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Ultrafiltration with in-line coagulation for the removal of natural humic acid and membrane fouling mechanism

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Journal of Environmental Sciences 2006年第5期18卷 880-884页

作者： WANG Jin WANG xiao-chang Department of Municipal and Environmental Engineering Beijing Jiaotong University Beijing 100044 China School of Environmental and Municipal Engineering Xi＇an University of Architecture and Technology Xi＇an 710055 China

Experimental and theoretical analysis were made on the natural humic acid removal and the membrane fouling of ultrafiltration （UF） with in-line coagulation. The results showed dissolved organic carbon （DOC） and UV254 removals by the UF with in-line coagulation at pH 7 were increased from 28% to 53% and 40% to 78% in comparison with direct UF treatment respectively. At the same time, the analysis of high performance liquid chromatography showed that UF with coagulation had significant improvement of removal of humic acid with molecular weights less than 6000 Da in particular. Compared to direct UF, the in-line coagulation UF also kept more constant permeate flux and very slight increase oftransmembrane pressure during a filtration circle. Two typical membrane fouling models were used by inducing two coefficients Kc and Kp corresponding to cake filtration model and pore narrowing model respectively. It was found that membrane fouling by pore-narrowing effect was effectively alleviated and that by cake-filtration was much decreased by in-line coagulation. Under the condition of coagulation prior to ultrafiltration at pH 7, the cake layer formed on the membrane surface became thicker, but the membrane filtration resistance was lower than that at pH 5 with the extension of operation time.

关键词： natural humic acid ultrafiltration (UF) in-line coagulation high performance liquid chromatography (HPLC) membrane fouling

A Thermo-Tunable Metamaterial as an Actively Controlled Broadband Absorber

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Engineering 2023年第1期20卷 143-152页

作者： xiao-chang Xing Yang Cao xiao-Yong Tian Lingling Wu State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an 710049China

Metamaterials have attracted increasing attention in recent years due to their powerful abilities in manipulating electromagnetic (EM) waves. However, most previously reported metamaterials are unable to actively control full-band EM waves. In this paper, we propose a thermo-tunable broadband metamaterial (T-TBM) using paraffin-based composites (PD-Cs) with different phase transition temperatures. Active control of the T-TBM reflection loss peaks from low to high frequency is realized by manipulating the solid–liquid state of the PD-Cs at different phase transition temperatures. The absorption peak bandwidth (where the reflection loss value is less than −30 dB) can be changed, while the broad bandwidth absorption (where the reflection loss value is less than −10 dB) is satisfied by adjusting the temperature of the T-TBM. It is shown that the stagnation of the phase transition temperature of the PD-Cs in the T-TBM provides a time window for actively controlling the EM wave absorption response under different thermal conditions. The device has a broad application prospect in the fields of EM absorption, intelligent metamaterials, multifunctional structural devices, and more.

关键词： Metamaterials Active control Thermally tunable Br oadband absorption

Pyrolyzed bacterial cellulose/graphene oxide sandwich interlayer for lithium–sulfur batteries

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Rare Metals 2017年第5期36卷 418-424页

作者： Yu-Di Shen Zhi-chang xiao Li-xiao Miao De-Bin Kong xiao-Yu Zheng Yan-Hong chang Lin-Jie Zhi Chinese Academy of Sciences Key Laboratory of Nanosystem and Hierarchical Fabrication CAS Center for Excellence in NanoscienceNational Center for Nanoscience and Technology Beijing 100190China Department of Environmental Engineering University of Science and Technology of BeijingBeijing 100083China Beijing Key Laboratory of Resource-Oriented Treatment of Industrial Pollutants University of Science and Technology of BeijingBeijing 100083China Institute of Forensic Science Ministry of Public SecurityBeijing 100038China

Herein, a facile strategy for the synthesis of sandwich pyrolyzed bacterial cellulose（PBC）/graphene oxide（GO） composite was reported simply by utilizing the large-scale regenerated biomass bacterial cellulose as precursor. The unique and delicate structure where three-dimensional interconnected bacterial cellulose（BC） network embedded in two-dimensional GO skeleton could not only work as an effective barrier to retard polysulfide diffusion during the charge/discharge process to enhance the cyclic stability of the Li–S battery, but also offer a continuous electron transport pathway for the improved rate *** a result, by utilizing pure sulfur as cathodes, the Li–S batteries assembled with PBC/GO interlayer can still exhibit a capacity of nearly 600 mAh·g^-1 at 3C and only 0.055% capacity decay per cycle can be observed over 200 cycles. Additionally, the cost-efficient and environmentfriendly raw materials may enable the PBC/GO sandwich interlayer to be an advanced configuration for Li–S batteries.

关键词： Biomass materials Graphene oxide Separator Lithium–sulfur batteries

Mechanism for acetic acid-catalyzed ester aminolysis

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Chinese Chemical Letters 2018年第8期29卷 1233-1236页

作者： chang xiao Song-Lin Zhang Key Laboratory of Synthetic and Biological Colloids Ministry of Education School of Chemical and Material Engineering Jiangnan University

This paper reports a computational study elucidating reaction mechanism for amide bond formation from esters and amines catalyzed by acetic acid. Two optional mechanisms（namely, classic stepwise and concerted acyl substitution mechanisms） have been studied. Calculation results establish the reaction energy profiles of both mechanisms and locate all the intermediates and transition states in both catalytic cycles. Our results propose that the concerted acyl substitution mechanism may be more likely wherein the formation of CààN bond and the cleavage of CààO bond occur concurrently without the need of rehybridization of the carbonyl carbon. This is also consistent with the fact that no significant racemization/epimerization were observed in the amide products when asymmetric esters and/or amines were used as the reactants, because concerted acyl substitution mechanism precludes the intermediacy of tetrahedral adducts and the accompanying generation/elimination of new chiral *** discussion implies that the concerted acyl substitution mechanism may widely occur in related amidation reactions in the presence of different types of coupling reagents.

关键词： Amide bond formation Aminolysis Mechanism Ester Concerted acyl substitution Acid catalyzed amidation

On the Ricci Curvature of a Randers Metric of Isotropic S-curvature

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Acta Mathematica Sinica,English Series 2008年第6期24卷 911-916页

作者： xiao Huan MO chang Tao YU Key Laboratory of Pure and Applied Mathematics School of Mathematical Sciences Peking University Beijing 100871 P. R. China

We derive the integral inequality of a Randers metric with isotropic S-curvature in terms of its navigation representation. Using the obtained inequality we give some rigidity results under the condition of Ricci curvature. In particular, we show the following result： Assume that an n-dimensional compact Randers manifold （M, F） has constant S-curvature c. Then （M, F） must be Riemannian if its Ricci curvature satisfies that Ric 〈 -（n - 1）c^2.

关键词： Finsler manifold Randers metric Ricci curvature

Integrating BDS and GPS for precise relative orbit determination of LEO formation flying

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Chinese Journal of Aeronautics 2018年第10期31卷 2013-2022页

作者： Bin YI Defeng GU xiao chang Kai SHAO College of Liberal Arts and Sciences National University of Defense Technology

Low-Earth-Orbit（LEO） formation-flying satellites have been widely applied in many kinds of space geodesy. Precise Relative Orbit Determination（PROD） is an essential prerequisite for the LEO formation-flying satellites to complete their mission in space. The contribution of the BeiDou Navigation Satellite System（BDS） to the accuracy and reliability of PROD of LEO formation-flying satellites based on a Global Positioning System（GPS） is studied using a simulation method. Firstly, when BDS is added to GPS, the mean number of visible satellites increases from9.71 to 21.58. Secondly, the results show that the 3-Dimensional（3 D） accuracy of PROD, based on BDS-only, GPS-only and BDS ＋ GPS, is 0.74 mm, 0.66 mm and 0.52 mm, respectively. When BDS co-works with GPS, the accuracy increases by 29.73%. Geostationary-Earth-Orbit（GEO） satellites and Inclined Geosynchronous-Orbit（IGSO） satellites are only distributed over the Asia-Pacific region; however, they could provide a global improvement to PROD. The difference in PROD results between the Asia-Pacific region and the non-Asia-Pacific region is not apparent. Furthermore, the value of the Ambiguity Dilution Of Precision（ADOP）, based on BDS ＋ GPS, decreases by 7.50% and 8.26%, respectively, compared with BDS-only and GPS-only. Finally, if the relative position between satellites is only a few kilometres, the effect of ephemeris errors on PROD could be ignored. However, for a several-hundred-kilometre separation of the LEO satellites, the SingleDifference（SD） ephemeris errors of GEO satellites would be on the order of centimetres. The experimental results show that when IGSO satellites and Medium-Earth-Orbit（MEO） satellites co-work with GEO satellites, the accuracy decreases by 17.02%.

关键词： Ambiguity Dilution Of Precision BeiDou Navigation Satellite System Geostationary-Earth-Orbit Global Positioning System LEO formation flying Precise Relative Orbit Determination

Overview on development of ASEAN traditional and herbal medicines

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Chinese Herbal Medicines 2021年第4期13卷 441-450页

作者： chang-xiao Liu Tianjin Institute of Pharmaceutical Research Tianjin 300462China State Key Laboratory of Drug Delivery Technology and Pharmacokinetis Tianjin 300462China China-ASEAN Joint Laboratory for International Cooperation in Traditional Medicine Research Nanning 530200China

Traditional medicine is an important and often underestimated part of health *** some countries,it has a long history of use in health maintenance and in disease prevention and treatment,particularly for *** has always emphasized the important role of traditional,complementary and alternative medicine in human *** this review article,the author provided some information from the following five aspects:(1)Development basis of China ASEAN traditional medicine and herbal medicine;(2)The development and afficacy of traditional medicine theory system;(3)Industry development and regulation management of traditional medicine and herbal medicine products;(4)China-ASEAN traditional medicine exchanges and cooperation to promote traditional medicine cooperation and medicine trade,and(5)Strengthening academic and industrial cooperation and promoting the healthy development of traditional medicine and herbal *** is believed that the information will have certain reference value for readers in studies on traditional and herbal medicines.

关键词： cooperation development herbal medicine information regulation research traditional medicine

Parameter Dependence of Stable Manifolds for Nonuniform (μ, ν)-dichotomies

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Acta Mathematica Sinica,English Series 2013年第6期29卷 1111-1130页

作者： Ji Min ZHANG Meng FAN xiao Yuan chang College of Mathematics Jilin University School of Mathematical Sciences Heilongjiang University School of Mathematics and Statistics Northeast Normal University School of Applied Sciences Harbin University of Science and Technology

We construct stable invariant manifolds for semiflows generated by the nonlinear impulsive differential equation with parameters x＇= A（t）x ＋ f（t, x, λ）, t≠τi and x（τ＋i） = Bix（τi）＋ gi（x（τi）, λ）, i ∈ N in Banach spaces, assuming that the linear impulsive differential equation x＇= A（t）x, t≠τi and x（τ＋i） = Bix（τi）, i ∈ N admits a nonuniform （μ, ν）-dichotomy. It is shown that the stable invariant manifolds are Lipschitz continuous in the parameter λ and the initial values provided that the nonlinear perturbations f, g are sufficiently small Lipschitz perturbations.

关键词： Stable invariant manifolds nonuniform ( μ ν )-dichotomies impulsive differential equations

Relationship of quantitative structure and pharmacokinetics in fluoroquinolone antibacterials

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World Journal of Gastroenterology 2007年第17期13卷 2496-2503页

作者： Die Cheng Wei-Ren Xu chang-xiao Liu Department of Pharmaceutical Engineering Schoolof Chemical Engineering and Technology Tianjin UniversityTianjin 300072 China National KeyLaboratory of Pharmacokinetics and Pharmacodynamics TianjinInstitute of Pharmaceutical Research Tianjin 300193 China

AIM： To study the relationship between quantitative structure and pharmacokinetics （QSPkR） of fluorocluinolone antibacterials.METHODS： The pharmacokinetic （PK） parameters of oral fluoroquinolones were collected from the literature. These pharmacokinetic data were averaged, 19 compounds were used as the training set, and 3 served as the test set. Genetic function approximation （GFA） module of Cerius2 software was used in QSPkR analysis.RESULTS： A small volume and large polarizability and surface area of substituents at C-7 contribute to a large area under the curve （AUC） for fluoroquinolones. Large polarizability and small volume of substituents at N-1 contribute to a long half life elimination.CONCLUSION： QSPkR models can contribute to some fluoroquinolones antibacterials with excellent pharmacokinetic properties.

关键词： Quantitative structure pharmacokinetic relationship Genetic function approximation Fluoro-quinolones Elimination half life