scholarly journals An EEMD-Based Denoising Method for Seismic Signal of High Arch Dam Combining Wavelet with Singular Spectrum Analysis

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Bo Li ◽  
Lixin Zhang ◽  
Qiling Zhang ◽  
Shengmei Yang
Keyword(s):  
High Frequency ◽  
Singular Spectrum Analysis ◽  
Low Frequency ◽  
Arch Dam ◽  
Seismic Signals ◽  
High Arch Dam ◽  
Denoising Method ◽  
Arch Dams ◽  
Frequency Components ◽  
High Arch Dams

Due to complicated noise interference, seismic signals of high arch dam are of nonstationarity and a low signal-to-noise ratio (SNR) during acquisition process. The traditional denoising method may have filtered effective seismic signals of high arch dams. A self-adaptive denoising method based on ensemble empirical mode decomposition (EEMD) combining wavelet threshold with singular spectrum analysis (SSA) is proposed in this paper. Based on the EEMD result for seismic signals of high arch dams, a continuous mean square error criterion is used to distinguish high-frequency and low-frequency components of the intrinsic mode functions (IMFs). Denoised high-frequency IMF using wavelet threshold is reconstructed with low-frequency components, and SSA is implemented for the reconstructed signal. Simulation signal denoising analysis indicates that the proposed method can significantly reduce mean square error under low SNR condition, and the overall denoising effect is superior to EEMD and EEMD-Wavelet threshold denoising algorithms. Denoising analysis of measured seismic signals of high arch dams shows that the performance of denoised seismic signals using EEMD-Wavelet-SSA is obviously improved, and natural frequencies of the high arch dams can be effectively identified.

Denoising Method for Calibration Data of Landing Guidance Radar Based on EMD and Wavelet

2014 ◽  
Vol 962-965 ◽  
pp. 2856-2862
Author(s):  
De Yi Sang ◽  
Jian Jun Zhao ◽  
Li Bin Yang
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Wavelet Denoising ◽  
Calibration Data ◽  
Wavelet Thresholding ◽  
Denoising Method ◽  
Calibration Process ◽  
Frequency Components

The noise resulted in the calibration process of the landing guidance radar can cause serious accidents. Analyse the principle of the EMD and wavelet denoising method. Points out the deficiencies of pure EMD or pure wavelet denoising method. Propose a denoising method based on EMD and wavelet. Improved the discriminanting method for high or low frequency components and the discriminanting method for wavelet thresholding. First EMD the signal, then denoise the high frequency components by wavelet, finally, combined the low frequency components and the denoised high frequency components to get the denoised data.

Research Progress of Protected Plunge Pool of High Arch Dam

2014 ◽  
Vol 919-921 ◽  
pp. 1244-1247 ◽  
Author(s):  
Ying Kui Wang ◽  
Ren Qiang Liao
Keyword(s):  
Energy Dissipation ◽  
Southwest China ◽  
Arch Dam ◽  
Research Progress ◽  
Project Design ◽  
High Arch Dam ◽  
Arch Dams ◽  
Plunge Pool ◽  
Large Investment ◽  
High Arch Dams

The security researches of energy dissipation were always the focus in the High arch dams. Statistically, the trajectory type energy dissipation is the most widely used in the built high arch dams, and the protected plunge poor were always set downstream the dam body. However, the widely used protected plunge poor need large investment with the disadvantage of complicated operation and maintenance. Along with the construction of concrete high arch dam in the Southwest China, the “Reventment-Protected and Non-Bottom-Protected Plunge Pool” has been studied and proposed, which has the advantage of more simplified project design and more economy investment.

The Research on the Relation between Flexibility Coefficient and Buckling Stability of High Arch Dam

2012 ◽  
Vol 594-597 ◽  
pp. 1932-1935
Author(s):  
Hui Li ◽  
Zheng Zhong Wang ◽  
Xuan She
Keyword(s):  
Differential Method ◽  
Arch Dam ◽  
Present Condition ◽  
High Arch Dam ◽  
North West ◽  
Arch Dams ◽  
South West ◽  
Buckling Stability ◽  
Flexibility Coefficient ◽  
High Arch Dams

As a result of many high arch dams that are building and would be built in the south-west and north-west of China, arch dam is a kind of compressed thin buckle, not only effect by tension, but also by deformation. Thinner dam body with usage of increased levels of concrete and optimum designing, the local regions of high arch dams approach thin shell structure，which will lead to the structural buckling. Base on the above present condition, this paper would establish a series of generalized high and thin arch dam models whose height are 240m, and make theoretical analysis based on one of the crown- cantilever method- differential method for them, which attempts to provide a new method for the" critical flexibility coefficient ". At last, this paper would provide the relation between coefficient and buckling stability of high arch dam

scholarly journals A monitoring model for the stress on a super-high arch dam during pre-impoundment construction

2020 ◽  
Vol 20 (8) ◽  
pp. 3604-3614
Author(s):  
Jingtai Niu ◽  
Xiang Luo ◽  
Zhiping Deng ◽  
Yang Zhang ◽  
Yingjia Guo ◽  
...  
Keyword(s):  
Structural Characteristics ◽  
In Situ Stress ◽  
Arch Dam ◽  
Stress Monitoring ◽  
High Arch Dam ◽  
Factors Affecting ◽  
Arch Dams ◽  
Monitoring Model ◽  
Elastoplastic Constitutive Model ◽  
High Arch Dams

Abstract This paper presents a proposed model for monitoring the stress on a super-high arch dam during construction. Using mathematics, mechanics, and dam engineering principles, the mathematical expressions of the self-weight component of the dam prior to and following the sealing of the bottom of the arch were derived. The visco-elastoplastic constitutive model of dam concrete during construction was identified and used to develop a stress monitoring model for a super-high arch dam. Based on in-situ stress monitoring data collected during the construction of a super-high arch dam, the stress monitoring model was applied to a super-high arch dam accounting for future impoundment, and the key components of the monitoring model were isolated. The results show that the model has high fitting accuracy and incorporates an appropriate selection of factors affecting dam stress. The hydrograph of each component conforms to the structural characteristics of super-high arch dams during construction. This model overcomes the limitations of applying the complete self-weight of the dam body on the cantilever beam and was validated using data from a super-high arch dam construction project. Thus, this paper provides evidence for a safety monitoring model for super-high arch dams during construction.

Study of Risk Evaluation System of High Arch Dam Based on Failure Mechanism

2009 ◽  
Vol 417-418 ◽  
pp. 541-544
Author(s):  
Zai Tie Chen
Keyword(s):  
Risk Evaluation ◽  
Evaluation System ◽  
Failure Modes ◽  
Quantitative Estimation ◽  
Arch Dam ◽  
Dam Failure ◽  
High Arch Dam ◽  
Arch Dams ◽  
Risk Evaluation System ◽  
High Arch Dams

In view of the randomness in terms of high arch dam load, resistance and failure calamity loss as well as the fuzziness in terms of evaluation conclusion, a high arch dam risk evaluation system is established by means of risk analysis method. Natural factors, structural factors and human factors that lead to high arch dam failure are summed up on the basis of statistics. Through qualitative analysis coupled with quantitative estimation, it is determined that high arch dams generally involve five major failure modes: abutment rock mass destabilization, excess cracking, arch dam & dam foundation entire destabilization, extreme dam-overflow and destabilization of dam body along base plane. The state functions of individual major failure modes are established. An approach is made to the correlativity among the major failure modes and among the random variables within individual failure modes, and it is suggested that risk rate, economic loss risk value and life loss risk value should be used to assess the risk of high arch dams. A certain high arch dam abutment instability risk evaluation has been provided.

Risk-Based Research on Failure Mode of High-Arch Concrete Dam

2008 ◽  
Vol 385-387 ◽  
pp. 269-272 ◽  
Author(s):  
Zai Tie Chen
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Safety Evaluation ◽  
Arch Dam ◽  
State Function ◽  
High Arch Dam ◽  
Arch Dams ◽  
Disaster Loss ◽  
Explosion Load ◽  
High Arch Dams

Risk analysis can overcome the weakness of conventional safety evaluation of high-arch dams where the random nature of the load and resistance effect are ignored and the failure mode and failure disaster loss are not taken into account. On the basis of statistical analysis of the data of the failure arch dams and faulty and perilous arch dams in the world, it is deduced that the failure of high arch dam is mainly caused by super elevation floods, highly intense earthquakes, mountain landslides, abnormal temperature variation, explosion load, etc. Five major failure modes for high arch dams are suggested, namely dam abutment rock instability, fundamental plane instability, entire entity instability, excess cracking and extreme dam overflow. Based on the study of the failure mechanism of the major failure modes, a state function is established to calculate the failure probability of the major failure modes. An approach is developed to obtain the statistical quantity and the regularities of distribution of the load and resistance random variables.

scholarly journals Zoning Elastic Modulus Inversion for High Arch Dams Based on the PSOGSA-SVM Method

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Bo Chen ◽  
Xiao Fu ◽  
Xuyuan Guo ◽  
Chongshi Gu ◽  
Chenfei Shao ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Search Algorithm ◽  
Arch Dam ◽  
Support Vector ◽  
Inversion Method ◽  
Training Set ◽  
High Arch Dam ◽  
Arch Dams ◽  
Inversion Model ◽  
High Arch Dams

Real-time monitoring of the actual elastic modulus is essential and necessary to ensure the safe operation of arch dams. The zoning elastic modulus of a high arch dam is inversed by using deformation safety monitoring data in the operation period, based on the particle swarm optimization with gravitation search algorithm for support vector machine (PSOGSA-SVM) method. Firstly, the measured data of multipoints with a pendulum are separated to construct the initial sample training set; then, an optimal inversion model is established to reflect the complex nonlinear relationship between the mechanical parameters of the high arch dam and the deformation of measured points; finally, the PSOGSA-SVM method is used to train and dynamically update the training set so as to realize the optimization solution of the inversion model. The proposed inversion method is successfully applied to a high arch dam in China to verify its feasibility and validity. The results show that the actual elastic modulus of the dam body is much larger than the initial elastic modulus, which is beneficial to structural stability.

scholarly journals Deformation Monitoring of Geomechanical Model Test and Its Application in Overall Stability Analysis of a High Arch Dam

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Baoquan Yang ◽  
Lin Zhang ◽  
Enlong Liu ◽  
Jianhua Dong ◽  
Honghu Zhu ◽  
...  
Keyword(s):  
Model Test ◽  
Deformation Monitoring ◽  
Arch Dam ◽  
Test Method ◽  
Geomechanical Model ◽  
High Arch Dam ◽  
Arch Dams ◽  
Overall Stability ◽  
The Stability ◽  
High Arch Dams

Geomechanical model testing is an important method for studying the overall stability of high arch dams. The main task of a geomechanical model test is deformation monitoring. Currently, many types of deformation instruments are used for deformation monitoring of dam models, which provide valuable information on the deformation characteristics of the prototype dams. However, further investigation is required for assessing the overall stability of high arch dams through analyzing deformation monitoring data. First, a relationship for assessing the stability of dams is established based on the comprehensive model test method. Second, a stability evaluation system is presented based on the deformation monitoring data, together with the relationships between the deformation and overloading coefficient. Finally, the comprehensive model test method is applied to study the overall stability of the Jinping-I high arch dam. A three-dimensional destructive test of the geomechanical model dam is conducted under reinforced foundation conditions. The deformation characteristics and failure mechanisms of the dam abutments and foundation were investigated. The test results indicate that the stability safety factors of the dam abutments and foundation range from 5.2 to 6.0. These research results provide an important scientific insight into the design, construction, and operation stages of this project.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

A Novel Adaptive PET/CT Image Fusion Algorithm

2019 ◽  
Vol 14 (7) ◽  
pp. 658-666
Author(s):  
Kai-jian Xia ◽  
Jian-qiang Wang ◽  
Jian Cai
Keyword(s):  
Lung Cancer ◽  
Image Fusion ◽  
High Frequency ◽  
Malignant Tumors ◽  
Low Frequency ◽  
Combination Method ◽  
Ct Image ◽  
Fusion Algorithm ◽  
Pet Ct ◽  
Frequency Components

Background: Lung cancer is one of the common malignant tumors. The successful diagnosis of lung cancer depends on the accuracy of the image obtained from medical imaging modalities. Objective: The fusion of CT and PET is combining the complimentary and redundant information both images and can increase the ease of perception. Since the existing fusion method sare not perfect enough, and the fusion effect remains to be improved, the paper proposes a novel method called adaptive PET/CT fusion for lung cancer in Piella framework. Methods: This algorithm firstly adopted the DTCWT to decompose the PET and CT images into different components, respectively. In accordance with the characteristics of low-frequency and high-frequency components and the features of PET and CT image, 5 membership functions are used as a combination method so as to determine the fusion weight for low-frequency components. In order to fuse different high-frequency components, we select the energy difference of decomposition coefficients as the match measure, and the local energy as the activity measure; in addition, the decision factor is also determined for the high-frequency components. Results: The proposed method is compared with some of the pixel-level spatial domain image fusion algorithms. The experimental results show that our proposed algorithm is feasible and effective. Conclusion: Our proposed algorithm can better retain and protrude the lesions edge information and the texture information of lesions in the image fusion.

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