Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties(e.g., density,velocity and discharge) using deposit as done in practice. Tracing the variatio...Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties(e.g., density,velocity and discharge) using deposit as done in practice. Tracing the variation of grain composition is thus more important than estimating some certain properties of flow because every debris flow event consists of a series of surges that are distinct in properties and flow regimes. We find that the materials of debris flows, both the fluid and the source soils, satisfy a universal grain size distribution(GSD) in a form of P(D) = CD –μexp(–D/D c), where the parameters C, μ and D c are determined by fitting the function to the grain size frequency. A small μ implies a small porosity and possible high excess pore pressure in flow; and a large D c means a wide range of grain composition and hence a high sediment concentration. Flow density increases as μ decreases or D c increases, in a power law form. A debris flow always achieves a state of certain mobility and density that can be well described by the coupling of μ and D c,which imposes a constraint on the fluctuations of flow surges. The GSD also describes the changes in grain composition in that it is always satisfied during the course of debris flow developing. Numerical simulation using the GSD can well illustrate the variation of μ and D c from source soils to deposits.展开更多
The size and the shape of non-reversal random-walking polymer chains near an impenetrable, non-interacting flat surface are investigated by means of Monte Carlo simulation on the simple cubic lattice. It wasfound that...The size and the shape of non-reversal random-walking polymer chains near an impenetrable, non-interacting flat surface are investigated by means of Monte Carlo simulation on the simple cubic lattice. It wasfound that both size and shape are dependent on the normal-to-surface distance z0 of the first segment of chain. Wefind that the size and shape of chains, characterized by mean square radius of gyration <S2> and mean asphericityparameter <A> respectively, show similar dependence on distance z0. Both <S2> and <A> reach the maximum atz0 = 0, then decrease with the increase of z0 and soon reach the minimum values, afterwards they go up continuouslyand approach to the limit values of free chain. The similar dependence of <S2> and <A> on z0 can be explained by apositive correlation between A and S2. However, the dependence of the correlation coefficient CA,S2 on z0 is verycomplicated and deserves further study. The overall density probability of segments is also investigated. Resultsshow that segments near the surface are relatively less, and the symmetrical distribution disappears when the chainlocates near the surface.展开更多
The phenomenon of phase transition in constraint satisfaction problems (CSPs) plays a crucial role in the field of artificial intelligence and computational complexity theory. In this paper, we propose a new random CS...The phenomenon of phase transition in constraint satisfaction problems (CSPs) plays a crucial role in the field of artificial intelligence and computational complexity theory. In this paper, we propose a new random CSP called d-p-RB model, which is a generalization of RB model on domain size d and constraint tightness p. In this model, the variable domain size d?Ε [ nα, nny], and all constraints are uniformly divided into several groups with different constraint tightness p. It is proved by the second moment method that the d-p-RB model undergoes phase transition from a region where almost all instances are satisfiable to a region where almost all instances are unsatisfiable as the control parameter increases. Moreover, the threshold value at which the phase transition occurs is located exactly.展开更多
It is a NP-hard problem to schedule a list of nonresumable jobs to the available intervals of an availability-constrained single machine to minimize the scheduling length. This paper transformed this scheduling proble...It is a NP-hard problem to schedule a list of nonresumable jobs to the available intervals of an availability-constrained single machine to minimize the scheduling length. This paper transformed this scheduling problem into a variant of the variable-sized bin packing problem, put forward eight bin packing algorithms adapted from the classic one-dimensional bin packing problem and investigated their performances from both of the worst-case and the average-case scenarios. Analytical results show that the worst-case performance ratios of the algorithms are not less than 2. Experimental results for average cases show that the Best Fit and the Best Fit Decreasing algorithm outperform any others for independent and precedence-constrained jobs respectively.展开更多
基金supported by the Key Research Program of the Chinese Academy of Sciences (Grant No.KZZD-EW-05-01)the National Natural Science Foundation of China (Grant No. 41471011)the Key Laboratory of Mountain Hazards and Earth Surface Processes,Chinese Academy of Sciences,China
文摘Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties(e.g., density,velocity and discharge) using deposit as done in practice. Tracing the variation of grain composition is thus more important than estimating some certain properties of flow because every debris flow event consists of a series of surges that are distinct in properties and flow regimes. We find that the materials of debris flows, both the fluid and the source soils, satisfy a universal grain size distribution(GSD) in a form of P(D) = CD –μexp(–D/D c), where the parameters C, μ and D c are determined by fitting the function to the grain size frequency. A small μ implies a small porosity and possible high excess pore pressure in flow; and a large D c means a wide range of grain composition and hence a high sediment concentration. Flow density increases as μ decreases or D c increases, in a power law form. A debris flow always achieves a state of certain mobility and density that can be well described by the coupling of μ and D c,which imposes a constraint on the fluctuations of flow surges. The GSD also describes the changes in grain composition in that it is always satisfied during the course of debris flow developing. Numerical simulation using the GSD can well illustrate the variation of μ and D c from source soils to deposits.
基金Supported by the National Natural Science Foundation of China (No. 20076038).
文摘The size and the shape of non-reversal random-walking polymer chains near an impenetrable, non-interacting flat surface are investigated by means of Monte Carlo simulation on the simple cubic lattice. It wasfound that both size and shape are dependent on the normal-to-surface distance z0 of the first segment of chain. Wefind that the size and shape of chains, characterized by mean square radius of gyration <S2> and mean asphericityparameter <A> respectively, show similar dependence on distance z0. Both <S2> and <A> reach the maximum atz0 = 0, then decrease with the increase of z0 and soon reach the minimum values, afterwards they go up continuouslyand approach to the limit values of free chain. The similar dependence of <S2> and <A> on z0 can be explained by apositive correlation between A and S2. However, the dependence of the correlation coefficient CA,S2 on z0 is verycomplicated and deserves further study. The overall density probability of segments is also investigated. Resultsshow that segments near the surface are relatively less, and the symmetrical distribution disappears when the chainlocates near the surface.
文摘The phenomenon of phase transition in constraint satisfaction problems (CSPs) plays a crucial role in the field of artificial intelligence and computational complexity theory. In this paper, we propose a new random CSP called d-p-RB model, which is a generalization of RB model on domain size d and constraint tightness p. In this model, the variable domain size d?Ε [ nα, nny], and all constraints are uniformly divided into several groups with different constraint tightness p. It is proved by the second moment method that the d-p-RB model undergoes phase transition from a region where almost all instances are satisfiable to a region where almost all instances are unsatisfiable as the control parameter increases. Moreover, the threshold value at which the phase transition occurs is located exactly.
文摘It is a NP-hard problem to schedule a list of nonresumable jobs to the available intervals of an availability-constrained single machine to minimize the scheduling length. This paper transformed this scheduling problem into a variant of the variable-sized bin packing problem, put forward eight bin packing algorithms adapted from the classic one-dimensional bin packing problem and investigated their performances from both of the worst-case and the average-case scenarios. Analytical results show that the worst-case performance ratios of the algorithms are not less than 2. Experimental results for average cases show that the Best Fit and the Best Fit Decreasing algorithm outperform any others for independent and precedence-constrained jobs respectively.
