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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 14 (1993), S. 215-237 
    ISSN: 1572-9443
    Keywords: Asymptotics ; head of the line processor sharing ; loss probability ; many queues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper the steady-state behavior of many symmetric queues, under the head of the line processor-sharing discipline, is investigated. The arrival process to each of n queues is Poisson, with rateλA, and each queue hasr waiting spaces. A job arriving at a full queue is lost. The queues are served by a single exponential server, which has a mean rateμn, and splits its capacity equally amongst the jobs at the head of each nonempty queue. The normal traffic casep=λ/μ〈 1 is considered, and it is assumed thatn≫1 andr= 0(1). A 2-term asymptotic approximation to the loss probabilityL is derived, and it is found thatL = 0(n −r ), for fixedp. If6=(1−p)/p≪ 1, then the approximation is valid if nδ2≫ 1 and (r+ 1)2≪nδ, and in this caseL ∼r!/(nδ)r. Numerical values ofL are obtained forr = 1,2,3,4 and 5,n = 1000,500 and 200, and various values ofp〈 1. Very small loss probabilities may be obtained with appropriate values of these parameters.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 7 (1990), S. 325-336 
    ISSN: 1572-9443
    Keywords: Birth-death queueing systems ; sojourn and waiting times ; state-dependent service ; two-server queue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A birth-death queueing system with two identical servers, first-come first-served discipline, and Poisson arrivals is considered. Only one of the servers is active when the number of customers in the system does not exceed a prescribed threshold, whereas both are active above the threshold. The problem of determining the equilibrium density of the waiting time is formulated. A generating function is given for the Laplace transform of the density of the waiting time, and it is pointed out that it leads to an explicit expression for this quantity. Explicit expressions are obtained for the first and second moments of the waiting and sojourn times, and they are compared with the corresponding quantities for a single-server system with the same state-dependent mean service rates.
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  • 3
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    Electronic Resource
    Springer
    Queueing systems 8 (1991), S. 165-182 
    ISSN: 1572-9443
    Keywords: Asymptotics ; heavy traffic ; Jackson network ; overtaking ; sojourn time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider a Jackson network consisting of three first-in-first-out (FIFO)M/M/1 queues. When customers leave the first queue they can be routed to either the second or third queue. Thus, a customer that traverses the network by going from the first to the second to the third queue, can be overtaken by another customer that is routed from the first queue directly to the third. We study the distribution of the sojourn time of a customer through the three node network, in the heavy traffic limit. A three term heavy traffic asymptotic approximation to the sojourn time density is derived. The leading term shows that the nodes decouple in the heavy traffic limit. The next two terms, however, do show the dependence of the sojourn times at the individual nodes and give quantitative measures of the effects of overtaking.
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  • 4
    Electronic Resource
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    Springer
    Queueing systems 4 (1989), S. 213-235 
    ISSN: 1572-9443
    Keywords: Birth-death queueing systems ; single-server queue ; sojourn and waiting times ; state-dependent service
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A birth-death queueing system with asingle server, first-come first-served discipline, Poisson arrivals and state-dependent mean service rate is considered. The problem of determining the equilibrium densities of the sojourn and waiting times is formulated, in general. The particular case in which the mean service rate has one of two values, depending on whether or not the number of customers in the system exceeds a prescribed threshold, is then investigated. A generating function is derived for the Laplace transforms of the densities of the sojourn and waiting times, leading to explicit expressions for these quantities. Explicit expressions for the second moments of the sojourn and waiting times are also obtained.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 4 (1989), S. 237-248 
    ISSN: 1572-9443
    Keywords: Birth-death queueing systems ; heavy-traffic approximation ; single server queue ; sojourn and waiting times ; state-dependent service
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A birth-death queueing system with asingle server, first-come first-served discipline, Poisson arrivals and mean service rate which depends linearly on the number of customers in the system, is considered. Explicit expressions are derived for the equilibrium densities of the sojourn and waiting times. Simple approximations to the densities, including the first order correction terms, are obtained in a heavy-traffic situation.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 9 (1991), S. 191-213 
    ISSN: 1572-9443
    Keywords: Asymptotics ; data networks ; discriminatory processor sharing ; heavy traffic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper the steady-state behavior of a closed queueing network with multiple classes and large populations is investigated. One of the two nodes of the network simply introduces random delays and the discipline in the other node is discriminatory processor sharing. The network is not product-form, so not even the steady-state behavior is known. We assume that the usage is moderately heavy, and obtain two-term asymptotic approximations to the mean number of jobs, and the mean sojourn time, of each class of jobs in the processor node. We also obtain the leading term in the asymptotic approximation to the joint distribution of the number of jobs in the processor node, which is a zero-mean multivariate Gaussian distribution around a line through the origin.
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  • 7
    Electronic Resource
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    Springer
    The European physical journal 276 (1976), S. 167-177 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A non-relativistic perturbation method of Brueckner-Goldstone type is used to calculate the hyperfine interactions in the lowest2 S and2 P states of the Li-like systems, Li, Be+, B2+, C3+, N4+, O5+ and F6+. The effect of the polarization of the closed shell is treated to all orders of perturbation, while the correlation effect is calculated in the lowest order, i.e. in the third order of the perturbation expansion. Experimental data are at present available only for Li, Be+ and F6+, and the agreement with the calculated values is in these cases very good, usually within the experimental uncertainties. This implies that the predictions made in the remaining cases should be quite reliable, which may simplify the experimental determination of these quantities. Theoretical values are also given for the quadrupole interaction, which can be used to determine the nuclear quadrupole moments, when accurate experimental information becomes available.
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  • 8
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    Springer
    The European physical journal 276 (1976), S. 179-185 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Theoretical fine-structure intervals forp andd states and the iso-electronic 4d sequence of Na are calculated using many-body theory. Higher-order contributions to the first-order Hartree-Fock value are expressed by means of a Rayleigh-Schrödinger perturbative expansion. These contributions can be divided into polarization and correlation effects. The former effect, which is described as single excitations, is included to all orders. The latter effect is not evaluated in this calculation. Comparison with experiment shows good agreement. The inversion of the fine structure interval in thed states is reproduced, and in most cases reasonable quantitative agreement with experiments is obtained.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 46 (1996), S. 269-269 
    ISSN: 1573-0867
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
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    Springer
    Nutrient cycling in agroecosystems 45 (1995), S. 117-122 
    ISSN: 1573-0867
    Keywords: growth curve ; response surface ; two variables ; Mitscherlich curve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We present a Mitscherlich-related response surface for two variables. The curve for one of the variables, with the other fixed is similar to a Mitscherlich curve, but the curvature changes as the other variable changes. This surface is useful for fitting growth and other responses to two nutrient treatments.
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