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Crack identification in concrete, using digital image correlation and neural network

Frontiers of Structural and Civil Engineering 2024年第4期18卷 536-550页

作者： Jingyi WANG Dong LEI Kaiyang ZHOU Jintao HE Feipeng ZHU Pengxiang BAI college of mechanics and materials Hohai UniversityNanjing 211100China

In engineering applications,concrete crack monitoring is very *** methods are of low efficiency,low accuracy,have poor timeliness,and are applicable in only a limited number of ***,more comprehensive detection of concrete damage under different scenarios is of high value for practical engineering *** image correlation(DIC)technology can provide a large amount of experimental data,and neural network(NN)can process very rich ***,NN,including convolutional neural networks(CNN)and back propagation neural networks(BP),can be combined with DIC technology to analyze experimental data of three-point bending of plain concrete and four-point bending of reinforced *** addition,strain parameters can be used for training,and displacement parameters can be added for comprehensive *** data obtained by DIC technology are grouped for training,and the recognition results of NN show that the combination of strain and displacement parameters,i.e.,the response of specimen surface and whole body,can make results more objective and *** identification results obtained by CNN and BP show that these technologies can accurately identify *** identification results for reinforced concrete specimens are less affected by noise than those of plain concrete *** is more convenient because it can identify some features directly from images,recognizing the cracks formed by macro *** can issue early warning of the microscopic cracks,but it requires a large amount of data and *** can be seen that CNN is more intuitive and efficient in image processing,and is suitable when low accuracy is adequate,while BP is suitable for occasions with greater accuracy *** two tools have advantages in different situations,and together they can play an important role in engineering monitoring.

关键词： digital image correlation convolutional neural network back propagation neural neural network damage detection concrete

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Formation adaptation in obstacle-cluttered environments via MPC-based trajectory planning

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science China(Information sciences) 2024年第7期67卷 321-323页

作者： Yuda CHEN Zhongkui LI Department of mechanics and Engineering science College of Engineering Peking University

Formation is a typical collective behavior in multiagent systems utilized in areas such as inspection, surveillance, and transportation. Commonly-used approaches to achieve formation include virtual structure [1], con...

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Fluid-structure interaction simulation of dynamic response and wake of floating offshore wind turbine considering tower shadow effect

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Acta Mechanica Sinica 2024年第8期40卷 67-84页

作者： Songyang Liu Zhiqiang Xin Lei Wang Zhiming Cai college of mechanics and Engineering science HoHai UniversityNanjing211100China

The comprehensive numerical simulation of the tower shadow effect on floating offshore wind turbines(FOWTs),an area less explored compared to fixed-bottom wind turbines,is presented in this *** atmospheric boundary layer inflow and the joint north sea wave project random wave are used as the operating conditions for *** combination of computational fluid dynamics(CFD)software simulator for wind farm applications and turbine simulation tool OpenFAST is used to implement fluid-structure interaction *** output power,platform motion,wake velocity deficit and vortex structures are analyzed to reveal the influence of the tower shadow effect on the *** results indicate that due to the fluctuation caused by the turbulent wind and the floating platform motion,the tower shadow effect of FOWT is less significant for its periodic power decay than that of fixed-bottom wind *** according to the velocity deficit analysis,the influence area of the tower shadow effect on the wake is mainly in the near wake region.

关键词： Floating offshore wind turbine Tower shadow effect Atmospheric boundary layer inflow JONSWAP wave Wind turbine wake

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Spatial construction of ultrasmall Pt-decorated 3D spinel oxidemodified N-doped graphene nanoarchitectures as high-efficiency methanol oxidation electrocatalysts

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Rare Metals 2024年第1期43卷 186-197页

作者： Qi Zhang Min-Min Yan Wen-Fa Du Chen-Yu Yin Jian Zhang Lu Yang Yun-Qing Kang Hai-Yan He Hua-Jie Huang college of mechanics and materials Hohai UniversityNanjing 210098China New Energy Technology Engineering Lab of Jiangsu Province College of ScienceNanjing University of Posts&Telecommunications(NUPT)Nanjing 210023China International Center for materials Nanoarchitectonics(WPIMANA) National Institute for Materials ScienceTsukuba 305-0044IbarakiJapan

Direct methanol fuel cell technology recently becomes the focus of both academic and engineering circles,which stimulates the exploitation and utilization of advanced electrode catalysts with high activity and long ***,we demonstrate a robust bottom-up approach to the spatial construction of three-dimensional(3D) spinel manganese-cobalt oxide-modified N-doped graphene nanoarchitectures decorated with ultrasmall Pt nanoparticles(Pt/MnCo_(2)O_(4)-NG) via a controllable selfassembly *** incorporation of MnCo_(2)O_(4)nanocrystals provides abundant hydroxyl sources to promote the oxidative removal of CO-like byproducts on Pt sites,while the existence of 3D porous N-doped graphene networks facilitates the transportation of both ions and electrons in the hybrid system,thus giving rise to remarkable synergetic coupling effects during the methanol oxidation ***,the optimized Pt/MnCo_(2)O_(4)-NG nano architecture expres ses exceptional electrocatalytic properties with a large electrochemically active surface area of 99.5 m^(2)·g^(-1),a high mass activity of1508.3 mA·mg^(-1),strong toxicity resistance and reliable long-term durability,which have obvious competitive advantages over those of conventional Pt/carbon black,Pt/carbon nano tube,Pt/graphene,and Pt/N-doped graphene catalysts with the same Pt usage.

关键词： Platinum MnCo_(2)O_(4) 3D graphene Electrocatalysts Methanol oxidation

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Quantifying the solid electrolyte interphase stress induced capacity fading of lithium-ion batteries via a multiscale mechanical-electrochemical coupling model

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science China Technological sciences 2024年第10期67卷 3168-3181页

作者： HE YaoLong XU Peng JIANG DengFeng HU HongJiu LI DaWei SHI SiQi Shanghai Institute of Applied Mathematics and mechanics School of Mechanics and Engineering ScienceShanghai University Shanghai Key Laboratory of mechanics in Energy Engineering Shanghai University Shanghai Frontier science Center of Mechanoinformatics Shanghai University School of Mechanical Engineering University of Shanghai for Science and Technology School of materials science and Engineering Shanghai University materials Genome Institute Shanghai University

The solid electrolyte interphase（SEI） is widely recognized as a critical factor leading to the capacity fading of lithium-ion batteries（LIBs）. Although SEI stress-related mechanical failure caused by the expansion or contraction of active materials upon cycles is well documented, previously reported SEI components and overpotential varying phenomena due to SEI stress and their effects on the electrochemical performance are poorly understood. Here, we establish a quantitative correlation between capacity fading and the SEI stress by considering its effects on side reactions, especially SEI component evolution, in a multiscale mechanical-electrochemical coupling model. Furthermore, the capacity fading behaviors of two typical cells（Li[NiMnCo]O2as the cathode, and graphite and silicon as the anode, respectively） were adopted as numerical examples to demonstrate its potential utility and applications. Stress within the SEI was indeed found to play a predominant role in the capacity fading of the graphite and silicon anodes, resulting in 27% and 69% of the total capacity loss after 200 and 100 cycles at 1 C, respectively. This study provides valuable mechanical insights into the variations of SEI properties related to the capacity degradation and SEI optimization and design for LIBs.

关键词： solid electrolyte interphase capacity fading multiscale mechanical-electrochemical coupling stress analysis

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Discontinuous phase diagram of amorphous carbons

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National science Review 2024年第4期11卷 164-171页

作者： YinBo Zhu ZhouYu Fang ZhongTing Zhang HengAn Wu CAS Key Laboratory of Mechanical Behavior and Design of materials Department of Modern MechanicsUniversity of Science and Technology of China State Key Laboratory of Nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences

The short-range order and medium-range order of amorphous carbons demonstrated in experiments allow us to rethink whether there exist intrinsic properties hidden by atomic disordering. Here we presented six representative phases of amorphous carbons（0.1–3.4 g/cm3）, namely, disordered graphene network（DGN）, high-density amorphous carbon（HDAC）, amorphous diaphite（a-DG）, amorphous diamond（a-D）, paracrystalline diamond（p-D）, and nano-polycrystalline diamond（NPD）, respectively, classified by their topological features and microstructural characterizations that are comparable with experiments. To achieve a comprehensive physical landscape for amorphous carbons, a phase diagram was plotted in the sp3/sp2versus density plane, in which the counterintuitive discontinuity originates from the inherent difference in topological microstructures, further guiding us to discover a variety of phase transitions among different amorphous carbons. Intriguingly, the power law, log（sp3/sp2） ∝ ρn, hints at intrinsic topology and hidden order in amorphous carbons, providing an insightful perspective to reacquaint atomic disorder in non-crystalline carbons.

关键词： amorphous carbons disordered carbons phase diagram microstructural topology phase transition

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MoO_(x) nanoclusters on Mo-doped TiO_(2) nanosheets with enhanced singlet oxygen generation and sulfide conversion abilities for photocatalytic aerobic oxidative desulfurization

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science China Chemistry 2024年第1期67卷 408-414页

作者： Suting Xie Xinyu Zhao Dongxiao Wang Huawei Yang Lixia Yang Liangjiu Bai Donglei Wei Wenxiang Wang Ying Liang Hou Chen Shaojun Guo college of Chemistry and materials science Ludong UniversityYantai 264025China college of materials science and Engineering Peking UniversityBeijing 100871China

Photocatalytic aerobic oxidation desulfurization(PAODS)is a promising and sustainable alternative to conventional,energyintensive desulfurization techniques for petroleum ***,its development is greatly plagued by the low capability in generating highly reactive oxygen species and sluggish kinetics of sulfide oxidation of reported *** we report a class of MoO_(x)nanocluster decorated on ultrathin Mo-doped TiO_(2)nanosheet(MoO_(x)/MoTiO)catalyst for efficiently facilitating the photocatalytic aerobic oxidation of *** demonstrate that MoO_(x)/MoTiO can not only promote the generation of highly reactive singlet oxygen(^(1)O_(2))but also enhance the aerobic conversion of sulfides,which leads to a record dibenzothiophene oxidation activity of 3.90 mmol g^(-1)h^(-1).The multiple experimental characterizations and density functional theory calculations collectively reveal that the doped-Mo sites can interact with the photogenerated excitons,enabling directly energy transfer generation of^(1)O_(2)through a new exciton modulation mechanism,and the coordination unsaturated MoO_(x)clusters play the role of co-catalyst to enhance the separation of charge carriers,and effectively catalyze the reaction between sulfides and1O_(2)to form sulfones.

关键词： titanium dioxide photocatalytic aerobic oxidation desulfurization dibenzothiophene singlet oxygen

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Volume of fluid simulation of single argon bubble dynamics in liquid steel under RH vacuum conditions

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Journal of Iron and Steel Research International 2024年第4期31卷 828-837页

作者： Gu-jun Chen Sheng-ping He college of materials science and Engineering Yangtze Normal UniversityChongqing 400044China college of materials science and Engineering Chongqing UniversityChongqing 400044China

Single argon bubble dynamics in liquid steel under Ruhrstahl-Heraeus(RH)vacuum conditions were simulated using the volume of fluid method,and the ideal gas law was used to consider bubble growth due to heat transfer and pressure *** simulation with a constant bubble density was also performed to validate the numerical method,and the predicted terminal bubble shape and velocity were found to agree with those presented in the Grace diagram and calculated by drag correlation,*** simulation results under RH conditions indicate that the terminal bubble shape and velocity cannot be *** primary bubble growth occurs within a rising distance of 0.3 m owing to heating by the high-temperature liquid steel;subsequently,the bubble continues to grow under equilibrium with the hydrostatic *** the initial diameter is 8-32 mm,the bubble diameter and rising velocity near the liquid surface are 80-200 mm and 0.5-0.8 m/s,*** bubble rises rectilinearly with an axisymmetric shape,and the shape evolution history includes an initial sphere,(dimpled)ellipsoid,and spherical cap with satellite bubbles.

关键词： Bubble dynamics Liquid steel Volume of fluid Bubble growth Bubble shape Rising velocity

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Prediction of liquid circulation flow rate in RH degasser:improvement of decarburization at low atmospheric pressure

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Journal of Iron and Steel Research International 2024年第7期31卷 1661-1667页

The two-fluid model coupled with population balance model was used for simulating the gas-liquid flow in the Ruhrstahl-Heraeus(RH)*** predicted circulation flow rate was compared with that measured from a water model experiment to validate the mathematical ***,influence of snorkel immersion depth on liquid circulation flow rate was numerically investigated under an atmospheric pressure of 101 and 84 kPa,*** result indicates that the circulation flow rate of the RH degasser in the high-altitude area was severely reduced because of the decrease in atmospheric ***,increasing the snorkel immersion depth from 0.5 to 0.7 m can compensate for the decrease in atmospheric *** test result indicates that decarburization rate is significantly enhanced by increasing the snorkel immersion *** optimization,the percentage of heats with a final carbon content less than 0.002 wt.%is significantly increased from 22.0%to 96.4%.

关键词： RH degasser Two-fluid model Population balance model-Circulation flow rate Decarburization Snorkel immersion depth

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Crystalline-amorphous M@MN_x(M=Co,Fe,Ni)encapsulated in nitrogen-doped carbon for enhanced efficient and durable hydrogen evolution reaction

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Rare Metals 2024年第4期43卷 1547-1556页

作者： Yang Yang Xiao-Chuan Duan Shao-Hui Guo Xian-Ming Zhang college of materials science and Engineering College of ChemistryKey Laboratory of Interface Science and Engineering in Advanced MaterialsTaiyuan University of TechnologyYuci030600China

Developing earth-abundant electrocatalysts for hydrogen evolution reaction(HER)is important for the sustainable energy ***,efficient and stable heterocatalysts consisting of crystalline-amorphous M@MN_(x)(M=Co,Fe,Ni)encapsulated in N-doped carbon layers supported with N-doped graphene sheets(denoted as M@MN_(x)@NC-NG)are synthesized by facile hydrothermal reaction and nitridation *** the nitriding process,metal ions in M(tzbc)_2(H_(2)O)_4(tzbc=4-(1H-1,2,4-triazol-1-yl)benzoic acid)complexes are reduced to crystalline M cores,accompanied by the formation of amorphous MN_(x)shells;the tzbc ligands are insitu carbonized to form outermost N-doped carbon(NC)layers that connect with inner MN_(x)via M-N-C motifs inherited from the complex precursors and inhibit the transition of MN_(x)from amorphous to crystalline *** Co@CoN_(x)@NC-NG catalyst exhibits excellent HER activity with small overpotentials of 45 and 64 mV at a cathode current density of 10 mA·cm^(-2)and low Tafel slopes of 40 and 85 mV·dec^(-1)in 0.5 mol·L^(-1)H_(2)SO_4 and1.0 mol·L^(-1)KOH electrolytes,*** Co@CoN_(x)@NC-NG retains 97%of the initial overpotential after 100,000 s in both acidic and alkaline *** outstanding HER performance originates from the crystalline-amorphous Co@CoN_(x)that redistributes electrons around the heterointerfaces,facilitating the conversion process of H^(+)/H_(2)O to hydrogen and thereby promoting HER *** outermost NC layers serve as the armor of Co@CoN_(x),and graphene nanosheets act as carriers of egg-like Co@CoN_(x)@NC and conduction paths for electron shuttles,ensuring stable and continuous electrocatalytic hydrogen production.

关键词： Hydrogen evolution reaction Electrocatalysts Iron group metals Heterojunction Crystalline-amorphous structure

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