Journal of Northeastern University(Natural Science)

Impact of Complex Eigenvalues on Their Robust H_∞ Control Performance in Second-Order Systems

WANG Zhan-shan， WANG Ji-dong， LIU Xiu-chong， SUN Jian

2019, 40 (9): 1217-1222. DOI: 10.12068/j.issn.1005-3026.2019.09.001

Abstract ( 654 )

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Robust H_∞ performance is studied for a class of second-order linear systems with complex eigenvalues， especially the impact of imaginary part of complex eigenvalues on the H_∞ performance is studied. It is found that when the real part of the complex eigenvalues is fixed， the impact of the imaginary part of the complex eigenvalues on the H_∞ performance becomes little when the value of the imaginary part exceeds a threshold. Based on this observation， a fixed proportional relation between the imaginary part and the real part of the complex eigenvalues is found for a given system matrix under the framework of H_∞ performance. Referring to the classical control theory of second-order systems in frequency domain， the relationship between the selection ranges of damping ratio and the complex eigenvalue is further discussed in the framework of H_∞ performance， in which a reasonable explanation on the selection ranges of damping ratio is presented. This analysis procedure forms the time-frequency domain interaction synthesis method， which provides a theoretical guidance for the selection and determination of the desired closed-loop poles in the control theory based on the pole placement method.

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Multi-exit Evacuation Strategy Based on Particle Swarm Optimization with Background Field

ZHANG Li-jie ， LIU Jian-chang ， TAN Shu-bin

2019, 40 (9): 1222-1227. DOI: 10.12068/j.issn.1005-3026.2019.09.002

Abstract ( 604 )

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In view of the crowd evacuation exit selection strategy question of complex buildings， this paper focuses on the cognitive difference of pedestrians in the synthetic shortest distance. The mixed distance strategy is established by introducing the distance factor and density factor， and combined with the modified background field modeling rules. The exit selection strategy is integrated into the particle swarm updating mechanism， and the exit selection strategy based on particle swarm optimization with background field is established. The evacuation performance of exit selection strategy is simulated by numerical experiments. The experimental results reveal the mechanism of group movement in multi-exit buildings， and reflect the dynamic adjustment performance of the evacuation strategy. The simulated evacuation process verifies the rationality and effectiveness of the multi-exit selection of the mixed distance strategy in group evacuation.

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Pedestrian Tracking Scale Algorithm Based on Multiple Correlation Filters

ZHANG Yun-zhou， ZHENG Rui， BAO Ji-ning， ZHU Shang-dong

2019, 40 (9): 1228-1234. DOI: 10.12068/j.issn.1005-3026.2019.09.003

Abstract ( 636 )

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Appearance and scale change are the difficulties of pedestrian tracking. To solve the problem of multi-scale pedestrian tracking is the key factor to enhance the practicability of the algorithm. On the basis of KCF(kernel correlation filter) algorithm，this paper uses multiple correlation filters(such as head and hip)to assist the tracking of the body trunk filter. The distance change rate which is obtained by comparing the distance between the pedestrian’s head and hip of every image frame(except the first frame)with the initial frame is used to zoom the search area， so as to avoid inaccurate target location and time waste. By adjusting the size of the target’s bounding box， the problem of target’s template shift caused by gradual change of the target template including background features or local features is solved. The experiment is conducted on eighteen pedestrian scene video sequences with obvious scale changes in VOT2016 dataset， and the experimental results show that the algorithm proposed has higher tracking accuracy.

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Rotor Position Estimation of Permanent Magnet Synchronous Motor Based on High-Frequency Signal Injection

WANG Da-zhi， LI Wen-hui， YUAN Tian-qing， ZHOU Ying-bin

2019, 40 (9): 1234-1239. DOI: 10.12068/j.issn.1005-3026.2019.09.004

Abstract ( 670 )

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An improved rotor position estimation method is proposed to enhance the dynamic performance of the sensorless control technology of permanent magnet synchronous motor(PMSM)in zero/low speed range. Firstly， the high-frequency excitation model of PMSM is established in the α-β coordinate system. Secondly， the rotor position estimation method based on heterodyne method is analyzed， and the method based on compensation matrix is proposed to improve the rotor position estimation performance. Finally， the MATLAB/Simulink is utilized to compare and analyze the rotor position estimation accuracy of the two methods. The simulation results show that the proposed method can not only obtain faster rotor position tracking speed， but also ensure higher rotor position estimation accuracy.

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Reconstruction of Aortic Pressure Wave Based on Subspace Algorithm

LIU Wen-yan， XU Li-sheng， LI Zong-peng， JIANG Zhi-hao

2019, 40 (9): 1240-1245. DOI: 10.12068/j.issn.1005-3026.2019.09.005

Abstract ( 594 )

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Invasive measurement of central aortic pressure waveform(CAPW)is risky and costly. Peripheral arterial pressure waveform(PAPW)has been used to substitute CAPW. However， there is a difference between PAPW and CAPW. Although the blind system identification technology can reconstruct in real-time and dynamically estimate CAPW， it needs to be improved in optimizing the model ordering. Accordingly， a rank-based ordering method was proposed based on Hankel matrix combining the subspace method to reconstruct the central aortic pressure waveform with two peripheral pressure waveforms. The results of the validation algorithm based on the clinical data showed that the root mean square error of the measured CAPW and the estimated CAPW is about 5.87mmHg， and the waveform fit is about 74.70%. The results of the validation algorithm based on the collecting animal data showed that the root mean square error of the measured CAPW and the estimated CAPW is about 8.82mmHg， and the waveform fit is about 54.57%. Thus the experiments verified the effectiveness of the method.

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Channel Automatic Selection Algorithm for P300 Signal with Group Sparsity Bayesian Logistic Regression

FENG Bao， ZHANG Shao-rong

2019, 40 (9): 1245-1251. DOI: 10.12068/j.issn.1005-3026.2019.09.006

Abstract ( 997 )

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In order to improve the classification accuracy and calculation speed of P300 electroencephalogram(EEG)signals in the brain-computer interface(BCI)， a channel automatic selection algorithm of P300 EEG signal based on group sparsity Bayesian logistic regression was proposed. First， the algorithm established the decoding model of P300 EEG signals under the Bayesian framework， and then， a priori group automatic relevance determination(GARD)was proposed to determine the weight coefficients of P300 EEG channels under group sparse constraints. Finally， the maximum likelihood estimation was used to solve the hyperparameters and select the optimal subset of P300 EEG channels， avoiding a large number of cross-validation processes. The proposed method was verified on the BCI competition dataset and self-acquisition dataset. The experimental results showed that the proposed method can automatically select P300 related channels and may improve the accuracy of P300 feature classification.

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Study on Bubble Behavior in a Three-Stage Carbonization Reactor

LIU Guan-ting， LIU Yan， ZHANG Ting-an

2019, 40 (9): 1252-1256. DOI: 10.12068/j.issn.1005-3026.2019.09.007

Abstract ( 613 )

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Aiming at the carbonization process of the calcification-carbonization method for low-graded bauxite and red mud， a “three-stage cross-flow Venturi jet reactor” was proposed to make bubble disintegrate and disperse uniformly and to improve carbonization rate. Physical simulation in carbonization reactor was also carried out. Local gas holdup and bubble rising velocity under different operating conditions were investigated. The results showed that the gas holdup increases with increase of the superficial gas velocity and decreased with increase of the superficial liquid velocity， while it also decreased along the axial direction of the reactor. The gas holdup in the latter stage of the reactor was higher than that in the former one. The bubble rising velocity increased with increase of the superficial gas velocity and superficial liquid velocity， and it decreased along the axial direction of the reactor. The bubble rising velocity in the latter stage of the reactor was higher than that in the former one. The results provide a theoretical and experimental basis to design the carbonization reactor and to guide its applications in industry.

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Kinetics of Indium Leaching from High Indium Sphalerite in Oxygen Pressure Acid Leaching Process

FAN Yang-yang， LIU Yan， NIU Li-ping， ZHANG Ting-an

2019, 40 (9): 1257-1262. DOI: 10.12068/j.issn.1005-3026.2019.09.008

Abstract ( 833 )

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Indium is an important multi-purpose strategic metal and has many potential high-valuable industrial applications. However， there are no independent deposits， often associated with sulfide ore such as lead and zinc. In this work， the indium leaching kinetics of oxygen pressure acid leaching were studied under a traditional electric heating condition. The effects of particle size， temperature， H₂SO₄ concentration， and oxygen partial pressure on leaching rate of indium were investigated. Indium leaching kinetics was studied using a "liquid-solid phase leaching reaction kinetics model with solid product layer". The results showed that indium leaching process was controlled by interfacial chemical reaction with the apparent activation energy of 69.735kJ/mol. Moreover， the leaching efficiency of indium increased with the increase of the initial acid concentration， oxygen partial pressure， leaching temperature， and the decrease of particle size.

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Effect of Al Content on Ignition Temperature of AZ Series Mg Alloys

CHENG Chun-long， LE Qi-chi

2019, 40 (9): 1263-1267. DOI: 10.12068/j.issn.1005-3026.2019.09.009

Abstract ( 662 )

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In this study， the effect of Al content on the onset melting temperature， ignition temperature and pyrolysis ignition state in AZ series Mg alloys were investigated. The onset melting and ignition temperatures of different AZ series Mg alloys were measured. The microstructure and surface morphology of the alloys before combustion were observed by field emission scanning electron microscopy(FESEM)， and X-ray diffraction(XRD)was used for the phase identification. The results show that with Al addition， the β-Mg₁₇Al₁₂ phase with a low melting temperature appears and increases， which can decrease the onset melting and ignition temperatures of the Mg alloys. Moreover， pure Mg and AZ31 are ignited in solid state， while AZ61 can be ignited in semi-solid state and the AZ80 can also be ignited in semi-solid state with less solid fraction. Meanwhile， the increase of Al content can make the oxide layers generated by heating more continuous and perfect， which delays decreasing of ignition temperature.

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Process Mineralogy of Baolun Gold Mine in Hainan Province

CHEN Qiao， TONG Lin-lin， CHEN Gui-min， YANG Hong-ying

2019, 40 (9): 1268-1272. DOI: 10.12068/j.issn.1005-3026.2019.09.010

Abstract ( 674 )

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In this work， the characterization of process mineralogy of the gold ore from Baolun gold mine was studied through chemical analysis， X-ray diffraction， optical microscope and scanning electron microscope analysis. That can provide a theoretical basis and guideline to select ore dressing process. The results show that the Au and S contents of the ore are 10.1g·t^-1 and 0.65%， respectively， and the main gangue minerals are quartz and muscovite. The gold minerals in the ore are mainly native gold with the relative content of 90.58%. The particle size range of gold mineral is wide， and the contents of giant-grained gold(>300μm)， coarse-grained gold(74~300μm)， medium-grained gold(37~74μm)， fine-grained gold(10~37μm)and micro-grained gold(0.10~10μm)are 3.84%， 28.85%， 18.04%， 23.52% and 25.75%， respectively. The occurrence state of gold minerals in the ore is wrapped by gold， intergranular gold and fissure gold， the content of which accounts for 48.37%， 43.24% and 8.39%， respectively. Based on the researches of process mineralogy， a Knelson gravity separation-flotation technology cooperated with multi-stage grinding process is proposed.

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Resonance Analysis of Non-sinusoidal Oscillations of Continuous Casting Mold

MENG Xiang-ning， CUI Yu， LYU Ze-sheng， PENG Xiu-xing

2019, 40 (9): 1273-1278. DOI: 10.12068/j.issn.1005-3026.2019.09.011

Abstract ( 754 )

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According to the harmonic resonance theory， when the continuous casting mold is non-sinusoidal oscillation and the vibration frequency is lower than the natural frequency of the oscillator in the mold， partial harmonics with a higher amplitude can lead to resonance because the harmonic frequencies is an integer multiple of the oscillation frequency， which can directly affect the quality of slab. Using Fourier transformation， the acceleration curve of non-sinusoidal oscillation of the mold is analyzed and the relationships between harmonic amplitude and other factors， such as initial amplitude， oscillation frequency， non-sinusoidal oscillation factor and harmonic order are obtained. Then， a theoretical method of restraining resonance can be given. When the natural frequency of the oscillator in the mold is known， the harmonic order of resonance under different oscillation frequencies is determined. The harmonic amplitude corresponding to the combination of different oscillation parameters can be given by the relationship between the harmonic amplitude and the variation of each oscillation parameter. Consequently， selecting an oscillation parameter combination with a smaller harmonic amplitude can reduce the adverse effect of resonance phenomenon on the oscillator in the mold， resulting to reduce the deflection of mold， maintain liquid level stabilizing and improve the working conditions of continuous casting machine.

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Effect of M_k on Slag Properties in the Process of Preparing Slag Wool from Modified-Blast-Furnace-Slag

DU Pei-pei， ZHANG Yu-zhu， LONG Yue

2019, 40 (9): 1279-1283. DOI: 10.12068/j.issn.1005-3026.2019.09.012

Abstract ( 663 )

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Blast furnace slag modifying experiments using iron tailings were conducted to investigate the effect of acidity coefficient(M_k)on crystallization property， viscosity and surface tension of modified-blast-furnace-slag. The results indicated that crystallization temperature of modified slag significantly decreases with the increase of M_k and the slag system is still unordered glass phase with slag temperature decreasing to 1100℃ when M_k is above 1.4. The sensitivity of slag viscosity to temperature change gradually decreases， the temperature range corresponding to theoretically suitable fiber-formation-viscosity range of slag wool gradually increases， and the difference between minimum fiber-formation-temperature and crystallization temperature in suitable fiber-formation-viscosity range(Δt=(t_○w-t_○l))， which is only 101.7℃ when M_k is 1.2， gradually increase with the increase of M_k. The effect of M_k on surface tension of slag is small and the ratio of surface tension to viscosity， σ/η， symbolizing difficult degree of slag-forming， gradually decreases with the increase of M_k in suitable fiber-formation-temperature range.

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Study on Decomposition of Monazite Concentrate in NaOH-Ca(OH)₂

ZHANG Bo， XUE Xiang-xin， YANG He， RI Jong-chol

2019, 40 (9): 1284-1290. DOI: 10.12068/j.issn.1005-3026.2019.09.013

Abstract ( 715 )

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In order to decrease alkali dosage and increase decomposition rate of monazite， decomposition experiment of monazite concentrate in system of NaOH-Ca(OH)₂ was implemented by roasting. The roasted products were characterized by using X-ray diffraction. The decomposition effect of monazite was further judged through leaching rate of rare earth in hydrochloric acid. The influence factors for roasting process， such as roasting temperature， NaOH dosage， Ca(OH)₂ dosage and roasting time were investigated. The optimum roasting decomposition parameters are proposed as the following: roasting temperature of 800℃， NaOH dosage of 25%， Ca(OH)₂ dosage of 20%， and roasting time of 1.5h. With these optimum parameters， rare earth phase transformed from REPO₄ into REO. Leaching experiments demonstrated that leaching rate of rare earth in concentrated hydrochloric acid reaches up to 98% in these optimum parameters. Comparing with index of industrial production process， alkali dosage in this process reduces about 55%. Additionally， decomposition rate of monazite increased about 2%.

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Clean Roasting Process for Treating Vanadium Slag by Using Binary Sodium Salts System

TENG Ai-jun， XU Hong-hong， XUE Xiang-xin

2019, 40 (9): 1291-1297. DOI: 10.12068/j.issn.1005-3026.2019.09.014

Abstract ( 680 )

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The vanadium slag was treated by NaOH-Na₂CO₃ binary sodium salts in the roasting process and the influence of related kinetic parameters on roasting effect was investigated. The results showed that during the NaOH-Na₂CO₃ binary roasting process， the roasting temperature， roasting time and NaOH to Na₂CO₃ mass ratio play significant roles in the extraction rate of vanadium and chromium. The ferriferous oxide(Fe₃O₄)is oxidized to ferric oxide(Fe₂O₃)while V₂O₅ and Cr₂O₃ are converted to the β-natrium-vanadate type structure of Na₃VO₄ and orthorhombic-type crystal structure of Na₂CrO₄， respectively. Under the optimum roasting conditions(roasting temperature of 600℃， roasting time of 60min， and NaOH to Na₂CO₃ mass ratio of 1.5∶1)， the extraction rate of vanadium and chromium is 98.66% and 83.57%， respectively. The major metal element in the leaching residue is Fe.

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Preparation of Al-Si Alloy with Low Concentration of Boron and Phosphorus by Molten Salt Electrolysis of Silica

GUAN Jin-zhao， LIU Ai-min， XU Jun-li， SHI Zhong-ning

2019, 40 (9): 1298-1304. DOI: 10.12068/j.issn.1005-3026.2019.09.015

Abstract ( 837 )

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Low-boron(B)/phosphorus(P)Al-Si alloys were prepared by electrolysis of silica in cryolite melts at 960℃ using high-purity graphite and Fe-Ni alloy as anodes. The effects of current density and the addition amount of silica to the melts on current efficiency， cathode composition， and impurity(B and P)contents were investigated. The phase composition and microstructure of the cathode product were characterized by XRD and SEM. The results showed that when using graphite anode， the silicon contents in the cathode product increased from 0.75% to 15.17% as the current density increased from 0.5A/cm² to 0.9A/cm²， and the current efficiency increased from 2.58% to 38.06%. The minimum contents of B and P were 3 ×10^-6 and 7×10^-6， respectively. Using Fe-Ni alloy anode， the silicon contents in the cathode product increased from 3.19% to 19.86%， and the current efficiency increased from 12.43% to 70.48% when the addition amount of silica increased from 2% to 6%. The minimum contents of B and P were 6×10^-6 and 11×10^-6， respectively. The phase compositions of the cathode product were Al， Si， and Al-Si alloy.

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Heat Source Rate Identification and Thermal Error Predictions of Ball Screw Feed Drive System for CNC Machine Tools

LI Zhen-jun， ZHAO Chun-yu， WEN Bang-chun， LU Ze-chen

2019, 40 (9): 1305-1309. DOI: 10.12068/j.issn.1005-3026.2019.09.016

Abstract ( 706 )

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The ball screw feed drive system of CNC(computerized numerical control)machine tools is characterized as multi-heat sources with strong time-varying heat rate. But the past work was scarely focused on the time-varying of the heat sources. This fact results in inaccuracy of predicting temperature rise and thermal error of the screw. In this paper， the heat rates of the multi-heat sources were captured by virtue of the FEM integrated with Monte Carlo method. Consequently， relationship of the ratio of each heat source to the total heat rate of the system with the running time was obtained. Then， based on heat ratios of the heat sources， the heat rates of the heat sources were determined using torque current of the servo motor in the ball screw feed drive system. Finally， numeric prediction model of temperature rise and thermal error of the screw was put forward based on finite difference method of one-dimension heat conduction equation， and the accuracy of the prediction method was verified by experimental results.

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Study on Grinding Surface Quality of Unidirection Carbon Fiber-Reinforced Ceramic Matrix Composites

QU Shuo-shuo， GONG Ya-dong， YANG Yu-ying， CAI Ming

2019, 40 (9): 1310-1315. DOI: 10.12068/j.issn.1005-3026.2019.09.017

Abstract ( 786 )

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To investigate the grinding surface quality of unidirection carbon fiber-reinforced ceramic matrix composites(C_f/SiC)， the orthogonal experiments were carried out by using resin-bonded diamond grinding wheel. In order to achieve the influence order of grinding wheel linear speed， grinding depth and feed speed on grinding surface quality， range analysis was adopted in this paper. The results indicate that: the grinding depth has maximum impact on the machining surface roughness; as the raises of grinding depth， the grinding surface roughness increases; as the raises of grinding wheel linear speed， the grinding surface roughness decreases; as the raises of feed speed， the grinding surface roughness increases. According to the result of orthogonal experiments， the best combination of grinding parameters was achieved. Based on the experiment results and surface topography， the grinding mechanisms of unidirection C_f/SiC were further analyzed， which supplies some useful technical reference for revaling the grinding mechanisms of unidirection C_f/SiC.

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Identification of Cutting Force Coefficients in Different Cutting Edges of Ball-End Milling Cutter

LI Bai-chun， WANG Zhen-yu， ZHANG Bin， WANG Wan-shan

2019, 40 (9): 1316-1322. DOI: 10.12068/j.issn.1005-3026.2019.09.018

Abstract ( 764 )

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In order to determine cutting force coefficients of a ball-end milling cutter， in which cutting edges have differences， a new method combining the average milling force method with particle swarm optimization(PSO)was proposed. Firstly， the milling force models and the identification models based on the average milling force method are constructed ignoring the differences of cutting edges. Then， the algorithm for searching more accurate cutting force coefficients based on PSO was given. The algorithm uses the coefficients obtained by the average milling force method as initial values， correction factors of cutting force coefficients as design parameters， and sum of squared deviations between the minimum cutting force of simulation and experiment as objective function. Finally， a series of simulations and experiments are performed. The results show that the predicted milling forces with corrected cutting force coefficients have a better consistency with measured forces.

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Study on Self-Adaptive Multistage Constant Current Charging Based on Electro-Thermal-Aging Coupling Model

LI Kui-ning， ZHANG Hong-ji， XIE Yi， FU Chun-yun

2019, 40 (9): 1323-1329. DOI: 10.12068/j.issn.1005-3026.2019.09.019

Abstract ( 775 )

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An electro-thermal-aging coupling multi-state joint-estimation model of lithium-ion batteries was built based on the first-order RC equivalent circuit model， the thermal network method and the aging model. Particle swarm optimization(PSO) algorithm was adopted to establish a self-adaptive multistage constant current(SMCC)charging strategy whose stages were adaptive to the objective function. By constructing the Pareto frontier of charging time and battery life， three charging strategies， including the minimum-time charge， the minimum-aging charge and the balanced charge， were obtained. Then they were compared with the CC-CV charges. The results show that the minimum-time charge is highly consistent with the 2C CC-CV. The aging losses of the minimum-aging charge and the 0.1C CC-CV are very small， but the former reduces charging time by 61.7%. Compared with the minimum-aging charge， the charging time of the balanced charge is reduced by 71.19% at the expense of 0.06%SOH. Compared with the 0.5C CC-CV charge， the charging time of the balanced charge is reduced by 44.9%.

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Error Analysis and Correction of 3D Laser Detection Data for High-Humidity and Dusty Goafs

XU Shuai， HOU Peng-yuan， LIANG Rui-yu， DU Yong-liang

2019, 40 (9): 1330-1336. DOI: 10.12068/j.issn.1005-3026.2019.09.020

Abstract ( 613 )

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As the high-humidity， dusty and complex environment leads to the distortion of 3D laser detection results for goafs in the underground metal mines， a device is developed to simulate the complex environment of goafs and to carry out 64 groups of point cloud error analysis and modification experiments with different dust concentrations and relative humidity. It could be observed that with the increase of dust concentration and relative humidity，the average error ratio of point cloud data showed an "S" trend. In particular，under the condition of 30.0mg/m³≤ρ≤85.0mg/m³ and 76.0%≤w≤85.0%，the error growth rate of point cloud data increases exponentially. It can be concluded that the ρ ranging from 0 to 5.6mg/m³ and the w ranging from 0 to 49.0% are favorable for the laser detection of goaf. In addition，the error correction formulas of point cloud are put forward for high humidity， dusty and complex environment. After the application of test results to a gold mine in Fujian Province，the revised parameters such as the elevation， the volume and the exposed area of the goaf are more practical，which proves the accuracy of detection data.

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Implicit 3D Geological Modeling Method for Borehole Data Based on Machine Learning

GUO Jia-teng， LIU Yin-he， HAN Ying-fu， WANG Xu-lei

2019, 40 (9): 1337-1342. DOI: 10.12068/j.issn.1005-3026.2019.09.021

Abstract ( 1247 )

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Considering the complex modeling process and difficulty in guaranteeing the model quality of traditional explicit 3D modeling methods， an implicit 3D geological modeling method for borehole data based on machine learning was proposed， which transformed the strata 3D modeling problem into a process of geological attribute classification of the underground spatial grid units. Based on the classification algorithms of support vector machine and BP neural network， automatic 3D geological modeling from borehole data was realized. The results demonstrate that for sparse and limited borehole data， support vector machine can generally perform better than explicit methods. Finally， the influence of hyper-parameter on modeling accuracy and model shape is studied through sensitivity analysis， which provides a new solution for controllable 3D geological modeling.

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Emission Inventory of Atmospheric Pollutants from on-Road Vehicles in Low-Temperature Areas in Winter

GAO Cheng-kang ， XU Qing-jiang ， XING Yu-hong ， NA Hong-ming

2019, 40 (9): 1343-1349. DOI: 10.12068/j.issn.1005-3026.2019.09.022

Abstract ( 633 )

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The emission inventory and pollution characteristics of on-road vehicles were studied in low temperature areas in winter. Taking Changchun as an example， and based on tests and the technical guide for emission inventory preparation of on-road vehicles， an emission inventory of Changchun was established in 2016. ArcGIS was used to allocate space， and the contribution rate of typical vehicles starting emission was analyzed based on the IVE model. The results showed that the annual emissions of CO， HC， NO_○x， PM_2.5 and PM₁₀ are 137700， 29000， 40900， 2200 and 2400 tons， respectively. Minibuses are the dominant contributors to CO and HC， while heavy-duty trucks are the main sources of NO_○x and PM₁₀. Meanwhile， the contribution rate during the start-up phase of typical vehicles in Changchun is higher than that in Shanghai.In addition， the emission intensity tends to decrease from the center of city to the outskirts.

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Triaxial Liquefaction Test of Saturated Stratified Sand

XIU Zhan-guo， WANG Shu-hong， LI Chun， WANG Fei-li

2019, 40 (9): 1350-1354. DOI: 10.12068/j.issn.1005-3026.2019.09.023

Abstract ( 626 )

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In order to study the developments of pore water pressure in the liquefaction processes of saturated sands with stratified structure， the liquefaction tests under equal amplitude strain control for saturated sands were carried out by using GCTS-STX-050 dynamic triaxial testing system. The effect of different thickness， position and number of layers on liquefaction was analyzed. It is showed that the cyclic loading times required for liquefaction is non-linearly related to the thickness of the silt interlayer. There is a critical thickness that causes the cyclic loading times to be maximum. And the silt can effectively prevent the transfer of excess pore water pressure generated by fine sand. But the inhibition of fine sand for excess pore water pressure generated by silt is not obvious. Under the same thickness of silt interlayer， the distribution of two-layered interlayer is more obvious than one layer on obstruction of excess pore water pressure. The conclusion can provide a reference for the liquefaction of saturated sand with stratified structure under earthquake.

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Experiment on the Effect of Environmental Humidity on the Pool Fire in Confined Space

ZHANG Pei-hong， HAO Yu-jun， LI Zi-jian

2019, 40 (9): 1355-1359. DOI: 10.12068/j.issn.1005-3026.2019.09.024

Abstract ( 728 )

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In order to analyze the complexity and uncertainty of fire development and smoke spreading in highly humid confined space， a 3.6m × 1.2m × 1.4m experimental model was set up， using a 600mm diameter alcohol pool as the fire source. Experimental ambient temperature was (20±2)℃， while the relative humidity was changed from 30% to 90% with 5% error. Several parameters were measured to analyze the pool fire development under different environmental humidity conditions， including the mass loss rate of fuel， the maximum flame temperature， the average temperature of upper hot smoke layer， the radiant heat from the flame， the radiant heat received by the ground， the O₂ concentration near the flame root and the CO₂ concentration in the smoke. The results showed that when the relative humidity reached about 90%， the mass loss rate of fuel， the maximum flame temperature， the average temperature of the upper hot smoke layer， the radiant heat from the flame and the radiant heat received by the ground decrease significantly. Also， the duration of the developing stage of fire was prolonged， and the temperature dropping gradient in the extinction stage decreases. In conclusion， with a normal temperature and high relative humidity of 90%， the development and spread of pool fire is significantly inhibited.

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Numerical Simulation on Characteristics of the Axial Flow Cyclone Separator

LIN Xiu-li， CAO Ya-ping， XIA Zhi-jun， LIU Jing-xian

2019, 40 (9): 1360-1364. DOI: 10.12068/j.issn.1005-3026.2019.09.025

Abstract ( 817 )

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The characteristics of an axial flow cyclone separator were studied. The effects of blade space， rotating angle and dust exhaust gap on the pressure drop and tangential velocity of the cyclone separator at 2.5~6m/s inlet air velocity were analyzed. The results showed that the pressure drop of the cyclone separator increases with the increase of inlet air velocity. The rotating angle of blades has little effect on the pressure drop of the cyclone， while the maximum tangential velocity increases with the increase of the rotating angle. The pressure drop and tangential velocity are greatly influenced by the change of blade space， and the pressure drop increases 31.1% when the blade space changes from 16mm to 12mm at 6 m/s inlet air velocity， while the tangential velocity increases 11%. Larger dust exhaust gap can significantly increase the pressure drop， and has little effect on tangential velocity. The efficiency of the cyclone separator with 16mm blade space， blade rotating angle of 90 degrees and dust exhaust gap of 7.15mm for A4 coarse dust can reach more than 85%. The results provide a basis for designing geometric parameters of axial flow cyclone separator.

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Effects of New Product Preannouncement on Customers’ Willingness to Buy

ZHANG Hao， QI Chen-yue， ZHANG Rui-ling， GAO Ming

2019, 40 (9): 1365-1368. DOI: 10.12068/j.issn.1005-3026.2019.09.026

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Based on the consumer perspective， the effects of new product preannouncements(NPPs) on customers’ willingness to buy were studied by using consumer behavior experiments. The results showed that NPPs have positive effects on customers’ willingness to buy. The clearer the NPP messages are， the higher willingness to buy is. The role of clearer NPP messages has stronger effects on willingness to buy for the new product with a high brand image. Compared with low-innovation consumers， the role of preannouncements clarity is more significant for high-innovation consumers’willingness to buy. The present study has theoretical contribution to the theory of NPP， which is of practical significance to rapidly expand the market share of new products and enhance the competitiveness of enterprises after the new products go on the market.

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