Hyperspectral imaging of art: Acquisition and calibration workflows

Abstract

Hyperspectral imaging has become an increasingly used tool in the analysis of works of art. However, the quality of the acquired data and the processing of that data to produce accurate and reproducible spectral image cubes can be a challenge to many cultural heritage users. The calibration of data that is both spectrally and spatially accurate is an essential step in order to obtain useful and relevant results from hyperspectral imaging. Data that is too noisy or inaccurate will produce sub-optimal results when used for pigment mapping, the detection of hidden features, change detection or for quantitative spectral documentation. To help address this, therefore, we will examine the speci c acquisition and calibration work ows necessary for works of art. These work ows includes the key parameters that must be addressed during acquisition and the essential steps and issues at each of the stages required during post-processing in order to fully calibrate hyperspectral data. In addition we will look in detail at the key issues that a ect data quality and propose practical solutions that can make signi cant di erences to overall hyperspectral image quality.

FTIR analysis of transient CO2 emissions in a circulating fluidized bed boiler

“…The devolatilization time obeys a power law relationship tv=adi^ (Eq. 2.58) for particles greater than 3.0 mm initial diameter, which corresponds to the work of previous researchers [16,17,25,50,51,52,54]. For dia, mm Figure 6.2: Plot of devolatilization time vs initial particle diameter for laboratory test.…”

“…2.29). Various researchers [16,17,25,50,51,52,54] have shown that the devolatilization time, tv, can be expressed as a power law relationship with initial diameter, Eq. 2.58.…”

“…Ragland and Weiss [52] observed both a and v to be equal to 1.5 for particles 2 to 12 mm in diameter. Other researchers [50,51,52] have found v to vary from .3 to 1.8 depending on coal type for particles less than 8 mm. Essenhigh [25] tested 10 coals from 3/16*' to 52 mesh (295 ^m) diameter one at a time in stagnant air between two heating plates.…”

“…This would indicate, for constant Sh and diffusion control, that Tq varies as the square of the initial diameter. Pillai [50] and Basu [4] observed char burning-initial particle diameter power laws between 1 and 2. They attributed this behavior to the combined effects of chemical kinetics and mass transfer.…”

“…Pillai [50] used the same power law relationship for 6-15 mm diameter particles in a 100 mm diameter fluidized bed. His bed had a relatively low 13% O2 concentration at the inlet (compared to 21% for Prins et al [51]) with fluidizing velocity of 1.2 m/s.…”