In order to solve the problem that the query efficiency of distributed database decreases with the increase of data scale, the Greenplum distributed database was taken as the research object, and a cost-based optimal query plan generation scheme was proposed from the perspective of optimizing the query path. Firstly, an effective cost model was designed to estimate the query cost. The parallel maximum and minimum ant colony algorithm was then used to search the join order with the minimum query cost, i.e. the optimal join order. Finally, the optimal query plan was obtained based on the Greenplum database's default optimal choice for different operations in the query plan. Multiple experiments were carried out on the self-generated data set and Transaction Processing Performance Council Benchmark H (TPC-H) standard data set by using the proposed scheme. The experimental results show that the proposed optimization scheme can effectively search out the optimal solution and obtain the optimal query plan, so as to improve the query efficiency of Greenplum database.

The numerical simulation of pollution dispersion within complex river course and its visualization on Geographic Information System (GIS) are very important to surface water Environmental Impact Assessment (EIA). But there still remain many difficulties and problems, such as grid generation, numerical simulation model of pollution dispersion and the visualization of result. To resolve these problems of area river pollution calculation and GIS-based visualization for point source side discharge situation, the ways of surface water EIA visualization based on Cartesian cut cell method were presented. The Cartesian cut cell method was applied to generate grid, by using cut cell intersection point chasing algorithm and choosing approach of background Cartesian grid in river course boundary, the Cartesian grids of complex river course were achieved. A self-adaptive grids refinement algorithm with steady state pollution decay model was proposed. Based on unstructured Cartesian grids, a point source river water pollution simulation model of side discharge was provided and an area filling algorithm was developed to achieve the visualization of EIA result. Through the visualization and analysis of a river pollution EIA example, the practicability and efficiency of the proposed methods were confirmed.

Focusing on security surveillance system, an approach about how to code different recorded object with different tactic and different precision was deduced. This paper used high precision to code the important object in the suspicious scene and, and used relatively low precision to code the other moving object. For the background scene, we only recorded one or several key frames about the background changing. Meanwhile, we deduced a fast algorithm to detect and track the suspicious motional scene which needed to be recorded and, omit the recorded frames about the quiescent scheme. Experimental results show that much storage resource could be saved and the rate assignment could be more reasonable during the coding course.