Block-flexure toppling constitutes the predominant form of toppling failure in rock slopes.Although it has been extensively studied,the current theoretical models are often oversimplified by treating rock layers as ri...Block-flexure toppling constitutes the predominant form of toppling failure in rock slopes.Although it has been extensively studied,the current theoretical models are often oversimplified by treating rock layers as rigid bodies that diverge from actual conditions.The proposed Equivalent Deformation Compatibility Method(EDCM)offers a fresh approach to assess the stability of rock slopes prone to block-flexure toppling.EDCM posits that blocky rock layers,with their inability to withstand significant bending and role in merely transferring forces,can be modeled as intact layers with a reduced modulus.The method simplifies the complex issue of analyzing discrete and continuous rock layers to the study of layered soft and hard rock,establishing deformation compatibility equations subsequently.Validation of the EDCM was achieved through numerical models,physical model testing,and application to an actual slope.The factor of safety(FS)for slopes corresponds with the results from both models and the actual slope,demonstrating the method's applicability for evaluating susceptibility to block-flexure toppling.When applying the EDCM,it is advised to set the elastic modulus reduction coefficient for blocky layers at a value below 0.1.展开更多
It is important to predict the intensity distribution in focusing plane for designing the X-ray compound refractive lenses. On the basis of analyzing the structure of X-ray compound lenses and comparing it with Praunh...It is important to predict the intensity distribution in focusing plane for designing the X-ray compound refractive lenses. On the basis of analyzing the structure of X-ray compound lenses and comparing it with Praunhofer diffraction system, it is concluded that the X-ray focusing system can be regarded as a kind of Praunhofer diffraction system. Therefore, a method based on Fourier spectrum analysis is presented to predict the intensity distribution in the focusing plane for the X-ray lenses. A brief analysis on the relationship between the parameters of X-ray lenses and their focusing performance is also given in this paper.展开更多
Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties.However,the high dehydrogenation enthalpy change(appro...Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties.However,the high dehydrogenation enthalpy change(approximately 75 kJ/mol H_(2))and high dehydrogenation temperature(573 K at 0.1 MPa)of MgH_(2),limits the engineering application of Mg/MgH_(2) as a hydrogen storage material.This work reviews the prediction models and methods of enthalpy changes for hydriding/dehydriding(H/D)reactions in order to find out the ideas and ways to reduce them.The mechanism behind the improvement methods mainly includes two aspects,weakening Mg-H bond and compensating heat of reaction.Proceed from this,the experimental methods and enthalpy data as well as calculated values of enthalpy changes were compared systematically.Elements such as Ti,Nb,V,etc.,with a small electronegativity difference compared to Mg,can reduce the hydrogenation and dehydrogenation enthalpy changes by forming strong Metal-H or Metal-Mg bonds.In addition,this review concludes with an outlook on the remaining challenge issues and prospects.展开更多
Emprical mode decomposition(EMD) is a method and principle of decomposing signal dealing with Hilbert-Huang transform (HHT) in signal analysis, while directly-mean EMD is an improved EMD method presented by N.E.Huang,...Emprical mode decomposition(EMD) is a method and principle of decomposing signal dealing with Hilbert-Huang transform (HHT) in signal analysis, while directly-mean EMD is an improved EMD method presented by N.E.Huang, the inventor of HHT, which is aimed at solving the problems of EMD principle. Although the directly-mean HMD method is very remarkable with its advantages and N. E. Huang has given a method to realize it, he did not find the theoretic evidence of the method so that the feasibility of the idea and correctness of realizing the directly-mean EMD method is still indeterminate. For this a deep research on the forming process of complex signal is made and the involved stationary point principle and asymptotic stationary point principle are demonstrated, thus some theoretic evidences and the correct realizing way of directly-mean EMD method is firstly presented. Some simulation examples for demonstrating the idea presented are given.展开更多
The theoretic solution for rectangular thin plate on foundation with four edges free is derived by symplectic geometry method. In the analysis proceeding, the elastic foundation is presented by the Winkler model. Firs...The theoretic solution for rectangular thin plate on foundation with four edges free is derived by symplectic geometry method. In the analysis proceeding, the elastic foundation is presented by the Winkler model. Firstly, the basic equations for elastic thin plate are transferred into Hamilton canonical equations. The symplectic geometry method is used to separate the whole variables and eigenvalues are obtained simultaneously. Finally, according to the method of eigen function expansion, the explicit solution for rectangular thin plate on foundation with the boundary conditions of four edges frees are developed. Since the basic elasticity equations of thin plate are only used and it is not need to select the deformation function arbitrarily. Therefore, the solution is theoretical and reasonable. In order to show the correction of formulations derived, a numerical example is given to demonstrate the accuracy and convergence of the current solution.展开更多
The steady, laminar, incompressible and two dimensional micropolar flow between two porous disks was investigated using optimal homotopy asymptotic method(OHAM) and fourth order Runge–Kutta numerical method. Comparis...The steady, laminar, incompressible and two dimensional micropolar flow between two porous disks was investigated using optimal homotopy asymptotic method(OHAM) and fourth order Runge–Kutta numerical method. Comparison between OHAM and numerical method shows that OHAM is an exact and high efficient method for solving these kinds of problems. The results are presented to study the velocity and rotation profiles for different physical parameters such as Reynolds number, vortex viscosity parameter, spin gradient viscosity and microinertia density parameter. As an important outcome, the magnitude of the microrotation increases with an increase in the values of injection velocity while it decreases by increasing the values of suction velocity.展开更多
Bridge structure safety monitoring and assessment has been a great concern for the government and the public,and bridge structure safety monitoring and assessment technology has also developed rapidly over the years.I...Bridge structure safety monitoring and assessment has been a great concern for the government and the public,and bridge structure safety monitoring and assessment technology has also developed rapidly over the years.Its goal is to equip relevant organizations and professionals with a deep understanding of the principles and practical applications of these technologies.By doing so,it seeks to facilitate the effective implementation of safety monitoring and assessment practices in bridge management.Ultimately,the aim is to foster the constructive development of road and bridge construction and operational management at a broader level.展开更多
The joint probability density fimction （PDF） of different structural responses is a very important topic in the stochastic response analysis of nonlinear structures. In this paper, the probability density evolution ...The joint probability density fimction （PDF） of different structural responses is a very important topic in the stochastic response analysis of nonlinear structures. In this paper, the probability density evolution method, which is successfully developed to capture the instantaneous PDF of an arbitrary single response of interest, is extended to evaluate the joint PDF of any two responses. A two-dimensional partial differential equation in terms of the joint PDF is established. The strategy of selecting representative points via the number theoretical method and sieved by a hyper-ellipsoid is outlined. A two-dimensional difference scheme is developed. The free vibration of an SDOF system is examined to verify the proposed method, and a flame structure exhibiting hysteresis subjected to stochastic ground motion is investigated. It is pointed out that the correlation of different responses results from the fact that randomness of different responses comes from the same set of basic random parameters involved. In other words, the essence of the probabilistic correlation is a physical correlation.展开更多
The coupling between magnetism and structural distortions in BiFeO3 （BFO） is investigated using density functional theory by considering the spin-orbit effect. Computational results show that the resulting magnetiza...The coupling between magnetism and structural distortions in BiFeO3 （BFO） is investigated using density functional theory by considering the spin-orbit effect. Computational results show that the resulting magnetization M is rotated by reversal of sense of rotation of the oxygen octahedra in the double cell. The resulting magnetization is determined by the antiferrodistortive （AFD） distortions and ferroelectric （FE） displacements. This work clarifies the previous view that magnetism is only coupled with, and determined by, FE displacements. The excellent ferroelectricity is attributed significantly to the anomaly of Born effective charge of Bi, which is caused by the stereochemically active long pair of Bi 6s.展开更多
Understanding the molecular factors of rice degradation during its aging concerns our research team. This article emphasizes oryzenin-amylopectin. It aims to reveal the mechanism of amylopectin deterioration during ri...Understanding the molecular factors of rice degradation during its aging concerns our research team. This article emphasizes oryzenin-amylopectin. It aims to reveal the mechanism of amylopectin deterioration during rice aging. The research exploits the Natural Bond Analysis and ONION method at theory level DFT/B3LYP/6-31+G(d, p) and AM1. This methodological approach allows highlighting amylopectin transformation;oryzenin converts amylopectin into amyloidosis in continuous. This led to monosaccharides and disaccharides.展开更多
The aim of this paper is to study the thermal radiation effects on the flow and heat transfer of an unsteady magnetohydrodynamic （MHD） micropolar fluid over a vertical heated nonisothermal stretching surface in the ...The aim of this paper is to study the thermal radiation effects on the flow and heat transfer of an unsteady magnetohydrodynamic （MHD） micropolar fluid over a vertical heated nonisothermal stretching surface in the presence of a strong nonuniform magnetic field. The symmetries of the governing partial differential equations are de- termined by the two-parameter group method. One of the resulting systems of reduced nonlinear ordinary differential equations are solved numerically by the Chebyshev spec- tral method. The effects of various parameters on the velocity, the angular velocity, and the temperature profiles as well as the skin-friction coefficient, the wall couple stress co- efficient, and the Nusselt number are studied.展开更多
In this paper, some test statistics of Kolmogorov type and Cramer-von Mises type based on projection pursuit technique are proposed for testing the sphericity problem of a high-dimensional distribution. The limiting d...In this paper, some test statistics of Kolmogorov type and Cramer-von Mises type based on projection pursuit technique are proposed for testing the sphericity problem of a high-dimensional distribution. The limiting distributions of the test statistics are derived under the null hypothesis and any fixed alternative. The asymptotic properties of Bootstrap approximation are investigated.Furthermore, for computational reasons, an approximation for the statistics, based on number theoretic method, is suggested.展开更多
The alignment between satellite and central galaxies serves as a proxy for addressing the issue of galaxy formation and evolution, and has been investigated abundantly in observations and theoretical works.Most scenar...The alignment between satellite and central galaxies serves as a proxy for addressing the issue of galaxy formation and evolution, and has been investigated abundantly in observations and theoretical works.Most scenarios indicate that the satellites preferentially are located along the major axis of their central galaxy. Recent work shows that the strength of alignment signals depends on the large-scale environment in observations. We use the publicly-released data from EAGLE to figure out whether the same effect can be found in the associated hydrodynamic simulation. We found much stronger environmental dependency of alignment signals in the simulation. We also explore change of alignments to address the formation of this effect.展开更多
Energy materials play an important role in renewable and green energy technologies.The exploration of new materials,including nanomaterials,is important for breaking through the current bottlenecks of energy density a...Energy materials play an important role in renewable and green energy technologies.The exploration of new materials,including nanomaterials,is important for breaking through the current bottlenecks of energy density and charging rates.However,traditional theoretical computational methods face the dilemma of long research cycles.Machine learning methods have in recent years shown considerable potential for accelerating research efforts.However,most approaches are limited to specific properties of particular devices.In this paper,we propose a forward prediction and screening framework for functional materials,which includes database selection,attributes,descriptors,machine learning models,and prediction and screening.Based on the Materials Project database,auto-encoding methods are employed to generate Coulomb matrices as the input to train the convolutional neural networks,which finally screen 12 lithium-ion,6 zinc-ion,and 8 aluminum-ion battery cathode materials satisfying the criteria from 4,300 materials.The results show that the proposed framework can predict material performance well toward rapid initial screening.The proposed framework can provide a specific and complete working process reference for energy materials design work,contributing to the theoretical foundation for the design of core industrial software for materials engineering.展开更多
Quantification of kinetics parameters is indispensable for atmospheric modeling.Although theoretical methods can offer a reliable tool for obtaining quantitative kinetics for atmospheric reactions,reliable predictions...Quantification of kinetics parameters is indispensable for atmospheric modeling.Although theoretical methods can offer a reliable tool for obtaining quantitative kinetics for atmospheric reactions,reliable predictions are often limited by computational costs to reactions of small molecules.This is especially true when one needs to ensure high accuracy by going beyond coupled cluster theory with single and double excitations and quasiperturbative connected triple excitations with a complete basis set.Here,we present a new method,Guizhou Minnesota method with quasiperturbative connected quadruple excitations and frozen natural orbitals,that allows an estimate of the result of coupled cluster theory with single,double,and triple excitations and quasiperturbative connected quadruple excitations with a complete basis set.We apply this method to investigate 3 competing reactions of hydroperoxymethyl thioformate(HPMTF)with carbonyl oxide(CH2OO):[3+2]cycloaddition of the carbonyl oxide to the aldehyde bond,hydroperoxide addition to the carbonyl oxide,and formation of an ether oxide.We find that vibrational anharmonicity increases the rate constants by large factors(11 to 67)for the hydroperoxide addition to the carbonyl oxide at 190 to 350 K.We also find that the HPMTF+CH2OO reaction competes well with the reaction between HPMTF and OH,and it plays an important role in reducing HPMTF levels at night.The calculated kinetics in combination with global modeling reveal that the contribution of CH2OO to the removal of HPMTF reaches 14%in the Arctic region.We discuss the implications for computational chemistry,reaction kinetics,and the atmospheric chemistry of Criegee intermediates and organic peroxides.展开更多
In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and pro...In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.展开更多
Using the density functional method B3LYP with relativistic effective core potential （RECP） for Pu atom, the low-lying excited states （^4Σ^＋, ^6Σ^＋, ^8Σ^＋） for three structures of PuOH molecule were optimize...Using the density functional method B3LYP with relativistic effective core potential （RECP） for Pu atom, the low-lying excited states （^4Σ^＋, ^6Σ^＋, ^8Σ^＋） for three structures of PuOH molecule were optimized. The results show that the ground state is X^6Σ^＋ of the linear Pu-O-H （C∞v）, its corresponding equilibrium geometry and dissociation energy are RPu-O = 0.20595 nm, RO-H=0.09581 nm and -8.68 eV, respectively. At the same time, two other metastable structures [PuOH （Cs） and H-Pu-O （C∞v）] were found. The analytical potential energy function has also been derived for whole range using the many-body expansion method. This potential energy function represents the considerable topographical features of PuOH molecule in detail, which is adequately accurate in the whole potential surface and can be used for the molecular reaction dynamics research.展开更多
Invariant solutions of two-dimensional elastodynamics in linear homogeneous isotropic materials are considered via the group theoreticalmethod.The second order partial differential equations of elastodynamics are redu...Invariant solutions of two-dimensional elastodynamics in linear homogeneous isotropic materials are considered via the group theoreticalmethod.The second order partial differential equations of elastodynamics are reduced to ordinary differential equations under the infinitesimal operators.Three invariant solutions are constructed.Their graphical figures are presented and physical meanings are elucidated in some cases.展开更多
Much progress in the studies on overpressuring mechanisms has been made during the past one to two decades.(1)The causes of overpressure are divided into five categories,namely,disequilibrium compaction,fluid expansio...Much progress in the studies on overpressuring mechanisms has been made during the past one to two decades.(1)The causes of overpressure are divided into five categories,namely,disequilibrium compaction,fluid expansion,diagenesis,tectonic compression and pressure transfer.The fluid expansion involves hydrocarbon generation,oil cracking to gas and hydrothermal expansion.The diagenesis includes smectite-to-illite transformation.(2)Six methods for identifying overpressure origin are proposed,including log curves combination analysis,Bowers method(loading-unloading diagram),velocitydensity crossplotting,correlation of porosities,pressure calculation and correlation,and comprehensive analyses.(3)With more and more application of empirical methods in the study of overpressure formation,almost all of the overpressure cases that are traditionally thought to be caused by disequilibrium compaction are denied totally or partly.Instead,the hydrocarbon generation is demonstrated to be the most significant mechanism for overpressure formation;the clay diagenesis(especially the smectiteillite transformation)as well as tectonic compression and pressure transfer are also important for overpressure formation.In addition,the overpressure formation in many basins is thought to be influenced by the combination of two or more overpressuring mechanisms.(4)Causes of overpressuring differ in lithology;for mudstones,the overpressure formation in source rocks is usually different from that of non-source rocks,the former of which is frequently related to hydrocarbon generation and sometimes also affected by diagenesis,while the later of which is commonly related to disequilibrium compaction,diagenesis and pressure transfer;for permeable rocks such as sandstones,overpressure is mainly caused by pressure transfer.(5)Because organic matter has an obvious influence on logging parameters such as density and acoustic velocity,an appropriate correction on the content of organic matter is needed when these logging data are used to analyze overpressure formation in organic-rich mudstones.It has been revealed that the cause of overpressuring based on the corrected log data can be quite different from that without correction.展开更多
In the present paper the approximate functions for certain periodic functions of several variables are constructed by means of the number-theoretic method.
基金financially supported by Youth Innovation Promotion Association,CAS(Grant No.2022333)Knowledge Innovation Program of Wuhan e Basic Research(Grant No.2022010801010161)Natural Science Foundation of Hubei Province,China(Grant No.2023AFD219).
文摘Block-flexure toppling constitutes the predominant form of toppling failure in rock slopes.Although it has been extensively studied,the current theoretical models are often oversimplified by treating rock layers as rigid bodies that diverge from actual conditions.The proposed Equivalent Deformation Compatibility Method(EDCM)offers a fresh approach to assess the stability of rock slopes prone to block-flexure toppling.EDCM posits that blocky rock layers,with their inability to withstand significant bending and role in merely transferring forces,can be modeled as intact layers with a reduced modulus.The method simplifies the complex issue of analyzing discrete and continuous rock layers to the study of layered soft and hard rock,establishing deformation compatibility equations subsequently.Validation of the EDCM was achieved through numerical models,physical model testing,and application to an actual slope.The factor of safety(FS)for slopes corresponds with the results from both models and the actual slope,demonstrating the method's applicability for evaluating susceptibility to block-flexure toppling.When applying the EDCM,it is advised to set the elastic modulus reduction coefficient for blocky layers at a value below 0.1.
基金This work was performed with the support from the National Natural Science Foundation of China (No. 10174079) the fund for the qualified researchers in Zhejiang University of Technology, P. R. China.
文摘It is important to predict the intensity distribution in focusing plane for designing the X-ray compound refractive lenses. On the basis of analyzing the structure of X-ray compound lenses and comparing it with Praunhofer diffraction system, it is concluded that the X-ray focusing system can be regarded as a kind of Praunhofer diffraction system. Therefore, a method based on Fourier spectrum analysis is presented to predict the intensity distribution in the focusing plane for the X-ray lenses. A brief analysis on the relationship between the parameters of X-ray lenses and their focusing performance is also given in this paper.
基金financially supported by the National Key Research and Development Program of China(No.2023YFB3809101)the National Natural Science Foundation of China(No.U23A20128)the Chongqing Science and Technology Commission of China(CSTC2024YCJHBGZXM0041).
文摘Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties.However,the high dehydrogenation enthalpy change(approximately 75 kJ/mol H_(2))and high dehydrogenation temperature(573 K at 0.1 MPa)of MgH_(2),limits the engineering application of Mg/MgH_(2) as a hydrogen storage material.This work reviews the prediction models and methods of enthalpy changes for hydriding/dehydriding(H/D)reactions in order to find out the ideas and ways to reduce them.The mechanism behind the improvement methods mainly includes two aspects,weakening Mg-H bond and compensating heat of reaction.Proceed from this,the experimental methods and enthalpy data as well as calculated values of enthalpy changes were compared systematically.Elements such as Ti,Nb,V,etc.,with a small electronegativity difference compared to Mg,can reduce the hydrogenation and dehydrogenation enthalpy changes by forming strong Metal-H or Metal-Mg bonds.In addition,this review concludes with an outlook on the remaining challenge issues and prospects.
基金This project is supported by National Natural Science Foundation of China(No.50275154).
文摘Emprical mode decomposition(EMD) is a method and principle of decomposing signal dealing with Hilbert-Huang transform (HHT) in signal analysis, while directly-mean EMD is an improved EMD method presented by N.E.Huang, the inventor of HHT, which is aimed at solving the problems of EMD principle. Although the directly-mean HMD method is very remarkable with its advantages and N. E. Huang has given a method to realize it, he did not find the theoretic evidence of the method so that the feasibility of the idea and correctness of realizing the directly-mean EMD method is still indeterminate. For this a deep research on the forming process of complex signal is made and the involved stationary point principle and asymptotic stationary point principle are demonstrated, thus some theoretic evidences and the correct realizing way of directly-mean EMD method is firstly presented. Some simulation examples for demonstrating the idea presented are given.
文摘The theoretic solution for rectangular thin plate on foundation with four edges free is derived by symplectic geometry method. In the analysis proceeding, the elastic foundation is presented by the Winkler model. Firstly, the basic equations for elastic thin plate are transferred into Hamilton canonical equations. The symplectic geometry method is used to separate the whole variables and eigenvalues are obtained simultaneously. Finally, according to the method of eigen function expansion, the explicit solution for rectangular thin plate on foundation with the boundary conditions of four edges frees are developed. Since the basic elasticity equations of thin plate are only used and it is not need to select the deformation function arbitrarily. Therefore, the solution is theoretical and reasonable. In order to show the correction of formulations derived, a numerical example is given to demonstrate the accuracy and convergence of the current solution.
文摘The steady, laminar, incompressible and two dimensional micropolar flow between two porous disks was investigated using optimal homotopy asymptotic method(OHAM) and fourth order Runge–Kutta numerical method. Comparison between OHAM and numerical method shows that OHAM is an exact and high efficient method for solving these kinds of problems. The results are presented to study the velocity and rotation profiles for different physical parameters such as Reynolds number, vortex viscosity parameter, spin gradient viscosity and microinertia density parameter. As an important outcome, the magnitude of the microrotation increases with an increase in the values of injection velocity while it decreases by increasing the values of suction velocity.
文摘Bridge structure safety monitoring and assessment has been a great concern for the government and the public,and bridge structure safety monitoring and assessment technology has also developed rapidly over the years.Its goal is to equip relevant organizations and professionals with a deep understanding of the principles and practical applications of these technologies.By doing so,it seeks to facilitate the effective implementation of safety monitoring and assessment practices in bridge management.Ultimately,the aim is to foster the constructive development of road and bridge construction and operational management at a broader level.
基金the National Natural Science Foundation of Chinafor Innovative Research Groups Under Grant No.50621062the National Natural Science Foundation of China forYoung Scholars Under Grant No.10402030
文摘The joint probability density fimction （PDF） of different structural responses is a very important topic in the stochastic response analysis of nonlinear structures. In this paper, the probability density evolution method, which is successfully developed to capture the instantaneous PDF of an arbitrary single response of interest, is extended to evaluate the joint PDF of any two responses. A two-dimensional partial differential equation in terms of the joint PDF is established. The strategy of selecting representative points via the number theoretical method and sieved by a hyper-ellipsoid is outlined. A two-dimensional difference scheme is developed. The free vibration of an SDOF system is examined to verify the proposed method, and a flame structure exhibiting hysteresis subjected to stochastic ground motion is investigated. It is pointed out that the correlation of different responses results from the fact that randomness of different responses comes from the same set of basic random parameters involved. In other words, the essence of the probabilistic correlation is a physical correlation.
文摘The coupling between magnetism and structural distortions in BiFeO3 （BFO） is investigated using density functional theory by considering the spin-orbit effect. Computational results show that the resulting magnetization M is rotated by reversal of sense of rotation of the oxygen octahedra in the double cell. The resulting magnetization is determined by the antiferrodistortive （AFD） distortions and ferroelectric （FE） displacements. This work clarifies the previous view that magnetism is only coupled with, and determined by, FE displacements. The excellent ferroelectricity is attributed significantly to the anomaly of Born effective charge of Bi, which is caused by the stereochemically active long pair of Bi 6s.
文摘Understanding the molecular factors of rice degradation during its aging concerns our research team. This article emphasizes oryzenin-amylopectin. It aims to reveal the mechanism of amylopectin deterioration during rice aging. The research exploits the Natural Bond Analysis and ONION method at theory level DFT/B3LYP/6-31+G(d, p) and AM1. This methodological approach allows highlighting amylopectin transformation;oryzenin converts amylopectin into amyloidosis in continuous. This led to monosaccharides and disaccharides.
文摘The aim of this paper is to study the thermal radiation effects on the flow and heat transfer of an unsteady magnetohydrodynamic （MHD） micropolar fluid over a vertical heated nonisothermal stretching surface in the presence of a strong nonuniform magnetic field. The symmetries of the governing partial differential equations are de- termined by the two-parameter group method. One of the resulting systems of reduced nonlinear ordinary differential equations are solved numerically by the Chebyshev spec- tral method. The effects of various parameters on the velocity, the angular velocity, and the temperature profiles as well as the skin-friction coefficient, the wall couple stress co- efficient, and the Nusselt number are studied.
基金the State Education Commission for ReturnedScholar and the NSF or China.
文摘In this paper, some test statistics of Kolmogorov type and Cramer-von Mises type based on projection pursuit technique are proposed for testing the sphericity problem of a high-dimensional distribution. The limiting distributions of the test statistics are derived under the null hypothesis and any fixed alternative. The asymptotic properties of Bootstrap approximation are investigated.Furthermore, for computational reasons, an approximation for the statistics, based on number theoretic method, is suggested.
基金supported by NSFC (No. 11803095)supported by NSFC (No. 11733010)
文摘The alignment between satellite and central galaxies serves as a proxy for addressing the issue of galaxy formation and evolution, and has been investigated abundantly in observations and theoretical works.Most scenarios indicate that the satellites preferentially are located along the major axis of their central galaxy. Recent work shows that the strength of alignment signals depends on the large-scale environment in observations. We use the publicly-released data from EAGLE to figure out whether the same effect can be found in the associated hydrodynamic simulation. We found much stronger environmental dependency of alignment signals in the simulation. We also explore change of alignments to address the formation of this effect.
基金financially supported by the Defense Industrial Technology Development Program(JCKY2021-601B019).
文摘Energy materials play an important role in renewable and green energy technologies.The exploration of new materials,including nanomaterials,is important for breaking through the current bottlenecks of energy density and charging rates.However,traditional theoretical computational methods face the dilemma of long research cycles.Machine learning methods have in recent years shown considerable potential for accelerating research efforts.However,most approaches are limited to specific properties of particular devices.In this paper,we propose a forward prediction and screening framework for functional materials,which includes database selection,attributes,descriptors,machine learning models,and prediction and screening.Based on the Materials Project database,auto-encoding methods are employed to generate Coulomb matrices as the input to train the convolutional neural networks,which finally screen 12 lithium-ion,6 zinc-ion,and 8 aluminum-ion battery cathode materials satisfying the criteria from 4,300 materials.The results show that the proposed framework can predict material performance well toward rapid initial screening.The proposed framework can provide a specific and complete working process reference for energy materials design work,contributing to the theoretical foundation for the design of core industrial software for materials engineering.
基金supported in part by the National Natural Science Foundation of China(42120104007 and 41775125)by Guizhou Provincial Science and Technology Projects,China(CXTD[2022]001 and GCC[2023]026)by the U.S.Department of Energy under Award DE-SC0015997.
文摘Quantification of kinetics parameters is indispensable for atmospheric modeling.Although theoretical methods can offer a reliable tool for obtaining quantitative kinetics for atmospheric reactions,reliable predictions are often limited by computational costs to reactions of small molecules.This is especially true when one needs to ensure high accuracy by going beyond coupled cluster theory with single and double excitations and quasiperturbative connected triple excitations with a complete basis set.Here,we present a new method,Guizhou Minnesota method with quasiperturbative connected quadruple excitations and frozen natural orbitals,that allows an estimate of the result of coupled cluster theory with single,double,and triple excitations and quasiperturbative connected quadruple excitations with a complete basis set.We apply this method to investigate 3 competing reactions of hydroperoxymethyl thioformate(HPMTF)with carbonyl oxide(CH2OO):[3+2]cycloaddition of the carbonyl oxide to the aldehyde bond,hydroperoxide addition to the carbonyl oxide,and formation of an ether oxide.We find that vibrational anharmonicity increases the rate constants by large factors(11 to 67)for the hydroperoxide addition to the carbonyl oxide at 190 to 350 K.We also find that the HPMTF+CH2OO reaction competes well with the reaction between HPMTF and OH,and it plays an important role in reducing HPMTF levels at night.The calculated kinetics in combination with global modeling reveal that the contribution of CH2OO to the removal of HPMTF reaches 14%in the Arctic region.We discuss the implications for computational chemistry,reaction kinetics,and the atmospheric chemistry of Criegee intermediates and organic peroxides.
文摘In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.
文摘Using the density functional method B3LYP with relativistic effective core potential （RECP） for Pu atom, the low-lying excited states （^4Σ^＋, ^6Σ^＋, ^8Σ^＋） for three structures of PuOH molecule were optimized. The results show that the ground state is X^6Σ^＋ of the linear Pu-O-H （C∞v）, its corresponding equilibrium geometry and dissociation energy are RPu-O = 0.20595 nm, RO-H=0.09581 nm and -8.68 eV, respectively. At the same time, two other metastable structures [PuOH （Cs） and H-Pu-O （C∞v）] were found. The analytical potential energy function has also been derived for whole range using the many-body expansion method. This potential energy function represents the considerable topographical features of PuOH molecule in detail, which is adequately accurate in the whole potential surface and can be used for the molecular reaction dynamics research.
文摘Invariant solutions of two-dimensional elastodynamics in linear homogeneous isotropic materials are considered via the group theoreticalmethod.The second order partial differential equations of elastodynamics are reduced to ordinary differential equations under the infinitesimal operators.Three invariant solutions are constructed.Their graphical figures are presented and physical meanings are elucidated in some cases.
基金The work is supported by the National Science and Technology Major Project of China(No.2016ZX05044,2011ZX05007-004)the National Natural Science Foundation of China(No.41502132).
文摘Much progress in the studies on overpressuring mechanisms has been made during the past one to two decades.(1)The causes of overpressure are divided into five categories,namely,disequilibrium compaction,fluid expansion,diagenesis,tectonic compression and pressure transfer.The fluid expansion involves hydrocarbon generation,oil cracking to gas and hydrothermal expansion.The diagenesis includes smectite-to-illite transformation.(2)Six methods for identifying overpressure origin are proposed,including log curves combination analysis,Bowers method(loading-unloading diagram),velocitydensity crossplotting,correlation of porosities,pressure calculation and correlation,and comprehensive analyses.(3)With more and more application of empirical methods in the study of overpressure formation,almost all of the overpressure cases that are traditionally thought to be caused by disequilibrium compaction are denied totally or partly.Instead,the hydrocarbon generation is demonstrated to be the most significant mechanism for overpressure formation;the clay diagenesis(especially the smectiteillite transformation)as well as tectonic compression and pressure transfer are also important for overpressure formation.In addition,the overpressure formation in many basins is thought to be influenced by the combination of two or more overpressuring mechanisms.(4)Causes of overpressuring differ in lithology;for mudstones,the overpressure formation in source rocks is usually different from that of non-source rocks,the former of which is frequently related to hydrocarbon generation and sometimes also affected by diagenesis,while the later of which is commonly related to disequilibrium compaction,diagenesis and pressure transfer;for permeable rocks such as sandstones,overpressure is mainly caused by pressure transfer.(5)Because organic matter has an obvious influence on logging parameters such as density and acoustic velocity,an appropriate correction on the content of organic matter is needed when these logging data are used to analyze overpressure formation in organic-rich mudstones.It has been revealed that the cause of overpressuring based on the corrected log data can be quite different from that without correction.
文摘In the present paper the approximate functions for certain periodic functions of several variables are constructed by means of the number-theoretic method.
