StochProc_2014_04_answers (2)
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Transcript of StochProc_2014_04_answers (2)
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- pi 2014
1. (25) 3 pi pi i pi, i = 1, 2, 3, . 1 . 2 pi . 2 3 1 .() pi pi pi- pi pi .() .() pi 1 , pi pi ;
pi() pi 0 < pi < 1, i = 1, 2, 3. n = 1, 2, Xn pi n- , Xn {1, 2, 3}. Xn = i, i pi pi pi . pi , pi pi pi pi pi pi pi . pi , pi. pi Xn, n = 1, 2, . . . pi pi pi pi:
P =
1 p1 p1 00 1 p2 p2p3 0 1 p3
3
21
1 p1 p1 1 p2
p2
1 p3
p3
1: 1:
() pi pipi, pipi. pipi i, pii > 0, pi. pi pi pi =(pi1, pi2, pi3) pi :
pi1 = (1 p1)pi1 + p3pi3pi2 = (1 p2)pi2 + p1pi1
pi1 + pi2 + pi3 = 1
1
-
pi pi pipi
pi1p1 = pi2p2 = pi3p3
pi1 + pi2 + pi3 = 1.
pi
pi1 =
1p1
1p1
+ 1p2 +1p3
, pi2 =
1p2
1p1
+ 1p2 +1p3
, pi3 =
1p3
1p1
+ 1p2 +1p3
.
() 1 pi ( ) 0 pi , Xn = i,
Rn(Xn, Xn+1) =
{1, pi pi0, pi 1 pi
pi pi i
r(i) = E(Rn(Xn, Xn+1)|Xn = i) = pi. pi pi pi
C =iS
r(i)pii =3i=1
pi
1pi
1p1
+ 1p2 +1p3
=3
1p1
+ 1p2 +1p3
.
2. (30) , pi pi. pi pi p pi 1 p. pi pi pi pi . pi pi pi .() pi pi;() pi pi ;() pi pi pi pi pi pi;
pi: {Xn, n = 0, 1, . . .} pi X0 = 0 Xn n- pi.
pi() Xn n- pi. Xn = 2 2, pi , . Xn = 1, 0, 1 pi pi 1 ( pi 1 p) 1 (pi p). pi, pi , Xn, Xn+1 pi . pi
-2 -1 0 1 21
p
1 p
p
1 p
p
1 p1
2
-
-2 2 pi -1, 0, 1 pi. - pi pi 0 pi -2 2. pi, fi pi i pi -2 2. f1, f0, f1 pi pi , pi pipi pi pi :
f1 = 1 + pf0f0 = 1 + (1 p)f1 + pf1f1 = 1 + (1 p)f0.
pi pi:
f0 = 1 + (1 p) + (1 p)pf0 + p+ p(1 p)f0 = 2 + 2p(1 p)f0 pi
f0 =2
1 2p(1 p)pi pi pi.() pi pi pi pi 2 0. xi pi pi 2 X0 = i. x2 = 0, x2 = 1. x1, x0, x1 pi pi , pi pipipi pi :
x1 = px0x0 = (1 p)x1 + px1x1 = p 1 + (1 p)x0.
pi pi:
x0 = (1 p)px0 + p2 + p(1 p)x0 = p2 + 2p(1 p)x0 pi
x0 =p2
1 2p(1 p)pi pi pi .() pi pi p pi.pi pi pipi pi x0 p. x0 pi:
p2
1 2p(1 p) pp
1 2p(1 p) 1 p 1 2p(1 p) 1 3p+ 2p2 0.
2p2 3p+ 1 1 12 . pi 12 p 1, pi pi pi ( pi pi ).
3. (25) {Xn, n = 0, 1, . . .}
3
-
S = {1, 2, . . . , 7} pi pi pi
P =
14
34 0 0 0 0 0
1 0 0 0 0 0 015
15
15
15
15 0 0
0 1414 0 0
14
14
0 0 0 0 1 0 00 0 0 0 0 0 10 0 0 0 0 1 0
.
() pi pi pipi pi.() pi pi :
limn p
(n)12 , limn p
(n)32 , limn p
(n)17 , limn p
(n)45 , limn p
(n)42 , limn p
(n)34 .
() X0 = 6, pi pi pi pi pi 7;() X0 = 1, pi pi pi pi pi 1;
pi() pi pi pi pi pi:
1
2
3
4
6
5
7
14
34 1
151
5
15
15
1515
14
14
14
14
1
1 1
pi pi pi:
1. C1 = {1, 2} pipi pipi 2. C2 = {5} pi 3. C3 = {6, 7} pipi pipi 4. C = {3, 4} pi pi
4
-
pi pipi, C1 pi pi p11 > 0 C3 pi pi 2.() pipi .
pi C2 pi pi pi pi
pi1 =1
4pi1 + pi2
pi1 + pi2 = 1
pi pi pipi pi1 = 47 , pi2 =37 .
C2 pi pi pi pi 5 pi pi pi5 = 1.
C3 pi pi pi, pi pi pi :
pi6 = pi7
pi6 + pi7 = 1
pi pi pipi pi6 = pi7 = 12 . pi pipi pi pi pi pi
pi pi pi pipi . C1 pi pi x3,C1 , x4,C1 pi -
x3,C1 = p31 1 + p32 1 + p33x3,C1 + p34x4,C1 + p35 0x4,C1 = p42 1 + p43x3,C1 + p46 0 + p47 0
pi
x3,C1 =2
5+
1
5x3,C1 +
1
5x4,C1
x4,C1 =1
4+
1
4x3,C1
pi pi pipi x3,C1 =35 , x4,C1 =
25 .
C2 pi pi x3,C2 , x4,C2 pi -
x3,C2 = p34 1 + p33x3,C2 + p34x4,C2x4,C2 = p43x3,C2
pi
x3,C2 =1
5+
1
5x3,C2 +
1
5x4,C2
x4,C1 =1
4x3,C2
pi pi pipi x3,C2 =415 , x4,C2 =
115 .
C3 pi pi pipi pi :
x3,C3 = 1 x3,C1 x3,C2 = 13
5 4
15=
2
15
x4,C3 = 1 x4,C1 x4,C2 = 12
5 1
15=
8
15.
5
-
pi pi.
pi limn p(n)12 = pi1 =
47 , C1 pipi pi
pipi pi.
pi limn p(n)32 = x3,C1pi2 =
3537 =
935 , pi pipi pi C1
pi pi 2.
pi limn p(n)17 = 0 1 pi
pi C1. pi :
limn p
(n)45 = x4,C2pi5 =
1
15
limn p
(n)42 = x4,C1pi2 =
1
15
limn p
(n)34 = 0,
pi 4 pi.() 6, pi pi pipi C3. pi , pi pi6, pi7 pi pi pi 6 7 , pi pi pi7 = 12 .() 1, pi pi pipi C1, pi pi pi1 = 47 .
4. (30) pi pi pi pi Poisson(). pi pi pi - . X(t) pi t.() {X(t), t 0} .() pi pi Chapman-Kolmogorov pi - pij(t), i, j S.() pi pipi , . ;() 100 pi pi - 1 , pi pi pi pi ; (pi pi pi .)
pi () pi pi pi . pi X(t), t 0 -.
n = , n = 0, 1, . . .. pi n pi
pi pi pi n pi. pi pi - n, n = n, n = 0, 1, 2, . . ..
6
-
0 1 2 n 1 n
() pi Chapman-Kolmogorov :
pi0(t) = pi0(t) + pi1(t), i 0,pij(t) = (+ j)pij(t) + pi,j1(t) + (j + 1)pi,j+1(t), i 0, j > 0
() . pi pi, pi pi, pipi pipi. , pipipipi pi . pipi pi. pi pi {0, 1, . . . , n}, {n+ 1, . . .}, n = 0, 1, . . ., pi
p0 = p1
p1 = p22
pn1 = pnn
pi pi pipi
p1 =
p0, p2 =
2p1 =
2
22p0, . . . , pn =
n
n!np0
pi pn pi pin=0
pn = p0
n=0
n
n!n= 1.
n=0
n
n!n=n=0
(
)nn!
= e
pipi , > 0, pi pi pi pipi
p0 = e
pn = e
(
)nn!
> 0, n = 0, 1, 2, . . .
pi pipi pi. , pi Poisson pi .() pi () pi X(t) t pi Poisson pi . pi
limtE(X(t)) =
.
, = 100 60 = 6000, 1/ = 1, pilimtE(X(t)) = 6000.
7