Grapevine shelter cultivation produces some influence on the quality of grape berry,at the same time of reducing the occurrence of diseases.Under the condition of rain-shelter cultivation,the effects of microenvironme...Grapevine shelter cultivation produces some influence on the quality of grape berry,at the same time of reducing the occurrence of diseases.Under the condition of rain-shelter cultivation,the effects of microenvironment,such as light,temperature and humidity,on the quality of grape berry were investigated in this paper.In addition,the relationships between microenvironmental changes and sugar,acid,color,aromatic substances and phenolic substances contents of the grape berry were analyzed.The current research status was analyzed,and the future study direction was discussed.展开更多
This paper presents a vision-based obstacle avoidance method for blind pedestrians in an outdoor sidewalk environ- ment. Unlike many existing travel-aid systems using stereo-vi- sion based methods, the proposed method...This paper presents a vision-based obstacle avoidance method for blind pedestrians in an outdoor sidewalk environ- ment. Unlike many existing travel-aid systems using stereo-vi- sion based methods, the proposed method is able to get obstacle position as well as user motion information by just one monocu- lar camera fixed at the belly of the user. To achieve this goal, a top-view transformation of the road image is used for obstacle detection and user motion estimation, based on which a grid map is generated for navigation. For detection part, the bottom points of erect obstacles are detected by extracting local-maxima and minima on the top-view image while user motion is estimat- ed by analysing the optical flow vector field in the user sur- rounding area. For the obstacle avoidance part, a step score is calculated on the grid map for evaluating the safety of next moving step. Experiments with several sidewalk video-clips show that the proposed obstacle avoidance method is able to provide useful guidance instructions under certain sidewalk environments.展开更多
For real-time and distributed features of multi-robot system,the strategy of combining the improved artificial potential field method and the rules based on priority is proposed to study the collision avoidance planni...For real-time and distributed features of multi-robot system,the strategy of combining the improved artificial potential field method and the rules based on priority is proposed to study the collision avoidance planning in multi-robot systems. The improved artificial potential field based on simulated annealing algorithm satisfactorily overcomes the drawbacks of traditional artificial potential field method,so that robots can find a local collision-free path in the complex environment. According to the movement vector trail of robots,collisions between robots can be detected,thereby the collision avoidance rules can be obtained. Coordination between robots by the priority based rules improves the real-time property of multi-robot system. The combination of these two methods can help a robot to find a collision-free path from a starting point to the goal quickly in an environment with many obstacles. The feasibility of the proposed method is validated in the VC-based simulated environment.展开更多
This paper demonstrates how much the forest was used by medieval writers as a symbolic space where critical events take place deeply affecting their protagonists. The forest motif can be found in the works of St. Augu...This paper demonstrates how much the forest was used by medieval writers as a symbolic space where critical events take place deeply affecting their protagonists. The forest motif can be found in the works of St. Augustine as well as in Dante＇s Divina Commedia （ca. 1308-1321）, and then in a plethora of other texts. Here the author examines more closely the symbolic meaning of the forest as a mysterious, dangerous, yet also spiritual location in Wolfram von Eschenbach＇s Titurel （ca. 1220） and then in two 15th-century prose novels： Thtiring von Ringoltingen＇s Melusine （1456） and the anonymous Fortunatus （1509）. Each time we recognize how much the poets placed their central figures one in the forest where their life takes a major turn. Recognizing this intriguing function of the forest as a metaphor and symbol, we can employ the modern interest in and fascination with the forest as a refuge from the destruction of the natural environment through modem civilization as segue to attract students to the study of medieval literature once again.展开更多
Using 3-dimensional Langevin dynamics simulations, we investigated the dynamics of loop formation of chains with excluded volume interactions, and the stability of the formed loop. The mean looping time ι1/scales wit...Using 3-dimensional Langevin dynamics simulations, we investigated the dynamics of loop formation of chains with excluded volume interactions, and the stability of the formed loop. The mean looping time ι1/scales with chain length N and corresponding scaling exponent α increases linearly with the capture radius scaled by the Kuhn length a/l due to the effect of finite chain length. We also showed that the probability density function of the looping time is well fitted by a single exponential. Finally, we found that the mean unlooping time ιu hardly depends on chain length N for a given a/l and that the stability of a formed loop is enhanced with increasing a/l.展开更多
Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata in large aggregations, which is often ex...Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata in large aggregations, which is often explained by its preferences for conspecifics, though direct evidence for such preferences has been rather limited so far. We studied the reactions of zebra mussels to con- specifics, hypothesizing that they may either be attracted to one another or form aggregations only in the absence of alternative attachment sites, in Experiment 1, we tested mussel tendency to detach from existing druses depending on druse size （2-25 individuals） and substratum type （soft： sand; hard： glass）. Mussels detached significantly more often on the hard substratum and from larger druses compared to soft substratum and smaller druses, respectively. This indicates that mussels tended to avoid conspecifics at high density, particularly when alternative substratum was available. In Experiment 2, we tested the responses of single mussels to distant （3 or 15cm） conspecifics （0, 3, 15 individuals per 2.51 tank） on the sandy substratum. The presence of conspecifics, regardless of their distance and density, resulted in single unattached mussels staying more often in their initial positions. Mussels did not move preferentially towards or away from the conspecifics. Thus, even on unsuitable substratum mussels were not attracted by conspecifics and probably exhibited an avoidance reaction by reducing their movement. This suggests that dense mussel aggregations are formed due to the lack of available alternative attachment sites rather than due to their preferences for conspecifics.展开更多
Obstacle avoidance is quite an important issue in the field of legged robotic applications, such as rescuing and detecting in complicated environment. Most related researchers focused on the legged robot’s gait gener...Obstacle avoidance is quite an important issue in the field of legged robotic applications, such as rescuing and detecting in complicated environment. Most related researchers focused on the legged robot’s gait generation after ssuming that obstacles have been detected and the walking path has been given. In this paper we propose and validate a novel obstacle avoidance framework for a six-legged walking robot Hexapod-III in unknown environment. Throughout the paper we highlight three themes: (1) The terrain map modeling and the obstacle detection; (2) the obstacle avoidance path planning method; (3) motion planning for the legged robot. Concretely, a novel geometric feature grid map (GFGM) is proposed to describe the terrain. Based on the GFGM, the obstacle detection algorithm is presented. Then the concepts of virtual obstacles and safe conversion pose are introduced. Virtual obstacles restrict the robot to walk on the detection terrain. A safe path based on Bezier curves, passing through safe conversion poses, is obtained by minimizing a penalty function taking into account the path length subjected to obstacle avoidance. Thirdly, motion planning for the legged robot to walk along the generated path is discussed in detail. At last, we apply the proposed framework to the Hexapod-III robot. The experimental result shows that our methodology allows the robot to walk safely without encountering with any obstacles in unknown environment.展开更多
文摘Grapevine shelter cultivation produces some influence on the quality of grape berry,at the same time of reducing the occurrence of diseases.Under the condition of rain-shelter cultivation,the effects of microenvironment,such as light,temperature and humidity,on the quality of grape berry were investigated in this paper.In addition,the relationships between microenvironmental changes and sugar,acid,color,aromatic substances and phenolic substances contents of the grape berry were analyzed.The current research status was analyzed,and the future study direction was discussed.
基金supported by the Brain Korea 21 Project in2010the ITRC support program supervised by the NIPA(National IT Industry Promotion Agency)(NIPA-2010-(C1090-1021-0010))
文摘This paper presents a vision-based obstacle avoidance method for blind pedestrians in an outdoor sidewalk environ- ment. Unlike many existing travel-aid systems using stereo-vi- sion based methods, the proposed method is able to get obstacle position as well as user motion information by just one monocu- lar camera fixed at the belly of the user. To achieve this goal, a top-view transformation of the road image is used for obstacle detection and user motion estimation, based on which a grid map is generated for navigation. For detection part, the bottom points of erect obstacles are detected by extracting local-maxima and minima on the top-view image while user motion is estimat- ed by analysing the optical flow vector field in the user sur- rounding area. For the obstacle avoidance part, a step score is calculated on the grid map for evaluating the safety of next moving step. Experiments with several sidewalk video-clips show that the proposed obstacle avoidance method is able to provide useful guidance instructions under certain sidewalk environments.
基金Sponsored by the Science Foundation for Youths of Heilongjiang province (Grant No.QC08C05)
文摘For real-time and distributed features of multi-robot system,the strategy of combining the improved artificial potential field method and the rules based on priority is proposed to study the collision avoidance planning in multi-robot systems. The improved artificial potential field based on simulated annealing algorithm satisfactorily overcomes the drawbacks of traditional artificial potential field method,so that robots can find a local collision-free path in the complex environment. According to the movement vector trail of robots,collisions between robots can be detected,thereby the collision avoidance rules can be obtained. Coordination between robots by the priority based rules improves the real-time property of multi-robot system. The combination of these two methods can help a robot to find a collision-free path from a starting point to the goal quickly in an environment with many obstacles. The feasibility of the proposed method is validated in the VC-based simulated environment.
文摘This paper demonstrates how much the forest was used by medieval writers as a symbolic space where critical events take place deeply affecting their protagonists. The forest motif can be found in the works of St. Augustine as well as in Dante＇s Divina Commedia （ca. 1308-1321）, and then in a plethora of other texts. Here the author examines more closely the symbolic meaning of the forest as a mysterious, dangerous, yet also spiritual location in Wolfram von Eschenbach＇s Titurel （ca. 1220） and then in two 15th-century prose novels： Thtiring von Ringoltingen＇s Melusine （1456） and the anonymous Fortunatus （1509）. Each time we recognize how much the poets placed their central figures one in the forest where their life takes a major turn. Recognizing this intriguing function of the forest as a metaphor and symbol, we can employ the modern interest in and fascination with the forest as a refuge from the destruction of the natural environment through modem civilization as segue to attract students to the study of medieval literature once again.
基金supported by the National Natural Science Foundation of China(21225421,21174140)the National Basic Research Program of China(2014CB845605)the Hundred Talents Program of the Chinese Academy of Science
文摘Using 3-dimensional Langevin dynamics simulations, we investigated the dynamics of loop formation of chains with excluded volume interactions, and the stability of the formed loop. The mean looping time ι1/scales with chain length N and corresponding scaling exponent α increases linearly with the capture radius scaled by the Kuhn length a/l due to the effect of finite chain length. We also showed that the probability density function of the looping time is well fitted by a single exponential. Finally, we found that the mean unlooping time ιu hardly depends on chain length N for a given a/l and that the stability of a formed loop is enhanced with increasing a/l.
文摘Zebra mussel Dreissena polymorpha is a Ponto-Caspian species invasive in Europe and North America, with great environmental impact. It lives byssally attached to hard substrata in large aggregations, which is often explained by its preferences for conspecifics, though direct evidence for such preferences has been rather limited so far. We studied the reactions of zebra mussels to con- specifics, hypothesizing that they may either be attracted to one another or form aggregations only in the absence of alternative attachment sites, in Experiment 1, we tested mussel tendency to detach from existing druses depending on druse size （2-25 individuals） and substratum type （soft： sand; hard： glass）. Mussels detached significantly more often on the hard substratum and from larger druses compared to soft substratum and smaller druses, respectively. This indicates that mussels tended to avoid conspecifics at high density, particularly when alternative substratum was available. In Experiment 2, we tested the responses of single mussels to distant （3 or 15cm） conspecifics （0, 3, 15 individuals per 2.51 tank） on the sandy substratum. The presence of conspecifics, regardless of their distance and density, resulted in single unattached mussels staying more often in their initial positions. Mussels did not move preferentially towards or away from the conspecifics. Thus, even on unsuitable substratum mussels were not attracted by conspecifics and probably exhibited an avoidance reaction by reducing their movement. This suggests that dense mussel aggregations are formed due to the lack of available alternative attachment sites rather than due to their preferences for conspecifics.
基金supported by the National Basic Research Program of China (Grant No. 2013CB035501)
文摘Obstacle avoidance is quite an important issue in the field of legged robotic applications, such as rescuing and detecting in complicated environment. Most related researchers focused on the legged robot’s gait generation after ssuming that obstacles have been detected and the walking path has been given. In this paper we propose and validate a novel obstacle avoidance framework for a six-legged walking robot Hexapod-III in unknown environment. Throughout the paper we highlight three themes: (1) The terrain map modeling and the obstacle detection; (2) the obstacle avoidance path planning method; (3) motion planning for the legged robot. Concretely, a novel geometric feature grid map (GFGM) is proposed to describe the terrain. Based on the GFGM, the obstacle detection algorithm is presented. Then the concepts of virtual obstacles and safe conversion pose are introduced. Virtual obstacles restrict the robot to walk on the detection terrain. A safe path based on Bezier curves, passing through safe conversion poses, is obtained by minimizing a penalty function taking into account the path length subjected to obstacle avoidance. Thirdly, motion planning for the legged robot to walk along the generated path is discussed in detail. At last, we apply the proposed framework to the Hexapod-III robot. The experimental result shows that our methodology allows the robot to walk safely without encountering with any obstacles in unknown environment.
