Table of Content

    16 June 2011
    Volume 41 Issue 3
    A message propagation algorithm computing set of key literals of a formula
    WANG Xiao-feng, XU Dao-yun, QIN Yong-bin
    Abstract ( 360 )   PDF (542KB) ( 1280 )   Save
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    The difficulty of solving Boolean formulae is mainly decided by the key literals. If the key literals or subset of formulas could be found, they  would be tractable to solve the formula. The principle of the warning propagation was studied, and it was found that the decision part variables of high probability were important for solving the Boolean formulae. It was also found that if the warning message had consistency between the clause and variable, the variable could decide the clause satisfiability, while other variables did not contribute to satisfiability of the clause. Furthermore, it was proved that the part variables were the subset of the key literals when the warning propagation was convergent, which showed that the warning propagation could be used to find the key literals for the formulae. Finally, the massage passing algorithm to find the key literals was given by the warning propagation characterization.

    Ensemble learning based feature selection for imbalanced problems
    LI Xia1, WANG Lian-xi2, JIANG Sheng-yi1
    Abstract ( 340 )   PDF (381KB) ( 2024 )   Save
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    The traditional feature selection methods are basically aimed for getting the optimal accuracy without full consideration of the data distribution, which can not achieve promising results on imbalanced datasets. A new feature selection method was proposed based on the data distribution modification  for imbalanced data sets. This approach could modify data distribution  many times by sampling with replacement. The instances of large classes were equal to the minor class samples in each new dataset. Finally, the final selected features were generated by voting mechanism for ensemble learning, which could combine the selected features by receiving more votes   than half from all the new training datasets. Experimental results on several UCI datasets showed that the proposed method was an effective feature selection approach for imbalance problems.

    An algorithm for clustering uncertain categorical data
    based on similarity probability
    ZHANG Xinmeng, JIANG Shengyi
    Abstract ( 378 )   PDF (382KB) ( 1319 )   Save
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    Aimed at processing the uncertain categorical data, an efficient uncertain data clustering algorithm, the USqueezer algorithm, was proposed based on the squeezer algorithm. First, this algorithm computed the sum of similarity probability between  uncertain categorical data and each existing cluster. Comparing the largest similarity with a given threshold, it was found that if the largest similarity was greater than the threshold value, the uncertain data would be assigned to this cluster, otherwise the uncertain categorical data was created as a new cluster. Experimental results showed that this algorithm could be effectively used in clustering the uncertain categorical data with a small amount of memory and time.

    Pose estimation based on semi-supervised latent Dirichlet allocation
    WEI Wei, ZHANG Yanning
    Abstract ( 364 )   PDF (983KB) ( 3091 )   Save
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    Topics cannot be labeled in the unsupervised topic model, while the labeling work in supervised topic models is tedious and subjective. To solve these problems, a semisupervised topic model was proposed. First, the locationirrelevant local features were detected and described by the scaleinvariant feature transform (SIFT), based on which images were represented by a bag of visual words. Then partial labels were introduced to the topicword level distribution in the latent Dirichlet allocation (LDA) model to guide the classification of the unlabeled data, which resulted in a semisupervised LDA (SSLDA) model. The validation on head pose estimation showed the classification rate of the proposed method was 9.0%~24.7% higher than that of LDA. And the pose classification rate on partially occluded and misaligned face images was 8.8% and 21.5%~39.8% higher than multi-pose PCA method. With a small amount of labeled images, the proposed SSLDA model approaches the fully supervised LDA method. And it is applicable to other image classification problems.

    The application of a multi-output support vector regression
    machine in time-dependent variational inequalities
    ZHAO Yanyan, FAN Liya
    Abstract ( 361 )   PDF (616KB) ( 1250 )   Save
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    The method of a support vector regression machine was  developed for solving single output regression problems. However many questions belong to multioutput regression in practice. In order to deal with these  problems, the support vector regression machine was extended to multioutput by parallel operation. And it was applied to solve the problem of timedependent variational inequalities which describe dynamic traffic equilibrium. The result of one experiment showed that it had faster calculation speed and better fitting effect than a singleoutput support vector regression machine and linear interpolation. The algorithm promoted the study of a multioutput support vector regression machine and provided a novel means to solve the problem of timedependent variational inequalities.

    Multi-channel color image blind watermarking algorithm based on DCT
    LIU Zhijun
    Abstract ( 335 )   PDF (712KB) ( 1566 )   Save
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    The embedding algorithm,  based on the property of human visual system(HVS) calculating watermarking intensity factor of carrier image blocks, applied transmitting diversity technique embedding encryption watermarking in 3 color channels of carrier image DCT and the extraction algorithm, which extracted 3 watermarking from 3 color channels, made use of image fusion methods achieving the last watermarking to heighten the resisting attack ability of watermarking was proposed. The algorithm, image capacity experiments, JPEG compression, cutting operation, noise and filter attacking experiments were  achieved in the matlab. Experimental results showed  that the algorithm has larger embedding capacity, lower bit error  rate and stronger invisibility and robustness when images are attacked.

    Novel model for brain MR images segmentation and bias correction
    in the presence of intensity inhomogeneity
    WANG Haijun, LIU Ming
    Abstract ( 467 )   PDF (1831KB) ( 1636 )   Save
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    To solve the intensity homogeneity in the segmentation of magnetic resonance (MR) images, a twophase level set model for segmentation of brain MR images was presented. The proposed model which utilized local image intensities can segment brain MR images and simultaneously corrects bias. The results showed that the new model could effectively segment MR images and there were better views of recuperative images.

    Sub-sampling in flat delay estimation with application to an acoustic
     echo cancellation system
    WANG Xin-yi1, DU Guang2*
    Abstract ( 403 )   PDF (1306KB) ( 1825 )   Save
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     A sub-sampling flat delay estimation algorithm was proposed. The proposed algorithm performed speech signal whitening and desampling before the delay estimation. This arithmetic could effectively suppress the side lobe of the generalized crosscorrelation function  and could overcome the robust problem in the conventional time delay estimation algorithm based on the generalized cross-correlation function. Finally, an acoustic echo cancellation system was designed with the proposed flat delay estimation module. Computer simulation showed that the proposed algorithm performed better than the conventional one.

    Resilient static output feedback stabilization for
    controlled positive time-delay systems
    LI Zhenbo1, ZHU Shuqian2
    Abstract ( 276 )   PDF (362KB) ( 1398 )   Save
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    The problem of resilient static output feedback stabilization was investigated for controlled positive timedelay systems with interval uncertainties. By introducing a small scalar, a necessary and sufficient condition was obtained for the asymptotical stability of positive timedelay systems, which was more useful when designing output feedback controllers since the Lyapunov matrix was separated from the system matrices. Based on the above condition and by utilizing the technique of matrix inequality, for different cases of the control matrix, necessary and sufficient/sufficient conditions were established for the existence of the resilient controller with interval additive gain variation and  detailed expressions of the controller were also given. The desired controller gain matrices could be effectively determined  via  cone complementarity linearization techniques. A numerical example was presented to illustrate the effectiveness of the proposed method.

    Fault estimator design for switched systems-application
    to the three-tank system
    YUAN Shuai1, LIU Xinzhi1, 2*
    Abstract ( 348 )   PDF (698KB) ( 1796 )   Save
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    The fault estimation problem of a practical switched system composed of the threetank system was addressed. By using the mechanism modeling approach, a general mathematic model was established. All the possible faults were considered in the modeling process. Then based on the average dwell time approach and the H  filtering technique, sufficient existence conditions of the fault estimator were derived. Moreover, the parameter matrices and suitable switching rule were obtained by solving a set of linear matrix inequalities (LMIs). An example was given to show the effectiveness of the obtained results.

    An efficient method for the passivity enforcement of
    delayed macromodels
    LI Junhui
    Abstract ( 345 )   PDF (809KB) ( 1076 )   Save
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    Passivity violated delayed macromodels will lead to exponential divergence of the waveform in  time domain simulation. The causality of the delayed macromodels was ensured by conventional modeling strategies. But the passivity was not guaranteed. Based on this consideration, an efficient method for the passivity enforcement of delayed macromodels was presented, which is a generalization of the passivity enforcement method for lumped models. The method was based on quadratic programming with equality constraint, which was solved by using conjugate gradient. This method could enforce the passivity of the delayed macromodels while being optimal in the least squares sense. This procedure can greatly improve the efficiency. Numerical examples showed the efficiency and the accuracy of the method.

    Study on unbalanced signal extraction from a dynamic
    balancing machine based on wavelet analysis
    MU Shigang, FENG Xianying*, YAN Zhiwen, YANG Jingfang
    Abstract ( 312 )   PDF (1575KB) ( 1360 )   Save
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    The unbalanced signal is periodic and carries intense background noise. In view of these characteristics, a de-noising method using a multilevel threshold based on the analysis of the autocorrelation of detailed coefficients was  proposed. This method uses the discrete wavelet transform technique to decompose the signal into approximations and details.The autocorrelation sequences of the detailed coefficients were  determined.According to whether the sequence reflects the autocorrelation of white noise, the threshold was  determined.The results of experiments and the application in practical dynamic balancing measurement system indicate the presented method was  fit to apply in dynamic balancing measurement, which satisfies the requirement of high precision.

    Research on camera imaging simulation technology
    YAN Long1,2,3
    Abstract ( 298 )   PDF (968KB) ( 2599 )   Save
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    Imaging essence was studied and compared between OpenGL  and a real camera, which proved that  the rendering result of OpenGL was in theory in accordance with imagery of a real camera. A camera imaging simulation platform was built to get the check board image by previously setting the intrinsic parameters, then the parameters of a virtual camera was computed with a calibration toolbox. Experimental  results showed that two sets of parameter were nearly the same, which indirectly proves the theory right. It was learned that the process of camera imaging by the platform was without disturbance  coming from any other elements. The theory and system can be used to verify the algorithm in a vision system such as calibration, stereo match, and distortion rectification.

    Research on the temperature response feature of a rock mass
    around a  water-bearing structure and affecting factors
    ZHANG Qingsong, GAO Yang, LI Shucai, YUAN Xiaoshuai, ZHAO Jiangang, LI Zhipeng
    Abstract ( 243 )   PDF (1484KB) ( 1001 )   Save
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    A three-dimensional numerical model was built for the rock temperature method for a  water forecast. The thermal diffusion effect was simulated with the help of the finite difference software FLAC3D. The temperature response feature of a rock mass was analyzed and the distance affected by the water temperature was concluded to be around 25m. The impact of the roadway excavation process, the thermal conductivity of rock, the location of monitoring points, the buried depth of the monitoring points and the roadway environment temperature were also qualitatively studied. The best monitoring depth was  about 4~6m, and the location of a waterbearing structure was determined by comparing the slope of temperature curves at different positions. Finnally, the temperature fitting curve of a rock mass was found. It provides the theoretical foundation for  forecasting water with rock mass temperature.

    Test study on dynamic characteristics of saturated
    silt in the Yellow River flood area
    LI Xiaojing1, YAO Kai2*, LI Shucai1, ZHANG Chao2
    Abstract ( 317 )   PDF (926KB) ( 1126 )   Save
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     Four kinds of samples were obtained, and their density and content of clay were different from each other. The dynamic characteristics of saturated silt in the Yellow River flood area were studied. From the triaxial test results, it was showed that the dynamic strength of saturated silt was influenced by its density and content of clay. The dynamic strength increased with density when the content of clay、consolidation ratio and consolidation stress were the same. The dynamic strength increased with the consolidation ratio when the content of clay and dry density were the same. The dynamic strength increased with the content of clay when the dry density was the same. The conclusions provide an important theoretical basis for preventing liquefaction of silt in  road construction.

    Temperature monitoring and finite element analysis of
    preventing construction cracks in a continuous box girder
    WANG Haiyuan1,2, ZHANG Long3, ZHANG Lewen1*, ZHANG Feng1
    Abstract ( 244 )   PDF (2403KB) ( 1115 )   Save
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    The features of uneven distribution temperature stress in recently poured  concrete and the effective measures to prevent temperature cracks were studied. The 0# box girder in the Weihe Specially Long Bridge located  in the highway from Xi’an to Tongchuan was taken as a research project, which was  computed on  MIDAS/FEA(multitier distributed applications services/finite element analysis)finite analysis element software. The temperature field of hydration heat of the concrete in the construction period was numerically calculated by the finite element method. The effects of three different mechanical control measures of crack control were analyzed. Combined with the results of  temperature detection, the mechanical control measure was optimized.The results showed that the temperature inside the concrete rose to a  peak about 52 hours after the  concrete was poured, with or without cooling water pipes in the box temperature difference of the maximum temperature about 10℃.When the temperature difference between inside and outside of the concrete at 20℃ was a good time to remove the template.Temperature stress was concentrated in the junction web plate and diaphragm of the box girder, thus setting the cooling water pipes could improve the uneven distribution of temperature stress. Compared with other results, the whole process temperature monitoring and the finite element dynamic analysis by this method was better at  optimizing the engineering measures of crack prevention.

    Study of  strength properties of reinforced expensive
    soils with fault material
    DING Wantao, LI Shucai
    Abstract ( 269 )   PDF (923KB) ( 1329 )   Save
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    Based on  triaxial tests, the stressstrain relationship and strength properties of reinforced expensive soils were studied to obtain the relation between the strength index of reinforced soil and that of  corresponding plain soil. The macro behavior of reinforced soil strength was analyzed. Combining the stressstrain relationship of reinforced  soil with different layers and equivalent surrounding pressure analysis principle, the strength properties of reinforcement soil were analyzed when the reinforced material broke. Mohr circles were tangent to the same line when the reinforced materials of one layer broke. With the increase of axial compression, many layers reinforced materials begin to break,  and the Mohr circles extended outward. It showed that the strength of reinforced soil increases with the increase of reinforced layers. The test showed  that strength envelope of different reinforce layers is approximately parallel and the increase of reinforced soil strength was caused by the increase of cohesion when the reinforced materials are flexible materials.

    Numerical experiments and analysis for liquefaction in a non-free-field with
    gravel stone drainage layer around underground structures
    HE Jianping1,3, CHEN Weizhong2
    Abstract ( 260 )   PDF (2562KB) ( 1251 )   Save
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    The gravel drainage layer was set around underground structure. The numerical liquefaction experiment was separately completed  in the free field, the non-free-field and the gravel drainage layer non-free-field using FLAC3D.  The liquefaction distributed characteristic of the gravel drainage layer non-free-field was studied. The antiliquefaction effect of the gravel drainage layer was investigated, and the  dynamic characteristic change of underground structures after imposition of a gravel drainage layer in liquefaction field was analyzed. Calculations indicate that  the gravel drainage layer around the underground structure was not liquefied, the excess static pore pressure was obviously reduced in the distant liquefaction field, the structure did not float, and the horizontal drift was reduced. As the overall quality and rigidity of the structure with gravel drainage layer increased, the stability of the structure increased. Further research  will provide a theoretical and experimental basis for the design of underground structures through the liquefaction soil layer.

    Research on the influence of constructing localization of vertical
    prestress tendons to their  prestress loss
    LI Shoukai, ZHANG Feng, LI Shucai*, SHAO Dongliang
    Abstract ( 343 )   PDF (697KB) ( 1328 )   Save
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    The location error of vertical prestress tendons and anchor plates could lead to the appearance of the angle θ between the top surface of an anchor plate and the bottom surface of an anchoring nut, which could increase the set back amount of vertical prestress tendons and have notable influence on the prestress loss. The influence of angle θ on the prestress loss was studied.400 samples were acquired by SDC620 3D north finder to measure the angles. Regression analysis was performed assuming PearsonⅢ curve and moment estimation, which was appraised using the inspection method of Pearson χ2. Comparison of results showed that the angle θ followed the distribution of PearsonⅢ. Prestress loss of instant anchoring was measured by JMZX-3108AT. The results also showed that the prestress loss of instant anchoring F was in inverse proportion to the length of tendons l, and there was a linear relationship between F and the angle  θ. The angle θ  had significant influence on the prestress loss.The measuring method of the angle  θ  and the formula of prestress loss of instant anchoring were  proposed, and will  be helpful for the design and construction of vertical prestressing.

    Experimental research and numerical simulation of the concrete-filled
    steel tube arch rib cross-section temperature during the hydration
    process of a complex binder
    SUN Guofu1,2, LI Shucai2, LU Wei2, CHEN Lei3
    Abstract ( 306 )   PDF (1444KB) ( 983 )   Save
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    Experimental observation of  the concrete-filled steel tube(CFST) arch rib cross-section temperature was continuously  carried out during the hydration process of a complex binder. By means of the heat conductivity theory and finite method, an analytical  model was built and calculated in the CFST arch rib  several factors were  considered, including inertial conditions and the model of cement hydration thermal. The influence on the crosssection temperature field caused by different steel tube thickness and diameter during the hydration process of a complex binder was dicussed. The results of analysis and study indicate that the model of cement hydration thermal was satisfactory  using the hyperbolic formula, and that steel tube thickness has little influence when less than  2~3℃ on the temperature field of the CFST arch rib, however tube diameter has  more influence up to 20℃.

    Integrity, deformation and stability of a rock mass around  underground
    crude oil storage caverns in containment of groundwater
    WANG Zhechao1,2, LI Shucai1,2, XUE Yiguo1,2, QIAO Liping2, LIN Chunjin1,2
    Abstract ( 335 )   PDF (2684KB) ( 1312 )   Save
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    The integrity, deformation and stability of a rock mass are of great importance for the construction of underground crude oil storage caverns with the containment of groundwater. Triaxial compression tests were  performed to determine the properties of the rock mass around a pilot underground crude oil storage cavern. The integrity, deformation and strength of the rock mass were  assessed using elastoplastic theory. According to the test results, it was found that the integrity of rock specimen is destroyed upon the occurrence of volumetric dilation. Therefore, the friction angle at this point could be used to determine the excavation induced loose zone in the construction of underground facilities. In the case of this pilot storage cavern, the extension of the excavation induced loose zone ranged from 0 to 156 m, depending on the buried depth of the caverns. According to numerical simulation results, both the crown settlement and side wall convergence ranged from 8 to 45 mm, and the displacement vectors along cavern walls aligned with the ground surface. There are tensile zones in the cavern floors, and high shear stress zones in the bottom and springline of the cavern sidewalls. The stability of pillars between different caverns is different, as a result of their different stress paths experienced in the excavation.

    Study of large deformation construction mechanical behavior and support
    measures of soft rock in a deep buried extra long tunnel
    LIU Qin1,2, LI Shucai1, LI Liping1, SUN Keguo1,3, ZHAO Yan1
    Abstract ( 339 )   PDF (3146KB) ( 1456 )   Save
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    Large deformation of surrounding rock is a common construction geological disaster of great harm. Some studies  were done to abate or even eliminate the influence to the engineering. First, the cause of extrusion large deformation of soft rock in a typical section was revealed based on engineering geological conditions and stress test results analysis. Then, combined with field monitoring data, stress and deformation characteristics of the rock mass were studied by a finite difference program in a soft rock section construction process. The effect of supporting structure on the surrounding rock stability was analyzed. Surrounding rock deformation was effectively controlled  by considering support, and the influence scope caused by excavation decreased from two times as much as the tunnel diameter to one time. Extrusion deformation of the working face was effectively controlled. According to the analysis of a construction process simulation considering support, control measures were presented to control the soft rock large deformation in this section, and specific treatments were proposed to deal with the intrude limit caused by large deformation. Good effects were gained by these  measures, and it has reference meaning to similar engineering.

    Vibration characteristic analysis of a vehicle-rail-steel
    spring floating slab track coupling system
    SUN Xiaojing, LI Shucai, ZHANG Dunfu, XUE Yiguo, SUN Zheng, NIE Yiguo
    Abstract ( 305 )   PDF (1487KB) ( 1250 )   Save
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    A vhicl-track dynamics analysis model was established according to the analytic dynamics theory. Then nature frequency and vibration mode of the system were obtained by modal analysis  and harmonic response analysis  that were carried out by ANSYS. The amplitude spectrum curves of the foundation reaction and force transmission rate were presented according to vibration theory. The riding comfort based on the Sperling index. The variation of riding comfort and foundation reaction were profiled with different steel spring stiffness and damping. The results showed that greater steel spring stiffness and damping means better riding comfort, smaller stiffness and greater damping means smaller foundation reaction.

    Study of  failure analysis and the acoustic emission signature of 3-D crack
     from  different origins  under uniaxial compression
    SHAO Dongliang1, LI Shucai1, LI Mingtian1,2, ZHANG Bo1, ZHANG Gongshi1
    Abstract ( 308 )   PDF (1258KB) ( 1225 )   Save
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    With the material, the fracture process under different backfilling conditions was  studied. Using the acoustic emission test technology,  the acoustic emission signature of the whole rupture process of the test specimen was analyzed, including the initiation, propagation and disruption. It was shown  by the test that  different origins  would influence the failure mode of the crack propagation in some way, or, to be exact, the crack initiation strength and compressive strength varied from different origin conditions, and there were  some differences in the hits-t curve. The acoustic emission hits-t duration curve synchronized with the stresstime curve, and the volatility of the curve reflected the burstiness of the energy release in crack propagation.

    Deformation and analyzing of a tunnel country rock
    based on non-contact monitoring
    WU Ke1, LI Shucai1, MA Mingyue2
    Abstract ( 335 )   PDF (1324KB) ( 1363 )   Save
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    In order to obtain the deformation rule of the construction at the side of opening in an expansive rock tunnel, the noncontact monitoring technology, such as the system comprising a total station, was used to monitor the deformation of  2nd  Nada Tunnel on the  Yungui Railroad (Guangxi). Though monitoring and analyzing of the deformation, it was  obtained that  the deformation of convergence and ground surface became  stabilized  with the increase of time of excavation and after tunnel invert. The deformation was decreased  with the time of construction. Because of  continuous rainfall, the strength of swelling rock was reduced and the surface produced a  big crack, which caused the surface submersion to increase and a local region presented a landslide. According to the results of monitoring and analysis, the control measurements of casualties were established in the view of features of swelling rock. The measurements, such as anchor inject and micro-anti-slide pile, were able to guarantee this tunnel′s constructs safe construction.

    Study on the fissure evolution law of overlying strata during mining
    LI Zhi1, WANG Hanpeng1, LI Shucai1*, WANG Qi1,2, LI Weiteng1, JIANG Bei2
    Abstract ( 346 )   PDF (2145KB) ( 1406 )   Save
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     A typical mining face of the Huainan mining area was taken for example, and the puking of the nether roof was simulated by UDEC(universal distinct element code). The stress field and the development of overlying coal fissure were monitored and analyzed by  the numerical model. The fissure evolution law was obtained through numerical simulation. The results showed that, after stoping, the caving zone, fractured zone and separation zone appeared in overlying coal, and the O-ring fracture zone developed on the upper side of the acting surface, of which the maximum height was 45 meters. The strike model study showed that the first presses pace was 50 meters, and the period presses pace was 20 meters. The fissures of overlying coal expanded at a 45degree angle above goaf, which developed from down to up and moved forward continuously with  the  advancing mining. This conclusion will give some help for determining borehole location of gas extraction.

    Separation of gingerols from ginger oleoresin
    with D4020 macroporous resin
    WANG Yan, DU Ailing*, XUE Yanming, DU Aiqin
    Abstract ( 336 )   PDF (1488KB) ( 1439 )   Save
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    In order to find an efficient clean method to separate the gingerol, a  ethanolwater solution was used as mobile phase, and the D4020 macroporous resin was used as the stationary phase. Based on  column chromatography analysis, the gingerols were  separated from supercritical carbon dioxide extracted ginger oleoresin. Eluates in every stage were measured by UV to find out the sections  containing gingerols. Then, the samples containing gingerols were measured by HPLC and GC-MS. The results showed that a  average peak area percentage was 71.98% at the yield of 86.11%. After further purification, the peak area percentage of gingerols rose  to 96.27% at a  yield of 76.75%. This method could achieve good results in both purity and yield.

    Separation and purification of toosendanin extraction solution
    by  an ultrafiltration membrane
    WANG Longde1, CUI Peng2, LU Xuwang2, TONG Ling1, YAO Lulu2
    Abstract ( 354 )   PDF (1551KB) ( 1193 )   Save
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    Microfiltration and ultrafiltration membrane separation methods were studied for purifying  toosendanin from crude extracts of the bark of azedarach by microwave-assisted extraction. The polysulfone ultrafiltration membranes  UEOS-503, USIC-503 and UPIS-503 were studied for  separating and purifying toosendanin. The results showed that polysulfone UEOS-503 ultrafiltrating membrane with retenting molecular weight 6 K was much better than USIC-503(10K) and UPIS-503(20~50K) in separating and purifying toosendanin. In order to improve the toosendanin purity and transfer rate, the optimal separating and purifying conditions were investigated and obtained as follows: the raw concentration of toosendanin was 0.369mg/mL, the temperature was 35℃, the operating pressure of 0.10MPa, the cross flow velocity was 6.17×10-4m/s, and the pH value was 7.0. Under the optimum conditions, the toosendanin transfer rate was 92.8%, and the purity of toosendanin increased from 0.89% to 15.22%.

    Parameter optimization for immobilization and Pb (II) adsorption of
    microbe exopolysaccharide SM-A87 EPS
    MENG Fanping, ZHOU Weizhi*, MA Yuhong, GAO Jinqiang
    Abstract ( 258 )   PDF (827KB) ( 971 )   Save
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    In order to improve the separation efficiency of microbe exopolysaccharide(EPS) Wangia profunda SMA87 EPS (SMA87 EPS) from aqueous solution, the preparation of immobilized SMA87 EPS was optimized by orthogonal array design experiments. The four main factors were concentration of the polyvinylalcohol (PVA), sodium alginate (SA), EPS, and the hardening time. The major relevant indicator was Pb(II) removal rate, while three subordinate indicators were the spherical shape, extraction rate of the polysaccharide and acid resistance of the immobilized EPS grains. The results showed that the optimal ratio  of immobilized SMA87 EPS was obtained as m(PVA)∶m(SA)∶m(EPS)∶m(H2O)=80∶20∶1∶1000, and the hardening time was 16 h. Effects of immobilized EPS beads dosage, pH, and adsorption time were studied by batch experiments. The results showed that the removal rate increased with the immobilized EPS beads dosage increasing. The adsorption of Pb(II) onto the immobilized beads depended on the  pH value. The adsorption rate of the immersed beads was faster than that of the dry beads. The thermodynamic isotherm of Pb(II) adsorption on immobilized EPS beads could be best  described by the Langmuir model, with a regression coefficient of 0.954 and a  theoretical maximum adsorption capacity of 82.64mg/g. The pseudo-second-order model well fitted the kinetic process of Pb(II)  adsorption by immobilized EPS beads, and the adsorption process was controlled by more than two steps.

    Bi-level programming research on unit commitment
    YANG Pengpeng, WANG Kui, LI Lei, ZHAO Lanming
    Abstract ( 350 )   PDF (623KB) ( 2112 )   Save
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    A bi-level decision-making method for the network-constrained unit commitment (UC) problem was  proposed. The upper level with the objective to minimize the total cost of subsystems solves the optimal power flow problems including network constraints and determines the generations of subsystems in the lower level. A subsystem is composed of generators in one system without network constraints and minimizes its generation cost to give the units states. The two levels are solved alternatively according to the marginal information of the lower level. Two study cases were analyzed to exhibit the effectiveness of the method presented.