():
() ____________________
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___________________________________
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7 2
: .
: -, , .
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...
....
........
:
(2.3.)
:
L ......................
d ......................
λ ......................
, ..
S 1 S 2 (. .), d , ( d<<L) 
, 腅, α ...
(. .)
(2.3) d 
.
α (2.3).
a :
(2.4)
.
57 α:
1. l α.
L l,
.
|
|
|
| / | a, | l, | N | D x, | l, | L, |  ,
| d, | <d>, | D d, | e d, % |
| 1 |
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() . ____ _________________________________ ( )
_________ _________________
2. :
N
3. (2.3) 
a:
α = 0 
α = 30 
α = 60 
.
4. (2.4) d :
α = 0 d =
α = 30 d =
α = 60 d=
.
5. :
<d> =
6. d i :
Δd1 =
Δd2 =
Δd3 =
5.
6. α (0,9 0,95)
tα = α =
7. :
∆d = tαSd =
8. 
.
.. ..
.
....
,
. .
..
,
.
.
α ...
.
.
:
充.
.....
