Updating D_time

self.D_time[filename] was defined such that, even though it didn't start until one data point after the valve opened, the first data point was set such that t=0. Now, the first time in the PP tab is set to one timestep after zero, which generates better fits that has the additive time constant approximately equal zero.

This commit brings mimics a similar commit made to HyPAT v2.0 yesterday.

HyPAT/source_code/permeation_plots.py

@@ -1052,7 +1052,7 @@ def calculate_diffusivity(self, filename, data):
             (R * (self.Tg_mean.loc[self.t0[filename] + 1:self.tss[filename] + self.ss_range[filename]].to_numpy() +
                   self.storage.standard_temp) * self.A_perm.get())
         self.D_time[filename] = data.loc[self.t0[filename] + 1:self.tss[filename] + self.ss_range[filename], 't'] - \
-            data.loc[self.t0[filename] + 1, 't']
+            data.loc[self.t0[filename], 't']
         J0 = np.mean(data.loc[self.t0[filename] - self.leak_range[filename]:self.t0[filename] - 1, 'dSecP']) * \
             self.volume.get() / (R * self.Tg0[filename] * self.A_perm.get())  # leak rate
         Jinf = np.mean(data.loc[self.tss[filename] + 1: