First, the main procedures and the distinctive features of the most-obtuse-angle（MOA）row or column pivot rules are introduced for achieving primal or dual feasibility in linear programming. Then, two special auxilia...First, the main procedures and the distinctive features of the most-obtuse-angle（MOA）row or column pivot rules are introduced for achieving primal or dual feasibility in linear programming. Then, two special auxiliary problems are constructed to prove that each of the rules can be actually considered as a simplex approach for solving the corresponding auxiliary problem. In addition, the nested pricing rule is also reviewed and its geometric interpretation is offered based on the heuristic characterization of an optimal solution.展开更多
City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation,affecting the surface environment and the safety of the tunnels.Due to its strong dis...City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation,affecting the surface environment and the safety of the tunnels.Due to its strong dispersion,sandy cobble strata can be easily disturbed by shield tunneling.Based on the project of the Chengdu Metro Line 1,field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves,ground loss ratios and construction influence zones.The discrete element method(DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level.Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil.The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.展开更多
Satisfiability modulo theories (SMT) play a key role in verification applications. A crucial SMT problem is to combine separate theory solvers for the union of theories. In previous work, the simplex method is used to...Satisfiability modulo theories (SMT) play a key role in verification applications. A crucial SMT problem is to combine separate theory solvers for the union of theories. In previous work, the simplex method is used to determine the solvability of constraint systems and the equalities implied by constraint systems are detected by a multitude of applications of the dual simplex method. We present an effective simplex tableau-based method to identify all implicit equalities such that the simplex method is harnessed to an irreducible minimum. Experimental results show that the method is feasible and effective.展开更多
基金The National Natural Science Foundation of China(No.10371017).
文摘First, the main procedures and the distinctive features of the most-obtuse-angle（MOA）row or column pivot rules are introduced for achieving primal or dual feasibility in linear programming. Then, two special auxiliary problems are constructed to prove that each of the rules can be actually considered as a simplex approach for solving the corresponding auxiliary problem. In addition, the nested pricing rule is also reviewed and its geometric interpretation is offered based on the heuristic characterization of an optimal solution.
基金Project supported by the National Basic Research (973) Program of China (No. 2010CB732105)the National Natural Science Foundation of China (Nos. 50908193,50925830,and 51208432)
文摘City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation,affecting the surface environment and the safety of the tunnels.Due to its strong dispersion,sandy cobble strata can be easily disturbed by shield tunneling.Based on the project of the Chengdu Metro Line 1,field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves,ground loss ratios and construction influence zones.The discrete element method(DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level.Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil.The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.
基金Project supported by the National Natural Science Foundation of China (Nos 60635020 and 90718039)the National Basic Research Program (973) of China (No 2004CB719406)
文摘Satisfiability modulo theories (SMT) play a key role in verification applications. A crucial SMT problem is to combine separate theory solvers for the union of theories. In previous work, the simplex method is used to determine the solvability of constraint systems and the equalities implied by constraint systems are detected by a multitude of applications of the dual simplex method. We present an effective simplex tableau-based method to identify all implicit equalities such that the simplex method is harnessed to an irreducible minimum. Experimental results show that the method is feasible and effective.
