毎日の作業時間の長さを均等化できる可能性を,まぐろ延縄調査船が2年間中部太平洋の東部で行った392 回の資料のうち,前報は直線に沿って投縄した139回について検討した。これは利用できる資料の35.4%に 過ぎず,作業時間の均等化の基礎にするためには,それら以外の資料を含めなければならない。本報告では 投縄中に変針を行った例を含め, 355回の資料についてこの問題を検討した。それらは漁場・漁期・漁具構 造によって23群に分けられた。枝縄2,400本の延縄を投入するのに平均約5時間,揚げるのに12.5時間かかっ た。実測作業時問を,群平均投揚縄速度または速度の鉢数・短縮率・風速に対する回帰式から求めた作業時 間と比べた。実用許容誤差を投縄では10分,揚縄では30分と仮定すると,群平均速度を用いた場合には投縄 時間では85.6%,揚縄時間では68.5%がこの範囲内にあった。回帰式を用いるとこの比率はそれぞれ91.0% と77.7%に上昇した。この範囲以上の差が見られた例は投縄では4群,揚縄では10群に集中した。前者は各 年の操業初期の群であった。後者に関しては,これらの群とその他の群の違いは明らかにできなかった。上 述の結果は次のことを示唆する。予め設定できる条件に応じて1延の長さを調整すれば,毎日の作業時問の 長さを均等化できる可能性がある。

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The theoretical formula of three stratified interfacial long waves are deduced and its validity is verified by the experiment. The three stratified interfacial long waves consist of two modes that are Mode I and Mode II. These waves velocity are expressed c_I and c_II in equation (1') respectively. The wave numbers of these waves are expressed k₁ and k₂ in equation (3). These stratified interfacial wave profiles of first and second interface are expressed ζ_I1, ζ_I2, ζ_II1 and ζ_II2 in equation (8) respectively. The water particle velocities of these waves in first, second and third stratified layers are expressed u_I1, u_I2, u_I3, u_II1, u_II2 and u_II3 in equation (9) respectively. These relations between the profiles and the velocities are shown in figure 2.

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This paper presents details of a second order accurate Godunov-type numerical model of the two-dimensional shallow water equations and shows the application of the model to flow in a vertical sIot fishway. The model employs Roe's flux function for the convection tems and a non-linear slope limiter to prevent unwanted spurious oscillations. The model is also based on quadtree grids that adapt to inherent flow parameters, such as depth-averaged vorticity. Three test cases are demonstrated using a typical vertical slot fishway. The first test case uses relative coarse numerical grids and the second uses fine grids. The third one uses solutio-adaptive grids. Comparing the results between the first and second cases, it is shown that the results largely depends on the size of grids in interior flow region, even though the flow boundaries are fitted correctly by quadtree grids. Through the comparison between the results of second and third cases, the advantage of solutio-adaptive grids is demonstrated.

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DGPSは,基準局で決定した測位誤差をもとにユーザー局の測位精度を向上させるシステムである。基準 局の偏位は,ユーザー局の測位に影響を及ぼし,独自にDGPSを構築する場合にも,基準局位置の絶対値の 問題が,ユーザー測位精度に関わると考えられる。そこで,著者らは模擬的に基準局に偏位を与え,基準局 の位置の偏位がユーザー測位に定量的にどのような影響を及ぼすかを検証した。実験では測位誤差要因を抑え るために, 1つのGPSアンテナに対して,基準局と移動局(ユーザ一局) 2台のGPS受信機を接続し,基線 が0mのDGPS測位を行なった。実験より,基準位置の偏位がユーザー測位に対して方位距離とも同等に偏 位する結果を得た。すなわち,独自のDGPSを構築する際は,基準局の絶対位置に,より高い精度が求めら れる。

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This paper reports on the development and testing of the new type seawater intake works using wave energy. The one is 'the seawater intake works with cylindrical holes',. one of the most important characteristics of the works is to having the aeration ability for the improvement of aquatic environment. A hydraulic model test on the works was conducted in the basin and in the channel. The adequate specifications of the works had to be found by trial and error. According to the various studies, the works has proved to be good enough. The main results are as follows : (1) The works with 10 meters length has the ability of training seawater 40,000m³/day when the coastal waves has the condition that is head incident, 0.5 meter significant wave height and 4 seconds wave period ; (2) In case of the tide level locates the quarter diameter below from the center of the cylindrical hole ; the works functions the most effectively ; (3) The reflection coefficient is 0.63 to 0.65 ; the transmission coefficient is no detected in random waves ; and (4) When the ceiling slab cIoses the wave chamber, the air duct with 0.5 to 1 percent of the ceiling slab area must be constructed to prevent air compression.

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Propagation of the seagrass, Zostera marina, was examined by using artificial seeding methods on polypropylene mats named as a sediment stabilizer mat (SS-mat) used to decreasing sediment disturbance on the sand substratum off Kushiki, Naruto, Tokushima prefecture, eastem Seto Inland Sea. SS-mats (1m x 1m, 4cm, 23 and 31kg of weights) were made of pemeable meshes. The first experiment was started in autumn, 1995 and the second experiment in autumn, 1996. Plants of Z. marina, seeded on to the mats, grew successfully for four years even under a harsh environmental condition of high wave height and fluctuations of the sand bottom level in the winter season. In both experiments, the shoot density on the SS-mats was observed to decrease after the maximum number of individual shoots (50-60 shoots/m²) in the first summer season to several shoots/m² in the 2nd and 3rd summer seasons. Z. marina plants made reproductive flowering shoots on the SS-mats since 2nd spring maturing period. The SS-mats were useful in germination of seed and growth of seedlings for Z. marina, but not useful for the survival of adult plants due to the lack of sand accumulation on the mats. Such long term monitoring of continuous growth of Z. marina plants on the SS-mats is required for promoting the methodoIogy of establishing sea grass beds restoration.

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インターロック繊維を濾材として用いた浸漬濾床と回転円板装置について,流量,回転数,浸漬率がアン モニア除去に与える影響を処理水のアンモニア態窒素(NH4-N)濃度1, 0.5mg-N/Lにおいて調べ比較した。 浸漬滅床では,流量に比例してアンモニア浄化能が増加した。 RBCでは,アンモニア浄化能に対して回転数 12-18rpm,浸漬率40%以上で高い値を示した。流量の増加に伴って,アンモニア浄化能も少し増加したが, 浸浅漬床より影響は小さかった。 NH4-N濃度1mg-N/Lにおけるアンモニア浄化能は浸漬濾床(流量,240L/h) では最大約0.25g-N/m2/day, RBC (回転数12rpm,浸漬率50%,流量120L/h)では最大約0.15g-N/正2/dayと なり,浸浅濾床の方が高い値が得られた。

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This study examined the effects of bottom disturbance associated with wave action on the burrowing behaviors of the surf clam Mactra chinensis (shell length = 28.5 - 85.0mm) using a vertical circulating water channel. The burrowing speed of the clam tended to increase with shell length and Shields number as an index of bottom disturbance regardless of burrowing posture toward water flow. The relationship between the burrowing speed (V : mm/s), Shell length (L : mm) and Shields number (ψ) was described as V=0.022L+5.989ψ. A large number of the clams apparently burrowed with orienting their lateral toward the flow. The critical conditions when the clams could not burrow into the sand and would be washed out of the sand by bottom disturbance were shown as functions of the shell length and Shields number with ψ =3.087×10^-4L＋0.081 and ψ=0.004L＋0.099, respectively. The critical Shields number to wash the clams out of the sand corresponded to that of shallower limit of water depth in the clam habitat.

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海中に設置した電極に微弱電流を流すことにより,海洋生物の付着を防止する試みを行った。水産大学校 前の海面に8枚の測定板(塩ビ板)を沈め,測定板への生物付着状況を調べた。電流を加えた海面を試験区 とし,電流を加えない海面を対照区とした。 1998年7月と8月の2ヶ月間(第1期)と,同年9月下旬から 翌年1月下旬までの4ヶ月間(第2期)に分けて実験を行った。電源には太陽電池と充電式電池を用いた。 電極には白金メッキしたチタン細線(0.5mmのを用いた。約2.5V, 20mAの電流を加えた第1期の実験で は,試験区と対照区とで付着状況に差が見られたものの,電流を加えた試験区にも生物付着が確認された。 そこで,電圧を上げ,約5V, 50mAの電流を加えた第2期の実験では,当初,試験区と対照区で差がみら れたが, 12月から1月に,両者共に海藻類の付着が見られた。しかしながら,フジツボに関しては,両者に大 きな差がみられ,約5V, 50mAの電流には,フジツボの付着防止効果があると考えられる。

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The mean fish body length, the fish body weight and cultured fish number per unit volume of the pen are estimated from the practical fish culture data of yellowtail, sea bream and so on. Depending on these data, the relationship between the body length and body weight and numbers of cultured fish per unit volume of the pen are clarified. Moreover the dissolved oxygen consumption by fish per unit volume of the pen are discussed.

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