A parametric study on the buckling of functionally graded material plates with internal discontinuities using the partition of unity method

In this paper, the effect of local defects, viz., cracks and cutouts on the buckling behaviour of functionally graded material plates subjected to mechanical and thermal load is numerically studied. The internal discontinuities, viz., cracks and cutouts are represented independent of the mesh within the framework of the extended finite element method and an enriched shear flexible 4-noded quadrilateral element is used for the spatial discretization. The properties are assumed to vary only in the thickness direction and the effective properties are estimated using the Mori-Tanaka homogenization scheme. The plate kinematics is based on the first order shear deformation theory. The influence of various parameters, viz., the crack length and its location, the cutout radius and its position, the plate aspect ratio and the plate thickness on the critical buckling load is studied. The effect of various boundary conditions is also studied. The numerical results obtained reveal that the critical buckling load decreases with increase in the crack length, the cutout radius and the material gradient index. This is attributed to the degradation in the stiffness either due to the presence of local defects or due to the change in the material composition.Comment: arXiv admin note: text overlap with arXiv:1301.2003, arXiv:1107.390

Photonic bandgap materials: design, fabrication, and characterization

The last few decades have seen a tremendous explosion in the area of new synthetic materials. As we begin to better understand the nature of the atomic and molecular bonds it has been possible to systematically search for materials with specific properties thanks to the availability of powerful supercomputers. Due to significant advances in materials synthesis a rich variety of artificial materials whose mechanical, chemical, electronic and optical properties can be suitably tailored can now be produced. Some of the materials (plastics, synthetic fibers, ceramics, alloys etc.) can replace or substitute traditional materials; some others have managed to create new applications themselves (semiconductors, superconductors, optical fibers etc.). Over the last decade there has been a growing interest in a new material called photonic bandgap structures which can manipulate light in an extraordinary way opening up new possibilities in the area of optics and optoelectronics, eventually paving the way for optical computing. Proof of principle structures that demonstrates the expected property has been successfully fabricated for low frequency electromagnetic waves. However, making photonic bandgap structures that can operate at visible frequency is quite challenging. This is because photonic bandgap material are essentially periodic dielectric structures where the periodicity is on the order of the wavelength of light. The goal of this dissertation is to develop a technique for the fabrication inverse FCC photonic crystals that can operate at the visible and near infrared frequencies. The technique essentially focuses on employing self organizing systems such as monodisperse colloidal systems of polystyrene microspheres as a basis for forming periodic structure at submicron dimensions. The main aspects are first to show that the experimental procedure for fabrication developed in this dissertation actually has the desired structural property. Demonstration of structural properties is done by means of optical microscopy and scanning electron microscopy. The other aspect is to demonstrate that the photonic structure so produced indeed shows effects due to photonic bandgap. Optical spectroscopy of the samples is used to show that these samples indeed show the pseudogap that has been theoretically predicted for photonic crystals made with the materials used

Bending and vibration of functionally graded material sandwich plates using an accurate theory

In this paper, the bending and the free flexural vibration behaviour of sandwich functionally graded material (FGM) plates are investigated using QUAD-8 shear flexible element developed based on higher order structural theory. This theory accounts for the realistic variation of the displacements through the thickness. The governing equations obtained here are solved for static analysis considering two types of sandwich FGM plates, viz., homogeneous face sheets with FGM core and FGM face sheets with homogeneous hard core. The in-plane and rotary inertia terms are considered for vibration studies. The accuracy of the present formulation is tested considering the problems for which three-dimensional elasticity solutions are available. A detailed numerical study is carried out based on various higher-order models to examine the influence of the gradient index and the plate aspect ratio on the global/local response of different sandwich FGM plates.Comment: 28 pages, 6 figures, 9 table

Soil bacterial communities of a calcium-supplemented and a reference watershed at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA

Soil Ca depletion because of acidic deposition-related soil chemistry changes has led to the decline of forest productivity and carbon sequestration in the northeastern USA. In 1999, acidic watershed (WS) 1 at the Hubbard Brook Experimental Forest (HBEF), NH, USA was amended with Ca silicate to restore soil Ca pools. In 2006, soil samples were collected from the Ca-amended (WS1) and reference watershed (WS3) for comparison of bacterial community composition between the two watersheds. The sites were about 125 m apart and were known to have similar stream chemistry and tree populations before Ca amendment. Ca-amended soil had higher Ca and P, and lower Al and acidity as compared with the reference soils. Analysis of bacterial populations by PhyloChip revealed that the bacterial community structure in the Ca-amended and the reference soils was significantly different and that the differences were more pronounced in the mineral soils. Overall, the relative abundance of 300 taxa was significantly affected. Numbers of detectable taxa in families such as Acidobacteriaceae, Comamonadaceae, and Pseudomonadaceae were lower in the Ca-amended soils, while Flavobacteriaceae and Geobacteraceae were higher. The other functionally important groups, e.g. ammonia-oxidizing Nitrosomonadaceae, had lower numbers of taxa in the Ca-amended organic soil but higher in the mineral soil

Linear free flexural vibration of cracked functionally graded plates in thermal environment

In this paper, the linear free flexural vibrations of functionally graded material plates with a through center crack is studied using an 8-noded shear flexible element. The material properties are assumed to be temperature dependent and graded in the thickness direction. The effective material properties are estimated using the Mori-Tanaka homogenization scheme. The formulation is developed based on first-order shear deformation theory. The shear correction factors are evaluated employing the energy equivalence principle. The variation of the plates natural frequency is studied considering various parameters such as the crack length, plate aspect ratio, skew angle, temperature, thickness and boundary conditions. The results obtained here reveal that the natural frequency of the plate decreases with increase in temperature gradient, crack length and gradient index

Induced genetic diversity in banana

Induced genetic diversity in banana.Peer reviewe

Reliability of biometry.

INTRODUCTION: The refractive power of Pseudophakos is final and the patient must live with any mistake committed (or) be subjected to a very dangerous operation, namely, to the removal and replacement of the intraocular lens (IOL). To ensure that our patient will have the optimal correction, the power of the lens to be implanted must be determined precisely and perfectly in every case. AIM OF THE STUDY: To study the reliability of A–scan biometry in Tertiary Institution where measurements were taken by multiple persons. MATERIALS AND METHODS: A retrospective series of 110 cases of cataract extraction and in the bag fixation of the IOL done in RIO-GOH were investigated. Cataract extraction done by 1) extra capsular cataract extraction 2) small incision cataract surgery and 3) phacoemulsification were included in the study. CONCLUSION: With the evolution of small incision techniques that minimize surgically induced astigmatism, IOL power selection becomes a crucial step for the refractive outcome of cataract surgery. The present study has shown that in Institution where multiple persons perform Biometry chances of postoperative refractive error can be minimized if precise and proper technique is followed and it is possible to have prediction errors below 1.00 D on the average. The chance of postoperative refractive error could be further reduced if SRK T formula is used for IOL power calculation