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15 April 2018, Volume 39 Issue 4 Previous Issue    Next Issue
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Information & Control

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Thermal Analysis of Axial-Flux Permanent Magnet Couplers Using Electromagnetic-Thermal Coupling Method ZHENG Di， WANG Da-zhi， LI Shuo， YU Lin-xin 2018, 39 (4):  457-461.  DOI: 10.12068/j.issn.1005-3026.2018.04.001 Abstract ( 814 )   HTML   PDF (627KB) ( 1063 )   The temperature of axial-flux permanent magnet couplers was analyzed using the electromagnetic-thermal coupling method. On the basis of analytical magnetic field calculation， a magnetic field analytical model of the axial-flux permanent magnet couplers was presented to derive the eddy current loss formula. The thermal resistance and heat transfer coefficient were calculated， and a thermal model of axial-flux permanent magnet couplers was established by taking the eddy current loss as the heat source. The electromagnetic-thermal coupling method was analyzed to predict the effect of various loads on eddy current loss and copper plate temperature rise. The analytical results compared with the finite element results showed that the magnetic field analytical model and the thermal model of axial-flux permanent magnet couplers using electromagnetic-thermal coupling method could predict the eddy current loss and the copper plate temperature rise reasonably and quickly. References | Related Articles | Metrics

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Formal Mapping Approach of Fuzzy OWL 2 Ontologies to Fuzzy Relational Databases LI Wei-jun， MA Zong-min， YAN Li， ZHANG Fu 2018, 39 (4):  462-467.  DOI: 10.12068/j.issn.1005-3026.2018.04.002 Abstract ( 629 )   HTML   PDF (361KB) ( 839 )   A relational database-based approach to store the fuzzy OWL 2 ontologies on the semantic Web was proposed. The structural and semantic characteristics of fuzzy OWL 2 ontologies were analyzed， and according to the fuzzy relational databases， storage architecture for the fuzzy OWL 2 ontologies were introduced， based on which， a formal mapping approach from the fuzzy OWL 2 ontologies to the fuzzy relational databases was presented. The results showed that the proposed formal mapping approach is rational and feasible. References | Related Articles | Metrics

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Adaptive Beamforming Algorithm for Medical Ultrasound Imaging BAO Xi-rong， LI Yu-zhen， SU Ting， ZHANG Shi 2018, 39 (4):  468-473.  DOI: 10.12068/j.issn.1005-3026.2018.04.003 Abstract ( 992 )   HTML   PDF (585KB) ( 1436 )   The traditional minimum variance(MV)adaptive beamforming algorithm for medical ultrasound has the disadvantages of poor robustness， limited image contrast enhancement and high algorithm complexity. So， according to the minimum variance beamforming based on QR decomposition(QRMV)， the sign coherence factor was introduced， and an adaptive beamforming algorithm of QRMV combined with sign coherence factor was proposed. The simulation results showed that the proposed algorithm in the aspects of resolution and contrast is superior to the conventional delay and sum(DAS)， MV and QRMV， and its performances are very close to SFMV， but its computational complexity is far lower than SFMV. References | Related Articles | Metrics

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Beaforming Algorithm Based on Minimum Variance Delay Multiplication and Sum for Medical Ultrasound SU Ting， YAO Ding-jie， LI Da-yu， ZHANG Shi 2018, 39 (4):  473-477.  DOI: 10.12068/j.issn.1005-3026.2018.04.004 Abstract ( 983 )   HTML   PDF (707KB) ( 901 )   Based on the characteristics of high correlation of ultrasonic echo signals， a minimum variance delay multiplication and sum beamforming(MVDMAS) algorithm was proposed. Firstly， according to the main idea of minimum variance beamforming， the weights of the received echo signals were calculated to decrease the side lobe level of echo signal. Then， the multiplication and sum operation was used for the weighted echo signals to reduce the correlation of the echo signals. Finally， the mathematical theory derivation and computer simulation verify the effectiveness of the proposed algorithm. Simulation results showed that the image contrast and resolution of the proposed algorithm are improved to some extent. The main lobe width， side lobe height， and speckle noise are reduced effectively. Compared with delay and sum (DAS)， minimum variance (MV)， and delay multiplication and sum (DMAS) beamforming， the comprehensive evaluation index contrast ratio (CR) and contrast noise ratio (CNR) are improved by 100.24%， 33.91%， 17.41% and 30.61%， 17.55%， 11.36%， respectively. References | Related Articles | Metrics

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Modeling Error Sources in Level Crossing Analog-to-Digital Converters JIN Shuo-wei， LI Jing-jiao， SU Rui-qin， LI Zhen-ni 2018, 39 (4):  478-482.  DOI: 10.12068/j.issn.1005-3026.2018.04.005 Abstract ( 576 )   HTML   PDF (512KB) ( 679 )   Level crossing analog-to-digital converter adopts asynchronous sampling method for data conversion. Different timing schemes in asynchronous sampling ADC were studied， and the effect of main error sources on the asynchronous sampling ADC performance was analyzed， especially for the limited resolution of the timer and the limited accuracy of the quantization levels. By optimizing the design， the maximum quantization error of the sampling time was reduced to half of the clock cycle， based on which the system SNR could be effectively improved. The equation of SNR was presented，and when the quantization resolution was large enough， SNR could be about 62dB for the fixed clock frequency. The correctness of the equation was confirmed by simulation. References | Related Articles | Metrics

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Improved Region-Scalable Fitting Image Segmentation Method GONG Zhao-xuan， TAN Wen-jun， GUO Wei， ZHAO Da-zhe 2018, 39 (4):  483-487.  DOI: 10.12068/j.issn.1005-3026.2018.04.006 Abstract ( 656 )   HTML   PDF (1101KB) ( 646 )   The region-scalable fitting(RSF) model can effectively solve the problem of intensity inhomogeneities， but the traditional RSF model only considers the case where the point on the image intersects with the zero level set in its local extension area， which easily leads to over-segmentation. To solve the problem， an improved region-scalable fitting method was proposed， i.e.， the case where every point in the image does not intersect with the zero level set in its extended neighborhood was considered based on the RSF model， and the value of intensity energy in this case was redefined to make the inner intensity energy and the outer intensity energy strictly equal. Experiment results showed the proposed method effectively solves the over-segmentation caused by the initialization problem. References | Related Articles | Metrics

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FAST Node Displacement Control Method Using Self-Tunning Fuzzy PID Control SHA Yi， FAN Qian-wen， ZHANG Li-li， ZHU Li-chun 2018, 39 (4):  487-491.  DOI: 10.12068/j.issn.1005-3026.2018.04.007 Abstract ( 727 )   HTML   PDF (822KB) ( 826 )   To solve the problem of achieving the expected moving position of more than 2400 nodes under the influence of the tension of adjacent points， wind， temperature and other factors， FAST node displacement control method was studied by using the self-tuning fuzzy PID combined with the improved scheme of variable domain scaling. By analyzing FAST node hydraulic actuator servo system， a transfer function of the controlled object was obtained. The controller was designed by analyzing the error and its corresponding rate of change， and feasible and effective variable domain scaling factor was chosen. The improved algorithm was modeled and simulated by Simulink. The results showed the feasibility of self-tuning PID control based on the variable domain for the FAST node displacement control. References | Related Articles | Metrics

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Robust Watermarking Algorithm Based on Combination of Phase and Amplitude of CS-SCHT Domain DU Li， GAO Li-ping， WEN Xin 2018, 39 (4):  492-496.  DOI: 10.12068/j.issn.1005-3026.2018.04.008 Abstract ( 629 )   HTML   PDF (721KB) ( 832 )   In order to improve the robustness of watermarking algorithms， a watermarking algorithm based on the phase and amplitude of CS-SCHT coefficient was proposed. Since the anti-interference ability of the phase is stronger than that of the amplitude， and the amplitude is invariant to rotation， shear， and scaling， a watermark was divided equally and then embedded in the phase and amplitude of the same transformation coefficient， respectively， which can combine the advantages of phase algorithms and amplitude algorithms and achieve the purpose of improving the robustness. Simulation results showed that the PSNR of the proposed algorithm is 47.4517dB without attack， and the normalized correlation coefficients are above 0.9 with various attacks. The proposed algorithm is more invisible. Moreover， it is robust to brightening， rotation， cutting， noise attack， and low-pass filter attack of Gaussian and JPEG compression. References | Related Articles | Metrics

Materials & Metallurgy

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As-Cast Microstructures of Low-Carbon Microalloyed Steel Produced by Twin-Roll Strip Casting WANG He-song， YUAN Guo， CAO Guang-ming， WANG Guo-dong 2018, 39 (4):  497-500.  DOI: 10.12068/j.issn.1005-3026.2018.04.009 Abstract ( 796 )   HTML   PDF (2944KB) ( 768 )   Low-carbon microalloyed steel was produced via twin-roll strip casting in the laboratory. The solidification structure， microstructure at room temperature， precipitate and dislocation of the as-cast strip were analyzed by OM， SEM and TEM. The results showed that the secondary dendrite arm spacing of the solidification structure is in the range of 12~15μm， which is much finer than that of the slab produced by the traditional process. The prior austenite grain of the as-cast strip is quite coarse with a size range of 250~410μm. The microstructure of the as-cast strip consists of Widmanstatten ferrite， pearlite and irregular ferrite. The nano-sized TiC precipitate and rod-like cementite are observed in the as-cast structure. The TiC precipitate in the as-cast strip is not obviously suppressed by the rapid solidification rate and secondary cooling rate (cooling in air) of the twin-roll strip casting. Furthermore， a large amount of dislocations in the as-cast strip are also observed， formed by rolling force among the casting rollers and nonuniform cooling rate of the second cooling process. References | Related Articles | Metrics

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Effect of Tempering Temperature on Microstructure and Mechanical Properties of High Cr Martensitic Heat Resistant Steel CUI Chen-shuo ， GAO Xiu-hua， SU Guan-qiao ， QUAN Xiu 2018, 39 (4):  501-505.  DOI: 10.12068/j.issn.1005-3026.2018.04.010 Abstract ( 868 )   HTML   PDF (3594KB) ( 1025 )   The microstructure and mechanical properties of 9% chromium martensitic heat resistant steel tempered at different temperature were investigated with the OM，TEM， SEM and EPMA．The results showed that the dislocation network，precipitation phase and lath martensite fragmentation after tempering were the main factors for the variations of mechanical properties. It was found that after normalizing and tempering at 760℃， the test steel had an excellent integrated mechanical properties， where the tensile strength at room temperature and 550℃ reached 657MPa and 556MPa， respectively， and the impact absorbing energy at 0℃ reached 285J. Tempering at 700， 820 and 850℃， promoted a substantial reduction in toughness. Under a high temperature service， the MX phase was dispersed uniformly in the ferrite and martensite without coarsening， and metastable polygonal structure was formed during the recovery of martensite at high temperature. Such combination of substructure and dispersed distribution can effectively enhance the high-temperature creep resistance of this heat-resistant steel. References | Related Articles | Metrics

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Microstructure and Fracture Toughness of Laser Remelting Treatment on FeNiCrAl Coating by High-Velocity Arc Spraying SHENG Zhong-qi， ZHOU Jing， HU Lan， WEI Shi-cheng 2018, 39 (4):  506-511.  DOI: 10.12068/j.issn.1005-3026.2018.04.011 Abstract ( 662 )   HTML   PDF (1763KB) ( 743 )   Remelting treatment of FeNiCrAl coating deposited by high-velocity arc spraying was conducted using laser technology. The microstructure， phase composition， microhardness and fracture toughness of the coating before and after remelting were analyzed. The results showed that the layer stack structure and pores of the spraying coating were eliminated， the microstructure of the coating became uniform and dense， and the interaction between the coating and the substrate were changed from mechanical combination to metallurgical bonding after remelting. Compared with the phases of the spraying coating， which consisted of α-Fe and intermetallic compounds， such as AlFe3， AlFe and Al0.4Fe0.6， three more phases could be observed after remelting， which were a new phase of Fe-Cr， the solid solution of ［Fe， Ni］ and carbide NiC○x. The average microhardness of the coating after remelting was 7.79GPa， which was about 3 times than that of the substrate (2.5GPa) and about 1.3 times than that of the spraying coating (6.0GPa). In the indentation test of the spraying coating， the indentation cracks appeared at the loads of 4.9 and 9.8N， corresponding to the average fracture toughness of spraying coating of 1.20MPa·m1/2， while no crack was found during loading of 2.94~9.8N after remelting. References | Related Articles | Metrics

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Effect of Heat Input on Microstructure and Tensile Deformation Behavior of Q460 Steel Weld Joint FENG Xiang-li ， WANG Lei， LIU Yang 2018, 39 (4):  511-515.  DOI: 10.12068/j.issn.1005-3026.2018.04.012 Abstract ( 690 )   HTML   PDF (5289KB) ( 760 )   The effect of heat input by submerged arc welding on microstructure and tensile deformation behavior of weld joint in Q460 steel was studied and its mechanism was also discussed. The results showed that with the increase of the heat input， the width of the heat affected zone (HAZ) of the welding joint and the proportion of columnar zone in the fusion zone (FZ) increase， meanwhile the microstructure becomes finer near the weld zone and the welding softening in the FZ is improved. It is also found that the heat input has little effect on the tensile strength of the welding joint， while the fracture elongation of the joint increases with increasing heat input. When the heat input is 19.0kJ/cm， the fracture of the joint occurs very easily due to the mismatch of plastic deformation at the joint interface between the FZ and HAZ. With increasing heat input， the microstructure in the FZ becomes finer and the hardness difference at the interface between the FZ and HAZ can be reduced. Therefore， the plasticity of the overall joint can be improved and the fracture of the joints is located from the FZ to BM. References | Related Articles | Metrics

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Removing Methylene Blue from Water by Steel Slag Adsorption HU En-zhu， LI Qiu-yan， GAO Han， WANG Na-na 2018, 39 (4):  516-521.  DOI: 10.12068/j.issn.1005-3026.2018.04.013 Abstract ( 848 )   HTML   PDF (1437KB) ( 795 )   The effect of steel slag on adsorption behavior of methylene blue was studied using static batch experiments. The experimental results showed that the removal rate of methylene blue increases with the increase of the steel-slag dosage and decreases with the initial concentration of methylene blue. However， the removal efficiency， (i.e. the adsorbance per unit quality of the adsorbent) denotes an opposite tendency. When the initial pH value of the solution is 4， the adsorption of methylene blue onto steel slag is the best. The adsorption kinetics of methylene blue by steel slag obeys the Lagergren first-order equation. The equilibrated adsorption capacity increases with the increase of the initial concentration of methylene blue， while decreases with the increase of the steel-slag dosage. Analyzed by the Freundlich isotherm model， it indicates that the adsorption of methylene blue by steel slag is a favorable and spontaneous adsorption， which is mainly deduced by ion exchange in the outer surface of steel slag. The cations of methylene blue adsorb on the negative-charged spots on the steel-slag surface， meanwhile the adsorption can also be enhanced by the polymer formed by the methylene blue reacted with CaO. References | Related Articles | Metrics

Mechanical Engineering

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Prediction Method of Locomotive Wheel Degradation Based on Gamma Process ZHANG Yi-min， LIN Lu-yang， LYU Hao 2018, 39 (4):  522-526.  DOI: 10.12068/j.issn.1005-3026.2018.04.014 Abstract ( 697 )   HTML   PDF (581KB) ( 1033 )   According to measured wheel wear data， the nonstationary Gamma process was used to establish the degradation model of locomotive wheel rim， and the repair time of 95% reliability was predicted by using the two methods a and b combined with wheel rim wear threshold. Method a uses the Bootstrap method to randomly generate a set of empirical distributions of pseudo-life， with Weibull distribution fitting forecasting repair time of 473900km. Method b uses the secondary fourth-order moment method based on the maximum entropy to predict the repair time of 488900km. The results showed that the lifetime of method a is more conservative than that of the empirical method， and the failure distribution of method b is more consistent with that of the experience distribution， and the repair time is 450000km. References | Related Articles | Metrics

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Iterative Finite Element Method for Predicting Deformations of Micro Thin Wall LI Peng-fei， LIU Yu， GONG Ya-dong， LI Liang-liang 2018, 39 (4):  527-531.  DOI: 10.12068/j.issn.1005-3026.2018.04.015 Abstract ( 646 )   HTML   PDF (1047KB) ( 821 )   The iterative finite element method was introduced to the milling process of micro thin wall. A predicted model was established， and the milling deformations were predicted at different radial cutting depths and different thicknesses. The predicted model was validated by experiments and the Deform-3D simulation. The results showed that the deformation prediction value of the iterative finite element method is close to that of experimental machining. The residual thickness of the thin wall is greater than the thickness under the ideal conditions. The maximum deformation keeps maximal and then gradually reduces to 0 with increasing the wall thickness. The thickness of the thin wall should be coordinated with the cutting parameters in order to keep the adaptability between the stiffness and cutting force， otherwise it will lead to excessive deformation. References | Related Articles | Metrics

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Kinematics Analysis and Optimization Design of Noval 4-DOF Parallel Mechanism WANG Xue-lei， ZHAO Dong-jie， ZHANG Bin， LI Wei 2018, 39 (4):  532-537.  DOI: 10.12068/j.issn.1005-3026.2018.04.016 Abstract ( 657 )   HTML   PDF (664KB) ( 869 )   A novel 3UPS-UPR 4-DOF parallel mechanism (PM) with three UPS-type active legs and one UPR-type active leg was presented. A three-dimensional model and the inverse kinematic formulas of this PM were constructed， the first-order and second-order comprehensive influence coefficient matrices were derived based on virtual mechanism method， and analytic formulas for solving the velocity and acceleration of this PM were derived. The global performance index of this PM was analyzed using the condition number of Jacobian matrix， the impact trend of the moving platform and fixed base’s dimensions on global performance index was obtained， and the dimensions with good velocity and acceleration performances were obtained. Numerical examples verified the correctness of global performance index， and provided foundation for the optimization design of PMs. References | Related Articles | Metrics

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Local Grid Refinement Implementation of Lid Driven Cavity Flow Based on MRT-LBM CHEN Song-ying， WANG Chao， QU Yan-peng， WANG Run-kun 2018, 39 (4):  538-542.  DOI: 10.12068/j.issn.1005-3026.2018.04.017 Abstract ( 822 )   HTML   PDF (1156KB) ( 1002 )   Employing the D2Q9 model， grids at the double singular corners were locally refined to investigate the flow peculiarity of the lid driven cavity based on the multi-relaxation time of lattice Boltzmann method (MRT-LBM). The transferring formulae of the distribution functions were established between the coarse and fine grids. Parameters were interpolated with cubic spline implementation on the refined layers， and the stress expressions were given on the basis of the Chapman-Enskog. For the cavity flow with the Reynolds number 1000， the simulation results showed that the velocity distribution along the cavity mid plane agrees with that of the classical benchmark very well， the noises on the pressure and vortex contours are significantly reduced， and the stress fluctuation obviously decreases. The computational results showed validation of the present method. References | Related Articles | Metrics

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Cutting Force Fluctuation Characteristics of Ultra-Fine-Pitched Milling Cutters and Its Influence ZHANG Jun， WANG Tuo， ZHANG Xing， ZHAO Wan-hua 2018, 39 (4):  543-548.  DOI: 10.12068/j.issn.1005-3026.2018.04.018 Abstract ( 744 )   HTML   PDF (983KB) ( 737 )   Considering the low machining efficiency of traditional milling cutters， an ultra-fine-pitched milling cutter was developed， the cutting force models in the x and y directions were established， and cutting force and its fluctuation were discussed by using the model. The results showed that during the cutter rotation， the cutting force fluctuation along the feed direction increases at first and then decrease with the increase of entrance angle， and then repeats when it decreases to the minimum. For the cutting force fluctuation vertical to the feed direction， it increases at first then decreases with the increase of entrance angle. The results showed that ultra-fine-pitched milling cutter is far superior to coarse-pitched one. Furthermore， cutting force per material removal rate was put forward to evaluate the performance of two kinds of cutters. Experiments by using the ultra-fine-pitched milling cutter validate the cutting force model and indicate that force fluctuation has a great effect on the surface roughness of workpiece， which confirms the advantage of ultra-fine-pitched milling cutter. References | Related Articles | Metrics

Resources & Civil Engineering

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Modeling of Complicated Goaf Groups and Its Application on Determining Rock Movement Boundary REN Feng-yu ， LIU Yang ， HE Rong-xing ， DING Hang-xing 2018, 39 (4):  549-552.  DOI: 10.12068/j.issn.1005-3026.2018.04.019 Abstract ( 739 )   HTML   PDF (2576KB) ( 704 )   Based on the SURPAC software， a 3D modeling method on complicated geologic body combined with Delaunay triangularization method and linking adjacent contour method were introduced. Taking the Dalingxishan magnesium mine as an example， the digital terrain model and the 3D model of the goaf group were built. Based on the TCL language and the automatic modeling program of rock movement scope according to the goaf bottom contour data， the critical angle of rock deformation and the target projection height were developed. Then the program was used in the Dalingxishan magnesium mine to obtain the 3D model of the rock movement scope. According to the Boolean calculation result of the rock movement scope model and the digital terrain model， the surface movement boundary was determined immediately. References | Related Articles | Metrics

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Slope Strength Indexes Based on Extension Theory WANG Fei-li， WANG Shu-hong， ZHANG Zi-shan， XIU Zhan-guo 2018, 39 (4):  553-557.  DOI: 10.12068/j.issn.1005-3026.2018.04.020 Abstract ( 566 )   HTML   PDF (419KB) ( 589 )   An evaluation index system on slope stability using three levels and five indexes were established on the basis of the extension theory to study the effect of internal friction angle and cohesion on the slope stability. The quantitative relation between the shear strength and the safety factor was given. The results showed that the safety factor increases linearly with the increase of the internal friction angle and the cohesion， and the internal friction angle is more sensitive than the cohesion to the safety factor. Finally， the Xiaopanling slope in Liaoning Province was reinforced by bolt based on the principles of safety， economy and efficiency. References | Related Articles | Metrics

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Stress Influenced Area in Front of Fully-Mechanized Mining Face Before First Weighting YU Jian-yang， LI Yuan-hui， YU Shi-wei， LIU Shuai 2018, 39 (4):  558-563.  DOI: 10.12068/j.issn.1005-3026.2018.04.021 Abstract ( 630 )   HTML   PDF (782KB) ( 643 )   Based on the rock beam transmission theory and the key strata theory， the stress distribution characteristics in front of the fully-mechanized mining face were analyzed， and a warping beam structure composed by the main roof covering the mining face and the support pressure area in front of the fully-mechanized mining face was proposed. A mechanical analysis model of the warping beam structure was built to deduce the quantitative formula of the supporting area before the first weighting. The FLAC numerical simulation was used to obtain the transfer coefficient of elastic damage. The SW4102 mining face of Xiaonan coal mine was adopted as a real case to study the ranges of the warped stress zone and the support pressure zone， and results was verified by the in-situ monitoring data. References | Related Articles | Metrics

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Toroidal Fracturing Mode in Surrounding Rock Mass and Its Impact Factors Under High Axial Stress JIA Peng， QIN Bing， WANG Liang， LIU Zhi-chao 2018, 39 (4):  564-569.  DOI: 10.12068/j.issn.1005-3026.2018.04.022 Abstract ( 624 )   HTML   PDF (2269KB) ( 808 )   Hole containing cylindrical specimens confined by thick steel drum were compressed in the axial direction to investigate the development of toroidal fractures and its impact factors under high axial stress. Results showed that toroidal fractures develop from the intersection of shear-slip lines and propagate sub-parallelly away from tunnel boundary mainly in tension. For the close twin tunnel with overlapped concentrated stress in between， the toroidal fractures enclose the twin tunnel and take on an elliptical shape; for distant twin tunnel with little overlapped concentrated stress in between， the toroidal fractures enclose each single tunnel respectively. The shape of toroidal fractures and the distance between the fractures are affected by tunnel curvature and tunnel span as well as the heterogeneity of the rock mass. References | Related Articles | Metrics

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Influence of Multi-factors on Ultimate Pit Design of Open Pit Mine XU Xiao-chuan， GU Xiao-wei， WANG Qing ， LIU Jian-ping 2018, 39 (4):  570-574.  DOI: 10.12068/j.issn.1005-3026.2018.04.023 Abstract ( 670 )   HTML   PDF (576KB) ( 689 )   Based on the ecological-economic parameters and occurrence of orebody， the cone exclusive method was used to design the profit-maximum pit without constraint. According to the location of surface structures at the ore district， constraint lines were built to restrain optimization region， and the profit was obtained from ores outside constraint lines by underground mining. An ecological costs model of mine was built to calculate the ecological cost of two optimization schemes. The results showed that under only considering economic condition， it’s suitable for a unrestrained pit to mine if the moving cost of surface structures is less than 0.99×108￥(NPV). The restrained pit is the best choice while ecological costs are considered. References | Related Articles | Metrics

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Relationship Between Cut-off Grade and Ultimate Pit of Open Pit Mine GU Xiao-wei， ZHAO Yun-qi， WANG Qing， XU Xiao-chuan 2018, 39 (4):  575-578.  DOI: 10.12068/j.issn.1005-3026.2018.04.024 Abstract ( 867 )   HTML   PDF (300KB) ( 848 )   The relationship between the cut-off grade and the ultimate pit was analyzed under the conditions of technological and economical parameters change. Based on production data of Sijiaying open pit mine， the model of break-even grade was established to calculate the cut-off grade for needn’t to be mined and the cut-off grade for must be mined under the different conditions of market. According to the value of cut-off grade， the ultimate pit was optimized in different market context. For a preset cut-off grade， the ultimate pit was optimized at the same market context， and the ultimate pits of two methods were compared. The results indicated that under the same condition of market， the ultimate pit based on break-even method is better than that based on the preset cut-off grade. References | Related Articles | Metrics

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Calculation on Deformation of Layered Sandy with Weak Interlayer Under Large Foundation LI Chun， XIU Zhan-guo， WANG Fei-li 2018, 39 (4):  579-584.  DOI: 10.12068/j.issn.1005-3026.2018.04.025 Abstract ( 763 )   HTML   PDF (841KB) ( 883 )   A settlement calculation models of layered subgrade under large foundation was established based on theories of saturated soil. Taking the different soil properties and the modified Cam-Clay and Mohr-Coulomb models into account， the compressive modulus were derived by considering the plastic deformations under the condition of K○0. Based on the subfield of planar mesh and the layer-wise summation method， a settlement calculation model of layered sandy foundation base with weak interlayer under large foundation was established， which is more close to the engineering practice. The results showed that the calculation results by the suggested model are comparatively close to the numerical simulation results， and can clearly reflect the characteristic of deformation in weak interlayer. The suggested calculation model can provide basis to the settlement calculation of layered sandy foundation base with weak interlayer under large foundation. References | Related Articles | Metrics

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Calculation Method of Frictional Force Along Flanged Steel Jacking Pipe in Shenyang Sandy Strata JI Xin-bo， ZHAO Wen， CHENG Cheng， ZHU Mao-guo 2018, 39 (4):  584-588.  DOI: 10.12068/j.issn.1005-3026.2018.04.026 Abstract ( 629 )   HTML   PDF (581KB) ( 726 )   Based on the Staheli’s method for calculating the vertical soil pressure on circular jacking pipes， a vertical earth pressure calculation model for the circular flanged jacking pipe in Shenyang sandy strata was derived. The mechanical parameters of the sandy strata were tested， and the friction coefficients between soil and pipe was measured using a modified direct-shear test. The changing rules of the jacking forces and the frictional forces during the jacking process were monitored in situ. Then， a new calculation method was proposed to estimate the frictional resistance of the flanged jacking pipe in the sandy strata of Shenyang. Results from the proposed method agree well with field monitoring data， which proves the feasibility of the proposed method. References | Related Articles | Metrics

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Jacking Forces of Fringed STS Pipe Based on Stress Arch Theory JIANG Bao-feng ， ZHAO Wen， JIA Peng-jiao， CHENG Cheng 2018, 39 (4):  589-593.  DOI: 10.12068/j.issn.1005-3026.2018.04.027 Abstract ( 677 )   HTML   PDF (707KB) ( 728 )   The STS (steel tube slab) method was applied in the Olympic metro station project in Shenyang. Based on the pressure arch theory， a formula of STS pipe-jacking friction resistance was deduced based on the cause of the earth pressure on the pipe week. The theoretical calculation result agrees well with the in-situ monitoring data. The influence of the fringe on the jacking force is obvious and the calculation of which cannot use the simple superposition method. Affected by the "embolism" effect， the soil pressure on the tube side is small. The jacking force of STS pipe calculated according to the international design codes is smaller than the monitoring results by 28% ~ 40% due to not taking the fringe effect into account. References | Related Articles | Metrics

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Experimental Research on Flexural Behavior of T-Beams Strengthened with Combination of Prestressed CFRP and Steel Plate ZHU Guang-shan， ZHU Fu-sheng，SHENG Guo-hua 2018, 39 (4):  594-598.  DOI: 10.12068/j.issn.1005-3026.2018.04.028 Abstract ( 631 )   HTML   PDF (558KB) ( 587 )   Through the experiments on the flexural behaviors of 10 pieces of T-beams， the influence of different prestress degrees， numbers of strengthening layers of CFRP as well as the pre-splitting degree on the load， midspan deflection and ductility factor of T-beams strengthened by the combination of CFRP and steel plate were studied. The results showed that the ultimate load P○u of the strengthened T-beam is over 90% higher than that of the comparison beam. The impact of prestress degree on the ultimate midspan deflection f○max and the ductility factor μ is obvious in such a way that the f○max reduces about 25% when the prestressing force increases 5%. The yield load P○y and the ultimate load P○u increase linearly with the increase of the strengthening layers， and decrease linearly with the increase of the pre-splitting degree. The P○u of the T-beam strengthened by three-layer CFRP increases 52.8% than that strengthened by one-layer CFRP. When the pre-splitting degree is 60%， the f○max reduces about 10%. References | Related Articles | Metrics

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Interaction Mechanism of Sodium Oleate with Fine Wolframite MENG Qing-you， YUAN Zhi-tao， MA Long-qiu， LU Ji-wei 2018, 39 (4):  599-603.  DOI: 10.12068/j.issn.1005-3026.2018.04.029 Abstract ( 715 )   HTML   PDF (559KB) ( 804 )   The flotation mechanism of fine wolframite using sodium oleate as the collector was systematically studied through flotation experiments， solution chemistry calculations， adsorption tests， zeta potential measurements and infrared spectroscopic analysis. The flotation results showed that the adsorption of sodium oleate is responsible for the floatability of wolframite， and fine wolframite performs a better floatability at pH 7.0~9.0. In this pH range， the ions and ion-molecular associations of sodium oleate are dominated species， which play a critical role in the flotation of wolframite. Solution chemistry calculations suggest that the adsorption amount of sodium oleate and the floatability of wolframite have a direct relationship with the species concentration of metal oleate precipitates. In the presence of sodium oleate， the zeta potential of wolframite particles shifts negatively. Infrared spectroscopic analysis indicated that sodium oleate chemisorbs onto the wolframite surface， producing metal oleate precipitates， and thus it is contributed to the floatability of fine wolframite. References | Related Articles | Metrics

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High Precision Recursive Algorithm for Computing Fractional-Order Derivative and Integral BAI Lu， XUE Ding-yu 2018, 39 (4):  604-608.  DOI: 10.12068/j.issn.1005-3026.2018.04.030 Abstract ( 738 )   HTML   PDF (344KB) ( 689 )   A high precision numerical algorithm was designed to compute fractional-order derivative and integral， and a simple method was proposed to construct the generating function. An algorithm based on fast Fourier transform was analyzed. It could be concluded that the reasons of its large computation error were using the inaccurate coefficient of the generating function and no considering the effect of nonzero initial condition of the original function on calculation precision. The recursive formula was used to compute the coefficient of the generating function in the new algorithm， what’s more， the original function was decomposed into two parts， i.e.， zero initial condition and nonzero initial condition， and their fractional-order derivative and integral were computed to decrease the computation error. The error analysis and the illustrative numerical examples showed that the computation accuracy of the new algorithm was very high. References | Related Articles | Metrics