Time reversal mirror (TRM) can use the physical characteristics of the underwater acoustic (UWA) channel to focus on the desired user in multi-user UWA communication. The active average sound intensity (AASI) de...Time reversal mirror (TRM) can use the physical characteristics of the underwater acoustic (UWA) channel to focus on the desired user in multi-user UWA communication. The active average sound intensity (AASI) detector can estimate all azimuths of users with the same frequency band at the same time in order to achieve directional communication by vector combination. Space-division multiple access (SDMA) based on TRM combined with the AASI detector is proposed in this paper, which can make the capacity of the code division multiple access (CDMA) UWA system significantly increase. The simulation and lake test results show that the 7-user UWA multi-user system can achieve low bit error communication.展开更多
阅读本文,1999年发生在世界各地的一次次大地震又重现眼前。共计22000人在1999年的地震中失去生命。而世界地震年平均死亡人数仅为10000人。1997年的死亡人数仅为2907人,1998年为8928人。20世纪,地震造成的伤亡最为惨重的年份是1976年: ...阅读本文,1999年发生在世界各地的一次次大地震又重现眼前。共计22000人在1999年的地震中失去生命。而世界地震年平均死亡人数仅为10000人。1997年的死亡人数仅为2907人,1998年为8928人。20世纪,地震造成的伤亡最为惨重的年份是1976年: The deadliest year in this century was 1976 when at least 255,000 people,and perhaps more than 600,000,were killed after one quake hit Tangshan,China. 文章告诉读者,世界每年发生地震的次数为:several million! 阅读本文之时,我国云南省姚安县发生了6.5级地震(2000年1月15日7时37分)。这是新的千年伊始之际,发生在我国的首次6级以上的地震。 1999年的地震死亡人数超出以往的年平均数,是否说明地震之害正在走向高峰呢? 专家给了读者一个回答:Overall,earthquake activity isn’t on the rise.展开更多
基金supported by the National Natural Science Foundation of China(6147113751179034)+3 种基金the Ships Pre-research Support Technology Fund(13J3.1.5)the Natural Science Foundation of Heilongjiang Province(F201109)the Innovation Talents of Science and the Technology Research Projects of Harbin(2013RFQXJ101)the National Defense Basic Technology Research(JSJC2013604C012)
文摘Time reversal mirror (TRM) can use the physical characteristics of the underwater acoustic (UWA) channel to focus on the desired user in multi-user UWA communication. The active average sound intensity (AASI) detector can estimate all azimuths of users with the same frequency band at the same time in order to achieve directional communication by vector combination. Space-division multiple access (SDMA) based on TRM combined with the AASI detector is proposed in this paper, which can make the capacity of the code division multiple access (CDMA) UWA system significantly increase. The simulation and lake test results show that the 7-user UWA multi-user system can achieve low bit error communication.
文摘阅读本文,1999年发生在世界各地的一次次大地震又重现眼前。共计22000人在1999年的地震中失去生命。而世界地震年平均死亡人数仅为10000人。1997年的死亡人数仅为2907人,1998年为8928人。20世纪,地震造成的伤亡最为惨重的年份是1976年: The deadliest year in this century was 1976 when at least 255,000 people,and perhaps more than 600,000,were killed after one quake hit Tangshan,China. 文章告诉读者,世界每年发生地震的次数为:several million! 阅读本文之时,我国云南省姚安县发生了6.5级地震(2000年1月15日7时37分)。这是新的千年伊始之际,发生在我国的首次6级以上的地震。 1999年的地震死亡人数超出以往的年平均数,是否说明地震之害正在走向高峰呢? 专家给了读者一个回答:Overall,earthquake activity isn’t on the rise.