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1

An unconditionally positive and global stability preserving NSFD scheme for an epidemic model with vaccination

Ding D., Ma Q., Ding X.

International Journal of Applied Mathematics and Computer Science

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2014

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Vol. 24, no. 3

635--646

EN

In this paper, a NonStandard Finite Difference (NSFD) scheme is constructed, which can be used to determine numerical solutions for an epidemic model with vaccination. Here the NSFD method is employed to derive a set of difference equations for the epidemic model with vaccination. We show that difference equations have the same dynamics as the original differential system, such as the positivity of the solutions and the stability of the equilibria, without being restricted by the time step. Our proof of global stability utilizes the method of Lyapunov functions. Numerical simulation illustrates the effectiveness of our results.

2

Numerical Simulations of Heat and Moisture Transport in Thermal Protective Clothing Under Flash Fire Conditions

Song G., Chitrphiromsri P., Ding D.

International Journal of Occupational Safety and Ergonomics

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2008

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Vol. 14, No. 1

89--106

EN

A numerical model of heat and moisture transport in thermal protective clothing during exposure to a flash fire was introduced. The model was developed with the assumption that textiles are treated as porous media. The numerical model predictions were compared with experimental data from different fabric systems and configurations. Additionally, with the introduction of a skin model, the parameters that affect the performance of thermal protective clothing were investigated.

3

Some Algorithms for Extension Computation of Nonmonotonic Rule Systems

Zhao X., Ding D.

Fundamenta Informaticae

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2001

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Vol. 48, nr 1

930-106

EN

In this paper, we will place our emphasis on the problem of existence of extensions and on finding more efficient algorithms for computing extensions of nonmonotonic rule systems. First, in order to dedicate further research into nonmonotonic rule systems a new characterization and some new results are given. This characterization and these results lead to new algorithms for computing extensions. Second, a class of nonmonotonic rule systems, called regular nonmonotonic rule systems, is developed. The existence of extensions and semi-monotonicity of regular nonmonotonic rule systems are proved. Third, we prove that each regular nonmonotonic rule system has at most 1.47n extensions, where n is the number of elements occurring in the system.

4

Complexity results for 2CNF default theories

Zhao X., Ding D.

Fundamenta Informaticae

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2001

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Vol. 45, nr 4

393-404

EN

This paper is concerned with the complexity of default reasoning with 2CNF default theories (D,W) in which W is a set of literals and D is a set of 2CNF defaults. It is proved that the problem whether a literal occurs in at least one extension can be solved in polynomial time. But the problem whether a literal appears in all extensions is proved to be co-NP-complete. The complexity of some subclasses of 2CNF default theories is also analyzed.