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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, China 2. Imaging Department of Tongji Hospital of Tongji University, Shanghai 2.0065, China 3. College of Mathematics and Physics, Nanjing University of information science and technology, Nanjing 2.0044, China) 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.

Fuzzy dynamic characteristic model based attitude control of hypersonic vehicle in gliding phase

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science China(information sciences) 2011年第3期54卷 448-459页

作者： LUO Xiong 1,2.& LI Jiang 1 1 Department of Computer science and technology, Key {2.oratory of Advanced Control of Iron and Steel Process (Ministry of Education), University of science and technology Beijing, Beijing 100083, China 2.national {2.oratory of Space Intelligent Control, Beijing 100190, China Department of Computer science and technology Key Laboratory of Advanced Control of Iron and Steel Process (Ministry of Education) University of Science and Technology Beijing Beijing China national laboratory of Space Intelligent Control Beijing China

The intelligent autonomous control of hypersonic vehicles has aroused great interest from the field of spacecraft. To solve the problem of longitudinal attitude control of hypersonic vehicle in gliding phase, a new intelligent controller is proposed in this paper. This new controller is based on the fuzzy dynamic characteristic modeling method. The fuzzy logic is introduced into the characteristic modeling by dividing the whole restriction range into several subspaces. Simulations show that this modification greatly improves the performance of the original method. With the same whole restriction range the fuzzy dynamic characteristic modeling decreases the time of convergence, and at the same time makes the attitude angle tracing more precise and robust. Since the sub-model is a characteristic model that has stronger adaptiveness than a fixed local model, the number of fuzzy rules is greatly reduced. Our model sharply reduces the complexity in constructing a fuzzy dynamic model. Finally, simulation results are given to show the effectiveness of the proposed approach in dealing with the attitude control problem of hypersonic vehicle in gliding phase.

关键词： hypersonic vehicle gliding attitude control fuzzy dynamic characteristic modeling

Super-orthogonal space-time code design based on the trellis diagram integrated operation

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science China(information sciences) 2011年第7期54卷 1481-1490页

作者： AO Jun 1,2.MA ChunBo 1,AO FaLiang 1 & LIAO GuiSheng 3 1 College of information and Communication,Guilin University of Electronic and technology,Guilin 541004,China 2.{2. Key laboratory of Electromagnetic Environment,QingDao,2.6107,China 3 {2. lab of Radar Signal Processing,Xidian University,Xi’an 710071,China College of information and Communication Guilin University of Electronic and Technology Guilin China national Key laboratory of Electromagnetic Environment QingDao China national lab of Radar Signal Processing Xidian University Xi’an China

By studying the super-orthogonal space-time coding designs for 2.transmit antennas and superquasi orthogonal space-time coding designs for 4 transmit antennas,a novel super-orthogonal space-time coding design for 4 transmit antennas is *** exploiting the inherent structure association between OSTBC and QOSTBC,the proposed schemes can obtain the full-rate and good performance while keeping the coding complexity as super-orthogonal space-time coding schemes for 2.transmit *** results demonstrate that the proposed schemes outperforms the existing super-quasi orthogonal space-time coding schemes by almost 2.dB.

关键词： STBC TCM SOSTTC SQOSTTC

Spray and forward:Efficient routing based on the Markov location prediction model for DTNs

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science China(information sciences) 2012年第2期55卷 433-440页

作者： DANG Fei1,YANG XiaoLong1,2.& LONG KePing2.1 Research Center for Optical Internet and Mobile information Networks(COIMIN),University of Electronic science and {2. of China,Chengdu 611731,China 2.School of Computer and Communications Engineering,University of science and {2. Beijing,Beijing 100083,China Research Center for Optical Internet and Mobile information Networks (COIMIN) University of Electronic Science and Technology of China Chengdu China School of Computer and Communications Engineering University of Science and Technology Beijing Beijing China

Typical delay tolerant networks(DTNs)often suffer from long and variable delays,frequent connectivity disruptions,and high bit error *** DTNs,the design of an efficient routing algorithm is one of the key *** existing methods improve the accessibility probability of the data transmission by transmitting many copies of the packet to the network,but they may cause a high network *** address the tradeoff between a successful delivery ratio and the network overhead,we propose a DTN routing algorithm based on the Markov location prediction model,called the spray and forward routing algorithm(SFR).Based on historical information of the nodes,the algorithm uses the second-order Markov forecasting mechanism to predict the location of the destination node,and then forwards the data by greedy routing,which reduces the copies of packets by spraying the packets in a particular *** contrast to a fixed mode where a successful-delivery ratio and routing overhead are contradictory,a hybrid strategy with multi-copy forwarding is able to reduce the copies of the packets efficiently and at the same time maintain an acceptable successful-delivery *** simulation results show that the proposed SFR is efficient enough to provide better network performance than the spray and wait routing algorithm,in scenarios with sparse node density and fast mobility of the nodes.

关键词： delay tolerant networks spray and forward Markov position prediction routing algorithm

Synthesis of nanostructural ZnO using hydrothermal method for dye-sensitized solar cells

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science China(Technological sciences) 2010年第4期53卷 1146-1149页

作者： WANG ChunXiao1,2.ZHANG XiaoDan1,WANG DongFeng1,YANG ZhenHua1,2.JI WeiWei1,ZHANG CunShan2.& ZHAO Ying1 1 Institute of Photo-electronic Thin Film Devices and technology of Nankai University,Key laboratory of Photo-electronic {2. science and technology(Nankai University),Ministry of Education,Tianjin 300071,China 2.College of {2. Engineering,Hebei University of technology,Tianjin 300130,China Key laboratory of Photo-electronic information {2. and technology (Nankai University) Ministry of Education Institute of Photo-electronic Thin Film Devices and Technology of Nankai University Tianjin China College of information Engineering Hebei University of Technology Tianjin China

ZnO nanocrystals with different morphologies were successful synthesized by a simple hydrothermal method combined with and without hexadecyl trimethyl ammonium bromide(CTAB).The phases and morphologies of the products were measured using X-ray diffraction(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM),*** results indicated that the ZnO nanocrystals with different morphologies were of hexagonal wurtzite *** nanorods were obtained without using CTAB,and then the morphology of ZnO changed to ZnO nanoflower and the density of nanoflower became denser with the increase of CTAB *** nanoflower and ZnO nanorod as photoanode were applied to dye-sensitized solar cells(DSSC),*** nanoflower shows a higher dye loading,so DSSC with the use of the ZnO nanoflower possesses a higher conversion efficiency than ZnO nanorod.

关键词： DSSC ZnO

A characterization for a graphic sequence to be potentially C_r-graphic

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science China Mathematics 2010年第11期53卷 2893-2905页

作者： YIN JianHua Department of Mathematics, College of information science and {2., Hainan University, Haikou 5702.8, China Department of Mathematics College of Information Science and Technology Hainan University Haikou China

Let r 3, n r and π = (d1, d2. . . . , dn) be a graphic sequence. If there exists a simple graph G on n vertices having degree sequence π such that G contains Cr (a cycle of length r) as a subgraph, then π is said to be potentially Cr-graphic. Li and Yin (2.04) posed the following problem: characterize π = (d1, d2. . . . , dn) such that π is potentially Cr-graphic for r 3 and n r. Rao and Rao (1972. and Kundu (1973) answered this problem for the case of n = r. In this paper, this problem is solved completely.

关键词： graph cycle degree sequence

A three-dimensional variational ocean data assimilation system:Scheme and preliminary results

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science China Earth sciences 2006年第11期49卷 1212-1222页

作者： ZHU Jiang1,2. ZHOU Guangqing1, YAN Changxiang1, FU Weiwei1 & YOU Xiaobao1,3 1. International Center for Climate and Environment sciences, Institute of Atmospheric Physics, Chinese Academy of sciences, Beijing 10002., China 2. Jiangsu Key laboratory of Meteorological Disaster, Nanjing University of information science and technology, Nanjing 2.0044, China 3. Beijing Institute of Applied Meteorology, Beijing 10002., China International Center for Climate and Environment sciences Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Jiangsu Key laboratory of Meteorological Disaster Nanjing University of Information Science and Technology Nanjing China Beijing Institute of Applied Meteorology Beijing China

A new 3DVAR-based Ocean Variational Analysis System (OVALS) is developed. OVALS is capable of assimilating in situ sea water temperature and salinity observations and satellite altimetry data. As a component of OVALS, a new variational scheme is proposed to assimilate the sea surface height data. This scheme considers both the vertical correlation of background errors and the nonlinear temperature-salinity relationship which is derived from the generalization of the linear balance constraints to the nonlinear in the 3DVAR. By this scheme, the model temperature and salinity fields are directly adjusted from the altimetry data. Additionally, OVALS can assimilate the temperature and salinity profiles from the ARGO floats which have been implemented in recent years and some temperature and salinity data such as from expendable bathythermograph, moored ocean buoys, etc. A 2.-year assimilation experiment is carried out by using OVALS and the Tropical Pacific circulation model. The results show that the assimilation system may effectively improve the estimations of temperature and salinity by assimilating all kinds of observations. Moreover, the root mean square errors of temperature and salinity in the upper depth less than 42. m reach 0.63℃ and 0.34 psu.

关键词： data assimilation, 3DVAR, sea surface height, ARGO floats.

Influence of mesoscale topography on vortex intensity

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Progress in Natural science:Materials International 2008年第1期18卷 71-78页

作者： Zhexian Luo*,Yun Gao Remote Sensing College,Nanjing University of information science and {2.,Najing 2.0044,China Remote Sensing College Nanjing University of Information Science and Technology Najing 210044 China

The effect of mesoscale topography on multi-vortex self-organization is investigated numerically in this paper using a barotropic prim- itive equation model with topographic *** the initial field there are one DeMaria major vortex with the maximum wind radius rm of 80 km at the center of the computational domain,and four meso-b vortices in the vicinity of rm to the east of the major vortex center. When there is no topography present,the initial vortices self-organize into a quasi-final state flow pattern,i.e.a quasi-axisymmetric vor- tex whose intensity is close to that of the initial major ***,when a mesoscale topography is incorporated,the spatial scale of the quasi-final state vortex reduces,and the relative vorticity at the center of the vortex and the local maximum wind speed remarkably *** possible mechanism for the enhancement of the quasi-final state vortex might be that the negative relative vorticity lump, generated above the mesoscale topography because of the constraint of absolute vorticity conservation,squeezes the center of positive vorticity towards the mountain slope area,and thus reduces the spatial range of the major ***,because the total kinetic energy is basically conservative,the squeezing directly leads to the concentration of the energy in a smaller area,*** strengthening of the vortex.

关键词： Mesoscale topography Vortex Self-organization Intensity change

A formal model of fair exchange protocols

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science in China(Series F) 2005年第4期48卷 499-512页

作者： QING Sihan1,2.3 & LI Gaicheng1,2.3 1. Engineering Research Center for information Security technology, Institute of Software, Chinese Aca- demy of {2.s, Beijing 100080, China 2. Beijing Zhongke Ansheng Corporation of information technology, Beijing 100080, China 3. Graduate School of the Chinese Academy of {2.s, Beijing 100039, China Engineering Research Center for information Security technology Institute of Software Chinese Academy of Sciences Beijing China Beijing Zhongke Ansheng Corporation of information technology Beijing China Graduate School of the Chinese Academy of sciences Beijing China

Based on the study of existing fair exchange protocols, this paper sets up an accurate formal model by stepwise refinement. In the process of refinement an unreliable channel is employed to simulate an attack behavior. The model provides a novel formal definition of exchanged items, and presents the formal goals for fairness, accountability, etc., reflecting the inherent requirements for fair exchange protocols across-the-board. In order to check, prove, and design fair exchange protocols effectively and efficiently, the model puts forward a novel property of abuse-freeness which applies to all fair exchange protocols, gives a formal definition for trust strand of the third party, and presents general criteria of designing a secure and effective fair exchange protocol. Taking a typical fair exchange protocol as an example, this paper presents the analysis steps of fair exchange protocols appealing to our model. An unknown attack is uncovered. The analysis reveals the process of a complete attack, discovering deeper reasons for causing an attack. Finally, we modify the flawed protocol and the revised protocol ensures the desirable properties.

关键词： events local causal relation local temporal relation global relation exchanged item security goals.