To investigate decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast,a new exponential decay(ED)law was proposed.The results show that th...To investigate decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast,a new exponential decay(ED)law was proposed.The results show that the micro-fracture activity decay law after multistage stress loading and blasting disturbance conforms to the ED model,in which the sum of A and n represents the number of initial micro-fracture events,and n represents the level of background micro-fracture events.The ED model can describe the number of initial micro-fracture events with a deviation less than 10%.The ED model outperforms the traditional aftershock models in describing the micro-fracture event decay law in the three cases considered.The ED model can provide a reference for selecting the blasting interval in mines,which is of great significance to maintain the stability of the surrounding rock and ensure safe production in metal mines.展开更多
We study the large time behavior of solutions of scalar conservation laws with periodic initial data. Under a very weak nonlinearity condition,we prove that the solutions converge to constants as time tends to infinit...We study the large time behavior of solutions of scalar conservation laws with periodic initial data. Under a very weak nonlinearity condition,we prove that the solutions converge to constants as time tends to infinity. Our results improve the earlier ones since we only require the flux to be nonlinear at the mean value of the initial data.展开更多
Using the form factors from light-cone sum rules, we study the branching ratios and forward-backward asymmetries （FBAs） of the exclusive decays Bu^＋→π^＋e^＋e^- and Bu^＋ →ρ^＋e^＋e^- （e= e,μ） in the standar...Using the form factors from light-cone sum rules, we study the branching ratios and forward-backward asymmetries （FBAs） of the exclusive decays Bu^＋→π^＋e^＋e^- and Bu^＋ →ρ^＋e^＋e^- （e= e,μ） in the standard model （SM） and the top quark two-Higgs-doublet model （T2HDM）. From the numerical results, we find that the new physics contributions cannot provide very large enhancement to the branching ratios and the theoretical predictions are in good agreement with the SM ones. The T2HDM effects on FBAs of these decays are small. Precision measurements of the dilepton invariant mass distributions, especially in the lower dilepton mass region, and the FBAs in the decays Bu^＋ → π^＋ （ρ^＋ ）e^＋ e^- will greatly help in discriminating among the SM and the new physics models.展开更多
The occurrence and transmission attenuation of surge is always a problem that researchers pay much attention to. The influence of the first wave height of landslide surge and the following transmission attenuation of ...The occurrence and transmission attenuation of surge is always a problem that researchers pay much attention to. The influence of the first wave height of landslide surge and the following transmission attenuation of surge are involved with many factors, which are mainly： landslide water entry angle, river course depth, river course geometrical properties and landslide mass and material, etc.. This thesis is mainly a research on the properties and transmission attenuation rules of landslide surge which is caused by linear narrow river course. Numerical value simulation will be applied in this thesis to discuss about the features and rules of the occurrence and transmission of surge in different landslide water entry angles and under different influences.展开更多
The numerical simulation of jet flow field in Laval tube was carried out first by commercial software CFX4.4, and it is used to determine inlet pressure condition out of nozzle in order to its numerical simulation. Th...The numerical simulation of jet flow field in Laval tube was carried out first by commercial software CFX4.4, and it is used to determine inlet pressure condition out of nozzle in order to its numerical simulation. The decay rule of jet middle line velocity of axial symmetry turbulence jet and cross section＇s expand situation out of the tube in different stagnation pressure and surrounding temperature were analyzed systematically. The result showed that K-e model is suitable for numerical simulation. The conclusion will have important guide and referent function to research of two important craft parameters, impact depth and the impact area which are related to steel-making production practice.展开更多
To evaluate the strength attenuation law of soft rock in the western mining area of China, we established an evolution model for the strength parameters of soft mudstone at the post-peak stage by employing a tri-linea...To evaluate the strength attenuation law of soft rock in the western mining area of China, we established an evolution model for the strength parameters of soft mudstone at the post-peak stage by employing a tri-linear strain softening model. In the model, a stiffness degradation coefficient co and a softening modulus coefficient a were introduced to take into account the stiff- ness degradation, and the subsequent yield surfaces at post-peak stage were all assumed to meet the Molar-Coulomb yield criterion. Furthermore, attenuation laws of stiffness and strength parameters of soft mudstone were analyzed according to an engineering case. Finally, the model＇s accuracy was verified by comparison of results from numerical calculation and tri-axial compression tests. Results showed that the attenuation of the friction angle was dominated mainly by the instantaneous stress states and damage features, while the attenuation law of cohesion was also related to the plastic behavior. The degradation rates of strength param- eters decreased with increasing confining pressure and the friction angle tended towards its initial value. Residual strengths were also enhanced with increasing confming pressure. The results indicate that the evolution model can accurately describe the strain softening behavior of soft rock.展开更多
In this paper, we consider the large perturbation around the viscous shock of the scalar conservation law with viscosity in one dimension case. We divide the time region into t ≤T0 and t 〉 To for a fixed constant To...In this paper, we consider the large perturbation around the viscous shock of the scalar conservation law with viscosity in one dimension case. We divide the time region into t ≤T0 and t 〉 To for a fixed constant To when applying energy method. Since To is fixed, the case t ≤ To is easy to deal with and when t 〉 To, from the decaying property of the solution, there is a priori estimate for the solution. Thus we can succeed to control the nonlinear term and get the pointwise estimate for the perturbation by the weighted energy method.展开更多
基金financial supports from the National Natural Science Foundation of China(Nos.51704056,51974059)the China Postdoctoral Science Foundation(No.2017M621152)the Fundamental Research Funds for the Central University of China(Nos.N160103006,N180115010,N2001001)。
文摘To investigate decay law of acoustic emission and microseismic activities caused by disturbances associated with multilevel loading and mining blast,a new exponential decay(ED)law was proposed.The results show that the micro-fracture activity decay law after multistage stress loading and blasting disturbance conforms to the ED model,in which the sum of A and n represents the number of initial micro-fracture events,and n represents the level of background micro-fracture events.The ED model can describe the number of initial micro-fracture events with a deviation less than 10%.The ED model outperforms the traditional aftershock models in describing the micro-fracture event decay law in the three cases considered.The ED model can provide a reference for selecting the blasting interval in mines,which is of great significance to maintain the stability of the surrounding rock and ensure safe production in metal mines.
文摘We study the large time behavior of solutions of scalar conservation laws with periodic initial data. Under a very weak nonlinearity condition,we prove that the solutions converge to constants as time tends to infinity. Our results improve the earlier ones since we only require the flux to be nonlinear at the mean value of the initial data.
基金National Natural Science Foundation of China under Grant No.10575052the Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP) under Grant No.20050319008the Special Study Foundation of Nanyang Normal University under Grant No.nynu200750
文摘Using the form factors from light-cone sum rules, we study the branching ratios and forward-backward asymmetries （FBAs） of the exclusive decays Bu^＋→π^＋e^＋e^- and Bu^＋ →ρ^＋e^＋e^- （e= e,μ） in the standard model （SM） and the top quark two-Higgs-doublet model （T2HDM）. From the numerical results, we find that the new physics contributions cannot provide very large enhancement to the branching ratios and the theoretical predictions are in good agreement with the SM ones. The T2HDM effects on FBAs of these decays are small. Precision measurements of the dilepton invariant mass distributions, especially in the lower dilepton mass region, and the FBAs in the decays Bu^＋ → π^＋ （ρ^＋ ）e^＋ e^- will greatly help in discriminating among the SM and the new physics models.
文摘The occurrence and transmission attenuation of surge is always a problem that researchers pay much attention to. The influence of the first wave height of landslide surge and the following transmission attenuation of surge are involved with many factors, which are mainly： landslide water entry angle, river course depth, river course geometrical properties and landslide mass and material, etc.. This thesis is mainly a research on the properties and transmission attenuation rules of landslide surge which is caused by linear narrow river course. Numerical value simulation will be applied in this thesis to discuss about the features and rules of the occurrence and transmission of surge in different landslide water entry angles and under different influences.
文摘The numerical simulation of jet flow field in Laval tube was carried out first by commercial software CFX4.4, and it is used to determine inlet pressure condition out of nozzle in order to its numerical simulation. The decay rule of jet middle line velocity of axial symmetry turbulence jet and cross section＇s expand situation out of the tube in different stagnation pressure and surrounding temperature were analyzed systematically. The result showed that K-e model is suitable for numerical simulation. The conclusion will have important guide and referent function to research of two important craft parameters, impact depth and the impact area which are related to steel-making production practice.
基金Project supported by the National Natural Science Foundation of China （No. 51174128）, and the Specialized Research Fund for the Doctoral Program of Higher Education of China （No. 20123718110007）
文摘To evaluate the strength attenuation law of soft rock in the western mining area of China, we established an evolution model for the strength parameters of soft mudstone at the post-peak stage by employing a tri-linear strain softening model. In the model, a stiffness degradation coefficient co and a softening modulus coefficient a were introduced to take into account the stiff- ness degradation, and the subsequent yield surfaces at post-peak stage were all assumed to meet the Molar-Coulomb yield criterion. Furthermore, attenuation laws of stiffness and strength parameters of soft mudstone were analyzed according to an engineering case. Finally, the model＇s accuracy was verified by comparison of results from numerical calculation and tri-axial compression tests. Results showed that the attenuation of the friction angle was dominated mainly by the instantaneous stress states and damage features, while the attenuation law of cohesion was also related to the plastic behavior. The degradation rates of strength param- eters decreased with increasing confining pressure and the friction angle tended towards its initial value. Residual strengths were also enhanced with increasing confming pressure. The results indicate that the evolution model can accurately describe the strain softening behavior of soft rock.
基金supported by National Natural Science Foundation of China (Grant Nos.11141004,11201296,11071162 and 11231006)
文摘In this paper, we consider the large perturbation around the viscous shock of the scalar conservation law with viscosity in one dimension case. We divide the time region into t ≤T0 and t 〉 To for a fixed constant To when applying energy method. Since To is fixed, the case t ≤ To is easy to deal with and when t 〉 To, from the decaying property of the solution, there is a priori estimate for the solution. Thus we can succeed to control the nonlinear term and get the pointwise estimate for the perturbation by the weighted energy method.
