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2008-09-16
镜头边界检测是基于内容的视频检索基础，其检测的鲁棒性和效率直接影响检索结果。但是，很少研究考虑到鲁棒性和效率这两个问题。本文回顾近几年的努力成果。首先介绍改善鲁棒性的多门限与自适应门限算法；其次，介绍提高效率的压缩算法和颜色空间变换方法。
Zn1-xNixO ( =0.02, 0.03, 0.04, 0.05, 0.07) films were prepared using magnetron sputtering. X-ray diffraction indicates that all samples have a wurtzite structure with c-axis orientation. X-ray photoelectron spectroscopy results reveal that the Ni ion is in a +2 charge state in these films. Magnetization measurements indicate that all samples have room temperature ferromagnetism. In order to elucidate the origin of the ferromagnetism, Zn0.97Ni0.03O films were grown under different atmospheric ratios of argon to oxygen. The results show that as the fraction of oxygen in the atmosphere decreases, both the saturation magnetization and the number of oxygen vacancies increase, confirming that the ferromagnetism is correlated with the oxygen vacancy level.
2008-09-25
Jiang Ming-yan,WEI Guang-Mei,LIU Yu-Ping,FENG Qian,MENG Xiang-Hua
The inhomogeneous variable-coefficient nonlinear Schrodinger equation is hereby under investigation. Painleve analysis leads to the explicit constraint on the variable coefficients for such an equation to pass the Painleve test.With the help of symbolic computation, the bilinear form is obtained through the modified bilinear transformation, and the multi-soliton solutions are given by means of the formal parameter expansion technique.A Backlund transformation in bilinear form is also presented.
2008-09-28
国家自然科学基金（0）
国家自然科学基金（0）
Department of Mathematics and LMIB, Beijing University of Aeronautics and Astronautics,Department of Mathematics and LMIB, Beijing University of Aeronautics and Astronautics,Department of Physics, Beijing University of Aeronautics and Astronautics,Ministry-of-Education Key Laboratory of Fluid Mechanics and National Laboratory for Computational Fluid Dynamics, Beijing University of Aeronautics and Astronautics,School of Science, Beijing University of Posts and Telecommunications
2008-10-08
近年来出现的分布式拒绝服务攻击(DDoS)对网络安全和信息的可用性造成了巨大的威胁。随着DDoS攻击的发展，出现了一种新型攻击方式：低速率攻击。由于之前用于检测DDoS的入侵检测系统（IDS）多是建立在对入侵者的高速数据流统计检测的基础上，导致低速率攻击可以逃过这种高速率IDS。本文将提出一种针对低速率DDoS攻击的入侵检测系统。该系统可设定识别概率、漏报概率，根据用户要求对攻击进行有效检测并具有多种报警方式。
2008-10-22
在网络监测中，对监测生成的海量数据的进行存储和分析是网络监测的一大瓶颈，如何在满足监测要求的前提下减少存储的数据量并简化分析过程是目前人们非常关注的问题。本文从网络监测的实际需求出发，提出一中基于存储统计指标和DBMS的网络监测分析方法，并且在实际网络中实现和部署了一个原型。实际应用的效果表明，该方法很好的解决了网络监测中的数据瓶颈问题。
2008-11-03
本文利用库伦爆炸模型来模拟计算高电荷态离子轰击氘化固体靶氘离子获的动能。在低速极端高电荷态离子的轰击下，固体表面会形成一个等离子区。在这个等离子体区域内会形成一个强的电场，区域内的离子在强电场的排斥力作用下会产生库伦爆炸现象，在库伦爆炸下离子获的动能有可能达到keV 水平。以此同时区域内会产生高温高压现象，因此在这种环境下高能的氘氘离子有可能产生核聚变。
2008-12-02
在极稀溶液中，通过改变反应溶剂去离子水的量或原料中铝源的量，可以可控合成不同粒径（20~70nm）、形貌和孔道结构的纳米介孔氧化硅颗粒和纳米介孔铝掺杂氧化硅材料。这种材料具有高比表面（BET比表面1000 m2/g）和较大的孔容(1.1~1.8 cm3/g)。反应物浓度降低或反应物中添加铝源后，介孔材料的有序性下降，粒径减小，孔容增大，并产生大量的间隙孔。通过小角XRD、透射电镜、氮气吸附-脱附实验表征了样品。
国家自然科学基金，国家自然科学基金（50572046，50573043）
兰州大学化学化工学院,清华大学材料科学与工程系,清华大学材料科学与工程系,清华大学材料科学与工程系,兰州大学化学化工学院,清华大学材料科学与工程系
#化学#
In this paper, the possibility using micromegas (Micro-Mesh Gaseous Structure) as neutron detector in 14 MeV neutron computed tomography (CT) is studied by simulation. The simulation results show that micromegas neutron detector has high spatial resolution and is a good candidate for neutron radiography. The three-dimensional images of plant roots in soil are successfully and clearly obtained by the 14 MeV neutron CT with micromegas as neutron detector. In the present simulation, MCNP is employed for 14MeV neutron transport in the sample and Matlab for the 3-D photograph reconstruction.
2008-12-18
国家自然科学基金（10575046 ）
国家自然科学基金（10775062）
School of Nuclear Science and Technology, Lanzhou University, Lanzhou,School of Nuclear Science and Technology, Lanzhou University, Lanzhou, School of Nuclear Science and Technology, Lanzhou University, Lanzhou
Yong-Hui Zhang,Guo-Ping Wu,Kai-Ge Zhou,Ke-Feng Xie,Cai-Hong Liu,Hao-Li Zhang,Yong Peng,Yu-Qing Xiong
The adsorption of cytosine on graphene surface is studied using density functional theory with local density approximation. The cytosine is physisorbed onto graphene through π-π interaction, with a binding energy around -0.39 eV. Due to the weak interaction, the electronic properties of graphene show little change upon adsorption. The cytosine/graphene interaction can be strongly enhanced by introducing metal atoms. The binding energies increase to -0.60 and -2.31 eV in the presence of Li and Co atoms, respectively. The transport behavior of an electric sensor based on Co-doped graphene shows a sensitivity one magnitude higher than that of a similar device using pristine graphene. This work reveals that the sensitivity of graphene-based bio-sensors could be drastically improved by introducing appropriate metal atoms.
2009-01-05
国家自然科学基金（20503011）
国家自然科学基金（ 20621091）
,,,,,State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University,Department of Engineering Materials, Sheffield University,National Key Lab of Surface Engineering, Lanzhou Institute of Physics
2009-01-08
软件行为监控技术一直是信息安全领域的研究方向之一，现有方法主要是基于系统底层过滤驱动技术，占用系统资源较多，而且可能会与杀毒软件冲突。而本文提出的方法基于在用户层截获系统API（应用程序编程接口）技术。本文阐述了如何利用微软的Detours开发包，通过在用户层截获软件对系统API的调用，获取软件的API操作信息，从而对软件行为进行监控的方法，并给出了参考实现。测试表明，本方法具有对应用程序和操作系统透明，并且占用系统资源少，并且不与杀毒软件冲突等特点，而且可以分线程实时显示日志信息。而且通过扩展此方法，可以开发更多的应用。
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