Suchergebnisse

Micro absolute distance measurement (MADM) is widely used in industrial and military fields. To achieve high accuracy and frequency response, a polarized low-coherence interferometry (PLCI)-based method for MADM is proposed. The nearly linear relationship between the envelope center and m-order PLCI fringe (PLCIF) peak center is found and verified. Dispersion compensation is achieved by fringe peak position estimation and polynomial fitting to get rid of the dependence on an a priori model and birefringence parameters, and make this method very robust. Meanwhile, the zero-order PLCIF center is estimated and located to demodulate the measured displacement. Then, the measurement accuracy is raised by polynomial fittings. In comparison to conventional methods, the proposed method can effectively avoid jump errors and has a higher accuracy. Experimental results indicate that the measurement accuracy is higher than 19.51 nm, the resolution is better than 2 nm, and its processing data rate can reach 35 kHz.

Abstract
High-density and nanosized deformation twins in face-centered cubic (fcc) materials can effectively improve the combination of strength and ductility. However, the microscopic dislocation mechanisms enabling a high twinnability remain elusive. Twinning usually occurs via continuous nucleation and gliding of twinning partial dislocations on consecutive close-packed atomic planes. Here we unveil a completely different twinning mechanism being active in metastable fcc materials. The transformation-mediated twinning (TMT) is featured by a preceding displacive transformation from the fcc phase to the hexagonal close-packed (hcp) one, followed by a second-step transformation from the hcp phase to the fcc twin. The nucleation of the intermediate hcp phase is driven by the thermodynamic instability and the negative stacking fault energy of the metastable fcc phase. The intermediate hcp structure is characterized by the easy slips of Shockley partial dislocations on the basal planes, which leads to both fcc and fcc twin platelets during deformation, creating more twin boundaries and further enhancing the prosperity of twins. The disclosed fundamental understanding of the complex dislocation mechanism of deformation twinning in metastable alloys paves the road to design novel materials with outstanding mechanical properties.

AbstractA rapid headspace gas chromatography method has been developed for the determination of residual organic solvents in photoinitiators. Using water‐glyceryl triacetate as the solvent, the method was used to determine the residual levels of 11 volatile organic compounds (VOCs), namely, benzene, toluene, xylene, methanol, ethanol, acetonitrile, acetone, n‐hexane, dichloromethane, tetrahydrofuran, and ethyl acetate, in photoinitiators. Under the selected instrument operating conditions, all the residual solvents were completely separated. A detailed analysis was conducted on these 11 organic solvents. The mass concentrations of these solvents were linearly correlated with the chromatographic peak area, with a linear R2 is called determination coefficient R2 ≥ 0.99, and the relative standard deviation (n = 5) was less than 5.8%. The recovery rates of n‐hexane and toluene were 90.3% and 102.9%, respectively. The method exhibits good precision and accuracy, making it suitable for the rapid detection and inspection of 11 residual VOC components in photoinitiators. The practical applicability of the method was evaluated by blue applicability grade index and the score was 75.0 demonstrating its good practicality and applicability.