The relationship between the molecular aggregation structures and the optical properties of fully aromatic and semialiphatic polyimide (PI) films were analyzed by synchrotron wide-angle X-ray diffraction (WAXD), infrared absorption, and UV/visible absorption spectroscopy at very high pressures up to 8 GPa. The PIs showed significant reduction in the interchain distances in the first stage of compression up to 1 GPa, which resulted in an appreciable decrease in the interchain free volume. In addition, reduction in the C−C bond lengths of aromatic rings by ca. 0.7% was confirmed by the pressure-induced high wavenumber shift of the infrared stretching vibration of the PIs. Furthermore, pressure-induced bathochromic shifts were observed in the locally excited (LE) absorption band of PIs, which are related to the enhanced van der Waals interaction caused by the reduced interchain distances. The intensity of the charge transfer (CT) absorption band of s-BPDA/PDA poly(p-phenylene biphenyltetracarboximide) PI was reduced up to 0.3 GPa, indicating that conformational changes affect the intramolecular CT interactions. In contrast, the CT absorptions of PMDA/ODA (poly(4,4′-oxidiphenylene pyromelliticimide) and PMDA/DCHM (poly(4,4′-diaminocyclohexylmethane pyromelliticimide) PIs were enhanced by increasing the pressure, which was caused by an enhancement of intermolecular CT interactions. The significant variations observed in the LE and intermolecular CT bands below 1 GPa accord with the significant decrease in the interchain distance, as indicated by synchrotron WAXD.

This study proposes a track condition monitoring technique using car-body acceleration that can be easily measured by an in-service vehicle for the sake of an increase in safety of railway transportation. This paper demonstrates the possibility of estimating track irregularities of conventional railway tracks using car-body acceleration only. The methodology proposed uses inverse dynamics to estimate track irregularity from car-body acceleration, applying a Kalman filter to solve this problem. This technique estimates the track irregularity in the longitudinal plane (track geometry and 10m-chord versine). The Kalman filter is able to apply to inverse analysis by expressing track geometry as a random walk model, and incorporating the model in an equation of state. The estimation technique can support a change of the vehicle velocity by selecting an appropriate impulse response in the measurement equation for the vehicle velocity. Estimation results in simulation and full scale tests revealed that the proposed estimation technique is effective for track condition monitoring with acceptable accuracy for conventional railways.

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