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排序方式: 共有10000条查询结果,搜索用时 203 毫秒
931.
Rahul Sen B. C. Satishkumar Gargi Raina C. N. R. Rao 《Fullerenes, Nanotubes and Carbon Nanostructures》1997,5(3):489-502
In the light of the finding that carbon nanotubes get functionalized on reaction with acid and other oxidizing agents, the structures and shapes of nanotube derivatives resulting from possible reaction between functionalized nanotubes, are obtained by an energy minimization procedure and the structures, so obtained, are compared with the observed microscopic images. The shapes of fullerene -like and nanotupe - like structures containing seven - membered rings, in addition to six and five - membered rings, are depicted along with the structures of bent nanotubes containing similar ring systems. Diamond - graphite hybrid structures which constitute an important class of carbon materials are also investigated. 相似文献
932.
Soma Venugopal Rao Moutzouris K. Ebrahimzadeh M. De Rossi A. Gintz G. Calligaro M. Ortiz V. Berger V. 《Quantum Electronics, IEEE Journal of》2003,39(3):478-486
The influence of scattering and two-photon absorption on the optical loss in GaAs-Al/sub 2/O/sub 3/ semiconductor nonlinear waveguides has been studied using femtosecond pulses. By deploying a scattering technique, loss coefficients were evaluated over an extended wavelength range of 1.3-2.1 /spl mu/m in the near-infrared. A systematic study involving intensity and wavelength dependence of the loss revealed the presence of two-photon absorption for wavelengths below 1.6 /spl mu/m. A simple nonlinear transmission study enabled the separation of the two-photon absorption coefficient from scattering and linear absorption. The calculated two-photon absorption coefficients were /spl sim/9-20 cm/GW. 相似文献
933.
K. Sundar Rao G. P. Jones D. E. Rivett D. J. Tucker 《European Journal of Lipid Science and Technology》1992,94(1):37-38
In the course of our search for new sources of oil, fatty acid compositions of the seed oils of 18 species belonging to three families are reported. Five species from Sterculiaceae, one species from Cucurbitaceae and twelve species from Sapindaceae were analysed. Linoleic acid predominated (43.4–76.2%) in the component fatty acids of all the oils followed by oleic (9.7–23.3%) and palmitic (8.4–14.7%) acids. 相似文献
934.
Anish Kumar K. Laha T. Jayakumar K. Bhanu Sankaro Rao Baldev Raj 《Metallurgical and Materials Transactions A》2002,33(6):1617-1626
Modified 9Cr-1Mo ferritic steel (T91/P91) has been subjected to a series of heat treatments consisting of soaking for 5 minutes
at the selected temperatures, starting from the α-phase region (1073 K) to the γ + δ-phase region (1623 K), followed by oil quenching. Hardness measurements, microstructural features, and grain-size measurements
by the linear-intercept method have been used for correlating them with the ultrasonic parameters. Ultrasonic velocity and
attenuation measurements, and spectral analysis of the first backwall echo have been used for characterization of the microstructures
obtained by various heat treatments. As the soaking temperature increased above Ac
1, the ultrasonic velocity decreased because of the increase in the volume fraction of martensite in the structure. There were
sharp changes in the ultrasonic velocities corresponding to the two critical temperatures, Ac
1 and Ac
3. Ultrasonic longitudinal- and shear-wave velocities were found to be useful in identifying the Ac
1 and Ac
3 temperatures and for the determination of hardness in the intercritical region. However, ultrasonic attenuation and spectral
analysis of the first backwall echo were found to be useful to characterize the variation in the prior-austenitic grain size
and formation of δ ferrite above the Ac
4 temperature. The scattering coefficients have been experimentally determined for various microstructures and compared with
the theoretically calculated value of the scattering coefficients for iron reported in literature. 相似文献
935.
Tapan K. Sarkar Pallab Midya Zoran A. Maricevic Masoud Kahrizi Sadasiva M. Rao Antonije R. Djordjevic 《国际射频与微波计算机辅助工程杂志》1992,2(3):168-178
Triangular patch modeling is used for analysis of arbitrarily shaped microstrip patch antennas over a single lossy dielectric medium. Since the Sommerfeld formulation is used, both the single dielectric layer (over which the microstrip patch is located) and the ground plane are considered to be infinitely wide. Typical numerical results are presented for rectangular, circular, semicircular, pentagonal, and triangular patch antennas. © 1992 John Wiley & Sons, Inc. 相似文献
936.
A nonlinear finite element static analysis is used to predict the damage in rectangular/circular plates due to large deformation simulating low-velocity impact. The impact due to the ball impactor is modelled by an equivalent static load and load distribution is taken according to Hertzian law. Tsai-Wu criterion is used to predict the failure of each ply at Gauss points. The failure mode (fibre breakage or matrix cracking) is identified using maximum stress criterion. The material properties at each failed Gauss point is degraded appropriately and the stress analysis is carried out again. This iterative process is repeated until no further damage condition occurs. Numerical examples for both circular and rectangular composite plates are presented. 相似文献
937.
This is the second in a series of two papers generated from a study on probabilistic meshless analysis of cracks. In this
paper, a stochastic meshless method is presented for probabilistic fracture-mechanics analysis of linear-elastic cracked structures.
The method involves an element-free Galerkin method for calculating fracture response characteristics; statistical models
of uncertainties in load, material properties, and crack geometry; and the first-order reliability method for predicting probabilistic
fracture response and reliability of cracked structures. The sensitivity of fracture parameters with respect to crack size,
required for probabilistic analysis, is calculated using a virtual crack extension technique described in the companion paper
[1]. Numerical examples based on mode-I and mixed-mode problems are presented to illustrate the proposed method. The results
show that the predicted probability of fracture initiation based on the proposed formulation of the sensitivity of fracture
parameter is accurate in comparison with the Monte Carlo simulation results. Since all gradients are calculated analytically,
reliability analysis of cracks can be performed efficiently using meshless methods.
Received 20 February 2001 / Accepted 19 December 2001 相似文献
938.
Of the 378 cases of stage 3 carcinoma uterine cervix, only 10 showed vesical invasion, while 19 of 24 cases of stage 4 disease had vesical invasion. Results of this procedure did not alter the management of the disease in any of these cases. From the whole series it was concluded that cysto-urethroscopy is an unnecessary, cost ineffective, invasive procedure which has no role in either diagnosis or in planning the definitive treatment of carcinoma uterine cervix. 相似文献
939.
940.