Tracking rapidly changing dynamical systems using a non‐parametric statistical method based on wavelets     

Jianye Ching  Steven D. Glaser 《地震工程与结构动力学》2003,32(15):2377-2406

A non‐parametric statistical method of tracking rapidly changing dynamical systems is introduced. The method implements the non‐linear wavelet thresholding estimator to estimate the evolutionary transfer function of the system. The consistency and optimality of the resulting estimate of our method on rapidly changing systems are stated, while no linear estimator can achieve the same optimality. Two examples of real data are studied using this non‐parametric method, including two vertical seismic array case studies and a series of seismic slope experiments. The analysis results are consistent with previous research for the vertical seismic array data. Moreover, our estimate is superior to those from previous research in the sense that our estimate is neither over‐smoothed nor under‐smoothed. The ana‐ lysis results are also consistent with the experimental observations for the seismic slope experimental data. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Two adaptive algorithms for multipath time delay estimation   总被引：1，自引：0，他引：1  

Ching  P.C. So  H.C. 《Oceanic Engineering, IEEE Journal of》1994,19(3):458-463

The problem of time delay estimation (TDE) with multipath transmissions arises often in many sonar and radar systems. Two adaptive algorithms based on a parameter estimation approach are proposed to estimate the difference in arrival times of a signal at two separated sensors in the presence of multipath propagation. The first method uses an adaptive IIR filter to eliminate the multipath signal in each transmission channel prior to applying a constrained delay estimation algorithm to extract the time difference between the two received outputs. The second employs two constrained adaptive FIR filters to perform equalization of the multipath arrivals, and time delay is then derived using a constrained delay estimator similar to that in the first method. Computer simulations are presented to compare and contrast the tracing capability and convergence behavior of these multipath TDE methods  相似文献   

Application of Persistent Scatterer Interferometry (PSI) in monitoring slope movements in Nainital,Uttarakhand Lesser Himalaya,India     

Akano Yhokha  Pradeep K Goswami  Chung-Pai Chang  Jiun-Yee Yen  Kuo-En Ching  K Manini Aruche 《Journal of Earth System Science》2018,127(1):6

Orogenic movements and sub-tropical climate have rendered the slopes of the Himalayan region intensely deformed and weathered. As a result, the incidences of slope failure are quite common all along the Himalayan region. The Lesser Himalayan terrane is particularly vulnerable to mass-movements owing to geological fragility, and many parts of it are bearing a high-risk of associated disaster owing to the high population density. An important step towards mitigation of such disasters is the monitoring of slope movement. Towards this, the Persistent Scatterer Interferometry (PSI) technique can be applied. In the present study, the PSI technique is employed in Lesser Himalayan town of Nainital in Uttarakhand state of India to decipher and monitor slope movements. A total of 15 multi-date ENVISAT ASAR satellite images, acquired during August 2008 to August 2010 period, were subjected to PSI, which revealed a continuous creep movement along the hillslopes located towards the eastern side of the Nainital lake. The higher reaches of the hill seem to be experiencing accelerated creep of \({\sim }21\) mm/year, which decreases downslope to \({\sim }5\) mm/year. Based on spatial pattern of varying PSI Mean LOS Velocity (MLV) values, high (H), moderate (M), low (L) and very low (S) creeping zones have been delineated in the hillslopes. Given the long history of mass movements and continuously increasing anthropogenic activities in Nainital, these results call for immediate measures to avert any future disaster in the town.  相似文献   

Cyclic tests of four two‐story narrow steel plate shear walls. Part 2: experimental results and design implications     

Keh‐Chyuan Tsai  Pei‐Ching Chen 《地震工程与结构动力学》2010,39(7):801-826

This paper is the second part of a two‐part paper presenting the cyclic tests of four two‐story narrow steel plate shear walls (SPSWs). The first paper introduces the analytical studies and the specimen designs. This paper describes the test results. Some design implications including the capacity design for the first story column and the width‐to‐thickness ratio check for the beam web are discussed based on key observations from the tests. Test results confirm that the simplified strip model can accurately predict the inelastic responses of the specimens. Test results also confirm that the proposed capacity design method is effective in ensuring the plastic hinge formation at the bottom end of the first story column for SPSW with or without restrainers. Test results also show that the horizontal restrainers are effective in reducing the member forces in the boundary beam and column elements. Comparing the test results of the typical SPSW with those of the restrained SPSW (R‐SPSW) specimens, it is found that the R‐SPSW possesses an improved cyclic performance and reduced material weight. Analytical results predict the compressed column moments at the onset of the column plastic hinge formation well. The analytical hysteretic energy distribution in the first story column agrees very well with the observed inelastic actions developed in the four specimens. The detailed frame response analyses and the test results confirm that the assumptions made in developing the proposed column capacity design method are reasonable. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Bidirectional substructure pseudo‐dynamic tests and analysis of a full‐scale two‐story buckling‐restrained braced frame          下载免费PDF全文

Hsen‐Han Khoo  Keh‐Chyuan Tsai  Ching‐Yi Tsai  Cheng‐Yu Tsai  Kung‐Juin Wang 《地震工程与结构动力学》2016,45(7):1085-1107

A two‐story buckling‐restrained brace (BRB) frame was tested under bidirectional in‐plane and out‐of‐plane loading to evaluate the BRB stability and gusset plate design. The test comprised pseudo‐dynamic loadings using the 1999 Chi‐Chi earthquake scaled to the 50%, 10%, and 2% probability of exceedance in 50 years and a cyclic regime of increasing amplitudes of up to 3.0% story drift ratio (SDR). The specimen had a unique configuration where the beams were connected to the columns through shear tabs welded to the column flanges and bolted to the beam webs. Stable hysteretic behavior with only minor cracking at the gusset‐to‐column welds was observed under the pseudo‐dynamic tests, with maximum in‐plane and out‐of‐plane SDRs of 2.24% and 1.47% respectively. Stable behavior continued into the cyclic test where fracture of the gusset‐to‐column welds occurred in the first cycle to simultaneous bidirectional SDR of 3.0%. The observed BRB stability is consistent with a methodology developed for BRB frames under simultaneous in‐plane and out‐of‐plane drifts. The specimen behavior was studied using a finite element model. It was shown that gusset plates are subjected to a combination of BRB force and frame action demands, with the latter increasing the gusset‐to‐beam and gusset‐to‐column interface demands by an average of 69% and 83% respectively. Consistent with the test results, failure at the gusset‐to‐column interfaces is computed when frame action demands are included, thus confirming that not considering frame action demands may results in unconservative gusset plate designs. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Spectral responses of water level in tidal river and groundwater     

David Ching‐Fang Shih  Kin‐Forie Chiou  Chin‐Dee Lee  I‐Sen Wang 《水文研究》1999,13(6):889-911

The water level of five river stages and seven groundwater wells in the Taipei Basin were analysed by spectral analysis in the frequency domain. The diurnal, semi‐diurnal and quarter‐diurnal tidal components of the Tanshui River appear to relate closely to astronomical tides as K₁, M₂ and M₄, respectively. It is also found that the diurnal component reveals a reversed phase angle in the middle section of the Tanshui River; the phase of the quarter‐diurnal component is also found to be reversed at stations upstream in the Tanshui River and Hsintien Stream. It is believed that these phenomena could be caused by local variation in the river channel topography. The autospectrum and cross‐spectrum between groundwater elevation and nearby river stage were observed to correlate highly with the frequency of the astronomical tides K₁, M₂ and M₄. From the study of the phase shift and time lag of water level fluctuations at river stages and groundwater wells, it was found that the tidal effects of diurnal, semi‐diurnal, and quarter‐diurnal components were significantly different. The relationships between phase and the fluctuated range of atmospheric pressure and water level imply that change in atmospheric pressure does not affect water level fluctuation in the river stage and groundwater well. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Modeling for critical state line of granular soil with evolution of grain size distribution due to particle breakage     

Ching S.Chang  Yibing Deng 《地学前缘(英文版)》2020,(2):473-486

Determination of the critical state line(CSL)is important to characterize engineering properties of granular soils.Grain size distribution(GSD)has a significant influence on the location of CSL.The influence of particle breakage on the CSL is mainly attributed to the change in GSD due to particle breakage.However,GSD has not been properly considered in modeling the CSL with influence of particle breakage.This study aims to propose a quantitative model to determine the CSL considering the effect of GSD.We hypothesize that the change of critical state void ratio with respect to GSD is caused by the same mechanism that influences of the change of minimum void ratio with respect to GSD.Consequently,the particle packing model for minimum void ratio proposed by Chang et al.(2017)is extended to predict critical state void ratio.The developed model is validated by experimental results of CSLs for several types of granular materials.Then the evolution of GSD due to particle breakage is incorporated into the model.The model is further evaluated using the experimental results on rockfill material,which illustrates the applicability of the model in predicting CSL for granular material with particle breakage.  相似文献   

Seismic performance analysis of BRBs and gussets in a full‐scale 2‐story BRB‐RCF specimen          下载免费PDF全文

Ching‐Yi Tsai  Keh‐Chyuan Tsai  Li‐Wei Chen  An‐Chien Wu 《地震工程与结构动力学》2018,47(12):2366-2389

The implementation of buckling‐restrained braces (BRBs) for new reinforced concrete frame (RCF) constructions is limited. This study investigates the seismic forces and stability in the BRBs and gussets of a 2‐story full‐scale RCF specimen by using Abaqus models and a newly proposed stability evaluation method. The hybrid and cyclic loading test results are accurately predicted by the Abaqus analyses. Existing methods for computing the gusset interface forces for steel buildings from both the brace and the frame actions are compared with the Abaqus results. The applicability of these methods for the BRB‐RCF design is critically evaluated. It is confirmed that the Parallel‐2 method is suitable for estimating the BRB force demand imposed on the corner gusset and the generalized uniform force method is good for the corner gusset at the base. In addition, existing stability evaluation methods for BRBs and gussets are applied to investigate the out‐of‐plane (OOP) buckling of the first‐story BRB observed at the end of tests. The proposed stability model incorporates the BRB restrainer's flexural effects and 4 rotational springs in assessing the BRB's buckling. This model confirms that the BRB and the gusset's OOP buckling limit states could be coupled and must be evaluated together. By incorporating the flexural effects of the steel casing and the infilled grout, the proposed model satisfactorily predicts the OOP buckling of the first‐story BRB and gussets. These research results can be used for the implementation of BRBs in new RC frame constructions.  相似文献   

Extraction of agar from Eucheuma cottonii and Gelidium amansii seaweeds with sonication pretreatment using autoclaving method     

Din  Siti Sabariah  Chew  Kit Wayne  Chang  Yu-Kaung  Show  Pau Loke  Phang  Siew Moi  Juan  Joon Ching 《中国海洋湖沼学报》2019,37(3):871-880

The effect of sonication pretreatment condition on Eucheuma cottonii and Gelidium amansii seaweed towards agar extraction wae studied. Four parameters were changed during sonication to investigate the effects on agar yield and quality. These parameters include the time interval, concentration ratio, frequency, and intensity. The highest amount of agar extracted from Eucheuma cottonii species could be obtained from the time interval of 30 min, seaweed weight to solvent volume ratio of 1:20, the frequency of 35 Hz, and the sonication power intensity of 30%. For Gelidium amansii species, the best agar yield also could be obtained from the time interval of 30 min, 1:20 of seaweed weight to water volume ratio, the frequency of 35 Hz, and power intensity of 30%. From the experiment, sonication pretreatment significantly influenced the yield and properties of extracted agar. The sonication with autoclaved seaweed produced agar containing less sulfate content, which is an excellent chemical property for gel electrophoresis applications.The gel strength of sonication with autoclaving for both seaweeds, Eucheuma and Gelidium species was the highest among those by sonication with direct heating, which proved that sonication pretreatment with autoclaving could enhance the physical properties of the agar.  相似文献   

Uncertainty in applying the linear poroelasticity model to field situations as a result of periodic loading in heterogeneous aquifers          下载免费PDF全文

Ching‐Min Chang  Hund‐Der Yeh 《水文研究》2015,29(10):2454-2462

The solid Earth's surface frequently experience changes in total stresses as a result of periodic loading. When the fluid‐saturated porous media deform in response to changes in stress, the induced variations in pore volume affect the pore water pressure. The fluid flow therefore occurs in response to the gradient in the induced excess pore water pressure. This work aims at quantifying the spatial variability in excess pressure head produced by the periodic loading accounting for the variation of log hydraulic conductivity (lnK). It is important for the rational management of groundwater resources. A closed‐form expression is developed by the nonstationary spectral approach to analyse the influence of the statistical properties of lnK process, the hydraulic parameters, and the spatial position. The general stochastic framework outlined in this work provides a basis for assessing the impact of statistical properties of input aquifer parameters on the output variability (or uncertainty). Copyright © 2014 John Wiley & Sons, Ltd.  相似文献