检索结果-南通市图书馆

Thermostable α-Diimine Nickel Complexes with Substituents on Acenaphthequinone-backbone for Ethylene Polymerization

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2020年第11期38卷 1214-1220,I0007页

作者： Rui-Fang Zhang Yan-Hui Hou Xu-ling Wei Ding-Ding Zhao Mi-Mi Cui Fei-Fan Zhai xiang-liu li Bin-Yuan liu Min Yang Hebei Key Laboratory of Functional Polymers Tianjin Key Laboratory of Chemical Process SafetyInstitute of Polymer Science and EngineeringHebei University of TechnologyTianjin 300130China State Key Laboratory of Separation Membranes and Membrane Processes School of Material Science and EngineeringTiangong UniversityTianjin 300160China Lanzhou Petrochemical Research Center Petrochemical Research Institute of CNPCLanzhou 730060China

In order to promote the thermostability of a-diimine nickel complex by ligand backbone structure,a series of α-diimine nickel complexes with substituents on acenaphthequinone backbone were synthesized and used as catalysts for ethylene *** the hydroxyethyl phenoxyl group was introduced to the acenaphthequinone-backbone,the thermal stability and activity of the catalyst could be significantly *** catalytic activity of complex C2[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-diisopropyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide with isopropyl substituents on N-aryl reached 8.2×10^6g/(molNi·h)at 70℃and 2 *** activity of[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-dibenzhydryl-4-menthylphenyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide(C3)still maintained at 6.7×10^5 g/(molNi·h)at 120℃.Compared with C3 containing bulky dibenzhydryl substituents,the activity of C2 was sensitive to the change of the polymerization ***,the polyethylenes obtained from complex C3 had lower branching ***,the molecular weight could reach 971 kg/mol,which is almost 5 times as much as that of the polyethylene obtained from complex C2.

关键词： α-Diimine nickel Ethylene polymerization Thermostability ligand backbone structure

Temperature prediction model in multiphase flow considering phase transition in the drilling operations

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第3期21卷 1969-1979页

作者： Yang Zhang Yong-An li xiang-Wei Kong Hao liu Teng-Fei Sun College of Mechanical and Electrical Engineering Beijing University of Chemical TechnologyBeijing 100027China School of Petroleum Engineering Yangtze UniversityWuhan430000HubeiChina

The study considers gas compression properties,gas slippage,back pressure(BP),phase transition(PT),well depth,and differences in gas-liquid physical properties.A new temperature model for multiphase flow is proposed by considering phase transition in the drilling *** mathematical model of multiphase flow is solved using the finite difference method with annulus mesh division for grid nodes,and a module for multiphase flow calculation and analysis is *** results indicate that the temperature varies along the annulus with the variation of gas influx at the bottom of the *** the process of controlled pressure drilling,as gas slips along the annulus to the wellhead,its volume continuously expands,leading to an increase in the gas content within the annulus,and consequently,an increase in the pressure drop caused by gas *** temperature increases with the increase in BP and decreases in gas influx rate and wellbore *** gas influx,the thermal conductivity coefficient for the gas-drilling mud two phases is significantly weakened,resulting in a considerable change in temperature along the *** the context of MPD,the method of slightly changing the temperature along the annulus by controlling the back pressure is feasible.

关键词： Managed pressure drilling Phase transition Temperature Gas-drilling mud two phase

Transfer-free chemical vapor deposition graphene for nitride epitaxy: challenges, current status and future outlook

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第3期67卷 824-840页

作者： xiang Gao Senlin li Jingfeng Bi Kaixuan Zhou Meng li Zhongfan liu Jingyu Sun College of Energy Soochow Institute for Energy and Materials InnovationsSUDA-BGI Collaborative Innovation CenterKey Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu ProvinceSoochow UniversitySuzhou 215006China Beijing Graphene Institute Beijing 100095China Xiamen Silan Advanced Compound Semiconductor Co.Ltd. Xiamen 361026China

Graphene, a two-dimensional material with outstanding electrical and mechanical properties, has attracted considerable attention in the field of semiconductor technologies due to its potential use as a buffer layer for the epitaxial Ⅲ-nitride growth. In recent years, significant progress has been made in the chemical vapor deposition growth of graphene on various insulating substrates for the nitride epitaxy, which offers a facile, inexpensive, and easily scalable methodology. However, certain challenges are still present in the form of producing high-quality graphene and achieving optimal interface compatibility with Ⅲ-nitride *** this review, we provide an overview of the bottlenecks associated with the transferred graphene fabrication techniques and the state-of-the-art techniques for the transfer-free graphene growth. The present contribution highlights the current progress in the transfer-free graphene growth on different insulating substrates, including sapphire, quartz, SiO_(2)/Si, and discusses the potential applications of transfer-free graphene in the Ⅲ-nitride epitaxy. Finally, it includes the prospects of the transfer-free graphene growth for the Ⅲ-nitride epitaxy and the challenges that should be overcome to realize its full potential in this field.

关键词： Transfer-free chemical vapor deposition graphene for nitride epitaxy challenges current status and future outlook graphene

A Composite Elastomer with Photo-responsive Shape Memory and Programmable Hygroscopic Actuation Functionalities

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第10期42卷 1470-1478,I0009页

作者： xiang-Xi Cui li Shang Zhong-Wen liu Zhao-Tie liu Jin-Qiang Jiang Guo li Key Laboratory of Syngas Conversion of Shaanxi Province School of Chemistry and Chemical EngineeringShaanxi Normal UniversityXi’an710062China

Developing hydroscopic actuators with simultaneous high elasticity,shape programmability and tunable actuating behaviors are highly desired but still *** this study,we propose an orthogonal composite design to develop such a *** developed composite elastomer comprises carboxyl group-grafted polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene(SEBS-g-COOH)as the elastic substrate,and a synthesized azobenzene derivative as the functional filler(Azo12).By surface treatment using acidic and base solutions,the carboxyl groups on the surface can reversibly transform into carboxylate groups,which render the composite tunable hygroscopic actuating *** another aspect,the added filler undergoes trans-to-cis isomerization when exposed to UV light irradiation,leading to liquefaction of the crystalline aggregates formed by Azo12 *** liquefied Azo12 molecules can autonomously resotre their trans form and reform the crystalline *** reversible change in crystralline structure is utilized to realize the shape memory property,and 5 wt%of Azo12addition is adequate for the composite to exhibit photo-responsive shape memory behavior without compromising much of the *** regualtion of external geometry by shape memory effect is effective in altering the actuating *** proposed method can be extend to designing different composites with the demonstrated functionalities.

关键词： Actuator Shape memory Photo-responsive Hygroscopic responsive Azobenzene

Identifying malicious traffic under concept drift based on intraclass consistency enhanced variational autoencoder

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第8期67卷 238-252页

作者： xiang LUO Chang liu Gaopeng GOU Gang XIONG Zhen li Binxing FANG Institute of Information Engineering Chinese Academy of Sciences School of Cyber Security University of Chinese Academy of Sciences School of Computer Science and Technology Harbin Institute of Technology (Shenzhen)

Accurate identification of malicious traffic is crucial for implementing effective defense countermeasures and has led to extensive research efforts. However, the continuously evolving techniques employed by adversaries have introduced the issues of concept drift, which significantly affects the performance of existing methods. To tackle this challenge, some researchers have focused on improving the separability of malicious traffic representation and designing drift detectors to reduce the number of false ***, these methods often overlook the importance of enhancing the generalization and intraclass consistency in the representation. Additionally, the detectors are not sufficiently sensitive to the variations among different malicious traffic classes, which results in poor performance and limited robustness. In this paper, we propose intraclass consistency enhanced variational autoencoder with Class-Perception detector(ICE-CP) to identify malicious traffic under concept drift. It comprises two key modules during training:intraclass consistency enhanced(ICE) representation learning and Class-Perception(CP) detector construction. In the first module, we employ a variational autoencoder(VAE) in conjunction with Kullback-Leibler(KL)-divergence and cross-entropy loss to model the distribution of each input malicious traffic flow. This approach simultaneously enhances the generalization, interclass consistency, and intraclass differences in the learned representation. Consequently, we obtain a compact representation and a trained classifier for nondrifting malicious traffic. In the second module, we design the CP detector, which generates a centroid and threshold for each malicious traffic class separately based on the learned representation, depicting the boundaries between drifting and non-drifting malicious traffic. During testing, we utilize the trained classifier to predict malicious traffic classes for the testing samples. Then, we use the CP det

关键词： concept drift malicious traffic identification variational autoencoder intrusion detection cyberspace security

Energy Absorption by 3D-Printed Mesh Structures with a Negative Poisson’s Ratio

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 205-212页

作者： Wenyu li Weiming Yang Mingze li xiang Zhang Ping Zhang Yucheng Zhao Peijian Chen Haishun liu School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou221116China School of Materials Sciences and Physics China University of Mining and TechnologyXuzhou221116China

A negative Poisson's ratio(NPR)structure represents optimal impact-resistance with applications in various fields,including the crash box in vehicles,which absorbs impact kinetic *** crash box is designed to deform in response to impact,increasing local structural density,which enhances impact resistance *** studies have only focused on the NPR effect in the plane dimension at low-speed *** studies have considered high-speed impact loads on three-dimensional NPR *** have developed two types of AlSi10Mg alloy energy-absorbing structures with NPR using three-dimensional printing technology,and have compared our systems with a conventional hexagonal mesh *** testing involved split-Hopkinson pressure bar measurements,which showed good agreement with dynamic numerical *** subjected to an impact load,the NPR structure exhibited better impact resistance and energy absorption compared with the positive Poisson's ratio *** proposed dual-layer hexagonal structure ensures an NPR effect while exhibiting higher strength and improved stability relative to the conventional concave hexagon structure.

关键词： Negative Poisson’s ratio Energy absorption 3D printing Split-Hopkinson pressure bar Numerical simulation

The miR164-TaNAC14 module regulates root development and abiotic-stress tolerance in wheat seedlings

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2023年第4期22卷 981-998页

作者： CHI Qing DU lin-ying MA Wen NIU Ruo-yu WU Bao-wei GUO li-jian MA Meng liu xiang-li ZHAO Hui-xian College of life Sciences Northwest A&F UniversityYangling 712100P.R.China

Previous studies have revealed the miR164 family and the miR164-targeted NAC transcription factor genes in rice(Oryza sativa)and Arabidopsis that play versatile roles in developmental processes and stress *** wheat(Triticum aestivum L.),we found nine genetic loci of tae-miR164(tae-MIR164 a to i)producing two mature sequences that downregulate the expression of three newly identified target genes of TaNACs(TaNAC1,TaNAC11,and TaNAC14)by the cleavage of the respective *** of tae-miR164 or one of its target genes(TaNAC14)demonstrated that the miR164-TaNAC14 module greatly affects root growth and development and stress(drought and salinity)tolerance in wheat seedlings,and TaNAC14 promotes root growth and development in wheat seedlings and enhances drought tolerance,while tae-miR164 inhibits root development and reduces drought and salinity tolerance by downregulating the expression of *** findings identify the miR164-TaNAC14 module as well as other taemiR164-regulated genes which can serve as new genetic resources for stress-resistance wheat breeding.

关键词： Triticum aestivum L. tae-miR164 miR164-targeted TaNACs miR164-TaNAC14 module growth and development abiotic-stress tolerance

Sensitivity impacts owing to the variations in the type of zero-range pairing forces on the fission properties using the density functional theory

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第3期35卷 198-207页

作者： Yang Su Ze-Yu li li-Le liu Guo-xiang Dong Xiao-Bao Wang Yong-Jing Chen China Nuclear Data Center China Institute of Atomic EnergyBeijing 102413China School of Science Huzhou UniversityHuzhou 313000China

Using the Skyrme density functional theory,potential energy surfaces of^(240)Pu with constraints on the axial quadrupole and octupole deformations(q_(20)and q_(30))were *** volume-like and surface-like pairing forces,as well as a combination of these two forces,were used for the Hartree–Fock–Bogoliubov *** in the least-energy fission path,fission barrier,pairing energy,total kinetic energy,scission line,and mass distribution of the fission fragments based on the different forms of the pairing forces were analyzed and *** fission dynamics were studied based on the timedependent generator coordinate method plus the Gaussian overlap *** results demonstrated a sensitivity of the mass and charge distributions of the fission fragments on the form of the pairing *** on the investigation of the neutron-induced fission of^(239)Pu,among the volume,mixed,and surface pairing forces,the mixed pairing force presented a good reproduction of the experimental data.

关键词： Nuclear fission Density functional theory Pairing force Potential energy surfaces Fission fragment distribution

BIO-inspired intelligent navigation: from methodology, system theory, to behavioural science

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第9期67卷 333-335页

作者： Wenshuo li Xin liu Pengwei HU Jian YANG xiang YU Lei GUO Hangzhou Innovation Institute of Beihang University School of Automation Science and Electrical Engineering Beihang University School of Instrumentation and Optoelectronic Engineering Beihang University

It is crucial for unmanned systems to determine their motion information accurately, reliably, and in real time. This function is accomplished by the autonomous navigation module of the unmanned systems. By analogy to the animals,the autonomous navigation module can be regarded as the“sensory nerve center” of an unmanned system.

关键词：