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Solidification Structure of Continuous Casting Large Round Billets under Mold Electromagnetic Stirring

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Journal of Iron and Steel Research International 2016年第4期23卷 329-337页

作者： Tao SUN Feng YUE hua-jie wu Chun GUO Ying LI Zhong-cun MA Metallurgical Engineering Research Institute University of Science and Technology Beijing Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beiman Special Steel Co. Ltd.

The solidification structure of a continuous casting large round billet was analyzed by a cellular-automaton-finite-element coupling model using the ProCAST software. The actual and simulated solidification structures were compared under mold electromagnetic stirring （MEMS） conditions （current of 300 A and frequency of 3 Hz）. Thereafter, the solidification structures of the large round billet were investigated under different superheats, casting speeds, and secondary cooling intensities. Finally, the effect of the MEMS current on the solidification structures was obtained under fixed superheat, casting speed, secondary cooling intensity, and MEMS frequency. The model accurately simulated the actual solidification structures of any steel, regardless of its size and the parameters used in the continuous casting process. The ratio of the central equiaxed grain zone was found to increase with decreasing superheat, increasing casting speed, decreasing secondary cooling intensity, and increasing MEMS current. The grain size obviously decreased with decreasing superheat and increasing MEMS current but was less sensitive to the casting speed and secondary cooling intensity.

关键词： continuous casting large round billet solidification structure cellular-automaton-finite-element method mold electromagnetic stirring central equiaxed grain zone grain size

Study on the oscillating phenomena of electrical potential across a liquid membrane

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Chinese Chemical Letters 2007年第3期18卷 309-312页

作者： Jin Zhang Gao Hong Xia Dai hua Chen jie Ren wu Yang Chemistry ＆ Chemical Engineering College Northwest Normal University Lanzhou 730070 China

The electrical oscillations across a liquid membrane in water/oil/water system was studied with octanol as oil phase by introducing two opposite charged surfactants in oil and aqueous phase, respectively. The sustained and rhythmic oscillation was observed. To a certain extent, the features of the oscillation （e.g. induction time, frequency, life time and orientation of the pulse pikes） strongly depend on the property of surfactant, dissolved in octanol. The mechanism may be explained by the formation and destruction of dual-ion surfactant membrane accompanying with emulsification at the interface and considering the coupling effect of diffusion and associated reaction in the vicinity of the interface.

关键词： Liquid membrane Chemical oscillation Electrical potential Surfactant

Water modeling of molten steel flow in a multi-strand tundish with gas blowing

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International Journal of Minerals,Metallurgy and Materials 2010年第2期17卷 143-148页

作者： Jing Jiang Jing-she Li hua-jie wu Shu-feng Yang Tao Li Hai-yan Tang School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Engineering Research Institute University of Science and Technology Beijing Beijing 100083 China

Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling *** is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence *** dramatically increases the peak concentration time,and greatly decreases the dead volume,and reduces the minimum residence *** gas blowing location,gas flow rate,and porous plug area greatly influence the flow characteristics in the tundish; the gas blowing location near the baffle,smaller gas flow rate,and smaller porous plug area are better for improving the fluid flow *** gas blowing can reduce the difference of flows at the middle outlets and side outlets for the multi-strand *** produced by gas blowing can absorb small inclusions and provide the condition for inclusion collision and ***,introducing gas blowing into a tundish and combining the turbulence inhibitor can improve inclusion floating and removal,and the cleanness of molten steel can be advanced.

关键词： continuous casting tundish water modeling gas blowing porous plug

Fatigue Performance of Microalloyed High-strength Rebar and Analysis of Fracture Mechanism

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Journal of Iron and Steel Research International 2015年第12期22卷 1149-1155页

作者： Peng-yan LU Yu LIU hua-jie wu Gang LIU Xiang MENG Yang XU Engineering Research Institute University of Science and Technology Beijing School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing

Fatigue performance of hot-rolled ribbed-steel bar with the yield strength of 500 MPa （HRB500） was stud- ied with bend-rotating fatigue test at a stress ratio of R = -1. It is determined by staircase method that its fatigue strength for 107 cycles is 451 MPa, which is higher than that of common carbon structural steel. This should be at- tributed to the fine-grain strengthening resulting from the high content of alloy element V and Thermo-Mechanical Control Process （TMCP）. The S-N curve function is also obtained by nonlinear regression with three parameters power function. The fatigue fractures of the specimen were further analyzed with Scanning Electron Microscopy （SEM） and Energy Disperse Spectroscopy （EDS） to study the fracture mechanism. Taking into account microstruc- ture, hardness and cleanliness of the material, it implies that the fatigue fractures of HRB500 rebar all arise from surface substrates in which many brittle inclusions are contained, and that the fatigue crack propagation is principally based on the mechanism of quasi-cleavage fracture, because of the intracrystalline hard spots leading to stress con- centration and thus to the cracks. Moreover, the transient breaking area exhibits microvoid coalescence of ductile fracture due to the existing abundant inclusions.

关键词： HRB500 bend-rotating fatigue performance fracture mechanism inclusion

Effect of M-EMS on the solidification structure of a steel billet

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International Journal of Minerals,Metallurgy and Materials 2011年第2期18卷 159-164页

作者： hua-jie wu Ning Wei Yan-ping Bao Guo-xin Wang Chao-ping Xiao Jin-jin Liu Engineering Research Institute University of Science and Technology Beijing Beijing 100083 China School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing100083 China

Effects of mold electromagnetic stirring （M-EMS） on the solidification structure of 45# steel billet were investigated by examination of interdendritic corrosion. The results show that the primary and secondary dendrite arm spacings increase from the edge of the billet to the center and decrease obviously with increasing electromagnetic torque, which will be beneficial to refine the solidification structure and enlarge the equiaxed crystal zone. The ratio of equiaxed crystal increases by 15.9% with the electromagnetic torque increasing from 230 to 400 cN·cm. The increase of stirring intensity can improve the cooling rate and the impact of M-EMS on it reduces from the edge of the billet to the central area, where the cooling rates are similar at different torques. The closer to the central area, the less the influence of M-EMS on the cooling rate is. The ratio of the primary to secondary dendrite arm spacing is approximately 2.0, namely, λ1≈2λ2, and is constant irrespective of the stirring intensity and position of the billet. Original position analysis （OPA） results indicate that the center segregation of the billet is greatly improved, and the more uniform and compact solidification structure will be obtained with the increase of stirring intensity.

关键词： continuous casting electromagnetic stirring dendrite arm spacing cooling rate solidification

The RNA-binding domain of DCL3 is required for long-distance RNAi signaling

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aBIOTECH 2024年第1期5卷 17-28页

作者： jie Li Bo-Sen Zhang hua-Wei wu Cheng-Lan Liu Hui-Shan Guo Jian-hua Zhao State Key Laboratory of Plant Genomics Institute of MicrobiologyChinese Academy of SciencesBeijing 100101China CAS Center for Excellence in Biotic Interactions University of the Chinese Academy of SciencesBeijing 100049China Qilu Zhongke Academy of Modern Microbiology Technology Jinan 250022China

Small RNA(sRNA)-mediated RNA silencing(also known as RNA interference,or RNAi)is a conserved mechanism in eukaryotes that includes RNA degradation,DNA methylation,heterochromatin formation and protein translation *** plants,sRNAs can move either cell-to-cell or systemically,thereby acting as mobile silencing signals to trigger noncell autonomous ***,whether and what proteins are also involved in noncell autonomous silencing have not been *** this study,we utilized a previously reported inducible RNAi plant,PDSi,which can induce systemic silencing of the endogenous PDS gene,and we demonstrated that DCL3 is involved in systemic PDS silencing through its RNA binding *** confirmed that the C-terminus of DCL3,including the predicted RNA-binding domain,is capable of binding short *** affecting RNA binding,but not processing activity,reduced systemic PDS silencing,indicating that DCL3 binding to RNAs is required for the induction of systemic *** mosaic virus infection assays showed that the RNA-binding activity of DCL3 is required for antiviral RNAi in systemically noninoculated *** findings demonstrate that DCL3 acts as a signaling agent involved in noncell autonomous silencing and an antiviral effect in addition to its previously known function in the generation of 24-nucleotide sRNAs.

关键词： RNAi signaling DCL3 RBD RNAs Cucumber mosaic virus

Terminal-selective C（sp3）–H borylation of unbranched alkanes enabled by intermolecular radical sampling and LMCT photocatalysis

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National Science Review 2024年第5期11卷 96-98页

作者： Zhexuan Lei jie wu Department of Chemistry National University of Singapore

The selective functionalization of C（sp3）–H bonds with subtle differences in alkanes is highly sought after due to its atom-and step-efficiency. The activation of C（sp3）–H bonds through hydrogen atom transfer （HAT） has been extensively exploited to produce a valueadded product from unfunctionalized material [1,2].

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3D simulation of image-defined complex internal features using the numerical manifold method

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Science China(Technological Sciences) 2024年第4期67卷 1023-1039页

作者： wu jie MA GuoWei School of Civil and Transportation Engineering Hebei University of TechnologyTianjin 300401China Tianjin Key Laboratory for Prefabricated Building and Intelligent Construction Tianjin 300401China

The numerical simulation of internal features,such as inclusions and voids,is important to analyze their impact on the performance of composite ***,the complex geometries of internal features and the induced continuous-discontinuous(C-D)deformation fields are challenges to their numerical *** this study,a 3D approach using a simple mesh to simulate irregular internal geometries is developed for the first *** the help of a developed voxel crack model,image models that are efficient when recording complex geometries are directly imported into the *** reconstructions,which are usually labor-intensive,are excluded from this ***,using image models as the geometric input,image processing techniques are applied to detect material interfaces and develop contact ***,the C-D deformations of the complex internal features are directly calculated based on the numerical manifold *** accuracy and convergence of the developed3D approach are examined based on multiple *** 3D C-D simulation of sandstones with naturally formed complex microfeatures demonstrates the capability of the developed approach.

关键词： 3D continuous-discontinuous simulation image-based simulation complex internal features numerical manifold method voxel crack model structured mesh

Sequential enantioselective Ugi-4CR/post-Ugi transformation strategy:a precise construction of structurally diverse azaspiro polycyclic scaffolds

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Science China Chemistry 2024年第2期67卷 576-586页

作者： Xiao-Bao wu Jun-Xiu Shi Yi-Ming Ou hua-jie Jiang Yi-Jun Fang Qi-Ming Wang Quan Gao jie Yu Department of Applied Chemistry Anhui Province Engineering Laboratory for Green Pesticide Development and ApplicationAnhui Province Key Laboratory of Crop Integrated Pest ManagementAnhui Agricultural UniversityHefei230036China

A privileged strategy has been developed for the precise construction of enantioenriched azaspiro polycyclic *** diverse azaspiro polycycles bearing multiple contiguous stereocenters are obtained with excellent results(up to 99:1 e.r.,>95:5 d.r.) via sequential enantioselective four-component Ugi reactions/post-Ugi transformations with substrates containing prerequisite functional groups in the presence of anionic stereogenic-at-cobalt(Ⅲ) complexes.

关键词： asymmetric catalysis post-Ugi transformation anionic stereogenic-at-cobalt(Ⅲ)complex azaspiro polycyclic scaffold one-pot synthesis