Final | AOE 2074 - Computational Methods, Quizzes of Aerospace Engineering

Class: AOE 2074 - Computational Methods; Subject: Aerospace and Ocean Engineerin; University: Virginia Polytechnic Institute And State University; Term: Fall 2010;

Typology: Quizzes

Pre 2010

Uploaded on 12/06/2010

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TERM 1
Valid Algorithms Must be...
DEFINITION 1
1) Unambigous 2) Executable 3)Ordered
TERM 2
Properties of algorithms
DEFINITION 2
1) Not Unique 2)Devoid of Theory for INstructions 3)Some
more efficient than others 4)Modified often
TERM 3
2 kinds of M files
DEFINITION 3
!)script 2) function
TERM 4
Function Format
DEFINITION 4
outvar=funcname(arglist)
TERM 5
Primary Function
DEFINITION 5
1)listed 1st in m file 2)function name same as file name
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Valid Algorithms Must be...

  1. Unambigous 2) Executable 3)Ordered TERM 2

Properties of algorithms

DEFINITION 2

  1. Not Unique 2)Devoid of Theory for INstructions 3)Some more efficient than others 4)Modified often TERM 3

2 kinds of M files

DEFINITION 3 !)script 2) function TERM 4

Function Format

DEFINITION 4 outvar=funcname(arglist) TERM 5

Primary Function

DEFINITION 5 1)listed 1st in m file 2)function name same as file name

Sub Functions

1)only accessible by primary function or sub functions within the same m file. 2) Not accesible by command window TERM 7

Anonymous functions

DEFINITION 7 simple one line functions created without need for a seperate m file TERM 8

function functions

DEFINITION 8 functions that operate on other functions -passed to it as input arguments TERM 9

for loop

DEFINITION 9 -ends after certain number of iterations - index=start:step:finish TERM 10

while loop

DEFINITION 10 ends based on a condition being met

Open roots methods

-fixed point iteration -Newt-raphson -CAN DIVERGE -Require only single starting guess -IF converge, converge faster than bracketing methods TERM 17

Newton-Raphson

DEFINITION 17 -Mostly widely used for finding roots -Start with inital guess - calculate tangent at f(guess) -intersection of tangent with x- axis becomes next guess -may have problems with 1) multiple roots, 2) slow convergence or divergence TERM 18

PRos/cons NEwt

Raph

DEFINITION 18 Pro=quadratic convergence Con=sometimes poor or slow convergence TERM 19

Accuracy

DEFINITION 19 How closely a computed value agress with the true value TERM 20

Precision

DEFINITION 20 How closely individual measurements agree with each other

True Error

difference between true value and its approximate TERM 22

Absolute Error

DEFINITION 22 absolute difference between true value and the approximate TERM 23

TRue fractional relative

DEFINITION 23 (present-previous)/present TERM 24

percent relative error

DEFINITION 24 (present-previous)/present * 100% TERM 25

Using error estimates

DEFINITION 25 -usually sign of error ignored -computations usually computed until ea

OTher Kinds of errors....

---Blunders- errors caused by computer/human imperfections ----Model Errors= errors resulting from incorrect mathematical models ------Data uncertainty=errors resulting from the accuracy/precision of data TERM 32

Optimization

DEFINITION 32 Process of creating something as efficient as possible TERM 33

Global optimum

DEFINITION 33 represents very best solution TERM 34

local optimum

DEFINITION 34 is better than its immediate neighbor ----want to find global optimum though TERM 35

golden ratio

DEFINITION 35

Parabolic interpolation

uses 3 points to estimate optimum location TERM 37

fminbnd

DEFINITION 37 -matlab function combines parablolic interpolation and golden ratio ---fminbnd(func,x1,x2) TERM 38

fminsearch

DEFINITION 38 matlab code to determine minimum of multidimensional function -------fminshearch(function,x0) TERM 39

SLAE

DEFINITION 39 Systems of Linear Algebraic Equations TERM 40

Over determined system

DEFINITION 40 More equations than unknowns

LU Factorization Steps

  1. decomposition step=Matrix A decomposed into Upper and Lower Triangular Matrix 2)Substitution step= L and U used to determine a solution x for right-hand-side vector b - intermediate vector d is composed and then used to solve for x when Ux=d ----matlab=lu(A) TERM 47

Symmetric Systems

DEFINITION 47 --occur comonly in engineering --special techniques to solve TERM 48

Cholesky Factorization

DEFINITION 48 -Most popular way to solve symmetric systems ---Symmetric system decomposed into A=U(transpose) *U --matlab=== U=chol(A) TERM 49

Left division operator

DEFINITION 49 examines most efficient way to solve a system -----Banded Solvers -----Back or forward substitutions if triangular matrix - ----Cholesky Factorization if symmetric -----Gauss+partial pivoting if square TERM 50

Ill conditioning checks

DEFINITION 50 ---Scale matrix A so largest element in each row is 1 and invert. IF A inverse has larger elements its ill ---Multiply A by A(invert), if don't real close to identity its illl ----invert A to see if close to A, if not its ill

Matrix Condition Number

Single Number utilized to indicate if ill conditioned TERM 52

Norm

DEFINITION 52 real-valued function ---provides measure of length of multi component mathematical entities TERM 53

Gauss-Seidel

DEFINITION 53 -solves each equation in a system for a particular variable --- Then uses that value later on in the equation TERM 54

Diagonal Dominance

DEFINITION 54 ---If diaganoly dominant a system will converge TERM 55

Relaxation

DEFINITION 55 Enhancement of convergence utilizing relaxation

matlab std(s)

calculates standard deviation of s TERM 62

Linear-Least Squares regression

DEFINITION 62 Minimize the sum of the squares of the residuals TERM 63

Matlab Polyfit

DEFINITION 63 p=polyfit(x,y, n) ---n=order of polynomial to fit TERM 64

Matlab polyval

DEFINITION 64 ---computes coefficients ----y=polyval(p,x) p=matrix from polyfit TERM 65

Vandermonde matricies

DEFINITION 65 -----ill-conditioned ----due to exponential growth, large round- off errors

Newton-Interpolating polynomial

---Linear Interpolation formula uses similar triangles ---- smaller the interval the better the approximate TERM 67

Lagrange Interpolating Polynomials

DEFINITION 67 --shifts values to express interpolating polynomial TERM 68

Inverse Interpolation

DEFINITION 68 -finding x where f(x) is a certain value TERM 69

Extrapolation

DEFINITION 69 The process of estimating a value f(x) that lies outside the range of the base points --extends curve beyond know region TERM 70

Oscillations

DEFINITION 70 Higher-order polynomials can lead to ill conditioning and may introduce oscillations where there shouldnt be

clamped end conditions

assume 1st derivative at 1st and last knots known TERM 77

'not a knot' end condition

DEFINITION 77 forces continuity of 3rd derivative TERM 78

matlab equation of a spline

DEFINITION 78 yy=spline(x, y, xx) -----performs cubic spline interpolation ----- uses 'not a knot' condition by default TERM 79

interp1 matlab

DEFINITION 79 yi=interpl1(x,y,xi,'method') ---x&y are original data sets ----- xi= contains points at which want to interpolate ----- method=sting containing desired method TERM 80

'Method' in interp

DEFINITION 80 nearest=nearest neighbor interpolation ------linear=connects points with straight line(default) ------spline=not-a-knot cubic interpolation ------pchip=piecewise hermite interpolation

Richardson Extrapolation

Use 2 estimates of an integral to compute a 3rd more accurate approximate TERM 82

Gauss Quadrature

DEFINITION 82 class of techniques for evaluating area under a straight line -- --choose line that minimizes error TERM 83

Gauss-Legendre Formula

DEFINITION 83 optimizes estimates to integrals for functions over intervals from -1 to 1 ------other intervals require a change to -1 to 1 TERM 84

Disadvantages of fixed Quadrature

DEFINITION 84 disadvantage of equal spacing ----functions with regions of abrupt change need small step over entire domain to achieve a certain accuracy TERM 85

Adaptive Quadrature

DEFINITION 85 small steps are taken in regions of sharp variations ------- larger steps where function changes gradually

Matlab's built in functions for

differentiation

diff(x) returns the difference between adjacent elements in x


fx=gradiant (f,h) determines derivative of data in f at each point TERM 92

matlab contour

stuff

DEFINITION 92 contour(x,y,z) generates contour plot TERM 93

Quiver

DEFINITION 93 quiver(x,y,fx,fy) ___generates vector field