Page 214 - ExtendSim User Guide
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188 Processing
Bringing an activity on-line
the Create (Item library) or Lookup Table (Value library) block connected to and controlling a Gate block (Item library), by using a Create block to schedule the capacity of an Activity, or by using a Shift block to control an Activity. As seen below, the Scheduling Activities 1 model uses a Gate block and the Scheduling Activities 2 model schedules an Activity’s capacity. Shift blocks are discussed in “The Shift block” on page 232.
☞ So that you can compare both the Scheduling Activities 1 and Scheduling Activities 2 models, they have the same random seed, as seen in their Run > Simulation Setup > Random Number tabs.
Scheduling Activities 1 model
The following example shows how to schedule the availability of a portion of an operation using a Gate block. The Scheduling Activities 1 model represents a diner that opens at 10 AM and closes eight hours later. Customers arrive exponentially throughout the day, with most cus- tomers arriving during the lunch period, which is from 11 AM until 2 PM (from hour 1 to hour 4). There is 1 dining section that can service 5 people at a time throughout the day. A second dining section that can also service 5 people at a time is available only for the lunch shift.
Scheduling Activities 1 model
The scheduling of random customer arrivals is accomplished by entering values in a Lookup Table block (Value library), set to Lookup the: time. The output of the Lookup Table block is connected to the mean input of a Create block, which generates customers exponentially. As seen in the table to the right, the Lookup Table outputs a smaller value from time 1 to time 4. The output represents the average time between arrivals, so arrivals will occur more frequently from time 1 to time 4.
Customer arrivals
Opening the second dining section is accomplished by connecting a Create block to a Gate block, allowing customers access only during certain hours.
The Gate block is set to set to Mode: conditional gating with values, so that it only allows items through when its demand connector is activated by a value. This is accomplished by con- necting a value connector, such as the one on the Create block when it is in Create values by schedule mode, to the demand connector. As long as the value connector is true (outputs 1), the Gate stays open; when the value is 0, for false, it closes. Running the model with animation on shows that, even though the queue length is increasing, the Gate shuts down after three hours.
Discrete Event

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