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SOLUTIONS MANUAL for Stochastic Modeling: Analysis and ...

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112 CHAPTER 8. QUEUEING PROCESSES<br />

(d) We now have a network of 3 queues, with queue 3 being the rework station <strong>for</strong><br />

station 1.<br />

R =<br />

⎛<br />

⎜<br />

⎝<br />

0 0.9 0.1<br />

0 0 0<br />

0 0.5 0<br />

λ (1) =20<br />

λ (2) =0.9 λ (1) +0.5λ (3)<br />

λ (3) =0.1 λ (1)<br />

There<strong>for</strong>e,<br />

λ (1) =20<br />

λ (2) =18+1=19<br />

λ (3) =2<br />

For station 1 nothing changes. For station 2<br />

⎞<br />

⎟<br />

⎠<br />

ρ 2 = 19/30 ≈ 0.63<br />

c = 6<br />

(<br />

l (2) = λ (2)<br />

ρ 2 2<br />

λ (2) (1 − ρ 2 ) + 1 )<br />

µ (2)<br />

= 19/11 ≈ 1.7 jobs<br />

(e) This change has no impact on the results from part (d), but would change the<br />

per<strong>for</strong>mance of the rework stations.<br />

28. Model as a Jackson network of infinite-server queues, with a queue corresponding to<br />

each type of transaction.<br />

transaction i a 0j µ (j) per hour<br />

log on 1 1000 or 1500 20<br />

fetch 2 0 20<br />

read 3 0 5<br />

log off 4 0 100<br />

⎛<br />

R = ⎜<br />

⎝<br />

0 0.79 0.01 0.2<br />

0 0.17 0.63 0.2<br />

0 0.16 0.4 0.44<br />

0 0 0 0<br />

⎞<br />

⎟<br />

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