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

Wenxuan CAO; Junjie LI

《结构与土木工程前沿（英文）》 2022年 第16卷 第11期   页码 1378-1396 doi: 10.1007/s11709-022-0855-8

摘要： It is of great significance to quickly detect underwater cracks as they can seriously threaten the safety of underwater structures. Research to date has mainly focused on the detection of above-water-level cracks and hasn’t considered the large scale cracks. In this paper, a large-scale underwater crack examination method is proposed based on image stitching and segmentation. In addition, a purpose of this paper is to design a new convolution method to segment underwater images. An improved As-Projective-As-Possible (APAP) algorithm was designed to extract and stitch keyframes from videos. The graph convolutional neural network (GCN) was used to segment the stitched image. The 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 processing. The 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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Detection for transverse corner cracks of steel plates’ surface using wavelet

Qiong ZHOU, Qi AN

《机械工程前沿（英文）》 2009年 第4卷 第2期   页码 224-227 doi: 10.1007/s11465-009-0017-x

摘要： An algorithm is presented for detecting transverse corner cracks at a steel plate surface using wavelet transform. According to characteristics of transverse corner crack images, the wavelet transform is used for the multi-scale analysis of detecting the image edges and disintegrating the image into four directions at the same time. The proper threshold value is chosen to segment the image into vertical components to obtain the final detection result. The experiment shows that transverse corner cracks of steel plates can be more effectively extracted by the proposed method than the other two common methods.

关键词： transverse corner cracks     defect detection     multi-scales wavelet analysis    

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Microbial self-healing of cracks in cement-based materials and its influencing factors

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0986-6

摘要： Cement-based materials are brittle and crack easily under natural conditions. Cracks can reduce service life because the transport of harmful substances can cause corrosion damage to the structures. This review discusses the feasibility of using microbial self-healing agents for crack healing. Tubular and spherical carriers can be used to load microbial self-healing agents and protect microbes, which prolongs the self-healing time. The area self-healing ratio, permeability, mechanical strength, precipitation depth method, numerical modeling, and ultrasonic method can be employed to identify the self-healing effect of cracks. Moreover, the self-healing mechanism is systematically analyzed. The results showed that microbial self-healing agents can repair cracks in cement-based materials in underground projects and dam gates. The difficulties and future development of self-healing cracks were analyzed. A microbial self-healing agent was embedded in the cement-based material, which automatically repaired the developing cracks. With the development of intelligent building materials, self-healing cracks have become the focus of attention.

关键词： cement-based materials     cracks     microbial self-healing agent     mechanism     intelligent building materials    

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Turbidity-adaptive underwater image enhancement method using image fusion

《机械工程前沿（英文）》 2022年 第17卷 第3期 doi: 10.1007/s11465-021-0669-8

摘要： Clear, correct imaging is a prerequisite for underwater operations. In real freshwater environment including rivers and lakes, the water bodies are usually turbid and dynamic, which brings extra troubles to quality of imaging due to color deviation and suspended particulate. Most of the existing underwater imaging methods focus on relatively clear underwater environment, it is uncertain that if those methods can work well in turbid and dynamic underwater environments. In this paper, we propose a turbidity-adaptive underwater image enhancement method. To deal with attenuation and scattering of varying degree, the turbidity is detected by the histogram of images. Based on the detection result, different image enhancement strategies are designed to deal with the problem of color deviation and blurring. The proposed method is verified by an underwater image dataset captured in real underwater environment. The result is evaluated by image metrics including structure similarity index measure, underwater color image quality evaluation metric, and speeded-up robust features. Test results exhibit that the method can correct the color deviation and improve the quality of underwater images.

关键词： turbidity     underwater image enhancement     image fusion     underwater robots     visibility    

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Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

Himanshu PATHAK,Akhilendra SINGH,I.V. SINGH,S. K. YADAV

《结构与土木工程前沿（英文）》 2015年 第9卷 第4期   页码 359-382 doi: 10.1007/s11709-015-0304-z

摘要： This paper deals with the fatigue crack growth simulations of three-dimensional linear elastic cracks by XFEM under cyclic thermal load. Both temperature and displacement approximations are extrinsically enriched by Heaviside and crack front enrichment functions. Crack growth is modelled by successive linear extensions, and the end points of these linear extensions are joined by cubic spline segments to obtain a modified crack front. Different crack geometries such as planer, non-planer and arbitrary spline shape cracks are simulated under thermal shock, adiabatic and isothermal loads to reveal the sturdiness and versatility of the XFEM approach.

关键词： 3-D cracks     fatigue life     Paris law     thermal load     XFEM    

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Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

Jaroon RUNGAMORNRAT, Bounsana CHANSAVANG, Weeraporn PHONGTINNABOOT, Chung Nguyen VAN

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 280-298 doi: 10.1007/s11709-019-0586-7

摘要： This paper investigates the influence of crack geometry, crack-face and loading conditions, and the permittivity of a medium inside the crack gap on intensity factors of planar and non-planar cracks in linear piezoelectric media. A weakly singular boundary integral equation method together with the near-front approximation is adopted to accurately determine the intensity factors. Obtained results indicate that the non-flat crack surface, the electric field, and the permittivity of a medium inside the crack gap play a crucial role on the behavior of intensity factors. The mode-I stress intensity factors ( ) for two representative non-planar cracks under different crack-face conditions are found significantly different and they possess both upper and lower bounds. In addition, for impermeable and semi-permeable non-planar cracks treated depends strongly on the electric field whereas those of impermeable, permeable, and semi-permeable penny-shaped cracks are identical and independent of the electric field. The stress/electric intensity factors predicted by permeable and energetically consistent models are, respectively, independent of and dependent on the electric field for the penny-shaped crack and the two representative non-planar cracks. Also, the permittivity of a medium inside the crack gap strongly affects the intensity factors for all crack configurations considered except for of the semi-permeable penny-shaped crack.

关键词： crack-face conditions     intensity factors     non-flat cracks     permittivity     piezoelectric media     SGBEM    

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Fast detection algorithm for cracks on tunnel linings based on deep semantic segmentation

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 732-744 doi: 10.1007/s11709-023-0965-y

摘要： An algorithm based on deep semantic segmentation called LC-DeepLab is proposed for detecting the trends and geometries of cracks on tunnel linings at the pixel level. The proposed method addresses the low accuracy of tunnel crack segmentation and the slow detection speed of conventional models in complex backgrounds. The novel algorithm is based on the DeepLabv3+ network framework. A lighter backbone network was used for feature extraction. Next, an efficient shallow feature fusion module that extracts crack features across pixels is designed to improve the edges of crack segmentation. Finally, an efficient attention module that significantly improves the anti-interference ability of the model in complex backgrounds is validated. Four classic semantic segmentation algorithms (fully convolutional network, pyramid scene parsing network, U-Net, and DeepLabv3+) are selected for comparative analysis to verify the effectiveness of the proposed algorithm. The experimental results show that LC-DeepLab can accurately segment and highlight cracks from tunnel linings in complex backgrounds, and the accuracy (mean intersection over union) is 78.26%. The LC-DeepLab can achieve a real-time segmentation of 416 × 416 × 3 defect images with 46.98 f/s and 21.85 Mb parameters.

关键词： tunnel engineering     crack segmentation     fast detection     DeepLabv3+     feature fusion     attention mechanism    

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Ductile extension of 3-D external circumferential cracks in pipe structures

Wuchao YANG, Xudong QIAN

《结构与土木工程前沿（英文）》 2011年 第5卷 第3期   页码 294-303 doi: 10.1007/s11709-011-0115-9

摘要： This study investigates the ductile fracture resistance of 3-D external circumferential cracks in the wall of a steel pipe under remote tension, using a damage-mechanism model originally proposed by Gurson and Tvergaard. The ductile crack extension utilizes an element extinction technique implemented in the computational cell framework. The key parameter for the computational cell method, i.e., the initial porosity ratio , is calibrated using both the fracture resistance and the load-deformation responses obtained from fracture tests of multiple single-edge bend [SE(B)] specimens made of high-strength steel, HY80, which has a yield strength of 630 MPa. The fracture resistance along the 3-D semi-elliptical crack front is computed from the calibrated cell model. Based on the similarity concept in the near-tip stress-strain fields, this study demonstrates that an equivalent 2-D axi-symmetric model provides conservative estimations of the fracture resistance for 3-D circumferential cracks in pipes.

关键词： ductile fracture     computational cell method     G-T model     J-R curve    

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水下交通隧道的设计与施工

王梦恕

《中国工程科学》 2009年 第11卷 第7期   页码 4-10

摘要：

综合论述了水下隧道在穿越江河湖海时所有的优势，介绍了水下交通隧道的设计与施工概况，讨论了水下隧道勘察设计、施工的几项关键技术，详细介绍了水下隧道施工的常用方法。

关键词： 水下隧道     设计     施工    

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Centrifuge experiment and numerical analysis of an air-backed plate subjected to underwater shock loading

Zhijie HUANG, Xiaodan REN, Zuyu CHEN, Daosheng LING

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1350-1362 doi: 10.1007/s11709-019-0559-x

摘要： In this study, systematic centrifuge experiments and numerical studies are conducted to investigate the effect of shock loads due to an underwater explosion on the dynamic responses of an air-backed steel plate. Numerical simulations with three different models of pressure time history generated by underwater explosion were carried out. The first model of pressure time history was measured in test. The second model to predict the time history of shock wave pressure from an underwater explosion was created by Cole in 1948. Coefficients of Cole’s formulas are determined experimentally. The third model was developed by Zamyshlyaev and Yakovlev in 1973. All of them are implemented into the numerical model to calculate the shock responses of the plate. Simulated peak strains obtained from the three models are compared with the experimental results, yielding average relative differences of 21.39%, 45.73%, and 13.92%, respectively. The Russell error technique is used to quantitatively analyze the correlation between the numerical and experimental results. Quantitative analysis shows that the simulated strains for most measurement points on the steel plate are acceptable. By changing the scaled distances, different shock impulses were obtained and exerted on the steel plate. Systematic numerical studies are performed to investigate the effect of the accumulated shock impulse on the peak strains. The numerical and experimental results suggest that the peak strains are strongly dependent on the accumulated shock impulse.

关键词： underwater explosion     centrifuge experiment     shock load     dynamic response     accumulated shock impulse    

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Effects of thermocline on performance of underwater glider’s power system propelled by ocean thermal

Hai YANG, Jie MA,

《能源前沿（英文）》 2009年 第3卷 第4期   页码 472-479 doi: 10.1007/s11708-009-0052-7

摘要： The thermal glider’s changeable volume produces propelling force to power the glider’s descending and ascending through the thermocline. The different depth, thickness, and intensity of the thermocline at different seasons and locations affect the working processes of the glider’s power system. Based on the enthalpy method, a mathematical model of the underwater glider’s power system was established and the time efficiency of operation was introduced, so that the effects of different thermoclines on the underwater glider’s power system were analyzed theoretically. The simulation result shows that the thermocline affects the transition time of the phase change processes of working fluids within the thermal engine tubes. There exist the threshold values of the thermocline’s depth and upper thickness for the power system’s operation. A depth or upper thickness of the thermocline less than the corresponding threshold leads the power system to work abnormally. To keep the power system working efficiently, a glider must be kept in warm surface water for a certain period before it moves through cold water, so that the time efficiency of operation is reduced. A less time efficiency of operation is unfavorable to the thermal glider to penetrate through the ocean currents.

关键词： mathematical     underwater glider     system working     certain     corresponding threshold    

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Effect of calcium lactate on compressive strength and self-healing of cracks in microbial concrete

Kunamineni VIJAY, Meena MURMU

《结构与土木工程前沿（英文）》 2019年 第13卷 第3期   页码 515-525 doi: 10.1007/s11709-018-0494-2

摘要： This paper presents the effect on compressive strength and self-healing capability of bacterial concrete with the addition of calcium lactate. Compared to normal concrete, bacterial concrete possesses higher durability and engineering concrete properties. The production of calcium carbonate in bacterial concrete is limited to the calcium content in cement. Hence calcium lactate is externally added to be an additional source of calcium in the concrete. The influence of this addition on compressive strength, self-healing capability of cracks is highlighted in this study. The bacterium used in the study is and was added to both spore powder form and culture form to the concrete. spore powder of 2 million cfu/g concentration with 0.5% cement was mixed to concrete. Calcium lactates with concentrations of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of cement, was added to the concrete mixes to test the effect on properties of concrete. In other samples, cultured with a concentration of 1×10 cells/mL was mixed with concrete, to study the effect of bacteria in the cultured form on the properties of concrete. Cubes of 100 mm×100 mm×100 mm were used for the study. These cubes were tested after a curing period of 7, 14 and 28 d. A maximum of 12% increase in compressive strength was observed with the addition of 0.5% of calcium lactate in concrete. Scanning electron microscope and energy dispersive X-ray spectroscopy examination showed the formation of ettringite in pores; calcium silicate hydrates and calcite which made the concrete denser. A statistical technique was applied to analyze the experimental data of the compressive strengths of cementations materials. Response surface methodology was adopted for optimizing the experimental data. The regression equation was yielded by the application of response surface methodology relating response variables to input parameters. This method aids in predicting the experimental results accurately with an acceptable range of error. Findings of this investigation indicated the influence of added calcium lactate in bio-concrete which is quite impressive for improving the compressive strength and self-healing properties of concrete.

关键词： calcium lactate     bacillus subtilis     compressive strength     self-healing of cracks    

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Fracture behavior of two non-symmetrical collinear cracks emanating from an elliptical hole in a piezoelectric

Junhong GUO, Zixing LU

《机械工程前沿（英文）》 2011年 第6卷 第3期   页码 296-300 doi: 10.1007/s11465-011-0236-9

摘要：

Based on the Stroh-type formalism and the technique of conformal mapping, the problem of two non-symmetrical collinear cracks emanating from an elliptical hole in a piezoelectric solid is investigated under remotely uniform in-plane electric loading and anti-plane mechanical loading, which allowed us to take the electric field inside the hole and cracks into account. The analytical solutions of the field intensity factors and the energy release rate are presented in closed-form, which includes the extreme cases for an impermeable crack and a permeable crack. Numerical results are then presented to reveal the effects of geometrical parameters, crack permeability and combined mechanical and electric loadings on the energy release rate.

关键词： piezoelectric materials     elliptical hole     semi-permeable crack     energy release rate     analytic solution    

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Aslotted floor acquisitionmultiple access based MACprotocol for underwater acoustic networks withRTS

Liang-fang QIAN,Sen-lin ZHANG,Mei-qin LIU

《信息与电子工程前沿（英文）》 2015年 第16卷 第3期   页码 217-226 doi: 10.1631/FITEE.1400187

摘要： Long propagation delay, limited bandwidth, and high bit error rate pose great challenges in media access control (MAC) protocol design for underwater acoustic networks. A MAC protocol called slotted floor acquisition multiple access (slotted-FAMA) suitable for underwater acoustic networks is proposed and analyzed. This FAMA based protocol adds a time slot mechanism to avoid DATA packet collisions. However, slotted-FAMA is not suitable for dense networks since the multiple request-to-send (RTS) attempts problem in dense networks is serious and greatly limits the network throughput. To overcome this drawback, this paper proposes a slotted-FAMA based MAC protocol for underwater acoustic networks, called RC-SFAMA. RC-SFAMA introduces an RTS competition mechanism to keep the network from high frequency of backoff caused by the multiple RTS attempts problem. Via the RTS competition mechanism, useful data transmission can be completed successfully when the situation of multiple RTS attempts occurs. Simulation results show that RC-SFAMA increases the network throughput efficiency as compared with slotted-FAMA, and minimizes the energy consumption.

关键词： Underwater acoustic networks     Medium access control (MAC)     Request-to-send (RTS) competition     Throughput     Energy consumption    

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海洋水下立体观测技术装备发展研究

马蕊,赵修涛,柳存根

《中国工程科学》 2020年 第22卷 第6期   页码 19-25 doi: 10.15302/J-SSCAE-2020.06.003

摘要：

建立水下立体观测网来获得科学、实时、全面的数据，是未来认识、开发、利用海洋的重要方向。本文分析了发展海洋水下立体观测技术装备的需求和必要性，对比了国内外相关装备的发展现状，进一步剖析我国领域发展面临的问题，研判作为海洋水下观测关键环节的传感器技术进展点。研究认为，我国海洋观测平台技术有了很大进步，但在海洋关键传感器、高精度传感器方面依然落后于世界先进水平；海洋观测的大数据与实际需求之间有所脱节，海洋传感器缺乏改进平台支撑。研究提出了支持海洋关键传感器研究成果高效转化、统筹管理国家海洋水下立体观测技术装备、建立海上仪器装备国家公共试验平台等对策建议，以期为相关领域中长期发展提供方向参照。

关键词： 海洋观测     海底观测网     水下移动观测平台     水下传感器    

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标题 作者 时间 类型 操作

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

Wenxuan CAO; Junjie LI

期刊论文

Detection for transverse corner cracks of steel plates’ surface using wavelet

Qiong ZHOU, Qi AN

期刊论文

Microbial self-healing of cracks in cement-based materials and its influencing factors

期刊论文

Turbidity-adaptive underwater image enhancement method using image fusion

期刊论文

Fatigue crack growth simulations of 3-D linear elastic cracks under thermal load by XFEM

Himanshu PATHAK,Akhilendra SINGH,I.V. SINGH,S. K. YADAV

期刊论文

Investigation of Generalized SIFs of cracks in 3D piezoelectric media under various crack-face conditions

Jaroon RUNGAMORNRAT, Bounsana CHANSAVANG, Weeraporn PHONGTINNABOOT, Chung Nguyen VAN

期刊论文

Fast detection algorithm for cracks on tunnel linings based on deep semantic segmentation

期刊论文

Ductile extension of 3-D external circumferential cracks in pipe structures

Wuchao YANG, Xudong QIAN

期刊论文

水下交通隧道的设计与施工

王梦恕

期刊论文

Centrifuge experiment and numerical analysis of an air-backed plate subjected to underwater shock loading

Zhijie HUANG, Xiaodan REN, Zuyu CHEN, Daosheng LING

期刊论文

Effects of thermocline on performance of underwater glider’s power system propelled by ocean thermal

Hai YANG, Jie MA,

期刊论文

Effect of calcium lactate on compressive strength and self-healing of cracks in microbial concrete

Kunamineni VIJAY, Meena MURMU

期刊论文

Fracture behavior of two non-symmetrical collinear cracks emanating from an elliptical hole in a piezoelectric

Junhong GUO, Zixing LU

期刊论文

Aslotted floor acquisitionmultiple access based MACprotocol for underwater acoustic networks withRTS

Liang-fang QIAN,Sen-lin ZHANG,Mei-qin LIU

期刊论文

海洋水下立体观测技术装备发展研究

马蕊,赵修涛,柳存根

期刊论文