Cross section design of holey optical fibers with coating based on stress analysis in tension

In this paper, the mechanical behavior of newly developed holey optical fibers with and without coating was investigated by numerical analysis. Based on experimental work, the tensile failure characteristics were observed. The stress characteristics of some typical holey fibers with different section design were studied though the finite element method under tensile load. The optimum design of air hole arrangements and sizes were proposed according to the numerical results. The influence of the coating thickness on the axial stress of holey optical fiber was also investigated. The numerical results and conclusions will be useful for the cross section optimum design of holey optical fiber for increase its strength

Analysis of fracture damage in silica optical fibers

Microstructured optical fibres (with a periodic transverse microstructure) are of interest since they offer a simple alternative to controlling the index profile of optical waveguides. Although many types of optical fibres and cables have been developed to meet the needs of communications service providers for longterm performance and reliable operation, the brittle nature, aging and fatigue of these fibres, remains to be the key materials issues. The flaws on the surface of fibres caused by processing (drawing) or subsequent assembling make the situation more complex. In this work, experimental investigation and fracture mechanics analysis have been conducted to understand the fracture behavior of these newly developed optical fibres. The results are believed to be useful for design, fabrication and evaluation of optical fibres for a variety of applications

Estimating the H I gas fractions of galaxies in the local Universe

We use a sample of 800 galaxies with H I mass measurements from the HyperLeda catalogue and optical photometry from the fourth data release of the Sloan Digital Sky Survey to calibrate a new photometric estimator of the H I to-stellar mass ratio for nearby galaxies. Our estimator, which is motivated by the Kennicutt-Schmidt star formation law, is log(G_{HI}/S) = -1.73238(g-r) + 0.215182mu_i - 4.08451, where mu_i is the i-band surface brighteness and g-r is the optical colour estimated from the g- and r-band Petrosian apparent agnitudes. This estimator has a scatter of sigma = 0.31 dex in log(G_{HI}/S), compared to sigma ~ 0.4 dex for previous estimators that were based on colour alone. We investigate whether the residuals in our estimate of log(G_{HI}/S) depend in a systematic way on a variety of different galaxy properties. We find no effect as a function of stellar mass or 4000A break strength, but there is a systematic effect as a function of the concentration index of the light. We then apply our estimator to a sample of 10^5 emission-line galaxies in the SDSS DR4 and derive an estimate of the H I mass function, which is in excellent agreement with recent results from H I blind surveys. Finally, we re-examine the well-known relation between gas-phase metallicity and stellar mass and ask whether there is a dependence on H I-to-stellar mass ratio, as predicted by chemical evolution models. We do find that gas-poor galaxies are more metal rich at fixed stellar mass. We compare our results with the semi-analytic models of De Lucia & Blaizot, which include supernova feedback, as well as the cosmological infall of gas.Comment: 12 pages, 9 figures, accepted for publication in MNRA

Product market competition returns to skill and wage inequality

This paper shows that increasing product market competition can have a direct impact on the employment relationship and on wage inequality. I develop a simple model in which an increase in product market competition increases returns to skill through the effect of competition on the sensitivity of profits to cost reductions. I then show empirically that relative wages increase with competition using a large panel of United Kingdom workers with complete work histories. I identify the impact of competition on returns to skill in the panel, using two exogenous measures of competition provided by two quasi-natural experiments. Quantile regressions indicate that increased competition also raised returns to unobserved ability

Effects of surface cracks and coating on fracture behaviour of microstructured silica optical fibers

The fracture behavior of microstructured silica optical fibers containing surface cracks in tension was investigated using a simplified 3D analysis. Strengthening caused by the polymer coating was considered to be associated with the closure stresses uniformly applied to the crack surfaces, which were generally created by the thermal mismatch between the coating resin and the silica glass. The stress intensity factor of the surface cracks in tension was evaluated with considering the crack configurations and surface coating. The effects of crack configurations and closure stresses on the failure loads were also discussed

A Simplified Solution Method for End-of-Term Storage Energy Maximization Model of Cascaded Reservoirs

In medium-term scheduling, the end-of-term storage energy maximization model is proposed to create conditions for the safety, stability and economic operation of the hydropower system after control term, which satisfies the system load demand undertaken by the cascaded system in a given scheduling period. This paper presents a simplified solution method based on the Lagrangian relaxation method (LR) to solve the end-of-term storage energy maximization model. The original Lagrange dual problem with multiple Lagrange multipliers is converted to that with only one Lagrange multiplier by an entropy-based aggregate function method, which relaxes the complex cascaded hydropower system load balance constraints. The subgradient method and successive approximation of dynamic programming (DPSA) are adopted to update the Lagrange multiplier iteratively and solve the subproblem of the Lagrange dual problem, respectively. The Wujiang cascaded hydropower system is studied, and the result shows that the simplified solution method for the end-of-term storage energy maximization model both improves solving efficiency and ensures solving accuracy to a great extent

Nonlinear analysis of a Ball Grid Array package under thermal cycles

In this study, the stress-strain distributions and interface failure in a BGA (Ball Grid Array) package subjected to thermal cycling were investigated using 2D and 3D finite element analyses. The viscous behavior of the adhesive material and thermal mismatch between the dissimilar materials in the package were considered. The potential failure sites in the solider and adhesive joints were analyzed

Effect of nano-scale constraint on the mechanical behaviour of osteopontin-hydroxyapatite interfaces

In many biological materials, the interfacial behaviour between constituents such as protein and minerals greatly contributes to the overall mechanical behaviour. However, the governing mechanisms, in particular at small material length scales, have not been clearly understood. This paper presents a molecular dynamics (MD) study of the mechanical behaviour of osteopontin (OPN) and hydroxyapatite (HA) interfaces under different geometrical constraints. The results indicate that some OPN residues are attracted to the HA layers during loading. The formation of new interfacial bonds leads to a stick-slip type motion of the OPN peptides along the HA surfaces, resulting in high pulling force and energy dissipation. The attractive interaction energy and energy dissipation generally increase with reducing the gap distance between the HA layers, demonstrating a significant nano-scale constraint effect

Interfacial debonding behavior of composite beam/plates with PZT patch

This paper studies interfacial debonding behavior of composite beams which include piezoelectric materials, adhesive and host beam. The focus is put on crack initiation and growth of the piezoelectric adhesive interface. Closed-form solutions of interface stresses and energy release rates are obtained for adhesive layer in the piezoelectric composite beams. Finite element analyses have been carried out to study the initiation and growth of interfaces crack for piezoelectric beams with interface element by ANSYS, in which the interface element of FE model is based on the cohesive zone models to characterize the fracture behavior of the interfacial debonding. The results have been compared with analystical solution, and the influence of different geometry and material parameters on the interfacial behavior of piezoelectric composite beams have been discussed