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Multi-scale simulation of columnar-to-equiaxed transition during laser selective melting of rare earth magnesium alloy

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Journal of Materials Science & Technology 2022年第24期119卷 11-24页

作者： w.l.wang w.Q.liu X.Yang R.R.Xu Q.Y.Dai School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an 710055China

A model of coupling macro finite volume method(FVM) and cellular automata(CA) is proposed in this paper to explore the columnar-to-equiaxed transition(CET) during selective laser melting(SlM) of rare earth magnesium alloy.Taking into account the impact of recoil pressure and Marangoni convection on the molten pool temperature field,the grain structure is simulated.As suggested by the simulation results,with the undissolved Zr serving as heterogeneous nucleation sites,the liquid undercooled layer under the combined action of forced cooling,the temperature gradient and the liquid solute concentration gradient leads to CET.while considering the dissolution of Zr in magnesium matrix,the results demonstrate that the dissolution of element Zr is effective in significantly inhibiting the growth of columnar crystals and ensuring the sufficient constitutional supercooling(CS) required for nucleation.In addition,to raise the preheating temperature contributes to enhancing the outcome of nucleation and incresing the grain size.Invoking the interdependence model(IM),with the cooling rate gradually increasing in the SlM process of magnesium alloy,the nucleation-free zone(NFZ) reduces by decreasing the solute diffusion layer in the front of the solid/liquid(Sl) interface and the temperature gradient.The reduction in temperature gradient can promote undercooling for nucleation and facilitate the development of equiaxed crystals.The simulation results are qualitatively verified as highly consistent through experimentation.

关键词： Multi-scale simulation Columnar-to-equiaxed transition Selective laser melting Rare earth magnesium alloy Constitutional supercooling

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ElECTROCHEMICAl INVESTIGATION ON CARBON NANOTUBE FIlM wITH DIFFERENT PRETREATMENTS

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Acta Metallurgica Sinica(English letters) 2003年第4期16卷 295-301页

作者： C.G.Hu w.l.wang w.Zhu DepartmentofAppliedPhysics ChongqingUniversityChongaing400044China KeylaboftheEducationMinistryforPhotoelectricTechnologyandSystem ChongqingUniversityChongqing400044China DepartmentofChemistry ChongqingUniversityChongqing400044ChinaManuscriptreceived25November2002

wide potential windows were found at carbon nanotube film electrodes in neutral solutions after being treated with nitric acid and mixed acid. Electrochemical reversibility was investigated at carbon nanotube films with different pretreatments for ferri/ferrocyanide and quinone /hydroquinone. Carbon nanotube film electrodes presented quasi-reversible electrochemical behavior for both electrolytes. In the range of scan rate, carbon nanotube film electrodes treated with acids showed heterogeneous electron-transfer properties, which was mainly controlled by its electron state density on the surface of the film. On the whole, the carbon nanotube electrode with nitric acid treatment presented the best electrochemical behaviors, so we chose it as an analytical electrode to determine the trace compound in dilute solution. The results demonstrated that this new electrode material exhibits superior performance characteristics for the detection of azide anion.

关键词： carbon nanotubes cyclic voltammetry treatment azide anion

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INFlUENCES OF DENSITY AND DIMENSION OF CARBON NANOTUBES ON THEIR FIElD EMISSION

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Acta Metallurgica Sinica(English letters) 2003年第4期16卷 302-308页

作者： Y.B.Zhu w.l.wang C.G.Hu DepartmentofPhysics JiangsuNormalUniversitySuzhou221009ChinaManuscriptreceived25November2002 DepartmentofAppliedPhysics ChongqingUniversityChongqing400044China

The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays. The results obtained here are in good agreement with the experimental data.

关键词： carbon nanotube array field emission optimum density

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Effect of relative humidity on the desulfurization performance of calcium-based desulfurizer

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Journal of Environmental Sciences 2024年第4期138卷 179-188页

作者： Juan lǖ Yu Fu Haiyan Yu Huanwang Zhe wang Haiyan Chen School of Environment and Resource Southwest University of Science and TechnologyMianyang 621010China Guangyuan Emergency Management bureau Guangyuan 628000China

low desulfurization efficiency impedes the wide application of dry desulfurization technology,which is a low-cost and simple process,and one significant solution is the development and manufacture of high-performance desulfurizers.In this study,firstly,a steam jet mill was used to digest quicklime;then,we utilized numerical simulation to study the flow field distribution and analyze the driving factors of quicklime digestion;and lastly,the desulfurization performance of the desulfurizer was evaluated under different relative humidities.The results show that the desulfurizer prepared via the steam jet mill had better apparent activity than traditional desulfurizers.Also,the entire jet flow field of the steam jet mill is in a supersonic and highly turbulent flow state,with high crushing intensity and good particle acceleration performance.Sufficient contact with the nascent surface maximizes the formation of slaked lime.The experiments demonstrated that the operating time with 100%desulfurization efficiency and the“break-through”time for the desulfurizer prepared via the steam jet mill is longer than that of traditional desulfurizers,and has significant advantages,especially at low flue gas relative humidity.Compared with traditional desulfurizers,the desulfurizer prepared via steam jet mill expands the range of acceptable flue gas temperature,and the failure temperature is 1.625 times that of traditional desulfurizers.This work breaks through the technical bottleneck of low dry desulfurization efficiency,which is an important step in pushing forward the application of dry desulfurization.

关键词： Dry desulfurization Relative humidity Desulfurization efficiency High-efficiency desulfurizer Quicklime digestion

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ElECTROANAlYTICAl APPlICATIONS OF CARBOXYl-MODIFIED CARBON NANOTUBE FIlM ElECTRODES

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Acta Metallurgica Sinica(English letters) 2003年第4期16卷 289-294页

作者： C.G.Hu w.l.wang K.J.liao w.Zhu DepartmentofAppliedPhysics ChongqingUniversityChongqing400044China KeylaboftheEducationMinistryforPhotoelectricTechnologyandSystem ChongqingUniversityChongqing400044China DepartmentofChemistry ChongqingUniversityChongqing400044ChinaManuscriptreceived25November2002

The electrochemical behavior of a carboxyl-modified carbon nanotube films was investigated to explore its possibility in electroanalytical applicaton. Cyclic voltammetry of quinone was conducted in 1mol/l Na2SO4, which showed a stable, quasi-reversible voltammetric response for quinone / hydroquinone, and the anodic and the cathodic peak potentials were 0.657V and -0.029V (vs. SCE) at a scan rate of 0.1V.s-1, respectively. Both anodic and cathodic peak currents depended linearly on the square root of the scan rate over the range of 0.01-0.5V.s-1, which suggested that the process of the electrode reactions was diffusion-controlled. Carboxyl-modified carbon nanotube electrodes made it possible to determine low level of dopamine selectively in the presence of a large excess of ascorbic acid in acidic media using derivative voltammetry. The results obtained were discussed in details. This work demonstrates the potential of carboxyl-modified carbon nanotube electrodes for electroanalytical applications.

关键词： carbon nanotube electrochemistry carboxyl modification dopamine

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The role of a novel antibacterial substance,cyclic opine-producing lacticaseibacillus rhamnosus lS8 in ameliorating ulcerative colitis:a fecal microbiota transplantation study

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Food Science and Human wellness 2024年第2期13卷 778-790页

作者： Tao wang Shuang wang Shuchen Dong Ruiling wang Shuxuan wang Jie Yang Xin wang Xin lü College of Food Science and Engineering Northwest Agriculture and Forestry UniversityYangling 712100China Faculty of Food Science and Engineering Kunming University of Science and TechnologyKunming 650500China School of life Science and Technology Xinjiang UniversityUrumqi 830046China

Intestinal microbiota imbalance may worsen the progression of ulcerative colitis(UC).lacticaseibacillus rhamnosus lS8(lR)has the potential ability to regulate microbiota through producing a novel antibacterial substance,cyclic opine:cycloalanopine.This study aimed to investigate whether lR could ameliorate dextran sulfate sodium-induced UC in mice via modulating intestinal microbiota using fecal microbiota transplantation(FMT)experiment.The results showed that both lR and FMT attenuated UC as evidenced by 1)alleviating disease activity index and colonic pathology;2)up-regulating MUCs and tight junction proteins;3)increasing oxidative mediators and decreasing antioxidant mediators;4)down-regulating proinflammatory cytokines and chemokines.These results were mainly attributable to the microbiota-regulating effect of lR,including increasing beneficial bacteria(like Akkermansia)and its related SCFAs,while decreasing harmful bacteria(like Proteobacteria)and its related lPS,thereby suppressing the hyperactivation of TlR4/NF-κB pathway.Consequently,lR can alleviate UC and is a potential dietary supplement to attenuate UC.

关键词： Gut barrier Gut microbiota Fecal microbiota transplantation lacticaseibacillus rhamnosus Oxidative stress Ulcerative colitis

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Precipitation of multi-type nano-quasicrystals in a Mg-Zn-Y alloy

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Journal of Magnesium and Alloys 2024年第3期12卷 997-1008页

作者： w.Z.wang X.Z.Zhou l.F.Zhang H.Q.Ye Z.Q.Yang Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of ScienceShenyang 110016China Ji Hua laboratory Foshan 528251China Foshan University Foshan 528231China

Mg-6Zn-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging treatments.Microstructural evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy techniques.Two new kinds of decagonal quasicrystals were formed in aged ribbons,in addition to precipitation of nanometer icosahedral quasicrystals.Atomic-resolution observations reveal that both decagonal quasicrystals can be modeled by quasiperiodic tiling with decagonal clusters of 2.5 nm in diameter,but overlap of neighboring clusters in both decagonal quasicrystals is different from the Gummelt model observed in other quasicrystals.A shell composed of complex laves Mg-Zn domains was formed surrounding each decagonal quasicrystal precipitate upon prolonged aging.In addition,all kinds of nanoprecipitates exhibit excellent structure and size stability at 573 K.Our findings may have implications for not only fundamental studies about quasicrystals,but also microstructural manipulation of high-performance Mg alloys.

关键词： Quasicrystal Mg alloys Rapid solidification Scanning-transmission electron microscopy.

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Experimental clearance rate and intraguild predation of jellyfish Cyanea nozakii

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Journal of Oceanology and limnology 2024年第1期42卷 128-140页

作者： Pengpeng wang Fang ZHANG Song SUN Shuguo lÜ CAS Key laboratory of Marine Ecology and Environmental Sciences Institute of OceanologyChinese Academy of SciencesQingdao 266071China laboratory for Marine Ecology and Environmental Sciences Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China University of Chinese Academy of Sciences Beijing 100049China Jiaozhou Bay Marine Ecosystem Research Station Chinese Academy of SciencesQingdao 266071China Center for Ocean Mega-Science Chinese Academy of SciencesQingdao 266071China Institute of Marine Ecology and Environment Hainan Academy of Environmental SciencesHaikou 570100China

Cyanea nozakii,a common jellyfish distributed in offshore China,has a complex trophic relationship with other zooplankton groups.However,few studies have reported the predation rates and prey selection patterns of C.nozakii medusae on different prey items.Research is also lacking on the intraguild predation of Aurelia coerulea(another common bloom jellyfish in offshore China)by C.nozakii.To address the knowledge gaps,the clearance rates of C.nozakii for different prey items,including copepods(smalllarge>1000μm),fish larvae,and gelatinous prey(hydromedusae,A.coerulea ephyrae,and chaetognaths),were measured.The influence of predator size on the clearance rate was also determined.Additionally,we examined the intraguild predation of C.nozakii on A.coerulea medusae.The clearance rates of C.nozakii varied widely with prey organisms,being independent of prey concentrations.Gelatinous organisms,except for chaetognaths,were captured with considerably high efficiency,followed by fish larvae and copepods,indicating the preferential prey selection of gelatinous organisms by C.nozakii.The clearance rate increased linearly with the cross-sectional area of C.nozakii.Body size in medusae may,to some extents,underpin their capacity to capture more prey by increasing the encounter rate and capture success through ontogeny.C.nozakii preyed voraciously on A.coerulea in high feeding efficiency,but the clearance rate decreased with increasing A.coerulea(as prey)size.This phenomenon of intraguild predation suggests a speculative hypothesis of potential population regulation of A.coerulea by C.nozakii.The information regarding the feeding ecology of C.nozakii reported in this study is important for understanding plankton dynamics in marine ecosystems with extensive occurrences of this jellyfish.

关键词： Scyphomedusae predation rate gelatinous organisms prey selection feeding mechanism

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Study on the dynamic mechanical properties of winding-block axial structure considering short circuit strain rate effect

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High Voltage 2024年第2期9卷 380-390页

作者： Xinyu wang Ping wang Jianghai Geng Zikang Zhang Fangcheng lü Shuguo Gao Hebei Provincial Key laboratory of Power Transmission Equipment Security Defense North China Electric Power UniversityBaodingChina State Grid Hebei Electric Power Research Institute ShijiazhuangChina

Transformers may suffer multiple short-circuit impacts during long-term operation,and axial instability is one of the typical types of serious accidents caused by short-circuit faults.The axial instability form of the winding-block structure is analysed,and the dynamic solution of the winding short-circuit electromagnetic force is obtained by estab-lishing the three-dimensional magnetic-circuit-force multi-physical field coupling simulation model.The influence of strain rate on the cushion block constitutive equation is corrected,and the modified model is verified by short-circuit impact test and quasi-static test.The research results show that for 110 kV 31.5 MVA transformers,the maximum electromagnetic axial resultant force of winding is 363.16 kN,and the ultimate tilt force is 1214.2 kN.The pre-tightening force configuration is accordingly recom-mended to range from 363.16 to 608.28 kN,which is narrowed by 18.49%compared with the static calculation method;Meanwhile,adding a logarithmic strain rate correction term to the classical constitutive equation of the cushion block can achieve a good correction of the stress-strain relationship with the coefficient of determination above 0.99,and the cushion block has a larger elastic modulus under high strain rate load.The research results provide an important theoretical reference for the axial stability structure of transformers.

关键词： axial correction structure

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The Consistency of lSE Estimators in Partial linear Regression Models under Mixing Random Errors

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Acta Mathematica Sinica,English Series 2024年第5期40卷 1244-1272页

作者： Yun Bao YAO Yu Tan lÜ Chao lU wei wang Xue Jun wang School of Mathematical Sciences Anhui UniversityHefei 230601P.R.China School of Big Data and Artificial Intelligence Chizhou UniversityChizhou 247000P.R.China School of Big Data and Statistics Anhui UniversityHefei 230601P.R.China

In this paper,we consider the partial linear regression model y_(i)=x_(i)β^(*)+g(ti)+ε_(i),i=1,2,...,n,where(x_(i),ti)are known fixed design points,g(·)is an unknown function,andβ^(*)is an unknown parameter to be estimated,random errorsε_(i)are(α,β)-mix_(i)ng random variables.The p-th(p>1)mean consistency,strong consistency and complete consistency for least squares estimators ofβ^(*)and g(·)are investigated under some mild conditions.In addition,a numerical simulation is carried out to study the finite sample performance of the theoretical results.Finally,a real data analysis is provided to further verify the effect of the model.

关键词： (α,β)-mixing random variables partial linear regression model least squares estimator consistency

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