Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bend...Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.展开更多
A k-regular spanning subgraph of graph G is called a k-factor of G. Graph G is called a k-deleted graph if G-e has a k-factor for each edge e. A graph G=(X,Y) with bipartition (X,Y) is called a bipartite graph if ever...A k-regular spanning subgraph of graph G is called a k-factor of G. Graph G is called a k-deleted graph if G-e has a k-factor for each edge e. A graph G=(X,Y) with bipartition (X,Y) is called a bipartite graph if every edge of G has one endpoint in X and the other in Y.It is proved that a bipartite graph G=(X,Y) with X=Y is a k-deleted graph if and only if kS≤r 1+2r 2+...+k(r k+...+r Δ)-ε(S) for all SX. Using this result we give a sufficient neighborhood condition for a bipartite to be a k-deleted graph.展开更多
Let (X,Y) be an R^d×R^1 valued random vector (X_1,Y_1),…, (X_n,Y_n) be a random sample drawn from (X,Y), and let E|Y|<∞. The regression function m(x)=E(Y|X=x) for x∈R^d is estimated by where, and h_n is a p...Let (X,Y) be an R^d×R^1 valued random vector (X_1,Y_1),…, (X_n,Y_n) be a random sample drawn from (X,Y), and let E|Y|<∞. The regression function m(x)=E(Y|X=x) for x∈R^d is estimated by where, and h_n is a positive number depending upon n only, nad K is a given nonnegative function on R^d. In the paper, we study the L_p convergence rate of kernel estimate m_n(x) of m(x) in suitable condition, and improve and extend the results of Wei Lansheng.展开更多
基金financially supported by the National Natural Science Foundation of China (No.51374139)the Natural Science Foundation of Shandong Province (No.ZR2013EEM018)the Scientific Research Innovation Team Support Plan of Shandong University of Science and Technology
文摘Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.
文摘A k-regular spanning subgraph of graph G is called a k-factor of G. Graph G is called a k-deleted graph if G-e has a k-factor for each edge e. A graph G=(X,Y) with bipartition (X,Y) is called a bipartite graph if every edge of G has one endpoint in X and the other in Y.It is proved that a bipartite graph G=(X,Y) with X=Y is a k-deleted graph if and only if kS≤r 1+2r 2+...+k(r k+...+r Δ)-ε(S) for all SX. Using this result we give a sufficient neighborhood condition for a bipartite to be a k-deleted graph.
文摘Let (X,Y) be an R^d×R^1 valued random vector (X_1,Y_1),…, (X_n,Y_n) be a random sample drawn from (X,Y), and let E|Y|<∞. The regression function m(x)=E(Y|X=x) for x∈R^d is estimated by where, and h_n is a positive number depending upon n only, nad K is a given nonnegative function on R^d. In the paper, we study the L_p convergence rate of kernel estimate m_n(x) of m(x) in suitable condition, and improve and extend the results of Wei Lansheng.
