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941.
In-Situ and Real-Time Investigation of Columnar-to-Equiaxed Transition in Metallic Alloy 总被引:1,自引:0,他引:1
H. Nguyen-Thi G. Reinhart N. Mangelinck-Noël H. Jung B. Billia T. Schenk J. Gastaldi J. Härtwig J. Baruchel 《Metallurgical and Materials Transactions A》2007,38(7):1458-1464
In this article, we present a review of observations during Al-3.5 wt pct Ni alloy solidi.cation experiments performed at
the European Synchrotron Radiation Facility (ESRF) in Grenoble. These experiments provide direct access to dynamical phenomena
during columnar growth (initial transient and breakdown of a planar solid-liquid interface), and for the first time to the
transition from columnar-to-equiaxed microstructure (nucleation ahead of a columnar front and blocking of a columnar front
by an equiaxed microstructure) and fully equiaxed growth (propagation of an effective front). Based on these experimental
observations, critical parameters such as columnar growth velocity variation during the transition or equiaxed-grain diameter
are measured and discussed.
This article is based on a presentation made in the symposium entitled “Solidi.cation Modeling and Microstructure Formation:
In Honor of Prof. John Hunt,” which occurred March 13–15, 2006, during the TMS Spring Meeting in San Antonio, Texas, under
the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee. 相似文献
942.
943.
Tiwari S.P. Namdas E.B. Ramgopal Rao V. Fichou D. Mhaisalkar S.G. 《Electron Device Letters, IEEE》2007,28(10):880-883
Solution-processed n-type organic field-effect transistors (OFETs) based on the fullerene derivative {6}-1-(3-(2- thienylethoxycarbonyl)-propyl)-{5}-l-phenyl-[5,6]-C61 (TEPP) and phenyl-C61-butyric acid methyl ester (PCBM) in a multiring source/drain structure are reported. Devices with TEPP show high electron mobility up to 7.8 x 10-2 cm2/Vs in the saturation regime for bottom-contact OFETs with Au S/D electrodes with a solution-processed fullerene derivative. The ON/OFF ratios reported in this letter, which are in the range of 105 -106, are among the highest values reported for such devices. This mobility is always higher compared to PCBM devices prepared in identical conditions. The mobility of TEPP and PCBM increased with increasing temperatures in the range of 100-300 K with activation energy of 78 and 113 meV, respectively, which suggests that the thermally activated hopping of electrons is dominant in TEPP. 相似文献
944.
El-Husseini M.H. Venet P. Rojat G. Joubert C. 《Industry Applications, IEEE Transactions on》2002,38(3):713-718
In this paper, the authors use an analytical model to calculate the losses in the metallized polypropylene film capacitors. The model is validated experimentally for capacitors having the same capacitance but different geometry. For each group of capacitors, a temperature distribution in the roll is assumed with the aim of optimizing its thermal performance. It appears that the heating of a long capacitor is higher than that of an equivalent flat capacitor subjected to the same electric stresses 相似文献
945.
Metal Science and Heat Treatment - 相似文献
946.
Mesh network resiliency using GMPLS 总被引:4,自引:0,他引:4
Lang J.P. Drake J. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2002,90(9):1559-1564
The generalized multiprotocol label switching (GMPLS) is being developed as the control plane for the evolving photonic network. We describe how GMPLS can be used with mesh networks to provide efficient network resiliency. In particular we examine the key aspects of GMPLS that are used to support protection and restoration. We also study the various protection and restoration techniques, and we highlight the tradeoffs between recovery time and resource redundancy 相似文献
947.
S. Abiraman H. K. Varma T. V. Kumari P. R. Umashankar Annie John 《Bulletin of Materials Science》2002,25(5):419-429
This study investigates quantitatively and qualitatively the sol-gel derived bioactive glass-ceramic system (BGS)—apatite-wollastonite
(AW) type granules in the size range of 0.5–1 mm, as an effective graft material for bone augmentation and restoration. Scanning
electron micrographs (SEM) of the sintered granules revealed the rough material surface with micropores in the range 10–30
μm. X-ray diffraction (XRD) pattern of the granules revealed the presence of crystalline phases of the hydroxyapatite and
wollastonite, and the functional groups of the silicate and phosphates were identified by Fourier transform infrared spectroscopy
(FT-IR). Thein vitro cell culture studies with L929 mouse fibroblast cell line showed very few cells adhered on the BGS disc after 24 h. This
could be due to the highly reactive surface of the disc concomitant with the crystallization but not due to the cytotoxicity
of the material, since the cellular viability (MTT assay) with the material was 80‰ Cytotoxicity and cytocompatibility studies
proved that the material was non-toxic and biocompatible. After 12 weeks of implantation of the BGS granules in the tibia
bone of New Zealand white rabbits, the granules were found to be well osteointegrated, as observed in the radiographs. Angiogram
with barium sulphate and Indian ink after 12 weeks showed the presence of microcapillaries in the vicinity of the implant
site implicating high vascularity. Gross observation of the implant site did not show any inflammation or necrosis. SEM of
the implanted site after 24 weeks revealed good osteointegration of the material with the newly formed bone and host bone.
New bone was also observed within the material, which was degrading. Histological evaluation of the bone healing with the
BGS granules in the tibial defect at all time intervals was without inflammation or fibrous tissue encapsulation. After 2
weeks the new bone was observed as a trabeculae network around the granules, and by 6 weeks the defect was completely closed
with immature woven bone. By 12 weeks mature woven bone was observed, and new immature woven bone was seen within the cracks
of the granules. After 24 weeks the defect was completely healed with lamellar bone and the size of the granules decreased.
Histomorphometrically the area percentage of new bone formed was 67.77% after 12 weeks and 63.37% after 24 weeks. Less bone
formation after 24 weeks was due to an increased implant surface area contributed by the material degradation and active bone
remodeling. The osteostimulative and osteoconductive potential of the BGS granules was established by tetracycline labelling
of the mineralizing areas by 2 and 6 weeks. This sol-gel derived BGS granules proved to be bioactive and resorbable which
in turn encouraged active bone formation. 相似文献
948.
Developing competency-based methods for near-real-time air combat problem solving assessment 总被引:1,自引:0,他引:1
Air combat scenarios present unique problems where the solution is not obvious. An advanced networked simulation environment can be used to train high-level cognitive air combat skills such as problem solving. A problem in the development of principled and construct oriented assessment is related to determining the level of specificity of the assessment. We present a detailed discussion of the definition of critical competencies associated with combat mission problem solving performance, and we describe our approach to develop and implement an embedded performance assessment system that maps outcomes to these competencies. Finally, we discuss the implications for our approach for comprehensive assessment and discuss our goals for an evaluation of the competency-based approach to assessment. 相似文献
949.
B. Volesky L. Yerushalmi J. H. T. Luong 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1982,32(6):650-659
A specially developed temperature control system on a laboratory scale fermenter enabled continuous measurement of the rate of heat production during undisturbed growth of microbial cultures. Apart from being correlated with oxygen uptake rate, the heat of fermentation was established as an additional indicator of metabolic activity. The ‘aerobic respiration’ energetic activity of Candida utilis, Candida lipolytica and Saccharomyces cerevisiae on different carbon substrates was investigated with cultures of the latter species being also studied under the ‘aerobic fermentation’ conditions induced by glucose catabolite repression. 相似文献
950.
Robert H. Doremus Denis Murphy Narottam P. Bansal William A. Lanford Chandra Burman 《Journal of Materials Science》1985,20(12):4445-4453
When liquid water contacts a zirconium-barium-lanthanum fluoride glass, at least three different processes occur. Barium and zirconium fluoride dissolve into the water, water penetrates into the glass, and zirconium fluoride crystals grow on the glass surface, in static solution. The rate of dissolution, as measured by solution analysis, is possibly controlled by diffusion in the solid surface; surface blockage and surface reactions are other possible kinetic steps involved. Diffusion in solution is not the controlling mechanism. Hydrogen profiles in the glass surface suggest that the penetration rate of water into the glass is controlled by diffusion and a surface reaction. 相似文献