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Detecting large-scale underwater cracks based on remote operated vehicle and graph convolutional neural network

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Frontiers of Structural and Civil Engineering 2022年第11期16卷 1378-1396页

作者： Wenxuan cao Junjie li Faculty of Infrastructure Engineering Dalian University of TechnologyDalian 116024China College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210098China

It is of great significance to quickly detect underwater cracks as they can seriously threaten the safety of underwater *** to date has mainly focused on the detection of above-water-level cracks and hasn’t considered the large scale *** this paper,a large-scale underwater crack examination method is proposed based on image stitching and *** addition,a purpose of this paper is to design a new convolution method to segment underwater *** improved As-Projective-As-Possible(APAP)algorithm was designed to extract and stitch keyframes from *** graph convolutional neural network(GCN)was used to segment the stitched *** GCN’s m-IOU is 24.02%higher than Fully convolutional networks(FCN),proving that GCN has great potential of application in image segmentation and underwater image *** result shows that the improved APAP algorithm and GCN can adapt to complex underwater environments and perform well in different study areas.

关键词： underwater cracks remote operated vehicle image stitching image segmentation graph convolutional neural network

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Chinese Physics Letters 2010年第6期27卷 27-30页

作者： ZHANG li cao li College of Biomedical Engineering South-Central University for Nationalities Wuhan 430074 School of Physics Huazhong University of Science and Technology Wuhan 430074

The Stratonovich stochastic differential equation is used to analyze genotype selection in the presence ot correlatecl Gaussian white noises. We study the steady state properties of the genotype selection and discuss the effects of the correlated noises. It is found that the degree of correlation of the noises can be used to select one type of genes from another type of mixing genes. The strong selection of genes caused by a large value of multiplicative noise intensity can be weakened by the intensive negative correlation.

关键词： CORRELATION (Statistics) WHITE noise theory STOCHASTIC differential equations GENOTYPE-environment interaction STATISTICAL physics

Towards application-level elasticity on shared cluster： an actor-based approach

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Frontiers of Computer Science 2017年第5期11卷 803-820页

作者： Donggang cao lianghuan kang Hanglong ZHAN Hong MEI Key Lab of High Confidence Software Technologies (Peking University) Ministry of Education Beijing 100871 China Beida (Binhai) Information Research Tianjin 300450 China

In current cluster computing, several distributed frameworks are designed to support elasticity for business services adapting to environment fluctuation. However, most existing works support elasticity mainly at the resource level, leaving application level elasticity support problem to domain-specific frameworks and applications. This paper proposes an actor-based general approach to support application-level elasticity for multiple cluster computing frameworks. The actor model offers scalability and decouples language-level concurrency from the runtime environment. By extending actors, a new middle layer called Unisupervisor is designed to ＂sit＂ between the resource management layer and application framework layer. Actors in Unisupervisor can automatically distribute and execute tasks over clusters and dynamically scale in/out. Based on Unisupervisor, high-level profiles （MasterSlave, MapReduce, Streaming, Graph, and Pipeline） for diverse cluster computing requirements can be supported. The entire approach is implemented in a prototype system called UniAS. In the evaluation, both benchmarks and real applications are tested and analyzed in a small scale cluster. Results show that UniAS is expressive and efficiently elastic.

关键词： elasticity elastic scaling actor programmingmodel cluster computing concurrent and parallel processing

Primary and secondary control in DC microgrids: a review

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Journal of Modern Power Systems and Clean Energy 2019年第2期7卷 227-242页

作者： Fei GAO Ren kang Jun cao Tao YANG Department of Engineering Science University of OxfordOxfordUK Mixergy OxfordUK School of Geography Geology and the EnvironmentKeele UniversityKeeleUK Department of Electric and Electronic Engineering The University of NottinghamNottinghamUK

With the rapid development of power electronics technology, microgrid(MG) concept has been widely accepted in the field of electrical engineering. Due to the advantages of direct current(DC)distribution systems such as reduced losses and easy integration with energy storage resources, DC MGs have drawn increasing attentions nowadays. With the increase of distributed generation, a DC MG consisting of multiple sources is a hot research topic. The challenge in such a multi-source DC MG is to provide voltage support and good power sharing performance. As the control strategy plays an important role in ensuring MG’s power quality and efficiency, a comprehensive review of the state-of-art control approaches in DC MGs is necessary. This paper provides an overview of the primary and secondary control methods under the hierarchical control architecture for DC MGs. Specifically,inner loop and droop control approaches in primary control are reviewed. Centralized, distributed and decentralized approach based secondary control is discussed in *** findings and future trends are also presented at last.

关键词： Primary control Secondary control DC microgrids Droop control Power sharing

Effect of CaF_(2) and cao/Al_(2)O_(3) on viscosity and structure of TiO_(2)-bearing slag for electroslag remelting

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Journal of Iron and Steel Research International 2021年第12期28卷 1541-1550页

作者： Jian-tao Ju kang-shuai Yang Zhi-hong Zhu Yue Gu li-zhong Chang School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina Shaanxi Engineering Research Center of Metallurgical Xi’an710055ShaanxiChina School of Metallurgy Engineering Anhui University of TechnologyMa’anshan243002AnhuiChina

The relationship between the viscosity and structure of CaF_(2)-cao-Al_(2)O_(3)-MgO-TiO_(2)slag with different CaF_(2)contents and cao/Al_(2)O_(3)ratios was studied using the rotating cylinder method,Fourier transform infrared spectroscopy,and Raman *** activity coefficients of CaF_(2)and the cao/Al_(2)O_(3)ratio were determined to understand the correlation between viscosity and structure of the *** results suggest that the slag viscosity reduces gradually with an increase in CaF_(2)content from 14.1 to 28.1 wt.%or cao/Al_(2)O_(3)ratio from 0.9 to 1.5,and correspondingly apparent activation energy for viscous flow *** addition of CaF_(2)does not change the structure of the molten slag;however,the relaxation effect of the anionic species and the hindrance effect of the cationic species are promoted by substituting part of the non-bridging oxygens(NBO)with F−ions from CaF_(2),which is attributed to the formation of NBO-Ca^(2+)-F−and NBO-Ca^(2+)-NBO,***,as the cao/Al_(2)O_(3)ratio increases,some of the Q4 units in the aluminate structure are depolymerized into Q2 units,so that the relative strength of the Al-O-Al linkage decreases,and the relative fraction of Ti2O64−chains increases,whereas that of O-Ti-O chains decreases slightly,resulting in depolymerization on the slag ***,the effect of the cao/Al_(2)O_(3)ratio on the structure was greater than that of CaF_(2)because of the greater depolymerization *** variation in the activity can indirectly explain the relationship between the viscosity and structure of the aluminate structural units based on thermodynamic analysis.

关键词： Viscosity TiO_(2)-bearing slag Fourier transform infrared spectroscopy Raman spectrum Thermodynamic

Physics-informed deep Koopman operator for Lagrangian dynamic systems

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Science China(Information Sciences) 2024年第9期67卷 146-163页

作者： Xuefeng WANG Yang cao Shaofeng CHEN Yu kang Department of Automation University of Science and Technology of China State Key Laboratory of Fire Science University of Science and Technology of China Institute of Advanced Technology University of Science and Technology of China

Accurate mechanical system models are crucial for safe and stable control. Unlike linear systems,Lagrangian systems are highly nonlinear and difficult to optimize because of their unknown system *** research thus used deep neural networks to generate linear models of original systems by mapping nonlinear dynamic systems into a linear space with a Koopman observable function encoder. The controller then relies on the Koopman linear model. However, without physical information constraints, ensuring control consistency between the original nonlinear system and the Koopman system is tough, as the learning process of the Koopman observation function is unsupervised. This paper thus proposes a two-stage learning algorithm that uses structural subnetworks to build a physics-informed network topology to simultaneously learn the Koopman observable functions and the system energy representation. In the Koopman matrix learning session, a quadratic-constrained optimization problem is solved to ensure that the Koopman representation satisfies the energy difference matching hard constraint. The proposed energy-preserving deep Lagrangian Koopman(EPDLK) framework effectively represents the dynamics of the Lagrangian system while ensuring control consistency. The effectiveness of EPDLK is compared with those of various Koopman observable function construction methods in multistep prediction and trajectory tracking tasks. EPDLK achieves better control consistency by guaranteeing energy difference matching, which facilitates the application of the control law generated on the Koopman system directly to the original nonlinear Lagrangian system.

关键词： Koopman operator Lagrangian physics-informed nonlinear model predictive control (MPC)

High-accuracy calibration for multi-laser powder bed fusion via in situ detection and parameter identification

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Advances in Manufacturing 2022年第4期10卷 556-570页

作者： Qi Zhong Xiao-Yong Tian Xiao-kang Huang Zhi-Qiang Tong Yi cao Di-Chen li State Key Laboratory of Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an710049People’s Republic of China

Multi-laser powder bed fusion(ML-PBF)adopts multiple laser-scanner systems to increase the build envelope and build speed,but its calibration is an iterative and time-consuming *** particular,multiple large-scale scan fields have a complex distortion in the overlap area,challenging the calibration *** this study,owing to the enormous workload and alignment problems in the calibration of multiple scan fields,a novel calibration system is designed in this study to realize in situ auto-detection of numerous laser spots in the build chamber to ensure high efficiency and ***,because the detectable area could not cover the entire build area and the detection data still contained errors,a virtual laser-scanner system was established by identifying the assembly defects and galvo nonlinearities of the ML-PBF system from the detection data,which served as the system's controller to improve calibration *** multi-field alignment error was less than 0.012%,which could avoid the intersection and separation of scan paths in multi-laser scanning and therefore meet the requirements for high-precision ***,the reliability of the method was verified theoretically using principal component analysis.

关键词： Powder bed fusion Multi-laser technology Galvo calibration Assembly defects System identification

Microstructural evolution of ECAPed 1050 alloy under magnetic annealing

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International Journal of Minerals,Metallurgy and Materials 2014年第12期21卷 1205-1214页

作者： Yi-heng cao Pin-feng Jia kang Wang li-zi He Ping Wang Jian-zhong Cui Key Lab of Electromagnetic Processing of Materials Ministry of Education Northeastern University

Hardness and microstructure evolutions in 1050 aluminum alloy prepared by equal-channel angular pressing （ECAP） were inves- tigated by hardness testing, optical microscopy, and transmission electron microscopy after samples were annealed at different temperatures for 1 h both in the absence and presence of a 12-T magnetic field. The results showed that the hardness of samples after magnetic annealing were lower than that of samples after normal annealing at 150-250℃, but it was higher than that of samples after normal annealing at 〉250℃. During annealing, the rate of softening was faster, and the grains were more homogeneous in 8-ECAPed samples than in 2-ECAPed samples. A rapid grain growth occurred when 2-ECAPed samples were annealed at high temperature （〉300℃）. The magnetic field enhanced the mobility of dislocations and grain boundaries. A more homogeneous grain size was observed in samples prepared under an applied magnetic field.

关键词： aluminum alloys magnetic annealing equal channel angular pressing microstructural evolution grain growth

Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

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Science China(Technological Sciences) 2015年第5期58卷 870-875页

作者： WANG TongMin cao Fei CHEN ZongNing kang HuiJun ZHU Jing FU YaNan XIAO TiQiao li TingJu Key Laboratory of Materials Modification by Laser Ion and Electron Beams (Ministry of Education) School of Material Science and Engineering Dalian University of Technology Shanghai Institute of Applied Physics Chinese Academy of Sciences

The three dimensional(3D) microstructures of Al-Bi alloys with different grain refiners(Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy(SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.

关键词： finer uniformly Electron refined verified refinement spherical friction adding dispersed