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91.
A new electron beam control system was developed in a general vacuum electron beam machine by assembling with industrial control computer, programmable logic control (PLC), deflection coil, data acquisition card, power amplifier, etc. In this control system, scanning track and energy distribution of electron beam could be edited off-line, real-time adjusted and controlled on-line. Ti-Mo gradient material (GM) with high temperature resistant was fabricated using the technology of electron beam melting. The melting processes include three steps, such as preheating, melting, and homogenizing. The results show that the GM prepared by melting technology has fine appearance, and it has good integrated interface with the Ti alloy. Mo and Ti elements are gradually distributed in the inter.face of the gradient material. The microstructure close to the Ti alloy base metal is α + β basket-waver grain, and the microstructure close to the GM is a single phase of β solid solution. 相似文献
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93.
板料成形中,压边力是控制板料流动的重要因素。前人大量的研究表明,在拉伸成形的不同行程施加合适的变压边力(VBHF),可有效避免板料成形中起皱和破裂的缺陷。文章基于压边力成形窗口的定义和分析,提出新的控制目标,并采用PID闭环控制策略来优化不同冲压行程中分块压边圈上的压边力。针对一个具有不同角部半径的盒型件进行了闭环的变压边力优化模拟,得到其不同位置的分块压边圈随行程变化的最优压边力曲线,并在变压边力压机上进行实验验证,结果表明,使用铝合金板料并在恒定压边力下难以成形的盒形件,在最优变压边力下成功成形。 相似文献
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95.
设计了一种基于多功能热管的高效吸附式制冰机组,采用氯化钙/活性炭复合吸附剂和氨作为吸附工质对。吸附床的加热解吸、冷却吸附及回热过程均由热管工作完成,对该新型吸附制冰机组进行了回质回热研究,结果表明,回质回热型循环可使机组的制冷性能系数COP提高25.5 %,加热量减小约13 %,同时冷却器负荷降低约21 %;采用先回质后回热方式,在回质过程中继续加热解吸床可进一步增加机组制冰量。与传统回质相比,系统COP和单位质量吸附剂制冷功率SCP提高幅度均在15 %以上,且机组SCP的提高幅度高于COP的幅度;吸附制冰机组性能随冷却水温度的升高而下降,但系统的SCP始终维持在较高的水平。当冷却水温度为27℃、蒸发温度为-18.9℃时,系统的SCP仍然高达356.5 W·kg-1。 相似文献
96.
Poly (vinyl alcohol) (PVA)/Hydroxy apatite (HA) composite prepared from aqueous solution of the polymer and dimethylsulfoxide (DMSO) by freezing and thawing method are developing to repair or replace articular cartilage. In the present study, the tribological behaviors of this composite were investigated in a three‐factor, three‐level designed experiment using an improved four‐ball tester. Factors include sliding velocity, applied load, and HA content of composite. Friction coefficient of the PVA‐H/HA was found to depend significantly on load and sliding velocity, while HA content had small effects on the friction coefficient of PVA‐HA composite. We also found that wear loss of PVA‐H/HA increased sharply with the increasing loads and HA content of specimen. Increased HA content from 0.5% to 1.5% resulted in an increasing of 355% in wear loss, while increasing sliding velocity slightly decreases wear loss of specimen. We also found some correlation between friction coefficient and wear loss of specimen under the given condition. These results may be useful in the tribological design of PVA‐H/HA composite for both low wear and low friction using as artificial cartilage substitutes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
97.
Formation of Titanium Carbide/Aluminum Oxide Nanocomposite Powder by High-Energy Ball Milling and Subsequent Heat Treatment 总被引:1,自引:0,他引:1
The preparation of titanium carbide/aluminum oxide (TiC/Al2 O3 ) nanocomposite powders from a mixture of titanium, carbon, and Al2 O3 powders via a high-energy ball milling process and subsequent heat treatment was investigated. The microstructure development of the powder mixtures was monitored by X-ray diffraction and transmission electron microscopy. The ball milling of an elemental carbon, titanium, and Al2 O3 powder mixture at ambient temperature resulted in the formation of TiC within 15 h of milling. With further milling of up to 25 h, the resulting powder mixture was composed of nanosized TiC particles and nanocrystalline carbon, titanium, and Al2 O3 . The nanocrystalline titanium and carbon were transformed into nanosized TiC particles after subsequent heat treatment. The final product was composed of nanosized TiC and microcrystalline Al2 O3. Most of the nanosized TiC particles were located within Al2 O3 grains. 相似文献
98.
目的观察重组人干扰素α2b阴道泡腾片对单纯疱疹病毒性阴道炎动物模型的疗效。方法采用单纯疱疹病毒感染建立豚鼠实验性阴道炎模型,并分别用重组人干扰素α2b阴道泡腾片600、3 000和15 000 IU/只进行治疗。以阿昔洛韦(无环鸟苷)和干扰素α2b栓剂15 000 IU/只作为对照。对治疗前后豚鼠阴道外观及组织切片进行评分。结果应用重组人干扰素α2b阴道泡腾片对豚鼠实验性单纯疱疹病毒性阴道炎进行治疗后,豚鼠阴道外观病变与组织切片病变评分均显著降低,其中15 000 IU/只效果最好。同样剂量的α2b泡腾片药效优于栓剂。结论重组人干扰素α2b阴道泡腾片对实验性单纯疱疹病毒性阴道炎有明显的疗效。 相似文献
99.
Bo He Fei Li Hong Zhou Yongbing Dai Baode Sun 《Journal of Coatings Technology and Research》2007,4(3):335-340
Two kinds of thermal barrier coatings (TBCs), consisting of NiCoCrAlY bond coats (BCs) deposited by electron beam-physical
vapor deposition (EB-PVD) and high velocity oxy-fuel (HVOF) thermal spraying, respectively, and top 8 wt%Y2O3–ZrO2 (8YSZ) ceramic layers deposited by EB-PVD were prepared on near-α titanium alloys. The field emission scanning electronic
microscopy and microhardness indentation are used to study the microstructure and microhardness. Different failure features
including cracking patterns and the delamination degree of these two TBCs are discussed according to the thermal cycling tests
in the atmosphere. It is found that the morphology of the two BCs deposited by different methods (EB-PVD and HVOF) determines
the microstructure and microhardness of their corresponding top 8YSZ layers. The BC prepared by EB-PVD is dense and homogeneous,
which leads to a dense and hard 8YSZ with clustered slim columnar grains. The BC prepared by HVOF, however, is porous and
inhomogeneous in microstructure and, as a result, the top ceramic layer is loose with low microhardness and clustered coarse
columnar grains. 相似文献
100.