检索结果-南通市图书馆

Chinese Journal of Chemistry 2022年第2期40卷 215-222页

作者： ao chen Daohong Liao Changle chen Hefei National Laboratory for Physical Sciences at the Microscale CAS Key Laboratory of Soft Matter ChemistryDepartment of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefeiAnhui 230026China

In the past few decades,the development of high-performance catalysts has been a key driving force and a center of research efforts in the field of olefin ***,a major discrepa ncy exists between in dustrial researches which utilize aliphatic hydrocarb on solventsz and academic researches which predominantly focus the catalytic properties in aromatic *** this con-tribution,a novel diaryl-methyl aniline bearing eight tert-butyl groups was prepared and subsequently transformed to four different kinds of imine-type *** corresponding nickel complexes as well as their counterparts derived from diphenyl-methyl aniline without the tert-butyl groups were prepared and investigated in ethylene polymerization.

关键词： Ethylene polymerization Polyethylene Nickel Solvent effects Steric hindranee

Polyolefin vitrimers bearing acetoacetate functionality

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第11期67卷 3861-3867页

作者： Zihao Wang Yue Liu Wenmin Pang ao chen Min chen Chinese Academy of Sciences(CAS)Key Laboratory of Soft Matter Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefei 230601China

Polyolefin vitrimers are polymer networks bearing reversible covalent crosslinking points, enabling them to be reprocessed and recycled. In this contribution, a series of polyolefin vitrimers were designed based on the acetoacetate-functionalized polyolefin copolymers, which were produced through the direct copolymerization of ethylene with polar comonomers using a phosphinesulfonate palladium catalyst. The pendant acetoacetate group could mediate several characteristic reactions, such as the Michael addition reaction, ketone-amine condensation and metal coordination reaction. As such, structurally adjustable polyolefin vitrimers can be accessed by introducing various dynamic crosslinking bonds, including disulfide exchange, transamination of vinylogous urethane and labile metal coordination bond. The utilization of different crosslinking reactions and the mole ratio of crosslinkers significantly impact the material properties of the resultant polymers. Specifically, the generated polyolefin vitrimers demonstrated excellent reprocessability and closed-loop recycling properties. The study in this work provides an efficient strategy to access various polyolefin vitrimers.

关键词： polyolefin vitrimers acetoacetate group polar monomer olefin copolymerization

Positional Electronic Effects in Iminopyridine-N-oxide Nickel Catalyzed Ethylene Polymerization

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2021年第6期39卷 1683-1689页

作者： Mingjun Chi ao chen Wenmin Pang chen Tan Changle chen CAS Key Laboratory of Soft Matter Chemistry Hefei National Laboratory for Physical Sciences at the MicroscaleDepartment of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefeiAnhui 230026China Institutes of Physical Science and Information Technology Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of EducationAnhui UniversityHefeiAnhui 230026China

A series of dibenzhydryl-based iminopyridine-N-oxide ligands bearing a range of electron-donating or-withdrawing substituents(OMe,H;and NO_(2))and corresponding nickel pre-catalysts are prepared and *** substituents are installed at different positions on the ligand structure,including 4-position of the pyridine-N-oxide moiety(position X)and 4-position of the aniline moiety(position Y).These nickel pre-catalysts are highly active in ethylene polymerization with the addition of very little amount of aluminum cocatalysts,leading to the formation of polyethylenes with molecular weights of well above one ***-donating substituents make the catalysts sensitive to polymerization *** contrast,the catalysts bearing electron-withdrawing NO_(2) substituents show relatively steady performances at different *** importantly,we demonstrate that different substituents and different positions both play important roles in determining the properties of nickel *** provides an alternative strategy for the future design of high-performance polymerization catalyst.

关键词： Ethylene Polymerization Nickel lminopyridine-N-oxide Substituent effects

Global Existence and Extinction Behaviour for a Doubly Nonlinear Parabolic Equation with Logarithmic Nonlinearity

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Wuhan University Journal of Natural Sciences 2023年第2期28卷 99-105页

作者： LIU Dengming chen ao School of Mathematics and Computational Science Hunan University of Science and TechnologyXiangtan 411201HunanChina

This paper is mainly focused on the global existence and extinction behaviour of the solutions to a doubly nonlinear parabolic equation with logarithmic nonlinearity. By making use of energy estimates method and a series of ordinary differential inequalities, the global existence of the solution is obtained. Moreover, we give the sufficient conditions on the occurrence(or absence)of the extinction behaviour.

关键词： global existence extinction behaviour doubly nonlinear parabolic equation logarithmic nonlinearity

Molecular understanding of cation effects on double layers and their significance to CO-CO dimerization

在线全文

学校读者我要写书评

暂无评论

National Science Review 2023年第9期10卷 125-135页

作者： Jia-Bo Le ao chen Yongbo Kuang Jun cheng Key Laboratory of Advanced Fuel Cells and Electrolyzers Technology of Zhejiang Province Ningbo Institute of Materials Technology and EngineeringChinese Academy of Sciences State Key Laboratory of Physical Chemistry of Solid Surfaces iChEM College of Chemistry and Chemical EngineeringXiamen University Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province(IKKEM)

Cation effects have been shown in numerous experiments to play a significant role in electro *** understand these effects at the molecular level,we systematically investigate the structures and capacitances of electric double layers with a variety of cations as counter charges at Pt(111)-COad/water interfaces with ab initio molecular *** is encouraging to find that the computed Helmholtz capacitances for different cations are in quantitative agreement with experiments,and that the trend of cation effects on capacitances shows clear correlation with the structures of interface cations of differing sizes and hydration *** importantly,we demonstrate the Helmholtz capacitance as the key descriptor for measuring the activity of CO-CO dimerization,the rate-determining step for C2+formation in electroreduction of CO and *** work provides atomistic insights into cation effects on electric double layers and electrocatalysis that are crucial for optimizing electrode and electrolyte materials.

关键词： cation effect electrocatalysis electric double layer CO-CO dimerization ab initio molecular dynamics

Cluster-Based Massive Access for Massive MIMO Systems

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China Communications 2024年第1期21卷 24-33页

作者： Shiyu Liang Wei chen Zhongwen Sun ao chen Bo Ai State Key Laboratory of Advanced Rail Autonomous Operation Beijing Jiaotong UniversityBeijing 100091China School of Electronic and Information Engineering Beijing Jiaotong UniversityBeijing 100091China Frontiers Science Center for Smart High-speed Railway System Beijing Jiaotong UniversityBeijing 100091China Key Laboratory of Railway Industry of Broadband Mobile Information Communications Beijing Jiaotong UniversityBeijing 100091China Beijing Engineering Research Center of High-speed Railway Broadband Mobile Communications Beijing Jiaotong UniversityBeijing 100091China School of Information Engineering Zhengzhou UniversityZhengzhou 450001China

Massive machine type communication aims to support the connection of massive devices,which is still an important scenario in *** this paper,a novel cluster-based massive access method is proposed for massive multiple input multiple output *** exploiting the angular domain characteristics,devices are separated into multiple clusters with a learned cluster-specific dictionary,which enhances the identification of active *** detected active devices whose data recovery fails,power domain nonorthogonal multiple access with successive interference cancellation is employed to recover their data via *** results show that the proposed scheme and algorithm achieve improved performance on active user detection and data recovery.

关键词： compressive sensing dictionary learning multiuser detection random access

Development of fish collagen in tissue regeneration and drug delivery

在线全文

学校读者我要写书评

暂无评论

Engineered Regeneration 2022年第3期3卷 217-231页

作者： Meison Furtado Liang chen Zehao chen ao chen Wenguo Cui Department of Orthopaedics Shanghai Key Laboratory for Prevention and Treatment of Bone and Joint DiseasesShanghai Institute of Traumatology and OrthopaedicsRuijin HospitalShanghai Jiao Tong University School of MedicineShanghai 200025P.R.China

Tissues rely on collagen for structural and biological integrity,as well as for function and *** collagen sources have been investigated due to its wide variety of applications,such as collagen from cows and ***,mammalian-based collagen has been limited by diseases like bovine spongiform encephalopathy(BSE)and other religious ***,fish collagen has caught the attention of the research community because it is easy to extract,has a high level of collagen content,excellent absorption properties,a low molecular weight,biocompatibility,little risk of disease transmission from animals to humans,negligible environmental contamination,and fewer ethical and religious concerns,posing as an ideal resource for product *** review focuses on the growing role of marine collagen in the advances of various biomedical applications,such as drug delivery,tissue engineering,regeneration,and wound healing,which will be covered in depth.

关键词： Collagen Fish collagen Marine collagen Drug delivery Tissue engineering

Multi-blade rubbing characteristics of the shaft-disk-blade-casing system with large rotation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 111-136页

作者： Zhiyuan WU Linchuan ZHao Han YAN Ge YAN ao chen Wenming ZHANG State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Institute of Aerospace Systems Engineering Shanghai 201108China

Blade rubbing faults cause detrimental impact on the operation of aeroengines. Most of the existing studies on blade rubbing in the shaft-disk-blade-casing(SDBC) system have overlooked the elastic deformation of the blade, while some only consider the whirl of the rotor, neglecting its spin. To address these limitations, this paper proposes a dynamic model with large rotation for the SDBC system. The model incorporates the spin and whirl of the rotor, enabling the realistic reproduction of multiblade rubbing faults. To verify the accuracy of the SDBC model with large rotation and demonstrate its capability to effectively consider the rotational effects such as the centrifugal stiffening and gyroscopic effects, the natural characteristics and dynamic responses of the proposed model are compared with those obtained from reported research and experimental results. Furthermore, the effects of the rotating speed, contact stiffness,and blade number on the dynamic characteristics of the SDBC system with multi-blade rubbing are investigated. The results indicate that the phase angle between the rotor deflection and the unbalance excitation force increases with the increasing rotating speed,which significantly influences the rubbing penetration of each blade. The natural frequency of the SDBC system with rubbing constrain can be observed in the acceleration response of the casing and the torsional response of the shaft, and the frequency is related to the contact stiffness. Moreover, the vibration amplitude increases significantly with the product of the blade number under rubbing, and the rotating frequency approaches the natural frequency of the SDBC system. The proposed model can provide valuable insight for the fault diagnosis of rubbing in bladed rotating machinery.

关键词： shaft-disk-blade-casing(SDBC) large rotation spin and whirl multi-blade rubbing rotational effect

Analysis of the internal charging data in medium earth orbit with numerical simulation and ground experiment

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2022年第4期65卷 977-986页

作者： SONG SiYu chen HongFei YU XiangQian ZOU Hong ZONG QiuGang chen ao SHI WeiHong YE YuGuang Institute of Space Physics and Applied Technology School of Earth and Space SciencesPeking UniversityBeijing 100871China

The deep dielectric charging effect monitor(DDCEM)has been designed to study the internal charging effect by measuring the charging currents and potentials inside the *** is equipped on three Chinese navigation satellites in a circular medium earth orbit(MEO)with 22000 km average height and 55°*** simulation based on the Geant4-RIC method was used to evaluate the data of *** data during May to November 2019 on one of the three satellites show that the charging currents of DDCEM were negatively enhanced when the satellite moved into the outer radiation *** currents reached the negative maximum during a significant electron enhancement in September *** currents were also detected besides negative currents that were caused by the deposition of electrons in the *** causation of positive currents in the space environment may be that the low-energy electrons cannot penetrate the satellite skin and make it charging to negative potential,the reference ground of DDCEM that is connected to the satellite skin drops below zero by the low-energy electrons so that the output currents turn to *** experiment was used to simulate the causation of positive currents and the result verified our theory.

关键词： deep dielectric charging effect monitor internal charging effect charging currents and potentials medium earth orbit space environment

Knowledge Graph-Based Image Recognition Transfer Learning Method for On-Orbit Service Manipulation

在线全文

学校读者我要写书评

暂无评论

Space(Science & Technology) 2021年第1期2021卷 164-172页

作者： ao chen Yongchun Xie Yong Wang Linfeng Li Beijing Institute of Control Engineering BeijingChina Science and Technology on Space Intelligent Control Laboratory BeijingChina

Visual perception provides state information of current manipulation scene for control system,which plays an important role in on-orbit service *** the development of deep learning,deep convolutional neural networks(CNNs)have achieved many successful applications in the field of visual *** CNNs are only effective for the application condition containing a large number of training data with the same distribution as the test data;however,real space images are difficult to obtain during large-scale ***,deep CNNs can not be directly adopted for image recognition in the task of on-orbit service *** order to solve the problem of few-shot learning mentioned above,this paper proposes a knowledge graph-based image recognition transfer learning method(KGTL),which learns from training dataset containing dense source domain data and sparse target domain data,and can be transferred to the test dataset containing large number of data collected from target *** average recognition precision of the proposed method is 80.5%,and the average recall is 83.5%,which is higher than that of ResNet50-FC;the average precision is 60.2%,and the average recall is 67.5%.The proposed method significantly improves the training efficiency of the network and the generalization performance of the model.

关键词： Service Visual manipulation