man 2 test

Question 1

3 main characterizations of the supply chain process

Answer 1

processing
assembly
distribution

Question 2

principles of manufacturing systems

Answer 2

• little’s law
• matter is conserved
• more components = less reliability
• exponential growth in complexity - N^M possible states
• system components appear to behave randomly
• limits of human rationale

Question 3

USA Principle

Answer 3

Understand existing processes
Simplify the process
Automate the process

Question 4

Prescriptive vs Descriptive Models

Answer 4

Prescriptive - model determines how to set decision variables to optimize system performance
Descriptive - given a set of values for the decision variables, model estimates systems performance - rely on these for detailed decision making

Question 5

heuristic procedures - definition and evaluation of

Answer 5

• rational method that attempts to find a good solution to a model
• evaluation: Quality of solution (“distance” from optimal and bounds), and effort expended generating solution

Question 6

Computational Time: empirical vs. theoretical

Answer 6

• empirical: run heuristic on a sample of “representative” problems
• theoretical: worst-case running time based on # of computations required, classification of problem in terms of # computations (P polynomial vs NP) - you can solve vs you cant solve

Question 7

Queuing

Answer 7

analysis of system behavior based on long-run avg performance

Question 8

Simulation

Answer 8

• experimental model that mimics events that occur in real system
• allows experimentation by running model with different operating parameters or control logic: sensitivity analysis, robustness
• requires verification and validation of model

Question 9

verification and validation

Answer 9

verification - model does what you want it to do - implemented correctly
validation - model correctly represents real system

Question 10

Modeling Loss

Answer 10

• don’t necessarily want to minimize these losses - simply want to build the simplest model that answers your question
• Losses:
• perception and measurement
• model simplification
• solution approximation
• implementation

Question 11

Tc for single unit

Answer 11

Tc = Tm + Ts

Question 12

Tc for storage cell

Answer 12

Tc = max(Tm,Ts) + Tr

if Ts > Tm, you have forced idle time

Question 13

Fundamental imbalance law

Answer 13

you cant buffer against fundamental imbalance (b/c speed is always dictated by max(Ts,Tm)), but you can buffer against variability (adding a machine helps variability of setup)

Question 14

Tm for machine clusters

Answer 14

Tm = NTr + (n-1)Ts

Question 15

how many machines 1 person can handle in a cluster

Answer 15

n = (Tm + Ts) / (Tr + Ts)

Question 16

Capacity

Answer 16

= (n * AT) / Tm

= 1 / (Tc1 + Tc1 + …)

Question 17

Suppose you want to find minimum W - how?

Answer 17

M/G/1
set Var(service time) = 0
Solve for L
Solve for W

Question 18

Sequencing vs Scheduling

Answer 18

Sequencing - permutation of the job set (order)

scheduling - assigning start/end/preemption times to individual jobs on each machine

Question 19

Regular vs. Non-regular measures of performance

Answer 19

-regular: non-decreasing in job completion times (if any job is made to finish later, the measure will stay the same or increase) - flowtime, makespan, tardiness, etc
non-regular - lateness and earliness penalties (the larger the deviation, the larger the penalty)

Question 20

Non-Delay Schedules

Answer 20

no machine is kept idle when there is an operation available for processing

Question 21

active schedules

Answer 21

no operation can be completed earlier by altering processing sequences on machines and not delaying any other operation - Never make a job in queue wait when it can be completely processed before the next job is scheduled to start

Question 22

semi-active schedules

Answer 22

No operation can be completed earlier without altering the processing sequence on any of the machines

Question 23

single machine scheduling: SPT vs EDD

Answer 23

• SPT minimizes mean flow timed

- EDD minimizes max lateness

Question 24

makespan and mean flow time in single machine scheduling

Answer 24

Makespan is independent of sequence

mean flow time is dependent on sequence

Question 25

Single Pass Construction Heuristic

Answer 25

Minimize Mean flow time with respect to Max Lateness = 0

Question 26

Single Machine Scheduling with non-zero ready times

Answer 26

Makespan DOES depend on sequence b/c ri is not equal to zero

Question 27

Single Machine Scheduling: Setup Times

Answer 27

• sequence - independent setup times: doesn’t matter what you did before - makespan is independent of sequence - just add setup times to process times
• sequence-dependent setup times: makespan is no longer independent of sequence - solve using TSP

Question 28

TSP formulation

Answer 28

Min sum sum (Cij) * (Xij)
s.t.
sum Xij = 1 ("enter" each city once)
sum Xij = 1 ("exit" each city once)
no subtours
Xij = 0,1

Question 29

closest insertion algorithm

Answer 29

• maintains a partial sequence throughout entire procedure

- is a TSP algorithm