Volume 34,Issue 4,2011 Table of Contents

1 Experimental analysis of coal bed methane desorption and seepage under sonic vibrating of cavitation water jets

LI Xiao-hong , FENG Ming-tao , ZHOU Dong-ping , XIA Bin-wei

2011, 34(4):1-5. DOI: 10.11835/j.issn.1000-582X.2011.04.001

[Abstract](2326) [HTML](0) [PDF 5.97 M](1810)

Abstract:
A way to enhance coal bed methane desorption and seepage by sonic vibrating of cavitataion water jets is proposed because the gas coal seams have the intrinsic properties of micro-porosity, low permeability and high adsorption. The mechanisms of how the sonic vibrating effects promote methane desorption and seepage are analyzed, and the contrast experiments of methane desorption and seepage under sonic vibrating effects are also provided. The results show: when the cavitation number is 0.020 0, under sonic vibrating effects, the volume of coal bed methane desorption increases by 36.9%, and the time for coal bed methane desorption reduces by 19.6%. The speed of coal seams methane seepage is significantly increased by 35.3% and arrives at 0.383 3 ml/s.

2 Experimental analysis of the deformation of sandstone under cyclic pore water pressure and wavelet transformation

YANG Hong-wei , XU Jiang , WU Xin , PENG Shou-jian , ZHANG Yuan

2011, 34(4):6-12. DOI: 10.11835/j.issn.1000-582X.2011.04.002

[Abstract](3959) [HTML](0) [PDF 10.16 M](10189)

Abstract:
To explore the characteristics of deformation of sandstone under cyclic pore water pressure, the experiments with different axial stresses (60%, 70% and 80% of peak intensity) of sandstone subjected to cyclic pore water loading are investigated by using MTS815 rock mechanics testing system, and irregular small deformation in deformation curve of sandstone are also processed by wavelet transformation of Matlab. The results show that with the increase of constant axial stress, fatigue deformation under cyclic pore water pressure will accelerate the failure of the sandstone. With the increase of the number of cyclic pore water pressure, the deformation evolution of the plastic-loop is illustrated as sparse-dense-sparse. The deformation curves of sandstone under cyclic pore water pressure affected by many factors are decomposed, reconfigurable processed and evaluated by using wavelet transformation, which indicates that the basic curve with optimal decomposition scale fits well with the experimental curves and reveals the deformation evolution of sandstone.

3 Simulation and analysis of mechanics of coal and gas delay outburst

LI Xiao-quan , YIN Guang-zhi , CAI Bo , JIANG Chang-bao , LI Gao-shuai

2011, 34(4):13-19. DOI: 10.11835/j.issn.1000-582X.2011.04.003

[Abstract](1862) [HTML](0) [PDF 8.19 M](1356)

Abstract:
By using the large-scale test device for coal and gas outburst simulation, the experiments of coal and gas delay outburst are conducted under the conditions of no disturbance and ball stricked disturbance of unbalanced load. The results show that delay outburst has four stages: preparation, occurrence, development and dissolution. The coal particle of outburst has size classification. The outburst coal can be divided into three parts: outburst holes, disturbed and no disturbed zone. The threshold value of delay outburst decreases and outburst possibility increases under the disturbance. The critical gas pressure has linear relation with the horizontal stress of delay outburst. The relationship between the intensity of outburst and the critical gas pressure is nonlinear. The conception of coal and gas delay outburst is redefined as the coal and gas outburst that is occurred when the main breaking coal or rocks works completed and the new mining spaces formed or when the auxiliary operation finished. The preliminary analysis of mechanics of coal and gas delay outburst is also presented.

4 Mechanism analysis of permeability based on promoting coal matrix shrinkage by water jet

LU Yi-yu , SONG Chen-peng , LIU Yong , KANG Yong

2011, 34(4):20-23. DOI: 10.11835/j.issn.1000-582X.2011.04.004

[Abstract](2386) [HTML](0) [PDF 3.52 M](1257)

Abstract:
High pressure pulsed water jet (HPWJ) is a new technology of effectively improving coal seam permeability. However, the mechanism of increased permeability is not yet clear, which restricts the application of HPWJ in different coal seams. From the perspective of improving permeability by coal matrix shrinkage, the impelled dynamic equations is established based on analysis of coal dynamic effects by water jet. According to theoretical analysis of the stress state of coal matrix, it is concluded that HPWJ can promote coal matrix shrinkage, and the relationship equation between jet impact-coal matrix is derived. Besides, the gas seepage function in the coal slotted by the HPWJ is gained by using PM model, which provides theoretical support for generalizing the technology in the coal mine.

5 Numerical simulation of seepage field of gas extraction drilling of single bedding of mining-coal bed

JIANG Jiji , WANG Hongtu , WANG Zai-qing , HU Guo-zhong , YUAN Zhi-gang

2011, 34(4):24-29. DOI: 10.11835/j.issn.1000-582X.2011.04.005

[Abstract](2684) [HTML](0) [PDF 6.23 M](1386)

Abstract:
Aiming at the problem of reasonable decorate of coal gas extraction drilling, combining with the initial and boundary condition of borehole extraction, the solid and gas coupling mathematical model of gas seepage of borehole extraction is deduced based on established control equations of seepage field and deformation field. Taking gas extraction of stone coal slit as an example, according to the characteristics of coal seam in the research, the numerical simulation method is used to obtain the distribution rule of gas pressure, coalbed gas permeability, and coalbed gas seepage velocity as well as seam deformation. The effective radius of gas extraction drilling of single bedding about mining-coal bed is determined, which provides the basis for optimum arrangement of gas extraction drilling of single bedding. The results show that the effective radius of stone coal is about 4 m. If the prolonging drilling drainage time is less than 20%, the drilling quantities would reduce by about 50%.

6 Multi-field coupling effect on coalbed methane seepage characteristics and numerical simulation

JIANG Yong-dong , YANG Xing-yang , XIONG Ling , ZHENG Quan

2011, 34(4):30-35. DOI: 10.11835/j.issn.1000-582X.2011.04.006

[Abstract](2017) [HTML](0) [PDF 7.17 M](1317)

Abstract:
This paper studies the seepage of coal samples under the influence of each single factor, the axial stress, confining pressure, gas pressure, and temperature by experiments. It uses Ansys12.0 to numerically simulate the law of coalbed methane seepage, coal deformation, pore pressure, the distribution of flow field under the influence of each single field and multi-field coupled. The numerical simulation show that the result of numerical simulation of gas seepage law in the coal under each single fields is basically the same as the experimental result. The curve of gas seepage and average effective stress under the condition of multi-field coupled is negative exponential relationship. Stress influenced the deformation of the specimen is greater than the seepage field. The axial stress on the deformation of the specimen is greater than confining presses The influence on the flow field by confining pressure is greater than axial stress, the influence of axial stress on the pore pressure is greater than confining pressure, pore-pressure under the action of multi-field is bigger than pro-pressure under each single field. To study the seepage law of coalbed methane, it should consider the influence of gas-solid-heat at the same time.

7 Performance analysis of StimGun technology

LI Lin , CHEN Feng , JIANG De-yi , LIU Chun

2011, 34(4):36-39. DOI: 10.11835/j.issn.1000-582X.2011.04.007

[Abstract](2219) [HTML](0) [PDF 6.00 M](1222)

Abstract:
With further exploration and development of oil and gas wells, it is found that the unconventional oil-gas bed occupies a major proportion in gas reserves. However, it is difficult to obtain satisfactory control by using conventional perforation technology because of its characteristics of low pore, low permeability and compact lithology in the unconventional oil-gas bed. The StimGun tech (synergize compound perforation) is described as following: after the perforating gun is fired, propellant burns with high-energy gas produced. Then the high-energy gas enters the perforating hole and forms multi-path cracks around perforated hole, which connects with the natural cracks and improves the permeability of oil and gas bed. The application and advantage of StimGun are introduced. The Stimgun is successfully applied in Sichuan LG oilfield. It can control the fracture heights effectively and remove contamination formation with no water producing, and it is also a great help to increase productivity of the oil-gas bed with low permeability.

8 Numerical simulation on damage field of high pressure waterjet breaking rock under high ambient pressure

LIU Jia-liang , SI Hu

2011, 34(4):40-46. DOI: 10.11835/j.issn.1000-582X.2011.04.008

[Abstract](2452) [HTML](0) [PDF 8.41 M](2052)

Abstract:
This paper uses ALE algorithm to develop a numerical model of breaking rock under high pressure water jet, in consideration of rock in a state of high ambient pressure. The simulation results show that damage evolution speed along axial direction of rock under high ambient pressure is lower than rock without ambient pressure, and ambient pressure has less impact on the damage evolution speed along radial direction. Through analyzing damage evolution of four typical element under water jet with different speed, it shows that increasing water jet speed can improve breaking rock efficiency. The relationship between water jet speed and performance of high pressure water jet breaking rock wis explained in theory.

9 Kinetic mechanism of inorganic scale plugging removal atnear wellbore zone by high power ultrasonic technology

PU Chun-sheng , RAO Peng , XU Hong-xing , WU Fei-peng

2011, 34(4):47-52. DOI: 10.11835/j.issn.1000-582X.2011.04.009

[Abstract](2158) [HTML](0) [PDF 5.54 M](3164)

Abstract:
Based on the theory of solid and liquid coupling wave mechanics, the micro-dynamical characteristics caused by the transport of ultrasonic in porous media at near wellbore zone, including the elastic deformation of rock, the elastic crossflow of pore fluid and frame solid, and fluid squirt-flow produced by pore elastic deformation, are analyzed. Analysis of kinetics of peristaltic difference of porosity radius in porous media is presented. The characteristics of the removal of inorganic scale particle in porous media by using ultrasonic technology are also studied. Besides, by applying high power ultrasonic technology, the acoustic energy gathering in porous media at near wellbore zone leading to fracture of part rocks is illustrated. According to these analyses, the micro-dynamical mechanisms, such as inorganic scale fragmentation, ultrasonic cavitations, ultrasonic friction, ultrasonic peristaltic transport and ultrasonic fracture-making, occurred in inorganic scale plugging removal by high power ultrasonic technology are proposed.

10 Characteristics of immiscible CO2 displacement in extremely low permeability reservoir

SU Yu-liang , WU Chun-xin , ZHANG Qi , WU Xiao-dong

2011, 34(4):53-57. DOI: 10.11835/j.issn.1000-582X.2011.04.010

[Abstract](1858) [HTML](0) [PDF 4.85 M](1280)

Abstract:
The research of characteristics of CO2 flooding in extremely low-permeability reservoirs are of great significance.A linear dimension immiscible CO2 displacement mathematics model considering threshold pressure gradient and characteristics of CO2 which describes extremely low permeability reservoir is established. After numerical resolution, analyze the influence of threshold pressure gradient and characteristics of CO2 on the displacement characteristics of extremely low permeability reservoir. The results show that: the existence of threshold pressure gradient make average gas saturation and gas rate increase rapidly, and then the efficiency of displacement is reduced; during CO2 flooding, the expansion and viscosity reduction of crude oil make effect displacement better. The research has theory direction for the reasonable development of low permeability reservoir.

11 Experimental study of coalbed methane seepage in fuxin basin

ZHANG Xian-min , FENG Qi-hong , CHEN Dong , HUANG Yong

2011, 34(4):58-61. DOI: 10.11835/j.issn.1000-582X.2011.04.011

[Abstract](2166) [HTML](0) [PDF 4.54 M](1354)

Abstract:
Taking raw coal samples collected from the wangying colliery in Fuxin basin as the research object, the experiment of coalbed methane seepage law is conducted by the triaxial osmoscope and the relationship between effective stress and coal permeability is presented. The experiment results indicate that the coal permeability is of stress sensitivity and tended to decline in exponent with the increment of effective stress, which is consistent with the former research results. The seepage flow curves from experiments demonstrate the nonlinear characteristics under different confining pressures and moisture contents, and it accurately reflecte the effect of coal body deformation on the coalbed methane seepage flow in the experimental process. Therefore considering the influence of effective stress on the coal body deformation, a new motion equation for the nonlinear percolation characteristic of coalbed methane is established. Moreover, the motion equation is correlated well with the experimental data, and the fitting correlation coefficients are above 99.6%.

12 Shale gas seepage mechanism and fractured wells’ production evaluation

DUAN Yong-gang , WEI Ming-qiang , LI Jian-qiu , TANG Yan

2011, 34(4):62-66. DOI: 10.11835/j.issn.1000-582X.2011.04.012

[Abstract](2824) [HTML](0) [PDF 5.16 M](1887)

Abstract:
To know the dynamic characteristics of shale gas reservoirs’ production and to improve shale gas wells production, it is very important to research on shale gas seepage mechanism and production evaluation. The main difference between shale gas reservoir and conventional gas reservoir is that shale gas reservoir has the adsorption and desorption characteristics. Combined with shale gas seepage characteristics, using point source function, the mass conservation law and Langmuir isotherm equation to describe the shale gas adsorption and desorption phenomena, it establishes dual media shale fracturing wells’ seepage model. By the numerical inversion and computer programming, it draws production decline curve charts and analysises the Langmuir volume, Langmuir pressure, elastic storativity ratio, cross flow coefficient, borders, fracture length and other factors on the impact of shale gas wells production.

13 Thickness Change of Water film—New Mechanism of Salt Sensitivity in Extra-low Permeability Sandstone Reservoirs

YU Yang-Feng , KANG Yi-Li , YOU Li-Jun

2011, 34(4):67-71. DOI: 10.11835/j.issn.1000-582X.2011.04.013

[Abstract](1855) [HTML](0) [PDF 5.42 M](1474)

Abstract:
Core samples of sandstone with extra-low permeability from Huimin area in Shengli oil field were selected, and the shape and composition of clay mineral in core samples were analyzed by SEM and XRD. Electrokinetic potential of clay minerals in four experimental fluids was measured, under reference to formation water’s salinity and different pH by means of Zeta Probe (potential measuring apparatus). The results show that the positive ion concentration in these experimental fluids is higher than the critical value to balance the negative ions on the face of clay minerals. That makes the positive ion in the state of over-saturated and keeps the value of electrokinetic potential positive in a wide range of pH value. We have evaluated the salt sensitivity extent of the samples, and analysed the data with electrokinetic potential of clay minerals in experimental fluids. The results show that the salt sensitivity mechanism of extra-low permeability sandstone reservoirs, with kaolinite-chlorite-illite and chlorite-illite as the main clay mineral composition, is that with the formation salinity decreasing, the thickness of water film increases, which brings about decreasing of effective pore-throat and enhancement of permeative resistance.

14 Test and numerical simulation on effect of enhanced coalbed methane drawing by injecting gas under coal mine

LI Zhi-qiang , WANG Zhao-feng

2011, 34(4):72-77. DOI: 10.11835/j.issn.1000-582X.2011.04.014

[Abstract](1966) [HTML](0) [PDF 7.47 M](1971)

Abstract:
In order to improve the extraction effect of ultra-low permeability coalbed methane, injecting and drawing industry test of enhanced coalbed methane recovery is carried out by injecting concentration 78% N2 under 850 m depth coal mine of Tianfu Mining Co. Ltd.，in Chongqing. The experiments of free methane emission, vacuum pumping, side injecting and side emission, side injecting and side drawing and intermittent injecting are tested under the condition of single hole and multi holes respectively. The testing results indicate that time-concentration curve of methane drawing is a single peak wave curve which increases and decreases during injecting N2 after reaching the limits of ordinary extraction. The methane concentration of intermittent injecting gas is greater than that of side injecting and side drawing. However, the former declines rapidly and has a shorter migration distance than the latter. The injecting effect of long time side injecting and side drawing is better than that of intermittent injecting. When hole space is 4 m, permeability 1.112×10-4mD, the methane recovery ratio increases to 58.6％ from conventional recovery ratio 52.4% after injecting 5 day. Meanwhile, the seepage flow equation of injecting air is provided and the parameters, such as rational hole mesh space, time and pressure of injecting gas, are simulated. At the same time, application condition and assistant technology about injecting gas are discussed, which provides engineering and theoretical reference to promote the injecting gas technology. Also, the problem of variable definite conditions seepage flow equation is put forward.

15 Fractal analysis of Kozeny-Carman constant in the homogenous porous media

XU Peng , QIU Shu-xia , JIANG Zhou-ting , JIANG Ying

2011, 34(4):78-82. DOI: 10.11835/j.issn.1000-582X.2011.04.015

[Abstract](6864) [HTML](0) [PDF 5.03 M](2304)

Abstract:
The semi-empirical Kozeny-Carman (KC) equation，the most well-known permeability-porosity relation, is widely used in the field of seepage flow in porous media. However, the physical mechanisms behind the empirical KC constant are not clear, and the KC constant has not been proved to be a constant. The fractal scaling laws of pores have been extensively found in porous media. Therefore, the effective permeability of homogenous porous media is presented and the analytical expression of KC constant is derived based on the fractal characteristics of porous media and the microcosmic geometrical model. The results indicate that the fractal analytical expression of KC constant depends on the micro-structure of porous media. As a function of porosity and fractal dimensions, KC constant increases with the increase of porosity.

16 Experimental study on permeability rules of coal considering sorption and long-term stress

SUN Wei-ji , LIANG Bing , LI Hui , BAI Yun-peng , GAI Di

2011, 34(4):83-87. DOI: 10.11835/j.issn.1000-582X.2011.04.016

[Abstract](1687) [HTML](0) [PDF 7.28 M](1276)

Abstract:
The paper studies the permeability rules of coal during methane sorption and long-term triaxial load by self-manufactured triaxial permeation apparatus. The experimental coal samples are excavated from Fuxin Stratum Coal seam of HengDa Coal Industry Co., Ltd in Fuxin city. The experiment results show that: the value of coal permeability considering methane adsorption is lower than that without methane adsorption, reducing by 48.94%~82.18%; slippage effect exists in coal after sorpting methane. Coal permeability has significant reduce by 82.05%~92.65% under 18 MPa total stress after 78 day, coal permeability variations with time can be described by negative exponential function. The value of permeability of coal sample is higher than that without stress release condition, but is lower than that under initial condition, which is loaded again after stress release. The value of coal permeability is higher than reservoir permeability under initial stratum condition by current experiment methods.

17 The fractal characterization of pore structure for some numerical rocks and prediction of permeabilities

ZHAO Ming , YU Bo-ming

2011, 34(4):88-94. DOI: 10.11835/j.issn.1000-582X.2011.04.017

[Abstract](2080) [HTML](0) [PDF 5.93 M](1810)

Abstract:
This paper uses the fractal theory of pore structures for porous media to study the fractal characterization of pore structure for nine numerical rocks. The results show that the fractal dimension of solid phase is usually greater than the pore fractal dimension, and its fractal scaling regions is less than the one of pore phase. This indicates that the numerical rock is an approximate two-phase fractal porous media. The porosities, volume fractions and permeabilities of nine numerical rocks are predicted. The results show that the fractal theory about pore structures of numerical rocks is effective in describing the porosity and permeability. Moreover, it seems to be more effective for solid phase in approximate two-phase fractal porous media. When predicting permeability using the fractal theory, it is very important to accurately determine the maximum pore size and the range of statistical self-similarity. By comparing the two kinds of predicted permeabilities，it is found that the FT method used by this paper is more accurate, more general and less computational cost than the PNEM method which has been worldwide used.

18 The influence of stress sensitivity on productionof hydraulically-fractured tight gas wells

LUO Rui-lan , LEI Qun , FAN Ji-wu , LIAO Hong-mei , WANG Zhe

2011, 34(4):95-99. DOI: 10.11835/j.issn.1000-582X.2011.04.018

[Abstract](1891) [HTML](0) [PDF 7.53 M](1313)

Abstract:
This paper takes Sulige Gas Field as a case study and used three methods including laboratory experiments,production performance analysis and reservoir simulation to study the influence of stress sensitivity on production of fractured tight gas wells.The results show that the fracture length and conductivity of hydraulically created fracture are reduced more than 50%,and the stress sensitivity of hydraulically created fracture is stronger than that of matrix.With the increase of gas production,the influence of stress sensitivity becomes stronger,and finally results in 18% reduction of gas production,and hydraulically created fractures play an important role in the influence of stress sensitivity.

19 Study on strain localization and progressive failureof surrounding rock under high pressure environment

ZHAO Yu , ZHANG Chun-wen , LIU Xing-rong , CHEN Lu-wang

2011, 34(4):100-106. DOI: 10.11835/j.issn.1000-582X.2011.04.019

[Abstract](2587) [HTML](0) [PDF 7.69 M](1754)

Abstract:
This paper uses the Mohr-Coulomb criterion with tension cut-off strain-softening model and the large-strain calculation method to study the localized deformation and progressive failure.It investigates the process of stain localization appearing,growing and sample failure,and uses the physical and numerical simulation to explore the relationship between strain localization and progressive failure of surrounding rock.The results show that the soften character of rock sample is caused by stain localization.The breach point of progressive failure is founded based on the distribution law of plastic zones and soften strips.The key causes of the tunnel convergence deformation after opening are the plastic extrusion and the elastic deformation of rock yield units caused by stress release.

20 Analysis of concrete strength effective factors of diagonal strutmechanism on frame exterior beam-column joints

CUI Jian-yu , SUN Jian-gang , SONG Yu-pu , WATANABE Fumio

2011, 34(4):107-112. DOI: 10.11835/j.issn.1000-582X.2011.04.020

[Abstract](2103) [HTML](0) [PDF 6.39 M](1319)

Abstract:
This paper uses the strut-truss model to analyze the shear strength of reinforced concrete frame exterior joints through thirty-five shear failure type joints without beam flexural yield and six shear failure joints after beam flexural yield.It discusses the influence of parameters including concrete compressive strength,column axial-compression ratio,amount of joint horizontal or vertical hoop,and angle of strut mechanism etc.,on concrete strength effective factor ρ of diagonal strut mechanism.The analysis results show that ρ value deterioration ratio at peak load increases with the increase od concrete strength.The effect of joint hoop on ρ value deterioration is more significant using ordinary strength concrete than the case using high strength concrete.The contribution of strut mechanism to joint shear force is more than 80% when joint shear reinforcement ration is less than 0.3%.The joint strength equation is proposed based on the analysis results of the factor ρ,and the calculated values agree well with the experimental results.

21 Low complexity rate control scheme for real-time video coding

LIU Xiao-ming , LI Yu-hui , ZHONG Yuan-hong

2011, 34(4):113-117. DOI: 10.11835/j.issn.1000-582X.2011.04.021

[Abstract](2150) [HTML](0) [PDF 5.32 M](1755)

Abstract:
Considering the deficiency of H.264 rate control scheme and the coding efficiency requirements for real-time encoding,a low complexity rate control algorithm in MB-layer is proposed..MAD is predicted by combining motion vector and the temporal and spatial correlation to reduce the complexity of G012-MAD prediction algorithm from linear regression to the complexity of the weighted average. For the rate-distortion model,the linear model with low computational complexity instead of the quadratic fitting algorithm in G012 is used,while the possibility of is discussed combining with SSIM. For the fluctuation of the PSNR of the coded image with large movement,the determination of QP in GOP layer and the bit allocation of P frame are improved,and the current quantization parameter is adjusted by making full use of the information of coded MBto control the rateeffectively. The experimental results show that the algorithm is more effective in resisting the fluctuation of PSNR for smoothly output sequence,and can decrease computational complexity.

22 Attack modeling using colored petri net and alerts correlation algorithms design

DU Jian-jun , WU Zhong-fu , CHEN Ming

2011, 34(4):118-124. DOI: 10.11835/j.issn.1000-582X.2011.04.022

[Abstract](1759) [HTML](0) [PDF 7.86 M](1423)

Abstract:
In order to improve the alerts quality and prediction capability of traditional intrusion detection systems (IDS), the advanced alerts correlation algorithms are proposed, which is based on attack scenarios modeling using colored petri net (CPN). The current analysis approach information filtering is updated to messages logic deduction by reasoning under the model. The alert and the attack are converted to two different parameters for computation. By means of transforming CPN model and calculating the minimal covering set, the algorithms for multi-step attack and cooperative attack are designed. The experimental alerts correlation analysis system (ACAS) is programmed. That experiment results indicate that these algorithms could be applied to improve the alerts quality and prediction ability of IDS effectively.

23 Energy-aware scheduling of reward maximum in real-time systems

FU Li , LUO Jun , CHEN Wei-min , LIU Yong-feng

2011, 34(4):125-129. DOI: 10.11835/j.issn.1000-582X.2011.04.023

[Abstract](2196) [HTML](0) [PDF 5.43 M](1242)

Abstract:
A novel algorithm is proposed for energy-aware scheduling of periodic tasks on variable voltage processors in the real-time systems. Based on the combined idea of artificial bee colony algorithm with greedy algorithm, different speed is allocated for different tasks to ensure the execution of tasks with higher value density. Simulation results show that the system reward of energy per unit is increased with the decreasing of energy constraint, therefore the scheduling algorithm is of the energy awareness. Compared with the greedy algorithm, the rewards of the real-time system using the greedy artificial bee colony algorithm are averagely improved by 78% while energy constraint factor is 0.1. Mmore system rewards can be obtained with the increasing number of tasks or energy constraints.

24 Better subcarrier bases for powerline communication system

LI Jiao-jun , LI Heng , SU Li-yun , LI Gang

2011, 34(4):130-133. DOI: 10.11835/j.issn.1000-582X.2011.04.024

[Abstract](2556) [HTML](0) [PDF 3.64 M](1302)

Abstract:
To solve the frequency dispersive feature in powerline channel, the quthors analyzed the anti-interference performance of modulation schemes with different subcarrier bases, and use orthogonal wavelet packet as subcarrier base instead of sine base in OFDM to suppress multi-path effect and frequency selective fading by its orthogonality in powerline channel. Through experiment, performances of wavelet packet modulation with different wavelet packets and OFDM are analyzed. Experiment results indicate that when the SNR has reached a certain level, orthogonal wavelet packet modulation has better performance than bi-orthogonal wavelet packet and sine base.

25 Shearer self-adaptive memory cutting

XU Zhi-peng , WANG Zhong-bin , MI Jin-peng

2011, 34(4):134-140. DOI: 10.11835/j.issn.1000-582X.2011.04.025

[Abstract](2732) [HTML](0) [PDF 7.32 M](1656)

Abstract:
Considering the previous technology of memory cutting cannot adapt to the complicated geological condition in China, the technology of shearer self-adaptive memory cutting based on fuzzy control theory, the shearer positioning system and fuzzy control system of self-adaptive cutting are designed. These systems can get the message of shearer’s position and attitude at any point, trace the memorial cutting path automatically, judge whether the shearer cuts rocks based on fuzzy control theory and find the optimal scheme when it works. The authors make the experiment of path tracing in laboratory and the experiment of self-adaptive adjust in Xi'an Coal Mining Machinery Co., Ltd. All the experimental results show that this technology not only can realize the shearer memory cutting but also can discriminate the abnormal state of shearer cutting rocks, then adjust the drawing speed and drum height self-adaptively. This technology can satisfy the control requirements under the complicated geological condition.

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