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Effect of clay content to the strength of gravel soil in the source region of debris flow

Journal of Mountain science 2018年第10期15卷 2320-2334页

作者： CHEN Ning-sheng GAO Yan-chao Yang cheng-lin HU Gui-sheng key Laboratory of Mountain Hazards and Land surface Process Institute of Mountain Hazards and EnvironmentCASChengdu 60041China chengdu Center China Geological SurveyChengdu 610081China University of Chinese Academy of sciences Beijing 100049China

The production of runoff in the source area of a debris flow is the consequence of a reduction in soil strength. Gravel soil is widely distributed in the source region, and the influence of its clay content on soil strength is one of the important questions regarding the formation mechanism of debris flows. In this paper, the clay content in gravel soil is divided into groups of low clay content(1%, 2, 5%), moderate clay content(3.75%, 5.00%, 6.25%, 7.5%) and high clay content(10.0%, 12.5%, 15%). Tests of the unconsolidated undrained shear strength and consolidated drained shear strength were performed. The unconsolidated undrained shearing(UU) experiment simulates the rapid shear failure of loose gravel soil under the conditions of brief heavy rainfall. The consolidated drained shearing(CD) experiment simulates creep failure of consolidated sediment during extended rainfall. The pore water pressure first increased and then decreased as the clay content increased, and the increase in pore pressure was relatively high in the gravel soil sample when the clay content is in the range of 3.25-7.50%, and stress in the gravel soil is relatively low for a moderate clay content. Gravelly soils with a moderate clay content are moreprone to debris-flow initiation. This paper presents a mathematical formula for the maximum shear stress and clay content of gravel soil under two conditions. The key processes whereby the soil fails and triggers a debris flow—volume contraction of soil, expansion of clay soil, and rise of pore pressure―cause reductions in the soil friction force and enhancement of the water content in the clay particles, and subsurface erosion of soil reduces the soil viscosity, which eventually reduces the soil strength so that the soil loses its stability, liquefies and generates a debris flow.

关键词： Debris flows Gravel soil Clay content Maximum shear stress Pore water pressure

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An approach to extracting surface supply relationships between glaciers and lak.s.on the Tibetan Plateau

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International Journal of Digital Earth 2018年第11期11卷 1151-1165页

作者： Bei-Bei Ai cheng-Zhi Qin Qinghua Ye A-Xing Zhu Graham Cogley state key Laboratory of Resources and Environmental Information system Institute of Geographic Sciences and Natural Resources ResearchCASBeijingPeople’s Republic of China College of Resources and Environment University of Chinese Academy of SciencesBeijingPeople’s Republic of China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application and school of Geography Nanjing Normal UniversityNanjingPeople’s Republic of China key Laboratory of Tibetan Environment Changes and Land surface Processes Institute of Tibetan Plateau ResearchCASBeijingPeople’s Republic of China Department of Geography University of Wisconsin-MadisonMadisonWIUSA key Laboratory of Virtual Geographic Environment Ministry of EducationNanjing Normal UniversityNanjingPeople’s Republic of China Department of Geography Trent University PeterboroughCanada

surface supply relationships between glaciers and lak.s.are needed to analyze and understand hydrological processes at regional and global ***,these supply relationships still cannot be extracted efficiently by existing *** paper proposes an automatic and efficient approach to extracting surface supply relationships between glaciers and lak.s.based on meltwater flow *** approach includes two stages:(1)identifying direct connections between objects(*** and lak.s.based on flow direction derived from digital terrain analysis on a gridded digital elevation model(DEM)and(2)deriving all(or user-specified)kinds of surface supply relationships based on graph *** computation-intensive steps in this approach have been parallelized;and all steps in the proposed approach have been integrated as an automatic *** for the Tibetan Plateau show that given outline data for glaciers and lak.s.and the shuttle Radar Topography Mission DEM,the proposed approach can automatically derive diverse surface supply relationships under userspecified restrictions on the attributes of the supply *** parallelization in the approach effectively improves the computing *** proposed approach could also be applied to developing a detailed fundamental dataset of supply relationships between glaciers and lak.s.for other region or period.

关键词： Glaciers and lakes surface supply relationship digital terrain analysis parallel computing Tibetan Plateau

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surface ozone observations during voyages to the Arctic and Antarctic regions

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Chinese science Bulletin 2001年第23期46卷 1995-2000页

作者： Longhua Lu Lingen Bian Yanjie cheng Changgui Lu Jie Tang Chinese Acad Meteorol sci Beijing 100081 Peoples R China

surface ozone concentration and UV-B data between 75° N and 70° s were obtained aboard the Chinese polar scientific vessel 'Xue-long' (snow-Dragon) during the first voyage to the Arctic and the 16th to the Antarctic in 1999-2000. Analysis of these data presents that variations of the surface ozone concentration have small amplitude during voyages except the mid-latitude in the Northern Hemisphere. As a whole, average surface ozone concentration in the Northern Hemisphere is higher than that in the southern, and high value occurred when the ship sailed close to the continents. The average diurnal variations of the surface ozone in the Northern Hemisphere are also higher compared to the southern counterparts, and high diurnal variations were found at low latitudes, and relative low level in the polar region.

关键词： Arctic and Antarctic expedition route observations surface ozone characteristics.

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Birkhoff's theorem and viscosity solutions of Hamilton-Jacobi equations

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science China Mathematics 2009年第8期52卷 1796-1800页

作者： cheng Wei Department of Mathematics, Nanjing University, Nanjing 210093, China Department of Mathematics Nanjing University Nanjing China

We obtain a partial generalization of Birkhoff's theorem of invariant curve to higher dimesional case in the context of viscosity solutions of Hamilton-Jacobi equations, or weak kAM theory. This is a new approach afte... 详细信息

关键词： Hamilton-Jacobi equation viscosity solution semiconcave function

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Freshwater algae chemotaxonomy by high-performance liquid chromatographic(HPLC)analysis

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Frontiers of Environmental science & Engineering 2011年第1期5卷 84-91页

作者： Yansong HOU Wei LIANG Liping ZHANG shuiping cheng Feng HE Zhenbin WU state key Laboratory of Freshwater Ecology and Biotechnology Institute of HydrobiologyChinese Academy of SciencesWuhan 430072China Graduate University of the Chinese Academy of sciences Beijing 100049China

The study of community composition of algae is essential for understanding the structure and dynamics of the aquatic ecosystem and for evaluating the eutrophic level of the water body.A high-performance liquid chromatographic(HPLC)method based on a reversephase C_(18) nonpolar column was developed for the main algal taxa,which includes cyanophytes,bacillariophytes,euglenophytes,dinophytes,and *** on the elution order using HPLC,19 pigments were identified,and they were chlorophyllide a,19′-butanoyloxyfucoxanthin,chlorophyll c_(1)+c_(2),phephorbides a,peridinin,methyl-chlorophyllide a,fucoxanthin,neoxanthin,violaxanthin,myxoxanthophyll,diadinoxanthin,diatoxanthin,lutein,zeaxanthin,chlorophyll b allomer,chlorophyll b,chlorophyll a allomer,chlorophyll a,andβ,β-carotene.A comparison study of cell microscopic counts and accessory pigment analysis indicated that HPLC analysis could be a useful tool for monitoring phytoplankton communities and their abundance.

关键词： high-performance liquid chromatographic(HPLC) algae pigment chemotaxonomy

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Preparation of super-aligned carbon nanotube-reinforced nickel-matrix laminar composites with excellent mechanical properties

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International Journal of Minerals,Metallurgy and Materials 2019年第1期26卷 133-141页

作者： Ze-cheng Hou Lun-qiao Xiong Yuan-feng Liu Lin Zhu Wen-zhen Li school of Materials science and Engineering Tsinghua University Tsinghua-Foxconn Nanotechnology Research Center Tsinghua University

A homogeneous and compact super-aligned carbon nanotube(sACNT)-reinforced nickel-matrix composite was successfully prepared by electrodeposition. The mechanical properties of the laminar sACNT/Ni composites were substantially improved compared with those of pure nickel. With increasing content of sACNTs, the tensile strength of the composite increased and the elongation decreased because of the high-strength sACNTs bearing part of an applied load and the fine-grained strengthening mechanism. The nanohardness of the sACNT/Ni composites was improved from 3.92 GPa(pure nickel) to 4.62 GPa(Ni-4 vol%sACNTs). The uniform distribution of sACNTs in the composites and strong interfacial bonding between the sACNTs and the nickel matrix resulted in an improvement of the mechanical properties of the sACNT/Ni composites. The introduced sACNTs refined the nickel grains, increased the amount of crystal twins, and changed the preferred orientation of grain growth.

关键词： nickel-matrix laminar composite super-aligned carbon nanotube electrodeposition mechanical properties

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synthesis and characterization of new soluble poly(aryl ether nitrile)s containing phthalazinone moiety

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Chinese Chemical Letters 2007年第5期18卷 595-597页

作者： Ming Jing Wang cheng Liu Li Ming Dong Xi Gao Jian Department of Polymer science ＆ Materials Dalian University of Technology Dalian 116012 China

A series of novel poly（aryl ether nitrile）s containing phthalazinone moiety were synthesized by the nucleophilic displacement reaction of bisphenol-like monomers （I） with 2,6-difluorobenzonitrile. The inherent viscosities ranged from 0.46 to 1.07 dL g^-1. The glass transition temperatures were in the range of 277-295℃, and the temperatures for 10% weight loss in nitrogen atmosphere were found between 495 and 527 ℃. The structures of these resultant polymers were confirmed by FT-IR and 1^H NMR. Moreover, the properties of poly（aryl ether nitrile）s including solubility and crystallinity were also studied.

关键词： Poly(aryl ether nitrile)s Phthalazinone Heat-resistance solubility

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A structurally ordered thiophene-thiazole copolymer for organic thin-film transistors

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science China Chemistry 2012年第5期55卷 760-765页

作者： CHEN DuGang ZHAO Yan ZHONG cheng YU Gui LIU YunQi QIN JinGui Department of Chemistry and Hubei key Lab on Organic and Polymeric Optoelectronic Materials Wuhan UniversityWuhan 430072China Beijing National Laboratory for Molecular sciences Institute of ChemistryChinese Academy of SciencesBeijing 100190China

This paper reports a new donor-acceptor copolymer semiconductor, PTBTh, comprising bithiophene and bithiazole where the regular coplanar structure and the intramolecular charge transfer are expected to increase the opportunity for --- stacking and charge transport. The AFM image shows lamellar stacking of the polymer on the surface. The field-effect transistor (FET) properties of PTBTh have been evaluated by a bottom-contact/bottom-gate TFT configuration. The device showed a high hole mobility of 1.14×10-2 cm2 V-1 s-1 and a current on/off ratio of 3×105 with the polymer thin film annealed at a mild temperature of 120 ℃ when measured under ambient conditions.

关键词： thin-film transistors copolymer mobility atomic force microscopy

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Evaluation of Intensive Urban Land Use Based on an Artificial Neural Network Model:A Case study of Nanjing City,China

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Chinese Geographical science 2017年第5期27卷 735-746页

作者： QIAO Weifeng GAO Junbo LIU Yansui QIN Yueheng LU cheng JI Qingqing Institute of Geographic sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China school of Geography science Nanjing Normal UniversityNanjing 210023China Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application Nanjing 210023China school of Geography science Xinyang Normal UniversityXinyang 464000Henan ProvinceChina

In this paper, the artificial neural network(ANN) model was used to evaluate the degree of intensive urban land use in Nanjing City, China. The construction and application of the ANN model took into account the comprehensive, spatial and complex nature of urban land use. Through a preliminary calculation of the degree of intensive land use of the sample area, representative sample area selection and using the back propagation neural network model to train, the intensive land use level of each evaluation unit is finally determined in the study area. Results show that the method can effectively correct the errors caused by the limitations of the model itself and the determination of the ideal value and weights when the multifactor comprehensive evaluation is used alone. The ANN model can make the evaluation results more objective and practical. The evaluation results show a tendency of decreasing land use intensity from the core urban area to the periphery and the industrial functional area has relatively low land use intensity compared with other functional areas. Based on the evaluation results, some suggestions are put forward, such as transforming the mode of urban spatial expansion, strengthening the integration and potential exploitation of the land in the urban built-up area, and strengthening the control of the construction intensity of protected areas.

关键词： urban land intensive use functional area artificial neural network (ANN) model Nanjing City

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Evolution of Precipitates of s31042 Heat Resistant steel During 700℃ Aging

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Journal of Iron and steel Research International 2013年第10期20卷 113-121页

作者： WANG Jing-zhong LIU Zheng-dong BAO Han-sheng cheng shi-chang Xi'an University of Architecture and Technology Central Iron and steel Research Institute

The evolution of precipitates of s31042 steel during 700 ℃ aging was investigated by using a scanning elec- tron microscope, a transmission electron microscope, and electron energy spectrum technology. The various combi nations of M23C6, MX, NbCrN, and σ and G phases in the steel were found at different aging states. In the begin ning of aging, M23C6 precipitates swiftly along the grain boundaries. When the aging time exceeds 6 000 h, precipita- ted M23C6 carbides along the grain boundaries turn to be granular. It was found that si element segregates to grain boundaries during above process, which may enhance the granular shape of M23C6 carbides and its transformation to and G phases. When the aging time exceeds 10 000 h, various shaped a phase and granular G phase appear along the grain boundaries and there are no continuous M23C6 carbides along the grain boundaries. Meanwhile, a large quantity of granular M23C6 carbides and a minor amount of G phase precipitate near the grain boundaries. Based on the segre- gation of silicon to the grain boundaries, a precipitation evolution model during aging was concluded.

关键词： s31042 heat resistant steel aging precipitation evolution

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