A pressurized cylindrical shell with a fixed end which contains an axial part-through or through crack

A cylindrical shell having a very stiff and plate or a flange is considered. It is assumed that near the end the cylinder contains an axial flaw which may be modeled as a part through surface crack or a through crack. The effect of the end constraining on the stress intensity factor which is the main fracture mechanics parameter is studied. The applied loads acting on the cylinder are assumed to be axisymmetric. Thus the crack problem under consideration is symmetric with respect to the plane of the crack and consequently only the Mode 1 stress intensity factors are nonzero. With this limitation, the general perturbation problem for a cylinder with a built in end containing an axial crack is considered. Reissner's shell theory is used to formulate the problem. The part through crack problem is treated by using a line spring model. In the case of a crack tip terminating at the fixed end it is shown that the integral equations of the shell problem has the same generalized Cauchy kernel as the corresponding plane stress elasticity problem

The crack problem in a reinforced cylindrical shell

In this paper a partially reinforced cylinder containing an axial through crack is considered. The reinforcement is assumed to be fully bonded to the main cylinder. The composite cylinder is thus modelled by a nonhomogeneous shell having a step change in the elastic properties at the z=0 plane, z being the axial coordinate. Using a Reissner type transverse shear theory the problem is reduced to a pair of singular integral equations. In the special case of a crack tip touching the bimaterial interface it is shown that the dominant parts of the kernels of the integral equations associated with both membrane loading and bending of the shell reduce to the generalized Cauchy kernel obtained for the corresponding plane stress case. The integral equations are solved and the stress intensity factors are given for various crack and shell dimensions. A bonded fiberglass reinforcement which may serve as a crack arrestor is used as an example

A note on the cracked plates reinforced by a line stiffener

The problem of a cracked plate reinforced by a line stiffener is reconsidered. The original solution of this problem was given in the literature. Also, a variation of the problem with debonding between the plate and the stiffener near the cracked region was reported in the literature. However, the special case of the problem in which the crack tip terminates at the stiffener does not appear to have been studied. In practice, the solution may be necessary in order to assess the crack arrest effectiveness of the stiffener. The problem of a stiffened plate with a crack is reformulated, the asymptotic stress state near the crack tip terminating at the stiffener is examined, and numerical results are given for various stiffness constants

The crack problem in a reinforced cylindrical shell

A partially reinforced cylinder containing an axial through crack is considered. The reinforcement is assumed to be fully bonded to the main cylinder. The composite cylinder is thus modelled by a nonhomogeneous shell having a step change in the elastic properties at the z = 0 plane, z being the axial coordinate. Using a Reissner type transverse shear theory the problem is reduced to a pair of singular integral equations. In the special case of a crack tip touching the bimaterial interface it is shown that the dominant parts of the kernels of the integral equations associated with both membrane loading and bending of the shell reduce to the generalized Cauchy kernel obtained for the corresponding plane stress case. The integral equations are solved and the stress intensity factors are given for various crack and shell dimensions. A bonded fiberglass reinforcement which may serve as a crack arrestor is used as an example

A cylindrical shell with an arbitrarily oriented crack

The general problem of a shallow shell with constant curvatures is considered. It is assumed that the shell contains an arbitrarily oriented through crack and the material is specially orthotropic. The nonsymmetric problem is solved for arbitrary self equilibrating crack surface tractions, which, added to an appropriate solution for an uncracked shell, would give the result for a cracked shell under most general loading conditions. The problem is reduced to a system of five singular integral equations in a set of unknown functions representing relative displacements and rotations on the crack surfaces. The stress state around the crack tip is asymptotically analyzed and it is shown that the results are identical to those obtained from the two dimensional in plane and antiplane elasticity solutions. The numerical results are given for a cylindrical shell containing an arbitrarily oriented through crack. Some sample results showing the effect of the Poisson's ratio and the material orthotropy are also presented

Effects of L-Carnitine on Growth of Individually Cultured Cladoceran, Moina micrura

The cladoceran, Moina micrura, is a potential alternative live food for fish larvae. The effects of L-carnitine enrichment on first reproduction age, population density, and growth rate in M. micrura were determined. The cladocerans were enriched at 10 levels of L-carnitine (0, 0.001, 0.01, 0.1, 1, 10, 100, 500, 1000, and 1500 mg/l) dissolved in 30 ml Chlorella vulgaris culture medium for 17 days. The first reproduction age was stimulated by the supplemental L-carnitine. The population density was highest in the 1 mg/l treatment. The highest population growth rate was obtained in the 10 mg/l treatment, but it did not differ from the growth rate in the 0.1, 1, or 100 mg/l treatments. Consequently, the optimum L-carnitine concentration for M. micrura is 1 mg/l. Results suggest that L-carnitine can be a positive factor in enhancing the use of M. micrura as an alternative live food for fish larvae

Competitive Aggressiveness of Contractors: A Study of Indonesia

AbstractHigh level of competition are consideredto be a major challenge for contractors. As such, ‘winning the competition’ is an important goal for contractors in running their businesses. Contractors need to be aggressive in competition to respond to their competitors’ actions and gain competitive advantage against their business rivals for survival and growth. This study aims to clarify the issue of competitive aggressiveness of contractors by identifyingits key factors. Semi-structured interviews were carried out with 19 top managers of contracting companies in Indonesia, in order to explore the concept of contractors’ competitive aggressiveness. The qualitative data collected during the interviews were analysed using an inductive thematic analysis method. The analysis resulted in identifying five key factors of contractors’competitive aggressiveness: 1) acting as a problem solver for clients; 2) being different compared to competitors; 3) building and maintaining clients’ confidence in the company's trustworthiness and reliability; 4) maintaining good relationships with clients; and 5) positioning on markets that are concerned about quality. Based on these findings, contractors will be able to establish an appropriate strategy to allow them to be aggressive in competition

Highly senstivive determination of 2.4,6-Trinitrotolunene and Related Byproducts Using a Diol Functionalized Column for High Performance Liquid Chromatography

Cataloged from PDF version of article.In this work, a new detection method for complete separation of 2,4,6-trinitrotoluene (TNT); 2,4-dinitrotoluene (2,4-DNT); 2,6-dinitrotoluene (2,6-DNT); 2-aminodinitrotoluene (2-ADNT) and 4-aminodinitrotoluene (4-ADNT) molecules in high-performance liquid-chromatography (HPLC) with UV sensor has been developed using diol column. This approach improves on cost, time, and sensitivity over the existing methods, providing a simple and effective alternative. Total analysis time was less than 13 minutes including column re-equilibration between runs, in which water and acetonitrile were used as gradient elution solvents. Under optimized conditions, the minimum resolution between 2,4-DNT and 2,6-DNT peaks was 2.06. The recovery rates for spiked environmental samples were between 95-98%. The detection limits for diol column ranged from 0.78 to 1.17 μg/L for TNT and its byproducts. While the solvent consumption was 26.4 mL/min for two-phase EPA and 30 mL/min for EPA 8330 methods, it was only 8.8 mL/min for diol column. The resolution was improved up to 49% respect to two-phase EPA and EPA 8330 methods. When compared to C-18 and phenyl-3 columns, solvent usage was reduced up to 64% using diol column and resolution was enhanced approximately two-fold. The sensitivity of diol column was afforded by the hydroxyl groups on polyol layer, joining the formation of charge-transfer complexes with nitroaromatic compounds according to acceptor-donor interactions. Having compliance with current requirements, the proposed method demonstrates sensitive and robust separation. © 2014 Gumuscu et al