Three-Cornered Hats is a classical method to obtain the frequency stability of one single atomic clock without more stable frequency standards available. In this paper, the measurement data of three hydrogen masers in a ground station is used to analyze the frequency stability of one single atomic clock. The analysis steps and problems in application of this method are introduced. The negative values of the calculated Allan variance of one clock with averaging time larger than 4000s occur. It probably implies that the hypothesis of uncorrelated clocks is not acceptable, which will be analyzed further.

The relaxation behaviors of PS below Tg and its variation trend along with aging time were studied by DSC, fluorescence spectrum and XRD. On the basis of DSC results, the kinetics of the volume and enthalpy relaxation process were analyzed, and the influence of the aging time on the relaxation behaviors were discussed. The results of fluorescence spectrum and XRD indicated the presence of the rearrangement of polymer chains in the physical aging of polystyrene.

To remove the disadvantage of conventional stretch forming machine (CSFM), a flexible stretch forming machine (FSFM) has been developed by authors recently. Based on finite element simulation and experiments, the advantages of FSFM have been detailed discussed. Our results indicated that the discrete multi-gripping jaws can swing and rotate in any direction automatically, which can solve the wasteful production of CSFM by increase the rate of materials utilization and close-fitting dies. Furthermore, the value of springback and thickness gradient in the parts formed by discrete multi-gripping jaws is smaller compare with that of integrally gripping jaws, which can help to achieve a high quality of stretch forming parts. A series of double-curved sheet panels have been formed by FSFM easily and used in the cabinet covers of high-speed train and the Dongdaemun Design Park building successfully. This work has a strong value in enhance the way to flexible and reproducible stretch forming technology.