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941.
Chemical reactions between aluminum and fly ash during synthesis and reheating of Al-fly ash composite 总被引:5,自引:0,他引:5
Thermodynamic analysis indicates that there is the possibility of chemical reactions between aluminum melt and cenosphere
fly ash particles. These particles contain alumina, silica, and iron oxide, which, during solidification processing of aluminum-fly
ash composites or during holding of such composites at temperatures above the melting temperature of aluminum, are likely
to undergo chemical reduction. These chemical reactions between the fly ash and molten aluminum have been studied by metallographic
examination, differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX)
and X-ray analysis after holding the aluminum-fly ash composites for different periods above the liquidus temperature. The
experiments indicate that there is progressive reduction of silica and mullite in the fly ash, and formation of alumina with
holding time of composites at a temperature of 850 °C. The walls of the cenosphere fly ash particles progressively disintegrate
into discrete particles as the reaction progresses. The rate of chemical reaction was high at the start of holding the composite
at a temperature of 850 °C, and then the rate significantly decreased with time. The reaction was almost complete after 10
hours. 相似文献
942.
943.
944.
945.
Person identification using multiple cues 总被引:6,自引:0,他引:6
Brunelli R. Falavigna D. 《IEEE transactions on pattern analysis and machine intelligence》1995,17(10):955-966
This paper presents a person identification system based on acoustic and visual features. The system is organized as a set of non-homogeneous classifiers whose outputs are integrated after a normalization step. In particular, two classifiers based on acoustic features and three based on visual ones provide data for an integration module whose performance is evaluated. A novel technique for the integration of multiple classifiers at an hybrid rank/measurement level is introduced using HyperBF networks. Two different methods for the rejection of an unknown person are introduced. The performance of the integrated system is shown to be superior to that of the acoustic and visual subsystems. The resulting identification system can be used to log personal access and, with minor modifications, as an identity verification system 相似文献
946.
Occlusion of large atrial septal defects with a centering buttoned device: early clinical experience
EB Sideris M Leung JH Yoon CR Chen R Lochan AM Worms C Rey B Meier 《Canadian Metallurgical Quarterly》1996,131(2):356-359
A feasibility clinical study was conducted for the transcatheter occlusion of large ostium secundum atrial septal defects with the centering buttoned device. The centering buttoned device is a modification of the regular buttoned device in which a centering counter-occluder is sutured at the central 40% portion of the occluder. During centering it is stretched, forming a parachute-shaped structure and pulling the occluder over the center of the defect. During buttoning, the counter-occluder forms a double figure eight, opposing the right atrial side of the atrial septum. Occlusion was performed in 12 patients aged 6 to 56 years. All had been rejected for transcatheter occlusion by the regular buttoned device, because of either their defect size or the lack of adequate septal rim. The defect size varied between 23 and 31 mm, and the device size varied between 45 and 60 mm. Nine had immediate effective occlusions of their defects and three residual shunts. One patient with unbuttoning had hemolysis at 2 weeks and underwent surgery. Early results of the transcatheter occlusion of large atrial septal defects are promising, and larger clinical trials are justified. 相似文献
947.
M Schietroma A Risetti F Carlei MV Santirocco F Muzi G Maggi C De Santis CL Recchia D Iannucci R Rampa M Simi 《Canadian Metallurgical Quarterly》1996,48(4):43-46
Adhesions have been suggested as a possible cause of chronic abdominal pain, but the reports of their etiological role conflict. Lysis of adhesions has been proposed as the therapeutic modality of choice, although the reports of success are controversial. The aim our prospective study was to determine whether laparoscopic adhesiolysis ameliorates chronic abdominal pain in patients with abdominal adhesions. Forty-one patients with chronic abdominal pain lasting for more than 6 months, but with no abnormal findings other than adhesions found at laparoscopy, underwent laparoscopic adhesiolysis. 37 patients (90.2%) were available for follow-up after a median time interval of 18 months (range: 12-41 months). Twenty-two patients (59.4%) were free from abdominal pain and 9 (24.3%) patients reported significant amelioration of their pain. Six (16.2%) patients had no amelioration. In conclusion the laparoscopy is an effective tool for the evaluation of patients with chronic abdominal pain, and laparoscopic adhesiolysis cures of ameliorates chronic abdominal pain in more than 80% of patients. 相似文献
948.
N Ivanovska S Philipov R Istatkova P Georgieva 《Canadian Metallurgical Quarterly》1996,54(2-3):143-151
The antimicrobial and immunological properties of ethanol extracts, non-alkaloid, tertiary alkaloid and quaternary alkaloid fractions, obtained from roots and aerial parts of Isopyrum thalictroides were examined. The non-alkaloid fraction from aerial parts inhibited the growth of seven test microorganisms and was the most effective suppressor of classical pathway (CP) complement activity in normal human serum (NHS) and guinea pig serum (GPS). The alkaloid fractions, containing quaternary alkaloids expressed suppressive effect on mitogen-induced splenocyte proliferation. The in vitro antibody response against sheep red blood cells (anti-SRBC) was inhibited by ethanol extracts and quaternary alkaloid fraction. The intraperitoneal (i.p.) application of ethanol extract and tertiary alkaloid fraction from aerial parts showed that they possess in vivo effect on alternative pathway (AP) complement activity, anti-SRBC response and delayed type hypersensitivity (DTH). 相似文献
949.
Sabate J.A. Jovanovic M.M. Lee F.C. Gean R.T. 《Industrial Electronics, IEEE Transactions on》1995,42(1):63-71
The analysis and design of an LCC resonant inverter for a 20 kHz AC distributed power system are presented. Several resonant converter topologies are assessed to determine their suitability for high efficiency power conversion, under resistive and reactive loads. Two LCC-resonant inverter designs were implemented. One with all switches operating with zero voltage switching (ZVS), and another with two switches operating with ZVS and two switches with zero current switching (ZCS). The experimental results are presented along with a performance comparison of the two versions 相似文献
950.