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Visualization and characterization of experimental hydraulic fractures interacting with karst fracture-cavity distributions

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Journal of Rock Mechanics and Geotechnical engineering 2024年第5期16卷 1667-1683页

作者： Hanzhi Yang Xin Chang Chunhe Yang Wuhao Guo Lei Wang Guokai Zhao Yintong Guo State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing400044China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

Karst fracture-cavity carbonate reservoirs,in which natural cavities are connected by natural fractures to form cavity clusters in many circumstances,have become significant fields of oil and gas exploration and *** fracturing is considered as the best method for exploiting carbonate reservoirs;however,previous studies primarily focused on the effects of individual types of geological formations,such as natural fractures or cavities,on fracture *** this study,true-triaxial physical simulation experiments were systematically performed under four types of stress difference conditions after the accurate prefabrication of four types of different fracture-cavity distributions in artificial ***,the interaction mechanism between the hydraulic fractures and fracture-cavity structures was systematically analyzed in combination with the stress distribution,cross-sectional morphology of the main propagation path,and three-dimensional visualization of the overall fracture *** was found that the propagation of hydraulic fractures near the cavity was inhibited by the stress concentration surrounding the *** contrast,a natural fracture with a smaller approach angle(0°and 30°)around the cavity can alleviate the stress concentration and significantly facilitate the connection with the *** addition,the hydraulic fracture crossed the natural fracture at the 45°approach angle and bypassed the cavity under higher stress difference conditions.A new stimulation effectiveness evaluation index was established based on the stimulated reservoir area(SRA),tortuosity of the hydraulic fractures(T),and connectivity index(CI)of the *** findings provide new insights into the fracturing design of carbonate reservoirs.

关键词： Karst fracture-cavity reservoir Fracturing experiment Fracture propagation Cross-sectional morphology Stimulation effectiveness

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Feature-Aligned Stacked Autoencoder: A Novel Semisupervised Deep Learning Model for Pattern Classification of Industrial Faults

IEEE Transactions on Artificial Intelligence

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IEEE Transactions on Artificial Intelligence 2023年第4期4卷 592-601页

作者： Zhang, Xinmin Zhang, Hongyi Song, Zhihuan Zhejiang University College of Control Science and Engineering State Key Laboratory Industrial Control Technology Hangzhou310027 China

Autoencoder is a widely used deep learning method, which first extracts features from all data through unsupervised reconstruction, and then fine-tunes the network with labeled data. However, due to the limited number of labeled data samples, the network may lack sufficient generalization ability and is prone to overfitting. This article proposes a new semisupervised deep learning method called feature-aligned stacked autoencoder (FA-SAE). FA-SAE takes advantage of the unlabeled data during the fine-tuning process by aligning the feature of both labeled and unlabeled data. In FA-SAE, a new training loss function is designed by integrating the Sinkhorn distance measure of the difference between the features extracted from labeled and unlabeled data through the neural network into the cross-entropy classification loss. The effectiveness of the proposed FA-SAE is verified through its application to two industrial processes, and the application results demonstrated that the proposed FA-SAE has better generalization ability and higher fault classification accuracy as compared to the state-of-the-art methods. © 2020 IEEE.

关键词： Deep learning

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A probe into the acid deposition mitigation path in China over the last four decades and beyond

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National Science Review 2024年第4期11卷 84-92页

作者： Qian Yu Xiaodong Ge Haotian Zheng Jia Xing Lei Duan Dongwei Lv Dian Ding Zhaoxin Dong Yisheng Sun Posch Maximilian Danni Xie Yu Zhao Bin Zhao Shuxiao Wang Jan Mulder Thorj?rn Larssen Jiming Hao State Key Laboratory of Environmental Simulation and Pollution Control School of EnvironmentTsinghua University State Key Laboratory of Pollution Control &Resource Reuse and School of the Environment Nanjing University State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex School of EnvironmentTsinghua University International Institute for Applied System Analysis(IIASA) School of Land Engineering Chang'an University Faculty of Environmental Sciences and Natural Resource Management Norwegian University of Life Sciences Norwegian Institute for Water Research

China currently has the highest acid deposition globally, yet research on its status, impacts, causes and controls is lacking. Here, we compiled data and calculated critical loads regarding acid deposition. The results showed that the abatement measures in China have achieved a sharp decline in the emissions of acidifying pollutants and a continuous recovery of precipitation p H, despite the drastic growth in the economy and energy consumption. However, the risk of ecological acidification and eutrophication showed no significant decrease. With similar emission reductions, the decline in areas at risk of acidification in China(7.0%) lags behind those in Europe(20%) or the USA(15%). This was because, unlike Europe and the USA, China's abatement strategies primarily target air quality improvement rather than mitigating ecological impacts. Given that the area with the risk of eutrophication induced by nitrogen deposition remained at 13%of the country even under the scenario of achieving the dual targets of air quality and carbon dioxide mitigation in 2035, we explored an enhanced ammonia abatement pathway. With a further 27% reduction in ammonia by 2035, China could largely eliminate the impacts of acid deposition. This research serves as a valuable reference for China's future acid deposition control and for other nations facing similar challenges.

关键词： acid deposition critical loads acidification eutrophication ammonia abatement

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Experimental Study on Impingement Processes of Fuel Sprays on Biomimetic Structured Surfaces

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Journal of Bionic engineering 2024年第1期21卷 362-373页

作者： Yanling Chen Liang Guo Wanchen Sun Yuying Yan Rong Xuan Junfeng Zhang State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130025China Faculty of Engineering University of NottinghamNottingham NG72RDUK

To improve the controllability of the wall-wetting process after the fuel spray-wall impingement in internal combustion engines,the methods of laser etching,chemical etching and surface free energy modification are used to prepare biomimetic structured surfaces with different *** impingement processes of diesel and n-butanol sprays on the walls under different conditions are experimentally *** the surface oleophilicity increases,the spreading radius of wall-impinging sprays *** about 5 s after the fuel injections,the fuel spray droplets hit the walls for the first time,and the secondary breakup and rebound *** mixture concentrations of different fuels hitting the various walls reach the peak *** a higher surface temperature,the peak value of the mixture concentration is mainly related to the heat flux to the fuel droplets in different boiling regimes from the metal *** concentration of the air–fuel mixture in the near wall region increases with increasing surface oleophilicity,increasing wall temperature and decreasing ambient *** with diesel,n-butanol presents a higher air–fuel mixture concentration in the near wall region.

关键词： Spray-wall impingement Morphological development Air-fuel mixture concentration Surface wettability Wall temperature:Ambient pressure

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Temperature-Dependent Tearing Behavior of Rubber Materials:Characterization and Modeling

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Acta Mechanica Solida Sinica 2024年第2期37卷 316-326页

作者： Qinyuan Yao Feilong Zhang Pan Dong Ziyuan Zhao Yi He Weiguo Li Liming Chen State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing400044China College of Aerospace Engineering Chongqing UniversityChongqing400044China

With the increasingly widespread application of rubber in many fields,there is a growing demand for quantitative characterization of temperature-dependent mechanical properties in high-temperature service *** critical tearing energy is an important criterion for determining whether rubber materials will experience tearing instability,while tear strength is a key parameter for rubber materials to resist *** is necessary to quantitatively characterize their evolution with *** theoretical research mainly relies on fitting a large amount of experimental data,which is not convenient for engineering ***,in this work,a temperature-dependent critical tearing energy model is firstly developed based on the force-heat equivalence energy density *** model considers the equivalent relationship between the critical tearing energy required for crack instability propagation and the thermal energy stored in the rubber *** is demonstrated that our model has higher prediction accuracy when compared to other ***,combining with the Griffith fracture theory,temperature-dependent tear strength models applicable to three different crack modes are separately *** models are validated using experimental data for Mode I opening cracks and ModeⅢtearing cracks,and good consistency is ***,a quantitative analysis of the influence of elastic modulus on tear strength at different temperatures is *** work provides a reliable way for predicting temperature-dependent tearing instability behavior and offers beneficial suggestions for improving the tear strength of rubber materials at different temperatures.

关键词： Temperature-dependent Critical tearing energy Tear strength Rubber Theoretical model

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Ultralow friction of ion-containing water nanodroplets

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Nano Research 2023年第1期16卷 1792-1797页

作者： Jie Tan Yufeng Guo Wanlin Guo State Key Laboratory of Mechanics and Control of Mechanical Structures MOE Key Laboratory for Intelligent Nano Materials and DevicesCollege of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

We reveal the ultralow friction or superlubricity of water nanodroplets containing cations and anions on graphene substrates at high ion concentration by molecular dynamics *** the ion concentration is higher than 7 wt.%and the nanodroplet diameter is larger than 10 nm,the friction coefficients of water nanodroplets are lower than 10−2,and can decrease to the order of 10−3 with increasing the ion concentration *** a certain ion concentration,the optimal nanodroplet diameter of 17–20 nm exists at which the friction coefficient is the *** ultralow friction behaviors of water nanodroplets containing cations and anions are mainly attributed to the opposite variation trends between the interfacial adhesion energy and surface energy of water nanodroplet with ion concentration,and the interfacial hydrophobicity sustained by high ion *** results unveil the essential role of ions in achieving the superlubricity of water nanodroplets.

关键词： water nanodroplet ion ultralow friction molecular dynamics

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Ion-Induced Friction Reduction in Water Nanoflow over Graphene

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Acta Mechanica Solida Sinica 2023年第2期36卷 214-220页

作者： Yue Wang Yufeng Guo Wanlin Guo State Key Laboratory of Mechanics and Control of Mechanical Structures MOE Key Laboratory for Intelligent Nano Materials and DevicesCollege of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

Our extensive nonequilibrium and equilibrium molecular dynamics simulations reveal the ion-induced interfacial friction reduction of NaCl-containing water nanoflow over *** under a normal pressure,with the increase in ion concentration,the friction coefficients of water nanoflow at the water/graphene interfaces decrease,and the slip lengths and shear viscosities of water nanoflow *** interfacial friction reduction with the increase in ion concentration is mainly attributed to the decrease in interfacial hydrated ions and the weaker binding of water molecules with graphene at a higher ion *** presence of ions changes the hydrogen bond networks and structural configuration of water molecules close to the underlying graphene sheets and plays a key role in reducing the interfacial friction between water nanoflow and graphene.

关键词： Water nanoflow Ion Friction reduction Molecular dynamics

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Influence of nanosized magnesia on the hydration of borehole-sealing cements prepared using different methods

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International Journal of Coal Science & Technology 2023年第4期10卷 343-360页

作者： Quanle Zou Jinfei Zhan Xin Wang Zhen Huang State Key Laboratory of Coal Mine Disaster Dynamics and Control School of Resources and Safety EngineeringChongqing UniversityChongqing 400044China

Gas drainage is an efective technology for gas control in coal mines.A high borehole-sealing quality is the fundamental precondition for efcient gas *** expansibilities of cement pastes used in borehole-sealing processes are critical for the borehole-sealing *** magnesia expansive agents are used to improve the expansibilities of cement pastes and improve the borehole-sealing *** magnetic resonance spectrometry and scanning electron microscopy were adopted to study the efects of nanosized magnesia on the hydration of borehole-sealing cements used with diferent preparation *** results showed that an increase in the mass fraction of the nanosized magnesia promoted cement hydration,and the mass fraction was positively correlated with the promotion *** use of diferent preparation methods did not change the water-phase distribution in the *** using the wet-mixing preparation method,nanosized magnesia promoted the induction,acceleration,and deceleration periods of hydration;when using the dry-mixing preparation method,the nanosized magnesia promoted the induction period of cement hydration,and the promotion efect was less obvious than that seen when using the wet-mixing *** using the wet-mixing preparation method,the nanosized magnesia was uniformly dispersed,thus enlarging the surface area of the reaction,which provided more nucleation sites for the hydration products of the cement and therefore accelerated the hydration *** using the dry-mixing preparation method,the nanosized magnesia powders were dispersed nonuniformly and *** these conditions,only a few nanosized magnesia particles on the surfaces of the aggregated clusters took part in hydration,so only a small number of nucleation sites were provided for the hydration products of *** led to inconsistent hydration of cement pastes prepared using the dry-mixing *** surface porosity of the cement prepared with the wet-mi

关键词： Borehole-sealing cement Nanosized magnesia Preparation method Hydration Morphological analysis Nuclear magnetic resonance relaxation analysis

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Formal management-specifying approach for model-based safety assessment

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Journal of Systems engineering and Electronics 2023年第6期34卷 1589-1601页

作者： XU Changyi DUAN Yiman ZHANG Chao School of Control Science and Engineering Key Laboratory of Intelligent Control and Optimization for Industrial Equipment of Ministry of EducationDalian University of TechnologyDalian 116024China State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310027China

In the field of model-based system assessment,mathematical models are used to interpret the system ***,the industrial systems in this intelligent era will be more *** management operations will be dynamically set,and the system will be no longer static as it is initially ***,the static model generated by the traditional model-based safety assessment(MBSA)approach cannot be used to accurately assess the *** mainly exists three ***:huge and complex behaviors make the modeling to be trivial manual;Dynamic:though there are thousands of states and transitions,the previous model must be resubmitted to assess whenever new management arrives;Unreusable:as for different systems,the model must be resubmitted by reconsidering both the management and the system itself at the same time though the management is the *** by solving the above problems,this research studies a formal management specifying approach with the advantages of agility modeling,dynamic modeling,and specification design that can be ***,three typical managements are specified in a series-parallel system as a demonstration to show the potential.

关键词： model-based safety assessment(MBSA) management availability reliability maintainability continuous time Markov chain.

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Nanoscale Zero-Valent Iron(nZVI)for Heavy Metal Wastewater Treatment:A Perspective

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engineering 2024年第5期36卷 16-20页

作者： Shaolin Li Lei Li Weixian Zhang State Key Laboratory for Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092China

Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater(HMW)worldwide annually,posing a severe challenge to conventional wastewater treatment plants and harming the *** is traditionally treated via chemical precipitation using lime,caustic,or sulfide,but the effluents do not meet the increasingly stringent discharge *** issue has spurred an increase in research and the development of innovative treatment technologies,among which those using nanoparticles receive particular *** such initiatives,treatment using nanoscale zero-valent iron(nZVI)is one of the best *** nZVI is already well known for its site-remediation use,this perspective highlights its application in HMW treatment with metal *** demonstrate several advantages of nZVI in this wastewater application,including its multifunctionality in sequestrating a wide array of metal(loid)s(>30 species);its capability to capture and enrich metal(loid)s at low concentrations(with a removal capacity reaching 500 mg·g^(-1)nZVI);and its operational convenience due to its unique *** these advantages are attributable to nZVI’s diminutive nanoparticle size and/or its unique iron *** also present the first engineering practice of this application,which has treated millions of cubic meters of HMW and recovered tons of valuable metals(e.g.,Cu and Au).It is concluded that nZVI is a potent reagent for treating HMW and that nZVI technology provides an eco-solution to this toxic waste.

关键词： Nanoscale zero-valent iron Wastewater Heavy metal Resource recovery

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