Volume 44,Issue 5,2021 Table of Contents

1 Evaluation of visual suitability of illumination color temperature in night lighting of ancient tower building

HOU Wanjun , JIA Tie , WANG Lixiong , WANG Qingchen , LI Jing

2021, 44(5):1-8. DOI: 10.11835/j.issn.1000-582X.2020.053

[Abstract](346) [HTML](803) [PDF 5.37 M](785)

Abstract:
Currently, the night lighting performance of pavilion-style ancient tower buildings is poor and there are few special studies in this area. In order to improve the current situation of poor night lighting effects of pavilion-style ancient tower buildings and optimize their color temperature to show visual suitability, on the basis of only considering the visual presentation of the color temperature effect, subjective evaluation experiments on the visual comfort of the color temperature of the night lighting under different simulation scenarios are carried out, combining with the actual environmental characteristics of the night lighting around the ancient tower, the presentation of the color temperature and the color temperature recommendation of the lighting manual. In the subjective evaluation experiment, the visual comfort evaluation value is used as the label, and C-SVM support vector machine (SVM) classification algorithm is used to construct the subjective evaluation model. By comparing the classification interface and results of different classification models through the scatter diagram and ROC curve, the best color temperature and brightness performance interval of pavilion-style ancient tower buildings and the mapping relationship between the visual comfort under different color temperature and brightness conditions are obtained. Then, the color temperature performance of the night lighting of the ancient towers is evaluated and predicted. Combining the C-SVM classification algorithm with the problems in the lighting field, this study provides a theoretical basis and guidance for designers to better use lighting methods to restore the essential architectural characteristics of pavilion-style ancient towers in people’s minds, so as to improve the night lighting effect of pavilion-style ancient tower buildings.

2 Study on the performance of phase change materials in thermal insulation of container buildings in summer

GUO Juanli , YANG Xinyue , LIU Gang , XU He

2021, 44(5):9-17. DOI: 10.11835/j.issn.1000-582X.2021.05.002

[Abstract](402) [HTML](1178) [PDF 4.98 M](816)

Abstract:
The energy consumption of the container that has no energy storage enclosure is large and its indoor temperature fluctuates greatly. The traditional enclosure design method cannot effectively maintain the indoor temperature in a comfortable temperature range. Application of phase change energy storage technology in the design of retaining structure of the container building can greatly improve its thermal performance and effectively adjust indoor temperature fluctuations. Taking the microcapsule phase change material as an example, the influence of parameters such as building internal disturbance and phase change layer design on temperature regulation performance was studied by using Design Builder software simulation analysis method. After analyzing the adaptive design method of phase change materials in the composite enclosure structure of container box, it is found that the phase change composite wall with 30 mm thick and phase change point of 29 ℃ can effectively improve the thermal comfort of the building in the summer. In addition, the optimal design method of phase change composite retaining structure and its influence on indoor thermal comfort are obtained. This study provides the theoretical support for the application of phase change materials in container building design and evaluation.

3 Numericals simulation method of cooling fan based on surface toughness correction

FU Jiahong , ZHANG Yu , XIAO Baolan , ZHANG Xufang , ZUO Qiang

2021, 44(5):18-25. DOI: 10.11835/j.issn.1000-582X.2020.056

[Abstract](491) [HTML](596) [PDF 1.10 M](780)

Abstract:
In order to further improve the numerical simulation accuracy of the multi-reference frame(MRF) model of cooling fan, the roughness of the model was modified by the wall function, and the influential factors of the MRF model were analyzed. Firstly, the algebraic relationship among roughness constant, roughness height and y⁺ was obtained based on the dimensionless velocity u⁺ and distance y⁺ of the first layer mesh from the wall in the viscous sublayer. Then, according to the actual wall type, the revised y⁺ value and the first layer mesh height were obtained, and they were substituted into the standard wall function for near wall correction. Finally, taking a cooling fan as an example, the effects of turbulence model, mesh number and surface roughness correction on the numerical simulation results of the fan were studied. The results show that the model can better deal with the flow with high strain rate and bending streamline, and is more suitable for the rotating flow of fans, and has higher accuracy for the simulation of rotating machinery such as fans. Over-dense mesh number will make the calculation results fluctuate. Surface roughness correction improves some abnormal points on the performance curve, and within the range of fan common operating conditions, the deviation between test values and simulation values reduced from 5% to 3% after correction.

4 Study on strength and deformation characteristics of loess under nonlinear continuous unloading path

FU Yingpeng , LIAO Hongjian , LIU Xuegang , LI Yao , ZHANG Jiwen

2021, 44(5):26-37. DOI: 10.11835/j.issn.1000-582X.2020.05.004

[Abstract](399) [HTML](682) [PDF 8.44 M](745)

Abstract:
The strength and deformation characteristics of loess under vertical unloading state have important theoretical significance for the study of slope instability in excavation area. From the perspective of engineering application, this paper improves the indoor direct shear apparatus based on Bernoulli equation, which uses water tank instead of weight to load and unload. The strength and deformation characteristics of remolded loess under nonlinear continuous unloading path are studied. The results show that the shear stress-displacement curve of the soil under the nonlinear continuous unloading path is different from that under the non-loading state, which is reflected in that the shear stress in the process of nonlinear continuous unloading is related not only to the shear displacement but also to the unloading ratio (R). In the shear stress (τ)-shear displacement (δ) space, under the same initial consolidation pressure, the shear stress-shear displacement curve of the sample is basically coincident with that without unloading when the unloading ratio (R) is small. When the unloading ratio (R) increases to a certain value, the shear stress-shear displacement curve appears softening, and the greater the unloading rate, the more obvious the softening is. At the same time, under nonlinear continuous unloading conditions, the shear strength is related to the initial consolidation pressure. With the increase of the initial consolidation pressure, the over-consolidation effect caused by unloading increases significantly. Based on Mohr-Coulumb strength criterion, the mathematical model of exponential decay can be used to describe the evolution of the strength parameters in the process of nonlinear continuous unloading.

5 Online parameters identification method of Bouc-Wen model based on modified particle algorithm

WANG Tao , LIU Yuan , PAN Yi , MENG Liyan , BAO Yunlei

2021, 44(5):38-49. DOI: 10.11835/j.issn.1000-582X.2020.055

[Abstract](746) [HTML](1181) [PDF 6.57 M](784)

Abstract:
Online model parameter updating is an effective method to improve the model accuracy of numerical substructure in the hybrid simulation. In order to improve the precision of online parameters identification for the nonlinear model, an improved auxiliary unscented particle filter (AUPF) was proposed in this paper base on the standard particle filter algorithm. In the stage of the importance sampling, the unscented Kalman filter (UKF) method was adopted to calculate estimates of all particles using the latest observation information in order to improve estimation precision of the nonlinear transformation of the particles. In the stage of the resampling, an auxiliary factor was introduced to modify particle weights, which enriched the particle diversity and weaken the particle degradation phenomenon. Parameters online identification for the Bouc-Wen were conducted with the AUPF, and both the identification precision and the calculation efficiency of results were compared with the standard particle filter algorithm (PF), The rextended Kalman particle filter algorithm (EPF), and unscented particle filter algorithm (UPF). The results show that compared with the other three algorithms, the proposed AUPF algorithm can effectively improve the precision of online parameters identification of the Bouc-Wen model and reduce the fluctuation of parameters identification values on the basis of increasing computing time-consuming in a single step. Finally, the effectiveness of the Bouc-Wen model parameter identification method using the AUPF algorithm was verified through the quasi-static test of the rubber isolation bearing.

6 Mechanical properties of emulsified asphalt cold recycling mixture with different forming methods

YI Yong , JIANG Yingjun , TAN Yunpeng , HU Yonglin , CHEN Zhejiang

2021, 44(5):50-58. DOI: 10.11835/j.issn.1000-582X.2020.211

[Abstract](366) [HTML](1035) [PDF 4.71 M](537)

Abstract:
In order to investigate the influence of different moulding methods on the mechanical properties of cold recycled emulsified asphalt mixture, the effects of vertical vibration method and traditional method on the mechanical properties of cold recycled asphalt mixture were studied by preparing Marshall specimens and cylinder specimens, and the fatigue equation was established by Weibull distribution. The results show that by the vertical vibration method, the optimal moisture content and optimal emulsified asphalt content of the mixture are reduced by 10% respectively, and the maximmum dry density of the mixtare are increased 1.021 times, compared with the mixture by the traditional method. Compared with Marshall Specimens, the Marshall stability M_S, 25 ℃splitting strength and freeze-thaw splitting strength of vertical vibration cylinder specimens increase by 40%, 32% and 57% respectively. Through the intercept a and slope b of fatigue equation, it can be seen that the fatigue resistance and sensitivity of vertical vibration specimens to stress change under high stress are better than those of Marshall method specimens, that is, the value of a in the vertical vibration method is greater than that of Marshall method, and the value of b in the vertical vibration method is less than that of Marshall method.

7 Experimental research on zipped ice-shedding of transmission line under the influence of multiple parameters

LI Mengzhu , YAN Zhitao , XIONG Hui , YOU Yi

2021, 44(5):59-67. DOI: 10.11835/j.issn.1000-582X.2020.209

[Abstract](303) [HTML](501) [PDF 2.13 M](589)

Abstract:
The dynamic tension caused by the ice-shedding of the transmission lines will cause the line fracture and collapse. Taking a project as the prototype, this paper designed a test model of an iced conductor with scale ratio of 1∶30 on the basis of dynamic similarity theory to simulate the ice shedding of transmission lines, using electromagnet to control the shedding of concentrated weight in the cases of zippered and simultaneous ice-shedding. The influence of deicing velocity, deicing direction, elevation difference and vibration-proof hammer on the vibration response of transmission lines ice-shedding were studied. The results show that the displacement of zippered ice-shedding is lower than that of simultaneous ice-shedding. Whether it is zippered ice-shedding or simultaneous ice-shedding, the maximum jump height of zippared ice-shedding decreases with the decrease of the deicing velocity, and eventually reaches up to 50% of simultaneous ice-shedding. With the vibration-proof hammer, the jump height of zippered ice-shedding is more obvious.The maximum jump height of the mid span increases sharply with the increase of the elevation difference angle, and the deicing mode from the middle to both sides is the most unfavorable.

8 Precision pre-evaluation method for high-voltage distribution network project considering business status and overall situation of the whole network

ZHANG Lin , WANG Hao , DENG Qiang , XIANG Fei , HUANG Gang , LU Zhengmei , YAN Wei

2021, 44(5):68-77. DOI: 10.11835/j.issn.1000-582X.2020.213

[Abstract](348) [HTML](557) [PDF 969.66 K](685)

Abstract:
Existing pre-evaluation methods for high-voltage distribution network project do not consider the power supply company’s investment ability and the overall techno-economic status of the whole high-voltage distribution network, which may cause great investment risk and "repetitive investment". Moreover, these methods evaluate the local network influenced by the project based on a single rather than sequential load status, which cannot reflect the local network’s condition from the perspective of the whole year. Therefore, the proposed method firstly evaluates the company’s business status(CBS) and the overall situation of the whole network(OSWN). Then the whole year’s sequential operation state of the local network is simulated and evaluated. The simulation results show that the method can reflect the influence of CBS, the OSWN and the project’s improvement effect from the perspective of the whole year.

9 Drive and light intensity stabilization method of hot cathode low-pressure mercury lamp

QIN Yuqian , DUAN Fajie , FU Xiao , HUANG Tingting

2021, 44(5):87-94. DOI: 10.11835/j.issn.1000-582X.2020.216

[Abstract](589) [HTML](1152) [PDF 1.68 M](924)

Abstract:
Hot cathode low-pressure mercury lamp can be used as the light source for cold atomic absorption mercury detector, but the light intensity has problems of large fluctuation and serious drift when the lamp is driven by the conventional electronic ballast. This condition cannot meet the low detection limit requirement. Therefore, a lamp drive and light intensity stabilization method is proposed in this paper. To realize warm-up start and maintain normal illumination of lamp, a self-excited current-fed push-pull resonant inverter was constructed, and the parameters were designed according to the equivalent circuit model. To improve the light intensity stability, a closed-loop control system with light intensity feedback mode was established, and the frequency domain of the system was analyzed and optimized. The feasibility of circuit was verified by simulation. The stability of light intensity was tested by a cold atomic absorption mercury detector. The results show that the mercury light intensity fluctuation is less than 0.15‰, and the baseline drift is less than 0.06‰ within 50 min.

10 Inspecting defects of ACCC by linear scanning CT

LYU Zhongbin , TIAN Zhongjian , LIU Guanghui , ZHANG Bo , YE Zhongfei , LIU Fenglin

2021, 44(5):95-103. DOI: 10.11835/j.issn.1000-582X.2021.05.011

[Abstract](546) [HTML](737) [PDF 2.95 M](738)

Abstract:
As one of the common capacity-building conductors, aluminum conductor composite core (ACCC) is widely used in overhead power transmission lines. However, its mandrel is vulnerable to damage in the construction process, which may lead to breakage of conductor strand and wire. Therefore it is urgent to study the nondestructive testing technique for ACCC in service. Because the ACCC is made of outer aluminum conductor and inner composite core, the traditional detection methods cannot effectively inspect the defects in the mandrel. This paper proposes a method to detect defects of in-service ACCC using a linear scanning computed tomography (CT). In this CT method, an X ray source and a detector are moved in a relatively parallel line around the fixed detection object, which has the advantages of simple structure and convenient installation. Furthermore, one and two linear CT scanning modes are designed according to different situations, and the corresponding principle experiment platform is built. The three common mandrel defects of fracture, split and crack were tested in small batches under laboratory conditions. The experimental results show that one relative linear scanning CT can be used for rapid detection of mandrel defects with large defects, and two relative linear scanning CT can be used for fine detection of small defects existing in mandrel. Compared to traditional X-ray transmission imaging detection, the method in this paper provides a new idea and reference for inspecting the internal defects of the ACCC.

11 Control of hydrostatic transmission based on BP neural network

CHEN Yang , YAO Liping , XIE Shouyong , LI Mingsheng , ZHANG Junhui

2021, 44(5):104-114. DOI: 10.11835/j.issn.1000-582X.2021.05.012

[Abstract](426) [HTML](567) [PDF 1.86 M](798)

Abstract:
The maneuverability of hydrostatic transmission (HST) is a key factor in improving the performance of agricultural vehicles. In this paper, a new control strategy based on BP (back propagation) neural network is applied to study the dynamic characteristics of the output speed of HST motor. First, the control effects of traditional PID, fuzzy and BP neural network are compared based on the mathematical model of variable pump-quantitative motor. The results indicated that compared to traditional PID control and fuzzy control, BP neural network control can not only effectively suppress the overshoot of the system, but also reduce the fluctuation of motor speed and the adjustment time for system to reach stability. And it has excellent robustness. Therefore, the BP neural network is suggested in this paper to investigate the control effect of the variable pump-variable motor system (VPVM system) with larger motor speed variation range. The results show that this method can be used to achieve stable switching effect and reduce performance loss in segmented control of variable pump and variable motor. For the cases of different equivalent moment of inertia of load, all the motor speed can reach a stable state and the speed fluctuation caused by the load is reduced. The results indicate that BP neural network has a potential advantage in VPVM system control.

12 UKF-based optimization algorithm for asynchronous data fusion of wireless sensor

ZHANG Hui , HUANG Xiangsheng

2021, 44(5):115-123. DOI: 10.11835/j.issn.1000-582X.2021.05.013

[Abstract](347) [HTML](676) [PDF 1.81 M](912)

Abstract:
A UKF-based algorithm for asynchronous data fusion of wireless sensor is proposed. The RNAT mechanism is used to identify redundant nodes in the wireless sensor network, and a data redundancy tree is constructed to implement redundant data removal. According to the result of deduplication, in the environment where the radius of each sensor's detection range is equal, two nodes that detect the target information are arbitrarily selected by the four-circle positioning method to calculate the intersection of the boundaries of two circular detection regions, finding and approximating the target according to the iterative method. The preconditions that the original sensors of different sensors are independent of each other and the different original quantity measurements of the same sensor are independent of each other are set, and the measured values of each channel are calculated. The unmeasured Kalman filter is used to update the measured value in the form of filtering, the Kalman filter gain matrix is introduced, and the asynchronous data positioning result is combined to realize data fusion. The experimental results show that the data utilization after fusion is higher than the current results, and the algorithm has short time-consuming, low energy consumption, and high data fusion precision. The accuracy of the whole fusion is more than 90%.

13 Precise motion control design of three-wheeled mobile robots

WEN Xiangrong , ZHOU Yusheng

2021, 44(5):124-134. DOI: 10.11835/j.issn.1000-582X.2021.05.014

[Abstract](431) [HTML](786) [PDF 809.10 K](1110)

Abstract:
At first, the non-holonomic and holonomic constraints of the three-wheeled mobile robot were clarified by means of its geometric relation. Then, its dynamical equation was deduced by using the Euler-Lagrange equation of non-holonomic mechanical systems. In order to make the three-wheeled mobile robot move along a given trajectory curve accurately, the target trajectory curve was transformed into a speed form. After that, the speed target was converted to a form approximating to the actual initial speed by introducing a differential homeomorphic transformation. In this case, the initial speed error and cumulative position error of the controlled systems can be minimized. Finally, the trajectory tracking control of the three-wheeled mobile robot was designed by using optimal control and integral sliding mode control. Simulation results show that the proposed control method can compel the three-wheeled mobile robot to move along a given trajectory curve accurately with a certainty of robustness.

14 3D soil layer reconstruction of deep foundation pit based on machine learning

WANG Zhuhe , LI Nan , ZHANG Xirui , SU Xiang

2021, 44(5):135-145. DOI: 10.11835/j.issn.1000-582X.2021.05.015

[Abstract](550) [HTML](618) [PDF 2.52 M](825)

Abstract:
In the process of deep foundation pit construction, a small amount of borehole data is needed to reconstruct the 3D model of the soil layer to obtain the distribution of soil information. This paper proposes a method of soil layer reconstruction based on machine learning. First, a soil layer generation algorithm is designed to enhance the data of the soil layer training data set. Then, the prediction model feature coding method is designed according to the data structure of the borehole information. As the standard input of the prediction model, the convolutional neural network model is built to extract the features of the soil layer structure to form the soil layer prediction model. Subsequently, the prediction model is used to predict the soil layer attributes of the discrete grid points in the predicted block to obtain soil layer data. Finally, the Marching Cubes algorithm is used to generate closed isosurfaces for the soil layer data to form solid blocks of the soil layer, thereby realizing the reconstruction of the three-dimensional soil layer. This model can adapt to different layers and different types of strata, and has the preliminary conditions for practical engineering applications.

15 Control radar target calibration method using improved density-based spatial clustering of applications with noise (DBSCAN) algorithm

JIN Huibin , LIU Haibo , HU Zhanyao , HUO Baiming

2021, 44(5):146-154. DOI: 10.11835/j.issn.1000-582X.2021.05.016

[Abstract](436) [HTML](534) [PDF 1.06 M](624)

Abstract:
In order to explore the target calibration method of air traffic control radar based on eye movement data, the radar control simulator and eye tracker and other devices were used to build an experimental platform. Eight controller students were recruited to participate in the simulation control experiment and eye movement data were collected. Based on the collected eye movement data, the radar target calibration was performed by using the DBSCAN algorithm. However, it is found that the subjective input parameters will lead to the inability to complete the clustering well. Therefore, we propose to improve the DBSCAN algorithm from the two aspects of adaptive selection of neighborhood values and variable density threshold design based on the K-nearest neighbor algorithm and the variable density threshold setting method. And the adaptive operation of the algorithm is realized. The method of determining the neighborhood value by using the fitting distribution density function extreme point and the amplification factor in the improvement process was verified. And the error of other radar targets is only 8.6% and 10%, indicating that the improved processing method has certain applicability. By comparing the extraction results of different aircraft target areas of interest, it is found that the proposed method of calibrating radar targets has certain accuracy and universality.

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