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91.
The role of tin dioxide (SnO2) interphase for the alumina/glass composite system was investigated using fractography. Alumina (Al2O3) and glass form a strong chemical bond which is undesirable for toughness in a ceramic matrix composite. SnO2 interphase was incorporated to prevent this strong bond between alumina and glass. SnO2 was deposited on Al2O3 substrates via chemical vapour deposition and bonded with glass. The role of the interphase was then studied by characterizing
the fracture surfaces of the bend test and special composite disc samples loaded in diametral compression. Bend tests results
showed that the SnO2 interphase and/or the SnO2/Al2O3 interface acted as a plane of weakness. Secondary cracking at 90° to the major crack direction was observed along this plane
of weakness, which appears to be in accord with the Cook and Gordon model. Crack deflection and secondary cracking were also
observed in the SnO2 region of the compression samples. These results indicate the suitability of SnO2 interphase for the alumina/glass composite system. 相似文献
92.
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94.
N. Chawla U. Habel Y. -L. Shen C. Andres J. W. Jones J. E. Allison 《Metallurgical and Materials Transactions A》2000,31(2):531-540
The effect of matrix microstructure on the stress-controlled fatigue behavior of a 2080 Al alloy reinforced with 30 pct SiC
particles was investigated. A thermomechanical heat treatment (T8) produced a fine and homogeneous distribution of S′ precipitates,
while a thermal heat treatment (T6) resulted in coarser and inhomogeneously distributed S′ precipitates. The cyclic and monotonic
strength, as well as the cyclic stress-strain response, were found to be significantly affected by the microstructure of the
matrix. Because of the finer and more-closely spaced precipitates, the composite given the T8 treatment exhibited higher yield
strengths than the T6 materials. Despite its lower yield strength, the T6 matrix composite exhibited higher fatigue resistance
than the T8 matrix composite. The cyclic deformation behavior of the composites is compared to monotonic deformation behavior
and is explained in terms of microstructural instabilities that cause cyclic hardening or softening. The effect of precipitate
spacing and size has a significant effect on fatigue behavior and is discussed. The interactive role of matrix strength and
SiC reinforcement on stress within “rogue” inclusions was quantified using a finite-element analysis (FEA) unit-cell model. 相似文献
95.
96.
Alexander Vasiliev Hakim Ferroukhi Martin A. Zimmermann Rakesh Chawla 《Annals of Nuclear Energy》2008
Studies in support of the assessment of aging structural materials in pressurized water reactors are being performed at the Paul Scherrer Institut. To that aim, a state-of-the-art methodology based on applying a CASMO-4/SIMULATE-3/MCNPX calculation scheme has been developed. In the frame of the methodology validation, an investigation is currently reported pertaining to the sensitivity of the calculated results, for a specific reactor pressure vessel scraping test, to the nuclear data used with the Monte Carlo code. Thus, the MCNPX-2.4.0 calculations have been carried out using three different data libraries, based on JEF-2.2, ENDF/B-VI.8 and JENDL-3.3 evaluations, respectively. 相似文献
97.
An important class of singular second order initial value problems is y″ + (2/x)y′+f(x,y) = 0, 0 < x < xf, y(0) = a, y′(0) = 0; this class includes, for example, the well-known singular equations of Emden and Liouville. The purpos of this paper is to show the interesting result that explicit Nyström methods, existing for the direct integration of special second order regular initial value problems, can be used for the integration of this class of singular initial value problems and the methods show their proper respective orders of convergence. This is justified mathematically and demonstrated computationally. 相似文献
98.
Echocardiography may be an accurate method of measuring left ventricular (LV) volumes and mass of the horse's heart. If so, studies of the heart size and hypertrophy would be possible. This study evaluated geometric models of the external and internal LV shapes, to determine which could be applied to echocardiographic measurements. We preserved 30 horses' hearts and measured their dimensions and cross sectional areas. These measurements were entered into seven formulae representing different geometric models of the ventricle and its chamber. We derived a correction factor to estimate the long axis as a fixed proportion of the external diameter, so that volumes could be determined from an M-mode or a cross sectional echocardiogram. Statistical analysis of the regressions of known volumes against calculated volumes measured by water displacement, demonstrated that the ellipsoid formula using cross sectional areas was very accurate in representing the external shape of the left ventricle (slope = 1.01 r2 = 96.3) and its chamber (slope = 0.83, r2 = 94.3). Myocardial volume, measured by subtracting internal (chamber) volume from external volume, was also calculated accurately (slope = 1.01, r2 = 96.5). The ellipsoid formula using directly measured diameter was only slightly less accurate. LV mass could be calculated by applying the specific gravity of equine myocardium, 1.05, to the myocardial volume. Formulae recommended for evaluating are, with M-mode echocardiography: [equation: see text] and with 2D echocardiography [equation: see text] where De is the external diameter, Di is the internal diameter, Ae the external area and Ai the internal area. 相似文献
99.
Busson P. Chawla N. Bach J. Le Tual S. Singh H. Gupta V. Urard P. 《Solid-State Circuits, IEEE Journal of》2010,45(1):84-94
A digital channel multiplexer for satellite outdoor unit running at 1 GHz clock frequency is implemented in 65 nm CMOS mixed oxide dual voltage technology. This multiplexer, based on a 1 GS/s digital signal processor (DSP) approach with 500 MHz input and output bandwidth, embeds two 8 bit 1 GS/s analog-digital converters (ADCs) and two 8 bit 1 GS/s digital-analog converter (DACs). It consumes less that 1022 mW at ambient temperature while achieving noise rejection up to 42.5 dB on a single tone, and > 37 dB on modulated satellite channels. 相似文献
100.