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Highly Cis-1,4 Selective Polymerization of Conjugated Dienes Catalyzed by ^-heterocyclic Carbene-ligated Neodymium Complexes

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Chinese Journal of Polymer Science 2020年第12期38卷 1305-1312页

作者： Shu Zhang Na wu Yi-xian wu State Key Laboratory of Chemical Resource Engineering Beijing Advanced Innovation Center for Soft Matter Science and EngineeringBeijing University of Chemical TechnologyBeijing 100029China

Neodymium complexes containing N heterocyclic carbene(NHC)ligands,NdCl5[1,3,R(NCH=)2C]-THF,(Nd1:R=2,6-Pr2C6H3,x=0;Nd2:R=2,6-Et2C6H3,x=1;Nd3:R=2.4,6-Me3C6H2,x=1)were synthesized and employed as precatalysts for the coordination polymerization of conjugated dienes(butadiene and isoprene).In combination with trisobutylaluminium(TIBA),Nd1 promoted butadiene polymerization to produce extremely high cis-1,4(up to 99.0%)polybutadienes with high molecular weight(Mw=250-780 kg·mol 1).The Nd1/TIBA catalytic system also exhibited both high catalytic activity and cis-1,4 selectivity(up to 97.8%)for isoprene *** catalytic activity,molecular weight and molecular weight distribution of resulting polydienes were directly influenced by Al/Nd molar ratio,aging method,and polymerization *** interestingly,the high cis-1,4 selectivity of the catalyst towards butadiene and isoprene kept almost unchanged under different reaction *** cis-1,4 polyisoprenes with high molecular weight(Mw=210-530 kg·mol 1)and narrow molecular weight distribution (Mw/Mn=1.9-2.7)as well as high cis-1.4 selectivity(-~97%)could be synthesized by using the aged Nd1/TIBA catalytic system in the presence of isoprene(100 equivalent to Nd)at low AlNd molar ratios of *** with low molecular weights(Mw=12-76 kg·mol-7)and narrow molecular weight distributions (Mw/Mn=1.7-2.6)were obtained by using Nd2 and Nd3 as precatalysts,indicating that the molecular weight of resulting polyisoprenes can be adjusted by changing the substitutes of ligand in Nd complex.

关键词： Neodymium complex N heterocydic carbene igand Coordination polymerization Cis-14 sletivity Aging method

Therapy of acute severe pancreatitis awaits further improvement

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World Journal of Gastroenterology 1998年第4期4卷 13-14页

作者： wu xianZhong Tianjin Inst. of Acute Abdom. Dis. Tianjin 300100 China Faculty of Medicine Shenyang Medical College China Department of Surgery China Chinese Assoc. Intgd. Chinese W. M. China Tianjin Inst. of Acute Abdom. Dis. Tianjin 300100 Nankai District China

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ＴｈｅｒａｐｙｏｆａｃｕｔｅｓｅｖｅｒｅｐａｎｃｒｅａｔｉｔｉｓａｗａｉｔｓｆｕｒｔｈｅｒｉｍｐｒｏｖｅｍｅｎｔＷＵＸｉａｎＺｈｏｎｇＳｕｂｊｅｃｔｈｅａｄｉｎｇｓｐａｎｃｒｅａｔｉｔｉｓ／ｔｈｅｒａｐｙ；ｐａｎｃｒｅａｔｉｔｉｓ／ｄｒｕｇｔｈｅｒ...

关键词： pancreatitis/therapy pancreatitis/drug therapy pancreatitis/mortality pancreatitis/complication TCMWM therapy

A Survey of Image Synthesis and Editing with Generative Adversarial Networks

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维普期刊数据库

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Tsinghua Science and Technology 2017年第6期22卷 660-674页

作者： xian wu Kun Xu Peter Hall TNList and the Department of Computer Science and Technology Tsinghua UniversityBeijing 100084China the Department of Computer Science University of BathBathUK

This paper presents a survey of image synthesis and editing with Generative Adversarial Networks（GANs）. GANs consist of two deep networks, a generator and a discriminator, which are trained in a competitive way. Due to the power of deep networks and the competitive training manner, GANs are capable of producing reasonable and realistic images, and have shown great capability in many image synthesis and editing *** paper surveys recent GAN papers regarding topics including, but not limited to, texture synthesis, image inpainting, image-to-image translation, and image editing.

关键词： image synthesis image editing constrained image synthesis generative adversarial networks imageto-image translation

Effect on greenhouse gas balance of converting rice paddies to vegetable production

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Acta Geochimica 2017年第3期36卷 353-354页

作者： Lei wu xian wu Ronggui Hu College of Resources and Environment Huazhong Agricultural University Wuhan 430070 China

Rice paddies are increasingly being converted to vegetable production due to economic benefits related,in part,to changes in demand during recent ***,we implemented a parallel field experiment to simultaneously measure annual emissions of CH_4and N_2O,and soil organic carbon(SOC)stock changes,in rice paddies(RP),rice paddy–converted conventional vegetable fields(CV),and rice paddy–converted greenhouse vegetable fields(GV).Changing from rice to vegetable production reduced CH_4emissions by nearly 100%,and also triggered substantial N_2O ***,annual N_2O emissions from GV significantly exceeded those from CV due to lower soil p H and higher soil *** SOC losses occurred after one year of cultivation of RP,CV,and GV,contributing an important share(3.4%,32.2%,and 10.3%,respectively)of the overall global warming potential(GWP)*** decline in CH_4emissions outweighed the increased N_2O emissions and SOC losses in CV and GV,leading to a 13%–30%reduction in annual GWP as compared to *** results suggest that large-scale expansion of vegetable production at the expense of rice paddies is beneficial for mitigating climate change in terms of the overall GWP.

关键词： Greenhouse gas balance Land management change CH4 N2O Soil organic carbon

On Fixed Point and Almost Fixed Point Problems of Lower Semicontinuous Type Multivalued Mappings

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Acta Mathematica Sinica,English Series 2005年第5期21卷 1027-1034页

作者： Liang Yu LUAN xian wu Institute of Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 P. R. China Department of Mathematics Yunnan Normal University Kunming 650092 P. R. China

In the present paper, some new almost fixed point theorems and fixed point theorems for lower semicontinuous type multivalued mappings are obtained in metrizable H-spaces.

关键词： Lc.-metric space H-space Lower semicontinuous multivalued mapping Locally-uniformly weak lower semicontinuous multivalued mapping

Recrystallization Modelling of Hot Deformed Si-Mn TRIP Steel

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Journal of Iron and Steel Research International 2007年第2期14卷 61-65页

作者： wu Di ZHAO xian-ming State Key Laboratory of Rolling Technology and Automation Northeastern University Shenyang 110004 Liaoning China

By means of hot compression single and double hit experiments, the kinetics of dynamic and static recrystallization in hot-rolled Si-Mn TRIP steel was studied, and the emphasis was put on the influence of high silicon content. The results show that the calculated parameters are consistent with the experimental ones, and addition of silicon retards both dynamic and static recrystallization as well as increases the flow stress of austenite, and the non-recrystallization zone can be enlarged by increasing the silicon contents.

关键词： dynamic recrystallization static recrystallization mathematical model TRIP steel silicon

Intraband Dynamics and Terahertz Emission in Biased GaAs/In_(0.53)Ga_(0.47)As Semiconductor Superlattices

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Communications in Theoretical Physics 2009年第12期52卷 1134-1138页

作者： LI Min MI xian-wu College of Physics Science and Information Engineering Jishou University Jishou 416000 China

Using an excitonic basis, we investigate the intraband polarization, optical absorption spectra, and terahertzemission of semiconductor superlattice with the density matrix theory. The excitonic Bloch oscillation is driven by thedc and ac electric fields. The slow variation in the intraband polarization depends on the ac electric field frequency. Theintraband polarization increases when the ac electric field frequency is below the Bloch frequency. When the ac electricfield frequency is above the Bloch frequency, the intraband polarization downwards and its intensity decreases. Thesatellite structures in the optical absorption spectra are presented. Due to excitonic dynamic localization, the emissionlines of terahertz shift in different ac electric field and dc electric field.

关键词： semiconductor superlattices terahertz optical spectra excitons

Necessary Optimality Conditions for a Class of Nonsmooth Vector Optimization

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Acta Mathematicae Applicatae Sinica 2009年第1期25卷 87-94页

作者： Hui-xian wu He-zhi Luo College of Science Hangzhou Dianzi University Hangzhou 310018 China Department of Applied Mathematics Zhejiang University of Technology Hangzhou 310032 China

The Kuhn-Tucker type necessary conditions of weak efficiency are given for the problem of mini- mizing a vector function whose each component is the sum of a differentiable function and a convex function, subjcct to a set of differentiable nonlinear inequalities on a convex subset C of R^n, under the conditions similar to the Abadie constraint qualification, or the Kuhn-Tucker constraint qualification, or the Arrow-Hurwicz-Uzawa constraint qualification.

关键词： Vector optimization problems necessary conditions weak efficiency constraint qualifications

Sharp upper bounds for the adjacency and the signless Laplacian spectral radius of graphs

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Applied Mathematics(A Journal of Chinese Universities) 2019年第1期34卷 100-112页

作者： wu xian-zhang LIU Jian-ping College of Mathematics and Computer Science Fuzhou University College of Mathematics and Data Science Minjiang University Key Laboratory of Intelligent Metro of Universities in Fujian Province Fuzhou University

Let G be a simple graph with n vertices and m edges. In this paper, we present some new upper bounds for the adjacency and the signless Laplacian spectral radius of graphs in which every pair of adjacent vertices has at least one common adjacent vertex. Our results improve some known upper bounds. The main tool we use here is the Lagrange identity.

关键词： graph spectral radius signless Laplacian spectral radius upper bound