tese de doutorado utilização de técnicas ... - Pfi.uem.br - UEM
tese de doutorado utilização de técnicas ... - Pfi.uem.br - UEM
tese de doutorado utilização de técnicas ... - Pfi.uem.br - UEM
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s<<strong>br</strong> />
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sl<<strong>br</strong> />
s<<strong>br</strong> />
−<<strong>br</strong> />
⎛ l<<strong>br</strong> />
⎛<<strong>br</strong> />
s ⎞ I0<<strong>br</strong> />
β ( b + 1)(<<strong>br</strong> />
r −1)<<strong>br</strong> />
e − ( b −1)(<<strong>br</strong> />
r + 1)<<strong>br</strong> />
e + 2(<<strong>br</strong> />
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θ ⎜ ⎟ =<<strong>br</strong> />
⎜<<strong>br</strong> />
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⎝ 2 ⎠ σ − ⎝ g + b + e − g − b − e<<strong>br</strong> />
s ks<<strong>br</strong> />
( r 1)<<strong>br</strong> />
( 1)(<<strong>br</strong> />
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Absorção traseira<<strong>br</strong> />
s<<strong>br</strong> />
β<<strong>br</strong> />
ls<<strong>br</strong> />
⎞<<strong>br</strong> />
⎟<<strong>br</strong> />
⎠<<strong>br</strong> />
(2.15)<<strong>br</strong> />
Para a iluminação da face traseira, consi<strong>de</strong>rando a absorção homogênea a expressão é:<<strong>br</strong> />
E a fonte <strong>de</strong> calor para esta absorção é:<<strong>br</strong> />
I(<<strong>br</strong> />
z)<<strong>br</strong> />
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f ( z)<<strong>br</strong> />
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k<<strong>br</strong> />
s<<strong>br</strong> />
l s<<strong>br</strong> />
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⎛ ls<<strong>br</strong> />
⎞<<strong>br</strong> />
−β<<strong>br</strong> />
⎜ + z ⎟<<strong>br</strong> />
⎝ 2 ⎠<<strong>br</strong> />
A integração da eq. (2.14) nos limites da espessura da amostra, dá a oscilação térmica<<strong>br</strong> />
<strong>de</strong>vida á iluminação traseira<<strong>br</strong> />
⎛ ls<<strong>br</strong> />
θ ⎜<<strong>br</strong> />
⎝ 2<<strong>br</strong> />
⎞<<strong>br</strong> />
⎟<<strong>br</strong> />
⎠<<strong>br</strong> />
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sls<<strong>br</strong> />
− βls<<strong>br</strong> />
I 0 β ⎛ [( b + 1)(<<strong>br</strong> />
r + 1)<<strong>br</strong> />
e − ( b −1)(<<strong>br</strong> />
r −1)<<strong>br</strong> />
e ] e − 2(<<strong>br</strong> />
b + r)<<strong>br</strong> />
⎞<<strong>br</strong> />
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⎜<<strong>br</strong> />
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σ sls<<strong>br</strong> />
−σ<<strong>br</strong> />
sls<<strong>br</strong> />
σ − ⎝ g + b + e − g − b − e<<strong>br</strong> />
s k s ( r 1)<<strong>br</strong> />
( 1)(<<strong>br</strong> />
1)<<strong>br</strong> />
( 1)(<<strong>br</strong> />
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⎠<<strong>br</strong> />
Absorção superficial<<strong>br</strong> />
)<<strong>br</strong> />
(2.16)<<strong>br</strong> />
No caso <strong>de</strong> uma amostra fortemente absorvedora, as equações anteriores são<<strong>br</strong> />
simplificadas. Neste caso temos β>>as e βl>>1. A absorção superficial é consi<strong>de</strong>rada como<<strong>br</strong> />
uma função <strong>de</strong>lta “δ”, para uma profundida<strong>de</strong> z0. Assim, a fonte <strong>de</strong> calor passa a ser escrita<<strong>br</strong> />
por<<strong>br</strong> />
I 0β<<strong>br</strong> />
s<<strong>br</strong> />
f ( z)<<strong>br</strong> />
=<<strong>br</strong> />
− δ ( z0<<strong>br</strong> />
)<<strong>br</strong> />
k<<strong>br</strong> />
s<<strong>br</strong> />
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