Ophthalmomyiasis is pathology of eye due to presence of fly larva, which rarely occurs in the world, and most cases has been reported in developing countries. These days incidence of Ophthalmomyiasis has been decreased in Iran. Most cases of Ophthalmomyiasis caused by presence of fly Larvae Oestrus Ovis.In summer 2011, a fourty year old rural woman with a good hygine presented to Ophthalmology department of Rouhani Hospital. She had no background of any disease.After physical examination External Ophthalmomyiasis was diagnosed. all seven larva has been removed, Topical antibiotic and corticosteroid were prescribed for daily use. Two days later in follow up the eye was asymptomatic.

Power stations with high heads are nowadays almost without exception designed so as to have one pipeline, or only very few pipelines, supplying the water to the generating station. The penstocks is connected to a distributor, which has the task of distributing the flow, with the lowest possible losses of energy, to the individual turbines. The function and location of this section of the plant make it understandable that its safety is regarded as a matter of outstanding importance. Furthermore, well-substantiated method of computation and experimental stress and instability investigations make it possible to control stresses occurring in the complicated bifurcations. Thus adequate safety and economical design of the construction methods are ensured by suitable matching of stress levels to the properties of the thin walled structure and materials used. Generally, in this type of structures, External pressures can occur either during the tunnel grouting operation or on tunnel dewatering after a prolonged period of use, and very often it is the External rather than the internal pressure that determines thickness of the steel liner. In cases where a substantial increase in liner thickness would be required to prevent buckling due to External pressure, it may be more economical to provide External stiffener ribs. A 4-node Quasi-conforming stress/strain resultant shell element, 4-node assumed strain shell elements are developed and implemented for the nonlinear static solution of stability problems of stiffened plates and shells. The geometric non-linear shell elements, which are based on the updated Lagrangian method. The formulation of these elements uses Mindlin-Reissner theory, which the formulation of the linear and geometrical stiffness is exactly defined by incorporating membrane forces, bending moment and transverse shear resultant forces. In order to remove rigid body rotations, the co-rotational method is used. The material is assumed to be isotropic and elastic material. By using six degrees of freedom per node, the present element can model stiffened plate and shell structures. Linear analysis and large deformation analysis of the elastic shell using 4-node quasi-conforming shell element are carried out.

The aim of this paper is to determine the critical buckling load for simply supported thin shallow spherical shells made of functionally graded material (FGM) subjected to uniform External pressure. A metal-ceramic functionally graded (FG) shell with a power law distribution for volume fraction is considered, where its properties vary gradually through the shell thickness direction from pure metal on the inner surface to pure ceramic on the outer surface. First, the total potential energy functional is obtained using the first-order shell theory of Love and Kirchhoff, Donnell-Mushtari-Vlasov kinematic equations and Hooke's Law. Then, equilibrium equations are derived through the minimization of the total potential energy functional by employing the Euler equations. The stability equations are derived by application of the adjacent-equilibrium criterion. As the nonlinear strain-displacement relations are employed, so the presented analysis is nonlinear with high accuracy. The Galerkin method is used to determine the critical buckling load. The present problem is also analyzed numerically by simulating it in Abaqus software. For validation, the present analytical results are compared with the present numerical results and with the known data in the literature. Also, the effects of some important geometrical and mechanical parameters on the hydrostatic buckling pressure are investigated.

In this study, the analysis, manufacturing and experimental buckling test of a composite warhead subjected to External pressure and axial load are investigated. Variation of angle and thickness along the none length are obtained, also the optimum filament winding design is achieved by considering minimum disordered patterns and wasting materials. In continue the static and buckling analysis of the composite warhead is performed using FEM software with Eigen value Analysis. The variation of the wound angle and the thickness are surveyed and the optimum angle is extracted. The composite warhead is manufactured based on the optimum angle. The process and equipments of the External pressure test are designed and the composite warhead is tested. The obtained buckling results of the FEM and the experimental are compared and also the efficiency of this method in prediction of buckling behavior of the composite warhead is demonstrated.

One of the common failure modes of thin cylindrical shell subjected External pressure is buckling. The buckling pressure of these shell structures are dominantly affected by the geometrical imperfections present in the cylindrical shell which are very difficult to alleviate during manufacturing process. In this work, only three types of geometrical imperfection patterns are considered namely (a) eigen affine mode imperfection pattern, (b) inward half lobe axisymmetric imperfection pattern extended throughout the height of the cylindrical shell and (c) local geometrical imperfection patterns such as inward dimple with varying wave lengths located at the mid-height of the cylindrical shell. ANSYS FE non-linear buckling analysis including both material and geometrical non-linearities is used to determine the critical buckling pressure. From the analysis it is found that when the maximum amplitude of imperfections is 1t, the eigen affine imperfection pattern gives out the lowest critical buckling pressure when compared to the other imperfection patterns considered When the amplitude of imperfections is above 1t, the inner half lobe axisymmetric imperfection pattern gives out the lowest critical buckling pressure when compared to the other imperfection patterns considered.

In recently years, Stiffened cylindrical shells are used in the major components of aviation, missile and marine structures. In this study has been analyzed buckling of composite lattice cylinder with inner and outer shell under External pressure. This was accomplished by developing an analytical model for determination of the equivalent stiffness parameters of a grid stiffened composite cylindrical shell. This stiffness contribution of the stiffeners was superimposed with the stiffness contribution of the shell to obtain the equivalent stiffness parameters of the whole panel. Equations governing the cylindrical lattice structures are solved based on the displacement and stress-strain relations in the form of a matrix using classical shell theory under boundary conditions clamp supported and simply supported. The results show increase in grid cell length, angle and cross-section parameters caused increase in stiffness and critical buckling load but increase further them cause local and global buckling. Finally for all of them can be considered optimal value and for prevent local and global buckling and the effectiveness of the lattice structure to a limited number of stiffener with optimal angle, longitudinal and cross sections required.

1. Introduction Structural applications of composite materials are used in various structures of the oil and gas industry, water supply and sewage systems and a wide range of industries, such as marine, aerospace, and military industries. Experimental and numerical studies show that structural buckling failure is the major dangerous action for thin-walled cylindrical shells. Uniform lateral loading in tanks occurs when tanks are in a state of liquid discharge. Moreover, if special contrivances such as the drainage valves do not work or properly, then buckling phenomenon and will cause an overall failure in the tank. There is extensive research on the buckling and post-buckling of thin-walled steel tanks under External pressure, but research on composite cylindrical shells is very low. The only studies in the context of buckling of External pressure are done, by Hur et al. (2008) and Moreno et al. (2008), with the difference that in both studies, the type of material and loading is different from the present study. In this paper, the effect of the L/R geometrical parameters on the buckling behavior of GFRP cylindrical tanks will be studied...