La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solutio...La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solution precursor plasma spraying (SPPS). After the solution precursors were prepared and the spraying parameters were optimized, the thermophysical properties and thermal shock performance of the coatings were tested. It was found that the SPPS coating with segmentation crack density of 6 mm^-1 had the porosities of about 33.5% at spray distances of 35 mm. The thermal conductivity of the SPPS coatings is 0.50-0.75 W·m^-1·K^-1, much lower than that of the atmospheric plasma spraying (APS) coatings (0.85-1.25 W·m^-1·K^-1). The thermal shock performance of the SPPS coatings reached 60 cycles, much better than the APS coatings. This improvement is due to the segmentation cracks in the coatings, which can improve strain tolerance and effectively relieve internal stress. This study provides reference significance for further research on thermal barrier coatings.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51571002 and 51401003)Beijing Municipal Natural Science Foundation(Nos. 2172008 and KZ201310005003)
文摘La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solution precursor plasma spraying (SPPS). After the solution precursors were prepared and the spraying parameters were optimized, the thermophysical properties and thermal shock performance of the coatings were tested. It was found that the SPPS coating with segmentation crack density of 6 mm^-1 had the porosities of about 33.5% at spray distances of 35 mm. The thermal conductivity of the SPPS coatings is 0.50-0.75 W·m^-1·K^-1, much lower than that of the atmospheric plasma spraying (APS) coatings (0.85-1.25 W·m^-1·K^-1). The thermal shock performance of the SPPS coatings reached 60 cycles, much better than the APS coatings. This improvement is due to the segmentation cracks in the coatings, which can improve strain tolerance and effectively relieve internal stress. This study provides reference significance for further research on thermal barrier coatings.
文摘为了提高基于图像处理的沥青路面病害识别效率和精度,引入图像增强处理中的多尺度视网膜(multi-scale Retinex,MSR)算法以减弱光照不均匀、道路场景多变等因素对路面病害图像质量的影响。针对SegNet网络难以精确分割沥青路面微小病害的问题,采用比视觉几何群网络(visual geometry group network,VGG)效果更好的残差网络(residual network,ResNet)作为主干网络,同时加入空洞卷积(dilation convolution)层,提高网络对细小病害的识别性能;针对改进网络在识别病害时误检率较高的问题,运用阈值法剔除分割结果中的假阳性。为了验证改进算法的有效性,将其与具有代表性的语义分割方法(如SegNet、BiSeNet)在相同数据集上进行对比,三者的平均交并比(mean intersection over union,MIoU)分别为0.7763、0.6743、0.6971,三者的F_(1)分数(F_(1)-score,F_(1))分别为0.8999、0.8743、0.8990。运用所提方法对甘肃省部分路段的路面灌封裂缝进行识别,结果与人工检测相比,漏检率为0.09%,误检率为2.49%。实验结果表明:所提方法能够更精确地提取沥青路面灌封裂缝。
