Fluid identification and anisotropic parameters characterization are crucial for shale reservoir exploration and development.However,the anisotropic reflection coefficient equation,based on the transverse isotropy wit...Fluid identification and anisotropic parameters characterization are crucial for shale reservoir exploration and development.However,the anisotropic reflection coefficient equation,based on the transverse isotropy with a vertical axis of symmetry(VTI)medium assumption,involves numerous parameters to be inverted.This complexity reduces its stability and impacts the accuracy of seismic amplitude variation with offset(AVO)inversion results.In this study,a novel anisotropic equation that includes the fluid term and Thomsen anisotropic parameters is rewritten,which reduces the equation's dimensionality and increases its stability.Additionally,the traditional Markov Chain Monte Carlo(MCMC)inversion algorithm exhibits a high rejection rate for random samples and relies on known parameter distributions such as the Gaussian distribution,limiting the algorithm's convergence and sample randomness.To address these limitations and evaluate the uncertainty of AVO inversion,the IADR-Gibbs algorithm is proposed,which incorporates the Independent Adaptive Delayed Rejection(IADR)algorithm with the Gibbs sampling algorithm.Grounded in Bayesian theory,the new algorithm introduces support points to construct a proposal distribution of non-parametric distribution and reselects the rejected samples according to the Delayed Rejection(DR)strategy.Rejected samples are then added to the support points to update the proposal distribution function adaptively.The equation rewriting method and the IADR-Gibbs algorithm improve the accuracy and robustness of AVO inversion.The effectiveness and applicability of the proposed method are validated through synthetic gather tests and practical data applications.展开更多
Qingshankou shale(Gulong area,China)exhibits strong acoustic anisotropy characteristics,posing significant challenges to its exploration and development.In this study,the five full elastic constants and multipole resp...Qingshankou shale(Gulong area,China)exhibits strong acoustic anisotropy characteristics,posing significant challenges to its exploration and development.In this study,the five full elastic constants and multipole response law of the Qingshankou shale were studied using experimental measurements.Analyses show that the anisotropy parametersϵandγin the study region are greater than 0.4,whereas the anisotropy parameterδis smaller,generally 0.1.Numerical simulations show that the longitudinal and transverse wave velocities of these strong anisotropic rocks vary significantly with inclination angle,and significant differences in group velocity and phase velocity are also present.Acoustic logging measures the group velocity in dipped boreholes;this differs from the phase velocity to some extent.As the dip angle increases,the longitudinal and SH wave velocities increase accordingly,while the qSV-wave velocity initially increases and then decreases,reaching its maximum value at a dip of approximately 40°.These results provide an effective guide for the correction and modeling of acoustic logging time differences in the region.展开更多
Based on the extensive-dilatancy anisotropy theory, the method of synthetic seismogram is used to estimate the anisotropic parameters. The advantages of the method lie in that it avoids the singularity resolution and ...Based on the extensive-dilatancy anisotropy theory, the method of synthetic seismogram is used to estimate the anisotropic parameters. The advantages of the method lie in that it avoids the singularity resolution and saves calculation time of computer by using the eigenvalue and eigenvector analytical expressions of Christoffel equation, at the same time, the result is tested by coherence function. The test result reveals that there exists a fine linear relation between original records and synthetic records, indicating the anisotropic parameters estimated by synthetic seismogram can reflect and describe the anisotropic characteristics of the given region medium.展开更多
Torque measurements were performed on single crystal samples of Ca0.73La0.27(Fe0.96Co0.04)As2 in both the normal and superconducting states.Contributions to the torque signal from the paramagnetism and the vortex latt...Torque measurements were performed on single crystal samples of Ca0.73La0.27(Fe0.96Co0.04)As2 in both the normal and superconducting states.Contributions to the torque signal from the paramagnetism and the vortex lattice were identified.The superconducting anisotropy parameterγwas determined from the reversible part of the vortex contribution based on Kogan's model.It is found thatγ≈7.5 at t=T/Tc=0.85,which is smaller than the result of CaFe0.88Co0.12AsFγ≈15 at t=0.83,but larger than the result of 11 and 122 families,whereγstays in the range of 2-3.The moderate anisotropy of this 112 iron-based superconductor fills the gap between 11,122 families and 1111 families.In addition,we found that theγshows a temperature dependent behavior,i.e.,decreasing with increasing temperature.The fact thatγis not a constant point towards a multiband scenario in this compound.展开更多
Many rock types have naturally occurring inherent anisotropic planes, such as bedding planes, foliation,or flow structures. Such characteristic induces directional features and anisotropy in rocks＇ strength anddeform...Many rock types have naturally occurring inherent anisotropic planes, such as bedding planes, foliation,or flow structures. Such characteristic induces directional features and anisotropy in rocks＇ strength anddeformational properties. The HoekeBrown （HeB） failure criterion is an empirical strength criterionwidely applied to rock mechanics and engineering. A direct modification to HeB failure criterion toaccount for rock anisotropy is considered as the base of the research. Such modification introduced a newdefinition of the anisotropy as direct parameter named the anisotropic parameter （Kb）. However, thecomputation of this parameter takes much experimental work and cannot be calculated in a simple way.The aim of this paper is to study the trend of the relation between the degree of anisotropy （Rc） and theminimum value of anisotropic parameter （Kmin）, and to predict the Kmin directly from the uniaxialcompression tests instead of triaxial tests, and also to decrease the amount of experimental work. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.展开更多
Hexaferrites'magnetic and structural properties are highly sensitive to changes in sintering temperature and cationic replacements.We fabricated Ca_(0.5)Cu_(0.5)Fe_(12-x)DyxO_(19)hexaferrites using the sol-gel tec...Hexaferrites'magnetic and structural properties are highly sensitive to changes in sintering temperature and cationic replacements.We fabricated Ca_(0.5)Cu_(0.5)Fe_(12-x)DyxO_(19)hexaferrites using the sol-gel technique.We examined the phase,microstructure and magnetic aspects of the samples with respect to varying doping of rare earth dysprosium.The results show the expansion in the lattice upon incorporation of dysprosium against iron.Morphological studies confirm the uniform distribution of particles with slightly longitudinal nanoflakes in one direction.Magnetic investigations show an increase in magnetic saturation(Ms)with increasing dysprosium incorporation till optimum level is achieved for 15%doping concentration,with negligible change for maximum doping level.Furthermore,coercivity(Hc)and magnetic moment(mB)in terms of Bohr's magneton(μB)also show an increasing trend with dysprosium substitution levels.The maximum saturation magnetization of 33.355 emu/g is achieved with magnetic remanence of 18.290 emu/g,along with optimum magnetic moment of 6.249μB.In addition to the traditional magnetic parameters,magnetic anisotropy parameters were explored for the deep insights into magnetic parameters.These outcomes suggest that improved magnetic properties of Ca_(0.5)Cu_(0.5)Fe_(12-x)DyxO_(19)ferrites make it good substitute for storage devices,magnetic filters,and other magnetic applications.展开更多
Reservoirs with a group of vertical fractures in a vertical transversely isotropic(VTI)background are considered as orthorhombic(ORT)medium.However,fracture detection in ORT medium using seismic inversion methods rema...Reservoirs with a group of vertical fractures in a vertical transversely isotropic(VTI)background are considered as orthorhombic(ORT)medium.However,fracture detection in ORT medium using seismic inversion methods remains challenging,as it requires the estimation of more than eight parameters.Assuming the reservoir to be a weakly anisotropic ORT medium with small contrasts in the background elastic parameters,a new azimuthal elastic impedance equation was first derived using parameter combinations and mathematical approximations.This equation exhibited almost the same accuracy as the original equation and contained only six model parameters:the compression modulus,anisotropic shear modulus,anisotropic compression modulus,density,normal fracture weakness,and tangential fracture weakness.Subsequently,a stepwise inversion method using second-order derivatives of the elastic impedance was developed to estimate these parameters.Moreover,the Thomsen anisotropy parameter,epsilon,was estimated from the inversion results using the ratio of the anisotropic compression modulus to the compression modulus.Synthetic examples with moderate noise and field data examples confirm the feasibility and effectiveness of the inversion method.The proposed method exhibited accuracy similar to that of previous inversion strategies and could predict richer vertical fracture information.Ultimately,the method was applied to a three-dimensional work area,and the predictions were consistent with logging and geological a priori information,confirming the effectiveness of this method.Summarily,the proposed stepwise inversion method can alleviate the uncertainty of multi-parameter inversion in ORT medium,thereby improving the reliability of fracture detection.展开更多
Photodissociation dynamics of ketene at 218 nm has been investigated using the velocity map ion-imaging method. Both angular and translational energy distributions for the CO products at different rotational and vibra...Photodissociation dynamics of ketene at 218 nm has been investigated using the velocity map ion-imaging method. Both angular and translational energy distributions for the CO products at different rotational and vibrational states have been obtained. The 2＋1 REMPI spectrum of CO products is also obtained. The results are as bellow： （i） CO products in the first two vibrational states （ v＂=0 and v＂=1 ） exhibit significant rotational excitation. Furthermore the rotational excitation of CO at the v＂=0 level is noticeably higher than that at the v＂=1 level. （ii） It was found that the major photodissociation pathway of ketene at 218 nm is the CH2（ǎ^1A1）＋CO（X^1∑^＋） channel, while the CH2（b^1B1）＋CO（X^1∑^＋） channel and the CH2（X^3B1）＋CO（X^1E^＋） channel are also likely present, （iii） The anisotropy parameters β of CO different rovibronic states all appear to be larger than zero. No significant difference is observed at the two vibrational states,展开更多
Vacuum ultraviolet photodissociation dynamics of N2O+hν→N2(X^(1)Σg+)+O(^(1)S0)in the short wavelength tail of D^(1)Σ+band has been investigated using the time-sliced velocity-mapped ion imaging technique by probin...Vacuum ultraviolet photodissociation dynamics of N2O+hν→N2(X^(1)Σg+)+O(^(1)S0)in the short wavelength tail of D^(1)Σ+band has been investigated using the time-sliced velocity-mapped ion imaging technique by probing the images of the O(^(1)S0)photoproducts at a set of photolysis wavelengths including 121.47 nm,122.17 nm,123.25 nm and 123.95 nm.The product total kinetic energy release distributions,vibrational state distributions of the N2(X^(1)Σg+)photofragments and angular anisotropy parameters have been obtained by analyzing the raw O(^(1)S0)images.It is noted that additional vibrationally excited photoproducts(3≤v≤8)with a Boltzmann-like feature start to appear except the non-statistical component as the photolysis wavelength decreases to 123.25 nm,and the corresponding populations become more pronounced with decreasing of the photolysis wavelength.Furthermore,the vibrational state specific anisotropy parameterβat each photolysis wavelength exhibits a drastic fluctuation nearβ=1.75 at v<8,and decreases to a minimum as the vibrational quantum number further increases.While the overall anisotropy parameterβfor the N2(X^(1)Σg+)+O(^(1)S0)channel presents a roughly monotonical increase from 1.63 at 121.47 nm to 1.95 at 123.95 nm.The experimental observations suggest that there is at least one fast nonadiabatic pathway from initially prepared D^(1)Σ+state to the dissociative state with bent geometry dominating to generate the additional vibrational structures at high photoexcitation energies.展开更多
When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energ...When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.展开更多
We introduce a method to study anisotropic flow parameter v n as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatia...We introduce a method to study anisotropic flow parameter v n as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients ε n of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by v n /ε n . In this paper, we will discuss in particular the second （n = 2） and the fourth （n = 4） harmonics.展开更多
基金the sponsorship of the Key Technology for Geophysical Prediction of Ultra-Deep Carbonate Reservoirs(P24240)the National Natural Science Foundation of China(U24B2020)the National Science and Technology Major Project of China for New Oil and Gas Exploration and Development(Grant No.2024ZD1400102)。
文摘Fluid identification and anisotropic parameters characterization are crucial for shale reservoir exploration and development.However,the anisotropic reflection coefficient equation,based on the transverse isotropy with a vertical axis of symmetry(VTI)medium assumption,involves numerous parameters to be inverted.This complexity reduces its stability and impacts the accuracy of seismic amplitude variation with offset(AVO)inversion results.In this study,a novel anisotropic equation that includes the fluid term and Thomsen anisotropic parameters is rewritten,which reduces the equation's dimensionality and increases its stability.Additionally,the traditional Markov Chain Monte Carlo(MCMC)inversion algorithm exhibits a high rejection rate for random samples and relies on known parameter distributions such as the Gaussian distribution,limiting the algorithm's convergence and sample randomness.To address these limitations and evaluate the uncertainty of AVO inversion,the IADR-Gibbs algorithm is proposed,which incorporates the Independent Adaptive Delayed Rejection(IADR)algorithm with the Gibbs sampling algorithm.Grounded in Bayesian theory,the new algorithm introduces support points to construct a proposal distribution of non-parametric distribution and reselects the rejected samples according to the Delayed Rejection(DR)strategy.Rejected samples are then added to the support points to update the proposal distribution function adaptively.The equation rewriting method and the IADR-Gibbs algorithm improve the accuracy and robustness of AVO inversion.The effectiveness and applicability of the proposed method are validated through synthetic gather tests and practical data applications.
基金supported by Major Science and Technology Special Project of China National Petroleum Corporation"Research on Large scale Storage and Production Increase and Exploration and Development Technology of Continental Shale Oil"(2023ZZ15)。
文摘Qingshankou shale(Gulong area,China)exhibits strong acoustic anisotropy characteristics,posing significant challenges to its exploration and development.In this study,the five full elastic constants and multipole response law of the Qingshankou shale were studied using experimental measurements.Analyses show that the anisotropy parametersϵandγin the study region are greater than 0.4,whereas the anisotropy parameterδis smaller,generally 0.1.Numerical simulations show that the longitudinal and transverse wave velocities of these strong anisotropic rocks vary significantly with inclination angle,and significant differences in group velocity and phase velocity are also present.Acoustic logging measures the group velocity in dipped boreholes;this differs from the phase velocity to some extent.As the dip angle increases,the longitudinal and SH wave velocities increase accordingly,while the qSV-wave velocity initially increases and then decreases,reaching its maximum value at a dip of approximately 40°.These results provide an effective guide for the correction and modeling of acoustic logging time differences in the region.
基金National Natural Science Foundation of China (D4007410) and Joint Seismological Science Foundation of China (603006).
文摘Based on the extensive-dilatancy anisotropy theory, the method of synthetic seismogram is used to estimate the anisotropic parameters. The advantages of the method lie in that it avoids the singularity resolution and saves calculation time of computer by using the eigenvalue and eigenvector analytical expressions of Christoffel equation, at the same time, the result is tested by coherence function. The test result reveals that there exists a fine linear relation between original records and synthetic records, indicating the anisotropic parameters estimated by synthetic seismogram can reflect and describe the anisotropic characteristics of the given region medium.
基金Project supported by NSAF,China(Grant No.U1530402)P.G.Li acknowledges the support of the National Natural Science Foundation of China(Grant No.51572241).
文摘Torque measurements were performed on single crystal samples of Ca0.73La0.27(Fe0.96Co0.04)As2 in both the normal and superconducting states.Contributions to the torque signal from the paramagnetism and the vortex lattice were identified.The superconducting anisotropy parameterγwas determined from the reversible part of the vortex contribution based on Kogan's model.It is found thatγ≈7.5 at t=T/Tc=0.85,which is smaller than the result of CaFe0.88Co0.12AsFγ≈15 at t=0.83,but larger than the result of 11 and 122 families,whereγstays in the range of 2-3.The moderate anisotropy of this 112 iron-based superconductor fills the gap between 11,122 families and 1111 families.In addition,we found that theγshows a temperature dependent behavior,i.e.,decreasing with increasing temperature.The fact thatγis not a constant point towards a multiband scenario in this compound.
文摘Many rock types have naturally occurring inherent anisotropic planes, such as bedding planes, foliation,or flow structures. Such characteristic induces directional features and anisotropy in rocks＇ strength anddeformational properties. The HoekeBrown （HeB） failure criterion is an empirical strength criterionwidely applied to rock mechanics and engineering. A direct modification to HeB failure criterion toaccount for rock anisotropy is considered as the base of the research. Such modification introduced a newdefinition of the anisotropy as direct parameter named the anisotropic parameter （Kb）. However, thecomputation of this parameter takes much experimental work and cannot be calculated in a simple way.The aim of this paper is to study the trend of the relation between the degree of anisotropy （Rc） and theminimum value of anisotropic parameter （Kmin）, and to predict the Kmin directly from the uniaxialcompression tests instead of triaxial tests, and also to decrease the amount of experimental work. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.
基金the Deanship of Scientific Research at King Khalid University for funding this work through a large group Research Project under grant(RGP2/111/45)。
文摘Hexaferrites'magnetic and structural properties are highly sensitive to changes in sintering temperature and cationic replacements.We fabricated Ca_(0.5)Cu_(0.5)Fe_(12-x)DyxO_(19)hexaferrites using the sol-gel technique.We examined the phase,microstructure and magnetic aspects of the samples with respect to varying doping of rare earth dysprosium.The results show the expansion in the lattice upon incorporation of dysprosium against iron.Morphological studies confirm the uniform distribution of particles with slightly longitudinal nanoflakes in one direction.Magnetic investigations show an increase in magnetic saturation(Ms)with increasing dysprosium incorporation till optimum level is achieved for 15%doping concentration,with negligible change for maximum doping level.Furthermore,coercivity(Hc)and magnetic moment(mB)in terms of Bohr's magneton(μB)also show an increasing trend with dysprosium substitution levels.The maximum saturation magnetization of 33.355 emu/g is achieved with magnetic remanence of 18.290 emu/g,along with optimum magnetic moment of 6.249μB.In addition to the traditional magnetic parameters,magnetic anisotropy parameters were explored for the deep insights into magnetic parameters.These outcomes suggest that improved magnetic properties of Ca_(0.5)Cu_(0.5)Fe_(12-x)DyxO_(19)ferrites make it good substitute for storage devices,magnetic filters,and other magnetic applications.
基金sponsorship of the National Natural Science Foundation of China(42430809,42274157,42030103,42404132)the Fund of State Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China)(SKLDOG2024-ZYTS-02)+5 种基金the Postdoctoral Fellowship Program of CPSF(GZB20240850)the Postdoctoral Project of Qingdao(QDBSH20240102082)the Fundamental Research Funds for the Central Universities(24CX07004A,24CX06036A)the CNPC Innovation Fund(2024DQ02-0505,2024DQ02-0136)the Innovation fund project for graduate student of China University of Petroleum(East China)the Fundamental Research Funds for the Central Universities(24CX04002A).
文摘Reservoirs with a group of vertical fractures in a vertical transversely isotropic(VTI)background are considered as orthorhombic(ORT)medium.However,fracture detection in ORT medium using seismic inversion methods remains challenging,as it requires the estimation of more than eight parameters.Assuming the reservoir to be a weakly anisotropic ORT medium with small contrasts in the background elastic parameters,a new azimuthal elastic impedance equation was first derived using parameter combinations and mathematical approximations.This equation exhibited almost the same accuracy as the original equation and contained only six model parameters:the compression modulus,anisotropic shear modulus,anisotropic compression modulus,density,normal fracture weakness,and tangential fracture weakness.Subsequently,a stepwise inversion method using second-order derivatives of the elastic impedance was developed to estimate these parameters.Moreover,the Thomsen anisotropy parameter,epsilon,was estimated from the inversion results using the ratio of the anisotropic compression modulus to the compression modulus.Synthetic examples with moderate noise and field data examples confirm the feasibility and effectiveness of the inversion method.The proposed method exhibited accuracy similar to that of previous inversion strategies and could predict richer vertical fracture information.Ultimately,the method was applied to a three-dimensional work area,and the predictions were consistent with logging and geological a priori information,confirming the effectiveness of this method.Summarily,the proposed stepwise inversion method can alleviate the uncertainty of multi-parameter inversion in ORT medium,thereby improving the reliability of fracture detection.
基金This work is suppotted by the Chinese Academy of Sciences,the Ministry of Science and Technology,and the National Natural Science Foundation of China.
文摘Photodissociation dynamics of ketene at 218 nm has been investigated using the velocity map ion-imaging method. Both angular and translational energy distributions for the CO products at different rotational and vibrational states have been obtained. The 2＋1 REMPI spectrum of CO products is also obtained. The results are as bellow： （i） CO products in the first two vibrational states （ v＂=0 and v＂=1 ） exhibit significant rotational excitation. Furthermore the rotational excitation of CO at the v＂=0 level is noticeably higher than that at the v＂=1 level. （ii） It was found that the major photodissociation pathway of ketene at 218 nm is the CH2（ǎ^1A1）＋CO（X^1∑^＋） channel, while the CH2（b^1B1）＋CO（X^1∑^＋） channel and the CH2（X^3B1）＋CO（X^1E^＋） channel are also likely present, （iii） The anisotropy parameters β of CO different rovibronic states all appear to be larger than zero. No significant difference is observed at the two vibrational states,
基金supported by the National Natural Science Foundation of China(No.21773213)。
文摘Vacuum ultraviolet photodissociation dynamics of N2O+hν→N2(X^(1)Σg+)+O(^(1)S0)in the short wavelength tail of D^(1)Σ+band has been investigated using the time-sliced velocity-mapped ion imaging technique by probing the images of the O(^(1)S0)photoproducts at a set of photolysis wavelengths including 121.47 nm,122.17 nm,123.25 nm and 123.95 nm.The product total kinetic energy release distributions,vibrational state distributions of the N2(X^(1)Σg+)photofragments and angular anisotropy parameters have been obtained by analyzing the raw O(^(1)S0)images.It is noted that additional vibrationally excited photoproducts(3≤v≤8)with a Boltzmann-like feature start to appear except the non-statistical component as the photolysis wavelength decreases to 123.25 nm,and the corresponding populations become more pronounced with decreasing of the photolysis wavelength.Furthermore,the vibrational state specific anisotropy parameterβat each photolysis wavelength exhibits a drastic fluctuation nearβ=1.75 at v<8,and decreases to a minimum as the vibrational quantum number further increases.While the overall anisotropy parameterβfor the N2(X^(1)Σg+)+O(^(1)S0)channel presents a roughly monotonical increase from 1.63 at 121.47 nm to 1.95 at 123.95 nm.The experimental observations suggest that there is at least one fast nonadiabatic pathway from initially prepared D^(1)Σ+state to the dissociative state with bent geometry dominating to generate the additional vibrational structures at high photoexcitation energies.
文摘When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.
基金Supported by Knowledge Innovation Program of Chinese Academy of Sciences (kjcx2-yw-a14)NSFC (11005083)+3 种基金Sub-topics of 973 for Ministry of Science and Technology (2008CB817707)Key Laboratory of Quark and Lepton Physics (Huazhong Normal University)Ministry of Education, China (QLPL2009P01)Guided Project B, Educational Commission of Hubei Province of China (B20101103)
文摘We introduce a method to study anisotropic flow parameter v n as a collective probe to Quark Gluon Plasma in relativistic heavy ion collisions. The emphasis is put on the use of the Fourier expansion of initial spatial azimuthal distributions of participant nucleons in the overlapped region. The coefficients ε n of Fourier expansion are called the spatial anisotropy parameter for the n-th harmonic. We propose that collective dynamics can be studied by v n /ε n . In this paper, we will discuss in particular the second （n = 2） and the fourth （n = 4） harmonics.
