Modeling & Simulation Flashcards

1
Q

George Box

A

Statistician responsible for several breakthroughs in the areas of experimental design, time series analysis, and statistical modeling (Box-Cox Transformation, Box-Behnken Design, and Box-Jenkins Methodology)

The quote “All models are wrong, some models are useful” is attributed to George Box.”

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2
Q

Model

A

an abstract representation of a system

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3
Q

Simulation

A

Simulation is the process of (1) developing a system model & (2) conducting experiments with this model for the purpose of understanding the behavior of the system or evaluating various strategies for the operation of the system

It is an imitation of system performance over time to a predefined degree of fidelity
– design analyses (model the system & the environment)
– breadboards (model the system)
– qualification testing (models the environment)
– training (models the mission)

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4
Q

The “Real World”

A

Consists of Problems and Actions

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5
Q

The “Model World”

A

Consists of the Model and Results

Models must be validated and have the appropriate levels of fidelity

Results must be meaningful and verified

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6
Q

Model Scope

A
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7
Q

Model Breadth

A
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8
Q

Model Generality

A
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9
Q

“Model Breadth” v. “Model Generality”

A
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10
Q

Model Depth

A
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11
Q

Model Fidelity

A
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12
Q

Model Realism

A
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13
Q

“Model Fidelity” v. “Model Realism”

A
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14
Q

Model Precision

A
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15
Q

Tradeoff between generality and realism

A
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16
Q

Model Accreditation

A

1) Face Validity
2) Peer Review
3) Functional Decomposition
4) Comparison or Empirical Validation

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17
Q

Classes of System Models

A

1) Continuous Systems
2) Discrete-time Systems
3) Hybrid Systems

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18
Q

Continuous Systems v. Discrete-time Systems

A

Continuous - Variables change continuously with respect to time
Discrete - Variables only change at distinct/finite instants of time

*There are also Hybrid systems which have elements of both

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19
Q

Deterministic v. Stochastic Models

A

Both are types of Statistical Models

Deterministic - Non-probabilistic relationships between system variables
– Tend to be continuous systems; typified by mathematical models
* lift of an airplane wing
* thrust of a rocket engine

Stochastic - Probabilistic relationships between system variables
– Tend to be discrete-time systems; typified by random discrete event models
* wind velocities encountered by a flight vehicle during ascent
* component failures during system operation

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20
Q

Model Building Process

A

1) FIND

2) FACTORS
- Exogeneous variables
- Endogenous variables
- Assumptions

3) MODEL SELECTION
- Based on what can be measured/calculated

4) MODEL VERIFICATION

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21
Q

Simulation Building Process

A

1) Build a model

2) Strategic & Tactical Planning

3) Experimentation

4) SME Validation

5) Analysis of Results

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22
Q

Model Building tips

A

1) Simpler models are better. Simplify wherever you can

2) Only develop a model to answer a question. No modeling for the sake of modeling

3)

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23
Q

Four types of models

A

1) Physical Models: Tangible representations of objects or systems

2) Graphical Models: Represent systems or relationships between elements using visual elements such as charts, graphs, or diagrams

3) Mathematical Models: Rely on equations, algorithms, and mathematical structures to represent systems and processes quantitatively

4) Statistical Models: Represent systems based on probabilistic relationships between variables, often developed from empirical data

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24
Q

Physical Models

A

Definition: Physical models are tangible representations of objects or systems. They are usually scaled versions, prototypes, or replicas that allow for hands-on interaction and observation.

Purpose: Used for visualizing complex structures and testing physical properties in real-world conditions. They are often applied in engineering, architecture, and product design.

Examples: Wind tunnel models of airplanes, architectural scale models, and anatomical models in medicine.

Advantages: Provide a concrete understanding and direct interaction, useful for testing physical forces and dynamics in prototypes.

Limitations: Expensive and time-consuming to build, not easily adjusted for hypothetical scenarios or scaling variables

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25
Q

Graphical Models

A

Definition: Graphical models represent systems or relationships between elements using visual elements such as charts, graphs, or diagrams. They illustrate complex interactions in an accessible, visual format.

Purpose: Used to communicate relationships, dependencies, and hierarchies among components. Common in fields like systems engineering, project management, and network analysis.

Examples: Flowcharts, network diagrams, UML diagrams, and decision trees.

Advantages: Simple to interpret, useful for identifying patterns, connections, and bottlenecks, and ideal for presenting to stakeholders.

Limitations: Limited quantitative analysis capabilities and can be overly simplified, failing to capture all system nuances

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26
Q

Mathematical Models

A

Definition: Mathematical models use equations, algorithms, and mathematical structures to represent systems and processes quantitatively. They are designed to predict behavior and provide solutions based on input variables.

Purpose: Used to analyze and predict outcomes by quantifying relationships between variables, often involving formulas or complex calculations. Common in physics, economics, and engineering.

Examples: Newton’s laws of motion, economic supply-demand models, and fluid dynamics equations.

Advantages: Precise and capable of handling complex, dynamic systems; useful for optimization and predictive analysis.

Limitations: Requires accurate data and assumptions; can be challenging to interpret for non-technical stakeholders

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27
Q

Statistical Models

A

Definition: Statistical models represent systems based on probabilistic relationships between variables, often developed from empirical data. These models are used to make inferences or predictions about real-world phenomena.

Purpose: Used for data analysis, risk assessment, and forecasting by evaluating patterns and correlations in data. Commonly applied in data science, finance, and healthcare.

Examples: Linear regression models, ARIMA models for time series forecasting, and logistic regression for classification.

Advantages: Useful for dealing with uncertainty, analyzing trends, and making data-driven predictions.

Limitations: Dependent on quality and quantity of data; prone to inaccuracies if assumptions about data distribution or correlations are incorrect​

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28
Q

Monte Carlo Simulations

A

Type of Statistical model

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29
Q

Linear Regression Modeling

A

Type of Statistical model

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30
Q

Logistic regression modeling

A

Type of Statistical model

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31
Q

ARIMA models for time series forecasting

A

Type of Statistical model

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32
Q

Process Modeling

A

Type of Statistical model

33
Q

Sequence Estimation Modeling

A

Type of Statistical model

34
Q

Manufacturing Layout Modeling

A

Type of Statistical model

35
Q

Mass-Spring-Damper Models

A

Type of Mathematical Model

36
Q

Stability in Dynamic motion models

A

Type of Mathematical Model

37
Q

Vibrational Analysis (Waves)

A

Type of Mathematical Model

38
Q

Control Systems Modeling

A

Type of Mathematical Model

39
Q

Fluid dynamics modeling

A

Type of Mathematical Model

40
Q

Production Throughput Analysis

A

Type of Mathematical Model

41
Q

Decision Analysis

A

Type of Mathematical Model

42
Q

Network Analysis (Nodal)

A

Type of Mathematical Model

43
Q

Cost modeling

A

Type of Mathematical Model

44
Q

Linear Programming

A

Type of Mathematical Model

45
Q

Finite Element Based Structural Analysis

A

Type of Mathematical Model

46
Q

Phase Space Model

A

Type of Mathematical Model

47
Q

State Variable Model

A

Type of Mathematical Model

48
Q

Polynomial-fitting Based Structural Analysis

A

Type of Mathematical Model

49
Q

S-I-R Model

A

Type of Mathematical Model

50
Q

Chemical Kinetics Model

A

Type of Mathematical Model

51
Q

Functional Flow Charts

A

Type of Graphical model

52
Q

Block Diagrams

A

Type of Graphical model

53
Q

Behavioral Diagrams

A

Type of Graphical model

54
Q

N2 Charts

A

Type of Graphical model

55
Q

PERT Charts

A

Type of Graphical model

56
Q

Logic Trees

A

Type of Graphical model

57
Q

Document Trees

A

Type of Graphical model

58
Q

Timelines

A

Type of Graphical model

59
Q

Waterfall Charts

A

Type of Graphical model

60
Q

Floor Plans

A

Type of Graphical model

61
Q

Blueprints

A

Type of Graphical model

62
Q

Schematics

A

Type of Graphical model

63
Q

Topographical Representations

A

Type of Graphical model

64
Q

CAD

A

Type of Graphical model

65
Q

Wind tunnel Model

A

Type of Physical model

66
Q

Hanger Queen

A

Type of Physical model

67
Q

Testbed

A

Type of Physical model

68
Q

Breadboard

A

Type of Physical model

69
Q

Prototypes

A

Type of Physical model

70
Q

Mass/Inertial Model

A

Type of Physical model

71
Q

Scale Model

A

Type of Physical model

72
Q

Laser Lithographic Model

A

Type of Physical model

73
Q

Structural Test Model

A

Type of Physical model

74
Q

Acoustic Model

A

Type of Physical model

75
Q

Digital Twins

A
76
Q

Multi-domain Simulation (MDS)

A
77
Q

Simulating Stochastic Models with a “Random Walk”

A
78
Q

Three Evils of Simulations

A

There are three underlying reasons why things go wrong in systems engineering in general,
and in systems modeling, analysis, & simulation in particular:
1) Complexity – arises from the relationships between various system elements, particularly when these relationships are over-simplified, not as assumed, or just unknown.
2) Lack of understanding – can arise from ambiguous requirements, lack of domain knowledge, or usage of a system in a manner not intended by the developer.
3) Communication issues – can occur at the interpersonal, inter-group, or inter-organizational, and/or system-to-system levels.
* These three “evils” can lead to inefficient system engineering at best and project or system failure at worst.

79
Q

Common Pitfalls in Modeling and Simulation

A

– Using a model outside the range of variation for which it has been validated.
– Using a model for other than its intended usage. In particular, the rationale underlying the
neglected vs. included variables may be invalidated.
– Failure to validate or certify/accredit a model.
– Failure of the modeler to keep their eye on the ball. The objective is to be as general in scope, realistic & precise in behavior as necessary (vs. possible).
* Significant resources are often wasted over-developing models.
– Failure to recognize or account for inter-dependencies between concurrent modeling efforts. Failure to base concurrent model developments on a common system baseline
design.
* Both these topics will be addressed in “Technical Integration.”