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Application of A* Algorithm for Real-time Path Re-planning of an Unmanned Surface Vehicle Avoiding Underwater Obstacles

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Journal of Marine Science and Application 2014年第1期13卷 105-116页

作者： Thanapong Phanthong toshihiro maki Tamaki Ura Takashi Sakamaki Pattara Aiyarak Department of Physics Faculty of Science Prince of Songkla University Institute of Industrial Science the University of Tokyo 4-6-1 Komaba Meguro-ku Tokyo 153-8505 Japan Department of Computer Science Faculty of Science Prince of Songkla University

This paper describes path re-planning techniques and underwater obstacle avoidance for unmanned surface vehicle(USV) based on multi-beam forward looking sonar(FLS). Near-optimal paths in static and dynamic environments with underwater obstacles are computed using a numerical solution procedure based on an A* algorithm. The USV is modeled with a circular shape in 2 degrees of freedom(surge and yaw). In this paper, two-dimensional(2-D) underwater obstacle avoidance and the robust real-time path re-planning technique for actual USV using multi-beam FLS are developed. Our real-time path re-planning algorithm has been tested to regenerate the optimal path for several updated frames in the field of view of the sonar with a proper update frequency of the FLS. The performance of the proposed method was verified through simulations, and sea experiments. For simulations, the USV model can avoid both a single stationary obstacle, multiple stationary obstacles and moving obstacles with the near-optimal trajectory that are performed both in the vehicle and the world reference frame. For sea experiments, the proposed method for an underwater obstacle avoidance system is implemented with a USV test platform. The actual USV is automatically controlled and succeeded in its real-time avoidance against the stationary undersea obstacle in the field of view of the FLS together with the Global Positioning System(GPS) of the USV.

关键词： underwater obstacle avoidance real-time pathre-planning A* algorithm sonar image unmanned surface vehicle

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NAD＋ Accumulation during Pollen Maturation in Arabidopsis Regulating Onset of Germination

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Molecular Plant 2013年第1期6卷 216-225页

作者： Shin-nosuke Hashida Hideyuki Takahashi Kentaro Takahara maki Kawai-Yamada Kazuyoshi Kitazaki Kazuhiro Shoji Fumiyuki Goto toshihiro Yoshihara Hirofumi Uchimiya Institute of Molecular and Cellular Biosciences (IMCB) University of Tokyo 1-1-1 Yayoi Bunkyo-ku Tokyo 113-0032 Japan Environmental Science Research Laboratory Central Research Institute of Electric Power Industry (CRIEPI) 1646 Abiko Chiba 270-1194 Japan Iwate Biotechnology Research Center (IBRC) Kitakami Iwate 024-0003 Japan Department of Environmental Science and Human Engineering Saitama University Sakura-ku Saitama 338-0825 Japan Institute for Environmental Science and Technology Saitama University 255 Shimo-Okubo Sakura-ku Saitama 338-8570 Japan

Although the nicotinamide nucleotides NAD（H） and NADP（H） are essential for various metabolic reactions that play major roles in maintenance of cellular homeostasis, the significance of NAD biosynthesis is not well under- stood. Here, we investigated the dynamics of pollen nicotinamide nucleotides in response to imbibition, a representative germination cue. Metabolic analysis with capillary electrophoresis electrospray ionization mass spectrometry revealed that excess amount of NAD＊ is accumulated in freshly harvested dry pollen, whereas it dramatically decreased immedi- ately after contact with water, importantly, excess of NAD~ impaired pollen tube growth. Moreover, NAD~ accumulation was retained after pollen was imbibed in the presence of NAD^-consuming reaction inhibitors and pollen germination was greatly retarded. Pollen deficient in the nicotinate/nicotinamide mononucleotide adenyltransferase （NMNAT） gene, encoding a key enzyme in NAD biosynthesis, and a lack of NAD＊ accumulation in the gametophyte, showed precocious pollen tube germination inside the anther Iocule and vigorous tube growth under high-humidity conditions. Hence, the accumulation of excess NAD＊ is not essential for pollen germination, but instead participates in regulating the timing of germination onset. These results indicate that NAD＋ accumulation acts to negatively regulate germination and a decrease in NAD＋ plays an important role in metabolic state transition.

关键词： Arabidopsis nicotinamide adenine dinucleotide (NAD) NAD biosynthesis NAD consumption NMNAT pollengermination pollen longevity.

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