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15 September 2018, Volume 39 Issue 9 Previous Issue    Next Issue
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Information & Control
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Information & Control

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Modeling and Optimal Control for Microgrid Using Matrix Perturbation Theory YAN Shi-jie， ZHAO Xiao-li， GAO Wen-zhong， HAN Yi-ming 2018, 39 (9):  1217-1221.  DOI: 10.12068/j.issn.1005-3026.2018.09.001 Abstract ( 618 )   HTML   PDF (551KB) ( 576 )   Aiming at the issue of microgrid system stability and output consensus， an optimal control method was proposed . The small signal model， coefficient matrix and an incremental perturbation matrix of microgrid system were established， which solved the problem that caused by large computation in the solution of system eigenvalues. On this basis， the objective function of the initial optimization was established by taking the stability， damping ratio and stability margin as the performance indexes. Combining the matrix perturbation theory with the artificial fish swarm algorithm， the initial optimal control of the system was achieved. Meanwhile， in order to ensure the consensus of frequency and voltage of the output of each micro-source in microgrid， the further optimization objective function was established and the artificial fish swarm algorithm was applied a second time for the further optimal control of the system. Finally， the simulation results show that the proposed control strategy is of validity and effectiveness. References | Related Articles | Metrics

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Spatio-Temporal Model Based on UML CHEN Xu， ZHANG Fu， CAO Dong-xia 2018, 39 (9):  1221-1225.  DOI: 10.12068/j.issn.1005-3026.2018.09.002 Abstract ( 653 )   HTML   PDF (732KB) ( 607 )   There are a lot of spatio-temporal data in the real world. The management of spatio-temporal data has proposed higher requirements for spatio-temporal modeling， which has become a hotspot in many fields. UML is a widely used unified modeling language， and the spatio-temporal extension model based on UML has become an important spatio-temporal modeling approach of many fields. This paper presents a spatio-temporal UML model， which can deal with a variety of spatio-temporal topology relationships (including RCC-8 spatial topology and Allen-13 temporal topology relationships) and the complex semantic relations among the spatio-temporal objects. In addition， this paper provides a formal definition and semantic interpretation of spatio-temporal UML model. Finally， an example of cadastral change is provided to demonstrate the feasibility and practicability of the proposed model. References | Related Articles | Metrics

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Image Retrieval Algorithm of Pulmonary Nodules Based on Similarity Measurement WEI Guo-hui， QI Shou-liang， QIAN Wei， ZHANG Kui-xing 2018, 39 (9):  1226-1231.  DOI: 10.12068/j.issn.1005-3026.2018.09.003 Abstract ( 724 )   HTML   PDF (610KB) ( 641 )   In order to overcome the shortcomings that CT of pulmonary lesions is complex and is very easy to lead to misdiagnosis， a medical image retrieval algorithm based on similarity measurement was proposed to diagnose lung cancer. The similarity measurement maintains the semantic relevance and visual similarity of the image. Firstly， a distance metric learning algorithm was constructed to learn a Mahalanobis distance on the basis of the proposed similarity measurement. Secondly， a novel medical image retrieval algorithm was proposed based on the learned distance metric to diagnose lung cancer. The study results demonstrate the feasibility and effectiveness of the proposed retrieval algorithm in lung cancer diagnosis. References | Related Articles | Metrics

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Quantitative Analysis of Diffusion Tensor Imaging of Subjects with Multiple Sclerosis QI Shou-liang， LI Meng， GAO Qing-jun， YU Hui 2018, 39 (9):  1232-1237.  DOI: 10.12068/j.issn.1005-3026.2018.09.004 Abstract ( 645 )   HTML   PDF (964KB) ( 692 )   A novel analysis method of magnetic resonance diffusion tensor imaging (DTI) was proposed， which combined the voxel-based analysis (VBA) with the white matter parcellation mapping (WMPM). Using this method， the locations and severities of white matter lesions of multiple sclerosis (MS) patients have been clarified. The voxels with significant difference of the fractional anisotropy (FA) and the mean diffusivity (MD) between MS patients and healthy controls (HC) are identified by VBA， and the distributions of these voxels in different white matter parcellations can be determined. It is shown that FA in MS group is significantly lower in 11 parcellations， mainly located at body and splenium of corpus callosum and both sides of corona radiate top. On the contrary， the higher MD is found in 22 parcellations including body and splenium of corpus callosum and posterior limb of right internal capsule. Therefore， the quantitative analysis of DTI through the proposed method provides effective references for the diagnosis and treatment of MS patients. References | Related Articles | Metrics

Materials & Metallurgy

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High-Temperature Oxidation Behavior of X80 Pipeline Steel CAO Guang-ming， LIN Fei， LI Zhi-feng， LIU Zhen-yu 2018, 39 (9):  1237-1241.  DOI: 10.12068/j.issn.1005-3026.2018.09.005 Abstract ( 692 )   HTML   PDF (1049KB) ( 634 )   The high-temperature oxidation behavior of X80 pipeline steel was studied systematically by the thermogravimetric analysis. The oxidation weight gain， morphologies of the oxide scale and the distribution of alloying elements at the oxide/substrate interface at different temperatures were analyzed. The results show that in the range of 700~1200℃， the curves of oxidation weight gain of X80 steel follow the parabolic law and the thickness of the oxide scale increases with the temperature， especially when the temperature is higher than 800℃， owing to the phase transformation in the substrate. The oxide scale of X80 steel has a typical three-layer structure at high temperature， consisting of the outer thin Fe2O3 layer， the middle Fe3O4 layer and the inner FeO layer with the coarse columnar. Also， there is an internal oxidation layer with fine grains formed near the steel substrate. The internal oxidation layer suppresses the interdiffusion of iron and oxygen ions， and improves the high-temperature corrosion resistance of X80 pipeline steel. References | Related Articles | Metrics

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Numerical Simulation for the Influence of Cohesive Zone Shape on Distribution of Unburned Pulverized Coal in Blast Furnace DING Zhi-min， JIANG Xin， WEI Guo， SHEN Feng-man 2018, 39 (9):  1242-1247.  DOI: 10.12068/j.issn.1005-3026.2018.09.006 Abstract ( 647 )   HTML   PDF (797KB) ( 622 )   In order to improve blast furnace (BF) operation and reduce the negative influence of unburned pulverized coal on BF performance， the "Euler-Euler" method was used to simulate the distribution of unburned pulverized coal in BF. The distribution of unburned pulverized coal in BF with three kinds of cohesive zone and the influence of cohesive zone shape on the distribution of unburned pulverized coal were investigated. For different cohesive zones， the total amount of unburned pulverized coal and the regional accumulation amount of unburned pulverized coal were compared. The simulation results show that the unburned pulverized coal is mainly accumulated below the cohesive zone of BF. The deadman， the region below the raceway， the cohesive area， and the top and root of the cohesive zone are the main regions where the unburned coal powder easily accumulates. The W-shape cohesive zone is the best blast furnace operation mode. The reasons are: the distribution of unburned pulverized coal in BF is relatively uniform; more pulverized coal can be accommodated under a specific differential pressure condition. References | Related Articles | Metrics

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Integrated Model of Oxygen-Enriched Blast Furnace YU Xiao-bing， NI Wen-jie， ZOU Zong-shu 2018, 39 (9):  1248-1253.  DOI: 10.12068/j.issn.1005-3026.2018.09.007 Abstract ( 723 )   HTML   PDF (546KB) ( 651 )   Aiming to solve the problem of “hot lower part and cool upper part” in blast furnace with oxygen enrichment blowing， this work has developed a model considering necessary conditions in practice to calculate the heat balances of both the high- and low-temperature zones respectively. The model is expected to study the variation of thermal state of blast furnace and the possible corresponding countermeasures in oxygen enrichment blowing operation. This paper describes the process of model development and validation through comparing with practical production data. The result under conditions of the base case shows that， when oxygen enrichment ratio increases by 1%， the top gas temperature decreases by 14℃. For the operation with an oxygen enrichment rate of 1.7%， the heat balances of both high-and low-temperature zones can be ensured with no additional countermeasures. Besides， the difference between the theoretical minimum direct reduction degree calculated by this model and the reduction degree acquired in practice proves that there is still some room to further reduce the fuel rate in blast furnace ironmaking. References | Related Articles | Metrics

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Preparation and Photocatalytic Properties of Visible Light for YFeO3 Powders LI Feng-hua， ZHOU Shuang， YUE Hong-rui， SHI Xiao-guo 2018, 39 (9):  1253-1257.  DOI: 10.12068/j.issn.1005-3026.2018.09.008 Abstract ( 782 )   HTML   PDF (640KB) ( 729 )   The YFeO3 powder of different crystallographic structures was prepared by using the sol-gel method. The products were characterized by X-ray diffraction (XRD)， differential thermal analysis-thermogravimetric (DTA-TG) analysis， special surface area analysis (the BET method)， and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The photocatalytic activities of the samples were evaluated by using the photocatalytic degradation of methylene blue (MB) under visible light. The results show when the temperature increases from 973K to 1073K， the crystallographic structure of the YFeO3 power changes from hexagonal to orthorhombic phase. Compared with orthorhombic phase of the YFeO3， the hexagonal phase presents a relatively larger specific surface area， a wider absorption edge， a narrower bandgap width， a more negative valence position， and a more positive conduction band position. Meanwhile， the performance of photocatalytic degradation of the MB is better. References | Related Articles | Metrics

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Influence of Internal Structure of Round Jet Nozzle on Heat Transfer Performance ZHANG Fu-bo， ZHANG Yong-chen， YANG Li-juan 2018, 39 (9):  1257-1261.  DOI: 10.12068/j.issn.1005-3026.2018.09.009 Abstract ( 624 )   HTML   PDF (654KB) ( 754 )   The impingement heat transfer performance of jets from conical and cylindrical nozzles was studied. Under the same initial and boundary conditions， the simulations of coupled heat transfer and fluid flow in the impingement heat transfer process of the two nozzles were conducted by using computational fluid dynamics software Fluent. The fluid flow and temperature field data at the fluid-solid interface， such as static pressure， shear stress， turbulence intensity， convection heat transfer coefficient， were compared and analyzed. The simulation results show that the heat transfer performance of jet from conical nozzle is better than that from cylindrical nozzle. The conclusions obtained are of guiding significance to the design of nozzles for ultra fast cooling equipment of hot rolled steel. References | Related Articles | Metrics

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Effect of Acetate on Precipitation Behavior of Desilication Products During Bayer Process PAN Xiao-lin， WU Yan， JIANG Tao， TU Gan-feng 2018, 39 (9):  1262-1266.  DOI: 10.12068/j.issn.1005-3026.2018.09.010 Abstract ( 689 )   HTML   PDF (625KB) ( 642 )   The effect of acetate concentration in sodium aluminate solution at 145℃ on the mineral composition， microstructure and precipitation activity of desilication products was studied. The results show that when the acetate exists in sodium aluminate solution， the crystalline sodium aluminosilicate hydrate is comprised of zeolite and methylol-sodalite and the corresponding lattice constant increases with the acetate concentration. Furthermore， with the increasing acetate concentration， the crystallinity of zeolite and methylol-sodalite reduces， and the content of zeolite decreases， in contrast with that of the methylol-sodalite. The effect of the acetate on the structure of functional group and microstructure of desilication products is very little. However， the additive of acetate can increase the molar ratio of Na2O to Al2O3 and decrease the molar ratio of SiO2 to Al2O3. Moreover， with the increasing acetate concentration， the particle size of desilication products decreases and the precipitation activity in sodium aluminate solution increases. References | Related Articles | Metrics

Mechanical Engineering

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Effect of Hovering State Rotor Parameters on the Nonlinear Vibration of the Rolling Bearing System SUN Zhao-ning， LI Xiao-peng， LI Mu-yan， WEN Bang-chun 2018, 39 (9):  1266-1271.  DOI: 10.12068/j.issn.1005-3026.2018.09.011 Abstract ( 721 )   HTML   PDF (1791KB) ( 589 )   Based on the model of the double disc rotor-rolling bearing system， a dynamic equation was established by using the finite element method， the vibration response of the rotor system was obtained by the numerical method， and the maneuver load was analyzed. The influence of eccentricity and maneuver load on the nonlinear vibration and bifurcation characteristics of the rotor system was analyzed， which provided theoretical guidance for researching the rotor dynamic system that is more in line with the actual coupling faults under complex working conditions. There are abundant nonlinear dynamic phenomena in the system near the double critical speed. With the increase of the maneuver load， the main resonance speed increases， and the vibration forms of the system tend to stabilize the single-period motion within the rotational speed range. The rotor system can not only produce 1/2 subharmonic resonance， but also produce some low frequency vibrations under some parameters. References | Related Articles | Metrics

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Modeling and Simulation of Micro-cantilever Vibrating in Inviscid Fluid Domains MA Shu-jun， XUAN Hang， SUN Jia-wei， YANG Lei 2018, 39 (9):  1272-1276.  DOI: 10.12068/j.issn.1005-3026.2018.09.012 Abstract ( 642 )   HTML   PDF (1228KB) ( 803 )   Based on the Euler-Bernoulli beam theory， the resonant frequency of micro-cantilever in vacuum was derived and calculated， then the resonant frequency of micro-cantilever in fluids with different density was calculated according to the classical non-viscous theoretical model. In the finite element software ANSYS (16.0) simulation environment， the solid45-fluid30 and shell63-fluid30 units were used to establish a three-dimensional model of micro-cantilever in the fluid domain and modal analysis was also performed. Finally， the simulation results were compared with the experimental and theoretical data reported by other researchers. Besides， experiments were done to verify the correctness of the finite element model. The theory that density of inviscid fluid is the main factor affecting the resonant frequency of micro-cantilever， is further verified by the finite element method and experimental method. References | Related Articles | Metrics

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Dynamic Load Identification Based on the Houbolt Method ZHAO Chun-yu， HUANG Qing-yun， ZHANG Yi-min 2018, 39 (9):  1277-1282.  DOI: 10.12068/j.issn.1005-3026.2018.09.013 Abstract ( 943 )   HTML   PDF (626KB) ( 769 )   The formulae of the dynamic response related to the excitation and dynamic parameters for a multiple-degree-of-freedom linear vibration system were deduced by virtue of the Houbolt integration and backward difference methods. Then a new method for load identification of unconditional stability was proposed. Taking a linear elastic cantilever beam as an example， the exciting loads were identified using the simulation results of the single inputs of single frequency and dual frequencies， and the dual inputs of dual frequencies. Compared with the conventional state space method， the relative errors and frequency spectrum of the loads identified by the proposed method were smaller in both time and frequency domains， and there was no frequency increasing. This proposed method has improved identification accuracy and has a good anti-noise performance. References | Related Articles | Metrics

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Wear Experiment of Carbide Tool for Milling Nickel-Based Single Crystal Superalloy DD5 GONG Ya-dong， LIANG Cai-xia， LI Qiang， LIU Ming-jun 2018, 39 (9):  1283-1288.  DOI: 10.12068/j.issn.1005-3026.2018.09.014 Abstract ( 764 )   HTML   PDF (1799KB) ( 709 )   To explore the regulation of tool wear on milling surface of DD5 under the conditions of dry cutting and water-based minimum quantity lubrication(WMQL)， carbide tool with four blades and PVD-TiAlN coating， super depth of field microscope and scanning electron microscopy(SEM)were employed. Taking the wear width of minor flank surface of cutting tool as the evaluation indicator， tool wear forms and wear mechanism were analyzed and studied. Three-dimensional measuring system profiler was used to measure the machined surface roughness. The result shows that， compared to dry cutting， water-based MQL technology can prolong tool life and improve the milling performance. The wear of carbide tool is caused by adhesion wear， oxidative wear， abrasive wear and diffusion wear. References | Related Articles | Metrics

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Method for Grinding State Monitoring of Novel Point Grinding Wheels Based on AE Signal YIN Guo-qiang， GONG Ya-dong， LI You-wei， WANG Fei 2018, 39 (9):  1288-1292.  DOI: 10.12068/j.issn.1005-3026.2018.09.015 Abstract ( 846 )   HTML   PDF (1232KB) ( 619 )   A method for grinding state real-time monitoring of a novel point grinding wheel was proposed based on the acoustic emission(AE) signal. The correspondence between surface roughness and the AE signals were established， which provided the condition for monitoring the surface roughness. Single factor experiments were used to obtain the influence of parameters on RMS values of the AE signals. The conclusion further proves the correspondence. Firstly， the AE signals of different wear state of grinding wheel were compared and analyzed. According to this signal， the grinding process could be monitored in real time. Secondly， in order to distinguish the sources of the AE signals， spectrum analysis of the AE signals was carried out. When the grinding wheel worn， the energy of AE signals in 45~65kHz， 80~90kHz and 100~110kHz were significantly increased and there is a high spike at 15kHz. Therefore， the as-proposed method is feasible and effective. References | Related Articles | Metrics

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Research on Milled Surface Roughness of DD5 Single Crystal Superalloy Based on Water-Based MQL Method LI Qiang， GONG Ya-dong， LIANG Cai-xia， LIU Ming-jun 2018, 39 (9):  1293-1298.  DOI: 10.12068/j.issn.1005-3026.2018.09.016 Abstract ( 701 )   HTML   PDF (1211KB) ( 622 )   In order to explore the relative problems of milled surface roughness of DD5 single crystal Ni-based superalloy， based on the response surface method(RSM)and water-based minimum quantity lubrication(MQL)technique， a series of milling experiments on(001)crystal plane along ［110］ crystal direction with the four flute whole end mill were conducted. The main spindle linear speed， tool feed per tooth， cutting fluid flow rate， air pressure and the flow rate ratio of water and oil were selected as the variables， while the surface roughness R○a was chosen as the evaluation indicator. Based on the range and variance analysis， the milling and cooling parameters that significantly affect the surface quality were found out and the interactive effects were deeply studied. Moreover， the surface roughness was predicted and optimized with stepwise regression and particle swarm optimization(PSO)method， respectively. The results were verified based on the uniform design method. References | Related Articles | Metrics

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Adaptive Control of the Nonlinear Suspension System Based on Road Estimation SUN Jin-wei， QIN Ye-chen， WANG Zhen-feng， GU Liang 2018, 39 (9):  1299-1303.  DOI: 10.12068/j.issn.1005-3026.2018.09.017 Abstract ( 744 )   HTML   PDF (852KB) ( 826 )   To adjust the control parameters according to road levels and study the characteristics of suspension nonlinear parameters under different road levels， an algorithm was proposed based on cuckoo search optimization and road estimation. Firstly， a quarter nonlinear suspension model with nonlinear dampers and springs was created， which sprung mass acceleration and tire deflection were taken as the optimization objective and the current of nonlinear dampers was taken as the optimization variable. Then， a cuckoo search-based multi-objective optimization method was used to calculate the optimal control parameter， and a road estimation method was used to identify the road level to adaptively adjust the system performance according to road input. The simulation results showed that: 1) the road estimation and cuckoo search-based algorithm can adjust the control parameter adaptively according to road levels， and the proposed method can improve riding comfort when the tire keeps contacting the road surface; 2) compared with the particle swarm optimization(PSO)， the current calculated by cuckoo search can provide better suspension performances. References | Related Articles | Metrics

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Numerical Analysis of Fracture Splitting Technology of Rear Axles’ Main Reducer Shell Bearing Seats JIN Wen-ming， YAO Juan， ZHAO Yong， GUO Bei-bei 2018, 39 (9):  1304-1308.  DOI: 10.12068/j.issn.1005-3026.2018.09.018 Abstract ( 689 )   HTML   PDF (2187KB) ( 639 )   The initial fracture splitting process of rear axles’ main reducer shell bearing seats was simulated by ABAQUS and a numerical analysis was carried out. The material of the shell bearing seats is QT450 with 50% pearlite in the matrix structure. The position of the starting cracking point was determined by J integral， and the splitting force was then calculated. The plastic deformation of the crack tip region when cracking and its effect on the loss of circle were analyzed， and an experimental study was conducted. The results show that the starting cracking point of the bearing is located near the middle of the crack tip. The plastic area located at the root of the crack tip is of butterfly-shaped distribution， resulting in the small loss of circle of bearing holes. The processing quality of fracture splitting is qualified， which is suitable for the application of fracture splitting technology.The research result lays a solid theoretical foundation for improving the production process of shell bearing seats， and provides a reference for the selection of splitting materials of shell bearing seats， the design of splitting equipment and the formulation of processing procedures. References | Related Articles | Metrics

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Layout and Size Optimization Design of Tower Crane Boom Webs WU Qing-long， ZHOU Qi-cai， XIONG Xiao-lei， JIAO Hong-yu 2018, 39 (9):  1309-1314.  DOI: 10.12068/j.issn.1005-3026.2018.09.019 Abstract ( 869 )   HTML   PDF (1545KB) ( 845 )   For the layout and size optimization of tower crane booms， a two-stage topology and size optimization method was proposed. In the first stage， a periodic plate-beam topology optimization model of the boom was established， and the continuum topology optimization of the web plate was performed by using the periodic SKO method. After getting the optimized topology of web plate， the optimized web topology was transformed into a discrete web layout through the extraction of the principal stress path. In the second stage， the size optimization mathematical model was established with the web radius taken as the design variable， the boom compliance as the objective function and the material volume of the boom as the constraint. The size optimization criterion was deduced by the Lagrange multiplier method and Kuhn-Tucker condition. In addition， the stability constraints of the webs were proposed to ensure the boom stability during the size optimization process based on the Euler formula. By comparing the original boom with the optimal booms， the optimization method can effectively reduce the mass of the boom， increase the rigidity of the boom， and reduce the deformation and structural stress level. References | Related Articles | Metrics

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Column Generation Scheduling Algorithm of Reentrant Hybrid Flow Shops(RHFS) with Queue Constraints ZHOU Bing-hai， WANG Ke 2018, 39 (9):  1315-1320.  DOI: 10.12068/j.issn.1005-3026.2018.09.020 Abstract ( 650 )   HTML   PDF (426KB) ( 610 )   To effectively enhance the production efficiency of multi-reentrant workshop， the queue constraint was considered where products were processed layer by layer， and then a scheduling method of reentrant hybrid flow shops(RHFS)was proposed based on column generation algorithm. Firstly， a two-stage scheduling model of RHFS was described and a mathematical programming model was built with an objective of minimizing the total completion time. A column generation algorithm was developed and dynamic programming with multiple decision-making was designed to solve each sub-problem. Further， the adaptive accelerating strategy was applied to effectively improve the algorithm convergence. In the process of generating integral solutions by using branch-and-bound method， column pool was built and neighborhood mutation method was emploied. Finally， numerical experiments in different problem scales were carried out to analyze the proposed algorithm. Results verify the validness and feasibility of the proposed algorithm. References | Related Articles | Metrics

Resources & Civil Engineering

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Improved Induced Caving Mining Method for Hanging Wall Ore with Deep Concave Features FAN Xiao-ming， REN Feng-yu， XIAO Dong， MAO Ya-chun 2018, 39 (9):  1321-1326.  DOI: 10.12068/j.issn.1005-3026.2018.09.021 Abstract ( 703 )   HTML   PDF (1492KB) ( 631 )   The Dagushan iron mine is a large deep concave open-pit iron mine. During the transitional period from open-pit to underground mining， a new underground transition mode of improved induced caving mining for hanging wall ore was adopted. The 3D modeling of the existing hanging wall ore was carried out in Dagushan mine. Based on the the safety requirements of open-pit and underground cooperative mining in transitional mode， the south-hanging wall ore was selected as the open-pit and underground cooperative mining area during the first phase of the transitional period. By adopting a reasonable sequence of extraction， the range and volume of collapse pit at the slope were controlled， so that the slip body slides into the collapse pit. In the second stage of the transition from open-pit to underground mining， the mining of the east hanging wall ore was used to rapidly improve the underground mining capacity and to control the sliding rock mass of the east side slope in a reasonable manner. Finally， it was used to design and verify the mining method of transition from open-pit to underground in Dagushan iron ore mine. References | Related Articles | Metrics

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Required Strength Model and Influence Factors of Stage Backfill-Pillar with Double Exposed Faces YANG Lei ， QIU Jing-ping， SUN Xiao-gang， XING Jun 2018, 39 (9):  1327-1331.  DOI: 10.12068/j.issn.1005-3026.2018.09.022 Abstract ( 604 )   HTML   PDF (821KB) ( 563 )   Stage backfill-pillar with double exposed faces subjected to biaxial loads is prone to shear failure. In order to determine the required strength of backfill reasonably， Terzaghi theory on loosing earth pressure and limit equilibrium theory of sliding wedge were used to build a required strength model of stage backfill-pillar. Influencing factors for the required strength of stage backfill-pillar were analysed. The results show that stope depth and structure parameters have a positive effect on the required strength of stage backfill-pillar， while internal friction angle of backfill， and the coefficient of friction and angle between backfill and surrounding rock have a negative effect on it. The results are of great practical significance in guiding backfilling ratio， preventing ground subsidence and protecting the environment. References | Related Articles | Metrics

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Study of Hierarchical Adaptive Threshold Micro-seismic Signal Denoising Based on Wavelet Transform CHENG Hao， YUAN Yue， WANG En-de， FU Jian-fei 2018, 39 (9):  1332-1336.  DOI: 10.12068/j.issn.1005-3026.2018.09.023 Abstract ( 688 )   HTML   PDF (999KB) ( 661 )   Random noise contained in the mine micro-seismic signal has serious interference to the micro-seismic monitoring and the accurate positioning of the micro-seismic source. According to the previous research and the actual application effects， the paper proposed a new denoising method with the hierarchical adaptive threshold based on the characteristics of mine micro-seismic signals. It adds the layered adaptive factors to the hierarchical threshold. According to the low frequency characteristic of the mine micro-seismic effective signal， the noise signal of the high frequency part is removed greatly by using the layered adaptive factor to improve the signal to noise ratio of the mine micro-seismic signal. And the signal of the low frequency part is maximally kept. The validity and superiority of the method are illustrated by comparing the hierarchical threshold with the real-field micro-seismic data. References | Related Articles | Metrics

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Effects of Stirring Intensity on the Flow Field Characteristics for Liquid-Solid Two Phases in Flotation Machine WANG Xue-tao， WEI De-zhou， GAO Shu-ling， CUI Bao-yu 2018, 39 (9):  1337-1342.  DOI: 10.12068/j.issn.1005-3026.2018.09.024 Abstract ( 591 )   HTML   PDF (2125KB) ( 592 )   The internal flow field characteristics of KYF flotation machine of 20 L for liquid-solid two phases were numerically simulated using standard k-ε turbulence model and particle model. The study results show that the flow field in the flotation machine distributes into two cycles up and down， the flow velocity of the mixing and rising zones is higher than that of separating zone. The velocity of mineral particles in mixing and rising zones is inversely proportional to particle size， while the velocity in the separating zone is proportional to particle size. The higher pressure distribution zone is located at the windward of the stator or impeller respectively. Besides， the absolute pressure is proportional to the stirring intensity. The volume fraction of particles is proportional to the particles size in mixing and rising zones and it decreases with the increasing of stirring intensity， which is contrary to the separating zone. Therefore， the rotational impeller speed of 600r/min is more advantageous to improve the working performance of the flotation machine. References | Related Articles | Metrics

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Flexural Behavior of Corroded Steel Beams Strengthened with Prestressed CFRP Sheets Under Overloading HOU Wen-yu， WANG Lian-guang 2018, 39 (9):  1342-1347.  DOI: 10.12068/j.issn.1005-3026.2018.09.025 Abstract ( 551 )   HTML   PDF (1307KB) ( 581 )   In order to investigate the flexural behavior of corroded steel beams strengthened with prestressed CFRP sheets under static loading or overloading， the bending tests of seven steel beams were carried out to study the failure mode， bearing capacity and stiffness of the corroded steel beams. The results showed that the CFRP sheets could improve the stiffness and bearing capacity， and adding prestress to the steel beam could remarkably improve the use of CFRP sheets. The corrosion could influence both the stiffness and bearing capacity. The bearing capacity decreased by about 50% when the corrosion degree increased by 1 times. The improvement of the overloading numbers can improve the stiffness by 13% because of the steel’s age hardening， but the bearing capacity can reduce. And the prestress can improve the ductility of the steel beam. The formula of ultimate bearing capacity was established， and the calculated results agreed well with the experimental results. References | Related Articles | Metrics

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Calculation on Active Limit Support Pressure of Shield Tunnel Excavation Face in Dry Cohesionless Soil CHENG Cheng， ZHAO Wen， CHENG Chao-nan， LI Fei 2018, 39 (9):  1348-1352.  DOI: 10.12068/j.issn.1005-3026.2018.09.026 Abstract ( 640 )   HTML   PDF (833KB) ( 654 )   Reasonable calculation on the support pressure of tunnel face is important for tunnel stability. Based on the silo theory and the 3D wedge model， the sliding block ahead of the face was assumed as an arc wedge composed by part of a sphere and half a circular truncated cone; and the upper silo of the sliding block is assumed as half a cylinder. The active limit face support pressure on the excavation face in dry cohesionless soil was derived based on the equilibrium of the sliding block according to the equations of Terzaghi loose earth pressure and Rankine active earth pressure. The calculation results from the proposed equation are less than that from Wei Gang’s model and the 3D wedge model， but is close to the results by Chambon’s centrifuge model tests. The restrictions of this method was discussed through calculation error analysis. References | Related Articles | Metrics

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Stability Assessment and Mechanical Effects Analysis on Deep Foundation Pit in Sandy Soil CHEN Yang， ZHAO Wen， JIA Peng-jiao， HAN Jian-yong 2018, 39 (9):  1353-1357.  DOI: 10.12068/j.issn.1005-3026.2018.09.027 Abstract ( 725 )   HTML   PDF (1093KB) ( 1015 )   The horizontal and lateral displacements of pile-cap and the ground settlement of the surrounding soils of a foundation pit of a subway station in sandy soil were investigated based on the in-situ monitoring data. The changing rules of the displacement of the inner supporting system and the deformation of the surrounding soils with excavation time and excavation depth were obtained. A two-dimensional finite element model was built to analyze the internal forces of the supporting structures as well as the stress redistribution in soils behind those piles. Numerical results agree well with the in-situ monitoring data. Results indicate that the horizontal displacement of the pile-cap in the long side direction of the foundation pit is three times than that in the short side direction; the maximum lateral displacement of the piles occurs at 1/2H(H is the depth of the foundation pit). The range of the ground settlement induced by excavation and drainage is 3H. The largest deformation in the surrounding soil is located 22m away from the excavation edge(0.82H~0.96H). It is found that the inner supporting system can effectively improve the stability of the foundation pit. References | Related Articles | Metrics

Management Science

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Impact of Compulsory Citizenship Behavior on Employees’Job Burnout—A Mediated Moderation Model ZHANG Lan-xia， YANG Shuo， ZHANG Liang-ting， LI Bing 2018, 39 (9):  1358-1363.  DOI: 10.12068/j.issn.1005-3026.2018.09.028 Abstract ( 766 )   HTML   PDF (396KB) ( 761 )   Based on the relevant theories and literatures together with a survey questionnaire from 313 employees， the transfer mechanism of employees’ perceptions of organizational justice between compulsory citizenship behavior and employees’ job burnout was investigated， and the moderating effect of employees’ psychological capital was tested. The results showed that compulsory citizenship behavior has significant positive impacts on employees’ job burnout， employees’ perceptions of organizational justice mediate the relationship between compulsory citizenship behavior and employees’ job burnout， and employees’ psychological capital adjusts the moderating effect of compulsory citizenship behavior on employees’ job burnout via their perceptions of organizational justice. References | Related Articles | Metrics

力学

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Experiment and Finite Element Simulation for Laser Ultrasonic Measurement of the Elastic Constants of Metal Materials ZHAN Yu， LIN Zhong-ya， LIU Chang-sheng 2018, 39 (9):  1363-1368.  DOI: 10.12068/j.issn.1005-3026.2018.09.029 Abstract ( 681 )   HTML   PDF (824KB) ( 917 )   The elastic constants of aluminum plates were inversed by the wave velocity of various modal ultrasonic waves induced by lasers. In the experiment， the pulse laser was focused into the line source to induce the ultrasonic wave on the surface of the aluminum plate， and the dual channel non-contact method was used to receive the time domain information of the surface wave and then its velocity was measured. In the finite element analysis， the laser was equivalent to the pulse load that is satisfied with the Gaussian distribution both in time and space. A thermal coupling analysis model was built to simulate the process of laser induced ultrasonic. The time domain information of the ultrasonic signals were received to calculate the surface wave’s and longitudinal wave’s velocities. Then the elastic constants of aluminum plates were obtained by using the acoustic elastic equation. The numerical results agreed with the theoretical values， which indicates that the established laser ultrasonic model can effectively simulate the physical process of ultrasonic induced by lasers， and provide the basis for further studies on the mechanical properties of the materials by laser ultrasonic techniques. References | Related Articles | Metrics