In this paper, the authors put forward a brief and practical arithmetic for auto extracting terrain lines from digital terrain data after analyzing and comparing current arithmetics.This paper gives an experiment resu...In this paper, the authors put forward a brief and practical arithmetic for auto extracting terrain lines from digital terrain data after analyzing and comparing current arithmetics.This paper gives an experiment result that the ridge and valley extracted by the arithmetic is consistent with the experimental terrain.展开更多
Some agriculture machinery like the transplanter,needs to operate by following the crop-free ridges.In order to improve working efficiency and quality,some autonomous navigation systems were developed and applied to r...Some agriculture machinery like the transplanter,needs to operate by following the crop-free ridges.In order to improve working efficiency and quality,some autonomous navigation systems were developed and applied to ridge-following machinery.At present,agricultural navigation systems are mainly the satellite navigation system and the machine vision system.The satellite navigation system is difficult to apply to the machinery that needs to work by following the ridge because it cannot distinguish the shape of the navigated ridge and guide the machinery working along the ridge.In this study,697 cloudy ridge images and 235 sunny ridge images were taken in the field,and these images were used as the dataset.Moreover,a machine vision navigation method based on the color of ridges was proposed.Firstly,the regions of interest(ROI)in the ridge image were extracted according to the reaction time and the forward speed of the machine.Then,a gray reconstruction method was used to enlarge the color difference between the ridge and the furrow.The optimal threshold for the gray image segmenting was calculated real-timely by using the threshold segmentation method.Then,based on the contour detection method,the ridge contour which was not surrounded by holes was extracted.Finally,the approximate quadrilateral method was proposed to recognize the ridge center line as the navigation line.The method proposed in this study was verified by four types of ridges with different colors and textures.The experimental results showed that the recognition success rates of the light ridge,the dark ridge,the film-covered ridge,and the sunny ridge were 100%,97.5%,100%,and 98.7%,respectively.The recognition success rate of the proposed method was at least 8%higher than that of the existing ridge-furrow recognition methods.The results indicate that this method can effectively realize navigation line recognition.This method can provide technical support for the autonomous navigation of agricultural machinery,such as transplanters,seeders,etc.,operating on the ridge without crops.展开更多
The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS...The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS） of the rotational motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic motions completely; the characteristics of each component, especially rotational motions, need to be studied. The damage line of the structure and TFRS of ground motion are important for seismic design, only the TFRS of input seismic wave is suitable, the structure design is reliable.展开更多
The analysis of the 40-year averaged daily data in this paper suggests that the vertical structure and movement of subtropical high (SH) ridge in summer evidently differ in different areas,which is close related with ...The analysis of the 40-year averaged daily data in this paper suggests that the vertical structure and movement of subtropical high (SH) ridge in summer evidently differ in different areas,which is close related with spatially nonuniform heating.The SH ridge over the West Pacific tilts northwards with height,while one over the Central Pacific tilts southwards.The northward movements of the Central/West Pacific SH ridges both show distinct low frequency oscillations of 10-20 days,and the movement over the East Asian monsoon area shows obvious oscillations of quasi-40-days as well.The analysis shows that the solar radiation drives the seasonal meridional movement of SH,while the spatially nonuniform heating modifies its movement speed and intensity,thus resulting in its anomalous motion.展开更多
文摘In this paper, the authors put forward a brief and practical arithmetic for auto extracting terrain lines from digital terrain data after analyzing and comparing current arithmetics.This paper gives an experiment result that the ridge and valley extracted by the arithmetic is consistent with the experimental terrain.
基金financially supported by the Construction of Technical System of Green Leafy Vegetable Industry in Shanghai-Development and application of key technologies for high-density transplanting of green leafy vegetables[Shanghai Agricultural Science and Production(2023)No.2]the Jiangsu Provincial Key Research and Development Program(Grant No.BE2021342)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions(No.PAPD-2023-87).
文摘Some agriculture machinery like the transplanter,needs to operate by following the crop-free ridges.In order to improve working efficiency and quality,some autonomous navigation systems were developed and applied to ridge-following machinery.At present,agricultural navigation systems are mainly the satellite navigation system and the machine vision system.The satellite navigation system is difficult to apply to the machinery that needs to work by following the ridge because it cannot distinguish the shape of the navigated ridge and guide the machinery working along the ridge.In this study,697 cloudy ridge images and 235 sunny ridge images were taken in the field,and these images were used as the dataset.Moreover,a machine vision navigation method based on the color of ridges was proposed.Firstly,the regions of interest(ROI)in the ridge image were extracted according to the reaction time and the forward speed of the machine.Then,a gray reconstruction method was used to enlarge the color difference between the ridge and the furrow.The optimal threshold for the gray image segmenting was calculated real-timely by using the threshold segmentation method.Then,based on the contour detection method,the ridge contour which was not surrounded by holes was extracted.Finally,the approximate quadrilateral method was proposed to recognize the ridge center line as the navigation line.The method proposed in this study was verified by four types of ridges with different colors and textures.The experimental results showed that the recognition success rates of the light ridge,the dark ridge,the film-covered ridge,and the sunny ridge were 100%,97.5%,100%,and 98.7%,respectively.The recognition success rate of the proposed method was at least 8%higher than that of the existing ridge-furrow recognition methods.The results indicate that this method can effectively realize navigation line recognition.This method can provide technical support for the autonomous navigation of agricultural machinery,such as transplanters,seeders,etc.,operating on the ridge without crops.
基金funded by the National Natural Science Foundation of China under grant No.50578125
文摘The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS） of the rotational motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic motions completely; the characteristics of each component, especially rotational motions, need to be studied. The damage line of the structure and TFRS of ground motion are important for seismic design, only the TFRS of input seismic wave is suitable, the structure design is reliable.
基金This work was financially supported by the Key Project (No.40135020) of the National Natural Science Foundation of China
文摘The analysis of the 40-year averaged daily data in this paper suggests that the vertical structure and movement of subtropical high (SH) ridge in summer evidently differ in different areas,which is close related with spatially nonuniform heating.The SH ridge over the West Pacific tilts northwards with height,while one over the Central Pacific tilts southwards.The northward movements of the Central/West Pacific SH ridges both show distinct low frequency oscillations of 10-20 days,and the movement over the East Asian monsoon area shows obvious oscillations of quasi-40-days as well.The analysis shows that the solar radiation drives the seasonal meridional movement of SH,while the spatially nonuniform heating modifies its movement speed and intensity,thus resulting in its anomalous motion.
