29 results on '"Y.J. Xie"'
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2. Cold spray additive manufacturing of Invar 36 alloy: microstructure, thermal expansion and mechanical properties
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Jiang Wang, Longtao Liu, Shanqing Li, Renzhong Huang, Y.J. Xie, Hanlin Liao, Zhongming Ren, Chaoyue Chen, Ruixin Zhao, and Xiaoli Jin
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Materials science ,Polymers and Plastics ,Annealing (metallurgy) ,Mechanical Engineering ,Metals and Alloys ,Gas dynamic cold spray ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Thermal expansion ,0104 chemical sciences ,Grain growth ,Mechanics of Materials ,Residual stress ,Materials Chemistry ,Ceramics and Composites ,engineering ,Composite material ,0210 nano-technology ,Invar ,Tensile testing - Abstract
In this work, the Invar 36 alloys were manufactured using cold spray (CS) additive manufacturing technique. The systematic investigations were made on the microstructural evolution, thermal expansion and mechanical properties under as-sprayed (AS) and heat-treated (HT) conditions. XRD (X-ray diffraction) and ICP-AES (inductively coupled plasma atomic emission spectroscopy) analyses show that no phase transformation, oxidation, nor element content change have occurred. The X-ray computed tomography (XCT) exhibited a near fully dense structure with a porosity of 0.025% in the helium-produced sample under as-sprayed condition, whereas the nitrogen-produced samples produced at 5 MPa and 800 °C show more irregular pore defects. He-AS sample shows a more prominent grain refinement than that of nitrogen samples due to the more extensive plastic deformation. The post heat-treatment exhibited a promoted grain growth, inter-particle diffusion, as well as the formation of annealing twins. Between 25 °C and 200 °C, the nitrogen samples possessed lower CTE (coefficient of thermal expansion) values (1.53 × 10-6/°C) compared with those produced by casting and laser additive manufacturing. The He-AS samples exhibited a noticeable negative CTE value between 25 °C and 200 °C, which may due to the significant compressive residual stress (-272 MPa) compensating its displacement with temperature increase during CTE test. The N2-HT and He-HT Invar 36 samples present a notable balance between strength and ductility. In conclusion, the CS technique can be considered as a potential method to produce the Invar 36 component with high thermal and mechanical performance.
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- 2021
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3. A tale of two genera: Exotic Eucalyptus and Acacia species in China. 2. Plantation resource development
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R. J. Arnold, S.J. Midgley, H.R. Wang, J.Z. Luo, and Y.J. Xie
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Ecology ,biology ,Agroforestry ,Geography, Planning and Development ,Foundation (engineering) ,Acacia ,Climate change ,Forestry ,biology.organism_classification ,Eucalyptus ,Geography ,Resource development ,Wood processing ,Domestication ,China - Abstract
In China a substantial plantation industry involving 5.4 M ha of exotic eucalypts and up to 50 000 ha of exotic acacias, has been built on a foundation of collaborative R&D sponsored by both China and Australia over the past 40 years. Germplasm derived from some of the early collaboration still provides the majority of trees deployed in current eucalypt plantations in China. But, whilst the past 2 decades has been the best of times for plantation eucalypts in China, the past decade has simultaneously been the worst of times for plantation acacias. Improved plantation productivities achieved through R&D programs coupled with innovations in processing markedly increased the profitability of young eucalypt plantations; this provided strong market pull for expansion of these plantations. For exotic acacias though, plantation areas in China have declined over the past decade. Factors that have contributed to the contrasting fates of these species in China, along with their future outlooks, are reviewed in this report.
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- 2020
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4. A tale of two genera: exotic Eucalyptus and Acacia species in China. 1. Domestication and research
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R. J. Arnold, S.J. Midgley, J.Z. Luo, Y.J. Xie, and H.R. Wang
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Germplasm ,Ecology ,biology ,Agroforestry ,Geography, Planning and Development ,Acacia ,Forestry ,biology.organism_classification ,Eucalyptus ,Geography ,Southern china ,Genetic resources ,China ,Domestication ,Silviculture - Abstract
In China a substantial plantation industry, including 5.4 M ha of eucalypts and up to 50,000 ha of acacias, has been built on a foundation of R&D and germplasm acquisition for exotic eucalypt and acacia species over the past 40 years. From the 1980s through to the early 2000s a suite of Chinese-Australian collaborative R&D projects made major contributions to domestication, genetic improvement, silviculture and other aspects of plantation eucalypts and acacias in southern China. Even today, germplasm derived from earlier projects still provides the majority of planting stock deployed in China's current eucalypt plantations. For eucalypts, improvements in plantation productivities have been achieved through solid, well managed R&D programs. For acacias, despite work done in past decades to develop breeding populations and production capacities for improved seeds, genetic resources of acacias in China have deteriorated greatly in recent years. Factors affecting domestication and genetic improvement of both genera in China are reviewed in this report along with the research undertaken for both genera over the past 40 years.
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- 2020
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5. The effects of fabrication atmosphere condition on the microstructural and mechanical properties of laser direct manufactured stainless steel 17-4 PH
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Xuejun Chen, Y.J. Xie, Yulong Li, Chi Changtai, Wuyou Wang, Muqin Wang, Duoming Wang, Zhongjun Chen, and Cheng Xiangping
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Austenite ,Materials science ,Fabrication ,Polymers and Plastics ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Nitrogen ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Phase (matter) ,Ultimate tensile strength ,Materials Chemistry ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Dispersion (chemistry) ,Porosity - Abstract
The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4PH components fabricated by laser direct manufacturing (LDM) were investigated through measurements on phase constitution, porosity, tensile strength, fracture morphology, hardness and evolution of substrate temperature. Results showed that the samples produced in air atmosphere condition possessed higher tensile strength and hardness for both as-deposited and heat-treated states than that in Ar chamber condition, due to dispersion strengthening effect of amorphous oxide particles and nitrogen solution strengthening as a result of higher content of oxygen and nitrogen. The temperature of substrate heat accumulation was higher in Ar chamber condition, leading to dramatically lower porosity and more reverse austenite, which also contributed to the lower strength and hardness.
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- 2019
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6. Underlying fracture trends and triggering on Mode-II crack branching and kinking for quasi-brittle solids
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J. Li, Y.M. Cai, Y.J. Xie, and X.Y. Zheng
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Strain energy release rate ,Conservation law ,Materials science ,Mechanical Engineering ,0211 other engineering and technologies ,02 engineering and technology ,Mechanics ,Computer Science::Computational Geometry ,Physics::Classical Physics ,Instability ,Physics::Geophysics ,Condensed Matter::Materials Science ,020303 mechanical engineering & transports ,Fracture toughness ,0203 mechanical engineering ,Mechanics of Materials ,Fracture (geology) ,General Materials Science ,Brittle solids ,Fracture configurations ,021101 geological & geomatics engineering - Abstract
A geometrical model on multiple cracks initiation from boundary with singular stress fields has been proposed for the fracture analysis of Mode-II crack. The conservation law has been explored utilizing a partial integral path, from which an analytical solution of the energy release rate for multiple cracks initiation from a crack tip has been established. Some underlying fracture trends of cracks initiation from a crack tip, including crack side-branching and crack kinking, for quasi-static Mode-II deformation have been theoretically investigated, which implies actually some degree of instability for Mode-II fracture. The K-based criterions and fracture toughness for Mode-II crack side-branching and kinking have been defined. The fracture configurations of crack side-branching and kinking under Mode-II loading and corresponding fracture toughness predicted by the present modelling agree well with the experimental observations on the rock fracture reported in the literatures.
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- 2019
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7. A computational method of stress intensity factor for flat-oval cross-section thin-walled pipe
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Z.Y. Hu, C. Li, H.F. Zhao, B.F. Zhao, Y.J. Xie, Wei Yin, and L.Y. Xie
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0209 industrial biotechnology ,Materials science ,Mechanical Engineering ,Fracture mechanics ,02 engineering and technology ,Mechanics ,Bending ,Stress field ,Cross section (physics) ,020303 mechanical engineering & transports ,020901 industrial engineering & automation ,0203 mechanical engineering ,Mechanics of Materials ,Fracture (geology) ,General Materials Science ,Stress intensity factor ,Intensity (heat transfer) ,Parametric statistics - Abstract
As an important parameter of fracture criterion, stress intensity factor (SIF) is considered to be one metric of the singular stress field intensity near the crack tip, also a main parametric in fracture mechanics. Therefore, solving technique on the stress intensity factor takes an important role in engineering applications. In view of typical three-dimensional features of flat-oval thin-walled pipes, it is relatively tough to obtain the stress intensity factors for the special-shaped shells with multi-transverse cracks by classical methods. In this paper, a very simple method based on J2-integral and bending theory is proposed to calculate the SIFs. Examples demonstrate that this technique is feasible, especially, that, suitable for the determination of the stress intensity factors of three-dimensional complicated structures. And the results show that not only the solution process is simple and available, but also the closed-form solutions can be derived effectively.
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- 2019
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8. Mode-I stress intensity factors for cracked special-shaped shells under bending
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Y.J. Xie, H. Yuan, and W.J. Liu
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Conservation law ,Materials science ,Mechanical Engineering ,0211 other engineering and technologies ,Mode (statistics) ,Shell (structure) ,02 engineering and technology ,Bending ,Mechanics ,Finite element method ,Stress (mechanics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,General Materials Science ,Beam (structure) ,Stress intensity factor ,021101 geological & geomatics engineering - Abstract
The slender special-shaped shells possess both shell and beam characteristics, which are widely used in practical engineering. A slender special-shaped shell under bending with some complex cracks, such as a frost flower-shaped crack and circumferential periodic cracks in a pipeline, is actually a typical three-dimensional complex crack problem with many different singular stress fields and stress intensity factors. In the present article, a very simple and practical technique based on the elementary mechanics and the concept of the conservation law is proposed to determine the stress intensity factors. The results from present method are shown to agree well with available solutions and FEM. In particular, the present method can also be easily applied to the other similar cracked structural shells.
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- 2019
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9. Windows to trigger crack branching for cracked solids under mixed Mode-I/II loading
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W.J. Yuan, Y.J. Xie, and H. Yuan
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Mechanics of Materials ,Applied Mathematics ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Condensed Matter Physics - Published
- 2022
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10. Synthesis of carbon nanotube reinforced Al matrix composite coatings via cold spray deposition
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Hongjian Wu, Xingchen Yan, Zhanqiu Tan, Zhiqiang Li, Xinliang Xie, Hanlin Liao, Y.J. Xie, Shuohong Gao, Gang Ji, Chaoyue Chen, Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), Université de Technologie de Belfort-Montbeliard (UTBM)-Université de Bourgogne (UB)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS), Institute of Mechanics, Materials and Civil Engineering [Louvain] (IMMC), Université Catholique de Louvain = Catholic University of Louvain (UCL), Unité Matériaux et Transformations - UMR 8207 (UMET), Centrale Lille-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Shanghai Jiao Tong University [Shanghai], University of Shanghai [Shanghai], Laboratoire Interdisciplinaire Carnot de Bourgogne [Dijon] (LICB), Université de Bourgogne (UB)-Université de Technologie de Belfort-Montbeliard (UTBM)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Centrale Lille Institut (CLIL), UCL - SST/IMMC/IMAP - Materials and process engineering, Univ. Bourgogne Franche-Comté - ICB UMR 6303, CNRS, Univ. Lille - Unité Matériaux et Transformations, Shanghai Jiao Tong University - State Key Laboratory of Metal Matrix Composites, Shanghai University - State Key Laboratory of Advanced Special Steels, and Guangdong Academy of Sciences - National Engineering Laboratory for Modern Materials Surface Engineering Technology
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Materials science ,Composite number ,Gas dynamic cold spray ,02 engineering and technology ,Carbon nanotube ,engineering.material ,Carbon nanotube reinforced ,01 natural sciences ,law.invention ,Coating ,law ,0103 physical sciences ,Materials Chemistry ,Composite material ,Plastic deformation ,Ball mill ,Mechanical property ,010302 applied physics ,Al matrix composite ,Cold spray ,Surfaces and Interfaces ,General Chemistry ,[CHIM.MATE]Chemical Sciences/Material chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Surfaces, Coatings and Films ,engineering ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Particle ,0210 nano-technology ,Metallic bonding - Abstract
International audience; For the fabrication of high-strength carbon nanotube (CNT) reinforced Al matrix composites, the uniform dispersion, strong interface bonding and high structural integrity of CNTs have been regarded as the three most important issues. In this work, two distinct approaches, namely high shear dispersion (HSD) and shift-speed ball milling (SSBM), were applied to disperse CNTs (1.5 wt%) into pure Al powders. These two kinds of CNT/Al composite powders as well as the pure Al powder (as a comparison) were deposited onto stainless steel plates by cold spraying using different processing parameters. The velocity and the temperature of the particle prior to impact was simulated by the commercial code of Fluent. The deposition efficiency, microstructure evolution, as well as the distribution and structural integrity of CNTs in the composite coatings produced from different starting powders were comparatively investigated in terms of X-ray diffraction (XRD), Raman spectra, and electron back scanning diffraction (EBSD). According to the XRD and Raman analysis, no new phases such as oxides or brittle Al4C3 were detectable in both CNT/Al composite coatings. Some structural damages of CNTs were found in both composite coatings, especially the one fabricated from HSD composite powder. The dispersion of CNTs onto Al particle surfaces by HSD approach did not achieve a significant strengthening effect on the composite coatings, but adversely affected the metallic bonding of the particles and the substrate. The microhardness of the CNT/Al composite coating produced from SSBM powders reached around ~115 HV0.1, showing a significant improvement compared to the pure Al coating mainly due to the grain refinement and CNTs strengthening.
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- 2021
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11. Geometrical effect of a notch tip on fracture toughness test
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W.J. Yuan and Y.J. Xie
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Applied Mathematics ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
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12. Disturbance effect of weak Mode-II loading on the fracture of Mode-I crack
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H. Yuan, Y.J. Xie, and W. Wang
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2022
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13. Instability of cracks initiation from a mixed-mode crack tip with iso-stress intensity factors KI and KII
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Y.J. Xie, W.J. Yuan, X.W. Cui, X.Y. Zheng, Y. Wang, and X.H. Li
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Strain energy release rate ,Materials science ,Applied Mathematics ,Mechanical Engineering ,0211 other engineering and technologies ,02 engineering and technology ,Mechanics ,Condensed Matter Physics ,Mixed mode ,Instability ,Intensity (physics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Present method ,Critical energy ,Fracture (geology) ,General Materials Science ,Stress intensity factor ,021101 geological & geomatics engineering - Abstract
For a special case of mixed-mode crack with iso-stress intensity factors KI and KII, the instability of cracks initiation from a crack tip has been investigated based on the principle of the energy-based driving force. By using the J i -integrals over the crack boundary, the fracture modelling and relevant energy release rate on the multiple-crack initiation have been formulized. It has been found that when stress intensity factors KI and KII close to each other, more possible forms of multiple-cracks initiation from a crack tip may occur theoretically including the crack side-branching and kinking, which is remarkable and conducive to better understand the complex fractural phenomena in engineering and fracture tests. By using the present method, which part of the crack tip boundary fracture can be identified and the relevant critical energy release rate can be found.
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- 2018
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14. Influence of Cr addition on the interface purification of vacuum brazed NiCr-Cr 3 C 2 coatings on single crystal superalloy
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Y.J. Xie, Wenqin Wang, Xiuwen Han, Muqin Wang, Chi Changtai, Xuejun Chen, and Duoming Wang
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010302 applied physics ,Materials science ,Diffusion ,Metallurgy ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Surfaces, Coatings and Films ,Coating ,Phase (matter) ,0103 physical sciences ,Materials Chemistry ,engineering ,Brazing ,Nichrome ,0210 nano-technology ,Base metal ,Layer (electronics) - Abstract
In order to improve the high temperature wear- and oxidation resistance of single crystal superalloy, NiCr-Cr3C2 coatings were vacuum brazed on the surface. Different weight ratios of Cr were added into the coatings to control the diffusion of Si and C into the base metal, which would be harmful to the base metal stability. The results show that, when no Cr was added into the coatings, a layer of Ni3Si phase at the interface and MC precipitates in base metal were produced. With the increase of the Cr addition, the coating/base metal interface was gradually purified. The Ni3Si layer and the MC precipitates disappeared when the Cr addition increased to 30 wt% and an interface was clearly presented with the γ′ phases on both sides epitaxially growing on some extent. After 200 thermal fatigue cycles, the total crack lengths were measured, which decreased with increasing Cr addition, indicating that the thermal fatigue resistance was improved.
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- 2017
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15. Tribological and corrosion behaviors of Zr-doped graphite-like carbon nanostructured coatings on Ti6Al4V alloy
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W.Q. Bai, Li Lingling, X.L. Wang, Y.J. Xie, J.P. Tu, and C.D. Gu
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Materials science ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Corrosion ,symbols.namesake ,Materials Chemistry ,Graphite ,Composite material ,Nanocomposite ,Metallurgy ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,Tribology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,0104 chemical sciences ,Surfaces, Coatings and Films ,chemistry ,symbols ,0210 nano-technology ,Raman spectroscopy ,Carbon - Abstract
Biomedical Ti6Al4V alloy exhibits excellent mechanical and anti-corrosion properties but poor wear resistance. In order to improve the combination performance of Ti6Al4V alloy, Zr-doped graphite-like carbon (GLC) nanomultilayer and nanocomposite coatings are deposited by magnetron sputtering. The microstructures of the coatings are characterized by transmission electron microscopy (TEM) and Raman spectroscopy. The Zr-doped GLC nanomultilayer shows low friction coefficient and wear rate at applied loads of 1 N and 3 N in Hank's solution. In addition, both the Zr-doped GLC nanomultilayer and nanocomposite coatings present high corrosion resistance, which results from the corrosion-resistant GLC and zirconium oxide. Compared to the Zr-doped GLC nanocomposite, the nanomultilayer is more promising in the applications under simultaneously tribological and corrosive conditions.
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- 2017
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16. Adhesion and tribological properties of gradient designed a-C film on ultrahigh molecular weight polyethylene
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X.L. Wang, G. Jin, W.Q. Bai, Y.J. Xie, Li Lingling, and J.P. Tu
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010302 applied physics ,Equiaxed crystals ,Materials science ,Metals and Alloys ,Biasing ,02 engineering and technology ,Surfaces and Interfaces ,Sputter deposition ,Tribology ,Nanoindentation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Film coating ,Amorphous carbon ,0103 physical sciences ,Materials Chemistry ,Composite material ,0210 nano-technology ,Tribometer - Abstract
Amorphous carbon (a-C) film is deposited with a gradient designed bias voltage on the ultrahigh molecular weight polyethylene (UHMWPE) substrates and Si3N4 balls via a closed field unbalanced magnetron sputtering. The designed bias voltage continuously increases from − 40 V to − 80 V with two different increasing rate. The film with a thickness of approximately 1000 nm is made up of equiaxed grains with size of around 20 nm. Nanoindentation tests show that the hardness of the UHMWPE increases from 44 MPa to 2.16 GPa after deposition of a-C film with gradient designed bias voltage. The wear rate and friction coefficient of the a-C film sliding against a-C films coated on Si3N4 balls is tested in air and Hank's solution by means of a reciprocating tribometer. The a-C film deposited with gradient bias voltage exhibits superior adhesion and tribological performance, compared with those deposited with balanced bias voltage. The a-C film wearing against Si3N4 balls with a-C film coating shows a lower wear rate, compared with a-C films wearing against uncoated balls, decreasing from 1.95 × 10− 15 m3 N− 1 m− 1 to 1.23 × 10− 15 m3 N− 1 m− 1. There is a further enhancement of the anti-wear performance in Hank's solution.
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- 2017
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17. Corrosion and tribocorrosion performance of M (M Ta, Ti) doped amorphous carbon multilayers in Hank's solution
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Y.J. Xie, J.P. Tu, G. Jin, Li Lingling, X.L. Wang, Liu Dongguang, and W.Q. Bai
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010302 applied physics ,Materials science ,Tribocorrosion ,Metallurgy ,Doping ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Sputter deposition ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Surfaces, Coatings and Films ,Corrosion ,Amorphous carbon ,Breakage ,Residual stress ,0103 physical sciences ,Materials Chemistry ,Artificial joints ,0210 nano-technology - Abstract
Amorphous carbon (a-C) and Ta- or Ti-doped a-C multilayer films are deposited onto Ti6Al4V alloy by an industrial closed field unbalanced magnetron sputtering. The corrosion and tribocorrosion performances of these films are investigated in Hank's solution at 37 °C. The a-C film exhibits enhanced wear and corrosion resistance compared with the bare Ti6Al4V alloy, but the cracks propagate during the tribocorrosion process, which leads to serious breakage. Interestingly, the tribocorrosion resistance of a-C film is improved by introducing Ta- or Ti-doped multilayered structure. The high mechanical properties (high hardness and low residual stress), good corrosion, and wear resistance of Ta- and Ti-doped a-C multilayer films make them excellent protective materials for artificial joints.
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- 2016
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18. Developing new microstructure through laser melting of electrospark layer of precipitation hardened nickel based superalloy
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Hamid Reza Shahverdi, Y.J. Xie, M. Ebrahimnia, and F. Malek Ghaini
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Materials science ,Alloy ,Metallurgy ,Laser beam welding ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,Grain size ,020501 mining & metallurgy ,Superalloy ,Precipitation hardening ,0205 materials engineering ,engineering ,General Materials Science ,0210 nano-technology ,Electrospark deposition ,Layer (electronics) - Abstract
Highly oriented fine microstructure was achieved through laser melting of electrospark layer of a precipitation hardened nickel based superalloy. Using electron back scattered diffraction analysis, it was found that the new layer has preferred orientation toward the surface. This microstructure grows epitaxially on the electrospark layer, which consists of very fine grains. Having lower elemental segregation and finer grain size, this new modified microstructure has higher hot cracking resistance compared to the conventional autogenous laser weld microstructure on cast alloy.
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- 2016
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19. An integrated statistical and data-driven framework for supporting flood risk analysis under climate change
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Xiaosheng Qin, Y.J. Xie, and Yan Lu
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010504 meteorology & atmospheric sciences ,Flood myth ,Meteorology ,Hydrological modelling ,0208 environmental biotechnology ,Climate change ,02 engineering and technology ,01 natural sciences ,020801 environmental engineering ,HadCM3 ,Climatology ,100-year flood ,Generalized extreme value distribution ,Range (statistics) ,Environmental science ,0105 earth and related environmental sciences ,Water Science and Technology ,Downscaling - Abstract
Summary An integrated statistical and data-driven (ISD) framework was proposed for analyzing river flows and flood frequencies in the Duhe River Basin, China, under climate change. The proposed framework involved four major components: (i) a hybrid model based on ASD (Automated regression-based Statistical Downscaling tool) and KNN (K-nearest neighbor) was used for downscaling rainfall and CDEN (Conditional Density Estimate Network) was applied for downscaling minimum temperature and relative humidity from global circulation models (GCMs) to local weather stations; (ii) Bayesian neural network (BNN) was used for simulating monthly river flows based on projected weather information; (iii) KNN was applied for converting monthly flow to daily time series; (iv) Generalized Extreme Value (GEV) distribution was adopted for flood frequency analysis. In this study, the variables from CGCM3 A2 and HadCM3 A2 scenarios were employed as the large-scale predictors. The results indicated that the maximum monthly and annual runoffs would both increase under CGCM3 and HadCM3 A2 emission scenarios at the middle and end of this century. The flood risk in the study area would generally increase with a widening uncertainty range. Compared with traditional approaches, the proposed framework takes the full advantages of a series of statistical and data-driven methods and offers a parsimonious way of projecting flood risks under climatic change conditions.
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- 2016
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20. Enhancement of adhesion by a transition layer: Deposition of a-C film on ultrahigh molecular weight polyethylene (UHMWPE) by magnetron sputtering
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Li Lingling, J.P. Tu, W.Q. Bai, Y.J. Xie, F.F. He, X.L. Wang, and G. Jin
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Materials science ,General Physics and Astronomy ,Biasing ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Adhesion ,Substrate (electronics) ,Tribology ,Sputter deposition ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Amorphous carbon ,Composite material ,0210 nano-technology ,Deposition (law) ,Tribometer - Abstract
An amorphous carbon (a-C) film is deposited on the plasma-treated UHMWPE substrate using a closed field unbalanced magnetron sputtering to improve its tribological properties. During the plasma treatment period, a transition layer is prepared by high energy ion bombardment at a bias voltage of −500 V to enhance the adhesion between the a-C film and the substrate. The mechanical and tribological properties of the a-C film were evaluated by nano-indentation and ball-on-disk tribometer. After deposition of a-C film with a thickness 900 nm, the nano-hardness of UHMWPE significantly increases from 47 MPa to 720 MPa and the wear rate decreases from 9.82 × 10 −15 m 3 N −1 m −1 to 4.78 × 10 −15 m 3 N −1 m −1 in bovine calf serum solution. The formation of the transition layer is believed to be the reason why the vertical adhesion between the a-C film and the UHMWPE substrate is enhanced.
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- 2016
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21. Disturbance effects of weak Mode-II loading on K-based Mode-I fracture toughness test
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Y.J. Xie and H. Yuan
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Disturbance (geology) ,Materials science ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Work (physics) ,Mode (statistics) ,Experimental data ,Structural engineering ,Condensed Matter Physics ,Experimental data processing ,Fracture toughness ,Fracture (geology) ,General Materials Science ,business - Abstract
It is well known that making of specimens, experimental set up, fixtures and testing procedure could inevitably affect the experimental accuracy, which will actually induce the disturbance from weak Mode-II loading on the specimen in K-based Mode-I fracture toughness tests. How to quantitatively analyse the disturbance effects is quite interesting and challenging work. In present article, an energy-based modelling on multiple underlying cracks initiation from a crack tip has been suggested to capture and quantify the disturbance effects. Conventional experimental data processing will lead to higher Mode-I fracture toughness values, which would affect the accuracy of fracture assessment, and cannot truly reflect the fracture property of materials. The current investigation has revealed that three theoretical predictable values of K-based Mode-I fracture toughness may be measured in tests if weak Mode-II loading acting on the specimen is inevitable, which is helpful to identify the real value of the fracture toughness and better understand scattered experimental data.
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- 2020
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22. Calculation of characteristic size and fatigue life of structural members with blunt notches
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Xianbing Xu, S.L. Liu, C. Li, L.Y. Xie, T. Mu, and Y.J. Xie
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Stress gradient ,Critical distance ,Characteristic length ,business.industry ,Mechanical Engineering ,0211 other engineering and technologies ,Fatigue testing ,02 engineering and technology ,Unified Model ,Structural engineering ,Fatigue limit ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Crack size ,General Materials Science ,business ,021101 geological & geomatics engineering ,Mathematics - Abstract
In order to evaluate notch effects and size effects on fatigue performances, smooth specimens without stress gradient and a group of notched specimens particularly designed are investigated in this paper. From the perspective of probability, the statistical size effect of the latter is worth studying for bodies weakened by notches. A unified model of combination of the improved theory of critical distance (TCD), along with the concept of highly-stressed-volume (CHSV) is established to identify the initiation crack size, evaluate the fatigue strength, and determine the fatigue lifetime of notched members, and even similar large-scale components in high cycle fatigue regime. The predicted results are compared with the experimental data sets taken from literatures. Fortunately, we find that, the novel model not only inherits the generality of existing methods, such as TCD, but also provides necessary support for predictions of characteristic length and fatigue lifetime of components containing any blunt-notch geometries.
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- 2020
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23. Surface hardening of laser melting deposited 12CrNi2 alloy steel by enhanced plasma carburizing via hollow cathode discharge
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Zhang Dong, H.W. Kang, Y.J. Xie, X. Peng, M. Ebrahimnia, and Wei Zhang
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010302 applied physics ,Materials science ,Metallurgy ,Alloy steel ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,Indentation hardness ,Cathode ,Surfaces, Coatings and Films ,Carburizing ,law.invention ,law ,Martensite ,0103 physical sciences ,Volume fraction ,Materials Chemistry ,engineering ,0210 nano-technology ,Layer (electronics) - Abstract
Plasma carburizing of 12CrNi2 alloy steel fabricated by laser melting deposition was carried out in a propane-containing atmosphere at temperature of 930 °C with and without hollow cathode discharge (HCD). The generation of the HCD in the carburizing process was achieved by adding an auxiliary cathode opposite the alloy steel sample. The carburized samples were characterized by analysis of microstructure, microhardness and wear performance. The assistance of HCD increased the carbon concentration in the carburized layer and the case depth without changing the carburizing atmosphere and discharge voltage, indicating the improvement of carburizing kinetics. This leads to an increased volume fraction of acicular martensite and an increased the microhardness of the carburized layer as well as the improvement of the wear resistance of alloy steel.
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- 2020
- Full Text
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24. Potential fracture paths for cracked rocks under compressive-shear loading
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H. Yuan, Y.L. Duo, and Y.J. Xie
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Strain energy release rate ,Conservation law ,Materials science ,0211 other engineering and technologies ,Complex fracture ,02 engineering and technology ,Geotechnical Engineering and Engineering Geology ,Instability ,Compressive load ,Fracture toughness ,Shear (geology) ,Composite material ,021102 mining & metallurgy ,021101 geological & geomatics engineering - Abstract
An energy-based model on multiple cracks initiation from a crack tip has been proposed to capture the physical process of fracture, which can be used to predict and analyse the fracture behaviours of cracked rocks and rock-model materials under compressive-shear loading. The conservation law has been explored utilizing a partial integral path, from which an analytical solution of the energy release rate for multiple cracks initiation from a crack tip has been founded. Some underlying fracture behaviours on cracks initiation from a crack tip, including the crack kinking, side-branching, branching and tri-branching, have been theoretically investigated, which implies actually a degree of instability on a cracked rock under compressive-shear loading. The K-based criteria and fracture toughness for crack kinking, side-branching, branching and tri-branching have been defined. The predictions based on present modelling should help to refresh the understanding of some important experimental observations, such as so called wing cracks and secondary cracks observed in the experiments of cracked rock under compressive loading. As an alternative solution, the energy-based driving mechanism behind complex fracture phenomenon have been suggested.
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- 2020
- Full Text
- View/download PDF
25. Underlying fracture trends on Mode-I crack multiple-branching
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W. Wang, H. Yuan, and Y.J. Xie
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Strain energy release rate ,Fracture toughness ,Materials science ,Mechanics of Materials ,Mechanical Engineering ,Crack initiation ,General Materials Science ,Fracture configurations ,Mechanics ,Impulse (physics) ,Branching (polymer chemistry) ,Instability - Abstract
An energy-based modelling has been proposed to capture the physical process of multiple cracks initiation from a Mode-I crack tip. The underlying fracture trends and instability on crack tri-branching, symmetric branching and side-branching induced by dominant Mode-I loading are formulized. The solutions of the energy release rate, crack initiation angles and K-based fracture criterion for multiple cracks initiation have been investigated. The upper limit on the number of possible crack initiation is given for a Mode-I crack. The discussions in present article indicate that some underlying fracture configurations for Mode-I crack can be triggered by using impulse loading. Many fracture behaviours for a Mode-I crack can be better explained and understanding based on the present theoretical modelling. The fracture toughness predicted by the present modelling and Griffith’s criterion agree well with experimental results.
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- 2020
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26. Down-regulation of miR-1246 in cervical cancer tissues and its clinical significance
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Y. Yang, Y.J. Xie, Qian Xu, Yi Zhang, J.X. Chen, and Nianchun Shan
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Pathology ,medicine.medical_specialty ,Colorectal cancer ,Down-Regulation ,Uterine Cervical Neoplasms ,Protein Serine-Threonine Kinases ,Transfection ,medicine.disease_cause ,Cell Line, Tumor ,microRNA ,medicine ,Humans ,Clinical significance ,Lung cancer ,Neoplasm Staging ,Cervical cancer ,Human papillomavirus 16 ,business.industry ,Papillomavirus Infections ,Obstetrics and Gynecology ,Oncogene Proteins, Viral ,Middle Aged ,Protein-Tyrosine Kinases ,Prognosis ,medicine.disease ,Gene Expression Regulation, Neoplastic ,Repressor Proteins ,MicroRNAs ,Real-time polymerase chain reaction ,Oncology ,Cancer research ,Female ,business ,Liver cancer ,Carcinogenesis ,HeLa Cells - Abstract
Objective MicroRNAs (miRNAs) are non-coding RNAs that regulate the expression of mRNAs by binding to their 3′-untranslated regions (UTRs). Accumulating evidences show that miRNAs are involved in tumorigenesis such as lung cancer, liver cancer, colon cancer, and cervical cancer. In this study, we focused on the expression of miR-1246 in clinical cervical cancer tissues as well as the relationship between miR-1246 and HPV16E6 infection status. Methods Real-time quantitative polymerase chain reaction technology was used to detect the expression of miR-1246 in 68 cervical cancer tissues and 52 normal tissues. The expression of miR-1246 also was tested in HPV16E6 negative cervical cell line (SiHa) or HPV16E6 positive cell line (C33A). Western blot was performed to detect the expression of DYRK1A after knocking down HPV16E6. Results Our data showed that the expression of miR-1246 was dramatically decreased in cervical cancer tissue, compared with normal control group (p=0.0012), and miR-1246 was negatively correlated with clinical stage and HPV16E6 infected status (p=0.0410), but no correlation was observed with age, tumor diameter, cervical invasion depth, lymph node metastasis, or vascular invasion (p>0.05). Knock down of HPV16E6 significantly raised DYRK1A protein expression targeted by miR-1246. Conclusions The expression of miR-1246 is negatively correlated with cervical cancer procedure as well as HPV16E6 infection status and the miR-1246 may act as a diagnostic biomarker for cervical cancer. In addition, HPV16E6 infection may be a major reason leading to decrease the expression of miR-1246 in cervical cancer. This finding contributes to deep understanding of the miR-1246 function in cervical carcinogenesis.
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- 2015
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27. Fracture-based model of periodic-arrayed indentation for rock cutting
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Xiaozhi Hu, X. Z. Zhu, X. H. Wang, and Y.J. Xie
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Stress (mechanics) ,Stress field ,Cracking ,Materials science ,Breakage ,Indentation ,Fracture (geology) ,Geotechnical engineering ,Fracture mechanics ,Composite material ,Geotechnical Engineering and Engineering Geology ,Stress intensity factor - Abstract
Periodic singular stress fields and K-dominant regions arise adjacent to sharp 90° indenter edges if an elastic substrate is subject to indentation with rigid, flat-ended and periodic indenters. The concept of indentation stress intensity factor Kind is convenient to describe such a singular indentation stress field, which is mathematically similar to that of a Mode-I crack. The singular indentation stress field is sufficient to induce surface cracking even if the substrate surface is free of any micro-cracks. This surface cracking mechanism generated from the flat-ended indentation potentially can play a significant role in damage analysis of rock cutting. During the rock-cutting processing, those periodic singular-stress fields will move along the rock surface, leading to continuous rock surface fracture. In this study, a fracture mechanics model is proposed for rock breakage by using an energy-based approach. The indentation stress intensity factor Kind and indentation cracking equation for rock-cutting/breakage have thus been formulated analytically.
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- 2015
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28. Quasibrittle fracture beneath a flat bearing surface
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D.A. Hills and Y.J. Xie
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Bearing (mechanical) ,Materials science ,Fissure ,business.industry ,Mechanical Engineering ,Structural engineering ,Strength of materials ,law.invention ,medicine.anatomical_structure ,Fracture toughness ,Brittleness ,Mechanics of Materials ,law ,Indentation ,medicine ,Fracture (geology) ,General Materials Science ,Material properties ,business - Abstract
The problem of fracture of the quasibrittle and brittle material such as glass when subject to indentation by a relatively rigid, square-ended uniform punch is considered, using classical energy principles. The strain energy needed to form a crack adjacent to the punch edge is found, and from this the load needed to initiate fracture given. The calculation is of practical interest in the design rating of bearing blocks supporting structural glass. Additionally, it implies also the potential possibility to set up a very simple and practical technique for evaluating some strength-related properties of materials such as the fracture toughness using specimens without macro-pre-existing cracks.
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- 2016
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29. A Study of the Relationships Between Lexical Richness and Writing Quality: Taking the English Majors at Guangxi University as an Example
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Y. Shen and Y.J. Xie
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Lexical density ,Computer science ,media_common.quotation_subject ,Quality (business) ,Species richness ,Writing quality ,English vocabulary ,Sophistication ,Linguistics ,media_common - Abstract
The present paper aims to investigate the correlation of lexical richness with writing quality by measuring lexical richness in EFL English writing. The research was performed by measuring timed compositions of 56 senior English majors with four indices of lexical richness, including text length, high frequency words, lexical density, and lexical sophistication. The finding of this study is that lexical richness is indeed taken into consideration in scoring the quality of English writing. The measure of the four indices of lexical richness can distinguish between the higher-scoring compositions and lower-scoring compositions, which shows, to a statistically significant extent, that lexical richness correlates with the quality of English writing. It is hoped that the findings of the present study will be useful for improving the teaching and learning of English vocabulary. KEYWORD: lexical richness; writing Quality; English majors
- Published
- 2015
- Full Text
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