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Surface Characterisation of Silicon Based MEMS

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Chemical Research in Chinese Universities 2004年第4期20卷 407-410页

作者： li J. CUI z M. A. Baker The Surface Analysis Laboratory School of Engineering University of SurreyRutherford Appleton LaboratoryThe Surface Analysis Laboratory School of Engineering University of Surrey Guildford GU2 7XH UKChilton Didcot UKGuildford GU2 7XH UK

Polysilicon Microelectromechanical systems(MEMS) are the subject of intensive researches. Surface chemistry and topography of a MEMS test structure fabricated at Sandia National Laboratory, USA, were studied by means of scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and atomic force microscopy(AFM). XPS C_ 1sand Si_ 2pspectra from the polysilicon components, silicon nitride substrate and a reference silicon wafer were compared. The results confirm the presence of a self-assembled monolayer(SAM) on the MEMS surface. An island-like morphology was found on both polysilicon and silicon nitride surfaces of the MEMS. The islands take the form of caps, being up to 0.5 μm in diameter and 20 nm in height. It is concluded that the co-existence of columnar growth and equiaxed growth during the low pressure chemical vapor deposition(LPCVD) of these layers leads to the observed morphology and the islands are caps to the columnar structures.

关键词： Microelectromechanical systems XPS Atomic force microscopy

PREPARATION AND XRD STUDY OF liTHIUM DEFICIENT liB COMPOUND

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 667-671页

作者： z.J.liu B.Y.Huang z.Y.li StateKeyLaboratoryforPowderMetallurgy CentralSouthUniversityChangsha410083China

The liB compounds in lithium deficient state were prepared by three methods and its crystal structure was investigated by using XRD. It is found that the lattice constant c of the compound will increase step by step with decreasing li content from 0.2796nm of the normal liB to 0.2886, 0.2981 and 0.3118nm of the lithium deficient liB. The change of the lattice constant is reversible.

关键词： liB compound crystal structure electrode materials X-ray diffraction

Correlation between Porosity and Fracture Mechanism in High Pressure Die Casting of AM60B Alloy

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Journal of Materials Science & Technology 2016年第1期32卷 54-61页

作者： X.li S.M.Xiong z.Guo School of Materials Science and Engineering Tsinghua University State Key Laboratory of Automobile Safety and Energy Tsinghua University

X-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation, propagation and subsequent fracture of specimen. Results showed that four types of porosi- ties, including gas-shrinkage pore, gas pore, net-shrinkage and island-shrinkage, could be identified according to the formation mechanism and morphology characterization. During tensile deformation, it was shown that the gas-shrinkage pore and net-shrinkage, rather than gas pore or island-shrinkage, were the main sources for crack initiation. In addition, the crack propagated by interconnecting the po- rosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals （ESCs） were present, the crack would propagate along the ESC boundaries in an inter- granular mode, while at these locations without ESCs, the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.

关键词： High pressures die casting AM60B alloy Fracture mechanism Porosity

Influence of plasma condition on carbon nanotube growth by rf-PECVD

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Nano-Micro Letters 2010年第1期2卷 37-41页

作者： Y.H.Man z.C.li z.J.zhang Advanced Materials Laboratory Department of Materials Science and Engineering Tsinghua University

Carbon nanotubes(CNTs)have been synthesized from Ar-CH_4 mixtures using rf-plasma enhanced chemical vapor deposition(rf-PECVD)at *** gases such as H_2 and NH_3 were found unnecessary for carbon nanotube formation compared to thermal *** relationship between the growth of CNTs and the plasma condition in PECVD has been investigated by in situ self bias *** conditions were controlled by changing the interelectrode distance,rf power and the applied substrate negative *** increasing the interelectrode distance and rf power,the spatial density of CNTs was on a rise as a result of the increase in ions density and self *** the applied substrate negative bias increased,the spatial density of CNTs decreased possibly due to the positive ions over bombarding effect.

关键词： Carbon nanotube Plasma enhanced CVD Plasma condition

Diagnosing the Dynamic and Thermodynamic Effects for the Exceptional 2020 Summer Rainy Season in the Yangtze River Valley

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Journal of Meteorological Research 2022年第1期36卷 26-36页

作者： Na WEN Shujie liU Laurent z.X.li College of Atmospheric Sciences Nanjing University of Information Science&TechnologyNanjing 210044China Key Laboratory of Meteorological Disaster of Ministry of Education Nanjing University of Information Science&TechnologyNanjing 210044China Qingdao Engineering Technology Research Center for Meteorological Disaster Prevention Qingdao Meteorological BureauQingdao 266003China Laboratoire de Météorologie Dynamique Centre National de la Recherche ScientifiqueSorbonne UniversitéEcole Normale SupérieureEcole PolytechniqueParis 75252France

An exceptional rainy season occurred in the Yangtze River valley of eastern China in June-July *** relative importance of the dynamic and thermodynamic effects on this unusual event is evaluated through the budget equations of moisture and moist static energy(MSE).The moisture budget analysis suggests that the thermodynamic effect contributes to the precipitation anomaly by 8.5%through the advection of abnormal water vapor by mean vertical motion,while the dynamic effect,related to water vapor advection by anomalous vertical motion,has the dominant *** MSE budget analysis further reveals that the anomalous vertical motion is both constrained by the dynamic effect related to changes in atmospheric circulation and the thermodynamic effect related to changes of the atmospheric thermal state,with a ratio of thermodynamic versus total effects estimated at 45.3%.The dynamic effect is linked to the advection of warm and humid air by the abnormal southwesterly wind,which is related with an anomalous anticyclone over the Philippine *** thermodynamic effect is partly induced by the positive advection of anomalous MSE(mainly latent energy)by the mean vertical *** analysis of the dynamic and thermodynamic effects is useful to understand the underlying physical mechanisms leading to the unusual rainy season in the Yangtze River valley in summer *** is also helpful to put forward a few speculations on the potential role of global warming whose primary effect is,after all,to change the thermal state of the atmosphere.

关键词： exceptional rainfall Yangtze River valley global warming dynamic and thermodynamic effects

Mathematical Simulation of Evaporating Brine by Solar Radiation for the Production of Salt

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Journal of Thermal Science 1993年第2期2卷 143-151页

作者： Y.z.zhang C.D.li 等 Dept.ofEngineeringThermophysics UniversityofScienceandTechnologyofCHinaHefeiAnhui230026china Scien

A computer simulation model of salt pan is *** transient behavior and the effects of various parameters of the salt pans,such as the depth of the brine layer,the absorptance of the soil surface,the thermal properties of the soil beneath the brine layer and the depth of the underground water table,on the evaporation process of salt pans are *** effects of extra insulation layer and the intensity of solar radiation are also examined.

关键词： salt pan solar radiation simulation

Surface deformation-dependent mechanical properties of bending nanowires:an ab initio core-shell model

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Applied Mathematics and Mechanics(English Edition) 2022年第2期43卷 219-232页

作者： Ye XIAO J.SHANG L.z.KOU Chun li School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an710072China MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical UniversityXi’an710072China School of Mechanical Medical and Process EngineeringQueensland University of TechnologyBrisbaneQLD4000Australia

An ab initio core-shell model is proposed to evaluate the surface effect in bending nanowires,in which the elastic modulus depends on the surface relaxation and deformation induced by external *** using first-principles calculations based on the density functional theory(DFT),the surface and bulk properties are calculated for Ag,Pb,and Si *** obtained theoretical predictions of the effective Young’s modulus of nanowires agree well with the experimental data,which shows that the fixed-fixed nanowire is stiffened and the cantilevered nanowire is softened as the characteristic size of the cross section ***,the contrastive analysis on the two kinds of nanowires demonstrates that increasing the nanowire aspect ratio would enhance the surface *** present results could be helpful for understanding the size effect in nanowires and designing nanobeam-based devices in nanoelectromechanical systems(NEMSs).

关键词： surface effect density functional theory(DFT) surface relaxation surface stress nanowire

A novel friction stir diffusion bonding process using convex-vortex pin tools

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Journal of Materials Science & Technology 2020年第13期47卷 23-30页

作者： S.D.Ji Q.Wen z.W.li College of Aerospace Engineering Shenyang Aerospace UniversityShenyang 110136China State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China

In this work,a novel friction stir diffusion bonding(FSDB)method was proposed to eliminate hook when joining thin *** tools,with several convex-vortex pins were innovatively designed to improve the diffusion bonding effect of the lap *** showed that sound joints,excellently bonded at the lap interface and without hook,were *** lap interfaces on the joints welded using the T-tool and F-tool almost remained intact,thereby indicating that they were formed by diffusion *** material flow behavior was also simulated by FLUENT software and the results showed that the material flow along thickness was significantly enhanced by increasing the pin *** joint welded by the T-tool showed shear fracture *** bonding was formed at the lap interface when using the F-tool and thus the joint showed tensile fracture.

关键词： Friction stir diffusion bonding Convex-vortex pin Hook Material flow Failure

An interactive web-based solar energy prediction system using machine learning techniques

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Journal of Management Analytics 2023年第2期10卷 308-335页

作者： Priyanka Chawla jerry zeyu Gao Teng Gao Chengchen Luo Huimin li Yiqin We Department of Computer Science and Engineering National Institute of TechnologyWarangalIndia San Jose State University San JoseCAUSA

Solar energy being one of the most inexpensive renewable energy sources,has shown to be a viable alternative to traditional fossil-fuel and wood-based electricity *** the purpose of creating a more trustworthy and successful energy planning strategy,accurate projections of sun irradiation,solar energy generation,and revenues are ***,in this work we have proposed webbased optimal prediction system that estimates solar radiation based on location and meteorological data using Machine Learning ***,an interactive dashboard solar digital map has been developed that enables real-time investigation of solar energy consumption,production,solar radiation,and investment potential for a specific county in *** model’s performance has been measured using Root Mean Square Error(RMSE),Mean Square Error(MSE),Mean Average Error(MAE),and Mean Absolute Percentage Error(MAPE)*** results demonstrate that stacking model outperformed all the models with the lowest RMSE,MSE,and MAE.

关键词： solar radiation solar energy renewable energy machine learning solar map