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Two new flavonoid diglycosides from Cephalotaxus sinensis

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Chinese Chemical Letters 2007年第7期18卷 837-839页

作者： Wei Li Rong Ji dai yu Hong yu Liang Li Wei Wei Meng yu Lin Deng School of Life Science and Technology Beijing Institute of Technology Beijing 100081 China

Two new acetylated flavonoid diglycosides, scutellarein-5-O-[α-L-rhamnopyranosyl-（1 → 4）-β-D-6-O-acetylglucopyranoside]（1）, apigenin-5-O-[α-L-rhamnopyranosyl-（1→ 2）-β-D-3,6-di-O-acetylglucopyranoside] （2）, were isolated from the leaves of Cephalotaxus sinensis. Their structures were determined by chemical and spectroscopic methods including HR-FAB-MS,^1H-^1H COSY, HSQC and HMBC experiments.

关键词： Cephalotaxus sinensis (Rehd et Wile) Li Flavonoid diglycosides Scutellarein-5-O-[α-L-rhamnopyranosyl-(1→ 4)-β-D-6-O-acetylglucopyranoside] Apigenin-5-O-[α-L-rhamnopyranosyl-(1 → 2)-β-D-3,6-di-O-acetylglucopyranoside]

A Text Categorization System with Soft Real-Time Guarantee

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Wuhan University Journal of Natural Sciences 2006年第1期11卷 226-229页

作者： WANG Hua-yong CHEN yu dai Yi-qi Department of Computer Science and Technology Tsinghua University Beijing 100084 China

In order to provide predictable runtime performante for text categorization （TC） systems, an innovative system design method is proposed for soft real time TC systems. An analyzable mathematical model is established to approximately describe the nonlinear and time-varying TC systems. According to this mathematical model, the feedback control theory is adopted to prove the system＇s stableness and zero steady state error. The experiments result shows that the error of deadline satisfied ratio in the system is kept within 4 of the desired value. And the number of classifiers can be dynamically adjusted by the system itself to save the computa tion resources. The proposed methodology enables the theo retical analysis and evaluation to the TC systems, leading to a high-quality and low cost implementation approach.

关键词： information retrieval text categorization soft real-time system feedback control theory

Effect of Ti on microstructure and strengthening behavior in press hardening steels

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Journal of Central South University 2017年第10期24卷 2215-2221页

作者： WEN yu-hui ZHU Guo-ming dai Si-yu KANG Yong-lin School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China State Key Laboratory for Advanced Metals and Materials(University of Science and Technology Beijing) Beijing 100083China

Effect of Ti addition on the microstructure and strengthening behavior in press hardening steels(PHS)was analyzed by optical metallography(OM),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and X-ray diffraction(XRD).The results show that the microstructure of PHS is martensite,and two sizes of particles disperse in the martensite matrix during the forming and quenching *** size of the bigger particles is between 100 and 200 nm,and the small particles are *** quantity of the particles has a positive relation with the Ti *** importantly,the microstructure and strengthening mechanism are affected by the precipitating behavior of the *** the prior austenite grain,martensite packet,block and lath are refined by Ti *** steels are strengthened by the fine grains,martensite substructure and *** uniformly distributed dislocation in the martensite lath,the density of which is between 3.0?10^(14) cm^(–2) and 5.0?10^(14) cm^(–2),strengthens the steels through associating with fine carbide particles.

关键词： martensite particles prior austenite grain martensite lath press hardening steel

A spillover network analysis of the global crude oil market:Evidence from the post-financial crisis era

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Petroleum Science 2021年第4期18卷 1256-1269页

作者： Zhi-Yi Ouyang Zheng Qin Hong Cao Tian-yu Xie Xing-yu dai Qun-Wei Wang College of Economics and Management Nanjing University of Aeronautics and Astronautics29 Jiangjun AvenueNanjing211106China Research Center for Soft Energy Science Nanjing University of Aeronautics and AstronauticsNanjing211106China

The frequent occurrence of geopolitical crises in the post-financial crisis era is driving the rethinking behind whether the global crude oil market is still a highly connected"great pool".Using the spillover network model suggested by Baruník and Krehlík(2018),and the daily data of 31 global crude oil markets from 2009 to 2019,this study examines the return and volatility spillover effects and their timevarying behavior in six crude oil market segments at different *** findings indicate that heterogeneity exists in the co-movements between global crude oil markets in the post-financial crisis *** the medium term,both return and volatility spillover effects are not significant,which makes the diversified portfolio strategy *** in the Europe and Central Asian regions take the lead in return *** contrast,Asia-Pacific regional prices contribute the most in terms of volatility ***-term volatility spillovers increase sharply when confronted with oil-related events in the postfinancial crisis ***,policymakers should take effective measures to prevent any large-scale risk transmission in the long run.

关键词： Oil price Network analysis Spillover effect Multiscale analysis Baruník and Krehlík model

Synthesis, Crystal Structure and Luminescence of a New Europium(Ⅲ) Coordination Polymer with Imidazole Carboxylic Ligand

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Chinese Journal of Structural Chemistry 2019年第6期38卷 970-976页

作者： dai yu-Mei LIU Meng-Jia XU Jie Department of Chemistry and Life Sciences Minnan Science and Technology InstituteFujian Normal University

A new luminescent compound, {[Eu3（L）4（H2 O）8]·（NO3）·4 H2 O}n（1, H2 L = 2-（pyridine-3-yl）-imidazole-4,5-dicarboxylic acid） has been solvothermally synthesized and structurally characterized by elemental analyses, IR and single-crystal X-ray diffraction. 1 crystallizes in monoclinic, space group C2/c with a = 21.0183（19）, b = 9.5227（6）, c = 28.227（3） ?, β = 106.885（5）o, V = 5406.1（8） ?3, Dc = 2.038 g/cm3, μ = 3.358 mm-1, Mr = 1658.76, F（000） = 3247, Z = 4, the final R = 0.0488, wR = 0.1195 and S = 1.075. The deprotonated L ligand employs a μ4-bridge to coordinate with three Eu（Ⅲ） ion, forming a wave-like（3,4）-connected 2 D structure. The existence of π···π interaction between the pyridine rings of L ligands leads to an infinite 3 D network. Furthermore, the thermal analysis, powder diffraction and solid-state photoluminescent properties of compound 1 have also been investigated.

关键词： europium(Ⅲ) coordination polymer 2-(pyridine-3-yl)-1H-imidazole-4,5-dicarboxylate photoluminescence

A Gradient-Domain Based Geometry Processing Framework for Point Clouds

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Journal of Computer Science & Technology 2018年第4期33卷 863-872页

作者： Hong-Xing Qin Jin-Long He Meng-Hui Wang yu dai Zhi-Yong Ran College of Computer Science and Technology Chongqing University of Posts and Telecommunications Chongqing 400065 China

The use of point clouds is becoming increasingly popular. We present a general framework for performing geometry filtering on point-based surface through applying the meshless local Petrol-Galelkin （MLPG） to obtain the solution of a screened Poisson equation. The enhancement or smoothing of surfaces is controlled by a gradient scale parameter. Anisotropic filtering is supported by the adapted Riemannian metric. Contrary to the other approaches of partial differential equation for point-based surface, the proposed approach neither needs to construct local or global triangular meshes, nor needs global parameterization. It is only based on the local tangent space and local interpolated surfaces. Experiments demonstrate the efficiency of our approach.

关键词： point clouds processing partial differential equation meshless method gradient-domain

Cyclodextrin nanofilms with hydrophobic and hydrophilic channels for solvent permeation and molecular sieving

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Nano Research 2024年第7期17卷 6638-6644页

作者： Kai Zhang yu dai Yongli Shi Zhaoxin Zhang Linji Li Xiaojin Zhang Fan Xia Faculty of Materials Science and Chemistry China University of GeosciencesWuhan 430074China Henan Academy of Geology Zhengzhou 450052China

Nanofilms that can fast permeate solvents and accurately sieve molecules are of significant importance for separation.A promising strategy is to align the inner cavities of macrocycles into the channels within nanofilms,and control the channel size by selecting the ***,the channels outside the macrocycles are ***,we prepare nanofilms with hydrophobic channels(cyclodextrin inner cavity)and hydrophilic channels(cyclodextrin outer space)through interfacial polymerization of azobenzene-4,4’-dicarbonyl dichloride and amino-functionalizedβ-*** utilizing the significant geometric changes caused by the photoisomerization of azobenzene,nanofilms with adjustable hydrophilic channel sizes were *** nanofilms have high permeability to polar and non-polar solvents,and can distinguish molecules with almost the same molecular weight but different *** work expands the development of next-generation nanofilms generated through interfacial polymerization by incorporating rational molecular design.

关键词： nanofilm β-cyclodextrin azobenzene interfacial polymerization solvent permeation molecular sieving

Regulation of electronic structure of monolayer MoS_(2) by pressure

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Rare Metals 2022年第5期41卷 1761-1770页

作者： Qiao-Lu Lin Zheng-Fang Qian Xiang-yu dai Yi-Ling Sun Ren-Heng Wang Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China

Understanding pressure-regulated electronic properties is crucial for integrating two-dimensional semiconductors into flexible electronic devices and pressure sensors. We thoroughly explored the tunability of the electronic structure of monolayer MoS_(2) upon the application of perpendicular pressure and shear stress by using first-principles calculations. The band gap increased at low pressures and then decreased as the pressure *** in the band gap are caused by the combined interaction of the increasing and decreasing trends in the band gap. The increase in the band gap is induced by the enhancement of the p–d orbital interaction at the top of the valence band(TVB). The delocalization of charge and unstable hybridization bonding causes a reduction in the band gap. The band gap under perpendicular pressure modes is closely related to the structural variation. Shear stress can effectively reduce the band gap with minimal change to the crystal structure. The maximum point at the TVB and the minimum point at the bottom of the conduction band are different for all pressure modes, resulting in various anisotropic properties. This study provides a theoretical basis for modulating the electrical and optical properties of monolayer MoS_(2).

关键词： Band gap Pressure Monolayer MoS_(2) Electronic structure Shear stress

Aggregation Behavior and Structure of Associated Polyacrylamide Hydrophobically Modified with 2-Phenoxylethylacrylate

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Chemical Research in Chinese Universities 2009年第6期25卷 957-962页

作者： dai yu-hua WU Fei-peng LI Miao-zhen WANG Er-jian Department of Materials Science and Engineering Beijing Institute of Petrochemical Technology Beijing 102617 P. R. China Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100101 P. R. China

The aggregation behavior and structure of hydrophobically modified block copolymers of acrylamide and 2-phenoxylethylacrylate were investigated by viscometry, 1H NMR relaxation, 2D NOESY, fluorescence and dynamic light scattering. It Was found that the aggregation behavior was strongly dependent on the concentration of polymer solution and the hydrophobe contents. With varying concentration from 2.0, 6.0, 8.0 to 12.0 g/L, there were different aggregate morphologies distributed in aqueous solutions, such as monopolymer chain, micelle-like aggregate, multi-micelle aggregate and cross-linked network. According to the model of aggregation, it can give a reasonable explanation on the large magnitude enhancement of viscosity with the increasing of polymer concentration. Additional data of 2D NOESY and fluorescence show that the copolymer with higher hydrophobe content（molar fraction≥ 1%） is likely to form intra-molecular association.

关键词： Aggregation behavior and structure Hydrophobically modified Copolymer P(AM/POEA)