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排序方式: 共有10000条查询结果,搜索用时 19 毫秒
961.
M. Ritchie P. D. Lee A. Mitchell S. L. Cockcroft T. Wang 《Metallurgical and Materials Transactions A》2003,34(3):863-877
An energy dispersive X-ray (EDX) detector mounted on a laboratory scale electron beam furnace (30 kW) was employed to assess
the potential use of X-rays as a means of on-line composition monitoring during electron beam (E B) melting of alloys. The
design and construction of the collimation and protection systems used for the EDX are described in Part I. In Part II, a
mathematical simulation of the heat, mass, and momentum transfer was performed for comparison to the EDX and vapor deposition
results. The predicted flow patterns and evaporation rates are used to explain the differences between the two experimental
methods. For the EDX spectra measured, the X-rays generated were from the center of the hearth where fluid flow rising from
the bulk of the pool is sufficient to maintain the bulk composition despite the high evaporative flux from the surface. The
flow moves radially outward from the center of the pool, with the volatile species being depleted. The vapor deposition technique
measures the entire region, giving an average surface composition, and it therefore differs from the EDX results, which gave
a near bulk composition. This combined study using in-situ EDX measurements and numerical simulations both provided an insight into the phenomena controlling the evaporation in an
EB-heated system and demonstrated the viability of using EDX to measure the bulk composition during EB melting processes. 相似文献
962.
Expressions describing the threshold sensitivity of a quantum converter of IR radiation into visible light are obtained for two schemes of energy levels in the active atoms. Based on these expressions, practical criteria for the creation of such devices are formulated. 相似文献
963.
1Introduction Archaeologicalfindingsdatingbacktothe4thcentury BCshowedthatmissinghumanteethhavebeenreplaced bymaterialswhichincluded:animalteeth,coral,shells,ivory(elephanttusk),wood,andmetals[1].Inmodern times,autografts(boneobtainedfromanothersiteinthe … 相似文献
964.
965.
John Tsinias 《Systems & Control Letters》1991,17(1)
In this paper we generalize the Vidyasagar's well known theorem on the local stabilizability problem of nonlinear systems using state detection [11]. Our purpose is to prove that if a system is weakly detectable and stabilizable by means of a continuous state feedback u = γ(x), for which no differentiability assumption is imposed, then the system is also stabilized by the law u = γ(z), where z is the output of a weak detector for the state x. The result above is applicable to several cases not covered by other works. 相似文献
966.
V. S. Bessmertnyi N. I. Min’ko P. S. Dyumina V. P. Krokhin S. V. Semenenko M. A. Lipko 《Glass and Ceramics》2005,62(11-12):386-387
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
967.
V. Ocelík V. Z. Bengus E. B. Korolkova K. Csach J. Miškuf P. Duhaj 《Journal of Materials Science》1991,26(24):6699-6705
The fracture stress and the critical stress intensity factor of the Fe40Ni40B20 amorphous metallic ribbons 20 μm thick were measured in the temperature range 4.2–300 K and at deformation rates from 3.3×10−6 to 1.25×10−3 m−1 with the aim to obtain more information on the condition for the onset and development of the inhomogeneous plastic deformation
and fracture. 相似文献
968.
P. Tsakiropoulos 《Materials Letters》1985,3(12):508-512
The response of a crystallite to the thermal fields developing during the solidification of a droplet and the mode of growth on a S?L interface are discussed. Stresses are relieved by causing the crystallite to deform plastically. The dislocations and/or twins that arise alter the morphology of the S?L interface and can enhance its growth rate. The analysis concentrates on crystallites growing in the bulk or at the surface of a droplet. For the hexagonal metals Cd, Mg and Zn, when the temperature varies only through the thickness of a thin floating raft, the growth helixes arise mainly as a result of the relief of strain energy due to the action of surface tension forces. Their calculated height is lower than the height measured on spherical particles of Cd. 相似文献
969.
Polycrystalline magnesium films were deposited under ultrahigh vacuum by thermal evaporation onto a cooled silica substrate. During the growth process of a film a number of lattice defects are incorporated. It was found that the defect density decreases with increasing thickness. An annealing study of the electrical resistance and defect density in magnesium films was made. The results were interpreted on the basis of Vand's theory. The function F0 expressing the law of distribution of the decay energies exhibited a maximum. For thick films there was no appreciable variation in the activation energy with thickness. In this case the evaluated activation energy E was found to be about 0.35 eV. For very thin films this energy decreases with increasing thickness. 相似文献
970.
A possible method for the simulation of nonideal op-amps with a finite gain and bandwidth by means of an equivalent SC circuit, containing ideal components, is presented. The approach is extended by the case of an op-amp with non-switched input SC building blocks. 相似文献