Stochastic optimization of fiber reinforced composites considering uncertainties

Briefly, the two basic questions that this research is supposed to answer are: 1. Howmuch fiber is needed and how fibers should be distributed through a fiber reinforced composite (FRC) structure in order to obtain the optimal and reliable structural response? 2. How do uncertainties influence the optimization results and reliability of the structure? Giving answer to the above questions a double stage sequential optimization algorithm for finding the optimal content of short fiber reinforcements and their distribution in the composite structure, considering uncertain design parameters, is presented. In the first stage, the optimal amount of short fibers in a FRC structure with uniformly distributed fibers is conducted in the framework of a Reliability Based Design Optimization (RBDO) problem. Presented model considers material, structural and modeling uncertainties. In the second stage, the fiber distribution optimization (with the aim to further increase in structural reliability) is performed by defining a fiber distribution function through a Non-Uniform Rational BSpline (NURBS) surface. The advantages of using the NURBS surface as a fiber distribution function include: using the same data set for the optimization and analysis; high convergence rate due to the smoothness of the NURBS; mesh independency of the optimal layout; no need for any post processing technique and its non-heuristic nature. The output of stage 1 (the optimal fiber content for homogeneously distributed fibers) is considered as the input of stage 2. The output of stage 2 is the Reliability Index (b ) of the structure with the optimal fiber content and distribution. First order reliability method (in order to approximate the limit state function) as well as different material models including Rule of Mixtures, Mori-Tanaka, energy-based approach and stochastic multi-scales are implemented in different examples. The proposed combined model is able to capture the role of available uncertainties in FRC structures through a computationally efficient algorithm using all sequential, NURBS and sensitivity based techniques. The methodology is successfully implemented for interfacial shear stress optimization in sandwich beams and also for optimization of the internal cooling channels in a ceramic matrix composite. Finally, after some changes and modifications by combining Isogeometric Analysis, level set and point wise density mapping techniques, the computational framework is extended for topology optimization of piezoelectric / flexoelectric materials

Breeding waterbird populations of the islands of the Northern Persian Gulf, Iran.

In 2010, we estimated the breeding waterbird popula tions on the uninhabited islands of the northern Persian Gulf, some of the most important waterbird nesting sites in Southwest Asia. We also compared the 2010 census results with data from the 1970s. Over 120,000 breeding pairs of waterbirds of nine species were estimated on seven islands in 2010. The most abundant species were Bridled Tern Sterna anaethetus (74,113 pairs) and Lesser Crested Tern Sterna bengalensis (30,799 pairs). The results indicated that 20% of the global population of Crab Plover Dromas ardeola breed in the northern part of the Persian Gulf. The breeding population of White Cheeked Terns Sterna repressa had decreased by about 98% since the 1970s, while the populations of all the other species had increased. Further monitoring of the breeding waterbirds is needed in order to suggest appropriate measures for the conservation of these important waterbird populations. Compared with the situation in the 1970s, some islands are no longer suitable as nestingsites for waterbirds because of human exploitation, occupation by the military and development for the oil and gas industries

Association of miR-146a and miR196a2 genotype with susceptibility to idiopathic recurrent pregnancy loss in Iranian women: A case-control study

Background: Recurrent pregnancy loss (RPL) is the most common complaint of pregnancy in females with a prevalence of 5%. Numerous documents have shown that single nucleotide polymorphisms are able to change miRNA transcription and/or maturation, which may alter the incidence of disorders such as RPL. Objective: To assess the relationship of miR-146aC > G (rs2910164) and miR-196a2T > C (rs11614913) with RPL susceptibility in Iranian women. Materials and Methods: Blood samples were collected from 214 women who had experienced at least two consecutive spontaneous miscarriages (case) and 147 normal individuals without a history of miscarriage (control). MiR-146aC > G and miR-196a2T > C genotypes were evaluated via the restriction fragment length polymorphism technique. Results: The genotypes incidence did not show a significant difference in pre-miR-146aC > G polymorphism CC vs CG + GG (p = 0.854; OR = 0.933; 95% CI) and CC + CG vs GG (p = 0.282; OR = 1.454; 95% CI). Also, no significant difference was observed between pre-miR-196a2T > C polymorphism TT vs TC + CC (p = 0.862; OR = 0.938; 95% CI) and TT + TC vs CC and (p = 0.291; OR = 1.462; 95% CI) in both the case and control groups. Conclusion: The results showed that although the distribution of miR-146aC > G and miR-196a2T > C was different between the unknown RPL and control groups, these variances were not statistically significant. Key words: RPL, miR-146a, miR196a2, Polymorphism, RFLP