Kurs_vysshei_matematiki_UP_Berkov_N.A._2007-2
.pdf
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u x=0 |
= 0, |
∂x |
x=l |
= |
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, |
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t = 0 |
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t = 0 |
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ESux(x, 0) = P u (x, 0) = |
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x |
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ux(x, 0)dx = |
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x u(x, 0) − u(0, 0) = |
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x. |
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ES |
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0 |
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u(0, 0) = 0 |
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u(x, 0) = |
= u|t=0 = |
P |
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x |
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ES |
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ut|t=0 = 0. |
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P |
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U |t=0 = |
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x, ut|t=0 |
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ES |
σ Θ σ1
Θ + dΘ
Θ(x, t)
σ σ1
σ σ1 σ
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σ |
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σ1 |
dσ |
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L |
r |
dθ |
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K |
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K |
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r |
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x1=x+dx |
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0 |
θ |
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x |
θ |
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l |
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L |
R |
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L |
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θ |
x |
α |
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K |
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K |
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K |
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γ |
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dσ r
τ KK KL
= ·
τ G L KK G
= tg = | |
L KK L KK L K /dx.
|K L | ≈ | K L | = rdΘ
≈ Θ
L KK rd /dx.
τ τ = Gr ddxΘ .
dσ
τ dσ = Gr ddxΘ dσ.
dMx dσ
dMx = rτ dσ = Gr2 ddxΘ dσ.
Ml = 0 GJ0 ∂x |
x=l |
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Ml |
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x=l = 0. |
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= 0 ∂t |
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∂Θ |
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∂Θ |
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x |
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∂Θ |
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Θ|t=0 = α |
l |
, |
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∂t |
t=0 |
= 0. |
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Θ|x=0 = 0, |
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∂x x=l = 0. |
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∂Θ |
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J1
α
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Θ|x=0 = 0 |
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Ml |
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∂2Θ |
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GJ |
∂Θ |
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+ J |
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∂2Θ |
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J1 |
= ∂t2 |
x=l |
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0 |
∂x x=l |
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1 |
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∂t2 x=l |
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∂Θ |
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∂2Θ |
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Θx=0 = 0, GJ0 |
∂x |
x=l + J1 |
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∂t2 |
x=l |
= 0. |
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x :
−∞ < x < ∞
ξ = x − at η = x + at
∂2u
∂ξ∂η
= 0,
u(ξ, η) = F (ξ) + (η)
x t u(x, t) = F (x − at) + (x + at).
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F (x−at) |
F (x) |
at |
a |
(x + at) |
(x) |
a |
t = 0 |
u = F (x) + (x) |
F (x − at) |
a |
(x + at)
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U |
F(x) |
F(x-at) |
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Φ (x+at) |
Φ(x) |
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F(x-at)+ Φ (x+at) |
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x |
F(x-at)+ Φ (x+at) |
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F(x-at)+ Φ (x+at) |
F
u(x, 0) = F (x) + (x) = ϕ(x).
ut(x, t) = −aF (x − at) + a (x + at), ut(x, 0) = −aF (x) + a (x) = ψ(x)
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z |
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x |
x ψ(z)dz = −a x F (z)dz + a x |
(z)dz = −a |
F (x) − F (0) |
+ |
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0 |
0 |
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+a( (x) − (0)) = a ( (x) − F (x)) − aC, |
C = (0) − F (0). |
t = 0; 0.1; 0.2; 0.4; 0.6 1.0