ABSTRACT:The phase stability and melting behavior of nylon 6 were studied by high-temperature wide-angle X-ray diffraction and differential scanning calorimetry (DSC). The results show that most of the a phase obtained by a solution-precipitation process [nylon 6 powder (Sol-Ny6)] was thermodynamically stable and mainly melted at 221 C; the double melting peaks were related to the melt of a crystals with different degrees of perfection. The c phase formed by liquid nitrogen quenching (sample LN-Ny6) melted within the range 193-225 C. The amorphous phase converted into the c phase below 180 C but into the high-temperature a phase at 180-200 C. Both were stable over 220 C. a-and c*-crystalline structures were formed by annealing but were not so stable upon heating. Typical double melting peaks were shown on the DSC curve; melt recrystallization happened within the range 100-200 C. The peak at 210 C was mainly due to the melting of the less perfect crystalline structure of the c phase and a fraction of the a phase; the one at 219 C was due to the high-temperature a-and c-phase crystals.
Imaging through multimode fibers (MMFs) is a challenging task. Some approaches, e.g. transmission matrix or digital phase conjugation, have been developed to realize imaging through MMF. However, all these approaches seem sensitive to the external environment and the condition of MMF, such as the bent condition and the movement of the MMF. In this paper, we experimentally demonstrate the high-fidelity imaging through a bent MMF by the conventional neural network (CNN). Two methods (accuracy and Pearson correlation coefficient) are employed to evaluate the reconstructed image fidelity. We focus on studying the influence of MMF conditions on the reconstructed image fidelity, in which MMF for imaging is curled to different diameters. It is found that as an object passes through a small bent diameter of the MMF, the information of the object may loss, resulting in little decrease of the reconstructed image fidelity. We show that even if MMF is curled to a very small diameter (e.g. 5 cm), the reconstructed image fidelity is still good. This novel imaging systems may find applications in endoscopy, etc.
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