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针对海洋环境下高耐久性清水混凝土外观缺陷问题,进行混凝土的圆桶及方模试验,研究掺合料对其外观的影响。结果表明,单掺矿粉的清水混凝土表面气泡较多,且直径较大;双掺矿粉和粉煤灰的清水混凝土的色泽会偏黑,偏暗;双掺矿粉和石粉的清水混凝土表面有较多大直径气泡;而双掺矿粉和硅粉的清水混凝土,色泽较为明亮均匀、气泡较少且气泡尺寸较小,整体均匀性在双掺体系中最好;三掺矿粉、粉煤灰和硅粉的清水混凝土,相对于所有其他系列的清水混凝土,外观改善情况最好,整体色泽均匀明亮,且气泡较少,将其应用于某海洋环境下清水混凝土工程,效果良好。 相似文献
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The Northern Sea Route (NSR) has tremendous potential for ocean shipping between Europe and Asia due to the savings from shorter transit time and distance. However, the Arctic area is environmentally vulnerable and thus there is a trade-off between NSR’s impacts on environment vs. its economic benefits, especially when compared with the traditional route, such as through the Suez Canal Route (SCR). This study estimates the market shares of different transport modes and alternative shipping routes for the container transport market between Europe and Asia, and the resulting environmental costs. Our result suggests that NSR can be a viable option under the status quo. However, its environmental costs tend to be higher than SCR due to small ship size and low load factor in the present, thus the development of NSR would lead to worse environment outcomes. If these issues can be resolved, NSR can benefit from lower operational and environmental costs, which will lead to higher market share and social welfare. Otherwise, increased use of NSR may lead to higher total environment costs than the status quo. 相似文献
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Integrated choice and latent variable (ICLV) model incorporates latent factors into standard discrete choice model with aim to provide greater explanatory power. Using simulated datasets, this study makes a comparison among three estimation approaches corresponding to the sequential approach and two simultaneous approaches including the maximum simulated likelihood with GHK estimator and maximum approximate composite marginal likelihood (MACML) approach, to evaluate their abilities to recover the underlying parameters of multinomial probit-kernel ICLV model. The results show that both simultaneous approaches outperform the sequential approach in terms of estimates accuracy and efficiency irrespective of the sample sizes, and the MACML approach is the most preferable due to its best performance on recovering true values of parameters with relatively small standard errors, especially when the sample size is large enough. 相似文献