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Structure and Dynamics of Confined Polymer Melts from Attractive Interaction to Repulsive Interaction Between Polymer and Smooth Wall

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Chemical Research in Chinese Universities 2015年第3期31卷 477-483页

作者： li sijia ZHANG Wanxi YAO Weiguo SHI Tongfei College of Materials Science and Engineering Jilin University Changchun 130022 P.R.China State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences Changchun 130022 P.R.China College of Materials Science and Engineering Jilin University Changchun 130022 P.R.China State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences Changchun 130022 P.R.China

We studied the static and dynamic properties of unentangled polymer chains which have a variable strength of interaction with the confining smooth walls by means of the lattice Monte Carlo simulation based on the bond-fluctuation model, that is, investigated the wall-polymer interactions which systematically vary from attraction to repulsion. A critical value of attractive potential（ewe） is found to be -0.6kilT, and only below it can the adsorption layer of monomers be formed near the wall. At the critical point of attraction ewe, attractive interaction counterba- lances the wall-polymer excluded volume effect, which minimizes the confinement effects on both chain dimension and mobility. Influences on both chain dimension and mobility increase with the increasing of either attraction or repulsion imposed by the walls. Despite of the nature and strength of the wall-polymer interaction, with the decrease of film thickness, configurations more parallelly aligned and flattened are adopted by confined chains, and a systematic trend of deceleration is found. Variations of chain dynamics with both film thickness and wall-polymer interaction can be well explained by the corresponding changes in the confinement of the nearest-neighboring particles that surround the chains. Besides, the thickness of the interfacial layer inside polymer films, where chains adopt a flattened ＂pancake＂ shape, is about two times the bulk radius of gyratioia and independent of the wall-polymer interaction.

关键词： Confinement effect Wall-polymer interaction Critical point of attraction Lattice Monte Carlo simulation

Kinetic hydrate inhibitor performance of new copolymer poly(N-vinyl-2-pyrrolidone-co-2-vinyl pyridine)s with TBAB

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Journal of Natural Gas Chemistry 2012年第2期21卷 126-131页

作者： Jun Hu sijia li Yanhong Wang Xuemei Lang Qingping li Shuanshi Fan Key Laboratory of Enhanced Heat Transfer and Energy Conversation Ministry of EducationSchool of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou 510641GuangdongChina State Key Laboratory of Of fshore Oil Exploitation Beijing 100027China

In oil and gas field, the application of kinetic hydrate inhibitors （KHIs） independently has remained problematic in high subcooling and high water-cut situation. One feasible method to resolve this problem is the combined use of KHIs and some synergists, which would enhance KHIs’ inhibitory effect on both hydrate nucleation and hydrate crystal growth. In this study, a novel kind of KHI copolymer poly（N-vinyl-2-pyrrolidone-co-2-vinyl pyridine）s （HGs） is used in conjunction with TBAB to show its high performance on hydrate inhibition. The performance of HGs with different monomer ratios in structure II tetrahydrofuran （THF） hydrate is investigated using kinetic hydrate inhibitor evaluation apparatus by step-cooling method and isothermal cooling method. With the combined gas hydrate inhibitor at the concentration of 1.0 wt%, the induction time of 19 wt% THF solution could be prolonged to 8.5 h at a high subcooling of 6℃. Finally, the mechanism of HGs inhibiting the formation of gas hydrate is proposed.

关键词： clathrate hydrate kinetic hydrate inhibitors combined hydrate inhibitors poly(N-vinyl-2-pyrrolidone-co-2-vinyl pyridine)

Coupling effect of bifunctional ZnCe@SBA-15 catalyst in 1,3-butadiene production from bioethanol

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Chinese Journal of Chemical Engineering 2022年第5期35卷 162-170页

作者： Zheng Wang sijia li Shengping Wang Jiaxu liu Yujun Zhao Xinbin Ma Key Laboratory for Green Chemical Technology of Ministry of Education School of Chemical Engineering and TechnologyCollaborative Innovation Center of Chemical Science and EngineeringTianjin UniversityTianjin 300072China State Key Laboratory of Fine Chemicals Department of Catalytic Chemistry and EngineeringDalian University of TechnologyDalian 116024China

A series of bifunctional Zn Ce@SBA-15 catalysts with different Zn/Ce ratios were prepared by a solid-state grinding strategy and used in the conversion of ethanol to 1,3-butadiene(ETB).For the supported metal oxides,Zn O serves as the active sites for the dehydrogenation of ethanol,and CeO_(2) promotes the aldolcondensation *** on the results of Py-FTIR and NH_(3)-TPD,it suggests that the yield of 1,3-butadiene is positively correlated with the number of weak Lewis acid sites on the catalyst surface,given their benefit for aldol-condensation *** catalyst with an optimal Zn/Ce ratio of about 1:5 has the highest concentration of weak Lewis *** with the Zn O sites,it contributes to a 98.4%conversion of ethanol and a 45.2%selective of 1,3-butadiene under relatively mild reaction conditions(375°C,101.325 k Pa,and 0.54 h^(-1)).

关键词： Biomass Catalyst Coupling effect Lewis acid 1 3-butadiene Optimization

Long-Term Variation of Global GEOV2 and MODIS Leaf Area Index (LAI) and Their Uncertainties: An Insight into the Product Stabilities

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Journal of Remote Sensing 2021年第1期2021卷 302-318页

作者： Hongliang Fang Yao Wang Yinghui Zhang sijia li LREIS Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China

Leaf area index(LAI)is an essential climate variable that is crucial to understand the global vegetation ***-term satellite LAI products have been applied in many global vegetation change ***,these LAI products contain various uncertainties that are not been fully considered in current *** objective of this study is to explore the uncertainties in the global LAI products and the uncertainty *** global LAI datasets—the European Geoland2 Version 2(GEOV2)and Moderate Resolution Imaging Spectroradiometer(MODIS)(2003-2019)—were *** qualitative quality flags(QQFs)and quantitative quality indicators(QQIs)embedded in the product quality layers were analyzed to identify the temporal anomalies in the quality *** results show that the global GEOV2(0.042/10a)and MODIS(0.034/10a)LAI values have steadly increased from 2003 to *** global LAI uncertainty(0.016/10a)and relative uncertainty(0.3%/10a)from GEOV2 have also increased gradually,especially during the growing season from April to *** uncertainty increase is larger for woody biomes than for herbaceous ***,the MODIS LAI product uncertainty remained stable over the study *** uncertainty increase indicated by GEOV2 is partly attributed to the sensor shift in the product *** algorithm enhancement is necessary to improve the cross-sensor *** study highlights the importance of studying the LAI uncertainty and the uncertainty *** variations in the LAI products and the product quality revealed herein have significant implications on global vegetation change studies.

关键词： uncertainty qualitative season

Ensemble Mean Forecast Skill and Applications with the T213 Ensemble Prediction System

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Advances in Atmospheric Sciences 2016年第11期33卷 1297-1305页

作者： sijia li Yuan WANG Huiling YUAN Jinjie SONG Xin XU Key Laboratory of Mesoscale Severe Weather Ministry of EducationSchool of Atmospheric SciencesNanjing University

Ensemble forecasting has become the prevailing method in current operational weather forecasting. Although ensemble mean forecast skill has been studied for many ensemble prediction systems（EPSs） and different cases, theoretical analysis regarding ensemble mean forecast skill has rarely been investigated, especially quantitative analysis without any assumptions of ensemble members. This paper investigates fundamental questions about the ensemble mean, such as the advantage of the ensemble mean over individual members, the potential skill of the ensemble mean, and the skill gain of the ensemble mean with increasing ensemble size. The average error coefficient between each pair of ensemble members is the most important factor in ensemble mean forecast skill, which determines the mean-square error of ensemble mean forecasts and the skill gain with increasing ensemble size. More members are useful if the errors of the members have lower correlations with each other, and vice versa. The theoretical investigation in this study is verified by application with the T213 EPS. A typical EPS has an average error coefficient of between 0.5 and 0.8; the 15-member T213 EPS used here reaches a saturation degree of 95%（i.e., maximum 5% skill gain by adding new members with similar skill to the existing members） for 1–10-day lead time predictions, as far as the mean-square error is concerned.

关键词： skill ensemble Ensemble questions rarely verified forecast explain saturation discussion

New ZnCe catalyst encapsulated in SBA-15 in the production of 1,3-butadiene from ethanol

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Chinese Chemical Letters 2020年第2期31卷 535-538页

作者： Yujun Zhao sijia li Zheng Wang Shengnian Wang Shengping Wang Xinbin Ma Key Laboratory for Green Chemical Technology of Ministry of Education.Collaborative Innovation Center of Chemical Science and Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China Chemical Engineering Institute for MicromanufacturingLouisiana Tech UniversityRustonLA 71272United States

ZnO-CeO2/SBA-15 catalysts were prepared by two kinds of solid-state grinding method and used for the production of 1,3-butadiene(1,3-BD) from ethanol.A mixture of SBA-15(with or without organic template) and metal precursors were ground in *** obtained catalysts were characterized by TG,N2 adsorption-desorption,TEM,XRD,Py-FTIR and NH_3-TPD *** dispersion of metal oxides and more exposed acid sites were achieved on the catalyst lOZn_1Ce_5-AS with the presence of organic template in SBA-15 during the solid-state grinding *** catalytic performance was evaluated in a fixed-bed reactor and a 1,3-butadiene selectivity of as high as 45% is *** is attributed to the coupling effect of Zn and Ce species in the mesopores of SBA-15,in which Zn promotes ethanol dehydrogenation and Ce enhances aldol-condensation,***,solvent-free method inspires new catalyst synthesis strategy for the production of 1,3-butadiene from ethanol.

关键词： 1,3-Butadiene Ethanol SBA-15 Dehydrogenation Aldol-condensation

Low-cost fabrication of highly dispersed atomically-thin MoS2 nanosheets with abundant active Mo-terminated edges

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Nano Materials Science 2021年第3期3卷 205-212页

作者： Fei Wang Ming Hao Wei liu Penji Yan Baizeng Fang sijia li Jinsheng liang Maomao Zhu li Cui Key Laboratory of Special Functional Materials for Ecological Environment and Information(Hebei University of Technology) Ministry of EducationTianjin300130China Institute of Power Source and Ecomaterials Science Hebei University of TechnologyTianjin300130China Dalian National Laboratory for Clean Energy Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian116023China College of Chemistry and Chemical Engineering Key Laboratory of Hexi Corridor Resources Utilization of Gansu UniversitiesHexi UniversityZhangye734000China Department of Chemical&Biological Engineering University of British ColumbiaVancouverV6T 1Z3Canada

In this work,highly dispersed atomically-thin MoS2 nanosheets were fabricated at one thousandth of the commercial cost using sepiolite(SEP)mineral nanofibers as carriers via a microwave hydrothermal *** microscopy revealed the MoS2 nanosheets were only 1–4 atomic layers *** Mo atoms anchored on the mineral surface served as nucleation sites for the nanosheet *** MoS2 layers were in staggered stacking yielding abundant atomic steps at the nanosheets’edges,where catalytically active molybdenum terminations dominated instead of the inert sulfur atoms commonly *** calculations disclosed that the bonding of Mo(MoS2)and O(SEP)at the MoS2/sepiolite(MSEP)interface enabled SEP to be a unique support,superior to the other minerals for growing such highly-dispersed ultrathin MoS2 *** a typical photocatalyisis application,the MSEP demonstrated a significantly improved photocatalytic performance for RhB degradation compared with the MoS2 nanosheets assembled *** work provides an important new strategy for low-cost batch preparation of high quality 2D materials via assembly on mineral materials.

关键词： Molybdenum disulfide Nanosheets Mineral nanofibers Microwave hydrothermal Molybdenum termination Density functional theory

Single-beam leaky-wave antenna with wide scanning angle and high scanning rate based on spoof surface plasmon polariton

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Chinese Physics B 2022年第10期31卷 399-405页

作者： Huan Jiang Xiang-Yu Cao Tao liu liaori Jidi sijia li Information and Navigation College Air Force Engineering UniversityXi’an 710077China Shaanxi Key Laboratory of Artificially-Structured Functional Materials and Devices Air Force Engineering UniversityXi’an 710051China

We propose a single-beam leaky-wave antenna(LWA) with a wide-scanning angle and a high-scanning rate based on spoof surface plasmon polariton(SSPP) in this paper. The SSPP transmission line(TL) is etched with periodically arranged circular patches, which converts the slow-wave mode into the fast-wave region for radiation. The proposed LWA is designed, fabricated, and tested. The simulated results imply that the proposed LWA not only achieves a high radiation efficiency of about 81.4%, and a high scanning rate of 12.12, but also has a large scanning angle of 176° over a narrow operation bandwidth of 8.3-9.6 GHz(for |S_(11)| lidating its performance. An antenna with high radiation efficiency, wide scanning angle range, and high scanning rate has great potential for application in radar and wireless communication systems.

关键词： spoof surface plasmon polariton(SSPP) leaky wave antenna wide scanning angle high scanning rate

Preliminary Assessment of the COVID-19 Outbreak Using 3-Staged Model e-ISHR

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Journal of Shanghai Jiaotong university(Science) 2020年第2期25卷 157-164页

作者： li sijia SONG Kun YANG Boran GAO Yucen GAO Xiaofeng School of Electronic Information and Electrical Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China Zhiyuan College Shanghai Jiao Tong UniversityShanghai 200240China

The outbreak of coronavirus disease 2019(COVID-19)in Wuhan has aroused widespread concern and attention from all over the *** articles have predicted the development of the *** of them only use very basic SEIR model without considering the real *** this paper,we build a model called e-ISHR model based on SEIR *** we add hospital system and time delay system into the original model to simulate the spread of COVID-19 ***,in order to take the government's control and people's awareness into consideration,we change our e-ISHR model into a 3-staged model which effectively shows the impact of these factors on the spread of the *** using this e-ISHR model,we fit and predict the number of confirmed cases in Wuhan and China except *** also change some of parameters in our *** results indicate the importance of isolation and increasing the number of beds in hospital.

关键词： coronavirus disease 2019(COVID-19) epidemic prediction 3-staged model hospital system government's control