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15 June 2020, Volume 41 Issue 6 Previous Issue    Next Issue
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Information & Control

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Multi-objective Planning of Personnel Evacuation Route in Complex Building Fire ZHANG Li-jie， LIU Jian-chang， TAN Shu-bin 2020, 41 (6):  761-766.  DOI: 10.12068/j.issn.1005-3026.2020.06.001 Abstract ( 890 )   HTML   PDF (742KB) ( 1423 )   Aiming at the strategy of personnel evacuation dynamic path optimization in complex building fire， the path optimizing model with the shortest time， the maximum evacuation capacity and the minimum risk level as the optimization objective was constructed， which was based on the dynamic evacuation network data model in fire situation and combined with the network flow optimization and swarm intelligence method. Dynamic evacuation path planning with limited node and path capacity was realized by the modified adaptive fruit fly optimization algorithm. Through the performance test and evacuation process experiment on the established model， the effectiveness of the multi-objective path optimization model was verified. The experimental results also indicates that the multi-objective path planning strategy is closer to the evacuation practice in complex building fire. It is feasible for planning complex space evacuation path under the influence of uncertain factors. References | Related Articles | Metrics

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User Location Prediction Based on Parallel Pattern Mining and Path Matching XU Xian-ze， TAN Sheng-huang， LIU Jing， SHI Yuan 2020, 41 (6):  767-771.  DOI: 10.12068/j.issn.1005-3026.2020.06.002 Abstract ( 542 )   HTML   PDF (423KB) ( 663 )   In order to improve the accuracy of location prediction for mobile users， a method of location prediction for mobile users was proposed based on parallel pattern mining and path matching. Based on the traditional FP-GROWTH algorithm， the method of node load allocation was optimized， and frequent patterns of mobile users were mined on Spark platform. The index-based path similarity algorithm was improved， and the repulsion algorithm based on the shortest path distance was proposed to improve the applicability of missing trajectory data. Experiments on real user trajectory data sets show that the proposed model based on track dissimilarity prediction method has higher prediction accuracy than that of Markov model and Kalman filter model， which is improved by about 7% on average. References | Related Articles | Metrics

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A Big Data Method to Rebuild 3D Road Map Based on Vehicle Data HUANG Chuan， HU Ping， LIAN Jing 2020, 41 (6):  771-777.  DOI: 10.12068/j.issn.1005-3026.2020.06.003 Abstract ( 534 )   HTML   PDF (1027KB) ( 722 )   A big data based 3D map reconstruction method was presented based on multiple vehicles data. On individual vehicle site， in the proposed algorithm， the least square method and Kalman filter were used， and the refined vehicle instant 3D position was uploaded to the server. The original GPS signal error was reduced by over 50%. Next， genetic algorithm was used instead of Kalman filter， resulting in the error being further reduced by over 16%. On the server site， a 3D road surface point cloud database was generated based on the data from multiple vehicles. K-means method was used as the data mining strategy to search for the lane centers from roads with multiple lanes. The reconstructed map can be used by every online vehicles that support the relevant researches for the optimum driving strategy. References | Related Articles | Metrics

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A New Stereo Image Disparity Algorithm Based on FPGA LI Zhen-ni， WANG Jiao， LI Jing-jiao， WANG Ze-kun 2020, 41 (6):  778-783.  DOI: 10.12068/j.issn.1005-3026.2020.06.004 Abstract ( 701 )   HTML   PDF (1536KB) ( 728 )   A new stereo image disparity algorithm was proposed based on FPGA. Based on the block matching algorithm and according to the characteristics of FPGA， the formula of image correlation was optimized. Moreover， by combining exhaustive search and prediction search method， the execution speed of the algorithm was improved. The Stereo image disparity algorithm IP core was designed， and the processing speed and performance of the system could be improved by making full use of the FPGA’s unique parallel processing mechanism and powerful computing ability. The test results show that the stereo image disparity algorithm based on FPGA can reach the processing capacity of 33 frames per second and the processing speed can reach more than 200 times of PC， with good real-time performance. It can process 500 frames of image data continuously and has good stability. References | Related Articles | Metrics

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SSA:CQF-oriented Scheduling Algorithm in Time-Sensitive Networking JIANG Xu-yan， YAN Jin-li， QUAN Wei， SUN Zhi-gang 2020, 41 (6):  784-791.  DOI: 10.12068/j.issn.1005-3026.2020.06.005 Abstract ( 1386 )   HTML   PDF (775KB) ( 1615 )   Time-sensitive networking (TSN) is designed for providing determined transmission service with low latency and jitter in industrial control network and 5G.Resource scheduling， the core of TSN， is very crucial to guarantee the quality of service (QoS). Recently， TSN puts forward cyclic queuing and forwarding model (CQF). However， the corresponding scheduling algorithm is demanded for allocating resource rationally to avoid transmission collision.Since the TSN flow is periodic and predetermined， how to allocate resource for multiple TSN flows rationally from time dimension was researched. Resource allocation into multi-constrained maximization problem was abstracted. Then， a start-slot assignment based scheduling algorithm (SSA) was proposed. By adjusting the send slot at end system， SSA maximizes the queue resource utilization with meeting related constraints， which avoids complex time slot allocation hop by hop. Compared with the case without adjusting sending slot， experimental results demonstrate that SSA improves the number of flows scheduled successfully by 41.84% on average. References | Related Articles | Metrics

Materials & Metallurgy

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High Temperature Oxidation Behavior of Ni-based Low Temperature Steel CAO Guang-ming， GAO Xin-yu， SHAN Wen-chao， PAN Shuai 2020, 41 (6):  792-800.  DOI: 10.12068/j.issn.1005-3026.2020.06.006 Abstract ( 755 )   HTML   PDF (7319KB) ( 786 )   The oxidation behavior of Fe-3.5Ni and Fe-9Ni at 700~1200℃ was investigated using Setsys Evolution high-temperature thermal gravimetric analyzer to study the high temperature oxidation behavior of Ni-based low temperature steel. The oxide morphology and phase composition were analyzed with electron-probe microanalyzer (EPMA)， scanning electron microscopy (SEM)， X-ray diffraction (XRD). The results show that the oxidation mass gain curves of Fe-3.5Ni steel and Fe-9Ni steel are similar after oxidation for 2h at 700~1200℃. Under the same oxidation temperature， the unit area mass gain of Fe-9Ni steel is lower than that of Fe-3.5Ni steel. As the oxidation temperature increases， agglomerate floc， whisker and irregular polygonal Fe2O3 appear on the surface of the sample. Further results indicate oxidation is divided into internal and external oxidation. As the oxidation temperature increases， the thickness of the external oxide layers and subscale gradually increases， and 900℃ is the critical point at which the thickness of the outer oxide layers of the two steels changes. The subscale compound consists of FeNi3 and a mixture (FeO+Fe3O4). The external oxidation consists of Fe2O3， Fe3O4 and FeO， and the crystallite phase NiFe2O4 is encapsulated in the external oxide layer; as the Ni content increases， more NiFe2O4 is produced. References | Related Articles | Metrics

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Microstructure and Mechanical Properties of V-N Microalloyed X80 High Deformability Pipeline Steel WANG Ming-ming， GAO Xiu-hua， DU Lin-xiu， ZHANG Da-zheng 2020, 41 (6):  801-806.  DOI: 10.12068/j.issn.1005-3026.2020.06.007 Abstract ( 619 )   HTML   PDF (6018KB) ( 995 )   The dynamic continuous cooling transformation behavior of undercooled austenite in a V-N microalloyed steel was studied by means of thermal simulation test machine. Furthermore， the rolling and cooling process parameters of V-N microalloyed X80 high deformability pipeline steel were designed and the relationship between microstructure and mechanical properties was analyzed. The dynamic CCT curve shows a separation of high temperature transformation region and intermediate temperature transformation region， and the transformation ranges are 637~728℃ and 441~601℃， respectively. When the cooling rate is in the range of 10~20℃/s， the microstructure mainly consists of acicular ferrite. The microstructure of V-N microalloyed pipeline steel is dominated bypolygonal ferrite and acicular ferrite. Yield strength， tensile strength， uniform elongation and -20℃ Charpy impact energy are 603MPa， 724MPa， 11.1% and 214J， respectively. These meet the requirements of X80 pipeline steels according to the API Spec 5L specification that the produced pipeline steel should have a good combination of strength and ductility. References | Related Articles | Metrics

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Numerical Simulation of Influence of Atomization Pressure on Particle Size of GH4169 Alloy Powders GUO Kuai-kuai， SHANG Shuo， CHEN Jin， LIU Chang-sheng 2020, 41 (6):  807-811.  DOI: 10.12068/j.issn.1005-3026.2020.06.008 Abstract ( 558 )   HTML   PDF (840KB) ( 816 )   Aiming at exploring the complex relationship between vacuum induction gas atomization (VIGA) process parameters and particle sizes of superalloy powders， the ANSYS-Fluent software was used to simulate the breaking behavior of droplets during the GH4169 superalloy VIGA process. The influence of atomization pressure on the atomization process and particle size distributions of the melt metal was analyzed. The results showed that the thickness of the strip-shaped liquid film and the droplet area in the first atomization process gradually decreased， while the crushing effect of the secondary atomization on the melt was gradually enhanced. The particle size of the atomized powders was reduced from 81.10 to 69.80， 64.77， 52.30 and finally to 41.80 μm. Correspondingly， the yield of fine powders was gradually improved from 1.72% to 12.62%， 18.89%， 56.50%， and finally to 71.54%. References | Related Articles | Metrics

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Corrosion Products of X65MS Steel Under Saturated H2S/CO2 Environment WANG Hong-yan， YU Chi， GAO Xiu-hua 2020, 41 (6):  812-817.  DOI: 10.12068/j.issn.1005-3026.2020.06.009 Abstract ( 533 )   HTML   PDF (2256KB) ( 712 )   The corrosion behavior of a X65MS pipeline steel in saturated H2S/CO2 environment is studied by simulating oil and gas delivery environment with high temperature and high pressure reactor. The corrosion rate under different immersion time periods is measured by the mass loss method， and the phase composition and morphology of corrosion products are analyzed by means of X-ray diffraction (XRD)， scanning electron microscope (SEM)， energy disperse spectroscopy (EDS) and electron probe microanalysis (EPMA)， respectively. The results show that the corrosion rate can be divided into three stages， i.e. the initial corrosion rate decreases rapidly， then changes slowly and finally flattens out. The corrosion process is mainly controlled by H2S corrosion， and the products are dominated by ferrosulfur compound (Fe○xS○y). With the increase of immersion time， the proportion of iron decreases， the proportion of sulfur-rich phase increases， the film thickness of corrosion products increases， and the structure changes from loose to uniform and compact gradually. The corrosion products are mackinawite→troilite→pyrrhotite， and the stable pyrrhotite has a protective effect on the corrosion resistance of X65MS pipeline steel matrix. References | Related Articles | Metrics

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Contact Fatigue Damage and Subsurface Microstruture of Cr5 Backup Roll LI Yan-long， WU Qiong， QIN Xiao-feng， LIU Chang-sheng 2020, 41 (6):  818-823.  DOI: 10.12068/j.issn.1005-3026.2020.06.010 Abstract ( 668 )   HTML   PDF (3331KB) ( 703 )   Optical microscope (OM)， scanning electron microscope (SEM)， transmission electron microscope (TEM)， micro-indentation tester and X-ray stress meter were employed to investigate the microstructure of backup rolls’ subsurface after rolling contact fatigue. The maximum value of fatigue damage was located on the subsurface of the backup roll which was about 400μm away from the surface. The increased hardness， reduced residual stress and elevated corrosion resistance of the subsurface resulted from rolling contact fatigue. Microstructure of the subsurface was broken into small pieces and dislocation density was increased. Under one constant contact stress， fatigue damage of backup roll increased with the increasing percentage of fatigue life. References | Related Articles | Metrics

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Effect of Oxygen Concentration on Hot Metal Desulfurization with Magnesium Vapor SU Jian-ming， DOU Zhi-he， ZHANG Ting-an， LIU Yan 2020, 41 (6):  824-827.  DOI: 10.12068/j.issn.1005-3026.2020.06.011 Abstract ( 639 )   HTML   PDF (693KB) ( 687 )   In view of the low utilization rate of magnesium generally obtained under traditional desulfurization processing， the method of bottom-blown magnesium vapor was used for hot metal desulfurization in order to optimize the dynamic conditions and to improve the utilization rate of magnesium in hot metal desulfurization. Thermodynamic calculation of the equilibrium concentration of sulfur under different oxygen concentrations was carried out， and the effect of oxygen concentration on the kinetics of hot metal desulfurization process was studied by experiments. The results show that the reduction of oxygen concentration in molten iron is helpful for promoting the desulfurization with magnesium vapor. When oxygen concentration arrives 62×10-6， the utilization rate of magnesium can reach 78%， leading to a desulfurization rate of 82% and a mass transfer coefficient of desulfurization of 0.0122m/s. References | Related Articles | Metrics

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Effects of the Size of Cast Iron and Stub on the Physical Field of Anode in Aluminium Reduction Cell LI Tuo-fu， TAO Wen-ju， WANG Zhao-wen， LIU Xiao-zhen 2020, 41 (6):  828-834.  DOI: 10.12068/j.issn.1005-3026.2020.06.012 Abstract ( 679 )   HTML   PDF (1452KB) ( 699 )   Cast iron and stub act as thermo-electro-mechanical connectors in an anode of aluminium reduction cell. The effects of their size on the physical field of anode are investigated by performing numerical simulations.For this purpose， a 3D thermo-electro-mechanical (TEM) coupled model is developed based on the ANSYS software. When the thickness of the cast iron increases from 12.5 to 32.5mm， the temperature and stress distributions of the carbon block show insignificant changes， while anode voltage drop decreases by 17.7mV. When the stub diameter increases from 135 to 175mm， the temperature of each component decreases by 50℃ utmost and anode voltage drop decreases by 26.4mV， respectively.Meanwhile stress in the carbon block increases. References | Related Articles | Metrics

Mechanical Engineering

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Trajectory Tracking Control of Unmanned Vehicles Based on Adaptive MPC LIANG Zhong-chao， ZHANG Huan， ZHAO Jing， WANG Yong-fu 2020, 41 (6):  835-840.  DOI: 10.12068/j.issn.1005-3026.2020.06.013 Abstract ( 1935 )   HTML   PDF (562KB) ( 2312 )   According to the principle of adaptive MPC(model predictive control)， a trajectory tracking control strategy for unmanned vehicles is designed. Based on the vehicle dynamics model， the trajectory tracking controller is established， and the objective function and related constraints are designed. The adaptive MPC control algorithm is used for solution. At each control point of operation， the Kalman state estimator correlation gain coefficient matrix and the state of the controller are continuously updated to adapt to the current working environment of the unmanned vehicle， thereby compensating for the nonlinearity of the vehicle and the effect of state measurement noise. The simulation model is built in MATLAB and verified by simulation. It is concluded that the adaptive MPC has better control precision and robustness for the trajectory tracking of unmanned vehicles. The effectiveness of the algorithm in the trajectory tracking control layer is verified. In addition， it provides a reference for the research of future trajectory tracking control. References | Related Articles | Metrics

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A RGB-D SLAM Optimal Method for Fusing Monocular Information MA Shu-jun， WANG Ying-lei， JIN Tie-zheng， BAI Xin-hui 2020, 41 (6):  841-846.  DOI: 10.12068/j.issn.1005-3026.2020.06.014 Abstract ( 576 )   HTML   PDF (796KB) ( 831 )   Owing to the limitations of RGB-D sensor， there will be some situations where the depth information does not exist or is incomplete in the practical application， which will affect the accuracy of RGB-D SLAM system that mostly depends on the depth information.An RGB-D SLAM optimization method is proposed to fuse monocular information.Through the analysis of depth image， three judging conditions are put forward respectively from the existence， accuracy and discreteness of depth information， which can be used as the basis of the selection of monocular or RGB-D processing mode.This new system makes the SLAM system with RGB-D camera more accurate and robust.Finally， the system is compared with other SLAM systems by running data sets， and the experimental results verify its feasibility. References | Related Articles | Metrics

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Experimental Study on the Grinding Metamorphic Layer of Nickel-based Single Crystal Superalloy GONG Ya-dong， ZHANG Wei-jian， CAI Ming， ZHOU Xian-xin 2020, 41 (6):  846-851.  DOI: 10.12068/j.issn.1005-3026.2020.06.015 Abstract ( 581 )   HTML   PDF (1171KB) ( 860 )   In order to explore the processing property of grinding metamorphic layers of nickel-based single crystal superalloy， a single-factorial plain grinding experiment was conducted to investigate the effect of different grinding parameters and cooling conditions on the thickness of grinding metamorphic layers. The results showed that the grinding metamorphic layer with certain thickness appears on the grinding surface and subsurface of nickel-based single crystal superalloy DD5. The γ phase and γ′ phase in the plastic deformation layer of the metamorphic layer are distorted severely， and the hardness of the grinding metamorphic layer is greater than that of the matrix. The grinding metamorphic layer thickness varies with the grinding parameters and cooling conditions. With the increase of grinding wheel tangential velocity， the metamorphic layer thickness first decreases， and then increases; with the increase of grinding depth， the metamorphic layer thickness increases continuously; with the increase of workpiece feed velocity， the metamorphic layer thickness first increases， and then decreases. Within the range of experiment parameters， the minimum quantity lubrication (MQL) cooling condition can reduce the corresponding grinding metamorphic layer thickness， which can be reduced by up to 3.5μm. References | Related Articles | Metrics

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Milling Force Characteristics of Titanium Alloy Parts Machined by Ball-end Milling Cutter ZHANG Yao-man， LI Wan-peng， YANG Ming-yu 2020, 41 (6):  852-857.  DOI: 10.12068/j.issn.1005-3026.2020.06.016 Abstract ( 671 )   HTML   PDF (662KB) ( 787 )   In the milling process of titanium alloy parts， the cutting force characteristics will exert an important influence on the final machining quality of the parts. The cutting force characteristics of milling titanium alloy with ball-end milling cutter are studied. Firstly， the mathematical model of cutting force for Ti-6Al-4V milling with ball-end milling cutter is established， and the instantaneous cutting force and its variation law are obtained by compiling program. Secondly， the simulation model of Ti-6Al-4V milling with ball-end milling cutter is established by using finite element analysis software， and the stress field and temperature field in milling area are obtained. Finally， the cutting force test experiment is designed and completed， and the experimental data are analyzed by orthogonal design. The results show that the influence of cutting parameters on the average milling force is in the order of axial cutting depth， feedrate per tooth， radial cutting depth and spindle speed. References | Related Articles | Metrics

Resources & Civil Engineering

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Flow-Through Features of Tailings in Subsidence Area Under Ore Drawing Conditions REN Feng-yu， LIU Yang， HE Rong-xing， ZHANG Jing 2020, 41 (6):  858-863.  DOI: 10.12068/j.issn.1005-3026.2020.06.017 Abstract ( 500 )   HTML   PDF (1601KB) ( 770 )   The feasibility of dry filling of tailings in the subsidence mine area was studied to overcome those problems caused by stockpiling and land occupation of tailings. The experiment of flow-through features of tailings under mining influence was designed， and the height of overburden rock and tailings was set as influencing factors. The visualization of tailings’ moving process was realized by high-speed camera. The results showed that the tailings cannot reach the drawing holes when the height of the loosening zone is lower than that of the interface between the tailing and the granular media. When the height of the loosening zone is higher than that of the interface， the tailing and the connected rock are loosened by ore drawing， so that the tailing can reach the drawing holes thus affecting mining activities. With the increase of the tailings height， the initial inflow volume of tailings increases， however， it cannot reach the drawing holes if the height of the loosening zone is lower than that of the interface. Therefore， the influence of the dry filling on the stripping ratio of the ore is little. References | Related Articles | Metrics

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Experimental Study on Failure Mode of Tunnel Model Containing Cavity in Different Locations WANG Shu-hong， WANG Peng-yu， LIU Yu， ZHU Bao-qiang 2020, 41 (6):  863-869.  DOI: 10.12068/j.issn.1005-3026.2020.06.018 Abstract ( 655 )   HTML   PDF (1808KB) ( 1165 )   Cavity is an important factor affecting the stability of the tunnel. A cavity was set at the shoulder， the side wall， the arch and the floor of each tunnel model to study the failure modes and failure sequences of the tunnel. The results showed that when the cavity is near the shoulder of the tunnel， failure occurs at the boundary of the cavity and the floor， accompanied by compressive failure at the arch foot. When the cavity is near the side wall， the side wall is buckled and the crown is cracked. For model with a cavity near the arch foot， the lining near the cavity and the crown are cracked as a consequence. For model with a cavity at the bottom of the floor， failure occurs at the floor， the shoulder and the crown. These results can give some references for the construction and maintenance of tunnel. References | Related Articles | Metrics

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Experimental Study on Properties of Recycled Tyre Polymer Fiber Reinforced Concrete CHEN Meng， LIU Yang-bo， TAO Yun-xiao， WANG Hao 2020, 41 (6):  870-874.  DOI: 10.12068/j.issn.1005-3026.2020.06.019 Abstract ( 642 )   HTML   PDF (958KB) ( 755 )   To study the effect of recycled rubber tyre polymer fiber (RTPF) on the working performance and mechanical properties of concrete， tests on the properties of the mixtures， the basic mechanical properties and the mechanism of the fiber performances were conducted on the plain concrete (F0)， RTPF concrete and polypropylene fiber (PPF) concrete. The results showed that the air content increases with the increasing of the RTPF fraction， and the air entraining capacity of PPF is better than that of the RTPF with the same volume fraction (0.1%). The slump decreases with the increasing of the RTPF fraction， and the slump of the PPF concrete is lower than that of the RTPF concrete under the same volume fraction (0.1%); the compressive strength of concrete decreases with the increasing of the RTPF fraction. Both the splitting tensile strength and the flexural strength of the RTPF concrete increase at the initially stage and then decrease; 0.2% is determined as the optimal volume fraction. The SEM showed that the RTPF was pulled out from the matrix or broken by tension， which indicates that the RTPF can effectively provide bridging effect. This study showed that the RTPF can improve the mechanical properties of concrete and can replace the PPF effectively within a certain range of the fiber fraction. References | Related Articles | Metrics

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Consolidation and Permeability Characteristics of Transparent Clay with Different Grain Composition WU Ya-jun， LI Jun-peng， JIANG Hai-bo， KONG Gang-qiang 2020, 41 (6):  875-880.  DOI: 10.12068/j.issn.1005-3026.2020.06.020 Abstract ( 660 )   HTML   PDF (580KB) ( 849 )   In order to visualize the internal deformation of clay during consolidation， transparent clay with similar consolidation characteristics needs to be prepared. A transparent clay which can simulate the consolidation of clay soil was prepared by using amorphous silica powder， the mixture of white mineral oil and n-dodecane. Permeability test and compression consolidation test on transparent clay with different grain composition were carried out. The experimental results show that the e-lgk， Cv-p and Es-p curves of transparent clay are similar to those of natural clay. The higher the clay content is， the smaller the permeability coefficient is， and the smaller the consolidation coefficient is， the higher the compressibility is. The similarity between transparent clay and natural clay in consolidation and permeability shows the feasibility of using transparent clay to qualitatively simulate the consolidation deformation of natural clay. References | Related Articles | Metrics

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Thermal Runaway Analysis of NCM Lithium-Ion Battery in Humid and Hot Environment ZHANG Pei-hong， YUAN Wei， WEI Zhong-yuan， LI Zi-jian 2020, 41 (6):  881-887.  DOI: 10.12068/j.issn.1005-3026.2020.06.021 Abstract ( 987 )   HTML   PDF (1362KB) ( 1181 )   From the perspective of heat abuse， the thermal runaway behavior of the NCM ternary lithium-ion battery in hot and high humid environment were analyzed based on tests and simulations. The NCM523 nickel-cobalt-manganese lithium-ion power battery with 50% SOC was selected as the object of study. An electric furnace with a constant power of 1kW was used as an external heat source， after 660s of heating， the external heat source was removed， and the heat abuse experiment of NCM ternary lithium-ion battery in humid and hot environment was carried out. The simulation was conducted by COMSOL Multiphysics software. The results show that for NCM lithium-ion battery with normal relative humidity， the increase of the initial surrounding temperature can lead to an earlier occurrence of the thermal runaway. Under 50% relative humidity， when the ambient temperature increases from 20℃ to 40℃， the time for the battery to reach thermal runaway is shortened by 20.2%. At 30℃， when the ambient humidity increases from 50% to 100%， the peak temperature in the process of thermal runaway is increased by 37.2%. The hot and high relative humidity has a significant enhancement effect on the risk of the thermal runaway of the NCM lithium-ion battery. References | Related Articles | Metrics

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Simulation Method on Hydraulics and Water Quality of Mine Water Supply Network for Dust Control and Its Application PENG Ya， JIANG Zhong-an 2020, 41 (6):  888-895.  DOI: 10.12068/j.issn.1005-3026.2020.06.022 Abstract ( 531 )   HTML   PDF (1555KB) ( 731 )   Hydraulic and water quality simulation is an important method to study the performance of water supply network. In order to call the EPANET calculation engine of hydraulics and water quality analysis in MATLAB environment， so as to study the characteristics of mine water supply network for dust control， two types of effective EPANET-MATLAB hybrid programming methods were realized and compared. Based on the one adopting the object-oriented data structure， EPANET was called to establish hydraulic and water quality models of mine water supply network for dust control. According to the daily water demand of the network， dynamic simulations of hydraulic operating condition and water age distribution were carried out for a duration of 24h and 48h respectively. Research results show that the hybrid programming using EPANET-MATLAB Toolkit is more flexible and efficient to simulate and analyze the hydraulic behaviors and water quality. Water consumption of the network shows a periodic feature with obvious peaks and troughs. The variation range of the water pressure at demand nodes is between 1.5~5.5MPa， and the variation rule is negatively correlated to water consumption. The change of water age also shows a diurnal periodicity. Generally， the longer the distance between the demand node and the water source is， the bigger the water age is. The water age of all demand nodes is lower than 15h. References | Related Articles | Metrics

Management Science

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Profit Distribution Model Based on Moral Hazards in the Unified Credit Mode LI Li-jun， YI Jun-lin，， CHENG Fu 2020, 41 (6):  896-901.  DOI: 10.12068/j.issn.1005-3026.2020.06.023 Abstract ( 495 )   HTML   PDF (435KB) ( 617 )   In the unified credit mode of inventory pledge financing， logistics enterprises may undergo moral hazards of less efforts in credit reviewing because of the information asymmetry between them and banks， and banks as clients need to design incentive mechanisms to prevent moral hazards. As an incentive mechanism， profit distribution can play a certain role in restraining moral hazards. Considering the moral hazards of logistics enterprises， based on the principal-agent theory， the incentive problem of banks to logistics enterprises was studied， the profit distribution model was established and the optimal profit distribution proportion was obtained， and the changing trend of optimal profit distribution proportions by numerical examples was analyzed. It was shown that the optimal profit distribution proportion enables logistics enterprises to invest the best effort level and realize the maximization of combined benefits for both banks and logistics enterprises. References | Related Articles | Metrics

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Pricing and Recycling Decision of Closed-Loop Supply Chains Considering Risks and Capital Constraints LIU Chun-yi， YOU Tian-hui， CAO Bing-bing 2020, 41 (6):  902-908.  DOI: 10.12068/j.issn.1005-3026.2020.06.024 Abstract ( 569 )   HTML   PDF (782KB) ( 738 )   Based on a closed-loop supply chain with recycler capital constraints， the pricing and recycling decision of closed-loop supply chains is studied considering participators’ risk attitudes faced with stochastic demands. The risk attitudes of participators are described based on mean-variance. The optimal wholesale price， retail price and recycling rate in centralized and decentralized decisions are determined respectively. Then the impacts of risk attitudes of participators， loan interest rates and demand uncertainty on the optimal strategies and the utility of members and closed-loop supply chains are analyzed. The results show that the recyclers of risk neutrality is beneficial to all participators， while the retailers and manufacturers of risk neutrality are only beneficial to themselves. The increase of loan interest rates will reduce the utility of participators， while lower demand uncertainty is beneficial to the retailers， recyclers and closed-loop supply chains in decentralized decisions. References | Related Articles | Metrics

Mathematics

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K-Type Pseudo Null Helixes in the 3D Minkowski Space QIAN Jin-hua， LIU Jie 2020, 41 (6):  909-912.  DOI: 10.12068/j.issn.1005-3026.2020.06.025 Abstract ( 550 )   HTML   PDF (276KB) ( 702 )   The k-type pseudo null helixes in the 3D Minkowski space are defined， and then the geometric properties of such kind of curves are discussed via the new defined structure functions of pseudo null curves. Firstly， the structure functions of pseudo null curves are defined according to the concept of pseudo null curves， then the representation forms of pseudo null curves are obtained and the relationship between the structure functions and the curvature functions of pseudo null curves is revealed by the defined structure functions. Secondly， the geometric properties of k-type pseudo null helixes in the 3D Minkowski space are discussed. The results show that any pseudo null curve is a 1-type pseudo null helix， there does not exist 2-type pseudo null helix， and a differential equation satisfying the curvature function of a 3-type pseudo null helix can be obtained. Meanwhile， the expressing forms and types (spacelike axis， timelike axis， lightlike axis) of axes for k-type pseudo null helixes are given. References | Related Articles | Metrics