In this paper, we develop several high-order finite difference schemes to simulate ground water flow in heterogeneous porous media. Our main purpose is to demonstrate that the high-order method can be used to resolve the fine scales efficiently for flow in heterogeneous porous media. The effectiveness of this approach is illustrated by two examples and detailed comparison with the classic second-order method and homogenization technique.

The static analysis of secure information flow has been studied for many years. The existing methods tend to be overly conservative or to be overly attention to location information leak. This paper uses data flow analysis to deal with secure information flow. Two variables of dynamic update security levels were introduced. The program is secure without any variable of downgrade security level at exit of a program. The analysis can deal with more secure programs. The soundness of the analysis is proved.

The  static  analysis  of  secure  information  flow  has  been  studied  for  many  years.  The  existing methods tend to be overly conservative or to be overly attention to location information leak. This paper uses data  flow  analysis  to  deal  with  secure  information  flow.  Two  variables  of  dynamic  update  security  levels were introduced. The program is secure without any variable of downgrade security level at exit of a program. The analysis can deal with more secure programs. The soundness of the analysis is proved.

Distributed database system technology is one of the major developments in information technology area. It will continue to have a very significant impact on data processing in the upcoming years because distributed database systems have many potential advantages over centralized systems for geographically distributed organizations. The continuing interest in distributed database systems in the research community and the marketplace and the introduction of many commercial products indicate that distributed database systems will play a more important role in data processing and eventually will replace centralized systems as the major database technology in the future. The availability of high speed communication networks and, especially, the phenomenal popularity of the Internet and the intranets will undoubtedly speed up the transition process. Some challenging problems must be solved before the full potential benefits of distributed database technology can be realized. Among them is query processing (including query optimization), one of the most important issues in distributed database system design. The query optimization problem in large-scale distributed databases is NP-hard in nature and difficult to solve. In this study, the query optimization problem is reduced to a join ordering problem similar to a variant of traveling salesman problem. We explored several heuristics and a genetic algorithm for solving the join ordering problem. Some computational experiments on these algorithms were conducted and solution qualities compared. The computation experiments show that heuristics and genetic algorithms are viable methods for solving query optimization problem in large scale distributed database systems.

This paper investigates the method for controlling the uncertain Liu chaotic system with known parameters k and h via adaptive backstepping control. With the method, parameters identification and control can be achieved simultaneously and quickly with only one controller within finite steps based on Lyapunov stabilization theorem. Numerical stimulations are provided to show the effectiveness and feasibility of this method.

In this paper, the implementation of Berlekamp-Massey algorithm to find the linear complexity for any given sequences is introduced. A new two methods for attacking stream cipher are proposed. The first one is attacking with known combining part using hypothesis test to find the data significant level compromising the appropriate one, while the second method for attacking unknown combining part by finding the behavior (truth table) of the combining part through two algorithms. Once the truth table of the combining part is found, the initial values of the registers can be found in the driving part or drawing the combining part functions using Carnough map or Mcloski algorithm for reverse engineering and reconstruct the combining part.