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題 名 | 魚群個體密度所對應之平均後方散亂反射強度的模擬試驗研究 |
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作 者 | 李國添; 青山恒雄; | 書刊名 | 技術學刊 |
卷 期 | 2:2 1987.09[民76.09] |
頁 次 | 頁341-346 |
分類號 | 439.2 |
關鍵詞 | 反射; 密度; 強度; 魚群; 散亂; |
語 文 | 中文(Chinese) |
中文摘要 | 利用對超音脈波反射沒有方向性的尼龍球 (直徑12.7 mm) ,組成5種分布模式共25組的模擬魚群 (群密度298-4,033 inds./m3) ,在水槽中進行音波反射計測,200KHz之收發控器所發射之超音脈波 (0.5 ms) 入射模擬魚群後,其反射之類比信號被收錄於磁帶錄音機中,並且於實驗室中將信號重現,以微電腦及類比數位變換器施以數值化處理,求取平均後方散亂反射強度SV (dB/m3)。實測結果顯示,密度在1,500 inds./m3以下之各模擬魚群之群密度的對數與SV成比例關係,而高於此密度則否;所以,魚群在一界限密度下,由SV值推測魚群量是可行的,但超越此一界限密度,群反射信號之幅長、波形及強度均十分不穩定,以SV推測魚群量將產生極大之誤差。 |
英文摘要 | An experiment using spherical nylon balls which simulated fish schools is described in this paper. The acoustic response was studied in an octagon pool measuring 21 m diagonally and 3 m deep. The target densities ranging from 298 to 4,033 individuals/m3 were insonified by a pressure pulse at a carrier frequency of 200 KHz. The recieved echo signals were recorded on magnetic tape, digitized and then processed in a microcomputer to obtain the average backscattering strength (SV in dB/m3) of each target array. The results showed that the SV is proportional to the individual density of the model schools up to ca. 1,500 individuals/m3 but that it is independent to the distribution of the targets. At high density, the echo patterns were, in most cases, irregular and the echo length was extended. |
本系統中英文摘要資訊取自各篇刊載內容。