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A machine learning methods for identifying the properties of Chinese medicinal materials from infrared spectrum data TIAN Chun-ting, ZHAO Ning, QIN Jian-wei, MENG Xiao-feng Journal of Lanzhou University of Technology    2023, 49 (3): 55-59.   Abstract （307）      PDF（pc） （2953KB）（710）       Knowledge map    Save There are great differences in the characteristics of near-infrared and mid-infrared spectra of different kinds of traditional Chinese medicine. Due to the different chemical components such as inorganic elements and organic substances, even if the origin of the same traditional Chinese medicine is different, the labeling effect under near-infrared and mid-infrared spectral irradiation will have different spectral characteristics which can be used to classify Chinese herbal medicine and identify the origin of Chinese herbal medicine. With the help of MATLAB software tool and K-means clustering algorithm in SPSS classification tool, unsupervised machine learning is carried out on traditional Chinese medicine to classify traditional Chinese medicine; Using SPSS neural network multilayer perceptron and the random forest algorithm provided by Python language, 70% of the data set is used as the training set and 30% as the verification set to train the supervised machine learning model which is finally used to identify and predict the origin of traditional Chinese medicine. Reference | Related Articles | Metrics

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Influence of high rate charge and discharge cycle on the electronic performance and thermal safety of lithium ion battery LI Dong-qi, ZHANG Qing-song, ZHENG Shao-shuai Journal of Lanzhou University of Technology    2023, 49 (3): 30-35.   Abstract （459）      PDF（pc） （2624KB）（654）       Knowledge map    Save Lithium-ion batteries are widely used in electric vehicles and various energy storage devices. In this paper, cyclic aging and thermal runaway experiments under different charge-discharge rates were carried out, and the effects of large-rate charging and discharging on the performance and thermal safety of single lithium-ion batteries were studied. The results showed that the actual capacity of single lithium-ion battery is attenuated under the large-rate charge-discharge cycle, and the degree of attenuation is positively relevant to the charge-discharge rate. With the charge-discharge rate increasing, the constant current ratio is stepwise attenuation, but the coulombic efficiency still maintains in the range of 99%-100%, indicating that the reversible performance of lithium-ion batteries is normal. With the increase of the magnification, the thermal runaway trigger time, explosion pressure and jet flame temperature first increase and then decrease. The average surface temperature of the battery during explosion is 655.8 ℃, which is close to the melting point of aluminum. The explosion injection powder products are mainly metal aluminum, graphite and lithium cobalt oxide. Reference | Related Articles | Metrics

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Effect of impeller exit width on performance and pressure fluctuation of centrifugal pump ZHAO Wei-guo, ZHAI Li-jing, XIAN Li-xia, MA Liang-liang Journal of Lanzhou University of Technology    2020, 46 (2): 62-68.   Abstract （814）      PDF（pc） （6499KB）（853）       Knowledge map    Save Taking a single-stage end-suction centrifugal pump as study object and assuring the inlet and outlet setting angle and diameter and as well as other parameters unchanged, five sets of pump models with different outlet width of impeller were designed respectively, their numerical simulation was carried out one after another and the influence of impeller outlet width on the performance and pressure fluctuation was analyzed. It was shown by the study result that with the increase of impeller outlet width, the lift and shaft power would increase to different extent, the efficiency curve would be hump shaped, indicating that there would be an optimum impeller outlet width to make the flow loss minimum; increasing the width of the impeller outlet, flow separation phenomenon in flow channel would be enhanced, blocking phenomenon there would decrease hydraulic loss would decrease thereby, indicating that an appropriate width of impeller outlet would be effective for reducing the energy loss of centrifugal pump. With progressive decrease of impeller outlet width, the shaft frequency peak would change obviously, assuming progressive increase trend, indicating that an excessive narrow impeller outlet width would easily lead to flow blocking in flow passage and hinder the development of the flow mode, At the same time, the impeller outlet width would also have a greater effect on pressure pulsation in centrifugal pump. Reference | Related Articles | Metrics

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Evaluation and analysis of electronic structure and optical properties of Cu-Cd co-doped ZnO by means of primary principle LI Wei-Xue, XUE Xiao-feng, DAI Jian-feng, WANG Qing, SUO Zhong-qiang Journal of Lanzhou University of Technology    2020, 46 (2): 166-172.   Abstract （376）      PDF（pc） （1887KB）（536）       Knowledge map    Save Based on the primary principle of density functional theory (DFT) system, five super-cell models of the pure ZnO, Cd doped ZnO, Cu doped ZnO, Cu-Cd co-doped ZnO, and Cu-2Cd co-doped ZnO, were optimized respectively for their geometric structure. The cell structure, energy band structure, state density, and their optical properties such as the imaginary component of dielectric function, absorption rate and reflectivity of each system were calculated and analyzed. The investigation result showed that the single doping of Cu or Cd could increase the carrier concentration of the ZnO and make the conductivity of ZnO improved. Never the less, in the case of Cu-Cd co-doping, the state of ZnO system would be more stable due to lower E. In connection with optical properties, the Cd-doping would make red shift of the edge of the ultraviolet region and the absorption would be slightly enhanced. When the ZnO was doped by Cu and Cu-Cd co-doped, the absorption coefficient of the system at the visible light and ultraviolet band would increase remarkably, making the photocatalytic activity of ZnO enhanced. When the characteristics single doping of ZnO with Cu and Cd was taken into consideration, the Cu-Cd co-doping of ZnO would make the semiconductor produce different transmittance if the doping concentration of Cd was controlled. So that the transparent devices with different efficiency could be propered by managing the doping of ZnO with different ratio of Cu-Cd. Reference | Related Articles | Metrics

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Analysis of thrust and velocity variation of permanent magnet synchronous linear motor under variable load SHEN Hao, ZHANG Wang, TAN Wei-rong, DANG Sheng-hui Journal of Lanzhou University of Technology    2021, 47 (2): 54-59.   Abstract （681）      PDF（pc） （1152KB）（1210）       Knowledge map    Save Taking the permanent magnetic synchronous linear motor as the research object, its force was analyzed; mathematical model was established, and the simulation model of the linear motor by using Matlab/Simulink in order to study the thrust and speed change of the linear motor when different loads are applied. The results show that with the increase of the workpiece’s mass, the state response time and maximum deviation of the linear motor increased; the response time curve of the speed is flat; the response time curve of thrust changed obviously; the overshoot curve of thrust increase flatly; the overshoot curve of velocity increased stably, the overshoot curve of speed is obvious.When the quality of the workpiece is 240 kg, the over-adjusting amount of motor speed exceeds 30%, which seriously affects the operation of the motor. In order to reduce the effect of load change on linear motor stability, the maximum load quality and maximum motor thrust are calculated. Reference | Related Articles | Metrics

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Cleaning and modeling of abnormal data of wind farm power curve CAO Li-xin, LIU Wei-min, GUO Hu-quan Journal of Lanzhou University of Technology    2022, 48 (4): 64-70.   Abstract （469）      PDF（pc） （3178KB）（764）       Knowledge map    Save The wind speed and power data of wind farms usually contain a large number of abnormal data, which is difficult to reflect the real working conditions of wind turbines, affect the accuracy of wind power prediction, and then cause certain economic losses. To solve this problem, the characteristics of abnormal data are analyzed, a slip-quartile abnormal data elimination method is proposed, and the wind speed power curve of the eliminated data is modeled by using high-order polynomial and Logistic function. Finally, the applicability and effectiveness of this method are verified by variance, root means square error and determination coefficient. The analysis in the example shows that the method is simple, efficient and versatile, and can significantly improve the accuracy of wind turbine power characteristic analysis. Reference | Related Articles | Metrics

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Research on noise addition and precision analysis in differential privacy WANG Xiao-shi, KANG Hai-yan Journal of Lanzhou University of Technology    2023, 49 (3): 94-103.   Abstract （269）      PDF（pc） （2751KB）（595）       Knowledge map    Save Differential privacy, as a definition of privacy protection with a strong mathematical background and rigorous mathematical derivation, has received great attention and has been widely studied. However, up to now, there is a lack of strict and clear proof and derivation processes for the definition of differential privacy and the basic mechanism used in China, which makes it difficult for scholars to get started. Therefore, in this paper, the Laplace and exponential mechanism in differential privacy are analyzed in detail by means of analysis, proof, and application examples, and a complete mathematical derivation process and application examples are given to address this gap. It is pointed out that there is a problem of excessive scaling in the accuracy formula of the Laplace and exponential mechanism. After proving the accuracy formula of Laplace and the exponential mechanism, the reason why this paper considers excessive scaling is given. It is not difficult to conclude from experiments that the Laplace mechanism precision formula and the exponential mechanism precision formula are formulas with an excessive range of accuracy. Reference | Related Articles | Metrics

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Bipartite consensus of multi-agent systems triggered by distributed events WANG Jun, WEI Ya-ping Journal of Lanzhou University of Technology    2024, 50 (3): 77-83.   Abstract （48）      PDF（pc） （3605KB）（96）       Knowledge map    Save This paper deals with the problem of bipartite consistency in multi-agent control systems based on distributed event triggering. A coherent control protocol with a cooperative and competitive topology for achieving consensus among multi-agent systems is proposed, aiming to drive the system to converge to states with binary disagreement yet identical magnitudes. On the basis of graph theory and matrix theory, the problem of binary consensus in multi-agent systems is reformulated into a stability issue for closed-loop error systems. By establishing an appropriate Lyapunov function, the asymptotic stability of the closed-loop error system is validated. Moreover, event-triggering conditions are introduced for each agent to reduce control update frequencies and communication resource consumption. Additionally, it is demonstrated that there exists a strict lower bound for the time intervals between successive triggers for neighboring agents, thereby preventing Zeno phenomena. Finally, through simulation instances, the feasibility and effectiveness of the proposed method are verified. Reference | Related Articles | Metrics

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Fatigue strength analysis of high-strength bolts for tower flange of wind turbine LIANG Yuan, WANG You-liang, WEI Tai, LIU Jian-hui Journal of Lanzhou University of Technology    2023, 49 (2): 65-69.   Abstract （250）      PDF（pc） （1391KB）（637）       Knowledge map    Save An analysis method for high-strength bolts of wind turbine tower flange was established by considering the influence of external load on fatigue damage. Firstly, the maximum load section was determined with the aid of the tower equivalent model according to the damage parameters of the stress state on the connection section. Secondly, the external load on any sector of the tower was obtained by Schmidt-Neuper algorithm. Afterwards, the fatigue damage distribution model of high-strength bolts was established and the relationship between the external load and the internal stress of high-strength bolts was explored based on the finite element model. Finally, the optimal bolt pretightening force was determined with comparing the fatigue cumulative damage values with different bolt pretightening forces by considering the influence of pretightening forces. The results show that the positions of the maximum fatigue cumulative damage of flange bolts were －4.17° and 175.87°, and the bolt pretightening force was the most suitable value when the bolt pretightening force ratio was 70%. Reference | Related Articles | Metrics

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Study on the evolution of urban space form and the relationship between city and water in zhangye city ZHANG Xiao-juan, WAN Qing, PU Fa-liang Journal of Lanzhou University of Technology    2021, 47 (6): 138-144.   Abstract （196）      PDF（pc） （3302KB）（306）       Knowledge map    Save Based on the aerial imagery and ancient literature data, the spatial data analysis method was used to study the dynamic evolution of urban spatial morphology in Zhangye City from 1949 to 2012. The results show that: The city has changed from slow development to rapid development, and the land intensive utilization rate has increased. The relationship between city and water is from far to near, from passive to interactive, the urban ecological function of the water system is increasingly prominent, and the water environment has been given more rich connotations. Based on the goals of sustainabledevelopment and water ecological construction, in the future, Zhangyeshould renovatethe river system, construct the water ecological security pattern, repair and protect the urban wetland and strengthen the ecological green space construction to create the water culture characteristic, and to promote sustainable development. Reference | Related Articles | Metrics

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Microstructure and properties of AlCoCrFeNi 2.1 high entropy alloy modified by deformation heat treatment WANG Peng-hui, ZHANG Xiao-bo Journal of Lanzhou University of Technology    2024, 50 (4): 1-5.   Abstract （43）      PDF（pc） （2366KB）（53）       Knowledge map    Save High-entropy alloys have become a focal point in the field of materials in recent years due to their combination of high strength, toughness, high-temperature mechanical properties, oxidation resistance, and corrosion resistance. Eutectic high-entropy alloys combine the advantages of eutectic alloys and high-entropy alloys, making it possible to cast large-scale components. The mechanical properties of the alloy are regulated by cold rolling and annealing, and the changes inmicrostructure organization and mechanical properties of the eutectic high-entropy alloy after annealing at different temperatures are investigated by XRD, SEM, EDS, and tensile testing machine. The results showed that the tensile strength of the alloy is abnormally improved after 30% cold rolling, while the elongation plummeted. After annealing at temperatures of 800 ℃, 900 ℃, and1 000 ℃ after 30% cold rolling, the organization gradually changes from partial recrystallisation to complete recrystallisation, accompanied by slight grain growth. After annealing at 800 ℃, there are deformed large grains and recrystallised small grains, and a variety of reinforcement mechanisms work in a coordinated way to make the tensile strength and elongation to 1 272 MPa and 12.39%, respectively. Reference | Related Articles | Metrics

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Research on life prediction and life extension method of feedback control system under actuator degradation LI Wei, WANG Cheng-wen Journal of Lanzhou University of Technology    2020, 46 (4): 84-90.   Abstract （336）      PDF（pc） （2152KB）（631）       Knowledge map    Save During long-term operation, the control system may be affected by complex working environment, the actuator may be damaged to varying degrees and its performance will be degraded, which will cause the performance of the feedback control system to drop or even not work properly. Therefore, in view of the deterioration of system performance caused by actuator degradation, this paper establishes a degradation model for the actuator that works under combinative action of wear and shock. The working condition of the actuator is incorporated in the controller design, and the method based on the probability distribution of failure time is employed to predict remaining life of the system. By adjusting control constraints and modifying set points on line, a trade-off between system performance and actuator health index is found to delay actuator degradation and extend the life cycle of the control system. Finally, the effectiveness of the proposed method is verified by simulated examples. Reference | Related Articles | Metrics

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Sentiment analysis of Chinese text based on feature fusion ZHAO Hong, FU Zhao-yang, WANG Le Journal of Lanzhou University of Technology    2022, 48 (3): 94-102.   Abstract （284）      PDF（pc） （1771KB）（598）       Knowledge map    Save To address the problems that the existing methods cannot comprehensively consider the semantic information of text in terms of syntactic structure, contextual information and local semantic features, a feature fusion-based Chinese text sentiment analysis method is proposed. Firstly, Jieba word segmentation tool is used for word segmentation and part of speech tagging of the review text, and a word vector training tool GloVe is used to obtain pre-trained word vectors with part of speech. Then, the word vector is used as the input of BiGRU and TextCNN with self attention respectively. The global features are extracted from the syntactic structure and the contextual information of the text using BiGRU with Self-Attention, and the local semantic ones are extracted using TextCNN. Finally, the global features and local semantic features are integrated, and Softmax is used for text sentiment classification. The experiment result shows that the proposed method can effectively improve the accuracy of text sentiment analysis. Reference | Related Articles | Metrics

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Study of field test of cement-modified soil road bed in collapsible loess area JIN Ming-liang, WEI Zheng-peng Journal of Lanzhou University of Technology    2023, 49 (3): 135-139.   Abstract （132）      PDF（pc） （1214KB）（258）       Knowledge map    Save In order to solve the problem of reflective cracks often existed in the pavement structure layer, the construction effect of cement-improved soil pavement bed under the action of ordinary roller and large vibration force roller was compared by taking the construction of an expressway in Longdong region of Gansu Province as an example. Through rolling combined process and compaction parameters, the optimum filling thickness of cement-modified soil under the action of high vibration force roller is obtained. Through the different arrangement of construction period of pavement structure layer on the top surface of pavement bed, the effective way to reduce the reflection crack is studied. The test results show that: Influenced by the hydration reaction of cement-modified soil, with the increase of delay time, its maximum dry density decreases, while its optimum moisture content increases gradually. It is beneficial to improve the compaction degree of cement-improved soil by adopting strong vibration of high-exciting force road roller and increasing the number of compaction times. Due to the development of construction machinery, the compaction thickness can be appropriately increased on the basis of the limit specified in the specification. The reflective cracks of the pavement structural layer are obviously reduced with the increase of the placement time of the formed road bed. The test results can provide reference for the construction of cement improved soil road bed. Reference | Related Articles | Metrics

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An improved grey wolf optimization for solving flexible job shop scheduling problem ZHANG Qi-wen, WANG Chao Journal of Lanzhou University of Technology    2022, 48 (3): 103-109.   Abstract （207）      PDF（pc） （1364KB）（380）       Knowledge map    Save This paper focuses on the flexible job shop scheduling problem and proposes an improved gray wolf optimization (IGWO) algorithm, with the goal of minimizing the maximum completion time. A two-phase coding method is used to construct the relationship between the individual locations and the scheduling scheme. The initial population method based on the heuristic rule is used to improve the quality of initial solution. In order to balance global search and local search, a hyperbolic-tangent-function-based non-linear convergence factor formula is proposed, in the individual update stage of the algorithm, a weighting method based on fitness value is proposed, the variable neighborhood search algorithm is embedded into the decision-making layer of the algorithm. Simulation results show that the algorithm is effective in solving the flexible job shop scheduling problem. Reference | Related Articles | Metrics

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Dynamic output feedback control of cyber-physical systems under false data injection attacks ZHU Chao-qun, ZHU Yi-rong Journal of Lanzhou University of Technology    2023, 49 (1): 74-82.   Abstract （256）      PDF（pc） （1259KB）（622）       Knowledge map    Save In this paper, an H-infinity dynamic output feedback control strategy with attack defense ability is investigated to deal with the problem of security control of cyber-physical system (CPS) under false data injection (FDI) attacks, which is taken as a special kind of external disturbance. Firstly, the effect of FDI attacks in the measurement channel and random time-delay on the communication network is considered, and a closed-loop system model with FDI attack, random time-delay, and external disturbance is established. Secondly, the sufficient conditions for the asymptotic stability of the closed-loop system under FDI attacks are derived based on the Lyapunov stability theory, and then the design scheme of H-infinity dynamic output feedback controller by utilizing linear matrix inequality technology is presented. Finally, a simulation example is given to demonstrate the feasibility and effectiveness of the proposed method. Reference | Related Articles | Metrics

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Design of virtual and real interactive monitoring system for CNC machine tools based on digital twins HUANG Hua, LI Jia-ran, LI Dian-lun Journal of Lanzhou University of Technology    2023, 49 (1): 36-43.   Abstract （423）      PDF（pc） （5660KB）（612）       Knowledge map    Save Aiming at the problem that the actual operating status of CNC machine tools is not directly reflected by traditional monitoring technology and virtual simulation technology, a virtual-real interactive monitoring system for CNC machine tools based on digital twins technology is designed by combining the new generation of information technology and the concept of digital twins. In addition, taking a CNC machine tool as example, the system architecture and related functions are first designed through Portal software. Based on that, the information collected by the sensor is transmitted to the system through PLC and Ethernet for analog conversion; and the digital twins data in the system is connected with the digital twins to realize the reception and transmission of information, then the combination of virtual and real are completed through OPC-DA. Finally, this method is used to monitor the vibration signal of the machine tool in real time and design a remote control panel. The experimental results show that the system using the virtual-real interactive monitoring system and digital twins of the CNC machine tool to double monitor the machining process can reflect the actual operating status of the machine tool more effectively and intuitively. Meanwhile the digital twins is virtually controlled by the virtual-real interactive monitoring system, and the application field of digital twins technology is further expanded. Reference | Related Articles | Metrics

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Preparation of composite emulsified asphalt and its properties of micro-surface mixtures SHI Fu-zhou, JIA Xiao-jun, WANG Zhen, LIU Xiao-pei, WU Jia-yun Journal of Lanzhou University of Technology    2021, 47 (2): 138-143.   Abstract （312）      PDF（pc） （2508KB）（482）       Knowledge map    Save In order to improve the road performance of ordinary emulsified asphalt in the micro surface mixture, the emulsified asphalt with high performance was prepared by the method of emulsification first and then modification. The addition method of modifier and the proportion of modifier blending were determined by using the indexes of ductility and softening point, and then it is used as cementing material for the micro-surface mixture. The performance of resistance to water damage and wear resistance of the wet wheel were verified by the wear test (WTAT), and its crack resistance and shear resistance were verified by splitting test and high-temperature rut test. The results show that the softening point and ductility of the composite modified emulsified asphalt are better than ordinary emulsified asphalt, while the blending ratio of SBR with waterborne epoxy resin is 3.5% to 2.5%, ductility and softening point can reach 400 mm and above 70 ℃.The performance test of the mixture showed that the micro surface mixture made of modified emulsified asphalt had significant advantages in water loss resistance/wear resistance, crack resistance and shear resistance compared with the ordinary micro surface mixture. Reference | Related Articles | Metrics

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General model for kinematic analysis of swash plate axial piston pump WANG Jian-sen, CAO Wei-dong, HE Xin-long, WANG Zheng-rong, ZHANG Zhi-wei Journal of Lanzhou University of Technology    2021, 47 (5): 59-64.   Abstract （545）      PDF（pc） （3701KB）（775）       Knowledge map    Save Based on the comprehensive consideration of swash plate angle, cross angle and piston inclination angle of the swash plate axial piston pump, the general piston kinematics model is established by coordinate transformation method. The analysis results show that the cross angle of swash plate and the inclination angle of piston will increase the maximum amplitudes of displacement, velocity and acceleration of piston, and then increase the displacement of pump, the maximum transient flow velocity in the piston chamber and the inertia force of piston; the cross angle of swash plate will change the phase of piston movement and make the internal and external dead points deflect, which will change the pre-compression and pre-expansion angle of valve plate; the inclination angle of piston will affect the movement of the piston, the smaller the inclination angle of the plunger, the closer the movement of the plunger is to the simple harmonic motion, on the contrary, the larger the deviation is, the maximum deflection angle of internal and external dead center is 90°, the smaller the absolute value of the cross angle is, the smaller the deflection angle of internal and external dead center changes in the range of big swash plate angle, and the greater the gradient of change when swash plate angle is close to zero displacement. Reference | Related Articles | Metrics

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Optimal groove design of cylindrical gas seal based on approximate model ZHANG Wei-zheng, FENG Fan, REN Ya-nan, SUN Yue-yue Journal of Lanzhou University of Technology    2023, 49 (5): 67-76.   Abstract （100）      PDF（pc） （5441KB）（194）       Knowledge map    Save Aiming at the new type of cylindrical gas film seal with reverse herringbone groove on the side of rotating shaft sleeve, the mathematical model of cylindrical gas film seal was established and the pressure distribution of reverse herringbone groove gas film was numerically solved by finite difference method. Through the Isight platform integrated with MATLAB software, the optimal Latin hypercube test design and its post-processing module were used to extract the key groove structure parameters affecting the sealing performance parameters. An approximate model was established instead of time-consuming numerical calculation, and the multi-objective optimization of groove structure parameters was carried out by integrating the NSGA-Ⅱ multi-objective optimization algorithm, which provided theoretical reference for the multi-objective optimization design of groove type for cylindrical gas film seal slotted on the side of shaft sleeve. Reference | Related Articles | Metrics