Chapter 14

1. Chapter 14 Simulation and Other Applications

2. Chapter Goals • Define simulation • Give examples of complex systems • Distinguish between continuous and discrete event simulation • Explain how object-oriented design principles can be used in building models

3. Chapter Goals • Name and discuss the four parts of a queuing system • Explain the complexity of weather and seismic models • Explain the concept of embedded systems and give examples from your own home • Describe the important issues in graphics image generation

4. Chapter Goals • Explain the additional concerns for animation versus single images • Define and explain the role of e-commerce in society today • List three types of authentication credentials • Define the following terms related to computer security: malicious code,virus, worm, Trojan horse, logic bomb, spoofing, phishing, back door, buffer overflow, denial of service, and man-in-the-middle

5. What Is Simulation? • Simulation • A model of a complex system and the experimental manipulation of the model to observe the results Systems that are best suited to being simulated are dynamic, interactive, and complicated • Model • An abstraction of a real system It is a representation of the objects within the system and the rules that govern the interactions of the objects

6. Constructing Models • Continuous simulation • Treats time as continuous • Expresses changes in terms of a set of differential equations that reflect the relationships among the set of characteristics • Meteorological models falls into this category

7. Constructing Models • Discrete event simulation • Made up of entities, attributes, and events • Entity The representation of some object in the real system that must be explicitly defined • Attribute Some characteristic of a particular entity • Event An interaction between entities

8. Queuing Systems • Queuing system • A discrete-event model that uses random numbers to represent the arrival and duration of events • The system is made up of • servers • queues of objects to be served Please wait!

9. Queuing Systems • Can you name at least three queuing systems that you interact with every day? Please wait!

10. Queuing Systems • To construct a queuing model, we must know • The number of events and how they affect the system in order to determine the rules of entity interaction • The number of servers • The distribution of arrival times in order to determine if an entity enters the system • The expected service time in order to determine the duration of an event

11. Queuing Systems • Given a hypothetical service station, what are • the events? • the number of servers? • How can you determine • distribution of arrival time? • expected service time?

12. Meteorological Models • Meteorological models • Models based on the time-dependent partial differential equations of fluid mechanics and thermodynamics • Initial values for the variables are entered from observation, and the equations are solved to define the values of the variables at some later time

13. Meteorological Models How much math does it take to be a meteorologist ?

14. Meteorological Models • Computer models are designed to aid the weathercaster, not replace him or her • The outputs from the computer models are predictions of the values of variables in the future • It is up to the weathercaster to determine what the values mean

15. Meteorological Models • Relocatable models • Models applied to a moving target • Can you think of an example? • What is special about weather models?

16. Hurricane Tracking (GFDL) Geophysical and Fluid Dynamics Laboratory Figure 14.2 Improvements in hurricane models

17. Graphics • Graphics • Originally the language of communications for engineers, designers, and architects • Computer-aided design (CAD) • A system that uses computers with advanced graphics hardware and software to create precision drawings or technical illustrations • What does the term encompass today?

18. Graphics Figure 14.3 Geometric modeling techniques

19. Graphics How does light work? Figure 14.4 The normal (N), light (L), and Reflection (R) vectors

20. Graphics • Shape and surface influence an object’s • appearance • Equations used to describe planes, spheres, • and cylinders • Real world surfaces are rough, which scatter • light differently, requiring texture mapping • techniques

21. Graphics Illumination model Simulation of light interaction at one point on an object Shading model (shading) Process of using an illumination model to determine the appearance of an entire object Rendering The process of creating an entire image What is the problem with this model ?

22. Modeling Complex Objects What graphics challenges are inherent in natural landscapes ? Figure 14.5 A natural computer generated landscape

23. Modeling Complex Objects Figure 14.6Midpoint subdivision for creating fractal terrains

24. Modeling Complex Objects Figure 14.7 Water pouring into a glass

25. Modeling Complex Objects What mathe- matical technique is used in modeling cloud formation ? Figure 14.8 Cellular automata-based clouds

26. Modeling Complex Objects What do smoke and fire have in common? Figure 14.9 A campfire

27. Modeling Complex Objects Figure 14.11 A simulation of cloth showing ending and draping

28. Modeling Complex Objects What is the most difficult object to model? What is the next step up in complexity?

29. Embedded Systems • Embedded systems • Computers that are dedicated to perform a narrow range of functions as part of a larger system • Empty your pockets or backpacks. • How many embedded systems do you have?

30. E-Commerce Electronic commerce The process of buying and selling products and services using the WEB Can you name at least 4 e-commerce sites that you have visited lately? What made e-commerce feasible and easy? What problems does e-commerce face?

31. Computer Security • Authentication credentials • Information users provide to identify themselves for computer access • User knowledge name, password, PIN • Smart cardcard with embedded memory chip used for identification • Biometrics human characteristics such as fingerprints, retina or voice patterns

32. Computer Security • Malicious Code • A computer program that attempts to bypass appropriate authorization and/or perform unauthorized functions • Worm stand alone, targets network resources • Trojan horse disguised as benevolent resource • Virusself-replicating • Logic bomb set up to execute at system event

33. Computer Security • Security Attacks • An attack on the computer system itself • Password guessing obvious • Phishing trick users into revealing security information • Spoofing malicious user masquerades as authorized user • Back door unauthorized access to anyone who knows it exists

34. Computer Security • Buffer overflow defect that could cause a system to crash and leave the user with heightened privileges • Denial-of-service attach that prevents authorized user from accessing the system • Man-in-the-middlenetwork communication is intercepted in an attempt to obtain key data • Have you ever experienced one of these?

35. Ethical Issues Breaking into a University’s Computer System to Inquire About One’s Admission Status into a Graduate Program Is breaking into a computer system ever justified? Is breaking into a house to view something different from breaking in to steal something? Would you have viewed your own admissions data if given the chance?

36. Who am I? I am a generalist; I have done many different things. Do you know for what my Turing Award was given ?

37. Do you know? What was the first object-oriented language? What are scientists using to detect tsunamis? What is haptic technology? Give an example. How could the second-hand auction industry change the way people shop?