TiO2 nanoceramic films were deposited on polycarbonate (PC) substrate by electron beam evaporation. This deposition technique is well established for producing dense and adhesive optical films. At high power, the particles arrived at the substrate with high kinetic energy, and high impact also led to low density due to porous structure. The porous TiO2 films resulted in low linear refractive index. As the film thickness increased, the surface of TiO2 films exhibited the grain growth obviously, resulting in high surface roughness. The transparent TiO2 films showed red-shift because of large grain size. Transparent materials generally have optical Kerr effect. The knowledge of nonlinear refractive index of materials is of great interest due to its potential applications in designing optical devices. Moiré deflectometry is a powerful tool for measuring nonlinear refractive index of materials. In this study, this method is applied for measuring the nonlinear refractive index of TiO2 nanoceramic films on PC substrates. The nonlinear refraction index can be measured to be in order of 10(-8) cm2 W(-1) and the change in refractive index is in order of 10(-5).
Many education systems globally adopt an English proficiency test (EPT) as an effective mechanism to evaluate English as a Foreign Language (EFL) speakers’ comprehension levels. Similarly, Taiwan’s military academy also developed the Military Online English Proficiency Test (MOEPT) to assess EFL cadets’ English comprehension levels. However, the difficulty level of MOEPT has not been detected to help facilitate future updates of its test banks and improve EFL pedagogy and learning. Moreover, it is almost impossible to carry out any investigation effectively using previous corpus-based approaches. Hence, based on the lexical threshold theory, this research adopts a corpus-based approach to detect the difficulty level of MOEPT. The function word list and Taiwan College Entrance Examination Center (TCEEC) word list (which includes Common European Framework of Reference for Language (CEFR) A2 and B1 level word lists) are adopted as the word classification criteria to classify the lexical items. The results show that the difficulty level of MOEPT is mainly the English for General Purposes (EGP) type of CEFR A2 level (lexical coverage = 74.46%). The findings presented in this paper offer implications for the academy management or faculty to regulate the difficulty and contents of MOEPT in the future, to effectively develop suitable EFL curriculums and learning materials, and to conduct remedial teaching for cadets who cannot pass MOEPT. By doing so, it is expected the overall English comprehension level of EFL cadets is expected to improve.
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