Models and Simulation

1. Models and Simulation Rachel, Tyler, Garrett, Luke & Exelman

2. Computer Models • A computer model is a computer program that creates a simplified, mathematical representation of a real world process. Computer models can be created using spreadsheet software. Computer models are used to model two main types of events: • 1. Those which are difficult or impossible to observe: for example, the future of the Earth’s climate or the births and deaths of stars in space. • 2. Events which are expensive or dangerous to test by experimentation: for example, the effects of car cashes on passengers or changes to a city’s transportation infrastructure. • Computer models use variables and processes to create a representation of the real world. Their outputs are predictions. Decisions are made based on these predictions so it is very important to understand how accurate a model is.

3. Application of Models • Transportation Models: used to model traffic levels at different times of the day, and predict how these will change in response to changes in the transportation infrastructure. • Structural Models: can predict the strength of buildings and bridges in severe events such as earthquakes and storms. • Drug Interaction Models: to improve understanding of bacteria and viruses that cause disease, and the effect of different doses of medication on patients. • Car Crash Models: are increasingly being used by vehicle manufacturers to observe the effects of accidents on cars, passengers, and pedestrians. • Computational Fluid Dynamics: models the flow of liquids and gasses, and is commonly used to test aerodynamics.

4. Computer Simulations • A computer simulator provides the user with experience of a real life situation by combing computer models of the world with realistic input and output devices, and realistic graphics. • Flight simulators are used by the military and commercial airlines to train pilots. • Driving simulators are used to train young, learning drivers or to provide a refresher course for experienced drivers. • Other examples of simulators include ship simulators, train simulators, and space craft simulators.

5. Advantages and Disadvantages of Simulators • Advantages: Simulators offer many advantages over real life training. Unusual or rare events can be programmed to happen as often as needed to prepare to user for dangerous situations, without harming them or equipment. • Disadvantages: Simulators cannot offer exact real world events. They also cannot recreate the exact feeling and pressure of being in a real world situation.

6. Spreadsheets • All spreadsheets are based around the fundamental concepts of cells of data and references to them. • Commonly used by businesses or for financial purposes. May be used to: organize data; create a visual representation of data; find trends of a data set which can be used to predict future outcomes. • Cell reference: Each cell has an individual reference (A1, B2, C3, D4, etc.) • Cell Range: A sequence of cells (A1:A4, which refers to cells A1, A2, A3 and A4)

7. Cell Referencing • Relative Cell Referencing: When ‘click and drag’ method changes reference cell according to ‘drag’. (If formula=B4=C4, and you click and drag down to the next row, the formula will become =B5+C5.) • Absolute Cell Referencing: Same concept as above, but the cell reference stays the same. To do this, insert a ‘$’ between the letter and number in the cell reference you do not want changing. (If formula =B4+C4+C$1, when dragged down to next row, the formula will change to =B5+C5+C$1. Notice how C$1 did not change with the rest of the formula.)

8. Functions and Formulae • Functions: Features built into the spreadsheet software, such as SUM, AVERAGE, and MIN functions. • Proper use of function: to find the sum of the cell range A1:A4, you would enter into the formula bar ‘=SUM(A1:A4).’ • Formulae: Created by typing cell references and mathematical operators to calculate • Proper use of Formulae: to find the sum of cells A1 and B2, then divide by cell C3, you would enter into the formula bar ‘=(A1+B2)/C3’

9. Helpful Tips • Being familiar and knowledgeable with spreadsheets will set you apart from other applicants when applying for jobs. • When starting a formula, always begin with ‘=‘ • Order of Operations are very important when dealing with spreadsheets ‘(=A1+A2/A3’ will NOT bring the same result as ‘=(A1+A2)/A3’ • Any questions?

10. High Performance Computing • Models and Simulations are used for scientific research with complex calculations which means you need super computers. • Super computers use parallel processing techniques than one task quickly at the same time. • Two approaches to parallel processing: • Centralized processing- numerous processors installed in the same computer system. • Dual core and quad core systems found in many desktop and laptop PCs are examples of basic centralized processing. • Distributed Processing- uses a different approach to achieving parallel processing. Instead of using one specialized computer, distributed processing uses multiple, separate computers connected by a network. This process works by sending a separate part of the task to each connected computer, which processes it independently and returns the result to a central computer.

11. Visualization • The majority of computer models use graphical outputs in the form of graphs, maps, images, or animations. All graphical outputs are visualizations of the numeric data generated by the computer models. The main advantage of graphical output is that a large amount of info/data can be displayed in a relatively compact form.

12. Video • http://proxy0server.appspot.com/youtube.com/watch?v=OVWbYJtpoao