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171.
The paper presents an approach for the formulation of general laminated shells based on a third order shear deformation theory.
These shells undergo finite (unlimited in size) rotations and large overall motions but with small strains. A singularity-free
parametrization of the rotation field is adopted. The constitutive equations, derived with respect to laminate curvilinear
coordinates, are applicable to shell elements with an arbitrary number of orthotropic layers and where the material principal
axes can vary from layer to layer. A careful consideration of the consistent linearization procedure pertinent to the proposed
parametrization of finite rotations leads to symmetric tangent stiffness matrices. The matrix formulation adopted here makes
it possible to implement the present formulation within the framework of the finite element method as a straightforward task. 相似文献
172.
Manawwer Alam Anees A. Ansari Mohammed Rafi Shaik Naser M. Alandis 《Arabian Journal of Chemistry》2013,6(3):341-345
Polyaniline(PANI)/Tin oxide (SnO2) hybrid nanocomposite with a diameter 20–30 nm was prepared by co-precipitation process of SnO2 through in situ chemical polymerization of aniline using ammonium persulphate as an oxidizing agent. The resulting nanocomposite material was characterized by different techniques, such as X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared spectroscopy (FT-IR) and Ultraviolet–Visible spectroscopy (UV–Vis), which offered the information about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology of the nanocomposite materials and the distribution of the metal particles in the nanocomposite material. SEM observation showed that the prepared SnO2 nanoparticles were uniformly dispersed and highly stabilized throughout the macromolecular chain that formed a uniform metal-polymer nanocomposite material. UV–Vis absorption spectra of PANI/SnO2 nanocomposites were studied to explore the optical behavior after doping of nanoparticles into PANI matrix. The incorporation of SnO2 nanoparticles gives rise to the red shift of π–π1 transition of polyaniline. Thermal stability of PANI and PANI/SnO2 nanocomposite was investigated by thermogravimetric analysis (TGA). PANI/SnO2 nanocomposite observed maximum conductivity (6.4 × 10?3 scm?1) was found 9 wt% loading of PANI in SnO2. 相似文献
173.
AbstractPoly(vinylidene fluoride)-based nanocomposite films with different loadings of PMMA-modified graphene sheets were prepared by a solution-mixing and solvent casting method. The prepared films were annealed at three different temperatures and the crystalline structures of the samples were investigated. X-ray diffraction data confirmed the PMMA-modified graphene nanosheets enhanced the preferential β-crystalline structure when increasing the annealing temperature to 90?°C, while increasing the annealing temperature to 120?°C led to a β → γ phase conversion. The tendency of the graphene sheets to restack by increasing the annealing temperature was confirmed by XRD. The PMMA-modified graphene sheets, however, didn’t showa nucleating effect on the PVDF crystallizationduring DSC cooling scans. 相似文献
174.
Manawwer Alam Naser M. Alandis Fahmina Zafar Eram Sharmin Yasser M. Al-Mohammadi 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):698-708
AbstractVegetable oil based environmentally friendly polyurethane-TiO2 nanocomposite coatings have been synthesized by using sunflower oil derived diol, toluene diisocyanate and TiO2 nanoparticles. The chemical structure was confirmed by FTIR and NMR techniques while physico-chemical testing was carried out by standard laboratory methods. Physico-mechanical and anticorrosive tests of the coatings (in different corrosive media) have been investigated by standard methods. In addition to this the morphology and thermal stability behavior of the coatings have been carefully investigated by different techniques like XRD, TEM, TGA/DTG and DSC. The comparison of the performance of nanocomposites with the respective virgin polyurethane coatings reveals that the dispersion of nanoTiO2 enhanced the mechanical, corrosion and thermal stability behavior of the polymer. The synthesized nanocomposites can be used safely upto 250–275?°C. These sunflower oil derived polyurethane nanocomposites can be used in the world of protective coatings, as an alternative of petroleum derived corrosion protective coating materials. 相似文献
175.
Naser Beyraghi Abdollah Khoei Khayrollah Hadidi 《Analog Integrated Circuits and Signal Processing》2014,80(3):473-481
In this paper a CMOS current-mode analog multiplier circuit based on a novel current-mode squarer circuit is proposed. The circuit is simulated using HSPICE simulator and designed in 0.35 µm standard CMOS technology with ± 1.5 V supply voltage. The simulation results of proposed multiplier for input current range of ±10 μA demonstrate a ?3 dB bandwidth of 24.5 MHz, 475 μW as maximum power consumption, nonlinearity of 1.3 % and a THD of 0.87 % at 1 MHz. 相似文献
176.
A new one-pot, multicomponent condensation reaction of aldehydes, 2-naphthol, and 1-acylthiosemicarbazides is described as an efficient method for the synthesis of novel 4-substituted 1-acylthiosemicarbazides in the presence of p-toluenesulfonic acid (p-TSA) as a catalyst under two conditions: organic solvent and solvent-free media. The present procedure offers several advantages, such as good yields, low cost, and very easy workup. 相似文献
177.
A detail study involving flow visualization, Laser Doppler Velocimeter (LDV) measurements and numerical prediction is presented. The visualization experiments revealed striking results of a pulsatile motion in the separated flow region associated with the formation and passage of large eddy structures. Measurements of mean velocities and turbulence intensity profiles across the separated flow field, provided information about the separated shear layer development and the recirculating flow pattern. The numerical predictions, obtained with a two-layer turbulence model in conjunction with the SIMPLE algorithm, failed to reproduce the coherent eddies and the pulsatile motion, but the mean velocities are reasonably reproduced. 相似文献
178.
M. Naser 《Mathematical Notes》1973,13(2):113-115
It is shown that every one-to-one pluriharmonic mapping of a neighborhood of 0 R4 into itself has nonvanishing Jacobian.Translated from Matematicheskii Zametki, Vol. 13, No. 2, pp. 189–194, February, 1973.In conclusion, the author wishes to thank B. V. Shabat and E. M. Chirka for their help with this work. 相似文献
179.
Sanaz Khosravi Saber Khodabandeh Naser Agh Mahdieh Bakhtiarian 《Photochemistry and photobiology》2013,89(2):400-405
We investigated the effects of salinity and artificial UV radiation on the accumulation of mycosporine‐like amino acids (MAAs) in sexual and parthenogenetic Artemia from Lake Urmia. The nauplii hatched from the cysts were cultured until adulthood under two salinities (150 and 250 g L?1) and two light treatments (PAR and PAR+UVR) in the laboratory. Finally, the Artemia were analyzed for their concentration of MAAs. In most of the cases, the higher salinity level applied was found to increase the MAA concentrations in both Artemia populations significantly. The acquisition efficiency of MAAs in both Artemia populations increased under exposure to UVR‐supplemented photosynthetically active radiation (PAR) compared to those raised under PAR, except for Porphyra‐334. It was observed that combination of UV radiation and elevated salinity significantly increased the bioaccumulation of MAAs. Thus, the presence of these compounds in these populations of Artemia may increase their adaptability for living in high‐UV and high‐salinity conditions prevailing in Lake Urmia. Higher concentrations of MAAs in the parthenogenetic population of Artemia could be probably attributed to its mono sex nature and higher adaptation capacities to extreme environmental conditions. 相似文献
180.
In a nanocomposite structure,it is anticipated that high damping can be achieved by taking advantage of the interfacial friction between the nanotubes and the polymer.The purpose of this paper is to investigate the structural damping characteristics of polymeric composites containing Carbon nanotubes(CNTs) with various kinds and amounts.The damping characteristics of the specimens with 0 wt% and 0.5 wt% nanotube contents were computed experimentally.Through comparing with neat resin specimens,the study show... 相似文献