Georgia Institute Of TechnologyISYE 6644 Week 7 Homework - Spring 2021Due Mar 14 at 11:59pm Points 24 Questions 24 Available Mar 5 at 8am - Apr 30 at 11:59pm about 2 months Time Limit None Attempt History Attempt Time ScoreLATEST Attempt 1 436 minutes 24 out of 24 Score for this quiz: 24 out of 24 Submitted Mar 12 at 2:21am This attempt took 436 minutes. Question 1 1 / 1 pts(Lesson 5.15: T
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Week 7 Homework - Spring 2021
Due Mar 14 at 11:59pm Points 24 Questions 24
Available Mar 5 at 8am - Apr 30 at 11:59pm about 2 months Time Limit None
Attempt History
Attempt Time Score
LATEST Attempt 1 436 minutes 24 out of 24
Score for this quiz: 24 out of 24
Submitted Mar 12 at 2:21am
This attempt took 436 minutes.
Question 1 1 / 1 pts
(Lesson 5.15: Two-Channel Manufacturing Example.) Consider the
demo from class:
Module05-15 - Model 04-01-ElectronicAssembly-slow.doe
If you run the thing for a while, you’ll see that the rework Station gets
pretty clogged up every once in a while – probably because the service
times are EXPO(45) minutes. Let’s suppose that management has
noticed this as well and decides to upgrade that station so that the
service times are now EXPO(10). Go ahead and make this change
and comment on what you see.
! c. There are occasionally short lines, but long lines are very rare.
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(c).
Question 2 1 / 1 pts
(Lesson 5.15: Two-Channel Manufacturing Example.) To get you in the
mood for this problem, let’s recall the slightly different demo that
incorporates a logic-based equation in the Sealer Process module:
Module05-15 - Model 04-01-ElectronicAssembly-Logic-slow.doe
I’m not going to ask you to run this model, but I’d simply like to know the
value of the related logic expression,
( (1 == 1) * 10 ) + ( (1 == 0) * 5 )
! d. 10
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Since “1 == 1” is true and “1 == 0” is false, we have
( (1 == 1) * 10 ) + ( (1 == 0) * 5 ) = (1*10) + (0*5) = 10,
so that the answer is (d).
Question 3 1 / 1 pts
(Lesson 5.16: Fake Customers.) Let’s use fake customers to calculate
an exponential probability. In particular, modify the following demo from
class so that you can estimate the probability that an EXPO(2) random
variable (this is the Arena notation for an exponential RV with mean 2)
is > 2.
Module05-16 - Model 04-05 – NormalProb.doe
Hints on how to do the necessary modification:
Go to the Assign module and change the normal RV to the
exponential.
Optional: You might also want to change the name of the fake
customer’s attribute from “Normal Observation” to “Exponential
Observation” just to make things clearer.
Go to the Decide module and make the obvious change to the
condition.
Optional: You might also want to change the counter names in the
Record modules to something more obvious.
Let the run complete and then look at the output! Note that the
demo runs for 1 million samples, so the estimate ought to be very
good.
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! c. about 0.368
Solution: The answer is (c). In fact, when I ran my simulation,
367460 out of the 1 million fake customers satisfied the
inequality.
Of course, you can calculate the answer exactly (without using
simulation):
P(EXPO(2) > 2) = e-λx = e-(1/2)2 = 0.3679.
Question 4 1 / 1 pts
(Lesson 5.17: The Advanced Process Template.) TRUE or FALSE? You
can find individual Seize, Delay, and Release modules in this template.
! True
Question 5 1 / 1 pts
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(Lesson 5.17: The Advanced Process Template.) Grab the file
Module05-ReleaseHospitalRoomLater.doe
from the website. In this model, customers come in to the hospital, use
a Process module to Seize and Delay an operating room, and then get
Dispose’d. So how are the operating rooms Release’d? Well, any
good hospital room needs to be cleaned. So each time a customer is
about to be Dispose’d, we use a Separate module to clone a copy of
the customer; and this clone uses a Process block to Seize-DelayRelease a cleaning person. After the cleaning is done, we use an
additional Release module to free up the operating room. The program
runs for 24 simulated hours.
What I would like you to do is to run the same program, except replace
both of the Process modules with appropriate Seize and Delay modules
from the Advanced Process template (the only Release module you’ll
need is already there).
After the program runs for its 24 simulated hours, what is the
approximate utilization of the cleaning person?
! b. 21%
Solution: (b). You should get pretty much the same (and maybe
even exactly the same) utilization here as you would if you had
run the original program
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Question 6 1 / 1 pts
(Lesson 5.18: Resource Failures + Maintenance.) What do the entries
in the following screenshots do?
d. The resource Drill Press will fail after 10 customers use it, and will
remain down for Expo(30) minutes.
!
(d).
Question 7 1 / 1 pts
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(Lesson 5.19: The Blocks Template.) Where can you find some sort of
Seize?
! d. All of the above
(d).
Question 8 1 / 1 pts
(Lesson 5.19: The Blocks Template.) Where can you set the buffer size
of a certain queue?
! d. In a Queue block in the Blocks template
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(d).
Question 9 1 / 1 pts
(Lesson 5.20: The Joy of Sets.) Consider the file
Module05-22 - Model 05-01 - CallCenter.doe
from the website. Go to the Set spreadsheet in the Basic Process
template and figure out which resource sets the resource Molly belongs
to. Give the best answer.
! d. Product 1 and Product 3
(d).
Question 10 1 / 1 pts
(Lesson 5.20: The Joy of Sets.) TRUE or FALSE? It’s possible to
request servers in a set randomly, cyclically, or according to some
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priority characteristic (such as the order in which they are placed in the
set).
! True
Question 11 1 / 1 pts
(Lessons 5.21 and 5.22: Call Center Demo.) Again consider the file
Module05-22 - Model 05-01 - CallCenter.doe
We’ll do a little bit of analysis on this model. In order to do so,
Go to Run > Setup > Replication Parameters and change the
Replication Length to 550 hours. This will allow the simulation to run
long enough to yield meaningful results.
Then go to Run > Run Control > Batch Run. This will turn off the
animation and allow the simulation to run very quickly.
When I ran this simulation for 550 hours with the server schedules as
specified in the notes, I obtained a mean tech support customer waiting
time of 5.68 minutes. (Hopefully, you’ll be able to replicate that just by
hitting the Go button.)
Here’s what I’d like you to do:
Go to the Resource spreadsheet.
Change all of the 11 tech support resources (Charity, Noah,…,
Christie) to a Fixed Capacity of 1. In other words, take them all off of
their schedules and force the poor souls to work all 11 hours / day.
Re-run the simulation with everyone working full-time.
What is the approximate mean tech support customer waiting time
when we use our full-time crew?
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! c. 2.53 min. (pretty good improvement)
(c).
Question 12 1 / 1 pts
(Lesson 5.23: An Inventory Model.) Consider the demo model from
class,
Module05-23 - Model 05-04 - Inventory.doe
What would I do to change the lead time of orders from my supplier to
UNIF(0,1) days (which happens to be a little faster than the current lead
time)?
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! e. Either (b) or (c), since both are correct.
(e).
Question 13 1 / 1 pts
(Lesson 5.24: One Line vs. Two Lines?.) Consider the demo model
from class,
Module05-24 - OneLine-vs-TwoLines.doe
I’d like you to modify the demo in order to determine which of the
following is better:
(a) Customers join one line in front of three identical servers and then
go to whichever server is available first.
(b) Customers randomly choose which of three lines (in front of single
servers) to join.
This won’t take too much work.
Go to the Resource spreadsheet and change the fixed capacity of
Drill Press to 3
Add another resource Drill Press3 with capacity 1
Make the obvious additions to the bottom half of the Arena model
Press Go and watch the fireworks for a while.
So what’s your answer — (a) or (b)?
! (a)
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(a) easily beats (b) (shorter cycle times and queue).
Question 14 1 / 1 pts
Lesson 5.25: A Re-entrant Queue
BONUS: Consider the demo model from class, in which we observe
crazier and crazier behavior as time passes,
Module05-25 - ReentrantQueue.doe
In particular, the various queues build up and them calm down; but the
peaks tend to get bigger and bigger as time passes.
One of the issues is due to the fact that we have strange priorities on
the two servers depending on where the customer is in the model.
Those priorities are set in the Process modules, just to the right of the
Seize-Delay-Release sequence.
Question: What happens when you set the priorities to “Medium” in
each of the 5 process modules?
! c. Surprisingly, things pretty much calm down!
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The answer is (c). [Apparently, the goofy priorities in the original
set-up were messing things up!]
Question 15 1 / 1 pts
(Lesson 5.26: SMARTS Files and Rockwell Demos.) BONUS: Let’s look
at one of the Rockwell SMARTS demo models from class, in which the
arrival rate changes over the week (a different arrival rate each day),
Module05-26 - SMARTS - Arrivals Varying Rate via Expression.doe
Salient features of the model:
day_rate is a vector of length 7 defined in the Variable spreadsheet
in the Basic Process template. It keeps track of 7 daily customer
arrival rates.
The first Create module generates customers with constant
interarrival times 1/(day_rate(day)), which obviously depends on the
day of the week.
The second Create module generates fake customers once every
day to update the day of the week (1,2,…,7).
The constant interarrival times are relatively large compared to the
smaller service times given in the first Process module. So there’s
never really a line… VERY BORING!
Here’s what I want you to do:
Instead of constant interarrival times every day, let’s make the
interarrivals random.
To this end, augment the Time Between Arrivals Expression in the
first Create module to EXPO(1/(day_rate(day))), and tell me what
happens.
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! b. Occasional small line.
(b).
Question 16 1 / 1 pts
(Lesson 5.27: A Manufacturing System Demo.) I’d like you to play
around with the demo
Module05-27 - Model 07-01 - Basic Mfg Center.doe
What sequence of station visitations do Part Type 1 customers go
through?
! a. 1-> 2 -> 3 -> 4
(a).
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Question 17 1 / 1 pts
(Lesson 5.27: A Manufacturing System Demo (continued).) If you
wanted to change Part Type 1’s sequence of stations, what would you
do?
b. Use the Sequence spreadsheet in the Advanced Transfer template
!
(b).
Question 18 1 / 1 pts
Lesson 5-28: The ROUTE module is found in the Advanced Transfer
template and allows you to move entities from Station to Station.
! True
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Question 19 1 / 1 pts
Lesson 5-29: A Sequence must consist of unique visitation locations...
no repeat visits!
! False
Question 20 1 / 1 pts
Lesson 5-30: You could use the Advanced Set functionality to define a
"Set of Sequences".
! True
Question 21 1 / 1 pts
Lesson 5-30: The name of the automatically supplied ARENA attribute
that stores a particular entity's sequence is Entity.Sequence (what a
surprise)!
! True
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Question 22 1 / 1 pts
Lesson 5-31: Cell 3 actually had TWO servers -- an "old"/slow guy and
a "new"/fast guy.
! True
Question 23 1 / 1 pts
Lesson 5-32: You SEIZE-DELAY-RELEASE a conveyor.
! False
Question 24 1 / 1 pts
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Lesson 5-32: An ENTER module is usually paired with what other
module?
! LEAVE
Quiz Score: 24 out of 24
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