AN ANALYSIS OF THE APPLICABILITY OF FUZZY CLUSTERING IN ESTABLISHING AN INDEX FOR THE EVALUATION OF METEOROLOGICAL SERVICE SATISFACTION

An evaluation index is a prerequisite for the scientific evaluation of a public meteorological service.This paper aims to explore a technical method for determining and screening evaluation indicators.Based on public satisfaction survey data obtained in Wafangdian,China in 2010,this study investigates the suitability of fuzzy clustering analysis method in establishing an evaluation index.Through quantitative analysis of multilayer fuzzy clustering of various evaluation indicators,correlation analysis indicates that if the results of clustering were identical for two evaluation indicators in the same sub-evaluation layer,then one indicator could be removed,or the two indicators merged.For evaluation indicators in different sub-evaluation layers,although clustering reveals attribute correlations,these indicators may not be substituted for one another.Analysis of the applicability of the fuzzy clustering method shows that it plays a certain role in the establishment and correction of an evaluation index.

Efficient Parallel Algorithms for Some Graph Theory Problems

In this paper,a sequential algorithm computing the all vertex pair distance matrix D and the path matrix Pis given.On a PRAM EREW model with p,1≤p≤n^2,processors,a parallel version of the sequential algorithm is shown.This method can also be used to get a parallel algorithm to compute transitive closure arrayof an undirected graph.The time complexify of the parallel algorithm is O(n^3/p).If D,P andare known,it is shown that the problems to find all connected components, to compute the diameter of an undirected graph,to determine the center of a directed graph and to search for a directed cycle with the minimum(maximum)length in a directed graph can all be solved in O(n^2/p^+ logp)time.

Discrete Morse Theory on Join of Digraphs

For given two digraphs,we can construct a larger digraph through join.The two digraphs that make up the join are called the factors of the join.In this paper,we give a necessary and sufficient condition that the function on the join determined by the discrete Morse functions on factors is a discrete Morse function.Moreover,we further prove the discrete Morse theory on join when the factors satisfy certain conditions.

Hydrodynamics and modeling of a ventilated supercavitating body in transition phase

Compared to other underwater vehicles, supercavitating vehicles can attain a high speed because they eliminate drag by creating a large cavity, thus establishing the so-called ＂supercavitating condition.＂ Such a cavity is difficult to develop under normal conditions, hence, ventilation is used to attain the supercavitating condition in the initial phase of flight. In this paper, we focus on the hydrodynamic characteristics of a ventilated supercavitating vehicle. First, dynamic modeling of the supercavitating vehicle is performed to calculate the hydrodynamic force/moment acting on the vehicle for a given size of cavity. We then define the relationship between the ventilation rate and the cavitation number based on an air entrainment model of the ventilated cavity. Numerical simulations were performed to analyze the physical feasibility and characteristics of the modeling. The results show that the cavity length/radius increases with the ventilation rate, proving that ventilation can be used to attain the supercavitating condition.