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Critical slope gradient for compulsory abandonment of farmland on the hilly Loess Plateau

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Chinese Science Bulletin 1998年第5期43卷 409-412页

作者： TANG Keli+1. ZHANG Keli 1.2.and LEI Aling 1.3.1. Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling 71.0}00, China 2. Department of Hydraulic Engineering, Tsinghua university, beijing 1.0084, China 3. Water Resources C Institute of Soil and Water Conservation Chinese Academy of Sciences Yangling China Department of Hydraulic Engineering Tsinghua University Beijing China Water Resources Conservation Bureau of Yangtze River Ministry of Water Resources Wuhan China

Scientific evidence for the upper limit of farmland is proposed. Shallow gully erosion is one of erosion types distributed extensively on sloping farmland in the hilly regions of the Loess Plateau. Field observation and aerial photos interpretation, as well as laboratory experiments show that the shallow gully erosion occurring on the steeper farmland in the hilly regions of the Loess Plateau is an important factor leading to intensive erosion on slope, because of its extensive distribution and intensive runoff collection. The data on the formation, development and distribution of shallow gullies on sloping farmland indicate that critical slope gradient for shallow gully initiation ranges from 1. to 2. degrees with an average of 1..2.degrees. Therefore, it is suggested that critical slope gradient for compulsory abandonment of farmland on the hilly Loess Plateau should be kept within the critical slope gradient for shallow gully initiation to prevent shallow gully formation in order to control soil loss more effectively. But as the first step, the cultivation on the slopes with slope larger than 2. degrees where the maximum erosion occurs should be strictly forbidden.

关键词： hilly region of Loess Plateau upper limitation for farmland shallow gully erosion erosion dynamic.

Empirical likelihood confidence regions of the parameters in a partially linear single-index model

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Science China Mathematics 2005年第10期48卷 1333-1348页

作者： XUE Liugen~1.& ZHU Lixing~2.1. College of Applied Sciences,{1. university of Technology,{1. 1.002.,China 2. Department of Mathematics,Hong Kong Baptist university,Hong Kong,China College of Applied Sciences Beijing University of Technology Beijing China Department of Mathematics Hong Kong Baptist University Hong Kong China

In this paper, a partially linear single-index model is investigated, and three empirical log-likelihood ratio statistics for the unknown parameters in the model are suggested. It is proved that the proposed statistics are asymptotically standard chi-square under some suitable conditions, and hence can be used to construct the confidence regions of the parameters. Our methods can also deal with the confidence region construction for the index in the pure single-index model. A simulation study indicates that, in terms of coverage probabilities and average areas of the confidence regions, the proposed methods perform better than the least-squares method.

关键词： partially linear single-index model, empirical likelihood, confidence region, chi-square distribution, coverage probability.

Reconstruction of precipitation variation from tree rings in recent 1.00 years in Delingha, Qinghai

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Science China Earth Sciences 2005年第7期48卷 939-949页

作者： SHAO Xuemei1. HUANG Lei1. LIU Hongbin2. LIANG Eryuan1. FANG Xiuqi3.& WANG Lili1.1. Institute of {1.graphic Sciences and Natural Resources Research, Chinese Academy of Sciences, beijing 1.01.1. China 2. National Climate Center, beijing 1.0081. China 3. beijing Normal university, beijing 1.0875, China Institute of geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing 100101 China National Climate Center Beijing 100081 China beijing Normal {1. Beijing 100875 China

Using seven well-replicated Qilian juniper (Sabina przewalskii Kom.) ring-width chronologies developed at Zongwulong and Shalike Mts. in the northeastern part of the Qaidam Basin annual precipitation from previous July to current June in the recent 1.00 years was re- constructed for Delingha. The reconstruction can capture 63.1. of precipitation variance and the equation was stable over time. For the reconstructed precipitation, wet periods occurred in AD1.{3.—1.3. and 1.3.—{3.01. whereas dry intervals in 1.{3.—1.1. and 1.3.—1.41. In ad- dition, the magnitude in precipitation variation was lower before 1.3. with about 1. mm, but it increased to 3. mm during the period of 1.3. to 1.50. After 1.50, the precipitation variance de- creased again. In contrast to the increase in temperature, a decrease in annual precipitation was evident since the 1.90s. The agreement in low-frequency variation between the reconstruction and the glacier accumulation and particulate content in Dunde ice cores during the recent several hundred years suggested that the precipitation reconstructed in this study was rather reliable, and represented a regional signal. This 1.00-year reconstruction could benefit our understanding of climatic variation in decadal to century-scale in this region, and provide basic data to climate models and to prediction of future climate in the {3.st century.

关键词： northeastern part of the Qaidam Basin tree-ring width series of Qilian juniper precipitation reconstruction in 1.00 years.

Solving the input data in error correc-tion of optical fabrication by finite Fourier coefficient algorithm

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Science China(Technological Sciences) 2006年第1期49卷 50-60页

作者： CHENG Haobo1.2. SUN Guozheng3.& FENG Zhijing2.1. Department of Optical Engineering, beijing Institute of Technology, beijing 1.0081. China 2. Department of Precision Instruments and Mechanology, Tsinghua {2., beijing 1.0084, China 3. China North Industries Group Corporation, beijing 1.0089, China Department of Optical Engineering Beijing Institute of Technology Beijing China Department of Precision Instruments and Mechanology Tsinghua University Beijing China China North Industries Group Corporation Beijing China

A free-form lens (FFL) is a special surface that is difficult to be fabricated. FFL are usually fabricated by computer-controlled optical surfacing (CCOS) technique. During CCOS, the material removal amount is determined by the unit removal function (URF) convoluting with the input data――the dwell time. When the removal amount and the URF are known, how to solve the input data involves the special algorithm――deconvolution. Usually, the input data are solved by virtue of low pass filter or iterative methods. However, an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS. In this paper, to solve the input data, a new method that is based on the finite Fourier coefficient is put forward. It can give a continuous and accurate solution for fabricating choice. Several parameters are simulated, which influ-ence the process of CCOS, and evaluating on the effect of the method is also carried out. Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.

关键词： optical fabrication, computer controlled optical surfacing, free-form lens, finite Fourier coefficient, error correction.

Seismic wave propagating in Kelvin-Voigt homogeneous visco-elastic media

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Science China Earth Sciences 2006年第2期49卷 147-153页

作者： YUAN Chunfang1. PENG Suping1. ZHANG Zhongjie2.& LIU Zhenkuan3.1. China {1. of Mining & Technology, beijing {2. China 2. Institute of geophysics, Chinese Academy of Sciences, beijing 1.01.1. China 3. Exploration and Development Research Institute of Daqing Oilfield, Daqing 1.3.1.0} China China university of Mining & Technology Beijing China Institute of geophysics Chinese Academy of Sciences Beijing China Exploration and Development Research Institute of Daqing Oilfield Daqing China

This paper studies, under a small disturbance, the responses of seismic transient wave in the visco-elastic media and the analytic solution of the corresponding third-order partial differential equation. A plane wave solution of Kelvin-Voigt homogeneous visco-elastic third-order partial differ-ential equation with a pulse source is obtained. By the principle of pulse stacking of particle vibration, the result is extended to the solution of Kelvin-Voigt homogeneous visco-elastic third-order partial differential equation with any source. The velocities of seismic wave propagating and the attenuation of seismic wave in Kelvin-Voigt homogeneous visco-elastic media are discussed. The velocities of seismic wave propagating and the coefficient of attenuation of seismic wave in Kelvin-Voigt homogeneous visco-elastic media are derived, expressed as functions of density of the media, elastic modulus and visco-elastic coefficient. These results can be applied in inversing lithology parameters in geophysical prospecting.

关键词： Kelvin-Voigt visco-elastic velocity attenuation seismic wave.

A new DNA algorithm to solve graph coloring problem

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Progress in Natural Science:Materials International 2007年第6期17卷 733-738页

作者： Jiang Xingpeng1. Li Yin2. Meng Ya3.and Meng Dazhi2.1. National Laboratory of Pattern Recognition,Institute of Automation, Chinese Academy of Sciences, beijing 1.0080, China 2. College of Applied Sciences, beijing {2. of Technology, beijing 1.002., China 3. School of Science, beijing Institute of Technology, beijing 1.0081. China) National Laboratory of Pattern Recognition Institute of Automation Chinese Academy of Sciences Beijing 100080 China College of Applied Sciences Beijing University of Technology Beijing 100022 China School of Science Beijing Institute of Technology Beijing 100081 China

Using a small quantity of DNA molecules and little experimental time to solve complex problems successfully is a goal of DNA computing. Some NP-hard problems have been solved by DNA computing with lower time complexity than conventional computing. However, this advantage often brings higher space complexity and needs a large number of DNA encoding molecules. One example is graph coloring problem. Current DNA algorithms need exponentially increasing DNA encoding strands with the growing of problem size. Here we propose a new DNA algorithm of graph coloring problem based on the proof of four-color theorem. This algorithm has good properties of needing a relatively small number of operations in polynomial time and needing a small number of DNA encoding molecules (we need only 6R DNA encoding molecules if the number of regions in a graph is R).

关键词： DNA computing NP-hard problem graph coloring problem.

A new orthogonality relationship for orthotropic thin plate theory and its variational principle

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Science China(Physics,Mechanics & Astronomy) 2005年第3期48卷 371-380页

作者： LUO Jianhui 1., LONG Yuqiu 2.& LIU Guangdong 1.1. College of Civil Engineering, Hunan {1., Changsha 41.082. China 2. Department of Civil Engineering, Tsinghua {1., {2. 1.0084, China College of Civil Engineering Hunan University Changsha China Department of Civil Engineering Tsinghua University Beijing China

The thought how dual vectors are constructed in a new orthogonality relationship for theory of elasticity is generalized into orthotropic thin plate bending problems by using the analogy theory between plane elasticity problems and plate bending problems. Dual differential equations are directly obtained by using a mixed variables method. A dual differential matrix to be derived possesses a peculiarity of which principal diagonal sub-matrixes are zero matrixes. Two independently and symmetrically orthogonality sub-relationships are discovered. By using the integral form for elastic bending theory of orthotropic thin plate the orthogonality relationship is demonstrated. By selecting felicitous dual vectors a new orthogonality relationship for theory of elasticity can be generalized into elastic bending theory of orthotropic thin plate. By using the integral form a variational principle which is relative to differential form and a whole function expression are proposed.

关键词： theory of elasticity, thin plate theory, dual vectors, orthogonality relationship, orthotropic, variational principle.

The study on Sanmenxia annual flow forecasting in the Yellow River with mix regression model

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Science China(Technological Sciences) 2004年第Z1期47卷 118-126页

作者： JIANG Xiaohui1. LIU Changming1.2. WANG Yu3.& WANG Hongrui1.1. {1. Normal university, {1. 1.0875, China 2. Institute of geographic Science and Natural Resources, Chinese Academy of Sciences, {1. 1.01.1. China 3. Reconnaissance, Planning, Design and Research Institute, YRCC, Zhengzhou 450003. China beijing Normal {1. Beijing China Institute of geographic Science and Natural Resources Chinese Academy of Sciences Beijing China Reconnaissance Planning Design and Research Institute YRCC Zhengzhou China

This paper established mix regression model for simulating annual flow, in which annual runoff is auto-regression factor, precipitation, air temperature and water consumption are regression factors; we adopted 9 hypothesis climate change schemes to forecast the change of annual flow of Sanmenxia Station. The results show : (1. When temperature is steady, the average annual runoff will increase by 8.3. if precipitation increases by 1.%; when precipitation decreases by 1.%, the average annual runoff will decrease by 8.{3.; when precipitation is steady, the average annual runoff will decrease by {3.4% if temperature increases 1.; if temperature decreases 1., runoff will increase by 1.{3.. The mix regression model can well simulate annual runoff. ({3. As to 9 different temperature and precipitation scenarios, scenario 9 is the most adverse to the runoff of Sanmenxia Station of Yellow River; i.e. temperature increases 1. and precipitation decreases by 1.%. Under this condition, the simulated average annual runoff decreases by 1..8%. On the contrary, scenario 1.is the best to the enhancement of runoff; i.e. when temperature decreases 1.℃ precipitation will increase by 1.%, which will make the annual runoff of Sanmenxia increase by 1..6%.

关键词： forecast annual flow, mix regression model, Sanmenxia Station

Interannual variability of Antarctic Oscillation and its influence on East Asian climate during boreal winter and spring

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Science China Earth Sciences 2006年第5期49卷 554-560页

作者： FAN Ke1.2.3.& WANG Huijun2.1. Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, beijing 1.002., China 2. Department of Atmospheric Science, Yunnan university, Kunming 650091. China 3. Graduate university of the Chinese Academy of Sciences, beijing 1.0049, China Nansen-Zhu International Research Center Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Department of Atmospheric Science Yunnan University Kunming China Graduate university of the Chinese Academy of Sciences Beijing China

The interannual variability of Antarctic Oscillation (AAO) and its influence on East Asian climate during both boreal winter and spring are addressed. The results show that the positive AAO anomaly decreases the cold activity over East Asia during both boreal winter and spring. AAO-related barotropic meridional teleconnection from Antarctic to Arctic is found through analysis of mean me- ridional circulations. This meridional teleconnection is remarkable over Eurasia during boreal winter and over the Pacific Ocean during boreal spring. The results also show that zonal mean zonal wind at high latitudes in Southern Hemisphere has well positive correlation with that of Eurasia during boreal winter and has negative correlation with Pacific North American teleconnection (PNA) during boreal spring, which again display the meridional teleconnection. Thus, local meridional teleconnection is a possible linkage for interaction of circulations at mid-high latitudes between both hemispheres.

关键词： Antarctic Oscillation, Eurasian west wind, meridional teleconnection, mean meridional circulation.