We develop a benchmark system for van der Waals interactions obtained with MP2+△CCSD(T)method at complete basis set limit.With this benchmark,we examine the widely used PBE+D3 method and recently developed SCAN+rVV10...We develop a benchmark system for van der Waals interactions obtained with MP2+△CCSD(T)method at complete basis set limit.With this benchmark,we examine the widely used PBE+D3 method and recently developed SCAN+rVV10 method for density functional theory calculations.Our benchmark is based on two molecules:glycine(or Gly,an amino acid)and uracil(or U,an RNA base).We consider six dimer configurations of the two monomers and their potential energy surfaces as a function of relative distance and rotation angle.The Gly-Gly,Gly-U,and U-U pairs represent London dispersion,hydrogen bonding,andπ–πstacking interactions,respectively.Our results show that both PBE+D3 and SCAN+rVV10 methods can yield accuracy better than 1 kcal/mol,except for the cases when the distance between the two monomers is significantly smaller than the equilibrium distance.In such a case,neither of these methods can yield uniformly accurate results for all the configurations.In addition,it is found that the SCAN and SCAN+rVV10 methods can reproduce some subtle features in a rotational potential energy curve,while the PBE,PBE+D3,and the local density approximation fail.展开更多
WITHDRAWAL:Zhang,J.J.,Guo,Y.Q.,Qin,Z.Y.,Wei,C.T.,Hu,Q.H.,Vandeginste,V.,Miao,H.Y.,Yao,P.,and Zhang,P.F.,“Predicting Irreducible Water Saturation of Unconventional Reservoirs by Using NMR T2 Spectra:Methods of Morphol...WITHDRAWAL:Zhang,J.J.,Guo,Y.Q.,Qin,Z.Y.,Wei,C.T.,Hu,Q.H.,Vandeginste,V.,Miao,H.Y.,Yao,P.,and Zhang,P.F.,“Predicting Irreducible Water Saturation of Unconventional Reservoirs by Using NMR T2 Spectra:Methods of Morphological Division and Fractal Models”,Acta Geologica Sinica-English Edition(Accepted Article):https://doi.org/10.1111/1755-6724.15094.展开更多
Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for st...Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for static analysis of such structures.In the MRRM for dynamic analysis, amplitudes of arriving and departing waves for joints are chosen as unknown quantities. However, for the present case of static analysis, displacements and rotational angles at the ends of each beam member are directly considered as unknown quantities. The expressions for stiffness matrices for anisotropic beam members are developed. A corresponding reverberation matrix is derived analytically for exact and unified determination on the displacements and internal forces at both ends of each member and arbitrary cross sectional locations in the structure. Numerical examples are given and compared with the finite element method（FEM） results to validate the present model. The characteristic parameter analysis is performed to demonstrate accuracy of the present model with the T beam theory in contrast with errors in the usual model based on the Euler-Bernoulli（EB） beam theory. The resulting reverberation matrix can be used for exact calculation of anisotropic framed structures as well as for parameter analysis of geometrical and material properties of the framed structures.展开更多
Based on analysis of NMR T2 spectral characteristics,a new method for identifying fluid properties by decomposing T2 spectrum through signal analysis has been proposed.Because T2 spectrum satisfies lognormal distribut...Based on analysis of NMR T2 spectral characteristics,a new method for identifying fluid properties by decomposing T2 spectrum through signal analysis has been proposed.Because T2 spectrum satisfies lognormal distribution on transverse relaxation time axis,the T2 spectrum can be decomposed into 2 to 5 independent component spectra by fitting the T2 spectrum with Gauss functions.By analyzing the free relaxation response characteristics of crude oil and formation water,the dynamic response characteristics of the core mutual drive between oil and water,the petrophysical significance of each component spectrum is clarified.T2 spectrum can be decomposed into clay bound water component spectrum,capillary bound fluid component spectrum,micropores fluid component spectrum and macropores fluid component spectrum.According to the nature of crude oil in the target area,the distribution range of T2 component spectral peaks of oil-bearing reservoir is 165-500 ms on T2 time axis.This range can be used to accurately identify fluid properties.This method has high adaptability in identifying complex oil and water layers in low porosity and permeability reservoirs.展开更多
A water rocket is a rocket system that obtains thrust by injecting water with compressed air of up to about 8 atmospheres. It is usually manufactured using a pressure-resistant PET bottle. The mechanical elements and ...A water rocket is a rocket system that obtains thrust by injecting water with compressed air of up to about 8 atmospheres. It is usually manufactured using a pressure-resistant PET bottle. The mechanical elements and principles contained in the water rocket have much in common with the actual small rocket system, and are suitable as educational and research teaching materials in the field of mechanics. Especially in the field of disaster prevention and mitigation, the use of water rockets is being researched and developed as a rescue tool in the event of a flood or earthquake as a disaster countermeasure. However, since the water rocket is a flying object based on the mechanical principle, it is important to ensure the accuracy and stability of the flight path. In this paper, a mechanical simulator is developed with a numerical calculation program based on the mechanical consideration of water rocket flight performance. In addition, the correlation between the flight distance obtained in the simulation and the estimated flight distance is analyzed by applying a multivariate analysis method and verifying the validity of the flight distance calculated from the result. Based on the verification results, we will apply a statistical optimization method to approach the optimization of flight stability performance conditions for water rockets.展开更多
To make the quantitative results of nuclear magnetic resonance(NMR) transverse relaxation(T;) spectrums reflect the type and pore structure of reservoir more directly, an unsupervised clustering method was developed t...To make the quantitative results of nuclear magnetic resonance(NMR) transverse relaxation(T;) spectrums reflect the type and pore structure of reservoir more directly, an unsupervised clustering method was developed to obtain the quantitative pore structure information from the NMR T;spectrums based on the Gaussian mixture model(GMM). Firstly, We conducted the principal component analysis on T;spectrums in order to reduce the dimension data and the dependence of the original variables. Secondly, the dimension-reduced data was fitted using the GMM probability density function, and the model parameters and optimal clustering numbers were obtained according to the expectation-maximization algorithm and the change of the Akaike information criterion. Finally, the T;spectrum features and pore structure types of different clustering groups were analyzed and compared with T;geometric mean and T;arithmetic mean. The effectiveness of the algorithm has been verified by numerical simulation and field NMR logging data. The research shows that the clustering results based on GMM method have good correlations with the shape and distribution of the T;spectrum, pore structure, and petroleum productivity, providing a new means for quantitative identification of pore structure, reservoir grading, and oil and gas productivity evaluation.展开更多
In this paper, the limitation of T matrix structure is analyzed. It is found that a solution by T matrix method can be transformed to a canonical solution when the boundary of the scatterer tends to the cylindrical ...In this paper, the limitation of T matrix structure is analyzed. It is found that a solution by T matrix method can be transformed to a canonical solution when the boundary of the scatterer tends to the cylindrical form and the scatterer is illuminated by E plane waves. It is concluded that a T matrix is diagonal with the scatter boundary in this limit situation. This is also the best result of numerical solution.展开更多
This paper mainly talks about a popular approach of volatility of a GARCH-type model in R, while the disturbances are independent and have identical Student-t distribution. It uses the Metropolis-Hastings method to pe...This paper mainly talks about a popular approach of volatility of a GARCH-type model in R, while the disturbances are independent and have identical Student-t distribution. It uses the Metropolis-Hastings method to perform the computations and gives the programs in details in R.展开更多
[Objectives] This study was conducted to further investigate the taxonomic status of Hainan population of Trimeresurus stejnegeri from the morphological point of view.[Methods]The difference coefficients between diffe...[Objectives] This study was conducted to further investigate the taxonomic status of Hainan population of Trimeresurus stejnegeri from the morphological point of view.[Methods]The difference coefficients between different populations were compared using the 75% law,and the relationship between scales and latitudes was analyzed.[Results] The scales(abdominal and subcaudal) of 325 Trimeresurus individuals were counted according to China Animal Fauna,including156 T.stejnegeri individuals.Some difference coefficients between the Hainan population and others were greater than 1.28,and there was no correlation between the number of scales and latitude.It conforms to subclassification criteria.[Conclusions]The view about the subspecies status of T.stejnegeri chenbihuii should be supported.展开更多
基金supported by US National Science Foundation under Grant No. DMREF-1627028
文摘We develop a benchmark system for van der Waals interactions obtained with MP2+△CCSD(T)method at complete basis set limit.With this benchmark,we examine the widely used PBE+D3 method and recently developed SCAN+rVV10 method for density functional theory calculations.Our benchmark is based on two molecules:glycine(or Gly,an amino acid)and uracil(or U,an RNA base).We consider six dimer configurations of the two monomers and their potential energy surfaces as a function of relative distance and rotation angle.The Gly-Gly,Gly-U,and U-U pairs represent London dispersion,hydrogen bonding,andπ–πstacking interactions,respectively.Our results show that both PBE+D3 and SCAN+rVV10 methods can yield accuracy better than 1 kcal/mol,except for the cases when the distance between the two monomers is significantly smaller than the equilibrium distance.In such a case,neither of these methods can yield uniformly accurate results for all the configurations.In addition,it is found that the SCAN and SCAN+rVV10 methods can reproduce some subtle features in a rotational potential energy curve,while the PBE,PBE+D3,and the local density approximation fail.
文摘WITHDRAWAL:Zhang,J.J.,Guo,Y.Q.,Qin,Z.Y.,Wei,C.T.,Hu,Q.H.,Vandeginste,V.,Miao,H.Y.,Yao,P.,and Zhang,P.F.,“Predicting Irreducible Water Saturation of Unconventional Reservoirs by Using NMR T2 Spectra:Methods of Morphological Division and Fractal Models”,Acta Geologica Sinica-English Edition(Accepted Article):https://doi.org/10.1111/1755-6724.15094.
基金Project supported by the Program for New Century Excellent Talents in Universities(NCET)by the Ministry of Education of China(No.NCET-04-0373)
文摘Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for static analysis of such structures.In the MRRM for dynamic analysis, amplitudes of arriving and departing waves for joints are chosen as unknown quantities. However, for the present case of static analysis, displacements and rotational angles at the ends of each beam member are directly considered as unknown quantities. The expressions for stiffness matrices for anisotropic beam members are developed. A corresponding reverberation matrix is derived analytically for exact and unified determination on the displacements and internal forces at both ends of each member and arbitrary cross sectional locations in the structure. Numerical examples are given and compared with the finite element method（FEM） results to validate the present model. The characteristic parameter analysis is performed to demonstrate accuracy of the present model with the T beam theory in contrast with errors in the usual model based on the Euler-Bernoulli（EB） beam theory. The resulting reverberation matrix can be used for exact calculation of anisotropic framed structures as well as for parameter analysis of geometrical and material properties of the framed structures.
基金Supported by the China National Science and Technology Major Project(2016ZX05050)
文摘Based on analysis of NMR T2 spectral characteristics,a new method for identifying fluid properties by decomposing T2 spectrum through signal analysis has been proposed.Because T2 spectrum satisfies lognormal distribution on transverse relaxation time axis,the T2 spectrum can be decomposed into 2 to 5 independent component spectra by fitting the T2 spectrum with Gauss functions.By analyzing the free relaxation response characteristics of crude oil and formation water,the dynamic response characteristics of the core mutual drive between oil and water,the petrophysical significance of each component spectrum is clarified.T2 spectrum can be decomposed into clay bound water component spectrum,capillary bound fluid component spectrum,micropores fluid component spectrum and macropores fluid component spectrum.According to the nature of crude oil in the target area,the distribution range of T2 component spectral peaks of oil-bearing reservoir is 165-500 ms on T2 time axis.This range can be used to accurately identify fluid properties.This method has high adaptability in identifying complex oil and water layers in low porosity and permeability reservoirs.
文摘A water rocket is a rocket system that obtains thrust by injecting water with compressed air of up to about 8 atmospheres. It is usually manufactured using a pressure-resistant PET bottle. The mechanical elements and principles contained in the water rocket have much in common with the actual small rocket system, and are suitable as educational and research teaching materials in the field of mechanics. Especially in the field of disaster prevention and mitigation, the use of water rockets is being researched and developed as a rescue tool in the event of a flood or earthquake as a disaster countermeasure. However, since the water rocket is a flying object based on the mechanical principle, it is important to ensure the accuracy and stability of the flight path. In this paper, a mechanical simulator is developed with a numerical calculation program based on the mechanical consideration of water rocket flight performance. In addition, the correlation between the flight distance obtained in the simulation and the estimated flight distance is analyzed by applying a multivariate analysis method and verifying the validity of the flight distance calculated from the result. Based on the verification results, we will apply a statistical optimization method to approach the optimization of flight stability performance conditions for water rockets.
基金Supported by the National Natural Science Foundation of China (42174142)National Science and Technology Major Project (2017ZX05039-002)+2 种基金Operation Fund of China National Petroleum Corporation Logging Key Laboratory (2021DQ20210107-11)Fundamental Research Funds for Central Universities (19CX02006A)Major Science and Technology Project of China National Petroleum Corporation (ZD2019-183-006)。
文摘To make the quantitative results of nuclear magnetic resonance(NMR) transverse relaxation(T;) spectrums reflect the type and pore structure of reservoir more directly, an unsupervised clustering method was developed to obtain the quantitative pore structure information from the NMR T;spectrums based on the Gaussian mixture model(GMM). Firstly, We conducted the principal component analysis on T;spectrums in order to reduce the dimension data and the dependence of the original variables. Secondly, the dimension-reduced data was fitted using the GMM probability density function, and the model parameters and optimal clustering numbers were obtained according to the expectation-maximization algorithm and the change of the Akaike information criterion. Finally, the T;spectrum features and pore structure types of different clustering groups were analyzed and compared with T;geometric mean and T;arithmetic mean. The effectiveness of the algorithm has been verified by numerical simulation and field NMR logging data. The research shows that the clustering results based on GMM method have good correlations with the shape and distribution of the T;spectrum, pore structure, and petroleum productivity, providing a new means for quantitative identification of pore structure, reservoir grading, and oil and gas productivity evaluation.
文摘In this paper, the limitation of T matrix structure is analyzed. It is found that a solution by T matrix method can be transformed to a canonical solution when the boundary of the scatterer tends to the cylindrical form and the scatterer is illuminated by E plane waves. It is concluded that a T matrix is diagonal with the scatter boundary in this limit situation. This is also the best result of numerical solution.
文摘This paper mainly talks about a popular approach of volatility of a GARCH-type model in R, while the disturbances are independent and have identical Student-t distribution. It uses the Metropolis-Hastings method to perform the computations and gives the programs in details in R.
基金Supported by Scientific Research Project of Colleges and Universities in Hainan Province(Hnky2017-47)Sanya Special Scientific Research Pilot Project(2016KS05)+2 种基金Provincial Key(Supporting)Discipline for Ordinary Colleges and Universities in Hainan Province:Zoology2018 Special Fund for the Development of Institutions of Higher Learning(phaseⅠ)Provincial Characteristic Discipline:Marine Science。
文摘[Objectives] This study was conducted to further investigate the taxonomic status of Hainan population of Trimeresurus stejnegeri from the morphological point of view.[Methods]The difference coefficients between different populations were compared using the 75% law,and the relationship between scales and latitudes was analyzed.[Results] The scales(abdominal and subcaudal) of 325 Trimeresurus individuals were counted according to China Animal Fauna,including156 T.stejnegeri individuals.Some difference coefficients between the Hainan population and others were greater than 1.28,and there was no correlation between the number of scales and latitude.It conforms to subclassification criteria.[Conclusions]The view about the subspecies status of T.stejnegeri chenbihuii should be supported.
