作者此前工作表明,在耦合簇CCSD (Coupled-Cluster approaches within the singles and doubles approximation)与CCSD(T)(CCSD approaches augmented by a perturbative treatment of triple excitations)计算中结合单精度数与消费型...作者此前工作表明,在耦合簇CCSD (Coupled-Cluster approaches within the singles and doubles approximation)与CCSD(T)(CCSD approaches augmented by a perturbative treatment of triple excitations)计算中结合单精度数与消费型图形处理单元(GPU),可以显著提高计算速度.然而由于CCSD(T)计算对内存的巨大需求以及消费型GPU的内存限制,在利用消费型GPU进行加速时,不考虑利用空间对称性的情况下,此前开发的CCSD(T)程序仅能用于计算300~400个基函数的体系.利用密度拟合(Density-Fitting,DF)处理双电子积分可以显著降低CCSD(T)计算过程中的内存需求,本工作发展了基于密度拟合近似并结合单精度数进行运算的DF-CCSD(T)程序,该程序可用于包含700个基函数的无对称性体系的单点能计算,以及包含1700个基函数的有对称性体系.本工作所使用的计算节点配置了型号为Intel I9-10900k的CPU和型号为RTX3090的GPU,与用双精度数在CPU上的计算相比,利用单精度数结合GPU进行运算可以将CCSD的计算速度提升16倍,(T)部分可提升40倍左右,而使用单精度数引入的误差可忽略不计.在程序开发过程中,作者发展了一套可利用GPU或CPU结合单精度数或双精度数进行含空间对称性的矩阵操作代码库.基于该套代码库,可以显著降低开发含空间对称性的耦合簇代码的难度.展开更多
Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties （e.g., density, velocity and discharge） using deposit as done in practice. Tracing the vari...Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties （e.g., density, velocity and discharge） using deposit as done in practice. Tracing the variation of grain composition is thus more important than estimating some certain properties of flow because every debris flow event consists of a series of surges that are distinct in properties and flow regimes. We find that the materials of debris flows, both the fluid and the source soils, satisfy a universal grain size distribution （GSD） in a form of P （D） = CD-zexp（-D/Dc）, where the parameters C, p and De are determined by fitting the function to the grain size frequency. A small At implies a small porosity and possible high excess pore pressure in flow; and a large D~ means a wide range of grain composition and hence a high sediment concentration. Flow density increases as 11 decreases or Dc increases, in a power law form. A debris flow always achieves a state of certain mobility and density that can be well described by the coupling of p and Dc, which imposes a constraint on the fluctuations of flow surges. The GSD also describes the changes in grain composition in that it is always satisfied during the course of debris flow developing. Numerical simulation using the GSD can well illustrate the variation ofμ and Dc from source soils to deposits.展开更多
This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and...This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research, Chinese snow temperature Academy of Sciences. lo-layer and the snow cover parameters were measured by the snow property analyzer （Snow Fork） in its Stable period, Interim period and Snow melting period. Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stableperiod, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1℃ cm-1 for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period-Interim period indirectly cause increase （decrease） of snow density mainly by increasing （decreasing） permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.展开更多
The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan statio...The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan station,Beijing where there are two different gravimeters( namely,L&R-804 and PET-031). Based on the original raw tidal records of two gravimeters from 2008 to 2011,we first remove various interference from raw data by the standard procedure software-Tsoft; then we model the solid earth tides, ocean tidal loading and pole tide through related parameters; after that we adopt a new segmented polynomial fitting method based on Tsoft to fit the complex drift of spring gravimeter; and finally we calculate the atmospheric loading effects by a linear regression model. After a series of processing we gain the non-tidal variation of the two gravimeters at Baijiatuan site,Beijing. Furthermore,to analyze the non-tidal variation preliminarily,we study the main component of related tidal data by power spectral density. Comparing the non-tidal variation of two different gravimeters,we find seasonal fluctuations in non-tidal results, which are in accordance with the water storage change. Therefore,we take into account the relevance of gravity changes and water storage based on the gravity data of GRACE and water data of the CMAP model from 2003 to 2011 at different sites in the Chinese mainland( Beijing, Chengdu, Shenyang and Shiquanhe), and make a preliminary analysis on the relationship between gravity changes and water storage.展开更多
Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of lo...Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of local damage to roof structures, par- ticularly at the edges and comers of long-span roofs. Thus, comparative errors would occur if a Gaussian model is used to de- scribe a non-Gaussian wind load, and structural security would not be guaranteed. This paper presents a simplified method based on the inverse fast Fourier transform （IFFT）, in which the amplitude spectrum is established via a target power spectrum. Also, the phase spectrum is constructed by introducing the exponential peak generation （EPG） model. Finally, a random pro- cess can be generated via IFFT that meets the specified power spectral density （PSD）, skewness and kurtosis. In contrast to a wind tunnel experiment, this method can avoid the coupled relation between the non-Gaussian and the power spectrum char- acteristics, and lead to the desired computational efficiency. Its fitting accuracy is not affected by phase spectrum. Moreover, the fitting precision of the kurtosis and PSD parameters can be guaranteed. In a few cases, the fitting precision of the skewness parameter is fairly poor, but kurtosis is more important than skewness in the description of the non-Gaussian characteristics. Above all, this algorithm is simple and stable and would be an effective method to simulate a non-Gaussian signal.展开更多
A hybrid LES (Large Eddy Simulation)/assumed sub-grid PDF (Probability Density Function) closure model has been devel-oped for supersonic turbulent combustion. Scalar transport equations for all species in a given che...A hybrid LES (Large Eddy Simulation)/assumed sub-grid PDF (Probability Density Function) closure model has been devel-oped for supersonic turbulent combustion. Scalar transport equations for all species in a given chemical kinetic mechanism were solved, which are necessary in the supersonic combustion where the non-equilibrium chemistry is essentially involved. The clipped Gaussian PDF of temperature and multivariate ? PDF of composition were used to close the sub-grid chemical sources that appear in the conservation equations. The sub-grid variances of temperature and composition were constructed based on scale similarity approach. A semi-implicit approach based on the PDF model was proposed to tackle the resulting numerical stiffness associated with finite rate chemistry. The model was applied to simulate a supersonic, coaxial H2-air burner, where both the mean and rms (root mean square) results were compared with the experimental data. In general, good agree-ments were achieved, which indicated that the present sub-grid PDF method could work well in simulating supersonic turbu-lent combustion. Moreover, the calculation showed that the sub-grid fluctuations of temperature and major species in the combustion region were of the order of 10%-20% of their rms, while the sub-grid fluctuation of hydroxyl might be as high as 40%-50% of its rms.展开更多
Based on the semi-classical Thomas-Fermi approximation together with the Skyrme energy-density functional, we study the deformation dependence of symmetry energy coefficients of finite nuclei. The symmetry energy coef...Based on the semi-classical Thomas-Fermi approximation together with the Skyrme energy-density functional, we study the deformation dependence of symmetry energy coefficients of finite nuclei. The symmetry energy coefficients of nuclei with mass number A = 40, 100, 150, 208 are extracted from two-parameter parabola fitting to the calculated energy per particle. We find that the symmetry energy coefficients decrease with the increase of nuclear quadrupole deformations, which is mainly due to the isospin dependence of the difference between the proton and neutron surface diffuseness. Large deformations of nuclei can cause the change of the symmetry energy coefficient by about 0.5 Me V and the influence of nuclear deformations on the symmetry energy coefficients is more evident for light and intermediate nuclei.展开更多
文摘作者此前工作表明,在耦合簇CCSD (Coupled-Cluster approaches within the singles and doubles approximation)与CCSD(T)(CCSD approaches augmented by a perturbative treatment of triple excitations)计算中结合单精度数与消费型图形处理单元(GPU),可以显著提高计算速度.然而由于CCSD(T)计算对内存的巨大需求以及消费型GPU的内存限制,在利用消费型GPU进行加速时,不考虑利用空间对称性的情况下,此前开发的CCSD(T)程序仅能用于计算300~400个基函数的体系.利用密度拟合(Density-Fitting,DF)处理双电子积分可以显著降低CCSD(T)计算过程中的内存需求,本工作发展了基于密度拟合近似并结合单精度数进行运算的DF-CCSD(T)程序,该程序可用于包含700个基函数的无对称性体系的单点能计算,以及包含1700个基函数的有对称性体系.本工作所使用的计算节点配置了型号为Intel I9-10900k的CPU和型号为RTX3090的GPU,与用双精度数在CPU上的计算相比,利用单精度数结合GPU进行运算可以将CCSD的计算速度提升16倍,(T)部分可提升40倍左右,而使用单精度数引入的误差可忽略不计.在程序开发过程中,作者发展了一套可利用GPU或CPU结合单精度数或双精度数进行含空间对称性的矩阵操作代码库.基于该套代码库,可以显著降低开发含空间对称性的耦合簇代码的难度.
基金supported by the Key Research Program of the Chinese Academy of Sciences (Grant No.KZZD-EW-05-01)the National Natural Science Foundation of China (Grant No. 41471011)the Key Laboratory of Mountain Hazards and Earth Surface Processes,Chinese Academy of Sciences,China
文摘Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties （e.g., density, velocity and discharge） using deposit as done in practice. Tracing the variation of grain composition is thus more important than estimating some certain properties of flow because every debris flow event consists of a series of surges that are distinct in properties and flow regimes. We find that the materials of debris flows, both the fluid and the source soils, satisfy a universal grain size distribution （GSD） in a form of P （D） = CD-zexp（-D/Dc）, where the parameters C, p and De are determined by fitting the function to the grain size frequency. A small At implies a small porosity and possible high excess pore pressure in flow; and a large D~ means a wide range of grain composition and hence a high sediment concentration. Flow density increases as 11 decreases or Dc increases, in a power law form. A debris flow always achieves a state of certain mobility and density that can be well described by the coupling of p and Dc, which imposes a constraint on the fluctuations of flow surges. The GSD also describes the changes in grain composition in that it is always satisfied during the course of debris flow developing. Numerical simulation using the GSD can well illustrate the variation ofμ and Dc from source soils to deposits.
基金supported by social welfare of Ministry Science and Technology Development of China (Grant No.GYHY200706008)the "Western Light" Project (RCPY200902) of the Chinese Academy of Sciencesthe Oasis Scholar "Doctor" Talent Training Program (0771021) of Xinjiang Institute of Ecology
文摘This article discussed about snow temperature variations and their impact on snow cover parameters. Automatic temperature recorders were used to sample at lo-minute intervals at the Tianshan Station for Snow-cover and Avalanche Research, Chinese snow temperature Academy of Sciences. lo-layer and the snow cover parameters were measured by the snow property analyzer （Snow Fork） in its Stable period, Interim period and Snow melting period. Results indicate that the amplitude of the diurnal fluctuation in the temperature during Snow melting period is 1.62 times greater than that during Stable period. Time up to the peak temperature at the snow surface lags behind the peak solar radiation by more than 2.5 hours, and lags behind the peak atmospheric temperature by more than 0.2 hours during all three periods. The optimal fitted function of snow temperature profile becomes more complicated from Stable period to Snow melting period. 22 h temperature profiles in Stable period are the optimal fitted by cubic polynomial equation. In Interim period and Snow melting period, temperature profiles are optimal fitted by exponential equation between sunset and sunrise, and by Fourier function when solar radiation is strong. The vertical gradient in the snow temperature reaches its maximum value at the snow surface for three periods. The peak of this maximum value occurs during Stableperiod, and is 4.46 times greater than during Interim period. The absolute value of temperature gradient is lower than 0.1℃ cm-1 for 30 cm beneath snow surface. Snow temperature and temperature gradient in Stable period-Interim period indirectly cause increase （decrease） of snow density mainly by increasing （decreasing） permittivity. While it dramatically increases its water content to change its permittivity and snow density in Snow melting period.
基金sponsored by the Basic Scientific Research of Institute of Geophysics,CEA(DQJB12B20,DQJB12C03,DQJB12B14)
文摘The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan station,Beijing where there are two different gravimeters( namely,L&R-804 and PET-031). Based on the original raw tidal records of two gravimeters from 2008 to 2011,we first remove various interference from raw data by the standard procedure software-Tsoft; then we model the solid earth tides, ocean tidal loading and pole tide through related parameters; after that we adopt a new segmented polynomial fitting method based on Tsoft to fit the complex drift of spring gravimeter; and finally we calculate the atmospheric loading effects by a linear regression model. After a series of processing we gain the non-tidal variation of the two gravimeters at Baijiatuan site,Beijing. Furthermore,to analyze the non-tidal variation preliminarily,we study the main component of related tidal data by power spectral density. Comparing the non-tidal variation of two different gravimeters,we find seasonal fluctuations in non-tidal results, which are in accordance with the water storage change. Therefore,we take into account the relevance of gravity changes and water storage based on the gravity data of GRACE and water data of the CMAP model from 2003 to 2011 at different sites in the Chinese mainland( Beijing, Chengdu, Shenyang and Shiquanhe), and make a preliminary analysis on the relationship between gravity changes and water storage.
基金supported by the National Natural Science Fund for Distinguished Young Scholars (Grant No. 51125031)
文摘Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of local damage to roof structures, par- ticularly at the edges and comers of long-span roofs. Thus, comparative errors would occur if a Gaussian model is used to de- scribe a non-Gaussian wind load, and structural security would not be guaranteed. This paper presents a simplified method based on the inverse fast Fourier transform （IFFT）, in which the amplitude spectrum is established via a target power spectrum. Also, the phase spectrum is constructed by introducing the exponential peak generation （EPG） model. Finally, a random pro- cess can be generated via IFFT that meets the specified power spectral density （PSD）, skewness and kurtosis. In contrast to a wind tunnel experiment, this method can avoid the coupled relation between the non-Gaussian and the power spectrum char- acteristics, and lead to the desired computational efficiency. Its fitting accuracy is not affected by phase spectrum. Moreover, the fitting precision of the kurtosis and PSD parameters can be guaranteed. In a few cases, the fitting precision of the skewness parameter is fairly poor, but kurtosis is more important than skewness in the description of the non-Gaussian characteristics. Above all, this algorithm is simple and stable and would be an effective method to simulate a non-Gaussian signal.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50906098 and 91016028)
文摘A hybrid LES (Large Eddy Simulation)/assumed sub-grid PDF (Probability Density Function) closure model has been devel-oped for supersonic turbulent combustion. Scalar transport equations for all species in a given chemical kinetic mechanism were solved, which are necessary in the supersonic combustion where the non-equilibrium chemistry is essentially involved. The clipped Gaussian PDF of temperature and multivariate ? PDF of composition were used to close the sub-grid chemical sources that appear in the conservation equations. The sub-grid variances of temperature and composition were constructed based on scale similarity approach. A semi-implicit approach based on the PDF model was proposed to tackle the resulting numerical stiffness associated with finite rate chemistry. The model was applied to simulate a supersonic, coaxial H2-air burner, where both the mean and rms (root mean square) results were compared with the experimental data. In general, good agree-ments were achieved, which indicated that the present sub-grid PDF method could work well in simulating supersonic turbu-lent combustion. Moreover, the calculation showed that the sub-grid fluctuations of temperature and major species in the combustion region were of the order of 10%-20% of their rms, while the sub-grid fluctuation of hydroxyl might be as high as 40%-50% of its rms.
基金supported by the National Natural Science Foundation of China(Grants Nos.11275052,11365005 and 11422548)
文摘Based on the semi-classical Thomas-Fermi approximation together with the Skyrme energy-density functional, we study the deformation dependence of symmetry energy coefficients of finite nuclei. The symmetry energy coefficients of nuclei with mass number A = 40, 100, 150, 208 are extracted from two-parameter parabola fitting to the calculated energy per particle. We find that the symmetry energy coefficients decrease with the increase of nuclear quadrupole deformations, which is mainly due to the isospin dependence of the difference between the proton and neutron surface diffuseness. Large deformations of nuclei can cause the change of the symmetry energy coefficient by about 0.5 Me V and the influence of nuclear deformations on the symmetry energy coefficients is more evident for light and intermediate nuclei.
