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Characterizations of precipitation behavior of Al-Mg-Si alloys under different heat treatments

China Foundry 2018年第2期15卷 89-96页

作者： Hui Li Jia-yi Wang Hai-tao Jiang zheng-feng Lu Zhen-feng Zhu College of Engineering Yantai Nanshan UniversityYantai 265700China Institute of Engineering Technology University of Science and Technology BeijingBeijing 100083China National Engineering Research Center for Plastic Working of Alulinum Alloys Shandong Nanshan Aluminum Co.Ltd.Yantai 265713China

The solidification-precipitation behavior of Al-Mg-Si multicomponent alloys has long been an absorbing topic. Experiments were carried out to analyze the precipitation behaviors of Al-Mg-Si alloys under different heat treatments. All specimens were homogenized at 570 ℃ for 8 h, and then solution treated at 540 ℃ for 55 min. Subsequently, the specimens were age treated for different times at temperatures of 100 ℃, 150 ℃ and 180 ℃, respectively. The experimental results show that the occurrence of dispersed free zones （DFZ） is caused by the uneven distribution of dispersed phase. During the aging process, pre-β＂ phases form at the initial stage and an aging temperature of 100 ℃is too low to complete the transformation of pre-β＂ to β＂. At 150℃, the precipitation sequence is concluded as SSSS-pre-β＂-pre-β＂＋β＂-β＂-β＇-β. Moreover, changes in sizes and densities of the pre-β＂, β＂and β＇ phases during the aging process has an important influence on the evolution of microhardness and electrical resistivity. The microhardness peak value of 150 ℃ is similar to that of 180 ℃, which is -141 HV. While, at 100℃, the microhardness increases slowly, and the attainable value is 127 HV up to 19 days. When the aging temperature is 100 ℃, the electrical resistivity has the highest average value. When the aging temperature exceeds 100 ℃, with the occurrence and growth of β＂and β＇, the resistivity has a distinct decrease with prolonged aging time.

关键词： Al-Mg-Si alloy heat treatment precipitation behavior electrical resistivity

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High-order finite volume methods for solving compressible multicomponent flows

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Science China Mathematics 2024年

作者： feng zheng Jianxian Qiu School of Mathematics and Statistics Fujian Key Laboratory of Mathematical Analysis and ApplicationFujian Normal University School of Mathematical Sciences and Fujian Provincial Key Laboratory of Mathematical Modeling& High-Performance Scientific Computing Xiamen University

In this paper, we propose a high-order finite volume method for solving multicomponent fluid problems. Our method couples the quasi-conservative form with the reconstruction of conservative variables in a characteristic manner. The source term and numerical fluxes are carefully designed to maintain the pressure and velocity equilibrium for the interface-only problem and preserve the equilibrium of physical parameters in a single-component fluid. These ingredients enable our scheme to achieve both high-order accuracy in the smooth region and the high resolution in the discontinuity region of the solution. Extensive numerical tests are performed to verify the high resolution and accuracy of the scheme.

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Turbulence Modulations in the Boundary Layer of a Horizontal Particle-Laden Channel Flow

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Chinese Physics Letters 2010年第6期27卷 129-132页

作者： LI Jing LIU Zhao-Hui WANG Han-feng CHEN Sheng LIU Ya-Ming HAN Hai-feng zheng Chu-Guang State Key Laboratory of Coal Combustion Huazhong University of Science and Technology Wuhan 430074

Turbulence modulations are experimentally investigated using particle image velocimetry （PIV） in the lower boundary layer of a fully developed horizontal channel flow. A simultaneous two-phase PIV measurement technique is adopted to acquire the turbulent statistics quantities and to examine the coherent structures in the near-wall region. Polythene beads with diameters of 60 μm are used as dispersed phases, and the PIV measurements have been performed at three mass loadings varying from 2.5 ×10^-4 to 5 × 10^-3. All the experiments are performed at a wall shear Reynolds number of Reτ = 430. The results show that the presence of the particles suppresses the coherent structures, with shorter streamwise extent of the quasistrearnwise structures, and then, the wall-normal velocity fluctuations and shear Reynolds stresses are both decreased in the near-core region. In addition, as a result of the particle wake, the turbulence intensity and shear Reynolds stress both increase in the vicinity of the wall. Due to the drag effects of the particles on the gas, the streamwise velocity gradients decrease in the outer region and increase in the viscous sublayer, meanwhile the thickness of the viscous sublayer also decreases. These results cause the peak values of the streamwise velocity fluctuations adjacent to the wall to increase, and the peak positions shift to the wall. This is the reason for decreasing the near-wall region and increasing the near-core region of the streamwise velocity fluctuations in appearance.

关键词： Reynolds stress Wakes Flow in channels Turbulence intensities Statistical analysis Drag

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Experimental research on the critical conditions and critical equation of chip splitting when turning a C45E4 disc workpiece symmetrically with a high-speed steel double-edged turning tool

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Advances in Manufacturing 2022年第2期10卷 159-174页

作者： Ming-Xian Xu Liang-Shan Xiong Bao-Yi Zhu Ling-feng zheng Kai Yin School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan 430074People's Republic of China

Chip splitting is a natural chip separation phenomenon that can significantly reduce cutting energy *** reveal its occurrence mechanisms,a method for obtaining its critical conditions through cutting experiments and establishing its critical equation is proposed in this *** on previous research results regarding the relationship between chip removal interference and chip splitting,the control variables that affect chip splitting are identified by analyzing a geometric model of the cutting process.A total of 366 experiments on turning a C45E4 disc workpiece with a high-speed steel double-edged turning tool based on the dichotomy method were conducted and 51 experimental data on chip splitting critical conditions were *** these experimental data,a critical equation expressed by a finitedegree polynomial with a cutting thickness equal to the other control variables was *** analyzing the critical surface,it was determined that chip splitting followed a law in which the smaller the cutting thickness and the larger the absolute value of the negative rake angle,edge angle,and edge inclination of the tool,the more likely chip splitting was to *** a verification experiment,it was determined that the derived critical equation could accurately predict the occurrence of 95.24%of chip *** was also determined that the occurrence of chip splitting led to a cliff-like drop in the specific total cutting force with a maximum drop of 51.23%.This research lays a foundation for the rational utilization of chip splitting in tool structure parameter design and cutting parameter energy saving optimization.

关键词： Chip splitting Critical conditions Critical equation Cutting force Experimental research Doubleedged turning tool symmetrical transverse cutting

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Controllable synthesis of nanorod/nanodisk TiO_2 from titanium-containing electric furnace molten slag

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Rare Metals 2015年第4期34卷 267-275页

作者： Zai-Qing Que Yang Li Hai-Yang Yu feng zheng Mei Zhang Min Guo State Key Laboratory of Advanced Metallurgy School of Metallurgical and Ecological Engineering University of Science and Technology Beijing

Nanostructured TiO2 with different morphologies and crystal phases was successfully synthesized from titanium-containing electric furnace molten slag by using a hydrothermal method followed by reflux process in acid solution. The effects of acid concentration, reflux time, and acid type on the formation of TiO2 were systematically investigated by scanning electron microscopy, X-ray dif- fraction （XRD）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, and X-ray fluorescence （XRF）. It is indicated that TiO2 nanorod with rutile phase is achieved in nitric or hydrochloric acid, while anatase TiO2 nanodisk is formed in sulfuric acid. With the increase of the concentration of hydrochloric acid from 0.3 to 1.5 mol-L-1, the dispersibility and crystallinity of the final product can be improved. With prolonging the reflux time from 6 to 14 h, the rutile TiO2 nanorod with uniform crystal size and high crystallinity is obtained. The growth mechanism of TiO2 nanorod and nanodisk prepared under different conditions was also discussed.

关键词： Titanium-containing electric furnace molten slag TiO2 Nanorod Nanodisk Hydrothermal method

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Chain damage effects of multi-spaced plates by reactive jet impact

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Defence Technology（防务技术） 2021年第2期17卷 393-404页

作者： Yuan-feng zheng Cheng-hai Su Huan-guo Guo Qing-bo Yu Hai-fu Wang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

Chain damage is a new phenomenon that occurs when a reactive jet impacts and penetrates multispaced *** reactive jet produces mechanical perforations on the spaced plates by its kinetic energy(KE),and then results in unusual chain rupturing effects and excessive structural damage on the spaced plates by its deflagration *** the present study,the chain damage behavior is initially demonstrated by *** reactive liners,composed of 26 wt%Al and 74 wt%PTFE,are fabricated through a pressing and sintering *** reactive liner thicknesses of 0.08 CD,0.10 CD and 0.12 CD(charge diameter)are chosen to carry out the chain damage *** results show a chain rupturing phenomenon caused by reactive *** constant reaction delay time and the different penetration velocities of reactive jets from liners with different thicknesses result in the variation of the deflagration position,which consequently determines the number of ruptured plates behind the ***,the finite-element code AUTODYN-3D has been used to simulate the kinetic energy only-induced rupturing effects on plates,based on the mechanism of behind armor debris(BAD).The significant discrepancies between simulations and experiments indicate that one enhanced damage mechanism,the behind armor blast(BAB),has acted on the ruptured ***,a theoretical model is used to consider the BAB-induced enhancement,and the analysis shows that the rupturing area on aluminum plates depends strongly upon the KE only-induced pre-perforations,the mass of reactive materials,and the thickness of plates.

关键词： Reactive materials Reactive jet Chain damage Behind armor blast

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Targeting of circulating hepatocellular carcinoma cells to prevent postoperative recurrence and metastasis

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World Journal of Gastroenterology 2014年第1期20卷 142-147页

作者： Yu Zhang Zhi-Long Shi Xia Yang zheng-feng Yin EMolecular Oncology Laboratory Eastern Hepatobiliary Surgery Hospital

Currently,the main treatment for hepatocellular carcinoma(HCC)involves the surgical removal of tumors or liver ***,these treatments are often not completely curative,as they are associated with a risk for postoperative recurrence and *** tumor cells(CTCs)are increasingly recognized as the main source for recurrence and metastasis after radical hepatectomies are *** studies have demonstrated the association between the presence of either pre-or postoperative CTCs and an increased risk for HCC *** improve the therapeutic outcome of HCC,a personalized,comprehensive and multidisciplinary approach should be considered,involving the application of appropriate diagnostic and therapeutic measures targeting HCC CTCs in different stages throughout the course of *** article proposes some HCC CTC-based strategies for the treatment of HCC,including the monitoring of HCC CTCs before,during and after radical hepatectomy,therapeutic targeting of HCC CTCs,prevention of the generation and colonization of CTCs,as well as the use of CTC indexes for the selection of indications,prediction of prognoses,and planning of individualized therapeutic *** and technological development of therapies targeting CTCs,as well as their translation into clinical practice,will help to effectively reduce postoperative recurrence and metastasis,and significantly prolong the survival of HCC patients.

关键词： Hepatocellular carcinoma Circulating tumor cells Recurrence and metastasis Surgical treatment Individualized treatment

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Construction of TiO2/silane nanofilm on AZ31 magnesium alloy for controlled degradability and enhanced biocompatibility

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Rare Metals 2019年第6期38卷 588-600页

作者： Lei Huang Kun Su Yu-feng zheng Kelvin Wai-Kwok Yeung Xiang-Mei Liu School of Materials Science and Engineering Hubei UniversityWuhan 430062China State Key Laboratory for Turbulence and Complex System Department of Materials Science and EngineeringCollege of EngineeringPeking UniversityBeijing 100871China Department of Orthopaedics and Traumatology Li Ka Shing Faculty of MedicineThe University of Hong KongPokfulam 999077Hong KongChina

A TiO2 nanofilm was prepared on the surface of AZ31 magnesium alloy with controllable thickness through atomic layer deposition(ALD) technique, which can adjust the corrosion behaviors of AZ31 Mg *** with the untreated Mg alloys, corrosion current densities(icorr)can decline by 58% in the 200-cycles TiO2-covered Mg alloy and further decline by up to 74% with the thickness of nanofilm up to 63 nm(400 cycles).The subsequent modification with a cross-linked conversion layer of 3-aminopropyltriethoxysilane(APTES) by a dipping method can produce a compact silane coating on TiO2 nanofilm, which can seal pinholes of TiO2 nanofilm and serve as a barrier to further adjust the corrosion behavior of the *** icorrcan decline about two orders of magnitude in the TiO2/silane composite *** the adjustable corrosion rate come true, which can be attributed to the precise control on the thickness of metal oxide nanofilm and additional protection from the compact silane *** vitro study discloses that the TiO2/silane hybrid coating shows higher expression of alkaline phosphatase(ALP)and can promote cellular adhesion and proliferation with better cytocompatibility than untreated Mg alloy.

关键词： Magnesium alloy TiO2 Biodegradability Atomic layer deposition Hybrid coating Biocompatibility

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Catalytic conjugate addition of indole toα,β-unsaturated ketones by Co(ClO_4)-2·6H_2O/bis-Schiff base complexes

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Chinese Chemical Letters 2012年第5期23卷 525-528页

作者： Yong Hai Hui Chun Mei Chen zheng feng Xie Key Laboratory of Oil and Gas Fine Chemicals Ministry of Education and Xinjiang Uyghur Autonomous RegionCollege of Chemistry and Chemical EngineeringXinjiang UniversityUrumqi 830046China

Co（ClO_4））_2·6H_2O/bis-Schiff base complexes promoted the conjugate addition of indole toα,β-unsaturated ketones under mild conditions,giving the corresponding addition products with high *** the complex has bee... 详细信息

关键词： Conjugate addition Indole α β-Unsaturated ketone Schiff base

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A new sesquilignan from Selaginella sinensis (Desv.) Spring

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Chinese Chemical Letters 2007年第10期18卷 1224-1226页

作者： Yan Zhi Wang Hui Chen Xiao Ke zheng Wei Sheng feng Henan College of Traditional Chinese Medicine Zhengzhou 450008 China

A new sesquilignan, namely sinensiol A, was isolated from the plant of Selaginella sinensis （Desv.） Spring. Its structure was identified on the basis of various spectroscopic data analysis.

关键词： Selaginella sinensis, Sinonsiol A Sesquilignan

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