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Tabbed Window: Data Fitting

Tabbed Window: Data Fitting

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Tabbed Window: Data Fitting

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Ribbon Bar: Menu Commands

During the download of the video clip the scrolling of this page may be disabled!
 

<%EXTOGGLE%>Command Group: Fitting Project

 

Command: Edit
Opens a property sheet for defining the mechanism and the thermodynamic/kinetic parameters used by the fitting procedure as starting parameters. The appearance of the individual property pages is identical with that raised by the Edit-command on the Tabbed Window:Simulations.  However, when closing the property sheet with OK the Run command is automatically executed and the current curve simulated on the basis of the entered mechanism and parameters is shown in the client area together with the current curve of the active experiment. This enables the user to check how well the experimental current curve can be approximated on the basis of the entered mechanism and starting parameters.
For this purpose the parameters edited on the Property Page:Simulation Parameters will be overwritten by those imported from the active experiment. In other words, when working in the Tabbed Window: Data Fitting the Property Page: Simulation Parameters is mainly provided only for viewing the simulation parameters imported by the active experiment. Only the Level of Multi-Core CPU-support or a modification of parameters belonging  to the groups Model Parameters, 2D-Simulation and FEM-Simulation is not reset when closing the property page. Please read Ribbon Bar Command: Edit for more details.

tipbulbIf the fitting project is empty (for instance after executing the Delete command) a new simulation object is automatically generated before opening the CV-Properties sheet. This simulation object is automatically filled with the Chemical Reactions and Charge Transfer Reactions entered for the active simulation on the Tabbed Window: Simulations.

 

Command: Run
Runs a fixed-grid simulation for the specified mechanism and starting parameters and compares the simulated current curve with that referring to the active experiment.

Command: Adaptive Grid Simulator
Runs an adaptive-grid simulation for the specified mechanism and starting parameters and compares the simulated current curve with that referring to the active experiment.

 

Command: Pause
Pauses or continues the currently running simulation or data fitting procedure.

Command: Break
Breaks  the currently running simulation or data fitting procedure.
 

Command: Delete
Deletes the fitting project and resets the mechanism and the starting parameters to "initial state" (i.e. both mechanism and the starting parameters are taken from the active simulation).

 

Command: Run Data Fitting
Starts the fitting procedure for the entered mechanism using the entered thermodynamic and kinetic constants as starting parameters. The parameters selected for being optimized are systematically varied by the fitting procedure such as to minimize the standard deviation between simulated and experimental current curves. The optimization of the parameters is done iteratively. It starts by showing the active experiment together with its simulated counterpart in the client are of the tabbed window. Then the next experiment will be compared with the simulated counterpart. If the comparison has been shown for all experiments involved in the Tabbed Window:Experiments an improved parameter set  is computed from the effect of the parameter variation on the standard deviation. The improved parameter set is  used then in the next iteration. The fitting procedure ends after a predefined number of iterations or if the improvement of the standard deviation obtained with the new parameter set remains below a predefined level in two successive iterations.
 

Command: Circles
The simulated current curve is plotted in the form of open circles. This setting remains active when the fitting procedure is running.

Command: Filled Circles
The simulated current curve is plotted in the form of filled circles. This setting remains active when the fitting procedure is running.

Command: Min/Max Info
Shows the E-I-couple referring to the minimum/maximum found in a rectangle of the screen display drawn by mouse.

Command: Next Scan Segment
Activates the next scan segment If the active simulation consists of more than one.

<%EXTOGGLE%>Command Group: Data Exchange

Command: Copy
Copies the active simulation and puts the copy on the clipboard.

Command: Select Couple
If data fitting has successfully succeeded, this command can be used for adding the selected couple to the couples shown on the Tabbed Window: Compare Curves

Command: Export
Exports the active simulation in use-format and stores the use-file on hard disk.

<%EXTOGGLE%>Command Group: Display

Command: Next
If data fitting has successfully succeeded, this command can be used for showing a comparison between simulated and experimental current curve for the next couple.

Command: Previous Couple
If data fitting has successfully succeeded, this command can be used for showing a comparison between simulated and experimental current curve for the previous couple.

 

Command: Zoom
Zooms the screen display by pressing down the left mouse button and draw a rectangle around the region which is to be zoomed. The zoom command can be repeatedly applied.

Command: Unzoom
Undo the zoom command.

Command: Refresh Screen
Removes Min/Max-Info and redraws the screen display.

<%EXTOGGLE%>Summary: Play Movie: Part 1

Topics

Creating and Running a Data Fitting Project having the experimental CVs stored in use-file format.

Import of use-files

Defining mechanism and starting parameters

Selecting parameters for being optimized by the fitting procedure

Running the fitting procedure

Viewing info such as standard deviation and the currently used parameter set while fitting procedure is running

 

<%EXTOGGLE%>Summary: Play Movie: Part 2

Topics

Creating and Running a Data Fitting Project having the experimental CVs stored in a third-party ASCII-file format (txt, dat, etc.).

Defining a template mechanism used for importing the experimental data

Customizing the import filter with respect to the structure of the ASCII files which are to be imported

Importing experimental target curves

Modifying parameters which are not imported from the ASCII files or which are different from those in the template mechanism

Defining the final mechanism and the starting parameters

Selecting parameters for being optimized by the fitting procedure

Running fitting procedure

Viewing info such as standard deviation and the currently used parameter set while fitting procedure is running

<%EXTOGGLE%>Summary: Play Movie: Part 3

Topics

Creating and Running a Data Fitting Project using simulated CVs as target curves.

The scenario shown in the video clip is the following one:

oSimulated CV are used to mimic real experimental CVs  for a simple charge-transfer mechanism measured at a disk electrode of 1 mm diameter without IR-compensation. The uncompensated ohmic resistance is assumed to be Ru = 300 Ohm.

oThe simulated CVs are used then as target curves in a data fitting project but the experimental parameters associated with each curve were modified in such a way that the curves pretend to refer to experiments not containing any IR-drop.

oIt is investigated then which combination of CT-parameters and diffusion coefficient is found by the fitting procedure to compensate the neglected IR-drop in the best possible way.

oIn the next step the experimental parameters associated with each curve are modified in such a way that the fitting procedure is going to approximate a "real" (two-dimensional) disk electrode by a equally-sized planar electrode for which only the diffusion perpendicular to the electrode surface is taken into account. (Such an approximation might be necessary in the case of complex mechanisms comprising several second-order chemical reactions where 2D-simulations can become very time consuming.)

oThe parameter errors effected by such an approximation are investigated again.