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