[Finite element analysis of determining corneal biomechanical properties in vivo based on Corvis ST].

The decrease of corneal stiffness is the key factor leading to keratoconus, and the corneal collagen fiber stiffness and fiber dispersion are closely related to the corneal biomechanical properties. In this paper, a finite element model of human cornea based on corneal microstructure, namely collagen fiber, was established before and after laser assisted in situ keratomileusis (LASIK). By simulating the Corvis ST process and comparing with the actual clinical results, the hyperelastic constitutive parameters and corneal collagen fiber stiffness modulus of the corneal material were determined before and after refractive surgery. After LASIK, the corneal collagen fiber stiffness modulus increased significantly, and was highly correlated with central corneal thickness (CCT). The predictive relationship between the corneal collagen fiber stiffness modulus and the corresponding CCT before and after surgery was: k 1 before = exp(9.14 - 0.009CCT before), k 1 after = exp(8.82 - 0.008CCT after). According to the results of this study, the central corneal thickness of the patient can be used to estimate the preoperative and postoperative collagen fiber stiffness modulus, and then a personalized corneal model that is more consistent with the actual situation of the patient can be established, providing a theoretical reference for more accurately predicting the safe surgical cutting amount of the cornea.

Industry star or production elite: evidence from total factor productivity of Chinese electricity sector's green transformation.

China is constantly seeking rapid, high-quality growth in order to meet its carbon peaking and neutrality goals. Approximately 40% of China's carbon emissions come from the electric power industry, which is beset by issues of poor efficiency and excessive emissions. Thus, it is essential to determine if environmental restrictions increase economic benefits total factor productivity while still preserving the environment. We use the Quasi-DID method to examine the impact of carbon emissions trading scheme on firm-level total factor productivity of electric power companies. The findings demonstrate the following: (1) carbon emissions trading scheme considerably impedes total factor productivity development; (2) the primary cause of this detrimental impact is the need for additional improvements in marketization since green innovation is still in its infancy; (3) additional study indicates that law enforcement's heterogeneity is what affects this restriction. Our research may both enhance the Chinese carbon emissions trading scheme's effectiveness assessment framework and point out several potential avenues for high-quality growth.

A review of human cornea finite element modeling: geometry modeling, constitutive modeling, and outlooks.

The cornea is a vital tissue of the human body. The health status of the cornea has a great impact on the quality life of person. There has been a great deal of research on the human cornea biomechancis. However, the difficulty in obtaining the human cornea has greatly limited the research of cornea biomechancis. Using finite element modelling has become a very effective and economical means for studying mechanical properties of human cornea. In this review, the geometrical and constitutive models of the cornea are summarised and analysed, respectively. Some factors affecting of the finite element calculation are discussed. In addition, prospects and challenges for the finite element model of the human cornea are presented. This review will be helpful to researchers performing studies in the relevant fields of human cornea finite element analysis.

Investigation on Flaw Evolution of Additively Manufactured Al2O3 Ceramic by In Situ X-ray Computed Tomography.

The additive manufacturing process may create flaws inside ceramic materials. The flaws have a significant influence on the macroscopic mechanical behavior of ceramic materials. In order to reveal the influence of flaws on the mechanical behavior of additively manufactured ceramic, flaw evolution under mechanical loads was studied by in situ X-ray computed tomography (XCT) in this work. In situ compression XCT tests were conducted on stereolithographic additively manufactured Al2O3 ceramic. The three-dimensional full-field morphologies at different compressive loads were obtained. The evolution of flaws, including pores, transverse cracks, and vertical cracks, during compressive loading was observed. The number and volume of pores, transverse cracks, and vertical cracks were extracted. It was found that most pores and transverse cracks tend to be compacted. However, high compressive loads cause vertical cracks near the upper surface to expand, leading to the failure of the specimen. Real flaws with morphological and positional information were introduced into the finite element models. The influence of different types of flaws on the mechanical behavior is discussed. It was found that vertical cracks have a greater influence on mechanical behavior than do transverse cracks under compression. The presence of transverse cracks contributes to the evolution of vertical cracks. This study may be helpful for process optimization and performance enhancement of additively manufactured ceramic materials.