ERRORS OF CALCULATIONS IN M/M/1/FIFO/N/F MODEL WITH LIMITED DURATION OF SHIFT

摘要

The popular models developed under of queueing theory describe how systems function within an infinitely long time interval. Yet, a real work is executed within the limited time intervals of work-shifts. The study was performed on the basis of one example involving excavations made by one excavator and the transportation of soils excavated using dumps tracks driving within "a closed circle". An Numerical Queueing Model (NQM; Polish abbreviation nmk) was developed, and, on its basis, it was found that the discrepancies among the results obtained were significant when the start and end conditions of work-shifts were omitted/disregarded. For example, relative errors referring to the mean number of units in a queue could amount to several dozen percentage points. In addition, the variations in those discrepancies were analyzed from the point of view of the magnitude of work-shift time intervals.