aug_moisture — Water-activity and moisture-band perturbation

Group: Augmentation · C ABI: n4m_augmentation_moisture_*

Description

Water activity and moisture-content spectral perturbation.

Parameters

Name

Type

Default

water_activity_delta

float

0.0

use_aw_range

bool

False

aw_low

float

0.0

aw_high

float

1.0

reference_water_activity

float

0.5

free_water_fraction

float

0.3

bound_water_shift

float

25.0

moisture_content

float

0.1

enable_shift

bool

True

enable_intensity

bool

True

wavelengths

—

None

rng

Optional[PCG64]

None

seed

int

0

API and bindings

C ABI (ABI 2): n4m_augmentation_moisture_apply · n4m_augmentation_moisture_create · n4m_augmentation_moisture_destroy. Use the linked public header for the exact signature, configuration, and result handles.

Python (verified public re-export):

from n4m.augmentation.instrument import MoistureAugmenter

Source signature: MoistureAugmenter(water_activity_delta: float = 0.0, use_aw_range: bool = False, aw_low: float = 0.0, aw_high: float = 1.0, reference_water_activity: float = 0.5, free_water_fraction: float = 0.3, bound_water_shift: float = 25.0, moisture_content: float = 0.1, enable_shift: bool = True, enable_intensity: bool = True, wavelengths = None, rng: Optional[PCG64] = None, seed: int = 0).

R: no current source-verified entry point was found for this catalog method.

MATLAB / Octave: no current source-verified entry point was found for this catalog method.

Explanations

Bibliographic source

No canonical paper specifies this combined sigmoid/free-bound-water model. It is an internal heuristic with source-defined 1435 and 1930 wavelength bands.

Mathematical principle

Set water activity \(a_w=\operatorname{clip}(a_{ref}+\Delta a,0,1)\), with fixed or uniformly drawn \(\Delta a\). A sigmoid allocates free versus bound water. Bound fraction shifts windows around 1435 and 1930; optional intensity adds Gaussian band profiles scaled by moisture_content/0.10 - 1 and the row mean magnitude.

Appropriate uses

Sensitivity studies for water-band displacement and amplitude changes in moist materials.

Limits and validation

Band centers assume compatible wavelength units and coverage. The model is qualitative, not a calibration from water activity or moisture percentage to absorbance.

Implementation

Python role API n4m.augmentation.instrument.MoistureAugmenter; ABI 2 family n4m_augmentation_moisture_{create,apply,destroy}.

The ABI-2 implementation is the n4m_augmentation_moisture_* lifecycle in libn4m.

Sources and provenance

https://github.com/GBeurier/nirs4all-methods/blob/main/cpp/src/core/augmentation/environmental/moisture.h

See also: methods index · interactive dashboard