共查询到17条相似文献，搜索用时 140 毫秒
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利用TrueType字体文件构造海图符号库 总被引：1，自引：0，他引：1
近几年,数字海图已由研制阶段逐渐过渡到规模化生产,其标准化工作也接近完善。本文介绍了关于数字海图显示的研究中,通过对TrueType字体文件和WindowsGDI函数的研究,设计了用TrueType字符和WindowsGDI图形函数结合构造海图符号库的算法,并通过VisualC++程序实现,在数字海图的显示中也得到了很好的应用。 相似文献
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通用电子地图符号库的研制 总被引：4，自引：1，他引：3
无论是纸质地图还是电子地图,地图符号库均是它们的重要组成部分。从当前电子地图符号库存在的问题出发,详细叙述了基于用户的通用电子地图符号库的研制过程,最后简述了其实现方法及功能。实验结果表明,研制的电子地图符号库不仅符合用户的视觉感受,而且完全符合电子地图的显示要求。 相似文献
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Milica Stojanovic Lee Freitag 《Oceanic Engineering, IEEE Journal of》2006,31(3):685-695
Direct-sequence (DS) code-division multiple access (CDMA) is considered for future wideband mobile underwater acoustic networks, where a typical configuration may include several autonomous underwater vehicles (AUVs) operating within a few kilometers of a central receiver. Two receivers that utilize multichannel (array) processing of asynchronous multiuser signals are proposed: the symbol decision feedback (SDF) receiver and the chip hypothesis feedback (CHF) receiver. Both receivers use a chip-resolution adaptive front end consisting of a many-to-few combiner and a bank of fractionally-spaced feedforward equalizers. In the SDF receiver, feedback equalization is implemented at symbol resolution, and receiver filters, including a decision-directed phase-locked loop, are adapted at the symbol rate. This limits its applicability to the channels whose time variation is slow compared to the symbol rate. In a wideband acoustic system, which transmits at maximal chip rate, the symbol rate is down-scaled by the spreading factor, and an inverse effect may occur by which increasing the spreading factor results in performance degradation. To eliminate this effect, feedback equalization, which is necessary for the majority of acoustic channels, is performed in the CHF receiver at chip resolution and receiver parameters are adjusted at the chip rate. At the price of increased computational complexity (there are as many adaptive filters as there are symbol values), this receiver provides improved performance for systems where time variation cannot be neglected with respect to the symbol rate [e.g., low probability of detection (LPD) acoustic systems]. Performance of the two receivers was demonstrated in a four-user scenario, using experimental data obtained over a 2-km shallow-water channel. At the chip rate of 19.2 kilochips per second (kc/s) with quaternary phase-shift keying (QPSK) modulation, excellent results were achieved at an aggregate data rate of up to 10 kb/s 相似文献
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OFDM(Orthogonal Frequency Divided Multiplication,正交频分复用)技术具有很高的频谱利用率和较好的抗多径衰落,在WLAN 802.11a/g,Wimax,高清数字电视广播和3Gpp-LTE等通信中都采用OFDM技术。OFDM通过循环前缀来抑制符号间干扰。基于802.11a无线帧结构,提出1种基于相关累加的OFDM符号起始位置估计算法,最大程度抑制OFDM符号间干扰(ISI,Inter Symbol Interfernce)。 相似文献
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