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An approach for wavelength characterization whereby dynamic Fresnel zone plate (FZP) patterns are written to a digital micromirror device (DMD) and used to focus incoming light onto a camera is proposed. The incoming wavelength is then assessed by scanning the focal length. Rectangular basis Zernike modes are implemented to match the rectangular geometry of the DMD, we believe for the first time. A procedure is developed to correct for inherent aberrations of the optical system by adjusting the Zernike mode amplitudes, thus improving focal spot quality. The aberration corrected FZPs are used to assess the focusing conditions needed for four lasers of different visible wavelengths ranging from blue (405 nm) to near infrared (760 nm). The system is able to produce focused beams with a width of twice the diffraction limit and achieve a wavelength resolution of 3 nm. The operational wavelength of the system is ultimately limited by the spectral bandwidth of the detector.

Transient behaviour of solid oxide fuel cells during various stages of operation, such as warmup, startup, load fluctuations, and shutdown, must be understood and predicted in order to design an efficient controller and prevent degradation/failure of the cell. The difficulty of measuring and monitoring solid oxide fuel cell thermal features necessitates an evaluation of the solid oxide fuel cell thermal dynamics using a hybrid tool that integrates both experimental and numerical methods. In this study, a hybrid measurement tool consisting of a quasi-two-dimensional microscale model and a test rig was used to investigate the solid oxide fuel cell thermal dynamics. Through the hybrid experiment-model approach, steady-state temperature differences across Positive-Electrolyte-Negative and along fuel flow direction were captured. Additionally, the speed of temperature difference change was estimated in two dimensions, which is crucial when estimating transient thermal stresses. Several thermal measures were used to evaluate the thermal dynamics of solid oxide fuel cells. The impact of the operating voltage regime on solid oxide fuel cell thermal dynamics was studied using the varying operating voltage (Voltage Interrupted Measurement) characterisation approach. The outcomes revealed that optimising the performance of solid oxide fuel cells requires a trade-off between thermal management and fuel utilisation due to the exponential effect of fuel utilisation on steady-state temperature differences. The effects of fuel humidity and oxygen content of the oxidant flow on solid oxide fuel cell thermal dynamics were also examined. The results shed light on the new aspects of fuel cell thermal dynamics that are key in designing future smart controllers.