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Flashcards in man 2 test Deck (29):
1

3 main characterizations of the supply chain process

processing
assembly
distribution

2

principles of manufacturing systems

-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

3

USA Principle

Understand existing processes
Simplify the process
Automate the process

4

Prescriptive vs Descriptive Models

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

5

heuristic procedures - definition and evaluation of

-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

6

Computational Time: empirical vs. theoretical

-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

7

Queuing

analysis of system behavior based on long-run avg performance

8

Simulation

-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

9

verification and validation

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

10

Modeling Loss

- 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

11

Tc for single unit

Tc = Tm + Ts

12

Tc for storage cell

Tc = max(Tm,Ts) + Tr
if Ts > Tm, you have forced idle time

13

Fundamental imbalance law

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)

14

Tm for machine clusters

Tm = NTr + (n-1)Ts

15

how many machines 1 person can handle in a cluster

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

16

Capacity

= (n * AT) / Tm
= 1 / (Tc1 + Tc1 + ...)

17

Suppose you want to find minimum W - how?

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

18

Sequencing vs Scheduling

Sequencing - permutation of the job set (order)
scheduling - assigning start/end/preemption times to individual jobs on each machine

19

Regular vs. Non-regular measures of performance

-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)

20

Non-Delay Schedules

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

21

active schedules

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

22

semi-active schedules

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

23

single machine scheduling: SPT vs EDD

- SPT minimizes mean flow timed
- EDD minimizes max lateness

24

makespan and mean flow time in single machine scheduling

Makespan is independent of sequence
mean flow time is dependent on sequence

25

Single Pass Construction Heuristic

Minimize Mean flow time with respect to Max Lateness = 0

26

Single Machine Scheduling with non-zero ready times

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

27

Single Machine Scheduling: Setup Times

- 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

28

TSP formulation

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

29

closest insertion algorithm

-maintains a partial sequence throughout entire procedure
- is a TSP algorithm