广州市灰霾监测颗粒物监测仪安装维护浅析

2008年广州市环境监测中心站成为了国家灰霍监测试点单位之一,并建立了灰霾监测试点实验室。灰霾的形成与细颗粒物PM2.5浓度有密切关系。实验室配置了美国赛默飞世尔公司新推出的1405-D双通道环境颗粒物监测仪对细颗粒物PM2.5和可吸入颗粒物PM10进行监测。本文着重介绍1405-D的安装、维护中容易出现的问题,并提出了一些维护经验和使用注意事项。希望为环境监测人员提供仪器安装和维护方面的参考,获得准确监测数据。经较长时间的使用维护,目前广州灰霾监测试点1405-D双通道环境颗粒物监测仪运行稳定。     

Cu-Cr粉体致密化及颗粒流变三维数值模拟分析

利用MSC.Marc有限元软件对Cu-Cr粉体致密化及颗粒流变行为进行了三维数值模拟。分析了不同颗粒排列方式压制载荷下Cu-Cr颗粒致密化、颗粒与节点的流动规律。首次再现了Cu-Cr颗粒在致密化过程中的三维流变行为。结果表明,六角形排列的Cu-Cr颗粒不仅流动性高,而且均匀性也好于方形排列的Cu-Cr颗粒。温粉冷模比温粉温模(恒温环境)在100℃条件下的致密度高0.36%,在800℃条件下高2.87%。六角形排列的Cu-Cr颗粒致密度在摩擦系数为0.1时最高为95.6859%,方形排列的Cu-Cr颗粒致密度在摩擦系数为0.5时最高为97.5343%。无摩擦理想状态下的Cu-Cr颗粒致密化并没有达到最大致密度。     

Optimization of a Multi Gravity Separator to produce clean coal from Turkish lignite fine coal tailings

In this study, the beneficiation of two lignite tailings by Multi Gravity Separator (MGS) was investigated. The tailings samples from the Tunçbilek/Kütahya and Soma/Manisa regions have ash contents of 66.21% and 52.65%, respectively. Significant operational parameters of MGS such as solid ratio, drum speed, tilt angle, shaking amplitude, wash water rate, and feed rate were varied. Empirical equations for recovery and ash content were derived by a least squares method using Minitab 15. The equations, which are second-order response functions, were expressed as functions of the six operating parameters of MGS. The results showed that it is possible to produce a coal concentrate containing 22.83% ash with a recovery of 49.32% from Tunçbilek coal tailings, and a coal concentrate containing 22.89% ash with a recovery of 60.01% from Soma coal tailings.     

Measurements of pollen grain dispersal in still air and stationary, near homogeneous, isotropic turbulence

The dispersal of ragweed, pine and corn pollen as well as polystyrene spheres in still air and stationary, near homogeneous, isotropic turbulence (HIT) was investigated using high-speed, digital inline holographic cinematography enabling Lagrangian tracking of the particles. Mean still air settling velocities were similar as reported literature values. Small discrepancies were most likely related to species/size differences and water content of the grains. Near-HIT was generated by loudspeakers mounted on the corners of a 40 cm³ chamber and the turbulent flow field at the center of the chamber was validated using stereoscopic Particle Image Velocimetry (PIV). Results showed near homogeneity and near isotropy with mean velocities 5–10 times smaller than the corresponding rms values of velocity fluctuations. The turbulent kinetic energy dissipation rate was determined from the PIV data sets and used to calculate the Kolmogorov scales and Taylor microscales. Experiments were carried out for two different loudspeaker amplifications corresponding to Taylor microscale Reynolds numbers, R_λ=144 and 162, respectively. The mean settling velocity in turbulent conditions was in all cases higher than the corresponding still air value, the difference becoming smaller as particle Stokes numbers increased. For the present conditions, the still air particle settling velocity was lower than the rms values of air fluctuating velocities. As a result, dispersion was dominated by inertia and for a given R_λ, particle fluctuating velocity autocorrelations fell more rapidly as the particle Stokes number decreased; corresponding particle diffusion coefficients also decreased. Transverse particle diffusion coefficients were lower than those in the direction of gravity in agreement with the continuity effect. Under the present range of experimental parameters, results showed that inertial particles (0.6<St<11) in highly turbulent conditions disperse more effectively than the air.     

Chatter milling modeling of active magnetic bearing spindle in high-speed domain

A new dynamical modeling of Active Magnetic Bearing Spindle (AMBS) to identify machining stability of High Speed Milling (HSM) is presented. This original modeling includes all the minimum required parameters for stability analysis of AMBS machining. The stability diagram generated with this new model is compared to classical stability lobes theory. Thus, behavior's specificities are highlighted, especially the major importance of forced vibrations for AMBS. Then a sensitivity study shows impacts of several parameters of the controller. For example, gain adjustment shows improvements on stability. Side milling ramp test is used to quickly evaluate the stability. Finally, the simulation results are then validated by HSM cutting tests on a 5 axis machining center with AMBS.     

超细滑石粉/聚乳酸复合材料的制备与表征

以偶联剂γ-(2,3-环氧丙氧)丙基三甲氧基硅烷(KH-560)处理后的超细滑石粉为增强相,聚乳酸(PLA)为基体,制备了超细滑石粉/PLA复合材料。通过傅里叶变换红外光谱(FT-IR)、电子扫描显微镜(SEM)、X射线衍射(XRD)、光学解偏振法、温度-形变曲线及热失重(TG)对复合材料进行了表征。结果表明,KH-560成功地包覆在滑石粉表面,滑石粉表面与PLA基体发生了化学键合,处理后的滑石粉粒子与PLA基体之间形成了良好的界面。适量的滑石粉能够提高PLA基体的结晶速率和结晶度,当滑石粉添加量增大到一定程度,PLA基体的晶格参数和晶体结构会发生变化。当滑石粉分散良好时,复合材料的玻璃化转变温度(Tg)和热稳定性显著提高。     

基于高速铣削的铝合金6061表面粗糙度试验研究

采用正交试验法,在高速加工中心上对铝合金进行高速切削试验,研究机床的切削速度、进给速度、切削深度对加工表面粗糙度的影响规律,为企业生产提供可靠的依据.     

弧面分度凸轮高速专用铣床的研究

在分析弧面分度凸轮加工原理的基础上,确定弧面分度凸轮高速专用铣床必须具有五轴联动的功能,且应有两个旋转坐标。通过对国内外现有加工设备的分析和比较,提出3种结构方案,经过对比分析,确定了一种相对合理的卧式结构方案及对应的机床传动系统方案。该机床的工件回转进给运动分别通过数控分度头和回转工作台实现,并采用电主轴技术,是一种CNC高速专用铣床。     

纯钛(TA2)表面纳米化及其热稳定性研究

利用超音速微粒轰击(SFPB)技术对纯钛(TA2)试样进行了表面纳米化处理,并对SFPB处理后的试样进行不同温度的热处理。通过X射线衍射(XRD)、金相显微镜(OM)、显微硬度计和透射电子显微镜(TEM)分析测试,研究纯钛表面SFPB处理后的纳米化机理及其热稳定性。结果表明:经SFPB处理后试样表层形成了尺寸约为20nm随机取向的等轴晶粒,变形机制以孪生为主,且随层深增加,形变孪晶逐渐由多系转变为单系。纳米化后在450℃热处理时,纳米晶未发生明显粗化,因而具有良好的热稳定性。     

TD-LTE高速铁路规划方案研究

伴随着电子商务及互联网的飞速发展,移动终端用户对数据传输速率的需要日趋强烈。4G时代的到来,使得高铁移动终端用户可以有良好的体验。但由于高铁的高速移动性以及高铁本身的结构特性,在LTE高铁网络规划建设中会遇到多普勒效应、车体高穿损、小区间切换困难等诸多难题。文章对以上问题做了相应的研究,并结合某市LTE高铁建设,提出了具体的解决方案。