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Theoretical Study on Photoisomerization of 2-Methylfuran to 3-Methylfuran

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Chinese Journal of Structural Chemistry 2006年第6期25卷 681-688页

作者： wang Yan-xia YE Song Department of Chemistry Yunnan University Kunming 650091 China

In the present work, the photoisomerization of 2-methylfuran to 3-methylfuran is investigated with the complete active space SCF （CASSCF） molecular orbital method. Geometries of minima and transition states on the excited and ground states are fully optimized at the CAS level with a 6-3 IG＊ basis set. A multireference MP2 algorithm that has been implemented in Gaussian is used to correct the energetics for dynamic correlation. The topology and reaction funnels of the singlet, triplet （S0, T1, T2） and potential energy surfaces have been characterized along the reaction coordinates corresponding to the mechanism. The reaction proceeds via two diradical intermediates, one intermediate product and four transition states. The two diradical S 1/T2 and T1/S0 energy surface crossing points are located along the reaction path and a T1/T2 conical intersection is also located. From this point the reaction soon returns to T1 surface. It is the most reasonable that the intersystem crossing from T1 to S0 takes place.

关键词： CASSCF photoisomerization intersystem crossing point reaction path

Theoretical Study on the Triplet-sensitized Photolysis of 2,5-Dimethylfuran

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Chinese Journal of Structural Chemistry 2005年第10期24卷 1145-1151页

作者： wang Yan-xia YE Song Department of Chemistry Yunnan University Kunming 650091 China

In the present work, the triplet-sensitized photolysis of 2,5-dimethylfuran has been investigated with the complete active space SCF （CASSCF） molecular orbital method. Two different reaction routes through diradical and carbene intermediates respectively have been systematically studied, and the reaction via carbene intermediate is the major part well compatible with experiment. Geometries of minima and transition states on S0T1 surface were fully optimized at the CAS level with a 6-31G^＊ basis set. A multireference MP2 algorithm that has been implemented in Gaussian was used to correct the energetics for dynamic correlation. Four intersystem crossing points have been located and discussed, and two of them are efficient. Our computation indicates that the reaction must occur on the triplet-excited state.

关键词： CASSCF photolysis intersystem crossing point reaction path

Recent advances in Ni-Al bimetallic catalysis for unreactive bond transformation

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Science China Chemistry 2018年第8期61卷 1004-1013页

作者： Yin-xia wang Mengchun Ye State Key Laboratory and Institute of Elemento-Organic Chemistry Nankai University Tianjin 300071 China Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) Tianjin 300071 China

Ni-Al bimetallic catalysis proves to be an efficient catalytic strategy for unreactive bond transformations. Recently, chiral bifunctional ligands, especially amphoteric secondary phosphine oxide(SPO) ligand, are used for a more powerful synergistic effect in the bimetal-catalyzed reactions, providing not only milder reaction conditions and higher reactivity but also excellent reaction selectivity. Herein, we give a brief review on the development of Ni-Al bimetallic catalytic system and highlight recent advances in enantioselective Ni-Al bimetallic catalysis for unreactive bond transformation.

关键词： nickel aluminum bimetallic catalysis SPO ligand unreactive bond

Improved AHP–TOPSIS model for the comprehensive risk evaluation of oil and gas pipelines

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Petroleum Science 2019年第6期16卷 1479-1492页

作者： xia wang Qingquan Duan School of Safety and Ocean Engineering China University of Petroleum-BeijingChangpingBeijing 102249China

A comprehensive and objective risk evaluation model of oil and gas pipelines based on an improved analytic hierarchy process(AHP)and technique for order preference by similarity to an ideal solution(TOPSIS)is established to identify potential hazards in ***,a barrier model and fault tree analysis are used to establish an index system for oil and gas pipeline risk evaluation on the basis of five important factors:corrosion,external interference,material/construction,natural disasters,and function and ***,the index weight for oil and gas pipeline risk evaluation is computed by applying the improved AHP based on the five-scale ***,the TOPSIS of a multi-attribute decision-making theory is *** method for determining positive/negative ideal solutions and the normalized equation for benefit/cost indexes is improved to render TOPSIS applicable for the comprehensive risk evaluation of *** closeness coefficient of oil and gas pipelines is calculated by applying the improved ***,the weight and the closeness coefficient are combined to determine the risk level of *** research using a long-distance pipeline as an example is conducted,and adjustment factors are used to verify the *** show that the risk evaluation model of oil and gas pipelines based on the improved AHP–TOPSIS is valuable and *** model comprehensively considers the risk factors of oil and gas pipelines and provides comprehensive,rational,and scientific evaluation *** represents a new decision-making method for systems engineering in pipeline enterprises and provides a comprehensive understanding of the safety status of oil and gas *** new system engineering decision-making method is important for preventing oil and gas pipeline accidents.

关键词： Improved AHP–TOPSIS model Risk evaluation Oil and gas pipelines Improved TOPSIS Improved AHP

Enantiornithine Birds in China

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Acta Geologica Sinica(English Edition) 2011年第6期85卷 1211-1223页

作者： wang xia ZHANG Zihui College of Life Sciences Capital Normal University Beijing 100048 China School of Biology and Environmental Science University College Dublin Belfield Dublin 4 Ireland

A brief introduction to the morphology, flight, size, habits, diet, feathers and systematic paleontology of fossil enantiornithine birds known from the Mesozoic of China is provided. Enantiornithine birds were the dominant land birds of the Mesozoic （245-65 Myr）. Although they show great morphological differences from modern birds, their diversification in many respects mimics that of the modern land bird radiation and the reasons for their extinction at the end-Cretaceous remain a mystery.

关键词： enantiornithines distribution diversification Cretaceous China

A FAST CLASSIFICATION METHOD FOR SINGLE-PARTICLE PROJECTIONS WITH A TRANSLATION AND ROTATION INVARIANT

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Journal of Computational Mathematics 2013年第2期31卷 137-153页

作者： xia wang Guoliang Xu LSEC ICMSEC Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

The aim of the electron microscopy image classification is to categorize the projection images into different classes according to their similarities. Distinguishing images usually requires that these images are Migned first. However, alignment of images is a difficult task for a highly noisy data set. In this paper, we propose a translation and rotation invariant based on the Fourier transform for avoiding alignment. A novel classification method is therefore established. To accelerate the classification speed, secondary-classes are introduced in the classification process. The test results also show that our method is very efficient and effective. Classification results using our invariant are also compared with the results using other existing invariants, showing that our invariant leads to much better results.

关键词： Classification Fourier transform Translation and rotation invaxiant Secondaryclass.

Theoretical Study of the Photochemical Reaction Mechanism of Bicyclo[4.1.0]heptane

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Chemical Research in Chinese Universities 2006年第4期22卷 520-523页

作者： wang Yan-xia YE Song Department of Chemistry Yunnan University Kunming 650091 P. R. China

The photochemical reaction of bicyclo[4.1.0]heptane was studied at the complete active space SCF（CASSCF） level with a 6-31G^＊ basis set. A muhireference MP2 algorithm that has been implemented in the Gaussian program was used to correct the energetics for the dynamic correlation. Starting from the Franck-Condon excitation of bicyclo [ 4.1.0 ] heptane, the reaction is via two bonds＇ breakage to give rise to 1,6-heptdiene. One internal conversion （IC） and two intersystem crossing points（ISC） were located and are discussed separately. The reaction proceeds to its own characteristic product on the ground state.

关键词： CASSCF Intersystem crossing Photochemical reaction mechanism Internal conversion Bicyclo-[ 4.1.0 ] heptane 1-6 Heptadiene

Microstructure of nano precursors of La-Mg hydrogen storage alloy synthesized by sol-gel technology at different pH values

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Rare Metals 2012年第5期31卷 466-469页

作者： wang Dahui xia Jihong ZHANG Sha Key Laboratory of Non-ferrous Metal Alloys and Processing of Ministry of Education Lanzhou University of Science and Technology Lanzhou 730050 China

Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.

关键词： pH value microstructure nano precursors sol-gel technology

Cochannel interference cancelation for multiple access systems

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Journal of Systems Engineering and Electronics 2007年第2期18卷 223-228页

作者： wang xia Zhu Shihua Sun Delong School of Electronics and Information Engineering Xi'an Jiaotong Univ Xi'an 710049 P. R. China

Many properties of frequency-hopped spread-spectrum multiple access （FH/SSMA）, such as, robustness against frequency selective fading and jamming make it a preferred multiple access communication scheme. But cochannel interference （CCI） can seriously harm the system＇s performance. On the basis of the analysis of the CCI pattern of frequency hopped multiple access signal, a new multiuser detection algorithm for canceling the CCI in frequency hopped multiple access systems is proposed. In the proposed scheme, the CCI is canceled by first detecting the frequency hopping slot, and then classifying and regenerating the candidates of the interference pattern from the time-frequency matrix. Both the theoretical analysis and computer simulation results show that compared to the conventional detector and Mabuchi＇s detector, this new multiuser detector has lower complexity, better convergence stability, and is suitable for both additive white Gaussian noise （AWGN） channels and Rayleigh fading channels.

关键词： Communication and informance systems Cochannel interference cancellation Multiuser detection Frequency hopped.