories can be determined by 4 pattern characteristics. Based on the above analysis, a Bayes-based pattern characteristics classifier for interpretation of ASPRs is developed. 展开更多
关键词 In line pattern recognition of the acoustic Sea-bed Profiling
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Pattern recognition of acoustic sea-bed profiling records (An expert system based on the fuzzy set theory) 被引量:1
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作者 CAO Min and ZHANG Shuying(Shanghai Acoustics Lab., Academia Sinica Shanghai 200032) 《Chinese Journal of Acoustics》 1997年第1期39-46,共8页
An expert system based on the fuzzy set theory has been developed for geological interpretation of Acoustic Seabed Profiling Records(ASPR). After successively extracting each state of several main pattern characterist... An expert system based on the fuzzy set theory has been developed for geological interpretation of Acoustic Seabed Profiling Records(ASPR). After successively extracting each state of several main pattern characteristics shown on the ASPRs, the similarities between this pattern characteristic-state set and the standard ones corresponding to different geological categories of marine sediments are computed respectively By comparillg these values of sidrilarities, the conclusion of geological classification to the ASPR can be derived. 展开更多
关键词 pattern recognition of acoustic sea-bed profiling records An expert system based on the fuzzy set theory
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Parametric array differential Pattern time delay shift coding underwater acoustic communication in the under-ice environment 被引量:1
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作者 YIN Jingwei ZHANG Xiao +2 位作者 ZHU Guangping TANG Shengyu SUN Hui 《Chinese Journal of Acoustics》 CSCD 2016年第4期431-439,共9页
In order to meet the demands of underwater acoustic communication in under ice environment,a differential Pattern time delay shift coding underwater acoustic communication method based on parametric array is introduce... In order to meet the demands of underwater acoustic communication in under ice environment,a differential Pattern time delay shift coding underwater acoustic communication method based on parametric array is introduced in this paper.The under ice underwater acoustic channel is characterized by heavy multipath transmission.Under this model,a parametric array emission method of Pattern signal is derived and the system performance is analyzed.A broadband low frequency sound waves with narrow beam-pattern,which will reduce the interface reflections and suppress the effects of multipath transmission,can be obtained by the emission method.The Songhua River under ice trial results show that there is an anti-multipath property and a higher data rate in the under-ice acoustic channel in proposed approach. 展开更多
关键词 TIME LFM Parametric array differential pattern time delay shift coding underwater acoustic communication in the under-ice environment
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Pattern recognition of acoustic sea-bed profiling records(part 1: a dynamic reasoning expert system)
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作者 JI Wenyun, LIN Yijun, ZHANG Shuying (Shanghai Acoustics Laboratory, Academia Sinica Shanghai Shanghai 200032) 《Chinese Journal of Acoustics》 2001年第2期111-120,共10页
A computer-based pattern recognition systems has been developed for geological interpretation of Acoustic Sea-bed Profiling Records. Based on practical experience accumu- lated by specialists, the main pattern charact... A computer-based pattern recognition systems has been developed for geological interpretation of Acoustic Sea-bed Profiling Records. Based on practical experience accumu- lated by specialists, the main pattern characteristics of Acoustic Sea-bed Profiling Records (ASPRs) corresponding to typical geological categories of marine sediment layers in the area of the East China Sea have been expressed altogether in 9 aspects, and a dynamic reasoning expert system designed correspondingly. Starting from an initial premise Characteristic and makes the next step reasoning until the final conclusion (i.e. which geological category the sediment layer belongs to.) is derived, in the mean time, for quantitatively estimating the correctness of the final conclusions, the so-called certainty factor is calculated. 展开更多
关键词 part 1 pattern recognition of acoustic sea-bed profiling records a dynamic reasoning expert system HIE line
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Analytic study on acoustic interference pattern in shallow water
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作者 CHEN Shouhu ZHAO Lianjun +4 位作者 CAO Jianguo GAO Bing ZHU Mo HU Yuan MA Li 《Chinese Journal of Acoustics》 CSCD 2018年第1期18-34,共17页
Analytic formulas for acoustic interference patterns in shallow water are derived by ray method. Which can be used to guide acoustic measurements with limited horizontal distances. Some necessary approximations are ta... Analytic formulas for acoustic interference patterns in shallow water are derived by ray method. Which can be used to guide acoustic measurements with limited horizontal distances. Some necessary approximations are taken for a concise expression. The analytic for- mulas represent the quantitative relationships between the interference-pattern and the signal frequency, bandwidth, depth of source and horizontal distance. Monofrequent signals, com- plicated signals and frequency-modulated signals are all studied. Several inferences are also deduced from the formulas. Both numerical simulations and experiment data are presented to prove that these formulas and their inferences can describe the critical characters of the acoustic interference pattern in the waveguide with a satisfying precision. 展开更多
关键词 Analytic study on acoustic interference pattern in shallow water
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A study on pattern time delay shift coding underwater acoustic communication
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作者 HUI Junying LIU li +1 位作者 FENG Haihong LIU hong(Underwater Acoustics Institute, Harbin Engineering University Harbin 150001) 《Chinese Journal of Acoustics》 1999年第2期105-120,共16页
The high rate digital acoustic communication technique for horizontal channels has been studied in this article. It is called as 'Pattern Time Delay Shift Coding (PDS) communication system.' The aim of the PDS... The high rate digital acoustic communication technique for horizontal channels has been studied in this article. It is called as 'Pattern Time Delay Shift Coding (PDS) communication system.' The aim of the PDS is to improve the quality of communication in shallow water. The open water experiments shoe that at the condition of 2 kHz bandwidth, the communication rate is more than 300 bit/s and error rate is at the level of 10-4. The details of PDS technique will be shown, including: principle of PDS coding, the model of Anti-multipath illterference and open water experimenis 展开更多
关键词 IEEE TIME A study on pattern time delay shift coding underwater acoustic communication
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