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| 1 | Leak Detection of Gas Pipelines Based on Characteristics of Acoustic Leakage and Interfering Signals显示文摘When acoustic method is used in leak detection for natural gas pipelines,the external interferences including operation of compressor and valve,pipeline knocking,etc.,should be distinguished with acoustic leakage signals to improve the accuracy and reduce false alarms.In this paper,the technologies of extracting characteristics of acoustic signals were summarized.The acoustic leakage signals and interfering signals were measured by experiments and the characteristics of time-domain,frequency-domain and time-frequency domain were extracted.The main characteristics of time-domain are mean value,root mean square value,kurtosis,skewness and correlation function,etc.The features in frequency domain were obtained by frequency spectrum analysis and power spectrum density,while time-frequency analysis was accomplished by short time Fourier transform.The results show that the external interferences can be removed effectively by the characteristics of time domain,frequency domain and time-frequency domain.It can be drawn that the acoustic leak detection method can be applied to natural gas pipelines and the characteristics can help reduce false alarms and missing alarms. | Lingya Meng Cuiwei Liu Liping Fang Yuxing Li Juntao Fu | 2019 | Sound & Vibration2019，53，4： | 2 |
| 2 | Path planning of the fruit tree pruning manipulator based on improved RRT-Connect algorithm显示文摘Aiming to realize the obstacle avoidance of the fruit tree pruning manipulator in unstructured complex natural environment,an improved bidirectional fast extended random tree(RRT-Connect)algorithm was presented in this study.The manipulator and obstacles were properly simplified based on their geometrical characteristics to build collision detection models taking account of the obstacles,ground,and manipulator itself and to carry out the obstacle avoidance path planning.Goal-biased strategy and adaptive step size adjustment principle were introduced to accelerate the path search speed.Bidirectional pruning optimal strategy and cubic non-uniform B-spline interpolation method were adopted to optimize the path generated by RRT-Connect.The simulation path planning experiment was carried out in the simulation system of the fruit tree pruning manipulator and the practical obstacle avoidance path planning experiment was carried out on the real fruit tree pruning manipulator path planning experiment platform.The results showed that the path planning time and the path length of the improved RRT-Connect algorithm reduced by about 55%and 60%respectively compared with the basic RRT-Connect algorithm.The path planning success rate of the improved RRT-Connect algorithm was 100%,and the planned path was smooth,continual and executable,which could effectively guide the manipulator to avoid obstacles and lead the end effector of the manipulator to the goal point.The proposed improved algorithm not only has certain application value for obstacle avoidance of the fruit tree pruning manipulator in fruit tree pruning environment,but also has theoretical reference value for path planning of other types of robots. | Yaya Chen Yuxing Fu Bin Zhang Wei Fu Congju Shen | 2022 | International Journal of Agricultural and Biological Engineering2022，15，2： | 0 |
| 3 | The Research of Carbon Emission and Carbon Sequestration Potential of Forest Vegetation in China显示文摘The study of China s carbon emissions and carbon sequestration potential is of great practical significance to the formulation of carbon neutrality strategies and methods of China.Carbon emission is an inevitable outcome of the initial stage of economic development,especially the right of developing countries existence and development.The carbon emission of China has been maintained at a low level for a long time and reached the top of the world in 2005.However,per capita carbon emission was still only 46.28%of the United States in 2016.China s total CO_(2) emissions are expected to reach 17-19 Gt/a by 2030.To achieve the goal of carbon neutrality in 2060,the main problems are the low technical capacity of emission reduction and the unreasonable structure of energy consumption.Therefore,replacing coal with gas is one of the most effective ways of emission reduction.By 2060,the carbon sequestration capacity of forest vegetation will reach or exceed 759.14 Mt/a and the CO_(2) sequestration capacity will reach 2783.5 Mt/a.According to that,China s carbon intensity must reduce by 95.39%on the basis of the carbon intensity in 2017,reaching 640 t/100 million yuan.The carbon sequestration capacity of terrestrial vegetation(forest,grassland)will reach or exceed 1380.3 Mt/a and the CO_(2) sequestration capacity will reach 5069.3 Mt/a.According to that,China s carbon intensity must reduce by 91.07%on the basis of the carbon intensity in 2017,reach 1152 t C per 100 million yuan. | Yuxing ZHANG Jingping YIN Yao FU Xuejun WANG Guosheng WANG | 2021 | Meteorological and Environmental Research2021，12，6： | 0 |
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