Volume 46,Issue 5,2023 Table of Contents

1 Point cloud registration of vehicle-mounted lidar based on improved FPFH-ICP algorithm

JIANG Fengyang , LIU Yonggang , CHEN Zhihang , CHEN Zheng

2023, 46(5):1-10. DOI: 10.11835/j.issn.1000-582X.2022.105

[Abstract](570) [HTML](80) [PDF 4.75 M](871)

Abstract:
To solve the problems of low accuracy and slow calculating speed of the traditional point cloud registration methods for vehicle-mounted lidar, an improved FPFH-ICP registration combining fast point feature histograms (FPFH) initial matching with improved iterative closest point (ICP) accurate registration was proposed. Firstly, voxel grid and statistical-outlier-removal filter were used for preprocessing data before registration. Then, based on sample consensus initial alignment (SAC-IA), FPFH was used for initial registration to provide good pose information for accurate registration. Finally, a K-D tree was established, and a normal vector threshold was added to traditional ICP registration for accurate registration. In the experiments of four different scenarios, the root mean square error and registration time of the improved FPFH-ICP registration were reduced by 7.56% and 41.22%, respectively, compared with ICP registration, and by 30.28% and 18.95%, respectively, compared with point feature histograms (PFH) registration, suggesting that the improved FPFH-ICP registration can achieve accurate and efficient registration of point cloud data of vehicle-mounted lidar.

2 Modeling and optimizing the frame structures of PEMFCs

DONG Fan , YANG Daijun , LI Bing , MING Pingwen , ZHANG Cunman , XIAO Qiangfeng

2023, 46(5):11-20. DOI: 10.11835/j.issn.1000-582X.2023.05.002

[Abstract](423) [HTML](161) [PDF 2.95 M](959)

Abstract:
The frames in PEMFCs are usually bound with membrane by the adhesive. The frames function as the rigid protecting structure for membrane and play an important role in sealing. However, due to the complex operation environment in fuel cells, the performance of the frame and adhesive could be degraded, which could endanger the gas tightness of the whole fuel cells. Therefore, with the help of finite element software and cohesive element model, series of new-type frames were designed and compared. Their effects on the frame-adhesive samples were investigated. The results show that by making convex structure (triangle or trapezoid) on the low elasticity modulus frames surface can effectively extend the separated displacement of the sample. On the contrary, these new structures can degrade the adhesive performance in high elasticity modulus frames. Moreover, the sizes and shapes of the optimized structures also have effects on the adhesive performance. Furthermore, among the optimized structures, the convex triangle structure with the 1.5 mm base shows the best adhesive performance.

3 Method of contact ultrasonic-attenuation coefficient correction considering surface roughness

LIU Huaqiang , PENG Xianmin , ZHANG Guichuan , FU Tong , YIN Aijun

2023, 46(5):21-30. DOI: 10.11835/j.issn.1000-582X.2022.104

[Abstract](259) [HTML](69) [PDF 2.18 M](768)

Abstract:
The surface quality of material significantly affects the accurate measurement of the ultrasonic attenuation coefficient. According to the influence of surface roughness on the propagation of a vertical incident ultrasonic beam, a method of contact ultrasonic-attenuation coefficient correction considering surface roughness was proposed. Firstly, based on the correction theory of reflection coefficient of rough interface in the case of uncoupling and the calculation formula of reflection coefficient of smooth interface in the case of coupling, the formula of reflection coefficient of rough interface in the case of coupling was derived. Then, a method of contact ultrasonic attenuation coefficient correction including roughness information based on the formula of attenuation coefficient was proposed. Finally, cylinder specimens of 45 steel and 304 stainless steel with different surface roughness were prepared, and the ultrasonic measurement platform of attenuation coefficient was established. The influence of surface roughness on signal time domain and frequency domain was investigated to verify the validity and practicability of the proposed correction method. Experimental results show that the proposed attenuation model can effectively compensate the attenuation of ultrasonic backscattered signal caused by roughness, and the relative measurement error of transmission method is less than 6%.

4 Corrosion mechanism of aluminum alloy materials under high corrosion conditions

LI Bo , FAN Lei , SUN Bo , BAI Jie , MAO Xianyin , SONG Shoubo , YANG Daning , ZHANG Zhiqing , CHEN Keyu , DI Rui

2023, 46(5):31-39. DOI: 10.11835/j.issn.1000-582X.2022.103

[Abstract](424) [HTML](61) [PDF 3.70 M](849)

Abstract:
With the advantages of low density, low melting point, high specific strength and excellent corrosion resistance, aluminum alloys are widely used in aerospace, construction, shipbuilding and other industries. During service, the surface oxide film of aluminum alloys is susceptible to corrosion by active anions in the environment, causing serious damage to its performance. Therefore, studying the corrosion behavior of aluminum alloys in a highly corrosive environment is very important for engineering material selection. In this work, 6061 aluminum alloy, 2195 aluminum-lithium alloy and 7075 aluminum alloy were taken as the research objects, their corrosion process and mechanical properties in specific corrosive media were analyzed, and their corrosion morphology and mechanical properties in specific corrosive media were investigated. The results show that in the early stage of corrosion, in a corrosive environment with high Cl^-,

, and

^- concentrations, the oxide films of the three aluminum alloys undergo pitting corrosion after being damaged by anions, which exposes the matrix of the alloys to the corrosive environment, resulting in electrochemical corrosion. The corrosion of both 6061 aluminum alloy and 2195 aluminum-lithium alloy progresses from pitting corrosion to surface corrosion, while the 7075 aluminum alloy corrosion mode is intergranular corrosion. After corrosion, 6061 aluminum alloy maintains stable strength and plasticity, but the strength and plasticity of 7075 aluminum alloy and 2195 aluminum-lithium alloy are significantly reduced.

5 Ground wire energy extraction method for overhead transmission lines

HUANG Huan , DENG Yulong , MA Xiaohong , JIANG Xingliang , WU Jianrong , HU Qin , YANG Qi , LYU Qianyong , YANG Liuqing

2023, 46(5):40-49. DOI: 10.11835/j.issn.1000-582X.2021.217

[Abstract](329) [HTML](55) [PDF 1.39 M](909)

Abstract:
Taking energy from the ground wire is a way of supplying energy for all kinds of sensing and monitoring equipment in the power system transmission network. In this paper, firstly, the principle of taking electricity of a typical overhead ground wire was examined. Next, its equivalent parameter model was established. Finally, the equivalent voltage and equivalent impedance of the electricity taking port were mathematically derives. Simulation of a 220 kV line with ATP-EMTP software was carried out. The influence of the energy load on the distribution of ground wire current and the influence of factors including wire current, ground resistance, span range, energy load on the electricity parameters were analyzed. The results show that limited by the induced potential and ground wire self-impedance, the ground wire current did not exceed 10 A. The voltage showed an increasing trend with the increase of impedance, and finally stabilized at about 27 V. When the energy extraction load was 2.5 Ω, the maximum energy extraction power obtained was 175.03 W. These results provide a data basis for the design of subsequent energy takers.

6 Operation state assessment and situation prediction of distribution transformer for cloud edge collaboration

ZHANG Bo , LIU Haitao , PENG Gang , FAN Min , JIA Shitao , SUN Yong

2023, 46(5):50-61. DOI: 10.11835/j.issn.1000-582X.2021.218

[Abstract](271) [HTML](79) [PDF 2.65 M](870)

Abstract:
The construction of the Power Internet of Things has been under rapid progress. With the guidance of the “cloud-pipe-edge-terminal” construction system, this paper presents a general technical framework for operation state evaluation and trend prediction of distribution transformer. The framework is deployed in cloud center and edge nodes, and use the cloud edge collaboration mechanism to analyze and process massive power data so as to complete the operation management of large-scale distribution transformer cluster. The specific process includes extracting multi-dimensional characteristics of distribution transformer, such as basic state, real-time state and cumulative state, constructing evaluation index system, and realizing real-time portrait description of distribution transformer operation state through dynamic evaluation model. According to the time order and change trend of the characteristic data stream, Long Short-Term Memory network (LSTM) is used for extracting the regulations of characteristic data, and Support Vector Regression model (SVR) for its prediction. Then, the future characteristic data flow is obtained and input into the dynamic evaluation model to realize the future operation trend prediction of the distribution transformer. Finally, examples are given to illustrate the advanced nature and applicability of the technology framework.

7 Burst detection in district metering areas based on long sequence time-series forecasting

WEN Siqi , LONG Tianyu

2023, 46(5):62-71. DOI: 10.11835/j.issn.1000-582X.2021.267

[Abstract](293) [HTML](72) [PDF 1.39 M](591)

Abstract:
For the rapid detection of burst pipes in water supply networks of district metering area, a new prediction-classification-correction three-stage Infomer-Z-score algorithm was proposed. The Infomer-Z-score algorithm solves the problem of low data processing efficiency and abnormally low water consumption in traditional methods. In the prediction stage, the deep learning Informer algorithm was used to predict long sequence time-series of pressure data for the pipe network so as to improve the accuracy of water pressure prediction and the efficiency of data processing. In the classification stage, the robustness of water pressure data over time was improved by using a multi-threshold classification method. In the pipe burst simulation test, the Infomer-Z-score algorithm achieved a 99.5% (DA) detection accuracy with a 90.9% true positive rate (TPR), and a 1.7% false positive rate (FPR). Long sequence time-series pressure forecasting can be used not only for burst detection, but also for effective pressure control in the network to reduce the risk of bursts.

8 The characteristics of a manganese oxidizing bacterium AL-6 coupled with grapefruit peel biochar to repair groundwater polluted by electrolytic manganese slag field

AN Qiang , JIAO Yixiao , ZHANG Chenyi , DENG Shuman , JIN Ningjie , YANG Maolin

2023, 46(5):72-82. DOI: 10.11835/j.issn.1000-582X.2022.253

[Abstract](277) [HTML](80) [PDF 3.48 M](471)

Abstract:
In order to study the remediation of complex wastewater from the groundwater polluted by the electrolytic manganese slag field, the biochar made from pomelo peel was used as the immobilized carrier for the strain Acinetobacter baumannii AL-6 (MBC), and the strain biochar coupling system (MBC) was obtained. The comprehensive treatment performance of the coupling system for composite wastewater containing manganese, ammonia nitrogen and high calcium and magnesium ions was investigated, and a Sequential Batch Reactor (SBR) was constructed to explore its application potential in wastewater treatment. The experimental results showed that MBC removed 98.46% of manganese within 48 h. Compared with two independent experimental groups (biochar group and strain AL-6 group), MBC had an excellent synergistic effect on the removal of manganese and the average removal rate of manganese was 15.87 mg/(L?h), 1.09 times of that of the strain AL-6 and 14.33 times of that of the biochar group. In addition, MBC had a maximum removal rate of 71.92% for ammonia nitrogen, and also had a certain removal effect for calcium and magnesium ions, with removal rates of 41.46% and 26.95%, respectively. In the SBR, 90.1% of manganese and 85.44% of ammonia nitrogen were removed. The results show that immobilized biochar of strain AL-6 made from pomelo peel has great potential and can be used to treat wastewater polluted by electrolytic manganese slag.

9 Re-recognition of design and safety evaluation of high-grade steel mountain pipeline

HU Wenjun , ZHAO Yu , HU Kaiheng , CHEN Guiyu , FU Kaiwei , ZHANG Xiaopeng

2023, 46(5):83-92. DOI: 10.11835/j.issn.1000-582X.2021.266

[Abstract](206) [HTML](117) [PDF 2.41 M](630)

Abstract:
Permanent ground deformation (PGD) is one of the main causes of buckling, fracture and leakage of mountain pipeline, resulting in heavy loss of life and property. The existing “strain-based method” and technical standards cannot satisfy the urgent needs of design and safety evaluation of in-service high-grade steel pipelines in PGD zone and need further research. The current situation of “strain-based” failure discrimination is firstly analyzed and summarized. Technical actualities and imperfections of strain calculation methods (analytical, numerical, and experimental methods) and safety evaluation methods for pipe-soil interaction are indicated by the main patterns of pipe failure with the “allowable strain” and “calculated strain” under complex PDG working conditions. Future research topics and path of the design and safety evaluation based on actual working conditions and pipe-soil interactions are synthetically proposed, while considering the future development trend and production needs of mountain pipelines in China.

10 Optimization of generative adversarial network based image super-resolution by using image mask

JIANG Qilei , MA Yuanxi

2023, 46(5):93-101. DOI: 10.11835/j.issn.1000-582X.2023.05.010

[Abstract](341) [HTML](56) [PDF 2.35 M](548)

Abstract:
Inferring high resolution image from single low resolution (LR) input is ill-posed and deep learning helps to some extent. The latest algorithms take the advantage of the Generative Adversarial Network (GAN) and present photo-realistic results by learning low/high resolution mappings from super resolution datasets. However, training of GANs can be hard and traditional GAN-based architectures often exhibit noise and texture distortion in their super-resolution (SR) results. In this paper, a mask-aided adversarial training strategy for current GAN-based SR frameworks is proposed. During training, mask module helps the discriminator by introducing additional perceptual quality information with generator’s outputs and the ground truth images. In experiment, three current state-of-the-art GAN-based SR models are selected and the mask module is integrated into their adversarial training. The improved mask-aided models yield better results in both quantitative and qualitative benchmarks than the original ones. Mask module only modifies GAN framework and thus is suitable for many GAN-based solutions for further improving the SR perceptual quality.

11 Optimization of covariance distance measurement algorithm for multidimensional clustering analysis

LIU Yun , ZHANG Yi , ZHENG Wenfeng

2023, 46(5):102-110. DOI: 10.11835/j.issn.1000-582X.2023.05.011

[Abstract](222) [HTML](117) [PDF 1.30 M](468)

Abstract:
In order to use effective distance measurement methods to characterize the proximity of data objects in multi-dimensional clustering analysis, a covariance distance measurement (CDM) algorithm is proposed. First, fuzzy C-means (FCM) is used to assign weights to the data objects, so that the membership degree of each sample point relative to the category feature is obtained. Based on the membership degree, the difference degree of each sample is calculated. Then, as the first optimization criterion, the variance distance measure is used to replace the Euclidean distance measure in fuzzy clustering to make similar data objects closer. Finally, the covariance distance measure between the sample points is used as the second optimization criterion to make the different data objects separate from each other. The optimal solution is calculated iteratively with alternate fixed variables, so that the clustering index and distance measurement learning parameters are optimized at the same time, and better clustering results are obtained. Experimental results on different data sets show that compared with FCM-Sig and UNCA algorithms, CDM algorithm has better performance in clustering accuracy and algorithm convergence.

12 Text classification method based on improved long-short term memory network

LI Jianping , CHEN Haiou

2023, 46(5):111-118. DOI: 10.11835/j.issn.1000-582X.2023.05.012

[Abstract](263) [HTML](119) [PDF 1.14 M](594)

Abstract:
Traditional long-short term memory network (LSTM) cannot automatically select the most important latent semantic factors in text categorization. To solve the problem, this paper proposes an improved LSTM model. First, the traditional LSTM operation relationship is extended to the bidirectional mode, so that the network fully remembers the context of the input feature words. Then, the pooling layer is added in front of the output layer to better select the most important latent semantic factors. The experiment on the Internet Movie Database review data show that the model is superior to the traditional long-short term memory neural network and other similar models, revealing that the improved scheme proposed in this paper can improve the accuracy of text classification.

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