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排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
A series of high nitrogen austenitic stainless steels were successfully developed with a pressurized electroslag remelting furnace. Nitride additives and deoxidizer were packed into the stainless steel pipes, and then the stainless steel pipes were welded on the surface of an electrode with low nitrogen content to prepare a compound electrode. Using Si3N4 as a nitrogen alloying source, the silicon contents in the ingots were prone to be out of the specification range, the electric current fluctuated greatly... 相似文献
992.
In-situ Al2O3/TiAl composites were successfully synthesized from the starting powders of Ti, Al, TiO2 and Nb2O5. The oxidation behavior of the composites at 900℃ in static air was investigated. The results indicate that the composite samples present a much lower oxidation mass gain. Under long-time intensive oxidation exposure, the formed oxide scale is multi-layer. The formation of the outer TiO2 layer is fine and dense, the internal Al2O3 scale has good adhesiveness with the outer TiO2 scale, and the TiO2+Al2O3 mixed layer forming the protective oxide scale is favorable for the improvement of oxidation resistance. It is believed that the incorporation of Al2O3 particulates into the metal matrix decreases the coefficient of thermal expansion of the substrate, and forms a local three-dimensional network structure that can hold the oxide scale. The formation of the oxide scale with fmer particle size, stronger adherence, less micro-defects and slower growth rate can contribute to the improvement of oxidation resistance. Nb element plays an important role in reducing the internal oxidation action of the materials, restraining the growth of TiO2 crystals andpromoting thc stable formation of the Al 2O3-riched layer,which is benfeicial to improve the oxidation properties. 相似文献
993.
田红旗 《中南工业大学学报(英文版)》2009,16(1):166-171
Aerodynamic drag is proportional to the square of speed. With the increase of the speed of train, aerodynamic drag plays an
important role for high-speed train. Thus, the reduction of aerodynamic drag and energy consumption of high-speed train is
one of the essential issues for the development of the desirable train system. Aerodynamic drag on the traveling train is
divided into pressure drag and friction one. Pressure drag of train is the force caused by the pressure distribution on the
train along the reverse running direction. Friction drag of train is the sum of shear stress, which is the reverse direction
of train running direction. In order to reduce the aerodynamic drag, adopting streamline shape of train is the most effective
measure. The velocity of the train is related to its length and shape. The outer wind shields can reduce train’s air drag
by about 15%. At the same time, the train with bottom cover can reduce the air drag by about 50%, compared with the train
without bottom plate or skirt structure.
Foundation item: Project(2001AA505000) supported by the National High-Tech Research and Development of China 相似文献
994.
Chromium ore fines containing coal (COFCC) can be rapidly heated by microwave to conduct the voluminal reduction, which lays
a foundation of getting sponge ferrochromium powders with a lower content of C. Under the conditions of COFCC with n(O):n(C) (molar ratio) as 1.00:0.84 and n(SiO2):n(CaO) as 1.00:0.39, the samples were heated by 10 kW microwave power to reach the given temperatures and held for different
times respectively. The results show that the low-C-Cr ferrochromium metal phase in the reduced materials forms before the
high-C-Cr ferrochromium metal phase does. With increasing temperature the C content of ferrochromium metals is in a positive
correlation with the content of Cr. The C content of ferrochromium metal in reduced materials is 0–10.07% with an average
value of 4.68%. With the increase of holding time the Cr content in ferrochromium metals is in a negative correlation with
the content of C, while the content of Fe changes in the contrary way. In the microwave field the kinetic conditions of carburization
are closely related with the temperature of microwave heating, holding time and carbon fitting ratio.
Foundation item: Project(50474083) supported by the National Natural Science Foundation of China; Project supported by the Baoshan Iron &
Steel Co. Ltd. of China 相似文献
995.
996.
997.
CAO Wei LI Bing-wen GUO Chu'wen MAO Xin-yuan MA Qin-qin 《中国矿业大学学报(英文版)》2009,19(1):133-136
High-speed steel W18Cr4V is commonly used in industries such as blade and mould manufacturers because of its high level of hardness and toughness, red-hardness and resistance. Ion implantation is an effective method to improve the wear resis-tance of W18Cr4V. In our investigation, Ta and Ta+N ion implantation was performed on W18Cr4V high-speed steel. The surface properties after implantation were evaluated by measuring friction coefficients while the carbonyl phase of the surface was ana-lyzed by X-ray diffraction analysis. It was found that the friction coefficients of the treated samples were much lower. Samples implanted with Ta+N had a lower friction coefficients than samples implanted only with Ta. This can be attributed to the formation of a new chemical compound, Fe7Ta3, on both surfaces. An even harder chemical compound, Fe2N, was formed on both sttrfaces of Ta+N implanted samples. 相似文献
998.
提出了一种采用共沉淀法合成镁掺杂的锂离子正极材料LiFePO4的新方法,研究了合成条件,采用XRD,SEM,循环伏安测定,电化学阻抗谱分析,以及充放电测试对合成的材料作了表征分析.结果表明,采用共沉淀合成方法可以获得性能良好的LiFePO4;Mg^2+掺杂对LiFePO4结构没有产生明显的影响,但掺杂量的大小对LiFePO4的放电性能有较大影响. 相似文献
999.
青岛财富大厦是一座复杂的超限高层建筑.设计除利用SATWE程序及ETABS和ANSYS有限元分析程序进行弹性和弹塑性计算分析外,还对结构进行了静力弹塑性分析(Pushover Analysis).研究表明:静力弹塑性分析方法在超限高层结构设计中,由于受高振型的影响,虽然理论上会存在一定的误差,但是通过Pushover分析可以从宏观上发现结构在罕遇地震作用下的破坏机制,从而对可能存在的薄弱部位进行有针对性的加强,提高结构可靠度. 相似文献
1000.
郭昆丽 《陕西科技大学学报》2009,27(3):125-129
建立了VSC-HVDC系统的数学模型,基于鲁棒控制理论,将系统对VSC-HVDC的控制目标转化为对其交流侧有功和无功电流的控制来实现,并进行了控制方案设计.仿真实验表明所设计的控制器能够快速反应达到预定的指令目标,具有良好的鲁棒性. 相似文献