Wear and friction of 6061-T6 aluminum alloy treated by laser shock processing

Laser shock processing (LSP) is becoming an important surface treatment to induce a compressive residual stress field, which improves fatigue and fracture properties of components. In this work, we examine the effect of laser shock processing on the wear and friction behavior of 6061-T6 aluminum alloy. Wear rate and friction coefficient evolution are investigated for different process parameters of LSP. Roll-on-flat tribometer is used with different loading conditions. Hardness and residual stresses are assessed as well. It is observed that wear rate decreases as pulse density increases; this is explained in light of residual stress distribution.     

一种新的基于极大似然估计的系统辨识方法

进化计算是一种基于自然选择和自然变异机制的并行随机优化算法。由于递推极大似然估计法难以实现性能指标函数的全局寻优，所以本文提出了将改进的进化计算用于系统参数辨识的方法。计算机仿真结果表明，该算法能够实现似然函数的全局寻优。     

一流本科专业建设背景下高校“金课”建设研究

一流本科专业建设是新时代高等教育体制创新的重要举措,是高校贯彻科教兴国战略的落脚点。通过对“金课”建设的现状进行调查,以国际交流英语课程为切入点,分析了过于强调语言技能训练、“两性一度”尚有距离、不符合创新人才培养举措的问题,提出了“金课”建设的措施,即厘清课程实践目标、优化课程建设结构、丰富课程建设形态、提升教师实践能力,为高素质人才培养提供了新思路,实现高等教育的高质量发展。     

区块链在分布式电力交易中的研究领域及现状分析

国家发改委、能源局陆续指出:要全面放开经营性电联用户发电计划,支持中小用户参与市场化交易,健全全面放开经营性发电计划后的价格形成机制。行政引导市场,市场发展技术,基于区块链技术的电力交易研究迎来了前所未有的行政和市场机遇。区块链以分布、公开、不可篡的区域共治模式,为社会和市场提出了一套全新的商业解决方案。该文依托区块链技术,探讨了基于分布式交易的电力交易市场、产消者以及相关服务产业的需求和行业现状,分析了区块链电力交易的发展趋势;归纳了电力交易领域区块链追求创新实验的主要方向,研究了电力交易区块链的总体架构设计创新、电力交易场景应用创新和区块链性能提升研究创新等内容;最后通过文献综述和百余个区块链电力交易系统实施案例,梳理了区块链技术在电力交易行业面临的挑战与应用前景。以期通过该文综述对分布式电力交易领域的未来研究有一定贡献。     

Misorientation characteristics of interphase boundaries in particulate Al2O3-based composites

It is well known that the character and distribution of interphase boundaries has a significant impact on the properties of polycrystalline materials. For the quantitative characterization of interfaces between matrix and inclusions in two composite systems (Al₂O₃/WC and Al₂O₃/W), large sets of crystallographic misorientation data has been used. The misorientations were measured between the neighbouring regions of different phases. The experiment was based on orientation maps obtained by Electron BackScatter Diffraction (EBSD) in an Environmental Scanning Electron Microscope (ESEM). For the particular arrangements of crystallite symmetries, Misorientation Distribution Functions (MDF) have been developed in such a way that each physically distinct misorientation was represented only once. Preferences for the special crystallographic correlations between matrix grains and inclusions, as well as the shares of interphase boundaries characterized by those correlations, have been evaluated in both composites.     

当代广告文化多元性的表现形式与应对策略

在信息时代发展的过程中,广告作为一种较为独特的信息传播形式,也有着较久远的历史。社会生产力和文化相互结合促使了广告文化形成和发展,不同地区的经济水平、地域环境、民族传统、风俗习惯、宗教信仰的多元化赋予广告文化新的内涵,从特征和表现形式上呈现出显著的多元性。文章从当代广告符号元素背后蕴含的文化入手,呈现多元化特征,着重论述了广告文化多元性的表现形式,即时空多元性及性质多元性,旨在为当代广告人应对广告文化多元性提供应对策略和有益的指导。     

决策粗糙集属性约简算法与属性核研究

属性约简是粗糙集理论的重要研究内容之一。在Pawlak粗糙集模型中,正区域大小随着属性增多而变大,呈现单调性。然而,在决策粗糙集模型中,概率正区域与属性集之间不具有单调性,从而产生各种属性约简定义。为此,深入研究了决策粗糙集属性约简问题,阐述了几种约简定义之间的关系,证明了保持局部最大概率正区域的约简具有较大的代价,指出了保持所有对象的正决策不变的约简呈现稳定性和存在属性核。     

干式切削中刀具选用试验

切削液的使用带来了许多负面问题,鉴于环境考虑,研究绿色加工技术将是机械制造业必须重视的课题.干式切削是解决途径之一,它不用切削液,可完全消除切削液带来的一系列负面影响.本文通过选用一些新型刀具,在干式切削条件下对不同的刀具材料、刀具几何参数和切削用量进行试验比较,以寻求适用于干式切削的刀具材料与切削规律.     

摩托车启动电机轴气体氮碳共渗

摩托车上的启动电机是摩托车的关键部件之一,全国整车产量在一千万辆以上.其中启动电机在常州地区产量达300万台以上.该电机转轴（或称齿轴）是电机的转子轴,头部是长约15～20 mm的齿轴,模数为m=0.6,0.8,1.0,1.25。     

Microdefects and electron densities in NiTi shape memory alloys studied by positron annihilation

1Introduction NiTi alloys are the most successful shape memory alloys as a result of their combination of good functional properties and excellent mechanical strength[1,2].The thermal and mechanical shape memory behavior in these alloys is dependent upon …