材料期刊网

Three Dimensional Simulation of Upset Forging by Using Variational Upper Bound Method

Jiang QIN(School of Mechanical Engineering , University of Bath , Claverton Down , Bath BA27AY , UK)

材料科学技术（英文）

The variation principle is discussed and Rayleigh-Ritz method is proposed for construction of veloci ty field. A kinematically admissible velocity field based on polynomials was appIied to the determina tion of forging load and deformed buIge profile during upset forging of blocks. Simulation of upsetforging of rectangular blocks under various friction condjtions was performed. Comparison of the computed results with experiments and FEM shows good agreement. It is shown that this techniquecan be used for 3D simulation of metal forming process.

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“top down”和“bottom up”——评我国纳米科技发展的导向问题

赵大庆 , 杨锋

材料导报

纳米科技有"top down"和"bottom up"两种研究方法,这两种研究方法中"top down"方法是今后一个时期的主要科研方法,但是决不能忽略甚至放弃"bottom up"方法的探索和研究,因为"bottom up"方法代表着纳米科技发展的未来.这是对我国纳米科技发展策略的挑战.

关键词: 纳米科技 , 研究方法 , 发展策略

基于灰色系统理论、top-down技术和质控数据评估不确定度的方法

刘攀

冶金分析 doi:10.13228/j.boyuan.issn1000-7571.009850

基于top-down技术,提出一种应用灰色系统理论定义的标准差评估实验室内质控数据的测量不确定度的方法(简称质控-灰色评定法).采用冶金分析、环境监测(水质检测)及生物检测、物理测量等测量系统的45套(35个检测项目)质控数据验证了方法的可行性和准确性.方法与控制图法(现行标准方法)及稳健统计-迭代法(算法1和算法2)的评估结果的比值分别为:SGrey/SMR=1.00±0.13,SGrey/Srsl=0.96±0.05、SGrey/Srs2=1.00±0.08,方法间具有较好的一致性.质控-灰色评定法对质控数据的分布类型的依赖性较小,不需要进行复杂的正态性检验,评估过程更加简单、实用.

关键词: 测量不确定度 , 质控-灰色评定法 , 灰色系统理论 , top-down技术 , 质控数据 , 标准差 , 控制图法 , 稳健统计-迭代法

Enhancing the performance of photovoltaic cells by using down-converting KCaGd(PO4)2∶Eu3+ phosphors

稀土学报(英文版) doi:10.1016/S1002-0721(10)60565-0

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Ratio of a strange quark mass ms to up or down quark mass mu,d predicted by a quark propagator in the framework of the chiral perturbation theory

中国物理C doi:10.1088/1674-1137/37/4/043101

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Deep Ultraviolet Emission from Water-Soluble SnO2 Quantum Dots Grown via a Facile "Top-Down" Strategy

Shusheng Pan , Wei Lu , Zhaoqin Chu , Guanghai Li

材料科学技术（英文）

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Structure and Mechanical Performance of Nitrogen Doped Diamond-like Carbon Films

Huayu ZHANG , Liangxue LIU , Yulei WANG

材料科学技术（英文）

Nitrogen doped diamond-like carbon (DLC:N) films were prepared by electron cyclotron resonance chemical vapor deposition (ECR-CVD) on polycrystalline Si chips. Film thickness is about 50 nm. Auger electron spectroscopy (AES) was used to evaluate nitrogen content, and increasing N2 flow improved N content from 0 to 7.6%. Raman and X-ray photoelectron spectroscopy (XPS) analysis results reveal N-sp3C and N-sp2C structure. With increasing the N2 flow, sp3C decreases from 73.74% down to 42.66%, and so does N-sp3C from 68.04% down to 20.23%. The hardness decreases from 29.18 GPa down to 19.74 GPa, and the Young′s modulus from 193.03 GPa down to 144.52 GPa.

关键词: Nitrogen doped diamond-like carbon films , doped , diamond-like , carbon , films

Magnetotransport and current-induced spin transfer torque in a ferromagnetically contacted graphene

Journal of Physics-Condensed Matter

We theoretically investigate the spin-dependent transport through a graphene sheet between two ferromagnetic (FM) leads with arbitrary polarization directions at low temperatures, where a magnetic insulator is deposited on the graphene to induce an exchange splitting between spin-up and spin-down carriers. By using standard nonequilibrium Green's function (NGF) techniques, it is demonstrated that the density of states (DOS) decreases for spin-up and increases for spin-down when the polarization strength of the two leads in parallel alignment increases. For the electron energy around the exchange splitting, the DOS for both spin-up and spin-down channels is independent of the polarization. In contrast, the conductance increases for spin-up but decreases for spin-down with an increase of the polarization. Interestingly, the magnitude of tunneling magnetoresistance (TMR) can be dramatically suppressed with the increase of the exchange splitting in graphene. Furthermore, the current-induced spin transfer torque (STT) dependence on the relative angle. between the magnetic moments of the two leads shows a sine-like behavior and is enhanced with an increase of the polarization and/or the bias voltage. We attribute these spin-resolved effects to the breaking of the insulator-type properties of graphene with an exchange splitting between spin-up and spin-down carriers.

关键词: magnetic multilayers;room-temperature;magnetoresistance;junctions

STUDY ON THERMAL FATIGUE OF NI BASE ALLOY CHROMIUM CARBIDE COMPOSITE COATING

H.C.Lin1) , J.Y.Wang1) , Q.Z.Yang1) , L.J.Guo2) and D.X.Lan2) 1)Departmentof Mechanical Engineering , QingDao Institute of Architecture and Engineering , Qingdao 266033 , China 2)Institute of Machinery , Qingdao266000 , China

金属学报(英文版)

Thermalfatiguebehaviorsof Nibased alloychromium carbidecompositecoating madeby a vacu um fusionsintering method are discussed. Resultsshowedthatthermalfatiguebehaviorisassoci ated with cyclic uppertemperature and coating thickness. Asthe thickness of coating decreases,thethermalfatigueresistanceincreases. Thethermalfatigueresistancecuts down with thether malcyclic uppertemperature rising. Thecrack growth rate decreases with theincreasein cyclicnumber untilcrackarrests. Thetractofthermalfatiguecrackcracksalongtheinterfacesof phas es. Thecompositecoating possesseshigheroxidation resistance.

关键词: compositecoating , null , null

MECHANICAL REDUCTION OF CuO BY Mg AT ROOM TEMPERATURE

MA Xueming YUE Lanping DONG Yuanda Institute of Solid State Physics , Academia Sinica , Hefei , China

金属学报(英文版)

The mechanical reduction of CuO by pure metallic Mg has been investigated during pulver- izing in ball mill at room temperature.The reduction was towards its completion of an average particle size down to 20 nm after milling for 32 h.The mechanism of the mechanical reduction of oxides seems to be the surface activation of nano-metre sized particles driven by mechani- cal force.

关键词: CuO , null , null , null