Exam 3 Flashcards
Why do Queues form?
Queues form when the Capacity rate is smaller than the Demand Rate
Queues form from?
Variability (Customer Arrival and Service Time)
What is the implication of PK Formula?
Time in queue increases in Utilization Rate and Varivility of both arrival time and service time
#
/
OOO--->#--->OO-- #
\ #
How many phases? How many servers in second phase?2 phases
3 servers in phase 2
Service happens only when
Capacity and demand are available at the same time
What is the benefit of serving the Shortest processing time first?
Reduces the average waiting time
Which type of queue would use a first come first serve approach?
Single Queue
___/____/____
Distribution of time between arrivals (M,D)
Distribution of service time (M,D)
Number of servers (1,c)
Difference between M and D
M= Random, exponentially distributed D= Deterministic
Difference between 1 and C
1= Single Server c= Multiple servers
The key feature of of Erlang Loss Model
Customer leaves if system is full, there is no queue
Where can Erlang Loss model be applied
DVD rental- there is no wait for the movie if the movie is not there
Throughput Rate assuming no demand loss
Throughput rate= minimum( Demand rate, Capacity Rate)
Throughput rate assuming demand loss:
Throughput Rate< minimum (demand rate, capacity rate)
In a general waiting system, how do you reduce throughput loss?
Create buffer to keep customers
Decrease waiting time to avoid customer balking
What is customer balking
customers leaving after they join the queue due to long waiting time
Who determines tolerance limits?
Customers, Designers
Who determines control limits?
Producers, Quality Controllers
What happens beyond tolerance limits?
Defects
What happens beyond Control Limits?
Actions need to be taken
When control limits are violated but tolerance limits are satisfied….
Need to check system
Pull System
The production dynamic is initiated from demand part (make to order). Information flows from downstream to upstream. Baked Cookies
Push System
The upstream station or suppliers initiate the production schedule (make to stock), information flows from upstream to downstream. MacBook’s
Three levels of customer fulfillment:
Customer Service
Customer Satisfaction
Customer Success
Customer Service
Fulfill basic service requirements
Customer satisfaction
Meet or exceed customer expectations
Customer Success
Assist customers in meeting their objectives, long-term relationship
Basic Customer Service includes:
Product Availabilty
Lead-Time Performance
Service Reliability
Product Availability: Unit Fill Rate
% of ordered units delivered= Units Delivered/Units Ordered
Product Availability: Order Fill Rate
% of orders shipped complete= Orders delivered/ Orders Demand
Lead Time
The time between start and end of an activity
Service Reliabilty
No Errors: Damage free, right quantity, right time
Provide critical information of inventory and order status
What kind of product can be outsourced?
The product NOT in the area of core competencies
Mature products with standard processes
Tradeoff related to too few suppliers
Risk(shortage, lack of competition)
Tradeoff related to too many suppliers
Complexity
Which supplier do you chose in the weighted point model
Supplier with highest score
Select supplier by online auction when
Price is the most important factor
Select supplier by negotiation when
Requirement is complicated, supplier involved, complex start up (Divorce)
How to manage the relationship with suppliers?
Share information
Performance monitoring and improvement
Throughput Rate
How many customers served in a given amount of time
r=
Arrival rate/Service Rate
Throughput=
Arrival Rate(1-probability system is full)
Average Waiting Time=
Average Length of Queue/Arrival Rate (Little’s Law)
Score=
Weight X Rating
