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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Telecommunication systems 2 (1993), S. 225-238 
    ISSN: 1572-9451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract This paper develops and analyzes some statistical sampling methods suitable in a class of telecommunications applications including network cost calculations. The main objective is to obtain the smallest possible sample from a population in such a way that a prespecified desired level of accuracy of the estimated cost is achieved. The cost is assumed to be a function of a number of variables such as CCS and Message. Principal component analysis is used first to reduce the dimensionality of original variables. On the basis of the first few principal components, a graphical analysis is performed to determine the number of clusters, and then cluster analysis is employed to decompose the population into nine nearly homogeneous groups. We have also studied the performance of two sampling designs. Compared to the simple random sampling without any preliminary analysis, the stratified random sampling method with the proposed preliminary analysis provided a considerable reduction in sample size. In a typical application that we tested, the sample sizes required to guarantee the specified accuracy were 1 692 and 359 for simple random sampling and the proposed stratified random sampling, respectively.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology letters 19 (1997), S. 195-198 
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Accumulation of nitrite occurred during the aerobic phase of a sequencing batch reactor (SBR) operating to remove nitrogen from synthetic waste water. Although present, heterotrophic nitrifiers were not involved in the nitrification of the SBR. The activity of autotrophic nitrite oxidizers was reduced in the SBR where free ammonia was the main inhibitor for the nitrite oxidation. Nitrite build-up in the SBR was reduced when the aerobic phase was extended. All the ammonia could be oxidized when the aerobic phase was longer than four hours. The accumulated nitrite and nitrate were removed completely in the post-anoxic phase.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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