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An unprecedented synthesis of axially chiral biaryls by rearrangement and aromatization of carbocations with central-to-axial conversion of chirality

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Science China Chemistry 2024年第9期67卷 2998-3003页

作者： qi Liu xue-Dong Li Liang cheng Li Liu Beijing National Laboratory for Molecular Sciences(BNLMS) CAS Key Laboratory of Molecular Recognition and FunctionCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The central-to-axial chirality conversion represents a fascinating class of chemical processes consisting of the destruction of stereogenic centers and the simultaneous installation of axial chiral elements,which provides efficient methods for the preparation of axially chiral ***,developing catalytic asymmetric approaches for constructing these central chirality precursors and the efficient central-to-axial chirality conversion remains a challenge due to the requirement of aromatization or elimination *** this work,we have developed an unprecedented enantioselective intramolecular FriedelCrafts alkylation with unactivated-ketone carbonyls from which a chiral tertiary alcohol was generated with high efficiency and excellent *** addition,the central-to-axial chirality conversion strategy has been successfully applied to the synthesis of enantioenriched biaryls via a less-explored carbocation-initiated rearrangement and aromatization under the promotion of Lewis *** methodology provided a straightforward and sustainable access to a broad range of biaryl-2-carboxylic acid and in excellent yields(up to 92%)and excellent central-to-axial chirality conversion(up to 99%conversion percentage).This work could be a great model for developing new methods for synthesizing axially chiral biaryls and a general protocol for the rearrangement and aromatization of carbocations for further functionalization.

关键词： br?nsted acid catalysis desymmetrization phosphoric acid axially chiral biaryls central-to-axial conversion

A SURVEY ON SEMI-TENSOR PRODUCT OF MATRICES

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Journal of Systems Science & Complexity 2007年第2期20卷 304-322页

作者： Daizhan cheng Hongsheng qi Ancheng xue Institute of Systems Science Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

Semi-tensor product of matrices is a generalization of conventional matrix product for the case when the two factor matrices do not meet the dimension matching condition. It was firstly proposed about ten years ago. Since then it has been developed and applied to several different fields. In this paper we will first give a brief introduction. Then give a survey on its applications to dynamic systems, to logic, to differential geometry, to abstract algebra, respectively.

关键词： Abstract algebra differential geometry dynamic systems logic semi-tensor product

Ecological Responses to Holocene Millennial-Scale Climate Change at High Altitudes of East and Central Asia: A Case Study of Picea/Abies Pollen Changes in Lacustrine Sediments

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Journal of Mountain Science 2014年第3期11卷 674-687页

作者： LI Yu ZHANG cheng-qi ZHOU xue-hua College of Earth and Environmental Sciences Center for Hydrologic Cycle and Water Resources in Arid Region Lanzhou University

Ecosystem response to climate change in high-altitude regions is a focus on global change research. Picea/Abies forests are widely distributed at high altitudes of East and Central Asia, and their distribution changes are sensitive to climate change. Humidity is an important climatic factor that affects high-altitude ecosystems; however, the relationship between distribution changes of Picea/Abies forests and millennial-scale variability of humidity is still not dear. Palynological records can provide insights into millennial-scale paleovegetation changes, which have been successfully used to reconstruct past climate change in East and Central Asia. In this study, we synthesized 24 Picea/Abies pollen and humidity/moisture changes based upon Holocene lake records in East and Central Asia in order to explore the response of high-latitude ecosystem to millennial-scale climate change. The changing pattern of Holocene lacustrine Picea/Abies pollen in arid Central Asia differs from that of monsoonal East Asia, which can be due to different millennial-scale climate change patterns between monsoonal and arid Central Asia. Then, the relationship between changes in Picea/Abies pollen and humidity/moisture conditions was examined based on a comparison of pollen and humidity/moisture records. The results indicate that millennial-scale Picea/Abies distribution changes aremainly controlled by moisture variability at high altitudes, while the temperature effect plays a minor role in Picea/Abies distribution changes. Moreover, this research proves that lacustrine Picea/Abies pollen can be used as an indicator of millennial-scale humidity/moisture evolution at high altitudes in East and Central Asia.

关键词： Lake sediments Palynological records High-altitude regions Picea/Abies Asian summermonsoon Millennial-scale Climate change

A Normal Criterion Concerning Omitted Holomorphic Function

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Acta Mathematica Sinica,English Series 2019年第12期35卷 1972-1978页

作者： Jin Hua YANG qi YANG xue cheng PANG School of Mathematical Sciences Xinjiang Normal UniversityUrumqi 830054P.R.China Department of Mathematics East China Normal UniversityShanghai 200062P.R.China

In this paper,we continue to discuss the normality concerning omitted holomorphic function and get the following *** F be a family of meromorphic functions on a domain D,k≥4 be a positive integer,and let a(z)and b(z)be two holomorphic functions on D,where a(z)■0 and f(z)≠∞ whenever a(z)=*** for any f∈F,f'(z)?a(z)f^k(z)≠b(z),then F is normal on D.

关键词： Normal family holomorphic functions omitted functions

Effect of ceramic work rolls on surface roughness of rolled SUS304 ultra-thin strips

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Journal of Iron and Steel Research International 2024年第7期31卷 1704-1718页

作者： Peng-cheng Li Tao Wang Chen-chen Zhao qi Liu qing-xue Huang College of Mechanical and Vehicle Engineering Taiyuan University of TechnologyTaiyuan 030024ShanxiChina Engineering Research Center of Advanced Metal Composites Forming Technology and Equipment of Ministry of Education Taiyuan University of TechnologyTaiyuan 030024ShanxiChina National Key Laboratory of Metal Forming Technology and Heavy Equipment Taiyuan University of TechnologyTaiyuan 030024ShanxiChina

Surface morphology and roughness are important parameters of surface quality of cold-rolled ultra-thin strip *** order to study the effect of Si_(3)N_(4) ceramic work rolls on the surface roughness of SUS304 ultra-thin strip,ABAQUS finite element model calculation,3D laser profilometry,and other methods were adopted based on the physical characteristics of Si_(3)N_(4) ceramic roll and 9Cr2MoV steel roll,like anti-flattening performance and oil *** surface morphology and roughness of SUS304 ultra-thin strip rolled by different material work rolls under oil lubrication conditions were *** results showed that under the rolling force of 10 kN,the maximum flattening amount of Si_(3)N_(4) ceramic roll was reduced by 35.14%compared to that of 9Cr2MoV steel *** reduction rate of SUS304 ultra-thin strip rolled by ceramic roll was 34.19%,while that rolled by steel roll was only 22%;Si_(3)N_(4) ceramic roll can further increase the number of alternating convex peaks and concave valleys in the rolled thin strip,reduce the profile steepness,reduce surface roughness,and enhance the planarization effect of surface micro-convex bodies,with improving surface quality and surface ***,the mechanism of Si_(3)N_(4) ceramic roll significantly improving the surface roughness of rolled SUS304 ultra-thin strip was proposed.

关键词： Ceramic work roll-Steel roll SUS304 ultra-thin strip Reduction Surface roughness

An experimental study on the velocity fluctuations generated by the flow past fixed spheres

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Journal of Hydrodynamics 2022年第2期34卷 214-225页

作者： Ling-xin Zhang Xin-sheng cheng Ze-cai Zhou qi Gao xue-ming Shao State Key Laboratory of Fluid Power and Mechatronic Systems Department of MechanicsZhejiang UniversityHangzhou310027China

We perform a series of experiments to study the velocity fluctuations generated by the flow past fixed *** particle image velocimetry(PIV)is carried out to characterize the properties of the liquid *** fluctuation induced by the spheres can be decomposed into the temporal fluctuation and the spatial fluctuation,which represent the contribution of flow instability and spatial inhomogeneity,*** particularly,we focus on the contributions of temporal fluctuations and spatial fluctuations between low and high Reynolds *** low Reynolds number(20200,but not for Re<*** ending scale is aroundλ=0.5d and decreases slightly as Re increases.

关键词： Multiphase flow turbulence modulation particle image velocimetry(PIV)

Autism spectrum disorders: autistic phenotypes and complicated mechanisms

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World Journal of Pediatrics 2019年第1期15卷 17-25页

作者： Xi-cheng Zhang Li-qi Shu Xing-Sen Zhao xue-Kun Li Children's Hospital Zhejiang University School of MedicineHangzhou 310003China Institute of Translational Medicine School of MedicineZhejiang UniversityHangzhou 310029China School of Medicine and Health Sciences George Washington UniversityWashingtonDCUSA

Background Autism spectrum disorder (ASD),a pervasive developmental neurological disorder,is characterized by impairments in social interaction and communication,and stereotyped,repetitive patterns of interests or *** mechanism of ASDs is complex,and genetic components and epigenetic modifications play important *** this review,we summarized the recent progresses of ASDs focusing on the genetic and epigenetic *** also briefly discussed current animal models of ASD and the application of high-throughput sequencing technologies in studying *** sources Original research articles and literature reviews published in PubMed-indexed *** Individuals with ASDs exhibit a set of phenotypes including neurological *** components including gene mutation,copy-number variations,and epigenetic modifications play important and diverse roles in *** establishment of animal models and development of new-generation sequencing technologies have contributed to reveal the complicated mechanisms underlying autistic *** Dramatic progress has been made for understanding the roles of genetic and epigenetic components in *** basic and translational studies should be carried out towards those candidate therapeutic targets.

关键词： Autism spectrum disorders Genetics Epigenetics CNV Next-generation sequencing

Modeling the Correlations of Relations for Knowledge Graph Embedding

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Journal of Computer Science & Technology 2018年第2期33卷 323-334页

作者： Ji-Zhao Zhu Yan-Tao Jia Jun Xu Jian-Zhong qiao xue-qi cheng College of Computer Science and Engineering Northeastern University Shenyang 110169 China Key Laboratory of Network Data Science and Technology Institute of Computing Technology Chinese Academy of Sciences Beijing 110190 China

Knowledge graph embedding, which maps the entities and relations into low-dimensional vector spaces, has demonstrated its effectiveness in many tasks such as link prediction and relation extraction. Typical methods include TransE, TransH, and TransR. All these methods map different relations into the vector space separately and the intrinsic correlations of these relations are ignored. It is obvious that there exist some correlations among relations because different relations may connect to a common entity. For example, the triples （Steve Jobs, PlaceOfBrith, California） and （Apple Inc., Location, California） share the same entity California as their tail entity. We analyze the embedded relation matrices learned by TransE/TransH/TransR, and find that the correlations of relations do exist and they are showed as low-rank structure over the embedded relation matrix. It is natural to ask whether we can leverage these correlations to learn better embeddings for the entities and relations in a knowledge graph. In this paper, we propose to learn the embedded relation matrix by decomposing it as a product of two low-dimensional matrices, for characterizing the low-rank structure. The proposed method, called TransCoRe （Translation-Based Method via Modeling the Correlations of Relations）, learns the embeddings of entities and relations with translation-based framework. Experimental results based on the benchmark datasets of WordNet and Freebase demonstrate that our method outperforms the typical baselines on link prediction and triple classification tasks.

关键词： knowledge graph embedding low-rank matrix decomposition

Gustiness and coherent structure under weak wind period in atmospheric boundary layer

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Atmospheric and Oceanic Science Letters 2016年第1期9卷 52-59页

作者： Li qi-Long cheng xue-Ling Zeng qing-Cun State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China University of Chinese Academy of Sciences Beijing 100049 China

Statistical analysis of turbulent and gusty characteristics in the atmospheric boundary layer under weak wind period has been carried *** data used in the analysis were from the multilevel ultrasonic anemometer-thermometers at 47 m,120 m,and 280 m levels on Beijing 325 m meteorological *** time series of 3D atmospheric velocity were analyzed by using conventional Fourier spectral analysis and decompose into three parts:basic mean flow(period > 10 min),gusty disturbances(1 min < period < 10 min)and turbulence fluctuations(period < 1 min).The results show that under weak mean wind condition:1)the gusty disturbances are the most strong fluctuations,contribute about 60% kinetic energy of eddy kinetic energy and 80% downward flux of momentum,although both the eddy kinetic energy and momentum transport are small in comparison with those in strong mean wind condition;2)the gusty wind disturbances are anisotropic;3)the gusty wind disturbances have obviously coherent structure,and their horizontal and vertical component are negatively correlated and make downward transport of momentum more effectively;4)the friction velocities related to turbulence and gusty wind are approximately constant with height in the surface layer.

关键词： Atmospheric boundary layer gusty wind coherent structure weak wind downward flux of momentum