The determination and indetermination of service times in manufacturing systems
The notion of service times is of such fundamental importance in the analysis of queues that it has long been taken for granted. Intuitively, it is used to represent the time interval that a server is capable of completing a dispatched job. However, actua...
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| Main Authors: | , |
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| Other Authors: | |
| Format: | Article |
| Language: | English |
| Published: |
2011
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| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/79917 http://hdl.handle.net/10220/7207 |
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| Summary: | The notion of service times is of such fundamental importance
in the analysis of queues that it has long been taken for
granted. Intuitively, it is used to represent the time interval that a
server is capable of completing a dispatched job. However, actual
measurements of service times under simple queues in production
lines have encountered practical difficulties, in spite of its seemingly
deterministic nature.
Previous studies have introduced concepts of effective process
times to quantify service times. Besides notions of theoretical processing
times, raw process times and queueing times, among others,
are commonly used in various applications. Their existence causes
confusion in the determination of service times and clarification of
such terminologies is needed.
A simple model is examined to quantify the various concepts
and establish their interrelationships. This paper brings out new
properties of effective process times with a dynamic dependence
on utilization. Discrete event simulations are conducted to verify
these properties and explain the phenomenon of indetermination
of service times. Both theoretical prediction and simulation results
show that unless the system is fully loaded, service time and effective
process time are not equivalent and it cannot be measured
directly from observations of effective process times. |
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