Real-Time In Situ Microscopic Observation of Dynamic Contact and Friction Between a Wire Rope and Friction Lining

Yongbo Guo,Zheyingzi Zhu,Dekun Zhang,Kai Chen,Songquan Wang 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.3

An experiment was conducted using a microslip friction test machine to measure reciprocating sliding friction between a K25 friction lining and a 6 × 19 steel wire rope under dynamic loading. Real-time in situ microscopic observation of the interfacial friction in the contact were performed by using a high-speed micro camera. The results showed that during the loading and unloading stages of friction, adhesion, partial adhesion and slip states were observed. The friction coefficient decreases with increasing dynamic load. In the lightly loaded area (3kN-10kN), the variation of the friction coefficient in the sliding stage was stable. In the heavily loaded area (3kN-14kN), the friction coefficient in the slip stage decreased with increasing load, and the proportion of the slip stage in the loading time increased. The wear debris generated at the interface of the contact increased gradually with increasing dynamic load. Then, a dense third body formed, which reduced the friction coefficient. The wear rate of the lining under these experimental conditions was 3.23 × 10–4 after 18 h.

Two Compound Heterozygous Were Identified in SLC26A4 Gene in Two Chinese Families With Enlarged Vestibular Aqueduct

Yongbo Yu,Yang Yang,Jie Lu,Yaqiong Jin,Yeran Yang,Enyu Hong,Jin Shi,Feng Chen,Shujing Han,Ping Chu,Yongli Guo,Xin Ni 대한이비인후과학회 2019 Clinical and Experimental Otorhinolaryngology Vol.12 No.1

Objectives. To investigate the genetic causes of hearing loss with enlarged vestibular aqueduct (EVA) in two children from unrelated two Chinese families. Methods. Sanger sequencing of all coding exons in SLC26A4 (encoding Pendrin protein) was performed on the two patients, their sibling and parents respectively. To predict and visualize the potential functional outcome of the novel variant, model building, structure analysis, and in silico analysis were further conducted. Results. The results showed that the proband from family I harbored a compound heterozygote of SLC26A4 c.1174A>T (p.N392Y) mutation and c.1181delTCT (p.F394del) variant in exon 10, potentially altering Pendrin protein structure. In family II, the proband was identified in compound heterozygosity with a known mutation of c.919-2A>G in the splice site of intron 7 and a novel mutation of c.1023insC in exon 9, which results in a frameshift and translational termination, consequently leading to truncated Pendrin protein. Sequence homology analysis indicated that all the mutations localized at high conservation sites, which emphasized the significance of these mutations on Pendrin spatial organization and function. Conclusion. In summary, this study revealed two compound heterozygous mutations (c.1174A>T/c.1181delTCT; c.919-2A>G/c.1023insC) in Pendrin protein, which might account for the deafness of the two probands clinically diagnosed with EVA. Thus this study contributes to improve understanding of the causes of hearing loss associated with EVA and develop a more scientific screening strategy for deafness.

Effect of Initial Indentation Position on Plastic Deformation Behaviors of Polycrystalline Materials via Molecular Dynamics Simulation

Pengyue Zhao,Yongbo Guo 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.1

Polycrystalline materials can be divided into four types of microstructural components, including grain cell (GC), grain boundary (GB), triple junction (TJ) and vertex points (VP). Nanoindentation at different microstructural components on the polycrystalline materials surface can lead to different plastic deformation behaviors of the polycrystalline materials. Due to experimental limitations, the indentation-induced internal stress and defect evolution process are difficult to investigate directly, especially for the polycrystalline materials with grain size less than 100 nm. The molecular dynamics (MD) simulations were performed to unravel the initial indentation position effect on the elasticity/plastic deformation mechanism of polycrystalline copper. The results reveal that the initial indentation position governs the indentation force variation and defect distribution range due to the different dimensionalities of the microstructural components. The defect propagation as well as the internal stress transmission in the GC regions tend to transfer to the low-dimensional microstructural components of the interfaces. In addition, the atomic internal stress and potential energy accumulation/release of the microstructural component atoms during the nanoindentation process are also investigated, revealing that the atomic internal stress and potential energy in the VPs vary earliest, followed by the TJs, GBs and GCs.

The domestication event of the Tibetan pig revealed to be in the upstream region of the Yellow River based on the mtDNA D-loop

Ge, Qianyun,Gao, Caixia,Cai, Yuan,Jiao, Ting,Quan, Jinqiang,Guo, Yongbo,Zheng, Wangshan,Zhao, Shengguo Asian Australasian Association of Animal Productio 2020 Animal Bioscience Vol.33 No.4

Objective: Evidence from previous reports indicates that pig domestication in East Asia mainly occurred in the Mekong region and the middle and downstream regions of the Yangtze River. Further research identified two new origin centers for domestic pigs in the Tibetan Plateau and the islands of Southeast Asia. However, due to the small sample size of Tibetan pigs, details of the origin and spread of Tibetan pigs has not yet been established. Methods: We analyzed mitochondrial DNA control region (D-loop) variation in 1,201 individuals from nine Tibetan pig populations across five provinces. Comprehensive Tibetan pig samples were taken to perform the most detailed analysis of Tibetan pigs to date. Results: The result indicate that Rkaze pigs had the lowest level of diversity, while Changdu pigs had the highest diversity. Interestingly, these two populations were both in the Tibetan Plateau area. If we calculate diversity in terms of each province, the Tibetan Plateau area had the lowest diversity, while the Chinese province of Gansu had the highest diversity. Diversity gradient analysis of major haplotypes suggested three domestication centers of Tibetan pigs in the Tibetan Plateau and the Chinese provinces of Gansu and Yunnan. Conclusion: We found two new domestication centers for Tibetan pigs. One is in the Chinese province of Gansu, which lies in the upstream region of the Yellow River, and the other is in the Chinese province of Yunnan.

Evaluating genetic diversity and identifying priority conservation for seven Tibetan pig populations in China based on the mtDNA D-loop

Ge Qianyun,Gao Caixia,Cai Yuan,Jiao Ting,Quan Jinqiang,Guo Yongbo,Zheng Wangshan,Zhao Shengguo 아세아·태평양축산학회 2020 Animal Bioscience Vol.33 No.12

Objective: Tibetan pigs, an excellent species unique to China, face serious threats, which in turn affects the development and utilization of the outstanding advantages of plateau hypoxia adaptability and reduces their genetic diversity. Therefore, a discussion of measures to conserve this genetic resource is necessary. The method, based on genetic diversity, genetic divergence and total genetic contribution rate of population, reflects the priority conservation order and varies depending on the three different purposes of conservation. Methods: We analyzed mitochondrial DNA control region (D-loop) variation in 1,201 individuals from nine Tibetan pig populations across five provinces and downloaded 564 mtDNA D-loop sequences from three indigenous pig breeds in Qinghai, Sichuan, and Yunnan Provinces distributed near the Tibetan pigs. Results: We analyzed three different aspects: Changdu Tibetan pigs have the highest genetic diversity, and from the perspective of genetic diversity, the priority conservation is Changdu Tibetan pigs. Hezuo Tibetan pigs have the highest genetic contribution, so the priority conservation is Hezuo Tibetan pigs in the genetic contribution aspect. Rkaze Tibetan pigs were severely affected by indigenous pig breeds, so if considering from the perspective of introgression, the priority conservation is Rkaze Tibetan pigs. Conclusion: This study evaluated genetic diversity and comprehensively assessed conservation priority from three different aspects in nine Tibetan pig populations.