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991.
钕对AZ91镁合金组织及机械性能的影响 总被引:14,自引:0,他引:14
采用微观分析、机械性能测试及断口分析等方法研究了钕对AZ91-Nd镁合金(w(Nd)=0,0.1%,0.3%,0.5%,1.0%,1.5%)的微观组织和机械性能的影响。结果表明:Nd以固溶和金属间化合物(A l11Nd3)的形式存在时具有细化晶粒、抑制二次β相析出、使不完全离异共晶转化为离异共晶的作用;Nd通过固溶强化、析出强化和细晶强化增加了合金强度和硬度,并改善了塑性;加入Nd后合金的断裂机制从脆性解理断裂转变为准解理断裂。 相似文献
992.
雕塑艺术作品的产生是艺术家的智能与辛劳的结晶,反映出艺术家的内心感情世界,由于雕塑大师的个性和艺术道路的不同,使得他们的作品呈现出不同的风貌。当今,只有保持独立个性和挑战态度的艺术家,才能走出属于自己的艺术之路。 相似文献
993.
磷渣基复合矿化剂对水泥熟料烧成的影响 总被引:2,自引:0,他引:2
研究了在水泥生料中掺入不同矿化剂对水泥生料的易烧性、硅酸盐水泥熟料矿物形成和岩相结构的影响:结果表明,与传统的萤石和磷渣矿化剂相比,磷渣与萤石复合的矿化剂可有效降低水泥熟料中游离氧化钙(f-CaO)的含量,改善生料的易烧性;在煅烧温度与时间增加的情况下,改善作用仍然明显;通过XRD、SEM与岩相结构分析表明,磷渣与萤石的复合矿化剂降低了液相的粘度,促进了A矿的生长,对矿物的结晶形态有改善作用,有利于晶体尺寸的生长发育。 相似文献
994.
黄河水系悬浮物和沉积物重金属质量基准研究 总被引:7,自引:0,他引:7
利用已有的资料和国际上流行的相平衡分配法和生物效应数据库法,研究提出了黄河悬浮物和沉积物重金属质量基准的建议值。 相似文献
995.
This paper deals with the problem of optimization of job sequence in a two-machine flow shop problem in the presence of uncertainty.
It is assumed that the processing times of jobs on the machines are described by triangular fuzzy sets. A new optimization
algorithm based on Johnson”s algorithm for deterministic processing times and on an improvement of McCahon and Lee”s algorithm
is developed and presented. In order to compare fuzzy processing times, McCahon and Lee use mean values of their corresponding
fuzzy sets. It is shown that this approach cannot fully explore possible relationships between fuzzy sets. In order to overcome
this drawback we consider different fuzzy sets determined by λ-cuts of the fuzzy processing times. Extensive experiments show
that the new algorithm gives better solutions with respect to makespan than existing McCahon and Lee's algorithm. 相似文献
996.
Metal matrix composites reinforced by three-dimensional (3-D) continuous network structure reinforcement (3DCNRMMC) are difficult to machine due to serious tool wear and poor surface roughness caused by the brittle and hard reinforcement which interpenetrate into ductile matrix. In order to achieve the approach of low cost of 3DCNRMMC, the machinability of it needs to be understood. The influences of three cutting parameters and volume fraction of reinforcement on cutting force were analyzed in detail. The results indicate that: (1) Due to the brittle phase(s) introduced into ductile matrix of composites, there is a large fluctuation of cutting force causing deterioration of machinability. The fluctuation ranges of cutting forces, initially increase rapidly with the increase of volume fraction of reinforcement and then decrease finally, are largest at the range of the volume fraction of 55–65%; (2) The influence of cutting parameters on cutting force is obvious. With the increases of cutting speed, cutting force decreases gradually unless cutting speed exceeds the value of 209 m/min. Cutting forces increase with increasing feed rate and depth of cut; (3) Owing to the large fluctuation of cutting force, there were some cratered surfaces caused by Si3N4 reinforcement pulling-out and flaking-off. Some brittle phase protruding from the machined surface caused the deterioration of machined surface. 相似文献
997.
为降低60000m^3/h空分设备的氧气放散率,武钢氧气公司实施了空分设备的手动快速变工况生产。分析了空分设备运行工况不稳定和自动变工况系统难以实施的原因,介绍了手动快速变工况的理论依据、前期准备工作和实施过程,阐述了手动快速变工况实施进程中应注意的事项。 相似文献
998.
The effect of carbon precursor on the pore size distribution of mesoporous carbon during templating synthesis process 总被引:1,自引:0,他引:1
Wenzhong Shen Xiangping Yang Qingjie Guo Yihong Liu Yanru Song Zhongxiang Han Qinglei Sun Jian Cheng 《Materials Letters》2006,60(29-30):3517-3521
The starch and cyclodextrin were selected as the precursors and the mixture of surfactant and tetraethyl orthosilicate (TEOS) as template to prepare mesoporous carbon. The result showed that a bimodal pore size distribution in mesoporous carbon derived from starch appeared; one was around 3.4 nm and the other ranged from 3.8 to 16.2 nm. However, there existed a concentrated pore size distribution from 3.2 to 4.2 nm in mesoporous carbon derived from cyclodextrin. The different molecular structure of starch and cyclodextrin and their polymerization process in the presence of sulfur acid were responsible for the resulted mesoporous carbon structure; the starch could polymerize by head to head or side by side, but the cycleodextrin was only polymerized by head to head. 相似文献
999.
Guojian Wang Xiumei Han Mingjun Song Guofu Wang Xifa Long 《Materials Letters》2006,60(29-30):3710-3713
(Ba0.32Sr0.68)5Nb4O15 crystal with sizes of Ø 17 × 35 mm was grown successfully by Czochralski technique method. The thermal anisotropy was discussed. The principal coefficients of thermal expansion along (100), (010), (001) directions were precisely measured to be 1.308 × 10− 5, 1.288 × 10− 5, 1.478 × 10− 5 K− 1, respectively. Its optical transparency range has been measured and found to span from 323 to 5500 nm. The bands present in the IR spectra were identified and assigned to the corresponding vibration modes of NbO6 anions. 相似文献
1000.
Alumina coatings on aluminum alloy were prepared by micro-arc oxidation (MAO) process using DC and AC power supplies, respectively. In comparison with the coating deposited by DCMAO, the influence of the cathodic current on the composition, structure and properties of the ACMAO coating was investigated. It is found that the coating deposited by DCMAO is composed of α-Al2O3, whereas the coating deposited by ACMAO has a mixture composition of α-Al2O3 and γ-Al2O3. The results of properties show that compared with the coatings deposited by DCMAO, the ACMAO coatings possess higher density, hardness and corrosion resistance. It can be attributed to that the DCMAO coating is rougher and existing much more micro-cracks in its inner layer. As a result, the adhesion of the DCMAO coating to the substrate decreases. 相似文献