The fracture and migration patterns of direct roofs play a critical role in excavation stability and mining pressure.However,current methods fail to capture the irregular three-dimensional(3D)behavior of these roofs.I...The fracture and migration patterns of direct roofs play a critical role in excavation stability and mining pressure.However,current methods fail to capture the irregular three-dimensional(3D)behavior of these roofs.In this study,the problem was solved by introducing an innovative 2.5-dimensional(2.5D)Voronoi numerical simulation method,dividing rock layers into 2.5D Voronoi blocks and developing cohesive element-based failure models,supported by a strain-softening HoekeBrown model.The method was applied to the 8311 working face in the Taishan Mine in China,and its accuracy was confirmed through physical experiments.The following conclusions were drawn.The first roof break typically followed an"O-X"pattern.The direct roof did not break randomly over time;instead,it followed three distinct scenarios:(1)A complete break of the direct roof occurred,followed by a sequential collapse(ScenarioⅠ).(2)Regional irregular stacking in one area was followed by sequential collapse in other zones(ScenarioⅡ).(3)The staged breakdown of the direct roof led to separate and sequential collapses on the left and right flanks(ScenarioⅢ).Scenario I was quite common during the 400 m advance of the working face and occurred five times.The fracture characteristics in Scenario I led to widespread pressure on the hydraulic supports in the middle of the working face.Finally,the direct roof from the working face towards the goaf area underwent phases of overhanging,hinging,and collapsing plates.After the first and periodic breaks,the basic roof formed stable hinged plate structures reinforced by overhanging plates and irregular accumulations of the direct roof.展开更多
Weak turbulence often occurs during heavy pollution events in eastern China(EC).However,existing mesoscale meteorology models cannot accurately simulate turbulent diffusion under weakened turbulence,particularly under...Weak turbulence often occurs during heavy pollution events in eastern China(EC).However,existing mesoscale meteorology models cannot accurately simulate turbulent diffusion under weakened turbulence,particularly under the nocturnal stable boundary layer(SBL),often leading to significant turbulent diffusivity underestimation and surface aerosol overestimation.In this study,a new parameterization of minimum turbulent diffusivity coefficient(Kz_(min))was tested and applied to PM_(2.5)simulations in EC under SBL conditions in WRF-Chem.The original model overestimated the PM_(2.5)simulation and the simulation performance can be improved by adding Kz_(min).Sensitivity experiments revealed different ranges of available Kz_(min)values over the northern(0.8 to 1.2 m^(2)/s)and southern(1.0 to 1.5 m^(2)/s)regions of EC.The geographically related Kz_(min)was parameterized by sensible heat flux(H)and latent heat flux(LE),which also exhibited regional differences related to the climate and underlying surface.Furthermore,we assign physical significance to the parameterized formula Kz_(min)and found that our proposed Kz_(min)scheme can reasonably yield dynamic Kz_(min)values over EC.The revised Kz_(min)scheme(EXP_(NEW))enhanced the turbulent diffusion(north:0.93 m^(2)/s,south:1.10 m^(2)/s on average)in the SBL,simultaneously improving the PM_(2.5)simulations on the surface(north:65.78 to 0.67μg/m^(3);south 30.48 to 12.86μg/m^(3))and upper SBL.A process analysis showed that vertical mixing was the key process for improving PM_(2.5)simulations on the surface in EXP_(NEW).This study highlighted the importance of improving turbulent diffusion in current mesoscale models under SBL and has great significance for aerosol simulation.展开更多
Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves, while no well accepted method can be e...Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves, while no well accepted method can be employed for transverse waves. In order to investigate the essential deformation law of leveling for plates with transverse waves, a 2.5-dimensional （2.5- D） analytical approach was proposed. In this model, the plate was transversely divided into some strips with equal width; the strips are considered to be in the state of plane strain and each group of adjacent strips are assumed to be deformation compatible under stress. After calculation, the bending deformation of each strip and the leveling effect of overall plate were obtained by comprehensNe consideration of various strips along with the width. Bending of roller is a main approach to eliminate the transverse waves, which is widely accepted by the industry, but the essential effect of bending of roller on the deformation of plates and the calculation of bending of roller are unknown. According to the 2.5-D analytical model, it can be found that, for plates, it is neutral plane offsetting and middle plane elongation or contraction under inner stress that can effectively improve plate shape. Taking double side waves as an example, the appropriate values of bending of roller were obtained by the 2.5-D analytical model related to different initial unevenness, which was applicable to the current on-line adjusting of bending of roller in rolling industry.展开更多
环境细颗粒物(PM_(2.5))已被列为全球第六大死亡和残疾风险因素。为精准防治PM_(2.5)污染,需要以足够的分辨率捕捉PM_(2.5)时空变化,开发基于有限数量监测站点的建模模拟方法。以2014—2023年杭州核心区7个国控站点监测的PM_(2.5)浓度...环境细颗粒物(PM_(2.5))已被列为全球第六大死亡和残疾风险因素。为精准防治PM_(2.5)污染,需要以足够的分辨率捕捉PM_(2.5)时空变化,开发基于有限数量监测站点的建模模拟方法。以2014—2023年杭州核心区7个国控站点监测的PM_(2.5)浓度为响应变量,城市土地利用景观格局为解释变量,结合土地利用回归(Land Use Regression,LUR)模型、极限梯度提升(XGBoost)算法和斯皮尔曼相关性分析构建模型,采用数据分割、10倍交叉验证和外部数据验证法检验性能,探讨解释变量对PM_(2.5)的影响机制,分析PM_(2.5)污染的时空变异性。结果表明,混合模型表现性能更优,R^(2)和调整R^(2)都在0.90以上,交叉验证的MSE值、RMSE值和MAE值分别为1.32μg/m^(3)、1.15μg/m^(3)和1.08μg/m^(3)。500 m缓冲区内林地斑块形状复杂度和1000 m不透水面平均斑块面积与PM_(2.5)显著相关;林地、耕地和不透水面用地对PM_(2.5)的预测能力分别为44%、33%和23%;年均浓度整体呈波动下降趋势和西北高、西南低、由南向北递增的空间分布格局;体现了“冬高夏低”的“U”形季节变化特征,低值区位于西湖区、拱墅区局地,高值区位于拱墅区、滨江区境内。展开更多
Spectral properties of magnetohydrodynamic （MHD） turbulence with a strong back- ground mean magnetic field in 2.5-dimensional compressible plasmas are studied by high-resolution numerical simulations. The spatial pr...Spectral properties of magnetohydrodynamic （MHD） turbulence with a strong back- ground mean magnetic field in 2.5-dimensional compressible plasmas are studied by high-resolution numerical simulations. The spatial properties of MHD turbulences and the energy transfer process in the k-space are analyzed through angle-averaged energy spectrum. It is found that in the inertial phase, the energy spectrum index of compressible MHD turbulences during the decaying phase is evolved with time. The index varies in a quite wide regime from Kolmogorov＇s 5/3 to IK＇s 3/2 during the late simulation period. The energy spectrum index in the later nonlinear stage is also dependent on the chosen initial conditions. The spectral index increases with the increase of the initial magnetic fluctuation while the index decreases with the increase of the initial flow perturbation.展开更多
Numerical simulation of oil migration and accumulation is to describe the history of oil migration and accumulation in basin evolution. It is of great value in the exploration of oil resources and their rational evalu...Numerical simulation of oil migration and accumulation is to describe the history of oil migration and accumulation in basin evolution. It is of great value in the exploration of oil resources and their rational evaluation. In this paper, from such actual conditions as the effects of mechanics of fluids in porous media and 3-dimensional geology characteristics, a kind of modified method of second order splitting-up implicit interactive scheme is pur forward. For the famous hydraulic experiment of secondary migration-accumulation, the numerical simulation test has been done, and both the computational and experimental results are basically identical. For the actual problem of Dongying hollow of Shengli Petroleum Oil Field, the numerical simulation test and the actual conditions are basically coincident. Thus the well-known problem has been solved.展开更多
The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exp...The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exponent 5 is estimated using the power law relations and the finite size scaling functions for the magnetization and the susceptibility in the range -0.1≤ h = H/J ≤0. The estimated value of the field critical exponent 5 is in good agreement with the universal value （δ = 5） in three dimensions. The simulations are carried out on a simple cubic lattice under periodic boundary conditions.展开更多
The spatial distdbution and deposition of PM2.5 in coastal areas of eastern China in 2010 were simulated using the CMAQ model. The results show that the simulated data were consistent with the observed data, and the m...The spatial distdbution and deposition of PM2.5 in coastal areas of eastern China in 2010 were simulated using the CMAQ model. The results show that the simulated data were consistent with the observed data, and the model could simulate the regional distribution of PM2.5 concentration. There were obvious seasonal variations in PM2.5 concentration in eastern China, and the spatial distribution of PM2.5 concentration which increased from the edge to the center of a city coincided well with that of the sources. In North China, the high-value center of PM2.5 concentration reached above 120 μg/m3. Wet deposition was the main way to remove PM2.5 , and wet deposition flux of PM2.5 was at least five times more than that of the dry deposition flux. Deposition flux of PM2.5 was the largest in summer, while it was the smallest in winter. The high-value center of deposition flux of PM2.5 in eastern China exceeded 30 mg/（ m2 · d）. Wet deposition of PM2s in each province or region accounted for more than 91% of total deposition of PM2.5. Total deposition of PM2.5 in all simulated regions amounted to 4.67 ×10^6 /a, and total deposition of PM2.5 in Beijing, Tianjin and Hebei was up to 1.65 ×10^6 t/a.展开更多
基金supported by the Autonomous General Projects of the State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,China(Grant No.2011DA105287-MS202209)the National Natural Science Foundation of China,China(Grant Nos.52304149 and 52204127).
文摘The fracture and migration patterns of direct roofs play a critical role in excavation stability and mining pressure.However,current methods fail to capture the irregular three-dimensional(3D)behavior of these roofs.In this study,the problem was solved by introducing an innovative 2.5-dimensional(2.5D)Voronoi numerical simulation method,dividing rock layers into 2.5D Voronoi blocks and developing cohesive element-based failure models,supported by a strain-softening HoekeBrown model.The method was applied to the 8311 working face in the Taishan Mine in China,and its accuracy was confirmed through physical experiments.The following conclusions were drawn.The first roof break typically followed an"O-X"pattern.The direct roof did not break randomly over time;instead,it followed three distinct scenarios:(1)A complete break of the direct roof occurred,followed by a sequential collapse(ScenarioⅠ).(2)Regional irregular stacking in one area was followed by sequential collapse in other zones(ScenarioⅡ).(3)The staged breakdown of the direct roof led to separate and sequential collapses on the left and right flanks(ScenarioⅢ).Scenario I was quite common during the 400 m advance of the working face and occurred five times.The fracture characteristics in Scenario I led to widespread pressure on the hydraulic supports in the middle of the working face.Finally,the direct roof from the working face towards the goaf area underwent phases of overhanging,hinging,and collapsing plates.After the first and periodic breaks,the basic roof formed stable hinged plate structures reinforced by overhanging plates and irregular accumulations of the direct roof.
基金supported by the National Natural Science Foundation of China(Nos.92044302 and 42275115)the Natural Science Foundation of Jiangsu Province(No.BK20241711)the Postgraduate Research and Practice Innovation of Jiangsu Province Program(No.KYCX20_0952)。
文摘Weak turbulence often occurs during heavy pollution events in eastern China(EC).However,existing mesoscale meteorology models cannot accurately simulate turbulent diffusion under weakened turbulence,particularly under the nocturnal stable boundary layer(SBL),often leading to significant turbulent diffusivity underestimation and surface aerosol overestimation.In this study,a new parameterization of minimum turbulent diffusivity coefficient(Kz_(min))was tested and applied to PM_(2.5)simulations in EC under SBL conditions in WRF-Chem.The original model overestimated the PM_(2.5)simulation and the simulation performance can be improved by adding Kz_(min).Sensitivity experiments revealed different ranges of available Kz_(min)values over the northern(0.8 to 1.2 m^(2)/s)and southern(1.0 to 1.5 m^(2)/s)regions of EC.The geographically related Kz_(min)was parameterized by sensible heat flux(H)and latent heat flux(LE),which also exhibited regional differences related to the climate and underlying surface.Furthermore,we assign physical significance to the parameterized formula Kz_(min)and found that our proposed Kz_(min)scheme can reasonably yield dynamic Kz_(min)values over EC.The revised Kz_(min)scheme(EXP_(NEW))enhanced the turbulent diffusion(north:0.93 m^(2)/s,south:1.10 m^(2)/s on average)in the SBL,simultaneously improving the PM_(2.5)simulations on the surface(north:65.78 to 0.67μg/m^(3);south 30.48 to 12.86μg/m^(3))and upper SBL.A process analysis showed that vertical mixing was the key process for improving PM_(2.5)simulations on the surface in EXP_(NEW).This study highlighted the importance of improving turbulent diffusion in current mesoscale models under SBL and has great significance for aerosol simulation.
基金Sponsored by National Science and Technology Major Project of China(2012ZX04012011)National Natural Science Foundation of China(51375306)
文摘Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves, while no well accepted method can be employed for transverse waves. In order to investigate the essential deformation law of leveling for plates with transverse waves, a 2.5-dimensional （2.5- D） analytical approach was proposed. In this model, the plate was transversely divided into some strips with equal width; the strips are considered to be in the state of plane strain and each group of adjacent strips are assumed to be deformation compatible under stress. After calculation, the bending deformation of each strip and the leveling effect of overall plate were obtained by comprehensNe consideration of various strips along with the width. Bending of roller is a main approach to eliminate the transverse waves, which is widely accepted by the industry, but the essential effect of bending of roller on the deformation of plates and the calculation of bending of roller are unknown. According to the 2.5-D analytical model, it can be found that, for plates, it is neutral plane offsetting and middle plane elongation or contraction under inner stress that can effectively improve plate shape. Taking double side waves as an example, the appropriate values of bending of roller were obtained by the 2.5-D analytical model related to different initial unevenness, which was applicable to the current on-line adjusting of bending of roller in rolling industry.
文摘环境细颗粒物(PM_(2.5))已被列为全球第六大死亡和残疾风险因素。为精准防治PM_(2.5)污染,需要以足够的分辨率捕捉PM_(2.5)时空变化,开发基于有限数量监测站点的建模模拟方法。以2014—2023年杭州核心区7个国控站点监测的PM_(2.5)浓度为响应变量,城市土地利用景观格局为解释变量,结合土地利用回归(Land Use Regression,LUR)模型、极限梯度提升(XGBoost)算法和斯皮尔曼相关性分析构建模型,采用数据分割、10倍交叉验证和外部数据验证法检验性能,探讨解释变量对PM_(2.5)的影响机制,分析PM_(2.5)污染的时空变异性。结果表明,混合模型表现性能更优,R^(2)和调整R^(2)都在0.90以上,交叉验证的MSE值、RMSE值和MAE值分别为1.32μg/m^(3)、1.15μg/m^(3)和1.08μg/m^(3)。500 m缓冲区内林地斑块形状复杂度和1000 m不透水面平均斑块面积与PM_(2.5)显著相关;林地、耕地和不透水面用地对PM_(2.5)的预测能力分别为44%、33%和23%;年均浓度整体呈波动下降趋势和西北高、西南低、由南向北递增的空间分布格局;体现了“冬高夏低”的“U”形季节变化特征,低值区位于西湖区、拱墅区局地,高值区位于拱墅区、滨江区境内。
基金supported by National Natural Science Foundation of China (No. 40536030)
文摘Spectral properties of magnetohydrodynamic （MHD） turbulence with a strong back- ground mean magnetic field in 2.5-dimensional compressible plasmas are studied by high-resolution numerical simulations. The spatial properties of MHD turbulences and the energy transfer process in the k-space are analyzed through angle-averaged energy spectrum. It is found that in the inertial phase, the energy spectrum index of compressible MHD turbulences during the decaying phase is evolved with time. The index varies in a quite wide regime from Kolmogorov＇s 5/3 to IK＇s 3/2 during the late simulation period. The energy spectrum index in the later nonlinear stage is also dependent on the chosen initial conditions. The spectral index increases with the increase of the initial magnetic fluctuation while the index decreases with the increase of the initial flow perturbation.
文摘Numerical simulation of oil migration and accumulation is to describe the history of oil migration and accumulation in basin evolution. It is of great value in the exploration of oil resources and their rational evaluation. In this paper, from such actual conditions as the effects of mechanics of fluids in porous media and 3-dimensional geology characteristics, a kind of modified method of second order splitting-up implicit interactive scheme is pur forward. For the famous hydraulic experiment of secondary migration-accumulation, the numerical simulation test has been done, and both the computational and experimental results are basically identical. For the actual problem of Dongying hollow of Shengli Petroleum Oil Field, the numerical simulation test and the actual conditions are basically coincident. Thus the well-known problem has been solved.
文摘The Blume-Capel model in the presence of external magnetic field H has been simulated using a cellular automaton algorithm improved from the Creutz cellular automaton in three-dimension lattice. The field critical exponent 5 is estimated using the power law relations and the finite size scaling functions for the magnetization and the susceptibility in the range -0.1≤ h = H/J ≤0. The estimated value of the field critical exponent 5 is in good agreement with the universal value （δ = 5） in three dimensions. The simulations are carried out on a simple cubic lattice under periodic boundary conditions.
基金Supported by the National Natural Science Foundation of China(41373131)National Key Technology R&D Program(2014BA C23B03)
文摘The spatial distdbution and deposition of PM2.5 in coastal areas of eastern China in 2010 were simulated using the CMAQ model. The results show that the simulated data were consistent with the observed data, and the model could simulate the regional distribution of PM2.5 concentration. There were obvious seasonal variations in PM2.5 concentration in eastern China, and the spatial distribution of PM2.5 concentration which increased from the edge to the center of a city coincided well with that of the sources. In North China, the high-value center of PM2.5 concentration reached above 120 μg/m3. Wet deposition was the main way to remove PM2.5 , and wet deposition flux of PM2.5 was at least five times more than that of the dry deposition flux. Deposition flux of PM2.5 was the largest in summer, while it was the smallest in winter. The high-value center of deposition flux of PM2.5 in eastern China exceeded 30 mg/（ m2 · d）. Wet deposition of PM2s in each province or region accounted for more than 91% of total deposition of PM2.5. Total deposition of PM2.5 in all simulated regions amounted to 4.67 ×10^6 /a, and total deposition of PM2.5 in Beijing, Tianjin and Hebei was up to 1.65 ×10^6 t/a.
