Journal of Northeastern University(Natural Science)

Numerical Simulation of Shrinkage Porosities and Surface Cracks of Slab with Hot-Core Heavy Reduction Rolling

LI Tian-xiang， LI Hai-jun， WANG Zhao-dong， WANG Guo-dong

2021, 42 (7): 913-919. DOI: 10.12068/j.issn.1005-3026.2021.07.001

Abstract ( 675 )

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To study the effect of hot-core heavy reduction rolling(HHRR) process on internal shrinkage porosities and surface cracks of the slab， EH47 ship-plate steel was taken as a research material， and the processes of the HHRR and conventional hot rolling were analyzed and compared through numerical simulation. The results show that the temperature gradient along the thickness direction of slab becomes larger， and the strain level in the core region and the deformation uniformity along the thickness direction are improved in the HHRR process. When the reduction amount is 50 mm， the residual void volume after HHRR is 18.4% smaller than the conventional one. Due to the lower strain rate and deformation temperature on the slab surface during the HHRR， the cracking risk on the side surfaces and the corners is higher than the conventional one， however， it could not lead to the surface cracks.

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High Temperature Oxidation Behavior of 700MPa Grade High Strength Steel Under Water Vapor Condition

WANG Hao， CAO Guang-ming， TANG Jun-jian， LIU Zhen-yu

2021, 42 (7): 920-926. DOI: 10.12068/j.issn.1005-3026.2021.07.002

Abstract ( 554 )

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High temperature oxidation behavior of high strength steel was systematically studied by high-temperature thermal gravimetric analyzer(TGA) and the law of oxidation weight gain under different relative humidity conditions was analyzed. Electron probe microanalysis(EPMA) was used to characterize the thickness， cross-sectional morphologies and element distribution of oxide scale and X-ray diffraction(XRD) was used to analyze the phase composition of oxide layer. The experimental results show that the form of weight gain curves transformed from linear law to parabolic law， the curves showed an obvious turning point， and the corresponding mass of oxide scale at the turning point increased with the increasing of relative humidity at 1000℃. Vapor promoted the formation of a large number of defects， such as pores and microcracks inside the oxide scale， which became diffusion channels for the ions， thereby accelerating the oxidation reaction. Moreover， the vapor promoted the diffusion of Si and Mn elements， which can leads to the expansion of the element-rich layer.

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Effect of Tempering Temperature on Microstructure and Mechanical Properties of On-Line Quenched Q690q Bridge Steel

GAO Cai-ru， QU Bing-bing， TIAN Yu-dong， DU Lin-xiu

2021, 42 (7): 927-933. DOI: 10.12068/j.issn.1005-3026.2021.07.003

Abstract ( 612 )

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The effects of tempering temperatures on microstructure and mechanical properties of the on-line quenched Q690q bridge steel were investigated through optical and scanning electron microscopes and tensile tests. The results show that the microstructure of the on-line quenched steel is primarily the lath bainite. After tempering at 540~650℃， the microstructure is the tempered sorbite. It is also found that with the increase of the tempering temperature， the lath width and the averaged grain size become larger， and the amounts of the carbide precipitations and large-angle grain boundaries increase. Meanwhile， with the tempering temperature increasing， the strength of the tested steel trends to be decreased， in contrast to the plasticity and toughness. At 620℃， the tested steels have the best mechanical properties， in which the yield and tensile strengths are 878 MPa and 992 MPa， the percentage elongation after fracture is 20%， and the impact absorption energy at -40℃ is 143 J.

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Microstructure Evolution and Recrystallization Kinetics of CoCrFeNi High Entropy Alloy

BI Meng-yuan， XIE Ren-yi， ZHANG Yi-fan， YI Hai-long

2021, 42 (7): 933-938. DOI: 10.12068/j.issn.1005-3026.2021.07.004

Abstract ( 820 )

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Using a Gleeble-1500D thermal simulator， the non-equal molar CoCrFeNi high entropy alloy doped with minor carbon was conducted by hot deformation under different deformation conditions. The results show that when the temperature is 1123K and strain rate is 0.1s^-1， the microstructure is mainly composed of deformed grains. With the increase of temperature or decrease of strain rate， fine grains start to appear at the deformed grains edge. When the temperature increases to 1223K， all microstructure is transformed to equiaxed recrystallization grains. When the temperature is higher than 1223K， the grains become coarse. Arrhenius model and Avrami equation were used to build the kinetic model of recrystallization， and the activation energy was obtained as 526.078kJ/mol.

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Numerical Simulation of Void Closure in the Core of Continuous Casting Steel During Temperature Gradient Rolling Process

WANG Bin， NING Xin-yu， LI Fang-po， LI Hai-jun

2021, 42 (7): 939-946. DOI: 10.12068/j.issn.1005-3026.2021.07.005

Abstract ( 522 )

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Based on the high permeability temperature gradient rolling technology by temperature-deformation coupling control， the effects of the intensive water cooling before rolling and rolling reduction ratio on void closure in the core of the bloom were studied by numerical simulation using DEFORM software. The results show that temperature gradient greatly affects the deformation flow of the bloom. Increasing the water-cooling time increases the temperature difference between the core and the surface of the continuous casting steel， which leads to a larger temperature gradient， so that the deformation permeability of rolling can be enhanced effectively. Moreover， an increasing reduction ratio of the single-pass rolling combined with the temperature gradient can further increase the deformation flow in the core of the bloom， which promotes the void closure， so that the quality of the continuous casting steel can be greatly improved.

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Numerical Simulation of Influence of Intermediate Radiator on Heat Transfer Process in Heating Furnace

JIANG Tian-chi， ZHANG Wei-jun， LIU Shi， WANG Xin

2021, 42 (7): 947-952. DOI: 10.12068/j.issn.1005-3026.2021.07.006

Abstract ( 503 )

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The energy-saving mechanism of blackbody directional radiation technology was investigated. Based on a chamber heating furnace with an intermediate radiator in a steel plant， a physical model with intermediate radiators was established. A transient 3-D mathematical combustion model coupled with heat transfer and fluid flow in the furnace was developed based on the CFD commercial software Fluent to simulate the combustion and temperature distribution in the furnace. The model was verified according to experimental results. The research results show that the installation of the intermediate radiators changes the flow pattern in the combustion chamber of the furnace and the view factor of the furnace wall to the slab for solid radiation， and enhances the radiant heat transfer intensity of the slab surface for both gas radiation and solid radiation. The combustion temperature is reduced by about 20K， the slab heating speed is increased by 16.7%， and the highest temperature of the slab surface is increased by 40K. The improvement of heating efficiency brings a better energy-saving effect.

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Speaker Clustering Algorithm Based on Feature Fusion

ZHENG Yan， JIANG Yuan-xiang

2021, 42 (7): 952-959. DOI: 10.12068/j.issn.1005-3026.2021.07.007

Abstract ( 606 )

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Aiming at the limitation of single acoustic feature and k-means algorithm in speaker clustering technology， in order to better express the speaker’s personality information and improve the accuracy of speaker clustering， feature fusion and AE-SOM neural network are applied to speaker clustering， and an improved speaker clustering algorithm is proposed. The algorithm combines MFCC feature parameters with LPCC feature parameters to improve the speaker’s personality information. The AE-SOM neural network is added on the basis of k-means to reduce the dimension of input features， determine the number of speakers and select the cluster centers， so as to make up for the defects of k-means algorithm. Simulation results show that the improved clustering algorithm can effectively improve the accuracy of speaker clustering.

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Double Delay Multiplication and Accumulation Beamforming Algorithm Based on Weighting Factor

BAO Xi-rong， LI Zheng-shuang， GAO Hao-sen， ZHANG Shi

2021, 42 (7): 960-965. DOI: 10.12068/j.issn.1005-3026.2021.07.008

Abstract ( 523 )

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In order to solve the problem that the double delay multiplication and accumulation algorithm in ultrasonic imaging is not suitable for high noise environments， a double delay multiplication and accumulation algorithm based on mean-standard deviation weighting factor， namely RD-DMAS algorithm， is proposed. The weighted factor has a significant effects on solving the image speckle problem caused by strong noises， and the dual delay multiplication and accumulation beamforming algorithm can greatly improve the resolution of ultrasonic imaging， so the new method can obtain high resolution and high contrast image reconstruction. The algorithm was simulated in point scattering target replicas， cyst replicas and noise environments， and the results show that the RD-DMAS has the smallest sidelobe and narrower main lobe. The contrast ratios(CR)of DAS， DMAS， DS-DMAS and RD-DMAS were 9.72， 11.72， 13.28 and 19.86， respectively. RD-DMAS provides the best imaging performance regardless of noise in the environment.

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Modeling and Experimental Research of Constrained Damping Structure Considering Frequency-Dependent Characteristics

LUO Zhong， GUO Si-wei， YU Chang-shuai， HE Feng-xia

2021, 42 (7): 966-972. DOI: 10.12068/j.issn.1005-3026.2021.07.009

Abstract ( 435 )

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In order to improve the simulation accuracy of viscoelastic constrained damping structure model， a modeling method of constrained damping structure considering frequency-dependent characteristics was proposed and then a test was performed for verification. Firstly， the dynamic test of ZN-3 viscoelastic material was carried out， and the expressions of modulus and loss factor of viscoelastic material were obtained using the least squares method. Secondly， according to the expression of loss factor of ZN-3 viscoelastic material， the natural frequency and modal loss factor of constrained damping structure were solved using the modified modal strain energy method considering frequency-dependent characteristics. Finally， the cantilever constrained damping structure attaching the viscoelastic damping material was chosen and verified from both theory and test， whose results showed that the finite element model considering frequency-dependent characteristics has higher accuracy and the error of model to test is within 5%， which verifies the accuracy of the modeling method.

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Numerical Simulation on Corrosion Resistance of Pre-stress Grinding Surface of Stainless Steel

HOU Zhuang-zhuang， XIU Shi-chao， WANG Yu-shi， YAO Yun-long

2021, 42 (7): 972-979. DOI: 10.12068/j.issn.1005-3026.2021.07.010

Abstract ( 472 )

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In order to explore the evolution mechanism of surface corrosion of pre-stress grinding and the influence of grinding parameters on the corrosion resistance of stainless steel， 304 stainless steel was taken as the research object， a numerical model considering the influence of pre-stress grinding surface topography on the corrosion resistance of stainless steel was established. Firstly， the phase field equation for the corrosion field of rough surfaces was derived. Secondly， the surface topography model of the workpiece of pre-stress grinding was established. Finally， an auto-correlation wheel surface model with non-Gaussian distribution characteristics was built. With all the built models， the corrosion resistance of pre-stressed grinding surfaces was explored. Compared with the existing research results， the conclusions obtained conform to the general law， which verifies the rationality of the proposed method. The results showed that the pre-stress grinding surface has the "polishing effect" in the corrosive environment. As the corrosion time extends， the surface corrosion resistance is enhanced. In the condition of using coolant， appropriately increasing the pre-stress， wheel speed， and reducing feed speed can improve the corrosion resistance of the machined surface. When the pre-stress is a fixed value， the method of optimizing the linear speed and feed speed of the grinding wheel could also be used to further improve the corrosion resistance of the stainless steel workpiece.

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Theoretical Model and Experimental Verification of Surface Roughness of Fused Filament Fabrication Plates

JIANG Shi-jie， HU Ke， CHEN Pi-feng， SIYAJEU Yannick

2021, 42 (7): 980-986. DOI: 10.12068/j.issn.1005-3026.2021.07.011

Abstract ( 500 )

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Aiming at the surface quality defects of fused filament fabrication(FFF)products， a theoretical modeling method of the surface roughness of FFF products was proposed. Taking into account the actual conditions of the samples， the surface profile of the material filament was investigated， and the surface roughness theoretical models of FFF samples in two different directions(vertical and parallel to the fiber direction) were established respectively. At the same time， a series of corresponding experimental tests were performed using a laser microscope. Based on the comparison between theoretical and experimental results， the proposed model was verified. The sensitivity analysis of the theoretical model shows that increasing the extrusion width or printing layer thickness will increase the surface roughness of FFF products， while increasing the overlapping area width will decrease the surface roughness.

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Energy Transfer and Dynamic Characteristics of Jointed Phyllite

XU Jiang-bo， FEI Dong-yang， SUN Hao-hui， CUI Yi-lun

2021, 42 (7): 986-995. DOI: 10.12068/j.issn.1005-3026.2021.07.012

Abstract ( 647 )

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A SHPB device was conducted to investigate the energy transfer law and strength attenuation characteristics of phyllite with different joint angles under the same impact velocity. Dynamic characteristics of jointed phyllite under dry and saturated conditions was also analyzed. The results showed that the maximum strength is at 0°， and the minimum strength is at 60°. The peak dynamic strength of the phyllite is reduced and the ductility is enhanced under saturated state. The reflection energy of phyllite is significantly greater than the transmission energy， and these laws of the reflection energy and the transmission energy are opposite with the varying joint angle. The lag phenomenon occurs in the time required for the reflection energy and the transmission energy to reach the stable stage under saturated state. As the joint angle increases， the reflection energy ratio of phyllite increases first and then decreases， and the growth trend of transmission energy ratio and dissipation energy ratio are opposite. When the joint angle is 60°， the reflection energy ratio is the largest and the transmission energy ratio and the dissipation energy ratio is the smallest. With the increase of the joint angle， the energy dissipation and peak strength is U-shaped.

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Characteristics of Hydraulic Fracture in Homogeneous Porous Rock Material Based on EPHF Model

LI Ming， ZHANG Yan-kun， ZHAO Qi， LIANG Li

2021, 42 (7): 996-1004. DOI: 10.12068/j.issn.1005-3026.2021.07.013

Abstract ( 447 )

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Based on a coupled fluid-solid theory， an extended permeability-based hydraulic fracture(EPHF) model was developed according to the permeability-based hydraulic fracture(PHF) model. The proposed EPHF model assumed that the permeability of porous rock was a function of mean effective stress when a rock was fractured. The porous elastic constitutive law and Drucker-Prager plastic model were adopted to model the pre-failure and post-fracture process of rock material， respectively. The Darcy’s law was used to describe the liquid phase. To consider the influence of injection fluid， the LET model was integrated to modify the permeability of fracture zone with the mixed viscosity of injection and original fluid being used. The development of pore pressure， stress path， equivalent fracture zone and fracture height for different tensile strength were studied by using the proposed model. The simulation results indicated that the pore pressure in fracture path(except injection point) first decreased and then increased to propagation pressure. If the effective stress difference and pore pressure were kept the same or if the total stress was constant， the breakdown pressure decreased when the effective stress ratio increased.

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Design of Inlet Diameter of Hydrocyclone Based on Stable Flow Field

CUI Bao-yu， MA Cong-yu， SHEN Yan-bai， SONG Zhen-guo

2021, 42 (7): 1005-1011. DOI: 10.12068/j.issn.1005-3026.2021.07.014

Abstract ( 513 )

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There are no definite evaluation criteria for the optimum size of inlet diameter of hydrocyclone yet. Effects of inlet diameter on flow field characteristics and separation performance are investigated numerically. A theoretical design method of the inlet diameter based on the inner stable flow field was proposed. The results show that the lower limit of the inlet diameter can be determined based on energy consumption. When the inlet diameter is less than the lower limit， the collision between fluids is more severe， and part of the pressure energy is converted into the internal energy. Consequently， the outer free vortex region presents a characteristic similar to the forced vortex. The upper limit of the inlet diameter can be achieved according to the stable flow field. When the inlet diameter exceeds the upper limit， the feed stream will directly impinge on the vortex finder， causing poor flow field stability. As a result， the recovery of coarse particles in the underflow will decrease sharply and the separation sharpness will also decrease. Finally， the optimal range of the inlet diameter is determined as 0.18D≤D_i≤0.26D.

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Magnetic Bio-char Derived from Sewage Sludge and Its Adsorption Ability for Cu(Ⅱ) in Aqueous System

ZHAO Bing， ZHANG Ran， XU Xin-yang

2021, 42 (7): 1012-1018. DOI: 10.12068/j.issn.1005-3026.2021.07.015

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The novel magnetic bio-char(MBC)， which was derived from sewage sludge in municipal wastewater treatment plant after pyrolysis and Fe²⁺/Fe³⁺ modification by loading nano-sized iron oxide particles.The MBC can be used for the adsorption of heavy metal ions in aqueous system remediation. The physical/chemical characteristics of MBC were revealed by VSM， SEM-EDS， XRD， FTIR and batch adsorption experiments. The results showed that the nano-sized γ-Fe₂O₃ particles grew on the surface of bio-char uniformly， and the saturation magnetization of MBC reached 13.53Am²/kg. In adsorption experiments， when the dosage of MBC was 1.25g/L， adsorption time was 24h， pH was 5.0， the adsorption capacity was 67.68mg/g which increased by 60.08% than that of bio-char. The Langmuir isothermal and pseudo-second-order model can describe adsorption process of magnetic bio-char well. The MBC derived from sewage sludge has significant adsorption capacity， which is easy to separate from aqueous system. This disposition can recycle solid waste to pollution treatment.

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Research on Influencing Factors of Polystyrene Consumption by Zophobas atratus Larvae， and Gut Core Functional Microbiome

ZHAO Xin， LUO Li-ping， WANG Yu-meng， GUO Hong-qin

2021, 42 (7): 1019-1024. DOI: 10.12068/j.issn.1005-3026.2021.07.016

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The survival rate of Zophobas atratus in the styrofoam biodegradation investigation is affected by environmental factors. In order to reduce the interference on the experiments of plastic biodegradation， effects of environmental factors on the growth of Zophobas atratus and consumption of the styrofoam were investigated， and the potential core functional bacteria was speculated by using the MiSeq sequencing technology. The experimental results indicated that light condition， plastic density and contact area have significant impacts on the growth of Zophobas atratus and the consumption of polystyrene(PS) styrofoam. Dark condition is conducive to the growth and plastic consumption by Zophobas atratus. Styrofoam with low density and low contact area is favored by Zophobas atratus. However， plastic with high breakage degree is not conducive to Zophobas atratus， and taking styrofoam as sole diet can not meet the growth requirements of larvae. Significant changes in gut microbiome of Zophobas atratus was observed with PS styrofoam diet， and genera of unclassified Enterobacteriaceae， Dysgonomonas， Sphingobacterium and Enterococcus are closely related to the degradation of PS styrofoam.

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Experimental Study on Electric Heating of Tunnel Lining in Cold Region

WANG Lian-guang， XU Xiao， LI Xue

2021, 42 (7): 1025-1031. DOI: 10.12068/j.issn.1005-3026.2021.07.017

Abstract ( 468 )

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In winter， frost damage of tunnel such as lining damaged or even dripping and freezing often occurs in cold region. Therefore， the active heating system is necessary except for the insulation layer. The active heating system is mainly composed of the electric heating belt between the secondary lining and the insulation layer. In order to simulate the heating process of freezing-dripping-water tunnel lining， electric heating model tests on concrete specimen， including single specimen and triple test piece， was conducted from a negative temperature to a positive temperature. The results show that the surface temperature of the concrete specimen can be increased from -4℃ to over 0℃ within 60 minutes， if the electric heating belt with a length of 2 m， power of 30W， embedded depth of 10 mm and the polyurethane board with a thickness of 40mm are used as insulation layer. The research results can provide guidance for ice melting and antifreeze of tunnels in cold regions.

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Temporal-Spatial Response of Land Subsidence to Groundwater and Its Non-engineering Subsidence Control

JIA Chao， ZHANG Shao-peng， DING Peng-peng， WU Jing

2021, 42 (7): 1032-1040. DOI: 10.12068/j.issn.1005-3026.2021.07.018

Abstract ( 507 )

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Aiming at the problem of land subsidence in Weibei Plain， a three-dimensional numerical model of fluid-solid coupling for Weibei Plain land subsidence was established. The development law of Weibei Plain land subsidence in the future was discussed from a macro perspective， and the negative impact of groundwater exploitation on the ground subsidence was quantified by taking into account the mutual relationship between groundwater exploitation and land subsidence. The results show that the subsidence funnel center is mainly distributed in the east of Yingli Town and the north of Guangling Township. If the amount of groundwater exploitation in 2019 is maintained， the subsidence of Weibei Plain will continue to develop and increase in the next 10 years， and the maximum cumulative land subsidence will be as high as 565.42 mm in 2029， with an average annual growth rate of 38.97 mm/a， and the subsidence center will remain unchanged. With the decrease of groundwater exploitation， the development degree of land subsidence can be alleviated obviously， and will continue to decrease， causing the mitigation trend of land subsidence. When the reduction is controlled between 10% and 30%， the mitigation effect of land subsidence disaster could be better.

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Analysis and Simulation of Safety Production Management System Based on EPC Mode

QI Xi-jing， KANG Wei-xin， ZHAO Lei

2021, 42 (7): 1041-1048. DOI: 10.12068/j.issn.1005-3026.2021.07.019

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In view of the current situation that the design and procurement stages are not sufficiently considered in the safety production management in the EPC general contracting mode， a safety production management system of the EPC mode for construction organization was designed by using the system dynamics theory， by structuring the cause and effect diagram and the stock flow diagram， as well as considering the design and procurement environment safety production management problems. The simulation results show that the system built based on the system dynamics model can give full consideration to each internal elements for each subsystem(design， procurement， construction) and reflect the connections between the internal factors and the change of the safety production management risk dynamically.The system is able to provide references for safety production management decision of the EPC general contracting mode.

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Empirical Study on Influence of Directors’ Network Position on Executive Compensation

SUN Chen， ZHUANG Xin-tian

2021, 42 (7): 1049-1056. DOI: 10.12068/j.issn.1005-3026.2021.07.020

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The method of social network was used to analyze the influence of directors’ network position on executive compensation based on the directors’ network formed by the “director cross appointment”， and the mediating effect of management rights and the moderating effect of property rights.The results showed that after controlling the other factors， the higher the directors’ network centrality and structural hole index， the stronger the inhibition effect on executive compensation level. Compared with the non-state-owned enterprises， the negative correlation between directors’ network position and executive compensation is weaker in the state-owned enterprises. Management rights play an intermediary role in the inhibition of directors’ network position on executive compensation.

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Use Intention Model of Shared Autonomous Vehicles and Its Impact Factors

HUO Yue-ying， GUO Chen， ZHU Yuan， FENG Chen-xi

2021, 42 (7): 1057-1064. DOI: 10.12068/j.issn.1005-3026.2021.07.021

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In order to construct the use intention model of shared autonomous vehicles(SAV) and analyze its impact factors， use timing and use frequency were used to reflect the use intention for SAV. The attitude latent variables were converted into scores using confirmatory factor analyses and they were introduced into the traditional ordered Logit model. The method of modeling SAV use intention by using the ordered Logit models was proposed. Taking personal attributes， commuting characteristics and attitude latent variables as explanatory variables， the SAV use intention models were established. The results showed that the factors such as whether or not to use carpooling like Didi， paying parking fees at the work place and autonomous vehicles(AV) attitude have significant impacts on use timing and use frequency at different prices(1，2 and 3 yuan/km); the groups that use carpooling like Didi， pay parking fees at the work place and support AV tend to use SAV more frequently and earlier in future; the publics expect to use SAV at a price lower than the current price of the carpooling， i.e.1 or 2 yuan/km.

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