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Facile interconversions of topology and aromaticity of expanded porphyrin in solution

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Science China Chemistry 2014年第10期57卷 1369-1374页

作者： liu ZeYu MA Jing Key Laboratory of Mesoscopic Chemistry Ministry of Education School of Chemistry and Chemical Engineering Nanjing University Sericultural Research Institute Jiangsu University of Science and Technology

The dynamic transformations of conformations and aromatic properties of [32]octaphyrins（1.***.1.0.1.***.1.0） through rotating the pyrrolic ring of the macrocycles are demonstrated by theoretical simulations in CH2Cl2 solution. Facile multistep isomeriza- tions involving antiaromatic-Htickel and aromatic-Mobius topologies were also predicted by density functional theory （DFT）. The understanding of changes in topologies and aromaticities of free-base expanded porphrins may provide useful information to build new macrocycles with unique properties.

关键词： theoretical investigation expanded porphyrin conformational interconversion aromaticity

An output-based distributed observer and its application to the cooperative linear output regulation problem

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Control Theory and Technology 2019年第1期17卷 62-72页

作者： Tao liu Jie HUANG Department of Mechanical and Automation Engineering The Chinese University of Hong Kong Shatin N.T. Hong Kong China

In this paper, we first extend an existing stability result for a class of linear switched systems. This extended result will relax the existenceconditions of the output-based distributed observer for a leader system subject to jointly connected switching communication networks in the literature. As an application of this output-based distributed observer, we solve the cooperative output regulati on problem of a linear multi-age nt system subject to jointly connected switching communicatio n n etworks by composing a purely decentralized control law and the output-based distributed observer based on the certainty equivalence principle.

关键词： Output-based distributed observer switched systems cooperative output regulation

On the Study of Wave Propagation and Distribution in the Global Ocean

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Journal of Ocean University of China 2019年第4期18卷 803-811页

作者： liu Min ZHAO Dongliang Physical Oceanography Laboratory/Qingdao Collaborative Innovation Center of Marine Science and Technology Ocean University of China Qingdao 266100 China Ocean College Hebei Agricultural University Qinhuangdao 066000 China

Based on the simulation with SWAN wave model and data of ERA-Interim from 1979 to 2016, how the waves propagate globally and why swell pools distribute in the eastern ocean were investigated in this study. The simulation results show that waves from North Pacific and North Atlantic mainly propagate southeastward or southward and swells generated in Southern Ocean spread northeastward. The waves from high latitude regions spread along the east coast and encounter in the tropical Pacific and Atlantic to form swell fronts around equator and then turn eastward. As the weak wind field with numerous swell inflows, swell pools are gener- ally located on the eastern side of the ocean basin, where the swell index S are greater than 0.9 calculated using ERA-20C data for the period of 1981 2010. Another remarkable feature is that swell pools move southward and split into two parts in winter, while they move northward and merge together in summer.

关键词： wave propagation SWAN swell front swell pool wave energy density

NONOSCILLATORY COMBINATION OF MAC CORMACK AND WARMING-BEAM SCHEMES FOR HYPERBOLIC CONSERVA-TION LAWS

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Journal of Hydrodynamics 2000年第2期12卷 101-106页

作者： Yu, Heng liu, Yuping Fudan Univ Shanghai China

Based on the analysis of nonoscillatory conditions of second-order schemes, a very simple combination of the two famous second-order finite difference schemes, the Mac Cormack scheme and the Warming-Beam scheme, was achieved for hyperbolic conservation laws. It can avoid spurious oscillations near discontinuities and preserve uniformly second order accuracy in space and time. Numerical results show lower cost and even better resolution than ENO schemes under same conditions.

关键词： Finite difference method Nonlinear systems Oscillations

Response of Vegetation in the Qinghai-Tibet Plateau to Global Warming

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Chinese Geographical Science 2007年第2期17卷 151-159页

作者： XU Weixin liu Xiaodong Institute of Earth Environment Chinese Academy of Sciences Xi ＇an 710075 China MeteorologicalInstitute of Qinghai Province Xining 810001 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

Using satellite-observed Normalized Difference Vegetation Index （NDVI） dada and station-observed surface air temperature anomalies for the Northern Hemisphere （NH）, we analyze the spatio-temporal characteristics of vegetation variations in the Qinghai-Tibet Plateau and their correlations with global warming from 1982 to 2002. It is found that the late spring and early summer （May-June） are the months with the strongest responses of vegetation to global warming. Based on the Rotated Empirical Orthogonal Function （REOF） method, the study shows that the first REOF spatial pattern of average NDVI for May-June reveals the northern and southern zones with great inter-annual variations of vegetation, the northern zone from the eastern Ktmlun Mountains to the southwestern Qilian Mountain and southern zone from the northern edge of the Himalayas eastward to the Hengduan Mountains. The vegetation, especially grassland, in the two zones increases significantly with global warming, with a correlation coefficient of 0.71 between the first REOF of May-June vegetation and the April-May surface air temperature anomaly in the NH during 1982-2002. A long-term increasing trend in May-June vegetation for the plateau region as a whole is also attributed mainly to global warming although there are considerable regional differences. The areas with low NDVI （grassland and shrubland） usually respond more evidently to global warming, especially since the 1990s, than those with moderate or high NDVI values.

关键词： NDVI REOF global warming vegetation Qinghai-Tibet Plateau

Transition metal-catalyzed decarboxylative cross-coupling reactions

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Science China Chemistry 2011年第11期54卷 1670-1687页

作者： SHANG Rui liu Lei Key Laboratory of Bioorganic Phosphorus Chemistry ＆ Chemical Biology （Ministry of Education） Department of Chemistry Tsinghua University Beijing 100084 China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai 200032 China

Transition metal-catalyzed decarboxylative cross-coupling reactions have recently emerged as a new and important category of organic transformations that find versatile applications in the construction of carbon-carbon and carbon-heteroatom bonds. The use of relatively cheap and stable carboxylic acids to replace organometallic reagents enables the decarboxylative cross-coupling reactions to proceed with good selectivities and functional group tolerance. In the present review we summarize the various types of decarboxylative cross-coupling reactions catalyzed by different transition metal complexes. The scope and applications of these reactions are described. The challenges and opportunities in the field are discussed.

关键词： decarboxylation cross-coupling reaction transition metal catalysis organic synthesis

Hydrogen isotopic composition of plant leaf wax in response to soil moisture in an arid ecosystem of the northeast Qinghai-Tibetan Plateau, China

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Journal of Arid Land 2014年第5期6卷 592-600页

作者： Yuan YAO WeiGuo liu School of Human Settlements and Civil Engineering Xi'an Jiaotong University State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences

The hydrogen isotopic composition of plant leaf wax（δDwax） is used as an important tool for paleohydrologic reconstruction. However, the understanding of the relative importance of environmental and biological factors in determining δDwax values still remains incomplete. To identify the effects of soil moisture and plant physiology on δDwax values in an arid ecosystem, and to explore the implication of these values for paleoclimatic reconstruction, we measured δD values of soil water（δDwater） and δDwax values in surface soils along two distance transects extending from the lakeshore to wetland to dryland around Lake Qinghai and Lake Gahai on the northeast Qinghai-Tibetan Plateau. The results showed that the δDwater values were negatively correlated with soil water content（SWC）（R^2=0.9166）, and ranged from –67‰ to –46‰ with changes in SWC from 6.2% to 42.1% in the arid areas of the Gangcha（GCh） and Gahai（GH） transects. This indicated that evaporative D-enrichment in soil water was sensitive to soil moisture in an arid ecosystem. Although the shift from grasses to shrubs with increasing aridity occurred in the arid area of the GH transect, the δDwax values in surface soils from the arid areas of the two transects still showed a negative correlation with SWC（R^2=0.6835）, which may be due to the controls of primary evaporative D-enrichment in the soil water and additional transpirational D-enrichment in the leaf water on the δDwaxvalues. Our preliminary research suggested that δDwax values can potentially be applied as a paleo-humidity indicator on the northeast Qinghai-Tibetan Plateau.

关键词： hydrogen isotope D-enrichment soil water content northeast Qinghai-Tibetan Plateau

Strain-Modulated Photoelectric Responses from a Flexibleα-In_(2)Se_(3)/3R MoS_(2)Heterojunction

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Nano-Micro Letters 2021年第7期13卷 1-11页

作者： Weifan Cai Jingyuan Wang Yongmin He Sheng liu Qihua Xiong Zheng liu Qing Zhang Center for Micro-and Nano-Electronics School of Electrical and Electronic EngineeringNanyang Technological UniversitySingapore 639798Singapore School of Materials Science and Engineering Nanyang Technological UniversitySingapore 639798Singapore Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological UniversitySingapore 639798Singapore

Semiconducting piezoelectricα-In_(2)Se_(3) and 3R MoS_(2) have attracted tremendous attention due to their unique electronic *** van der Waals(vdWs)hetero-structures constructed withα-In_(2)Se_(3)and 3R MoS_(2)flakes have shown promising applications in optoelectronics and ***,we present the first flexibleα-In_(2)Se_(3)/3R MoS_(2)vdWs p-n heterojunction devices for photodetection from the visible to near infrared *** heterojunction devices exhibit an ultrahigh photoresponsivity of 2.9×10^(3)A W^(−1) and a substantial specific detectivity of 6.2×10^(10) Jones under a compressive strain of−0.26%.The photocurrent can be increased by 64%under a tensile strain of+0.35%,due to the heterojunction energy band modulation by piezoelectric polarization charges at the hetero-junction *** work demonstrates a feasible approach to enhancement of α-In_(2)Se_(3)/3R MoS_(2) photoelectric response through an appropriate mechanical stimulus.

关键词： α-In_(2)Se_(3)/3R MoS_(2)heterojunction Flexible Self-powered photodetector Strain modulation Piezoelectric charge

Improved smoothed L0 reconstruction algorithm for ISI sparse channel estimation

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The Journal of China Universities of Posts and Telecommunications 2014年第2期21卷 40-47页

作者： liu Ting ZHOU Jie Department of Communications Nanjing University of Information Science and Technology Department of Electronic and Electrical Engineering Niigata University

In this paper, the problem of inter symbol interference （ISI） sparse channel estimation in wireless communication with the application of compressed sensing is investigated. However, smoothed L0 norm algorithm （SL0） has ＇notched effect＇ due to the negative iterative gradient direction. Moreover, the property of continuous function in SL0 is not steep enough, which results in inaccurate estimations and low convergence. Afterwards, we propose the Lagrange multipliers as well as Newton method to optimize SL0 algorithm in order to obtain a more rapid and efficient signal reconstruction algorithm, improved smoothed L0 （ISL0）. ISI channel estimation will have a direct effect on the performance of ISI equalizer at the receiver. So, we design a pre-filter model which with no considerable loss of optimality and do analyses of the equalization methods of the sparse multi-path channel. Real-time simulation results clearly show that the ISL0 algorithm can estimate the ISI sparse channel much better in both signal noise ratio （SNR） and compression levels. In the same channel conditions, ISL0 algorithm has been greatly improved when compared with the SL0 algorithm and other compressed-sensing algorithms.

关键词： compressed-sensing channel model ISI improved SLO algorithm sparse channel estimation MIMO system