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Multi-phase field simulation of multi-grain peritectic transition in multiple phase transformation

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China Foundry 2020年第5期17卷 357-363页

Taking Fe-C binary alloy as an example,based on the multi-phase field model,the nucleation and growth ofδphase,peritectic reaction,peritectic transformation,and the growth of subsequent austenite are *** of the nucleation site of austenite on the peritectic reaction rate and the starting time of the peritectic transformation were *** simulation results show that theγphase,as a shell,surrounds theδphase and grows rapidly when the peritectic reaction occurs between the dendriticδgrains,and a layer ofγphase shell is formed aroundδphase after the peritectic *** theδphase is surrounded byγphase completely,the membrane shell separates the L phase from theδphase,so that the phase transfers from peritectic reaction to peritectic *** the peritectic transformation,since the solute diffusion coefficient of the liquid phase is much greater than that of the solid phase,the average growth rate of austenite in the liquid phase is visibly higher than that of theδ*** peritectic reaction rate is related to the curvature of the nucleation site of theγphase on theδphase *** peritectic reaction rate at the large curvatures is faster than that at small curvatures.

关键词： phase field Fe-C binary alloy peritectic transformation microstructure numerical simulation

Phase-field simulation of secondary dendrite growth in directional solidification of binary alloys

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China Foundry 2019年第2期16卷 97-104页

作者： Li Feng Ni-ni Lu Ya-long Gao Chang-sheng Zhu Jun-he Zhong rong-zhen xiao College of Materials and Engineering Lanzhou University of Technology State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals Lanzhou University of Technology

Phase field method was used to simulate the effect of grains orientation angle θ_(11) and azimuth θ_A of non-preferentially growing dendrites on the secondary dendrites of preferentially growing dendrites. In the simulation process, two single-factor influence experiments were designed for columnar crystal structures. The simulation results showed that, when θ_(11) < 45o and θ_A < 45o, as θ_(11) was enlarged, the growth direction of the secondary dendrites on the preferentially growing dendrites at the converging grain boundary(GB) presented an increasing inclination to that of preferentially growing dendrites; with increasing θ_A, the growth direction of the secondary dendrites on the preferentially growing dendrites at the converging GB exhibited greater deflection,and the secondary dendrites grew with branches; the secondary dendrites on the preferentially growing dendrites at diverging GBs grew along a direction vertical to the growth direction of the preferentially growing *** θ_A = 45o and θ_(11) = 45o, the secondary dendrites grew in a direction vertical to the growth direction of preferentially growing dendrites. The morphologies of the dendrites obtained through simulation can also be found in metallographs of practical solidification experiments. This implies that the effect of a grain's orientation angle and azimuth of non-preferentially growing dendrites on the secondary dendrites of preferentially growing dendrites does exist and frequently appears in the practical solidification process.

关键词： phase-field method binary alloy directional solidification secondary dendrites

Phase-field modeling of dendritic growth under forced flow based on adaptive finite element method

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Transactions of Nonferrous Metals Society of China 2015年第1期25卷 241-248页

作者：朱昶胜雷鹏肖荣振冯力兰州理工大学计算机与通信学院兰州730050 兰州理工大学有色金属先进加工与再利用国家重点实验室兰州730050

A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic growth was simulated from undercooled nickel melt under the forced flow. The simulation results show that the asymmetry behavior of the dendritic growth is caused by the forced flow. When the flow velocity is less than the critical value, the asymmetry of dendrite is little influenced by the forced flow. Once the flow velocity reaches or exceeds the critical value, the controlling factor of dendrite growth gradually changes from thermal diffusion to convection. With the increase of the flow velocity, the deflection angle towards upstream direction of the primary dendrite stem becomes larger. The effect of the dendrite growth on the flow field of the melt is apparent. With the increase of the dendrite size, the vortex is present in the downstream regions, and the vortex region is gradually enlarged. Dendrite tips appear to remelt. In addition, the adaptive finite element method can reduce CPU running time by one order of magnitude compared with uniform grid method, and the speed-up ratio is proportional to the size of computational domain.

关键词： dendritic growth phase-field model forced flow adaptive finite element method

Stewart被动隔振平台结构参数对系统固有频率的影响

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兰州理工大学学报 2018年第3期44卷 39-44页

作者：赵荣珍唐小斌马德福兰州理工大学机电工程学院甘肃兰州730050

为避免被动式Stewart隔振平台在外界激励下发生共振,对其结构参数变化对系统固有频率的影响进行了分析.依据Newtow-Euler方法,建立了一种计算该平台固有频率的动力学特征方程.借助ANSYS有限元模型进行验证,结果表明了所建模型的正确性.... 详细信息

为避免被动式Stewart隔振平台在外界激励下发生共振,对其结构参数变化对系统固有频率的影响进行了分析.依据Newtow-Euler方法,建立了一种计算该平台固有频率的动力学特征方程.借助ANSYS有限元模型进行验证,结果表明了所建模型的正确性.在此基础上,针对初始位姿下结构参数:支腿减振器刚度-阻尼系数、上平台铰接点半径、上下平台近铰点分布角、初始位姿下的上下平台质心距离和上平台位姿角,计算得到以上结构参数特定变化范围下系统的六阶固有频率的变化情况,进而对各结构参数敏感性作出分析.本研究可为Stewart隔振平台的结构参数优化设计提供理论参考作用.

关键词： Stewart平台被动隔振结构参数化固有频率敏感性

Comparative analysis of isothermal and non-isothermal solidification of binary alloys using phase-field model

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Transactions of Nonferrous Metals Society of China 2014年第11期24卷 3639-3644页

作者：肖荣振安国升朱昶胜王智平杨世银兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室兰州730050

Based on the entropy function, a two-dimensional phase field model of binary alloys was established. Meanwhile, an explicit difference method with uniform grid was adopted to solve the phase field and solute field controlled equations. And the alternating direction implicit(ADI) algorithm for solving temperature field controlled equation was also employed to avoid the restriction of time step. Some characteristics of the Ni-Cu alloy were captured in the process of non-isothermal solidification, and the comparative analysis of the isothermal and the non-isothermal solidification was investigated. The simulation results indicate that the non-isothermal model is favorable to simulate the real solidification process of binary alloys, and when the thermal diffusivity decreases, the non-isothermal phase-field model is gradually consistent with the isothermal phase-field model.

关键词： phase-field model binary alloys isothermal solidification non-isothermal solidification

A promising approach for quantifying focal stroke modeling and assessing stroke progression:optical resolution photoacoustic microscopy photothrombosis

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Neural Regeneration Research 2025年第7期20卷 2029-2037页

作者： xiao Liang Xingping Quan xiaorui Geng Yujing Huang Yonghua Zhao Lei Xi zhen Yuan Ping Wang Bin Liu Faculty of Health Sciences University of MacaoMacao Special Administrative RegionChina Center for Cognitive and Brain Sciences University of MacaoMacao Special Administrative RegionChina Department of Biomedical Engineering Southern University of Science and TechnologyShenzhenGuangdong ProvinceChina State Key Laboratory of Quality Research in Chinese Medicine Institute of Chinese Medical SciencesUniversity of MacaoTaipaMacao Special Administrative RegionChina Department of Emergency Zhujiang HospitalSouthern Medical UniversityGuangzhouGuangdong ProvinceChina

To investigate the mechanisms underlying the onset and progression of ischemic stroke,some methods have been proposed that can simultaneously monitor and create embolisms in the animal cerebral ***,these methods often require complex systems and the effect of age on cerebral embolism has not been adequately studied,although ischemic stroke is strongly *** this study,we propose an optical-resolution photoacoustic microscopy-based visualized photothrombosis methodology to create and monitor ischemic stroke in mice simultaneously using a 532 nm pulsed *** observed the molding process in mice of different ages and presented age-dependent vascular embolism ***,we integrated optical coherence tomography angiography to investigate age-associated trends in cerebrovascular variability following a *** imaging data and quantitative analyses underscore the differential cerebrovascular responses to stroke in mice of different ages,thereby highlighting the technique's potential for evaluating cerebrovascular health and unraveling age-related mechanisms involved in ischemic strokes.

关键词： age-dependent cerebral cortex ischemic stroke mouse model optical coherence tomography angiography photoacoustic microscopy photothrombosis vascular imaging

Forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy

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Rare Metals 2018年第5期37卷 399-406页

作者： xiao-Dai Yue Jia-rong Li xiao-Guang Wang zhen-Xue Shi Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

The forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy were investigated. The microstructures were observed with optical microscope （OM） and field emission microscope （FEM） after homogenization-solution heat treated at 1328℃ and 1350 ℃ for 2 h, 6 h and 9 h. Results indicate that when heat treated at 1328 ℃, pores appear at the interface of eutectic and matrix at first and then leave in the matrix with the shrink of eutectic. When heat treated at 1350 ℃, incipient melting happens at first, and some of them have a pore in the center. After that, with the homogenization-solution process, incipient melting microstructure fades away gradually. By analyzing the results with thermodynamics and kinetics methods, it is concluded that some pores nucleate during directional solidification and then become larger and visible during homogenization-solution heat treatments; some pores are generated by incipient melting, yet such pores are difficult to be distinguished from other pores; imbalanced elements cross-diffusion induces to the forming and growing of pores too, and such imbalanced diffusion also plays an important part on the growth of all preexisting pores.

关键词： Single crystal superalloy Pore Homogenization Solution Heat treatment Incipient melting

Practical effect of different teaching modes in teaching gastrointestinal surgery nursing

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World Journal of Gastrointestinal Surgery 2024年第1期16卷 166-172页

作者： xiao-Juan rong zhen Ning Department of Nursing Medical College in Jiangxi University of TechnologyNanchang 330098Jiangxi ProvinceChina

BACKGROUND With the continuous development and progress of medical technology,the position of surgical nursing in the field of clinical medicine is becoming in-creasingly *** an important branch of the surgical field,the nursing requirements and difficulty of gastrointestinal surgery are also *** order to improve the teaching quality of nursing care in gastrointestinal surgery,many educators and researchers are actively exploring new teaching *** them,the teaching method case-based learning(CBL),scene-simulated learning(SSL),task-based learning(TBL),combining self-evaluation and training mode is considered as an effective *** method aims to help students to better master knowledge and skills and improve their comprehensive quality by cultivating their self-evaluation *** To explore the practical effect of CBL-SSL-TBL combined with training mode and student self-assessment in nursing teaching of gastrointestinal *** Seventy-one nursing interns in our hospital from December 2020 to December 2021 were *** to different teaching modes,they were divided into observation group CBL-SSL-TBL combined with training mode combined with student self-assessment and control group(conventional teaching mode),of which 36 were in observation group and 35 were in control *** results of operational skills,theoretical knowledge,nursing students'satisfaction,learning effectiveness questionnaire and teaching effect were compared between the two *** Compared between the two groups,the operational skills and theoretical knowledge scores of the observation group were higher than those of the control group,and the difference was statistically significant(P<0.05).Compared between the two groups,the total satisfaction ratio of the observation group was higher than that of the control group,the difference was statistically significant(P<0.05).Compared between the two groups,the observation group was lower tha

关键词： Gastrointestinal surgery Nursing teaching Teaching model Practical effect Learning ability

Radial optic neurotomy in treating central retinal vein occlusion: a Meta-analysis

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International Journal of Ophthalmology(English edition) 2016年第6期9卷 898-903页

作者： zhen-Na Chen Yan Shao xiao-rong Li Eye Institute & School of Optometry and Ophthalmology Tianjin Medical University Eye Hospital

AIM： To assess the feasibility of radial optic neurotomy （RON） in central retinal vein occlusion （CRVO） treatment with a ***： Electronic databases were searched for comprehensive articles that compared efficacy of RON with that of other treatments in CRVO. Study quality was assessed and risk ratio （RR） and 95% confidence interval （Cl） with fix or random-effects model were calculated according to the heterogeneity. RESULTS： A total of 200 eyes from 5 studies were included. The results indicated that no significant differences were found between groups with and without RON in improvement of visual acuity （VA） at 6mo follow- up （pooled RR 0.51, 95%CI 0.22 to 1.18, P=0.117） while improvement of VA showed significantly favourable in patients receiving RON treatment at 12mo follow-up （pooled RR 2.27, 95% CI 1.31 to 3.95, P=0.004）. For complications, RON treatment was more effective in reducing neovascular glaucoma （pooled RR 0.45, 95%CI 0.21 to 0.97, P=0.042） but was comparable in retinal detachment （pooled RR 2.41, 95%CI 0.51 to 11.39, P=0.267） and vitreous hemorrhage （pooled RR 0.91, 95%CI 0.33 to 2.46, P=0.847）. CONCLUSION： Compared with some certain treatment modalities, RON might offer better VA at 12mo and decrease the rate of neovascular glaucoma without changing the rate of retinal detachment and vitreous hemorrhage. Further studies are required considering the limitation of the research.

关键词： radial optic neurotomy central retinal veinocclusion Meta-analysis