高速铣削钛合金Ti-6Al-4V切屑形态试验研究

对高速铣削的切屑进行了微观组织研究,建立了切削要素、切屑形态、切削力、表面粗糙度等因素之间的关系。研究发现,切削速度越高,热量向外扩散的时间越少,聚集在剪切带内的热量越多,剪切带内发生动态再结晶的可能性也就越高,大量的热量促进了剪切带内的热塑性失稳,进而使绝热剪切带产生的频率大幅度提高,切屑的锯齿化程度也就随之加大;计算了不同切削条件下绝热剪切带中心的温度、热量扩散速度等,发现热量扩散速度远低于其变形速度,进而证明了高速切削钛合金Ti-6Al-4V时,绝热剪切带内发生了动态再结晶现象。考虑到再结晶软化效应对材料本构的影响情况,建立了改进J-C本构模型,该模型用两个表达式表述不同临界应变值区间范围的材料本构特征,理论计算证明了改进J-C本构比J-C本构更准确。     

基于多尺度排列熵的铣削颤振在线监测方法

排列熵是系统复杂性和规则性的一种测度,具有概念简单、稳健和计算速度快等优点。考虑到单尺度排列熵在反映铣削力信号特征方面的不足,通过试验分析提出基于单尺度排列熵和尺度4排列熵作指标的铣削颤振在线检测方法。通过试验验证,所提出的方法能有效地检测铣削颤振。同时基于多尺度排列熵的方法对于铣削力信号采集过程中的噪声、工艺参数变化等不敏感,因此这种方法适用于实际工业生产中的在线铣削颤振监测。     

复合式镗铣加工中心箱体零件原点找正方法

由于箱体零件结构复杂,具有加工批量大和精度要求高的特点,为提高找正效率,提出关于箱体零件原点找正的方法。在研究过程中,以复合式镗铣加工中心为加工平台,构建了箱体零件的在线检测系统。通过数学建模和解析几何的知识,对置于加工中心回转台任意位置的箱体零件进行原点找正,同时确定工件原点坐标和偏转角的大小。此方法经实践检验,适合于复合式镗铣加工中心大批量生产箱体零件,提高了箱体零件加工精度和找正效率。     

变螺旋铣刀铣削力系数识别试验研究

基于变螺旋铣削模型,采用快速标定法,建立了变螺旋铣刀铣削力系数模型。对变螺旋铣刀铣削力系数识别进行了实验研究,在所给定的条件下获得了变螺旋铣刀铣削力系数。试验结果为后续铣削力实验的设计和数据处理提供了理论依据。     

井上下联合处理工艺处理矿井水过程中溶解性有机质变化特征

井上下联合处理工艺处理矿井水过程中,利用三维荧光光谱分析了矿井水中溶解性有机质的组成和变化特征。结果表明：不同处理工艺段对矿井水中DOM去除效果存在较大差异,采空区处理对矿井水中TOC和UV254的去除率分别达到67.453%和65.396%,深度处理可完全去除大分子有机物和芳香族化合物。三维荧光光谱显示,矿井水中表征出3类DOM,酪氨酸类芳香族蛋白质、色氨酸类芳香族蛋白质、溶解性微生物代谢产物。经过采空区处理后,3类有机质荧光强度都有较大降低,下降率分别为50.1%,54.4%和47.2%;深度处理使酪氨酸类有机质荧光峰消失,色氨酸类和溶解性微生物代谢产物荧光强度下降了75%左右。矿井水、采空区出水、常规处理出水中 DOM主要为生物来源;膜过滤出水中残留的DOM主要源于陆生植物和土壤有机质;总体上,矿井水处理过程中来自生物或水生细菌的新近自生源组分比例逐渐增加。     

铣挖法与综合机械化施工隧道定额编制

随着新的技术设备和施工方法在隧道工程中的应用推广,现行矿山法隧道定额编制方法已无法满足要求。该文探讨了采用铣挖法施工下隧道定额测算的方法,从工程量清单的构成出发,对隧道工程成本构成及影响因素进行了分析。以赵家湾隧道工程成本价估算工程为例,介绍了铣挖隧道工程成本估算的具体过程,并对估算结果进行了检验。     

基于PM-post的五轴数控铣床选项文件定制方法的研究

介绍了五轴数控铣床的机械结构与海德汉iTNC530数控系统五轴加工时的程序结构,研究了基于PM-post后处理器的五轴数控铣床选项文件的定制方法及与相关参数的设置方法,选择叶轮作为测试零件,在DMUmono BLOCK100五轴数控铣床上进行了加工,经实际加工结果表明,定制的机床选项文件可成功地应用到五轴铣削加工。     

An energy‐efficient asynchronous wake‐up scheme for underwater acoustic sensor networks

In addition to the requirements of the terrestrial sensor network where performance metrics such as throughput and packet delivery delay are often emphasized, energy efficiency becomes an even more significant and challenging issue in underwater acoustic sensor networks, especially when long‐term deployment is required. In this paper, we tackle the problem of energy conservation in underwater acoustic sensor networks for long‐term marine monitoring applications. We propose an asynchronous wake‐up scheme based on combinatorial designs to minimize the working duty cycle of sensor nodes. We prove that network connectivity can be properly maintained using such a design even with a reduced duty cycle. We study the utilization ratio of the sink node and the scalability of the network using multiple sink nodes. Simulation results show that the proposed asynchronous wake‐up scheme can effectively reduce the energy consumption for idle listening and can outperform other cyclic difference set‐based wake‐up schemes. More significantly, high performance is achieved without sacrificing network connectivity. Copyright © 2015 John Wiley & Sons, Ltd.     

锂离子电池SiO/C负极材料制备及电化学性能

以一氧化硅、葡萄糖以及AGP-8石墨为原料,通过行星球磨和后续的高温热解制备SiO/C复合负极材料。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对其进行了表征,经较高温度热处理得到的复合物中含有单质硅材料。复合材料电极电化学测试显示,经1 350℃热处理得到复合材料循环38周后,容量保持率接近100%,这主要源于稳定的材料结构能够在一定程度上承受嵌/脱锂过程中硅体积的变化。     

Efficiency of magnetic coupled boost DC‐DC converters mainly dedicated to renewable energy systems: influence of the coupling factor

This paper presents a specific analysis of an individual basic magnetically coupled direct current‐to‐direct current (DC–DC) converter specially designed for integration in a distributed architecture of renewable energy generators for smart grid applications. In such distributed architecture dedicated for renewable energy, parallel high‐voltage DC presents many advantages over the classical centralized one. We show that in such setup, high voltage can be advantageously produced using a specific magnetically coupled boost converter, and we point out the influence of the coupling factor, generally considered equal to one, on the overall performance of the converter and on the global energy efficiency of the installation. In this study, the generalized concepts of system energy parameters of DC–DC converters are introduced and applied to the transient analysis. Consequently, the operation of a magnetic coupled DC–DC converter with a recovery stage is modeled. The simulation results are compared with those of the behavioral study, deduced from the model pointing out the large influence of the coupling factor value on the global behavior and mainly on the value of the recovery voltage, in all the various parts of the switching cycle. The renewable energy generator operating parameters, such as current and voltage values, can then be predicted in a more useful way to compute new similar DC–DC converter systems. Copyright © 2014 John Wiley & Sons, Ltd.