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Independent Increments - Stochastic Structural Dynamics - Lecture Slides, Slides of Structural Analysis

Main points of this lecture are: Independent Increments, Properties of Processes, Stationary Independent Increments, Functional Equation, Gaussian Random Process, Autocorrelation and Cross Correlation, Rate of Upcrossing of Level, Spectral Moments

Typology: Slides

2012/2013

Uploaded on 04/24/2013

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Download Independent Increments - Stochastic Structural Dynamics - Lecture Slides and more Slides Structural Analysis in PDF only on Docsity!

Problem solving session-

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Discussion on properties of processes withIndependent increments

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   

^

^

^

^

^

^

^

^

 

 

^

^

^

 

 

^

 

^

^

 

^

 

 

 

  Let

stationary increments

We get the functional equation

(^
)^

is the solution.

Given

f t

X^

t

f t

X^

t^

X

f^

t^

s^

X^

t^

s^

X
X^

t^

s^

X^

s^

X^

s^

X
X^

t^

s^

X^

s^

X^

s^

X
X^

t^

X^
X^

s^

X

f t

f^

s

f t

s^

f t

f^

s

f^

t^

ct f^

X^

c

X^

t^

t

^

^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^

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^

 

 

^

^

^

^

^

^

^

^

 

 

^

^

^

 

 

^

 

^

^

 

^

^

^

 

 

   

 

Let

Var

Var

Var

Var

Var

Var

Var

Var

Var

stationary increments 1

Var

g t

X^

t

g t

X^

t^

X^

t^

X

g t

s^

X^

t^

s^

X
X^

t^

s^

X^

s^

X^

s^

X
X^

t^

s^

X^

s^

X^

s^

X
X^

t^

X^
X^

s^

X

g t

s^

g t

g s

g t

ct

g^

X
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^
^

 

2

2

2

Var

c

X^

t^

t

^
^

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^

^

^

^

^

^

^

^

^

2

2

2

2

Var^2

Var

Var

2COV

,

X

t^

X

s

X

t^

X

s^

X

t^

X

s

X

t^

X

t^

X

s^

X

s

X

t^

X

t^

X

s^

X

s

X

t^

X

t^

X

s^

X

s

X

t^

X

s^

X

t^

X

s

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

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^

^

^

^

^

2

2

2

COV

,

1

-Var

+Var

+Var

2

(^

)^

assuming that

2 COV

,^

min

,

X

t^

X

s

X

t^

X

s^

X

t^

X

s

t^

s^

t^

s^

s^

t^

s

X

t^

X

s^

t s

^

 

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

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^

^

2

2 2

2

2

2

0

2

2

2

2

2

2

2

2

2

2

4

2

4

4

2

exp -

;-

2

2

exp -

2

2

exp -

2

2

exp -

3

2

2

X

XX

X

X

X

X

X

X

S

d

d d





 

 

 



     

^

 

 

^

^

^

^

^

 ^

^

^

^

^

^

  

Spectral moments

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^

 ^

^

^

 

^

^

^

^

^

2

2 2

2

2 2

2

2

2

Autocorrelation function

exp -

;-

2

2 1

exp -

exp

2

2

2

=^

exp

2

Recall:

1

X

XX

X

XX

X

m^

n

n^

XX

m^

n

m^

n

S R

i^

d

d^

R

X

t^

X

t^

d





  

 

^

^

 

 

^

^

 

^

^

^

^



^

 ^

^

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^

 

^

^

^

^

^

^

^

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

exp

2

exp

2

exp

2

exp

2

exp

1

2

XX

X

XX

X

XX

X X

X

R d

R d d

R d

 

^

^

 

^

 

 

^

 

 

 

 

 

^

^



^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

 

^

^

^

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^

^

^

^

^

^



^

^

2

2

2

2

2

2

2

2 3

2

2

2

2

2

2

2

3

2

2

2

2

2

2

2

2

2

2

4

3

exp

exp

exp

exp

XX

X

XX

X X

X

d^

R

d d

R

d

 

^

 

 

 

^

 

 

 

 

 

 

 

 

 

 

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

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^

 

^

^

^

^

^

^

^

^

^

^

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2 3

2

2

2

2

2

4

3

3 4

2

2

2

2

2

4

2

6

4

4

exp

exp

exp

exp

exp

XX

X

XX

X

XX

X

XX

X

XX

X

R d

R

d d

R

d d

R

d d

R

d

 

^

^

 

^

 

 

^

 

 

 

^

 

 

 

 

^

 

^

 

 

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

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-^

-1.

-^

-0.

0

1

2

(^43210) -1 -

tau

acf

processderivative

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^

^

^

 

^

PDF of time for first crossing of levelFor high levels of crossings we can approximatethe number of times the level is crossed as a Poissonrandom variable.

exp

;^

k

T

P^

N

T^

k^

T^

k

k

n^

t

^

^

^

^

^

^

^

^

^

^

 

^

2 2

2 2

exp

First passage time

P^

No points in 0 to T

exp

exp

exp

;^

f

X

f

f T

a^

a

T

T^

T^

P^

P^

N^

T

T^

a

P^

t^

T^

T

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

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^

^

^

2

2

2

3

1

2

3

2

2

3

2

2

1

2

1

2

2

2

3

2 1

1

Average rate of peaks above level

,^

[^

exp

exp

]

x

m

t^

S^

x

S

x

x^

erf

dx

S

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

^

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