18 April 2013, Volume 31 Issue 11

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  • LI Benxian;LI Mengjun;SUN Duoyong
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    A dynamic society network analysis method is adapted to study terrorism organization structure and its invulnerability. Firstly, a selective attack method is proposed to destroy terrorism organization network. Secondly, the mesosphere is attacked, and then other segments are attacked according to the degree-distribution centralities of network. The minimal-cut set of graph theory is applied to scout the terrorism network of invulnerability and attack its augmentable chain. The experimental results show that these methods precede traditional attacking methods. It is easy to destroy the entire terrorism organization network.
  • YANG Yuying;CUI Zhanzhong;WANG Ling;WEI Shuangcheng
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    In view of that only the intensity information of retroreflection wave is used and the poor capacity of anti-interference in laser short-range detection, the polarization characteristics of laser beam on the metal target surface are analyzed and a reflection model of polarized laser is established. A target detection method based on polarization characteristics of reflection laser is putted forward and the simulation of polarization characteristics on the surfaces of several typical metal targets is conducted at last. By analyzing the Stokes vector of reflection laser, both of the linear polarized light and the circular polarized become elliptically polarized light after reflection and the elliptical angle and the azimuth angle vary with different metal materials. The polarization characteristics of reflection laser, which provide the basis for distinguishing targets with different materials, could improve the anti-interference capacity of laser short-range detection.
  • ZHANG Qinli;CHEN Qiusong;HU Wei;ZHOU Denghui
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    Interval layers are a key to ensure the safety of the transition from open pit to underground mining. Through simulation, finite element software is used to get the safety thickness of interval layers for Gushan Iron Mining. Firstly, a numerical simulation is carried out by using the software of ansys on several regular goaf models which have the same span(27.5m), but different thicknesses of ore pillar and different heights of goaf, optimally selecting the goaf height as 16 meters. Then, numerical simulation are created on other goaf models with different spans and thicknesses of interval layers and safety thickness of interval layers are obtained for these cases. Then five typical theoretical calculation methods are chosen to calculate its safety thickness. The result is similar with the former one. At the last, by making a combination of these two results, a consequence for different spans is got. And it is recommend 18 meters as safety thickness of interval layers for Gushan Iron Mining.
  • DENG Jun;LI Shirong;
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    Aiming at the accidents caused by moving fire source, for analyzing the influence law of moving fire on ceiling temperature of tunnels, through Fire Dynamic Simulator (FDS), the processes that fired vehicle with 20MW Heat Release Rate (HRR) travels at the speed of 0km/h (static in tunnel), 40km/h, and 60km/h, respectively in tunnel with natural ventilation are simulated. The longitudinal temperature distribution, change law of peak temperature, and its influence factors when moving fire stops and becomes stable combustion in tunnel are specially analyzed. It indicates that ventilation is main influential factor to the temperature in tunnel fire. Moving fire causes air turbulence and breaks the circulation balance of hot smoke and cold fresh air caused by ceiling jet in tunnel, making tunnel fire process more complicated. On one hand, the airflow filed movement induced by piston wind wake of moving fire promotes mixture and combustion of fuel and air, on another hand, it blocks the spread of heat released in the direction opposite to fire movement in certain degree and also entrains high temperature airflow into its spread. The research provides guidance for the study on mechanism of tunnel fire with moving fire as well as relevant fire fighting and rescue technique.
  • LI Xibing;WANG Xiran;DONG Longjun;SUN Feifei
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    Based on the uncertainty measurement theory, a thermal comfort level evaluation model for human body in mines is established. With the thermal environment of mines and the special features of human body in mind, ten factors that would influence the thermal comfort of human body are identified, and the uncertainty measurement function is formulated based on the in-situ data and investigation results. The uncertainty influencing factors in the thermal comfort evaluation are determined by qualitative and quantitative analyses, respectively. The entropy weight theory is used to calculate the index weight of these factors and the credibility degree recognition criteria are established to determine the levels. The thermal comfort evaluation is made. This model is used to evaluate the six different stages of a certain copper mine. The results show that the calculation results are consistent with the empirical values of investigations, therefore, the uncertainty measurement method is reasonable and can be applied to the practical engineering. In different depths of mines, different cooling standards should be established for the thermal comfort.
  • TONG Lili;SHAO Ge;GU Jian;XUE Junfeng;PENG Jianping;WANG Zhiqiang
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    When main feed water system or start-up feed water system is unavailable, auxiliary feed water system, as Engineered Safety Facility (ESF), provides water for Steam Generators (SG) to remove the stored and decay heat from the reactor core. In order to improve the safety of Nuclear Power Plants (NPPs) and increase operational flexibility, the water inventory of the auxiliary feed water tank is increased in the number one and two units of Fuqing NPP. The model of the NPP is built based on mechanical safety analytical code, and conservative assumptions are used in the calculation. Three typical accident sequences, such as loss of main feed water, loss of offsite power in category II accident, and main feed water line break in category IV, are selected to analyze whether or not the inventory in auxiliary water tank after improvement satisfies the relevant requirements in RCC-P. The results show that auxiliary water inventory of 713m3 is needed for loss of main feed water accident, auxiliary water inventory of 723m3 is needed for loss of offsite power accident, and auxiliary water inventory of 799m3 is needed for main feed water line break accident. The inventory in auxiliary water tank after improvement satisfies the requirements for category II and IV accidents. The safety of NPP is improved due to the inventory redundancy and a time window is also provided for the operators to perform related accident procedures.
  • ZHAO Shan;CHEN Xinhua;SUN Changyu;YU Huabing
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    The ship-radiated noise possesses a stable part of the line-spectrum at low frequency range, containing rich information, and it is meaningful for positioning and distinguishing underwater targets. In order to separate the ship-radiated noise line-spectra from the broadband background noise effectively, the method for analyzing the ship-radiated noise signals by using Adaptive Line-spectrum Enhancement (ALE) algorithm is put forward. As a variant of adaptive Finite Impulse Response (FIR) Digital Filter (DF), ALE is a typical application of adaptive noise canceller. The algorithm is able to find and match the line-spectrum signals and separate them from wide band addictive noise without reference signals. Then, the line-spectrum signals could be enhanced. By theoretical analysis simulation and actual ocean-trial, the research on the Low Frequency Acquisition and Ranging (LOFAR) spectrum shows that ALE algorithm is able to meet the expectation competently. Comparing with conventional methods, the detection performance enhances observably, and radiated noise line-spectra are able to be effectively extracted.
  • LI Sanqing;LIU Yaochi;YU Jingang;
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    Carboxyl groups are oxidized by nitric acid and introduced onto multi-walled carbon nanotubes (MWNTs). Catalyzed by ptoluenesulfonic acid (PTSA), the oxidized MWNTs (MWNTs-COOH) are reacted with hydroxypropyl-β-cyclodextrin (HP-β-CD) to obtain HP-β-CD-g-MWNTs with good dispersivity. The prepared composites are fully characterized by Transmission Electron Microscopy (TEM), Fourier Transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA), the results indicate that HP-β-CD is successfully grafted onto MWNTs. The dispersion performance test indicates that HP-β-CD-g-MWNTs are well-dispersed in the aqueous solutions, thus the composites are able to find their potential applications in biomedical materials or drug deliveries. The interactions between HP-β-CD-g-MWNTs and mandelic acid are investigated by using Ultraviolet-Visible light (Uv-Vis) absorption spectrum. The results indicate that mandelic acid is adsorbed on the surface of HP-β-CD-g-MWNTs by conjunct interactions, such as π-π stacking, polar interaction, and hydrogen bonding. Due to the molecular interactions, the absorbed molecules are able to realize controlled-releasing or sustained-releasing from the surface of MWNTs.
  • CHEN Qiuji
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    The simulation of mining subsidence plays an important role in mining environmental management and ecological restoration. Based on the GIS platform, the mining subsidence theory and geographical Cellular Automata (CA) are combined with each other, and then the mining subsidence cellular space is constructed by using the development tool of object-oriented method with the help of software of VS2010. The mining subsidence frame structure of CA model and realization method is discussed, and the mining subsidence simulation object relation graph is constructed. The evolution model of CA for mining subsidence is established based on the research result. Finally, the prototype system of mining subsidence CA is developed by taking a coal mine in Shanxi Province as an example. Based on the coal seam condition and mining method of the study area, the evolution of mining subsidence in the future is simulated using the prototype system in order to provide the basis for land reclamation and ecological restoration. The results show that object-oriented method is good for the analysis and exploitation of mining subsidence simulation system, and mining subsidence simulation based on GIS and CA, which is facilitated to the development of the system and has good compatibility, is able to show more spatiotemporal information, facilitating data management. In space division, the CA model could organically integrate into traditional method, and is able to accurately predict the future of surface subsidence damage, providing the basis for the treatment for subsidence area. Since mining subsidence relates to many subjects, there are many works need to be down in the future for further perfecting evolution model, exploring the evolution process of system in three-dimensional space, and enhancing the reality and practicability of simulation.
  • Reviews
  • LI Xiaoai;CHEN Yuhua;ZHANG Yun;WANG Xinping
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    Solving a large sparse linear system of equations is one of the most important problems in scientific and engineering computations. The Krylov subspace methods are widely used in this respect. This paper first reviews the Krylov subspace methods and their various types, such as, the orthogonal projection method (Ritz-Galerkin method), the orthogonalization method (or the minimal residual method), the bi-orthogonalization method (Petrov-Galerkin method), and the CGNE and CGNR methods for normal systems. The advantages and shortcomings of these methods are analyzed. Especially, we focus on the parallel computation of the sparse matrix-vector multiplication and the inner product. Then, this paper discusses the development of the preconditioning and the parallel preconditioning technique, the residual smoothing technology with its parallel implementation, the reasonable distribution of data, the bottleneck problem of the inner product.
  • LI Bin;CHEN Yuyan;LI Shunxiang
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    To summarize the research progress of porana genus plants in chemical constituents and pharmaceutical activities by retrieved litera tures home and abroad. It shows that 33 chemical constituents have been extracted from porana genus plants, including steroids and their glycosides, coumarins and their glycosides, flavonoids and their glycosides, lignans, benzoquinones, terpenes, amides, and phenols. Modern pharmacological research shows that compounds of porana genus plants have a variety of pharmacological activities,such as cardiac effect, anticoagulant, prevention of hyperuricemia, anti-inflammatory, antitumor, antibacterial, acaricidal activity, etc. To carry out the studies related to porana plants has the great significance for discovering and developing new medicines and new medicinal resources.