检索结果-南通市图书馆

Electronic structure and magnetism of Fe-doped SiC nanotubes

Science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 1582-1589页

作者： ZHANG WeiHu1,2,3.ZHANG FuChun3.ZHANG ZhiYong4,LU ShuYuan5 & YANG YanNing3.1 Xi’an Institute of Optics and Precision Mechanics,Chinese Academy of sciences,Xi’an 710068,china 2 Graduate university of Chinese Academy of sciences,Beijing 100049,china 3.college of Physics and Electronic Information,Yan’an university,Yan’an 716000,china 4 Information Science and Technology Institution,Northwest university,Xi’an 710127,china 5 Department of Telecommunications,Xi’an Institute of Posts and Telecommunications,Xi’an 710121,china 1. Xi’an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi’an 710068 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. College of Physics and Electronic Information Yan’an University Yan’an 716000 China4. Information Science and Technology Institution Northwest University Xi’an 710127 China5. Department of Telecommunications Xi’an Institute of Posts and Telecommunications Xi’an 710121 China

The electronic structure and magnetic properties of Fe-doped SiC nanotubes are investigated by using the first-principles method based on density functional theory(DFT) in the local spin density approximation(LSDA).The calculation results indicate that the SiC nanotube of Fe substitution for C exhibits antiferromagnetism while ferromagnetism features prominently when Fe substitutes *** is a kind of half-metal magnetic *** formation energy calculation results show that the formation energy of ferromagnetic structure is 3.2 eV lower than that of antiferromagnetic *** atoms are more likely to replace Si ***-orbit coupling induces electron spin polarization in the ground ***,the doping Fe atoms make relaxation towards the outside of the tube to some extent and larger geometric distortion occurs when Fe substitutes C,but the whole geometric structure of SiC nanotubes is not damaged due to the *** is revealed in the calculation of energy band structure and density of states that more dispersed distribution of energy levels is produced near the Fermi *** Fe substitution for Si,obviously there are spin-split and intense p-d hybrid effects by Si 3. electron spins and Fe 3. electron spins localized at the exchanging interactions between magnetic transitional metal(TM) *** electronic density results indicate that system magnetic moments are mainly generated by the unpaired 3. electrons of Fe *** these results show that the transition metal doping SiC nanotube could be a potential route to fabricating the promising magnetic materials.

关键词： SiC nanotube the first-principles doped magnetic properties

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Denitrification in Chongming east tidal flat sediment, Yangtze estuary, china

引用

Science china Earth sciences 2006年第10期49卷 1090-1097页

作者： WANG Dongqi1,2, CHEN Zhenlou1,3. XU Shiyuan1,2, HU Lingzhen1 & WANG Jun1,2 1. college of Resources & Environment, East china Normal university, Shanghai 200062, china 2. State Key Laboratory of Estuarine and Coastal Sediment Dynamics and Morphodynamics, East china Normal university, Shanghai 200062, china 3. Key Laboratory of Geographical Information Science of Ministry of Education,East china Normal university,Shanghai 200062, china 1. college of Resources & Environment East China Normal University Shanghai 200062 China 2. State Key Laboratory of Estuarine and Coastal Sediment Dynamics and Morphodynamics East China Normal University Shanghai 200062 China 3. Key Laboratory of Geographical Information Science of Ministry of Education East China Normal University Shanghai 200062 China

From July 2003.to July 2004, samples were collected on Chongming Island east tidal flat every two months. The research showed that the nitrous oxide (N2O) production rate was very low in the water, Chongming east tidal flat (CM) sediment was the N2O source of the water. Sediment N2O natural production rate was between -0.08 and 1.74 μmolN·m-2·h-1. N2O natural production rate was higher in the summer. The difference of the N2O natural production rate in the different tidal flats, the correlation between the N2O natural production rate and the denitrification rate, and those with the temperature and DO indicate that middle tidal flat sediment denitrification was the main process of the N2O production, while in the low tidal flat sediment, the production of the N2O came from several processes of the nitrogen cycling. Tidal flat sediment denitrification reaction was stronger in summer and winter but relatively lower in the late autumn and early spring. Seasonal change of the sediment denitrification rate was wide, from 1.12 to 3..3. μmolN·m-2·h-1. Temperature, DO and the coactions of them had the prominent effect on the tidal flat sediment denitrification.

关键词： Yangtze estuary, tidal flat sediment, denitrification, nitrous oxide, effect factor.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

LOD score exclusion analyses for candidate disease susceptibility genes using case-parents design

引用

Progress in Natural Science:Materials International 2006年第1期16卷 30-38页

作者： DENG Hongwen1,2,3.and GAO Guimin2,4 (1.Laboratory of Molecular and Statistical Genetics, college of Life sciences, Hunan Normal university, Changsha 410081, {3. 2.Osteoporosis Research Center, Creighton university Medical Center, Omaha NE 6813., USA 3. Department of Biomedical sciences, Creighton university, Omaha NE 6813., USA 4. Virginia Bioin format ics Institute and Department of Statistics, Virginia Polytechnic Institute and State university, Blacksburg VA 24061-03.5, USA) [a]Laboratory of Molecular and Statistical Genetics College of Life Sciences Human National University Changsha China [b]Osteoporosis Research Center Creighton University Medical Center Omaha NE USA [c]Department of Biomedical sciences Creighton University Omaha NE USA [d]Virginia Bioinformatics Institute and Department of Statistics Virginia Polytechnic Institute and State University Blacksburg VA USA

The focus of almost all the association studies of candidate genes is to test for their importance. We recently developed a LOD score approach that can be used to test against the importance of candidate genes for complex diseases and quantitative traits in random samples. As a complementary method to regular association analyses, our LOD score approach is powerful but still affected by the population admixture, though it is more conservative. To control the confounding effect of population heterogeneity, we develop here a LOD score exclusion analysis using case-parents design, the basic design of the transmission disequilibrium test (TDT) approach that is immune to population admixture. In the analysis, specific genetic effects and inheritance models at candidate genes can be analyzed and if a LOD score is ≤ - 2. 0, the locus can be excluded from having an effect larger than that specified. Simulations show that this approach has reasonable power to exclude a candidate gene having small genetic effects if it is not a disease susceptibility locus (DSL) with sample size often employed in TDT studies. Similar to association analyses with the TDT in nuclear families, our exclusion analyses are generally not affected by population admixture. The exclusion analyses may be implemented to rule out candidate genes with no or minor genetic effects as supplemental analyses for the TDT. The utility of the approach is illustrated with an application to test the importance of vitamin D receptor (VDR) gene underlying the differential risk to osteoporosis.

关键词： association studies candidate genes case-parents design disease susceptibility locus exclusion mapping LOD score.

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Mesh theory of angle modified dual tori double-enveloping toroidal worm drive

引用

Science china(Technological sciences) 2010年第7期53卷 1913-1927页

作者： ZHAO YaPing1, SU DaiZhong2, ZHANG Zhao1, WEI WenJun3.& DONG XueZhu3.1 college of Machinery and Automation, Wuhan university of Science and Technology, Wuhan 43.081, china 2 Advanced Design and Manufacturing Engineering Center, Nottingham Trent university, Nottingham NG1 4BU, UK 3.college of Engineering, china Agricultural university, Beijing 100083. china 1. college of Machinery and Automation Wuhan University of Science and Technology Wuhan 430081 China2. Advanced Design and Manufacturing Engineering Center Nottingham Trent University Nottingham NG1 4BU UK3. College of Engineering China Agricultural University Beijing 100083 China

In this paper, the meshing theory of the angle modified hourglass worm drive is enriched and developed. The ordinary condition of the angle modification is derived and the physical significance of the modification is interpreted. A normal section methodology is proposed for meshing analysis, which can be used to compute the normal distance near a singular meshing point of a conjugate surface couple. By means of the method and after analyzing the normal transversals, it is specified that the worm helicoid, the nominal former contact zone and the new contact zone intersect each other along the locus of singular points of the instantaneous contact lines of an angle-modified worm pair. As a result, it is explained clearly that those three osculate each other but the osculations are different in degree. Moreover, the mechanism of removing the twice-contacted zone from the worm gear tooth surface is clarified and the reason of shortening the worm working length is also elucidated. With the help of the theory described in the present paper and the thorough and systematic research on the relevant meshing characteristics, the angle modified dual tori double-enveloping toroidal worm drive has been shown to be an excellent new-fashioned hourglass worm set.

关键词： hourglass worm angle modification double-enveloping osculation normal transversal

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Constraints of authigenic carbonates on trace elements (Sr,Mg) of lacustrine ostracod shells in paleoenviron-ment reconstruction and its mechanism

引用

Science china Earth sciences 2008年第5期51卷 654-664页

作者： HU Guang1,2, JIN ZhangDong1 & ZHANG Fei3.1 State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of sciences, Xi’an 710075, china 2 Graduate university of the Chinese Academy of sciences, Beijing 100049, china 3.college of Resources and Environmental Science, Nanjing Agricultural university, Nanjing 210095, china State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China Graduate university of the Chinese Academy of sciences Beijing 100049 China college of Resources and Env

Molar ratios of Mg/Ca and Sr/Ca were measured in two species of ostracod shells preserved in the upper core (15–55 m) of the Hequing Basin in Yunnan Province, southwest china. By correlating the molar ratios between Mg/Ca and Sr/Ca and comparing them with Sr concentrations of the sediments, we suggested that: (1) the molar Mg/Ca and Sr/Ca ratio variations in respective ostracod primo reflected the changes in its ambient water composition and ecology; (2) the molar Sr/Ca ratios responded better to the salinity change linearly than Mg/Ca without aragonite precipitation in the system, and otherwise there was no linear relation between them; and (3. the molar Sr/Ca ratios were mainly controlled by salinity and authigenic carbonate precipitation, whereas the molar Mg/Ca ratios were related to both salinity and temperature. In fact, the rate of ostracod growth owing to temperature controls the fluctuation of Mg/Ca in shells. Here, more attentions should be paid to the constraint of authigenic mineral precipitation processes on the trace elements in ostracod shells and to the correlation between these trace elements in biogenic carbonates and compositions of the sediments in systems and in future in vitro experiments.

关键词： ostracod shell molar Sr/Ca ratio molar Mg/Ca ratio environmental response Heqing Basin

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Integrating MODFLOW and GIS technologies for assessing impacts of irrigation management and groundwater use in the Hetao Irrigation District,Yellow River basin

引用

Science china(Technological sciences) 2009年第11期52卷 3257-3263页

作者： XU Xu1,2, HUANG GuanHua1,2 & QU ZhongYi3.1 Center for Agriculture Water Research, china Agricultural university, Beijing 100083. china 2 Chinese-Israeli International Center for Research and Training in Agriculture, china Agricultural university, Beijing 100083. china 3.Water Conservancy and Civil Engineering college, Inner Mongolia Agricultural university, Hohhot 010018, china 1. Center for Agriculture Water Research China Agricultural University Beijing 100083 China 2. Chinese-Israeli International Center for Research and Training in Agriculture China Agricultural University Beijing 100083 China 3. Water Conservancy and Civil Engineering college Inner Mongolia Agricultural University Hohhot 010018 China

Due to severe water scarcity, water resources used in agricultural sector have been reduced markedly in Hetao irrigation district. Application of water-saving practices (WSPs) is required for the sustainable agricultural development. The human activities including WSPs and increase of groundwater abstraction can lower down the groundwater table, which is helpful to the salinity control. Meanwhile, an excessively large groundwater table depth may result in negative impact on crop growth and fragile ecological environment. In this paper, the Jiefangzha irrigation system in Hetao irrigation district was selected as a typical area, a groundwater flow model based on ArcInfo Geographic Information System (GIS) was developed and implemented to quantify the effect of human activities on the groundwater system in this area. The preand post-processing of model data was performed efficiently by using the available GIS tools. The time-variant data in boundary conditions was further edited in Microsoft Excel with programs of Visual Basic for Application (VBA). The model was calibrated and validated with independent data sets. Application of the model indicated that it can well describe the effect of human activities on groundwater dynamics in Jiefangzha irrigation system.

关键词： groundwater flow modeling MODFLOW GIS water-saving practices irrigation district

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

The impact of vegetation restoration on erosion-induced sediment yield in the middle Yellow River and management prospect

引用

Science china Earth sciences 2005年第6期48卷 724-741页

作者： CHEN Hao1, ZHOU Jinxing2, CAI Qiangguo1, YUE Zhongqi3. LU Zhongchen4, LIANG Guanglin1& HUANG Jianguo5 1. Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic sciences and Natural Resources Re-search, Chinese Academy of sciences, Beijing 100101, china 2. Institute of Forestry, Chinese Academy of Forestry sciences, Beijing 100091, china 3. Department of Civil Engineering, university of Hong Kong, Hong Kong, china 4. Eco-environmental Research Center, Chinese Academy of sciences, Beijing 100085, china 5. college of Resources and Environment, Southwest Agricultural university, Chongqing 400716, china Correspondence should be addressed to Chen Hao 1. Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences 100101 Beijing China 2. Institute of Forestry Chinese Academy of Forestry Sciences 100091 Beijing China 3. Department of Civil Engineering University of Hong Kong Hong Kong China 4. Eco-environmental Research Center Chinese Academy of Sciences 100085 Beijing China 5. college of Resources and Environment Southwest Agricultural University 400716 Chongqing China

According to the characteristics of water and erosion environments of different natural zones on the Loess Plateau, this paper studies changes of vegetation types, distribution boundaries of forest and grass as well as restoration capacity of vegetation in different natural zones in the middle Yellow River. The annual precipitation of 53. mm is the critical annual pre-cipitation for forest and grass distribution in the middle Yellow River. Among the zonal and azonal environmental factors affecting watershed sediment yield, the intermediate diameter D50 (mm) of suspended load and forest coverage (V, %) play the leading role. Of them the effect weight of forest coverage (V, %) on catchments sediment yield is only 3.4% less than the role of the intermediate diameter (D50, mm), they are almost the same. To effectively control soil erosion in semiarid, especially in hilly-gullied areas and make sediment transport modulus reduce to less than 6000 t/km2, it is rather difficult by merely relying on natural restoration of forest. In the process of cultivated land conversion into forest land and grassland, measures suiting local conditions should be adopted in tree species selection and artificial afforestation (grass planting) based on management with biological measures for slopeland and engineering measures for hilly-gullied areas, so that watershed forest coverage in key counties can reach at least over 3.%.Compared with the standard period of precipitation prior to the 1960s, with the decrease of an-nual precipitation at various periods, plant productivities decline to different degrees under natural conditions. The main reason accountable for the low survival rate of new seedlings and grass over years is due to precipitation decrease. In light with regression models of annual pre-cipitation and natural vegetation productivities, it is possible to obtain estimated values of wa-tershed natural vegetation productivity and eco-water consumption needed for the restoration to

关键词： vegetation restoration, eco-water requirement, watershed sediment yield, the middle Yellow River.

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Theory and methods of global stability analysis for high arch dam

引用

Science china(Technological sciences) 2011年第S1期54卷 9-17页

作者： REN QingWen 1,LI Qiang 1,JIANG YaZhou 2 & JIANG XiaoLan 3.1 Department of Engineering Mechanics,Hohai university,Nanjing 210098,china 2 college of Water Conservation and Hydropower Engineering,Hohai university,Nanjing 210098,china 3.Changjiang Academy of sciences,Wuhan 43.010,china 1. Department of Engineering Mechanics Hohai University Nanjing 210098 China2. College of Water Conservation and Hydropower Engineering Hohai University Nanjing 210098 China3. Changjiang Academy of Sciences Wuhan 430010 China

The global stability of high arch dam is one of the key problems in the safety study of arch dams,but no feasible method with theoretical basis is *** this paper,based on the stability theory of mechanical system,it is demonstrated that the global failure of high arch dams belongs to a physical instability starting from local strength failure,which is the extreme point instability according to the characteristics of load-displacement curve obtained from the failure process of dam-foundation system. So the global failure of dam-foundation system should be studied with the stability theory of mechanical *** is also pointed out that the current stability analysis methods used in engineering are consistent with the stability theory,but not established according to the mechanical system stability theory directly.A perfect method can be obtained through the study of physical disturbance equations.

关键词： high arch dam global stability physical instability extreme point instability

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Phase relationship of complex multi-component system in chromate cleaner production

引用

Progress in Natural Science:Materials International 2007年第7期17卷 845-850页

作者： Ge Xinlei~1 Wang Xidong~(1,3.*) Zheng Shili~2 Zhang Mei~1 Zhang Yi~2 (1.Department of Physical Chemistry,university of Science and Technology Beijing,Beijing 100083.china 2.Institute of Process Engineering,Chinese Academy of {3.,Beijing 100080,china 3.college of Engineering,Peking university,Beijing 100871,china) [a]Department of Physical Chemistry University of Science and Technology Beijing Beijing China [b]college of Engineering Peking University Beijing China [c]Institute of Process Engineering Chinese Academy of Sciences Beijing China

The phase relationships of the complex multi-component systems in the liquid-phase oxidization and separation process related with the chromate cleaner production are investigated theoretically and *** phase diagram of main system Fe- Cr2O4-KOH-O2of oxidization process and the relationship of its standard Gibbs free energy change with temperature are calculated.A se- ries of phase diagrams of the separation process at different temperatures,such as K（Na）OH-K（Na）2CrO4-H2O,KOH-KAlO2-H2O, K（Na）OH-K（Na）2CO3.H2O,K（Na）OH-K（Na）HCO3.H2O and K（Na）HCO3.K（Na）2CrO4-H2O have also been *** ex- periments are carried out to verify the calculated *** results showed that the sub-molten salt media are suitable for the oxidization and separation processes;FeCr2O4can be oxidized across a wide range of temperature;K（Na）2CrO4can be separated from K（Na）AlO2system at appropriate temperature and proper concentration;the crystallization of carbonate is easier than that of K（Na）2CrO4.

关键词： chromite chromate system thermodynamics calculation phase diagram

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

CONTROLLED RELEASE FROM PDMAEMA GELS PREPARED BY GAMMA RADIATION

引用

Chinese Journal of Polymer Science 2002年第5期20卷 409-412页

作者： Ning Liu Min Yi Shuang-ji Chen Hong-fei Ha college of Chemistry and Molecular Engineering Peking university Beijing 100871, china Department of Biochemistry college of Applied arts and Science, Beijing union university Beijing 100083. china Peking Univ Coll Chem & Mol Engn Beijing 100871 Peoples R China Beijing union Univ Coll Appl Arts & Sci Dept Biochem Beijing 100083 Peoples R China

Poly(N,N-dimethylaminoethyl methacrylate) (polyDMAEMA) hydrogels prepared by gamma-irradiation showed obvious temperature-sensitivity in a temperature range of 3.-40degreesC and pH-sensitivity at pH=2.5. They also showed electric response behavior although it was not typical. The hydrogels were used in controlled release at different pH, temperature, and electric voltage. The release rates of methylene blue (MB) from the gels at 52degreesC and pH=1.24 were faster than those at 20degreesC and pH=10.56, respectively. In addition, the release rate at a field voltage of 5.0 was also faster than that without electric field.

关键词： poly(N,N-dimethylaminoethyl methacrylate) environmental sensitivity hydrogel controlled release

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：