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Search Results: 1 - 10 of 27586 matches for " Hengshan Hu "
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Simulation of Acousto-Electric Well Logging Based on Simplified Pride Equations


地球物理学报 , 2003,
Abstract: A numerical full-waveform simulation method is proposed to study the acousto-electric well logging response. The acoustic field, taken as uninfluenced by the converted electric field, is solved separately. The electric field is taken as quasi-steady. A point pressure source is assumed to be on the borehole axis. The full Biot theory is adopted to obtain expressions of the acoustic field around the borehole. These acoustic expressions are then used to formulate the converted electric fields in and out of the borehole. In the calculated full waveforms of the converted electric field, there are electric waves that accompany the compressional, the shear and the Stoneley waves. And there is a critically refracted electromagnetic wave, which travels along the borehole wall. The waveforms are practically the same as calculated with the full Pride theory under frequency of 25kHz.
Simulation of Monopole and Multipole Seismoelectric Logging
Zhiwen Cui,Jinxia Liu,Yujun Zhang,Kexie Wang,Hengshan Hu
Advances in Acoustics and Vibration , 2011, DOI: 10.1155/2011/107827
Abstract: In a fluid-saturated porous formation, acoustics and electromagnetic waves are coupled based on Pride seismoelectric theory. An exact treatment of the nonaxisymmetric seismoelectric field excited by acoustic multipole sources is presented. The frequency wavenumber domain representations of the acoustic field and associated seismoelectric field due to acoustic multipole sources are formulated. The full waveforms of acoustic waves and electric and magnetic fields in the time domain propagation in borehole are simulated by using discrete wave number integration, and frequency versus axial-wave number responses are presented and analyzed. 1. Introduction The study of wave propagation in a fluid-saturated porous medium is of considerable interest in acoustics and geophysics due to its important applications in various technical and engineering processes. The investigation of wave propagation in fluid-saturated porous media was early developed by Biot [1, 2]. One of the major findings of Biot’s theory was that there is a compressional slow wave in a fluid-saturated porous medium. The first clear experimental observation of this slow wave was reported by Plona [3]. Biot predicted the slow waves should have an important bearing on electrokinetic effect [4]. This predication has been quantitatively confirmed by Pride [5] and Hu [6]. Elastic waves propagating in fluid-saturated porous media generate a movement of the ions in the pore fluid. Such movement induces an electromagnetic (EM) field. Thompson and Gist [7] have made field measurement clearly demonstrating that seismic waves can induce electromagnetic disturbances in saturated sediments. Pride [8] derived the governing equations for the coupled acoustics and electromagnetic waves in fluid-saturated porous media. Pride and Haartsen [9] analyzed the basic properties of seismoelectric waves. The electric field induced by elastic waves is weak and attenuates in propagation. In order to detect the seismoelectric signal effectively, Haartsen and Pride [10] suggested measuring vertical electroseismic profile. Mikhailov et al. [11] measured the electric field converted from low frequency Stoneley waves in a borehole and made theoretical analysis. Seismoelectric logging method has been proposed to detect deep target formation. The advantage of seismoelectric logging is the distance both from transmitter to target formation and from the transmitter to the receiver is small, and signals can be received with relative high amplitude. Zhu et al. [12–14] made laboratory experiments and observed the seismoelectric
Simulation of well-log response of the acoustically-induced electromagnetic field in a porous formation

Hu Hengshan Liu Jiaqi,

力学学报 , 2004,
Abstract: During acousto-electric logging, the acoustic wave excited by a point acoustic source in a fluidfilled borehole propagates into the fluid-saturated porous medium and causes relative motion between the charge-bearing pore fluid and the skeleton, inducing electromagnetic field. To simulate the logging response, a numerical full-waveform simulation method is proposed. The acoustic field is taken as uninfluenced by the converted electromagnetic field, and is solved separately. The electric field is taken as quasi-steady. The full Biot-Rosenbaum model is adopted to obtain expressions for the acoustic field around the borehole. These expressions are then used to formulate the converted electric and magnetic fields in and out of the borehole. Calculations show there are electric and magnetic fields that accompany the compressional, the shear and the Stoneley waves. And there is a critically refracted electromagnetic wave, which travels along the borehole wall. The amplitude of this wave is very weak in the full waveform. Both the axial and the radial components of the electric field increase when the receiver is placed farther off the borehole axis. On the borehole wall, the shape of the waveform of magnetic field is similar to that of the axial electric field.


地球物理学报 , 2003,
Abstract: Potapof's equations for the first and the second types of seismoelectric effects are analyzed. The first type of seismoelectric effect refers to elastic wave induced conductivity change. When no macroscopic static electric field exists, Potapof's equations are reduced to equations for the second type of seismoelectric effect, which is also described by Pride's equations. Comparison is made between these two sets of equations. When ignoring the coupling between elastic and electromagnetic field, both the Pride's and the Potapof's equations reduce to equations for poroelasticity. The elastodynamical parameters in Potapof's equations are explained with well-known parameters in Biot's theory for elastic waves. By comparison to Biot theory, it is clear that in Potapof's equations the mass coupling between fluid and solid frame is ignored. The square of porosity is erroneously taken as porosity in the viscous damping term, which may lead to exaggerated amplitudes of the elastic wave and its converted electric wave. And there is an error in the boundary condition about fluid filtration across the interface, which influence the study on the behavior of reflection and refraction of the seismoelectric waves on boundaries.
Effects of N rates on N uptake and yield in erect panicle rice  [PDF]
Guiyun Song, Zhengjin Xu, Hengshan Yang
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.49067

The field experiment was conducted in 2005 and 2006 at Northern Japonica Rice Cultivation and Breeding Research Center, Shenyang Agricultural University,Shenyang, northeast China. Shennong 265 (typical erect panicle rice cultivar), and Liaojing 294 (traditional semi-erect panicle rice cultivar) were grown under different N rates to assess N uptake and N use efficiency. Nitrgen (N) uptake of two rice cultivars increased in their response to N improvement. Grain N of Liaojing 294 predominantly came from root absorption on low N treatments, while grain N of Shennong 265 mainly came from root absorption and had less N re-transferring from vegetative organs under high N rates. Shennong 265 produced less N uptake before heading and more N uptake after heading than Liaojing 294. GY was highly related with N fertilizer rate (r2 = 0.870** for Shennong 265, r2 = 0.613* for Liaojing 294). Shennong 265 was a N-unefficient genotype, since it produced low yield at low N levels and responded well to N application. Liaojing 294 was a N-efficient genotype producing high yield at both low and high N rates. NNG and NFUE exhibited positive correlation with N application rates, but NUEPG showed negative correlation with N application rates; GY as well as BIO and N uses efficiency parameters (TN, NNG, NFUE) which were all positively correlate, while the correlation between GY as well as BIO and the other N efficiency indicators expressed negative correlation. The relationship between GY and TN as well as BIO and TN was observed with significant difference (r2 = 0.824**, r2 = -0.858

Financial Volatility Forecasting by Least Square Support Vector Machine Based on GARCH, EGARCH and GJR Models: Evidence from ASEAN Stock Markets
Phichhang Ou,Hengshan Wang
International Journal of Economics and Finance , 2010, DOI: 10.5539/ijef.v2n1p51
Abstract: In this paper, we aim at comparing semi-parametric method, LSSVM (Least square support vector machine), with the classical GARCH(1,1), EGARCH(1,1) and GJR(1,1) models to forecast financial volatilities of three major ASEAN stock markets. More precisely, the experimental results suggest that using hybrid models, GARCH-LSSVM, EGARCH-LSSVM and GJR-LSSVM provides improved performances in forecasting the leverage effect volatilities, especially during the recently global financial market crashes in 2008.
Modeling and Forecasting Stock Market Volatility by Gaussian Processes based on GARCH, EGARCH and GJR Models
PhichHang Ou,Hengshan Wang
Lecture Notes in Engineering and Computer Science , 2011,
Prediction of Stock Market Index Movement by Ten Data Mining Techniques
Phichhang Ou,Hengshan Wang
Modern Applied Science , 2009, DOI: 10.5539/mas.v3n12p28
Abstract: Ability to predict direction of stock/index price accurately is crucial for market dealers or investors to maximize their profits. Data mining techniques have been successfully shown to generate high forecasting accuracy of stock price movement. Nowadays, in stead of a single method, traders need to use various forecasting techniques to gain multiple signals and more information about the future of the markets. In this paper, ten different techniques of data mining are discussed and applied to predict price movement of Hang Seng index of Hong Kong stock market. The approaches include Linear discriminant analysis (LDA), Quadratic discriminant analysis (QDA), K-nearest neighbor classification, Na ve Bayes based on kernel estimation, Logit model, Tree based classification, neural network, Bayesian classification with Gaussian process, Support vector machine (SVM) and Least squares support vector machine (LS-SVM). Experimental results show that the SVM and LS-SVM generate superior predictive performances among the other models. Specifically, SVM is better than LS-SVM for in-sample prediction but LS-SVM is, in turn, better than the SVM for the out-of-sample forecasts in term of hit rate and error rate criteria.
Empirical Research on Associations among Information Technology, Supply Chain Robustness and Supply Chain Performance
Xinrui Zhang,Hengshan Wang
International Journal of Business and Management , 2011, DOI: 10.5539/ijbm.v6n2p231
Abstract: Supply chain reliability and ability to do with risks are important research fields in SCM. Although it is intuitive that supply chain’s ability to resist risks is likely to have a positive impact on supply chain performance, there is little systematic analysis and documentation of the magnitude of these impacts in the literature. This paper empirically documents the associations among information technology, supply chain robustness, and supply chain performance. Based on a sample of 186 questionnaires, the results show the positive impact of information technology on supply chain robustness and supply chain performance, and also the positive impact of supply chain robustness and supply chain performance.
Review on SCM Empirical Research Published in Chinese Journals: Trends and Future Research Directions
Xinrui Zhang,Hengshan Wang
Asian Social Science , 2010, DOI: 10.5539/ass.v6n8p104
Abstract: Supply chain management (SCM) is an important research field and has yield many valuable theories and methods. To use empirical research methods to build and testify the theories in SCM field is not only necessary but fruitful. This paper reviews and evaluates SCM empirical research in 63 papers published in Chinese journals from 2001 to 2009, to assess these papers’ research purposes, research industries, research contents, data collection approaches, and data analysis technologies. To compare the SCM empirical research in China with the research in USA, we find some interesting differences and make a conclusion of the problems in Chinese research. We also discuss the trends and directions for further empirical research in SCM.
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