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11.
丁晓东 《电子工业专用设备》2002,31(3):159-162,173
气压传动与控制已成为电子专用设备研制过程中一项不可缺少的内容 ,必须进行合理的气动系统设计及其控制 ,选择相应的气动元件以满足设备的功能要求。概述了气压传动与控制在电子专用设备上的应用。 相似文献
12.
位山引黄灌区泥沙淤积原因及处理对策 总被引:7,自引:2,他引:5
位山灌区是黄河下游大型引黄灌区 ,渠系泥沙淤积严重 ,泥沙处理困难。通过采用远距离输沙、集中处理沉沙区泥沙、分散沉沙和节水减淤等技术措施 ,减少了渠系的泥沙淤积。对清淤产生的泥沙 ,采取综合开发利用的技术和管理措施 ,取得了比较可靠的效果。 相似文献
13.
Effect of boron on the low-cycle fatigue behavior and deformation structure of INCONEL 718 at 650 °C
L. Xiao M. C. Chaturvedi D. L. Chen 《Metallurgical and Materials Transactions A》2004,35(11):3477-3487
Symmetrical push-pull low-cycle fatigue (LCF) tests were performed on INCONEL 718 (IN718) containing 12, 29, 60, and 100 ppm
B at 650 °C. The results showed that all the alloys experienced a relatively short period of initial cyclic hardening at low
strain amplitudes, followed by a regime of saturation or slightly continuous cyclic softening. The initial cyclic hardening
phase decreased with increasing strain amplitudes, and disappeared at the high strain amplitudes. A serrated flow was observed
in the plastic regions of cyclic stress-strain hysteresis loops. The saturated cyclic stress amplitude at a given strain amplitude
was highest for the alloy with 60 ppm B, and lowest for the alloy with 12 ppm B. The LCF lifetime increased with increasing
B concentration up to 60 ppm, and then decreased as the B content increased from 60 to 100 ppm. Fractographic analysis suggested
that the fracture mode changed from intergranular to transgranular cracking as the B concentration increased. The characteristic
deformation microstructures produced by LCF tests at 650 °C, examined via transmission electron microscopy, were regularly spaced arrays of planar deformation bands on {111} slip planes in all four
alloys. A ladderlike structure was observed in some local regions in the alloy with 12 ppm B. Heavily deformed planar deformation
bands were observed in the fatigued specimens with 100 ppm B. The mechanism of improvement in the LCF life of IN718 due to
B addition is discussed. 相似文献
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Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles. 相似文献
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18.
Tian Xiao Qing Huo Liu 《Antennas and Propagation, IEEE Transactions on》2008,56(3):765-773
In this paper, we present an enlarged cell technique (ECT) to avoid the time step reduction encountered in the conformal finite-difference time-domain (CFDTD) method due to small irregular cells truncated by metallic boundaries. We focus our efforts on the discussion of the accuracy and stability of the ECT and its comparison with other conformal methods, especially the one called the uniformly stable conformal (USC) method. We also provide a simplified ECT, which is much easier to implement. In the ECT, a stability criterion is first constructed to identify instable irregular cells, i.e., those having so small an area to cause instability. Those instable cells are then enlarged into their adjacent cells to obtain a large, stable area. Careful treatment is performed on the communication between the intruding and intruded cells in terms of electromotive force by keeping the total electromotive force conservative. This technique is verified by several 3-D numerical experiments. Results show that the ECT is second-order accurate and numerically stable at the regular Courant time step limit. 相似文献
19.
The effects of yttrium and cerium on microstructures and properties of Nb-Si system composites were investigated by scanning electron microscopy( SEM), energy dispersive spectrum(EDS), X-ray diffraction(XRD) and high temperature oxidation experiments.It is found that the coarse primary silicide phase became finer and more homogeneous with Y and Ce addition.The results of high temperature oxidation experiments show that the oxidation rates of NbSi system composites with an appropriate amount of Y and Ce decrease compared with those of alloys without Y or Ce addition, and oxidation products mainly distribute along the phase boundaries between the Nb solid solution and silicide. 相似文献
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