检索结果-南通市图书馆

Chinese Journal of Chemistry 2023年第8期41卷 909-914页

作者： Miao Wang On Ying yuen Chau Ming So State Key Laboratory of Chemical Biology and Drug Discovery and Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityKowloonHong KongChina Henan Key Laboratory of Function-Oriented Porous Materials College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyangHenan471934 China The Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenGuangdong518057 China

Comprehensive Summary This paper presents the first general examples of palladium-catalyzed desulfinative cross-coupling reaction of polyhalogenated aryl triflates with aryl sulfinate salts showing an inversion of the conventional reactivity order of C-Br>C-Cl>*** catalyst system,comprising of Pd(OAc)_(2)and tBuPhSelectPhos,exhibited excellent catalytic reactivity and chemoselectivity toward this *** reaction had a wide range of substrate scopes and provided a simple and efficient method for the construction of functionalized biaryl ***,the C-H···Pd interaction from the methine hydrogen of the C2-cyclohexyl group of the indolyl phosphine ligand with the Pd center may contribute a key factor in reactivity and *** with density functional theory(DFT)calculations,the results revealed that the oxidative addition step in this reaction was a controlling-chemoselectivity step.

关键词： Palladium Phosphane ligands IChemoselectivity Desulfurization Polyhalogenated aryl triflates

Influences of Lower-Mantle Properties on the Formation of Asthenosphere in Oceanic Upper Mantle

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Earth Science 2011年第2期22卷 143-154页

作者： David A yuen Nicola Tosi Ondrej adek Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA Department of Planetary Physics Institute of Planetary ResearchGerman Aerospace Center(DLR)BerlinGermany Department of Geophysics Faculty of Mathematics and PhysicsCharles UniversityPragueCzech Republic

Asthenosphere is a venerable concept based on geological intuition of Reginald Daly nearly 100 years ago. There have been various explanations for the existence of the asthenosphere. The concept of a plume-fed asthenosphere has been around for a few years due to the ideas put forth by Yamamoto et al.. Using a two-dimensional Cartesian code based on finite-volume method, we have investigated the influences of lower-mantle physical properties on the formation of a low-viscosity zone in the oceanic upper mantle in regions close to a large mantle upwelUng. The rheological law is Newtonian and depends on both temperature and depth. An extended-Boussinesq model is assumed for the energetics and the olivine to spinel, the spinel to perovskite and perovskite to post-perovskite （ppv） phase transitions are considered. We have compared the differences in the behavior of hot upweilings passing through the transition zone in the mid-mantle for a variety of models, starting with constant physical properties in the lower-mantle and culminating with complex models which have the post-perovskite phase transition and depth-dependent coefficient of thermal expansion and thermal conductivity. We found that the formation of the asthenosphere in the upper mantle in the vicinity of large upwellings is facilitated in models where both depth-dependent thermal expansivity and conductivity are included. Models with constant thermal expansivity and thermal conductivity do not produce a hot low-viscosity zone, resembling the asthenosphere. We have also studied the influences of a cylindrical model and found similar results as the Cartesian model with the important difference that upper-mantle temperatures were much cooler than the Cartesian model by about 600 to 700 K. Our findings argue for the potentially important role played by lower-mantle material properties on the development of a plume-fed asthenosphere in the oceanic upper mantle.

关键词： oceanic asthenosphere lower mantle thermal expansivity thermal conductivity phase transition.

Recent advances in the precise control of isolated single-site catalysts by chemical methods

在线全文

学校读者我要写书评

暂无评论

National Science Review 2018年第5期5卷 673-689页

作者： Zhijun Li Dehua Wang yuen Wu Yadong Li Department of Chemistry iChEM Collaborative Innovation Center of Chemistry for Energy MaterialsUniversity of Science and Technology of China Department of Chemistry Tsinghua University School of Pharmaceutical and Chemical Engineering Taizhou University

The search for constructing high-performance catalysts is an unfailing topic in chemical fields. Recently, we have witnessed many breakthroughs in the synthesis of single-atom catalysts(SACs) and their applications in catalytic systems. They have shown excellent activity, selectivity, stability, efficient atom utilization and can serve as an efficient bridge between homogeneous and heterogenous catalysis. Currently, most SACs are synthesized via a bottom-up strategy; however, drawbacks such as the difficulty in accessing high mass activity and controlling homogeneous coordination environments are inevitably encountered, restricting their potential use in the industrial area. In this regard, a novel top-down strategy has been recently developed to fabricate SACs to address these practical issues. The metal loading can be increased to 5% and the coordination environments can also be precisely controlled. This review highlights approaches to the chemical synthesis of SACs towards diverse chemical reactions, especially the recent advances in improving the mass activity and well-defined local structures of SACs. Also, challenges and opportunities for the SACs will be discussed in the later part.

关键词： single-atom catalysts bottom-up top-down catalytic performance

Submicron size-scale mapping of carbonate effective elastic properties from FIB-SEM images and finite element method

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Earth Sciences 2017年第3期60卷 557-575页

作者： CHENG HuiHong ZHU BoJing David A yuen SHI YaoLin Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences Beijing 100049China College of Earth Science University of Chinese Academy of SciencesBeijing 100049China Yunnan Observatories Chinese Academy of SciencesKunming 650216China Rock Mechanics and Carbon Store Lab Department of Earth SciencesDurham UniversityDurhamDH13LEUK Department of Earth Science and Minnesota Supercomputing Institute University of MinnesotaMinneapolis 55455USA

In this paper, an automatic unstructured focused ion beam （FIB） and scanning electron microscopy （SEM） images induced representative volume element （RVE） finite element （FE） method is developed to predict submicron scale carbonate rock effective Young＇s and bulk moduli and Poisson＇s ratio on parallel CPU-GPU platform. Based on high resolution-contrast surface morphology and internal fabric-texture structure images from carbonate rock specimen （covered 0.12-64 μm2 area and 8000 μm3 domain）, the cubic RVE FE models are constructed from different sites through Avizo with user-defined parameters Matlab coding. The effective Young＇s and bulk moduli and Poisson＇s ratio of the different RVEs and porosity and pore size are computed by using periodic boundary condition in the well-known FE software Abaqus. FE mesh sensitivity analysis has been conducted where all moduli converge to a certain constant value at larger FE mesh density. The effect of fabric-texture （pore size, shape, and distribution） on the elastic properties is discussed. The correlations between the computed effective elastic properties and pore size, porosity, RVE size have been established. The simulation results show that the effective Young＇s and bulk moduli and Poisson＇s ratio have strong anisotropic behavior and depend on RVE size, porosity and pore size. The RVE size, porosity and pore size are three independent factors in affecting of the effective elastic moduli, the effect mechanism of porosity and pore size is same while the effect mechanism of RVE size is difference.

关键词： Carbonate effective elastic properties Finite element analysis Focused ion beam Nano-porosity Nano pore size

Microcurvature landscapes induce neural stem cell polarity and enhance neural differentiation

在线全文

学校读者我要写书评

暂无评论

生物设计与制造(英文) 2023年第5期6卷 522-535页

作者： Ho-Yin yuen Wai-Sze Yip Suet To Xin Zhao Department of Biomedical Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARChina State Key Laboratory of Ultra-Precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARChina

Tissue curvature has long been recognized as an important anatomical parameter that affects intracellular behaviors,and there is emerging interest in applying cell-scale curvature as a designer property to drive cell fates for tissue engineering *** neural cells are known to undergo dramatic and terminal morphological changes during development and curvature-limiting behaviors have been demonstrated in neurite outgrowth studies,there are still crucial gaps in understanding neural cell behaviors,particularly in the context of a three-dimensional(3D)curvature landscape similar to an actual tissue engineering *** this study,we fabricated two substrates of microcurvature(curvature-substrates)that present a smooth and repeating landscape with focuses of either a concave or a convex *** these curvature-substrates,we studied the properties of morphological differentiation in N2a neuroblastoma *** contrast to other studies where two-dimensional(2D)curvature was demonstrated to limit neurite outgrowth,we found that both the concave and convex substrates acted as continuous and uniform mechanical protrusions that significantly enhanced neural polarity and differentiation with few morphological changes in the main cell *** enhanced differentiation was manifested in various properties,including increased neurite length,increased nuclear displacement,and upregulation of various neural *** demonstrating how the micron-scale curvature landscape induces neuronal polarity,we provide further insights into the design of biomaterials utilizing the influence of surface curvature in neural tissue engineering.

关键词： Curvature Neural differentiation Neurite outgrowth Mechanotransduction

Parallel Numerical Analysis on the Rheology of the Martian Ice-Rock Mixture

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2011年第2期22卷 176-181页

作者：景惠敏张怀李菡 David A yuen 石耀霖 Laboratory of Computational Geodynamics Graduate University of Chinese Academy of Sciences Department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA

The distribution and amount of ground ice on Mars is an important issue to be addressed for the future exploration of the *** occurrence of interstitial ice in Martian frozen ground is indicated by landforms,such as fluidized ejecta craters,softened terrain,and fretted ***-ever,experimental data on the rheology of ice-rock mixture under Martian physical conditions are sparse,and the amount of ground ice that is required to produce the viscous deformation observed in Martian ice-related landforms is still *** our study,we put forward a three-dimensional non-Newtonian viscous finite element model to investigate the behavior of ice-rock mixtures *** randomly distributed tetrahedral elements are generated in regular domain to represent the natural distribution of ice-rock *** simulation results show that when the volume of rock is less than 40%,the rheology of the mixture is dominated by ice,and there is occurrence of a brittle-ductile transition when ice fraction reaches a certain *** preliminary results contribute to the knowledge of the determination of the rheology and ice content in Martian ice-rock *** presented model can also be utilized to evaluate the amount of ground ice on Mars.

关键词： parallel simulation rheology,ice-rock mixture Mars.

New understanding of phase segregation of bimetallic nanoalloys

在线全文

学校读者我要写书评

暂无评论

Science China Materials 2015年第1期58卷 3-4页

作者： yuen Wu Yadong Li United Innovation Center of Catalysis and Department of Chemistry Tsinghua University Center of Advanced Nanocatalysis (CAN-USTC) and Department of Chemistry University of Science and Technology of China

In a recent online publication of Science,Professor Peter Strasser of the Technical University of Berlin,Germany,and his collaborators reported element-specific anisotropic growth of Pt and Ni in shaped Pt alloy synthesis[1].They showed that the surface steps in the Pt3Ni concave hexapod alloy formed in the initial stage of the synthesis were crucial in the segregation of an M-rich(M=Ni,Co,

关键词： In New understanding of phase segregation of bimetallic nanoalloys Pt

Eyes and stroke:the visual aspects of cerebrovascular disease

在线全文

学校读者我要写书评

暂无评论

Stroke & Vascular Neurology 2017年第4期2卷 211-221页

作者： John H Pula Carlen A yuen Department of Neurology NorthShore University HealthSystemChicagoIllinoisUSA Department of Neurology University of ChicagoChicagoIllinoisUSA

A large portion of the central nervous system is dedicated to vision and therefore strokes have a high likelihood of involving vision in some *** loss can be the most disabling residual effect after a cerebral *** vision problems can likewise be a harbinger of stroke and prompt evaluation after recognition of visual symptoms can prevent future vascular *** this review,we discuss the visual aspects of ***,anatomy and the vascular supply of the visual system are ***,the different stroke syndromes which involve vision are ***,topics involving the assessment,prognosis,treatment and therapeutic intervention of vision-specific stroke topics are reviewed.

关键词： anatomy ed. visual

Compressive strain in Cu catalysts:Enhancing generation of C2+products in electrochemical CO_(2)reduction

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science Bulletin 2024年第18期69卷 2881-2891页

作者： Qikui Fan Pengxu Yan Fuzhu Liu Zhongshuang Xu Pengfei Liang Xi Cao Chenliang Ye Moxuan Liu Lingyi Zhao Shan Ren Huanran Miao Xiai Zhang Zhimao Yang Xiangdong Ding Jian Yang Chuncai Kong yuen Wu MOE Key Laboratory for Non-Equilibrium Synthesis and Modulation of Condensed Matter Key Laboratory for Advanced Materials and Mesoscopic Physics of Shaanxi ProvinceSchool of PhysicsXi’an Jiaotong UniversityXi’an 710049China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China College of Chemistry and Materials Science Anhui Normal UniversityWuhu 241002China Department of Power Engineering North China Electric Power UniversityBeijing 102206China College of Chemistry and Chemical Engineering Xi’an University of Science and TechnologyXi’an 710054China Center for Materials and Interfaces Shenzhen Institutes of Advanced TechnologyChinese Academy of SciencesShenzhen 518055China Hefei National Laboratory for Physical Sciences at the Microscale Collaborative Innovation Center of Chemistry for Energy Materials(iChEM)School of Chemistry and Materials Scienceand National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230026China

Elastic strain in Cu catalysts enhances their selectivity for the electrochemical CO_(2)reduction reaction(eCO_(2)RR),particularly toward the formation of multicarbon(C_(2+))***,the reasons for this selectivity and the effect of catalyst precursors have not yet been ***,we employed a redox strategy to induce strain on the surface of Cu *** transformation was employed to convert Cu nanocrystals to CuxO nanocrystals;these were subsequently electrochemically reduced to form Cu catalysts,while maintaining their compressive *** a flow cell configuration,a current density of 1 A/cm^(2)and Faradaic efficiency exceeding 80%were realized for the C_(2+)*** selectivity ratio of C_(2+)/C1 was also remarkable at 9.9,surpassing that observed for the Cu catalyst under tensile strain by approximately 7.6 ***-situ Raman and infrared spectroscopy revealed a decrease in the coverage of K+ion-hydrated water(K·H_(2)O)on the compressively strained Cu catalysts,consistent with molecular dynamics simulations and density functional theory *** element method simulations confirmed that reducing the coverage of coordinated K·H_(2)O water increased the probability of intermediate reactants interacting with the surface,thereby promoting efficient C–C coupling and enhancing the yield of C_(2+)*** findings provide valuable insights into targeted design strategies for Cu catalysts used in the eCO_(2)RR.

关键词： Strain effect CO_(2)electroreduction to C^(2+) Catalytic selectivity Copper catalyst Water coverage

Survey on AI and Machine Learning Techniques for Microgrid Energy Management Systems

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2023年第7期10卷 1513-1529页

作者： Aditya Joshi Skieler Capezza Ahmad Alhaji Mo-yuen Chow the Department of Electrical and Computer Engineering North Carolina State UniversityRaleighNC27695 USA UM-SJTU Joint Institute Shanghai Jiao Tong UniversityShanghai 200240China

In the era of an energy revolution,grid decentralization has emerged as a viable solution to meet the increasing global energy demand by incorporating renewables at the distributed *** are considered a driving component for accelerating grid *** optimally utilize the available resources and address potential challenges,there is a need to have an intelligent and reliable energy management system(EMS)for the *** artificial intelligence field has the potential to address the problems in EMS and can provide resilient,efficient,reliable,and scalable *** paper presents an overview of existing conventional and AI-based techniques for energy management systems in *** analyze EMS methods for centralized,decentralized,and distributed microgrids ***,we summarize machine learning techniques such as ANNs,federated learning,LSTMs,RNNs,and reinforcement learning for EMS objectives such as economic dispatch,optimal power flow,and *** the incorporation of AI,microgrids can achieve greater performance efficiency and more reliability for managing a large number of energy ***,challenges such as data privacy,security,scalability,explainability,etc.,need to be *** conclude,the authors state the possible future research directions to explore AI-based EMS's potential in real-world applications.

关键词： Consensus energy management system(EMS) reinforcement learning supervised learning