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Synthesis and room Temperature Ferromagnetism of Flower-shaped Mn Doped ZnO Nanostructures

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Journal of Materials Science & Technology 2011年第6期27卷 513-517页

作者： Y.q. Chang P.W. Wang r.h. Tang q.L. Sun Y. Long School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Department of Physics National Key Laboratory of Mesoscopic Physics Peking University Beijing 100871 China

Large-scale flower-shaped Mn doped ZnO nanostructures have been grown on silicon substrates by simple thermal evaporation at atmospheric *** flower-shaped nanostructure makes up of many nanorods,which are rooted in one *** of X-ray diffraction,high-resolution transmission electron microscopy and raman spectra results reveal that the products are of single phase with wurtzite *** mapping results show that no impurity clusters exist in the doped *** photoluminescence spectra demonstrate that many oxygen vacancies exist in the doped materials,and the crystal quality is improved and the content of oxygen vacancies is decreased by annealing *** flower-shaped Mn doped ZnO nanostructures exhibit ferromagnetic ordering above room temperature,and its magnetization is decreased by the annealing treatment,which indicates that the magnetic behavior of the doped materials may be related to the interaction between Mn doping and the oxygen vacancies.

关键词： Mn doped ZnO nanomaterials Ferromagnetism Annealing treatment Chemical vapor deposition

rational design of AgGaS/ZnS/ZnS quantum dots with a near-unity photoluminescence quantum yield via double shelling scheme

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Journal of Materials Science & Technology 2024年第2期169卷 235-242页

作者： h.X.Lu h.Liu Z.Z.Fu Y.Y.Chen h.q.Dai Z.hu W.L.Zhang r.q.Guo Institute for Electric Light Sources School of Information Science and TechnologyFudan UniversityShanghai 200433China Institute of Future Lighting Academy for Engineering and TechnologyFudan UniversityShanghai 200433China Yiwu research Institute of Fudan University YiwuZhejiang 322000China Zhongshan-Fudan Joint Innovation Center Zhongshan 528437China

In this study,a two-step method was used to synthesize highly luminescent AgGaS/ZnS/ZnS quantum dots(qDs).In the first step,an inner ZnS shell was formed via a one-pot method,which resulted in a smaller lattice mismatch between the AgGaS core and the outer ZnS shell,thereby facilitating the formation of a thick outer *** the two-step shelling process,the synthesized AgGaS/ZnS/ZnS qDs showed an excellent photoluminescence quantum yield(PLqY)of 96.4%with a peak wavelength of 508 nm,repre-senting the highest PLqY reported thus far for AgGaS ***,the effect of halogen ions in Zn precursors on the shelling process was *** was proposed that the capacity of halogen ions to coordinate with the qDs influenced the balance between Zn cation diffusion and ZnS shelling ***,the ZnS shelling reaction was dominant when ZnCl_(2)was employed,while Zn cation diffusion was the dominant process under the I^(−)-rich *** work provides insights into the interfacial restructuring during the ZnS shelling and offers a clear map for the tailored synthesis of core/shell qDs.

关键词： AgGaS quantum dots Photoluminescence Core/shell Alloyed core/shell interface

Large Amplitude Low Frequency Waves in a Magnetized Nonuniform Electron-Positron-Ion Plasma

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Chinese Physics Letters 2004年第5期21卷 884-887页

作者： q.haque h.Saleem Abdus-SalamInternationalCentreforTheoreticalPhysicsTrieste Italy Permanentaddresses:DepartmentofPhysics COMSATSInstituteofInformationTechnologyH-8IslamabadPakistan.

It is shown that the large amplitude low-frequency electromagnetic drift waves in electron–positron–ion plasmas might give rise to dipolar vortices. A linear dispersion relation of several coupled electrostatic and electromagnetic low-frequency modes is obtained. The relevance of this work to both laboratory and astrophysical situations is pointed out.

关键词： Positrons

Influence of the lithium content on the negative difference effect of Mg-Li alloys

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Journal of Materials Science & Technology 2020年第22期54卷 138-145页

作者： C.q.Li D.K.Xu Z.r.Zhang E.h.han School of Materials and Energy Guangdong University of TechnologyGuangzhou 510006China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic *** this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NDE of Mg-Li alloys can be retarded by increasing lithium ***,galvanostatic and potentiodynamic polarization experiments using Mg-xLi(x=4,7.5 and 14 wt%) alloys electrodes indicated that Mg-4 Li alloy maintained the enhancing NDE prior to anodic dissolution as that of conventional Mg ***,the emergence of β-Li phase weakened the NDE of duplex Mg-7.5 Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value(more than 2 mA/cm^2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NDE for Mg-4 Li and Mg-7.5 Li ***,the NDE of Mg-14 Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.

关键词： Mg-Li alloy Negative difference effect Electrochemical property Corrosion Anodic dissolution

Soft computing approach for prediction of surface settlement induced by earth pressure balance shield tunneling

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Underground Space 2021年第4期6卷 353-363页

作者： W.G.Zhang h.r.Li C.Z.Wu Y.q.Li Z.q.Liu h.L.Liu Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing 400045China National Joint Engineering research Center of Geohazards Prevention in the reservoir Areas Chongqing UniversityChongqing 400045China School of Civil Engineering Chongqing UniversityChongqing 400045China Norwegian Geotechnical Institute(NGI) Sognsveien 720855 OsloNorway

Estimating surface settlement induced by excavation construction is an indispensable task in tunneling,particularly for earth pressure balance(EPB)shield *** this study,predictive models for assessing surface settlement caused by EPB tunneling were established based on extreme gradient boosting(XGBoost),artificial neural network,support vector machine,and multivariate adaptive regression *** from three tunnel construction projects in Singapore were used,with main input parameters of cover depth,advance rate,earth pressure,mean standard penetration test(SPT)value above crown level,mean tunnel SPT value,mean moisture content,mean soil elastic modulus,and grout *** performances of these soft computing models were evaluated by comparing predicted deformation with measured *** demonstrate the acceptable accuracy of the model in predicting ground settlement,while XGBoost demonstrates a slightly higher *** addition,the ensemble method of XGBoost is more computationally efficient and can be used as a reliable alternative in solving multivariate nonlinear geo-engineering problems.

关键词： EPB Surface settlement Soft computing XGBoost Multivariate adaptive regression spline

Extension/Compression-Controlled Complete Band Gaps in 2D Chiral Square-Lattice-Like Structures

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Acta Mechanica Solida Sinica 2018年第1期31卷 51-65页

作者： Y. L. huang N. Gao W.q. Chen r.h. Bao Department of Engineering Mechanics Zhejiang University Hangzhou 310027 China State Key Lab of CAD & CG Zhejiang University Hangzhou 310058 China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China Soft Matter research Center Zhejiang University Hangzhou 310027 China

Achieving tunable band gaps in a structure by external stimuli is of great importance in acoustic applications. This paper aims to investigate the tunability of band gaps in square-lattice-like elastic periodic structures that are usually not featured with notable band gaps. Endowed with chirality, the periodic structures here are able to undergo imperfection-insensitive large deformation under extension or compression. The influences of geometric parameters on band gaps are discussed via the nonlinear finite element method. It is shown that the band gaps in such structures with curved beams can be very rich and, more importantly, can be efficiently and robustly tuned by applying appropriate mechanical loadings without inducing buckling. As expected, geometry plays a more significant role than material nonlinearity does in the evolution of band gaps. The dynamic tunability of band gaps through mechanical loading is further studied. results show that closing, opening, and shifting of band gaps can be realized by exerting real-time global extension or compression on the structure. The proposed periodic structure with well-designed chiral symmetry can be useful in the design of particular acoustic devices.

关键词： Band gap Tunability Square-lattice-like periodic structure Chiral symmetry,Large deformation

Effects of the reversely rotating Assisted Shoulder on Microstructures During the reverse Dual-rotation Friction Stir Welding

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Journal of Materials Science & Technology 2015年第4期31卷 375-383页

作者： J.q.Li h.J.Liu State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Capital Aerospace Machinery Company

The reverse dual-rotation friction stir welding(rDr-FSW) has the capability to adjust the heat generation because of the separately designed tool shoulder and tool *** welding torque exerted on the workpiece by the reversely rotating shoulder is opposite to that exerted by the rotating tool pin,so the total welding torque is reduced,which is beneficial to reducing the clamping requirement of *** the present paper,a rDr-FSW joint was welded in a condition similar to the optimal welding condition of conventional FSW,and microstructures in various zones were investigated by comparison,aiming to highlight effects of the reversely rotating assisted *** to the heat conduction of the middle cylinder and the bottom end cover on which the assisted shoulder was machined,the thermal effect of rDr-FSW was smaller than that of the conventional ***,the effect of assisted shoulder on the plastic flow or deformation of material or was constrained in a thin layer near the weld top surface,and thus the flow of material especially along the thickness direction was clearly decreased in the *** the heat-affected zone(hAZ),the precipitate coarsening was the main evolution and was completed through the dissolution of small precipitates and the continuous growth of large *** contrast,the dissolution degree of precipitates increased significantly in the thermomechanically affected zone(TMAZ),and a small amount of original meta-stable precipitates transformed to block-shaped stable *** evolutions in the shoulder affected zone(SAZ)and the weld nugget zone were similar,*** majority of original meta-stable precipitates dissolved into the matrix and the remainder transformed to stable precipitates,though the dissolution degree was greater in the *** with the conventional FSW joint,the coarsening degrees of precipitates in the hAZ and TMAZ of rDr-FSW joint were much smaller,as well as the dissolution degrees of p

关键词： Friction stir welding reverse dual-rotation fricti

Damped electrostatic ion acoustic solitary wave structures in quantum plasmas with Bohm potential and spin effects

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Chinese Physics B 2019年第1期28卷 460-465页

作者： S hussain h hasnain Mahnaz q.haseeb Theoretical Physics Division(TPD) Department of Physics COMSATS University

Nonlinear properties of ion acoustic solitary waves are studied in the case of dense magnetized plasmas. The degenerate electrons with relative density effects from their spin states in the same direction and from equally probable up and down spinning states are taken up separately. quantum statistical as well as quantum tunneling effects for both types of electrons are taken. The ions have large inertia and are considered classically, whereas the electrons are degenerate. The collisions of ions and electrons with neutral atoms are considered. We derive the deformed Korteweg de–Vries(DKdV)equation for small amplitude electrostatic potential disturbances by employing the reductive perturbation technique. The runge–Kutta method is applied to solve numerically the DKdV equation. The analytical solution of DKdV is also presented with time dependence. We discuss the profiles for velocity, amplitude, and time variations in solitons for the cases when all the electrons are spinning in the same direction and for the case when there is equal probability of electrons having spin up and spin down. We have found that the wave is unstable because of the collisions between neutral gas molecules and the charged plasmas particles in the presence of degenerate electrons.

关键词： degenerate plasma collisions spin-up spin-down

hYBrID LINEAr AND qUADrATIC FINITE ELEMENT MODELS FOr 3D hELMhOLTZ PrOBLEMS

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Acta Mechanica Solida Sinica 2013年第6期26卷 603-618页

作者： q.h.Zhang K.Y.Sze Guangdong Province Key Laboratory of Computational Science Sun Yat-Sen University Department of Mechanical Engineering The University of Hong KongPokfulam

In this paper, linear and quadratic finite element models are devised for the three- dimensional helmholtz problem by using a hybrid variational functional. In each element, contin- uous and discontinuous helmholtz fields are defined with their equality enforced over the element boundary in a weak sense. The continuous field is based on the C° nodal interpolation and the discontinuous field can be condensed before assemblage. hence, the element can readily be in- corporated seamlessly into the standard finite element program framework. Discontinuous fields constructed by the plane-wave, Bessel and singular spherical-wave solutions are attempted. Nu- merical tests demonstrate that some of the element models are consistently and considerably more accurate than their conventional counterparts.

关键词： finite element hybrid helmholtz Bessel plane-wave spherical-wave radial basis function