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Chinese Journal of Chemistry 2017年第5期35卷 531-540页

作者： Zhifeng ma Wenhong Yang Wen-hua Sun Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

The design and synthesis of transition metal complexes with high thermal stability in olefin polymerization have become more and more important in order to meet the need of industrial *** review focuses on the transition metal complex catalyst with high thermal stability containing different structures,including the backbone of bis（imino）pyridine,a-diimine and other types of *** the catalytic activity,the influence of reaction temperature on the molecular weight and molecular weight distribution of the obtained polymer was also *** plausible mechanism on the stability of catalysts at high temperature was proposed,which may give guidance to design catalyst with good thermal stability.

关键词： thermal stability transition metal complex olefin polymerization homogenous catalysis ligand effects

Simulation of critical transitions and vulnerability assessment of Tibetan Plateau key ecosystems

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Journal of Mountain Science 2022年第3期19卷 673-688页

作者： YANG Fei ma Chao FANG hua-jun State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources Research of Chinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing 210023China

Critical transitions in ecosystems may imply risks of unexpected collapse under climate changes,especially vegetation often responds sensitively to climate *** type of vegetation ecosystem states could present alternative stable states,and its type could signal the critical transitions at tipping points because of changed climate or other *** study analyzed the distribution of four key vegetation ecosystem types:desert,grassland,forest-steppe ecotone and forest,in Tibetan Plateau in China,using the latent class analysis method based on remote sensing data and climate *** study analyzed the impacts of three key climate factors,precipitation,temperature,and sunshine duration,on the vegetation states,and calculated the critical transition tipping point of potential changes in vegetation type in Tibetan Plateau with the logistic regression *** studied results showed that climatic factors greatly affect the vegetation states and vulnerability of the Tibetan *** comparison with temperature and sunshine duration,precipitation shows more obvious impact on differentiations of the vegetations status *** precipitation tipping point for desert and grassland transition is averagely 48.0 mm/month,70.7 mm/month for grassland and forest-steppe ecotone,and 115.0 mm/month for forest-steppe ecotone and *** temperature and sunshine duration only show different probability change between vegetation and non-vegetation type,but produce opposite *** Tibetan Plateau,the transition tipping points of vegetation and nonvegetation are about 12.1°C/month and 173.6 h/month for the temperature and sunshine duration,***,vulnerability maps calculated with the logistic regression results presented the distribution of vulnerability of Tibetan Plateau key *** vulnerability of the typical ecosystems in the Tibetan Plateau is low in the southeast and is high in the *** meteorological factors affect tree co

关键词： Vulnerability Transition Tipping point Tibetan Plateau Latent class analysis

Flow regime and energy dissipation of SFS-type flip buckets

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Journal of Hydrodynamics 2020年第1期32卷 179-182页

作者： Ran Tian Jian-hua Wu Fei ma College of Water Conservancy and Hydropower Engineering.Hohai University Nanjing 210098China

In the present work,a slot-type flip bucket with separated flows,called SFS-type flip bucket,is developed,and flow regime and energy dissipation are experimentally *** with the circular-shaped or slot-type flip bucket buckets,the present SFS-type flip bucket has better flow regime and larger energy dissipation since the three branches of the flows are separated through the outlet of the flip ***,the energy dissipation for this flip bucket is estimated.

关键词： Energy dissipation flow region separated flow SFS-type flip bucket

Thorium distribution on the Moon:new insights from Chang’E-2 gamma-ray spectrometer

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Research in Astronomy and Astrophysics 2019年第6期19卷 1-14页

作者： Meng-hua Zhu Jin Chang Tao ma State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and Technology Taipa Macao China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210034 China CAS Center for Excellence in Comparative Planetology Hefei 230026 China

We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.

关键词： Moon-Chang'E-2 Gamma-ray Spectrometer-Thorium distribution

Secure proxy signature scheme with fast revocation in the standard model

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The Journal of China Universities of Posts and Telecommunications 2009年第4期16卷 116-124页

作者： LIU Zhen-hua HU Yu-pu ZHANG Xiang-song ma hua Applied mathematics Department Xidian University Xi'an 710071 China Key Laboratory of Computer Networks and Information Security Ministry of Education Xidian University Xi'an 710071 China

Proxy signature is an important cryptographic primitive and has been suggested in numerous applications, Tne revocation oI delegated rights is an essential issue of the proxy signature schemes. In this article, a security model of proxy signature schemes with fast revocation is formalized. Under the formal security framework, a proxy signature scheme with fast revocation based on bilinear pairings is proposed. A security mediator （SEM）, which is an on-line partially trusted server, is introduced to examine whether a proxy signer signs according to the warrant or he/she exists in the revocation list. Moreover, the proxy signer must cooperate with the SEM to generate a valid proxy signature, thus the proposed scheme has the property of fast revocation. The proposed scheme is provably secure based on the computational Diffie-Hellman （CDH） intractability assumption without relying on the random oracles, and satisfies all the security requirements for a secure proxy signature.

关键词： public key cryptography proxy signature proxy revocation security mediator bilinear pairings standard model

Differential Polymorphic Transformation Behavior of Polybutene-1 with Multiple Isotactic Sequences

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Chinese Journal of Polymer Science 2020年第2期38卷 164-173,I0007页

作者： Ya-Ping ma Wei-Ping Zheng Chen-Guang Liu hua-Feng Shao hua-Rong Nie Ai-hua He Shandong Provincial Key Laboratory of Olefin Catalysis and Polymerization Key Laboratory of Rubber-Plastics (Ministry of Education) Qingdao University of Science and Technology

For the solid-solid transformation from form Ⅱ to form Ⅰ of isotactic polybutene-1(iPB),the temperature dependence of form Ⅰ nucleation and growth was deemed to control the transformation ***,the relationship between formⅠ formation and form Ⅱ disappearance in the transformation process is not *** this work,the spontaneous crystal transformation from form Ⅱ to Ⅰ of iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of form Ⅱ and the yielding of form Ⅰ in a wide range of temperature spanning from 0℃ to 50℃ and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and *** the literature reports,the decay rate of form Ⅱ is firstly found to be lower than the yielding rate of form Ⅰ at all studied temperatures,especially at low transition *** is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of form Ⅱ.The regular chain folding and growth of i PB form Ⅰ from amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of form Ⅰ compared with that of initial form Ⅱ crystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.

关键词： Polybutene-1 Polymorphic transformation Isotactic sequence Crystallinity Lamellae thickness

Synthesis and Crystal Structure of an Acetate Radical Bridged Dinuclear Copper(Ⅱ) Complex

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Chinese Journal of Structural Chemistry 2007年第3期26卷 347-351页

作者： DU Qiao-Yun ma Liang QIN Jian-hua Department of Chemistry Luoyang Normal University Luoyang 471022 China

A new acetate radical bridged dinuclear copper（ Ⅱ ） complex [（C8H9NO2）2- Cu2（CH3COO）4] has been synthesized by the reaction of Cu（OAc）2 with pyridine-3-ethyl formate and further characterized by X-ray single-crystal diffraction. Crystal data for the title compound： triclinic system, space group Pí, with a = 8.1654（14）, b = 9.7010（16）, c = 9.9005（17） A, α = 83.266（2）, β = 78.887（2）, γ = 72.881（2）°, V= 733.9（2） A^3, Mr = 665.58, Z = 1, Dc = 1.506 g/cm^3, F（000） = 342,μ = 1.510 mm^-1, the final R = 0.0392 and wR = 0.1005. According to the structural determination, each unit of the title compound is composed of two Cu（ Ⅱ ） atoms, two pyridine-3-ethyl formate molecules and four acetate ions. Each Cu（Ⅱ） coordinates to oxygen atoms of acetate and nitrogen atoms of pyridine- 3-ethyl formate ligand to give a six-coordinate distorted octahedral geometry. It is worth mentioning that strong Cu-Cu bond can be observed in the title compound.

关键词： pyridine-3-carboxylic acetate radical bridge Cu( Ⅱ ) crystal structure

Critical behaviors of a(2+1)-dimensional black hole with a nonlinear electrodynamics source

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Communications in Theoretical Physics 2020年第10期72卷 125-130页

作者： Li-hua Wang Yun He Meng-Sen ma Department of Physics Shanxi Datong University037009 DatongChina State Key Laboratory for Mechanical Behavior of materials Xi'an Jiaotong University710049 Xi'anChina Institute of Theoretical Physics Shanxi Datong University037009 DatongChina

On the basis of a charged BTZ black hole,we add an extra term in the metric function to describe the contribution from nonlinear *** this way we artificially construct a(2+1)-dimensional black hole in general relativity coupled with a nonlinear electrodynamics *** thermodynamic quantities and Smarr formula are *** is found that this black hole has T-S criticality like that of an RN-Ad S black *** modifying the metric function,we obtain a(2+1)-dimensional black hole possessing P-V critical behaviors similar to that of van der Waals *** our knowledge,this is the first example of(2+1)-dimensional black holes having this kind of critical behavior.

关键词： phase transition critical phenomena (2+1)-dimensional black hole nonlinear electrodynamics

Nanocrystals of halide perovskite:Synthesis,properties,and applications

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Journal of Energy Chemistry 2018年第3期27卷 622-636页

作者： Chi Yang Yihui Wu Qingshan ma Wen-hua Zhang Sichuan Research Center of New materials Institute of Chemical MaterialsChina Academy of Engineering PhysicsChengdu 610200Sichaan.China National Energy Novel materials Center 596 Yinhe Road.Shuangliu.Chengdu 610200Sichuan.China

Recently, halide perovskite materials have become an exciting topic of research mainly due to their outstanding photovoltaic performance with the highest efficiency up to 22.1% at present. The nanocrystals（NCs） of these perovskites show quantum size effect, tunable bandgap, and excellent photoluminescence quantum yield（PLQY） in specific cases. Perovskite NCs have hence displayed great potentials in a broad range of applications, such as solar cells, light-emitting devices（LEDs）, photodetectors, and lasers. In this review, we summarized the recent progress on the synthesis, optoelectronic properties and applications of the nanostructures of these halide perovskite materials, including hybrid organic–inorganic perovskites,pure inorganic perovskite, and perovskite-derived NCs. We have also provided a critical outlook into the challenges ahead.

关键词： Perovskite Nanocrystals Photoluminescence Optoelectronic devices

Advances in Research on the ITCZ:Mean Position,Model Bias,and Anthropogenic Aerosol Influences

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Journal of Meteorological Research 2021年第5期35卷 729-742页

作者： hua ZHANG Xinyu ma Shuyun ZHAO Linghan KONG Department of Atmospheric Science School of Environmental StudiesChina University of GeosciencesWuhan 430078 Key Laboratory of Meteorological Disaster Ministry of Education/Collaborative Innovation Center on Forecast and Evaluation of Meteorological DisastersNanjing University of Information Science&TechnologyNanjing 210044 State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesChina Meteorological AdministrationBeijing 100081

The zonal-mean position of the intertropical convergence zone(ITCZ)and its shift in the meridional direction significantly influence both the tropical and even global *** work reviews three aspects of the progress in ITCZ-relevant research:1)the mechanism behind the asymmetry of the ITCZ annual-and zonal-mean positions relative to the equator;2)causes of the double-ITCZ problem(pervasive in climate models)and the efforts to solve it;and 3)the physical mechanisms by which anthropogenic aerosols affect the location of the zonal-mean *** to recent studies,the north-of-the-equator location of the annual-and zonal-mean ITCZ is mainly driven by the cross-equatorial energy transports in the ocean,induced by the Atlantic overturning circulation.A quantitative relationship between the ITCZ shift and the anomalous cross-equatorial energy transport in the atmosphere has been ***,the double-ITCZ problem is still the most common and pronounced bias in tropical precipitation simulations with climate ***,some studies have found that simply correcting the biases in hemispheric energy contrast does not improve the simulation of the ITCZ with climate models;whereas others have found that improving model resolutions and convective parameterizations in climate models,such as entrainment rate,raindroplet re-evaporation,and convection triggering function,can alleviate the double-ITCZ ***,it seems that the double-ITCZ problem in climate models is rooted in the complex physics of the models,which is not yet *** addition,anthropogenic aerosols are suggested to be able to induce meridional shifts of the ITCZ,but through various physical *** aerosols like black carbon influence the ITCZ position basically via instantaneous absorption of shortwave radiation in the atmosphere,whereas scattering aerosols like sulfate affect the location of the ITCZ through the cloud lifetime effect and the subsequent response

关键词： intertropical convergence zone(ITCZ) cross-equatorial energy transport double-ITCZ aerosol