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Two possible mechanisms for vortex self-organization

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science china Earth sciences 2006年第2期49卷 202-211页

作者： LUO Zhexian2. ZHOU Xiuji1 & GAO Shouting3 1. Chinese Academy of Meteorological sciences, Beijing 100081, china {2., nanjing university of information science and technology, nanjing 2.0044, china 3. Institute of Atmospheric Physics, Chinese Academy of sciences, Beijing 10002., china 2. department of Environmental science Nanjing University of Information Science and Technology Nanjing 210044 China 1. Chinese Academy of Meteorological sciences Beijing 100081 China 3. Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The vortex self-organization is investigated in this paper by four groups of numerical experiments within the framework of quasi-geostrophic model, and based on the experimental results two types of possible mechanisms for vortex self-organization are suggested. The meso-scale to-pography may enable separated vortices to merge into a larger scale vortex; and the interaction of meso-γ and meso-β scale systems may make separated vortices to self organize a typhoon-like vor-tex circulation.

关键词： vortex, self-organization, meso-scale topography, interaction of different scales.

Sufficient and necessary conditions for Lyapunov stability of Lorenz system and their application

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science china({2. sciences) 2010年第8期53卷 1574-1583页

作者： LUO Qi 1 , LIAO XiaoXin 2.& ZENG ZhiGang 2.1 College of information and Control, nanjing university of information science and technology,{2., china 2.department of Control science and Engineering, Huazhong university of science and technology, Image Processing and Intelligent Control Key Laboratory of Education Ministry of china, Wuhan 430074, china 1. College of information and Control Nanjing University of Information Science and Technology Nanjing 210044 China2. Department of Control Science and Engineering Huazhong University of Science and Technology Image Processing and Intelligent Control Key Laboratory of Education Ministry of China Wuhan 430074 China

The sufficient and necessary conditions for Lyapunov stability of the zero equilibrium point of Lorenz system are discussed, and some brief criteria are presented for globally exponential stability, globally asymptotical stability and instability. Furthermore, the behavior of the non-zero equilibrium point of Lorenz system is also investigated, and several sufficient and necessary conditions are provided for locally exponential stability and instability. The established theorems in this paper develop and extend the existing achievements on Lyapunov stability of Lorenz system. In conclusion, by applying the obtained results, some less conservative feedback-control laws are derived to guarantee the globally exponential stability of the chaos control of Chen system, Lu¨ system, Yang-Chen system and Yu-Xia Li system.

关键词： Lorenz system Lyapunov stability sufficient and necessary condition bifurcation values globally exponential synchronization

A Note on the Completeness of an Exponential Type Sequence

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Chinese Annals of Mathematics,Series B 2011年第4期32卷 527-532页

作者： Jinhui FANG department of Mathematics Nanjing University of Information Science and Technology Nanjing 210044 China

For any given coprime integers p and q greater than 1, in 1959, B proved that all sufficiently large integers can be expressed as a sum of pairwise terms of the form p^aq^b. As Davenport observed, Birch＇s proof can be modified that the exponent b can be bounded in terms of p and q. In 2.00, N. Hegyvari effective version of this bound. The author improves this bound.

关键词： Complete sequence Coprime Residue J. Birch distinct to show gave an

Features of aerosol optical depth and its relation to extreme temperatures in china during 1980–2.01

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Acta Oceanologica Sinica 2011年第2期30卷 33-45页

作者： HU Ting SUN Zhaobo LI Zhaoxin Jiangsu Key Laboratory of Meteorological Disaster Nanjing University of Information Scienceand Technology Nanjing 210044 China The department of Atmospheric science Nanjing University of Information Science andTechnology Nanjing 210044 China Laboratoire de Meteorologie Dynamique CNRS France

Based on Total Ozone Mapping Spectrometer （TOMS） monthly aerosol optical thickness （AOT） measurements in 1980–2.01 a study is made of space/time patterns and difference between land and sea of AOT 0.50 μm thick over china,which are put into correlation analysis with synchronous extreme temperature indices （warm/cold day and night）.Results suggest that 1） the long-term mean AOT over china is characterized by typical geography,with pronounced land-sea *** AOT has significant seasonality and its seasonal difference is diminished as a function of latitude.2. On the whole,the AOT displays an appreciably increasing trend,with the distinct increase in the eastern Qinghai-Tibetan plateau and SW china,North china,the mid-lower Changjiang （MiLY） valley as well as the South china Sea,but marginal decrease over western/northern Xinjiang and part of South china.3） The AOT over land and sea is marked by conspicuous intra-seasonal and -yearly oscillations,with remarkable periods at one-,two-yr and more （as interannual periods）.4） Land AOT change is well correlated with extremely temperature ***,the correlations of AOT to the extreme temperature indices are more significant in Eastern china with 110 ° E as the *** high-correlation regions are along the Southern china coastline,the Loess Plateau and the Sichuan Basin,and even higher in North china Plain and the mid-lower Changjiang River reaches.5） Simulations of LMDZ-regional model indicate that aerosol effects may result in cooling all over china,particularly in Eastern *** contribution of aerosol change may result in more decrease in the maximum temperature than the minimum,with decrease of 0.11/0.08 K for zonal average,respectively.

关键词： aerosol optical thickness extreme temperature index space/time pattern trend correlation

Spatial and Temporal Variability of N, P and K Balances for Agroecosystems in china

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Pedosphere 2005年第3期15卷 347-355页

作者： SHENRun-Ping SUNBo ZHAOQi-Guo InstituteofSoilscience ChineseAcademyofSciencesNanjing210008（China）／／DepartmentofSpatialInformationScienceNanjingUniversityofInformationScienceandTechnologyNanjing210044（China） InstituteofSoilscience ChineseAcademyofSciencesNanjing210008（China）

Nitrogen, phosphorus, and potassium balances for agroecosystems in china from 1993 to 2.01 were calculated at national and provincial levels using statistical data and related parameters, and their spatial and temporal variabilities were analyzed with GIS to estimate the potential impacts of nutrient N, P and K surpluses or deficits to soil, water and air. At the national scale, the N and P balances from 1993 to 2.01 showed a surplus, with the nitrogen surplus remaining relatively stable from 1997—2.01. Although during this period the P surplus pattern was similar to N, it had smaller values and kept increasing as the use of phosphate fertilizer increased year by year. However, K was deficient from 1993 to 2.01 even though from 1999 to 2.01 the K deficit decreased. The spatial analysis revealed higher N surpluses in the more developed southeastern provinces and lowest in the western and northern provinces where there was less chemical fertilizer input. The serious K deficit mainly occurred in Shanghai and Beijing municipalities, Jiangsu, Zhejiang and Hubei provinces, and Xinjiang autonomous regions. For the years 1992. 1996 and 2.01, N surpluses and K deficits had significant positive spatial correlations with per capita gross domestic product (GDP), per capita gross industrial output value, and per capita net income of rural households. This showed that the level of economic development played an important role on nutrient balances in the agroecosystems.

关键词： china economic factors NPK balance spatial and temporal variability

Performance analysis of variable-power adaptive modulation in space-time block coded MIMO diversity systems

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science china({2. sciences) 2010年第10期53卷 2106-2115页

作者： YU XiangBin 1,2.& SHI HuiBin 1 1 College of information science and {2., nanjing university of Aeronautics and Astronautics, nanjing 2.0016, china 2.National Mobile Communications Research Laboratory, Southeast university, nanjing 2.0096, china 1. College of information science and {2. Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China

In this paper, the performance analysis of multi-antenna MIMO systems with variable-power (VP) adaptive modulation and space-time coding is presented. The fading gain value is partitioned into a number of regions by which we decide the transmission power according to the region the fading gain falls in. The optimum fading gain region boundaries (switching thresholds) for maximizing spectrum efficiency (SE) under a target BER and average power constraint are derived. It is shown that the Lagrange multiplier in the constrained SE optimization will be unique if the existence condition for multi-antenna systems is satisfied, and is unique for single antenna systems. A practical iterative calculation method based on Steepest Descent Algorithm for finding the Lagrange multiplier is proposed. With the switching thresholds, the closed-form expressions of the SE and average BER, respectively for VP system and constant-power (CP) system are achieved. Simulation results for SE and average BER are in good agreement with the theory analysis. The results show that VP adaptive modulation with space-time coding provides better SE than the counterpart with CP under a target BER and average power constraint.

关键词： adaptive modulation variable power space-time block code constant power multiple input multiple output (MIMO)

Characteristics of fMRI BOLD signal and its neurophysiological mechanism

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Progress in Natural science:Materials International 2007年第6期17卷 630-638页

作者： Zhao Xiaohu1,2. Wu Yigen3 and Guo Shengli3(1. College of Life sciences, Zhejiang university, Hangzhou 310058,{2. 2. Imaging department of Tongji Hospital of Tongji university, Shanghai 2.0065,{2. 3. College of Mathematics and Physics, nanjing university of information science and technology, nanjing 2.0044,{2.) College of Life sciences Zhejiang University Hangzhou 310058 China Imaging department Tongji Hospital Tongji University Shanghai 200065 China College of Mathematics and Physics Nanjing University of Information Science and Technology Nanjing 210044 China

The functional magnetic resonance imaging (fMRI) based on blood oxygen level dependent (BOLD) contrast has emerged as one of the most potent noninvasive tools for mapping brain function and has been widely used to explore physiological, pathological changes and mental activity in the brain. Exploring the nature and property of BOLD signal has recently attracted more attentions. Despite that great progress has been made in investigation of the characteristics and neurophysiological basis, the exact nature of BOLD signal remains unclear. In this paper we discuss the characteristics of BOLD signals, the nonlinear BOLD response to external stimuli and the relation between BOLD signals and neural electrophysiological recordings. Furthermore, we develop our new opinions regarding nonlinear BOLD response and make some perspectives on future study.

关键词： functional magnetic resonance imaging blood oxygen level dependent nonlinear response neural electrophysiological activity.

information Fusion in Biometrics: A Case Study in Fingerprint

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微计算机信息 2005年第18期 151-153页

作者： (nanjing university of {2. science and technology,department of {2. and Engi- neering, nanjing 2.0044, china)Wang, Xiaoyan Fu, Desheng

Biometrics is an emerging topic in the field of signal processing. Multibiometric systems can improve the performance of identification by integrating information presented by single or multiple biometric indicators and a lot of researchers are working on it. As fingerprints is one of the most studied and popular biometrics, researches that have approached the challenges in fingerprints from an information fusion perspective is provided in this paper.

关键词： information fusion Biometrics Recognition Multi- modal

Optimal MAC based cooperative spectrum sensing in cognitive radio networks

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science china({2. sciences) 2012年第6期55卷 1388-1396页

作者： CHEN Zhong 1,ZHANG XianDa 1 & YANG LanJuan 2.1 State Key Laboratory of Intelligent technology and Systems,Tsinghua National Laboratory for information {2. and technology,department of Automation,Tsinghua university,Beijing 100084,china 2.Institute of Command Automation,PLA university of {2. and technology,nanjing 2.0007,china 1. State Key Laboratory of Intelligent technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Automation Tsinghua University Beijing 100084 China2. Institute of Command Automation PLA University of Science and Technology Nanjing 210007 China

This paper considers a cognitive radio (CR) system in non-ideal fading wireless channels and pro-poses cooperative spectrum sensing schemes based on coherent multiple access channels (MAC),serving as an alternative way to improve the cooperative spectrum sensing performance and provide space diversity for spec-trum *** statistics are transmitted using a common channel from the secondary users (SUs) to a fusion center (FC) where the global decision is *** optimal scaling factors of the proposed schemes are obtained by maximizing the detection probability under a target false alarm probability and a transmit power *** the proposed optimal MAC scheme has high computational complexity,a sub-optimal solu-tion based on maximization of the deflection coefficient (DC) is also *** results show that the proposed algorithms can significantly improve the spectrum sensing performance and approach the detection baseline.

关键词： cognitive radio (CR) spectrum sensing multiple access channel (MAC) deflection coefficient optimization