Dynamics Modelling and Simulating of Ultra-precision Fly-Cutting Machine Tool

Hanjing Lu,Yuanyuan Ding,Yu Chang,Gangli Chen,Xiaoting Rui 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.2

Dynamics modelling and simulating are the significant process to improve the machining accuracy of the machine tool. This paper is aimed to model and simulate the ultra-precision fly-cutting machine tool (UFMT) and find the relations between structure parameters and machined surface. In this paper, the multi-rigid-flexible-body dynamics model of the UFMT is firstly built by using transfer matrix method for multibody systems. After deducing overall transfer equation, overall transfer matrix, eigenfrequency equation and dynamics equations, the vibration characteristics and dynamics response of tool-tip are simulated and validated by tests. The machined surface is simulated by transferring displacement between the fly-cutting tool-tip and the workpiece into 3D curve. According to the simulation results, both the air-bearing stiffness of the flying-cutting head and cutting process parameters have effects on the machined surface.

Comparison of Chlorophyll Algorithms in the Bohai Sea of China

Peng Xiu,Yuguang Liu,Zengrui Rong,Haibo Zong,GangLi,Xiaogang Xing,Yongcun Cheng 한국해양과학기술원 2007 Ocean science journal Vol.42 No.4

Empirical band-ratio algorithms and artificial neural network techniques to retrieve sea surface chlorophyll concentrations were evaluated in the Bohai Sea of China by using an extensive field observation data set. Bohai Sea represents an example of optically complex case II waters with high concentrations of colored dissolved organic matter (CDOM). The data set includes coincident measurements of radiometric quantities and chlorophyll a concentration (Chl), which were taken on 8 cruises between 2003 and 2005. The data covers a range of variability in Chl in surface waters from 0.3 to 6.5 mg m-3. The comparison results showed that these empirical algorithms developed for case I and case II waters can not be applied directly to the Bohai Sea of China, because of significant biases. For example, the mean normalized bias (MNB) for OC4V4 product was 1.85 and the root mean square (RMS) error is 2.26.

Experimental Study on the Shear Behaviors of PolypropyleneFiber-Reinforced Sand

Gang Li,Jinli Zhang,Jia Liu 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12

With excellent water permeability and high shear strength S, fiber-reinforced sand (FRS) is an ideal material for subgrades and has promising application prospects. In this study, the FRS were formed by adding the randomly distributed fibers to the sand specimens. Based on the triaxial consolidated drained tests, the effects of factors such as fiber content ζ, fiber length lf, relative density Dr and confining pressure σ3 on the S of FRS were systematically investigated. The test results showed that the S of the FRS increased as ζ, lf, Dr and σ3 increased. Under axial loads, the stress-strain curve of the FRS exhibited a hardening trend. Under specific Dr and σ3, the S increment of the FRS had a strong linear relationship with ζ and lf. The Mohr's stress circle results showed that the FRS possessed not only frictional strength but also high cohesive strength. Based on the triaxial consolidated drained test results, the S of the FRS was calculated using the Zornberg model and Michalowski model. The calculation results showed that the S predicated by the Zornberg model differed significantly from the measured values. However, the S predicted by the Michalowski model were in good agreement with the measured values.

Cloning, Expression, and Characterization of a Highly Active Alkaline Pectate Lyase from Alkaliphilic Bacillus sp. N16-5

( Gang Li ),( Lang Rao ),( Yan Fen Xue ),( Cheng Zhou ),( Yun Zhang ),( Yan He Ma ) 한국미생물 · 생명공학회 2010 Journal of microbiology and biotechnology Vol.20 No.4

Patient radiation dose and protection from cone-beam computed tomography

Gang Li 대한영상치의학회 2013 Imaging Science in Dentistry Vol.43 No.2

After over one decade development, cone beam computed tomography (CBCT) has been widely accepted for clinical application in almost every field of dentistry. Meanwhile, the radiation dose of CBCT to patient has also caused broad concern. According to the literature, the effective radiation doses of CBCTs in nowadays market fall into a considerably wide range that is from 19 μSv to 1073 μSv and closely related to the imaging detector, field of view, and voxel sizes used for scanning. To deeply understan the potential risk from CBCT, this report also reviewed the effective doses from literatures on intra-oral radiograph, panoramic radiograph, lateral and posteroanterior cephalometric radiograph, multi-slice CT, and so on. The protection effect of thyroid collar a d leaded glasses were also reviewed.

Long Non-Coding RNA TUG1 Promotes Proliferation and Inhibits Apoptosis of Osteosarcoma Cells by Sponging miR-132-3p and Upregulating SOX4 Expression

Gang Li,Keyu Liu,Xinhui Du 연세대학교의과대학 2018 Yonsei medical journal Vol.59 No.2

Purpose: Long non-coding RNA taurine upregulated gene 1 (TUG1) is reported to be a vital regulator of the progression of various cancers. This study aimed to explore the exact roles and molecular mechanisms of TUG1 in osteosarcoma (OS) development. Materials and Methods: Real-time quantitative PCR was applied to detect the expressions of TUG1 and microRNA-132-3p (miR-132-3p) in OS tissues and cells. Western blot was performed to measure protein levels of sex determining region Y-box 4 (SOX4). Cell viability was assessed using XTT assay. Cell apoptosis was evaluated using flow cytometry and caspase-3 activity detection assays. Bioinformatics analysis and luciferase reporter experiments were employed to confirm relationships among TUG1, miR-132-3p, and SOX4. Results: TUG1 was highly expressed in human OS tissues, OS cell lines, and primary OS cells. TUG1 knockdown hindered proliferationand induced apoptosis in human OS cell lines and primary OS cells. Moreover, TUG1 inhibited miR-132-3p expression by direct interaction, and introduction of miR-132-3p inhibitor partly abrogated the effect of TUG1 knockdown on the proliferation and apoptosis of OS cells. Furthermore, SOX4 was validated as a target of miR-132-3p. Further functional analyses revealed that miR-132-3p inhibited proliferation and induced apoptosis of OS cells, while this effect was greatly abated following SOX4 overexpression. Moreover, TUG1 knockdown suppressed proliferation and promoted apoptosis by upregulating miR-132-3p and downregulatingSOX4 in primary OS cells. Conclusion: TUG1 facilitated proliferation and suppressed apoptosis by regulating the miR-132-3p/SOX4 axis in human OS cell lines and primary OS cells. This finding provides a potential target for OS therapy.

Effects of solar UV radiation on photosynthetic performance of the diatom Skeletonema costatum grown under nitrate limited condition

Gang Li,Kunshan Gao 한국조류학회I 2014 ALGAE Vol.29 No.1

Availability of nutrients is known to influence marine primary production; and it is of general interest to see how nutrient limitation mediates phytoplankton responses to solar ultraviolet radiation (UVR, 280-400 nm). The red tide diatom Skeletonema costatum was cultured under nitrate (N)-limited and N-replete conditions and exposed to different solar irradiation treatments with or without UV-A (315-400 nm) and UV-B (280-315 nm) radiation. Its photochemical quantum yield decreased by 13.6% in N-limited cells as compared to that in N-replete ones under photosynthetically active radiation (PAR)-alone treatment, and the presence of UV-A or UV-B decreased the yield further by 2.8 and 3.1%, respectively. The non-photochemical quenching (NPQ), when the cells were exposed to stressful light condition, was higher in N-limited than in N-replete grown cells by 180% under PAR alone, by 204% under PAR + UV-A and by 76% under PAR + UV-A + UV-B treatments. Our results indicate that the N limitation exacerbates the UVR effects on the S. costatum photosynthetic performance and stimulate its NPQ.

Patient radiation does and protection from cone-beam computed tomography

Gang Li 대한구강악안면방사선학회 2013 Imaging Science in Dentistry Vol.43 No.2

After over one decade development, cone beam computed tomography (CBCT) has been widely accepted for clinical application in almost every field of dentistry. Meanwhile, the radiation does of CBCT to patient has also caused broad concern. According to the literature, the effective radiation doses of CBCTs in nowadays market fall into a considerably wid range that is from 19 μSv and closely related to the imaging detector, field of view, and voxel sizes used for scanning. To deeply understand the potential risk from CBCT, this report also reviewed the effective doses from literatures on intra-oral radiograph, panoramic radiograph, lateral and posteroanterior cephalo-metric radiopraph, multi-slice CT, and so on. The protection effect of thyroid collar and leaded glasses were also reviewed.

Research on Embedded Image Edge Detection Algorithm

Gang Li,Ruixiang Huang 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.12

With the development of embedded technology, the embedded image processing algorithms are becoming more and more complex. Edge detection is the basic algorithm of image processing, which is used in the extraction of information from the image. Laplacian operator is useful for the edge detection. Especially, the operator can be determined by the zero crossing point of the two differential positive and negative peaks. In order to meet the fast hardware implementation of embedded image processing, this paper presents the hardware acceleration of Laplacian operator by Zynq-7000. Using HLS method, the complex image algorithm is automatically translated into hardware language, and the function of the algorithm can be quickly completed. The experimental results show that, the embedded hardware accelerated image based on Zynq-7000 can not only realize software programming and hardware programmable combination, but also improve the embedded system flexibility, scalability, and accelerate embedded image processing product design time.

Structural analysis and optimization of large cooling tower subjected to wind loads based on the iteration of pressure

Gang Li,Wen-bin Cao 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.5

The wind load is always the dominant load of cooling tower due to its large size, complex geometry and thin-wall structure. At present, when computing the wind-induced response of the large-scale cooling tower, the wind pressure distribution is obtained based on code regulations, wind tunnel test or computational fluid dynamic (CFD) analysis, and then is imposed on the tower structure. However, such method fails to consider the change of the wind load with the deformation of cooling tower, which may result in error of the wind load. In this paper, the analysis of the large cooling tower based on the iterative method for wind pressure is studied, in which the advantages of CFD and finite element method (FEM) are combined in order to improve the accuracy. The comparative study of the results obtained from the code regulations and iterative method is conducted. The results show that with the increase of the mean wind speed, the difference between the methods becomes bigger. On the other hand, based on the design of experiment (DOE), an approximate model is built for the optimal design of the large-scale cooling tower by a two-level optimization strategy, which makes use of code-based design method and the proposed iterative method. The results of the numerical example demonstrate the feasibility and efficiency of the proposed method.