Impulse control method for hydraulic propulsion system used in 3500 m work-class ROV

In terms of the nonlinear characteristics of hydraulic propulsion system used in 3500 m rated work-class ROV (remotely operated underwater vehicle), the paper improved the responsiveness of the hydraulic propulsion system by adding an impulse signal to the input end of the system. Because the maximum static damping moment provided from water is much larger than the dynamic damping moment, it results in large dead zone of thrust during the startup process of the hydraulic propulsion system. The dead zone of thrust caused by static damping moment can be effectively reduced by adding a specific impulse signal to the input end of the propulsion system. The results of numerical simulations and underwater experiments show that using this method, the nonlinear characteristics of the hydraulic propulsion system have been significantly improved.     

两种孔径网具对大洋微(小)型浮游植物调查结果的影响——以西南印度洋海域第34次大洋春季航次为例

浮游植物拖网是海洋浮游植物调查的重要工具,不同网具可以导致不同的调查结果。为研究两种孔径网具对大洋浮游植物调查的影响,于2015年4~5月在西南印度洋分别用筛绢孔径为20和77 μm的两种浮游生物网在多个站位进行浮游植物采样。对采集的样品进行浮游植物鉴定,分析比较了两者浮游植物的物种数、细胞丰度、物种丰富度、多样性指数、均匀度指数和优势种。结果表明,在相同采样站位,筛绢孔径为20 μm网采样品鉴定得到的平均物种数、平均细胞丰度和平均物种丰富度分别是筛绢孔径为77 μm网采样品的2.7、17和2倍,呈显著差异。但两种网采样品的平均多样性指数和平均均匀度指数都无显著差异。此外,筛绢孔径为20 μm网采样品中有9种优势种,而筛绢孔径为77 μm网采样品中有11种优势种,其中共同的优势种有6种。以上结果说明在寡营养海域使用20 μm孔径的网具可以获得更为全面的浮游植物信息。     

关于拖网选择性影响因子的分析研究

随着渔业资源的下降，除了通过渔业法规严格管理渔业生产行为外，更应该使用高选择性的渔具。拖网是1种选择性比较差的渔具，对渔业资源的破坏十分严重。提高拖网选择性对保护渔业资源具有重要意义，本文就影响拖网选择性的因子进行了分析探讨。     

不同尺寸虾拖网网囊网目对副渔获物的选择性研究

为了分析黄海区虾拖网网囊网目对副渔获物的选择性,运用套网法对30,33,40 mm 3种网目尺寸的网囊进行了选择性试验。用统计学方法求得几种优势副渔物的逃逸率,并用极大似然法对渔获数据进行处理求得相关的选择性参数。结果表明,大部分副渔获物的逃逸率随着网囊网目尺寸的增大而增大,在网目尺寸为30,33,40 mm时矛尾虎鱼(Chaeturichthys stigmatias)的逃逸率分别为48.3%,59.7%和62.6%;细巧仿对虾(Parapenaeopsis tenella)的逃逸率分别为67.0%,68.2%,68.7%。矛尾虎鱼的选择性参数也随着网目尺寸的增大而增大,在网目尺寸为30,33,40 mm时,矛尾虎鱼的50%选择体长L50分别为81.858,86.715和88.028 mm,选择范围SR分别为41.097,45.007和50.423 mm。研究表明,单靠放大网囊网目尺寸来释放虾拖网中副渔获物,效果不甚理想。     

拖网网线强度损耗的分析

本文对青渔４４１ｋｗ渔轮用双拖网的网线强度进行了测量和分析，得出了报废时的剩余强度平均为初始强度的５０％，最低的不足４０％。选择网线的初始强度为预定的报放废时余强度的两倍时，平均每天的折旧费最小。     

裤式拖网法校核试验和网形分析

裤式拖网法是渔具选择性研究方法之一 ,其网形和校核试验于 2 0 0 2年 1月在挪威特鲁姆瑟海湾进行。在 1 1 5～ 2 70 m的水深范围内 ,测量的裤式拖网网口的水平扩张平均为 (2 3.2 7± 0 .2 6) m,网口高度为 (6.53± 0 .1 2 ) m;右网囊对左网囊的虾渔获物重量之比为 1 .0 0± 0 .0 4 ,右网囊对左网囊的渔获物尾数之比为 1 .0 8± 0 .0 9,渔获物种类及体长频率分布相似 ,基本符合用裤式拖网法进行选择性研究的要求     

A laboratory study on capillary sealing efficiency of Iranian shale and anhydrite caprocks

Caprock has the most important role in the long term safety of formation gas storage. The caprocks trap fluid accumulated beneath, contribute to lateral migration of this fluid and impede its upward migration. The rapid upward passage of invasive plumes due to buoyancy pressure is prevented by capillary pressure within these seal rocks. In the present study, two main seal rocks, from the Zagros basin in the southwest of Iran, a shale core sample of Asmari formation and an anhydrite core sample of Gachsaran formation, were provided. Absolute permeabilities of shale and anhydrite cores, considering the Klinkenberg effect, were measured as 6.09 × 10⁻¹⁸ and 0.89 × 10⁻¹⁸ m², respectively. Capillary sealing efficiency of the cores was investigated using gas breakthrough experiments. To do so, two distinct techniques including step by step and residual capillary pressure approaches were performed, using carbon dioxide, nitrogen and methane gases at temperatures of 70 and 90 °C, under confining pressures in the range 24.13–37.92 MPa. In the first technique, it was found that capillary breakthrough pressure of the cores varies in the range from 2.76 to 34.34 MPa. Moreover, the measurements indicated that after capillary breakthrough, gas effective permeabilities lie in range 1.85 × 10⁻²¹ – 1.66 × 10⁻¹⁹ m². In the second technique, the minimum capillary displacement pressure of shale varied from 0.66 to 1.45 MPa with the maximum effective permeability around 7.76 × 10⁻²¹ – 6.69 × 10⁻²⁰ m². The results indicate that anhydrite caprock of the Gachsaran formation provides proper capillary sealing efficacy, suitable for long term storage of the injected CO₂ plumes, due to its higher capillary breakthrough pressure and lower gas effective permeability.