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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
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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
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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
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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 systemIt is a representation of the objects within the system and the rules that govern the interactions of the objects
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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
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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
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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!
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Queuing Systems
Can you name at least three queuing systems that you interact with every day?
Please wait!
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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
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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?
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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
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Meteorological Models
How muchmath
does ittake tobe a
meteorologist?
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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
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Meteorological Models
Relocatable models
Models applied to a moving target
Can you think of an example?
What is special about weather models?
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Hurricane Tracking
Figure 14.2 Improvements in hurricane models
(GFDL) Geophysical and Fluid DynamicsLaboratory
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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?
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Graphics
Figure 14.3 Geometric modeling techniques
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Graphics
How does light work?
Figure 14.4 The normal (N), light (L), and Reflection (R) vectors
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Graphics
Shape and surface influence an object’sappearance
Equations used to describe planes, spheres,and cylinders
Real world surfaces are rough, which scatter light differently, requiring texture mappingtechniques
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Graphics
Illumination modelSimulation of light interaction at one pointon an object
Shading model (shading)Process of using an illumination model to determine the appearance of an entire object
RenderingThe process of creating an entire image
What is
theproblem
withthis
model?
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Modeling Complex Objects
Whatgraphics
challengesare
inherentin
naturallandscapes
?
Figure 14.5 A natural computer generated landscape
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Modeling Complex Objects
Figure 14.6 Midpoint subdivisionfor creating fractal terrains
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Modeling Complex Objects
Figure 14.7 Water pouring into a glass
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Modeling Complex Objects
Figure 14.8 Cellular automata-based clouds
Whatmathe-matical
techniqueis
usedin
modelingcloud
formation?
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Modeling Complex Objects
Figure 14.9 A campfire
What do smoke andfire have in
Common, graphically?
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Modeling Complex Objects
Figure 14.11 A simulation of cloth showing ending and draping
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Modeling Complex Objects
What is the most difficult object to model?
What is the next step up in complexity?
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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?
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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?
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Computer Security
Authentication credentials
Information users provide to identify themselves for computer access
•User knowledge name, password, PIN
•Smart card card with embedded memory chip used for identification
•Biometrics human characteristics such as fingerprints, retina or voice patterns
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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
Virus self-replicating
Logic bomb set up to execute at system event
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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
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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-middle network communication is intercepted in an attempt to obtain key data
Have you ever experienced one of these?
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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?
