No abstract

Calibration maintenance is an important aspect of multivariate calibration. With spectral measurements, the goal of calibration maintenance involves sustaining the predictability of a primary calibration model in new secondary conditions. Among the many methodologies, penalty‐based Tikhonov regularization variants have been successful by sample augmenting primary calibration data with a matrix of just a few secondary samples as well as operating with an additional sparse penalty to include wavelength selection. Studied in this paper is a new sample‐wise (local) Tikhonov regularization–based penalty calibration approach. Penalized is a diagonal matrix with the residual vector (relative to the primary calibration space) of the new secondary sample. Thus, the same full calibration set is used for each new sample. Changing for each secondary sample is the corresponding sample‐wise residual vector on the penalized diagonal matrix. The intent of the presented approach is to form sample‐wise regression vectors desensitized to characteristics of the new sample not present in the primary calibration set. The more distinct the secondary conditions are relative to the primary conditions, the more unsuccessful this local model updating becomes. Proposed is a sample‐wise outlier mechanism to discern when the residual penalty can or cannot be used to form a useful updated model. The residual penalty modeling and outlier detection processes require tuning parameter optimizations. A fusion approach is used to automatically select tuning parameter values. Simulated and near‐infrared data are evaluated, demonstrating the applicability of the method.

No abstract

Active materials couple a stimulus (electrical, magnetic, and thermal) with a mechanical response. Typical materials such as piezoelectrics strain as bulk materials to the stimuli. Here we consider an undulation created by heterogeneous deformation within a magnetic shape memory alloy (MSM) transducer. We study the mechanical response of an MSM element vs two surface treatments: a polished state with minimal surface stresses, and a micropeened state with compressive surface stress. The polished element had a sharp-featured, faceted trough shape. The micropeened element had a smooth trough shape and an additional crest. The undulation was created by a rotating localized magnetic field, which caused heterogeneous variation of the twin-microstructure. For the polished and micropeened elements, the twin-microstructures were coarse and fine, respectively. For the polished element, the undulation moved by the nucleation of a few twin boundaries, which traveled along the entire element. For the micropeened sample, the twin boundaries moved back and forth over a short distance, thereby creating a dense twin lamellar, which formed the trough. The motion of the lamellar approximated the single thick twin while allowing additional degrees of freedom due to increased mobile interface density and different initial conditions of domain volume fraction. The dense twin microstructure also smoothed the magnetic flux pattern. The undulation amplitude was about 40 µm for the sample in both treatments.