How a dynamic optical system maintains image quality: Self-adjustment of the human eye

The eyeball is continually subjected to forces that cause alterations to its shape and dimensions, as well as to its optical components. Forces that induce accommodation result in an intentional change in focus; others, such as the effect of intraocular pressure fluctuations, are more subtle. Although the mechanical properties of the eyeball and its components permit mediation of such subtle forces, the concomitant optical changes are not detected by the visual system. Optical self-adjustment is postulated as the mechanism that maintains image quality. The purpose of this study was to investigate how self-adjustment occurs by using an optical model of the eyeball and to test the requisite optical and biometric conditions

Revealing the superior corrosion protection of the passive film on selective laser melted 316L SS in a phosphate-buffered saline solution

This study investigated the passivation behaviour of wrought 316L stainless steel (SS) and 316L manufactured by the Selective Laser Melting (SLM) process in phosphate-buffered saline (PBS). The 3D printing laser power influenced microstructure, passive film and corrosion resistance of SLM 316L SS were studied, and compared with the results of wrought 316L SS. The results indicated that a smaller corrosion current density and improved breakdown potential (Eb) of SLM 316L SS was associated with a higher proportion of Cr2O3 in the passive film at OCP conditions. The Transmission Electron Microscopy (TEM) proved that the passive film on SLM 316L SS was continuous and compact at 600 mV vs. Ag/AgCl applied potential. The increase in the applied potential resulted in a high content of hydroxide being recorded in the passive film. The results also suggest preferential facets of (1 1 0) and abundant grain/sub-grain boundaries for SLM 316L SS, as well as the increased work of separation and growth rate of the passive film from the substrate. Wrought 316L SS demonstrated preferred facets of (1 1 1)-γ and larger grains. There are confirmed via X-Ray Diffraction (XRD), Electron Backscatter Diffraction (EBSD) and the first-principle calculation

On the origin of the high tensile strength and ductility of additively manufactured 316L stainless steel: Multiscale investigation

We report that 316L austenitic stainless steel fabricated by direct laser deposition (DLD), an additive manufacturing (AM) process, have a higher yield strength than that of conventional 316L while keeping high ductility. More interestingly, no clear anisotropy in tensile properties was observed between the building and the scanning direction of the 3D printed steel. Metallographic examination of the as-built parts shows a heterogeneous solidification cellular microstructure. Transmission electron microscopy observations coupled with Energy Dispersive X-ray Spectrometry (EDS) reveal the presence of chemical micro-segregation correlated with high dislocation density at cell boundaries as well as the in-situ formation of well-dispersed oxides and transition-metal-rich precipitates. The hierarchical heterogeneous microstructure in the AM parts induces excellent strength of the 316L stainless steel while the low staking fault energy of the as-built 316L promotes the occurrence of abundant deformation twinning, in the origin of the high ductility of the AM steel. Without additional post-process treatments, the AM 316L proves that it can be used as a structural material or component for repair in mechanical construction