Three-dimensional analysis of 0/90s and 90/0s laminates with a central circular hole

Stress distributions were calculated near a circular hole in laminates, using a three dimensional finite element analysis. These stress distributions were presented three ways: through the thickness at the hole boundary, along radial lines at the 0/90 and 90/0 interfaces, and around the hole at these interfaces. The interlaminar normal stress, and the shear stress, distributions had very steep gradients near the hole boundary, suggesting interlaminar stress singularities. The largest compressive stress occurred at about 60 deg from the load axis. A simple procedure was introduced to calculate interlaminar stresses near the hole boundary. It used stresses calculated by an exact two dimensional analysis of a laminate with a hole as input to a quasi three dimensional model. It produced stresses that agreed closely with those from the three dimensional finite element model

Convergence of strain energy release rate components for edge-delaminated composite laminates

Strain energy release rates for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial strain was studied. The individual components of the strain energy release rates did not show convergence as the delamination tip elements were made smaller. In contrast, the total strain energy release rate converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes

Stress-concentration factors for finite orthotropic laminates with a pin-loaded hole

Stresses were calculated for finite size orthotropic laminates loaded by a frictionless steel pin in a circular hole of the same diameter. The calculations were based on finite element analyses for six laminates. Stress concentration factors, based on nominal bearing stress, were determined for wide ranges of the ratios of width to diameter, w/d and edge distance to diameter, e/d. An infinite laminate case was analyzed for each laminate. Orthotropy had a significant influence on the tensile stress concentration at the hole. For example, the stress concentration factors for the infinite laminate cases ranged from 0.82 to 2.16, compared with 0.87 for the quasi-isotropic laminate. The finite widths and edge distances strongly influenced the tensile stress concentration. For the practical range w/d or = 3, the peak tensile stresses were as much as 80% larger than the infinite laminate reference value. For e/d or = 3, these stresses were amplified by as much as 50%. In contrast, the finite width and edge distance had little effect on shear-out and bearing stress concentrations

A clinical study of closed reduction and percutaneous Kirschner wire fixation of displaced supracondylar fractures of humerus in children

Background: Supracondylar fractures of the humerus are the most common fracture pattern of the elbow in children. Displaced supracondylar fractures are notorious for difficulty in reduction, maintenance of reduction and frequent involvement of neurovascular structures. The purpose of this study was to evaluate the results of stabilization of these fractures by closed reduction and percutaneous Kirschner wire fixation.Methods: Thirty cases of displaced supracondylar humerus fractures were included in the study. The mean age of the patient was 8.3 years [ranges from 4-14 years]. The male to female ratio was 2:1 and left side was involved in 23 cases whereas 7 had right sided injuries. All fractures were of extension type [Gartland’s type III]. Posteromedial displacement was noted in 22 cases whereas 8 fractures were posterolaterally displaced. In 20 cases, lateral entry wires alone were used whereas in 10 cases one lateral and one medial K-wire were used. K- wires were removed after 3 weeks post-operatively and follow-up was done at 6 weeks,12 weeks, 6 months and 12 months, when they  were evaluated according to Flynn’s criteria.Results: Results were graded using Flynn’s criteria. Excellent results were achieved in 18 [60%], good in 6 [20%] fair in 4 [13.3%], while poor results were seen in 2 [6.7%] patients.Conclusions: Closed reduction and percutaneous fixation using Kirschner wires is a safe and efficient method for fixation of displaced supracondylar fractures of the humerus in children.

Intellectual Disability

Intellectual disability is a disability that occurs before age 18. People with this disability experience significant limitations in two main areas: 1) Intellectual functioning and 2) Adaptive behavior. These limitations are expressed in the person\u27s conceptual, social and practical everyday living skills. A number of people with intellectual disability are mildly affected, making the disability difficult to recognize without visual cues. Intellectual disability is diagnosed through the use of standardized tests of intelligence and adaptive behavior. In this article, we will examine the symptoms and causes of intellectual disability and go through the diagnosis of intellectual disability using standardized tests of intelligence and discuss the role of the community environment and needed support

Content-Centric Networking at Internet Scale through The Integration of Name Resolution and Routing

We introduce CCN-RAMP (Routing to Anchors Matching Prefixes), a new approach to content-centric networking. CCN-RAMP offers all the advantages of the Named Data Networking (NDN) and Content-Centric Networking (CCNx) but eliminates the need to either use Pending Interest Tables (PIT) or lookup large Forwarding Information Bases (FIB) listing name prefixes in order to forward Interests. CCN-RAMP uses small forwarding tables listing anonymous sources of Interests and the locations of name prefixes. Such tables are immune to Interest-flooding attacks and are smaller than the FIBs used to list IP address ranges in the Internet. We show that no forwarding loops can occur with CCN-RAMP, and that Interests flow over the same routes that NDN and CCNx would maintain using large FIBs. The results of simulation experiments comparing NDN with CCN-RAMP based on ndnSIM show that CCN-RAMP requires forwarding state that is orders of magnitude smaller than what NDN requires, and attains even better performance

Studies of new media radiation induced laser

Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed