排序方式: 共有51条查询结果,搜索用时 0 毫秒
1.
Based on the Modified Couple Stress Theory,a functionally graded micro-beam under electrostatic forces is studied.The FGM micro-beam is made of two materials and material properties vary continuously along the beam thickness according to a power-law.Dynamic and static pull-in voltages are obtained and it is shown that the static and dynamic pull-in voltages for some materials cannot be obtained using classic theories and components of couple stress must be taken into account.In addition,it is shown that the values of pull-in voltages depend on the variation through the thickness of the volume fractions of the two constituents. 相似文献
2.
采用初湿浸渍和溶胶凝胶法分别制备了Li/MgO催化剂和Li/MgO纳米催化剂. 比较两种Li/MgO催化剂对于甲烷氧化偶联反应的催化性能. 采用X射线衍射、BET吸附和透射电镜进行了表征.在973-1073 K和总压力为101 kPa下对催化剂进行了测试. 实验结果表明,Li/MgO纳米催化剂比普通催化剂对于甲烷氧化偶联反应表现为更高的甲烷转换率,较高选择性和较高的的主要产品(乙烷和乙烯)的产率. 相似文献
3.
This paper deals with the stability analysis of transverse motions of a cantilever microbeam sandwiched by two piezoelectric layers located on the lower and upper surfaces of the microbeam. Application of same DC and AC voltages to the upper and lower piezoelectric layers creates an axial force with steady and time-varying components. The eigenfunction expansion of the transverse motion equation leads to the creation of a Mathieu type parametric equation which is mostly seen in the stability analysis of the structures in the literature; using Floquet theory for single degree of freedom systems the stable and unstable regions of the problem are investigated. The effect of viscous damping and DC voltage on the stability region of the problem is also studied. The results show the stabilizing effect of the viscous damping and positive DC voltage on the behavior of the microbeam. The achieved results are finally compared with those reported in the literature. 相似文献
4.
Jamal Aalaie Ghader Khanbabaie Alireza R. Khoshniyat Ali Rahmatpour 《Journal of Macromolecular Science: Physics》2013,52(2):305-316
Nanocomposites of two different grades of polyamide 6 (PA6) with organically modified nanoclay were prepared via melt compounding in a twin‐screw extruder. The rheological behavior, morphology and mechanical properties of the nanocomposites were studied using a capillary rheometer, x‐ray diffraction (XRD), tapping‐mode atomic force microscopy (AFM), and tensile and flexural tests. XRD patterns indicate that the organically modified layered silicate was well dispersed in the PA6 matrix. From the AFM images the surface roughness of PA6 slightly increases with addition of organoclay. The rheological studies showed that the prepared nanocomposites have shear thinning behavior, obeying the power law equation. Addition of organoclay increases the shear stress and shear viscosity. At high rate of shear deformation the viscosity of nanocomposites are comparable to those of the pure polyamides. The activation energy of flow decreases with increasing nanoclay content. For most of the prepared nanocomposites the activation energy values increase with increasing shear rate. The tensile strength and flexural modulus and strength of the nanocomposites increase with increase of nanoclay content, but the extension at yield decreases with increasing clay loading. 相似文献
5.
6.
Fusion Energy and Stopping Power in a Degenerate DT Pellet Driven by a Laser-Accelerated Proton Beam
In this paper, we have improved the fast ignition scheme in order to have more authority needed for high-energy-gain. Due to the more penetrability and energy deposition of the particle beams in fusion targets, we employ a laser-to-ion converter foil as a scheme for generating energetic ion beams to ignite the fusion fuel. We find the favorable intensity and wavelength of incident laser by evaluating the laser-proton conversion gain. By calculating the source-target distance, proton beam power and energy are estimated. Our analysis is generalized to the plasma degeneracy effects which can increase the fusion gain several orders of magnitude by decreasing the ion-electron collisions in the plasma. It is found that the wavelength of 0.53 μm and the intensity of about 1020 W/cm2, by saving about 10% conversion coefficient, are the suitable measured values for converting a laser into protons. Besides, stopping power and fusion burn calculations have been done in degenerate and non-degenerate plasma mediums. The results indicate that in the presence of degeneracy, the rate of fusion enhances. 相似文献
7.
This paper describes the measurement of induction time in precipitation of silver nanoparticles at different temperatures and supersaturations, and models it with Smoluchowski's coagulation theory. Silver nanoparticles are synthesized by reaction of silver nitrate with hydrazine in the presence of sodium citrate as stabilizer. The rate of association between clusters is found to depend on temperature and their sizes. The activation energy for the association between two clusters and interfacial tension of silver nanoparticles were also estimated. The results also show that induction time decreases with increasing supersaturation and temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Masoud Salavati-Niasari Ghader Hosseinzadeh Omid Amiri 《Journal of Cluster Science》2012,23(2):459-468
In this work, monodisperse nanoparticles and nanorods of lanthanum hydroxide was synthesized from the reaction of lanthanum(III) nitrate and sodium hydroxide by sonochemical method. The effect of some of the parameters such as feeding rate of precursors, different solvents of reaction, time of sonication, and various surfactants on the particle size and morphology of products was studied. The as-prepared products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy. 相似文献
9.
AbstractChemical constitutes and phytotoxic activity of Cuminum cymiunm L. is investigated in the present study. For this means seeds of C. cyminum L. was harvested from Ilkhchi of Iran. The major components of essential oil (EO) with more than 94% were 3-caren-10-al, cuminal, 2-Caren-10-al, γ-Terpinene, (-)-β-Pinene and p-Cymene. This study found that cumin EO displayed meaningful inhibitory impacts on germination indices and the growth of the seedlings of Amaranthus retroflexus, Lactuca sativa, and Acroptilon repens. The germination indices showed severely concentration-dependent responses. In the case of A. retroflexus and L. sativa germination indices were controlled in the 500?ppm and in the A. repens were inhibited in the 1500?ppm of EO concentration. Overall, this study suggests that EO derived from C. cyminum L. looks to be a promising candidate for its utilization as a natural herbicide in large scale. 相似文献
10.
In this paper,thermoelastic damping (TED) in a micro-beam resonator with a pair of piezoelectric layers bonded on its upper and lower surfaces is investigated.Equation of motion is derived and the ther... 相似文献