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[[abstract]]Effects of parasitic crossings (near-miss collisions of two counter-rotating beams at unwanted positions near the IP) are studied in terms of computer simulations for an asymmetric B-factory, APIARY-6.3d. Beams are separated horizontally at the first parasitic crossing points by about 7.6 times the horizontal rms size of the low energy beam (the larger in size of the two beams). Simulations, including both the beam collision at the IP and parasitic crossings, have been performed for different separation distances.
[[abstract]]The split k-layer (k >= 2) circular topological via minimization (k-CTVM) problem is reconsidered here. The problem is finding a topological routing of the n nets, using k available layers, such that the total number of vias is minimized. The optimal solution of this problem is solved in O(n2k+1) time. However, such an algorithm is inefficient even for n >= 8 and k >= 2. A heuristic algorithm with complexity of O(k n4) is presented. When the experimental results of this algorithm and that of an exhaustive algorithm are compared, the same number of optimal solutions is obtained from this heuristic algorithm for all permutations of 1) n = 8 with k = 2 or 3, and 2) n = 10 with k = 3. For other cases, the number of optimal solutions from this algorithm depends on the permutations been selected; and this number, in general, will...
[[abstract]]The average lock range (ALR) is proposed as an evaluation factor for measuring the strengths and weaknesses of locking-based concurrency control methods, for both structural and nonstructural locking. The methodology provides a simple and general way to analyze the performance of any locking method, and requires no queueing model. Based on the concept of the ALR, two popular locking protocols, the 2PL protocol and the tree protocol, are analyzed and a simulation is done to validate the correctness of the ALR model
[[abstract]]The consensus problem in a fully connected network is discussed with the assumption of link failure. A simple and efficient protocol, FLINK, is proposed. The complexity of information exchange required by the protocol is O(n2). The protocol uses the minimum number of rounds to achieve a consensus and can tolerate the maximum number of allowable faulty components.
[[abstract]]The goals of this paper are to revise previous replication strategies and propose a new hierarchy structure, client-agent-server architecture, to fit a mobile computing system that has more resource constraints than a conventional distributed database system has. This three-tire agent-based mobile computing system frees the limitations on time and whereabouts of computing. Moreover, a new replication strategy, three-copy replication that is based on optimistic replication strategy, is proposed to deal with the problems of mobility management and disconnection management in a mobile computing system. It allows mobile clients to read and update the database while they are disconnected from the network, if the mobile copy is available. In addition, the implementation issues of this new replication strategy are also provided.
[[abstract]]The schema descriptions of most database management systems (DBMSs) are designed for computer processing, and are not suitable for human understanding. Therefore an interface is required between a logical database designer and the schema definition component of a DBMS. For this purpose a logical database design tool has been designed for a DBMS with a two-level network data structure. The tool consists of a description mode and a translation mode. The description mode, based on the entity-relationship model, provides an interactive and friendly interface that allows a user to describe an enterprise view easily. The translation mode translates the descriptions into a two-level network database description which is an acceptable database schema for the Humming-Bird general purpose DBMS
[[abstract]]Traditionally, the Byzantine Agreement (BA) problem is solved in a fully connected network with processor failure only. Here, the BA problem is reexamined under the syndrome of malicious fault on both processor and link. The proposed protocol FGEN can solve the BA problem for the failure of processor/link. The authors also prove that the protocol requires the minimum number of rounds and can tolerate the maximum number of allowable faulty components.
[[abstract]]Traditionally, the Byzantine Agreement (BA) problem is studied either in a fully connected network or in a broadcast network. A generalized network model for BA is proposed in this paper. A fully-connected network or a broadcast network is a special case of the new network architecture. Under the new generalized network model, the BA problem is reexamined with the assumption of malicious faults on both processors and transmission medium (TM), as opposed to previous studies which consider malicious faults on processors only. The proposed algorithm uses the minimum number of message exchanges, and can tolerate the maximum number of allowable faulty components to make each healthy processor reach a common agreement for the cases of processor failures, TM failures, or processor/TM failures. The results can also be used to solve...
[[abstract]]Traditionally, the problems of Byzantine agreement, consensus, and interactive consistency are studied in a fully connected network with processors in malicious failure only. Such problems are reexamined with the assumption of malicious faults on both processors and links. The proposed protocols use the minimum number of message exchanges and can tolerate the maximum number of allowable faulty components to make each fault-free processor reach a common agreement for the cases of processor failure, link failure, or processor and link failure.
[[abstract]]A number of researches on real-time databases have focused on systems where the semantics of transaction time constraints include only deadlines or values that are constant during a transaction's life time. For some real-time applications, the values of transaction may change dynamically with time. Under such circumstances, existing real-time scheduling algorithms may not be applicable. A new real-time scheduling algorithm that can efficiently schedule transactions with time-variant values is proposed. By exploiting the estimated execution time of transactions to estimate the expected values of transactions at completion time, the proposed algorithm can generate a better priority ordering of transactions than the existing algorithms. Moreover, a concurrency control protocol based on conditional-restart is also proposed to r...
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