Changes in thermomechanical behavior with structural relaxation taking place in epoxy glasses were studied. Differential scanning calorimetry measurements and thermostimulated strain recovery tests were performed for specimens deformed and then aged under fixed strain. In the course of heating, the specimens started to absorb thermal energy, whereas plastic strain was still stable. At higher temperatures, plastic strain started recovery, which was accompanied by exothermic behavior of the specimen. With an increase in the aging duration, the endothermic peak signified and moved to a higher temperature. These results indicated that the longer the aging duration was, the harder the plastic strain and strain energy were frozen in the glassy structure. This freeze-strain phenomenon was observed for crosslinked epoxy glass, as well as polymeric glasses with linear molecular structures, aged under strain.
The noniterative phase-retrieval method by use of Gaussian filtering is applied to the reconstruction of phase objects from experimental far-field intensities. In this method, the complex amplitude of transmitted light through an object is reconstructed from three far-field intensities, which are measured with the modulation of the object by laterally shifted and unshifted Gaussian filters. In the experiment, the amplitude of a Gaussian beam illuminating objects is utilized as a Gaussian filter, and, as the phase objects, a converging lens with a small exit pupil and a plastic fiber immersed in optical adhesive are used. The experimental results show that the Gaussian beam of a laser is capable of retrieving the phases of those objects with the accuracy of the range from approximately 1/10 to 1/4 of the laser's wavelength.
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