Molecular Dynamics Simulation to Investigate the Rake Angle Effects on Nanometric Cutting of Single Crystal Ni3Al

Rui-cheng Feng,Yong-nian Qi,Zong-xiao Zhu,Wen-yuan Song,Hai-yan Li,Mao-mao Wang,Zhi-yuan Rui,Feng-shou Gu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.4

Molecular dynamics, an eff ective method to gain an insight into nanometric behaviour of materials, was employed to studythe nano-cutting behaviour of single crystal Ni 3 Al in nanometric scale. In this paper, comparisons were made for compressive/tensile stress, subsurface damage and surface roughness with three rake angles of a diamond tool. Subsurface damage waspartitioned by region and studied with work hardening in detail. A model for precise characterization of surface roughnesswas established with consideration of local surface fl uctuation. Simulation results showed that the chip thickness increasedas rake angle changed from negative to positive, and the boundary formed between tensile and compressive stress was inconsistent with the glide direction of stacking fault. Subsurface damage decreased as the increase of rake angle, and regularglide planes of stacking faults were found in front of the cutting tool. Further, the pinned dissociated 1/2 < 110 > superpartialdislocation with anti-phase boundary was demonstrated. The model was tested and characterized by implanted pits onperfect surface. Results showed that surface roughness can be well characterized, and an evident discrepancy was observedamong three rake angles, especially for 30° rake angle, which showed an distinct smooth surface compared with the others.

Constant and ever-Changing

RUI QI MAO 한국색채학회 2023 International Invitation Exhibition of Color Works Vol.- No.-

Research and Improvement on Active Compliance Control of Hydraulic Quadruped Robot

Rui Zhu,Qingjun Yang,Jiaxing Song,Shangru Yang,Yudong Liu,Qi Mao 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.5

This paper focuses on active compliance control of hydraulic quadruped robot, especially the analysis of the inner-loop of the coupled system. Current researches on active compliance control regard the bandwidth of the inner loop of the system as infinite, while ignoring that the extra-load will cause the inner-loop response characteristics to deteriorate when the leg is in the stance phase. In this work, we first briefly introduced the structure of the robot, and its kinematics and dynamics are analyzed. Next, the robot’s active compliance control framework is established, and the inner-loop two-cylinder coupling system is analyzed in depth. It can be concluded that the existence of low frequency poles in the system is the main reason for the poor response characteristics. Then through the analysis of the state equation and transfer function matrix of the multi-input multi-output system, we show that the equivalent hydraulic spring stiffness (EHSS) is the main factor affecting the zero-pole distribution. Furthermore, we optimize the structure to increase the EHSS to improve the response characteristics of the system. Finally, the co-simulation platform and single-leg experiment bench are introduced. The simulation and experimental results show that the response speed of the inner-loop control is significantly improved after optimization, and the robot with active compliance control strategies can significantly reduce the impact of the foot.

Changes in Dust Activity in Spring over East Asia under a Global Warming Scenario

Qi Zong,Rui Mao,Dao-Yi Gong,Chenglai Wu,Bing Pu,Xingya Feng,Yijie Sun 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.4

Dust activity not only influences human health through dust storms but also affects climate at local and regional scales through the direct effects of dust aerosols on both solar and longwave radiative heating. In this study, based on dust simulations from seven Coupled Model Intercomparison Project Phase 5 (CMIP5) models, the spatial and temporal changes in dust activity over East Asia under a Representative Concentration Pathway 8.5 global warming scenario were examined for the periods of 2016– 2035 (P1), 2046–2065 (P2) and 2080–2099 (P3). The results show that the multimodel ensemble mean (MME) of the CMIP5 models largely captures the spatial distribution of dust emissions and dust optical depth (DOD) over East Asia during 1986–2005 (P0). The MME reproduces the increasing trend in dust emissions and DOD over dust sources in East Asia during P0. Accompanying emission reductions during P1 to P3, the DOD simultaneously decreases, and the evident DOD decline can also be found over downwind areas in eastern China and the Korean Peninsula. Simulations project increases in precipitation and the LAI (leaf area index). Simultaneously, the weakened East Asian trough leads to anomalous southerly winds and lower wind speeds at the surface. All these results indicate unfavorable conditions for dust emissions over the sources regions, resulting in a decreased DOD over East Asia during P1 to P3.

Clinical Reference Strategy for the Selection of Treatment Materials for Maxillofacial Bone Transplantation: A Systematic Review and Network Meta-Analysis

Zhang Shuxin,Zhang Xinyi,Li Yanling,Mao Xuran,Liu Rui,Qi Yanxin,Lee Eui-Seok,Jiang Heng Bo 한국조직공학과 재생의학회 2022 조직공학과 재생의학 Vol.19 No.3

Bone graft materials have mixed effects of bone repair in the field of oral maxillofacial surgery. The qualitative analyses performed by previous studies imply that autogenous odontogenic materials and autogenous bone have similar effects on bone repair in clinical jaw bone transplantation. This retrospective systematic assessment and network meta-analysis aimed to analyze the best effect of clinical application of autogenous odontogenic materials and autogenous, allogeneic, and xenogeneic bone grafts in bone defect repair. A systematic review was performed by searching the PubMed, Cochrane Library, and other journal databases using selected keywords and Medical Subject Headings search terms. 10 Papers (n = 466) that met the inclusion criteria were selected. The assessment of heterogeneity did not reveal any overall statistical difference or heterogeneity (P = 0.051 > 0.05), whereas the comparison between autogenous and allogeneic bone grafts revealed local heterogeneity (P = 0.071 < 0.1). Risk of bias revealed nine unclear studies and one high-risk study. The overall consistency was good (P = 0.065 > 0.05), and the local inconsistency test did not reveal any inconsistency. The publication bias was good. The confidence regarding the ranking of bone graft materials after GRADE classification was moderate. The effects on bone repair in the descending order were as follows: autogenous odontogenic materials, xenogeneic bone, autogenous bone, and allogeneic bone. This result indicates that the autogenous odontogenic materials displayed stronger effects on bone repair compared to other bone graft materials. Autogenous odontogenic materials have broad development prospects in oral maxillofacial surgery.

Mechanisms and kinetics of zinc and iron separation enhanced by calcified carbothermal reduction for electric arc furnace dust

Jiayong Qiu,Shui Yu,Jiugang Shao,Kaiqi Zhu,Dianchun Ju,Chunyu Chen,Dexing Qi,Fei Wang,Ni Bai,Rui Mao,Xiaoming Wang 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.4

A high basicity charge prepared with electric arc furnace dust (EAFD), carbonaceous reducing agent and CaO is proposed. The mechanisms of enhancing separation of zinc and iron by calcified carbothermic reduction of the high basicity charge were analyzed by combining thermal analysis kinetics and experiment. The influences of roasting temperature, carbon ratio (nc/no, molar ratio of carbon in graphitic carbon powder to oxygen in EAFD), and CaO dosage on phase transition and dezincification ratio in EAFD were investigated. The results show that the intermediates Ca2Fe2O5 and Fe0.85−xZnxO can be produced from the zinc-iron separation of zinc ferrate during the process of calcified carbothermic reduction of EAFD. Addition of CaO and C results in the following transition pathways: ZnFe2O4+ CaO→Ca2Fe2O5+ZnO→Ca2Fe2O5+Zn(g)→CaO+Fe; Fe0.85−xZnxO+CaO→Ca2Fe2O5+FeO+ZnO→CaO+Fe+Zn(g). In the range of nc/no of 0.4–1.2 and roasting temperature of 1,000–1,100 °C, the addition of CaO can promote reduction and dezincification. Based on the Kissinger-Akahira-Sunose (KAS) and Coats-Redfern methods, the kinetic results show that the calcified carbothermic reduction process can be divided into three stages: initial stage (α=0–0.3), middle stage (α=0.3–0.45), and final stage (α=0.45–1.0). The average activation energy of the initial stage is 305.01 kJ·mol−1, and the reaction mechanism is one-dimensional diffusion. The average activation energy is 315.67 kJ·mol−1 for the middle stage and 288.22 kJ·mol−1 for the final stage. The chemical reaction equation is found to be the most suitable mechanism in the medium and final stages. It is also found that the addition of CaO can reduce the average activation energy by about 32 kJ·mol−1 and shorten the intermediate stage of the reaction.