Journal of Northeastern University(Natural Science)

Research on Gust Response Factor and Wind-Resistance Performance of Transmission Lines Under Typhoon

FU Xing， DU Wen-long， ZHENG Shuai， LI Hong-nan

2022, 43 (7): 913-920. DOI: 10.12068/j.issn.1005-3026.2022.07.001

Abstract ( 685 )

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To study the gust response factors(GRF) of transmission lines under normal wind and typhoon， a finite element model is established based on a steel tower of the Guogu line in Guangdong Province. The typhoon wind field is simulated via a harmonic superposition method， and the dynamic analysis is carried out. First， the GRF methods in five design codes at home and abroad are compared. It turns out that none of them considers the strong fluctuating characteristics of typhoon. Then， the GRF is obtained based on the inertia force method， and the tower-line coupling effect on GRF is studied. Finally， the wind-resistance performance of the transmission line under the two wind fields is quantitatively evaluated by the method of birth to death element. The results showed that the high turbulence characteristics of typhoons lead GRF to be greater than that of normal wind and the conductor can increase the natural frequency of the tower in the cross-wind direction， changing the mode from the bending type of a single tower to the bending-shear type of the tower-line system， whose GRF at the cross arm is greater than that of a single tower. The critical collapse wind load will decrease by 11% if the turbulence intensity increases from 0.14 to 0.20. Thus， the design of transmission towers in typhoon-prone areas should properly increase the turbulence intensity and take into account the tower-line coupling effect when necessary.

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Filtering Feature Selection Algorithm Based on Entropy Weight Method

LI Zhan-shan， YANG Yun-kai，ZHANG Jia-chen

2022, 43 (7): 921-929. DOI: 10.12068/j.issn.1005-3026.2022.07.002

Abstract ( 492 )

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Mutual information-based filtering feature selection algorithms are often limited to the metric of mutual information. In order to circumvent the limitations of adopting only mutual information， a distance metric-based algorithm RReliefF is introduced on the basis of mutual information to obtain better filtering criteria. RReliefF is used for the classification tasks to measure the relevance between features and labels. In addition， maximal information coefficient(MIC) is used to measure the redundancy between features and the relevance between features and labels. Finally， entropy weight method is applied to objectively weigh the MIC and RReliefF. On this basis， a filtering feature selection algorithm based on entropy weight method(FFSBEWM) is proposed. Comparing experiments carried out on 13 data sets show that the average classification accuracy and highest classification accuracy of the feature subsets selected by the proposed algorithm are higher than those of the comparison algorithms.

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Motion Planning Algorithm of Autonomous Driving Considering Interactive Trajectory Prediction

LIU Qi-ran， LIAN Jing， CHEN Shi， FAN Rong

2022, 43 (7): 930-936. DOI: 10.12068/j.issn.1005-3026.2022.07.003

Abstract ( 703 )

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Aiming at the problem of predicting the surrounding traffic situation in autonomous vehicle motion planning， a motion planning algorithm considering the interactive trajectory prediction between surrounding vehicles is proposed. Firstly， for structured road information， an improved social force model is constructed to predict the trajectory of vehicles around autonomous vehicles. Secondly， the predicted trajectory and the trajectory set that is generated in the Frenet coordinate system are projected on the space-time occupancy map， and the shortest distance between the projection points is calculated for collision checking. To obtain candidate trajectories， the trajectories are selected by collision， acceleration and curvature checking. Then， the cost function is constructed to evaluate the candidate trajectories and obtain the optimal motion trajectory. Finally， the simulation results in different driving scenarios show that the motion planning algorithm can make decisions about driving behavior in advance. The planned speed curve is more stable and the safety， comfort and driving efficiency of the motion trajectory are better.

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Multi-dimensional Vector Ghost Imaging Video Based on Bidirectional Predictive Interpolation

LIU Yue，SANG Ai-jun，SONG Li-jun，WANG Shi-gang

2022, 43 (7): 937-943. DOI: 10.12068/j.issn.1005-3026.2022.07.004

Abstract ( 398 )

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To further improve the quality of moving object ghost image videos， a real-time imaging algorithm based on bidirectional predictive interpolation for multi-dimensional vector ghost image video is proposed according to the correlation characteristics between each frame in the video. That is to say， the multi-dimensional vector Walsh transform with energy concentration is used to divide a certain number of multi-dimensional Walsh basis patterns into fewer groups， doubling the effective basis patterns of each group， and then acting on the target object respectively. After reconstruction， the number of interframe images with better imaging quality is less， and then the intermediate frames are obtained by bidirectional predictive interpolation. Using this algorithm， the ghost image video of moving object can be realized in real time by acting on the object with 64×64 pixels. With the same sampling quantity and sampling time， high-quality reconstruction can be achieved and better quality ghost imaging video can be obtained.

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U-Net CSF Cells Segmentation Based on Attention Mechanism

DAI Yin， LIU Wei-bin， DONG Xin-yang， SONG Yu-meng

2022, 43 (7): 944-950. DOI: 10.12068/j.issn.1005-3026.2022.07.005

Abstract ( 596 )

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In order to solve the problem that part of the cell membrane in the pathological images of CSF (cerebrospinal fluid) is blurred and this is difficult to be distinguished from the image background. The U-Net based on attention mechanism is proposed to segment pathological images of CSF automatically. Attention mechanism is added to deep learning network to locate cells， suppress irrelevant information， improve semantic feature expression， and further improve the accuracy of cell segmentation. The datasets are preprocessed by mirroring and rotation. VGG16 pre-training model is used for transfer learning. Cross entropy is combined with Dice loss as Loss function which is validated in CSF clinical images and open dataset 2018 Data Science Bowl and compared with Otsu， PSPnet， Segnet， DeeplabV3+， U-Net. The results show that the proposed method is superior to other segmentation methods in all indexes.

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Effect of Zr Addition on Microstructure and Mechanical Properties of Al-10Zn-2.5Mg-1.6Cu Alloy Sheet

TIAN Ni ， ZHANG Yao-zhong， ZHOU Yi-ran， QIN Guang-hua

2022, 43 (7): 951-958. DOI: 10.12068/j.issn.1005-3026.2022.07.006

Abstract ( 498 )

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The mechanical properties and microstructure， such as the phase configuration and the grain characteristics of the T6 temper Al-10Zn-2.5Mg-1.6Cu alloy sheet were investigated with the Zr addition of 0， 0.046%， 0.098%， 0.151% and 0.185%， respectively. The results show that there is no obvious change of the micro-sized T and Al₇Cu₂Fe phases in the samples， the Zr-containing constituent phases cannot be formed and the number of Al₃Zr dispersoid nanoparticles increases with the Zr addition. Adding 0.046% Zr can refine the equiaxed Cube-oriented grains of the sample. When the Zr content exceeds 0.098%， the recrystallization nucleation can be inhibited， most of the grain shape are fibrous and the grain texture is mainly Brass， S， R and Copper orientations and its fraction increases with the Zr content. When the Zr content increases， the yield and tensile strength of the samples increase gradually and the final elongation firstly increases and then slightly decreases. The T6 temper Al-10Zn-2.5Mg-1.6Cu alloy sheet with the 0.151% Zr has the optimal performance， associated with the tensile and yield strength and final elongation of 706， 645MPa and 10.3%， respectively.

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New Technology for Extracting Silicon and Boron from Boron Mud

NING Zhi-qiang， SONG Yu-tao， ZHAO Run-yu， HAN Shuai-nan

2022, 43 (7): 959-965. DOI: 10.12068/j.issn.1005-3026.2022.07.007

Abstract ( 720 )

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Taking boron mud as raw material， the boron mud mixed with sodium carbonate was roasted at 900℃ for 2h， and the SiO₂ and B₂O₃ in the roasted boron mud were recovered by alkaline leaching method. The reaction in the calcination stage was analyzed by TG-DSC curve. The effects of n(NaOH)/n(SiO₂)， reaction temperature， reaction time and liquid-solid mass ratio on the extraction ratios of SiO₂ and B₂O₃ in boron mud were studied by single factor experiment. By orthogonal experiment， the order of factors affecting the extraction ratio of SiO₂ was determined as n(NaOH)/n(SiO₂) >liquid-solid mass ratio>reaction time>reaction temperature， and the order of factors affecting the extraction ratio of B₂O₃ was reaction time>reaction temperature>n(NaOH)/n(SiO₂)>liquid-solid mass ratio. The optimum recovery conditions were n(NaOH)/n(SiO₂) of 25， reaction temperature of 50℃， reaction time of 40min， and liquid-solid mass ratio of 8. Under these conditions， the extraction ratios of SiO₂ and B₂O₃ reached 83.11% and 75.28%，respectively.

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Numerical Simulation Study on Gas Gathering Structure of Aluminum Reduction Cell

LI Xue-jiao， YANG Hong-ying， ZHAO He-fei， HU Hong-sheng

2022, 43 (7): 966-972. DOI: 10.12068/j.issn.1005-3026.2022.07.008

Abstract ( 520 )

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In order to reduce the gas fugitive emission and improve the gas collection efficiency of aluminum electrolysis cell， the flow distribution in the original gas gathering structure of the electrolysis cell was numerically simulated. Based on this， the improvement scheme of the lower gas gathering structure was studied and a new upper gas gathering structure was developed. The results show that the pressure drop of the original lower gas gathering structure is 363 Pa， the gas gathering uniformity is poor， the flue dust accumulation is serious， and the gas gathering efficiency is low. The lower gas gathering structure is simple to be reformed and the investment is low. After the reformation， the gas collection efficiency can be significantly improved， but the pressure loss and dust accumulation have no notable improvement. The new upper gas gathering structure reformation is more complicated and the investment is relatively high. However， after the reformation， not only the gas gathering efficiency is significantly improved， the pressure drop is also reduced dramatically to 187 Pa， and there is no obvious dust accumulation in the flue.

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Research on Hydraulic Screw down-Vertical Vibration Characteristics of Strip Rolling Mill

HOU Dong-xiao， FANG Cheng， CHEN Shan-ping， YAN Shuang

2022, 43 (7): 972-980. DOI: 10.12068/j.issn.1005-3026.2022.07.009

Abstract ( 351 )

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Considering the effect of the vertical vibration of the strip mill on the non-linear flow rate of the four-way servo solenoid valve in the hydraulic system， the asymmetric segmented spring force of the hydraulic screw down cylinder under the non-linear flow rate change is derived. The dynamic equations of hydraulic screw down-vertical coupling vibration of the strip mill are established. The averaging method is used to solve the amplitude-frequency response equation of the coupled vibration system of the rolling mill， and the bifurcation characteristics of the rolling mill in the dynamic rolling process are solved using the singularity theory. Four different transition sets and their corresponding bifurcation diagrams are obtained. The effect of the unfolding parameters on the bifurcation characteristics of the rolling mill are analyzed. Finally， based on the actual rolling mill parameters， it is found through simulation that the amplitude-frequency curve of the system has turning characteristics at the section. Adjusting the response time of the servo valve can reduce the unstable frequency area of the coupling system. By adjusting the external excitation amplitude and damping ratio and other parameters， the resonance of the coupled system can be effectively improved. This can provide a theoretical reference for further suppressing the vibration of the roll system of the rolling mill.

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Intelligent Decision-Making of Machining Operation Method for STEP-NC-Compliant Freeform Surface Features

ZHANG Yu， HE Kai-wen， LI Qing-shu， GONG Ya-dong

2022, 43 (7): 981-987. DOI: 10.12068/j.issn.1005-3026.2022.07.010

Abstract ( 378 )

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In order to improve the integration and intelligence of process planning for complex parts， an intelligent decision-making of machining operation method for STEP-NC-compliant freeform surface features based on hybrid algorithm is proposed. Firstly， a BP neural network model for determining the machining operation method of freeform surface features compliant with STEP-NC is constructed. Then， an improved artificial fish swarm algorithm is presented based on the strategy of adaptive vision and adaptive step as well as chaos algorithm. Furthermore， the improved artificial fish swarm algorithm and the BP neural network algorithm are hybridized to realize efficient and intelligent decision-making of machining operation method for STEP-NC-compliant freeform surface features by using the normalized machining information of parts. Finally， a case study is made to verify the effectiveness and feasibility of the proposed method.

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Interference-Free Tool Path Generation for Milling of Spur Gears

WANG Zhen-yu， ZHANG Rong-chuang， YU Tian-biao

2022, 43 (7): 988-995. DOI: 10.12068/j.issn.1005-3026.2022.07.011

Abstract ( 391 )

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Regarding the finish machining of multi-axis milling， an interference-free tool path generating method for milling of spur gears was proposed. The kinematics model of gear enveloping was established to precisely describe the kinematic relation between the milling tool and workpiece. Based on the accurate model of gear tooth profiles， the scallop point is determined by intersection calculation between the circle of the cutter radius and scallop curve. According to the way that the tool radius is equal to the distance between the scallop point and center point of the cutter arc， the next cutter location(CL) point is identified on the tool path curve. All CL points are determined by the iterative method. On the basis of the CL points on the scallop curve， CL points of the equal radial feeding strategy and equal arc-length feeding strategy were calculated under the constraint of scallop height. The occurrence of global interference was judged by calculating the minimum distance between the milling tool and workpiece. Then the cutting edge angles corresponding to different CL points were given. The occurrence of local over-cut interference was avoided by adjusting the cutter radius. The simulation results showed the proposed method was feasible and effective.

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Optimal Design of a Micro-displacement Compliant Amplification Mechanism

GUO Fan-yi， SUN Zhi-li， ZHANG Sheng-nan， CAO Ru-nan

2022, 43 (7): 996-1002. DOI: 10.12068/j.issn.1005-3026.2022.07.012

Abstract ( 481 )

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A pseudo static parametric model of the micro-displacement compliant amplification mechanism is proposed based on the dynamic stiffness matrix of flexible beams and the matrix displacement method. This model can be used for rapid motion prediction and parametric motion analysis for the new mechanism. Then the analytical model of displacement amplification ratio is obtained. A new mechanism is obtained by optimizing the dimensions and shape of the structure based on simulated annealing algorithm. Compared with the original structure， its amplification ratio increases by 9% and the natural frequency is 409Hz. The optimization results are compared with FEA simulations with less than 2% difference， which verifies the accuracy of the model. The amplification ratio variation of the new mechanism with load and input displacement and the influence of manufacturing errors at key joints on output displacement are analyzed. The results show that the X-direction manufacturing errors of the top endpoint and output stage have the greatest influence on the output displacement.

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Structural Design of a 7-DOF Manipulator and Its Geometric Position Error Analysis

GAO Yue， FANG Li-jin， XU Ji-qian， GONG Yun-peng

2022, 43 (7): 1003-1010. DOI: 10.12068/j.issn.1005-3026.2022.07.013

Abstract ( 539 )

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A 7-DOF cooperative manipulator was designed and manufactured based on the joint driven by dual motor servo. The geometric error model of the end-effector of the manipulator was established， and the parameter errors were analyzed and synthesized based on the principle of independent action of the original parameter errors. Based on the law of large numbers of mathematical statistics and Monte Carlo method， the sensitivity of influencing factors of the geometric position errors was analyzed by numerical simulation， and the parameter errors which have relatively greater influence on the geometric position errors of the manipulator were found. Through the calculation and analysis of the geometric position errors of the end-effector of the manipulator， it was found that the errors obey the Rayleigh distribution in the workspace of the manipulator. The experimental measurement showed that the repeated positioning error of the manipulator is less than 0.0591mm， and the absolute positioning error obeys Rayleigh distribution significantly. It proved that the double motor servo-driven joint has the characteristics of small return errors and high transmission accuracy， and the error analysis is correct， which provides a theoretical basis for the precision design and application of the manipulator.

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Failure Characteristics and Crack Evolution Laws of Hard Rock Under Nonlinear Unloading Rates

SUN Hao ， ZHU Dong-feng ， JIN Ai-bing ， CHEN Shuai-jun

2022, 43 (7): 1010-1018. DOI: 10.12068/j.issn.1005-3026.2022.07.014

Abstract ( 379 )

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In order to study the failure characteristics of hard rock with nonlinear velocity variety in unloading phase， three unloading rate variety modes of cosine， linear and exponent were used to study the damage and failure of the hard rock by using the indoor triaxial compression tests and particle flow numerical simulation. The results show that the hard rock with exponential unloading rate first fails to stabilize， while the hard rock with cosine unloading rate is less likely to fail. The faster unloading rate in the early stage has a greater impact on the damage accumulation in the whole unloading process. The bearing strength of hard rock in unloading process is affected by both initial confining pressures and unloading modes， and the higher the confining pressure is， the more significant the influence of unloading mode is. According to the Mogi-Coulomb strength criterion， exponential unloading affects hard rock strength through internal friction angle， while the strength of hard rock under linear and cosine unloading mode is mainly affected by cohesion. Exponential unloading is easy to cause partial breakage at the end due to rapid unloading at the early stage. With the increase of confining pressure， linear unloading leads to multiple "V-shaped" shear failures from the steep dip shear fracture zone. Cosine unloading presents a plastic failure characteristic trend with the increase of confining pressure.

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Water-Rock Mechanism of Weakly Consolidated Sandstone: a Case Study of Qingyang North Grottoes

ZHANG Jing-ke， LIU Dun， MA Yu-jun， ZHANG Han

2022, 43 (7): 1019-1033. DOI: 10.12068/j.issn.1005-3026.2022.07.015

Abstract ( 875 )

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Qingyang north grottoes sandstone was selected as the research object， and two sets of single-factor weathering simulation experiments of freezing-thawing cycles and wetting-drying cycles for a total of 120d with 30 cycles were set up in laboratory. Combined with the deterioration characteristics of rock samples in different dimensions such as macro-scale， local scale， and micro-scale， as well as the migration patterns of surface mineral components and elements， the whole process of the water-rock interaction mechanism was tracked and evaluated. The experimental results showed that at the beginning of simulation experiments， the chemical interaction between water and rock was strong， and the chemical alteration coefficient of both groups increased sharply. With the cycles going on， the physical interaction between water and rock is getting stronger. The tensile and compressive stress are induced by the expansion of water volume between the particles during freezing-thawing cycles. The fracture was first induced at the part with highest moisture content. The granular structure is mechanically eroded by the flow of water during wetting-drying cycles， and the process is mutually controlled by moisture migration and pore distribution. For weakly consolidated sandstone， the key to sandstone deterioration is the change of particle coupling relation caused by frequent water-rock interaction.

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Global Optimization Search Method for Minimum Safety Factor of Slope Based on Chaotic Grey Wolf Optimization Algorithm

WANG Shu-hong， WEI Wei， HAN Wen-shuai， CHEN Hao

2022, 43 (7): 1033-1042. DOI: 10.12068/j.issn.1005-3026.2022.07.016

Abstract ( 478 )

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For the problems of uneven initial population and premature convergence in the basic grey wolf algorithm， grey wolf optimization(GWO) algorithm is improved from three aspects based on chaos theory， and a chaotic grey wolf optimization(CGWO) is proposed for determining the minimum safety factor of the slope. Firstly， an improved Tent chaotic mapping is used to improve the initial population diversity; Secondly， a chaotic perturbation strategy is used to avoid the algorithm from falling into a local optimal; Finally， a parametric chaotic non-linear adjustment mechanism is introduced to balance the global exploitation and local exploration arithmetic of the algorithm. Simulation results of 13 benchmark test functions show that the improved algorithm has a stronger integrated optimization search performance compared with the basic GWO， WOA， PSO and SCA. Selecting the ACADS side slope assessment questions for computation and analysis， the CGWO algorithm shows a high computational accuracy and convergence speed， and can effectively search for the minimum safety factor of complex stratified slopes. Compared with the finite element strength reduction method， the method has the advantages of easy operation and easy setting of the search area.

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Static Behavior and Blast Resistance Analysis for New Joint Assembled Rectangular Tunnel

HUANG Zhen ZHANG Chen-long， BAI Hai-wen， MA Shao-kun

2022, 43 (7): 1043-1055. DOI: 10.12068/j.issn.1005-3026.2022.07.017

Abstract ( 418 )

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A mortise and tenon joint applied to prefabricated rectangular tunnel is designed， and the static behavior and explosion resistance of prefabricated tunnel with this mortise and tenon joint are studied. A three-dimensional refined numerical model reflecting the nonlinear mechanical characteristics of the joint is established， and the TNT explosion simulation is realized by fluid-solid coupling analysis. The compressive bending capacity， explosion resistance and concrete damage characteristics of mortise joint and cast-in-situ joint under different confining pressures are compared and evaluated. The results show that the bending capacity of the new joint is slightly higher than that of the cast-in-situ joint rectangular tunnel. Under the same equivalent TNT explosive， the anti-explosion capacity of the new joint assembled rectangular tunnel is better than that of the cast-in-situ joint rectangular tunnel as a whole. The damage and failure of the new joint assembled rectangular tunnel mainly occurs in the steel column and roof wall joint area. The research results provide theoretical support for the structural design of prefabricated rectangular tunnel and disaster prevention and mitigation.

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Effect of Dust Loading Rate on Pressure Drop Characteristics of Non-high Efficiency Filter Media

LIN Xiu-li， ZHAO Yi-xuan， LIU Jing-xian

2022, 43 (7): 1056-1064. DOI: 10.12068/j.issn.1005-3026.2022.07.018

Abstract ( 396 )

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In order to study the effect of dust loading rate on the pressure drop of non-high efficiency filter media， four different grades of non-high efficiency glass fiber filter media were selected to carry out experimental tests on the change characteristics of filter media pressure drop under different face velocities and dust loading mass concentrations， and the empirical formula of pressure drop change in dust loading process of filter media was summarized. The results show that under the same face velocity and dust loading mass concentration， the lower the grade of filter media， the faster the growth rate of normalized pressure drop， and the greater the amount of dust required to enter the surface filtration period of the filter media. When the face velocity is the same， the higher the dust loading mass concentration of filter media， the slower the pressure drop increases with the dust load per unit area. And the higher the grade of filter media， the smaller the influence of dust loading mass concentration on its pressure drop. The effect of face velocity on the growth of the normalized pressure drop can be ignored under same dust loading rate.

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