Laser tempering based turning process for efficient machining of hardened AISI 52100 steel

Cost-effective machining of hardened steel components such as a large wind turbine bearing has traditionally posed a significant challenge. This paper presents an approach to machine hardened steel parts efficiently at higher material removal rates and lower tooling cost. The approach involves a two-step process consisting of laser tempering of the hardened workpiece surface followed by conventional machining at higher material removal rates with lower cost ceramic tools to efficiently remove the tempered material. The laser scanning parameters that yield the highest depth of tempered layer are obtained from a kinetic phase change model. Machining experiments are performed to demonstrate the possibility of higher material removal rates and improved tool wear behavior compared to the conventional hard turning process. Tool wear performance, cutting forces, and surface finish of Cubic Boron Nitride (CBN) tools as well as low cost ceramic tools are compared in machining of hardened AISI 52100 steel (~63 HRC). In addition, cutting forces and surface finish are compared for the laser tempering based turning and conventional hard turning processes. Experimental results show the potential benefits of the laser tempering based turning process over the conventional hard turning process.     

Characteristics of Important Stopover Locations for Migrating Birds: Remote Sensing with Radar in the Great Lakes Basin

Abstract:  A preliminary stage in developing comprehensive conservation plans involves identifying areas used by the organisms of interest. The areas used by migratory land birds during temporal breaks in migration (stopover periods) have received relatively little research and conservation attention. Methodologies for identifying stopover sites across large geographic areas have been, until recently, unavailable. Advances in weather-radar technology now allow for evaluation of bird migration patterns at large spatial scales. We analyzed radar data (WSR-88D) recorded during spring migration in 2000 and 2001 at 6 sites in the Great Lakes basin (U.S.A.). Our goal was to link areas of high migrant activity with the land-cover types and landscape contexts corresponding to those areas. To characterize the landscapes surrounding stopover locations, we integrated radar and land-cover data within a geographic information system. We compared landscape metrics within 5 km of areas that consistently hosted large numbers of migrants with landscapes surrounding randomly selected areas that were used by relatively few birds during migration. Concentration areas were characterized by 1.2 times more forest cover and 9.3 times more water cover than areas with little migrant activity. We detected a strong negative relationship between activity of migratory birds and agricultural land uses. Examination of individual migration events confirmed the importance of fragments of forested habitat in highly altered landscapes and highlighted large concentrations of birds departing from near-shore terrestrial areas in the Great Lakes basin. We conclude that conservation efforts can be more effectively targeted through intensive analysis of radar imagery.     

武器装备伪装毯研究

伪装器材是提高己方武器装备、设施及参战人员战时生存能力,保存有效战斗力的重要技术手段。采用来源广、价格低廉、伪装效果好的普通材料为选择依据,设计了一种武器装备伪装毯,其在从红外到雷达波波段内都有良好的伪装隐身效果。     

广西大范围低空急流暴雨的分型及雷达回波特征分析

对2002—2010年广西12个低空急流暴雨个例进行了普查分析,结果表明,广西大范围低空急流暴雨是在大尺度背景下,由天气系统和中小尺度系统共同影响的结果,在有低空急流存在的情况下,降水量有明显的增幅作用;通过对天气背景进行分析,对广西大范围低空急流暴雨天气形势进行了分型,得到了低涡急流型和深槽切变急流型以及副高加强急流型等3种型式。雷达回波主要有块状、带状和絮状3种类型;再通过对大范围低空急流暴雨过程的雷达回波强度、回波演变、其他产品特征、回波的源地移动和暴雨落区等内容的分析,提出了低空急流暴雨的短期预报模型,为今后广西大范围急流暴雨预报提供参考。     

电离层环境对地空信息系统的影响效应

目的为了减缓电离层对卫星通信、全球卫星导航系统、星载合成孔径雷达等系统的影响,提高系统的环境适应性。方法由穿越电离层的无线电信号传播原理出发,结合各种系统的工作原理,给出电离层影响的分析方法。结果针对电离层闪烁、极化旋转、时延和色散等传播效应造成卫星通信误码率上升、卫星导航定位误差增大、SAR图像偏移和分辨率下降等影响,分析给出了效应补偿和减缓应对方法。结论电离层延迟效应可以由电离层实测值或者模型来进行校正,而闪烁效应大多需采用规避的措施来减缓其影响。     

湘中地区2010年5月两次暴雨过程的雷达特征对比分析

2010年5月5~6日和5月12~13日，湘中发生了两次区域性暴雨。运用了自动站降水资料、多普勒天气雷达基本反射率和基本径向速度资料以及NCEP提供的FNL资料，分析了这两次暴雨的雷达回波特征，并从水汽和地形两方面分析了两次暴雨的影响因素。结果表明：两次暴雨的环流形势场不同。 “100506”暴雨强降水回波呈带状自西南向东北扫过娄底，而“100513”暴雨强降水回波呈块状自西往东范围逐渐加强；两次暴雨都有逆风区存在，逆风区的范围和强度对应着强降水的范围与强度。两次暴雨水汽主要来自孟加拉湾和南海，“100506”暴雨发生在切变线附近；“100513”暴雨发生在切边线南侧的辐合区内。娄底西部、北部、中部山地的阻挡和抬升作用以及冷暖气流交汇也是暴雨产生的重要原因之一     

石家庄市一次大气重污染过程的边界层特征和成因分析

针对石家庄市2015年12月5—14日出现的重污染过程,利用石家庄市逐日地基微波辐射计、风廓线雷达、地面气象观测资料以及同期的污染物观测资料,分析了重污染过程期间大气边界层温度、湿度、风变化特征及对PM_(2.5)的影响,采用Hysplit后向气团轨迹模式对污染来源进行分析。此次重污染以局地排放为主要形成源,期间冷空气势力弱,地面日平均风速均在1.5 m/s以下,日平均相对湿度均在70%以上,风速小、湿度大,稳定的大气环流形势为重污染提供了持续稳定的大气环境背景。逆温形成及快速增厚导致重污染开始,逆温层平均厚度为683 m,逆温层厚、强、不易消散,导致重污染持续时间长、污染重。近地面小风层厚(平均700 m左右),通风能力弱,导致污染物难以稀释扩散。同时近地层湿度大、厚度厚,使得PM_(2.5)更容易形成和积累,对重污染加重起到了促进作用。     

Emission of particulate and gaseous pollutants from household laser processing machine

Indoor air quality (IAQ) directly affects the health of occupants. Household manufacturing equipment (HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment (HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration (PNC) and particle emission rate (PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 mW, the mode diameters of particles were <150 nm, and PNCs were >2.0 × 10⁴ particles/cm³. Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C₈ aromatics (ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles (UFPs) was >5 × 10⁴ particles/cm³ during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.     

震后某工号建渣及土壤样品中铀的分析测定

采用激光荧光法对"5.12"地震后某工号建筑垃圾和土壤样品进行了铀的测定。方法检出下限D.L≤3×10-11g/mL,相对标准偏差RSD为7.4%,回收率达到86%~109%。对实验数据进行了分析和初步评价,结果表明,该工号所测样品铀含量基本处于天然本底水平。     

Safety management by use of laser mass spectrometry of polychlorinated biphenyls (PCBs) in the processed gas and work environment of a PCB disposal plant

This study demonstrates the applicability of laser mass spectrometry for safety management of the processed gas and the work environment in a polychlorinated biphenyl (PCB) disposal plant. By utilization of laser ionization/ion trapping storage/time-of-flight mass spectrometry (LI-IT-TOFMS), we analyzed gaseous PCBs from scrap capacitors with on-line detection. It was confirmed that few contaminants were detected in the spectrum. By the effect of laser-induced selective ionization, it was considered that there was little interference with the mass range of PCBs. The accuracy of LI-IT-TOFMS when analyzing environmental gas was almost the same as that for the PCB standard gas. It was possible to perform on-line analysis of the work environment for over 2000 h (120 000 data points). LI-IT-TOFMS was thus shown to be a very useful method for ensuring the safety of the work environment in disposal plants for PCBs.