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  • Articles  (144)
  • Computer Science  (128)
  • Information Science and Librarianship  (16)
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  • Articles  (144)
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    Publication Date: 2016-04-01
    Print ISSN: 0021-9991
    Electronic ISSN: 1090-2716
    Topics: Computer Science , Physics
    Published by Elsevier
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Distributed computing 2 (1987), S. 45-59 
    ISSN: 1432-0452
    Keywords: Database systems ; Concurrency ; Optimistic protocols ; Distributed algorithms ; Rollbacks ; Transactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Concurrency control algorithms have traditionally been based on locking and timestamp ordering mechanisms. Recently optimistic schemes have been proposed. In this paper a distributed, multi-version, optimistic concurrency control scheme is described which is particularly advantageous in a query-dominant environment. The drawbacks of the original optimistic concurrency control scheme, namely that inconsistent views may be seen by transactions (potentially causing unpredictable behavior) and that read-only transactions must be validated and may be rolled back, have been eliminated in the proposed algorithm. Read-only transactions execute in a completely asynchronous fashion and are therefore processed with very little overhead. Furthermore, the probability that read-write transactions are rolled back has been reduced by generalizing the validation algorithm. The effects of global transactions on local transaction processing are minimized. The algorithm is also free from dedlock and cascading rollback problems.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Multimedia systems 2 (1994), S. 218-227 
    ISSN: 1432-1882
    Keywords: Image coding ; Signal compression ; Wavelet transform ; Image transforms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The wavelet transform has become a cutting-edge technology in image compression research. This article explains what wavelets are and provides a practical, nuts-and-bolts tutorial on wavelet-based compression that will help readers to understand and experiment with this important new technology.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 52 (1991), S. 147-166 
    ISSN: 1436-4646
    Keywords: Data envelopment analysis ; sensitivity and robustness of optimal solutions ; nonlinear efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract The behavior of efficiency in the stochastic DEA model is examined here in terms of the influence curve approach which quantifies the influence of observed data on the empirical fit of the production frontier. Data influence is analyzed here through robustness. Two types of robustness and sensitivity issues are analyzed here in terms of (a) a new class of minimax measures, and (b) a set nonlinear efficiency measures and it is shown through empirical applications that in suitable cases these measures outperform the conventional ones.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of parallel programming 19 (1990), S. 185-211 
    ISSN: 1573-7640
    Keywords: Transactions ; Prolog databases ; optimistic concurrency control ; optimizations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The degree of concurrency allowed by a concurrency control scheme depends on the knowledge it has about the database and the transactions. This paper analyzes the syntactic information available in a Prolog database to improve concurrency. An optimistic concurrency control scheme is chosen since it is a natural choice for Prolog databases. The conflict criteria among transactions in a Prolog environment is translated into conditions on the query search tree. This aids in identifying concurrency related information from the depth-first search execution strategy. A spesented in stages such that progressively more information is considered to construct the read and the write sets (required to check conflicts) and better concurrency is achieved. An orthogonal contribution of the information analysis is a new query evaluation optimization. The price for better concurrency is paid in terms of increased storage and computation costs. The optimality of the algorithms with respect to the available information and derived concurrency is discussed qualitatively.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 1 (1986), S. 67-83 
    ISSN: 1572-9443
    Keywords: Assembly queue ; manufacturing ; approximations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we study a queueing model of assembly-like manufacturing operations. This study was motivated by an examination of a circuit pack testing procedure in an AT & T factory. However, the model may be representative of many manufacturing assembly operations. We assume that customers fromn classes arrive according to independent Poisson processes with the same arrival rate into a single-server queueing station where the service times are exponentially distributed. The service discipline requires that service be rendered simultaneously to a group of customers consisting of exactly one member from each class. The server is idle if there are not enough customers to form a group. There is a separate waiting area for customers belonging to the same class and the size of the waiting area is the same for all classes. Customers who arrive to find the waiting area for their class full, are lost. Performance measures of interest include blocking probability, throughput, mean queue length and mean sojourn time. Since the state space for this queueing system could be large, exact answers for even reasonable values of the parameters may not be easy to obtain. We have therefore focused on two approaches. First, we find upper and lower bounds for the mean sojourn time. From these bounds we obtain the asymptotic solutions as the arrival rate (waiting room, service rate) approaches zero (infinity). Second, for moderate values of these parameters we suggest an approximate solution method. We compare the results of our approximation against simulation results and report good correspondence.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 22 (1996), S. 121-127 
    ISSN: 1572-9443
    Keywords: Spatial requirements ; single server queues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we consider a MAP/G/1 queue in which each customer arrives with a service and a space requirement, which could be dependent. However, the space and service requirements of different customers are assumed to be independent. Each customer occupies its space requirement in a buffer until it has completely received its service, at which time, it relinquishes the space it occupied. We study and solve the problem of finding the steady-state distribution of the total space requirement of all customers present in the system. In the process of doing so, we also generalize the solution of the MAP/G/1 queue and find the time-average joint distribution of the queue-length, the state of the arrival process and the elapsed service time, conditioned on the server being busy. This problem has applications to the design of buffer requirements for a computer or communication system.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 11 (1992), S. 153-178 
    ISSN: 1572-9443
    Keywords: Cyclic server queue ; polling model ; limited service ; reservation scheme ; satellite communications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we examine a queueing problem motivated by the pipeline polling protocol in satellite communications. The model is an extension of the cyclic queueing system withM-limited service. In this service mechanism, each queue, after receiving service on cyclej, makes a reservation for its service requirement in cyclej + 1. The main contribution to queueing theory is that we propose an approximation for the queue length and sojourn-time distributions for this discipline. Most approximate studies on cyclic queues, which have been considered before, examine the means only. Our method is an iterative one, which we prove to be convergent by using stochastic dominance arguments. We examine the performance of our algorithm by comparing it to simulations and show that the results are very good.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 4 (1989), S. 249-261 
    ISSN: 1572-9443
    Keywords: Processor-sharing ; discrimination function ; gating mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we consider a single server queue in which arrivals occur according to a Poisson process and each customer's service time is exponentially distributed. The server works according to the gated process-sharing discipline. In this discipline, the server provides service to a batch of at mostm customers at a time. Once a batch of customers begins service, no other waiting customer can receive service until all members of the batch have completed their service. For this queue, we derive performance characteristics, such as waiting time distribution, queue length distribution etc. For this queue, it is possible to obtain the mean conditional response time for a customer whose service time is known. This conditional response time is a nonlinear function (as opposed to the linear case for the ordinary processor-sharing queue). A special case of the queue (wherem=∞) has an interesting and unusual solution. For this special case, the size of the batch for service is a Markov chain whose steady state distribution can be explicitly written down. Apart from the contribution to the theory of Markov chains and queues, the model may be applicable to scheduling of computer and communication systems.
    Type of Medium: Electronic Resource
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