你是如何变成“肉鸡”的？

没有人想让自己的计算机变成黑客的肉鸡，但怎样做才能避免成为肉鸡呢？ 目前来说，最好的解决方法就是通过分析黑客获取肉鸡的各种手段，来找到计算机成为黑客肉鸡的真正原因。也只有这样，我们才会知道哪些方面需要加强防范，并清楚使用什么样的安全产品才能进行有效的防范。     

查找内部攻击源

光纤、交换机这些物理设备可以做出冗余方案,服务器也可以最大限度地进行防护和审核,但对于内网电脑有意无意地攻击服务器和客户端这一问题,却让很多网管员束手无策。要想找到这些问题机,不妨试试黑客攻击的某些技巧。     

一种DCSK通信系统的延迟合并接收方案

提出一种多径衰落信道下DCSK通信系统的延迟合并接收方案. 理论分析和仿真结果证实了该方案的误码性能. 结果表明，和原DCSK通信系统相比，使用了延迟合并接收方案的DCSK通信系统误码性能有所提高；不同接收路径延迟对应的误码性能基本相同；各接收路径采用等增益合并方式时误码性能最好；其理论上限随着接收路径数增加而逐渐降低.     

First principles study on the electronic structure and magnetism of Fe1-xCoxSi alloys

Electronic and magnetic properties of Fe1-xCoxSi alloys were investigated by using a full-potential linear augmented-plane-wave method based on density functional theory. Electronic structure calculation demonstrates that half-metallic property appears in the Fe-rich region of 0 〈 x ≤ 0.25, while the alloys turn out to be a magnetic metal for x 〉 0.25. The concentration dependence of the magnetic moment of the alloys can be understood by the fixed Fermi level at minority band in Fe-rich region, as well as at the majority band in Co-rich region. In Fe-rich alloys, the electronic structure and the magnetic properties at Fe site depend mainly on the spin-polarization of nearest neighbouring Co atoms, while in Co-rich alloys, these features at Co site arise mainly from the neighbours of Fe atoms.     

基于UKF的多用户混沌通信

为克服信道噪声、系统参数误配及多用户干扰对混沌通信系统的影响,本文组合不同的状态空间模型并结合盲提取算法,提出了一种双无先导卡尔曼滤波器 (dual unscented Kalman filter, DUKF),以实现多用户的混沌通信.仿真结果表明,在多输入多输出信道的多用户通信环境下,该算法有较快的收敛速度,并能有效地实现多用户的混沌通信. 关键词： 混沌通信 多输入多输出 双无先导卡尔曼滤波器 盲提取     

反应情境联想法

通过分析近几年高考理科综合中化学试题的命题特点和能力要求,独创性地提出了反应情境联想法。对4本中学化学教材中的约225个化学方程式进行横向的加工重组、统摄整理,归纳了常见的反应情境,原创了5个情境例题,在高考复习课中运用反应情境联想法进行能力培养,收到了良好的复习效果。     

一种基于无先导卡尔曼滤波的混沌相移键控通信系统的非相干检测方法

基于UKF算法,该文提出一种CSK通信系统的非相干检测方法。第一个发送符号作为训练符号,接收端根据第一个发送周期内的接收信号,应用UKF算法估计载波信号;然后将估计的载波信号和后续接收信号相乘,解调后续发送符号。与相干检测方法相比,这种方法不需要混沌同步。仿真结果表明,与已有的非相干检测方法相比,这种方法具有较好的误码性能,甚至比FM-DCSK通信系统的误码性能更好。     

Intramolecular Resonance-assisted Hydrogen Bonds in N-Salicylidene-anilines

In the crystal structures of N-salicylidene-anilines, the ortho-OH group with the central N atom forms a planar six-membered ring through intramolecular hydrogen bonds (Fig. 1). The pseudo-aromatic ring is coplanar with its attached phenyl ring. The resonance strengthens the H-bond through proton transfer between the O and N atoms (Fig.1,Ⅰ←→Ⅱ): dco and dcc become shorter and dCN longer significantly. The d1～d6 are also changed regularly. According to the geometries obtained from X-ray analysis and retrieved from the Cambridge Structural Database (CSD, version 5.21), we believe that the main resonance, at least in solid state, is the molecular keto form (Ⅱ, Fig. 1) instead of the zwitterionic one (Ⅲ, Fig.1).     

C-H…O Hydrogen Bonds and π…π Interaction and the Crystal and Molecular Structures of 3-Nitro-benzylideneaniline-methyl-2’

The title compound (C14H12N2O2,Mr=240.26) crystallizes in the monoclinic system,space group P21/a with a=7.394(1),b=21.334(3),c=7.423(1)A,β=89.82(1)A°,V=1170.8(3)A3,Z=4,Dc=1.363 g/cm3,μ(MoKα)=0.93 cm-1 and F(000)=504.00.The final R and wR are 0.0440 and 0.1370 for 2153 observed reflections (I>2σ(I)),respectively.The dihedral angle between the two phenyl rings is 52.9°and that between the NO2 group and its attached ring is 3.0°.In the crystal,molecules are stacked along [100] throughπ…πinteractions.The C-H…O hydrogen bond (3.403 A,120.4°) laterally connects the stacks along [010] to form networks (001) which are further anti-parallelly connected by C-H…O(3.382 A,142.9°) andπ…πinteractions extending along [001].Also presented here is a brief study on the C-H…O hydrogen bonds in nitro-substituted benzyl-ideneanilines which can be classified into five types,namely,R12(5)R21(4),R22(8),R12(6),andR22(7),with the first three occurring more often.     

查找内部攻击源

光纤、交换机这些物理设备可以做出冗余方案,服务器也可以最大限度地进行防护和审核,但对于内网电脑有意无意地攻击服务器和客户端这一问题,却让很多网管员束手无策。