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chinese Science Bulletin 1999年第13期44卷 1224-1228页

作者： xu jiongxininstitute of geography, chinese academy of sciences , beijing 100101, china Institute of geography Chinese Academy of Sciences Beijing China

Based on data from more than 100 alluvial rivers, a systematic comparison of flow shear stress and energy expenditure has been made between sand- and gravel-bed rivers, by plotting the relationships between channel shape (i.e. channel width-depth ratio) and hydraulic indices in a two-dimensional plane. These relationships show clearly that the four channel patterns, i.e. sand-bed meandering, sand-bed braided, gravel-bed meandering and gravel-bed braided, are located in 4 different areas that can be divided by 2 straight lines.

关键词： sand-bed river gravel-bed river channel pattern channel pattern discrimination.

COMPLICATED FILL-SCOURBEHAVIORS OF THE YELLOW RIVER ANDTHE CHANNEL-FORMING PROCESSES

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International Journal of Sediment Research 1999年第2期14卷 259-266页

作者： xu JiongXin (1 Institute of geography, chinese academy of sciences, beijing 100101, china)

Based on the data from 159 events at the Tongguan station on the Yellow River, we have found the rule to describe the complicated relationship between the fill-scour features and the event-maximum suspended concentration (C_max). The depth of scour is large if the C_max is low. and is small if C_max is high. However, if C_max increases to the ranges of hyperconcentrated flows, scour occurs again. Controlled by the foregoing complicated fill-scour behaviors, the channel adjustment of the Yellow River is also complicated. When the suspended concentration is low, channel scour occurs, and thereby the channel shape tends to be narrower and deeper, and the thalweg more sinuous. When the suspended concentration increases, channel fill occurs, leading to an increase in the channel width-depth ratio and a decrease in the channel sinuosity. However, when the suspended concentration further increases and exceeds a certain threshold, channel scour occurs again, and the adjustment of channel morphology turns to the opposite direction. The rules outlined in the paper for the channel adjustment of the lower Yellow River may provide a new thinking for the regulation of the channel morphology of the lower Yellow River after the closure of the Xiaolangdi Dam, through the regulation of the lower Yellow River’s water and sediment by choosing some specific operation modes of the reservoir Either by releasing clear water or by releasing man-made hyperconcentrated flows, the downstream channel may tend to be narrowed, deeper and more sinuous.

关键词： Channel adjustment Fill-scour behavior Hyperconcentrated flows Lower Yellow River

Modified conceptual model for predicting the tendency of alluvial channel adjustment induced by human activities

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chinese Science Bulletin 2001年第S1期46卷 51-57页

作者： xu jiongxininstitute of Geographical sciences and Natural Resources Research, chinese academy of sciences, beijing 100101, china (e-mail: xujxin?***) 1. Institute of Geographical sciences and Natural Resources Research Chinese Academy of Sciences 100101 Beijing China

After a discussion about some limitations of Schumm’s conceptual model for prediction of river metamorphosis, this study introduces the channel boundary material as an independent variable, and thereby establishes a conceptual model that can be used to predict the direction of channel adjustment induced by human activities. This model has been tested by data from natural rivers and a laboratory model river, and can be used to explain the complex behavior of channel adjustment after reservoir construction.

关键词： human influence on channels channel boundary condi- tions feedback in channel system prediction of channel adjustment.

The evaluation of interregional status and development proposals of Chongqing

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Journal of Geographical sciences 1998年第3期8卷 74-82页

作者： xu Guanghong LU Dadao Institute of geography, chinese academy of sciences, beijing 100101 china

As the fourth municipality directly under the Central Government, there exist some economic development obstacles including dual economic structures and regional development disparity in Chongqing. According to the local position, economic basis and technical superiority, Chongqing should be an economic growth pole in the interior of china so that it is necessary to evaluate its interregional status. Although the position of economic strength is generally among all of the administrative divisions, the position of Chongqing is very prominent between Southwest china and the Yangtze River industrial zone. In order to give play to the spread action of a growth pole and to promote regional economic coordinated development of the Central and Western part of china, Chongqing should adopt the regional sustained and rapid development strategy. Correspondingly, a series of development proposals has also been put forward in the paper.

关键词： regional development interregional status Chongqing

Hyperconcentrated flows as influenced by coupled wind-water processes

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Science china Earth sciences 2005年第11期48卷 1990-2000页

作者： xu Jiongxin Institute of Geographical sciences and Natural Resources Research, chinese academy of sciences Key Laboratory of Water Cycle and Related Land Surface Processes, chinese academy of sciences, beijing 100101, china 1. Key Laboratory of Water Cycle and Related Land Surface Processes Chinese Academy of Sciences Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences 100101 Beijing China

Using data from more than 40 rivers in the middle Yellow River basin, a study has been made of the influence of coupled wind-water processes on hyperconcentrated flows. A simple “vehicle” model has been proposed to describe hyperconcentrated flows. The liquid phase of two-phase flows is a “vehicle”, in which coarse sediment particles are carried as solid-phase. The formation and characteristics of hyperconcentrated flows are closely related with the forma-tion and characteristics of this liquid-phase and solid-phase. Surface materials and geomorphic agents of the middle Yellow River basin form some patterns of combination, which have deep influence on the formation and characteristics of liquid- and solid-phases of hyperconcentrated flows. The combination of high percentages of relatively coarse material with low percentages of fine material appears in the area predominated by the wind process, where the supply of rela-tively coarse sediment is sufficient, but the supply of relatively coarse sediment is not. The com-bination of low percentages of relatively coarse material with high percentages of fine material appears in the area predominated by the water process, where the supply of fine sediment is sufficient, but the supply of fine sediment is not. In the area predominated by coupled wind-water processes appears the combination of medium percentages of coarse and fine materials, and thus both coarse and fine sediments are in relatively sufficient supply. The manner in which the mean annual sediment concentrations of liquid- and solid-phases vary with total suspended sediment concentration is different. With the increased total suspended sediment concentration, mean annual sediment concentration of liquid-phase increased to a limit and then remained constant; however, mean annual sediment concentrations of solid-phase in-creased continuously. Thus, the magnitude of total suspended sediment concentration depends on the supply conditions of relatively coarse sedime

关键词： river sediment, hyperconcentrated flows, liquid-solid two-phase flows, wind process, fluvial process, Yellow River

Plausible impact of global climate change on water resources in the Tarim River Basin

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Science china Earth sciences 2005年第1期48卷 65-73页

作者： CHEN Yaning & xu Zongxue Xinjiang Institute of Ecology & geography, chinese academy of sciences, Urumqi 830011, china College of Environmental sciences, beijing Normal University, beijing 100875, china 1. Xinjiang Institute of Ecology & geography Chinese Academy of Sciences 830011 Urumqi China 2. College of Environmental sciences Beijing Normal University 100875 Beijing China

Combining the temperature and precipitation data from 77 climatological stations and the climatic and hydrological change data from three headstreams of the Tarim River: Hotan, Yarkant, and Aksu in the study area, the plausible association between climate change and the variability of water resources in the Tarim River Basin in recent years was investigated, the long-term trend of the hydrological time series including temperature, precipitation, and streamflow was detected, and the possible association between the El Ni(n)o/Southern Oscillation (ENSO) and these three kinds of time series was tested. The results obtained in this study show that during the past years, the temperature experienced a significant monotonic increase at the speed of 5%, nearly 1℃ rise; the precipitation showed a significant decrease in the 1970s, and a significant increase in the1980s and 1990s, the average annual precipitation was increased with the magnitude of 6.8 mm per decade. A step change occurred in both temperature and precipitation time series around 1986, which may be influenced by the global climate change. Climate change resulted in the increase of the streamflow at the headwater of the Tarim River, but the anthropogenic activities such as over-depletion of the surface water resulted in the decrease of the streamflow at the lower reaches of the Tarim River. The study result also showed that there is no significant association between the ENSO and the temperature, precipitation and streamflow.

关键词： climate change, hydrological change, temperature, precipitation, streamflow, Tarim River.

Synthesis, complexation properties and crystal structure of 4',5'-dibromo-oxylyl-17-crown-5 ether

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chinese Journal of Chemistry 1996年第5期14卷 447-453页

作者： XIONG,Guo-Xiang ZHOU,Qing-Fu xu,Hui-JunInstitute of Photographic Chemistry,chinese academy of sciences,beijing 100101,china Institute of Photographic Chemistry Chinese Academy of Sciences Beijing 100101 China

4',5'-Dibromo-o-xylyl-17-crown-5 ether (2BrB17C5) was synthesized,starting from 1,2-dibromo-4,5-bis(bromomethyl)-benzene and tetraethylene glycol,and was characterized by 1H NMR,MS and elemental *** yellow prismatic single crystal obtained from anhydrous ethanol was investigated by X-ray structural *** complexation properties toward alkali metal ions were examined using the solvent extraction method and UV absorption *** crown ether was found to be conformationally deformed and oblate-like and is highly selective for lithium ion.

关键词： Crown ether complexation crystal structure

The boundary of palaearctic and oriental realms in western china

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Progress in Natural Science:Materials International 2008年第7期18卷 833-841页

作者： Ling Chen a,b,c, Yanling Songd,*, Shufang xu e a Northwest Institute of Plateau Biology, chinese academy of sciences, Xining 810001, china b Graduate University of the chinese academy of sciences, beijing 100039, china c National Science Foundation of china, beijing 100085, china d Institute of Zoology, chinese academy of sciences, beijing 100101, china e beijing academy of Agriculture and Forestry sciences, beijing 100097, china Northwest Institute of Plateau Biology Chinese Academy of Sciences Xining 810001 China Graduate University of the chinese academy of sciences Beijing 100039 China National Science Foundation of china Beijing 100085 China Institute of Zoology Chinese Academy of Sciences Beijing 100101 China beijing academy of Agriculture and Forestry sciences Beijing 100097 China

In the world-wide zoogeographic division, there has been no consentaneous understanding about the delimitation between palaearctic and oriental realms in western china. In this study, we will discuss the division based on amphibian distribution in Shaanxi, Gansu, Sichuan, Yunnan, and Tibet according to species coefficient similarity between each zoogeographic province. The results show that the northern border lies from Qinling Mountains–Feng Xian (Shaanxi)–Debu (Gansu)–Aba (Sichuan)–Batang–Bomi (Tibet), to Linzhi districts, and the southern border is from Taibai–Feng Xian in Shaanxi–Wen Xian (Gansu)–Songpan–Kangding–Daocheng (Sichuan), to Zhongdian–Gongshan in Yunnan, and westward to Motuo and Bomi district in Tibet.

关键词： Amphibian Zoogeography Palaearctic Oriental Hengduan Mt.

Synthesis and Cation-Mediated Electron Transfer in Fluorescence Quenching of Donor-Acceptor Podands

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chinese Chemical Letters 2000年第9期11卷 767-770页

作者： Hua JIANG Hui Jun xu Institute of Photographic Chemistry, chinese academy of sciences, beijing, 100101 chinese Acad Sci Inst Photog Chem Beijing 100101 Peoples R China

Reduced rate constants of photoinduced electron transfer in intramolecular fluorescence quenching of donor-acceptor podands induced by cation-complexation are observed in the highly exothermic reactions.

关键词： electron transfer donor acceptor podands

Uncertainty in magnetic activity indices

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Science china(Technological sciences) 2008年第10期51卷 1659-1664页

作者： xu WenYao Institute of Geology and Geophysics, chinese academy of sciences, beijing 100029, china Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

Magnetic activity indices are widely used in theoretical studies of solar-terrestrial coupling and space weather prediction. However, the indices suffer from various uncertainties, which limit their application and even mislead to incorrect conclu-sion. In this paper we analyze three most popular indices, Kp, AE and Dst. Three categories of uncertainties in magnetic indices are discussed: "data uncertainty" originating from inadequate data processing, "station uncertainty" caused by in-complete station covering, and "physical uncertainty" stemming from unclear physical mechanism. A comparison between magnetic disturbances and related indices indicate that the residual Sq will cause an uncertainty of 1―2 in K meas-urement, the uncertainty in saturated AE is as much as 50%, and the uncertainty in Dst index caused by the partial ring currents is about a half of the partial ring cur-rent.

关键词： magnetic activity indices Kp AE Dst solar-terrestrial coupling space weather