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排序方式: 共有267条查询结果,搜索用时 15 毫秒
1.
《自然科学进展(英文版)》2020,30(3):402-409
The effect of Al addition on microstructure and mechanical properties of hot extruded Mg–1 Mn alloy sheet was investigated. The results revealed that the dynamic recrystallization was promoted by increasing Al content. The ultimate tensile strength and yield strength of the alloy increased with the increase of Al content. The Mg–9 Al–1 Mn alloy exhibited the highest strength, with tensile strength of 308 MPa, 307 MPa, 319 MPa, yield strength of 199 MPa, 207 MPa, 220 MPa and the elongation of 20.9%, 20.1%, 19.2% in 0°, 45°, 90°, respectively.The high strength was mainly attributed to the formation of fine dynamically recrystallized grains and large amounts of the second phase. The strengthening mechanism of the alloys was explained. 相似文献
2.
《自然科学进展(英文版)》2020,30(4):485-493
Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing (ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ~239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and 445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated (SST) and peak-aged (T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain loads. The cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy. 相似文献
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4.
孤子效应脉冲压缩中的三阶色散抑制 总被引:1,自引:0,他引:1
曹文华 《五邑大学学报(自然科学版)》1997,11(4):1-5
最近的研究表明,色散位移光纤中的孤子效应脉冲压缩受三阶色散的影响很大。本文首次提出并通过数值计算证明,若周期性地改变光纤的三阶色散系数,则可有效地抑制三阶色散对色散位移光纤中孤子效应脉冲压缩的影响。 相似文献
5.
对基于ADSP2186的语音识别电话的硬件结构作了简明的介绍,并阐述了程序设计和内存空间管理的思想和方法。最后对语音识别电话的实用性进行了探讨。 相似文献
6.
谢子常 《五邑大学学报(自然科学版)》1997,11(4):33-37
本文对电视接收机的视频通道噪声功率互换前后进行了讨论。根据CCIR推荐的加权网络,采用加权压缩后对图象质量的实际受损情况进行修正,使被测结果与主观评价一致。 相似文献
7.
针对遥感影像的海量数据对其自身应用的影响,指出了研究图像压缩技术的必要性,从实用的角度出发,采用面向对象的技术方法,设计并实现了基于小波变换的数字遥感影像无损压缩编码系统。 相似文献
8.
This paper criticizes the traditional philosophical account of the quantization of gauge theories and offers an alternative. On the received view, gauge theories resist quantization because they feature distinct mathematical representatives of the same physical state of affairs. This resistance is overcome by a sequence of ad hoc modifications, justified in part by reference to semiclassical electrodynamics. Among other things, these modifications introduce ”ghosts”: particles with unphysical properties which do not appear in asymptotic states and which are said to be purely a notational convenience. I argue that this sequence of modifications is unjustified and inadequate, making it a poor basis for the interpretation of ghosts. I then argue that gauge theories can be quantized by the same method as any other theory. On this account, ghosts are not purely notation: they are coordinates on the classical configuration space of the theory—specifically, on its gauge structure. This interpretation does not fall prey to the standard philosophical arguments against the significance of ghosts, due to Weingard. Weingard’s argumentative strategy, properly applied, in fact tells in favor of ghosts’ physical significance. 相似文献
9.
Sandeep Chauhan Vikas Verma Ujjwal Prakash P. C. Tewari Dinesh Khanduja 《矿物冶金与材料学报》2017,24(8):918-925
Induction hardening of dense Fe-Cr/Mo alloys processed via the powder-metallurgy route was studied. The Fe-3Cr-0.5Mo, Fe-1.5Cr-0.2Mo, and Fe-0.85Mo pre-alloyed powders were mixed with 0.4wt%, 0.6wt%, and 0.8wt% C and compacted at 500, 600, and 700 MPa, respectively. The compacts were sintered at 1473 K for 1 h and then cooled at 6 K/min. Ferrite with pearlite was mostly observed in the sintered alloys with 0.4wt% C, whereas a carbide network was also present in the alloys with 0.8wt% C. Graphite at prior particle boundaries led to deterioration of the mechanical properties of alloys with 0.8wt% C, whereas no significant induction hardening was achieved in alloys with 0.4wt% C. Among the investigated samples, alloys with 0.6wt% C exhibited the highest strength and ductility and were found to be suitable for induction hardening. The hardening was carried out at a frequency of 2.0 kHz for 2-3 s. A case depth of 2.5 mm was achieved while maintaining the bulk (interior) hardness of approximately HV 230. A martensitic structure was observed on the outer periphery of the samples. The hardness varied from HV 600 to HV 375 from the sample surface to the interior of the case hardened region. The best combination of properties and hardening depth was achieved in case of the Fe-1.5Cr-0.2Mo alloy with 0.6wt% C. 相似文献
10.
《自然科学进展(英文版)》2014,24(2):97-179
<正>The journal of"Progress in Natural Science:Materials International(PROG NAT SCI-MATER)"sponsored and organized by both Chinese Materials Research Society(C-MRS)and Inter national Union of Materials Research Societies(IUMRS)started to publish 相似文献