2,273 research outputs found

    Random wave loads on a long detached breakwater considering diffraction

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    Battjes (1982) found the loads of short-crested random waves on a long structure decrease with the structure length and also with the obliqueness of wave incidence. These decreases come from the spatial phase difference along the structure. Lee et al. (2010) found that obliquely incident random waves in a nearshore area become directionally asymmetric due to refraction. They also found the asymmetry becomes more significant in shallower waters. Recently, Jung et al. (2011) studied random wave loads on a long structure considering diffraction and directional asymmetry. In this study, we further study random wave loads on a detached breakwater considering diffraction of waves which propagate at both ends of the breakwater. We also consider directional asymmetry. The structure may be placed along the bottom contours in order to protect on-shore incoming waves. In that case, refraction induced random waves may become asymmetric, i.e., on-shore components are more dominant than along-shore ones. Therefore, directional obliqueness on the structure becomes less and thus the wave loads decrease in less degree than the symmetric waves. When waves are obliquely incident on a long structure, the diffract ing waves give forces on the lee side of the structure. The diffracting wave has a spatial phase variation along the lee side which is different from that the obliquely incident wave has on the front side. Thus, the wave loads decrease with the existence of diffract ing waves and also the phase difference between the incident and diffracting waves

    Bayesian Forecasting for Financial Risk Management, Pre and Post the Global Financial Crisis

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    Value-at-Risk (VaR) forecasting via a computational Bayesian framework is considered. A range of parametric models are compared, including standard, threshold nonlinear and Markov switching GARCH specifications, plus standard and nonlinear stochastic volatility models, most considering four error probability distributions: Gaussian, Student-t, skewed-t and generalized error distribution. Adaptive Markov chain Monte Carlo methods are employed in estimation and forecasting. A portfolio of four Asia-Pacific stock markets is considered. Two forecasting periods are evaluated in light of the recent global financial crisis. Results reveal that: (i) GARCH models out-performed stochastic volatility models in almost all cases; (ii) asymmetric volatility models were clearly favoured pre-crisis; while at the 1% level during and post-crisis, for a 1 day horizon, models with skewed-t errors ranked best, while IGARCH models were favoured at the 5% level; (iii) all models forecasted VaR less accurately and anti-conservatively post-crisi

    Bayesian Forecasting for Financial Risk Management, Pre and Post the Global Financial Crisis

    Get PDF
    Value-at-Risk (VaR) forecasting via a computational Bayesian framework is considered. A range of parametric models are compared, including standard, threshold nonlinear and Markov switching GARCH specifications, plus standard and nonlinear stochastic volatility models, most considering four error probability distributions: Gaussian, Student-t, skewed-t and generalized error distribution. Adaptive Markov chain Monte Carlo methods are employed in estimation and forecasting. A portfolio of four Asia-Pacific stock markets is considered. Two forecasting periods are evaluated in light of the recent global financial crisis. Results reveal that: (i) GARCH models out-performed stochastic volatility models in almost all cases; (ii) asymmetric volatility models were clearly favoured pre-crisis; while at the 1% level during and post-crisis, for a 1 day horizon, models with skewed-t errors ranked best, while IGARCH models were favoured at the 5% level; (iii) all models forecasted VaR less accurately and anti-conservatively post-crisi

    Transient response analysis of a submerged floating tunnel under seismic and wave excitations

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    In this study, a numerical procedure is described for the transient response analysis of a submerged\ud floating tunnel with reference of a designed tunnel in Japan. Tension legs seizing the tunnel are simply modeled by a\ud spring elements and the tunnel itself is assumed by two rigid bodies between which a flexible joint is used. A recorded\ud seismic excitation is used while the wave load is calculated under a specific design condition. Hydro-damping and\ud added mass are considered for numerically modeling the underwater condition. A numerical procedure is validated with\ud compared to the previous results of the designed tunnel. Some modifications are proposed through the validating\ud process in terms of modeling and analysis procedure. Eventually, the modified numerical procedure will be used in\ud analyzing the transient response of a newly designed tunnel

    Prevention of Childhood Obesity: A Position Paper of the Global Federation of International Societies of Paediatric Gastroenterology, Hepatology and Nutrition (FISPGHAN)

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    Global childhood obesity increased more than 8-fold over 40 years, inducing a very large personal, societal, and economic burden. Effects of available treatments are less than satisfactory; therefore, effective prevention is of high priority. In this narrative review, we explore preventive opportunities. The available evidence indicates large benefits of improving nutrition and lifestyle during early life, such as promoting breast-feeding and improving the quality of infant and early childhood feeding. Promoting healthy eating patterns and limiting sugar-containing beverage consumption from early childhood onwards are of great benefit. Regular physical activity and limited sedentary lifestyle and screen time alone have limited effects but are valuable elements in effective multicomponent strategies. The home environment is important, particularly for young children, and can be improved by educating and empowering families. School- and community-based interventions can be effective, such as installing water fountains, improving cafeteria menus, and facilitating regular physical activity. Reducing obesogenic risk factors through societal standards is essential for effective prevention and limiting socioeconomic disparity; these may comprise food, drink, and physical activity standards for day cares and schools, general food quality standards, front-of-pack food labeling, taxation of unhealthy foods, restriction of food advertisements to children, and others. Effective prevention of childhood obesity is not achieved by single interventions but by integrated multicomponent approaches involving multiple stakeholders that address children, families, and societal standards. Pediatricians and their organizations should be proactive in supporting and empowering families to support their children's health, and in promoting societal measures that protect children
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