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Tuning surface active oxygen of lanthanum oxide via partial dissolution and regrowth of crystallites

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Journal of Natural Gas Chemistry 2011年第5期20卷 483-486页

作者： Zhiming Gao, Huili Li key laboratory of Cluster science, ministry of education of china Department of Chemistry, School of science, Beijing Institute of technology, Beijing 100081, china key laboratory of Cluster science Ministry of Education of China Department of Chemistry School of Science Beijing Institute of Technology Beijing 100081 China

A commercial lanthanum oxide was modified into X%-La2O3 samples via partial dissolution and regrowth of crystallites, wherein the X value denotes the weight percent of the initial metal oxide powder dissolved by nitric acid. BET measurements and TEM observations indicate that the 20%-La2O3 sample has an increased specific surface area, relatively thin and small crystallites in size. TPD/TPR profiles also show that the 20%-La2O3 sample has more surface active oxygen than the 0%-La2O3 sample. Among the four X%-La2O3 samples, the highest activity for methane oxidation was obtained over the 20%-La2O3 sample. Therefore, the present work proves that the method of partial dissolution and regrowth of crystallites are effective to modify surface property of lanthanum oxide.

关键词： solid state reaction surface oxygen crystallite regrowth TPR metal oxide

Shape description matrix and its applications to color-image retrieval and recognition

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science china(Technological sciences) 2004年第2期47卷 159-165页

作者： WANG Yi,ZHAI Hongchen,LIANG Yanmei,ZHANG Siyuan & MU Guoguang Institute of Modern Optics,Nankai University,tianjin 300071,china key laboratory of information Sci-ence and technology MOE,tianjin 300071,china Institute of Modern Optics Nankai University Tianjin China key laboratory of information science and technology MOE Tianjin China

Shape description matrix (SDM) describing regional pixel distribution characteristics of images is defined, with both radial and angular distribution messages taken into account to offer a comprehensive and exact description of the shape characteristics even upon a blurred edge. Using this SDM, a general color histogram (GCH) is developed. Both theoretical and experimental results show that the GCH can be applied to color-image retrievals and recognitions with a high efficiency.

关键词： SDM, similarity degree, match degree, general color histogram.

Simulation study of phase retrieval for hard X-ray in-line phase contrast imaging

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science china(Physics,Mechanics & Astronomy) 2005年第4期48卷 450-458页

作者： YU Bin1,2, PENG Xiang1,2, TIAN Jindong1, NIU Hanben1, DIAO Luhong3 & LI Hua3 1. key laboratory of optoelectronic Devices and Systems of ministry of education, Institute of Optoelec- tronics, Shenzhen University, Shenzhen 518060, china 2. State key laboratory of Precision Measuring technology and Instruments, tianjin University, tianjin 300072,china 3. key laboratory of Intelligent information Processing, Institute of Computing technology, Chinese Academy of sciences, Beijing 100080,china key laboratory of optoelectronic Devices and Systems of ministry of education Institute of Optoelectronics Shenzhen University Shenzhen China State key laboratory of Precision Measuring technology and Instruments Tianjin University Tianjin China key laboratory of Intelligent information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing China

Two algorithms for the phase retrieval of hard X-ray in-line phase contrast imaging are presented. One is referred to as Iterative Angular Spectrum Algorithm (IASA) and the other is a hybrid algorithm that combines IASA with TIE (transport of intensity equation). The calculations of the algorithms are based on free space propagation of the angular spectrum. The new approaches are demonstrated with numerical simulations. Comparisons with other phase retrieval algorithms are also performed. It is shown that the phase retrieval method combining the IASA and TIE is a promising technique for the application of hard X-ray phase contrast imaging.

关键词： X-ray optics, phase contrast imaging, phase retrieval, angular spectrum, hard X-ray.

Current progress and prospects of induced pluripotent stem cells

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science china(Life sciences) 2009年第7期52卷 622-636页

作者： CHEN LingYi & Liu Lin key laboratory of Bioactive Materials of ministry of education,College of Life sciences,Nankai University,tianjin 300071,china key laboratory of Bioactive Materials of ministry of education College of Life Sciences Nankai University Tianjin China

Induced pluripotent stem(iPS) cells are derived from somatic cells by ectopic expression of few transcription *** embryonic stem(ES) cells,iPS cells are able to self-renew indefinitely and to differentiate into all types of cells in the *** cells hold great promise for regenerative medicine,because iPS cells circumvent not only immunological rejection but also ethical *** the first report on the derivation of iPS cells in 2006,many laboratories all over the world started research on iPS cells and have made significant *** paper reviews recent progress in iPS cell research,including the methods to generate iPS cells,the molecular mechanism of reprogramming in the formation of iPS cells,and the potential applications of iPS cells in cell replacement *** problems that need to be addressed and the prospects for iPS research are also discussed.

关键词： induced pluripotent stem(iPS) cells somatic cell reprogramming pluripotency

An approach to determining the local boundaries of voltage stability region with wind farms in power injection space

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science china(Technological sciences) 2010年第12期53卷 3232-3240页

作者： MU YunFei & JIA HongJie key laboratory of Power System Simulation and Control of ministry of education, tianjin University, tianjin 300072, china key laboratory of Power System Simulation and Control of ministry of education Tianjin University Tianjin China

A new approach to determining the local boundaries of voltage stability region in power injection space (IVSR) for power system with wind farms is presented. It can be used for power system voltage stability analysis and on-line security assessment with considering the output uncertainty of the wind farms. Firstly, power flow tracing and double dispatching are used to determine the generators that are closely related to the wind farms, in order to balance the power fluctuations caused by the wind speed variation. Then, modal analysis is used to get the key generators to achieve an effective dimension reduction for IVSR. Finally, the forecasting output power (or wind speed) of wind farms is divided into several intervals. For each interval, the corresponding local IVSR boundaries can be calculated by the method based on small disturbance. Moreover, parallel process is used to accelerate the computing speed. The presented approach is validated by several power systems. It can be revealed that the approach can give the local IVSR boundaries at different wind speeds and has a good engineering application prospect.

关键词： voltage stability region power flow tracing modal analysis parallel process

Irregular wavelet frames on L^2 (R^n)

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science china Mathematics 2005年第2期48卷 277-287页

作者： YANG Deyun & ZHOU Xingwei Department of information & technology, Nankai University, tianjin 300071, china Department of Mathematics, Nankai University, tianjin 300071, china Department of Computer science, Taishan College, Taian 271000, china Department of information & technology Nankai University Tianjin China Department of Mathematics Nankai University Tianjin China Department of Computer science Taishan College Taian China

In this paper, we present the conditions on dilation parameter {sj}j that ensure a discrete irregular wavelet system to be a frame on L2(Rn), and for the wavelet frame we consider the perturbations of translation para... 详细信息

关键词： wavelet transform, frame, wavelet frame, irregular dilation.

On the interannual variation in spring atmospheric inter-hemispheric oscillation linked to synchronous climate in china

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Progress in Natural science:Materials International 2009年第9期19卷 1125-1131页

作者： Chuhan Lu, Zhaoyong Guan * key laboratory of Meteorological Disaster of ministry of education and College of Atmospheric sciences, Nanjing University of information science and technology, Nanjing 210044, china key laboratory of Meteorological Disaster of ministry of education and College of Atmospheric sciences Nanjing University of Information Science and Technology Nanjing 210044 China

Based on NCEP/NCAR monthly mean reanalysis data and surface observations of Chinese stations, inter-hemispheric oscillations (IHO) of spring atmospheric mass on an interannual basis in conjunction with the linkage to the synchronous climate over china are studied. Results suggest that the spring IHO exhibits a significant seesaw pattern for air mass at bi-hemispheric mid-high latitudes, with a consistent vertical circulation structure. The EOF decomposition of zonally mean surface pressures without signals of Arctic Oscillation (AO) and Antarctic Oscillation (AAO) indicates that the EOF1 IHO feature is remarkable, with the corresponding time coeficients correlated with the spring IHO index (IIHO) at 0.93; the spring IHO bears a close relation to the synchronous climate in china, showing the surface pressure, temperature and relative humidity over the country to be in good correlation with IIHO; the spring duststorms in Qinghai, Gansu, Shaanxi and Inner Mongolia have bearing on IHO. Positive-phase IIHO promotes the strengthening of the Siberian high, during which zonal winds between 60°E and 150°W show a longitudinal teleconnection structure extending from the Arctic to Antarctica, leading to positive westerly wind anomalies over Asia, affecting the spring climate of china.

关键词： Air mass Inter-hemispheric oscillation (IHO) Spring climate china

Effects of Current Frequency on the Microstructure and Wear Resistance of Ceramic Coatings Embedded with SiC Nano-particles Produced by Micro-arc Oxidation on AZ91D Magnesium Alloy

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Journal of Materials science & technology 2010年第10期26卷 865-871页

作者： Yue Yang and Hua Wu key laboratory of Advanced Structural Materials,ministry of education,Changchun University of technology,Changchun 130012,china key laboratory of Advanced Structural Materials Ministry of Education Changchun University of Technology Changchun 130012 China

To improve the surface wear resistance of the ceramic coating fabricated by micro-arc oxidation （MAO） on AZ91D magnesium alloy,ceramic coatings embedded with SiC nano-particles at different current frequency （500 Hz,700 Hz,and 900 Hz） were produced during the MAO *** morphology and phase composition of the coatings were investigated by scanning electron microscopy （SEM）,field emission scanning electron microscopy （FESEM）,and X-ray diffraction （XRD）.The surface roughness of the coatings was characterized by confocal laser scanning microscopy （CLSM）.Simultaneously,the tribological properties of the composite coatings were evaluated by using a universal materials tester （UMT）.The results shows that the wear resistance of the ceramic coatings with SiC nano-particles was improved significantly compared to the ceramic coatings without SiC ***,the composite coating formed at current frequency 900 Hz showed the better wear resistance than the others.

关键词： Magnesium alloy Micro-arc oxidation SiC nano-particles Wear resistance

A study on odd-parity high-lying states of the Sm atom with three-color resonant excitation

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science china(Physics,Mechanics & Astronomy) 2011年第6期54卷 1124-1130页

作者： LI Ming 1,2,DAI ChangJian 1,2 & XIE Jun 1,2 1 key laboratory of Display Materials and Photoelectric Devices,ministry of education,tianjin 300191,china 2 School of science,tianjin University of technology,tianjin 300384,china key laboratory of Display Materials and Photoelectric Devices Ministry of Education Tianjin China School of science Tianjin University of Technology Tianjin China

The odd-parity high-lying states of the Sm atom are investigated systematically by a three-color resonant excitation scheme with two different excitation *** two intermediate states,4f 6 6s7s 7 F 0 and 4f 6 6s7s 7 F 1 are employed for paths I and II,***-seven bound states are detected with paths I and II in the energy range between 44188 and 45515 cm 1,while 64 autoionizing states are found in the energy range from 45528 to 45761 cm *** only the level energies of all observed states,but also the line widths of autoionizing states are *** possible impact of configuration interaction on the line shape of autoionizing states is also *** addition,the total angular momentum is assigned uniquely to most of the states,whereas the information about the relative line intensity of all states is also presented.

关键词： high-lying states odd-parity the Sm atom resonant excitation