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101.
A shrinkage testimator, based on a test of hypothesis when an initial estimate of the scale parameter is available, has been proposed. The salient feature of the proposed testimator is that, being dependent on the test statistic, it removes arbitrariness in the choice of the shrinkage factor for a given level of significance. Expressions for bias, mean square error and relative efficiency with respect to the conventional estimator have been derived. Also, it has been shown that by taking the square of the shrinkage factor the relative efficiency of the testimator can be increased. 相似文献
102.
In this article, the tensile and fracture properties of a discontinuously reinforced aluminum (DRA) alloy composite are modeled
to determine the influence of constituent parameters on material behavior. Comparison of the elastic-modulus calculations
to the experimental data suggest that the angular particles are more effective in load transfer than spherical particles,
and that a unit cylinder geometry is a good representation of the particles under elastic conditions. This same geometry is
used in the finite element-based elastic-plastic model of Bao et al., and reasonably good agreement is obtained between the experimental and predicted yield strengths. A fracture-mechanics model
is proposed for predicting the elongation to failure. The model assumes the existence of particle cracks, and criticality
is based on the strain required for matrix rupture between cracked particles. The damage criterion of Cockcroft and Latham
is utilized, and model predictions are compared to data from different investigations. It is shown that the volume fraction
of particles and the work-hardening coefficient of the matrix have a strong influence on the strain to failure. Fracture toughness
modeling once again exposes the limitations of existing zero-degree crack-propagation models, such as that of Hahn and Rosenfield,
which predict increased toughness with yield strength rather than a decrease, which is observed experimentally. A shear-failure
model along a 45-deg direction is proposed for the higher-strength conditions, where concentrated slip bands were observed.
The model exhibits the inverse toughness dependence on strength and better correlation to peak-aged (PA) data, but shows poorer
agreement with underaged (UA) data. Thus, a transition from zero-degree propagation to 45-deg propagation with increasing
strength is suggested. A simplified method for extracting particle stresses is illustrated and is used to estimate a Weibull
modulus of 4.9 and a Weibull strength of 2450 MPa for the SiC particles of an average diameter of 10 μm.
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. 相似文献
103.
Archana Pandey Abhishek Prasad Sindhu Singh Om Parkash Devendra Kumar 《Journal of Materials Science: Materials in Electronics》2008,19(11):1122-1127
Effect of manganese and cobalt doping (0.50 mole%) on electrical properties of ZnO based varistors has been studied using
complex plane modulus analysis. It is found that total resistivity of Mn doped sample is more as compared to that of Co doped
sample. This has been ascribed to existence of Mn in variable valence states viz. Mn2+, Mn3+ and Mn4+ which promotes hopping conduction leading to increase in the conductivity as compared to Co doped sample, in which Co exists
predominantly in +3 state with traces of Co2+ or Co+4 states. This accounts for its less conductivity. Mechanism of conduction is the same for grains and grainboundaries. 相似文献
104.
105.
The influence of incident beam divergence on the length of the streak intercepted by the Ewald sphere is considered, as a relpHK·L of a faulted hexagonal crystal, mounted about itsc-axis on the goniometer head attached to the ø-circle, is brought into diffracting condition for the bisecting setting of a 4-circle diffractometer. For the special crystal mounting correction factors required to convert the measured intensities corresponding to a fixed length of the streak are derived. A procedure for experimentally verifying the mathematical approach employed in these derivations is also presented. 相似文献
106.
107.
Application of a new xylanase activity from Bacillus amyloliquefaciens XR44A in brewer's spent grain saccharification 下载免费PDF全文
108.
Kalim Deshmukh A. H. Shah Mayank Pandey G. M. Joshi 《Polymer-Plastics Technology and Engineering》2015,54(16):1743-1752
Graphene oxide was synthesized using modified Hummers method. The preparation of polyvinylchloride/graphene oxide nanocomposites was carried out using colloidal processing. The morphology of polyvinylchloride/graphene oxide nanocomposite confirms that graphene oxide was uniformly distributed within the polyvinylchloride matrix indicating complete exfoliation of graphene oxide. Significant improvement in the microhardness of the nanocomposite was observed as compared to neat polyvinylchloride. The impedance spectroscopy of nanocomposites was carried out in the frequency range (50 Hz to 35 MHz) and temperature range (80–150°C). Thus, based on the results obtained, we found that polyvinylchloride/graphene oxide nanocomposites hold great promise in many potential applications such as an electrode material for supercapacitors. 相似文献
109.
Rupesh Verma Ravi KumarDevesh M. Pandey Nishith Verma 《Chemical Engineering and Processing: Process Intensification》2010
A hydrodynamic study was carried out on our patented radially cross-flow fluidized bed staged column, with the salt laden water and solid resins flowing counter-currently, to determine the loading/flooding criterion for a stable operation of the column, and also to ascertain the mal-distribution in flow. Residense time distribution measurements were taken to address the latter part of the study. The data collected from the hydrodynamic measurements show a wider range of liquid and solid flowrates that can be used for the stable operation of the column, in comparison to that obtained in the conventional multi-staged column. The extent of mal-distribution or channeling is also relatively smaller in the former. The observations are consistent with the mass-transfer results obtained in our recent study, where the separation of dissolved solids using the radially cross-flow ion exchange column was found to be 40% larger than that in the conventional column. 相似文献
110.
Pragati Singh Raghvendra Pandey Prabhakar Singh 《International Journal of Applied Ceramic Technology》2023,20(2):1103-1113
The signature of oxide ion conductivity was perceived in acceptor-doped (alkaline-earth metals) Y3GaO6. An acceptor doping of 2%Ca in Y3GaO6 (i.e., Y2.94Ca0.06GaO6) has been found to exhibit a remarkable conductivity. The present work examines the conductivity behavior of 2% Ca-doped tri-yttrium gallate (Y2.94Ca0.06GaO6) and also the effect of Mg-substitution on the phase formation and electrical conductivity of Y2.94Ca0.06GaO6 for its possible application as a solid electrolyte. Polycrystalline dense ceramic samples of Y2.94Ca0.06Ga1−xMgxO6−δ (with x = .00–.04) were fabricated using the conventional solid-state reaction route. The X-ray diffraction patterns were recorded to confirm the phase formation. The solid solubility limit of Mg2+ at Ga3+ site was found for x < .03. All the samples were observed to exhibit orthorhombic structure with Cmc21 symmetry (ICSD no.: 155086). Scanning electron microscopy (SEM) morphology reveals dense polygonal grains with vibrant grain boundaries. A significant increase in the conductivity is observed by substituting 1 mol% of Mg2+ at the Ga3+ site of Y2.94Ca0.06Ga1−xMgxO6−δ. However, a further addition of higher dopant concentration of Mg2+ leads to a decline in the electrical conductivity. A relationship between the dopant concentration, phase formation, and structural characterizations has been established to analyze the conductivity behavior. 相似文献