排序方式: 共有9条查询结果,搜索用时 15 毫秒
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通过显微硬度和抗拉强度试验、X射线衍射仪、扫描电镜和金相显微镜观察,研究经旋转摩擦挤压法制备的CNTs/Mg复合材料的组织及性能。结果表明:CNTs/Mg复合材料的组织为细小等轴晶,且随着CNTs含量的增加,复合材料晶粒尺寸逐渐细化,当CNTs含量为5%时,晶粒尺寸最小,由63μm减小至3.79μm,为AZ91基材晶粒尺寸的6.01%。经过旋转摩擦挤压加工后基材内第二相β-Al12Mg17相的量减少,CNTs的加入使复合材料中出现了Al4C3相,且第二相β-Al12Mg17相网状结构消失。加工后的镁合金抗拉强度提高,最大值为330.9 MPa,较原基材提高了90.6%,当CNTs含量小于2%时,复合材料强度高于原基材。复合材料硬度随着CNTs含量的增加呈先增加后降低的趋势,当CNTs含量为2%时,硬度最高,达101.3HV,比AZ91基材提高了40.3%。 相似文献
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Croskey C.L. Kampfer N. Belivacqua R.M. Hartmann G.K. Kunzi K.F. Schwartz P.R. Olivero J.J. Puliafito S.E. Aellig C. Umlauft G. Waltman W.B. Degenhardt W. 《Microwave Theory and Techniques》1992,40(6):1090-1100
The Millimeter Wave Atmospheric Sounder (MAS) will be launched in the spring of 1992 as part of the ATLAS 1 (Atmospheric Laboratory for Application and Science) mission. Using passive limb-scanning millimeter-wave radiometry, it will sense the thermal emission produced by ozone at 184 GHz, water vapor at 183 GHz, chlorine monoxide at 204 GHz, and oxygen (for retrieval of temperature and pressure) at 60 GHz. From these observations, concentration profiles of these gases throughout the middle atmosphere will be made. The fundamentals of the measurements, the design of the radiometers, and the approaches used for the data analysis are described 相似文献
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Jungang Miao Thomas Rose Klaus Kunzi Peter Zimmermann 《Journal of Infrared, Millimeter and Terahertz Waves》2002,23(8):1159-1170
The instrument concept of a future spaceborne millimeter/sub-millimeter radiometer is proposed in this paper for the remote sensing of ice clouds from satellite. The proposed radiometer is expected to operate at a series of frequencies within the millimeter and sub-millimeter wave range from 150 to about 900 GHz. Five frequencies are selected in the atmospheric windows, i.e., 150, 220, 463, 683, 874 GHz, and at each frequency there are two orthogonally polarized channels. Three water vapor channels located close to 183.31 GHz are also included in this instrument, since they can provide water vapor information, which is needed for ice cloud parameter retrieval. To simplify system design and test, a modular design philosophy is followed in the receiver frontend design and two antennas are used separately for the millimeter and sub-millimeter channels. Overall, the instrument requirements can be met with today's technology, except for the channels at the highest frequencies, where the radiometric sensitivity can be larger than the required 1.0 K for the 10 km spatial resolution (2.5 ms integration time). However, this situation can be improved by averaging neighboring pixels in data processing if certain compromise in the spatial resolution can be made at these frequencies. 相似文献
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Snow-Cover Parameters Retrieved from Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) Data 总被引:6,自引:0,他引:6
Kunzi Klaus F. Patil Subash Rott Helmut 《Geoscience and Remote Sensing, IEEE Transactions on》1982,(4):452-467
The Nimbus-7 satellite launched on October 24, 1978, carries a multifrequency, dual-polarized microwave imager. The instrument is designed to sense the ocean surface, the atmosphere, and land surfaces remotely. From previous ground-based and satellite-based microwave experiments, it is well known, that snow cover over land has a very distinct effect on the microwave signatures of the earth surface. It was the goal of this study to show that the three snow-cover parameters: extent, snow water equivalent, and onset of snow melt can be determined using scanning multichannel microwave radiometer (SMMR) data. Our analysis has shown, that the three snow parameters mentioned above are retrievable with sufficient accuracy to be of great value in climatology, meteorology, and hydrology. Snow extent is determined for dry snow cover with depth ?5 cm, snow water equivalent can be determined on a regional basis with ?2 g/cm2 rms accuracy, and the onset of snow melt is clearly visible by the detection of melt and refreeze cycles prior to snow runoff. The algorithms derived are simple enough to be incorporated in fully automated operational data analysis schemes. 相似文献
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往复加工常见于磨削和刨削等金属切削中,加工过程的平稳性直接影响到产品的加工质量、能源效率乃至机床的寿命。首先探究往复(冲程)运动速度规划对运动过程平稳性的影响,在分析了常见速度规划运动学性能的基础上,针对磨削冲程运动的特点,提出通过改变急动度空间分布来降低柔性冲击对加工表面质量的影响,并设计了两种基于急动度连续的速度规划算法。在此基础上,研究了速度规划算法和磨削力平稳性、加工表面粗糙度和加工能耗间的关系,提出了通过改变加速度空间分布来降低加工能耗的方法。试验结果表明,往复运动速度规划和磨削力平稳性、加工表面粗糙度以及加工能耗均相关,通过改变急动度和加速度空间分布提高了磨削力平稳性和加工表面质量,降低了加工能耗。所提出的Ⅱ型速度规划综合表现优于其他规划,与梯形速度规划相比,切削力波动、加工表面粗糙度和电机驱动能耗均有较为显著的下降。 相似文献
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