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51.
The growth of carbide particles in TiC-XC-2 vol.% Ni and TiC-XC-30 vol.% Ni alloys, where X=Zr, Cr, W, Ta and Mo, was fitted
to an equation of the form d3-do
3=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with the addition of Mo2C or WC, changed little for TaC, and increased with the addition of ZrC or Cr3C2. The grain contiguity decreased with increasing Ni content in the TiC−Mo2C−Ni alloy and was greater in the alloys with smaller growth rate constant. Consequently, the effect of carbide addition on
the grain growth of 2 vol.% Ni alloys was found to be similar to that of 30 vol.% Ni alloys. The grain growth mechanism could
be explained by the effect of contiguous carbide grain boundaries in restricting the overall grain growth, as well as the
area of the solid/liquid interfaces in the alloy by the usual solution/reprecipitation model. 相似文献
52.
53.
A model for building integrated photovoltaic systems has been developed and implemented in a dynamic simulation tool. This tool takes into account the thermal interactions between the PV collector and the building. The influence of the type of integration upon the PV collector efficiency has been evaluated and hybrid PV/air collectors have been studied. An overall efficiency is defined, including the production of electricity and heat. A case study has been performed on two different typical buildings. In the case of a multi-crystalline silicon PV collector integrated on the roof of a single family house located in Paris, the efficiency of unventilated PV modules fixed on the roof is 14%. If the PV collector is used to preheat the ventilation air, the efficiency reaches 20%. A proper building integration also improves the environmental balance of PV technologies over their life cycle. 相似文献
54.
机械锁定式测试技术操作简单,测试一次成功率高,资料录取准确全面,且测试结束后可直接进行封堵作业;解封时,机械锁紧产生一个向上的震击力,有利于解封,没有换位机构的测试阀在关井期间使管柱处于自由拉伸状态,有利于保护油管。在N阀上部管柱中加1-2根伸缩接头,便可用于海洋井测试。 相似文献
55.
Yen-Kang Liu Pei-Lum Tso 《The International Journal of Advanced Manufacturing Technology》2003,22(5-6):396-400
Grinding is the most suitable process for manufacturing good quality diamond tools. In this paper, diamond wheels have been studied. From the grinding of polycrystalline diamond (PCD) insets, the effects of certain factors such as the bonding material, the grit size and structure of a diamond wheel have been investigated. It is concluded that vitrified bond diamond wheels are the most suitable for grinding PCDs and the recommended grit size is mesh number 1000, which can get a good surface quality within an appropriate time. The wheel structure is another important factor. Rougher wheels (mesh #800, #1000) with the softer grade scale P yield a higher material removal rate (MRR) than scale Q. However, a finer wheel (mesh #1200) needs a tougher structure to promote its grinding ability and to have a higher MRR. 相似文献
56.
��������������˲��������̽�� 总被引:1,自引:1,他引:0
四川目前生产的天然气中含硫天然气占71%,而含硫天然气对高强度钻杆会产生硫化物应力腐蚀玻裂,因此,在含硫气井进行钻杆测试时,应重视钻杆的安全问题。文章探讨了高强度钻杆硫化物应力腐蚀玻裂的机理和影响钻杆脆断时间的各种因素,并提出在一定的条件下,高强度钻杆在含硫气并中进行测试是安全的。采用向钻杆内加缓蚀剂或内涂层钻杆,防硫油管测试,钻杆测试更加安全。建议继续开展高强度钻杆硫化物应力腐蚀玻裂时间的试验研究,以确定合理的钻杆测试安全时间。 相似文献
57.
58.
山特维克可乐满公司切削刀具涂层技术的发展 总被引:3,自引:0,他引:3
佘建芳 《稀有金属与硬质合金》2003,31(3):51-55
介绍了山特维克可乐满公司切削刀具涂层技术的发展,并对该公司自1979年以来硬质合金涂层产品的发展情况进行了总结。 相似文献
59.
60.
Minimizing the number of tool switches on a flexible machine 总被引:5,自引:0,他引:5
Yves Crama Antoon W. J. Kolen Alwin G. Oerlemans Frits C. R. Spieksma 《International Journal of Flexible Manufacturing Systems》1994,6(1):33-54
This article analyzes a tool switching problem arising in certain flexible manufacturing environments. A batch of jobs have to be successively processed on a single flexible machine. Each job requires a subset of tools, which have to be placed in the tool magazine of the machine before the job can be processed. The tool magazine has a limited capacity, and, in general, the number of tools needed to produce all the jobs exceeds this capacity. Hence, it is sometimes necessary to change tools between two jobs in a sequence. The problem is then to determine a job sequence and an associated sequence of loadings for the tool magazine, such that the total number of tool switches is minimized. This problem has been previously considered by several authors; it is here revisited, both from a theoretical and from a computational viewpoint. Basic results concerning the computational complexity of the problem are established. Several heuristics are proposed for its solution, and their performance is computationally assessed. 相似文献