2020 volumne 41卷 Issue 04
WANG Fuming1,2,3,4,HE Hang1,2,3,FANG Hongyuan1,2,3,4,LI Bin1,2,3
Abstract: The concrete pipe with the bell-and-spigot joints is the most common urban drainage pipe structure, but the coupling of the fluid and the overlying load in the pipe may cause damage to the joint and lead to pipe leakage. Based on Abaqus and Fluent finite element software, this paper establishes a three-dimensional refined model of the drainage pipe with gasketed bell-and-spigot joints and the flow field model inside the pipe. With the interaction of pipe and soil, the contact between the bell-and-spigot joint and the rubber as well as the fluid in the pipe being considered, the structure and fluid model are solved jointly by using MpCCI (Mesh-based parallel Code Coupling Interface) platform. The influence of different flow rates, different traffic load amplitude and different load position on the dynamic response of the socket is mainly studied. The results show that under the multi-field load, the maximum principal stress and vertical deformation of the central pipe joint are the largest, and the stress distribution of the pipe bottom and the pipe top is the same, both are tension stresses, but the stress value at the bottom of the pipe is slightly larger The change of flow rate has a little effect on the mechanical response of the bell-and-spigot joint The magnitude of traffic load amplitude has a significant effect on the maximum principal stress and vertical deformation of the bell-and-spigot joint, and the influence is concentrated on the central pipe joint The movement of the load position has obvious influence on the vertical deformation of the bell-and-spigot joint and the mechanical response of the top and bottom of the pipe.
YAN Yadan,LI Yang,TONG Pei
Abstract: Access point was important part of urban road sections.The number of entrances and exits was a main influencing factor on urban road capacity.Firstly,the influence of entrances and exits on capacity of a road section was analyzed.Effects caused by the number of entrances and exits was represented by the physical modification coefficient of entrances and exits on the outermost lane.Speed reduction and lane changing effects caused by the entering and exiting of vehicles on entrances and exits were represented by the transverse reduction coefficient.Furthermore,the comprehensive modification factor was proposed.Considering influences of entrances and exits,a calculating model of road section capacity was constructed.Secondly,taking into account the distance between access points and intersections,access spacing constraints,using the maximum sum of modified capacities as the objective function,an optimization method for access location was proposed.Finally,a residential area in Zhengzhou city was taken as an example to testify the feasibility.Results showed that in order to maximize the sum of modified capacities of roads around the residential area,accesses should be preferentially set in the middle of low-grade urban road sections.With the number of access increasing,the access roads should be selected from low-grade roads to high-grade roads in sequence.When road grades were same,priority should be given to roads with fewer lanes.
YUE Jinchao,ZHANG Shixing,YUE Mingjing,LI Ruixia
Abstract: This study aimed explore the evolution process of the self-healing behavior of asphalt mastics in different damage degrees and healing temperatures.The virgin asphalt mastic and rock asphalt mastic were used as the research objects.The Dynamic Shear Rheometer was used to examine the application of 0.001% small strain to different fatigue samples.The self-healing behavior of two asphalt mastics under different damage degrees and healing temperatures were observed during the healing period.The results showed that in the middle temperature stage,the self-healing curves of the two asphalt mastics under different damage degrees showed an overall growth trend,and the specific performance was a “two-stage” type,that was,a growth and development type before self-healing and a stable curve after self-healing .In the middle temperature stage,the effect of increasing the healing temperature on the healing rate of asphalt mastics become weaker and weaker.There was a certain threshold for the damage degree of asphalt mastic.When the fatigue damage degree was lower than the threshold damage degree,the asphalt mastic could be restored to the initial state.When the healing temperature was 25 ℃,the threshold damage degrees of virgin asphalt mastic and rock asphalt mastic were 50% and 55% respectively.The incorporation of rock asphalt increased the molecular force,and significantly improved the cohesive healing strength and rate of asphalt mastic,but at the same time its molecular fluidity was reduced,thereby weakening the initial stage of adhesive healing properties.
SHAO Yunhong1,3,PANG Yafeng2,ZHENG Yuanxun3,KONG Weixing3
Abstract: The recycling of waste concrete was in line with Chinese basic national policy of green environmental protection and sustainable development.Therefore,It was one of the urgent problems to be solved to effectively improve the mechanics and road performance of recycled concrete based on the research of recycled concrete failure model,and expand its application in infrastructure construction.Combined with the latest domestic and foreign research status,this paper summarized the studis of the failure mechanism and failure mode of recycled concrete from the aspects of compressive strength,tensile splitting strength and elastic modulus.On this basis,the replacement rate of recycled aggregate,type of recycled aggregate,specimen forming method,admixture addition,and addition of steel slag,steel fiber,carbon fiber,fiber fabric and addition of mineral fillers such as fly ash or silica powder were analyzed to strength mechanical properties of recycled concrete.The results had an important guiding role in strengthening the research mechanism of waste concrete collapse and mechanical strengthening measures,and provided reference for further improving the recycling and widespread promotion of waste coagulation.
ZHANG Maoqing1,WANG Lei1,CUI Zhihua2,GUO Weian3
Abstract: Fast Non-dominated Sorting Algorithm II(NSGA-II)is an classics multi-objective optimization algorithm, in which tournament selection strategy is used to select parent individuals to do crossover operator. However, Tournament selection strategy has the drawback that the same individual may be selected many times, resulting in the low diversity of offspring population. To tackle this problem, this paper proposes two strategies. The first is to introduce Lévy distribution to parent individuals for increasing the probability of discovering potential better individuals around patent individuals while the second is to introduce crossover strategy with three patent individuals to decrease the probability of repeatedly selecting the same parent individuals. By comparison with other algorithms, the proposed method can efficiently improve the overall performance of NSGA-II.
SUN Guodong,JIANG Yajie,XU Liang,HU Ye,XI Zhiyuan
Abstract: During instrument digital image acquisition,there were many phenomena of uneven illumination and character double shadow,which led to the difficulty of binarization and low recognition rate.A new binarization method is proposed.Before image binarization,the image would be preprocessed because of the poor image quality.Due to uneven illumination,the color image correction method based on nonlinear function was used.In view of the imaging ghosting,the image gray scale distribution statistics were taken as the input,and the adaptive binarization global threshold is used as the label of prediction model to train BP neural network.The trained BP network was used to predict the global threshold and binarize the image,in order to achieve the separating the ghosting.At the same time,the improved LeNet-5 network was adopted to recognize the single character after segmentation.The experimental results showed that the proposed binarization method was better than the classical methods,and the improved LeNet-5 could satisfy the instrument character recognition after segmentation,with the recognition rate of 98.94%,and the single character recognition time of only 0.0014s.
OUYANG Haibin1,QUAN Yongbin1,GAO Liqun2,ZOU Dexuan3
Abstract: Path planning was an important basic problem in the research field of mobile robot.In order to solve the problem of slow searching speed or easily falling into local extremum when using a path planning algorithm alone,a hierarchical path planning method based on hybrid genetic particle swarm optimization (HGA-PSO) was proposed.The main contents of this method include the following parts.Firstly,the triangle method was used to model the space environment path.Secondly,combined with artificial potential field method,an improved genetic algorithm for initial path planning was designed.Thirdly,the particle swarm optimization algorithm was used to optimize the results of the initial path planning to achieve a more reliable optimal path.The simulation results show that the proposed method could integrate the advantages of each algorithm and find the optimal path quick and efficient.
WANG Bingchen,SI Huaiwei,TAN Guozhen
Abstract: In order to improve the learning efficiency of the autopilot car control algorithm based on reinforcement learning,this paper proposes an autopilot strategy learning algorithm DDPGwE (Deep Deterministic Policy Gridient with Expert,DDPGwE) combined with expert experience.DDPGwE used a DDPG-based reinforcement learning framework to conduct online training of the model;used real human driving data to pre-train the Actor network,and added an LSTM prediction mechanism to the Actor network to improve the prediction of the future status of autonomous vehicles.The experimental results in the simulation platform TORCS showed that Compared with the original DDPG algorithm,the algorithm proposed in this paper greatly reduced the training time and speedsed up the convergence speed,which improved the stability and generalization ability of the model.
GAO Yuelin1,WU Shaohua2
Abstract: Particle swarm optimization algorithm was easy fall into local optimum,the convergence speed was slow in the late path search,and the path was not smooth in the robot path planning.An improve simulated annealing adaptive particle swarm optimization algorithm was proposed.The algorithm combined the advantages of simulated annealing and particle swarm optimization.In the early stage of the algorithm route search was fast,and the algorithm had the ability of sudden jump in the path search process,which could effectively avoid falling into the local optimal path.Using cubic spline interpolation smooth the path,and the convergence precision of the late search path was high.The simulation results showed that the algorithm could quickly find the shortest smooth path in different obstacle models,and the path effect was better than the traditional method.
ZHU Xiaodong,WANG Ding
Abstract: In order to solve the problems of basic hybrid ant colony algorithm in solving large-scale VRPTW,an improved bi-objective hybrid ant colony algorithm was proposed.Firstly,the peripheral selection strategy was used to improve the selection efficiency,and a first node selection strategy was proposed to accelerate the convergence of the algorithm.Secondly,a penalty function related to the number of vehicles was added to the pheromone superposition formula to optimize the number of vehicles while optimizing the distance.Finally,a new local optimization algorithm was proposed to improve vehicle utilization and expand the neighborhood solution by inserting nodes in routes with fewer nodes into other routes.Experiments and comparisons on Solomon benchmark problems showed that the improved algorithm had the advantages of strong search ability,fast convergence speed and strong robustness.
FAN Qinqin1,2,LIU Dixizi1,WANG Xiaowei1,HAN Xin3,WANG Weili1
Abstract: To improve the convergence speed and reliability of Teaching-learning-based optimization (TLBO) algorithm, an opposition-based learning TLBO with a micro population (OBL-μTLBO) is proposed in the current study. In the proposed algorithm, a micro population is used to speed up the convergence and an opposition-based learning is utilized to improve the global exploration capability of TLBO. Simulation results indicate that OBL-μTLBO not only has better overall performance, but also has more quick convergence speed when compared with other competitors. Finally, OBL- μTLBO is used to solve two Nash equilibrium problems of non-cooperative game, and satisfactory results are achieved.
Cheng Xian1,2Jianpeng Zhu1,2Zhao Haiyang1,2Yuan Xiaodong1,2He Xiang3Xu Mingming3
Abstract: The standardization and integration development of primary and secondary equipment of power distribution switches puts forward higher requirements for the reliable operation of secondary equipment under long-term complex electromagnetic environment. This paper builds a lightning impulse voltage test platform, and collect the secondary side of the voltage transformer, the feeder terminal unit (FTU) input and output voltage signals, and analyze the above-mentioned waveform to obtain the electromagnetic interference spectrum distribution of the secondary device port caused by the impulse voltage, which is effectively suppressed by the filtering method. The test results show that the lightning impulse will produce transient high frequency electromagnetic interference to the voltage transformer and feeder terminal unit, the peak value of the interference voltage caused by radiation coupling is about 3kV, the frequency band is 3.6~ 16.4MHz the peak value of the interference voltage caused by conduction coupling is about 4.5kV, the frequency bands are mainly distributed between 1.2~6.7MHz and 12.5~20MHz, after adding the filter, the positive and negative interference voltage peaks are reduced by more than 23%, and no fault occurs. The test results provide reference for the EMC research of secondary equipment for primary and secondary fusion distribution switches
HE Zhanshu1,CHEN Lei1,WANG Wujun2,MAO Jianwei2
Abstract: Due to the high temperature induced by the generation,the PCB locate in the central electrical junction box (or electrical box) was easily inflammable.It was necessary to investigate the temperature distribution of the PCB.The ABAQUS was used to simulate the temperature of PCB,relay,quick fuse,slow fuse,etc.The corresponding temperature rise experiments were conducted to compare with the simulation results and determine the parameters of each component,which were convective heat transfer coefficient,electrical contact resistance,thermal contact resistance,etc.The simulations and experiments at the assembled level of electrical box were conducted to analyze the influence of each component on the PCB temperature field.The simulation results showed that the temperature rise of PCB decreased with an increase in the width of copper cladding region and increased with an increase of current.Due to the complicated internal structure of the electrical box,the temperature distribution of the PCB was not uniform.The higher temperature of PCB was generated in the joint of large power components and the total entrance of electric current,and the maximum rise of temperature was 38.7 ℃.Through the actual measurement of the temperature of PCB and the electrical box,the measured results were qualitatively and quantitatively consistent with the simulated results.
CHEN Qiang1,WANG Hua1,WANG Kewen2,LIU Yanhong2
Abstract: The large capacity synchronous condenser equipped with power system voltage regulator PSVR could provide effective transient voltage support for UHV DC transmission.Taking two new large capacity synchronous condensers in Henan power grid as an example,PSVR parameters were adjusted from the point of view of condenser dynamic characteristics and small disturbance stability.The influence of condenser reactive power output and PSVR parameters on voltage characteristics and power angle characteristics was analyzed,and a approach for adjusting PSVR parameters was proposed.Time constants in PSVR phase shifting segments were adjusted to minimize the root mean square of voltage amplitude angle characteristic curve.Voltage oscillation modes relevant to condensers were determined by the eigenvalue calculation of small disturbance stability on whole system.According to voltage oscillation mode sunder different system operation modes and different condenser reactive power outputs,and combining with power angle oscillation mode check calculation,the adjustment ranges of PSVR gain coefficients were determined.The presented approach could reduce the influence of PSVR on power angle,facilitate the flexible adjustment of PSVR gain,and provide reference for parameter tuning.
XU Gang1,2,LIANG Shuai2,LIU Wufa1,ZHENG Peng1
Abstract: This study aimed to explore a microfluidic chip that could generate a single droplet with a short cycle,consume a small amount of continuous phase reagents,and have low processing costs.The FLUENT simulation and VOF method were employed to simulate 16 microfluidic chips with different structure sizes in orthogonal experiments.Finally,the TOPSIS was used to comprehensively evaluate the numerical simulation results,and the order of superiority and inferiority of 16 structures was obtained.The evaluation results showed that a microfluidic chip with the optimal size structure could be obtained under the conditons of the continuous phase channel size was 40 μm,the discrete phase channel size was 30 μm,the cross exit channel size was 25 μm and the channel depth was 20 μm.The microfluidic chip could be produced the performance with smaller droplets,highest frequency and consumes less continuous phase reagent per unit time.
ZOU Weihua,LIU Penglei,LIU Qiujie,MA Peili
Abstract: In this paper,magnetic biochar prepared from salix mongolica by a one-step method was used for sulfadiazine sodium removal from aqueous solution.The effects of initial concentration,adsorption time,pH and salt ion concentration on the adsorption were investigated.The results showed the maximum adsorption capacity of MBC for SAS was 248.4 mg/g at 298 K.The adsorption kinetics was best described by Elovich model and the whole adsorption process was controlled by both film diffusion and intraparticle diffusion.The equilibrium data was best fitted by the Freundlich and Koble-Corrigan models.The interaction of the π—π dispersion,the hydrophobic interaction and hydrogen bonding played a role in the adsorption of sulfadiazine sodium onto magnetic biochar.
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