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Search Results: 1 - 10 of 7654 matches for " Weixin Wan "
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Meteor radar observation of circulation near mesopause over Wuhan
Jiangang Xiong,Weixin Wan,Baiqi Ning,Libo Liu
Chinese Science Bulletin , 2003, DOI: 10.1007/BF03183974
Abstract: The Wuhan meteor radar is the first all-sky meteor radar in China. The circulation near the mesopause from February to September 2002 is studied based on the data obtained by the Wuhan meteor radar. The zonal wind is usually eastward in winter from 80 to 100 km. The mean zonal wind become westward from March to early of May, when the winter circulation reverses to the summer circulation. But at the meteor heights, the zonal circulation usually becomes eastward after the middle of May. The meridional circulation is always equatorward. The peaks of the meridional wind move downward with the height, and the peak value reaches its maximum of 21 ms 1 in July. Having made a comparison between monthly mean wind and HWM93 model wind, the value of southward wind, the maximal value of eastward wind as well as the reversal height of zonal wind are found to be quite different from each other.
Surface Reaction of TiAl with Water Vapor and Oxygen
Yexin CHEN,Xiaojing WAN,Weixin XU,
Yexin CHEN
,Xiaojing WAN and Weixin XU Institute of Materials,Shanghai University,Shanghai,China Shanghai Iron and Steel Research Institute,Shanghai,China

材料科学技术学报 , 2003,
Abstract: The interaction of water vapor and oxygen with TiAl-based alloy has been studied with Auger electron spectroscopy and X-ray photoelectron spectroscopy. The results indicate that both surface reactions initiate at a very short exposure water vapor reacts firstly with Al, and then reacts with Ti after certain exposure. The surface reaction of Al with water vapor may be responsible for the environmental embrittlement at room temperature in TiAl-based alloy.
Effects of Water and Nitrogen Addition on Species Turnover in Temperate Grasslands in Northern China
Zhuwen Xu, Shiqiang Wan, Haiyan Ren, Xingguo Han, Mai-He Li, Weixin Cheng, Yong Jiang
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039762
Abstract: Global nitrogen (N) deposition and climate change have been identified as two of the most important causes of current plant diversity loss. However, temporal patterns of species turnover underlying diversity changes in response to changing precipitation regimes and atmospheric N deposition have received inadequate attention. We carried out a manipulation experiment in a steppe and an old-field in North China from 2005 to 2009, to test the hypothesis that water addition enhances plant species richness through increase in the rate of species gain and decrease in the rate of species loss, while N addition has opposite effects on species changes. Our results showed that water addition increased the rate of species gain in both the steppe and the old field but decreased the rates of species loss and turnover in the old field. In contrast, N addition increased the rates of species loss and turnover in the steppe but decreased the rate of species gain in the old field. The rate of species change was greater in the old field than in the steppe. Water interacted with N to affect species richness and species turnover, indicating that the impacts of N on semi-arid grasslands were largely mediated by water availability. The temporal stability of communities was negatively correlated with rates of species loss and turnover, suggesting that water addition might enhance, but N addition would reduce the compositional stability of grasslands. Experimental results support our initial hypothesis and demonstrate that water and N availabilities differed in the effects on rate of species change in the temperate grasslands, and these effects also depend on grassland types and/or land-use history. Species gain and loss together contribute to the dynamic change of species richness in semi-arid grasslands under future climate change.
Magnetic fabrics of Cuizhao granitic pluton and its tectonic emplacement significance

Zhou Weixin,Wan Tianfeng,

岩石学报 , 1999,
Abstract: 侵入岩体的磁组构形成于岩浆运移侵位、固化的过程中,必然保留了岩体的构造侵位过程的信息.以玲珑复式花岗岩岩基南部的崔召岩体为例,对岩体磁组构的详细研究,可以揭示岩浆运移,就位和变形等一系列特征.崔召岩体的磁线理不发育,反映岩体侵位速度慢,岩体边部磁面理比内部发育,并且岩体边缘磁各向异性度P值明显大于岩体内部,磁线理倾角小,反映岩体侵位过程中侧向挤压作用比较强烈,具有类似于气球膨胀作用的侵位机制.并且此磁组构特征再没有受到后期构造热事件的影响.
Target Detection in Three-Dimension Sensor Networks Based on Clifford Algebra  [PDF]
Tiancheng HE, Weixin XIE, Wenming CAO
Wireless Sensor Network (WSN) , 2009, DOI: 10.4236/wsn.2009.12013
Abstract: The three-dimensional sensor networks are supposed to be deployed for many applications. So it is signifi-cant to do research on the problems of coverage and target detection in three-dimensional sensor networks. In this paper, we introduced Clifford algebra in 3D Euclidean space, developed the coverage model of 3D sensor networks based on Clifford algebra, and proposed a method for detecting target moving. With Clif-ford Spinor, calculating the target moving formulation is easier than traditional methods in sensor node’s coverage area.
Adsorption and reaction of CO and O2 on the Ag/Pt(110) surface studied by photoemission electron microscopy
Weixin Huang,Xinhe Bao
Chinese Science Bulletin , 2001, DOI: 10.1007/BF03183544
Abstract: The Ag/Pt(110) model catalyst was prepared by evaporating silver on Pt(110). Adsorption and reaction of CO and O2 on Ag/Pt(110) surface were studied in situ by photoemission electron microscopy (PEEM) during the pressure range of 10 5–10 2 Pa at 480 K. The Ag/Pt(110) surface consisted of Pt(110), AgPt interface and Ag area after annealing at 500 K. The dosing pressure of CO and O2 had a larger influence on their adsorption on the Ag area than on the Pt(110) and AgPt interface. Small Pt clusters formed on the Ag area and AgPt interface, which had a stronger ability to adsorb CO than Pt(110) terrace. The existence of Ag had an obvious influence on the kinetic of CO oxidation on Pt(110). No pattern was observed on the AgPt interface under the same condition when the formation of reaction-diffusion waves occurred on Pt(110).
Advances in theory and applications of fuzzy clustering
Xinbo Gao,Weixin Xie
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02884971
Abstract: The summarization and evaluation of the advances in fuzzy clustering theory are made in the aspects including the criterion functions, algorithm implementations, validity measurements and applications. Several important directions for a further study and the application prospects are also pointed out.
Glass ceramic of high hardness and fracture toughness developed from iron-rich wastes

Weixin HAN,

金属学报(英文版) , 2009,
Abstract: A study has been carried out on the feasibility of using high iron content wastes, gen-erated during steel making, as a raw material for the production of glass ceramic. The iron-rich wastes were mixed and melted in different proportions with soda-lime glass cullet and sand. The devitrification of the parent glasses produced from the different mixtures was investigated using differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The mechanical properties of the glass-ceramic were assessed by hardness and indentation fracture toughness measurement. A glass ce-ramic with mixture of 60 wt pct iron-rich wastes, 25 wt pct sand, and 15 wt pct glass cullet exhibited the best combination of properties, namely, hardness 7.9 GPa and fracture toughness 3.75 MPa.m1/2, for the sake of containing magnetite in marked dendritic morphology. These new hard glass ceramics are candidate materials for wear resistant tiles and paving for heavy industrial floors.
Target Classification with Low-Resolution Surveillance Radars Based on Multifractal Features
Qiusheng Li;Weixin Xie
PIER B , 2012, DOI: 10.2528/PIERB12091509
Abstract: The multifractal characteristics of return signals from aircraft targets in conventional radars offer a fine description of dynamic characteristics which induce the targets’ echo structure; therefore they can provide a new way for aircraft target classification and recognition with low-resolution surveillance radars. On basis of introducing the mathematical model of return signals from aircraft targets in conventional radars, the paper analyzes the multifractal characteristics of the return signals as well as the extraction method of their multifractal features by means of the multifractal analysis of measures, and puts forward a multifractal-feature-based classification method for three types of aircraft targets (including jet aircrafts, propeller aircrafts and helicopters) from the viewpoint of pattern classification. The analysis shows that the conventional radar return signals from the three types of aircraft targets have significantly different multifractal characteristics, and the defined characteristic parameters can be used as effective features for aircraft target classification and recognition. The results of classification experiments validate the proposed method.
Classification of Aircraft Targets with Surveillance Radars Based on Fuzzy Fractal Features
Qiusheng Li;Weixin Xie
PIER M , 2013, DOI: 10.2528/PIERM12121601
Abstract: The fuzzy fractal characteristics of return signals from aircraft targets in conventional radars offer a description of dynamic features which induce the targets' echo structure, therefore they can provide a new way for aircraft target classification and recognition with low-resolution surveillance radars. On basis of introducing fuzzy fractal theory, the paper analyzes the fuzzy fractal characteristics of return signals from aircraft targets in a VHF-band surveillance radar by means of the fuzzy fractal analysis, and puts forward a fuzzy-fractal-feature-based classification method for aircraft targets with a low-resolution radar from the viewpoint of pattern recognition. The analysis shows that the fuzzy fractal characteristic parameters such as the local fuzzy fractal dimension (LFFD) and local degree of fractality (LGF) can be used as effective features for aircraft target classification and recognition. The results of classification experiments validate the proposed method.
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