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81.
B. Fakrach A. Rahmani H. Chadli K. Sbai J.-L. Sauvajol 《Physica E: Low-dimensional Systems and Nanostructures》2009,41(10):1800-1805
Using the spectral moments method, the calculations of the Raman spectra of single-walled boron nitride nanotubes (SW-BNNTs) were performed in the framework of the force constants model. Spectra were computed for chiral and achiral nanotubes for different diameters and lengths. The Raman scattering intensities were determined using the bond-polarizability model and a good agreement with group theory analysis was found. We show that the modes in the low frequency region are very sensitive to the nanotube diameter variation, whereas the ones associated to the tangential region are chirality dependent. The number of Raman active modes, their frequencies, and intensities depend on the length of the nanotube. 相似文献
82.
Torsion rods are a primary component of many power transmission and other mechanical systems. The behavior of these rods under
elastoplastic torsion is of major concern for designers. Different methods have so far been proposed which deal with the elastoplastic
torsion of rods, most of which assume constant yield stress. This assumption produces rough and inaccurate results when the
rods are heat treated, since in the process of heat treatment the form of yield stress distribution across the rod cross section
changes. We propose a new method for calculating elastoplastic torsion of rods of simply connected cross section which is
based on heat treatment observations. In our method the full plastic stress function is obtained by using the semi-inverse method. Elastoplastic stress function is obtained by generalizing the idea of the membrane analogy and using a piecewise continuous stress function. Since the proposed form of yield stress distribution can not be handled
by the current Finite Element packages, we produce a computer package with a 3D graphical interface capable of calculating
and displaying the 3D elastoplastic stress function, shear stress contours, and torque-angle of rotation per unit length.
We show that our method produces excellent agreement for several known cross sections in comparison to methods which assume
constant yield stress. 相似文献
83.
Iron is incorporated in porous silicon (PS) by impregnation method using Fe(NO3)3 aqueous solution. The presence of iron in PS matrix is shown from energy-dispersive X-ray (EDX) analysis and Fourier transform infrared (FTIR) measurements. The optical properties of PS and PS-doped iron are studied by photoluminescence (PL). The iron deposited in PS quenched the silicon dangling bonds then increased the PL intensity. The PL peak intensity of impregnated PS is seven times stronger than that in normal PS. Upon exposing iron-PS sample to ambient air, there is no significant change in peak position but the PL intensity increases during the first 3 weeks and then stabilises. The stability is attributed to passivation of the Si nanocrystallites by iron. 相似文献
84.
85.
A simple and sensitive catalytic-photometric method for the determination of trace amounts of palladium(II) based on its heterogeneous catalytic effect on the reduction of neutral red (NR) by hypophosphite (HP) has been developed. The reaction was monitored at 530 nm and the time elapsed (At) for the absorbance to decrease from its initial value by 1.5 absorbance units was recorded using the variable time method. The influence of reaction variables is discussed. The ranges of linearity were 0.108–6.533 ppm and 0.032–0.653 ppm palladium(II) at temperatures of 30 and 55°C, respectively. The relative standard deviations of the developed method were 2.5 and 2.7% (for 8 replicate determinations of 1.110 ppm Pd(II)) at 30 and 55°C, respectively. The effect of interferences from other metal ions and some anions was studied. The developed method has been successfully tested for determination of Pd(II) in Al–Si–Pd catalysts. 相似文献
86.
In this work, the Exp-function method is employed to find new wave solutions for the Sine-Gordon and Ostrovsky equation. The equations are simplified to the nonlinear partial differential equations and then different types of exact solutions are extracted by this method. It is shown that the Exp-function method is a powerful analytical method for solving other nonlinear equations occurring in nonlinear physical phenomena. Results are presented in contour plots that show the different values of effective parameters on the velocity profiles. 相似文献
87.
Louvion N Gérard D Mouette J de Fornel F Seassal C Letartre X Rahmani A Callard S 《Physical review letters》2005,94(11):113907
We report the direct, room-temperature, near-field mapping and spectroscopy of the optical modes of a photonic-crystal microcavity containing quantum wells. We use a near-field optical probe to reveal the imprint of the cavity mode structure on the quantum-well emission. Furthermore, near-field spectroscopy allows us to demonstrate the strong spatial and spectral dependence of the coupling between the sources and the microcavity. This knowledge will be essential in devising future nanophotonic devices. 相似文献
88.
Design,Synthesis and Evaluation of Antibacterial Effects of a New Class of Piperazinylquinolone Derivatives
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Ali Darehkordi Mahin Ramezani Fariba Rahmani Mahnaz Ramezani 《Journal of heterocyclic chemistry》2016,53(1):89-94
Pentafluoropyridine derivatives and cyanuric chloride were used for the synthesis of new piperazinylquinolone derivatives. These reactions provided N‐fluoropyridiyl and N‐cyanoryl chloride piperazinylquinolone derivatives in good yields. Synthesized compounds were evaluated for their antibacterial activities. These compounds displayed good to excellent antibacterial activities. 相似文献
89.
This contribution presents an experimental approach to improve analytical performance of electromembrane extraction (EME) procedure, which is based on the scrutiny of current pattern under different extraction conditions such as using different organic solvents as supported liquid membrane, electrical potentials, pH values of donor and acceptor phases, variable extraction times, temperatures, stirring rates, different hollow fiber lengths and the addition of salts or organic solvents to the sample matrix. In this study, four basic drugs with different polarities were extracted under different conditions with the corresponding electrical current patterns compared against extraction recoveries. The extraction process was demonstrated in terms of EME-HPLC analyses of selected basic drugs. Comparing the obtained extraction recoveries with the electrical current patterns, most cases exhibited minimum recovery and repeatability at the highest investigated magnitude of electrical current. . It was further found that identical current patterns are associated with repeated extraction efficiencies. In other words, the pattern should be repeated for a successful extraction. The results showed completely different electrical currents under different extraction conditions, so that all variable parameters have contributions into the electrical current pattern. Finally, the current patterns of extractions from wastewater, plasma and urine samples were demonstrated. The results indicated an increase in the electrical current when extracting from complex matrices; this was seen to decrease the extraction efficiency. 相似文献
90.