Suchergebnisse

<p class="maintext">Reflected background infrared radiation is an important contributor to the aircraft total infrared radiation. A reverse Monte Carlo ray tracing method to compute the infrared radiation signature of aircraft was introduced. The impact of atmospheric and ground radiation on the long wave infrared radiation signature of aircraft at the altitude of 11 km is analysed. The flight speed is Mach 0.8. The horizontal detection directions, downward detection directions and upward detection directions are considered. The results show that in the horizontal plane, the ratio of reflected background infrared radiation to self infrared radiation is about 10 per cent in summer, and 7 per cent in winter; the ratio values distributed in the front and side of the aircraft are bigger than that in the rear; and the existence of atmospheric and ground infrared radiation makes the apparent radiance temperature of the lower part of the aircraft higher than that of the upper part of the aircraft.</p><p class="maintext"><strong>Defence Science Journal, Vol. 66, No. 1, January 2016, pp. 51-56, DOI: http://dx.doi.org/10.14429/dsj.66.8090</strong></p>

Abstract. Liquefaction-induced hazards such as sand boils, ground cracks, settlement, and lateral spreading are responsible for considerable damage to engineering structures during major earthquakes. Presently, there is no effective empirical approach that can assess different liquefaction-induced hazards in one model. This is because of the uncertainties and complexity of the factors related to seismic liquefaction and liquefaction-induced hazards. In this study, Bayesian networks (BNs) are used to integrate multiple factors related to seismic liquefaction, sand boils, ground cracks, settlement, and lateral spreading into a model based on standard penetration test data. The constructed BN model can assess four different liquefaction-induced hazards together. In a case study, the BN method outperforms an artificial neural network and Ishihara and Yoshimine's simplified method in terms of accuracy, Brier score, recall, precision, and area under the curve (AUC) of the receiver operating characteristic (ROC). This demonstrates that the BN method is a good alternative tool for the risk assessment of liquefaction-induced hazards. Furthermore, the performance of the BN model in estimating liquefaction-induced hazards in Japan's 2011 Tōhoku earthquake confirms its correctness and reliability compared with the liquefaction potential index approach. The proposed BN model can also predict whether the soil becomes liquefied after an earthquake and can deduce the chain reaction process of liquefaction-induced hazards and perform backward reasoning. The assessment results from the proposed model provide informative guidelines for decision-makers to detect the damage state of a field following liquefaction.