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排序方式: 共有496条查询结果,搜索用时 15 毫秒
41.
R Asthana 《Journal of Materials Science》1998,33(8):1959-1980
Interface evolution in metal-matrix composites is a thermodynamic necessity and interface design a kinetics challenge. The synergistic interaction between processing science and surface engineering has led to considerable progress in understanding, modelling and tailoring the fibre–matrix interface at the microstructural, crystallographic and atomic levels. The chemical, morphological, crystallographic and thermoelastic compatibilities between the fibre and the matrix influence the interfacial adhesion strength. This article examines the role of material properties and fabrication conditions in chemical interactions between the fibre and the matrix in metal-matrix composites synthesized using the solidification and casting techniques. © 1998 Chapman & Hall 相似文献
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Based on free electron layered electron gas model of quasi two dimensional CuO2 layers in La(Ba/Sr)CuO superconductors a model potentialV(q) is developed earlier with the electron-electron and electron-phonon interactions. The model approach facilitates the dielectric
functions and the dispersion relations of 2D acoustic phonon and plasmon modes. We have then worked out the coupling strength
(γ) linking electrons to the 2D acoustic phonon mode (ħω_) from the residue at the pole ofV(q). Furthermore, the scattering time (τ
e−ph) during electron-phonon interaction (EPI) for this simplified system is also estimated. The contribution to the normal state
in plane resistivity due to EPI is then evaluated. Finally, the variations ofτ andρ is studied with the doping concentration (x) and temperature (T) and the results obtained by us show reasonably good agreement with the available experimental data. 相似文献
45.
Interface- and diffusion-limited capillary rise of reactive melts with a transient contact angle 总被引:1,自引:0,他引:1
Rajiv Asthana 《Metallurgical and Materials Transactions A》2002,33(7):2119-2128
The kinetics of unidirectional capillary penetration by a reactive fluid under the limiting cases of diffusion control and
interface control has been derived for the reactive infiltration phenomenon characterized by a shrinking capillary radius
due to interphase formation and an exponentially decaying contact angle. The computational outcomes for the reactive penetration
of Si3N4 capillaries by AgCuTi brazes and of carbon capillaries by Si show that greater lengths are attained at lower values of the
parabolic rate constant (under diffusion control), and the limiting length is reached earlier at larger values of the linear
rate constant (under interface control). A capillary-driven flow analysis (Washburn equation) overestimates the infiltration
kinetics, whereas an analysis that considers pore shrinkage but assumes the contact angle and the capillary pressure to be
constant during flow underestimates the kinetics. The penetration lengths predicted by the analysis at pore closure due to
reaction choking exhibit a slightly better agreement with the recent measurements in the Si/C system than the models of reactive
flows currently in vogue. 相似文献
46.
D. Varshney K. K. Choudhary R. K. Singh 《Journal of Superconductivity and Novel Magnetism》2002,15(6):535-538
The temperature-dependent normal state resistivity of single crystal Nd1.85Ce0.15CuO4 ? δ is theoretically analyzed within the framework of classical electron–phonon i.e., Bloch-Gruneisen model of resistivity. For the reason of inherent acoustic (low frequency) phonons (ωac) as well as high-frequency optical phonons (ωop), the contributions to the resistivity were first derived. The optical phonons of the oxygen breathing mode yields a relatively larger contribution to the resistivity compared to the contribution of acoustic phonons. Estimated contribution to in-plane resistivity by considering both phonons, i.e., ωac and ωop, along with the zero-temperature-limited resistivity, when subtracted from single crystal data infers a quadratic temperature dependence over most of the temperature range [25 ≤ T ≤ 300]. Quadratic temperature dependence of ρdiff. = [ρexp. ? {ρ0 + ρe–ph (=ρac + ρop)}] is understood in terms of 3D electron–electron inelastic scattering. The comparison of single crystal experimental data appears favorable with the present analysis. 相似文献
47.
Michalka T.L. Varshney R.C. Meindl J.D. 《Semiconductor Manufacturing, IEEE Transactions on》1990,3(3):116-127
The mathematical foundation of common integrated--circuit yield models based on the assumption that the yield is dominated by random point defects is discussed. Various mathematical models which are commonly used to account for defect clustering are given a physical interpretation and are compared mathematically and graphically. A yield model applicable when the repair of some defects in a chip is possible is developed and discussed. Simple yield models for systems with two-fold block redundancy and triple modular redundancy in the presence of defect clustering are developed. and the implications for overall system yield are discussed. It is shown that the yield of systems with circuit redundancy can be substantially affected by defect clustering and, hence, that a correct understanding of defects and yield is essential to predict the yields and costs of wafer-scale products 相似文献
48.
Mobile Commerce: Framework,Applications and Networking Support 总被引:16,自引:2,他引:14
Advances in e-commerce have resulted in significant progress towards strategies, requirements, and development of e-commerce applications. However, nearly all e-commerce applications envisioned and developed so far assume fixed or stationary users with wired infrastructure. We envision many new e-commerce applications that will be possible and significantly benefit from emerging wireless and mobile networks. To allow designers, developers, and researchers to strategize and create mobile commerce applications, we propose a four-level integrated framework for mobile commerce. Since there are potentially an unlimited number of mobile commerce applications, we attempt to identify several important classes of applications such as mobile financial applications, mobile inventory management, proactive service management, product location and search, and wireless re-engineering. We discuss how to successfully define, architect, and implement the necessary hardware/software infrastructure in support of mobile commerce. Also, to make mobile commerce applications a reality, we address networking requirements, discuss support from wireless carriers, and present some open research problems. 相似文献
49.
50.
Pradeep Rohatgi D.Sc. Rajiv Asthana Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1991,43(5):35-41
The simplicity, economy and flexibility of solidification processes make them attractive methods for the production of particle-reinforced metal-matrix composites. At present, however, there is limited understanding of the phenomena occurring during solidification of these advanced materials. Nucleation and refinement of crystalline phases, physical and chemical interactions between dispersed particles and solidifying interfaces, and buoyancy-driven movement of the particles are areas where a knowledge base is beginning to be formed. Ultimately, the understanding of solidification processes in metal-matrix composites must become complete enough that microstructures can be tailored for specific applications. 相似文献