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Chinese Journal of Chemistry 2022年第23期40卷 2785-2793,I0002页

作者： Jiliang Tian wenzheng feng Shaofeng Liu Zhibo Li Key Laboratory of Biobased Polymer Materials College of Polymer Science and EngineeringQingdao University of Science and TechnologyQingdaoShandong 266042China College of Chemical Engineering Qingdao University of Science and TechnologyQingdaoShandong 266042China

A series of titanium amido complexes (1-Ti(NMe_(2))_(2) to 4-Ti(NMe_(2))_(2)) bearing NNO-tridentate ligands was synthesized from the reactions of phenoxy-imine-amine ligands with one equivalent of Ti(NMe_(2))_(4). Subsequently, titanium dichloride complexes (1-TiCl_(2) to 4-TiCl_(2)) were prepared by treatment of titanium amido complexes with excess Me3SiCl in toluene. All metal complexes were characterized by 1H and 13C NMR spectroscopy, and the molecular structures of complexes of 2-Ti(NMe_(2))_(2), 2-TiCl_(2), and 4-TiCl_(2) in the solid state were determined by single-crystal X-ray diffraction. Upon activation with MAO, titanium dichloride complexes as single-site catalysts were extremely active toward ethylene homopolymerization with great control on molecular weight and distribution. In particular, 3-TiCl_(2)/MAO exhibited an activity as high as 1.35 × 108 g(PE)·mol−1(Ti)·h−1 at 70°C and produced polyethylene with high molecular weight (41.7 × 10^(4) g∙mol^(−1)) and very narrow distribution (Đ = 1.23). In the presence of 1-octene as comonomer, linear low-density polyethylenes (LLDPEs) with ultrahigh molecular weights (Mw = 136—326 × 10^(4) g∙mol^(−1)) and narrow distributions (Đ = 1.20—1.50) were successfully synthesized.

关键词： Titanium Homogeneous catalysis Polymerization UHMWPE LLDPE

XiaoMu: an AI-driven assistant for MOOCs

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Science China(Information Sciences) 2021年第6期64卷 222-224页

作者： Zhengyang SONG Jie TANG Tracy Xiao LIU Wenjiang ZHENG Lili WU wenzheng feng Jing ZHANG Institute for Interdisciplinary Information Sciences Tsinghua University Department of Computer Science and Technology Tsinghua University School of Economics and Management Tsinghua University Center for Strategic Studies Chinese Academy of Engineering Information School Renmin University of China

Nowadays, massive open online courses(MOOCs), are attracting widespread interest as an alternative education model. Several MOOCs platforms, such as Coursera, edX,and Udacity have been built and they provide low-cost opportunities for anyone who needs to access a massive number of courses from the worldwide top universities. However, the learning completion rate of the learners via MOOCs is extremely low compared with that in real classroom learning.Thus, this study builds a system, called XiaoMu, to design intelligent intervention strategies for the learning process of learners and improve the learning efficiency through automatic analysis of courses and learners. We deployed our system on the website1), which is one of the largest MOOCs in China.

关键词： MOOCs Concept Extraction Question Answering Course Recommendation Video Navigation

Fucosyltransferase 8 regulates adult neurogenesis and cognition of mice by modulating the Itga6-PI3K/Akt signaling pathway

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Science China(Life Sciences) 2024年第7期67卷 1427-1440页

作者： Hongfeng Guo Qihang Sun Xiaoli Huang Xiaohao Wang feng Zhang wenzheng Qu Jinling Liu Xuejun Cheng Qiang Zhu Wen Yi Qiang Shu Xuekun Li The Children’s Hospital National Clinical Research Center for Child HealthSchool of MedicineZhejiang UniversityHangzhou 310052China The Institute of Translational Medicine School of MedicineZhejiang UniversityHangzhou 310029China College of Life Sciences Zhejiang UniversityHangzhou 310058China Binjiang Institute of Zhejiang University Hangzhou 310053China Zhejiang University Cancer Center Zhejiang UniversityHangzhou 310029China

Fucosyltransferase 8(Fut8)and core fucosylation play critical roles in regulating various biological processes,including immune response,signal transduction,proteasomal degradation,and energy metabolism.However,the function and underlying mechanism of Fut8 and core fucosylation in regulating adult neurogenesis remains unknown.We have shown that Fut8 and core fucosylation display dynamic features during the differentiation of adult neural stem/progenitor cells(aNSPCs)and postnatal brain development.Fut8 depletion reduces the proliferation of a NSPCs and inhibits neuronal differentiation of aNSPCs in vitro and in vivo,respectively.Additionally,Fut8 deficiency impairs learning and memory in mice.Mechanistically,Fut8 directly interacts with integrinα6(Itga6),an upstream regulator of the PI3kAkt signaling pathway,and catalyzes core fucosylation of Itga6.Deletion of Fut8 enhances the ubiquitination of Itga6 by promoting the binding of ubiquitin ligase Trim21 to Itga6.Low levels of Itga6 inhibit the activity of the PI3K/Akt signaling pathway.Moreover,the Akt agonist SC79 can rescue neurogenic and behavioral deficits caused by Fut8 deficiency.In summary,our study uncovers an essential function of Fut8 and core fucosylation in regulating adult neurogenesis and sheds light on the underlying mechanisms.

关键词： Fut8 adult neural stem/progenitor cells neurogenesis Itga6 PI3K/Akt

The evolving views of hematopoiesis:from embryo to adulthood and from in vivo to in vitro

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Journal of Genetics and Genomics 2024年第1期51卷 3-15页

作者： Yifan Zhang feng Liu Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology School of Life SciencesShandong UniversityQingdaoShandong 266237China State Key Laboratory of Membrane Biology Institute of ZoologyInstitute for Stem Cell and RegenerationUniversity of Chinese Academy of SciencesChinese Academy of SciencesBeijing 100101China

The hematopoietic system composed of hematopoietic stem and progenitor cells(HSPCs)and their differentiated lineages serves as an ideal model to uncover generic principles of cell fate transitions.From gastrulation onwards,there successively emerge primitive hematopoiesis(that produces specialized he-matopoietic cells),pro-definitive hematopoiesis(that produces lineage-restricted progenitor cells),and definitive hematopoiesis(that produces multipotent HSPCs).These nascent lineages develop in several transient hematopoietic sites and finally colonize into lifelong hematopoietic sites.The development and maintenance of hematopoietic lineages are orchestrated by cell-intrinsic gene regulatory networks and cell-extrinsic microenvironmental cues.Owing to the progressive methodology(e.g.,high-throughput lineage tracing and single-cell functional and omics analyses),our understanding of the developmental origin of hematopoietic lineages and functional properties of certain hematopoietic organs has been updated;meanwhile,new paradigms to characterize rare cell types,cell heterogeneity and its causes,and comprehensive regulatory landscapes have been provided.Here,we review the evolving views of HSPC biology during developmental and postnatal hematopoiesis.Moreover,we discuss recent advances in the in vitro induction and expansion of HSPCs,with a focus on the implications for clinical applications.

关键词： Hematopoietic stem and progenitor cell Developmental hematopoiesis Postnatal hematopoiesis In vitro hematopoiesis

Derivation of Expanded Isospectral-Nonisospectral Integrable Hierarchies via the Column-vector Loop Algebra

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 778-800页

作者： Hai-feng WANG Yu-feng ZHANG School of Science Jimei UniversityXiamen 361021China School of Mathematics China University of Mining and TechnologyXuzhou 221116China

A scheme for generating nonisospectral integrable hierarchies is introduced.Based on the method,we deduce a nonisospectral hierarchy of soliton equations by considering a linear spectral problem.It follows that the corresponding expanded isospectral and nonisospectral integrable hierarchies are deduced based on a 6 dimensional complex linear space ■.By reducing these integrable hierarchies,we obtain the expanded isospectral and nonisospectral derivative nonlinear Schr?dinger equation.By using the trace identity,the biHamiltonian structure of these two hierarchies are also obtained.Moreover,some symmetries and conserved quantities of the resulting hierarchy are discussed.

关键词： expanded isospectral-nonisospectral integrable hierarchies column-vector loop algebra bi-Hamiltonian structure symmetry

Carbon-based materials with combined functions of thermal management and electromagnetic protection: Preparation, mechanisms, properties, and applications

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Nano Research 2024年第3期17卷 883-903页

作者： Junwei Yue Yiyu feng Mengmeng Qin Wei feng School of Materials Science and Engineering and Tianjin Key Laboratory of Composite and Functional Materials Tianjin UniversityTianjin 300350China

The proliferation of high-power,highly informationized,and highly integrated electronic devices and weapons equipment has given rise to increasingly conspicuous issues about electromagnetic(EM)pollution and thermal accumulation.These issues,in turn,impose constraints on the performance of such equipment and jeopardize personnel safety.Carbon materials,owing to their diverse and modifiable structures,offer adjustable thermal and electric conductivity,rendering them highly promising for applications in fields such as thermal management and EM protection which have garnered extensive research and review.The pursuit of integrated device and equipment development has elevated the demand for multifunctional materials,prompting significant research into carbon-based composite materials that include both thermal management and EM protection functionalities.Notably,there are no relevant reviews on this topic at present.Consequently,this work consolidates research findings from recent years on carbon matrix composites exhibiting dual attributes of thermal management and EM protection.These attributes include thermally conductive electromagnetic interference(EMI)shielding materials,thermally insulating EMI shielding materials,thermally conductive EM wave(EMW)absorbing materials,and thermally insulating EMW absorbing materials.The paper elucidates the fundamental principles underpinning thermal conduction,thermal insulation,EMW absorbing,and EMI shielding.Additionally,it engages in discussions surrounding areas of contention,design strategies,and the functional properties of various material designs.Ultimately,the paper concludes by presenting the challenges encountered and potential research strategies about composites endowed with both thermal management and EM protection functionalities,while also envisaging the development of novel multifunctional EM protection materials.

关键词： carbon-based composites electromagnetic interference shielding microwave absorption thermal conduction thermal insulation

Design and identification of a double-acting piezoelectric-hydraulic hybrid actuator

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Chinese Journal of Aeronautics 2024年第3期37卷 456-467页

作者： Junjian ZHANG Zhihua feng Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes University of Science and Technology of ChinaHefei 230026China

Traditional single-acting piezoelectric-hydraulic hybrid actuators usually have the problem of inertial force caused by flow pulsation of the liquid,which degrades their output performance.To suppress or solve the associated inertial force and enhance its output capabilities,this paper proposes a new type of double-acting piezoelectric-hydraulic hybrid actuator with four check valves acting as mechanical diodes.The new hybrid actuator was fabricated and its output performance was tested.When the voltage is 700 Vp-pand the bias pressure is 2 MPa,the pulsation ratesδof the new actuator at 400 Hz,500 Hz and 600 Hz are 2.29,2.08 and 1.78,respectively,whileδof the single-acting hybrid actuator under the same conditions are 10.98,11.05 and 17.12.Therefore,the liquid pulsation rate of the new hybrid actuator is significantly reduced,which is beneficial for improving the flow uniformity and weakening the influence of inertial force on the hybrid actuator.This strategy ultimately leads to a maximum no-load velocity of 168.1 mm/s at 600 Hz and a maximum blocking force of 141 N at 450 Hz for the new hybrid actuator.In addition,this strategy has the potential to be used in other electrohydrostatic actuators to improve their performance.

关键词： Double-acting Flow pulsation Inertial force Piezoelectric actuators Piezoelectric devices Piezoelectric hydraulic actuation Piezoelectric pump

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无人机入水发射流场仿真及冲击特性分析

力学与实践 2023年第4期45卷 874-880页

作者：姜涛陈尚成冯文正关玉明河北工业大学机械工程学院天津300130

跨介质航行是近年来无人机应用领域的重要研究内容。本文通过数值模拟方法,对某型号飞翼式无人机在不同工况下发射入水过程流场演变及运动姿态进行对比分析,同时对其入水冲击响应进行了数值仿真研究,得到不同发射工况下无人机的入水冲... 详细信息

跨介质航行是近年来无人机应用领域的重要研究内容。本文通过数值模拟方法,对某型号飞翼式无人机在不同工况下发射入水过程流场演变及运动姿态进行对比分析,同时对其入水冲击响应进行了数值仿真研究,得到不同发射工况下无人机的入水冲击载荷响应情况。结果表明:该型号无人机入水过程的姿态变化同时受水面条件及发射工况影响,静水工况下以25°入水角、4 m/s的条件发射无人机入水时,可实现最优的姿态恢复时间及入水冲击载荷响应值。

关键词：跨介质航行数值仿真流场演变运动姿态冲击特性

Rational Solutions of First Order Algebraic Ordinary Differential Equations

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Journal of Systems Science & Complexity 2024年第2期37卷 567-580页

作者： feng Shuang SHEN Liyong School of Physical and Mathematical Sciences Nanjing Tech UniversityNanjing 211816China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China

Let f(t,y,y')=∑ _(i=0)^(n )a_(i)(t,y)y'^(i)=0 be an irreducible first order ordinary differential equation with polynomial coefficients.Eremenko in 1998 proved that there exists a constant C such that every rational solution of f(t,y,y')=0 is of degree not greater than C.Examples show that this degree bound C depends not only on the degrees of f in t,y,y' but also on the coefficients of f viewed as the polynomial in t,y,y'.In this paper,the authors show that if f satisfies deg(f,y)0,then the degree bound C only depends on the degrees of f in t,y,y',and furthermore we present an explicit expression for C in terms of the degrees of f in t,y,y'.

关键词： Degree bound first order AODE height rational solution

Turbulence Statistics of Thermo-Buoyancy Supercritical Fuel Flow in a Regenerative Cooling Channel

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Journal of Thermal Science 2024年第1期33卷 126-137页

作者： SUN feng XIE Gongnan School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072China Department of Thermal Engineering Tsinghua UniversityBeijing 100084China

Active regenerative cooling with supercritical hydrocarbon fuel is considered as the most promising thermal protection method.The existence of buoyancy force would lead to strongly anisotropic flow and thermal transport characteristics.It is closely related to the cooling performance of the engine.To elucidate the mechanisms of turbulent transport,the large eddy simulation(LES) was performed to assess turbulence statistics within different turbulence scales.The results indicated that the buoyancy and inertial force together dominated the change of turbulent structure.Moreover,the spatial thermal buoyancy effect significantly suppressed the vertical velocity fluctuation.This is due to the laminar motion caused by the buoyancy force,thereby weakening the thermal transport.For the statistics of velocity fluctuation,it was found that the buoyancy force and inertial force greatly weaken the vertical and streamwise velocity fluctuation,respectively.For the statistics of thermal transport,the results pointed out that the near-wall heat transport characteristics need to be paid more attention.The thickness of the temperature mixing boundary layer led to the attenuation of vertical heat flux,which inhibited vertical temperature diffusion and predisposed to extreme conditions of heat transfer deterioration.The results can enhance the academic understanding of the heat transfer mechanism of supercritical fluids,and give guidance for further applications of thermal protection.

关键词： active regenerative cooling large eddy simulation(LES) buoyancy force turbulence statistics