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
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
A 2.5D finite-difference(FD)algorithm for the modeling of the electromagnetic(EM)logging-whiledrilling(LWD)tool in anisotropic media is presented.The FD algorithm is based on the Lebedev grid,which allows for the disc...A 2.5D finite-difference(FD)algorithm for the modeling of the electromagnetic(EM)logging-whiledrilling(LWD)tool in anisotropic media is presented.The FD algorithm is based on the Lebedev grid,which allows for the discretization of the frequency-domain Maxwell's equations in the anisotropic media in 2.5D scenarios without interpolation.This leads to a system of linear equations that is solved using the multifrontal direct solver which enables the simulation of multi-sources at nearly the cost of simulating a single source for each frequency.In addition,near-optimal quadrature derived from an optimized integration path in the complex plane is employed to implement the fast inverse Fourier Transform(IFT).The algorithm is then validated by both analytic and 3D solutions.Numerical results show that two Lebedev subgrid sets are sufficient for TI medium,which is common in geosteering environments.The number of quadrature points is greatly reduced by using the near-optimal quadrature method.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
在创新、协调、绿色、开放、共享的新发展理念下,为探索完善PM_(2.5)污染预报预警、应急预案以及县域精细化管控等领域的理论体系与应用视角,基于SHAP(SHapley Additive exPlanations)和随机森林(RF)构建SHAP-RF预报模型,通过分析成都市...在创新、协调、绿色、开放、共享的新发展理念下,为探索完善PM_(2.5)污染预报预警、应急预案以及县域精细化管控等领域的理论体系与应用视角,基于SHAP(SHapley Additive exPlanations)和随机森林(RF)构建SHAP-RF预报模型,通过分析成都市2018−2021年国控/省控监测站点数据,结合欧洲中期天气预报中心细网格模式预报资料,实现对PM_(2.5)特征因子重要性动态识别与筛选,生成县域本地化特征因子集,并开展未来1~10 d PM_(2.5)浓度预报研究。结果表明:①识别出成都市影响PM_(2.5)浓度变化的关键特征因子以起报天CO浓度、起报天NO_(2)浓度、起报天PM_(2.5)浓度、气温、位势高度等变量为主。②所构建的SHAP-RF预报模型对未来1~10 d的PM_(2.5)逐日浓度预报准确性较好,预报未来1 d PM_(2.5)浓度的均方根误差(RMSE)为9.25~17.93μg/m^(3),拟合优度(R^(2))为0.67~0.84;预报未来1~3 d时,RMSE为10.60~20.45μg/m^(3),R^(2)为0.57~0.74;预报未来4~10 d时,RMSE为12.50~23.48μg/m^(3),R^(2)为0.42~0.69。③单站点长时间序列PM_(2.5)浓度逐日预报检验显示,模型能较好地捕捉到PM_(2.5)浓度秋冬高、春夏低的季节性波动特征和逐日变化特征。④PM_(2.5)污染超标预报检验显示,模型对于各站点污染超标预报准确率为89.59%~97.26%,且随着预报时效的增加,对于单站点污染超标预报准确率并没有明显减小。研究显示,SHAP值在预报模型中不仅能实现对模型可解释性的可视化呈现,同时可实现特征识别,显示特征因子重要性分布特征,SHAP-RF预报模型在实际应用中能较好地实现对未来1~10 d PM_(2.5)污染过程的预报预警。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
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A 2.5D finite-difference(FD)algorithm for the modeling of the electromagnetic(EM)logging-whiledrilling(LWD)tool in anisotropic media is presented.The FD algorithm is based on the Lebedev grid,which allows for the discretization of the frequency-domain Maxwell's equations in the anisotropic media in 2.5D scenarios without interpolation.This leads to a system of linear equations that is solved using the multifrontal direct solver which enables the simulation of multi-sources at nearly the cost of simulating a single source for each frequency.In addition,near-optimal quadrature derived from an optimized integration path in the complex plane is employed to implement the fast inverse Fourier Transform(IFT).The algorithm is then validated by both analytic and 3D solutions.Numerical results show that two Lebedev subgrid sets are sufficient for TI medium,which is common in geosteering environments.The number of quadrature points is greatly reduced by using the near-optimal quadrature method.
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.
文摘在创新、协调、绿色、开放、共享的新发展理念下,为探索完善PM_(2.5)污染预报预警、应急预案以及县域精细化管控等领域的理论体系与应用视角,基于SHAP(SHapley Additive exPlanations)和随机森林(RF)构建SHAP-RF预报模型,通过分析成都市2018−2021年国控/省控监测站点数据,结合欧洲中期天气预报中心细网格模式预报资料,实现对PM_(2.5)特征因子重要性动态识别与筛选,生成县域本地化特征因子集,并开展未来1~10 d PM_(2.5)浓度预报研究。结果表明:①识别出成都市影响PM_(2.5)浓度变化的关键特征因子以起报天CO浓度、起报天NO_(2)浓度、起报天PM_(2.5)浓度、气温、位势高度等变量为主。②所构建的SHAP-RF预报模型对未来1~10 d的PM_(2.5)逐日浓度预报准确性较好,预报未来1 d PM_(2.5)浓度的均方根误差(RMSE)为9.25~17.93μg/m^(3),拟合优度(R^(2))为0.67~0.84;预报未来1~3 d时,RMSE为10.60~20.45μg/m^(3),R^(2)为0.57~0.74;预报未来4~10 d时,RMSE为12.50~23.48μg/m^(3),R^(2)为0.42~0.69。③单站点长时间序列PM_(2.5)浓度逐日预报检验显示,模型能较好地捕捉到PM_(2.5)浓度秋冬高、春夏低的季节性波动特征和逐日变化特征。④PM_(2.5)污染超标预报检验显示,模型对于各站点污染超标预报准确率为89.59%~97.26%,且随着预报时效的增加,对于单站点污染超标预报准确率并没有明显减小。研究显示,SHAP值在预报模型中不仅能实现对模型可解释性的可视化呈现,同时可实现特征识别,显示特征因子重要性分布特征,SHAP-RF预报模型在实际应用中能较好地实现对未来1~10 d PM_(2.5)污染过程的预报预警。
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。
