Population dynamics of the seagrass Cymodocea nodosa in Ria Formosa lagoon following inlet artificial relocation

The population dynamics of the seagrass Cymodocea nodosa was investigated in three meadows differently affected by the artificial relocation of an inlet in the western sector of the Ria Formosa lagoon, southern Portugal. One meadow was subjected to increasing currents that caused erosion, another one was subjected to an initial episode of burial and a third meadow was undisturbed by the inlet opening. The hydrodynamic/sedimentary condition of meadows was assessed through comparative sediment analysis between the meadow and the adjacent unvegetated area.     

黄渤海沿岸海湾─溺谷型潮汐汊道的地貌结构

本文以丁字湾等基岩海湾为例，论述了黄渤海沿岸海湾－溺谷型潮汐汉道的地貌结构，尤其着重于口门段深槽及涨、落潮三角洲。认为涨、落潮三角洲的发育状况与入湾河流的供沙量、纳潮水域容量、被浪作用、潮差以及口少卜海域的开阔程度有关；泻湖型潮汐汉道的落潮三角洲的典型模式可以应用于海湾－溺谷型潮汐汉道，但涨潮三角洲因受基岩海湾的复杂岸线的限制而不能充分发育。本文还讨论了海湾型潮汐汉道与半开敞海湾在动力和形态中的差异。     

基于约束Landweber迭代的重建算法

针对较少投影数据图像重建问题,在最小二乘优化的基础上,提出将未知误差引入不等式约束中,并针对其不适定性提出运用Landweber迭代正则化技术进行迭代求解。数值实验表明相对以往各算法,此迭代算法更加稳定,并且在重建质量以及重建时间上都具有一定的优势。     

A sedimentological approach to P-A relationships for tidal inlet systems: an example from Yuehu Inlet, Shandong Peninsula, China

Power-law relationship between tidal prism (P) and the cross-sectional area of the entrance channel (A) is applicable to assess the equilibrium conditions of a tidal inlet system. The classic method of determining P-A relationships proposed by O’Brien depends on datasets from multi-tidal inlet systems, which has shown some limitations and is unable to assess equilibrium of a single tidal inlet. This paper focuses on establishing a new P-A relationship for a single tidal inlet. Our experimental result shows that in order to maintain the status, power n should be > 1, implying that the inlet width will narrow and current speed within the entrance will increase as tidal prism becomes smaller. A possible explanation for power n <,1.0, as many researchers argued before, is that the influence of tidal prism has been exaggerated. Meanwhile, the magnitude of coefficient C is dependent on many factors such as longshore drift, freshwater discharge, etc, resulting in a wide range of variation of C. It should be pointed out that P-A relationship given by the sediment dynamical approach is still a representative of average status for tidal inlets in equilibrium. As tide, wave, freshwater discharge and tidal inlet morphology change with time, actual P-A relationships will fluctuate also. The problems that need to be solved when applying sediment dynamic methods to P-A relationships include the cross-sectional distribution pattern of tidal current speeds in the entrance channel, the relationship between the tidal current and the tidal water level at the entrance, and the calculation of the ratio of width to depth. This paper will establish a sediment dynamical approach of P-A relationship for a single tidal inlet. The results are tested for P-A relationships of Yuehu Inlet, a small inlet-lagoon system located in Shandong Peninsula, China. __________ Translated from Oceanologia Et Limnologia Sinica, 2005, 36(3): 269–276 [译自: 海洋与湖沼]