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Frontiers of Materials Science 2021年第4期15卷 611-620页

作者： Shufen TAN Yajun ji fei CHEN Weimin OUYANG School of Materials and Chemistry University of Shanghai for Science and TechnologyShanghai 200093China

To construct supercapacitors(SCs)with high-efficient electrochemical properties,the morphology and structure of applied electrode materials are the key ***,three-dimensional(3D)sea urchin-like MnCo_(2)O_(4)nanoarchitectures grown on Ni foam(NF)were successfully synthesized via a simple solvothermal method and subsequent annealing *** tests revealed that the area specific capacitances of the MnCo_(2)O_(4)electrode and the corresponding assembled asymmetric device can achieve 1634 and 522 mF·cm^(-2),*** the power density of the assembled asymmetric supercapacitor(ASC)is 2.25 mW·cm^(-2),the maximum energy density can reach 0.163 mW·h·cm^(-2).After 5500 cycles of long-term stability test,the capacity retention rate maintains 91.7%.The excellent electrochemical performance can be mainly ascribed to the unique nanostructure of the material,which provides a great quantity of electroactive sites for Faraday redox reactions as well as accelerates the process of the ions/electrons *** work provides a certain reference value for the preparation of MnCo_(2)O_(4)electrode with novel structure and excellent electrochemical performance for SCs.

关键词： three-dimension nanoarchitecture solvothermal method MnCo_(2)O_(4) annealing treatment supercapacitor

Catalytically generated noncovalent ammonium dienolate:a versatile platform for the development of organocatalytic asymmetric cascade reactions

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Science China Chemistry 2024年第8期67卷 2524-2546页

作者： Jun-Bing Lin Dong-Sheng ji Peng-fei Xu State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical EngineeringLanzhou UniversityLanzhou 730000China Shaanxi Key Laboratory of Chemical Reaction Engineering College of Chemistry and Chemical EngineeringYan’an UniversityYan’an 716000China

Organocatalytic cascade reactions represent a powerful strategy for the rapid construction of complex chiral molecules with multiple stereocenters from simple substrates under mild conditions. The intriguing structural feature and diverse reactivity of catalytically generated dienolate species render them competent and versatile intermediates for the development of practical and valuable cascade reactions. Over the past years, a plethora of innovative and pioneering noncovalent ammonium dienolatemediated cascade reactions have been designed and implemented under the catalysis of chiral organocatalysts, making dienolate activation a general, robust, and complementary method for the functionalization of unsaturated carbonyl compounds and related substances. This review illustrates the recent advances in organocatalytic noncovalent ammonium dienolate-mediated cascade reactions(mainly from 2010 to 2023), including the cascade transformations of ammonium dienolates directly generated from unsaturated ketone/aldehyde, ester/lactone/azlactone, amide/lactam/pyrazolone/oxindole, and alkylidene nitrile compounds. The contents are arranged based on the reaction types of the ammonium dienolates, with an emphasis on cascade 2,5-, 3,5-, and 4,5-difunctionalizations of these intermediates. Furthermore, other cascade reactions involving the 1,3-, 2,3-, and even more complex 3,4,5-reactivities of ammonium dienolates were also discussed. The reaction pathway, reaction stereoinduction, and synthetic applications of the ammonium dienolate-mediated cascade reactions were highlighted throughout the article. As a stimulating and ever-growing research area, the organocatalytic noncovalent ammonium dienolate-mediated cascade reactions are expected to continue demonstrating their magic power for constructing chiral targets in the future and further expanding the boundaries of asymmetric catalysis.

关键词： organocatalysis asymmetric catalysis ammonium dienolate cascade reaction difunctionalization

Nuclearity and Finite-Representability in the System of Completely Integral Mapping Spaces

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Acta Mathematica Sinica,English Series 2024年第5期40卷 1197-1214页

作者： Zhe DONG ji Cheng TAO Ya fei ZHAO Department of Mathematics Zhejiang UniversityHangzhou 310027P.R.China Department of Mathematics China Jiliang UniversityHangzhou 310018P.R.China Department of Mathematics Zhejiang International Studies UniversityHangzhou 310023P.R.China

In this paper,we investigate local properties in the system of completely integral mapping *** introduce notions of injectivity,local reflexivity,exactness,nuclearity,finite-represent ability and WEP in the system of completely integral mapping *** we obtain that any finite-dimensional operator space is injective in the system of completely integral mapping *** we prove that C is the unique nuclear operator space and the unique exact operator space in this *** also show that C is the unique operator space which is finitely representable in{T_(n)}n∈Nin this *** corollaries,Kirchberg’s conjecture and QWEP conjecture in the system of completely integral mapping spaces are false.

关键词： Completely integral mapping space injectivity exactness nuclearity finite-representability WEP

Inverse Fluid-solid Interaction Scattering Problem Using Phased and Phaseless Far Field Data

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Acta Mathematicae Applicatae Sinica 2020年第1期36卷 74-94页

作者： Xia ji Yun-fei jiA Xiao-dong LIU LSEC Academy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China Academy of Mathematics and Systems Science Chinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100190China

We consider the inverse fluid-solid interaction scattering of incident plane wave from the knowledge of the phased and phaseless far field *** the phased data,one direct sampling method for location and shape reconstruction is *** inner product is involved in the computation,which makes it very simple and fast to be *** the help of the factorization of the far field operator,we give a lower bound of the proposed indicator functional for the sampling points inside the elastic *** for the sampling points outside,we show that the indicator functional decays like the Bessel function as the points go away from the boundaries of the elastic *** also show that the proposed indicator functional continuously dependents on the far field patterns,which further implies that the novel sampling method is extremely stable with respect to data *** the phaseless data,to overcome the translation invariance,we consider the scattering of point sources *** adding a reference sound-soft obstacle into the scattering system,we show some uniqueness results with phaseless far field ***,we introduce a phase retrieval algorithm to retrieve the phased data without the additional *** novel phase retrieval algorithm can also be combined with the sampling method for phased *** also design two novel direct sampling methods using the phaseless data ***,some numerical simulations in two dimensions are conducted with noisy data,and the results further verify the effectiveness and robustness of the proposed numerical methods.

关键词： fluid-solid interaction scattering direct sampling method far field pattern phaseless phase retrieval

Asymmetric Drying and Wetting Trends in Eastern and Western China

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Advances in Atmospheric Sciences 2024年第2期41卷 221-232页

作者： Wen WU fei ji Shujuan HU Yongli HE College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000China Collaborative Innovation Center for Western Ecological Safety Lanzhou UniversityLanzhou 730000China

As an important factor that directly affects agricultural production, the social economy, and policy implementation,observed changes in dry/wet conditions have become a matter of widespread concern. However, previous research has mainly focused on the long-term linear changes of dry/wet conditions, while the detection and evolution of the non-linear trends related to dry/wet changes have received less attention. The non-linear trends of the annual aridity index, obtained by the Ensemble Empirical Mode Decomposition(EEMD) method, reveal that changes in dry/wet conditions in China are asymmetric and can be characterized by contrasting features in both time and space in China. Spatially, most areas in western China have experienced transitions from drying to wetting, while opposite changes have occurred in most areas of eastern China. Temporally, the transitions occurred earlier in western China compared to eastern China. Research into the asymmetric spatial characteristics of dry/wet conditions compensates for the inadequacies of previous studies, which focused solely on temporal evolution;at the same time, it remedies the inadequacies of traditional research on linear trends over centennial timescales. Analyzing the non-linear trend also provides for a more comprehensive understanding of the drying/wetting changes in China.

关键词： aridity index EEMD dry/wet conditions asymmetric evolution

Long-term trend of oceanic surface carbon in the Northwest Pacific from 1958 to 2017

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Acta Oceanologica Sinica 2022年第5期41卷 90-98页

作者： Xuanliang ji fei Chai Peng Xiu Guimei Liu Key Laboratory of Research on Marine Hazards Forecasting National Marine Environmental Forecasting CenterMinistry of Natural ResourcesBeijing100081China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou310012China School of Marine Sciences University of MaineOronoME04469USA State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou510301China

Contrasting decrease and increase trends of sea surface temperature(SST)have been documented in the western Subarctic(WSA)and the rest of the Northwest Pacific(NWP)from 1958 to 2017,***,more(less)total carbon dioxide(TCO_(2))due to ocean cooling(warming)is transported to the surface,which leads to increase(decrease)of oceanic surface partial pressure of carbon dioxide(pCO_(2)).With the combined influence of the rising atmospheric carbon dioxide(CO_(2))level and changing ocean conditions,a prominent increase in oceanic surface pCO_(2) occurred with different rates of increase in summer and winter in the *** oceanic surface pCO_(2) is mainly controlled by the variation of TCO_(2) at the interdecadal timescale and by SST at the seasonal *** results also indicate that increasing SST tends to strengthen the capability of ocean in absorbing anthropogenic CO_(2) in the NWP,while ocean’s uptaking ability is weakened in the cooling area of the WSA.

关键词： sea surface temperature oceanic surface pCO_(2) ocean cooling(warming) control factor

Sol–gel derived porous ultra-high temperature ceramics

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Journal of Advanced Ceramics 2020年第1期9卷 1-16页

作者： fei LI Xiao HUANG ji-Xuan LIU Guo-Jun ZHANG State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Institute of Functional MaterialsDonghua UniversityShanghai 201620China Institute for the Conservation of Cultural Heritage Shanghai UniversityShanghai 200444China

Ultra-high temperature ceramics(UHTCs)are considered as a family of nonmetallic and inorganic materials that have melting point over 3000℃.Chemically,nearly all UHTCs are borides,carbides,and nitrides of early transition metals(e.g.,Zr,Hf,Nb,Ta).Within the last two decades,except for the great achievements in the densification,microstructure tailoring,and mechanical property improvements of UHTCs,many methods have been established for the preparation of porous UHTCs,aiming to develop high-temperature resistant,sintering resistant,and lightweight materials that will withstand temperatures as high as 2000℃for long periods of *** the synthesis methods for porous UHTCs,sol–gel methods enable the preparation of porous UHTCs with pore sizes from 1 to 500μm and porosity within the range of 60%–95%at relatively low *** this article,we review the currently available sol–gel methods for the preparation of porous ***,foaming,and solvent evaporation methods are described and compared in terms of processing–microstructure *** properties and high temperature resistance of sol–gel derived porous UHTCs are ***,directions to future investigations on the processing and applications of porous UHTCs are proposed.

关键词： sol–gel ultra-high temperature ceramics porous ceramics processing microstructure

Development of An Ionospheric Scintillation Monitor Using Single Frequency GPS Receiver

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Wuhan University Journal of Natural Sciences 2002年第2期7卷 189-194页

作者： Shu Di-fei Xu ji-sheng School of Electronic Information Wuhan UniversityWuhan 430072HubeiChina

Besides their intended use in radio navigation, global positioning system (GPS) satellite signals provide convenient radio beacons for ionospheric studies. Among other propagation phenomena, the ionosphere affects GPS signal propagation through amplitude scintillations that develop after radio waves propagation through ionospheric electron density irregularities. This paper outlines the design, testing, and results of a specialized GPS receiver to monitorL-band scintillations. The scintillation monitor system consists of a commercial GPS receiver development kit with its software designed to log signal strength and carrier phase from up to 12 channels at one sample per second rate. Other prime features of the monitor include the data compression transmission and processing. Here is the fact that they are inexpensive and compact and therefore can be readily proliferated.

关键词： global positioning system ionosphere scintillation irregularity

Path Planning in Complex 3D Environments Using a Probabilistic Roadmap Method

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International Journal of Automation and computing 2013年第6期10卷 525-533页

作者： fei Yan Yi-Sha Liu ji-Zhong Xiao School of Control Science and Engineering Dalian University of Technology School of Information Science and Technology Dalian Maritime University Department of Electrical and Engineering The City CollegeCity University of New York

This paper presents a 3D path planning algorithm for an unmanned aerial vehicle （UAV） in complex environments. In this algorithm, the environments are divided into voxels by octree algorithm. In order to satisfy the safety requirement of the UAV, free space is represented by free voxels, which have enough space margin for the UAV to pass through. A bounding box array is created in the whole 3D space to evaluate the free voxel connectivity. The probabilistic roadmap method （PRM） is improved by random sampling in the bounding box array to ensure a more efficient distribution of roadmap nodes in 3D space. According to the connectivity evaluation, the roadmap is used to plan a feasible path by using A＊ algorithm. Experimental results indicate that the proposed algorithm is valid in complex 3D environments.

关键词： 3D path planning complex environment unmanned aerial vehicle (UAV) probabilistic roadmap methed (PRM) octree.

Influence of Terabit Signal in Hybrid System with Multi-Rate and Multi-Modulation Format Channels

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China Communications 2016年第11期13卷 189-196页

作者： fei Xu Yaojun Qiao ji Zhou Huiping Tian State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications) Beijing 100876 China

We proposed a hybrid transmission system consist of 1Tbit/s Nyquist WDM channels,100Gbit/s PDM-QPSK WDM channels and 10Gbit/s NRZ WDM channels to study whether Terabit Nyquist WDM signal could transmit in the existing hybrid systems with DCM(dispersion compensation module). The simulation results demonstrated the influence of all these three kinds of signals. The 1Tbit/s Nyquist WDM channels introduced 1.5d B Q penalty to the 100Gbit/s PDM-QPSK signals and their influence on the 10Gbit/s NRZ signals was extremely slight. In the hybrid optical system,1Tbit/s Nyquist channel has 5d B Q penalty due to the inline DCM and 2.5d B Q penalty due to the channel interference from existing channels. Therefore,the total Q penalty is 7.5d B caused by strong nonlinear effects at the launch power of 0d Bm. The results have the guiding significance for the design of future backbone system and also support the feasibility of future dynamic optical system.

关键词： hybrid optical system Terabit transmission Nyquist signal WDM