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Computer modelling and simulations
- 1. Computer Modeling and Simulations
- 2. Computer Simulations and Models A simulation is basically an attempt to imitate reality. Simulation is used in many contexts, including the modeling of natural systems or human systems in order to gain insight into their functioning. A computer model is the mathematical representation of the functioning of a process, concept or system, presented in the form of a computer program.
- 3. Feedback Loops Good computer models are dependent of feedback loops. Essentially, feedback loops are the part of the system model that, based on the current output, allows for response and / or self-correction to achieve the desired output.
- 4. Feedback Loop Input Process Output Feedback Feedback - the response to the output, which inputs new information into the model to the desired effect
- 5. Steps involved in creating simulations Gather and prepare accurate data to re鍖ect the real world. Create mathematical formulas (algorithms) to generate output data from that which is input. Create animations, graphs or other output displays for the information. Verify and validate the data by re-testing the scenarios to ensure that the same result occurs.
- 6. Advantages of modeling and simulations Safety - able to test or experiment without harming the person or environment. Economic savings from the use of models to design and test new products before prototypes or the 鍖nal product is made. Projection - can look into the future and highlight potential impacts and address them before they occur. Visualisation - can see and understand relationships. Can speed up or slow down time. Replication - able to look at things under a variety of different scenarios
- 7. Disadvantages of modeling and simulations The mathematical (computational) calculations are very complex, maybe too complex, to simulate 'real life' situations or activities. Therefore, simulations really identify possible trends. Faulty or hidden assumptions Extent and effect of the simpli鍖cation of reality Processing power needed to create complex models Can be costly to purchase the processing power and labour
- 8. Complexity and Assumptions Mathematical models are built on assumptions, many of which are dif鍖cult to verify. Possibility for the assumptions to be faulty, the creators of the model to overlook things (hidden assumptions) and also clerical errors can be made with the programming. Daily weather report - to be 100% accurate is too dif鍖cult. Usually, the report is 55-65% accurate. Errors with computer models can have disastrous results.
- 9. Weather Forecasting and Climate Models The importance of the weather and the need to predict it accurately is illustrated by the fact that every local news show includes weather forecasts. People need to know what the weather will be likeeither where they are or where they are goingso that they can plan their activities accordingly.
- 10. A brief history Weather forecasting is no new trend. As far back as 650 BC, there is evidence of early humans attempting to read the weather. Observing cloud patterns Colour of the sunset e.g. red These forecasting methods proved to be primitive and unreliable.
- 11. A brief history 1837 did real weather forecasting truly begin. With the creation of the telegraph, people could now begin to draw more or less accurate reports of weather conditions. In the 1840s, the telegraph allowed people to record weather conditions over a much larger area.
- 12. A brief history 1922 when Lewis Fry Richardson proposed his idea of using numerical weather prediction to forecast the weather. Numerical weather prediction used mathematical models of the atmosphere to predict the weather. This new idea was not used until 1955.
- 13. Five basic steps of weather forecasting Data collection (observations from surface, stratosphere or satellite) Data assimilation - production of a model Numerical weather prediction Model processing - adds human observations Presentation of a forecast
- 14. Stakeholders General public Air traf鍖c Military / Navy Farmers Utility companies e.g. Origin Energy Private companies
- 15. Issues - Reliability Not always accurate; extent of situation could be overestimated Better safe than sorry or dont provide warnings
- 16. Issues - Integrity Accuracy of the data and the instruments collecting the data
- 17. Equality of Access Quite easy to translate forecasts because of visual information Not everyone has access to radio, TV, Internet for emergency warnings
- 18. Issues - Control The weather forecast may control our day Companies respond to forecasts - potential economic cost
- 19. Issues - People and Machines Requires people to interpret the information produced by the models Need for human observation to be added to the forecast Future weather forecasts may be able to be delivered without the aid of humans.
- 20. Digital Experimentation Digital Experimentation is the act of conducting experiments on a computer without ever physically touching the test subject. For example, engineers can create digital models to crash-test a car to observe how the crash-test dummies would react to the impact. Another way to digitally experiment is by using image- enhancing programs like Photoshop. Lets say youre wondering what you would look like with purple hair but you dont actually want to dye it: by using certain tools and techniques on Photoshop, you can!
- 21. Car Crash Simulators Car Crash simulations offer a way to gain information about the causes of the accidents and how to improve the safety of the car bodies.
- 22. How car crash test simulators work They use the 鍖nite element method - grid superimposed on the object and numerical data is entered to each corresponding square of the to provide information on density, strength and elasticity.
- 23. Calculating the effect of a head-on collision Data can be initialised to represent a crash into a wall at a speci鍖ed speed. The program computes the force, acceleration and displacement of each grid square, plus the stress and strain of each element of the model. Program relies on intense computation and highly dependent of graphics programs.
- 24. Bene鍖ts Can look at a variety of designs before building the prototype. Saves several design being built and having to be crash-tested. Each crash test costs between A$ 100,000 to 1.6 million. Saves on material waste.
- 25. Issues - Reliability Good understanding of the physics involved, especially force and acceleration. Material properties are relatively well known. Behaviour of the materials under abrupt acceleration e.g. high speed impact and at near breaking point are less understood
- 26. Issues - Reliability Simpli鍖cation involved in the model. Cars are smooth and a grid does not replicate this.You can produce smaller grids but such a model requires far more processing power and cost. Comparison with real-life situation is, arguably, good. Use of video cameras on actual crash tests with data, such as displacement points, fed back into the computer model.
- 27. Issues - Integrity Incorrect entry of data Hackers changing data
- 28. Issues - Equality of Access Small companies looking to break into the car market would need a lot of money to compete with big corporations such as GM.
- 29. Issues - Policy and Standards Saves on environment in terms of materials used Economic savings Saves time
- 30. Traf鍖c Simulation Models De鍖nition: A computer program that uses mathematical models to conduct experiments with traf鍖c events on a transportation facility or system over extended periods of time.
- 31. Complex Networks Network traf鍖c simulation is a process used in telecommunications engineering to measure the ef鍖ciency of a communications network. Telecommunications systems are complex real-world systems, containing many different components, which interact, in complex interrelationships.
- 32. Determining the ef鍖ciency of a road netwrok Most obvious ef鍖ciency factor - the pattern of roads that currently exist In addition, consider 鍖rst the travel behaviour - Number of trips (data loggers) Origin and destination of trips Transport mode Route taken
- 33. Use of zones Models incorporates zoning e.g. some 542 zones across the Greater Dublin area. Zones de鍖ne the demand for travel in terms of origins and destinations. Need to consider external zones for trips into and out of the area.
- 34. Increasing ef鍖ciency Once the general ef鍖ciency is found, control measures that may assist improve the ef鍖ciency of the model may be incorporated:- Speed limits Overtaking bans for trucks, especially at uphill or downhill sections Restrictions for lane changing, especially before or at merging regions Traf鍖c 鍖ow control at on on-off ramps at intersections
- 35. Improving Ef鍖ciency Traf鍖c simulation models can also be used to look at future scenarios:- To simulate the effect of new infrastructure before it has been build. To simulate the in鍖uence of vehicles with adaptive cruise-control systems. If an increasing percentage of vehicles has such systems, does traf鍖c become more stable? Can the traf鍖c 鍖ow per lane be increased? Finally one can even simulate different or new traf鍖c rules. For example, allowing overtaking on freeways at either side combined with a speed limit.
- 36. Advantages of traf鍖c simulation models It is possible to easily compare alternative designs so as to select the optimal system The actual process of developing the simulation can itself provide valuable insights into the inner workings of the network which can in turn be used at a later stage Time and money saving Possible to test new traf鍖c rules without putting humans into dangerous situations and comparing the results of different types of traf鍖c rules
- 37. Disadvantages of traf鍖c simulations Data can be incorrectly input Accurate simulation model development requires extensive resources The simulation results are only as good as the model and as such are still only estimates It is very costly to develop a good, reliable and realistic simulation
- 38. Issues - Reliability and Integrity Data can be incorrectly input Data becomes out of date quickly Vast networks dif鍖cult to survey Need for accurate for casting e.g. number trips determined by population projections and level of car ownership or even environmental consciousness
- 39. Issues - Security Need to protect the simulation from those who may wish to tamper with it.
- 40. Issues - Equality of Access Costly and extremely dif鍖cult to do in developing countries
- 41. Demographic Models Demographics refers to certain population characteristics such as race, age, gender, income, disabilities, literacy rate, home ownership, employment status, and location. It is useful for the government of a country, coming up with marketing strategies, and for economic research.