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Detecting forest landscape boundary between Mountain Birch and evergreen coniferous forest in the northern slope of Changbai Mountain

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Journal of Environmental sciences 2003年第2期15卷 182-186页

作者： CHANG Yu+1. BU Ren-cang+1. HU Yuan-man+1. XU Chong- gang+1. WANG Qing-li+2.(1. Institute of {1. Ecology, chinese academy of sciences, Shenyang 1.001.,{2.. 2. Shenyang Branch, CAS) Institute of applied Ecology Chinese Academy of Sciences Shenyang 110016 China Shenyang Branch CAS Shenyang China

Boundaries between different forest types in Changbai Mountain Eastern china are results from complex interactions between forest ecosystems, topography, and geomorphology. Detecting and quantifying the transitional zones are highly important since high environmental heterogeneity and biodiversity are often found within these zones. In this study, we used GIS and multivariate statistics techniques(PCA and MSWA) to analyze data from Landsat TM satellite imageries and quantitatively determined the positions and widths of the landscape boundary between mountain birch and evergreen coniferous forests in the northern slope of Changbai Mountain. The results showed that the widths of the landscape boundary ranges from 30—50m while using the MSWA or/and PC method. Such detected widths are consistent with field transect data that suggests a 50m transitional zone width. The results further suggest that TM data can be used in combination with GIS and statistical techniques in determining forest landscape boundaries; MSWA is more reliable than PCA, while PCA can also be used to determine the landscape boundary when transects are properly located.

关键词： Changbai Mountain forest landscape boundary PCA & MSWA

The mechanism of breakdown in laminar-turbulent transition of a supersonic boundary layer on a flat plate-temporal mode

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Science china(Physics,Mechanics & Astronomy) 2005年第5期48卷 614-625页

作者： HUANG Zhangfeng 1. CAO Wei 1.2.& ZHOU Heng 1.2.1. Department of Mechanics, Tianjin University, Tianjin 300072. china 2. Liu-Hui Center of applied {2., Nankai University and Tianjin University, Tianjin 300072. china 1. Department of Mechanics Tianjin University 300072 Tianjin China 2. Liu-Hui Center of {1. mathematics Nankai University and Tianjin University 300072 Tianjin China

Temporal mode direction numerical simulation has been done for the transition of a supersonic boundary layer on a flat plate with Mach number 4.5. Analysis of the result showed that during the breakdown process in laminar-turbulent transition, the mechanism causing the mean flow profile to evolve swiftly from laminar to turbulent was that the modification of mean flow profile by the disturbances,when they became larger,led to a remarkable change of its stability characteristics. Though the most unstable T-S wave was of second mode for laminar flow, the first mode waves played the key role in the breakdown process in laminar-turbulent transition.

关键词： supersonic boundary layer, transition, breakdown.

On the periodic solutions of a type of differential-iterative equations

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chinese Science Bulletin 1998年第3期43卷 204-206页

作者： GE Weigao 1. LIU Zhengrong 2.and YU Yuanhong 3 1. Department of {1. mathematics, Beijing Institute of Technology, Beijing 1.0081.{2. 2. Department of mathematics, Yunnan University, Kunming 650091.{2. 3. Institute of {1. mathematics, C Department of applied {1. Beijing Institute of Technology Beijing China Department of mathematics Yunnan University Kunming China Institute of applied {1. Chinese Academy of Sciences Beijing China

Sufficient conditions for the existence of periodic solutions to a type of nonautonomous differential_iterative equations are given.

关键词： differential_iterative equation periodic solution fixed point.

A class of additive-accelerated means regression models for recurrent event data

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Science china {1. 2010年第12期53卷 3139-3151页

作者： LIU Li 1, MU XiaoYun 2.& SUN LiuQuan 2.1 School of mathematics and Statistics, Wuhan University, Wuhan 430072. china 2.Institute of {2. mathematics, academy of mathematics and Systems Science, chinese academy of sciences, Beijing 1.0080, china 1. School of mathematics and Statistics Wuhan University Wuhan 430072 China2. Institute of Applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

In this article, we propose a class of additive-accelerated means regression models for analyzing recurrent event data. The class includes the proportional means model, the additive rates model, the accelerated failure time model, the accelerated rates model and the additive-accelerated rate model as special cases. The new model offers great flexibility in formulating the effects of covariates on the mean functions of counting processes while leaving the stochastic structure completely unspecified. For the inference on the model parameters, estimating equation approaches are derived and asymptotic properties of the proposed estimators are established. In addition, a technique is provided for model checking. The finite-sample behavior of the proposed methods is examined through Monte Carlo simulation studies, and an application to a bladder cancer study is illustrated.

关键词： additive-accelerated means model counting process marginal model model checking recurrent events

Prediction method for October 2.03 solar storm

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Science china(Technological {1.) 2006年第5期49卷 629-640页

作者： XIE Yanqiong1. 2. 3, WEI Fengsi1. FENG Xueshang1.& ZHONG Dingkun1. 2.1. State Key Laboratory of Space Weather, Center for Space Science and applied Research, chinese academy of sciences, Beijing {2., china 2. Graduate School, chinese academy of sciences, Beijing 1.0039, china 3. Institute of Meteorology, PLA University of Science and Technology, Nanjing 2.1.01. china State Key Laboratory of Space Weather Center for Space Science applied Research Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100039 China Institute of Meteorology PLA University of Science Technology Nanjing 211101 China

Aiming at two intense shock events on October 2. and 2., 2.03, this paper presents a two-step method, which combines synoptic analysis of space weather ——“observing” and quantitative prediction ——“palpating”, and then uses it to test predictions. In the first step of “observing”, on the basis of observations of the solar source surface magnetic field, interplanetary scintillation (IPS) and ACE spacecraft, we find that the propagation of the shocks is asymmetric relative to the normal direction of their solar sources, and the Earth is located near the direction of the fastest speed and the greatest energy of the shocks. As the two fast ejection shock events, the fast explosion of coronal mass of the extremely high temperature, the strong magnetic field, and the high speed background solar wind are also helpful to their rapid propagation. In the second step of “palpating”, we adopt a new membership function of the fast shock events for the ISF method. The predicted results show that for the onset time of the geomagnetic disturbance, the relative errors between the observational and the predicted results are 1.8% and 6.7%; and for the magnetic disturbance magnitude, the relative errors are 4.1. and 3.1., re- spectively. Furthermore, the comparison among the predicted results of our two-step method with those of five other prevailing methods shows that the two-step method is advantageous. The results tell us that understanding the physical features of shock propagation thoroughly is of great importance in improving the prediction precision.

关键词： solar storm, interplanetary shock, interplanetary scintillation, two-step method, ISF method.

Two-dimensional simulation of Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect

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Progress in Natural Science:Materials International 2007年第12期17卷 1389-1396页

作者： Hu Jun1.and Yin Xieyuan2.1. Institute of {1. Physics and Computational mathematics, Beijing 1.0088,{2. 2. Department of Modern Mechanics, University of Science and Technology of{2., Hefei 2.002.,{2.) Institute of applied Physics and Computational {1. Beijing 100088 China Department of Modern Mechanics University of Science and Technology of China Hefei 230027 China

Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect are directly simulated by a mixed finite element method. A temperature perturbation is used as an initial disturbed source for the basic parallel flows. The whole spatio-temporal evolution of the binary fluid flows is exhibited: initially only the disturbed mode with the wavenumber k=π is amplified while others are damped, and continuously the amplified mode grows further and the nonlinear effect becomes important; after a nonlinear evolution transition the flow system evolves finally into a periodic right traveling wave.

关键词： Poiseuille-Rayleigh-Bénard flow Soret effect through-flow.

Approximation of dense-n/2.subgraph and table compression problems

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Science china {1. 2005年第9期48卷 1223-1233页

作者： XU Dachuan~1 HAN Jiye~2.& DU Dongle~3 1. College of applied sciences,Beijing University of Technology,Beijing 10002.,{2. 2. Institute of applied mathematics,academy of mathematics and Systems Science,chinese academy of sciences,Beijing 1.0080,{2. 3. Faculty of Administration,University of New Brunswick,P.O.Box 4400,Fredericton,NB E3B 5A3,Canada College of applied {1. Beijing University of Technology Beijing 100022 China Institute of applied {1. Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China Faculty of Administration University of New Brunswick P.O. Box 4400 Fredericton NB E3B 5A3 Canada

We develop improved approximation algorithms for two NP-hard problems: the dense-n/2.subgraph and table *** on SDP relaxation and advanced rounding techniques,we first propose 0. 5982.and 0. 5970-approximation algorithms respec- tively for the dense-n/2.subgraph problem (DSP) and the table compression problem (TCP). Then we improve these bounds to 0. 62.3 and 0. 6708 respectively for DSP and TCP by adding triangle inequalities to strengthen the SDP *** results for TCP beat the 0. 5 bound of a simple greedy algorithm on this problem,and hence answer an open question of Anderson in an affirmative way.

关键词： dense-n/2.subgraph problem(DSP) table compression problem(TCP) SDP approximation ratio

Existence of solutions for the dynamic equation of ferrimagnets

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Progress in Natural Science:Materials International 2007年第11期17卷 1279-1283页

作者： Zeng Ming1. Guo Boling2.and Cheng Caozong1.1. College of {1. sciences, Beijing University of Technology, Beijing 1.002.,{2. 2. Center for Nonlinear Studies, Institute of {1. Physics and Computational mathematics, Beijing 1.0088,{2.) College of applied {1. Beijing University of Technology Beijing 100022 China Center for Nonlinear Studies Institute of Applied Physics and Computational Mathematics Beijing 100088 China

Ferrimagnet is a kind of basic and important multi-sublattice magnet material. It has attracted more and more attention of physicists and mathematicians. Many results of solitons and numerical computations on this topic have appeared. In this article, the dynamic equation for an isotropic ferrimagnet with two non-equivalent sublattices is studied, existence of weak solutions in multi dimension case is proved through the penalized method, the uniqueness and smoothness of the solution in one dimension case are also obtained by the relation between this equation and hyperbolic equation.

关键词： ferrimagnet weak solutions penalized method finite difference method

A complex variable meshless method for fracture problems

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Science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 46-59页

作者： CHENG Yumin1.& LI Jiuhong2.1. Shanghai Institute of {1. mathematics and Mechanics, Shanghai University, Shanghai 2.0072.{2. 2. Department of Building Engineering, Xi’an University of Technology, Xi’an 71.048,{2. Shanghai Institute of applied {1. Mechanics Shanghai University Shanghai 200072 China Department of Building Engineering Xi’an University of Technology Xi’an 710048 China

Based on the moving least-square (MLS) approximation, the complex variable moving least-square approximation (CVMLS) is discussed in this paper. The complex variable moving least-square approximation cannot form ill-conditioned equations, and has greater precision and computational efficiency. Using the analytical solution near the tip of a crack, the trial functions in the complex variable moving least-square approxi- mation are extended, and the corresponding approximation function is obtained. And from the minimum potential energy principle, a complex variable meshless method for fracture problems is presented, and the formulae of the complex variable meshless method are obtained. The complex variable meshless method in this paper has greater precision and computational efficiency than the conventional meshless method. Some examples are given.

关键词： moving least-square approximation, complex variable moving least-square approximation, meshless method, complex variable meshless method, fracture.