Page 223 - ExtendSim User Guide
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Processing 197
Interrupting processing
unnecessarily difficult to model the correct reliability behavior of this bicycle with three sepa- rate Shutdown blocks.
☞ For more detail, click the “Help” button in the lower left of the Shutdown block’s dialog.
Random Shutdown model
While the Scheduled Shutdown model on page 195 used a Create block to schedule when an Activity would be down, the Random Shutdown model uses the Shutdown block to halt pro- cessing on a random basis for a random amount of time. It does this by connecting the Shut- down block to an Activity block’s SD input.
Random Shutdown model
In this model the dialog of the Shutdown block is set to:
• Sendavaluetosignalshutdown
• Output a Down value: 1 and an Up value: 0
• Use an Exponential distribution with a Mean: 9 for the Set time between failures (TBF) parameter
• UseaTriangulardistributionwiththesettingsMinimum:1,Maximum:3,andMostlylikely: 2 for the Set time to repair (TTR) parameter.
With these settings both the TBF and TTR are random. A true signal (a value of 1) from the Shutdown block will cause the Activity block to shut down the entire block, halting all items currently in processing and blocking any new items from entering. It is only when the signal switches from true to false (a value of 0) that the block will resume processing. In this case, the Activity will remain down for approximately 2 hours before coming back online.
Model-related shutdown
The Scheduled Shutdown and Random Shutdown examples presented earlier showed how to shut down a process in isolation from other events in the model. You can also shut down activ- ities based on model factors such as the length of a waiting line or whether another activity is in process.
Discrete Event

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