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11.
Edelmann G.F. Akal T. Hodgkiss W.S. Seongil Kim Kuperman W.A. Hee Chun Song 《Oceanic Engineering, IEEE Journal of》2002,27(3):602-609
In July 1999, an at-sea experiment to measure the focus of a 3.5-kHz centered time-reversal mirror (TRM) was conducted in three different environments: an absorptive bottom, a reflective bottom, and a sloping bottom. The experiment included a preliminary exploration of using a TRM to generate binary-phase shift keying communication sequences in each of these environments. Broadside communication transmissions were also made, and single-source communications were simulated using the measured-channel response. A comparison of the results is made and time reversal is shown to be an effective approach for mitigating inter-symbol interference caused by channel multipath. 相似文献
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This article introduces the most advanced form of electronic chart display and information systems (ECDIS) which complies with the performance standards for ECDIS established by the International Maritime Organization (IMO) and International Hydrographic Organization (IHO). It also describes the key features and the important functions of ECDIS, which we developed. This system is different from the productions developed by C-map, Seven-cs, offshore, and others. It is more suitable for China Marine Safety Administration Bureau to manage the navigation marks real-time. Using this system charts were located and accessed rapidly, and displayed smoothly. This article also discusses in ECDIS application system how to dynamically access and desert charts data in a limited memory (limited computer memory and resource). We constructed a tridimensional structure to manage a large amount of charts data. Vertically, according to the scale range, all charts were divided into eight levels, and a data structure called as “Multiple Scale Quad-tree” was constructed. And horizontally, a grid (every unit has a fixed size) was given to a certain scale level. We call this data structure a “Regular Page.” We explore the implementation of such a structure on the worldwide charts management utilizing quad-trees. Then we discuss the future development of ECDIS and its application system in marine agencies in China. 相似文献
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本文总结了“青藏高原大地形及西太平洋暖池势力强迫对东亚及全球气候变化的影响”专题五年来的主要研究工作。其中包括青世故高原东部大气热源的时间演变特征,夏半年高原热源异常对我国降水和北半球环流的影响;西沙海温变化特征及其与我南方降水的关系,北太平洋海温主因子特征及其与华南前汛期降水的变化。 相似文献
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LIU Chun TONG Xiaohua 《地球空间信息科学学报》2005,8(3):183-188
The mathematic theory for uncertainty model of line segment are summed up to achieve a general conception, and the line error hand model of εσ is a basic uncertainty model that can depict the line accuracy and quality efficiently while the model of εm and error entropy can be regarded as the supplement of it. The error band model will reflect and describe the influence of line uncertainty on polygon uncertainty. Therefore, the statistical characteristic of the line error is studied deeply by analyzing the probability that the line error falls into a certain range. Moreover, the theory accordance is achieved in the selecting the error buffer for line feature and the error indicator. The relationship of the accuracy of area for a polygon with the error loop for a polygon boundary is deduced and computed. 相似文献
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月球某些资源的开发利用前景 总被引:18,自引:0,他引:18
21世纪月球探测的主要趋势是建立月球基地,开发利用月球的矿产资源,能源和特殊环境,为人类社会的可持续发展发挥长期而有效的支撑作用,通过对月海玄武岩中的钛铁矿,克里普岩中的U,Th,REE和月壤中的拟-3在月面的含量与分布的系统分析,月海玄武碉中蕴藏有极丰富的钛铁矿,TiO2总资源量超过70万亿t,钛铁矿还是月球基地生产水和火箭燃料的主要原料;克里普岩是未来月球探测与研究的热点之一,其蕴藏有巨量的铀,钍,钾,磷和稀土元素资源;月壤长期受到太阳风的辐射,使其蕴藏有极其丰富的氢,氦,氧,氮等气体资源,其中氦-3的资源量大于100万t,它是一种可供人类社会长期使用的,安全,清洁,高效,廉价的核聚变发电燃料,其含量与月壤的化学成分,矿物组分,颗粒大小等有密切的关系。 相似文献