高职道路养护与管理专业课程体系优化讨论

通过公路养护行业岗位任务及人才需求信息市场调研,进行典型工作任务筛选和分析、转换,以甘肃交通职业技术学院道路养护与管理专业2016年人才培养模式为平台,对高职高专道路养护与管理专业的课程体系提出了优化建议。     

九种M~(2+)掺杂对NaYF_4:Yb,Er上转换红光的影响研究

本文通过水热法合成不同浓度M~(2+)掺杂的NaYF_4:18%Yb~(3+),2%Er~(3+)上转换发光材料。系统的探讨了九种二价金属离子掺杂以及不同掺杂浓度对材料的上转换红光强度的影响。利用扫描电子显微镜(SEM)、X射线衍射分析(XRD)、荧光光谱等测量手段对样品进行了形貌、晶相、发光性质的表征。2%掺杂浓度下全部离子对上转换发光均稍有增强;5%掺杂浓度下,Sr、Ca对上转换荧光的增强效果最为显著,Ni、Zn、Co稍有增强,而Mg、Cu、Mn、Ba均降低了发光;10%掺杂浓度下,Mg、Ca对上转换荧光的增强效果最为显著,Zn稍有增强,而Ni、Sr、Cu、Mn、Ba、Co均降低了发光。荧光光谱结果表明碱土金属掺杂对发光的增强效果优于过渡金属掺杂,过渡金属对材料形貌的改善效果优于碱土金属。二价金属离子对红光的增强效果明显优于绿光。     

三轮汽车车架结构强度可靠性分析

三轮汽车产品的车架关键涉及到安全问题，车架强度可靠性设计是车辆设计的关键，在研究车架基本结构及可靠性的基础上，建立有限元模型，由数据分析及验证对比得出结论，对车架结构的设计给出了合理建议。     

早期地方城市近代化建设中的规划思想萌芽——“中华道路建设协会”构架下市政概念形成发展的历史过程解读

本文旨在梳理早期地方城市近代化过程中,基于建设实际需要引入市政概念,继而将概念发展成型加以传播的这段历史。这段本土探索的历史,有别于早期在租界、殖民地由外国人为主展开的实践,又早于国民党南京政权巩固后展开的规划实践,且直接影响并作用于大量地方城市的近代化转型。因而厘清这段历史,有利于进一步回答中国城市近代化发展研究中的一个基本问题,即中国古代城市转型过程中近代城市规划思想产生、传播与作用的路径。由于地方城市早期近代化的档案资料多零散不全,研究选取了聚集了各地建设领域精英人物、以上海为中心辐射全国城市建设的"中华道路建设协会",作为主要研究对象。从该协会举办初始单纯提倡修筑马路,到拆城筑路、再到市政并举的思路转换,为地方实践服务过程中逐步引入城市规划相关的技术知识、探讨发展和完善"市政"概念的实际贡献,以及后期主导长期不发挥作用的全国市政协会改组、集文出版《市政全书》推广市政理念等工作来看,该协会通过组织建设与刊物出版,地方实践的需求反馈与市政思想的引入和传播,提供了良好的路径,在中国早期城市规划思想的引进、推广和学术化,起到了非常重要的作用。     

Enhanced interfacial adhesion via interfacial crystallization between sisal fiber and isotactic polypropylene: direct evidence from single‐fiber fragmentation testing

Bioresource natural sisal fiber (SF) was used to prepare single fiber‐reinforced isotactic polypropylene (iPP) composites. Three kinds of interfacial crystalline morphologies, spherulites, medium nuclei density transcrystallinity (MD‐TC) and high nuclei density transcrystallinity (HD‐TC), were obtained in the single fiber‐reinforced composites by implementing quiescent or dynamic shear‐enhanced crystallization and by modulating the compatibility interaction between SF and iPP. The development of interfacial shear strength (IFSS) during the interfacial crystallization process was demonstrated for the first time using a combination of single‐fiber fragmentation testing and optical microscope observation. A close correlation between IFSS and morphological characteristics of interfacial crystallization was well elucidated. The increases in IFSS were very different for spherulitic, MD‐TC and HD‐TC morphologies. The highest IFSS obtained was 28 MPa, after the formation of HD‐TC, which was about 62% of the tensile strength of neat iPP (45 MPa). These results offer powerful and direct evidence that interfacial crystallization could play an important role in the enhancement of interfacial adhesion of real SF/iPP composites. © 2013 Society of Chemical Industry     

Effect of Heat Treatment on Microstructure and Properties of High Boron-High Speed Steel

A new type of high boron-high speed steel (HB-HSS) with different boron content was selected for oil quenching at 1050 °C, and different temperature of tempering treatment was chosen. By using optical microscopy, scanning electron microscopy, X-ray diffraction, Rockwell hardness tester, red hard treatment and wear test, the effects of heat treatment on microstructure and properties of HB-HSS were investigated. The experimental results indicate that the quenching microstructure of HB-HSS consists of α-Fe, M₂(B, C), M₇(B, C)₃ and a few of M₂₃(C, B)₆. When the tempering temperature is lower than 500 °C, the shape of carboborides will change from discontinuous sheet to continuous net, and the uniformity in microstructure is improved, and the hardness is not changed during the process. When the tempering temperature is higher than 500 °C, the continuous net of M₂(B, C) is recovered. When the tempering temperature is higher than 600 °C, the microstructure of HB-HSS get thickened because of overheating, and the hardness get significantly reduced. With the increase of tempering temperature, the weight loss of the sample is decreased, and the wear resistance of the sample is increased. When tempering temperature exceeds 500 °C, the weight loss of the sample has an obvious increase and its wear resistance decreases. The wear resistance of the sample decreases after the red-hardness treatment. The wear loss is about 8.4 mg when the boron content is 2.0% and the tempering temperature is 500 °C, which is the best of test samples.     

Gradient microstructure of TC21 alloy induced by hydrogen during hydrogenation

Through melt hydrogenation, a gradient microstructure (α″ + α′)/(α + β_H) has been observed in TC21 alloy. The addition of hydrogen induces martensite transformation and increases the volume fraction of β. It is found that the absorption process of hydrogen atoms can be divided into melting and cooling stages. During cooling, the continuous absorption of hydrogen and the corresponding decrease of freezing point of melt extend solidification time of melt and lead to hydrogen enrichment in the upper of the specimen, which induces the formation of the gradient structure. The hydrogenated TC21 alloy shows higher thermoplasticity compared with the unhydrogenated TC21 alloy. The flow stress of the upper part of the hydrogenated alloy is lower than that of the center part. A gradual variation has been observed in the microhardness along the gradient direction due to variation in the microstructure. The microhardness of the upper surface drops about 45% with 14.6 at.%H.     

Wear mechanisms of micro-drills during dry high speed drilling of PCB

In this paper, micro-drills with diameters of 0.1–0.3 mm were used to drill printed circuit boards (PCBs) with a highest spindle speed of 300 krpm. To study the wear mechanisms of PCB micro-drills, micro-drill morphology was observed, and the flank wear of the micro-drills was measured. The factors affecting flank wear were studied. In addition, hole wall roughness, nail head formation, and the accuracy of hole location were measured and analysed to determine how micro-drill wear influenced hole quality. It was found that abrasion was the main mechanism controlling the deterioration of cemented tungsten carbide micro-drills. The aggressive rubbing by glass fibre broken chips and reinforcing fillers, and the diffusion of cobalt caused abrasive wear of the flank, the chisel edge, the rake face, and the minor flank of the micro-drills. Resin that was softened by cutting heat would adhere to the micro-drills, which decreased chip removal and the accuracy of hole location. Micro-drill wear was inclined to cause nail heads and decrease the accuracy of hole location.