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Increasing demands call for the burr-free workpiece in precision manufacturing. Low-frequency vibration-assisted drilling (LFVAD) has been applied to improve the fabrication process. Prediction and minimization of burr size are one of the major research topics in precision machining. In this paper, an LFVAD parameters optimization model was proposed including harmony search (HS) algorithm and a modified LFVAD burr height analytical model. The burr height model of LFVAD was developed using existing analytical burr height model for conventional drilling (CD) and vibration-assisted drilling (VAD). The developed burr height models were then employed with HS algorithm, which is a new meta-heuristic optimization method based on the imitation of music improvisation process, to determine the optimal machining parameters for a given twist drill that results in minimum exit burr height. Experimental results show that the burr height of the optimized LFVAD decreased by 52.75% compared with the CD, and decreased by 17.59% compared with the un-optimized LFVAD. The simulation and experimental results demonstrate that under suitable LFVAD parameters, the burr height could be reduced.

Gaowei Xia,1,* Xiaoling Li,2,* Fuhui Chen,1 Zhenyu Shao3 1Department of Respiratory, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086, People’s Republic of China; 2Department of Oncology, General Hospital of Heilongjiang Province Land Reclamation Bureau China, Harbin 150088, People’s Republic of China; 3Department of Radiation Oncology, Qilu Hospital of Shandong University, Jinan 250012, People’s Republic of China*These authors contributed equally to this workCorrespondence: Fuhui ChenDepartment of Respiratory, The Second Affiliated Hospital of Harbin Medical University, Harbin 150086, People’s Republic of ChinaEmail fuhuichenhh@sina.comZhenyu ShaoDepartment of Radiation Oncology, Qilu Hospital of Shandong University, Jinan 250012, People’s Republic of ChinaEmail Athena2111@163.comPurpose: The aim of this study was to study the roles and potential mechanism of LINC00520 in the progression of lung cancer.Methods: The expression of LINC00520 and miR-3175 in lung cancer tissues and cells was detected by qRT-PCR. The disease stage and aggressive of patients were also recorded, and their relationship with LINC00520 level was also calculated. Kaplan–Meier survival curve was drawn to observe the survival difference between high and low expression patients. Lipofectamine 2000 was used to transfect siLINC00520, miR-3175 inhibitor and their controls in lung cancer cells. CCK8 and colony formation assay were processed for cell proliferation. Transwell assay was undertaken for migration and invasion of lung cancer cells. MiRDB predicts the combination of LINC00520 and miR-3175. Luciferase and RNA pulldown assay were applied to verify the binding site. Correlation analysis of miR-3175 and LINC00520 expression in lung cancer tissues was shown.Results: LINC00520 was highly expressed in lung cancer tissues and cells. Patients at III+IV stage were always with higher LINC00520 level than patients at I+II stage. Patients with high expression of lncRNA LINC00520 have short survival time (hazard ratio=1.7). Knockdown of LINC00520 inhibited proliferation, invasion and migration of lung cancer cells. LINC00520 targeted and negatively regulated miR-3175 (r=− 0.528; P< 0.001). MiR-3175 inhibitor rescued the effect of si-LINC00520 on lung cancer progression.Conclusion: LncRNA LINC00520 could predict poor prognosis and promote progression of lung cancer by inhibiting miR-3175 expression.Keywords: lncRNA LINC00520, lung cancer, prognosis, miR-3175