the rst one is to use | w w | <strong>in</strong>stead <strong>of</strong> w w <strong>in</strong> the comput<strong>in</strong>g (see gure 11), n+1 n n+1 n Figure 11: With | w w | n+1 n the second one is to consi<strong>de</strong>r that wn+1 wn has a positive me<strong>an</strong> (<strong>in</strong>stead <strong>of</strong> 0, see gure 12). That is, to <strong>in</strong>troduce a <strong>de</strong>rive vector to the Wiener process i.e. to consi<strong>de</strong>r the equation <strong>in</strong>stead <strong>of</strong> ∂ϕ ∂t ∂w = (1 ϕ) J( u) + b( u, ϕ)( cte + ) , <strong>in</strong> ∂t ∂ϕ ∂t = (1 ϕ) J( u) + b( u, ϕ) ∂w , <strong>in</strong> . ∂t Figure 12: With positive me<strong>an</strong> The shapes <strong>of</strong> the temperature curves are the same as the experimental one (cf. gure 10). But, we do not prove <strong>an</strong>y mathematical results for this stochastic context. An other way to take <strong>in</strong>to account this phenomenon is to modify the <strong>de</strong>term<strong>in</strong>istic mo<strong>de</strong>l by <strong>in</strong>troduc<strong>in</strong>g some convection terms, <strong>in</strong> the above equation, for example. To our knowledge, such a mo<strong>de</strong>l does not actually exist. 28
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