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Phase-Based Optical Flow Method with Optimized Parameter Settings for Enhancing Displacement Measurement Adaptability
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作者 Zhaoxin Peng Menglian Liu +2 位作者 Zhiliang Wang Wei Liu Xian Wang 《Open Journal of Applied Sciences》 2024年第5期1165-1184,共20页
To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizi... To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizing parameter settings is proposed. The optimized parameters include the best measurement points of the Region of Interest (ROI) and the levels of pyramid filters. Additionally, to address the issue of updating reference frames in practical applications due to the difficulty in estimating the maximum effective measurement value, a mechanism for dynamically updating reference frames is introduced. Experimental results demonstrate that compared to representative image gradient-based displacement measurement methods, the proposed method exhibits higher measurement accuracy in engineering applications. This provides reliable data support for structural damage identification research based on vibration signals and is expected to broaden the engineering application prospects for structural health monitoring. 展开更多
关键词 displacement measurement Phase-Based Optical Flow Optimized Parameter Setting
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Improved calibration method for displacement transformation coefficient in optical and visual measurements
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作者 Haopeng Li Zurong Qiu 《Nanotechnology and Precision Engineering》 CAS CSCD 2023年第1期12-25,共14页
Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement trans... Optical and visual measurement technology is used widely in fields that involve geometric measurements,and among such technology are laser and vision-based displacement measuring modules(LVDMMs).The displacement transformation coefficient(DTC)of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process,and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view(FFOV).To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands,a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV.First,an image coordinate system,a pixel measurement coordinate system,and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM.In addition,marker spots in the FFOV are selected,and the DTCs at the marker spots are obtained from calibration experiments.Also,a fitting method based on locally weighted scatterplot smoothing(LOWESS)is selected,and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots.Finally,the calibrated distribution functions of the DTCs are applied to the LVDMM,and experiments conducted to verify the displacement measurement accuracies are reported.The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than±15μm and±19μm,respectively,and that for oblique displacement is better than±24μm.Compared with the traditional calibration method,the displacement measurement error in the FFOV is now 90%smaller.This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV,and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated. 展开更多
关键词 displacement transformation coefficient(DTC) Laser and vision-based displacement measuring module(LVDMM) displacement measurement Locally weighted scatterplot smoothing(LOWESS) Calibration method
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Review of Electronic Speckle Pattern Interferometry(ESPI) for Three Dimensional Displacement Measurement 被引量:22
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作者 YANG Lianxiang XIE Xin +2 位作者 ZHU Lianqing WU Sijin WANG Yonghong 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2014年第1期1-13,共13页
Three dimensional(3D) displacements, which can be translated further into 3D strain, are key parameters tor design, manufacturing and quality control. Using different optical setups, phase-shift methods, and algorit... Three dimensional(3D) displacements, which can be translated further into 3D strain, are key parameters tor design, manufacturing and quality control. Using different optical setups, phase-shift methods, and algorithms, several different 3D electronic speckle pattern interferometry(ESPl) systems for displacement and strain measurements have been achieved and commercialized. This paper provides a review of the recent developments in ESPI systems for 3D displacement and strain measurement. After an overview of the fundamentals of ESP! theory, temporal phase-shift, and spatial phase-shift techniques, 3D deformation measurements by the temporal phase-shift ESPI system, which is suited well for static measurement, and by the spatial phase-shift ESPI system, which is particularly useful for dynamic measurement, are discussed. For each method, the basic theory, a brief derivation and different optical layouts are presented. The state of art application, potential and limitation of the ESPI systems are shown and demonstrated. 展开更多
关键词 electronic speckle pattern interferometry(ESPI) three dimensional displacement and strain measurement static loading dynamic loading phase-shift technology
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A Direct Inspection of Displacement Current Using Phase Measurement
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作者 Zihua Weng Jinpan Zhu +3 位作者 Jingyan He Zhimin Chen Huangping Yan Ying Weng 《通讯和计算机(中英文版)》 2013年第1期104-115,共12页
关键词 位移电流 相位测量 直接检测 经典电磁理论 电子测量技术 验证实验 麦克斯韦 四元数
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A Method of Measuring Large Displacement and Deformation with High Precision *
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作者 杨勇 钟秉林 +1 位作者 何小元 杨汉国 《Journal of Southeast University(English Edition)》 EI CAS 1998年第1期53-56,共4页
A CCD position detecting system measuring the displacement and deformation of structure is presented. The measure method takes advantage of the position detecting technique based on digital image processing. A bright ... A CCD position detecting system measuring the displacement and deformation of structure is presented. The measure method takes advantage of the position detecting technique based on digital image processing. A bright spot is pegged on the object to be measured and imaged to the target of CCD camera through a telescopic lens. The CCD target converts the optical signal to equivalent electric signal. The video frequency signal is digitized to an array of 512×512 pixels by the analog to digital converter (ADC), then transmitted to the computer. The computer controls the data acquisition, conducts image processing and detects the location of the target spot. Comparing the current position with the original position of the spot, the displacement of object is obtained. With the aid of analysis software, the system can achieve the resolution of 0 01 mm in the 6 m distance from the object to the point of observation. To meet the need of practice, the measuring distance can be extended to 100 m or even farther. 展开更多
关键词 displacement DEFORMATION CCD position detection long distance measurement
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Vertical Displacement Measurement in a Slow-Moving Sinkhole Using BOTDA
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作者 Pascual SEVILLANO Javier PRECIADO-GARBAYO +4 位作者 Jorge SEVIL Francisco GUTIERREZ Juan JMARTiNEZ Sonia MARTiN-LOPEZ Miguel GONZALEZ-HERRAEZ 《Photonic Sensors》 SCIE EI CSCD 2024年第1期23-39,共17页
The effectiveness of monitoring and early-warning systems for ground deformation phenomena,such as sinkholes,depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deforma... The effectiveness of monitoring and early-warning systems for ground deformation phenomena,such as sinkholes,depends on their ability to accurately resolve the ongoing ground displacement and detect the subtle deformation preceding catastrophic failures.Sagging sinkholes with a slow subsidence rate and diffuse edges pose a significant challenge for subsidence monitoring due to the low deformation rates and limited lateral strain gradients.In this work,we satisfactorily illustrate the practicality of the Brillouin optical time domain analysis(BOTDA)to measure the spatial-temporal patterns of the vertical displacement in such challenging slow-moving sagging sinkholes.To assess the performance of the approach,we compare the strain recorded by the distributed optical fiber sensor with the vertical displacement measured by high-precision leveling.The results show a good spatial correlation with the ability to identify the maximum subsidence point.There is also a good temporal correlation with the detection of an acceleration phase in the subsidence associated with a flood event. 展开更多
关键词 Distributed fiber optic sensing(DFOS) vertical displacement measurement slow subsidence rate sinkhole hazard early-warning system
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Study on the Method for Measuring Nano-Displacement
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作者 李银祥 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2001年第3期70-72,共3页
A new method for measuring nano-displacement is discussed. Theresolution of shift is as far as 1 nm. The principle of quantumtunneling effects was used to design the instrument. With the tunnelbetween the sample and t... A new method for measuring nano-displacement is discussed. Theresolution of shift is as far as 1 nm. The principle of quantumtunneling effects was used to design the instrument. With the tunnelbetween the sample and the needlepoint and under the control ofclosed loop system, the instrument works at constant current mode, sothat the high precision displacement can be got. 展开更多
关键词 NANOMETER displacement measurement
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Application of Digital Image Correlation and Geodetic Displacement Measuring Methods to Monitor Water Dam Behavior under Dynamic Load
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作者 Janina Zaczek-Peplinska Maria Elzbieta Kowalska +1 位作者 Krzysztof Malowany MarcinMalesa 《Journal of Civil Engineering and Architecture》 2015年第12期1496-1505,共10页
This paper presents experiment results of the measurement conducted at the Roznew Dam power plant. For a course of starting and operating of turbo-plants, downstream face of the dam was monitored in relation to its ev... This paper presents experiment results of the measurement conducted at the Roznew Dam power plant. For a course of starting and operating of turbo-plants, downstream face of the dam was monitored in relation to its eventual displacements on direction parallel to the construction axis. For the purpose of the experiment, geodetic measurement techniques and 2D DIC (digital image correlation) method (utilizing photographs of the object recorded with digital camera) were compared with regard to credibility, efficiency and accuracy. The vertical and horizontal displacements were monitored by tachometers measurements. The deformations in x-axis and y-axis on the wall surface was monitored by 2D DIC. It has been noticed that 2D DIC method is a surface method, continuous--not discreet. It allows for continuous observations of surface deformations, which is not possible in case of tachemetric measurements. Despite many advantages, the 2D DIC method lacks unambiguous evaluation of precision and relevance of designated displacements, which is rather significant for possibilities of utilization in technical control of large engineered objects. It should be also marked that the tachometric method is more reliable but is more laborious. Research of this type might comprise additional element for the assessment of the influence of dynamic loads, such as activating turbine water flow, onto the overall condition of the surveyed structure. 展开更多
关键词 Hydrotechnical structure structure dynamic load engineering object displacement geodetic displacement measurements.digital image correlation.
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Multi-Laser Beams Measuring System for High Precision Detection on Displacement of Wind Fields
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作者 Li-Min Zhou Ya-Dong Jiang 《Journal of Electronic Science and Technology》 CAS 2010年第2期135-139,共5页
A novel multi-laser beams measuring system (MLBM) for high precision detection on displacement of flow fields based on laser backscatter was designed and studied. MLBM has many advantages, such as simple structure, ... A novel multi-laser beams measuring system (MLBM) for high precision detection on displacement of flow fields based on laser backscatter was designed and studied. MLBM has many advantages, such as simple structure, high stability, and no limitation of the monochromaticity of laser. By circumventing the strong influence of atmospheric backscattering on the high sensitivity of target echo detection, high precision detection on backscatter density of laser by signal processing was achieved. Furthermore, the signal densities of various distances were extracted by time sampling and precise frequency control of digital circuit. Finally, the MLBM system including devices integrated of emitting and reviving equipments and program was obtained. Detection experiments showed that our system has high precision and the measurement error could be controlled within 5% to 10%. 展开更多
关键词 Index Terms--displacement laser backscatter multi-laser beams wind measurement.
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Double Beams to Measure Three-dimensional Rigid Body Displacements
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作者 ZHOU Jian,CHEN Wenyi,ZHAO Hong TIAN Feng,TAN Yushan (Research Institute for Laser and Infrared Applications,Xi’an Jiaotong University,Xi’an 710049,CHN) 《Semiconductor Photonics and Technology》 CAS 1997年第2期78-81,共4页
A new method for measuring 3-D rigid body displacements is proposed,in which two perpendicular beams are emitted onto two sensitive planes of PSDs being perpendicular to each other.The method can be used to measure 1-... A new method for measuring 3-D rigid body displacements is proposed,in which two perpendicular beams are emitted onto two sensitive planes of PSDs being perpendicular to each other.The method can be used to measure 1-D or 2-D displacements when required.Moreover,the experimental results are presented,which demonstrate that the new method has high accuracy,fast processing speed,high reliability,and easily being realized. 展开更多
关键词 displacements measurement PHOTODETECTOR PSD
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Surface seasonal mass changes and vertical crustal deformation in North China from GPS and GRACE measurements 被引量:6
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作者 Shuya Li Wenbin Shen +1 位作者 Yuanjin Pan Tengxu Zhang 《Geodesy and Geodynamics》 2020年第1期46-55,共10页
The Earth is an elastic body,and the surface mass loading changes will lead to elastic loading deformation on the surface of the Earth.In this study,we investigated the surface seasonal mass changes and vertical crust... The Earth is an elastic body,and the surface mass loading changes will lead to elastic loading deformation on the surface of the Earth.In this study,we investigated the surface seasonal mass changes and vertical crustal deformation in North China using the data obtained by the techniques of the Global Positioning System(GPS),Gravity Recovery and Climate Experiment(GRACE)and Surface Loading Models(SLMs).The seasonal annual signal and semi-annual signal obtained by the three techniques show strong correlations.The average value of the weighted root-mean-square(WRMS)of the all 30 sites is 58%after deducting the GRACE-obtained vertical deformation from the GPS-derived vertical deformation.However,the consistency of results between GPS and SLMs is not so good,with a 31%mean WRMS reduction,due to the fact that the global SLMs perform not well in North China.The GRACEmeasured long-term trend is deducted from the GPS-obtained vertical rates to reveal the crustal displacement caused by the underground factors such as tectonic movement and groundwater in North China.The results show that the rates of stations HECX and TJBH are very large,more than 10 mm/yr,which suggests that the surface subsidence is caused by excessive exploitation of groundwater. 展开更多
关键词 Continuous GPS measurement GRACE measurement SURFACE Loading Models SEASONAL mass changes VERTICAL crustal displacement
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Analysis of the Wenchuan Ms8.0 Earthquake's Co-seismic Stress and Displacement Change by Using the Finite Element Method 被引量:9
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作者 SUN Dongsheng WANG Lianjie +3 位作者 WANG Hongcai MA Yinsheng ZHOU Chunjing CUI Junwen 《Acta Geologica Sinica(English Edition)》 SCIE CAS CSCD 2013年第4期1120-1128,共9页
The variation of in situ stress before and after earthquakes is an issue studied by geologists. In this paper, on the basis of the fault slip dislocation model of Wenchuan Ms8.0 earthquake, the changes of co-seismic d... The variation of in situ stress before and after earthquakes is an issue studied by geologists. In this paper, on the basis of the fault slip dislocation model of Wenchuan Ms8.0 earthquake, the changes of co-seismic displacement and the distribution functions of stress tensor around the Longmen Shan fault zone are calculated. The results show that the co-seismic maximum surface displacement is 4.9 m in the horizontal direction and 6.5 m in the vertical direction, which is almost consistent with the on-site survey and GPS observations. The co-seismic maximum horizontal stress in the hanging wall and footwall decreased sharply as the distance from the Longmen Shan fault zone increased. However, the vertical stress and minimum horizontal stress increased in the footwall and in some areas of the hanging wall. The study of the co-seismic displacement and stress was mainly focused on the long and narrow region along the Longmen Shan fault zone, which coincides with the distribution of the earthquake aftershocks. Therefore, the co-seismic stress only affects the aftershocks, and does not affect distant faults and seismic activities. The results are almost consistent with in situ stress measurements at the two sites before and after Wenchuan Ms8.0 earthquake. Along the fault plane, the co-seismic shear stress in the dip direction is larger than that in the strike direction, which indicates that the faulting mechanism of the Longmen Shan fault zone is a dominant thrust with minor strike-slipping. The results can be used as a reference value for future studies of earthquake mechanisms. 展开更多
关键词 Wenchuan Ms8.0 earthquake co-seismic stress field co-seismic displacement field finiteelement method in sitn stress measurement
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Earthquake-induced landslide displacement attenuation models and application in probabilistic seismic landslide displacement analysis 被引量:3
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作者 Graeme H.McVerry 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2010年第2期177-187,共11页
A landslide displacement (DLL) attenuation model has been developed using spectral intensity and a ratio of critical acceleration coefficient to ground acceleration coefficient. In the development of the model,a New Z... A landslide displacement (DLL) attenuation model has been developed using spectral intensity and a ratio of critical acceleration coefficient to ground acceleration coefficient. In the development of the model,a New Zealand earthquake record data set with magnitudes ranging from 5.0 to 7.2 within a source distance of 175 km is used. The model can be used to carry out deterministic landslide displacement analysis,and readily extended to carry out probabilistic seismic landslide displacement analysis. DLL attenuation models have also been developed by using earthquake source terms,such as magnitude and source distance,that account for the effects of earthquake faulttype,source type,and site conditions. Sensitivity analyses show that the predicted DLL values from the new models are close to those from the Romeo model that was developed from an Italian earthquake record data set. The proposed models are also applied to an analysis of landslide displacements in the Wenchuan earthquake,and a comparison between the predicted and the observed results shows that the proposed models are reliable,and can be confidently used in mapping landslide potential. 展开更多
关键词 displacement LANDSLIDE intensity measures deterministic analysis probabilistic analysis
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A Real-Time System for Monitoring Distant Dynamic Displacement of Structures 被引量:4
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作者 CHEN Junfeng ZHAO Wenguang +2 位作者 LUO Hongbin LI Penghui WEN Yinping 《Geo-Spatial Information Science》 2008年第1期49-55,共7页
Based on digital image processing technique, a real-time system is developed to monitor and detect the dynamic displacement of engineering structures. By processing pictures with a self-programmed software, the real-t... Based on digital image processing technique, a real-time system is developed to monitor and detect the dynamic displacement of engineering structures. By processing pictures with a self-programmed software, the real-time coordinate of an object in a certain coordinate system can be obtained, and further dynamic displacement data and curve of the object can also be achieved. That is, automatic gathering and real-time processing of data can be carried out by this system simultaneously. For this system, first, an untouched monitoring technique is adopted, which can monitor or detect objects several to hundreds of meters apart; second, it has flexible installation condition and good monitoring precision of sub-millimeter degree; third, it is fit for dynamic, quasi-dynamic and static monitoring of large engineering structures. Through several tests and applications in large bridges, good reliability and dominance of the system is proved. 展开更多
关键词 dynamic displacement real-time monitoring and detecting sub-pixel system calibration dynamic tracking
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Study on Coaxiality Measurement System of Compound Gear Shaft Based on Non⁃contact Optic 被引量:2
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作者 YE Zhibin LU Yonghua +2 位作者 TAN Jie LI Yanlong CHAI Zhong 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2021年第3期393-403,共11页
Aiming at the shortcomings of traditional contact measurement methods such as low measurement efficiency,high cost and low accuracy,a non-contact optical measurement method based on the laser displacement sensor is pr... Aiming at the shortcomings of traditional contact measurement methods such as low measurement efficiency,high cost and low accuracy,a non-contact optical measurement method based on the laser displacement sensor is proposed.According to the relevant regulations of the coaxiality error evaluation standard and the structural characteristics of the compound gear shaft,we have designed and built a set of supporting software system as well as a hardware test platform.In this paper,the distance difference threshold and scale threshold methods are used to eliminate outlier data.The least squares circle is selected to calculate the center of the circle and the minimum containment cylinder axis method is used as the reference axis of the composite gear shaft.Compensated by the standard step shaft calibration,the coaxiality error of the composite gear shaft can be measured to be within 0.01 mm in less than two minutes.The range value of the multi-section measurement test is 0.065 mm.The average coaxiality error is∅0.476 mm. 展开更多
关键词 compound gear shaft non-contact measurement laser displacement sensor COAXIALITY measuring system
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Sampling Moiré method for full-field deformation measurement: A brief review 被引量:2
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作者 Qinghua Wang Shien Ri 《Theoretical & Applied Mechanics Letters》 CSCD 2022年第1期42-48,共7页
The sampling Moiré(SM) method is one of the vision-based non-contact deformation measurement methods, which is a powerful tool for structural health monitoring and elucidation of damage mechanisms of materials. I... The sampling Moiré(SM) method is one of the vision-based non-contact deformation measurement methods, which is a powerful tool for structural health monitoring and elucidation of damage mechanisms of materials. In this review, the basic principle of the SM method for measuring the twodimensional displacement and strain distributions is introduced. When the grid is not a standard orthogonal grating and cracks exist on the specimen surface, the measurement methods are also stated. Two of the most typical application examples are described in detail. One is the dynamic deflection measurement of a large-scale concrete bridge, and the other is the residual thermal strain measurement of small-scale flip chip packages. Several further development points of this method are pointed out. The SM method is expected to be used for deformation measurement of various structures and materials for residual stress evaluation, crack location prediction, and crack growth evaluation on broad scales. 展开更多
关键词 displacement measurement Strain distribution BRIDGE Flip chip package
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3D Microdisplacement Monitoring of Large Aircraft Assembly with Automated In Situ Calibration 被引量:1
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作者 Zhenyuan Jia Bing Liang +2 位作者 Wei Liu Kun Liu Jianwei Ma 《Engineering》 SCIE EI CAS 2022年第12期105-116,共12页
Three-dimensional(3D)microdisplacement monitoring plays a crucial role in the assembly of large aircraft.This paper presents a broadly applicable high-precision online 3D microdisplacement monitoring method and system... Three-dimensional(3D)microdisplacement monitoring plays a crucial role in the assembly of large aircraft.This paper presents a broadly applicable high-precision online 3D microdisplacement monitoring method and system based on proximity sensors as well as a corresponding in situ calibration method,which can be applied under various extreme working conditions encountered in the aircraft assembly process,such as compact and obstructed spaces.A 3D monitoring model is first established to achieve 3D microdisplacement monitoring based only on the one-dimensional distances measured by proximity sensors,which concerns the extrinsic sensor parameters,such as the probe base point(PBP)and the unit displacement vector(UDV).Then,a calibration method is employed to obtain these extrinsic parameters with high precision by combining spatial transformation principles and weighted optimization.Finally,calibration and monitoring experiments performed for a tailplane assembly process are reported.The calibration precision for the PBP is better than±10 lm in the X and Y directions and±2 lm in the Z direction,and the calibration precision for the UDV is better than 0.07°.Moreover,the accuracy of the 3D microdisplacement monitoring system can reach±15 lm.In general,this paper provides new insights into the modeling and calibration of 3D microdisplacement monitoring based on proximity sensors and a precise,efficient,and low-cost technical means for performing related measurements in compact spaces during the aircraft assembly process. 展开更多
关键词 Aircraft manufacture ASSEMBLY CALIBRATION Condition monitoring displacement measurement
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Study and application of monitoring plane displacement of a similarity model based on time-series images 被引量:5
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作者 Xu Jiankun Wang Enyuan +1 位作者 Li Zhonghui Wang Chao 《Mining Science and Technology》 EI CAS 2011年第4期501-505,共5页
In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring meth... In order to compensate for the deficiency of present methods of monitoring plane displacement in similarity model tests,such as inadequate real-time monitoring and more manual intervention,an effective monitoring method was proposed in this study,and the major steps of the monitoring method include:firstly,time-series images of the similarity model in the test were obtained by a camera,and secondly,measuring points marked as artificial targets were automatically tracked and recognized from time-series images.Finally,the real-time plane displacement field was calculated by the fixed magnification between objects and images under the specific conditions.And then the application device of the method was designed and tested.At the same time,a sub-pixel location method and a distortion error model were used to improve the measuring accuracy.The results indicate that this method may record the entire test,especially the detailed non-uniform deformation and sudden deformation.Compared with traditional methods this method has a number of advantages,such as greater measurement accuracy and reliability,less manual intervention,higher automation,strong practical properties,much more measurement information and so on. 展开更多
关键词 Plane displacement monitoring Similarity model test Time-series images displacement measurement
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Coseismic gravity and displacement changes of Japan Tohoku earthquake(Mw 9.0) 被引量:2
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作者 Xinlin Zhang Shuhei Okubo +1 位作者 Yoshiyuki Tanaka Hui Li 《Geodesy and Geodynamics》 2016年第2期95-100,共6页
The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku.Large tsunami and ground motions ca... The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku.Large tsunami and ground motions caused severe damage in wide areas, particularly many towns along the Pacific coast. So far, gravity change caused by such a great earthquake has been reported for the 1964 Alaska and the 2010 Maule events. However, the spatial-temporal resolution of the gravity data for these cases is insufficient to depict a co-seismic gravity field variation in a spatial scale of a plate subduction zone. Here, we report an unequivocal co-seismic gravity change over the Japanese Island, obtained from a hybrid gravity observation(combined absolute and relative gravity measurements). The time interval of the observation before and after the earthquake is within 1 year at almost all the observed sites, including 13 absolute and 16 relative measurement sites, which deduced tectonic and environmental contributions to the gravity change. The observed gravity agrees well with the result calculated by a dislocation theory based on a self-gravitating and layered spherical earth model. In this computation, a co-seismic slip distribution is determined by an inversion of Global Positioning System(GPS) data. Of particular interest is that the observed gravity change in some area is negative where a remarkable subsidence is observed by GPS, which can not be explained by simple vertical movement of the crust. This indicated that the mass redistribution in the underground affects the gravity change. This result supports the result that Gravity Recovery and Climate Experiment(GRACE) satellites detected a crustal dilatation due to the 2004 Sumatra earthquake by the terrestrial observation with a higher spatial and temporal resolution. 展开更多
关键词 Tohoku earthquake(Mw 9.0) Co-seismic gravity change Co-seismic displacement change Coseismic geoid change Dislocation theory Global Positioning System Absolute gravity measurement Relative gravity measurement
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Real-Time Vivo Tooth Mobility Measurement and Analysis 被引量:1
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作者 Richter EJ 《Chinese Journal of Biomedical Engineering(English Edition)》 2003年第3期93-102,共10页
The significance and research status of tooth mobility (TM) measurement are introduced. There are many methods to measure the TM, but up to now no one does vivo dynamic TM measurement. An optical-electronic method is ... The significance and research status of tooth mobility (TM) measurement are introduced. There are many methods to measure the TM, but up to now no one does vivo dynamic TM measurement. An optical-electronic method is raised to measure it in this paper. The measurement theory is introduced and a measurement system is setup. Special proceeding is done for this measurement because of the small oral cavity measurement area. It is the first time to get vivo dynamic TM measurement result at last. The measurement result is analysed and a new movement period is discovered. It shows that this method satisfies for the dynamical tooth movement. Further research is suggested. 展开更多
关键词 TOOTH MOBILITY Optical FIBER displacement Sensor VIVO measurement
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