Chapt 6 Resources & Gates Intro/ steps in the process Distributions...What & Why Resource...

Chapt 6 Resources & Gates

• Intro/ steps in the process• Distributions...What & Why• Resource Block• Await Node• Free node• Alter node• Group block• Open Node• Close node• Examples

Quiz non attributional

– Object flow thru network_________– Node that is an entry point in to a system______– Data attached to an entity________– A symbol that can represent the passage of time____– Node that generates a histogram______ – Node that represents people or item waiting in line___

Activity AWAIT COLCT CREATE

Entity TERMINATE QUE

ATRB NNQ GOON

Quiznon attributional

• Hand draw tonight….Turn next week a printed version sing AweSim software, a single server operation of a 7-11 store using AweSim objects, customers arrive at the counter at a rate that is Exponentially distributed with a mean of 4.5 minutes, the duration of the service time is normally distributed with a mean of 3.2 minutes and a standard deviation of 0.6 minutes, end the simulation after 1000 customers. Collect data to be able to produce a histogram of how long customers are in the system.

Distributions

• Use statistical distribution to represent your data or when an approximation is required.

• Want to simulate arrival times of customers can either:– Collect data, use real data…must collect vast amounts– Collect representative sample of data, use distribution

that best represents the data for the population– Have little or no data and make rough approximations of

the expected population

Uniform Distribution

• Used to generate random numbers between a range.

Exponential Distributions

• Used to represent the arrival or service time time of random variables. Also used to represent time to failure.

Normal Distributions

• Use statistical distribution to represent your data or when an approximation is known. Commonly used for service times.

Triangular Distributions

• Used when only an approximation of the population is known. Used for service times.

Introduction

• Entities move thru the network…waits at ques…encounters activities that take time…

• Can also model networks where the entity requires a resource to perform an activity

• Entity picks up resources at an AWAIT Node before going on to an activity

• Resource block dictates the priorities of resources

• Gate Nodes start & stop entity flow

RESOURCE Block

• Block = entities do not flow thru, no in/ out

• Identifies: resource name/ label = RLBL, initial # of resource units available = CAP, order which to AWAIT & PREEMPT allocate resources

• Resource # 1, called ScrapeMetal, capacity of 1000, files 3 & 7 will be polled for entities waiting for ScrapeMetal

AWAIT Node • Used to store entities waiting for units of

resources or a GATE to open

• AWAIT Node called Needbooks, entity requires 2 units of the resource BOOKS, if available they are allocated to the entity & branches M=1, no limit for # of entity that can wait in file 1.

AWAIT Node

• AWAIT Node called Needbooks1, # of books required by entity is prescribed by the value of attribute (4), if available they are allocated to the entity & branches M=2, no limit for # of entity that can wait in file 1.

FREE Node

• FREE Node used to release units of resources when entity arrives at the node

• Node called Freeupbooks, 4 BOOKS are made available when entity arrives

Inspector considered as a resource Ex

• TVs in a production line get inspected, go to packing or need to be adjusted, inspector also does adjustment, can’t be used for insp when performing adjust

Flex Machining System Ex

• Under const

ALTER Node

• Used to change the capacity of a resource type by CC units, + = increased, - = Decrease

• Decrease resource BOOKS by 3

Group Block

• Provides a method of grouping resources so that any member of the group can be used to provide service to an entity

• 3 examples of Group resources of BOOKS, Pencils, Packs

L IDLE

FM PREFERRED ORDER

NEXT FREE

PREEMPT Node

• Similar to AWAIT but an entity can preempt one unit of a resource that has been allocated to another entity

• High priority to preempt 2 units of resource Books put remaining resource in attribute 2

Machine tool w/ breakdowns Ex

• Parts are sent to Drill, Drill machine breaks down, which stops the processing of parts except by hand. Drill is modeled as a resources & parts require one unit of Drill. An entity representing Drill status is modeled in a disjoint network, delayed by time to failure, after which the Drill status arrives to a PREEMPT node. PREEMPT stops drilling by Drill, the part is drilled by hand & it takes twice as long

Byhand

Parts are sent to Drill, Drill machine breaks down, which stops the processing of parts except by hand. Drill is modeled as a resources & parts require one unit of Drill. An entity representing Drill status is modeled in a disjoint network, delayed by time to failure, after which the Drill status arrives to a PREEMPT node. PREEMPT stops drilling by Drill, the part is drilled by hand & it takes twice as long

PREEMPT

GATE Block

• Provides a method of grouping resources so that any member of the group can be used to provide service to an entity

• Ex LABELEDGATE is open, file # 1

OPEN Node

• Used to open a gate with a gate label (GLBL) or gate code specified by an expression

• Ex Open gate, called “Exampleopengate” is used to open gate “gatetomtl”

CLOSED Node

• Used to close a gate with a gate label (GLBL) or gate code specified by an expression

• Ex Close Gate, closegate, closes gate called, closetofuel

Gates to Model Shifts Ex

• Model the activity of a process only in operation during the day shift. Entities arrive and routed to an AWAIT node that is associated with the gate called dayshift. In a disjoint network an entity is created that closed the gate after 8 hours and opens it 16 hours later

Model the activity of a process only in operation during the day shift. Entities arrive and routed to an AWAIT node that is associated with the gate called dayshift. In a disjoint network an entity is created that closed the gate after 8 hours and opens it 16 hours later

Open gate Close gate

Exercises

• 6-2 two types of customers 1) regular, uniform distributed btwn 15-20 min, 2) harder, expon distributed , mean = 20 min. 60% are regular customers, 40% harder. Customers arrive at a rate represented with a triangular distribution min = 10, max = 50, mode = 20. Find statistics that represent time in system, Use AWAIT/FREE

Customer in Customer Serviced Customer out

Exercises6-2 two types of customers 1) regular, uniform distributed btwn 15-20 min, 2) harder, expon distributed , mean = 20 min. 60% are regular customers, 40% harder. Customers arrive at a rate represented with a triangular distribution min = 10, max = 50, mode = 20. Find statistics that represent time in system, Use AWAIT/FREE

Exercises

• Person arrives at bank cant find parking drives around block comes back parks.

ExercisesDue Monday 10/29

• 6-9 Machine tool processes 2 diff parts. T1 arrival time is tri dis 20-30-50. Interarrival time of T2 tri dis 35-50-60. Processing time for T1 is exp, m=20, T2 uniform min 15- max 20. Processing includes inspection, 1% fail, return to que the rework time =90% of original. Find time in system of part & utilization of machine. Use create/ await/ a conditional split of activities/ free/ collect/ terminate.

Chapt 5 Basic Network Modeling

• Intro/ steps in the process• Single server queuing system• CREATE Node• TERMINATE Node• ASSIGN Node• GOON Node • COLCT Node• SELECT Node• EXAMPLES