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Xiaodong Yu,Weicheng Gao,Yanan Feng,Guangqiang Shi,Shihao Li,Minmin Chen,Ruiming Zhang,Junfeng Wang,Wentao Jia,Jianhua Jiao,Ruichun Dai 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.6
Hydrostatic bearing has the advantages of wide speed range, large bearing capacity, high precision and stability. Hydrostatic-hydrodynamic hybrid bearing can make up for the lack of stiffness of hydrostatic bearing and prevent tribological failure under the condition of high speed and heavy load. Therefore, hydrostatic bearing and hydrostatic-hydrodynamic hybrid bearing have become important bearing parts of high-end computer numerical control (CNC) machine equipment. The research on hydrostatic and hydrostatic-hydrodynamic open a new way for precision improvement of high-end CNC machine equipment. This paper reviews research progress of hydrostatic linear guideway, hydrostatic rest and ram, hydrostatic thrust bearing, hydrostatic-hydrodynamic thrust bearing and hydrostatic-hydrodynamic spindle of high-end CNC machine equipment, and discusses the influence of structure and working parameters on lubrication performance, accuracy and stability of bearing parts. Finally, the future research direction in hydrostatic bearing and hydrostatic-hydrodynamic hybrid bearing are suggested. This review provides a theoretical basis for design and development of high-end CNC machine equipment in the future.
Tissue-Specific CRISPR/Cas9 System of Cotton Pollen with GhPLIMP2b and GhMYB24 Promoters
Lei Jianfeng,Dai Peihong,Li Jiyang,Yang Mi,Li Xiuqin,Zhang Wanqi,Zhou Guantong,WangzhenGuo,Liu Xiaodong 한국식물학회 2021 Journal of Plant Biology Vol.64 No.1
CRISPR/Cas9 technology is a powerful tool for improving crop genetic traits. However, CRISPR/Cas9 system for efficient expression of cotton germ cells has still not been established. In this study, we developed a tissue-specific vectors to drive Cas9 expression with GhPLIMP2b and GhMYB24 promoters and established the effective method to transform cotton pollen by Agrobacterium vacuum infiltration. GhPLIMP2b and GhMYB24 promoters of cotton pollen were cloned into Cas9 expression vectors. The sgRNAs targetting to CLA1, ERA1 and GGB (drought-resistant negative regulation genes) were designed and constructed into GhPLIMP2b and GhMYB24 promoter vectors. Cotton pollens were tranformed by Agrobacterium vacuum infiltration with GhPLIMP2b and GhMYB24 promoter vectors. The results of clone sequencing shown that mutation types of the sequence were mainly base substitutions wth the frequency from 3.29 to 6.45%. Eleven potential off-target sites were chosen and two sites were observed. Our results indicated that GhPLIM2bP::Cas9 and GhMYB24P::Cas9 editing vectors achieved targeted edition of endogenous genes in cotton pollen, but there were a few off-target effects. This study provides an effective gene-editing system for the rapid acquisition of cotton mutants using pollen as a transgenic receptor.
Investigation into the Effectiveness of Ultrasonic Tomography for Grouting Quality Evaluation
Jiangbo Lu,Shenghua Tang,Xiaodong Dai,Zhi Fang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.12
This study is aimed to determine the influence of the parameters relevant for the application of ultrasonic tomography in the field of grouting quality evaluation. The parameters tested were the wave velocity difference between concrete and grout (VDCG), the type of material used for a pipe, and the type of pre-stressed tendon within the pipe. Fourteen cube specimens were constructed, and a theoretical model was used to analyse the effects of these parameters. The results show that these parameters affect each other on the detection effectiveness of ultrasonic tomography, and that VDCG affects it most. It was found that ultrasonic tomography is suitable for the evaluation of grouting quality in post-tensioned structures when VDCG is small and the type of tendon used is a steel bar.