Using molecular dynamics (MD) simulation, the strain-induced phase transitions in pure body-centered-cubic (bcc) iron (Fe) thin films containing twin boundaries (TBs) with different TB fractions and orientations are studied. Two groups of bcc thin films with different TB-surface orientation relationships are designed. In film group 1, the (112) [ $11\overline{1}$ ] TBs are perpendicular to the ( $11\overline{1}$ ) free surfaces, while the (112) [ $11\overline{1}$ ] TBs are parallel to the free surfaces in film group 2. We vary the TB numbers inserted into the films to study the effect of TB fraction on the phase transition. Biaxial strains are applied to the films to induce the bcc to close packed (cp) phase transition. The critical strain, at which the first phase transition takes place, decreases with the TB fraction increase in film group 1 with a perpendicular TB-surface orientation, while such a relationship is not observed in film group 2 with parallel TB-surface orientation. We focus on the free surface and TB as the nucleation positions of the new phase and the afterward growth. In addition, the dynamics of the phase transition is discussed. This work may help to understand the mechanism of phase transition in nanoscale or surface-dominant systems with pre-existing defects.

Aiming at the problem of irregular shape and low contrast of the scratches in the image of mobile phone screen, a method based on machine vision was proposed to detect the surface scratches of mobile phone screen. Firstly, the PatMax algorithm and affine transformation were adopted to preprocess the screen images of mobile phone. Then the shear transformation was used to decompose the image into two parts: low frequency and high frequency, the element shapes in four directions of 0°, 45°, 90° and 135° were constructed to perform gray-scale closing operation on the low frequency part, and the N × M median filter denoising operation was performed on the high frequency part, the enhanced image was generated by the inverse shear transformation. Finally, the improved Otsu double threshold method was used to extract the target. 450 pieces of mobile phone screen images were randomly selected for experiments, and the highest detection rate is 98.7%. The results show that this method can effectively enhance the detail information of the images, which greatly guarantees the integrity of the scratch defects.

This study evaluated the feasibility of cantilever and fixed bridge restorations through finite element analysis of narrow-diameter implants (NDls) in a 4-unit anterior mandibular bridge. A total of five restoration models were analyzed using static, modal, and dynamic analyses. Results showed that the fixed bridge supported by three NDIs exhibited the lowest stress (crown: 27.429 MPa, implant: 58.608 MPa) and optimal stability (resonance frequency: 8653 Hz). The maximum stresses in cantilever bridge implants (crowns: 78.803 MPa, implants: 146.27) were 2–3 times higher than those in fixed bridges. Dynamic loading generated the highest stresses during the second phase of the masticatory cycle, with overall stress 10%–30% higher than under static loading. Fixed bridges supported by three NDIs are recommended for optimal stress distribution, while cantilever bridges should be used with caution.

The purpose of this study was to use finite element analysis (FEA) to evaluate the mechanical effects of eight different anti-rotation structures in fin-ty