Table of Content

25 August 2023, Volume 51 Issue 8

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Contents



2023, 51(8):  0. 

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Traffic & Transportation Engineering

Analysis of Crossing Behavior of Non-Motor Vehicle at Overlap Phase Signal Intersections



WEN Huiying, LIU Hao, DU Yingxin, et al

2023, 51(8):  1-11.  doi:10.12141/j.issn.1000-565X.220779

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In order to improve the safety level of non-motor vehicle traffic at signalized intersections, based on the survey data of signalized intersections with overlapping phase control in Guangzhou, this study analyzed the influencing factors of non-motor vehicle crossing behavior based on the C5.0 decision tree algorithm. Considering the influence of different periods on the crossing behavior of non-motor vehicles in the signal cycle, the study divided a complete signal cycle into four risk periods according to the risk conflict of non-motorized vehicles crossing the street, namely, the opposite green light risk period, the same direction green light safety period, the same direction green light risk period and the vertical direction risk period. And it divided the crossing behavior into three categories according to the waiting selection of non-motor vehicles at the intersection and whether or not to run red-light, namely, risky, opportunistic and law-abiding. It studied the influencing factors of the three types of crossing behavior by constructing a C5.0 decision tree model and analyzed and evaluated the classification effect of the model. The results show that the overall accuracy of the model classification results is greater than 83.04%, the AUC is greater than 0.880, and the model prediction accuracy is good. The crossing behavior of non-motorized vehicles at signalized intersections with overlapping phase control is mainly significantly related to the traffic environment, while the factors related to the rider’s behavior are less significant. The arrival risk period, non-motor vehicle signal light facilities, conflicting motor traffic flow, number of lanes and crossing risk have significant impacts on the occurrence of risk-taking crossing behavior, among which the arrival risk period is the most important influencing factor. The number of lanes, red-light time and arrival risk period have significant impacts on the occurrence of opportunistic crossing behavior, among which the number of lanes is the most important influencing factor. The conflicting motor traffic flow flow, signal period, number of lanes, crossing area and crossing risk have significant impacts on the occurrence of law-obeying crossing behavior, among which the conflicting motor traffic flow is the most important influencing factor.

Fracture Energy Test Method and Influencing Factors of Asphalt-Aggregate Interface



DENG Kailing, WANG Duanyi, FANG Qiuping

2023, 51(8):  12-20.  doi:10.12141/j.issn.1000-565X.220821

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As one of the common diseases of asphalt pavement, raveling can have a great adverse effect on the durability and road performance of asphalt pavement. To solve the problem of obtaining the asphalt-aggregate interface fracture energy required for asphalt pavement raveling prediction and sensitivity analysis, this research proposed a pendulum impact test method, by which the fracture energy of asphalt-aggregate interface was obtained by conducing lateral shear impact loading on “aggregate-asphalt-aggregate” specimens, causing a negligent failure at asphalt-aggregate interface. The research also analyzed the effects of temperature, asphalt type, aggregate type, water, and mineral filler on the asphalt-aggregate interface fracture energy. The results show that the asphalt-aggregate interface fracture energy can be used as the indicator to evaluate the asphalt-aggregate interface performance, reflecting the asphalt-aggregate adhesion performance, asphalt internal cohesion performance, and the mechanical characteristics of the asphalt-aggregate interface under different temperatures and loading conditions. Temperature has a great influence on the fracture energy of the asphalt-aggregate interface. As the temperature raises, the asphalt-aggregate interface fracture energy shows an upward trend followed by a downward trend, and the adhesion of asphalt and aggregate increases gradually, while the asphalt cohesion decreases. The fracture energy of SBS modified asphalt-aggregate interface and high-viscosity asphalt-aggregate interface are significantly greater than that of 70# asphalt-aggregate interface, while the difference between the fracture energy of the two modified asphalt and aggregate is not significant except for the peak value. The effect of aggregate types on the fracture energy of the asphalt-aggregate interface has no significant rule. Water will reduce the fracture energy of the asphalt-aggregate interface at all temperatures. The addition of mineral filler to asphalt can decrease the interface fracture energy and the range of optimum F/A ratio based on asphalt mixture performance do not have a positive effect on the asphalt-aggregate interface performance probably. The fracture energy of the asphalt-aggregate interface determined by the pendulum impact test can not only serve as a test basis for evaluating the performance of the asphalt-aggregate interface, but also provide material parameters for the numerical simulation analysis of raveling, and provide a criterion for the prediction of raveling and sensitivity analysis, so as to lay the foundation for the precise design of anti-raveling asphalt pavement.

Evolution of Interface Performance of Longitudinal Ballastless Track Under Temperature Load After Embedded Steel Bars



LU Hongyao, XU Yude

2023, 51(8):  21-31.  doi:10.12141/j.issn.1000-565X.220735

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In order to clarify the performance evolution of the interlayer interface of the longitudinal slab ballastless track under the temperature load, this study carried out the mechanical and fatigue performance tests of the interface after embedded steel bars of the composite specimen, and the load spectrum was generated by combining the temperature field monitoring data of the track slab on site.The spatial refined finite element model of ballastless track considering the whole process of interface damage was established and the stress state and damage characteristics of the interface between the lower layers under adverse temperature load were analyzed. The concept of initial temperature load of interface damage was introduced.The change in temperature load at the onset of damage at the interlayer interface after embedded steel bars was calculated and the evolution of debonding risk time after structural performance degradation was clarified. The results show that bearing capacity of the interlayer interface embedded with steel bar is significantly improved.The critical debonding failure displacement and the maximum load are increased by 76.38% and 153.41% respectively, and the fatigue performance is better, indicating that it is feasible to reduce the risk of interfacial debonding of ballastless track through embedding steel bars. The anchoring of embedded steel bars can not fundamentally limit the transmission of temperature force in the ballastless track and the damage suppression effect at the boundary of the slab is limited. It is easy to cause hidden damage near the reinforcement planting hole and the maximum damage value can reach 0.944. With the increase of service life,the initial temperature load that causes the initial damage of the interlayer interface decreases continuously. The safe temperature change range of good bonding state of the interface is reduced from 30.3 ℃ to 16.3 ℃.The number of days with possible interface damage risk is increased by 64.29% and the interlayer interface may have been damaged before extreme weather occurs.The railway department needs to adjust the temperature range of the concerned board based on the actual development of line diseases, and dynamically adjust the setting standards for maintenance thresholds.

Operational Reliability Optimization Strategies of Multi-type Bus Lines



ZHAO Xiaomei, ZHU Xiangyuan, WANG Qin, et al

2023, 51(8):  32-39.  doi:10.12141/j.issn.1000-565X.220493

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The unstable running time and the difficulty to accurately estimate the arrival time reduce passengers’ satisfaction with bus traveling. With the diversification of cities, bus line types are gradually becoming more diverse, and the variations in bus operating time of the various bus line types cause trouble in bus scheduling and inconvenience for passengers. To solve above problems, firstly, this paper used K-means ++ algorithm to cluster the stations with the sum of squares of error (SSE) as the measurement index. The operation characteristics and reliability influencing factors of different types of bus lines were taken into consideration to determine the alternative station sets of limited-stop bus service. Then, a joint optimization strategy model of limited-stop bus service and speed regulation was proposed to determine the limited-stop bus station, the departure time, and the running speed of all buses. This model took the minimization of bus operation cost, passenger travel cost, and reliability cost as the objectives, and took the constraints of operation process and headway of limited-stop bus service and all-stop bus service into consideration. Finally, genetic algorithm was used to solve the optimization model and Beijing bus system was selected for case analysis. The results show that the limited-stop bus service can reduce the operation cost of public transport, the speed regulation strategy can better lower the passenger travel cost and reliability cost, and the joint optimization strategy of limited-stop bus service and speed regulation can effectively reduce the total cost of the bus system.

Stuby on the Activity Patterns and Regularity of Public Transport Passengers



CHEN Yanyan, WANG Zifan, SUN Haodong, et al

2023, 51(8):  40-50.  doi:10.12141/j.issn.1000-565X.220658

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In order to explore the activity pattern and regularity of public transport passengers, this study constructed multi-day passenger travel activity sequences using three weeks smart card data in Beijing in October 2020. The frequent activity pattern sequences of passengers were mined through the PrefixSpan algorithm, and the similarity measure method of activity patterns was defined based on the longest common subsequence. The day-to-day activity sequence similarity of individual and activity pattern similarities among different passengers were calculated respectively, and passengers were classified according to activity pattern similarities among passengers by using the hierarchical clustering algorithm. The results show that the similarity between workdays and weekends is significantly lower than that within workdays or weekends. In workdays, the activity sequence similarity between Friday and the other days is low. Meanwhile, the activity sequence similarity of the same days in different weeks is high. The result of hierarchical clustering shows that there are four typical activity patterns, including entertainment and shopping orientation, life orientation, work orientation and personal affair orientation. Moreover, the day-to-day activity sequence similarity of passenger with work orientation pattern is higher than that of passenger with other activity patterns. The research results in this paper are helpful to scientifically formulate accurate public transport operation management and service policies.

Energy, Power & Electrical Engineering

Experimental Study of Non-Symmetry Micro Channel Flat Plate Pulsating Heat Pipe Under Variable Conditions



ZHANG Dong, XU Baorui, WANG Sen, et al

2023, 51(8):  51-61.  doi:10.12141/j.issn.1000-565X.220771

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In order to solve the problem of efficient heat dissipation of miniaturized electronic devices and the difficulty of horizontal operation of pulsating heat pipe, this study designed a non-symmetry micro-channel flat plate pulsating heat pipe (NCPHP) and built an experimental platform for its heat transfer performance. By controlling different incline angles, filling rate and cooling water temperature, the operation characteristics of NCPHP were investigated under the structure design of non-symmetry channel. The results show that the thermal resistance of NCPHP is sensitive to the change of incline angle at 30% and 50% filling rate, and the dry-out phenomenon of NCPHP is observed at 30% filling rate. At 50% filling rate, the thermal resistance of NCPHP can be as low as 0.622 and 0.545 K/W when incline angle is -5° and 0°, respectively. The minimum thermal resistance of NCPHP was 0.415 K/W when the incline angle is 60° and the filling rate is 50%. When the incline angle is -5° and the liquid filling rate is 50%, and the heating power reaches 40 W, the temperature in the evaporation section of NCPHP continues to rise in a short time, but this phenomenon disappears and changes into a stable and fluctuating characteristic when the heating power reaches 50 W. The influence of cooling water temperature on the average temperature difference in the evaporation section of NCPHP decreases with the increase of heating power. At 50% liquid filling rate, the temperature difference of NCPHP evaporation section decreases from 5.1 ℃ at 30 W to 4.2 ℃ at 60 W. Lower cooling water temperature can delay the dry-out phenomenon of 30% liquid filling rate.

Optimization Simulation of Ammonia Injection in SCR DeNO _x System of Coal-Fired Power Plant



LU Zhimin, LI Bohang, TANG Wen, et al

2023, 51(8):  62-70.  doi:10.12141/j.issn.1000-565X.220446

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To improve the uniformity of NO _x mass concentration distribution at the outlet of SCR (selective catalytic reduction) denitration reactor of a 660 MW unit, this paper proposed an optimal ammonia injection strategy based on the kinetic model with the objective of minimizing the relative standard deviation of NO _x mass concentration distribution at the outlet of SCR. The on-site measured data was used as the inlet boundary condition, and CFD numerical simulation calculations were conducted by coupling turbulent flow, component transport, and chemical reactions in the reactor. The ammonia flow characteristics was visually analyzed, and the flow influence coefficient of the ammonia injection grid partition/nozzle was defined. The optimal controllable ammonia injection flow of different partitions or nozzles of the ammonia injection grid can be obtained by directly solving the optimization matrix equation, and combining the mathematical relationship between the outlet NO _x concentration distribution and the inlet NH₃ concentration, which is based on the SCR reaction kinetics model. The simulation results show that under the uniform ammonia injection mode, the mixing matching degree of ammonia nitrogen concentration in different zones is not high, the relative standard deviation of NO _x mass concentration at the outlet of SCR reactor reaches 40.1%, and the uniformity of NO _x mass concentration distribution at the outlet is poor. After the optimization of ammonia injection according to the method proposed in the paper, the relative standard deviation of NO _x mass concentration at the outlet decreases to 6.8%, and the uniformity of the outlet is greatly improved. This can not only realize the pressure line emission of NO _x to meet environmental requirements but also avoid areas with high and low denitrification efficiency. The flow field was visualized through numerical simulation in the article, and ammonia injection optimization was carried out by quantitatively solving the ammonia injection volume of each valve. This can provide theoretical reference for actual ammonia injection optimization debugging in power plants and reduce the blindness of adjustment.

Kinetics of Dehydration/Adsorption Reaction of LaCl₃



LOU Bo, ZHOU Daheng, XIA Jun

2023, 51(8):  71-79.  doi:10.12141/j.issn.1000-565X.220352

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LaCl₃ is one of the most promising hydrated salt thermochemical heat storage materials, and its reaction kinetics plays a crucial role in the study of its reaction characteristics. The study tested the reaction characteristics of dehydration and adsorption of LaCl₃ by experiments and analyzed the reaction kinetics mechanism. The dehydration process of LaCl₃·7H₂O at the heating rates of 1, 10 and 20 K/min was tested by a synchronous thermal analyzer. The results show that the dehydration process of LaCl₃·7H₂O can be divided into three stages, where 4,2 and 1 water molecules are removed respectively.The initial temperature of each stage is different at different heating rates. The activation energy value of three stages was calculated by FWO method and the activation energy of the first stage was the largest. The Doyle method was used to solve the mechanism functions of each stage, in which the first stage conforms to the shrinking cylinder model in the phase boundary reaction, while the second and the third stage conformed to the random nucleation and subsequent growth model. The adsorption process of LaCl₃ was tested at the temperature of 15, 20, 25, 30 ℃ and at the relative humidity of 40%, 60%, 80% by a constant temperature and humidity chamber. The adsorption reaction rate of LaCl₃ is positively correlated with the temperature and humidity. When the relative humidity is 40%, LaCl₃ does not decompose. The reaction rate of LaCl₃ is faster in the initial stage of the adsorption process. As the adsorption process proceeds, LaCl₃·nH₂O crystals formed on the surface restricts the contact between LaCl₃ and water vapor. The kinetic equation of LaCl₃ adsorption reaction was fitted, the adsorption process of LaCl₃ conformed to the chemical reaction series model, and the reaction order was 0.837. The results show that LaCl₃ has good chemical kinetics and high heat release, and is a potential chemical thermal storage material.

Energy, Power & Electrical Engineering

Study on the Effect of Mooring Form on the Dynamic Response of Floating Offshore Wind Turbine



ZHANG Ruoyu, LI Yaolong, LI Yan, et al

2023, 51(8):  80-88.  doi:10.12141/j.issn.1000-565X.220250

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Mooring system is a key factor affecting the dynamic response of a floating wind turbine, and it is related to the safety and efficiency of the wind turbine system. To study the effect of different mooring systems on the dynamic response of floating wind turbines, this paper took a new type reduced-draft floating foundation as the research object. Based on the feature of large reserve buoyancy, two different mooring systems, namely the catenary lines and the tension legs, were used for positioning the 5 MW floating offshore wind turbines. The turbine-buoy-mooring coupled numerical model was established. The aerodynamic load was calculated based on the blade element momentum theory, the hydrodynamic load was calculated by the potential flow theory, and the tensions in the two kinds of mooring lines were calculated by the three-dimensional finite element dynamic model. Based on this coupled numerical model, the dynamic responses of two kinds of floating wind turbines under the operating state were simulated in the time domain. By comparing the results, it shows that under the rated operating sea conditions and compared with the catenary mooring system, the mean of surge motion of the floating wind turbine with the tension leg mooring system is reduced by 0.7 m, the amplitude of heave motion is reduced by 39%, and the mean and amplitude of pitch motion are reduced significantly. The floating wind turbine with the tension leg mooring system has better motion performance, but its mean and amplitude of the tension in the mooring lines are larger, and the variation amplitude of the output power and the tip deformation of the wind turbine are also more significant. Therefore, for the new floating foundation proposed in this work, the wind turbine with tension legs has better motion performance, but its mooring safety and power generation efficiency are not as good as the turbine with catenary mooring lines.

Electronics, Communication & Automation Technology

Reconfigurable GNSS RF Receiver for High-Precision Positioning and Orientation



LI Bin, WANG Riyan, CHEN Zhijian, et al

2023, 51(8):  89-97.  doi:10.12141/j.issn.1000-565X.220177

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Aiming at the problem of multiple types of requirements and large volume, this paper introduced a highly integrated and reconfigurable Global Navigation Satellite System (GNSS) Radio Frequency (RF) receiver for high-precision positioning and orientation of satellite navigation. By adopting four reconfigurable reception channels and receiving full frequency band GNSS signals in parallel, it achieved a single chip supporting high-precision positioning or orientation applications, significantly reducing the volume and cost of navigation terminals. To improve broadband signal reception, the paper proposed a new type of inductorless high linear low noise transconductance amplifier (LNTA). It can eliminate the use of source and load inductors, reduce gain and noise fluctuations when operating in navigation signals at different frequency points, and it is conducive to the reconfiguration of multimode and multi frequency reception and reduces the power consumption of LNTA. A novel IQ phase compensation method was proposed to address the issue of IQ phase imbalance. A programmable switch array with variable impedance was directly designed on the clock controlled latch path of the binary frequency division circuit. By changing the delay time of the 25% duty cycle orthogonal LO, the corresponding branch output LO phase adjustment was realized, achieving calibration of IQ imbalance and improving the image rejection rate (IRR). Testing data shows that the RF receiver achieves full band signal coverage of GNSS from 1.15 to 1.65 GHz, a minimum noise figure of 2.7 dB, and an output third-order intermodulation point power of 34.7 dBm. Adopting a low intermediate frequency and zero intermediate frequency reconfigurable architecture, it can flexibly receive multimode GNSS signals with a bandwidth of 0.8~80 MHz. By compensating for IQ imbalance and improving channel layout, 58.1 dB IRR and 57 dB channel isolation can be achieved, effectively reducing the impact of image interference and inter channel interference. Under a 1.2 V power supply, the power consumption of the receiving channel is only 24.7 mW, which can meet the high integration and diversified application requirements of high-precision positioning and orientation GNSS RF receivers.

Application of Haptic Feedback Technology in Automotive Information Systems



SUN Xiaoying, ZHAO Yinan

2023, 51(8):  98-109.  doi:10.12141/j.issn.1000-565X.220548

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In recent years, cars have been becoming more and more intelligently connected, and modern vehicles have been transformed into mobile computer platforms with information systems such as navigation systems, entertainment systems, climate control systems, and vehicle performance systems. The amount of information that drivers can access and interact with in the vehicle has increased significantly. However, operating a wide range of automotive information systems while driving can distract the driver’s visual and auditory attention, causing distracted driving and increasing the likelihood of traffic accidents. The use of haptic modalities while driving can complement audiovisual modalities, reduce the driver’s audiovisual burden, and improve driving safety, interaction reliability and comfort. On the basis of summarizing the development history of haptic feedback technology in automotive applications, this paper classified the specific types of in-vehicle interaction activities and haptic modalities that can be displayed in the vehicle, and analyzed the research progress of haptic feedback technology in automotive information systems from three directions, namely, in-vehicle haptic warning system, in-vehicle haptic navigation system, and in-vehicle haptic operation assistance system. It also summarized the main sources of haptic excitation in in-vehicle warning systems, navigation systems and operation assistance systems, respectively. And by analyzing the relevant literature, it expatiated the experimental environment, evaluation indexes, evaluation methods and results of the research on the influence of automotive haptic information systems on driving performance. Based on the shortcomings of existing technologies and research methods, the paper discussed and prospected the future research of automotive haptic information system from the perspectives of the location of haptic feedback excitation signals, the selection of modes and parameters, the study of behavioral adaptation problems, the improvement of the experimental environment, the consideration of different factors affecting haptic perception, and the integration of multiple automotive haptic information systems.

Hardware Acceleration Design of HEVC Entropy Encoding Syntax Elements Based on FPGA



LIN Zhijian, HUANG Ping, ZHENG Mingkui, et al

2023, 51(8):  110-117.  doi:10.12141/j.issn.1000-565X.220350

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High Efficiency Video Coding (HEVC/H.265) is a widely used video coding standard in the international market. As the core encoding method of HEVC video encoding, Context Adaptive Binary Arithmetic Coding (CABAC) can improve the compression efficiency of arithmetic coding by establishing a more accurate probability model. Moreover, HEVC defines a larger variety of syntax elements and establishes more complex coding structures, further reducing information redundancy and thus reducing the bit rate. However, as the input data to CABAC, syntax elements’ high complexity of preprocessing process increases the difficulty of hardware parallel processing. As a result, the throughput rate of entropy coding hardware is difficult to improve, which becomes one of the bottlenecks for HEVC encoder to achieve higher resolution real-time coding. To further speed up the entropy encoding modules, this study designed a high-throughput CABAC entropy encoding architecture based on FPGA. Within the architecture, the pre-header information coding, pre-initialization and coding unit (CU) are able to accelerate the generation of syntax elements, which is dedicated to CABAC. Due to the scheme of efficient residual coding and partial context index pipeline computing, the reduction of path latency and the improvement of operating frequency can be achieved as well as high throughput. In this study, the proposed design, which is synthesized by using a 90 nm standard cell library, occupies a total of 2.099×10⁴ logic gates and operates in the frequency of 200 MHz. This paper also simulated the video sequence provided by HEVC official, and counted the time required for encoding a coding tree unit (CTU) under different quantitative parameters (QP). The experimental statistics show that the time of encoding a CTU was saved by 38.2% on average.

Translation Optimization Technology of Automatic Speech Recognition Based on Industry-Specific Vocabulary



MA Xiaoliang, AN Lingling, DENG Congjian, et al

2023, 51(8):  118-125.  doi:10.12141/j.issn.1000-565X.220740

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Automatic speech recognition (ASR) technology has been developed relatively mature, and general ASR engines have been widely used in transportation, medical, communication and other industries. However, due to non-independent homology of industry-specific vocabulary in the large-scale training corpus, there comes to low recognition accuracy of industry-specific vocabulary when the general ASR engines are applied to various subdivisions of industries. As compared with 16 kHz audio sampling rate in Internet environment, narrowband low sampling (8 kHz) of call center may result in more significant decrease of recognition accuracy of ASR. In order to improve the accuracy of speech recognition of industry-specific words, this paper proposes a translation optimization technology of ASR based on industry-specific vocabulary. Specifically, first, convolutional neural network model and deep neural network BERT model are used to predict word for corpus text data, and an industry-specific error correction vocabulary is generated. Next, in the production environment, a general ASR engine is used to perform initial transcription of telephone call voice data. Then, the transcribed text is corrected by using the Soft-Masked BERT model combined with the industry-specific error correction vocabulary, thus improving the accuracy of speech recognition. Finally, by using 12345 hotline customer service call voice data for modeling and testing, the proposed translation optimization technology is proved efficient in improving the accuracy of general ASR recognition by 10 percentage points with high error correction speed and good applicability.

Soft-Sensor Modeling Method Based on Ensemble Kalman Filter-Elman Neural Network



FANG Gang, YUAN Longhua, WANG Xiaoming, et al

2023, 51(8):  126-136.  doi:10.12141/j.issn.1000-565X.220625

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Wastewater treatment system is a dynamic system with complex nonlinearity and large time delay. Due to the complexity of the process, the incompleteness of the testing equipment and the constraint of economic cost, some important effluent indicators cannot be detected accurately. To solve this problem, this paper proposes a soft-sensor method based on an ensemble Kalman filter-Elman neural network. The traditional dynamic neural network has the dynamic memory ability to process time-delay data, so it can be used in data-driven soft sensing modeling. However, the conventional training method is easy to trap in a local minimum, resulting in poor prediction performance. This paper introduces the ensemble Kalman filter and the dual finite-size ensemble Kalman filter, and, together with the Elman neural network for gradient-free training, to construct two soft sensor models, which not only improve the prediction performance of Elman neural network but also provide a simple and gradient-free training method for neural network. The two models are then applied to a dataset of the University of California, Irvine (UCI data). The results show that the proposed method based on ensemble Kalman filter-Elman neural network possesses good prediction performance, and that the ensemble Kalman filter can be used as an alternative gradient-free method to train neural networks.

Multi-Objective Optimization Based on Improved Distribution of Solutions



WANG Xuewu, FANG Junyu, GAO Jin, et al

2023, 51(8):  137-148.  doi:10.12141/j.issn.1000-565X.220668

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For low-dimensional multi-objective optimization problems, the existing multi-objective optimization algorithms have been able to ensure the proximity to the optimal front of the problem, and balance the convergence and the diversity of solution sets. However, the uniformity of the solution is ignored in most algorithms. In the multi-objective optimization problem with irregular Pareto front, the more uniform the distribution of solution is, the more the solution can reflect the true distribution of the optimal front of the problem, and the more reasonable the choices provided to decision makers. To improve the uniform distribution of solutions, a new multi-objective optimization algorithm CM-SPEA2 is proposed based on SPEA2 algorithm and the improved individual fitness calculation. In this algorithm, firstly, the initial population is divided into different clusters by means of hierarchical clustering. Next, the original calculation method of messy degree is improved to measure the messy degree of individuals in their clusters, and the individuals with the lowest messy degree are selected as reference points. Then, based on the Manhattan distance between other individuals and the reference point, the operator representing distribution is calculated and the fitness function is improved. Finally, the fitness threshold is set to screen non-dominated individuals near the reference point, so as to indirectly adjust the environmental selection strategy, make the distribution of retained individuals more uniform, thus improving the convergence and diversity. As compared with some similar multi-objective optimization algorithms, the proposed CM-SPEA2 algorithm has certain advantages in solving IMOP, ZDT and VNT test problems.