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Engineering yolk-shell CuCo_(2)S_(4)@Cu_(2)O Z-scheme nanoreactors for accelerating generation of value-added chemicals and of degradation multi-organic contaminants

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Journal of Materials Science & Technology 2023年第25期156卷 54-63页

作者： Xue Feng Lei Zhang College of Chemistry Liaoning University66 Chongshan Middle RoadShenyang 110036China

The synthesis of solar-driven chemical value-added products and the degradation of pollutants is a promising approach for sustainable development. However, achieving these works via photocatalysts with efficient charge-separation, photo-absorption is challenging. A yolk-shell CuCo_(2)S_(4)@Cu_(2)O Z-scheme nanoreactor (YS-CuCo_(2)S_(4)@Cu_(2) O-NR) with octahedron Cu_(2)O as the core and tubular CuCo2 S4 as the shell, has been synthesized by regulating composition and morphology. YS-CuCo_(2)S_(4)@Cu_(2)O-NR shows superior photocatalytic activities for producing H_(2) O_(2) collaborates by selective oxidation of benzyl alcohol (BA) to high value-added benzaldehyde (BAD)/utilized Fenton-like reaction to degrade multi-pollutants through space-confinement effect, reaching 80% conversion and 99% selectivity of BA, a yield of 12 mM g^(−1) for H_(2)O_(2) and above 90% degradation efficiency for multi-pollutants. A photocatalysis nanoconfinement reactor system is proposed and demonstrated by using yolk-shell to enhance the performance of the chemical reaction. Mechanism studies show that the yolk-shell provides confined space to accelerate redox reaction kinetics;while the inner void promotes light harvesting and keeps yolk Cu_(2) O from deactivation;combined with the Z-scheme charge transfer, engineering Cu^(+) /Cu^(2+) active composition, they are favorable for enhancing the H_(2) O_(2) generation and Fenton-like activity. These findings provide new opportunities for application of yolk-shell Z-scheme metal-oxide-based photocatalysts.

关键词： Octahedron yolk-shell structure catalyzer Z-scheme charge transfer H2O_(2)generation Selective oxidation of BA Fenton-like reaction

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An Insight into the Second-Harmonic Current Reduction Control Strategies in Two-Stage Converters

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Energy Engineering 2022年第3期119卷 1179-1196页

作者： lei Ren Lei Zhang School of Electrical Engineering Nantong UniversityNantong226019China

Due to the components at twice the fundamental frequency of output voltage in the instantaneous output power of a two-stage single-phase inverter(TSI),the second harmonic current(SHC)is generated in the frontend dc-dc converter(FDC).To reduce the SHC,optimizing the control strategy of the FDC is an effective and costless approach.Fromthe view of visual impedance,this paper conducts an intensive study on the SHC reduction strategies.Origin of the SHC is illustrated first.Then,the equivalent circuit models of the FDC under different control strategies are proposed to analyse the SHC propagation characteristic.The derived model can offer a better insight into how the inductor SHC is affected by the control parameters.According to the derived models,a synthesis of different control strategies is presented and the relevant parameters are listed for control design to achieve better suppression effect.The benefits and limitations of these control strategies are also discussed.Based on the proposed equivalent circuit models,several optimization methods are proposed to enhance the effect.A 1500 VA TSI prototype is built and simulated on MATLAB/Simulink,verifying the effectiveness of the proposed optimization methods.This paper is aimed to provide a guideline for the control design and control optimization of the TSIs.

关键词： Two-stage single-phase inverter(TSI) second harmonic current(SHC) equivalent circuit models optimization

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Error Estimate for Semi-implicit Method of Sphere-Constrained High-Index Saddle Dynamics

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Chinese Annals of Mathematics,Series B 2023年第5期44卷 765-780页

作者： Lei Zhang Pingwen zhang Xiangcheng ZHENG Beijing International Center for Mathematical Research Center for Machine Learning ResearchCenterfor Quantitative BiologyPeking UniversityBeijing 100871China School of Mathematics and Statistics Wuhan UniversityWuhan 430072China School of MathematicalSciences Laboratory of Mathematics and Applied MathematicsPeking UniversityBeijing 100871China School of Mathematics Shandong UniversityJinan 250100China

The authors prove error estimates for the semi-implicit numerical scheme of sphere-constrained high-index saddle dynamics,which serves as a powerful instrument in finding saddle points and constructing the solution landscapes of constrained systems on the high-dimensional sphere.Due to the semi-implicit treatment and the novel computational procedure,the orthonormality of numerical solutions at each time step could not be fully employed to simplify the derivations,and the computations of the state variable and directional vectors are coupled with the retraction,the vector transport and the orthonormalization procedure,which significantly complicates the analysis.They address these issues to prove error estimates for the proposed semi-implicit scheme and then carry out numerical experiments to substantiate the theoretical findings.

关键词： Saddle point Constrained saddle dynamics Solution landscape Semiimplicit Numerical analysis

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Effect of Refresh Time on XeF2 Gas-assisted FIB Milling of GaAs

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Nanomanufacturing and Metrology 2023年第4期6卷 16-23页

作者： Jining Sun Lei Zhang Yi zhang Yunlong Han Lei Zhang School of Mechanical Engineering Dalian University of TechnologyDalian 116024China State Key Laboratory of High-Performance Precision Manufacturing Dalian University of TechnologyDalian 116024China

Focused ion beam (FIB) machining can be used to fabricate gallium arsenide-based devices, which have a surface fnish of several nanometers, and the FIB machining speed and surface fnish can be greatly improved using xenon difuoride (XeF2) gas-assisted etching. Although the refresh time is one of the most important parameters in the gas-assisted etching process, its efect on the machining quality of the surface fnish has rarely been studied. Therefore, in this work, we investigated the efect of the refresh time on the etching process, including the dissociation process of XeF2, the refresh time dependency of the sputter in yield under diferent incident angles, and the surface fnish under diferent refresh times. The results revealed that a selective etching mechanism occurred at diferent refresh times. At an incidence angle of 0°, the sputtering yield increased with the refresh time and reached its maximum value at 500 ms;at an incidence angle of 30°, the sputtering yield reached its minimum value at a refresh time of 500 ms. For surface roughness, the incident angle played a more important role than the refresh time. The surface fnish was slightly better at an incidence angle of 30° than at 0°. In addition, both F and Xe elements were detected in the processed area: Xe elements were evenly distributed throughout the processing area, while F elements tended to accumulate in the whole processing area. The results suggest that the optimum surface can be obtained when a larger refresh time is employed.

关键词： Focused ion beam Gas-assisted etching Refresh time GaAs

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A dual-mode fiber-shaped flexible capacitive strain sensor fabricated by direct ink writing technology for wearable and implantable health monitoring applications

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Microsystems & Nanoengineering 2023年第6期9卷 321-331页

作者： Chi zhang Wenyu Ouyang Lei Zhang Dachao Li State Key Laboratory of Precision Measuring Technology and Instruments Tianjin University300072 TianjinChina

Flexible fiber-shaped strain sensors show tremendous potential in wearable health monitoring and human‒machine interactions due to their compatibility with everyday clothing.However,the conductive and sensitive materials generated by traditional manufacturing methods to fabricate fiber-shaped strain sensors,including sequential coating and solution extrusion,exhibit limited stretchability,resulting in a limited stretch range and potential interface delamination.To address this issue,we fabricate a fiber-shaped flexible capacitive strain sensor(FSFCSS)by direct ink writing technology.Through this technology,we print parallel helical Ag electrodes on the surface of TPU tube fibers and encapsulate them with a high dielectric material BTO@Ecoflex,endowing FSFCSS with excellent dual-mode sensing performance.The FSFCSS can sense dual-model strain,namely,axial tensile strain and radial expansion strain.For axial tensile strain sensing,FSFCSS exhibits a wide detection range of 178%,a significant sensitivity of 0.924,a low detection limit of 0.6%,a low hysteresis coefficient of 1.44%,and outstanding mechanical stability.For radial expansion strain sensing,FSFCSS demonstrates a sensitivity of 0.00086 mmHg−1 and exhibits excellent responsiveness to static and dynamic expansion strain.Furthermore,FSFCSS was combined with a portable data acquisition circuit board for the acquisition of physiological signals and human‒machine interaction in a wearable wireless sensing system.To measure blood pressure and heart rate,FSFCSS was combined with a printed RF coil in series to fabricate a wireless hemodynamic sensor.This work enables simultaneous application in wearable and implantable health monitoring,thereby advancing the development of smart textiles.

关键词： wear strain shaped

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Discretization and index-robust error analysis for constrained high-index saddle dynamics on the high-dimensional sphere

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Science China Mathematics 2023年第10期66卷 2347-2360页

作者： Lei Zhang Pingwen zhang Xiangcheng Zheng Beijing International Center for Mathematical Research Center for Machine Learning ResearchCenter for Quantitative BiologyPeking UniversityBeijing 100871China School of Mathematics and Statistics Wuhan UniversityWuhan 430072China School of Mathematical Sciences Laboratory of Mathematics and Applied MathematicsPeking UniversityBeijing 100871China School of Mathematics Shandong UniversityJinan 250100China

We develop and analyze numerical discretization to the constrained high-index saddle dynamics,the dynamics searching for the high-index saddle points confined on the high-dimensional unit sphere.Compared with the saddle dynamics without constraints,the constrained high-index saddle dynamics has more complex dynamical forms,and additional operations such as the retraction and vector transport are required due to the constraints,which significantly complicate the numerical scheme and the corresponding numerical analysis.Furthermore,as the existing numerical analysis results usually depend on the index of the saddle points implicitly,the proved numerical accuracy may be reduced if the index is high in many applications,which indicates the lack of robustness with respect to the index.To address these issues,we derive the error estimates for numerical discretization of the constrained high-index saddle dynamics on the high-dimensional sphere and then improve it by providing index-robust error analysis in an averaged norm by adjusting the relaxation parameters.The developed results provide mathematical support for the accuracy of numerical computations.

关键词： saddle dynamics saddle point solution landscape error estimate index-robust

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A Survey on Negative Transfer

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IEEE/CAA Journal of Automatica Sinica 2023年第2期10卷 305-329页

作者： Wen zhang Lingfei Deng Lei Zhang Dongrui Wu the Key Laboratory of the Ministry of Education for Image Processing and Intelligent Control School of Artificial Intelligence and AutomationHuazhong University of Science and TechnologyWuhan 430074China IEEE the School of Microelectronics and Communication Engineering Chongqing UniversityChongqing 400044China

Transfer learning(TL)utilizes data or knowledge from one or more source domains to facilitate learning in a target domain.It is particularly useful when the target domain has very few or no labeled data,due to annotation expense,privacy concerns,etc.Unfortunately,the effectiveness of TL is not always guaranteed.Negative transfer(NT),i.e.,leveraging source domain data/knowledge undesirably reduces learning performance in the target domain,and has been a long-standing and challenging problem in TL.Various approaches have been proposed in the literature to address this issue.However,there does not exist a systematic survey.This paper fills this gap,by first introducing the definition of NT and its causes,and reviewing over fifty representative approaches for overcoming NT,which fall into three categories:domain similarity estimation,safe transfer,and NT mitigation.Many areas,including computer vision,bioinformatics,natural language processing,recommender systems,and robotics,that use NT mitigation strategies to facilitate positive transfers,are also reviewed.Finally,we give guidelines on NT task construction and baseline algorithms,benchmark existing TL and NT mitigation approaches on three NT-specific datasets,and point out challenges and future research directions.To ensure reproducibility,our code is publicized at https://***/chamwen/NT-Benchmark.

关键词： Domain adaptation domain similarity negative transfer positive transfer transfer learning

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Experimental study of coal flow characteristics under mining disturbance in China

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International Journal of Coal Science & Technology 2022年第5期9卷 32-47页

作者： Lei Zhang Zihao Kan Cun zhang Jun Tang State Key Laboratory of Coal Resources and Safe Mining School of MinesChina University of Mining and TechnologyXuzhou 221116JiangsuChina School of Energy and Mining Engineering China University of Mining and Technology(Beijing)Beijing 100083China School of Safety Engineering China University of Mining and TechnologyXuzhou 221116JiangsuChina

With annually increased coal mining depth,gas extraction becomes more and more problematic.The gas extraction efect depends on coal seam permeability,which,in turn,is afected by many factors,including loading and unloading stresses and strains in the coal seam.Stresses induce internal cracks,resulting in cleats and gas emission channels,the coal seam permeability permanently changes accordingly.To clarify the stress-induced efects on coal seam permeability,this survey summarized the available approaches used to link the stress path and seepage law in the coal body seepage law,which can be classifed into two design methods:single load variation and combined feld mining method.The characterization methods used to observe the surface of coal samples and three-dimensional reconstruction include electron microscopy,CT scanning,and Nuclear Magnetic Resonance(NMR).According to the stress paths designed by the above two approaches,the seepage laws and similarities of three kinds of coal samples with the fractured structure were summarized in this paper.The following directions are recommended to study the seepage law of coal bodies with three kinds of fractured structures under stress.Firstly,the stress path of the experimental coal body should be designed by the combined feld mining method.The stressed environment of a deep coal seam is complicated,and the axial and confning pressures change simultaneously.Therefore,one cannot fully refect the real situation on-site by studying permeability evolution alone.Secondly,during the coal seam mining,the stressed state changes from time to time,and the development of coal seam fractures is afected by mining.When studying the stress efect on seepage of coal samples,the fractured structure of coal samples should be considered.Finally,the available structural characterization methods of coal samples can be combined with the 3D printing technology,which would produce artifcial samples with the fractured structure characteristics of natural coal.

关键词： Stress loading and unloading Structural characterization Permeability Fracture structure Broken coal

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Non-alkyl tin-oxo clusters as new-type patterning materials for nanolithography

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Science China Chemistry 2022年第1期65卷 114-119页

作者： Di Wang Xiaofeng Yi Lei Zhang State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China University of Chinese Academy of Sciences Beijing 100049China

Nanolithography plays crucial roles in the miniaturization of dense integrated circuit,which extremely depends on innovative resist materials.Recently,metal-containing resists have been explored due to their higher short-wavelength photon absorption than traditional polymer resists.Herein,for the first time,the patterning performance of non-alkyl tin-oxo clusters has been evaluated.Meanwhile,the influence of structural characteristics on resolution and sensitivity has been investigated.To evaluate the surface ligand effect,three non-alkyl Sn_(10)-oxo clusters with the same core were functionalized with pyrazole,3-methylpyrazole and 4-methylpyrazole,respectively.Furthermore,another Sn_(14)-oxo cluster with similar core configuration was also prepared using 4-methylpyrazole ligand to study the influence of Sn nuclearity.Spin-coating method was then applied to fabricate thin films of these non-alkyl tin-oxo clusters on Si substrate,which showed various thicknesses and roughnesses.More interestingly,electron beam lithography(EBL)patterning studies indicated that for the same Sn_(10)core,the 4-methylpyrazoledecorated clusters showed the best performance.As for the different cluster cores with the same 4-methylpyrazole ligand,the patterns of Sn_(10)with the higher ligand:Sn ratio are also better than those of Sn_(14).Finally,distinguishable 50 nm resolution was achieved by 4-methylpyrazole-decorated Sn_(10)at expose energy of 100μC/cm2which can be significantly improved by increasing expose energy to 1,000μC/cm2as confirmed by atomic force microscopy(AFM)images.This work not only opens the nanolithography applications of non-alkyl tin-oxo clusters,but also provides an effective structural methodology for improving their patterning performance in future.

关键词： non-alkyl tin-oxo clusters nanolithography ligands effect EBL patterning materials

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Investigating ionic liquids for optimizing lithium metal anode

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Green Energy & Environment 2022年第2期7卷 173-175页

作者： Lei Zhang Mohammad Al-Mamun Centre for Clean Environment and Energy Griffith UniversityGold Coast CampusGold CoastQLD 4222Australia

Developing renewable energy technology is an effective way to address the global warming and air pollution problems derived from depleting fossil fuels.Due to the high theoretical capacity(3860 m Ah g-1) and low electrochemical potential of lithium metal anode,lithium metal batteries(LMBs) have attracted tremendous research attention with the scalable application and vigorous deployment of electric vehicles.Unfortunately,the further commercialization of Li metal anode is hindered by the random growth of Li dendrites during the lithium plating/stripping processes,leading to the continuous consumption of active Li and the puncture on the separator.Just recently,Ma’s group proposed a new approach to systematically investigate the relationship between functional groups and Li dendrite generation during the Li plating/stripping processes.The proposed new approach could be of an effective tool to gain new insights into functional groups in the electrolyte additives and Li dendrites formation,highly valuable for the rational structural design of highperformance Li metal electrode materials.

关键词： lithium stripping electrolyte

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