床面冲淤计算机处理方法   总被引：2，自引：0，他引：2  

田林  孙志林 《海洋工程》2001,19(4):100-104

冲淤计算是河流，河口，海岸等水域中分析，预测床面变化的基础，利用非结构网络自动剖分技术形成覆盖计算区域的三角网，能较好地适应边界和特殊地形，基于高程内插建立三角网数字高程模型，采用垂直三棱柱体作为基本单位计算不同时段冲淤量，从而提高计算精度，通过网络剖分，利用在计算区域内任意选择子域进行淤量的计算和分析。同时将生成的非结构网格直接有于二维床面冲淤数学模型，便于对每个节点的计算结果进行检证以提高模型的可靠性。  相似文献   

The effects of mesh size, cod-end extension length and cod-end diameter on the selectivity of Scottish trawls and seines   总被引：5，自引：2，他引：5  

Reeves  S. A.; Armstrong  D. W.; Fryer  R. J.; Coull  K. A. 《ICES Journal of Marine Science》1992,49(3):279-288

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人工皮在烧伤创面的应用     

汤建平  包平涵 《中国海洋大学学报(自然科学版)》1989,(Z3)

16例烧伤病人应用CHIMEHERB人工皮覆盖26个创面,其中浅Ⅱ°及部分深Ⅱ°创面11个,深Ⅲ°削痂创面10个,切削痂覆盖自体网状皮创面5个,与辐照猪皮对照观察,临床获得较好效果.认为在有效的清创及正确的创面处理下覆盖人工皮能减少创面渗出,有利创面愈合.作为一种新型的生物性敷料,无同种异体皮或异种皮移植时的排异现象,但其本身不具抗菌能力.  相似文献   

一种适用于网箱耐流特性有限元分析的网目群化方法   总被引：3，自引：0，他引：3  

万荣  何鑫  王欣欣  刘莉莉 《中国海洋大学学报(自然科学版)》2007,37(6):885-888

养殖网箱耐流特性是网箱工程设计中的重要问题之一,探求对这一问题的数值解法在近几年得到了空前的重视。但是,由于深水抗风浪网箱箱体规模大,如果在有限元分析中单纯以网衣网目脚为单元进行数值计算,其计算量相当庞大。文中介绍1种可供网箱箱体有限元分析的网目群化方法,根据保持群化前后网衣水中重量和投影面积相等以保证网箱网衣总体水动力相同的原则,将若干个真实网目群化为1个虚拟的计算网目,以达到有效减少计算单元、提高运算效率和节省运算时间的目的。通过不同群化条件下数值例的计算结果与实验值的比较,验证网目群化方法的可行性。在一般条件下,8×8群化或6×6群化能够有效实现计算精度与计算效率的兼顾。  相似文献   

Numerical investigation of the immersion ratio effects on ventilation phenomenon and also the performance of a surface piercing propeller     

《Applied Ocean Research》2019

Surface Piercing Propellers (SPP) show high efficiency at high advance speeds. Regarding operational conditions, this kind of propellers generate an air layer when entering the water due to the rotation of the propeller; this phenomenon is called ventilation. The ventilation phenomenon divided into some mechanism with respect to air cavity length on the propeller surface; among them are partially ventilation mechanism and fully ventilation mechanism which has great importance. In this study, using numerical simulation, we have investigated ventilation patterns and also the performance of a five-blade SPP propeller (SPP 5.74) at immersion ratio of 33, 40, 50and 70% respectively. We used Sliding Mesh Technique for modeling. Also, we applied the volume of fluid method to simulate the open surface pattern. To validate numerical results, the four-blade propeller, 841-B was simulated, and then the results of thrust and torque coefficients compared with Olofsson experimental results and validated accordingly. The findings indicate that the maximum value for thrust and torque coefficient would occur at immersion ratio of 70% and the maximum propeller efficiency occurs at immersion ratio of 33% and advance coefficient of 1.1; Moreover, the critical advance coefficient (at the partially and the fully ventilation boundary) increases by a reduction in immersion ratio, so that critical advance coefficients are 0.6 and 0.76, respectively at immersion ratios of 70 and 33%. Meanwhile, as advance coefficient increases, length of ventilation zone will decrease, and consequently the propeller will be laid on partial ventilation zone.  相似文献   

基于组分反演的高光谱潮间带表层沉积物自动分类研究   总被引：4，自引：2，他引：2  

张东  张鹰  李欢  陈晔 《海洋学报》2008,30(3):62-71

利用星载高光谱遥感影像数据Hyperion并结合现场采样粒度分析资料,对潮间带表层沉积物类型的自动分类进行了研究.根据低潮位下沉积物的短波红外光谱反射率与沉积物组分(沙、粉砂、黏土)含量之间的强相关关系,选择2102nm为特征波段,建立了高光谱定量遥感反演模型,获取初步的逐像元沙、粉砂和黏土含量,然后采用线性均衡化处理方法对初步反演结果进行修正,并结合Shepard三角分类法建立对照表,自动确定出每一像元对应的沉积物类型,得到研究区潮间带表层沉积物的空间分布特征,总体分类验证精度为87.9%.研究结果表明,研究区分布着三种沉积物,分别为粉砂质砂、砂质粉砂和粉砂,所占比例分别为18.9%,64.6%和16.5%,它们的空间分布趋势与研究区内的植被分布状况、水动力条件以及沉积物来源密切相关.  相似文献   

The effects of resolving the Canadian Arctic Archipelago in a finite element sea ice model   总被引：1，自引：0，他引：1  

Olivier Lietaer  Thierry Fichefet  Vincent Legat 《Ocean Modelling》2008,24(3-4):140-152

Though narrow straits may have a strong influence on the large-scale sea ice mass balance, they are often crudely represented in coarse resolution sea ice models. Unstructured meshes, with their natural ability to fit boundaries and locally increase the mesh resolution, propose an alternative framework to capture the complex oceanic areas formed by coasts and islands. In this paper, we develop a finite element sea ice model to investigate the sensitivity of the Arctic sea ice cover features to the resolution of the narrow straits constituting the Canadian Arctic Archipelago. The model is a two-level dynamic-thermodynamic sea ice model, including a viscous-plastic rheology. It is run over 1979–2005, forced by daily NCEP/NCAR reanalysis data. Confronting qualitatively numerical experiments with observations shows a good agreement with satellite and buoys measurements. Due to its simple representation of the oceanic interactions, the model overestimates the sea ice extent during winter in the southernmost parts of the Arctic, while the Baffin Bay and Kara Sea remain ice-covered during summer. In order to isolate the benefits from resolving the Canadian Arctic Archipelago, a numerical experiment is performed where we artificially close the archipelago. Focusing on the large-scale sea ice thickness pattern, no significant change is found in our model, except in the close surroundings of the archipelago. However, the local and short-term influences of the ice exchanges are nonnegligible. In particular, we show that the ice volume associated to the Canadian Arctic Archipelago represents 10% of the Northern Hemisphere sea ice volume and that the annual mean ice export towards Baffin Bay amounts to 125 km³ yr⁻¹, which may play an important role on the convective overturning in the Labrador Sea.  相似文献   

拖网选择性对鱼类表型性状的选择作用研究          下载免费PDF全文

梁振林  孙鹏  唐衍力  黄六一  鲁泉  刘长东  刘群 《海洋与湖沼》2008,39(5):488-493

参照渔业生物学、渔业资源解析学、数量遗传学等有关理论模型，并应用数值模拟方法，对长期选择性捕捞（重点为渔具选择性）是否参与造成了渔业资源的生物学变化（体长、性成熟等）进行某些基础性探索。设计了一个具有一定体长遗传特征的模拟鱼类种群，并利用一种具有固定选择性参数的拖网对其进行长期捕捞。结果表明，多年的持续的捕捞压力使得模拟种群中鱼类体长逐渐减小，减小的幅度随开发率的增大而增大，而终止捕捞后种群的体长并没有发生恢复的迹象，说明这种变化很可能伴随种群遗传的变化，具有自然不可逆性。  相似文献   

Elastic settlements under linear surface pressures on rectangular areas     

Halil Murat Algin  Zeynep Algin 《国际地质力学数值与分析法杂志》2009,33(8):1087-1108

This paper presents the practical closed‐form solutions for elastic settlement under the linear full‐contact pressures on rectangular areas resting upon an elastic mass. The linear pressure distribution is mostly assumed in practice for the rectangular footing having biaxial bending. The equations presented here are determined by evaluating the integration of Steinbrenner's strain approximation based on the stress solutions from the Boussinesq equations. The presented formulae are validated to be used for the elastic settlement under any point of linear full‐contact loading, triangular and embankment types of pressure cases. In this respect, it represents a significant step forward in the understanding of elastic settlement and rotation under the practical loading cases. The presented solutions are concise and easy to use. The numerical examples are demonstrated and the resulting influence factors in graphical forms are presented for their practical use especially in the elastic settlement calculations of rectangular footing subjected to the biaxial bending. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Estimation of non-point source pollution loads under uncertain information   总被引：1，自引：0，他引：1  

Ruzhong Li 《中国地理科学(英文版)》2008,18(4):348-355

Many kinds of uncertainties are involved, such as random, fuzzy, grey, unascertained property and so on, in soil erosion process. To exactly predict the non-point source pollution loads, some uncertainties should be taken into consideration. Aiming at the deficiency of present blind number theory being helpless for fuzziness, a novel blind number, i.e. extended-blind number, was introduced by substituting a set of triangular fuzzy numbers （TFNs）, expressed as a-cuts, for interval values in present blind number, and the expected value of extended-blind number was also brought forward by referring to the current blind number theory. On the basis of denoting the parameters of Uni- versal Soil Loss Equation （USLE） as extended-blind parameters, a novel USLE model was established for quantitatively evaluating soil erosion loss and non-point source pollution loads. As a case, the uncertain USLE was employed for predicting the soil erosion loss and non-point source pollution loads of absorbed nitrogen and phosphorus in a dis- trict in the Hangbu-Fengle River basin, in the upstream of Chaohu Lake watershed. The results show that it is feasible in theory to extend blind number into fuzzy environment and reliable on conclusion to apply extended-blind number theory for predicting non-point source pollution loads.  相似文献