基于SIFT和LBP点云配准的接触网零部件三维重建研究

现有接触网的三维重建所需时间较长,工作繁琐,为解决此类问题,本文提出采用自动重建法利用点云数据实现其零部件的三维重建。点云配准是影响重建过程准确度及效率的重要因素,而目前普遍使用的SIFT匹配算法,由于构建的关键点特征向量维数高,计算量大,导致匹配速度慢。为解决此问题,本文提出利用均匀模式LBP特征值描述SIFT关键点,获取关键点特征向量,并用向量间的距离判断关键点的相似性,以确定关键点的对应关系,完成配准和重建,得到接触网零部件的三维模型。结果表明,本文所提算法可行有效,能提高匹配速度,加速三维重建。

Effects of Y addition on structural and mechanical properties of CuZrAl bulk metallic glass

The effects of Y addition on the structural and mechanical properties of CuZrAl bulk metallic glass（BMG） were studied.The results show that the glass forming ability of CuZrAl system is improved by the addition of Y and the fracture strength decreases with Y addition due to the reduction of binding energy induced by Y.The fracture surface is dominated by vein-like patterns in Cu45Zr48Al7 bulk metallic glass,and changes to smooth regions in Cu46Zr42Al7Y5 BMG.TEM observation shows that Cu45Zr48Al7 BMG has a composite microstructure of nanocrystalline phases dispersed in amorphous matrix.However,the Cu46Zr42Al7Y5 BMG shows a fully amorphous structure.

Effect of minor-addition of Fe on structural and mechanical properties of CuZrAl bulk metallic glass

The CuZrAl bulk metallic glass with minor-addition of Fe was prepared by rapid quenching method. The structures were examined by X-ray diffraction （XRD）. The effect of Fe on the glass-forming ability was studied by differential scanning calorimetry （DSC）. The minor-addition of Fe obviously extends the supercooled liquid region ΔTx. The plastic strain of the Cu44Zr48Al7Fe bulk metallic glass is about 1.5%. The microstructures were examined by transmission electron microscopy （TEM）. It is found that when 1%-2% Fe （mole fraction） were introduced into the CuZrAl alloy matrix, nanoscale phase separation occurs in the as-prepared Cu44Zr48Al7Fe bulk metallic glass.

First-principle calculations of ductile CeAg intermetallic compound

The first-principle calculations were performed to investigate the structural,mechanical,electronic and thermal properties of the binary ductile intermetallic compound CeAg with B2（CsCl） structure.The calculated value of lattice constant a0 for CeAg with generalized gradient approximation is 3.713-,which is in better agreement with experimental data than local spin density approximation.The negative energy of formation implies that CeAg with B2 structure is thermodynamically stable phase.The greater separation between the d bands of Ce and Ag results in weaker bond hybridization of Ce d—Ag d,which prevents formation of directional covalent bonding.The three independent elastic constants（C11,C12 and C44） are derived and the bulk modulus,shear modulus,elastic modulus,anisotropy factor,and Poisson ratio are determined to be 57.6 GPa,15.8 GPa,43.4 GPa,3.15 and 0.374,respectively.The elastic constants meet all the mechanical stability criteria.The value of Pugh＇s criterion is 3.65.The ductility of CeAg is predicted if Pugh＇s criterion is greater than 1.75.Furthermore,the variations of volume,bulk modulus,heat capacity,and thermal expansion coefficient with temperature and/or pressure were calculated and discussed.

大型离心泵轴断裂原因分析

某大型工业离心泵在起动运行中泵轴在全功率输入端的动静部件配合处发生断裂。通过外观检查、材料成分分析、断口分析、金相组织分析、力学性能测试以及结构和应力分析等手段对断裂原因进行诊断和分析。结果表明,材质确为35CrMoV,基体组织为回火索氏体加少量粒状贝氏体,力学性能远优于设计参数。究其断裂原因,主要是由于现场操作人员违规操作,导致低压进水端腔室G未被输送介质充满,使轴套等动静转子部件之间发生干摩而热量无法及时扩散开,引起轴表面温度剧升而发生软化;当轴表面的抗剪强度低于轴表面所承受的最大剪应力时,就会首先在轴表面产生裂纹进而在剪应力的作用下发生扩展直至轴发生断裂。

制样方法对固体粉末X射线光电子能谱测试结果的影响

为了得到准确且分辨率高的X射线光电子能谱(XPS)数据,采用不同制样方法对不同类型的导电、不导电和混合粉末的测试结果进行了研究.从图谱半峰宽、是否有荷电、真实性、制样效率和数据处理等方面阐述不同制样方法对测试结果的影响.试验结果表明,对于导电和不导电粉末,粘取制样略优于铟片制样,其中使用碳导电胶带制样效果更好.对于混合样品,Scotch双面胶带粘样后的测试结果优于其他3种制样方式.此外,铟片制样可作为数据处理时荷电校正的参考方法.