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Precise Positioning Method for Seafloor Geodetic Stations Based on the Temporal Variation of Sound Speed Structure 被引量:1
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作者 Shuang ZHAO Zhenjie WANG +3 位作者 Zhixi NIE Kaifei HE Huimin LIU Zhen SUN 《Journal of Geodesy and Geoinformation Science》 CSCD 2023年第2期81-92,共12页
At present,GNSS-Acoustic(GNSS-A)combined technology is widely used in positioning for seafloor geodetic stations.Based on Sound Velocity Profiles(SVPs)data,the equal gradient acoustic ray-tracing method is applied in ... At present,GNSS-Acoustic(GNSS-A)combined technology is widely used in positioning for seafloor geodetic stations.Based on Sound Velocity Profiles(SVPs)data,the equal gradient acoustic ray-tracing method is applied in high-precision position inversion.However,because of the discreteness of the SVPs used in the forementioned method,it ignores the continuous variation of sound velocity structure in time domain,which worsens the positioning accuracy.In this study,the time-domain variation of Sound Speed Structure(SSS)has been considered,and the cubic B-spline function is applied to characterize the perturbed sound velocity.Based on the ray-tracing theory,an inversion model of“stepwise iteration&progressive corrections”for both positioning and sound speed information is proposed,which conducts the gradual correction of seafloor geodetic station coordinates and disturbed sound velocity.The practical data was used to test the effectiveness of our method.The results show that the Root Mean Square(RMS)errors of the residual values of the traditional methods without sound velocity correction,based on quadratic polynomial correction and based on cubic B-spline function correction are 1.43 ms,0.44 ms and 0.21 ms,respectively.The inversion model with sound velocity correction can effectively eliminate the systematic error caused by the change of SSS,and significantly improve the positioning accuracy of the seafloor geodetic stations. 展开更多
关键词 GNSS-Acoustic sound speed structure temporal variation seafloor positioning
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Sound absorption performance of various nickel foam-base multi-layer structures in range of low frequency 被引量:3
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作者 Wei CHENG Cui-yun DUAN +1 位作者 Pei-sheng LIU Miao LU 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2017年第9期1989-1995,共7页
Commercial3D reticular nickel foam and its composite structure were investigated on the sound absorption at200-2000Hz.The absorption performance of foam plates1?5layers(1-layer thickness:2.3mm;porosity:89%;average por... Commercial3D reticular nickel foam and its composite structure were investigated on the sound absorption at200-2000Hz.The absorption performance of foam plates1?5layers(1-layer thickness:2.3mm;porosity:89%;average pore-diameter:0.57mm)was found to be poor,and could be improved by adding backed cavum or front perforated thin sheet.The absorption coefficient could reach about0.4at1000-1600Hz for the composite structure of5-layer foam with a backed5mm-thick cavum,and even0.68at about1000Hz for that of2-layer foam with the same cavum and a perforated plate closely in front of the foam. 展开更多
关键词 reticular metal foam reticular nickel foam composite structure for sound absorption low frequency sound absorption
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Sound absorption of several various nickel foam multilayer structures at aural frequencies sensitive for human ears 被引量:1
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作者 Pei-sheng LIU Xin-bang XU +1 位作者 Wei CHENG Jing-he CHEN 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2018年第7期1334-1341,共8页
Using the three-dimensional reticular nickel foam as experimental material, the sound absorption performance was investigated for several various multilayer structures in the frequency range of 2000-4000 Hz, which is ... Using the three-dimensional reticular nickel foam as experimental material, the sound absorption performance was investigated for several various multilayer structures in the frequency range of 2000-4000 Hz, which is aurally sensitive for human ears. The results showed that the 7.5 mm-thick foam sample, which was formed by piling of 5-layer foam plate(thickness: 1.5 mm; porosity: 96%; average pore-diameter: 0.65 mm) could exhibit an excellent sound absorption effect at 4000 Hz, with the absorption coefficient about 0.8. Constituting alternate air gap with the total thickness of about 18.5 mm can greatly improve the absorption performance at relatively low frequencies of 2000-3150 Hz, with the absorption coefficient up to about 0.5 or more. In addition, the research showed that alternate piling up the perforated plate inside the foam plates can also achieve a quite good effect of sound absorption at relatively low frequencies. 展开更多
关键词 reticular nickel foam composite structure of sound absorption aurally sensitive frequency sound absorption
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Sound Absorption Enhancement by Thin Multi-Slit Hybrid Structures 被引量:3
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作者 任树伟 孟晗 +1 位作者 辛锋先 卢天健 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第1期91-94,共4页
We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter sca... We report an extraordinary sound absorption enhancement in low and intermediate frequencies achieved by a thin multi-slit hybrid structure formed by incorporating micrometer scale micro-slits into a sub-millimeter scale meso-slit matrix. Theoretical and numerical results reveal that this exotic phenomenon is attributed to the noticeable velocity and temperature gradients induced at the junctures of the micro- and meso-slits, which cause significant loss of sound energy as a result of viscous and thermal effects. It is demonstrated that the proposed thin multi-slit hybrid structure with micro-scale configuration is capable of controling low frequency noise with large wavelength, which is attractive for applications where the size and weight of a sound absorber are restricted. 展开更多
关键词 sound Absorption Enhancement by Thin Multi-Slit Hybrid structures
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Development of a High Sound Absorption Material CEMCOM 被引量:4
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作者 马保国 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2002年第4期5-8,共4页
Based on sound absorption mechanism of material,the special sound absorption material CEMCOM for road sound insulation is introduced.This high sound absorption material is mainly composed of expanded perlite.Using mul... Based on sound absorption mechanism of material,the special sound absorption material CEMCOM for road sound insulation is introduced.This high sound absorption material is mainly composed of expanded perlite.Using multiple sound absorption structure can improve sound absorption property of material.According to the preparation principle and durability design of material,a new kind of material with low cost and high durability is developed. 展开更多
关键词 sound absorption coefficient sound absorption structure porous material
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Magnetotelluric sounding study in the region of Zhongshan Station,East Antarctica
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作者 孔祥儒 张建军 《Chinese Journal of Polar Science》 1995年第1期24-29,共6页
This paper deals with the results of the MT observations in the region of Zhongshan Station,Larsemann Hills area, East Antarctica and points out that the lithosphere thickness of the Larsemann Hills is 140 km and the ... This paper deals with the results of the MT observations in the region of Zhongshan Station,Larsemann Hills area, East Antarctica and points out that the lithosphere thickness of the Larsemann Hills is 140 km and the crustal high conductivity layer is situated in 22 km. 展开更多
关键词 Zhongshan Station magnetotelluric deep sounding electrical conductivity structure
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北京地区五种常见鸣虫的鸣声结构 被引量:32
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作者 何忠 陈念丽 《动物学报》 SCIE CAS 1985年第4期324-330,共7页
本文对寒蝉、蚱蝉、鸣鸣蝉、锐声鸣螽和大扁头蟋五种鸣虫雄虫的鸣声结构进行了较系统的研究。这些昆虫鸣声节律以及声谱和声压的瞬时变化均有显著的不同。一种昆虫的鸣声频谱范围虽然很大,但不同频率的图象却都和主频率的图象一样。
关键词 INSECT sound structure FREQUENCY Pulse train.
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Micro-perforated structures as stand-alone sound absorbers 被引量:3
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作者 Helmut V.Fuchs 《Chinese Journal of Acoustics》 2005年第4期289-299,共11页
1 Introduction Early attempts to create a sound absorber which would function without the involvement of any fibrous or porous damping material go far back to K. A. Veliszhanina, S. N. Rschevkin and others as was out... 1 Introduction Early attempts to create a sound absorber which would function without the involvement of any fibrous or porous damping material go far back to K. A. Veliszhanina, S. N. Rschevkin and others as was outlined in Ref. [1]. 30 years ago, D. Y. MAA[2] was first in proposing a practicable design concept and calculation model for Micro-Perforated Absorber (MPA) prototypes which still forms the basis for various applications. During the past 12 years the Fraunhofer IBP developed a whole family of MPA products in close cooperation with 8 or more industrial partners operating in a variety of widely differing market segments. Meanwhile a large number of MPA modules and surface elements have evolved from MAA's creative pioneer work. More and more ambitious acousticians have, more recently, caught on this attractive idea of employing absorbers made of non-fibrous, non-abrasive materials with non-polluting, almost closed and optically attractive surfaces. MPA structures have played an important part in a long-standing and on-going effort at IBP to establish novel Alternative Fibreless Absorber (ALFA) tools for a better noise control and acoustic comfort. 展开更多
关键词 MPA Micro-perforated structures as stand-alone sound absorbers POCO
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Development of a computer vision system to monitor pig locomotion 被引量:3
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作者 Jorgen Kongsro 《Open Journal of Animal Sciences》 2013年第3期254-260,共7页
Avoiding lameness or leg weakness in pig production is crucial to reduce cost, improve animal welfare and meat quality. Detection of lameness detection by the use of vision systems may assist the farmer or breeder to ... Avoiding lameness or leg weakness in pig production is crucial to reduce cost, improve animal welfare and meat quality. Detection of lameness detection by the use of vision systems may assist the farmer or breeder to obtain a more accurate and robust measurement of lameness. The paper presents a low-cost vision system for measuring the locomotion of moving pigs based on motion detection, frame-grabbing and multivariate image analysis. The first step is to set up a video system based on web camera technology and choose a test area. Secondly, a motion detection and data storage system are used to build a processing system of video data. The video data are analyzed measuring the properties of each image, stacking them for each animal and then analyze these stacks using multivariate image analysis. The system was able to obtain and decompose information from these stacks, where components could be extracted, representing a particular motion pattern. These components could be used to classify or score animals according to this pattern, which might be an indicator of lameness. However, further improvement is needed with respect to standardization of herding, test area and tracking of animals in order to have a robust system to be used in a farm environment. 展开更多
关键词 Video image Analysis Multivariate Image Analysis Principal Component Analysis Leg Weakness Structural soundness PIGS
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Diffusion and sound absorption properties of the quadratic residue diffuser structure with perforated panel 被引量:3
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作者 CAI Jun BAO Fei +1 位作者 WANG Yachen WANG Yanqin 《Chinese Journal of Acoustics》 CSCD 2016年第3期255-264,共10页
Acoustic structure study always is the academic research interest. Diffusion ab?sorbing structure(DiflFsorber) has good research value because it has both diflFusion property and sound absorption property. Quadrati... Acoustic structure study always is the academic research interest. Diffusion ab?sorbing structure(DiflFsorber) has good research value because it has both diflFusion property and sound absorption property. Quadratic residue diffusers(QRD) structure which had good diffusion property was combined with the perforated panel which had good sound absorption property in this study. According to standard AES-4id-2001, the diffusion experiments were carried out to study QRD structure and ones composited with perforated-panels which had1 mm-thickness and perforated percentage of 3%, 5%, 8% respectively. The polar coordinate diagrams of different structure were analyzed to derive the diffusion coefficients. Results showed that the composite structure still had good diffusion performance in the frequency range from100 Hz to 800 Hz. The reflection sound energy of composite structure reduced obviously in the perforated panel resonance frequency range where there was about 2 dB reduction averagely.The study result can provide the reference for the design and development of diifsorber. 展开更多
关键词 RATE Diffusion and sound absorption properties of the quadratic residue diffuser structure with perforated panel
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Control of sound radiation from vibrating structure using active constrained layer: Ⅱ. Numerical calculation
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作者 YANG Jun LI Xiaodong TIAN Jing(Institute Of Acoustics, Academia Sinica Beijing 100080) 《Chinese Journal of Acoustics》 1999年第2期163-170,共8页
The solution to the state response of active constrained layer and the expression of the sound field radiated from the vibrating structure are given, and the damping mechanisms of active constrained layer (ACL) are di... The solution to the state response of active constrained layer and the expression of the sound field radiated from the vibrating structure are given, and the damping mechanisms of active constrained layer (ACL) are discussed. Compaxisons are made with the passive constrained layer (PCL) and the traditional active control method in reducing the structural vibration. The numerical results indicate that: using the active constrained layer damping (ACLD) treatment to dissipate energyt not only the vibration amplitude of structtire is reduced, but also the sound radiated from vibrating structure is suppressed 展开更多
关键词 MPA Control of sound radiation from vibrating structure using active constrained layer
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Crustal and upper mantle structure and deep tectonic genesis of large earthquakes in North China 被引量:20
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作者 WANG ChunYong WU QingJu +2 位作者 DUAN YongHong WANG ZhiShuo LOU Hai 《Science China Earth Sciences》 SCIE EI CAS CSCD 2017年第5期821-857,共37页
From the 1960 s to 1970 s, North China has been hit by a series of large earthquakes. During the past half century,geophysicists have carried out numerous surveys of the crustal and upper mantle structure, and associa... From the 1960 s to 1970 s, North China has been hit by a series of large earthquakes. During the past half century,geophysicists have carried out numerous surveys of the crustal and upper mantle structure, and associated studies in North China.They have made significant progress on several key issues in the geosciences, such as the crustal and upper mantle structure and the seismogenic environment of strong earthquakes. Deep seismic profiling results indicate a complex tectonic setting in the strong earthquake areas of North China, where a listric normal fault and a low-angle detachment in the upper crust coexist with a high-angle deep fault passing through the lower crust to the Moho beneath the hypocenter. Seismic tomography images reveal that most of the large earthquakes occurred in the transition between the high-and low-velocity zones, and the Tangshan earthquake area is characterized by a low-velocity anomaly in the middle-lower crust. Comprehensive analysis of geophysical data identified that the deep seismogenic environment in the North China extensional tectonic region is generally characterized by a low-velocity anomalous belt beneath the hypocenter, inconsistency of the deep and shallow structures in the crust, a steep crustalal-scale fault,relative lower velocities in the uppermost mantle, and local Moho uplift, etc. This indicates that the lithospheric structure of North China has strong heterogeneities. Geologically, the North China region had been a stable craton named the North China Craton or in brief the NCC, containing crustal rocks as old as ~3.8 Ga. The present-day strong seismic activity and the lower velocity of the lower crust in the NCC are much different from typical stable cratons around the world. These findings provide significant evidence for the destruction of the NCC. Although deep seismic profiling and seismic tomography have greatly enhanced knowledge about the deep-seated structure and seismogenic environment, some fundamental issues still remain and require further work. 展开更多
关键词 North China Craton Crust and upper mantle structure Deep seismic sounding profile Deep seismic reflection profile Broadband seismic array Seismogenic environment
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