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Precise immobilization of metal single atoms into a porphyrinic metal-organic framework for an efficient alkene hydrosilylation

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Nano Research 2024年第7期17卷 5914-5921页

作者： Chun-Ying Chen Qi-Jie mo Fu-Zhen li Hai-li Song li Zhang mOE Laboratory of Bioinorganic and Synthetic Chemistry Lehn Institute of Functional MaterialsSchool of ChemistrySun Yat-Sen UniversityGuangzhou 510006China

Alkene hydrosilylation is one of the most concise and atom-economical methods to synthesize organosilicon ***,we reported the precise immobilization of metal single atoms(m-SAs;m=Ru,Rh,Ir,Pd,Pt,and Au)into a porphyrinic metalorganic framework(mOF)of PCN-222(PCN=porous coordination network),and then applied the resultant mOF composites of m-SAs@PCN-222 to alkene *** solvent-free conditions,Pt-SAs@PCN-222 displayed an especially high catalytic efficiency with the turnover frequency up to 119 s−1 and the maximum turnover number of 906,250 at room *** and theoretical studies revealed that there existed strong interactions between Pt-SAs@PCN-222 and the substrates,which helped to condense the substrates in the cavities of the porous *** density functional theory calculations and molecular dynamics simulations disclosed that PCN-222 could transfer electrons to Pt-SAs to enhance the silane oxidative addition and drive the reaction to proceed smoothly via Chalk–Harrod pathway.

关键词： alkene hydrosilylation single atom catalysts metal-organic frameworks precision chemistry synergistic catalysis

Optimal pivot path of the simplex method for linear programming based on reinforcement learning

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Science China mathematics 2024年第6期67卷 1263-1286页

作者： Anqi li Tiande Guo Congying Han Bonan li Haoran li School of mathematical Sciences University of Chinese Academy of SciencesBeijing100049China

Based on the existing pivot rules,the simplex method for linear programming is not polynomial in the worst ***,the optimal pivot of the simplex method is *** this paper,we propose the optimal rule to find all the shortest pivot paths of the simplex method for linear programming problems based on monte Carlo tree ***,we first propose the SimplexPseudoTree to transfer the simplex method into tree search mode while avoiding repeated basis ***,we propose four reinforcement learning models with two actions and two rewards to make the monte Carlo tree search suitable for the simplex ***,we set a new action selection criterion to ameliorate the inaccurate evaluation in the initial *** is proved that when the number of vertices in the feasible region is C_(n)^(m),our method can generate all the shortest pivot paths,which is the polynomial of the number of *** addition,we experimentally validate that the proposed schedule can avoid unnecessary search and provide the optimal pivot ***,this method can provide the best pivot labels for all kinds of supervised learning methods to solve linear programming problems.

关键词： simplex method linear programming pivot rules reinforcement learning

Analytical evaluation of steady-state solute distribution in through- diffusion and membrane behavior test under non-perfectly flushing boundary conditions

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Journal of Rock mechanics and Geotechnical Engineering 2024年第1期16卷 258-267页

作者： Guannian Chen Yuchao li Kristin mSample-Lord Shan Tong School of Civil&Environmental Engineering and Geography Science Ningbo UniversityNingbo315211China mOE Key Laboratory of Soft Soils and Geoenvironmental Engineering College of Civil Engineering and ArchitectureZhejiang UniversityHangzhou310058China Ningbo ZCONE High-tech Company limited Ningbo315000China Department of Civil and Environmental Engineering Villanova UniversityVillanovaPAUSA

The through-diffusion and membrane behavior testing procedure using a closed-system apparatus has been widely used for concurrent measurement of diffusion and membrane efficiency coefficients of low-permeability clay-based barrier ***,the common assumption of perfectly flushing conditions at the specimen boundaries could induce errors in analyses of the diffusion coefficients and membrane *** this study,an innovative pseudo three-dimensional(3D)analytical method was proposed to evaluate solute distribution along the boundary surfaces of the soil-porous disks system,considering the non-perfectly flushing *** results were consistent with numerical models under two scenarios considering different inflow/outflow *** proposed model has been demonstrated to be an accurate and reliable method to estimate solute distributions along the *** calculated membrane efficiency coefficient and diffusion coefficient based on the proposed analytical method are more accurate,resulting in up to 50%less relative error than the traditional approach that adopts the arithmetic mean value of the influent and effluent *** retar-dation factor of the clay specimen also can be calculated with a revised cumulative mass ***,the simulated transient solute transport matched with experimental data from a multi-stage through-diffusion and membrane behavior test,validating the accuracy of the proposed method.

关键词： Diffusion testing membrane behavior Coupled transport Clay barrier Transport modeling

Investigations of Water Flow Behaviors Induced by Local Temperature Variations through a Single Rough Fracture for the Enhanced Geothermal Systems

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Journal of Thermal Science 2024年第3期33卷 1055-1064页

作者： li Jiawei YE lin Department of Energy and Power Engineering Tsinghua UniversityBeijing100084China School of Power and Energy Northwestern Polytechnical UniversityXi’an710072China

In recent years,Enhanced Geothermal System(EGS)technologies have been applied to the geothermal resources production in the Hot Dry Rock(HDR).The core of EGS technologies is to adopt hydraulic fracturing in the reservoir to create a connected network of discrete fractures with the consideration of water as a working fluid for hydraulic fracturing and heat *** paper investigates the characteristics of water flow behaviors through a single rough fracture under different temperature and pressure conditions.A single fracture model with rough fracture surfaces is constructed and then characterized,and influences of the anisotropic factor on the average tortuosity and frictional resistance coefficient of water flow through a single fracture with rough surfaces have been compared and *** consideration of other impacting factors(temperature,pressure,fracture roughness),the impact of mass flow rate has also been *** simulation results present that changes of average tortuosity for water flow through a single rough facture are mainly affected by *** can be observed that higher temperature leads to larger average tortuosity but the frictional resistance coefficient shows an opposite *** for pressure conditions,it is found that effects of pressure on average tortuosity and frictional resistance coefficient is very small,which can be neglected under high pressure ***,the average tortuosity shows a progressively linear relationship with the mass flow *** the contrary,the frictional resistance coefficient has a negative relationship with the mass flow *** is revealed that when the mass flow rate reaches a critical point,the influences of temperature on the frictional resistance coefficient will be *** of single rough fractures with different anisotropic factors show that values of average tortuosity and frictional resistance coefficient have positive relationships with the increase

关键词： single rough fracture tortuosity frictional resistance enhanced geothermal system

Jet formation and penetration performance of a double-layer charge liner with chemically-deposited tungsten as the inner liner

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Defence Technology（防务技术） 2024年第3期33卷 374-385页

作者： Bihui Hong Wenbin li Yiming li Zhiwei Guo Binyou Yan ministerial Key Laboratory of ZNDY Nanjing University of Science and TechnologyNanjing 210094China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Xiamen Tungsten Co. Ltd.Xiamen 361004China

This paper proposes a type of double-layer charge liner fabricated using chemical vapor deposition(CVD)that has tungsten as its inner *** feasibility of this design was evaluated through penetration ***-layer charge liners were fabricated by using CVD to deposit tungsten layers on the inner surfaces of pure T2 copper *** microstructures of the tungsten layers were analyzed using a scanning electron microscope(SEm).The feasibility analysis was carried out by pulsed X-rays,slug-retrieval test and static penetration *** shaped charge jet forming and penetration law of inner tungsten-coated double-layer liner were studied by numerical simulation *** results showed that the double-layer liners could form well-shaped *** errors between the X-ray test results and the numerical results were within 11.07%.A slug-retrieval test was found that the retrieved slug was similar to a numerically simulated *** with the traditional pure copper shaped charge jet,the penetration depth of the double-layer shaped charge liner increased by 11.4% and>10.8% *** summary,the test results are good,and the numerical simulation is in good agreement with the test,which verified the feasibility of using the CVD method to fabricate double-layer charge liners with a high-density and high-strength refractory metal as the inner liner.

关键词： Shaped charge Chemical vapor deposition Tungsten Double-layer charge liner X-ray Penetration

Exciting lattice oxygen of nickel–iron bi-metal alkoxide for efficient electrochemical oxygen evolution reaction

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Journal of Energy Chemistry 2024年第1期88卷 194-201,I0005页

作者： Saihang Zhang Senchuan Huang Fengzhan Sun Yinghui li li Ren Hao Xu Zhao li Yifei liu Wei li lina Chong Jianxin Zou National Engineering Research Center of light Alloy Net Forming&State Key Laboratory of metal matrix Composites Center of Hydrogen ScienceSchool of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China Department of Chemistry Laboratory of Advanced MaterialsShanghai Key Laboratory of Molecular Catalysis and Innovative MaterialsiChEM and State Key Laboratory of Molecular Engineering of PolymersCollege of Chemistry and MaterialsFudan UniversityShanghai 200433China

High efficiency,cost-effective and durable electrocatalysts are of pivotal importance in energy conversion and storage *** electro-oxidation of water to oxygen plays a crucial role in such energy conversion ***,we report a robust method for the synthesis of a bimetallic alkoxide for efficient oxygen evolution reaction(OER)for alkaline electrolysis,which yields current density of 10 mA cm^(-2)at an overpotential of 215 mV in 0.1 m KOH *** catalyst demonstrates an excellent durability for more than 540 h operation with negligible degradation in *** spectra revealed that the catalyst underwent structure reconstruction during OER,evolving into oxyhydroxide,which was the active site proceeding OER in alkaline ***-situ synchrotron X-ray absorption experiment combined with density functional theory calculation suggests a lattice oxygen involved electrocatalytic reaction mechanism for the in-situ generated nickel–iron bimetal-oxyhydroxide *** mechanism together with the synergy between nickel and iron are responsible for the enhanced catalytic activity and *** findings provide promising strategies for the rational design of nonnoble metal OER catalysts.

关键词： Oxygen evolution reaction Nickel-iron bi-metal alkoxide Lattice oxygen-mediated reaction mechanism Alkaline electrolysis Electrocatalysts

Improving anammox activity and reactor start-up speed by using CO_(2)/NaHCO_(3) buffer

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Journal of Environmental Sciences 2024年第5期139卷 60-71页

作者： Shaoan Cheng Huahua li Xinyuan He Hua Chen Longxin li State Key Laboratory of Clean Energy Utilization College of Energy EngineeringZhejiang UniversityHangzhou 310027China

Anammox bacteria grow slowly and can be affected by large pH *** suitable buffers could make the start-up of anammox reactors easy and *** this study,the effects of three kinds of buffers on the nitrogen removal and growth characteristics of anammox sludge were *** with CO_(2)/NaHCO_(3)buffer solution(CCBS)performed the best in nitrogen removal,while 4-(2-hydroxyerhyl)piperazine-1-ethanesulfonic acid(HEPES)and phosphate buffer solution(PBS)inhibited the anammox *** with 50 mmol/L CCBS could start up in 20 days,showing the specific anammox activity and anammox activity of 1.01±0.10 gN/(gVSS·day)and 0.83±0.06 kgN/(m^(3)·day),*** Kuenenia was the dominant anammox bacteria,with a relative abundance of 71.8%.Notably,anammox reactors could also start quickly by using 50 mmol/L CCBS under nonstrict anaerobic *** findings are meaningful for the quick start-up of engineered anammox reactors and prompt enrichment of anammox bacteria.

关键词： Anammox bacteria Buffer solution CO_(2)/NaHCO_(3) Physiological characteristics microbial community shift

Effect of streamlined nose length on aerodynamic performance of high-speed train with a speed of 400 km/h

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第7期25卷 525-540页

作者： Nianxun li Tian li Zhiyuan DAI Deng QIN Jiye ZHANG State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu 610031China

The streamlined nose length(SNL)plays a crucial role in determining the aerodynamic performance of high-speed *** appropriate SNL can not only effectively reduce the magnitude of aerodynamic drag and lift forces,but also improve the performance of the high-speed train in tunnel passing and crosswind *** this study,a numerical simulation of the aerodynamic performance of high-speed trains at a speed of 400 km/h,with varying SNLs,is conducted using the k-ωshear stress transport(SST)turbulence *** different SNLs include 6.0,7.0,8.0,9.0,9.8,12.0,15.0,and 18.0 *** order to validate the accuracy of the numerical simulation,its results are compared with wind tunnel test data obtained from the *** simulation is carried out using compressible and incompressible gases to determine the effect of gas compressibility on *** impact of SNL on the aerodynamic performance of the trains is analyzed in terms of aerodynamic forces,velocity,and pressure *** comparison to the original train,the train with a 6.0 m SNL experienced a 10.8%increase in overall aerodynamic ***,the lift forces on the head and tail cars increased by 35.7%and 75.5%,*** the other hand,the train with an 18.0 m SNL exhibited a 16.5%decrease in aerodynamic ***,the lift forces on the head and tail cars decreased by 21.9%and 49.7%,*** aerodynamic drag force of the entire train varies linearly with the SNL,while the aerodynamic lift of the tail car follows a quadratic function in relation to the SNL.

关键词： Streamlined nose length(SNL) High-speed train Aerodynamic performance Numerical simulation Flow structures

Dynamic Vision-Based machinery Fault Diagnosis With Cross-modality Feature Alignment

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IEEE/CAA Journal of Automatica Sinica 2024年第10期11卷 2068-2081页

作者： Xiang li Shupeng Yu Yaguo Lei Naipeng li Bin Yang Key Laboratory of Education ministry for modern Design and Rotor-Bearing System Xi’an Jiaotong UniversityXi’an 710049China IEEE

Intelligent machinery fault diagnosis methods have been popularly and successfully developed in the past decades,and the vibration acceleration data collected by contact accelerometers have been widely *** many industrial scenarios,contactless sensors are more *** event camera is an emerging bio-inspired technology for vision sensing,which asynchronously records per-pixel brightness change polarity with high temporal resolution and low *** offers a promising tool for contactless machine vibration sensing and fault ***,the dynamic vision-based methods suffer from variations of practical factors such as camera position,machine operating condition,***,as a new sensing technology,the labeled dynamic vision data are limited,which generally cannot cover a wide range of machine fault *** at these challenges,a novel dynamic vision-based machinery fault diagnosis method is proposed in this *** is motivated to explore the abundant vibration acceleration data for enhancing the dynamic vision-based model performance.A crossmodality feature alignment method is thus proposed with deep adversarial neural networks to achieve fault diagnosis knowledge *** event erasing method is further proposed for improving model robustness against *** proposed method can effectively identify unseen fault mode with dynamic vision *** on two rotating machine monitoring datasets are carried out for validations,and the results suggest the proposed method is promising for generalized contactless machinery fault diagnosis.

关键词： Condition monitoring domain generalization eventbased camera fault diagnosis machine vision