To overcome the premature convergence caused by the ill-distribution of solutions in the basic Gaussian estimation of distribution algorithm (GEDA), this paper explores a novel GEDA variant with random walk strategies, namely RW-GEDA. In RW-GEDA, the weighted maximum likelihood estimation method is used to estimate the Gaussian distribution. The new candidates are sampled using a shifted mean to enhance exploration performance. When the algorithm stagnates, two random walk strategies, namely, Gaussian random walk and Lévy walk, are activated to enrich the population diversity. Moreover, RW-GEDA is executed in an Eigen coordinate framework to promote the evolution towards the dominant region. The performance of RW-GEDA is evaluated by using the CEC 2014 test suite and compared with other top algorithms from different communities as well as promising GEDA extensions. The statistical results demonstrate the competitive performance of our proposed RW-GEDA in terms of efficiency and accuracy. In addition, RW-GEDA is applied to solve the optimal missile guidance handover problem. To fill the gap in solving this problem, a novel missile guidance advantage model is established, and the optimal missile guidance handover is determined by optimizing the control variables of unmanned combat aerial vehicles. The validity and practicability of the problem model as well as the accuracy and efficiency of RW-GEDA are demonstrated by the experimental results. INDEX TERMS Gaussian estimation of distribution algorithm, CEC 2014, numerical optimization, air combat, UCAV.
Abstract. Floods caused by levee breaching pose disastrous risks to the lower reaches and the flood flow zones of rivers. Thus, a comprehensive assessment of flow and sediment transport during floods must be performed to mitigate flood disasters. Given that the flow state becomes relatively more complex and the range of the submerged area becomes more extensive after a levee breach, this paper established a flow and sediment model by using two-dimensional shallow water equations (SWEs) to explore the breach development process and the flow and sediment transport in a curved bed after a levee breach due to overtopping. A three-element weighted essentially non-oscillatory Roe scheme was adopted for the discretization of SWEs. In addition, a non-equilibrium totalload sediment transport model was established to simulate the scour depth development process of the breach. A stable equilibrium of the breach was established based on flow shear force and soil shear strength. The lateral widening of the breach was simulated by the scouring-collapse lateral widening mode. These simulations, together with the levee breach experiment conducted in the laboratory, demonstrate the validity of the flow and sediment transport process established in this paper. The effects of water head in and out of the watercourse, the flow rate, the levee sediment grading, and other variables during levee breaching were also analyzed. The mathematical model calculation provided a number of physical quantities, such as flow rate and flow state at the breach, that are difficult to measure by using the current laboratory facilities. The results of this research provide fundamental data for developing measures that can reduce casualties and asset loss due to floods caused by levee breaching.
Attempts have been made to investigate the effect of ultrathin fibrous sheets (UFSs) arranged on the ply interface on mode I interlaminar fracture of a glass/epoxy composite laminate. The UFSs were obtained by electrospinning of epoxy 609 polymer solution and then incorporated into the middle interface of the laminate with various thicknesses. Mode I interlaminar fracture behaviors of the resulting laminates were characterized using double cantilever beam (DCB) specimens. Scanning electron microscope (SEM) was applied to analyze the fracture characteristics of the tested specimens. Results have shown that the UFS with a reasonable thickness would have no effect on the mode I delamination resistance of the laminate. To further investigate the effect of the sheets on the fracture toughness, some UFSs with thinner thickness were inserted into different interfaces of the laminate. Testing data have also shown that no significant effect on the mode I delamination resistance was recognized, although a summation of the sheets was thick. Fractured specimens analysis indicated no obvious delamination was observed when the incorporated sheet was thin.
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