排序方式: 共有18条查询结果,搜索用时 960 毫秒
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C. Mauder B. Reuters L. Rahimzadeh Khoshroo M.V. Rzheutskii E.V. Lutsenko G.P. Yablonskii J.F. Woitok M. Heuken H. Kalisch R.H. Jansen 《Journal of Crystal Growth》2010,312(11):1823-1827
The anisotropic film properties of m-plane GaN deposited by metal organic vapour phase epitaxy (MOVPE) on LiAlO2 substrates are investigated. To study the development of layer properties during epitaxy, the total film thickness is varied between 0.2 and 1.7 μm. A surface roughening is observed caused by the increased size of hillock-like features. Additionally, small steps which are perfectly aligned in (1 1 −2 0) planes appear for samples with a thickness of ∼0.5 μm and above. Simultaneously, the X-ray rocking curve (XRC) full width at half maximum (FWHM) values become strongly dependent on incident X-ray beam direction beyond this critical thickness. Anisotropic in-plane compressive strain is initially present and gradually relaxes mainly in the [1 1 −2 0] direction when growing thicker films. Low-temperature photoluminescence (PL) spectra are dominated by the GaN near-band-edge peak and show only weak signal related to basal plane stacking faults (BSF). The measured background electron concentration is reduced from ∼1020 to ∼1019 cm−3 for film thicknesses of 0.2 μm and ∼1 μm while the electron mobilities rise from ∼20 to ∼130 cm2/V s. The mobilities are significantly higher in [0 0 0 1] direction which we explain by the presence of extended planar defects in the prismatic plane. Such defects are assumed to be also the cause for the observed surface steps and anisotropic XRC broadening. 相似文献
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Seyedeh Leila Hashemi Dashtaki 《Molecular physics》2013,111(14):2195-2203
ABSTRACTRate constants for the reactions of C2H6, C2H5D and C2D6 with .CCl3. for the production of CHCl3 and CDCl3 (k1, k2, k3 and k4) were computed using variational transition state theory coupled with hybrid-meta density functional theory (MPWB1K) over the temperature range of 200–2900 K. The ground-state vibrational adiabatic potential was plotted for all channels. Small- and large-curvature tunnelling were determined to include quantum effects in the calculation of rate constants. Harmonic vibrational frequencies along the reaction path were calculated in curvilinear coordinates with scaled frequencies. Anharmonicity was included in the lowest-frequency torsion. The position of formation and dissociation of bonds was specified using the variation in harmonic vibrational frequencies along the reaction path. Representative tunnelling energy and the thermally averaged transmission probability at 298 K (P(E)exp?( ? ΔE/RT)) were determined for the reactions in which tunnelling is important. The kinetic isotope effect was used to calculate the considerable contributions of tunnelling and vibration. The expressions for rate constants were determined using nonlinear least-square fitting over the temperature range of 200–2900 K. 相似文献
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Majid M. Heravi Mohammad Bakherad Mohammad Rahimzadeh Mehdi Bakavoli Mitra Ghassemzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2477-2482
Substituted 6-chloro-pyrimido[4,5-e][1,3,4] thiadiazine was converted to the corresponding 6-hydrazino derivative by treatment with hydrazine hydrate in DMF/Et 3 N. The latter was converted to various substituted [1,2,4]triazino[1,2-a] pyrimido[4,5-e][1,3,4]thiadiazines. 相似文献
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Cavitation is a dynamic phenomenon occurring in fluid flows, where the local static pressure is lower than the saturated vapor pressure at working temperature. The growth and collapse of cavitation bubbles leads to corrosion and pitting of metal surfaces. Considering the fact that erosion by cavitation is still one of the current problems, it is important to detect the initiation, fully developed point of cavitation and to analyze its characteristics. In this research, an attempt is made to study acoustic waveform of cavitation in the globe valve. The waveform is transformed by Fast Fourier Transform and its important parameters such as amplitude, energy, frequency and so on are analyzed. 相似文献
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An improved and rapid one-pot synthesis of tetrasubstituted imidazoles by condensing benzil, ammonium acetate, amines, and aromatic aldehydes and using a catalytic amount of silica structure MCM-41 or p-toluenesulfonic acid (p-TsOH) as efficient, green, reusable catalysts in excellent yields is reported. 相似文献
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Golnaz Rahimzadeh Saeed Bahadorikhalili Ebrahim Kianmehr Mohammad Mahdavi 《Molecular diversity》2017,21(3):597-609
A novel imidazole ionic liquid (IL)-functionalized \(\hbox {silica}@\gamma \)-\(\hbox {Fe}_{2}\hbox {O}_{3}\) (\(\hbox {IL-SiO}_{2}@\hbox {MNP}\)) is prepared by the functionalization of \(\hbox {SiO}_{2}@\hbox {MNP}\) by 1-butyl-3-(3-trimethoxypropyl)-1H-imidazol-3-ium chloride as the IL moiety. The catalyst is characterized by transmission electron microscopy, scanning electron microscope, vibrating sample magnetometer, dynamic light scattering and Fourier transform infrared spectroscopy. \(\hbox {IL-SiO}_{2}@\hbox {MNP}\) showed good activity in the synthesis of 6H-chromeno[4,3-b]quinolin-6-one derivatives via multicomponent reaction of 4-hydroxycoumarin, anilines and benzaldehydes. The nanocatalyst is magnetically separable and easily recoverable and showed successful activity up to 10 runs. 相似文献
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Cavitation is a common phenomenon in a fluid circuit especially wherever local pressure is lower than fluid saturated pressure. The cavitation negatively affects a fluid system and structure in different ways: i.e. erosion, flow rate reduction, noise and vibration. In order to diminish cavitation, adding some nanomaterials seem to be applicable in different ways. This research aims at assessing the effects of CMC (Carboxy methyl cellulose) additives on incipient cavitation by analyzing the resultant change in low frequency acceleration. Furthermore, this study attempts to examine the accuracy of low frequency acceleration for detecting incipient cavitation. 相似文献
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P. Talebizadeh H. Rahimzadeh G. Ahmadi R. Brown K. Inthavong 《Journal of nanoparticle research》2016,18(12):378
Non-thermal plasma (NTP) treatment reactors have recently been developed for elimination of diesel particulate matter for reducing both the mass and number concentration of particles. The role of the plasma itself is obscured by the phenomenon of particle deposition on the reactor surface. Therefore, in this study, the Lagrangian particle transport model is used to simulate the dispersion and deposition of nano-particles in the range of 5 to 500 nm in a NTP reactor in the absence of an electric field. A conventional cylindrical dielectric barrier discharge reactor is selected for the analysis. Brownian diffusion, gravity and Saffman lift forces were included in the simulations, and the deposition efficiencies of different sized diesel particles were studied. The results show that for the studied particle diameters, the effect of Saffman lift is negligible and gravity only affects the motion of particles with a diameter of 500 nm or larger. Time histories of particle transport and deposition were evaluated for one-time injection and a continuous (multiple-time) injection. The results show that the number of deposited particles for one-time injection is identical to the number of deposited particles for multiple-time injections when adjusted with the shift in time. Furthermore, the maximum number of escaped particles occurs at 0.045 s after the injection for all particle diameters. The presented results show that some particle reduction previously ascribed to plasma treatment has ignored contributions from the surface deposition. 相似文献