| 1 | Algorithm of simulation time synchronization over large-scale nodes显示文摘In distributed simulation,there is no uniform physical clock. And delay cannot be estimated because of jitter. So simulation time synchronization is essential for the event consistency among nodes. This paper investigates time synchronization algorithms over large-scale distributed nodes,analyzes LBTS(lower bound time stamp) computation model described in IEEE HLA standard,and then presents a grouped LBTS model. In fact,there is a default premise for existing algorithms that control packets must be delivered via reliable transportation. Although,a theorem of time synchronization message's reliability is proposed,which proves that only those control messages that constrain time advance need reliability. It breaks out the default premise for reliability. Then multicast is introduced into the transmission of control messages,and algorithm MCTS(multi-node coordination time synchronization) is proposed based on multicast. MCTS not only promotes the time advance efficiency,but also reduces the occupied network bandwidth. Experiment results demonstrate that the algorithm is better than others in both time advance speed and occupied network bandwidth. Its time advance speed is about 50 times per second when there are 1000 nodes,approximately equal to that of similar systems when there are 100 nodes. | ZHAO QinPing1,2,ZHOU Zhong1,2 & Lü Fang1,2 1 State Key Laboratory of Virtual Reality Technology and Systems,Beihang University,Beijing 100083,China 2 School of Computer Science and Engineering,Beihang University,Beijing 100083,China | 2008 | Science in China(Series F)2008，51，9： | 4 |
| 3 | Estimation of suspended sediment concentration based on bio-optical mechanism and HJ-1 image in Chaohu Lake显示文摘Synchronization experiment was conducted in June,2009 to get Inherent Optical Properties(IOP) of water component in Chaohu Lake.Water bio-optical mechanism was studied combined with multispectral data of Environmental Satellite 1(CCD),and then inversion models of total suspended matter(TSM),inorganic suspended matter(ISM) and organic suspended matter(OSM) concentration were built.The data indicated that:the absorption ratio of suspended particulate matter and CDOM to total were almost no change from band 1 to band 2 with about 85% and 9%,respectively.The ratio of pure water to total increased from 0.4% to 5.6%.Water reflectance in these two bands were influenced by absorption of three kinds of components:algae particles absorption surpassed non-algal particles in band 3,and so played an important role in total absorption with about 35.7%;the proportion of pure water absorption and particles matter backscattering both were 99% in band 4,so these two components decided the main inherent optical properties in band 4.The models of TSM and ISM concentration inversion based on band combination(band 3 + band 4)/(band 1 + band 2) were built,while OSM concentration was estimated by band 4/(band 1 + band 2) index.Inversed by image data,RE of TSM concentration between modeled and measured was 33.4%,and RMSE was 18.68 mg/L.RE of ISM and OSM concentration were 39.9% and 35.2% respectively.The inversion was more accurate when satellite-ground data were just in the same day.At this situation,RE of ISM concentration dropped to 25.4%,and that of TSM and OSM reduced to 26.5% and 26.8% as well. | WANG Qiao1,2,JIN Xin2,LI YunMei2,WU ChuanQing1,Lü Heng2,WANG YanFei2,ZHANG Hong2,YIN Bin2 & ZHU Li1 1Satellite Environment Center,Ministry of Environmental Protection,Beijing 100029,China 2Key Laboratory of Virtual Geographic Environment of Education Ministry,Nanjing Normal University,Nanjing 210046,China | 2010 | Science China Earth Sciences2010，53，S1： | 1 |
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