浅谈电力系统内网安全监视平台管理经验

电力调度运行维护日趋网络化,国内外黑客攻击导致大面积停电事故层出不穷,因此电力网路安全日益重要。调度专网内网监视平台能够实现对所辖变电站二次系统的安全防护装置远程维护和内网安全信息监视,可以及时发现不安全攻击行为,第一时间对网络攻击行为采取措施。本文主要从安全防护装置在线率、加密装置密通率、重要告警分析与消除三方面阐述内网安全监视平台日常维护工作,通过归纳总结形成行之有效的典型经验,一方面可以形成内网安全监视平台长效工作机制,另一方面为日常工作处理提供参考建议,从而确保公司电力调度数据专网安全稳定运行。

ON THE EQUIVALENCE OF PDA ALGORITHM AND SIC-MMSE ALGORITHM

In this letter,by employing Gaussian distribution to approximate the probability density function(pdf) of the extrinsic information at the output of the multiuser detector as a function of the pdf of the input extrinsic messages,it is concluded that the Probabilistic Data Association(PDA) algorithm is equivalent to the Soft Interference Cancellation plus Minimum Mean Square Error algo-rithm(SIC-MMSE) .

Power Equilibrium in Dense Wavelength Division Multiplexing Optical Communication Systems

The disequilibrium of the optical power among different channels is analyzed for the dense wavelength division multiplexing optical communication systems. And the new technologies and devices for optical amplifying, filtering, adding /dropping,etc,have been reviewed, which can be used to equalize dynamically the optical power in optical networks.

EVALUATION OF POWER SPECTRAL DENSITY OF PASSIVE INTERMODULATION DISTORTION IN HIGH-POWER COMMUNICATION SATELLITE SYSTEMS

In order to analyze the deleterious effects of Passive InterModulation (PIM) on high power communication satellite systems, the basic concept of PIM is introduced, and an equation for the power spectral density of the n-th order PIM distortion insuch systems is derived by applying flat signal-power spectrum assumption and Fourier transform method. It is indicated that PIM level generally decreases with order and the lowest frequency receive channel in the receive band is the channel of most affected by PIM interference.

Secrecy rate analysis of dual-hop AF relay wiretap channel

An amplify-and-forward(AF) dual-hop relay is proposed for secure communication within Wyner s wiretap channel.Based on an information-theoretic formulation,the average secrecy rate is characterized when two legitimate partners communicate over a quasi-static fading channel.Theoretical analysis and simulation results show that both cooperative strategies of average power scaling(APS) and instantaneous power scaling(IPS) are proved to be able to achieve information-theoretic security,and eavesdropper is unable to decode any information.

Robust background subtraction in traffic video sequence

For intelligent transportation surveillance, a novel background model based on Mart wavelet kernel and a background subtraction technique based on binary discrete wavelet transforms were introduced. The background model kept a sample of intensity values for each pixel in the image and used this sample to estimate the probability density function of the pixel intensity. The density function was estimated using a new Marr wavelet kernel density estimation technique. Since this approach was quite general, the model could approximate any distribution for the pixel intensity without any assumptions about the underlying distribution shape. The background and current frame were transformed in the binary discrete wavelet domain, and background subtraction was performed in each sub-band. After obtaining the foreground, shadow was eliminated by an edge detection method. Experimental results show that the proposed method produces good results with much lower computational complexity and effectively extracts the moving objects with accuracy ratio higher than 90%, indicating that the proposed method is an effective algorithm for intelligent transportation system.

HUFFMAN-BASED GROUP KEY ESTABLISHMENT SCHEME WITH LOCATION-AWARE

Time efficiency of key establishment and update is one of the major problems contributory key managements strive to address.To achieve better time efficiency in key establishment,we propose a Location-based Huffman(L-Huffman) scheme.First,users are separated into several small groups to minimize communication cost when they are distributed over large networks.Second,both user's computation difference and message transmission delay are taken into consideration when Huffman coding is employed to forming the optimal key tree.Third,the combined weights in Huffman tree are located in a higher place of the key tree to reduce the variance of the average key generation time and minimize the longest key generation time.Simulations demonstrate that L-Huffman has much better performance in wide area networks and is a little better in local area network than Huffman scheme.

Stochastic formulation of particle kinetics in wall-bounded two-phase flows

This paper presents a generalized framework of stochastic modeling for particle kinetics in wall-bounded flow.We modified a reflected Brownian motion process and straightforwardly obtained a Kramers equation for particle probability density function(PDF).After the wall effects were accounted for as a drift from zero in the mean displacement and suppression in the diffusivity of a particle,an analytical solution was worked out for PDF.Three distinguishable mechanisms were identified to affect the profile of particle probability distribution:external forces,turbophoresis effect,and wall-drift effect.The proposed formulation covers the Huang et al.(2009)model of a wall that produces electrostatic repulsion force and van der Waals force,as well as Monte-Carlo solutions for the Peter and Barenbrug(2002)model under a variety of relaxation times.Moreover,it successfully reproduces the two patterns of particle concentration profiles observed in experiments of sediment-laden open-channel flows.The strength of the wall-drift effect was found to be connected with the interaction frequency between particle and wall.Further exploration of the relationship among flow turbulence,particle inertia,and particle concentration is worthwhile.

HEAVY TRAFFIC LIMIT THEOREMS IN FLUID BUFFER MODELS

A fluid buffer model with Markov modulated input-output rates is considered.When traffic intensity is near its critical value, the system is known as in heavy traffic.It is shown that a suitably scaled sequence of the equilibrium buffer contents has a weakor distributional limit under heavy traffic conditions. This weak limit is a functional of adiffusion process determined by the Markov chain modulating the input and output rates.The first passage time of the reflected process is examined. It is shown that the mean firstpassage time can be obtained via a solution of a Dirichlet problem. Then the transitiondensity of the reflected process is derived by solving the Kolmogorov forward equation witha Neumann boundary condition. Furthermore, when the fast changing part of the generatorof the Markov chain is a constant matrix, the representation of the probability distributionof the reflected process is derived. Upper and lower bounds of the probability distributionare also obtained by means of asymptotic expansions of standard normal distribution.

The influence of Si substitution on soft magnetic properties and crystallization behavior in Fe_(83)B_(10)C_(6-x)Si_xCu_1 alloy system

In this study, the soft magnetic properties and crystallization behavior of Fes3B10C6-xSixCul （x=0-4） nanocrystalline alloys prepared by annealing the melt-spun amorphous ribbons have been investigated. It is found that in the Fe83B10C6-xSixCU1 alloy system, the coercivity （Hc） decreases slightly with increasing Si addition and exhibits a minimum value with composition of x = 2, while the effective permeability （Ue） shows an opposite variation trend. The saturation magnetic flux density （Bs） shows a slightly decreasing trend owing to the decreasing volume fraction of nanocrystalline phase. The Fe83B10CaSi2Cu1 nanocrystalline alloy exhibits excellent soft magnetic properties with a high Bs of 1.78 T, high ue of 13 600 and low Hc of 4 A/m.

The gamma-ray spectral index changes for blazars

Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars （53 FSRQs, 26 BL Lacs） is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence.