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Table of Content

    25 January 2012, Volume 40 Issue 1
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    Chemistry,Chemical & Energy Engineering
    Effects of Ti Doping on Structure and Electrochemical Performance of Cathode Material LiNi1/3 Co1/3 Mn1/3 O2
    Xiao Xin-yan Wang Dong
    2012, 40(1):  1-6. 
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    In order to reveal the effects of ion doping on the structure and electrochemical performance of modified cathode material LiNi1/3 Co1/3 Mn1/3 O2 ,three kinds of Ti-doped cathode materials for lithium ion battery,namely LiNi1/3-1/40 Co1/3 Mn1/3 Ti1/40 O2 ,LiNi1/3 Co1/3-1/40 Mn1/3 Ti1/40 O2 and LiNi1/3 Co1/3 Mn1/3-1/40 Ti1/40 O2 ,were synthesized via the coprecipitation of hydroxides. Then,the crystal forms and microstructures of the products were respectively characterized by means of XRD and SEM,and the electrochemical performances of the products were tested by using a high-precision battery-testing system. The results show that all the modified cathode materials with their Ni,Co and Mn components being partly substituted by Ti keep a typical α-NaFeO2 layered structure with perfect crystalline patterns,that LiNi1/3 Co1/3 Mn1/3-1/40 Ti1/40 O2 is of the clearest profile and even morphology,that the electrochemical performances of the three kinds of modified materials all improve after the Ti doping,especially LiNi1/3 -Co1/3 Mn1/3-1/40 Ti1/40 O2 ,and that,for LiNi1/3 Co1/3 Mn1/3-1/40 Ti1/40 O2 at the rates of 0. 1C,1. 0C and 2. 0C,the first specific discharge capacity respectively reaches 145. 35,140. 79 and 125. 60mA·h /g,and the capacity retention after 30 charge and discharge cycles at 1. 0 C is up to 88. 06%.

    Performance of Temperature-Controlled Electronic Heat Sink with Composite Paraffin /Expanded Graphite Phase Change Material
    Gao Xue-nong Li De-lun Sun Tao Cao Xin He Wen-xiang
    2012, 40(1):  7-12. 
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    In order to improve the capability of heat shock resistance of electronic devices and ensure the working reliability and stability of the devices,composite paraffin /expanded graphite PCM ( Phase Change Material) was prepared via the physical adsorption,with paraffin as a phase-change energy-storage material and with expanded graphite as a supporting matrix. Then,the product was applied to the thermal management of electronic devices,and the performance of a temperature-controlled heat sink with the composite PCM was investigated by the experiments on a simulated electronic chip. The results show that the thermal conductivity of the composite PCM containing 90% of paraffin is about 5 times that of pure paraffin ( 0. 3608W/( m·K) ),that the PCM filled in the heat sink effectively reduces the heating and cooling rates of the simulated electronic chip and prolongs the temperaturecontrolling time,and that,with the filling of the composite PCM in the heat sink,the temperature-controlling time of the chip at the heating powers of 15 and 20W increases by 59% and 20%,respectively,which reduces the possibility of burning out of electronic chips due to sharp temperature rise and provides the protection of electronic devices.

    Effect of Inlet Parameters on Performance of Regenerator Under Winter Conditions
    Li Yong-cun Chen Guang-ming Zhang Shao-zhi Tang Li-ming
    2012, 40(1):  13-18. 
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    As there have no sufficient performance data of the regenerators under winter conditions,the corresponding design and operation of regenerators are difficult to perform. In order to solve this problem,an experimental system is established to analyze the effects of inlet air and solution parameters on the performance of regenerators under winter conditions,and the corresponding laws are drawn when aqueous LiCl is used as the regeneration solution. The results indicate that the outlet air temperature,the outlet solution temperature and the outlet air humidity ratio all increase with the inlet solution temperature,the inlet air temperature,the inlet solution mass flowrate and the inlet air humidity ratio,while they all decrease with the increase in the inlet air mass flowrate,and that,with the increase in LiCl mass fraction,both the outlet air temperature and the outlet solution temperature increase but the outlet air humidity ratio decreases. In addition,a correlation of regeneration rate and regeneration efficiency is also proposed,which is suitable for the design,operation and performance investigation of regenerators under winter
    conditions.

    Characteristic Analysis and Evaluation Model of Thermal Aging of Paper Based on Thermogravimetry
    Chen Gang Liu Yu-sha Wen Ai He Bei-hai
    2012, 40(1):  19-23,29. 
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    In this paper,first,an accelerated thermal aging of paper was carried out,and the corresponding pyrolysis process was analyzed via the thermogravimetry. Then,the thermogravimetric characteristics of the paper during the aging were investigated,finding that the weight loss in the pyrolysis process contains two stages,namely the dehydration
    of paper and the weight loss caused by cellulose pyrolysis. TG kinetic analysis shows that the nonageing paper has the lowest activation energy,that the activation energy first increases and then decreases during the aging,and that,with the increases in aging time and temperature,the thermal stability of paper degrades,the temperature
    corresponding to a pyrolysis conversion rate of 0. 5,namely θ0.5 ,gradually decreases,while the gap Δθ0.5 between the θ0.5 values of aging and nonageing paper progressively increases. Moreover,it is found that there is a quantitative exponential relationship between the relative polymerization degree DP /DP0 and Δθ0.5 ,which means
    that Δθ0.5 can be used as a parameter to evaluate the aging degree of paper. Based on the above-mentioned findings,a model to rapidly and quantitatively evaluate the paper aging can be established by means of thermogravimetry,which is proved effective by the accordance between the evaluated and the experimental results.

    Pressured Hydrogen Peroxide Bleaching of Bagasse Pulp
    Zeng Jian Chen Ke-fu Xu Guang Li Jun Xu Jun Yang Fei
    2012, 40(1):  24-29. 
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    Two shot bleaching sequences,namely QP ( chelating pretreatment and hydrogen peroxide bleaching) and P0( pressured hydrogen peroxide bleaching) ,were performed for Soda-AQ bagasse pulp,and the possibility of single-stage P0 for bagasse pulp was discussed. Then,orthogonal tests were carried out and the optimal P0 conditions
    were determined,that is,a temperature of 100℃,a duration of 80min,an oxygen pressure of 0. 6MPa and a NaOH dosage of 0. 4%. It is found that the viscosity of the P0-bleached pulp reaches 825. 3mL /g and the brightness
    is up to 84. 0%ISO,which is 9. 9%ISO higher than that of the pulp with QP sequence,and that the P0-bleached
    pulp is a kind of high-strength pulp with a tensile index of 66. 67N·m/g,a tear index of 9. 34mN·m2 /g, a burst index of 4. 31 kPa·m2 /g and a folding endurance of 39 times. Moreover,it is indicated that P0 helps to greatly reduce the pollution discharge because P0 effluent can be totally countercurrent reused in the bleaching stage due to its low chemical oxygen demand,biochemical oxygen demand and chroma.

    Comparison of Chemical Constituents Between Essential Oil and Smog from Artemisia argyi
    Liu Mei-feng Zhou Hui
    2012, 40(1):  30-34. 
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    The smog from the flaming leaves of Artemisia argyi has the effects of moxibustion,isinfection and desinsectization. In order to find out the active substances of Artemisia argyi,methanol was used to absorb the smog,and the chemical constitutes in both the absorption liquid and the effective essential oil from Artemisia argyi were analyzed and compared by means of GC-MS. The results indicate that both the smog and the essential oil are of the same chemical constituents such as 4-hydroxy-4-methyl-2-pentanone,eucalyptol,borneol,thujone,β-caryophyllene, 2,2'-bithiophene, 3,3,6,8-tetramethyl-1-tetralone and selina-6-en-4-ol,that eucalyptol and β-caryophyllene are two active substances for moxibustion,disinfection and desinsectization,and that eucalyptol,borneol,thujone and β-caryophyllene in the smog may enter human body and play various bioactive role through moxibustion.

    Mechanical Engineering
    Formation Mechanism of Porous Grooves on Tube Walls by Ploughing-Heat Treatment
    Lu Long-sheng Liu Xiao-chen Deng Da-xiang
    2012, 40(1):  35-39,57. 
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    In order to overcome the difficulty in manufacturing pipe-wall porous grooves that possess excellent capability of heat transfer enhancement,first,a ploughing-heat treatment method was proposed,by which grooves were manufactured on the inner surface of a copper tube by ploughing and a porous layer was formed on the groove surface via the heat treatment in hydrogen environment. Next,the surface morphology of the porous grooves was observed by means of SEM and was further analyzed. Then,the formation mechanism of the porous grooves was investigated based on the plastic deformation theory and the thermal vacancy transition theory,finding that the proposed ploughing-heat treatment method helps to successfully fabricate porous grooves on tube walls,and that,with the comprehensive action of thermal energy and hydrogen disease during the heat treatment,the formation of porous grooves is mainly due to the complex influences of both the micro-crackers and the lattice defects of groove surface occurring in the ploughing process. Finally,all these above-mentioned findings were verified by metallographic analysis.

    Effect of Flattening Thickness on Performance of Flattened Sintered Micro Heat Pipe
    Li Yong He Heng-fei Jie Zhi-wei Zeng Zhi-xin
    2012, 40(1):  40-46. 
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    An experimental investigation into the heat transfer characteristics of flattened sintered micro heat pipes in different thicknesses was conducted,and the filling ratio of the working fluid was optimized for the pipe with a flattening thickness of 5 mm,namely a vacuum cavity thickness of 3 mm. Moreover,the effects of flattening thickness on the axial temperature distribution,the maximum heat transfer rate ( MHTR) ,the temperature difference and the thermal resistance of the micro heat pipe were analyzed at constant filling ratio. The results indicate that the thickness only has a slight effect on the MHTR when the working liquid quantity is a little less than that fully fills the wick ( mc ) ,and that the MHTR reaches 40,50 or 60W when the thickness is 5,4 or 3mm,respectively. On the contrary,when the working liquid quantity is more than mc,the thermal performance of the pipe degrades with the decrease in flattening thickness,the thermal resistance increases from 0. 15℃ /W to 0. 20℃ /W if the thickness decreases from 5mm to 4mm,and the heat pipe fails at a thickness of 3mm. Moreover,by analyzing the causes of the above-mentioned findings,it is concluded that the change of thermal performance of the heat pipe is due to the
    thickness change-induced distribution variation of in-pipe working liquid.

    Investigation into Residual Stress of Pre-Stress Cutting Based on Thermo-Mechanical Coupling Analysis
    Qin Meng-yang Ye Bang-yan He Ai-dong
    2012, 40(1):  47-52. 
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    In this paper,first,the residual stress state of the workpiece surface machined by pre-stress cutting was investigated via the thermo-mechanical coupling analysis. Next,three residual stress types of the machined surface were revealed by overlapping the mechanical stress and the thermal stress distributing on the workpiece surface,and the corresponding formation conditions are also qualitatively discussed. Then,the effects of the cutting edge roundness
    and the pre-stress on the residual stress state of the machined surface were further analyzed. Finally,some experiments of pre-stress hard cutting for 40Cr alloy steel with quench hardening were carried out at different cutting edge roundness and pre-stress,and the results were compared with the theoretical ones. It is found that both the value and the distribution of the residual stress depend on the cutting edge roundness,that both the residual compressive stress and the strained layer’s thickness increase with the blunt round radius,that the pre-stress effectively increases the residual compressive stress of the machined surface,but it basically has no influence on the stress distribution,and that the proposed theory is reasonable because the experimental results accord well with the theoretical ones.

    B-Spline Curve Fitting of Consecutive Micro-Segment Trajectory in NC Machining
    Pi You-guo Fan De-he
    2012, 40(1):  53-57. 
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    In order to overcome the frequent acceleration and deceleration,low machining feedrate and discontinuous machining path in the traditional consecutive micro-segment machining process,an algorithm of cubic B-spline
    curve fitting based on the least square method is proposed to approximate the consecutive micro-segment to a Bspline curve. By analyzing the geometric characteristics of the machining path of the consecutive micro-segment,a chord error constraint based on the arc approximation is presented to pick out appropriate points and keep the deviation of the fitted curve from the original path in a required range. Simulated results indicate that the proposed algorithm can effectively fit consecutive micro-segments into B-spline curves without reducing the precision.

    Genetic Algorithm-Based Sequence Planning for V-Bending of Sheet Metal
    Wang Fei You You-peng
    2012, 40(1):  58-63. 
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    As a reasonable bending sequence of sheet metal is important to the bending precision improvement and guarantee,an optimization design of the bending sequence is performed based on the genetic algorithm. In the investigation,first,the constraints of interference and accuracy during the sequence planning are extracted by analyzing the shape feature information of workpieces. Next,a constraint database of sequence planning is established. Then,the bending sequence planning is abstracted into a traveling salesman problem ( TSP) with constraints,and an optimization object function is constructed. Finally,the constraints are introduced in the crossover and mutation operators of the genetic algorithm for the bending sequence optimization. The results show that,for the workpieces with comparatively complex shapes,the proposed method is effective in obtaining optimal or approximate optimal bending sequence within a reasonable time range.

    Statistical Modeling-Based Image Matching Algorithm for Solder Joints of Electronic Components
    Wu Hao Zhang Xian-min Kuang Yong-cong Ouyang Gao-fei Xie Hong-wei
    2012, 40(1):  64-68,76. 
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    In order to reduce the programming time and overcome the experience dependence on the existing automatic
    optical inspection ( AOI) systems based on feature extraction,an image matching algorithm based on statistical
    modeling is proposed. In this algorithm,first,qualified sample images of solder joints are separated from the unqualified ones in training. Next,a standard learning template image is formed through a gray-level statistical modeling of the qualified sample images. Then,after an alignment,the component image to be tested is matched with the trained template image. Finally,the difference in pixel point gray is calculated and is used to determine whether the testing component image is qualified or not. Experimental results show that the proposed algorithm,with a false alarm rate of less than 2% and a missing report rate of 0,helps to obtain satisfying accuracy of AOI and greatly reduces the programming time of users for inspection.

    Dynamic Tabu Particle Swarm Optimization Algorithm for Flexible Job-Shop Scheduling
    Jia Zhao-hong Zhu Jian-jian Chen Hua-ping
    2012, 40(1):  69-76. 
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    Based on the fully-informed particle swarm optimization ( FIPS) and the dynamic tabu search ( TS) ,a hybrid Pareto algorithm is proposed to solve the complex multi-objective flexible job-shop scheduling problem( FJSP) ,which takes advantage of the global search capability of FIPS to determine the search direction and then performs a local search with TS to effectively improve the search performance. In this algorithm,first,a strengthbased fitness function is adopted to evaluate the quality of particles,which makes the non-dominated solutions uniformly distribute along the Pareto front. Then,several neighbourhoods based on public key blocks are employed to keep the diversity of the swarm,which avoids the trapping in the local optimum and effectively accelerates the convergence of the algorithm. Moreover,a self-adaptive perturbation based on mutation is introduced in the algorithm to enhance the diversity of solutions. The results of comparative experiments in different scales indicate that the proposed algorithm is of good search performance and is effective in solving the multi-objective FJSPs in both large and small scales.

    Tracking Control of Industrial Robot Based on Time Delay Estimation and Robust H∞ Control
    Liu Hai-tao Zhang Tie
    2012, 40(1):  77-81,87. 
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    Proposed in this paper is a tracking control algorithm of 6-DOF ( Degree of Freedom) industrial robots,which takes advantage of both the time delay estimation and the robust H∞ control. In this algorithm,no complicated dynamic models of robots are required,so that the on-line and real-time computation about the robotic inverse dynamics is avoided. Moreover,time delay estimation is used to obtain the unknown dynamics and the external disturbances
    of robots on line and to perform a compensation during the tracking control,and the L2-gain control is employed to guarantee the L2 disturbance attenuation for the time delay estimation error and to further improve the system robustness. In addition,the Lyapunov function and the Riccati inequality are employed to respectively guarantee
    the asymptotic stability and H∞ robustness of a robotic closed-loop system. The proposed algorithm is of simple
    computation,fixed structure and strong robustness and is easy to implement in practice. The simulations on a 2-DOF industrial robot demonstrate that the proposed algorithm is feasible and effective.

    Analysis of Energy Recovery Efficiency of Hydraulic Hybrid Excavator
    Shen Wei Jiang Ji-hai
    2012, 40(1):  82-87. 
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    In order to improve the fuel economy and reduce the emission of hydraulic excavators,a hydraulic hybrid excavator with the configuration based on the Common Pressure Rail is constructed. Then,by taking into consideration
    the high energy consumption and great energy recovery potential of the swing system,a simulation model of the swing system is established with Simulation X,and the main factors affecting the energy recovery efficiency ( ERE) are analyzed. The results show that the proposed swing system effectively recovers the energy in breaking,and that the ERE increases with the hydraulic accumulator volume and the initial braking speed. In addition,some experiments are carried out to verify the conclusions drawn by simulation,finding that there exists a good accordance between the simulated and the experimental results.

    Analysis of Interface Slip of Spiral Oil Wedge Bush
    Wang Li-li Lu Chang-hou
    2012, 40(1):  88-93. 
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    In order to investigate the interface slip of nonmetal bushes for the sliding bearing of spiral oil wedge,a mathematical model considering both the circumferential and the axial slips of bush surface is established based on the ultimate shear stress model. Then,with the help of the finite differential method,the effects of interface slip on the circumferential pressure,slip velocity,carrying capacity,end leakage and friction of the sliding bearing of a 2D spiral oil wedge are analyzed. The results show that interface slip may result in the increases of end leakage and the decrease of circumferential pressure,carrying capacity as well as friction,and that the threshold of the initial ultimate shear stress increases with the eccentricity,which prevents the interface slip from appearing on the bush surface. Moreover,it is found that the spiral angle has no obvious effect on the threshold of the initial ultimate shear
    stress and that the interface slip occurs first in the envelop zone.

    Materials Science & Technology
    Influence of Sn on Mechanical Properties and Corrosion Behaviors of Q125-Grade Tube Used for ERW
    Wang Li-dong Tang Di Wu Hui-bin Cai Zheng-xu
    2012, 40(1):  94-100. 
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    In this paper,the influences of Sn on the mechanical properties and CO2 corrosion resistance of the Q125-grade oil tube used for ERW were investigated by means of SEM,TEM,EBSD and electrochemical measurement. The results show that Sn has no influence on the microstructure of the steel as well as the forms and sizes of precipitates,so that there is no obvious change of the steel strength. However,the activity of the tested steel changes after the addition of a little Sn,which results in the negative shift of corrosion potential,the decrease in corrosion current density,the increase in the polarization resistance of electrode reaction and the deceleration of the corrosion,thus improving the corrosion resistance of the tube. Moreover,it is found that,with the addition of Sn,both the proportion of small-angle grain boundary and the corrosion resistance of the steel improve,while the proportion of large-angle grain boundary decreases,which results in a decrease in the elongation and impact energy of the steel.

    Formation Mechanism and Properties of Colored Ti /Zr-Based Conversion Coating on Aluminum Alloy
    Yi Ai-hua Li Wen-fang Du Jun Mu Song-lin Liu Ning-hua
    2012, 40(1):  101-106,124. 
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    In order to overcome the colorlessness of Ti /Zr conversion coatings applied in industry,a colored Ti /Zr conversion coating was prepared on the surface of aluminum alloy by adding tannic acid and film-forming accelerator in the treatment solution containing titanium and zirconium ions. Then,the growth process,morphology microstructure and corrosion resistance of the coating were characterized and analyzed by means of EDS,SEM,FT-IR,XRD,XPS and by using an electrochemical workstation. The results show that golden conversion coatings with strong corrosion resistance can be successfully prepared on the surface of aluminum alloy,that the coating mainly contains Na3AlF6,followed with the metal complexes of tannic acid hydrolysate and a small amount of Al2O3·3H2O and TiO2,that the formation of the golden coating undergoes a process consisting of nucleation,crystal growth and metal complex formation,and that the corrosion resistance of the coating greatly improves because there occurs a sharp decrease in corrosion current density from 5. 894 μA/cm2 to 0. 283 μA/cm2.

    Effect of Citric Acid on Corrosion Resistance and Self-Healing Ability of Lanthanum Conversion Coating
    Kong Gang Huang Wei Lin De-xin Wang Xia Li Han-chang Lu Jin-tang Liu Ling-yan
    2012, 40(1):  107-113. 
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    In this paper,first,hot-dip galvanized steels were immersed into passivation lanthanum solutions with or without citric acid to respectively obtain an improved lanthanum conversion coating or a traditional lanthanum conversion
    coating on the steel surface. Next,the corrosion resistances of the two kinds of coatings were investigated via the neutral salt spray ( NSS) test,the Tafel polarization and the electrochemical impedance spectroscopy. Then,the coatings scratched with a knife edge were corroded in a NSS chamber. Finally,the microstructure and chemical composition of the scratch surface during the corrosion were analyzed by means of SEM and EDS. The results
    show that the addition of citric acid in the passivation solution remarkably improves the corrosion resistance and the self-healing ability of the coating,and that,during the corrosion,lanthanum ions and citric acid anions produced by the dissolution of LaCit3 at the scratch migrate from the coating to the scratch to form a new passive coating containing Zn,O,La and C,thus effectively suppressing the corrosion of zinc at the scratch.

    Biological Engineering
    Package and Verification of Adeno-Associated Virus Vector Constructed with siRNA Targeting TTF-1
    Gao Qiang Cao Yi-cheng Yang Lei
    2012, 40(1):  114-119. 
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    In order to introduce siRNA targeting TTF-1 gene into lung adenocarcinoma cells,first,three TTF-1-gene-specific siRNAs for NCI-H1975 cells were respectively designed and constructed in adeno-assosiated virus( AAV) . Next,the primary culture liquid of AAV was harvested after the package of AAV in 293 cells. Then,thetiter of AAV was detected after the concentration by ultrafiltration and after the purification by column chromatography for the primary culture liquid of AAV. Finally,NCI-H1975 cells were infected by recombinant AAV,nd the interference effect of siRNA and the cell biology effect were respectively verified by Western-Blot experiments and cells apoptosis experiments,ith good interference effect of siRNA and apoptosis of NCI-H1975 being both revealed,which means that infective AAV-TTF-1-siRNA was successfully constructed.

    Construction of Metagenomic Fosmid Library from Activated Sludge
    Gou Min Qu Yuan-yuan Zhou Ji-ti Xu Bing-wen Cao Xiang-yu
    2012, 40(1):  120-124. 
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    The construction of large-fragment metagenomic library helps to discover large-fragment functional genes and analyze their organization and function. In this paper,first,three methods,namely the CTAB method,the kit and the agarose-embedding method,were used to extract metagenomic DNA from activated sludge,and DNA fragments larger than 23 kbp were extracted by the agarose-embedding method. Then,the metagenomic DNA was ligated into pCC1FOS vector to construct a Fosmid library consisting of 5280 clones with an average insert fragment size of 35 ～40 kbp,which covered about 200Mbp of metagenomic DNA. Finally,one clone exhibiting amylase activity was rapidly screened from 200 randomly-picked clones via the activity-based screening. It is thus concluded that the Fosmid library constructed from activated sludge is feasible in the screening of novel functional genes by activitybased methods.

    Extraction of Active Components from Plants Using Cellulase Immobilized on an Intelligent Gel Support
    Zhou Jian-qin Chen Shao-hua
    2012, 40(1):  125-130,137. 
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    In order to enhance the extraction of active components from plant materials and realize the reuse of enzyme,an intelligent gel,namely N-succinyl-chitosan ( NSC) ,was used as a support to immobilize cellulase. In the investigation,first,the structure of NSC was characterized via the FT-IR and the XRD,and the pH sensitivity of NSC was also discussed. Then,the conditions of NSC-immobilized cellulase ( NSCC) were optimized. Finally,the extraction of flavonoids from Ginkgo biloba leaf powders was carried out in the presence of NSCC,and the optimal temperature and pH value of NSCC for the extraction were determined. The results indicate that the production of NSC is due to the reaction of succinyl groups and the —NH2 groups in chitosan,that the crystalline region of chitosan becomes small due to the introduction of succinyl groups,that both NSC and NSCC possess similar pH-sensitive reversible solubility,that NSCC can be obtained under the optimal immobilization conditions of pH 5. 0,10mg of 1-( 3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride ( EDC) dosage and 15 mg of cellulase dosage,that NSCC with good reusability remarkably improves the extraction yield of flavonoids from Ginkgo biloba leaf powders,which is only a little less than that by using free cellulase,and that the optimal temperature and pH value of NSCC for the extraction are respectively 45 ～ 55℃ and 5. 0 .

    Computer Science & Technology
    An Efficient Integrity Technology of Distributed Database
    Miao De-cheng Xi Jian-qing Liu Yong Jia Lian-yin
    2012, 40(1):  131-137. 
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    In order to develop an efficient integrity technology of distributed database for the evaluation of prospective cost of integrity checking,a new integrity checking strategy is proposed,and two generation algorithms respectively based on the local pretest strategy and the support test strategy are designed. Moreover,a model to evaluate the cost of integrity checking is established by using the dimension-reducing technology of artificial intelligence,which provides a base for the quantitative intercomparsion of cost evaluation of integrity checking. Then,the integrity test,the amount of accessed data,the amount of transferred data and the number of sites involved in the computation are verified by some experiments of distributed database system. The results demonstrate that the proposed strategy and algorithms effectively reduce the integrity checking cost of distributed database,and that the established cost evaluation model is of high accuracy.

    KNN Query Technology of Mobile Terminals in Highway Networks
    Liang Ru-bing Liu Qiong
    2012, 40(1):  138-145,158. 
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    The dynamic POIs ( Points of Interest) in highway networks are difficult to query. Most current researches focus only on the static POIs with the help of the Euclidean distance metrics,which are inefficient for the weak connection and frequent movement of mobile terminals in mobile computing environments. In order to solve this problem,a structure to store cell data objects is designed to describe the highway network graph model,and a continuous KNN ( K-Nearest Neighbor) query ( CQ-KNN) algorithm for mobile terminals is presented. For the purpose of improving the existing MKNN algorithm proposed by Wang et al,CQ-KNN algorithm combines the progressive probe and the edge information list retrieval,thus saving the cost of range query execution in MKNN algorithm when fixed layers are insufficient. Moreover,CQ-KNN algorithm employs the local cache strategy to support the continuous query of mobile terminals and adopts the cache consistency maintenance strategy based on the invalid broadcast location report. Simulated results show that CQ-KNN algorithm is superior to MKNN algorithm in terms of CPU processing speed and network response delay,and that it effectively supports the off-line approximate KNN query of mobile terminals.

    Human Action Recognition in Complex Scenes Based on Fuzzy Integral Fusion
    Wu Qiu-xia Deng Fei-qi Kang Wen-xiong
    2012, 40(1):  146-151. 
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    The approach to representing a series of key points in videos by using local feature descriptors has been widely applied to the recognition of human action in complex scenes. However,the important structural information among the key points has not been investigated yet. In this paper,first,a scale-invariant key point detector and a 3D-Harris detector are used to find the local key points in video samples. Next,the existing local feature descriptor and shape descriptor are employed to describe the structural information about the positions of the key points. Then,the bag-of-features model is utilized to calculate the distribution of the features. Finally,the fuzzy integral scheme is used to fuse the local features,with the corresponding algorithm being also described. It is found form the experiments on the YouTube dataset in complex scenes that the proposed approach to local feature description effectively represents the human action in complex scenes,and that the fuzzy integral fusion scheme is effective in integrating the advantages of the descriptors on the decision level.

    An Improved Data Placement Strategy for Hadoop
    Lin Wei-wei
    2012, 40(1):  152-158. 
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    In the existing default data placement strategy for Hadoop,much time is needed to restore data from a remote DataNode when the local replicas become unavailable,and the load balancing may be destroyed due to the random selection of DataNode for data storage. In order to solve these problems,an improved data placement strategy is proposed,which chooses the most appropriate DataNode to place remote replicas according to the scheduling evaluation value of each DataNode based on DataNodes' network distance and data load. Thus,the load balancing for data storage is implemented and excellent data transmission is achieved. The proposed data placement strategy is then implemented in the Hadoop platform and the results show that the proposed strategy is superior to the existing default data placement strategy because it improves the local balancing for data storage and reduces the time for data placement.

    A Quantitative Approach to Locality Strength and Its Application
    Hou Fang Zhao Yue-long Wang Yu
    2012, 40(1):  159-164. 
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    As the existing working-set management algorithms ignore the locality strength in the procedure of working set adjustment,the resident set size is frequently adjusted so that the thrashing problem is inevitable. In order to solve this problem and to quantitatively analyze the locality strength,a quantitative approach to locality strength is proposed,which uses the sum of use bits and the number of page faults in a sampling period as two calculation indexes. Then,the corresponding algorithm of this approach is designed and the approach is systematically implemented. Experimental results show that the proposed quantitative approach helps to alleviate the thrashing of working set size in process switching and reduce the demands for system resources without degrading the performances of the whole system.

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