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Molecular dynamics simulation and continuum modelling of granular surface flow in rotating drums

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Chinese Science Bulletin 2007年第5期52卷 692-700页

作者： LI ShuiQing yAO Qiang CHEN Bing ZHANG Xuan ding y L Department of Thermal Engineering Tsinghua University Beijing 100084 China Department of Chemical Engineering University of Leeds Leeds LS29JT UK

Numerical simulations of granular flows in rotating drums operated at medium to high rates (Fr=0.1― 0.2) have been carried out by using a Molecular Dynamics (MD) algorithm that incorporates inelastic particle interactions, sliding friction and rolling friction. The results indicate that the behavior of granular flow in rotating drums can be classified into two distinct zones: a shear active layer at the bed surface and a quasi-static plug flow region adjacent to the wall. The residence time of a tracer particle in the active layer is approximately a third or a half of that in the plug flow region. The thickness of the active layer at mid-chord is about 0.57―0.61 times that of the plug flow region. It is found that all cases simulated in this work are in the rolling-cascading intermediate regime instead of the pure rolling re-gime. The simulated tangential velocity at the mid-chord is also compared with experimental results reported in the literature and good agreement has been obtained. Based on the MD simulations and experimental results, a continuum approach has also been developed. It is shown that the behavior of granular solids in the plug flow region experiences plastic deformation along the radial direction from the wall with the velocity profiles well described by an exponential function, whereas the active layer velocity follows a simple expression for the Couette shear flow. Discussion has also been made on the granular temperature and concentration profiles.

关键词：粒料颗粒表面流分子动力学模拟连续模型转鼓

FAILURES AND THE LIFE OF FURNACE TUBES

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 419-425页

作者： F.Z.Shen y.ding D.M.Hou Z.P.Ning y.Lü T.B.Dong A.R.Tuohuti Nanjing University of Technology Nanjing 210009 ChinaNanjing University of Technology Nanjing 210009 ChinaLutianhua Group Incorporated Luzhou 646300 ChinaLutianhua Group Incorporated Luzhou 646300 ChinaLutianhua Group Incorporated Luzhou 646300 ChinaSouthwestern Tarim Exploration & Development Company Zepu 844804 ChinaSouthwestern Tarim Exploration & Development Company Zepu 844804 China

It is showed after the furnace tubes serviced for 8-10 years that the density of damage in the HAZ (heat affected zone) of the weld has higher than in parent metals, though the depth of damage is not equal to. By the test of creep crack growth, it is also acquired that under same mechanic parameter C* (t), the rate of creep crack growth in the HAZ is more than twice as fast as in parent metals. Two mechanisms (overheating and thermal shock) of failure occurred in an accident are presented. The stress of thermal shock is analyzed, in which the change of the elasticity modulus with the radius ET = /(r) is considered. Based on it, the safety region of the thermal shock is obtained. Finally, two sets of curves for the safe life are suggested which can facilitate to estimate the remaining life of HK-40 or HP-Nb tubes by their creep rupture data.

关键词： failure thermal stock creep crack growth remaining life furnace tube

ISOTHERMAL SECTION OF Mg-Zn-La SySTEM IN Mg RICH CORNER AT 350℃

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Acta Metallurgica Sinica(English Letters) 2008年第5期21卷 329-335页

作者： M.L. Huang H.X. Li H. ding y.P. Ren S.M. Hao School of Materials and Metallurgy Northeastern University Shenyang 110004 China

Alloys of Mg-Zn-La system in Mg rich corner at 350℃ have been prepared in this study. Scanning electron microscopy （SEM）, electron probe microanalysis with energy dispersive X-ray spectroscopy （EPMA-EDS）, and X-ray diffraction （XRD） have been used to identify the phase equilibrium and the composition of each phase in the alloys. As a result, the isothermal section of Mg-Zn-La system in Mg rich corner at 350℃ has been determined. The result shows that, in addition to some binary phases, there exists a linear ternary compound called T-phase in Mg-Zn-La system at 350℃, in which the La content is about 8 at. pct ±0.4 at. pct and the Zn content is 8 at. pct- 48 at. pct. The T-phase has a C-centered orthorhombic crystal structure, and the lattice parameters are a=0.965-1.020 nm, b=1.121 1.142 nm, c=0.950-0.977 nm.

关键词： Mg-Zn-La system Phase equilibrium T-phase Isothermal section

Interfacial bonding mechanism in Al/coated steel dissimilar refill friction stir spot welds

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Journal of Materials Science & Technology 2019年第6期35卷 1027-1038页

作者： Z. Shen y. ding J. Chen B. Shalch Amirkhiz J.Z. Wen L. Fu A.P. Gerlich School of Materials Science and Engineering Northwestern Poly technical University Xi'an 710072 China Shanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Xi'an 710072 China State Key Laboratory of Solidification Processing Northwestern Poly technical University Xi'an 710072 China Centre of Advance Materials Joining Department of Mechanical and Mechatronics Engineering University of Waterloo 200 University Ave. Waterloo N2L3G1 Ontario Canada CanmetMATERIALS Natural Resources Canada Hamilton L8P 0A5 Canada

Defect-free dissimilar Al/zinc coated steel and Al/AlSi coated steel welds were successfully fabricated by refill friction stir spot welding. However, Al alloy and uncoated steel could not be welded under the same welding condition. Al-Zn eutectic layer formed at the Al/zinc coated steel interface showed nonuniformity in thickness and nanoscale intermetallic(IMC) produced was discontinuous. The bonding formation between the Al-Zn layer and the surrounding materials was attributed to a liquid/solid reaction mechanism. Bonding formation at Al alloy and AlSi coated steel interface was attributed to a solid/solid reaction mechanism, as the joining process did not involve with melting of base metals or AlSi coating materials. Kissing bond formed at the weld boundary acted as a crack initiation and propagation site,and the present study showed that weld strength of Al 5754/AlSi coated steel was greatly influenced by properties of original IMC layer.

关键词： Refill friction stir spot welding Al alloy Steel Coated materials Joining mechanism

Spatial associations of tree species in a subtropical evergreen broad-leaved forest

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Journal of Plant Ecology 2012年第3期5卷 346-355页

作者： Zheng R.Luo Ming J.yu De L.Chen you G.Wu Bing y.ding Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education and College of Life ScienceZhejiang UniversityHangzhou 310058China Management of Baishanzu Fengyangshan-Baishanzu National Nature ReserveQingyuan 323800China Department of Biology Science The School of Life and Environmental ScienceWenzhou UniversityWenzhou 325027China

Aims The spatial segregation hypothesis and the low-frequency hypothesis are two important proposed mechanisms that delay or prevent competitive exclusion in *** tree species interact with their neighbors,the importance of these potential processes can be investigated by analyzing the spatial structures of tree *** The distribution of the adults of 27 common tree species in a fully mapped 5-ha subtropical forest plot in Baishanzu,eastern China,was analyzed to investigate the community-level intra-and interspecific spatial association *** first tested for the overall spatial pattern in the 5-to 40-m neighborhoods and classified first-order bivariate associations with a diametric scheme based on Ripley’s K and nearest-neighbor statistic(G-function).Then heterogeneous Poisson null models were used to distinguish second-order interactions from overall spatial associations(including first-order effects).Finally,we analyzed correlations between the existence of species interactions and some attributes of the species *** Findings Partial overlap and segregation increased with scale,whereas mixing *** 70%of the species pairs occurred less than expected at random,and only 3.4%of the species pairs were well mixed;11.0%of all species pairs showed significant small-scale interactions,which was a greater frequency than expected by chance if species are abundant or prefer the same habitat,but less frequent than expected if species are highly *** suggests that both spatial segregation and low frequency of species facilitate species coexistence by reducing the opportunity that trees of two species encounter each *** study also revealed that positive interactions were more prevalent than negative interactions in the forest,which indicates that positive interactions may have important effects on forest species assemblies.

关键词： Baishanzu point pattern analysis spatial segregation low frequency interaction opportunity

A transmission electron microscopy study of microscopic causes for localized-corrosion morphology variations in the AA7055 Al alloy

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Journal of Materials Science & Technology 2018年第10期34卷 1719-1729页

作者： X.B. yang J.H. Chen G.H. Zhang L.P. Huang T.W. Fan y. ding X.W. yu Center for High-Resolution Electron Microscopy College of Materials Sdence and Engineering Hunan University Changsha Hunan 410082 China Department of Applied Physics School of Physics and Electronics Hunan University Changsha Hunan 410082 China

By Using （scanning） transmission electron microscopy, localized-corrosion morphology variations of the AA7055 AIZn（Cu）Mg alloy with different thermal processes and their underlying microscopic causes were investigated systematically. Our study shows that the corrosion resistance of the nanoscale precipitates varies with their structure type and Cu-content. Just like the Al-matrix, the early-stage precipitates are corrosion resistant, as compared with the ηp/η-precipitates without high Cu-content. With a high Cu-content, however, the η-precipitates become most corrosion resistant among all phases involved. Hence, tailoring the precipitate microstructure and chemistry though thermal processes may change the overall corrosion morphology and improve corrosion resistance property of the alloy.

关键词： Aluminum alloys Precipitates Corrosion Electron microscopy

恶性肿瘤患者治疗前后的心理特点及其心理干预回顾

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中国组织工程研究与临床康复 2007年第39期11卷 7951-7954页

作者：丁宇中南大学湘雅二医院医学心理学研究中心湖南省长沙市410011

目的:了解恶性肿瘤患者在诊断、治疗前后各不同时期的心理特点,针对性地提出适当的心理干预方法,为提高患者的生活质量提供可供参考的方向。资料来源:检索PubMed2004-01/2006-11与恶性肿瘤及心理干预相关的文章,检索词"cancer,psycholog... 详细信息

目的:了解恶性肿瘤患者在诊断、治疗前后各不同时期的心理特点,针对性地提出适当的心理干预方法,为提高患者的生活质量提供可供参考的方向。资料来源:检索PubMed2004-01/2006-11与恶性肿瘤及心理干预相关的文章,检索词"cancer,psychologicalintervention",限定文章语言种类为英文。同时检索清华全文数据库1999-01/2004-10关于恶性肿瘤和心理相关的文章,限定文章语言种类为中文,检索词"恶性肿瘤,心理干预"。资料选择:选取涉及恶性肿瘤患者各时期心理状态的调查报告,以及相关的心理干预文章。排除标准:个案研究,非调查、介绍性文章。资料提炼:共收集到56篇关于恶性肿瘤和心理干预的研究文章,42个调查、实验文章符合标准。排除的14篇文章为个案研究,非调查、介绍性文章。资料综合:大部分的调查、研究指出心理社会因素在恶性肿瘤患者病情的变化中起到重要的作用,主要体现在:内向不稳定的个性特点导致生活事件对患者的影响较大,负性生活事件较多,较为严重的焦虑、抑郁等情绪普遍存在于患者当中。而患者的心理状态会影响到患者的求医意愿和配合治疗的程度。针对患者在恶性肿瘤从发现到治疗这个过程中各时期的心理变化特点,结合患者特点有针对性地进行各种认知行为治疗等心理干预,对于改善患者生活质量、促进治疗效果、恢复免疫功能方面具有重要的意义。结论:恶性肿瘤患者普遍存在各种心理社会问题,心理社会因素对恶性肿瘤的发展起到较为重要的影响作用,而且贯穿于患者从决定是否进行检查、接受诊断到坚持治疗等阶段之中。在恶性肿瘤各干预过程中对患者进行心理干预十分必要。

关键词：恶性肿瘤心理特点心理干预综述文献

An Expert System Based on Multi-reasoning Mechanism for Port Machine Diagnosis

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Journal of Shipping and Ocean Engineering 2011年第2期1卷 101-108页

作者： y. ding G.L. Lin Logistics Research Center Shanghai Maritime University Shanghai 200135 China

Expert system plays an important role in port machine diagnosis, which aims at automatic equipment test for higher availability and efficiency of port operations. In this study, a port machine diagnosis expert system is proposed based on multi-reasoning mechanism. Relying on the knowledge acquired from the experienced experts in the port machine engineering, the system builds a library of relative experience and a set of rules of reasoning and estimating. Multi-reasoning mechanism that simulates the decision-making process of domain experts is employed to achieve reliable diagnosis results. The reasoning machine integrates artificial neural network, uncertain decision making and decision tree, which complements each other by sustainable growing voting mechanism. The effect of this multi-reasoning mechanism is evaluated and validated by means of Matthew＇s Correlation Coefficient （MCC）. The system incorporating the mechanism is successfully designed, implemented and applied in Shanghai Port.

关键词： Port machine diagnosis multi-reasoning mechanism ANN uncertain decision making decision tree.

Impact Factors on Fracturing Results of Coal Seams and Appropriate Countermeasures

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Journal of Energy and Power Engineering 2010年第6期4卷 16-26页

作者： X. Wang y.H. ding y. Xu y.y. Duan Fracturing ＆ Acidizing Technical Service Center Research Institute of Petroleum Exploration and Development China NationalPetroleum Corp. Langfang 065007 China

Hydraulic fracturing is one of the efficient means for the abundant low-permeability CBM （coal-bed methane） reserves in China, however, due to the unique features of coal seams （i.e., low temperature, strong adsorption and abnormal development of natural fracture systems） as compared with the conventional reservoirs, the fractures propagate is difficult and the risk of damage to coal seam itself and the hydraulic fractures would be extremely high in the course of fracturing. As a result, losses would be suffered on the post-frac production of CBM *** the mean of numerical simulation, in this paper, the main factors have impact on the post-frac results as well as the extent to which the impact is brought were researched, and the technical solutions for the improvement of the fracturing performance was put forwards.

关键词： Coal-seam fracturing hazard factors yield loss rate technical solutions.