Chapter 14 Simulation and Other Applications. 2 What Is Simulation? Simulation A model of a complex...

Chapter 14

Simulation and Other Applications

2

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

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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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

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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

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Graphics

Figure 14.3 Geometric modeling techniques

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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

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Modeling Complex Objects

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

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Modeling Complex Objects

Figure 14.9 A campfire

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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?

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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 3 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 attack 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?