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排序方式: 共有85条查询结果,搜索用时 15 毫秒
1.
Waleed Al-Shalfan John G. Speer David K. Matlock Kip Findley 《Metallurgical and Materials Transactions A》2006,37(1):207-216
The influence of annealing temperature and time on solute carbon levels was investigated in four ultralow-carbon (ULC) bake-hardenable
steels; two Ti-V ULC steels with different V/C levels and two Ti-Nb ULC steels with different Nb/C levels. Internal-friction
and scanning transmission electron microscopy (STEM) techniques were used to understand the precipitation/dissolution behavior
in the various steels. An effect of annealing time on the carbon Snoek-peak height was observed in both Ti-V steels and in
the Ti-Nb steel having a lower Nb/C ratio. Despite differences between these steels resulting from their composition (and,
thus, carbide solubility) differences, after cold rolling and annealing at different temperatures, the maximum Snoek-peak
height was achieved after annealing for shorter times in each instance, on the order of 1 minute. The highly stabilized Ti-Nb
ULC steel with a higher Nb/C ratio did not show the effect because of the absence of solute carbon. For the Ti-V steels, most
of the precipitates examined using STEM contained both Ti and V. The energy-dispersive X-ray (EDX) analysis indicated that
both the Ti-V steels annealed at 845 °C for 1 minute have greater Ti/V ratios compared to their corresponding Ti-V steels
in the as-received (hot-rolled) condition. This behavior is consistent with dissolution of carbides causing the carbon in
solution to increase, as indicated by a greater carbon Snoek-peak height for both Ti-V steels in the annealed condition. The
reduction in Snoek-peak height at longer annealing times is believed to be associated with segregation to lower-energy defect
sites. 相似文献
2.
This article assesses the use of micro-Raman imaging with respect to polymer science. This relatively novel technique allows, at high spatial resolution, the acquisition of chemical and morphological information over an area of a sample. Using Raman imaging by confocal laser line scanning, a wide range of problems in polymer analysis has been studied to outline the capabilities and limitations of the technique. Three ternary polymer blends consisting of polypropene/polyethene/ethene-propene copolymer, polybutyleneterephthalate/polycarbonate/very low density polyethene, and styrene-co-acrylonitrile/styrene-co-maleicanhydrate/poly-2,6-dimethylphenylene oxide were studied with regard to compositional and morphological heterogeneities. In a binary polymer blend consisting of two different acrylate monomers, the refractive index profile established after artificially induced diffusion of the main components was determined from the concentration gradients. The distribution of unreacted free melamine in a cured melamine-formaldehyde resin was analyzed. Furthermore, the general structure of a composite sample consisting of polyethene fibers in an epoxide matrix was studied. Raman imaging proved suitable for the characterization of heterogeneities in composition and morphology on a size scale equal to or larger than 1 μm. In this sense, the technique helps to close the gap between infrared microscopy, with its comparatively poor spatial resolution, on the one hand, and transmission electron microscopy, with its limited chemical information, on the other hand. For heterogeneities on a submicron scale, the value of the technique is limited to the determination of average information. When combined with curve fitting, Raman imaging permitted us to determine the composition of the polypropene/polyethene/ethene-propene copolymer blend with an accuracy of 5–10%. The main limitations to micro-Raman imaging of polymer systems based on the confocal laser line scanning technique have been identified as the destruction of the samples due to insufficient heat dissipation of the high-incident laser power, interferences due to fluorescence, and the stability of the instrumentation during long collection times required for good signal-to-noise ratio spectra of weak Raman scatterers. © 1996 John Wiley & Sons, Inc. 相似文献
3.
Voltage stability evaluation using modal analysis 总被引:3,自引:0,他引:3
The authors discuss the voltage stability analysis of large power systems by using a modal analysis technique. The method computes, using a steady-state system model, a specified number of the smallest eigenvalues and the associated eigenvectors of a reduced Jacobian matrix. The eigenvalues, each of which is associated with a mode of voltage/reactive power variation, provide a relative measure of proximity to voltage instability. The eigenvectors are used to describe the mode shape and to provide information about the network elements and generators which participate in each mode. A simultaneous iteration method, which is well suited to applications involving large power systems, is used for selective calculation of appropriate eigenvalues. Results obtained using a 3700 bus test system are presented illustrating the applicability of the approach 相似文献
4.
5.
6.
Evaluation of the degree of cure of a coating 总被引:1,自引:0,他引:1
Coating cure is compared using pencil hardness, MEK rubs, and thumb twist test to evaporation rate analysis (ERA). ERA is
rated most objective and reproducible.
Department of Polymer Science, Hattiesburg, MS.
Rockville, MD. 相似文献
7.
8.
Pei-Ying Chiang May-chen Kuo Jessy Lee C.-C. Jay Kuo Todd Richmond Milton Rosenberg Jeff Lund Kip Haynes Lindsay Armstrong 《Journal of Visual Communication and Image Representation》2010,21(3):200-209
The Automated Metadata Indexing and Analysis (AMIA) project aims to provide an effective digital asset management (DAM) tool for large digital asset databases. We began with text-based indexing since it is still the most reliable approach as compared with other content-based media features. AMIA not only searches for the text of the file name, but also utilizes embedded information such as the metadata in Maya files. The AMIA system builds a linked map between all dependency files. We present an approach of preserving previously established metadata created by the old DAM tools, such as AlienBrain, and integrating them into the new system. Findings indicate that AMIA has significantly improved search performance comparing to previous DAM tools. Finally, the ongoing and future work in the AMIA project is described. 相似文献
9.
Romain Sainte Beuve Ken R. Morison 《Chemical Engineering and Processing: Process Intensification》2010
A hydrodynamic cavitation system based on a venturi was used to test the effectiveness of cavitation for enhancing the enzymatic hydrolysis of canola oil using lipase from Candida rugosa. Cavitation led to the production of fine oil-in-water and water-in-oil emulsions with the enzyme in the water phase. Using venturi inlet pressures of up to 8 bar, the yield of fatty acids was only about 60% of the maximum possible. In contrast, a simple stirred batch reactor produced over 90% of the maximum possible yield with reaction rates equal to, or better than, those obtained in a cavitating system. It was concluded that cavitation inhibited the reaction in some way and is not effective for intensification of hydrolysis. 相似文献
10.
DR Holmes KE Kip W Yeh SF Kelsey KM Detre DO Williams 《Canadian Metallurgical Quarterly》1998,32(3):590-595
Researchers examining clinical decision-making often explored the role of the nurse's experience. In these studies, experience was conceptualized as either the time spent in nursing or the knowledge which came from practice. This paper reports on the conceptualization of the nurse's experience emerging from a grounded theory study describing one decision-making process: 'knowing the patient'. Data included in-depth interview text, participant observation fieldnotes, and documents. Data were analysed using the constant comparative method and open, axial and selective coding techniques. In the analysis, the nurse's experience was conceptually defined as 'the application of that learned from previous practice situations'. Three attributes of the nurse's experience emerged. These included a focus on the patient, confidence in practice, and knowledge of antecedents and consequences of similar patient situations. Each aspect enhanced the individualization of nursing interventions. The findings are related to other investigations in nursing and insights for practice are offered. 相似文献