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Micro-perforated (MPP) panels are acoustic absorbers that are non-combustible, acoustically tunable, lightweight, and environmentally friendly. In most cases, they are spaced from a wall, and that spacing determines the frequency range where the absorber performs well. The absorption is maximized when the particle velocity in the perforations is high. Accordingly, the absorber performs best when positioned approximately a quarter acoustic wavelength from the wall, and larger cavity depths improve the low frequency absorption. At multiples of one half acoustic wavelength, the absorption is minimal. Additionally, the absorption is minimal at low frequencies due to the limited cavity depth behind the MPP. By partitioning the backing cavity, the cavity depth can be strategically increased and varied. This will improve the absorption at low frequencies and can provide absorption over a wide frequency range.

To attain a reduction in NOx emissions, various aftertreatment technologies are being developed. In addition to the emission control, these systems require fault diagnostic schemes to detect failure and diagnose faults. For detecting faults, one approach is to measure NOx emissions using a NOx sensor that serves the purpose of control and diagnostics for these systems. Moreover, an alternative approach has been developed for Lean NOx Trap (LNT) catalysts which use substrate temperatures for feedback and diagnostics. This paper will exploit both approaches using an experimental setup up.

Process temperature profiles of a two-component rigid poly(urethane-isocyanurate) foam system were studied and compared with the predictions of a one-dimensional numerical simulation. This model is based on experimentally determined thermophysical properties including thermal diffusivity, enthalpy of reaction, and rate of reaction. Temperature profiles were measured at three positions within the foam and at the foam surface for mold temperatures of 25°C and 55°C. High rate of reaction and heat of reaction, along with low thermal diffusivity, cause temperatures near the foam center to be insensitive to mold temperatures for thick samples. Thermal analysis and spectroscopic methods were used for determination of thermophysical properties. Temperature dependent heat capacity was evaluated using dynamic DSC. Reaction kinetics were studied using FTIR and isothermal DSC measurements.