Environmental Engineering Reference
In-Depth Information
.
f
em..
=.f
ex
.log.t.logP.T.
(6.37)
where:
f
em
.is.the.output.receiving.frequency;
f
ex
.is.the.transmitting.input.frequency;
t.is.a.temperature;
P.is.the.pressure.under.elevation;
T.is.the.period.of.impulse.propagation.
We.input.T.from.Equation.(6.36).and.the.result.is.Equation.(6.38):
k =
f
f
c
em
ex
.
∗
log λ
.
(6.38)
t
The. critical. value. of. the. pressure. p
mn
. can. be. determined. using. Equation.
(6.39),
13
.which.covers.the.conditions.for.covering.stability.
1 2
/
1 2
/
4
2
2
π
g
h
m
k
m
k
(
)
2
4
p
=
D
+
2
D n
+ D n
1
+
δ
.
.
(6.39)
mn
1
3
2
2
h
λ
Here:
K.=.L/h;
δ.is.the.damping.coeficient;
.
D
ij.
is.the.stiffness.of.the.polymer.covered.by.using.PSP's.technique.
3
3
3
=
12
Q
h
12
; D = Q
h
12
; D
h
(
)
.
D = Q
12
+
2
Q ;
.
.(6.40)
1
11
2
22
3
66
Stiffness.constants.Qij.are.determined.from.Equation.(6.41).
Here:
h.is.the.height.of.the.covering;
λ.is.the.wavelength.of.the.cycle.of.ultrasound.wave.propagation.(λ.=.c.T);
g.is.the.density.of.the.polymer.covering;
η.is.the.acceleration.due.to.gravity;
L.is.the.length.of.the.covering;
m.is.the.digital.number.of.the.semiwaves.in.the.x.direction;
n.is.the.digital.number.of.the.semiwaves.in.the.y.direction.
Here:. Q
iknm
.are. the.stiffness.constants.for.components.that. are. satisied. by.
the.symmetrical.conditions:
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