检索结果-南通市图书馆

EXPERIMENTAL STUDY ON WHOLE TREE VERTICAL TENSILE STRENGTH

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2004年第2期19卷 154-160页

作者： Lihua CHEN, Xinxiao YU and Dongsheng ZHANG Prof., Doctor, college of Soil and Water Conservation, Beijing forestry University, E-mail: c_lihua@*** Prof., Doctor, college of Soil and Water Conservation, Beijing forestry University, E-mail: yuxinxiao@*** Postgraduate for doctorate, college of Soil and Water Conservation, Beijing forestry University college of Soil and Water Conservation Beijing Forestry University

This paper studies the vertical tensile strength of whole tree roots under the same soil and landformconditions. The experiments show that the shape of a root system’s distribution affects the verticaltensile strength of roots. Rhododendron trees have horizontal root systems, so the whole roots werepulled out in the experiment process. Populous purdomii has vertical roots, so the experimentcontinued quite a long time. Abies fabric has both vertical and horizontal main roots, so the P--Scurve shows a multi--peak shape.

关键词： Vertical strain Root system configuration P-S curve

THE GENERALIZED REFLEXIVE SOLUTION FOR A CLASS OF MATRIX EQUATIONS (AX-B,XC=D)

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematica Scientia 2008年第1期28卷 185-193页

作者：李范良胡锡炎张磊 Institute of Mathematics and Physics School of SciencesCentral South University of Forestry and Technology college of Mathematics and Econometrics Hunan University

In this article, the generalized reflexive solution of matrix equations （AX = B, XC = D） is considered. With special properties of generalized reflexive matrices, the necessary and sufficient conditions for the solvability and the general expression of the solution are obtained. Moreover, the related optimal approximation problem to a given matrix over the solution set is solved.

关键词： Matrix equations generalized reflexive matrix optimal approximation

Surface Characterization of Glass Fiber by Inverse Gas Chromatography

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2008年第5期23卷 687-690页

作者：黄小华李斌 Heilongjiang Key Laboratory of Flame Retarded Polymeric Materials College of Science Northeast Forestry University

The surface properties of glass fiber were quantificationally analyzed by inverse gas chromatography （IGC）. Five n-alkanes （C6, C7, C8, C9, and C10） were chosen as apolar probes to characterize the dispersive component of surface free energy. Trichloromethane （CHCl3）, acetone, and tetrahydrofuran （THF） were chosen as polar probes to detect the Lewis acid-base parameters. It is found that the dispersive components of free energy are 32.3, 30.5, 27.5, and 26.9 mJ/m^2 at 70, 80, 90, and 100 ℃. respectively. The Lewis acidic number Ka of the glass fiber is 0.512 4, and the basic number Kb is 2.862. The results mean the glass fiber is a Lewis basic material.

关键词： glass fiber inverse gas chromatography acid-base properties surface free energy

K~+channels inhibited by hydrogen peroxide mediate abscisic acid signaling in Vicia guard cells

在线全文

学校读者我要写书评

暂无评论

Cell Research 2001年第3期11卷 195-202页

作者： ZHANG XIAO, YU CHEN MIAO, GUO YONG AN, YUN ZHOU, ZHOU PING SHANGGUAN,JUN FENG GAO, CHUN PENG SONG college of life sciences, Norihwest Sci-Tech University of Agriculture and forestry, Yangling 712100, China Department of Biology, Henan University, Kaifeng college of life sciences Northwest Sci-Tech University of Agriculture and Forestry Yangling 712100 China. Department of Biology Henan University Kaifeng 475001 China. National Laboratory of Soil Erosion and Dryland Farming the Institute of Soil and Water Conservation Chinese Academy of Sciences Yangling 712100 China.

A number of studies show that environmental stress conditions increase abscisic acid (ABA) and hydrogen peroxide (H2O2) levels in plant cells. Despite this central role of ABA in altering stomatal aperture by regulating guard cell ion transport, little is known concerning the relationship between ABA and H2O2 in signal transduction leading to stomatal movement. Epidermal strip bioassay illustrated that ABA- inhibited stomatal opening and ABA-induced stomatal closure were abolished partly by externally added catalase (CAT) or diphenylene iodonium (DPl), which are a H2O2 scavenger and a NADPH oxidase inhibitor respectively. In contrast, internally added CAT or DPI nearly completely or partly reversed ABA-induced closure in half-stoma. Consistent with these results, whole-cell patch-clamp analysis showed that intracellular application of CAT or DPI partly abolished ABA-inhibited inward K+ current across the plasma membrane of guard cells. H2O2 mimicked ABA to inhibit inward K+ current, an effect which was reversed by the addition of ascorbic acid (Vc) in patch clamping micropipettes. These results suggested that H2O2 mediated ABA-induced stomatal movement by targeting inward K+ channels at plasma membrane.

关键词： Hydrogen peroxide abscisic acid K+ channels patch clamp vicia guard cell.

Effects of precipitation and landuse on runoff during the past 50 years in a typical watershed in the Loess Plateau, China

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2009年第3期24卷 352-364页

作者： Huaxing BI1, Bin LIU2, Jie WU3, Lei YUN3, Zhihan CHEN2 and Zhewei CUI31 Prof. in hydrology, college of soil and water conservation, Box 67, Beijing forestry University, 35 Qinghua East Road, Haidian District, Beijing 100083, China, 2 Researcher in hydrology, Xifeng station of soil and water conservation, Xifeng, Gansu Province, China 3 Graduate Assis., college of soil and water conservation, Beijing forestry University, Beijing 100083, China [a] Prof. in hydrology college of soil and water conservation Box 67 Beijing forestry University 35 Qinghua East Road Haidian District Beijing 100083 China [b] Researcher in hydrology Xifeng station of soil and water conservation Xifeng Gansu Province China [c] Graduate Assis. college of soil and water conservation Beijing forestry University Beijing 100083 China

In the past century, great progress has been made worldwide in our understanding of forest-water relationship. The successful forestation programs implemented in China-which have improved the ecological environmental conditions-have gained the attention of many researchers and highlighted the relationship between forestation and water yields. The arid and semi-arid Loess Plateau has received attention from water engineers and eco-hydrological researchers in China because of a shortage in water resources. We selected one of the oldest stations conducting soil and water conservation experiments, the Xifeng soil and water conservation station, and chose the Nanxiaohe catchment and its paired catchments (Yangjiagou catchment and Dongzhuanggou catchment) as our research areas. Trends in precipitation, air temperature, streamflow over the past 50 years, and the effect of changing land use on streamflow were analyzed. The Mann-Kendall test showed that precipitation had a negative trend (downward trend), whereas air temperature showed a positive trend (upward trend) from the past to present in the Nanxiaohe catchment. However, the trends seen in precipitation, air temperature did not contain any "jumping points." The paired catchment approach is used to detect the effects of land cover change on hydrology in the Yangjiagou and the contrast catchment, i.e., Dongzhuanggou catchment in our study. The results showed a large change in land use in the Yangjiagou catchment from 1954 to 2008. An increase in forested land (from 0% to 40.08% from 1954 to 2008) and a reduction of bare land (from 51.26% to 5.50% from 1954 to 2008) accounted for a large part of the change in land use. However, the land use changed little in the contrast catchment. The comparison of streamflow in the paired catchments showed that forestation reduced streamflow by 49.63% (or 6.5 mm) each year.

关键词： Surface water hydrology Climate variability/change Forests Land use/land cover change Loess Plateau of China

Reduction of defect-induced ferromagnetic stability in passivated ZnO nanowires

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics B 2015年第3期24卷 349-352页

作者：吴芳孟培雯罗康刘云飞阚二军 School of Science Nanjing Forestry University college of Information Science and Technology Nanjing Forestry University Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education) and Department of Applied PhysicsNanjing University of Science and Technology

First-principles calculations are performed to study the electronic structures and magnetic properties of ZnO nanowires（NM）. Our results indicate that the single Zn defect can induce large local magnetic moment（～ 2μB） in the ZnO NWs, regardless of the surface modification. Interestingly, we find that local magnetic defects have strong spin interaction, and favor room-temperature ferromagnetism in bared ZnO NW. On the other hand, although H passivation does not destroy the local magnetic moment of Zn vacancy, it does greatly reduce the spin interaction between magnetic defects. Therefore, our results indicate that H passivation should be avoided in the process of experiments to maintain the room-temperature ferromagnetism.

关键词： vacancy magnetic interaction ZnO nanowires DFT calculations

Study on urban gardens and China urban social life in the end of the twentieth century——A case study of Nanjing

在线全文

学校读者我要写书评

暂无评论

Study on urban gardens and China urban social life in the en...

Energetics and electronic structure of refractory elements in the dislocation of NiAl

作者： Xiaolan Tang college of Landscape Architecture, Nanjing forestry University, Nanjing 210037

＜正＞Urban gardens, as benchmark of urban societies, play a vital role in China urban society, and are ideal places for observing changes of society, economy, ecosystem and culture. For an extended period of time, urban gardens have been considered as negative input as waste of city construction funds or city land. At the end of the 20th century, with the rapid development of cities in China, Nanjing sees a great variety of urban gardens taking form in functional spaces in commercial, residential, colleges, industrial areas, and gardens. City gardens, originally a minor role in city space arrangement, are becoming an accelerator for urban development, which reflects a great need for city gardens, and its vigorousness.

关键词： urban gardens urban social life the end of the twentieth century China

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第8期21卷 402-408页

作者：陈丽群彭小方于涛 college of Sciences Central South University of Forestry&Technology Central Iron and Steel Research Institute

Using DMol and the discrete variational method within the framework of the density functional theory, we study the alloying effects of Nb, Ti, and V in the [100] （010） edge dislocation core of NiAl. We find that when Nb （Ti, V） is substituted for Al in the center-Al, the binding energy of the system reduces 3.00 eV （2.98 eV, 2.66 eV）. When Nb （Ti, V） is substituted for Ni in the center-Ni, the binding energy of the system reduces only 0.47 eV （0.16 eV, 0.09 eV）. This shows that Nb （Ti, V） exhibits a strong Al site preference, which agrees with the experimental and other theoretical results. The analyses of the charge distribution, the interatomic energy and the partial density of states show that some charge accumulations appear between the impurity atom and Ni atoms, and the strong bonding states are formed between impurity atom and neighbouring host atoms due mainly to the hybridization of 4d5s（3d4s） orbitals of impurity atoms and 3d4s4p orbitals of host Ni atoms. The impurity induces a strong pinning effect on the [100] （010） edge dislocation motion in NiAl, which is related to the mechanical properties of the NiAl alloy.

关键词： electronic structure dislocation intermetallic compounds impurity

A case study of spatial heterogeneity of soil moisture in the Loess Plateau,western China:A geostatistical approach

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2009年第1期24卷 63-73页

作者： BI Huaxing1,2,LI Xiaoyin3,LIU Xin3,GUO Mengxia3,and LI Jun3 1 Prof., college of Soil and Water Conservation, Beijing forestry University, Beijing 100083, China, Key Laboratory of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing 100083, China 2 Researcher, Ji-xian National Ecological Station of China, Beijing 100083, China 3 Graduate student, college of Soil and Water Conservation, Beijing forestry University, Beijing 100083, China [a]Prof. College of Soil and Water Conservation Beijing Forestry University Beijing 100083 China Key Laboratory of Soil and Water Conservation and Desertification Combating Ministry of Education Beijing 100083 China [b]Researcher Ji-xian National Ecological Station of China Beijing 100083 China [c]Graduate student College of Soil and Water Conservation Beijing Forestry University Beijing 100083 China

Soil moisture distribution shows highly variation both spatially and temporally. This study assesses the spatial heterogeneity of soil moisture on a hill-slope scale in the Loess Plateau in West China by using a geostatistical approach. Soil moisture was measured by time-domain reflectometry(TDR) in 313 samples. Two kinds of sampling scales were used(2 x 2 m and 20 x 20 m) at two soil layers(0-30 cm and 30-60 cm). The general characteristics of soil moisture were analyzed by a classical statistics method,and the spatial heterogeneity of soil moisture was analyzed using a geostatistical approach. The results showed that the spherical model is the best-fit model to simulate soil moisture on the experimental hill-slope. The parameters of this model indicated that the spatial dependence of soil moisture in the selected hill-slope was moderate. Even the 2 x 2 m sampling scale was too coarse to show the detailed spatial variances of soil moisture in this area. The dependent distance increased from 27.4 m to 494.16 m as the sampling scale became coarse(from 2 x 2 m to 20 x 20 m). A map of soil moisture was generated by using original soil moisture data and interpolated values determined by the Kriging method. The average soil moisture(area weighted) in the different layers of soil was calculated on the basis of this map(10.94% for the 0-30 cm soil layer,11.88% for the 30-60 cm soil layer). This average soil moisture is lower than the corresponding average effective soil moisture,which suggests that the soil moisture is not sufficient to support vegetation in this area.

关键词： Spatial heterogeneity Soil moisture Geostatistics Loess Plateau of China