Transforms¶

The Transform page provides data transformation tools for rheological analysis.

Available Transforms¶

Mastercurve (Time-Temperature Superposition)¶

Shift multi-temperature data to a reference temperature:

Usage:

Load datasets at different temperatures
Select Mastercurve transform
Set reference temperature
Choose shift method (auto or manual)
Apply transform

Parameters:

Reference Temperature: T_ref in °C or K
Auto Shift: Automatic shift factor calculation
Manual Shifts: Enter known shift factors

Output:

Mastercurve at T_ref
Shift factors (a_T)
Williams-Landel-Ferry (WLF) fit (if applicable)

FFT (Fourier Transform)¶

Convert between time and frequency domains:

Usage:

Select time-domain dataset
Choose FFT transform
Configure window and padding
Apply transform

Parameters:

Window: Hanning, Hamming, Blackman, None
Zero Padding: Extend data for resolution
Nyquist Warning: Alert for aliasing

Output:

Frequency-domain G*(ω)
\(G'(\omega)\) and \(G''(\omega)\)

IFFT (Inverse Fourier Transform)¶

Convert frequency to time domain:

Usage:

Select frequency-domain dataset
Choose IFFT transform
Apply transform

Output:

Time-domain G(t)

Derivatives¶

Numerical differentiation:

Usage:

Select dataset
Choose Derivative transform
Select order (1st or 2nd)
Choose method

Parameters:

Order: 1 (first derivative), 2 (second derivative)
Method: Central difference, Savitzky-Golay
Smoothing: Window size for noise reduction

Output:

dG/dt or d²G/dt²

SRFS (Strain-Rate Frequency Superposition)¶

Collapse flow curves at different shear rates:

Usage:

Load datasets at different shear rates
Select SRFS transform
Set reference shear rate
Apply transform

Parameters:

Reference Rate: γ̇_ref
Power Law Exponent: For scaling

Output:

Master flow curve
Shift factors

Using Transforms¶

Basic Workflow¶

Navigate to Transform page
Choose a transform from the sidebar list. Single-dataset transforms (FFT, IFFT, Derivative) act on the application’s active dataset; for multi-dataset transforms (Mastercurve, SRFS) check the datasets to include from the dataset checklist
Configure parameters in the auto-generated form
Review the live before/after preview, which updates automatically as you change parameters
Click Apply Transform to commit the result as a new dataset

Transform Preview¶

Before applying:

View the before/after transformed data plot (updates automatically, debounced, as parameters change)
Check data ranges
Verify expected behavior
Adjust parameters if needed

Transform History¶

All transforms are tracked:

Source dataset
Transform type
Parameters used
Timestamp
Random seed (if applicable)

This enables reproducibility and audit trails.

Chaining Transforms¶

Apply multiple transforms sequentially:

Apply the first transform (result is added as a new dataset and becomes active)
Select the new dataset if it isn’t already active
Apply the next transform
Repeat as needed

Transform Parameters¶

Mastercurve Settings¶

Shift Method:

Auto WLF: Automatic WLF fit
Auto Arrhenius: Automatic Arrhenius fit
Manual: User-specified shift factors

Overlap Region:

Minimum overlap decades for shifting
Default: 0.5 decades

Optimization:

JAX-accelerated shift optimization
Multi-start for robustness

FFT Settings¶

Windowing:

Reduces spectral leakage
Hanning recommended for most cases

Padding:

Zero-padding increases frequency resolution
Powers of 2 for efficiency

Detrending:

Remove DC offset
Linear detrend option

Derivative Settings¶

Method Comparison:

Central Difference: Fast, sensitive to noise
Savitzky-Golay: Smoother, preserves features

Window Size:

Larger = smoother, less detail
Smaller = noisier, more detail
Odd numbers only

Output Handling¶

New Dataset¶

Transforms create new datasets:

Original preserved
Transform result added to dataset list
Naming: original_name_transform

Metadata¶

Transformed datasets include:

Source dataset reference
Transform parameters
Provenance chain

Export¶

Export transformed data:

Select transformed dataset
Go to Export page
Choose format

Tips and Best Practices¶

Mastercurve¶

Ensure sufficient temperature range
Check for thermorheological simplicity
Use auto-shift first, then refine
Validate WLF parameters against literature

FFT¶

Use windowing to reduce artifacts
Ensure time data is evenly spaced
Check Nyquist frequency
Zero-pad for smooth spectra

Derivatives¶

Always smooth noisy data first
Start with larger windows
Compare methods on same data
Validate against known solutions

SRFS¶

Verify power-law scaling behavior
Check for shear banding (discontinuities)
Use consistent strain amplitudes