铂族金属可生产新型催化剂

据报道,新的铂金催化剂在丙烷转换成丙烯的脱氢过程中发挥着重要的作用。美国能源部-国家实验室里,科学家做了好多实验,想要把这个化学转换达到耗费少且对环境更友好的效果。     

中外科学家合作 高压理论获突破进展

据吉林大学消息：吉林大学超硬材料国家重点实验室马琰铭教授与德国马普所Eremets教授和瑞士苏黎世高工Oganov教授等科学家合作,在高压下碱金属钠的结构相变研究上取得突破性进展,发现金属钠在200万大气压转变为“透明”的宽带隙绝缘体。这一成果发表在3月12日最新一期的《自然》（Nature）杂志上（DOI：10．1038／namre07786）。学术界一直认为：高压可以有效缩短材料的原子间距,导致材料的价带和导带展宽,     

美国Villanova大学专家访问兰州化物所

前不久,应中国科学院兰州化学物理研究所固体润滑国家重点实验室张俊彦研究员邀请,美国宾夕法尼亚州Villanova大学机械工程系细胞生物力学与运动科学实验室主任吴千红教授到该所访问,并作了题为 “Lubrication theory for highly compressible porous media： from red cells to skiing to a new concept for a train track” 的学术报告。     

美国开发出一种可预防高温腐蚀的陶瓷涂层

美国太平洋西北国家实验室（PNNL）开发出一种低成本陶瓷涂层可防止钢铁或超合金在化工或发电时的高温腐蚀（700～1000℃）,这项技术是与华盛顿大学、中央弗罗里达大学、航空制品与化学公司、太阳能涡轮机、SRI和星火系统公司共同完成的。这种涂覆技术是将一种陶瓷先驱剂高分子液体化合物与铝片状粉末混合生成浆料。     

2009年全国现代焊接科学与技术学术会议（第一号通知）

为了推动全国焊接新技术、新方法和新工艺的发展,促进学术交流与合作,探索焊接研究未来发展方向和若干前沿科学问题,结合国家重大发展需要与现状.     

PVP保护下纳米银颗粒的液相化学还原法制备及表征

以PVP为表面活性剂,甲酸铵为还原剂,采用液相还原法制备了纳米银颗粒。采用X射线衍射(XRD)、透射电子显微镜(TEM)和紫外-可见光吸收光谱(UV-Vis)对所制备样品进行表征。结果显示：当PVP与AgNO3的质量比为2.2：1,陈化时间24 h,得到立方块和六棱柱的银混合颗粒。     

化学镀镍诱发过程催化活性的电化学本质

ＸＰＳ电子能谱技术的测定表明,化学镀诱发伊始,先只有镍的沉积,然后才有ＮｉＰ的共沉积出现。结合铜基试样在所设计的４种溶液体系中动电位扫描伏安曲线的结果,初步显示,对化学镀镍具有催化特性的金属,从电化学本质上来说,就是一种自身能提供到达或超过镍的析出电位的金属。通过电极电位的理论计算及混合电位的测定,说明了化学镀镍首先是镍析出,然后再发生ＮｉＰ共沉的机理     

第五届中国摩擦学国际会议暨第一届IFToMM摩擦学国际会议在北京召开

第五届中国摩擦学国际会议暨第一届IFToMM摩擦学国际会议于2008年9月24～27日在北京召开。会议由清华大学摩擦学国家重点实验室、中国科学院兰州化学物理研究所固体润滑国家重点实验室。     

Pd-Pt燃料电池催化剂

华盛顿大学与布卢克海文国家实验室的科学家们合作共同研制成功一种双金属Pd—Pt燃料电池催化剂,它较之当前商业催化剂的效果要高1～4倍,而且使用更耐久。这种催化剂是由Pd芯（或Pd“籽”）和固定在纳米结构上的树枝状铂枝所组成,Pd芯尺寸为9nm,臂长7nm。其合成过程包括在一种水溶液中用L-抗坏血酸（vitaminc）顺序将前驱体化合物还原成Pd和Pt。     

实验室工作的15条准则

很多科技工作者,可能一辈子在实验室呆的时间比在家里的时间还要长,以下就是一位高人的心得,我们都学习一下吧！1．要有目标和追求。没有目标和追求就没有动力,给自己定个目标,开动激情的发动机。2．相信自己的能力。不自信是任何事情都做不好的,即使做好了也是偶然。     

基于三角网格多节点覆盖的数值流形方法

以任意三角网格作为数学网格,应用无网格法理论,提出了一种新的权函数构造方法,建立基于任意三角网格的一种多节点流形单元覆盖。针对小挠度变形的薄板弯曲问题,推导出应用于薄板问题的流形格式和单元矩阵。单元节点的覆盖位移采用C0,C1阶的局部多项式形式,积分采用面积坐标的hammer积分。算例表明,与有限元分析相比,该方法的流形单元在计算精度和收敛性上,可得到大幅度提高。     

A new triangle element for the axisymmetric UBET

UBET is a useful technique for the analysis of forging and other metal forming processes. However, geometrical shape of a element used in this technique is limited to a rectangle or a right angle triangle. To overcome this problem, an arbitrary shape triangle element which define a kinematically admissible velocity field using stream function is proposed and applied to the UBET. Although, this triangle element is a proper element to be used for the analysis of plane strain problem, it has several problems to be applied to axisymmetric problem. Therefore, a new arbitrary shape triangle element which has constant inlet flow at the side of the triangle is developed. On this element, a kinematically admissible velocity field is expressed easily using stream function and a second order isoparametric triangle element. The power consumption is calculated by the numerical integration. Also, a new conversion technique is introduced for the minimization of power consumption, and it makes possible to use many variables on UBET.     

A new finite element method for binder wrap calculations

In forming a large automobile sheet metal part in a draw die, a blank is first clamped by curved binders to form a binder wrap. This paper presents a numerical method to calculate the binder wrap. Theanalysis domain, aliaspseudo blank, is the portion of the blank which goes into the die cavity. Since its boundary is not known in advance, an iteration method is used to calculate the pseudo blank and binder wrap simultaneously. Given a pseudo blank, each iteration cycle consists of two steps: calculation of the binder wrap from the pseudo blank subjected to boundary displacements, and correction of the pseudo blank. Two examples are presented. The calculated results for both examples closely match the measured data. In the first example, correct results were obtained in the initial calculation showing the correctness of the initial selection of the pseudo blank. For the second example, convergent results were obtained in one iteration.     

电液控制元件故障识别的新方法

本文利用神经网络构造映射图对电液伺服系统状态特征进行描述,结果表明,神经网络可以很好地反映电液阀的状态特征,并实现对故障的诊断。     

一种新的实体壳单元在板料成形中的应用

开发了一种新的实体壳MSSS单元,在厚向划分一层网格采用多点积分,精确获得了厚向应力应变分布;采取粘性沙漏控制算法,克服了零能模式。厚向多点积分求解内力以及应力应变的更新,使得MSSS单元表现出了极好的单元性能,可以准确描述板料成形回弹现象。基于FASTAMP板料成形模拟软件,论文给出了一个方板拉深成形算例,以及两个NUMISHEET国际标准考题回弹算例,并且与实验结果以及相关文献中的模拟结果做了比较。     

A new approach for the friction identification during machining through the use of finite element modeling

Finite Element Modeling (FEM) of chip formation has proved great sensitivity to tool/chip friction coefficient. This parameter cannot be adequately identified through conventional tests, because thermal and mechanical loadings during these tests are far from those encountered during machining. In this study, the inadequacy of using constant Coulomb's friction coefficient in FEM is showed. Although a good agreement is found for cutting force and chip thickness variables, significant differences can be found for feed force and tool–chip contact length. Differences of more than 50% are observed in some cases for those variables when FEM results are compared with experimental ones. A new approach to identify a friction model after experimental tests will be detailed. This new approach involves application of a variable friction coefficient at the tool–chip interface, which allows obtaining a better agreement between numerical results (differences close to 10%) regarding the feed force.     

Finite element modelling and control of new metal forming processes

The classical formulations for material forming either in the solid or in the liquid state are briefly recalled, in terms of material constitutive behavior, friction law, integral forms and finite element discretization. A few important numerical issues are discussed, including meshing, remeshing and adaptivity, parallel computing and coupling between work-piece and tools. Five examples of applications of finite element models to new processes are presented: friction stir welding, hot stamping of quenchable steels, tube hydroforming, thixoforming and self piercing riveting. It is concluded that many new forming processes can be designed and optimized much more effectively using the numerical simulation technology.     

Industrial applications of sheet stamping simulation using new finite element models

The paper is aimed to present industrial applications of sheet stamping simulation using new finite element formulations developed in the International Center for Numerical Methods in Engineering in Barcelona. Theoretical formulation is briefly reviewed. Both continuum and shell elements have been considered. The new shell elements developed are based on a geometrically exact shell model treating the shell as one-director Cosserat surface. The formulation of the continuum elements employs the multiplicative decomposition of the deformation gradient tensor into its elastic and plastic parts. The new finite element models have been implemented in the in-house explicit dynamic code STAMPACK. A number of practical problems of sheet metalforming have been solved with the program. Some of the problems, namely stamping of a kitchen sink, hydraulic forming of an aeronautical part and stamping of a food can, have been presented in the paper. The examples give an idea of practical information that can be obtained from the computer simulation of a forming process. The results confirm a good behaviour of the formulation and program used in the industrial applications.     

一种快速有限元网格的生成方法

借助汽车后大梁零件回弹现场调试,利用CAE软件(Dynaform)与逆向工程软件(Imageware)之间的数据接口,介绍了直接将扫描点云引入CAE软件内进行网格处理的方法与技巧,节省了大量的传统建模时间,在缩短模具生产周期的同时也降低了调试成本。     

Effectiveness of new spectral tools in the anomaly detection of rolling element bearings

This paper deals with the application of three advanced spectral methods aimed to be used for detection/diagnosis of localized defects in rolling element bearings. Second order power spectral density proves to be useful as a tool for peak identification and an aid to classical linear spectra. Bispectral techniques show its effectiveness in quadratic phase coupling peak detection, and because its a third order moment function noise background is eliminated in the estimation procedure, being capable of detecting them. Wavelet analysis using a simplified technique via Haar transform proves to be applicable in early detection of the burst generated during a fault development. Results are presented based on a digital simulation model.