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481.
Ganesh Soni Ramesh Singh Mira Mitra Brian G. Falzon 《International Journal of Solids and Structures》2014
A three-dimensional multi-fibre multi-layer micromechanical finite element model was developed for the prediction of mechanical behaviour and damage response of composite laminates. Material response and micro-scale damage mechanism of cross-ply, [0/90]ns, and angle-ply, [±45]ns, glass-fibre/epoxy laminates were captured using multi-scale modelling via computational micromechanics. The framework of the homogenization theory for periodic media was used for the analysis of the proposed ‘multi-fibre multi-layer representative volume element’ (M2RVE). Each layer in M2RVE was represented by a unit cube with multiple randomly distributed, but longitudinally aligned, fibres of equal diameter and with a volume fraction corresponding to that of each lamina (equal in the present case). Periodic boundary conditions were applied to all the faces of the M2RVE. The non-homogeneous stress–strain fields within the M2RVE were related to the average stresses and strains by using Gauss’ theorem in conjunction with the Hill–Mandal strain energy equivalence principle. The global material response predicted by the M2RVE was found to be in good agreement with experimental results for both laminates. The model was used to study effect of matrix friction angle and cohesive strength of the fibre–matrix interface on the global material response. In addition, the M2RVE was also used to predict initiation and propagation of fibre–matrix interfacial decohesion and propagation at every point in the laminae. 相似文献
482.
José A. Gálvez Asun Jiménez Pablo Mira 《Calculus of Variations and Partial Differential Equations》2012,44(3-4):577-599
Let Ω denote the upper half-plane ${\mathbb{R}_+^2}$ or the upper half-disk ${D_{\varepsilon}^+\subset \mathbb{R}_+^2}$ of center 0 and radius ${\varepsilon}$ . In this paper we classify the solutions ${v\in\;C^2(\overline{\Omega}\setminus\{0\})}$ to the Neumann problem $$\left\{\begin{array}{lll}{\Delta v+2 Ke^v=0\quad {\rm in}\,\Omega\subseteq \mathbb{R}^2_+=\{(s, t)\in \mathbb{R}^2: t >0 \},}\\ {\frac{\partial v}{\partial t}=c_1e^{v/2}\quad\quad\quad{\rm on}\,\partial\Omega\cap\{s >0 \},}\\ {\frac{\partial v}{\partial t}=c_2e^{v/2}\quad\quad\quad{\rm on}\,\partial\Omega\cap\{s <0 \},}\end{array}\right.$$ where ${K, c_1, c_2 \in \mathbb{R}}$ , with the finite energy condition ${\int_{\Omega} e^v < \infty}$ As a result, we classify the conformal Riemannian metrics of constant curvature and finite area on a half-plane that have a finite number of boundary singularities, not assumed a priori to be conical, and constant geodesic curvature along each boundary arc. 相似文献
483.
An easy, simple and versatile one step synthesis of 3‐(2‐oxo‐2H‐chromen‐3‐yl)‐6H,8H‐pyrimido[4,5‐c]‐pyridazine‐5,7‐diones is reported by reaction of 3‐acetylcoumarins ( 1 ) with alloxan monohydrate ( 2 ) in acetic acid followed by hydrazine hydrate. 相似文献
484.
V. Rajeswar Rao M. Madan Mohan Reddy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):461-471
3-acetyl coumarins on condensation with various aromatic aldehydes in the presence of piperidine gave corresponding chalcones in a solid state under solvent free conditions. These chalcones are isolated and characterized. The in-situ-formed chalcones (1) are also converted into corresponding 2-aryl-4-[2H-2-oxo[1]benzopyran-3-yl]-2,3-dihydro (3) and 2,5-dihydro-1,5-benzothiazepines (4) in one step by interacting with orthoamino thiophenol. Both the 2,3-dihydro (3) and 2,5-dihydrobenzothiazepines (4) have been converted into same tetrahydrobenzothiazepine (5). Finally, the tetrahydrobenzo thiazepine (5) is converted into its acetyl derivative (11). The structures of the title compounds have been confirmed on the basis of their microanalytical, IR, 1 H NMR, and mass spectral data. 相似文献
485.
A simple, sensitive and selective spectrophotometric method for determination of molybdenum is described. A solution containing 100 mug of Mo in 2.5M hydrochloric acid is treated with ascorbic acid and ammonium thiocyanate and after standing for 8 min is shaken with an equal volume of ethyl methyl ketone for 30 sec. The absorbance of the complex is measured at 465 nm against a reagent blank. The complex is stable for 1 hour. There is no interference from Re(VII), SO(2-)(4), Cl(-), CH(3)COO(-), PO(3-)(4), NO(-)(3), C(2)O(2-)(4), citrate or tartrate, and at least 5 mg of U(VI), 10 mg of Cr(III, VI), Th, or Ni, and 20 mg of W(VI) Can be tolerated. Vanadium(V) interferes at the 500 mug level, and fluoride slightly decreases the absorbance. 相似文献
486.
In this paper we prove a strong law of large numbers for Borel measurable nonseparably valued random elements in the case of Banach space valued fuzzy random variables. 相似文献
487.
C H Cheng M S Madan Y Gupta S So 《The Journal of the Operational Research Society》2001,52(8):952-959
In this research, we formulate and solve a type of the capacitated lot-sizing problem. We present a general model for the lot-sizing problem with backorder options, that can take into consideration various types of production capacities such as regular time, overtime and subcontracting. The objective is to determine lot sizes that will minimize the sum of setup costs, holding cost, backorder cost, regular time production costs, and overtime production costs, subject to resource constraints. Most existing formulations for the problem consider the special case of the problem where a single source of production capacity is considered. However, allowing for the use of alternate capacities such as overtime is quite common in many manufacturing settings. Hence, we provide a formulation that includes consideration of multiple sources of production capacity. We develop a heuristic based on the special structure of fixed charge transportation problem. The performance of our algorithm is evaluated by comparing the heuristic solution value to lower bound value. Extensive computational results are presented. 相似文献
488.
Sorption of51Cr(VI) by MnO2 has been studied as a function of pH and ionic concentration in the presence of certain added cations and anions. The findings are explained in the light of deprotonation/hydroxyl ion association reaction on oxide surface and its subsequent interaction with the tracer. Infrared spectroscopy has shown the chemical interaction of Cr(VI) on the surface of MnO2. The influence of certain interfering ions has been shown on the sorption of51Cr(VI) on MnO2 surface. An attempt has been made to concentrate traces of51Cr under optimum experimental conditions. The experimental observation shows that the activity sorbed under specified conditions can be recovered appreciably by leaching the pre-adsorbed carrier. 相似文献
489.
Very fine SnO2 powders were produced by (a) slow and (b) forced hydrolysis of aqueous SnCl4 solutions and (c) hydrolysis of tin(IV)-isopropoxide dissolved in isopropanol (sol-gel route) and then characterized by X-ray powder diffraction, Fourier transform infrared and laser Raman spectroscopies, TEM and BET. The XRD patterns showed the presence of the cassiterite structure. As found from XRD line broadening the crystallite sizes of all powders were in the nanometric range. TEM results also showed that the sizes of SnO2 particles in all powders are in nanometric range. Very fine SnO2 powders showed different features in the FT-IR spectra, depending on the route of their synthesis. The reference Raman spectrum of SnO2 showed four bands at 773, 630, 472 and 86 (shoulder) cm−1, as predicted by group theory. Very fine SnO2 powders showed additional Raman bands, in dependence on their synthesis. The broad Raman band at 571 cm−1 was ascribed to amorphous tin(IV)-hydrous oxide. The additional Raman bands at 500, 435 and 327 cm−1 were recorded for nanosized SnO2 particles produced by forced hydrolysis of SnCl4 solutions. However, these additional Raman bands were not observed for nanosized SnO2 particles produced by slow hydrolysis of SnCl4 solution or the sol-gel route. The aggregation effects of nanosized particles were considered in the interpretation of the Raman band at 327 cm−1. The method of low frequency Raman scattering was applied for SnO2 particle size determination. On the basis of these measurements it was concluded that the size of SnO2 particles was also in the nanometric range and that, the sol-gel particles heated to 400 °C consisted of several SnO2 crystallites. 相似文献
490.