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15 March 2015, Volume 36 Issue 3 Previous Issue    Next Issue
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Information & Control

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Multi-scale Shell Vibration Frequency Spectrum Analysis and Modeling Approach of Ball Mill LIU Zhuo， CHAI Tian-you， TANG Jian 2015, 36 (3):  305-308.  DOI: 10.12068/j.issn.1005-3026.2015.03.001 Abstract ( 632 )   HTML   PDF (727KB) ( 1245 )   Single-scale shell vibration frequency spectrum cannot reflect grinding mechanism of ball mill and analyze the composition of shell vibration signal. The empirical mode decomposition (EMD) based on soft sensor methods in present literature have poor prediction accuracy. Aiming at these problems， a new multi-scale shell vibration frequency spectrum analysis and modeling approach based on the partial least squares (PLS) algorithm was proposed. Firstly， the shell vibration acceleration signal was decomposed into different time-scale intrinsic mode functions (IMF) adaptively. Then， multi-scale frequency spectrum was obtained by using fast Fourier transform to different IMFs. Finally， different scale frequency spectrum was analyzed and selected by the latent variables contribution of the PLS algorithm. In addition， mill load parameters’ soft sensor model was constructed by fusing these selected multi-scale frequency spectrum. Simulation results based on experimental data of the laboratory ball mill validate the effectiveness of the proposed method. References | Related Articles | Metrics

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Design and Experiment of Operational Control System for Mineral Grinding Process Based on Soft PLC Technology QIN Yan， DAI Wei， YANG Jie， ZHOU Ping 2015, 36 (3):  309-314.  DOI: 10.12068/j.issn.1005-3026.2015.03.002 Abstract ( 705 )   HTML   PDF (1390KB) ( 928 )   To better overcome the operational control experimental problems of mineral grinding processes， a semi-physical simulation experiment system consisting of an operational monitoring subsystem， an operational control subsystem， a virtual sensors and actuators subsystem， and a virtual object subsystem was developed for operational control. In this system， an embedded controller based on soft PLC technology was adopted in operational monitoring subsystem for process control and optimization， and a monitoring software based on C sharp language was also programmed for process monitoring. Integrated with the virtual model of sensors and actuators， the virtual object subsystem and combined with the above subsystems， the developed system is characterized with high real-time capabilities， good portability and accord with the actual industrial processes. The experiment results show that the system can achieve satisfactory control performances for the mineral grinding process and can provide an appropriate， reliable and effective verification environment for operational control methods. References | Related Articles | Metrics

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H∞ Controller Design for a Class of Nonlinear Switched Systems with State Constraints LIU Qian， ZHAO Jun 2015, 36 (3):  314-317.  DOI: 10.12068/j.issn.1005-3026.2015.03.003 Abstract ( 749 )   HTML   PDF (331KB) ( 1036 )   The H∞ controller problem for a class of nonlinear switched systems with state constraints was investigated. Each subsystem is in lower triangular form. By employing the barrier Lyapunov function method， the issue of state constraints can be handled. Corresponding feedback controllers are constructed with the backstepping approach. To deal with the problem of state constraints， a barrier Lyapunov function is constructed to obtain the common barrier Lyapunov function for the whole system in every step， and a common virtual control is obtained step by step. A continuous state feedback H∞ controller is provided for the nonlinear switched systems under arbitrary switchings. A numerical example is given to demonstrate the effectiveness of the main results. References | Related Articles | Metrics

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Policy Iteration Algorithm for Nonzero-Sum Games with Unknown Models YANG Ming， LUO Yan-hong， WANG Yi-he 2015, 36 (3):  318-322.  DOI: 10.12068/j.issn.1005-3026.2015.03.004 Abstract ( 758 )   HTML   PDF (367KB) ( 1553 )   An online integral policy iteration algorithm was proposed to find the solution of two-player nonzero-sum differential games with completely unknown nonlinear continuous-time dynamics. Exploration signals can be added into the control and disturbance policies， rather than having to find the model information. An approximate dynamic programming (ADP) of model-free approach can be constructed， and the nonzero-sum games can be solved. The value function， control and disturbance policies simultaneously can be updated by the proposed algorithm， and converged policy weight parameters are obtained. To implement the algorithm， four neural networks are used respectively to approximate the two game value functions， the control policy and the disturbance policy. The least squares method is used to estimate the unknown parameters of the neural networks. The effectiveness of the developed scheme is demonstrated by a simulation example. References | Related Articles | Metrics

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Robust Pole Placement via Improved Global Harmony Search Algorithm ZHAI Jun-chang， GAO Li-qun， OUYANG Hai-bin， KONG Xiang-yong 2015, 36 (3):  322-326.  DOI: 10.12068/j.issn.1005-3026.2015.03.005 Abstract ( 757 )   HTML   PDF (372KB) ( 701 )   An improved global harmony search (IGHS) algorithm was proposed， and a novel position updating strategy was introduced in the IGHS algorithm. The interval solution can be generated dynamically with the proposed algorithm， and the ability of searching the solution space through the position updating strategy is improved， which prevents the phenomena of premature convergence and falling into a local optimum. The algorithm is employed in the robust pole placement problems， and it is easy to implement arbitrary pole placement for the linear control systems， and the convex conversion process in conventional condition number optimizations is not needed. Finally simulation investigation is carried out for a multivariable system， and the simulation result demonstrates the better robustness of the closed-loop system gained by the proposed algorithm. References | Related Articles | Metrics

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A New Multi-mode Identification Method of Batch Process GUAN Shou-ping， FU Chong， HOU Jin-fen 2015, 36 (3):  327-331.  DOI: 10.12068/j.issn.1005-3026.2015.03.006 Abstract ( 580 )   HTML   PDF (614KB) ( 741 )   A new method of multi-mode partition in the batch processes was presented on the basis of comparing the similarity of principal angles， which effectively overcomes the defects of noise or redundant data impaction on the phase partition. The main idea is to set up the principal component models of the batch data along time axis by employing the principal component analysis (PCA) approach， and then uses the principal angle method to compare the similarity of the principal component models， finally identify the steady phases and the transition phases effectively. Furthermore， an improved strategy is proposed to complete the partition criterion of the principal angle similarity. The simulation results demonstrate the effectiveness of the proposed method. References | Related Articles | Metrics

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VSI Nonlinearity Compensation Based on Extended PI Reference Model of PMSM YU Zi-song， WANG Da-zhi， GAO Qing-zhong 2015, 36 (3):  331-335.  DOI: 10.12068/j.issn.1005-3026.2015.03.007 Abstract ( 795 )   HTML   PDF (582KB) ( 896 )   Output voltage distortion due to voltage source inverter (VSI) nonlinear gain in the permanent magnet synchronous motor (PMSM) driving system could result in the current distortion. A new SVPWM-VSI nonlinear compensation strategy was proposed. Extended d，q axis PI reference model of PMSM was investigated to separate the unknown disturbance voltage， and a nonlinear compensator was designed to compensate it. Zero-current-clamping phenomenon could be approximately eliminated by configuring the parameters of PI regulator properly. The parameter robustness and validity of the presented nonlinear compensator was verified by the Matlab/Simulink PMSM driving system simulation. References | Related Articles | Metrics

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Simulation-Based Optimization on RFID-Enabled Push/Pull Control Strategy for Supply Chain LI Guo-jia， WANG Ding-wei 2015, 36 (3):  336-341.  DOI: 10.12068/j.issn.1005-3026.2015.03.008 Abstract ( 737 )   HTML   PDF (530KB) ( 936 )   The research on control methods of multi-echelon inventory systems is very important in reducing inventory cost， improving service level and enhancing the key competitive abilities. Radio frequency identification (RFID) technique provides an effective way in the innovation of inventory control strategies. The Push/Pull control strategy based on RFID was applied to multi-echelon inventory of supply chain， and a three-echelon inventory of supply chain was exemplified and eight kinds of RFID-enabled hybrid Push/Pull control strategies were designed. These strategies are optimized using the simulation-based particle-swarm optimization method. The results demonstrate the feasibility and the effectiveness of the method. The simulation results after optimization show that the hybrid Push/Pull control strategy that manufactures are controlled by the Push strategy， the distributions and retailers are controlled by the Pull strategy performs best among the eight kinds of strategies. References | Related Articles | Metrics

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Community Extraction Algorithm for Large-Scale Online Social Networks ZHANG Xi-zhe， ZHANG Yu-bo， CHEN Zhang-lu， ZHANG Bin 2015, 36 (3):  342-345.  DOI: 10.12068/j.issn.1005-3026.2015.03.009 Abstract ( 727 )   HTML   PDF (495KB) ( 948 )   Since the existing community analysis methods cannot be applied in large-scale networks， a community extraction algorithm is proposed. The community structure can be analyzed effectively with the algorithm. The topology of the network is not needed， with the combination of network search and community detection capabilities， the structure of the particular community can be effectively extracted from the social network with unknown topology. The analyzing of the community structure of large scale network is possible with the algorithm. Experiments on simulation data are performed to analyze the influence factor of accuracy， and it is concluded that the accuracy increases with the average degree. Furthermore， it is found that the accuracy of community extraction algorithm is close to existing methods， and the efficiency is much better， the results show the algorithm is feasible and effective. References | Related Articles | Metrics

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Research on Storage of RDF in Relational Database TONG Qiang， ZHANG Fu， CHENG Jing-wei， MA Zong-min 2015, 36 (3):  346-349.  DOI: 10.12068/j.issn.1005-3026.2015.03.010 Abstract ( 1151 )   HTML   PDF (822KB) ( 974 )   Resource description framework (RDF) is a normative language to describe the Web resource information. How to store RDF data is becoming an important research issue. By analyzing the characteristics of RDF data， a storage model of RDF was proposed based on relational databases. The storage rules and a storage example were given. On the basis of the proposed storage approach， a prototype storage tool was implemented， and the experiments shown that the approach and the tool are feasible. Also， the theory comparative analyses with the existing storage modules were done. References | Related Articles | Metrics

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Analysis of Accuracy of the Locating Information Source Method Based on Observers ZHANG Yu-bo， ZHANG Xi-zhe， ZHANG Bin 2015, 36 (3):  350-353.  DOI: 10.12068/j.issn.1005-3026.2015.03.011 Abstract ( 687 )   HTML   PDF (449KB) ( 1039 )   The research on the relationship between the position of the observers and the location accuracy has significant importance for the source location methods based on the observers. The information diffusion process for a single source was investigated as the starting point， and theoretical spread delay and real spread delay were then analyzed. It is found that for a fixed source， if the difference of the shortest path among observers is increasing， the similarity of both types of delay is increasing. Then the relationship between the position of the observers and the location accuracy of the fixed diffusion source was analyzed， and it was concluded that: when the sum of distance difference from the information source to the observers increases， the location accuracy for the source becomes larger. The conclusion is validated by simulation experiments on model network data. References | Related Articles | Metrics

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A Hierarchical Routing Protocol of Link Stability Prediction SHA Yi， LYU Fei， FANG Jing-jing， ZHU Li-chun 2015, 36 (3):  354-358.  DOI: 10.12068/j.issn.1005-3026.2015.03.012 Abstract ( 576 )   HTML   PDF (516KB) ( 792 )   An LSP-DOA routing protocol was proposed， in which the DOA algorithm’s advantages in local routing repairing were inherited. In this protocol， the link stability was calculated based on the Two-Ray radio propagation model and Friis formula， and a threshold value was set. When the link stability was less than the threshold value， a warning would be triggered and the route discovery process was started in order to find out a new path to replace the link which might be interrupted. Simulation results showed that the LSP-DOA routing protocol could reduce control overhead and end-to-end delay， improve packet delivery ratio， route repair success and average route length， maintain a stable efficient route for a long time， thus improve the network performance by comparing with DOA， AODV and DSR. References | Related Articles | Metrics

Materials & Metallurgy

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Effect of Hot Rolled Microstructure on Mechanical Properties of High Strength Cold Rolled TRIP Steel WANG Chao， DING Hua， ZHANG Jun 2015, 36 (3):  359-363.  DOI: 10.12068/j.issn.1005-3026.2015.03.013 Abstract ( 635 )   HTML   PDF (2409KB) ( 758 )   The effect of hot rolled microstructure on the final microstructure and mechanical properties of the cold rolled TRIP steel containing Al was investigated by means of scanning electron microscope (SEM)， X-ray-diffraction (XRD) and tensile test. Three different kinds of microstructure， fine grains F+B+P， F+P and F+B， were obtained under different cooling processes. After heat treatment， the fine grains sample contained granular bainite and a few retained austenite. The tensile strength of the sample was 996 MPa and the elongation was 20.8%. The microstructure of other two samples was polygonal ferrite， granular bainite and some retained austenite. The elongation reached up to 29.4% and the strength-ductility balance of 26812.8MPa·% were obtained for F+B sample. The band structure of F+P sample was hard to eliminate after heat treating， which was harmful to final mechanical properties. References | Related Articles | Metrics

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Optimization of Cooling Control System on the Run-out Table of Hot Strip Mill LI Hai-jun， JIANG Xiao， LI Xu-dong， WANG Guo-dong 2015, 36 (3):  364-368.  DOI: 10.12068/j.issn.1005-3026.2015.03.014 Abstract ( 618 )   HTML   PDF (508KB) ( 798 )   In order to guarantee high control accuracy of ultra-fast cooling zone delivery temperature and coiling temperature， the run-out table cooling control system was optimized according to the major problems emerging from the tuning process of ultra-fast cooling. Aiming at the longitudinal temperature fluctuations after ultra-fast cooling， a new self-learning method for the heat transfer coefficients of ultra-fast cooling was proposed. The strip surface re-reddening phenomenon after ultra-fast cooling process was simulated with the finite difference method， based on which a compensation for strip surface re-reddening was added to run-out table cooling control system. In order to eliminate the influence of strip conveying velocity fluctuations on temperature， the strip conveying velocity diagram and temperature were recalculated for all strip segments which had entered the cooling sections， as soon as a new strip segment came to the measuring point of finish mills delivery temperature (FDT). With the methods mentioned above， the new run-out table cooling control system are optimized and field application showed that the strip temperature control accuracy are improved obviously. References | Related Articles | Metrics

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Experiment Study on Section Shape Variations During Tapered Square Pipe Dieless Drawing XIA Hong-yan， BIAN Qing， WU Di 2015, 36 (3):  368-371.  DOI: 10.12068/j.issn.1005-3026.2015.03.015 Abstract ( 591 )   HTML   PDF (513KB) ( 764 )   Dieless drawing of tapered square pipe was carried out. The influences of process parameters on the variation of pipe profile， section shape and conical degree were studied. The influence factors and law on the section rounding of square pipe were analyzed and the methods of alleviating rounding factor were given out. In the experiments， square section steel pipes were mainly used， and tapered pipes with large angles were obtained. The drawing precise can be conducted within an error of 1.0% in taper angle. The tapered pipe profile drawn by dieless drawing is in good agrees with the calculated ones. The expansion rate of section shape decreases with the increase of deformation width. The thicker the wall， the larger the expansion rate. When the wall thickness and width are all relatively large， the expansion is relatively little. References | Related Articles | Metrics

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Research and Application of Tracking System in Wide Cross-Cutting All Line LIU Dong-ye， HE An-rui， WANG Hai-bin， HE Long-jun 2015, 36 (3):  372-377.  DOI: 10.12068/j.issn.1005-3026.2015.03.016 Abstract ( 798 )   HTML   PDF (814KB) ( 743 )   According to the technical character of the cross-cutting process， the whole production line was divided to different tracking zones， and then the tracking task was further divided to two levels. After finalizing the overall scheme， design thought and data flow of the track function for the whole cross-cutting line， the binary and hexadecimal material status description methods were employed to manage the material tracking process. Based on this theory， an applicable material tracking system for cross-cutting process was designed， and the general program flow was described. Setting parameters is gradually sent， which solving the problem that two steel rolls can’t be online at the same time. If no defect detectors are employed and the same technical flow is used with a certain factory， the annual output is predicted to increase 11% and the productivity is improved in indirectly. The long-time industrial application shows that this tracking system is reliable and accurate， and the problem of material information loses never happens， thus keeping the production line goes stably. References | Related Articles | Metrics

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Pulsed Laser Control Synthesis of Ag-SiO2 Nano-composite Particles CHEN Sui-yuan， LIANG Jing， WELLBURN Dan， LIU Chang-sheng 2015, 36 (3):  378-382.  DOI: 10.12068/j.issn.1005-3026.2015.03.017 Abstract ( 739 )   HTML   PDF (705KB) ( 654 )   Ag-SiO2 nano-composite particles were synthesized by pulsed laser gas phase evaporation control and liquid phase collection， and the mixture targets were composed of 0% ， 3% ， and 20% content micron-sized Ag powders and micron-sized SiO2 powders. The morphology， structure and synthesis mechanism of the samples were studied by means of TEM， XRD， infrared spectroscopy and other techniques. The results indicated that the Ag-SiO2 nano-composite particles prepared with this method are spherical. The diameters of the primary particles are from 15nm to 25nm. By comparison， Ag-SiO2 nano-composite particles are better than Ag nanoparticle in dispersion. Ag-SiO2 nano-composite particles have mixed composite structure. The spectral absorption peaks of Ag-SiO2 nano-composite particles show blue shift with the increase of SiO2 content， which proves that optical properties of Ag nanoparticles are adjusted by SiO2 composited in Ag. The ethylene glycol in the liquid phase is adsorbed on the surface of nano-composite particles which plays a role insitu dispersing nano-composite particles. References | Related Articles | Metrics

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Mechanical Properties of Ni-P Coatings Prepared by Electroless Plating on Surface of 5083 Aluminum Alloy REN Gui-hua， ZHANG Bin 2015, 36 (3):  383-387.  DOI: 10.12068/j.issn.1005-3026.2015.03.018 Abstract ( 822 )   HTML   PDF (779KB) ( 925 )   Amorphous Ni-P films were prepared on 5083 aluminum alloy substrates by electroless plating. The mechanical properties of Ni-P films with different strain rates were investigated by nanoindentation tests. It was found that the hardness of Ni-P films is not constant， which depends on depth. Elastic modulus is almost invariable. Discrete displacement bursts and jumping steps in load-depth curves are associated with the loading-rate. The slower the loading rate is， the more obvious the curve steps appear. The discrete displacement burst starts from a single shear band. In a high strain rate， jumping steps do not appear on curves. References | Related Articles | Metrics

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Behavior of Bottom Injection Bubbles in Liquid Under Elevated Pressures ZHONG Liang-cai， ZHOU Hang， WANG Long， ZHANG Ku 2015, 36 (3):  388-392.  DOI: 10.12068/j.issn.1005-3026.2015.03.019 Abstract ( 620 )   HTML   PDF (459KB) ( 1056 )   The influences of vessel pressure， nozzle diameter and gas flow rate on bubble’s behavior， diameter and rising velocity were investigated through physical experiment. The results showed that the bubbles from larger diameter nozzle show flat shape and their shapes change obviously during their up-rising process under atmosphere pressure， while the bubbles show oval-shaped and their shapes are stable in up-rising process under larger pressure. Gas flow rate has small effect on the bubble’s diameter with large diameter nozzle under atmosphere pressure， but it can obviously increase the bubble’s diameter and pressure has little influence on bubble’s diameter from small nozzle. With low gas flow rate and high pressure， the small bubbles can be obtained from the larger diameter nozzle. The difference of bubble’s diameter with different flow rates in injecting gas with the large nozzle is small under 0.1~0.2MPa pressure， while the difference becomes large when the pressure is increased to 0.3~0.4MPa. Rising velocity of bubbles decreases with increase in pressure and the influence of pressure on bubble’s rising velocity is more obvious at large gas flow rate. The bubbles from the large nozzles usually have higher rising velocity. Under atmosphere， the gas flow rate has important effect on rising velocity of bubbles， but under pressure up to 0.4MPa， the nozzle diameter has more important effect on their velocity. References | Related Articles | Metrics

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Improvements on Calculation Model of Theoretical Combustion Temperature in the Tuyere Raceway of BF LIU Cheng-song， LI Jing-she， TANG Hai-yan， GAO Ya-wei 2015, 36 (3):  392-396.  DOI: 10.12068/j.issn.1005-3026.2015.03.020 Abstract ( 919 )   HTML   PDF (604KB) ( 1018 )   Based on the original modified model for calculating theoretical combustion temperature (T○f)， the calculation methods for the combustion efficiency of pulverized coal， the decomposition heat of pulverized coal and the heat consumption of SiO2 in ash which was reduced at high temperature， were modified and improved in order to propose a more comprehensive model for calculating T○f. The effects of oxygen enrichment rate， blast temperature， blast humidity and coal rate on T○f were analyzed and compared among the traditional model， the original modified model and the present parameters model under different blast respectively. The results showed that compared with the traditional model and original modified model， the calculation value of T○f using the present model under different blast parameters tends to be flatter and the thermal state of hearth is relatively stable. Actually， according to two kinds of smooth operation conditions existing in the practical production which are “high oxygen enrichment rate， low coal injection rate” and “low oxygen enrichment rate， high coal injection rate” with suitable Tf， it was verified that this model could appropriately reflect the actual thermal state of hearth in blast furnace(BF). References | Related Articles | Metrics

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Microwave Hydrothermal Synthesis and Characterization of Y/SBA-15 SHI Chun-wei， WU Wen-yuan， BIAN Xue， BAI Yu-ting 2015, 36 (3):  397-401.  DOI: 10.12068/j.issn.1005-3026.2015.03.021 Abstract ( 670 )   HTML   PDF (1065KB) ( 797 )   A microwave radiation hydrothermal method to control synthesis of micro-and mesoporous Y/SBA-15 composite molecular sieves was reported. The effects of pH， molar ratio of silica and P123， microwave power， stirring speed， and crystallization temperature on the growth of Y/SBA-15 were observed by X-ray diffraction(XRD). The composite zeolite synthesis conditions were identified:the pH value was 2.5， the molar ratio of silica and P123 was 58， the microwave power was 200W， the stirring speed was 250r/min， and the crystallization temperature was 120℃. The synthesized samples were characterized by N2 adsorption-desorption and TEM. The results showed that synthetic products with regular crystallinity of short rod of uniform size show the microporous and the mesoporous structures at the same time. Pore size distribution of microporous and mesoporous structures is uniform. The adsorption study indicated that Y/SBA-15 has the average pore diameter of 4.05013nm， the pore volume of 0.350525cm3/g， and the hole wall thickness of 2.2nm， respectively. References | Related Articles | Metrics

Mechanical Engineering

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Design of Dynamic Similarity Model of Rotor System Considering the Bearing Stiffness LUO Zhong， CHEN Guang-kai， LI Jian-zhang， WANG Fei 2015, 36 (3):  402-405.  DOI: 10.12068/j.issn.1005-3026.2015.03.022 Abstract ( 628 )   HTML   PDF (366KB) ( 1061 )   To solve the design problem of dynamic similarity model experiment of bearing-rotor system， a design method of scale geometric distortion model was proposed. This model could keep the same intrinsic characteristics between the prototype and experimental verification. First， the dynamic similarity relations of rotor system were deduced by adopting integral simulation method. According to the theory of dimension analysis， the similarity relation of bearing support stiffness was established. Based on this， the model was designed to satisfy the intrinsic characteristic of prototype. The ANSYS simulation contrasts of the prototype and model were given. In order to demonstrate the validity of this method， experimental verification was given to verify the validity of the proposed design method of dynamic similarity. References | Related Articles | Metrics

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Numerical Simulation of Laser Ultrasonic Surface Wave Measurement of Residual Stress ZHAN Yu， LIU Chang-sheng， ZHANG Feng-peng， QIU Zhao-guo 2015, 36 (3):  406-409.  DOI: 10.12068/j.issn.1005-3026.2015.03.023 Abstract ( 789 )   HTML   PDF (627KB) ( 959 )   The propagation of surface wave which induced by the laser ultrasonic shock processing was simulated in half-space elastic materials by ABAQUS software. First， the effect of laser shock processing was equivalent to a modulated Gaussian pulse. To eliminate the undesirable reflections from boundary edges， the infinite elements were placed along the appropriate edges of the model. The received waves agree with the Rayleigh surface waves. Secondly， the effective elastic modulus method was introduced to simulate the initial residual stress in the surface region. Detection of surface velocity based on ultrasonic time-difference method was introduced. The numerical value and theory well fit experimental datas， which provid a way of using laser ultrasonic to measure of the residual stress. References | Related Articles | Metrics

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Analysis on Mechanical Properties of Human Intervertebral Disc Under Random Vibration GUO Li-xin， LI Rui 2015, 36 (3):  410-414.  DOI: 10.12068/j.issn.1005-3026.2015.03.024 Abstract ( 746 )   HTML   PDF (675KB) ( 775 )   A kind of 3D finite element model of L4-L5 segment intervertebral discs was developed. The relationship of compressive stress and shear stress with various body weight， body height and posture in driving cars was studied. The transfer function between the spine stress and the random vibration of the seat was researched. The results show that the maximum value of compressive stress and shear stress of the lumbar occurs during bending posture. The body height and weight influence the static shear stress and compression stress of the lumbar. The sitting posture of the driver influences the transfer function between the stress of spine and vibration acceleration. The stress of driving posture is smaller than bending posture regardless of the size of the human body， which indicates driving posture more comfortable. References | Related Articles | Metrics

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Molecular Dynamics Simulation of the Effect of Nanoparticles on the Tribological Properties of Lubricant Film HU Cheng-zhi， BAI Min-li， LYU Ji-zu， WANG Peng 2015, 36 (3):  415-418.  DOI: 10.12068/j.issn.1005-3026.2015.03.025 Abstract ( 690 )   HTML   PDF (534KB) ( 1199 )   The lubricant film has excellent load-carrying capacity， anti wear and friction-reducing properties with the addition of nanoparticles， but the physical mechanism is still unclear. Using molecular dynamics simulation， the difference of tribological properties between nanofluid and base fluid was studied when the lubricant film was confined to idealized atomistic surfaces. The interaction between nanoparticles and base fluid was studied. The results indicate that:under high load， liquid-solid transition takes place for both base fluid and nanofluid; the critical pressure of nanofluid phase transition is higher than that of the base fluid. After phase transition， nanofluid shows excellent friction-reducing properties. Nanoparticles can also increase the load-carrying capacity effectively and the enhancement effect is better after phase transition. The mechanisms responsible for the nanofluids friction properties are explained in detail. References | Related Articles | Metrics

Resources & Civil Engineering

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Control Method of Rock Caving Hazard During Transition from Open Pit to Underground Mining LI Hai-ying， REN Feng-yu， YAN Guo-fu， ZHAO Yun-feng 2015, 36 (3):  419-423.  DOI: 10.12068/j.issn.1005-3026.2015.03.026 Abstract ( 716 )   HTML   PDF (477KB) ( 791 )   Due to mutual interferences between the open pit & underground mining operations during the transition period from open pit to underground mining， poor safety production and difficult production continuation occur much more frequently. Aiming at the production conditions of ore-body at the open pit bottom and hanging-wall ore-body of underground mining during transition period， a method was proposed to control the hanging rock caving with the induced caving mining technology through the systematic study on the underground mining and rock caving. In this way， the safety conditions of open pit & underground mining could be improved， and the time and space of open pit & underground mining are also extended. The proposed method was adopted in Xiaowanggou Iron Mine to solve the problem of production discontinuation. The applied results show that a highly efficient and safe mining is realized during the transition from open pit to underground mining. References | Related Articles | Metrics

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Heat Transfer in Strata with Different Shape of Cross-Section and Dynamic Simulation of Thermal Environment for Deep Subsurface Mine LU Hao， LUO Zhou-quan， MOMAYEZ Moe 2015, 36 (3):  423-427.  DOI: 10.12068/j.issn.1005-3026.2015.03.027 Abstract ( 571 )   HTML   PDF (618KB) ( 710 )   It is a critical issue to adjust and control the subsurface mine climate based on the heat sources in airway and the temperature changes， heat gain and loss of key locations. By improving the traditional Fourier heat transfer model， a three-dimensional heat transfer model based on the actual cross-sectional shape of the ventilation airway was formulated. The momentum related boundary conditions which can reflex the velocity and quantity changes for different airway profiles also was specified， which associated with the time parameter to reveal the formation of heat conduction and exchange inside the strata and between the rock and airflow， and the heat transfer equation between wet wall and airflow was given at the meantime. On this basis， a large domestic ventilation system for deep subsurface metal mine was built， in order to obtain the trend and specialty of temperature， humidity， heat and some other parameters. This study lays the foundation for the deep subsurface mine to carry out climate regulation and control. References | Related Articles | Metrics

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Simulation of Critical Hydraulic Gradient in No Cohesive Soil with PFC3D WU Feng-yuan， LIANG Li， FAN Yun-yun， WANG Nan 2015, 36 (3):  428-432.  DOI: 10.12068/j.issn.1005-3026.2015.03.028 Abstract ( 953 )   HTML   PDF (764KB) ( 1230 )   In order to calculate the critical hydraulic gradient of no cohesive soil during water seepage， numerical simulation on seepage experiments was conducted with PFC3D. The numerical results agree well with the seepage experiments， thus verifying the effectiveness of PFC3D model. Then， the damage during seepage of no cohesive soils with different particle friction coefficient was numerically simulated. The results showed that critical hydraulic gradient of no cohesive soil during water seepage increases with the raising of particle friction coefficient. The PFC3D results agree well with the empirical results， and the effectiveness of calculation in seepage critical hydraulic gradient is validated. Compared to empirical formula， PFC3D can be available for analyzing the seepage under complex engineering and geological conditions. It can provide a scientific reference and basis for seepage calculation under complex conditions. References | Related Articles | Metrics

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Minimum Supporting Pressure of Shield Tunnel Face in Sandy Grand LIU Yu， TANG Chun-an， XIE Xin 2015, 36 (3):  433-436.  DOI: 10.12068/j.issn.1005-3026.2015.03.029 Abstract ( 797 )   HTML   PDF (526KB) ( 957 )   In the procedure of shield construction， the inappropriate controlling of support pressure on the tunnel face may cause risk of accident， such as the nearby pipeline rupture and the incline of existing buildings. The influence of different buried depth ratio (C/D)， internal friction angle on the instability mode of excavation face and the limit minimum support pressure was investigated on the basis of the Flac3D numerical model and limit equilibrium model. According to the comparison between the two different analysis methods， there is obvious difference between the support pressure predicted by the limit equilibrium model and the actual support pressure， which is caused by the fact that the limit equilibrium model cannot reflect the procedure that the coefficient of lateral pressure changes with the displacement of tunnel face and dynamic depth change. The research may provide great theoretical evidence to the engineering practice in the solid stratum. References | Related Articles | Metrics

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Analysis of Biomass Gasification Poisoning Accident Based on BN-bow-tie YAN Fang， XU Kai-li， YAO Xi-wen， WANG Yan-tong 2015, 36 (3):  437-441.  DOI: 10.12068/j.issn.1005-3026.2015.03.030 Abstract ( 863 )   HTML   PDF (701KB) ( 748 )   Occurrence probability of biomass gasification poisoning accident is 1.20298×10-4/d by transforming fault tree to Bayesian network. The two-way derived and diagnosed function of Bayesian network was used to calculate posterior probabilities and worth of each basic event. Then analyze the weak point which led to accident in the system. The reason and the consequence of failure were analyzed combining the bow-tie. Then prevention measures were got to prevent weak point from failure and control measures were adopted after it had turned to be failure. Thereby reduce the probability of accident. After adopting measures to weak point valve leakage it can reduce poisoning accident probability by 20.92%. The aim is to reduce accident probabilities. References | Related Articles | Metrics

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Fire Risk Assessment of Malls Based on the Cluster Analysis and AHP FANG Zheng， CHEN Juan-juan， XIE Tao ， WAN Xin 2015, 36 (3):  442-447.  DOI: 10.12068/j.issn.1005-3026.2015.03.031 Abstract ( 641 )   HTML   PDF (946KB) ( 959 )   According to the fire characteristics in malls， AHP (analytic hierarchy process)， which has the advantages in both semi-quantitative methods and qualitative methods， was used to establish fire risk assessment system. Through collecting expert questionnaires， the AHP and cluster analysis were integrated to calculate the index weight value in the system. According to the grading manual， this paper scored each index and calculated the values of the fire risk assessment to confirm the fire risk level of buildings. The practicability and reliability was verified by applying the assessment system in a clothing store in Wuhan. And the assessment system can be used not only in fire evaluation， but also in the insurance and others. References | Related Articles | Metrics

Management Science

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New Method for Total Factor Productivity Analysis: Fre-Primont Index HUANG Yi， SUN Guang-sheng， HUANG Jin-zhi 2015, 36 (3):  448-452.  DOI: 10.12068/j.issn.1005-3026.2015.03.032 Abstract ( 748 )   HTML   PDF (392KB) ( 823 )   To overcome the shortcomings of Malmquist index， Fre-Primont index was introduced on the basis of the total factor productivity definition. The properties and decomposition of total factor productivity were also discussed. Firstly， Fre-Primont index was developed with distance function as the aggregate function， and this index also exhibited multiplicative completeness and satisfied transitivity test. Then， with the economic connotations of related efficiencies， Fre-Primont index was decomposed into the product of technology progress， technical efficiency change， scale efficiency change and residual mix efficiency change completely. Finally， the total factor productivities of 29 provinces in China from 2001 to 2010 were studied empirically by using Fre-Primont index. References | Related Articles | Metrics

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Correlation Between Network Topological Index and Volatility of Shanghai Stock Market ZHUANG Xiao-wei， JIN Xiu 2015, 36 (3):  453-456.  DOI: 10.12068/j.issn.1005-3026.2015.03.033 Abstract ( 895 )   HTML   PDF (507KB) ( 977 )   Taking stocks and the correlation between stocks as network nodes and edge respectively， the network of Shanghai stock market was constructed by minimum spanning tree (MST). The basic topological index of network was calculated.And then the correlation between these indexes and stock market volatility was analyzed. The results show that there is a negative correlation between average path length of network and market volatility when market volatility is higher， distances between nodes are shorter， network contraction is closer; and there is a negative correlation between mean occupation layer and market volatility when the market volatility increases， nodes in the network close to the center node; and there is a positive correlation between the maximum number of links and market volatility when market volatility is higher， connection between the network nodes is strengthener，the co-movement tendency is reinforced. The volatility changing in the stock market is forecasted by analyzing the changing law of topological index of stock network. References | Related Articles | Metrics