MOD SIM PRELIM

Modeling and Simulation

is a powerful and increasingly popular method for studying various kinds of real-word facilities or process, particularly those that are complex.

System

defined as a collection of entities(people/machines) that act and interact together towards a logical and the state of system is the collection of variables necessary to describe it as a particular time relative to the study’s goal.

Model

is a representation of a system (physical, mathematical, or logical) also are enhirently approximations of the real world including only features deemed essential ofr the study’s purpose

Physical (ironic) models

tangible representation, like scale models of cars or buildings

Mathematical models

representations using logical and quantitative relationships, often in the form of equations

Computer models

software implementation of mathematical models that can be executed on a digital compters

Simulation

is the process of evaluation a model numerically using computer, gathering data to estimate the desired true characteristics of the model

Static simulation models

represent a system at a particular time, or where time plays no role (eg, certain Monte Carlo models).

Dynamic simulation models

represent a system as it evolves over time

Deterministic models

do not contain any probabilistic (random) components; their output is determined once inputs are specified.

Stochastic simulation models

include random input components, producing output that is also random and must be treated as an estimate

Continuous simulation models

represent systems where state variables change continuously over time, often involving differential equations (e.g., fluid flow, projectile motion)

Discrete-event simulation (DES) models

represent systems where state variables change instantaneously at separate points in time (events). DES is the focus of much simulation study due to the complexity of real-world systems

Monte Carlo Simulation

this is a type of static simulation that uses random sampling to predict probabilities of various outcomes, particularly useful in risk analysis and decision-making problems.

System state

the collection of variables describing the system at a given time.

Simulation clock

a variable tracking the current simulated time.

Event list

a list containing the next scheduled time for each type of event.

Statistical counters

variables used to store statistical information about system performance.

Initialization routine

a subprogram to set up the model at time 0.

Timing routine

a subprogram that determines the next event and advances the simulation clock

Event routine

a subprogram for each event type that updates the system state when that event occurs.

Report generator

a subprogram that computes estimates of performance measures and produces a report at the end of the simulation.

Main program

orchestrates the simulation flow by invoking other routines checking for termination.

Formulate the problem and model

clearly define the system, objectives, and specific questions to be answered, and develop a conceptual model. This includes determining the appropriate level of detail

Collect and analyze system data

gather high-quality information and data on the system, which informs the model's structure and input distributions.

Develop the computer program (model)

translate the conceptual model into a computer program, often using specialized simulation software

Verify the computer program

debug the simulation program to ensure it correctly translates the conceptual model.

Validate the model

determine whether the simulation model is an accurate representation of the real system for the study's objectives. This often involves comparing model output to real-world data or expert opinion.

Design and make simulation runs

plan experiments (runs) to gather necessary data for analysis.

Analyse output data

interpret the large quantities of performance data generated by the simulation, using statistical methods to draw conclusions and make recommendations.

Document, present, and use results

present the findings and conclusions in a clear, understandable manner to stakeholders, and ensure the results are used in decision-making.

Manufacturing systems

designing, analyzing, and optimizing production lines, logistics, and material handling.

Military and defense

evaluating weapons systems, logistics, battlefield networks, and war gaming

Transportation systems

designing and operating airports, freeways, and ports, including air traffic control and flight trajectories.

Communications networks

determining hardware requirements, protocols, and managing data traffic

Healthcare

planning hospital facilities, studying new equipment, and optimizing personnel scheduling

Economics and business

forecasting, optimizing inventory, financial planning, and supply chain management.

Social sciences

modeling human behavior, social relationships, and organizations, including population dynamics and spread of epidemics.

Life sciences

research in biology, chemistry, biochemistry, pharmacology, and bioengineering including 3D biomechanical modeling.

Computer systems

determining hardware/software requirements and performance analysis.

Time's Role

Time is either irrelevant or represents a fixed point

Output

For a given set of inputs, the output is always the same, as there are no probabilistic components affecting change over time.

State Variables

These describe the system at a specific moment, and their values do not change as the simulation progresses through time.

Architect's Building Model

A scaled-down physical model of a building, reflecting its rooms and outer design, is a static physical model.

Electrical Circuit (Static)

A model that gives relationships between system attributes when the system is in equilibrium.

Aircraft Static Model

A model where flight profile is affected by weather conditions (exogenous), but the model itself is static.

Costing Models

Models for evaluating the total cost of an aircraft sortie for a mission

Market Models (Simplistic Linear Case)

Models that compute probable price and demand assuming supply and demand are equal, without involving time as a changing factor.

Student Training Model

Optimizing marks allotted to students.

Behavior Over Time

Used to understand how system performance changes dynamically over time, especially when system characteristics vary.

Time-Advance Mechanisms

Dynamic discrete-event simulations use either next-event time advance (NETA) or fixed-increment time advance (FITA)

Computational Tools

Can be expressed as difference equations or differential equations and solved using analytical or simulation methods.

Queueing Systems

Models like a single-server barbershop or an information desk at an airport, where the number of customers in the bank changes only when a customer arrives or departs.

Conveyor Systems

Represent systems evolving over time, such as those in a factory

Inventory Systems

Models comparing alternative ordering policies over n months, where inventory levels and outstanding orders change over time.

Manufacturing Systems

Including job-shop models to identify bottlenecks in production processes.

Airplane Movement

State variables like position and velocity change continuously with respect to time.

World Population Growth

Models showing how population evolves over time, such as constant, proportional, or quadratic growth models.

Epidemiology (SIR Models)

Models describing the spread of disease in a susceptible population, with categories of susceptible, infectious, and recovered individuals changing over time.

Thermodynamics

Models of temperature change, like coffee cooling or milk warming.

Projectile Motion

The trajectory of a projectile or flight of an aircraft, where position and velocity change continuously.

Chemical Reactions

Described by complicated systems of differential equations.

National Economy

Models where current values of variables are expressed in terms of previous year's values (lagged variables).

Cobweb Models

Market models where supply depends on the previous year's price, demonstrating how price converges or diverges over time.

Biological Models

Such as predator-prey systems where populations fluctuate.

System Dynamics

A type of continuous simulation used for designing policies in business, government, and military, often involving differential equations.