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991.
992.
采用合金粉末烧结体表面观察法研究了稀土在WC-Co硬质合金中的作用机理。合金中的稀土分别以混合稀土(以La和Ce为主体成分)-Co预合金粉(简称RE-Co预合金粉)形式和La(NO3)3的丙酮溶液形式在湿磨时直接加入。用扫描电镜和能谱仪对平均粒径小于200μm的2种球形稀土硬质合金粉末(简称合金粉末)烧结体表面进行观察与分析,发现:以RE-Co预合金粉形式加入稀土时,在烧结过程中,合金中的稀土La和Ce以及杂质元素在合金粉末烧结体表面产生了明显的富集,形成了含La,Ce,S,Ca,W,C和O的复杂形式的化合物,在稀土富集物中没有检测到Co。以La(NO3)3形式加入稀土,在合金粉末烧结体表面没有检测到La。说明在合金粉末烧结体表面不存在La的富集或聚集。稀土的添加形式同时也影响合金粉末烧结体表面硬质相WC与粘结相的比例,以RE-Co预合金粉末形式加入稀土,合金粉末烧结体表面粘结相含量较少,因此,稀土的添加形式影响其在硬质合金中的作用机理。以RBCo预合金粉形式加入稀土,合金中的稀土不但具有较好的富集合金中杂质元素的作用,而且还可以阻止烧结体表面富粘结相结构的形成。 相似文献
993.
太钢不锈钢冷轧板材质量、性能改进技术的分析 总被引:1,自引:0,他引:1
太钢作为国内最大的、惟一的不锈钢全流程宽带钢生产企业,在国家的支持和有关科研院校的帮助下,以企业自主开发为主体,围绕不锈钢冷轧板主要品种,在提高不锈钢冷轧板内在质量和表面质量方面进行了技术研发。笔者对其有关技术进行了总结,并就产品实物质量与国际水平进行了比较。结果表明:太钢不锈钢冷轧板材质量达到国际先进水平,这对于带动我国不锈钢生产技术的快速发展,提高不锈钢的国产化率和国际市场竞争力具有重要意义。 相似文献
994.
The present study investigated the effects of speech recognition technology (SR) and advance planning on children's writing processes. Fluent and less fluent writers, ages 11 to 14, composed 4 narratives, via handwriting and SR, both with and without advance planning. Less fluent children's handwritten narratives were significantly inferior to those of fluent children in terms of length, quality, and surface errors. For less fluent writers, SR (a) significantly increased the length and (b) decreased the surface errors of narratives. Although narrative length related positively to holistic quality, SR did not significantly improve quality. Advance planning helped children to compose more fully developed stories. For children with writing difficulties, advance planning and SR may each independently support text generation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
996.
The algorithm is divided into two steps. The first step pre-locates the blank by aligning its centre of gravity and approximate normal vector with those of destination surfaces, with largest overlap of projections of two objects on a plane perpendicular to the normal vector. The second step is optimizing an objective function by means of gradient-simulated annealing algorithm to get the best matching of a set of distributed points on the blank and destination surfaces. An example for machining… 相似文献
997.
This paper presents an investigation into the hydraulics of regular ogee-profile spillways. The free-surfaces of the fluid for several flow heads as measured in the hydraulics laboratory are used as benchmarks. The finite element computational fluid dynamics software, ADINA, was used to predict the free surface over an ogee spillway and thus model the flow field. Since the actual flow is turbulent the k-ε flow model was used. For the cases considered in this paper, ADINA predicted reasonable free surface results that are consistent with general flow characteristics over spillways. The results are also in close agreement with measured free-surface profiles over the entire length of the spillway. 相似文献
998.
Michael N. Gardos 《Tribology Letters》1995,1(1):67-85
440C steel thrust ball bearing races lubricated with 1 m thick sputtered films of MoS2 were tested in the unidirectional and oscillatory modes against bare steel balls in moderate (10–4–10–5 Pa 10–6–10–7 Torr) vacuum and in 1 atmosphere of 99.999% pure ( 1 ppm water) N2 in the same unbaked environmental chamber. Over 90% of the residual gases in the chamber vacuum consisted of H2O vapor. The bearings operated in N2 showed substantially longer lives compared to the specimens tested in vacuum. Scanning electron microscope (SEM) tribometry was also performed on an MoS2 film powder-burnished onto a 440C flat. This flat was repeatedly oscillated against bare, hemispherical-tipped 440C pins on fresh wear tracks in the same type of N2 and column vacuum of ~10–3 Pa 10–5 Torr itself containing over 90% residual H2O. The SEM-generated results on the burnished film confirmed the same, atmosphere-dependent difference in wear life observed with the sputtered layers. Varying the moisture content of the burnished flat and its immediate environment by cryosorption predictably manipulated the coefficient of friction and wear life of MoS2. The various possible causes of this perplexing phenomenon are reviewed, and a plausible hypothesis is offered attributing the unexpected wear life reduction to the physico-chemical consequences of residual H2O hydrogen-bonding to the oxidized and/or hydrated edge and basal plane sites of MoS2 in moderate vacuum. The site-specific sorption of water is severely hindered in 1 atm N2 by the gas molecules disrupting the H-bonding mechanism. 相似文献
999.
The area of an individual bounded surface (e.g. the boundary of a properly sampled cell) can be estimated from an isotropic uniform random stack of parallel sections, or of non-invasive planar scans, using the well-known spatial grid. A standing problem was to estimate the area of an individual bounded surface with an arbitrary degree of accuracy from a vertical (i.e. not isotropic) stack of sections or scans. A new tool to do this, called the ‘vertical spatial grid’, is presented. 相似文献
1000.