Non-Fourier heat conduction in a thin gold film heated by an ultra-fast-laser

Based on the dual-phase-lagging(DPL)heat conduction model,the Cattaneo-Vernotte(CV)model and the improved CV model we investigate the one-dimensional heat conduction in gold films with nano-scale thickness exposed to an ultra-fast laser heating.The influence of system parameters on the temperature field is explored.We find that for all the non-Fourier heat conduction models considered in this work,a larger Knudsen number normally leads to a higher temperature.For the DPL model,the large ratio of the phase lag of temperature gradient to the phase lag of heat flux reduces the maximum temperature and shortens the time for the system to reach its steady state.The CV model and the improved CV model lead to the similar thermal wave behavior of the temperature field,but the thermal wave speeds for these two models are different,especially for large Knudsen numbers.When the phase lag of temperature gradient is smaller,the difference between the DPL model and the improved CV model is not significant,but for the large phase lag of temperature gradient the difference becomes quite significant,especially for the large Knudsen number.In addition,the effect of the surface accommodation coefficient,which is a parameter in the slip boundary condition,on the temperature field of the gold film heated by ultra-fast laser pulses is investigated based on the DPL model.     

离心铸造高速钢轧辊铸造缺陷形成与控制技术研究

采用离心铸造方法制造高速钢轧辊工艺简单,操作方便,但易出现偏析、裂纹、气孔、缩孔及夹杂等缺陷,影响轧辊的力学性能和使用性能.采用稀土-钛复合变质处理改善合金的组织和性能,同时改进离心铸造工艺参数可以消除高速钢轧辊铸造缺陷,提高力学性能,改善使用效果.     

双回转送进二辊冷轧管机凸轮设计研究

本文提出了双回转送进二辊冷轧管机凸轮理论轮廓曲线的新设计方法 ,其轮廓曲线加速度与跃度呈梯形 ,且跃度边界连续 ,给出了针对双回转送进二辊冷轧管机的两个过渡段具有等加速度和跃度的设计准则     

时效对接触线用Cu-Ag-Cr合金性能的影响

分析了固溶温度、时效及时效前冷变形量对Cu - 0 1 %Ag - 0 1 %Cr接触线用合金性能的影响 ,结果表明 :经 870℃固溶、 40 %～ 5 0 %冷变形及 480℃× 1 5h时效处理后 ,合金可获得良好的综合性能。     

含共晶碳化物Fe－Cr－Mn合金在高温含硫气氛中的腐蚀研究

对含碳量为０．５０－２．６３％的Ｆｃ－Ｃｒ－Ｍｎ合金在８００℃下含硫混合气氛中进行腐蚀试验．用Ｘ射线物相分析法分析了腐蚀产物种类及其相对含量，现实测定了元素在腐蚀产物中的分布及试样亚表层共晶碳化物的腐蚀行为。结果表明：试验合金比高Ｎｉ耐热钢具有高的抗腐蚀性；合金的腐蚀行为受硫化及氧化腐蚀双重制约，因而使合金的腐蚀增重呈现峰值，随气氛氧化性增强，峰值向低碳方向移动；共晶碳化物具有比金属基体略好的抗腐蚀性。     

Influencing factors on elastic-plastic deformation of multi-layered surfaces under sliding contact

Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness,layer number and elastic modulus ratio of layer to the substrate. A model of multi-layered surface contact with rough slider was studied. The effect of the surface structure parameters on the elastic-plastic deformation was analyzed.     

随机森林理论浅析

随机森林是一种著名的集成学习方法,被广泛应用于数据分类和非参数回归。本文对随机森林算法的主要理论进行阐述,包括随机森林收敛定理、泛化误差界以和袋外估计三个部分。最后介绍一种属性加权子空间抽样的随机森林改进算法,用于解决超高维数据的分类问题。     

Fast and effective color-based object tracking by boosted color distribution

In this paper, we propose a novel tracking algorithm, boosted color distribution (BCD), for tracking color objects. There exist three contributions in this paper. First, we propose a novel online gentle boost (OGB) algorithm for online learning. The essential idea of OGB is composed of two aspects: online updating candidate weak classifiers, and then choosing and combining them in a boosting way. Second, we design a novel weak classifier, log color feature distribution ratio, which focuses on the difference of color distributions rather than individual samples and provides a simple yet effective manner of mining color features for object tracking. Third, by combining our OGB algorithm and our log color features, we develop a fast yet effective color-based object tracking algorithm. Numerous experiments demonstrate that our tracking algorithm is better than or not worse than some state-of-the-art tracking algorithms on some public sequences.Overall, this paper presents a novel BCD algorithm for color object tracking that achieves good results at a fast speed.     

A Lyapunov functional approach to robust stability analysis of continuous-time uncertain linear systems in polytopic domains

In this paper, a sufficient linear matrix inequality (LMI) condition is presented for robust stability analysis of continuous-time linear time-invariant (LTI) systems in polytopic domains. The underlying idea behind the proposed approach is to introduce a family of complex functions which map the closed right-hand side of the complex plane into the inside of the closed unit circle centered at the origin. Then, the mapping properties are used to assure that all the eigenvalues of a system are located in the open left-hand side of the complex plane. Examples show the validity of the proposed condition.