Fully nonlinear numerical wave tank (NWT) simulations and wave run-up prediction around 3-D structures

A finite-difference scheme and a modified marker-and-cell (MAC) algorithm have been developed to investigate the interactions of fully nonlinear waves with two- or three-dimensional structures of arbitrary shape. The Navier–Stokes (NS) and continuity equations are solved in the computational domain and the boundary values are updated at each time step by the finite-difference time-marching scheme in the framework of a rectangular coordinate system. The fully nonlinear kinematic free-surface condition is implemented by the marker-density function (MDF) technique developed for two fluid layers.To demonstrate the capability and accuracy of the present method, the numerical simulation of backstep flows with free-surface, and the numerical tests of the MDF technique with limit functions are conducted. The 3D program was then applied to nonlinear wave interactions with conical gravity platforms of circular and octagonal cross-sections. The numerical prediction of maximum wave run-up on arctic structures is compared with the prediction of the Shore Protection Manual (SPM) method and those of linear and second-order diffraction analyses based on potential theory and boundary element method (BEM). Through this comparison, the effects of non-linearity and viscosity on wave loading and run-up are discussed.     

Experimental Investigation into the performance of the Axial-Flow-Type Waterjet according to the Variation of Impeller Tip Clearance

The tip clearance inside the duct from the tip of the impeller is very important to the performance of waterjet systems, which fact has been proven in the pump field. The tip clearance is especially important on the model scale because it is very difficult in manufacture to keep the tip clearance constant and minimally small along the inside of the duct. In the present study, a flush-type waterjet propulsion unit (duct, impeller, stator, and nozzle) was designed for an amphibious tracked vehicle. Two impellers of different inner diameter were designed and manufactured in order to investigate the gap effect. Resistance and self-propulsion tests with a 1/5-scale model were conducted in PNU towing tank. The flow rate at the nozzle exit, the static pressure at the various sections along the duct and also the nozzle, the revolution of the impeller, and the torque, thrust, and towing forces at various advanced speeds were measured. Based on these measurements, the performance was analyzed according to the ITTC 96 standard analysis method. Based on this analysis method, the full-scale effective and delivered power of the tracked vehicle was estimated according to the variation of tip clearance.     

不同生长期坛紫菜多糖中组分含量的变化

于１９９０－１９９１年，运用＾１３Ｃ－ＮＭＲ和化学分析方法研究南方产和移植北方养殖的不同生长发育阶段坛紫菜多糖的组分变化，结果表明，随着藻体生长发育，坛紫菜琼胶中３，６－内醚－Ｌ－半乳糖和６－ＯＣＨ３－Ｄ－半乳糖的含量逐渐增加，而硫酸基的含量呈现先增加后减少的规律；北移坛紫菜琼胶中３，６－内醚－Ｌ－半乳糖的含量高于南方坛紫菜，而硫酸基和６－ＯＣＨ３－Ｄ－半乳糖的含量低于南方坛紫菜。     

U37K,δ18O沉积地层记录:南海北部末次盛冰期以来SST和海面变化

应用U37^K和δ^18O重建末次盛冰期以来海水古温度和海平面变化，U37^K-SST沉积记录表现了冰期／间冰期模式．U37^K-SST在冰后期23．3-26．9℃；末次盛冰期22．2-23．8℃．末次盛冰期时古温度比目前平均低4．7℃，南海北部季节性温差冰后期在4．5-7．0℃；末次盛冰期在7．0-9．0℃，远远超过同一纬度太平洋季节温差．末次冰期以来在气候降温的同时，伴有海平面下降，气候的冷暖交替对海平面变化具有决定性的控制意义．     

An initial demonstration of underwater acoustic communication using time reversal

In July 1999, an at-sea experiment to measure the focus of a 3.5-kHz centered time-reversal mirror (TRM) was conducted in three different environments: an absorptive bottom, a reflective bottom, and a sloping bottom. The experiment included a preliminary exploration of using a TRM to generate binary-phase shift keying communication sequences in each of these environments. Broadside communication transmissions were also made, and single-source communications were simulated using the measured-channel response. A comparison of the results is made and time reversal is shown to be an effective approach for mitigating inter-symbol interference caused by channel multipath.     

一类全局最优化问题的动态隧道方法

研究了连续变量函数的全局最优化问题 ,给出了动态隧道方法。该动态隧道方法由局部搜索和动态隧道 2个阶段构成。在局部搜索阶段用了动态系统方法。对全局最优化问题的实例进行了数值实验 ,数值结果表明了该方法的稳健性和有效性。     

厦门港湾和闽南-台湾浅滩海域鱼类感染吸虫的调查研究

本文根据1980～1986年厦门港湾和闽南-台湾浅滩海域的调查资料,报道了该海区鱼类感染复殖吸虫的概况。在我们检查的106种鱼类中,从其中54种的消化道和1种的体腔中发现复殖吸虫标本1269个,感染率为28.24%。本海区鱼类生态习性虽有差异,其感染率和阳性鱼的感染度可能有明显差异,但从总体上看,不同生态类群鱼类的吸虫密度分布甚为均匀。     

养殖对虾与海捕对虾鉴别方法初探

通过对养殖中国对虾(Penaeus orientalis)和海捕中国对虾肌肉煮熟后的失水率,提取物中的甜菜碱和氧化三甲胺含量,以及虾肉脂质中所含脂肪酸组成和含量进行了分析比较,得到下列结果:(1)两类对虾鲜样煮熟后失水率相差6％以上;(2)海捕对虾肌肉中的甜菜碱和氧化三甲胺含量比养殖对虾的高,两者有显著差别;(3)养殖对虾肌肉所含C18:2ω6为17.3±1.5％,海捕对虾为2.0±0.8％。从以上结果本文推荐以脂肪酸C18:2ω6含量来鉴别养殖对虾与海捕对虾。     

虾蟹类亲体生殖营养需求研究的进展

本文综述了虾蟹类生殖营养的最新研究成果,并讨论了各营养素对虾蟹类亲体成熟、生殖和幼体质量的影响．此外,就今后在虾蟹类亲体生殖营养方面开展深入研究提出了一些建议。     

An Electronic Chart Display and Information System

This article introduces the most advanced form of electronic chart display and information systems (ECDIS) which complies with the performance standards for ECDIS established by the International Maritime Organization (IMO) and International Hydrographic Organization (IHO). It also describes the key features and the important functions of ECDIS, which we developed. This system is different from the productions developed by C-map, Seven-cs, offshore, and others. It is more suitable for China Marine Safety Administration Bureau to manage the navigation marks real-time. Using this system charts were located and accessed rapidly, and displayed smoothly. This article also discusses in ECDIS application system how to dynamically access and desert charts data in a limited memory (limited computer memory and resource). We constructed a tridimensional structure to manage a large amount of charts data. Vertically, according to the scale range, all charts were divided into eight levels, and a data structure called as “Multiple Scale Quad-tree” was constructed. And horizontally, a grid (every unit has a fixed size) was given to a certain scale level. We call this data structure a “Regular Page.” We explore the implementation of such a structure on the worldwide charts management utilizing quad-trees. Then we discuss the future development of ECDIS and its application system in marine agencies in China.