scholarly journals Near-field surface deformation during the April 20, 2013, Ms7. 0 Lushan earthquake measured by 1-Hz GNSS

2013 ◽  
Vol 4 (2) ◽  
pp. 1-5 ◽  
Author(s):  
Liu Gang ◽  
Zhao Bin ◽  
Zhang Rui ◽  
Huang Yong ◽  
Wang Jun ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Near Field ◽  
Lushan Earthquake

A study of brake disc modal behaviour during squeal generation using high-speed electronic speckle pattern interferometry and near-field sound pressure measurements

2000 ◽  
Vol 214 (3) ◽  
pp. 285-296 ◽  
Author(s):  
M Reeves ◽  
N Taylor ◽  
C Edwards ◽  
D Williams ◽  
C. H. Buckberry
Keyword(s):  
High Speed ◽  
Sound Pressure ◽  
Surface Deformation ◽  
Speckle Pattern ◽  
Near Field ◽  
Electronic Speckle Pattern Interferometry ◽  
Brake Disc ◽  
Pressure Measurements ◽  
Near Field Sound ◽  
Field Sound

The out-of-plane surface vibration of a brake disc during naturally excited squeal has been investigated using a combination of high-speed electronic speckle pattern interferometry (ESPI) and near-field sound pressure measurements. Both techniques provide visualization and quantification of the time-resolved surface velocity. A mathematical description of disc brake squeal modal behaviour is proposed that predicts accurately all of the experimentally observed interferometry and sound field measurements. The complex mode description proposed here is in agreement with that proposed by others for drum brake squeal. This assumes that two identical diametral modes are excited simultaneously, identical except for a spatial and temporal phase shift. The use of a near-field microphone array provided a convenient multipoint, non-contacting vibration probe which may find use in the study of other vibrations characterized by high surface amplitudes and efficient sound radiation. The high-speed ESPI provided a real-time visualization of surface deformation analogous to double- pulsed holographic interferometry, with the benefit of giving a true time series of the surface deformation during a single vibration cycle.

scholarly journals Co- and post-seismic surface deformation and gravity changes of MS7.0 Lushan, earthquake

2013 ◽  
Vol 26 (3-4) ◽  
pp. 207-212 ◽  
Author(s):  
Kai Wang ◽  
Chengli Liu ◽  
Xiong Xiong ◽  
Yong Zheng
Keyword(s):  
Surface Deformation ◽  
Lushan Earthquake ◽  
Gravity Changes

Solving surface deformation of radio telescope antenna by artificial neural network

2021 ◽  
Author(s):  
Boyang Wang ◽  
Qian Ye ◽  
Li Fu ◽  
Guoxiang Meng ◽  
jinqing Wang ◽  
...  
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Boundary Conditions ◽  
Surface Deformation ◽  
Near Field ◽  
Surface Measurement ◽  
Antenna Measurement ◽  
Trial Solution ◽  
Original Algorithm ◽  
Artificial Neural

Abstract Recent investigations have derived the relation between the near-field plane amplitude and the surface deformation of reflector antenna, namely deformation-amplitude equation (DAE), which could be used as a mathematical foundation of antenna surface measurement if an effective numerical algorithm is employed. Traditional algorithms are hard to work directly due to the complexity mathematical model. This paper presents a local approximation algorithm based on artificial neural network (ANN) to solve DAE. Length factor method is used to construct a trial solution for the deformation, which ensures the final solution always to satisfy the boundary conditions. To improve the algorithm efficiency, Adam optimizer is employed to train the network parameters. Combining the application of data normalization method proposed in this paper and a step-based learning rate, a further optimized loss function could be converged quickly. The algorithm proposed in this paper could effectively solve partial differential equations (PDEs) without boundary conditions such as DAE, which at the same time contains the first-order and the second-order partial derivatives, and constant terms. Simulation results show that compared with the original algorithm by FFT, this algorithm is more stable and accurate, which is significant for the antenna measurement method based on DAE.

Azobenzene polymer surface deformation due to the gradient force of the optical near field of monodispersed polystyrene spheres

2001 ◽  
Vol 64 (19) ◽  
Author(s):  
Taiji Ikawa ◽  
Takuya Mitsuoka ◽  
Makoto Hasegawa ◽  
Masaaki Tsuchimori ◽  
Osamu Watanabe ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Near Field ◽  
Polymer Surface ◽  
Gradient Force ◽  
Polystyrene Spheres ◽  
Azobenzene Polymer

scholarly journals Estimating the atmospheric phase delay for quantifying co-seismic deformation using repeat pass Differential SAR Interferometry: Observations from 20th April 2013 Lushan (China) Earthquake

2014 ◽  
Vol XL-8 ◽  
pp. 57-64 ◽  
Author(s):  
J. Mathew ◽  
R. Majumdar ◽  
K. Vinod Kumar
Keyword(s):  
Surface Deformation ◽  
Lushan Earthquake ◽  
Phase Delay ◽  
Sar Interferometry ◽  
Electron Content ◽  
Phase Component ◽  
Total Electron ◽  
China Earthquake ◽  
Delay Component ◽  
Seismic Deformation

Atmospheric phase contribution significantly influences co-seismic surface deformation estimates from repeat pass Differential Synthetic Aperture Radar Interferometry (DInSAR). Present study investigates the contribution of the atmosphere in co-seismic deformation estimation associated with the 20 April 2013 Lushan (China) earthquake. The Lushan Earthquake occurred in the south-western segment of the Longmenshan fault zone, on the eastern margin of the Qinghai-Tibetan Plateau. Using pre- and postearthquake Radarsat-2 interferometric pair, the co-seismic deformation of the Lushan earthquake has been estimated. The tropospheric phase delay component has been estimated using tropospheric models in conjunction with surface temperature and pressure data from MODIS atmospheric products. The ionospheric phase component has been computed using the Total Electron Content (TEC) data. The net atmospheric path addition in the study area varies from 3.022 m to 4.621 m for the pre-earthquake SAR acquisition and from 2.687 m to 4.199 m for the post-event data acquisition. Comparison of the Line of Sight (LOS) displacement values computed using un-corrected and corrected interferometric data shows that the atmospheric phase component has introduced considerable contribution in the LOS displacement values. The uncorrected LOS displacement values vary from 0.902 m to −0.157 m where as those from the phase-corrected interferometric data are in the range of 0.052 m and −0.062 m. The corrected LOS displacement values show close agreement to a few GPS based co-seismic surface deformation components from published literature. Thus removal of atmospheric phase contribution is a necessary step in using repeat pass DInSAR for co-seismic surface deformation estimation.

scholarly journals Deformation measurement by single spherical near-field intensity measurement for large reflector antenna

2021 ◽  
Vol 21 (10) ◽  
pp. 258
Author(s):  
Qian Ye ◽  
Bo-Yang Wang ◽  
Qiang Yao ◽  
Jin-Qing Wang ◽  
Qing-Hui Liu ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Focal Point ◽  
Spherical Surface ◽  
Outer Space ◽  
Near Field ◽  
Elevation Angle ◽  
Physical Optics ◽  
Electric Intensity ◽  
Deformation Intensity ◽  
Main Reflector

Abstract This paper presents a new method to obtain the deformation distribution on the main reflector of an antenna only by measuring the electric intensity on a spherical surface with the focal point as the center of the sphere, regardless of phase. Combining the differential geometry theory with geometric optics method, this paper has derived a deformation-intensity equation to relate the surface deformation to the intensity distribution of a spherical near-field directly. Based on the finite difference method (FDM) and Gauss-Seidel iteration, deformation has been calculated from intensity simulated by geometrical optics (GO) and physical optics (PO) methods, respectively, with relatively small errors, which prove the effectiveness of the equation proposed in this paper. By means of this method, it is possible to measure the deformation only by scanning the electric intensity of a single hemispherical near-field whose area is only about 1/15 of the aperture. The measurement only needs a plane wave at any frequency as the incident wave, which means that both the signals from the outer space satellite and the far-field artificial beacon could be used as the sources. The scanning can be realized no matter what attitude and elevation angle the antenna is in because the size and angle of the hemisphere are changeable.

Surface deformation on azobenzene polymer film induced by optical near-field around polystyrene microspheres

2001 ◽  
Vol 124 (1) ◽  
pp. 159-161 ◽  
Author(s):  
T. Ikawa ◽  
M. Hasegawa ◽  
M. Tsuchimori ◽  
O. Watanabe ◽  
Y. Kawata ◽  
...  
Keyword(s):  
Polymer Film ◽  
Surface Deformation ◽  
Near Field ◽  
Polystyrene Microspheres ◽  
Azobenzene Polymer

Characterizing near‐field surface deformation in the 1990 Rudbar earthquake (Iran) using optical image correlation

2021 ◽  
Author(s):  
Najmeh Ajorlou ◽  
James Hollingsworth ◽  
Zahra Mousavi ◽  
Abdolreza Ghods ◽  
Zohreh Masoumi
Keyword(s):  
Surface Deformation ◽  
Near Field ◽  
Optical Image ◽  
Image Correlation

Seismotectonic Mechanisms of Lushan (Ms7.0) Earthquake in the Frontal Propagation Belt of the Longmen Shan, Sichuan, China

2015 ◽  
Vol 09 (02) ◽  
pp. 1550005 ◽  
Author(s):  
Li Yong ◽  
Yan Liang ◽  
Zhou Rongjun ◽  
Shao Chongjian ◽  
Zhao Guohua ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Active Faults ◽  
Seismic Source ◽  
Seismic Intensity ◽  
Lushan Earthquake ◽  
Focal Mechanism Solution ◽  
Tectonic Deformation ◽  
Seismogenic Fault ◽  
Detachment Surface ◽  
Lushan Ms7.0 Earthquake

In recent years, the apparent seismic activity around Longmen Shan and its front has included the Wenchuan (Ms8.0) Earthquake and the Lushan (Ms7.0) Earthquake, occurring in 2008 and 2013, respectively. Based on the focal mechanism solution, rupture processes, seismic intensity, surface deformation, and aftershocks of the Lushan Earthquake and the active fault on Longmen Shan, we divided the Longmen Shan and its front into two tectonic deformation belts, the Longmen Shan thrust belt and the frontal propagation belt. By comparing the differences in the tectonic deformation styles, active faults, and earthquake histories of the two belts, we propose two kinds of seismotectonic models: one is a thrusting belt characterized by napping and detachment, and the other is a frontal propagation belt characterized by thrusting and detachment folding. By analyzing the seismogenic mechanisms of thrusting and detachment folding in the frontal propagation belt during the Lushan Earthquake, we have inferred that the Lushan Earthquake was formed by thrusting and detachment folding in the frontal propagation belt. The seismogenic fault of the Lushan Earthquake was the Dayi Fault, which dips NW with a listric surface, and converges on the detachment surface. The detachment surface is the seismic source layer of the Lushan Earthquake.

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