基于明暗恢复形状(shape from shading,简称SFS)方法进行海底侧扫声呐图像三维重建时,会因为方法中反射模型与海底表面不相符而降低重建精度。为此文章在分析大陆架海底表面特点及侧扫声呐工作机理的基础上,提出了基于SFS混合反射模型...基于明暗恢复形状(shape from shading,简称SFS)方法进行海底侧扫声呐图像三维重建时,会因为方法中反射模型与海底表面不相符而降低重建精度。为此文章在分析大陆架海底表面特点及侧扫声呐工作机理的基础上,提出了基于SFS混合反射模型的侧扫声呐图像海底地形重建方法。首先在保留Lambert漫反射模型的基础上引入Blinn-Phong镜面反射模型,并基于侧扫声呐图像粗糙度进行漫反射系数、镜面反射系数和镜面反射指数的自适应设计,从而形成适合复杂海底表面的混合反射模型;然后线性化处理辐射照度方程,并采用牛顿-拉夫逊方法来获得海底表面高程;最后根据海底点设计反演高程约束系数来约束表面高程,进而完成侧扫声呐图像的三维重建。试验测试结果表明,相较于其他三维重建方法,文中方法的平均绝对误差值VMAE平均降低了32.18%、相关系数值VCC平均提高了29.62%、信噪比值VSNR平均提升了27.23%,有效实现了侧扫声呐图像三维重建。展开更多
Weather variations present a major challenge for photovoltaic(PV)systems in obtaining the optimal output during maximum power point tracking(MPPT),particularly under partial shadowing conditions(PSCs).Bypass diodes ar...Weather variations present a major challenge for photovoltaic(PV)systems in obtaining the optimal output during maximum power point tracking(MPPT),particularly under partial shadowing conditions(PSCs).Bypass diodes are typically installed across the series-connected PV modules to avoid the occurrence of the hotspots.Consequently,the power curve exhibits several local peaks(LPs)and one global peak(GP).The conventional MPPTs typically become stuck in one of these LPs,presenting a significant decrease in both the power output and overall efficiency of the PV system.A major constraint of several optimization techniques is their inability to differ-entiate between the irradiancefluctuations and load alterations.In this study,we analyze seven different methods for MPPT.These include:the team game algorithm(TGA),social ki driver algorithm(SSD),differential evolution(DE),grey wolf optimization(GWO),particle swarm optimization(PSO),cuckoo search(CS),and the perturb and observe(P&O)method.These algorithms were applied in practice,and their effectiveness was experimentally demonstrated under different amounts of solar irradiation while maintain-ing a constant temperature.The results indicate that the CS and TGA approaches can accurately track the MPPT across various posi-tions on the P-V curve.These methods achieve average efficiencies of 99.59%and 99.54%,respectively.Additionally,the TGA achieves superior performance with the shortest average tracking time of 0.92 s,outperforming the existing MPPT algorithms.展开更多
Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparab...Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances.During fatigue,the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations.However,SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers.Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations.Dislocations are restricted locally and cannot glide long distances to specimen surfaces,which mitigates fatigue-induced extrusions and slip markings,ultimately leading to an increase in fatigue strength.These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.展开更多
在利用单幅影像的明暗恢复形状(Shape From Shading,SFS)三维重构算法的基础上,提出同时考虑外界辐射源和目标自身红外辐射的IR-SFS(infrared-SFS)算法。首先通过分析SFS算法原理和空间目标的红外成像特性,建立IR-SFS辐射方程并进行了...在利用单幅影像的明暗恢复形状(Shape From Shading,SFS)三维重构算法的基础上,提出同时考虑外界辐射源和目标自身红外辐射的IR-SFS(infrared-SFS)算法。首先通过分析SFS算法原理和空间目标的红外成像特性,建立IR-SFS辐射方程并进行了仿真研究,然后利用温度场估计获得红外差值图,在人工合成的理想半球体、半圆柱体卫星红外影像上进行算法测试,并以美国STS107真实红外影像作为实验目标进行三维重建。实验结果表明,所提出IR-SFS算法经过参数优化后,与原SFS算法相比,重建模型的峰值信噪比更高,对STS107顶部舱门、尾翼、机舱、机舱内方形部件具有更佳显示度,整体效果得到明显改善。展开更多
以特征点对应技术为基础的摄影测量术有着广泛应用，但存在着测量数据稀疏的缺陷，对此提出了SFS(Shape from shading)与特征点技术相结合的方法，加密插值点，解决复杂表面形状测量问题。首先设计了用于测量的摄像系统，然后讨论了图...以特征点对应技术为基础的摄影测量术有着广泛应用，但存在着测量数据稀疏的缺陷，对此提出了SFS(Shape from shading)与特征点技术相结合的方法，加密插值点，解决复杂表面形状测量问题。首先设计了用于测量的摄像系统，然后讨论了图像平面的剖分算法，最后给出SFS与特征点技术结合的有限单元形式，并设计了多重网格加速求解算法。算例表明，该方法效果令人满意。展开更多
文摘基于明暗恢复形状(shape from shading,简称SFS)方法进行海底侧扫声呐图像三维重建时,会因为方法中反射模型与海底表面不相符而降低重建精度。为此文章在分析大陆架海底表面特点及侧扫声呐工作机理的基础上,提出了基于SFS混合反射模型的侧扫声呐图像海底地形重建方法。首先在保留Lambert漫反射模型的基础上引入Blinn-Phong镜面反射模型,并基于侧扫声呐图像粗糙度进行漫反射系数、镜面反射系数和镜面反射指数的自适应设计,从而形成适合复杂海底表面的混合反射模型;然后线性化处理辐射照度方程,并采用牛顿-拉夫逊方法来获得海底表面高程;最后根据海底点设计反演高程约束系数来约束表面高程,进而完成侧扫声呐图像的三维重建。试验测试结果表明,相较于其他三维重建方法,文中方法的平均绝对误差值VMAE平均降低了32.18%、相关系数值VCC平均提高了29.62%、信噪比值VSNR平均提升了27.23%,有效实现了侧扫声呐图像三维重建。
基金supported by the Ministry of Higher Education(MOHE)of Malaysia through a research grant FRGS/1/2023/TK08/UNITEN/02/9.
文摘Weather variations present a major challenge for photovoltaic(PV)systems in obtaining the optimal output during maximum power point tracking(MPPT),particularly under partial shadowing conditions(PSCs).Bypass diodes are typically installed across the series-connected PV modules to avoid the occurrence of the hotspots.Consequently,the power curve exhibits several local peaks(LPs)and one global peak(GP).The conventional MPPTs typically become stuck in one of these LPs,presenting a significant decrease in both the power output and overall efficiency of the PV system.A major constraint of several optimization techniques is their inability to differ-entiate between the irradiancefluctuations and load alterations.In this study,we analyze seven different methods for MPPT.These include:the team game algorithm(TGA),social ki driver algorithm(SSD),differential evolution(DE),grey wolf optimization(GWO),particle swarm optimization(PSO),cuckoo search(CS),and the perturb and observe(P&O)method.These algorithms were applied in practice,and their effectiveness was experimentally demonstrated under different amounts of solar irradiation while maintain-ing a constant temperature.The results indicate that the CS and TGA approaches can accurately track the MPPT across various posi-tions on the P-V curve.These methods achieve average efficiencies of 99.59%and 99.54%,respectively.Additionally,the TGA achieves superior performance with the shortest average tracking time of 0.92 s,outperforming the existing MPPT algorithms.
基金supported by National Natural Science Foundation of China(Nos.12102280,12172238,12332012)Postdoctoral Fellowship Program of CPSF(No.GZB20230473)+1 种基金Support of Ultramicroscopy Research Center(URC,Kyushu University)are highly acknowledged.Yao Chen acknowledges the support of JSPS Fellowship(No.JP22F22720)JSPS KAKENHI(No JP22K03828).
文摘Both solute-segregated long-period stacking ordered(LPSO)structure and stacking faults(SFs)are essential in strengthening rare-earth(RE)Mg alloys.Herein,LPSO-enriched Mg and SFs-enriched Mg are fabricated and comparably investigated for fatigue performances.During fatigue,the Mg nanolayers between LPSO lamellae or SFs act as the gliding channels of dislocations.However,SFs-enriched Mg exhibits outstanding fatigue strength due to solute strengthening within Mg nanolayers.Solute strengthening is assumed to contribute to the local accumulation of basal dislocations and the activation of non-basal dislocations.Dislocations are restricted locally and cannot glide long distances to specimen surfaces,which mitigates fatigue-induced extrusions and slip markings,ultimately leading to an increase in fatigue strength.These findings guide the development of RE-Mg alloys towards a synergy between high tensile and high fatigue performances.
文摘在利用单幅影像的明暗恢复形状(Shape From Shading,SFS)三维重构算法的基础上,提出同时考虑外界辐射源和目标自身红外辐射的IR-SFS(infrared-SFS)算法。首先通过分析SFS算法原理和空间目标的红外成像特性,建立IR-SFS辐射方程并进行了仿真研究,然后利用温度场估计获得红外差值图,在人工合成的理想半球体、半圆柱体卫星红外影像上进行算法测试,并以美国STS107真实红外影像作为实验目标进行三维重建。实验结果表明,所提出IR-SFS算法经过参数优化后,与原SFS算法相比,重建模型的峰值信噪比更高,对STS107顶部舱门、尾翼、机舱、机舱内方形部件具有更佳显示度,整体效果得到明显改善。
文摘以特征点对应技术为基础的摄影测量术有着广泛应用，但存在着测量数据稀疏的缺陷，对此提出了SFS(Shape from shading)与特征点技术相结合的方法，加密插值点，解决复杂表面形状测量问题。首先设计了用于测量的摄像系统，然后讨论了图像平面的剖分算法，最后给出SFS与特征点技术结合的有限单元形式，并设计了多重网格加速求解算法。算例表明，该方法效果令人满意。
