Rebuilding of metal components with laser cladding forming

Laser cladding forming (LCF) is a novel powerful tool for the repairing of metal components. Rebuilding of V-grooves on medium carbon steel substrates has been carried out with laser cladding forming technique using stainless steel powder as the cladding material. Microstructure of the deposited layers has been characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDAX), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). Mechanical properties of the rebuilt V-groove samples have been evaluated by tensile and impacting tests and microhardness measurement. Experimental results show that good fusion bonding between the rebuilt layers and the substrate has been formed, and the microstructure of the cladding layers is mainly composed of fine, dense and defect-free epitaxial columnar dendrites. Due to the effect of grain size refinement, the tensile strength, impacting toughness, elongation and microhardness of the rebuilt samples have been greatly enhanced compared to those of the substrate. Microhardness is also very uniform throughout the rebuilt regions. With the growth of the deposited layers, the microhardness increases gradually. The good ductility of the deposited regions is verified by the SEM fracture analysis.     

Necessary and sufficient condition of the existence of global Hopf bifurcation for Hamiltonian systems

ForH C ² (,R) where 0 R ²ⁿ ,H (0)=0 and detH(0)0, the paper proves that there is a global Hopf bifurcation fromx=0 for Hamiltonian systemx=JH(x) iffJH(0)possesses purely imaginary eigenvalues. The work improves the corresponding result of J.C.Alexander and J. Yorke (Amer. J. Math., 100 (1978), 263–292).     

催化动力学电位法测定微量锰的研究

用结晶紫选择性电极（自制）以催化电位法对测定微量锰进行了研究。该方法测定标的线性范围为７～７４μｇ／Ｌ，对标准钢样中的锰含量测定结果满意，且操作方便。     

稀土铽配合物的有机发光二极管

有机小分子和有机高分子的发光二极管在可见光区内有非常高的量子效率，因而受到人们的高度重视．采用二胶（TPD），8羟基喹啉铝（Alq3）等有机小分子作为空穴和电子输运层所作的发光二极管[1]的量子效率可达10％，采用聚对苯乙炔（PPV）高分子聚合物作空穴输运层，有机小分子2     

微波相转移催化合成DL—苯丙氨酸

在微波作用下,仅用1min便完成了苯甲醛亚胺的固—液相转移催化苄基化反应,然后经酸水解得到d1—苯丙氨酸,全程总产率为62.5×10(-2)。     

用模糊综合评价值作为单纯形优化指标

本文介绍了一个模糊综合评价方法,讨论了模糊运算方法对运算结果即综合评价值的影响,并将模糊综合评价值用作单纯形优化指标。     

丙氨酸稀土二元和三元配合物的pH电位法研究

本文报道在生理条件下(37℃,I=150 mmol/L NaCl)用pH电位法研究Ala-Ln、GIu—Ln及Ala-Glu-Ln中(Ala=L-丙氨酸,Glu=L-谷氨酸,Ln=Ce,Pr,Nd,Y)二元及三元配合物的稳定常数,运用MINIQUAD-82A程序确定粒子组成,并由COMPLEX程序获得配位粒子分布图,结果表明,三价稀土离子形成配合物的稳定顺序为:Ce相似文献   

用铜（Ⅱ）—L—精氨酸配体交换薄层色谱拆分氨基酸对映体

报道了一种新的配体交换薄层色谱拆分氨基酸对映体的方法。以醋酸铜－Ｌ－精氨酸的络合物为配体交换剂，用浸渍的方法吸附在硅胶薄层板上，制成配体交换薄层，用ＰＲＩＳＭＡ优化法选择出展开剂的最佳组成为：甲醇／乙腈／四氢呋喃／水＝８０：８．２：５．８：６，在此色谱条件下，十对氨基酸对映体得到良好的分离，Ｄ－和Ｌ－氨基酸的相对比移值在１．０９－２．４０之间。文中对配体交换薄层的制备方法，样品的分子结构及色谱行为