Introductions

Class description / purpose Instructors

Carol Bjork – HeyCats! Web Solutions Kris Rudin – Ascentium Corporation

Student introductions

Scientific Modeling - Definition Modeling refers to the process of

generating a model as a conceptual representation of some phenomenon

A model is a physical or mathematical or otherwise logical representation of system or entity or process

Go out to real world and grab information about a real world system, business, or piece of equipment and drag it back into the simulation and write it into software

Forms of Scientific Modeling Business process modeling Cartography Climate modeling Data modeling Ecological modeling Economical modeling Environmental modeling Geologic modeling Graphical modeling Hydrological modeling Hydrogeological modeling Mathematical modeling Medical modeling Molecular modeling Morphological Modeling Ocean modeling Simulation Software modeling Statistical modeling Stochastic modeling Thought experiment

Simulation - Definition A simulation is an imitation of some real device or

state of affairs – an imitation of a real world process or system over time

A simulation is an interaction of models as they operate

The execution of the software you created is the simulation (verb)

Applications: Aid to thought Communication Training Prediction Experimentation Entertainment

Simulations – Where Used Modeling of natural systems and human

systems to gain insight into the operation of those systems

Simulation in technology and engineering where the goal is to test some real-world practical scenario.

Simulation, using a simulator or otherwise experimenting with a fictitious situation can show the eventual real effects of some possible conditions.

Simulation – Physical/Interactive

Physical simulation refers to simulation in which physical objects are substituted for the real thing, these physical objects are often chosen because they are smaller or cheaper, than the actual object or system.

Interactive simulation, which is a special kind of physical simulation, and often referred to as human in the loop simulations, are physical simulations that include humans, such as the model used in a flight simulator.

Computer Simulations Computer program which attempts to simulate an

abstract model of a particular system. Used in:

modeling natural systems in physics, chemistry and biology

human systems in economics and social science engineering new technology to gain insight into the

operation of those systems Build on the mathematical model: attempt to find

analytical solutions to problems that enable the prediction of the behavior of the system from a set of parameters and initial conditions.

History of Computer Simulations Computer simulation was developed hand-in-hand

with the rapid growth of the computer, following its first large-scale deployment during the Manhattan Project in World War II to model the process of nuclear detonation. It was a simulation of 12 hard spheres (impenetrable spheres that cannot overlap in space) using a Monte Carlo algorithm.

Common feature: The attempt to generate a sample of representative scenarios for a model in which a complete enumeration of all possible states of the model would be prohibitive or impossible.

Computer models were initially used as a supplement for other arguments, but their use later became rather widespread.

Types of Computer Simulation Stochastic (random process) or

deterministic (a computation that given an initial state of the system will always produce the same final state when given the same input)

Steady-state or dynamic Continuous (small changes in the input

result in small changes in the output) or discrete (ex: events over time)

Local or distributed (using two or more computers communicating over a network to accomplish a common objective or task)

Computer Simulation Examples Stochastic models use random number generators to

model the chance or random events; they are also called Monte Carlo simulations. Ex: rainfall/runoff models

A discrete event simulation (DE) manages events in time. Most computer simulations are of this type. In this type of simulation, the simulator maintains a queue of events sorted by the simulated time they should occur. The simulator reads the queue and triggers new events as each event is processed. It is not important to execute the simulation in real time. It's often more important to be able to access the data produced by the simulation, to discover logic defects in the design, or the sequence of events.

Examples (continued) A continuous simulation uses differential equations,

implemented numerically. Periodically, the simulation program solves all the equations, and uses the numbers to change the state and output of the simulation. Most flight and racing-car simulations are of this type. This may also be used to simulate electrical circuits.

Distributed models run on a network of interconnected computers, possibly through the Internet. Simulations dispersed across multiple host computers like this are often referred to as "distributed simulations". There are several military standards for distributed simulation.

Examples (continued)

Computer simulations are used in a wide variety of practical contexts, such as: analysis of air pollutant dispersion using

atmospheric dispersion modeling design of complex systems such as aircraft and

also logistics systems. design of Noise barriers to effect roadway noise

mitigation flight simulators to train pilots weather forecasting

Can you think of others?

NetLogo Demonstration Brief demonstration of NetLogo 3.1 History

Created by the Center for Connected Learning (CCL) and Computer-Based Modeling (http://ccl.northwestern.edu/)

Main features Programmable environment Extensive documentation and user groups Models Library HubNet – a classroom participatory-simulation

tool Models can run in a web environment