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Effects of nitrogen content on pitting corrosion resistance of non-magnetic drill collar steel

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Journal of Iron and Steel Research International 2020年第12期27卷 1466-1475页

作者： Li-wei Xu Hua-bing Li huai-bei zheng Peng-chong Lu Hao Feng Shu-cai Zhang Wei-chao Jiao Zhou-hua Jiang School of Metallurgy Northeastern UniversityShenyang 110819LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan 114002LiaoningChina

High-nitrogen (N) austenitic stainless steel (Cr-Mn-N series) is commonly used for non-magnetic drill collars, which exhibits excellent mechanical properties and corrosion resistance. The effects of N content (0.63 to 0.86 wt.%) on the pitting corrosion behavior of the experimental non-magnetic drill collar steel were investigated using the electrochemical tests and immersion tests. Besides, X-ray photoelectron spectroscopy was used to analyze the constitution of the passive film. The results show that with the enhancement of N content from 0.63 to 0.86 wt.%, the metastable pitting corrosion sensitivity of the tested materials in 3.5 wt.% NaCl solution decreased and the pitting corrosion resistance increased. Meanwhile, the corrosion rate in 6 wt.% FeCl3 solution at 30 ℃ decreased from 10.40 to 4.93 mm/a. On the other hand, nitrogen was concentrated in the form of ammonia (NH4+ and NH3)on the outermost surface of the passive films. The contents of Cr2O3 and Fe2O3 raised in the passive films, together with the content of CrN, at metal/film interface increased as N content increased from 0.63 to 0.86 wt.%, which facilitated protective ability of the passive films, thus contributing to higher pitting corrosion resistance.

关键词： Non-magnetic drill collar Nitrogen Stainless steel Pitting corrosion Passive film

Microstructure evolution and mechanical properties of PESR 55Cr17Mo1VN plastic die steel during quenching and tempering treatment

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Journal of Iron and Steel Research International 2021年第12期28卷 1625-1633页

作者： Cong-peng Kang Fu-bin Liu huai-bei zheng Hua-bing Li Zhou-hua Jiang Kui Chen Hao-yang Suo Xin-hao Yu School of Metallurgy Northeastern UniversityShenyang110819LiaoningChina State Key Laboratory of Metal Material for Marine Equipment and Application Anshan114002LiaoningChina

55Cr17Mo1VN high nitrogen martensitic stainless steel is usually applied to the high-quality mold,which is largely produced by the pressurized electro slag remelting *** microstructure evolution of quenching and tempering heat treatment were investigated and an optimal heat treatment process to achieve excellent mechanical properties was found *** main precipitates in the steel included carbon-rich type M_(23)C_(6) and nitrogen-rich type M_(2)*** increasing austenitizing temperature,the equivalent diameter of the precipitates got fined,and retained austenite content increased significantly when the austenitizing temperature exceeded 1020℃.The fracture mode gradually changed from brittle fracture to ductile fracture with increasing tempering temperature from 200 to 550℃.The experimental steel tempered at 350℃ achieved a good combination of hardness(60.6 HRC)and strength(2299.2 MPa)to meet service *** M_(23)C_(6) precipitated along martensite lath boundaries and the secondary hardening phenomenon occurred when the tempering temperature was 450℃.Due to the high nitrogen content,M_(2)N precipitated from the inside of laths and matrix when tempered at 550℃.

关键词： Microstructure Mechanical property Plastic die steel Quenching Tempering Precipitate

Some notes on numerical simulation of the turbulent cavitating flow with a dynamic cubic nonlinear sub-grid scale model in OpenFOAM

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Journal of Hydrodynamics 2020年第4期32卷 790-794页

作者： Zi-yang Wang Xian-bei Huang huai-yu Cheng Bin Ji State Key Laboratory of Water Resources and Hydropower Engineering Science School of Power and Mechanical EngineeringWuhan UniversityWuhan 430072China College of Electrical Energy and Power EngineeringYangzhou UniversityYangzhou 225127China

The accuracy of large eddy simulation(LES)is highly dependent on the performance of sub-grid scale(SGS)*** the present paper,a dynamic cubic nonlinear sub-grid scale model(DCNM)proposed by Huang et *** implemented for the simulation of unsteady cavitating flow around a 3-D Clark-Y hydrofoil in *** performance in predicting the evolution of cloud cavitation is discussed in *** simulation with a linear model,the dynamic Smagorinsky model(DSM),is also conducted as a *** results with DCNM show a better agreement with the available experimental *** comparison between DCNM and DSM further suggests that the DCNM is able to predict the backscatter more precisely,which is an important feature in *** characteristics of DCNM is analyzed to account for its advantages in the prediction of unsteady cloud cavitation as *** results reveal that it is the nonlinear terms of DCNM that makes DCNM capture sub-grid scale vortices better and more suitable for studying the transient behaviors of cloud cavitation than DSM.

关键词： Cavitation large eddy simulation(LES) nonlinear sub-grid scale model OpenFOAM

Strain-controlled graphdiyne membrane for CO2/CH4 separation:First-principle and molecular dynamic simulation

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Chinese Journal of Chemical Engineering 2020年第7期28卷 1898-1903页

作者： Xin zheng Shuai Ban bei Liu Guangjin Chen State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing 102249China College of New Energy and Materials China University of PetroleumBeijing 102249China

Tensile strain of porous membrane materials can broaden their capacity in gas *** this work,using van der Waals corrected density functional theory(DFT)and molecular dynamics(MD)simulations,the performance and mechanism of CO2/CH4 separation through strain-oriented graphdiyne(GDY)monolayer were studied by applying lateral *** is demonstrated that the CO2 permeance peaks at 1.29×10^6 gas permeation units(GPU)accompanied with CO2/CH4 selectivity of 5.27×10^3 under ultimate strain,both of which are far beyond the Robeson’s ***,the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile ***2 molecule tends to reoriented itself vertically to permeate the ***,the CO2 permeability decreases with the increase of the temperature from300 K to 500 K due to conserving of rotational freedom,suggesting an abnormal permeance of CO2 in relation to *** theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO2/CH4 separation,owing to its extremely high selectivity and permeability of CO2.

关键词： Graphdiyne Strain CO2 separation Molecular dynamics Density functional theory

Plausible Heterogeneous Graph k-Anonymization for Social Networks

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Tsinghua Science and Technology 2022年第6期27卷 912-924页

作者： Kaiyang Li Ling Tian Xu zheng bei Hui School of Computer Science and Engineering University of Electronic Science and Technology of ChinaChengdu 611731China School of Information and Software Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Trusted Cloud Computing and Big Data Key Laboratory of Sichuan Province Chengdu 610000China

The inefficient utilization of ubiquitous graph data with combinatorial structures necessitates graph embedding methods,aiming at learning a continuous vector space for the graph which is amenable to be adopted in traditional machine learning algorithms in favor of vector *** embedding methods build an important bridge between social network analysis and data analytics as social networks naturally generate an unprecedented volume of graph data *** social network data not only bring benefit for public health,disaster response,commercial promotion,and many other applications,but also give birth to threats that jeopardize each individual’s privacy and ***,most existing works in publishing social graph embedding data only focus on preserving social graph structure with less attention paid to the privacy issues inherited from social *** be specific,attackers can infer the presence of a sensitive relationship between two individuals by training a predictive model with the exposed social network *** this paper,we propose a novel link-privacy preserved graph embedding framework using adversarial learning,which can reduce adversary’s prediction accuracy on sensitive links while persevering sufficient non-sensitive information such as graph topology and node attributes in graph *** experiments are conducted to evaluate the proposed framework using ground truth social network datasets.

关键词： social network graph embedding privacy preservation adversarial learning

Denoising Stochastic Progressive Photon Mapping Renderings Using a Multi-Residual Network

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Journal of Computer Science & Technology 2020年第3期35卷 506-521页

作者： zheng Zeng Lu Wang bei-bei Wang Chun-Meng Kang Yan-Ning Xu School of Software Shandong UniversityJinan 250101China School of Computer Science and Engineering Nanjing University of Science and TechnologyNanjing 210094China School of Information Science and Engineering Shandong Normal UniversityJinan 250358China

Stochastic progressive photon mapping(SPPM)is one of the important global illumination methods in computer *** can simulate caustics and specular-diffuse-specular lighting effects ***,as a biased method,it always suffers from both bias and variance with limited iterations,and the bias and the variance bring multi-scale noises into SPPM *** learning-based methods have shown great advantages on denoising unbiased Monte Carlo(MC)methods,but have not been leveraged for biased *** this paper,we present the first learning-based method specially designed for denoising-biased SPPM ***,to avoid conflicting denoising constraints,the radiance of final images is decomposed into two components:caustic and *** two components are then denoised separately via a two-network *** each network,we employ a novel multi-residual block with two sizes of filters,which significantly improves the model’s capabilities,and makes it more suitable for multi-scale noises on both low-frequency and high-frequency *** also present a series of photon-related auxiliary features,to better handle noises while preserving illumination details,especially *** with other state-of-the-art learning-based denoising methods that we apply to this problem,our method shows a higher denoising quality,which could efficiently denoise multi-scale noises while keeping sharp illuminations.

关键词： denoising stochastic progressive photon mapping(SPPM) deep learning residual neural network

Asymmetric Oscillation and Acoustic Response from an Encapsulated Microbubble Bound within a Small Vessel

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Chinese Physics Letters 2010年第6期27卷 114-117页

作者： HUANG bei zheng Hai-Rong ZHANG Dong Institute of Acoustics Key Laboratory of Modern Acoustics (Ministry of Education) Nanjing University Nanjing 210093 Paul C. Lauterbur Research Center for Biomedical imaging IBHE Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Shenzhen 518055

Understanding the dynamics of ultrasonic excited microbubbles bound within microvessels is of significance for novel ultrasonic imaging, drug delivery and therapeutic biomedicad applications. A finite element model （FEM） considering acoustic nonlinearity is developed to describe the asymmetric oscillation and acoustic response from mn encapsulated microbubble bound within a small vessel. Numerical simulation is performed for a 2 μm encapsulated microbubble bound within 8-20μm vessels using 2 MHz ultrasound excitation. The oscillation of the bound microbubble becomes more asymmetric under larger ultrasound pressure or within the smaller vessel. The normalized difference between the major and minor axes of epllipse is estimated to be 2.16%for the 8 μm vessel at an acoustic pressure of 0.5 MPa. In addition, the fundamental component of the acoustic scattering from the bound microbubble is enhanced by 6 dB while the second harmonic component is decreased by approximately 29 dB compared with the free microbubble.

关键词： SYMMETRY (Physics) OSCILLATIONS MICROENCAPSULATION BUBBLE dynamics FINITE element method NONLINEAR acoustics ULTRASONIC imaging DRUG delivery systems NUMERICAL analysis

Investigation of Ag(Ga,In)Se_(2)as thin-film solar cell absorbers:A first-principles study

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Science China(Physics,Mechanics & Astronomy) 2022年第10期65卷 101-108页

作者： Rong Wang Baoying Dou Yifeng zheng Su-huai Wei Institute of Advanced Semiconductors&Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices ZJU-Hangzhou Global Scientific and Technological Innovation CenterHangzhou 311200China beijing Computational Science Research Center Beijing 100193China

Using first-principles calculations,the structural,electronic,and defect properties of AgInSe_(2)(AIS),AgGaSe_(2)(AGS),and their alloys(AIGS)are systematically studied and compared with their Cu counterparts as potential candidates for thin-film solar cell *** bandgap energies of AIS(1.24 eV)and AGS(1.84 eV)are larger than their Cu counterparts,despite their larger lattice *** to the Shockley-Queisser theory,AIS or AIGS could be more suitable for solar-cell-absorber materials than their Cu ***,after investigating the band structures and intrinsic defect properties of AIS and AGS,we find that,(i)AIS and AGS have large negative crystal field splitting,thus low density of states near the valence band maximum(VBM);(ii)similar to the Cu counterparts,Ag vacancy(V_(Ag))is the main hole-carrier provider,while In_(Ag)(or Ga_(Ag))serves as the hole-carrier killer in p-type AIS(or AGS).However,because the positions of theVBM and conduction band minimum of AIS(or AGS)are lower than those of Cu In Se_(2)(CIS)[or Cu Ga Se_(2)(CGS)],the compensation of the p-type doping in AIS(or AGS)is more ***,the p-type doping of AIS(or AIGS)is more difficult than that of CIS(or CIGS),which is consistent with the doping limit *** improve the p-type doping of the AIS(or AIGS)as the solar-cell absorber,thus,improve the power conversion efficiency(PCE),the Ag-rich/(In,Ga)-poor/Se-rich growth condition is *** engineering of AIS with AGS can enhance the PCE because it can tune the bandgap energy of the absorber and band alignment at the absorber/buffer *** importantly,we suggest that for AIS(or AIGS)solar cell,the traditional buffer material of Cd S is not suitable anymore due to the large conduction band offset between AIS and Cd S.A new buffer layer material with a lower conduction band edge is necessary for better electron transport in AIS(or AIGS)solar cell.

关键词： thin-film solar cells chalcopyrites point defects alloys first-principles calculations

Evaluation and prediction of slope stability using machine learning approaches

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Frontiers of Structural and Civil Engineering 2021年第4期15卷 821-833页

作者： Shan LIN Hong zheng Chao HAN bei HAN Wei LI Key Laboratory of Urban Security and Disaster Engineering Ministry of EducationBeijing University of TechnologyBeijing100124China

In this paper,the machine learning(ML)model is built for slope stability evaluation and meets the high precision and rapidity requirements in slope *** ML methods for the factor of safety(FOS)prediction are studied and compared hoping to make the best use of the large variety of existing statistical and ML regression methods *** data set of this study includes six characteristics,namely unit weight,cohesion,internal friction angle,slope angle,slope height,and pore water pressure *** whole ML model is primarily divided into data preprocessing,outlier processing,and model *** the data preprocessing,the duplicated data are first removed,then the outliers are filtered by the LocalOutlierFactor method and finally,the data are standardized.11 ML methods are evaluated for their ability to learn the FOS based on different input parameter *** analyzing the evaluation indicators R2,MAE,and MSE of these methods,SVM,GBR,and Bagging are considered to be the best regression *** performance and reliability of the nonlinear regression method are slightly better than that of the linear regression ***,the SVM-poly method is used to analyze the susceptibility of slope parameters.

关键词： slope stability factor of safety regression machine learning repeated cross-validation