The object occlusion is one serious issue in object tracking, especially when objects merge or split. The tracker may fail if it has no adaptability to such variations. In this paper, we present an improved solution of the appearance-based tracking for occlusion handling. The proposed method first recognizes the motion situations (merging and splitting of the moving objects), and then applies different template finding approach on each motion to get an association between detected blobs and targets. By this way, the accuracy of the data association can be improved when object occlusion occurs. Experiments were conducted to compare our results with those by other popular tracking algorithms. The proposed method is found robust for short time complete occlusion and partial occlusion.

Thresholding is the most commonly used technique in image segmentation. We first propose an efficient sequential algorithm to improve the relative entropy-based thresholding technique. This algorithm combines the concepts of the relative entropy with that of the local entropy and also includes the quadtree hierarchical structure in it. Second, we derive a constant time parallel algorithm to solve this problem on the reconfigurable array of processors with wider bus networks (RAPWBN). The system bus bandwidth determines the capacity of data communication between processors. According to the results as shown by Li and Maresca (1989) and by Maresca and Li (1989), we know that the silicon area used by the switching control mechanism is far less than that used by the processor. Instead of increasing the number of processors, we extend the number of buses to increase the power of a parallel processing system. Such a strategy of utilizing the reconfigurable array of processors with wider bus networks not only has the advantage of saving silicon area but also increases the system power enormously. So, we use the RAPWBN to solve the entropy-based thresholding problem.

Clustering techniques are usually used in pattern recognition, image segmentation and object detection. For N patterns and k centers each with M features, in this paper, we first design an O(kM) time optimal parallel algorithm for one pass process of clustering with the k-means method on a linear array of processors with a wider bus network using N/sup 1+1/c/ processors with one bus network, where c is any constant and c/spl ges/1. Then, based on the proposed algorithm, two O(k) and O(1) time optimal parallel clustering algorithms are also derived using MN/sup 1+1/c/ and kMN/sup 1+1/c/ processors with M row and MN row bus networks, respectively. These results improve the best known bounds and achieve cost optimal in their time and processor complexities.

Based on a geometric method, this paper presents an efficient and authenticated cryptoscheme for establishing secure group-oriented data communications in Internet environments. We assume that the Internet environments consist of many hosts, and each host has many users attached to it. The secure group-oriented communication scheme proposed in this paper incorporates the public-key distribution and the trigonometry concepts as the basic theory. Since this scheme does not need any trusted key distribution center to distribute the common secret session key between two parties and can reduce the computation time needed for securely sending messages to a group of receivers by using multiplication operations instead of modular exponentiation, it is quite suitable to be used in Internet environments so that the key distribution is convenient, time-saving and reparable. Furthermore, an authentication protocol is also proposed. Such a protocol can not only identify both the sender and the receiver of a group correctly, but can also make sure the transmitted message has reached its destination safely.

The parallel computation model upon which the proposed algorithms are based is the hyper-bus broadcast network. The hyper-bus broadcast network consists of processors which are connected by global buses only. Based on such an improved architecture, we first design two O(1) time basic operations for finding the maximum and minimum of N numbers each of size O(log N)-bit and computing the matrix multiplication operation of two N/spl times/N matrices, respectively. Then, based on these two basic operations, three of the most important instances in the algebraic path problem, the connectivity problem, and several related problems are all solved in O(log N) time. These include the all-pair shortest paths, the minimum-weight spanning tree, the transitive closure, the connected component, the biconnected component, the articulation point, and the bridge problems, either in an undirected or a directed graph, respectively.