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Effective Activation of Melamine for Synchronous Synthesis of Catalytically Active Nanosheets and Fluorescence-Responsive Quantum Dots

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Transactions of Tianjin University 2024年第3期30卷 284-296页

作者： Jie Xuan Guijian guan Ming-Yong Han Institute of Molecular Plus Tianjin UniversityTianjin 300072China

Because of the low reactivity of cyclic nitrides,liquid-phase synthesis of carbon nitride introduces challenges despite its favorable potential for energy-efficient preparation and superior *** this study,we demonstrate a strong interaction between citric acid and melamine through experimental observation and theoretical simulation,which eff ectively activates melamine-condensation activity and produces carbon-rich carbon nitride nanosheets(CCN NSs)during hydrothermal *** a large specific surface area and increased light absorption,these CCN NSs demonstrate significantly enhanced photocatalytic activity in CO_(2) reduction,increasing the CO production rate by approximately tenfold compared with hexagonal melamine(h-Me).Moreover,the product selectivity of CCN NSs reaches up to 93.5%to generate CO from CO_(2).Furthermore,the annealed CCN NSs exhibit a CO conversion rate of up to 95.30μmol/(g h),which indicates an 18-fold increase compared with traditional carbon *** the CCN NS synthesis,nitrogen-doped carbon quantum dots(NDC QDs)are simultaneously produced and remain suspended in the supernatant after *** QDs disperse well in water and exhibit excellent luminescent properties(QY=67.2%),allowing their application in the design of selective and sensitive sensors to detect pollutants such as pesticide 2,4-dichlorophenol with a detection limit of as low as 0.04μmol/***,the simultaneous synthesis of CCN NSs and NDC QDs provides a cost-eff ective and highly efficient process,yielding products with superior capabilities for catalytic conversion of CO_(2) and pollutant detection,respectively.

关键词： Carbon nitride Hydrothermal reaction Photocatalysis Carbon dioxide Quantum dots

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Combined UAMP and MF Message Passing Algorithm for Multi-Target Wideband DOA Estimation with Dirichlet Process Prior

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Tsinghua Science and Technology 2024年第4期29卷 1069-1081页

作者： Shanwen guan Xinhua Lu Ji Li Rushi Lan Xiaonan Luo guangxi Key Laboratory of Image and Graphic Intelligent Processing Guilin University of Electronic TechnologyGuilin 541004China Guilin Huigu Institute of AI Industrial Technology Guilin 541004China School of Information Engineering Nanyang Institute of TechnologyNanyang 473000China

When estimating the direction of arrival (DOA) of wideband signals from multiple sources, the performance of sparse Bayesian methods is influenced by the frequency bands occupied by signals in different directions. This is particularly true when multiple signal frequency bands overlap. Message passing algorithms (MPA) with Dirichlet process (DP) prior can be employed in a sparse Bayesian learning (SBL) framework with high precision. However, existing methods suffer from either high complexity or low precision. To address this, we propose a low-complexity DOA estimation algorithm based on a factor graph. This approach introduces two strong constraints via a stretching transformation of the factor graph. The first constraint separates the observation from the DP prior, enabling the application of the unitary approximate message passing (UAMP) algorithm for simplified inference and mitigation of divergence issues. The second constraint compensates for the deviation in estimation angle caused by the grid mismatch problem. Compared to state-of-the-art algorithms, our proposed method offers higher estimation accuracy and lower complexity.

关键词： wideband direction of arrival(DOA)estimation sparse Bayesian learning(SBL) unitary approximate message passing(UAMP)algorithm Dirichlet process(DP)

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Ni-catalyzed highly regio- and stereo-selective diborylative cyclization of 1,6-enynes with diboron reagent

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Science China Chemistry 2024年第3期67卷 981-989页

作者： Qitao guan zhen Shen Yiqiang Tian Genping Huang Chun zhang Institute of Molecular Plus Tianjin Key Laboratory of Molecular Optoelectronic ScienceDepartment of ChemistrySchool of SciencesTianjin UniversityTianjin 300072China State Key Laboratory of Elemento-Organic Chemistry Nankai UniversityTianjin 300071China

The Ni-catalyzed highly selective diborylative cyclization of 1,6-enynes with diboron reagent has been developed. When pinB-Bdan was used, multiple types of boron-containing functional groups could be installed into organic molecule with great chemoselectivity and regioselectivity though this reaction. Meanwhile, if B_2pai_2 was employed, the asymmetric diborylative cyclization could be well induced by using strategy of dynamic kinetic resolution. Importantly, the above reactions could afford desired product with 100% atomic economy, and could be compatible with different series of substituents. The studies of further transformation well illustrated that different type products could serve diverse synthetic strategy. Notably, the reaction mechanism was intensively studied by density functional theory(DFT) calculations, which could reveal the mechanism of regio- and enantio-selective control.

关键词： nickel-catalyzed organoboron cyclization regioselectivity enantioselectivity

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A multi-functional MgF_(2)/polydopamine/hyaluronan-astaxanthin coating on the biodegradable zE21B alloy with better corrosion resistance and biocompatibility for cardiovascular application

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Journal of Magnesium and Alloys 2024年第3期12卷 1102-1116页

作者： Yachen Hou Xueqi zhang Jingan Li Liguo Wang Shaokang guan School of Materials Science and Engineering and Henan Key Laboratory of Advanced Magnesium Alloy and Key Laboratory of Materials Processing and Mold Technology(Ministry of Education) Zhengzhou UniversityZhengzhou 450001China

The cardiovascular diseases(CVD)continue to be the major threat to global public health over the years,while one of the effective methods to treat CVD is stent *** magnesium(Mg)alloys have great potential applications in cardiovascular stents benefit from their excellent biodegradability and ***,excessive degradation rate and the delayed surface endothelialization still limit their further *** this study,we modified a Mg-zn-Y-Nd alloy(zE21B)by preparing MgF_(2) as the corrosion resistance layer,the dopamine polymer film(PDA)as the bonding layer,and hyaluronic acid(HA)loaded astaxanthin(ASTA)as an important layer to directing the cardiovascular cells *** electrochemical test results showed that the MgF_(2)/PDA/HA-ASTA coating improved the corrosion resistance of *** cytocompatibility experiments also demonstrated that this novel composite coating also selectively promoted endothelial cells proliferation,inhibited hyperproliferation of smooth muscle cells and adhesion of *** with the HAloaded rapamycin(RAPA)coating,our MgF_(2)/PDA/HA-ASTA coating showed better blood compatibility and cytocompatibility,indicating stronger multi-functions for the zE21B alloy on cardiovascular application.

关键词： Biodegradable zE21B alloy Reendothelialization Surface modification Hyaluronic acid Astaxanthin.

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Diatomic Fe-Co catalysts synergistically catalyze oxygen evolution reaction

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Nano Research 2024年第5期17卷 3794-3800页

作者： Tianmi Tang Jingyi Han zhenlu Wang Xiaodi Niu Jingqi guan Institute of Physical Chemistry College of ChemistryJilin UniversityChangchun 130021China College of Food Science and Engineering Jilin UniversityChangchun 130062China

The design of diatomic catalysts with uniformly dispersed metal atoms is expected to improve catalytic performance,which is conducive to the intensive comprehending of the synergistic mechanism between dual-metal sites for the oxygen evolution reaction(OER)at the atomic ***,we design a strategy to immobilize bimetallic Fe-Co atoms onto nitrogen-doped graphene to obtain a diatomic catalyst(DA-FC-NG)with FeN_(3)-CoN_(3) *** DA-FC-NG shows excellent OER activity with a low overpotential(η_(10)=268 mV),which is superior to commercial iridium dioxide *** calculations uncover that the excellent activity of DA-FC-NG is due to the interaction between Fe and Co diatoms,which causes charge rearrangement and induces the adsorption of intermediates on the Fe-O-Co bridge structure,thus improving the catalytic OER *** work is of great significance for the design of highly active diatomic catalysts to replace noble metal catalysts for energy-related applications.

关键词： oxygen evolution reaction diatomic catalyst FeN_(3)-CoN_(3) X-ray absorption spectroscopy(XAS)spectrum theoretical calculation

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Exploring a balance between strength and ductility of hexagonal BN nanoplatelet reinforced zK61 magnesium composite

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Journal of Magnesium and Alloys 2024年第5期12卷 1899-1910页

作者： Kewei zhang Xiaolong Lu Yufeng Sun Shaokang guan Yao Chen School of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China Key Laboratory of Advanced Magnesium Alloys in Henan Province Zhengzhou UniversityZhengzhou 450002China Key Laboratory of Advanced Materials Processing&Mold Ministry of EducationZhengzhou 450002China School of Mechanical and Electrical Engineering Soochow UniversitySuzhou 215021China

The practical applications of magnesium(Mg)alloys are usually beset by their relatively low strength and limited *** we attempt to fabricate hexagonal BN nanoplatelet(BNNP)reinforced zK61 magnesium composites using a combination of spark plasma sintering and friction stir *** resulting composites exhibit microstructural characteristics of homogeneous dispersion of BNNP in Mg matrix with refined equiaxed grains and(0002)basal texture roughly surrounding the pin column *** electron microscopy observation illustrates that trace amounts of Mg_(3)N_(2)and MgB_(2)form at BNNP-Mg interface,in which Mg_(3)N_(2)locates at the basal plane of a BNNP and MgB_(2)grows at its open *** spatial distribution of Mg_(3)N_(2)and MgB_(2)facilitates interfacial wetting and stronger BNNP-Mg interface in such a way that interfacial products act as anchors bonding between *** comparison with monolithic zK61 alloy,the BNNP/zK61 composites display simultaneous improvements in yield strength,hardness and ductility,achieving good strength-ductility *** research is expected to shed some light on BNNP potentials for designing and producing magnesium composites with high strength and good ductility.

关键词： BN nanoplatelet Magnesium composite Strength Ductility Spark plasma sintering Friction stir processing

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Effects of hot deformation and in-situ zrB2 particle on microstructure and tensile performance of AA7085 composite sheets

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Journal of Iron and Steel Research International 2024年第7期31卷 1778-1791页

作者： Jiang-jing Wu Xi-zhou Kai Chuang guan Yu-tao zhao School of Material Science and Engineering Jiangsu UniversityZhenjiang 212013JiangsuChina

To provide a new idea to reduce anisotropy for sheets in the thickness direction by microstructure modification and,mean-while,maintain or even enhance tensile performance,the in-situ zrB2 particle/AA7085 composite sheets with thicknesses of 1,2,3,and 6 mm were *** as-cast grain size was significantly refined by the heterogeneous nucleus of the zrB2 *** microstructure results show that severe hot deformation converts as-cast disordered microstructure into a sequential microstructure by crushing the remanent phases and matrix into a fiber *** the solid solution and aging heat treatment,the composite sheets exhibit largely recrystallized grains compared with partially recrystallized grains in the matrix sheets,and weak or even free texture exists in the *** grain size in the composite sheets decreases with the increase in thickness *** the thickness range of 1-3 mm,the composite sheets maintain a similar tensile per-formance as that in matrix sheets,while the strength and ductility in the 6-mm-thick composite sheet are improved.

关键词： Composite sheet Grain structure Texture Dislocation Strengthening

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Improving access to urban parks through public transit optimization

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Frontiers of Architectural Research 2024年第3期13卷 575-592页

作者： Ning Xu Kaidan guan Pu Wang School of Architecture Southeast UniversityNanjing 210096China Jiangsu Provincial Urban and Rural Digital Technology Engineering Center Nanjing 210096China

This study establishes an evaluation and optimization framework for the public transit network based on social network analysis and a greedy algorithm,aiming to explore a quantitative approach to improving access to urban parks through public transit *** network analysis and the ArcGIS platform are used to build a public transit network model within Nanjing Old City and analyze its overall network structure *** study also focuses on a method to improve the convenience of reaching regional and citylevel parks by public transit by increasing access and connecting points accordingly.A greedy algorithm is introduced to generate an optimized solution for improving public transit accessibility to regional and city-level parks,consequently enhancing their *** major findings include:(1)The greedy algorithm effectively enhances the performance of the public transit network,but its benefits gradually diminish as more stations are added.(2)Strategically adding stations enhances the performance of most public transit access points,creating efficient pathways for other stations to directly reach these access points and enter regional and city-level parks.(3)The optimized public transit network model offers guidance for the planning and layout of regional and city-level *** site selection for new parks should prioritize establishing connections with the“hubs”in the public transit *** proposed optimization of the public transit network in this study is specific to a single type of urban park,but subsequent research could be conducted to extend the optimization of public transit accessibility around more urban public resources.

关键词： Urban parks Social network analysis Accessibility optimization Public transit network Greedy algorithm

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ARTIFICIAL AGING TESTS WITH DEFECTIVE COMPOSITE INSULATORS 19th

ARTIFICIAL AGING TESTS WITH DEFECTIVE COMPOSITE INSULATORS

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The ⅪⅩ International Conference on Gas Discharges and Their Applications

作者： B.LUTz F.LIANG J.zHANG z.guan L.WANG Laboratory of Advanced Technology of Electrical Engineering and Energy Graduate School at ShenzhenTsinghua University

ISBN: (纸本)9771003651221

＜正＞In this study,artificial aging tests with composite insulators containing different defects at the sheath-core interface were *** including copper strips,wood strips and weak adhesion between sheath and core were *** samples were stressed by a stepwise increasing AC test voltage while the leakage current and the surface temperature were *** effect of the defect type,defect length and of absorbed water on the aging process was investigated in dry environment. In case that the leakage current exceeded 0.2 mA, samples containing wetted or conductive defects exhibited a significant increase of surface *** highest temperature developed at the defects’ edges near to the ground electrode where puncturing of the silicone rubber sheath finally *** puncturing mechanism is critical for the long-term performance of composite insulators since further aging mechanisms may be triggered afterwards.

关键词： composite insulators surface temperature leakage currents Grounding electrodes dry conditions Hygroscopic Water insulators Composites aging mechanism Sheaths Accelerated aging

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Multi-layer perceptron-based data-driven multiscale modelling of granular materials with a novel Frobenius norm-based internal variable

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2198-2218页

作者： Mengqi Wang Y.T.Feng Shaoheng guan Tongming Qu zienkiewicz Centre for Computational Engineering Faculty of Science and EngineeringSwansea UniversitySwanseaWalesSA18EPUK Institute of Theoretical and Computational Physics Graz University of TechnologyGraz8010Austria Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyClearwater BayKowloonHong KongChina

One objective of developing machine learning(ML)-based material models is to integrate them with well-established numerical methods to solve boundary value problems(BVPs).In the family of ML models,recurrent neural networks(RNNs)have been extensively applied to capture history-dependent constitutive responses of granular materials,but these multiple-step-based neural networks are neither sufficiently efficient nor aligned with the standard finite element method(FEM).Single-step-based neural networks like the multi-layer perceptron(MLP)are an alternative to bypass the above issues but have to introduce some internal variables to encode complex loading *** this work,one novel Frobenius norm-based internal variable,together with the Fourier layer and residual architectureenhanced MLP model,is crafted to replicate the history-dependent constitutive features of representative volume element(RVE)for granular *** obtained ML models are then seamlessly embedded into the FEM to solve the BVP of a biaxial compression case and a rigid strip footing *** obtained solutions are comparable to results from the FEM-DEM multiscale modelling but achieve significantly improved *** results demonstrate the applicability of the proposed internal variable in enabling MLP to capture highly nonlinear constitutive responses of granular materials.

关键词： Granular materials History-dependence Multi-layer perceptron(MLP) Discrete element method FEM-DEM Machine learning

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