10 April 2007, Volume 25 Issue 0707
    

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    网络在安全研究专题
  • A Detection-centered Classification of Network Attacks
    . 2007, 25(0707): 5-9.
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    An intrusion detection system with multi detection engines could overcome the limitations of one with a single detection engine. But up to now, the methodology dealing with network attacks lacks theoretical guidelines for the partition of the inference function. From the detector's point of view, this paper proposes a detection-centered methodology dealing with network attacks. Network attacks can, therefore, be divided into five categories: character string attack, overflow attack, repeating attack, multi-step attack and multi-stage attack. An intrusion detection system with isomerous detection engines is built on that basis. Experiments show that it can avoid the deficiencies of existing detection methods.
  • Research on Network Security Evaluation Technology Based on Attack-defense Confrontation
    . 2007, 25(0707): 9-12.
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    In order to improve the current network security evaluation systems, a novel evaluation algorithm, called the quantitative network security evaluation based on attack-defense confrontation, is proposed in this paper. In this algorithm, the traditional risk assessment is combined with network environment factors such as the network running status, asset security characteristics and so on, and several quantitative indexes are extracted based on the analysis of factors which can affect the LAN's security situation. Then, evaluations are made based on a classification of attacks. Experiment results show that the novel algorithm can be used to extract situation information more objective and detailed so the security administrator may form a clearer picture for the LAN's security situation.
  • A Method of Dynamic Knowledge Representation and Reasoning Based on Fuzzy Petri Nets
    . 2007, 25(0707): 13-17.
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    A method of dynamic knowledge representation and reasoning based on Fuzzy Petri Nets is proposed for problems of knowledge of Fuzzy characteristics, where frequent updating of knowledge is required in an expert system. Using the data obtained from the actual environment, the parameters of the knowledge model such as weights, threshold and reliability can be adjusted by training, so the knowledge can be updated dynamically. Some useful factors of knowledge representation based on production rules and Neural Networks are integrated into the knowledge model in a clear way, with well defined meanings for parameters, and with a learning and parallel reasoning ability. The result of simulation shows that the precision of the knowledge model is improved after training.
    • Articles
  • A Model of BP-network for Bio-enzymatic Degumming of Kenaf Fiber
    . 2007, 25(0707): 18-21.
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    The enzymatic degumming of kenaf bast fiber is a nonlinear process with various coupling characteristics. In this paper, the process parameters and results obtained in degumming experiments are used in a BP neural network with 5-12-3 structure trained by traincgf function. The forecast model of degumming process has been established successfully.
  • Robust Object Identification of RoboCup Mid-size Robot
    . 2007, 25(0707): 22-25.
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    The robot in the RoboCup mid-size group match must be capable of identifying the positions and directions of other objects in the match through predefined color patterns in real time. Because of the existence of noise and the complexity of signal objects, the identification algorithm must assure the whole process of identification stable and make the response time as short as possible. The objects should be correctly classified and the possible exceptional conditions must be taken care of. So one has to study various kinds of misidentification. This paper proposes a possible algorithm to deal with this problem. The algorithm minimizes the effects of noise through the use of the prediction of the objects' moving direction and the characteristic information of objects like the color pattern, area change ratio and the density of color dots. The experiment confirms that the algorithm can minimize the effects of noise, identify objects fast and accurately under the conditions of a match.
  • Preparation of Modified Nano-molybdenum Bisulfide and Their Properties at Extreme-pressure Condition
    . 2007, 25(0707): 26-32.
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    Using pyridine dialkyldithiophasphate(PyDDP) as the surface modifying reagent, nano-molybdenum disulfide (MoS2) particles are synthesized with sodium molybdenum acid, sodium sulfide, sulfuric acid and hydroxylamine as raw materials. The technological parameters of the reduction process, the sulfur replacement and the separation process with acid are all optimized. Infrared spectrum (IR), Thermal Gravity and Differential Thermal Analysis(TG-DTA), X-Ray Diffraction(XRD) are employed to analyze the structure of nano-particles prepared. The mechanism of the surface modified nano-molybdenum disulfide is also investigated and results show that the particles are built from a layer of organic materials and a core of inorganic compound. The tribological properties of molybdenum bisulfide(MoS2) are evaluated with a four-ball test method, and the surface micrograph and the elements compositions are obtained with SEM(Scan Electron Micrograph) and EDXA(Elctron Diffraction X-ray Analysis). It is shown that the modified process could provide the materials with better surface properties.
  • Investigation on Modeling of Ecological Factors of SRB in the Treatment of Sulfate Wastewater with GA-NN
    . 2007, 25(0707): 33-35.
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    The niche of SRB is a key factor in the sulfate wastewater treatment in acidogenic-desulfate reactor. In this paper, the weights of jointing in the network are optimized with Genetic Algorithms on the basis of BPNN(Back-Propagation Neural Network) and the model . Emulation of the acidogenic-desulfate reducing system is also made by combining Back Propagation Neural Network with Genetic Algorithms. The investigation shows that the mean error obtained from GA (Genetic Algorithms) model is more accurate and credible than that from RA (Regression Analysis) model .
  • Constraint Stress in Thick Beam due to Surface Cooling
    . 2007, 25(0707): 36-38.
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    In the analysis, it is assumed that the distribution of temperature in the thick beam is expressed by an exponential function. The expressions of constraint stress are obtained for practical engineering cases. It is shown that the results are reasonable.
  • Topology Optimization for Functionally Graded Materials
    . 2007, 25(0707): 38-40.
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    By using a new criteria of evolution, the traditional Bi-directional Evolutionary Structural Optimization (BESO) method is successfully applied to the topology optimization for FGM. Graded finite elements method are used in FEA in the process of optimization.
  • Finite Element Analysis of Depurators for Cooking Oil Fume and Spraying Lacquer Fog
    . 2007, 25(0707): 41-46.
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    Flotran cell in ANSYS software is used to analyze the air current field of the filtration hole of depurators. An analyzing model for purifying cooking oil fume and spraying lacquer fog is developed and detailed solutions are obtained. The effects of different shapes of filtration hole, different thicknesses of filtration net and different wind speeds are compared.
  • Design of Evacuation Decision Making System for Hazardous Chemical Accident
    . 2007, 25(0707): 47-50.
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    With respect to hazardous chemical accidents, this paper proposes an evacuation decision making system based on ArcGIS. Its framework, functions and database design are discussed in details. Through an example of liquid chlorine of twenty tons being leaked totally within a short time under the wind speed of 5.4 m/s, how to analyze the damage and find an effective evacuation method by using the system are demonstrated.
    • Reviews
  • On Exploitation of Tea Resource and the Bioactive Substances in Tea
    . 2007, 25(0707): 51-56.
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    Tea is one of common drinks around the world. It contains multiple bioactive substances with high concentrations, and is one of the most valuable plant resources for the development of bioactive products. China is faced with a serious problem of over-production of tea, at the expense tea farmers. This article gives a review of researches and exploitations of tea resource and the bioactive substances in tea.
  • Advances in Bio-control of Plant Diseases and Pests in China
    . 2007, 25(0707): 56-60.
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    The advances of biological control of plant diseases and pests in China are reviewed in this paper, based on the journal articles and works published within recent 5 years, including the national biological control research programs, the development of bio-pesticides, utilizations of natural enemies and their commercialisation.
    • 研究报告
  • Concept of Green Mining and Its Technical Framework
    . 2007, 25(0707): 61-65.
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    With respect to the serious environment problems of coal mining，a new concept of green mining is proposed, which is related to viewing and treating coal, coal-bed methane, ground water，rock waste and any other useful resources in a broad sense as "resources". It is based on the law of strata movement to prevent or to alleviate the adverse influence of coal mining on other resources and the environment as far as possible. The goal is to maximize the economic and social benefits. The technical framework of green mining includes water-preservation in mining areas, coal mining to retard surface subsidence，simultaneous extraction of coal and coal-bed methane, reduction of rock waste, underground coal gasification, and others.
  • Genetic Algorithm for Item Selections in Retail Business
    . 2007, 25(0707): 65-70.
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    A fundamental problem in retail business is selecting items with consideration of "cross-selling effect". Recent studies show that the problem is NP-hard. In this paper, the genetic algorithm is applied to this problem, and a quantitative analysis method for "cross-selling effect" is proposed, using quantitative association rules, and a newly developed data mining technique to identify quantitative affinities in large transaction databases. Based on the features of the genetic algorithm, a method of defining imprecise fitness function is proposed, which can be used for solving item selection problems with imprecision cross-selling effect.
  • Capacity Investments in Supply Chain with Rebate Contracts
    . 2007, 25(0707): 71-76.
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    In this paper, a supply chain consisting of one supplier and one manufacturer, with the latter being the only source for a customized product is considereel. Demand is stochastic, the supplier has to invest in capacity before seeing the demand, and the manufacturer makes his final order after seeing the demand. To allow for the loss of overcapacity, the supplier will build less capacity than what is the optimal for the supply chain. In this paper, two kinds of rebate contracts are put forward, the former can induce the supplier to invest in more capacity than under the wholesale price contract, the latter coordinates the supply chain. Finally the three kinds of contracts are compared.

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