DCT Analysis

Concepts:

Ship Container

... ...

Sea-Transpt

...

Truck

...

Bringingunload

Fetchingload

Jobcheck

0..1

0..1

1..1

1..1

0..*

0..*

0..* 0..*

UML-like class model of essential classesand actions.

Conceptual model:

keeper

crane

Simplest model: connected queues.More advanced models differ between 3 classesof trucks and various actions of crane.

keeper crane

Essence: 2 connected queues.(only 8 exceptions out of 500)

Most important parameters:k (keeper occupation rate)c (crane occupation rate)

Assume M/D/1 queues (exp arrival, const processing)if k ≥c, then crane queue empty.If k < c, then average queue length keeper: C/(1-k)average queue length crane+keeper: C/(1-c)(approximately for some constant C)

If e.g. k = 0.9 and c = 0.91,then keeper queue 10C and crane queue C.Greatest capacity problem with crane, though!c.f. Arena model DCT.doe in "examples" directory.

Problem: large queues; keeper queue largest.

Causes: keeper occupation rate too high, also crane capacity?

Crane queue waiting time 35% of keeper waiting time,so crane capacity is an issue!

Solutions: increase keeper productivity.Investigate crane occupation rate.Increase crane productivity also.

Short-term temporary solution: increase working hours.Cost: extra payment to workers, which is manageable("business is booming").Benefits: less dissatisfaction of customers.

Longer term solution for keeper problem: use IT!

Crane solutions (in any combination):- faster crane- double queue- improve container storage

Assignments

• 4-5 assignments throughout the course

• Bonus for exam: max. 2 points

• Bonuses awarded for overall qualityand nice parts (e.g. concepts, problem analysis and suggestions).

• This assignment:score ≥ 8: full bonus (.4)OK(7): small bonus (.2)

Impression

• Much enthousiasm and hard work.

• Some reports were very good (talent or experience). Need course?

• Others need not despair.Hopefully course will help you.