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111.
A series of 50%CuO-25%ZnO-25%Al(Zr) oxide catalysts was synthesized by a reverse co-precipitation method and characterized by XRD, N2 adsorption-desorption, H2-TPR, H2-TPD and CO2-TPD, and used as catalyst for CO2 hydrogenation to methanol under mild conditions(200-260℃ and 1-3 MPa). Consequently, H2-TPR exhibited that the dispersed CuO species increased with the zirconium content, while the H2-TPD showed that small amount of zirconia can increase the H2 desorption amount. As a result, Cat-2 and Cat-3 exhibited an enhanced H2-spillover effect, the most H2 desorption amount, which showed an optimum activity of about 7% methanol yield. 相似文献
112.
A title organic-inorganic hybrid material 2-amino-3-benzyloxy pyridinium perchlorate was synthesized by slow evaporation at room temperature using 2-amino-3-benzyloxypyridine as the structure-directing agent. The structure of the title compound was determined by means of single-crystal X-ray diffraction at 293 K. The results show that this compound crystallizes in the centrosymetric monoclinic system with a space group of P21/n and lattice parameters of a=0.7025(5) nm, b=1.2635(5) nm, c=1.5766(5) nm, Z=4 and V=1.3905(2) nm3. The crystal structure has been determined and refined to R1=0.0367 and wR2=0.1022 using 2326 independent reflections and can be described as a succession of organic and inorganic layers parallel to the bc plane. In this arrangement, hydrogen bonds and van der Waals interactions between different species play an important role in the two-dimensional(2D) network cohesion. This compound was also characterized by means of infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis-differential thermal analysis(TG-DTA). Moreover, protonic conduction of this compound determined by an impedance analyzer has been studied in the temperature range of 303-373 K. 相似文献
113.
This paper presents an investigation of the dynamics of electrically actuated single-walled carbon nanotube (CNT) resonators
including the effect of their initial curvature due to fabrication (slack). A nonlinear shallow arch model is utilized. A
perturbation method, the method of multiple scales, is used to obtain analytically the forced vibration response due to DC
and small AC loads for various slacked CNTs of higher and lower aspect ratio. Results of the perturbation method are verified
with those obtained by numerically integrating the equations of a multi-mode reduced-order model based on the Galerkin procedure.
The effective nonlinearity of the CNT is calculated as a function of the slack level and the DC load. To handle computational
problems associated with CNTs of small radiuses, results based on a nonlinear cable model are also demonstrated. The results
have indicated that the quadratic nonlinearity due to slack has dominant effect on the dynamic behavior of the CNT. 相似文献
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115.
A two variable refined plate theory for the bending analysis of functionally graded plates 下载免费PDF全文
Ismail Mechab Hassen Ait Atmane Abdlouahed Tounsi Hichem Abdesselem Belhadj EI Abbas Adda Bedia 《Acta Mechanica Sinica》2010,26(6):941-949
Bending analysis of functionally graded plates using the two variable refined plate theory is presented in this paper.The number of unknown functions involved is reduced to merely four,as against five in other shear deformation theories. The variationally consistent theory presented here has, in many respects,strong similarity to the classical plate theory. It does not require shear correction factors,and gives rise to such transverse shear stress variation that the transverse shear stresses vary parabolically across the thickness and satisfy shear stress free surface conditions.Material properties of the plate are assumed to be graded in the thickness direction with their distributions following a simple power-law in terms of the volume fractions of the constituents.Governing equations are derived from the principle of virtual displacements, and a closed-form solution is found for a simply supported rectangular plate subjected to sinusoidal loading by using the Navier method.Numerical results obtained by the present theory are compared with available solutions,from which it can be concluded that the proposed theory is accurate and simple in analyzing the static bending behavior of functionally graded plates. 相似文献
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This paper discusses the behaviour of the trajectories of asystem of differential equations with respect to two arbitrarysets and on a finite interval of time. The theory is an extensionof known work on finite-time stability using Liapunov techniquesbut allows controllability to be included as a special typeof stability. A number of examples illustrate the applicationof the theorems. 相似文献
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L.?Bouzaiene B.?Ilahi L.?Sfaxi F.?Hassen H.?MaarefEmail author O.?Marty J.?Dazord 《Applied Physics A: Materials Science & Processing》2004,79(3):587-591
Coherent InAs islands separated by GaAs spacer (d) layers are shown to exhibit self-organized growth along the vertical direction. A vertically stacked layer structure is useful for controlling the size distribution of quantum dots. The thickness of the GaAs spacer has been varied to study its influence on the structural and optical properties. The structural and optical properties of multilayer InAs/GaAs quantum dots (QDs) have been investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoluminescence (PL) measurements. The PL full width at half maximum (FWHM), reflecting the size distribution of the QDs, was found to reach a minimum for an inter-dots GaAs spacer layer thickness of 30 monolayers (ML). For the optimized structure, the TEM image shows that multilayer QDs align vertically in stacks with no observation of apparent structural defects. Furthermore, AFM images showed an improvement of the size uniformity of the QDs in the last layer of QDs with respect to the first one. The effect of growth interruption on the optical properties of the optimized sample (E30) was investigated by PL. The observed red shift is attributed to the evolution of the InAs islands during the growth interruption. We show the possibility of increasing the size of the QDs approaching the strategically important 1.3 m wavelength range (at room temperature) with growth interruption after InAs QD deposition. 相似文献