Geoscience Reference
In-Depth Information
Formulas (
2.67
) and (
2.68
) give a recurrent estimation for error. From them it is
possible to obtain an error estimation applicable to the entire interval [t0,T]:
0
,T]:
h
i
hP
1
p
0
k
k
E
k
e
0
ð
1
þ
hp
0
Þ
þ
ð
1
þ
hp
0
Þ
1
;
where the following notations are introduced
;
ð
j
Þ
i
h ¼ max
k
h
k
;
E
k
¼ max
i
;
j
e
ð
t
k
Þ
M ¼ max
i
M
i
;
m
¼ min
s
m
s
;
þ
l
1
s¼1
h
m
1
ðm þ
1
Þ!
;
p
0
¼ mM
h
m
1
m!
h
s
1
s
P
1
¼ M
;
l
¼ max
s
m
s
!
2.12.5.4 Solutions of Equations with Known Moments on the Right Side
Let us consider a particular case of Eq. (
2.49
):
L½y
¼y
ð
n
Þ
þ
X
n
p
i
y
ð
n
i
Þ
¼ f
ð
x
Þ;
x
0
ð
2
:
69
Þ
i¼1
where p
i
is the constant coef
cients,
f(x) is a single-valued and differentiable
function, f(x)
0asx
→
∞
and its moments are known:
→
Z
1
x
m
f
ð
x
Þ
dx
M
m
f
ð
x
Þ
¼
\
1;
m
¼ 0
;
1
; ...;
m
ð
2
:
70
Þ
0
It is necessary to solve the Eq. (
2.69
) with the following initial conditions:
y
ð
s
Þ
ð
x
0
Þ
¼y
ð
s
Þ
ð
s ¼ 0
;
1
; ...;
n
1
Þ
0
We shall approximate f(x) in the following manner:
f
ð
x
Þ
exp
ð
kx
Þ
X
m
a
i
x
i
¼ P
m
ð
x
Þ
exp
ð
kx
Þ;
ð
2
:
71
Þ
i¼0
where m > 0 is an integer, k > 0 and a
i
are constants to be determined. Then, from
(
2.70
) and (
2.71
) we have
"
#
dx ¼
X
Z
1
x
m
exp
ð
kx
Þ
X
m
m
a
i
ðm þ
i
Þ!
k
mþ
i
þ
1
M
m
f
ð
x
Þ
¼
a
i
x
i
i¼0
i¼0
0
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