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排序方式: 共有896条查询结果,搜索用时 31 毫秒
81.
N. Sridhar R. Massabò B.N. Cox I.J. Beyerlein 《International Journal of Fracture》2002,118(2):119-144
Bridged crack models using beam theory formulations have proved to be effective in modeling quasi-static delamination crack growth under large scale bridging conditions in through-thickness reinforced structures. In this paper, beam theory is used to study dynamic mode I crack propagation in through-thickness reinforced laminar structures. In particular, steady state dynamic crack growth for a Double Cantilever Beam (DCB) loaded with a flying wedge is examined. The steady state crack propagation characteristics are mapped out in terms of controllable loading and material parameters including the crack velocity and the properties of the through-thickness reinforcement. For small crack velocities, the through-thickness reinforcement considerably enhances the delamination resistance of the structure. At higher velocities, the kinetic energy term dominates the overall energetics and the relative effect of the reinforcement on the delamination resistance is insignificant. The model suggests a simple fracture test for estimating the properties of the through-thickness reinforcement under dynamic loading conditions. 相似文献
82.
The role of in situ stirring under microwave-hydrothermal (M-H) conditions on the synthesis of barium titanate was investigated for the first time by powder X-ray diffraction and scanning and transmission electron microscopy. Stirring under M-H conditions in the temperature range of 150–200 °C led to enhanced crystallization of Ba titanate as revealed by yields compared to the static condition. In addition, stirring led to smaller and more uniform crystals under M-H conditions compared to those crystallized without stirring. Powder X-ray diffraction revealed the formation of only cubic polymorph of Ba titanate at or below 200 °C in 4 h with or without in situ stirring under M-H conditions. These results show that stirring is an important parameter during M-H synthesis of nanophase Ba titanate. 相似文献
83.
The importance of gold and silver nanoparticles in the blood flow has immense applications in biomedicine for the treatment of cancer disease and wound treatment due to their large atomic number and antimicrobial property. The current study deals with the magnetohydrodynamic and electroosmotic radiative peristaltic Jeffrey nanofluid (blood–silver/gold) flow with the effect of slip and convective boundary conditions in the nonsymmetric vertical channel. The nondimensional governing equations have been solved analytically and the exact solutions have been presented for velocity, temperature, shear stress, trapping, entropy generation, pressure gradient and heat transfer coefficient. The pictorial representations have been prepared for the flow quantities with respect to fluid flow parameters of interest. It is noticed from the current study that the gold-based nanofluids exhibit higher velocity than silver-based nanofluids. Enhancement of thermal radiation decreases the total entropy generation. The size of the tapered bolus decreases with the enhancement of magnetic field strength. The present model is applicable in designing pharmacodynamic pumps and drug delivery systems. 相似文献
84.
C. Thiruvikraman V. Balasubramanian K. Sridhar 《Journal of Thermal Spray Technology》2014,23(5):860-875
High velocity oxygen fuel (HVOF)-sprayed cermet coatings are extensively used to combat erosion-corrosion in naval applications and in slurry environments. HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance have significant influence on coating characteristics like adhesion bond strength and shear strength. This paper presents the use of statistical techniques in particular response surface methodology (RSM), analysis of variance, and regression analysis to develop empirical relationships to predict adhesion bond strength and lap shear bond strength of HVOF-sprayed WC-CrC-Ni coatings. The developed empirical relationships can be effectively used to predict adhesion bond strength and lap shear bond strength of HVOF-sprayed WC-CrC-Ni coatings at 95% confidence level. Response graphs and contour plots were constructed to identify the optimum HVOF spray parameters to attain maximum bond strength in WC-CrC-Ni coatings. 相似文献
85.
Y. -M. Pan D. S. Dunn G. A. Cragnolino N. Sridhar 《Metallurgical and Materials Transactions A》2000,31(4):1163-1173
Alloy 825, a former candidate material for radioactive high-level waste containers, was investigated to assess its thermal
stability and the time-temperature conditions for sensitization. Alloy specimens with a carbon content of 0.01 wt pct in the
mill-annealed (MA) and solution-annealed (SA) conditions were studied after thermal exposure to temperatures ranging from
600 °C to 800 °C for periods of up to 1000 hours. Sensitization was evaluated by using corrosion tests that were correlated
to grainboundary chemistry analyses. Sensitized microstructures were found to contain M23C6-type carbides and a chromium-depleted region in the vicinity of the grain boundaries. Thermal aging at 700 °C for 100 hours
resulted in the highest sensitization. While heat treatment at 640 °C showed a progressive development of sensitization with
time, healing was found to occur after aging at 800 °C for 100 hours. The degree of sensitization, quantified by an equivalent
chromium-depleted-zone size, correlates well with the corrosion rate in the nitric acid test. Thermodynamic models were used
to calculate the interfacial chromium concentration, chromium depletion profile, and the depleted-zone width. Comparisons
between experimental measurements and model calculations indicate that reliable prediction depends on the selection of key
model parameters. 相似文献
86.
Interactions of refractory materials with molten gasifier slags 总被引:1,自引:0,他引:1
Jinichiro Nakano Seetharaman Sridhar James BennettKyei-Sing Kwong Tyler Moss 《International Journal of Hydrogen Energy》2011,36(7):4595-4604
The current study focuses on the analysis of sessile-drop interfacial reactions between two synthetic slags (based on average ash chemistries of coal and petcoke feedstock) and two refractory materials (90 wt% Cr2O3-10 wt% Al2O3 and 100 wt% Al2O3), using a Confocal Scanning Laser Microscope (CSLM). Ground slag samples (less than 325 mesh) were placed at specific microstructure locations on refractory substrates and heated to 1500 °C in an atmosphere of CO/CO2 gas mixture (volume ratio = 1.8), using a gold-image heating chamber. Cross-sections of the slag/refractory interface indicated unique slag penetration into preferred areas of the refractory and grain dissolution into the slag which promoted spalling of the refractory. Initially, the slag attacked both grain boundaries and fine microstructure areas, freeing alumina grains into the slag. The formation of VOx-based crystalline material in the petcoke slag was found to alter the liquid composition. Chemical spalling of Cr-containing crystal layer also facilitated degradation of the refractory. 相似文献
87.
In this work, we report electronic structure calculations aimed at computing the linear optical absorption spectrum and static
dipole polarizablity of a newly proposed boron-based planar aromatic compound borozene (B
12
H
6). For the purpose, we use the semiempirical INDO model Hamiltonian, accompanied by large-scale correlation calculations using
the multi-reference singles-doubles configuration-interaction (MRSDCI) approach. We present detailed predictions about the
energetics, polarization properties, and the nature of many-particle states contributing to various peaks in the linear absorption
spectrum. Our results can be used to characterize this material in future optical absorption experiments. We also argue that
one can deduce the aromaticity of the cluster from the optical absorption and static polarizability results. 相似文献
88.
Yong-Hong Ye Y.J. HuangW.T. Lu B.D.F. CasseD. Xiao S.P. BennettD. Heiman L. MenonS. Sridhar 《Optical Materials》2011,33(11):1667-1670
We fabricated a series of gold nanowires/alumina composite films with different wire lengths. Optical transmission measurements confirmed that the composite films exhibit transverse and longitudinal surface plasmon resonances. We show that the wavelength of the longitudinal resonance is sensitive to nanowire length, while that of the transverse resonance is not. The experimental results are in agreement with the modeled results based on the Maxwell Garnett effective medium theory. Moreover, the window for negative refraction of the samples can be tuned in synchronism with the longitudinal resonance by the nanowire length. 相似文献
89.
A non-linear form relating vegetation indices (VI) to crop grain yields which normalizes for differences in acquisition date is suggested. It is based on the assumption that deviations in VI near the peak VI follow a quadratic behaviour. This form gave a higher R2 value than a simple VI-yield linear model on a multi-year, multi-location data set of IRS (Indian Remote Sensing Satellite-1A) LISS-I(Linear Imaging Self Scanner-I) derived near-infrared (NIR)/red radiance ratios and wheat grain yields in a study site in Madhya Pradesh (India). As the suggested model includes time of peak as a variable, it allows integration of results from other sources, such as, weather-based crop phenology model or high repetivity spectral data into the VI-yield relation. 相似文献
90.
Ronald G. Harvey Qing Dai Chongzhao Ran Sridhar R. Gopishetty Trevor M. Penning 《Polycyclic Aromatic Compounds》2013,33(4-5):257-269
Three mechanisms have been proposed to explain the carcinogenic activities of polycyclic aromatic hydrocarbons (PAHs). On the basis of the nature of the active metabolites involved, they may be termed: the diol epoxide mechanism, the quinone mechanism, and the radical-cation mechanism. In connection with studies to evaluate the relative importance of these pathways, we required practical methods for the syntheses of the active PAH metabolites involved. We now report efficient new synthesis of the o-quinones of benzo[a]pyrene (BPQ), 7,12-dimethylbenz[a]anthracene (DMBAQ), and benz[a]anthracene (BAQ). These quinones are convenient synthetic precursors of the related o-catechols, trans-dihydrodiols, and diol epoxides, as well as the stable adducts of the o-quinones with 2-deoxyadenosine and 2′-deoxyguanosine. 相似文献