Influence of Forging Temperature on the Microstructures and Mechanical Properties of a Multi-Directionally Forged Al–Cu–Li Alloy

Hailin He,Kanghua Chen,Youping Yi,Wen You,Yonglin Guo,Bingxiang Wang,Jiaguo Tang,Research Institute of Light Alloy, Central South University,Shiquan Huang 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2

Optimization of forging process to improve the microstructure and mechanical properties of 2195 Al–Cu–Li alloy forgingsis an urgent issue. In this study, a homogenized 2195 alloy ingot was subjected to multi-directional forging (MDF), annealing,and forging at 500 °C, 420 °C, and 240 °C with a 50% reduction in cross-sectional area, followed by a T8 heat treatment(involving solution, quenching, cold compression, and aging). The microstructural evolution during the process and thefinal mechanical properties in three orthogonal directions were examined. The results showed that the grain structures ofthe alloy were significantly refined after MDF by dynamic recrystallization (DRX), but the structure was thermally unstableand formed coarse grains during subsequent annealing by static recrystallization (SRX). The T8-treated samples forged at500 °C, 420 °C, and 240 °C obtained fine and uniform grain structures by DRX, inhomogeneous grain structures by partialSRX, and uniform, equiaxed grain structures by full SRX, respectively. The average grain size of the forging increased withdecreasing forging temperature because more significant SRX occurred for the forging that was deformed at lower temperatures. The grain structures had minimal influence on precipitation behavior and strength but had a significant influence onelongation. The fine and uniform grain structures improved the elongation; whereas, the inhomogeneous grain structures,which contained extremely large grains, significantly deteriorated the elongation. The uniform, equiaxed grain structuresdecreased the anisotropy in three orthogonal directions and maintained fine elongation even though the average grain sizeof the forging was the largest.

Fabrication of copper ions-substituted hydroxyapatite/polydopamine nanocomposites with high antibacterial and angiogenesis effects for promoting infected wound healing

Bailong Tao,Chuanchuan Lin,Ai Guo,Yonglin Yu,Xian Qin,Kai Li,Hongchuan Tian,Weiwei Yi,Dengliang Lei,Lixue Chen 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.104 No.-

Infected wound healing remains a critical threat, which frequently delays the healing process and evenleads to severe life-threatening complications. Herein, we reported an effective anti-infection approach,which was based on copper ions-releasing hydroxyapatite/polydopamine (HA-Cu/PDA) nanocompositeswith photothermal effect. The HA-Cu/PDA nanocomposites was fabricated through a co-precipitationreaction between polydopamine (PDA)-coated hydroxyapatite nanoparticles (HA)-loaded Cu2+ (HA-Cu). Through a synergistic effect of released Cu2+ and photothermal efficiency of PDA coating, and the HACu/PDA nanocomposites exhibited extraordinary antibacterial capacities against Escherichia coli (E. coli)and Staphylococcus aureus (S. aureus). The nanocomposites presented good biocompatibility for mouseembryonic fibroblast (NIH-3T3) cells and promoted NIH3T3 cells to migrate toward wound sites. Additionally, this nanocomposite could stimulate the tissue remodeling-related gene expression toinduce the blood vessels formation, granulation tissues and collagen deposition, and eventually enhancewound healing. In vivo study further verified that HA-Cu/PDA nanocomposites with NIR irradiation couldsignificantly improve bacterial infected wound healing through the prominent antibacterial property,reduced inflammatory response, the formation of granulation tissue, collagen deposition, and angiogenesisability. Thus, this study develops a versatile strategy for a broad range of wound healing and skinreconstruction caused by bacterial infection.

Protection of the hematopoietic system against radiation-induced damage: drugs, mechanisms, and developments

Yuanyun Wei,Yaqi Gong,Shuang Wei,Yonglin Chen,Jian Cui,Xiang Lin,Yueqiu Yu,Hongxia Yan,Hui Qin,Lan Yi 대한약학회 2022 Archives of Pharmacal Research Vol.45 No.8

Sometimes, people can be exposed to moderateor high doses of radiation accidentally or through the environment. Radiation can cause great harm to several systemswithin organisms, especially the hematopoietic system. Severaltypes of drugs protect the hematopoietic system againstradiation damage in diff erent ways. They can be classifi edas “synthetic drugs” and “natural compounds.” Their cellularmechanisms to protect organisms from radiation damageinclude free radical-scavenging, anti-oxidation, reducinggenotoxicity and apoptosis, and alleviating suppression ofthe bone marrow. These topics have been reviewed to providenew ideas for the development and research of drugsalleviating radiation-induced damage to the hematopoieticsystem.

Numerical analysis of melt migration and solidification behavior in LBR severe accident with MPS method

Jinshun Wang,Qinghang Cai,Ronghua Chen,Xinkun Xiao,Yonglin Li,Wenxi Tian,Suizheng Qiu,G.H. Su 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.1

In Lead-based reactor (LBR) severe accident, the meltdown and migration inside the reactor core will lead to fuel fragment concentration, which may further cause re-criticality and even core disintegration. Accurately predicting the migration and solidification behavior of melt in LBR severe accidents is of prime importance for safety analysis of LBR. In this study, the Moving Particle Semi-implicit (MPS) method is validated and used to simulate the migration and solidification behavior. Two main surface tension models are validated and compared. Meanwhile, the MPS method is validated by the l-plate solidification test. Based on the improved MPS method, the migration and solidification behavior of melt in LBR severe accident was studied furthermore. In the Pb–Bi coolant, the melt flows upward due to density difference. The migration and solidification behavior are greatly affected by the surface tension and viscous resistance varying with enthalpy. The whole movement process can be divided into three stages depending on the change in velocity. The heat transfer of core melt is determined jointly by two heat transfer modes: flow heat transfer and solid conductivity. Generally, the research results indicate that the MPS method has unique advantage in studying the migration and solidification behavior in LBR severe accident.

Novel submodule voltage balancing topology for hybrid modular multilevel converters

Liu, Yiqi,Liu, Yanchao,Jin, Yonglin,Chen, Jianlong The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.10

A hybrid modular multilevel converter (HMMC) topology based on a bidirectional diode clamp circuit is proposed in this paper. The proposed topology ensures that the voltages at the ends of the capacitance between the two leads of each submodule in the same phase are clamped to be equal to each other through the diode clamp circuit. The balancing process through the diode clamp circuit is bidirectional, which is only achieved by the diode clamp circuit. This topology has two advantages when compared with the traditional voltage balance control method. First, the framework used for controlling the entire structure is simplified while the link controlling the voltage balance is eliminated. Second, the control schemes used for the voltage balance are simplified, and the number of the corresponding high-frequency voltage sensors is reduced. Hence, the complexity of the system control is decreased, and communication is realized more easily. When compared with other voltage balancing circuits, the proposed circuit achieves bidirectional equalization and reduces the usage of the inductors. Then, the hardware cost is reduced. Finally, the feasibility of the proposed converter is verified by simulation results given in MATLAB/Simulink.

Forensic biogeographical ancestry inference: recent insights and current trends

Wen Yufeng,Liu Jing,Su Yonglin,Chen Xiacan,Hou Yiping,Liao Linchuan,Wang Zheng 한국유전학회 2023 Genes & Genomics Vol.45 No.10

Background As a powerful complement to the paradigmatic DNA profiling strategy, biogeographical ancestry inference (BGAI) plays a significant part in human forensic investigation especially when a database hit or eyewitness testimony are not available. It indicates one’s biogeographical profile based on known population-specific genetic variations, and thus is crucial for guiding authority investigations to find unknown individuals. Forensic biogeographical ancestry testing exploits much of the recent advances in the understanding of human genomic variation and improving of molecular biology. Objective In this review, recent development of prospective ancestry informative markers (AIMs) and the statistical approaches of inferring biogeographic ancestry from AIMs are elucidated and discussed. Methods We highlight the research progress of three potential AIMs (i.e., single nucleotide polymorphisms, microhaplotypes, and Y or mtDNA uniparental markers) and discuss the prospects and challenges of two methods that are commonly used in BGAI. Conclusion While BGAI for forensic purposes has been thriving in recent years, important challenges, such as ethics and responsibilities, data completeness, and ununified standards for evaluation, remain for the use of biogeographical ancestry information in human forensic investigations. To address these issues and fully realize the value of BGAI in forensic investigation, efforts should be made not only by labs/institutions around the world independently, but also by inter-lab/institution collaborations.