Species richness and human activities in natural environments are among the most important recreational needs. Monthly studies of aquatic fauna, artisanal fisheries and tourism characteristics was conducted during wet...Species richness and human activities in natural environments are among the most important recreational needs. Monthly studies of aquatic fauna, artisanal fisheries and tourism characteristics was conducted during wet and dry seasons, over a two year period in the three landscapes along the 6817.7 m length of Agbokum waterfalls by using a close-ended pre-coded survey instrument. Through MANOVA analysis of the 1780 respondents we found strong positive association between peoples visits to the recreational areas and the type of landscape in which the respondents felt happy. People who felt happier in landscape dominated by waterfalls, visit the middle reaches of the river for outdoor recreation more often while people who feel happy in landscapes dominated by slow water current with an extensive wide area and floodplains, visit downstream reaches of the waterfalls more often. Activities performed more often along downstream reaches include fishing, bathing/swimming, boating and hunting while more frequent activities in the middle reaches (waterfalls) include taking photographs, picnics, enjoying nature, outing with family and friends, looking at view, resting and relaxing. A total of 5484 fish representing 22 species belonging to 16 genera from 9 families were sampled with 10 species being restricted to wet season and only 1 in the dry. The number of taxa and individuals present at upstream, midstream and downstream reaches were 16 (2003), 13 (1034), 17 (2447), respectively. Tilapia zillii, Clarias gariepinus and Labeo coubie dominated overall catch constituting 35.5%. Twenty five operational boats counted during the period of study, were only used downstream by 25 full-time fishermen, 87 part-time, 44 shoreline fishermen and 36 assistant fishermen. Common gears were the hook and line constituting 45.8%, cast and dip net (10.1%) bailing (8.7%), gill nets (7.3%), seine net (6.4%) Traps (5.5%), lift net (4.7%) Dip nets (0.9%), poisoning (2.8%), cutlass (3.3%) and spear (1%). Seasonally occurring aquatic fauna include展开更多
This paper puts forward a model of Pearl River Delta (PRD) fishery in the South China Sea (SCS) that integrates the ecological, social and economic costs and benefits of fisheries activities in a multidisciplinary fra...This paper puts forward a model of Pearl River Delta (PRD) fishery in the South China Sea (SCS) that integrates the ecological, social and economic costs and benefits of fisheries activities in a multidisciplinary framework. In particular, an integrated ECOST model is composed of links between an ecological model constructed by Ecopath with Ecosim (EwE) software and a region Social Accounting Matrix (SAM). Then the costs and benefits of five fishing methods are compared from economic, ecological and social three dimensions base on the ECOST model. The potential effects of fishing effort reduction on fishing communication are explored by a series of dynamic simulations for a 10-year period. Key results from prediction (2005-2015) and policy simulations illustrate that fisheries of PRE are geared toward short-term economic profits at the expense of ecological gains and the whole group of societal benefits associated with fishing. However, the status quo can be improved to better levels by reducing fishing efforts.展开更多
鱼骨柔性翼(Fish bone active camber,FishBAC)是一种依靠结构变形实现机翼弯度变化的结构形式,相较于传统的离散式控制面和增升装置,可以在实现机翼弯度变化的同时保持气动表面的连续与光滑。然而,其依靠结构弹性变形实现机翼变弯度的...鱼骨柔性翼(Fish bone active camber,FishBAC)是一种依靠结构变形实现机翼弯度变化的结构形式,相较于传统的离散式控制面和增升装置,可以在实现机翼弯度变化的同时保持气动表面的连续与光滑。然而,其依靠结构弹性变形实现机翼变弯度的基本特征可能引发潜在气动弹性问题。针对柔性翼潜在的气动弹性问题,本文从结构特性和气动弹性特性两方面进行了研究。在结构特性方面,基于欧拉梁理论和逐段刚化法建立等效结构模型,经有限元验证发现简化模型在计算非均质梁结构保持精度的同时提高了计算效率。在气动弹性特性分析方面,基于等效刚柔耦合翼型模型和非定常气动理论完成了气动弹性特性分析。结果表明,FishBAC建模时需考虑结构柔性,忽略结构柔性会对气动弹性特性的预测存在一定偏差。在驱动力矩低于1.5 N·m时,本文简化的等效结构模型可较好地预测考虑静气动弹性特性的机翼结构形变。使用本文提出的翼型模型考虑结构存在刚柔耦合特性,并预测柔性段所发生的弯度颤振,简化模型与MSC Nastran相比在颤振速度预测上保持了一致性。展开更多
文摘Species richness and human activities in natural environments are among the most important recreational needs. Monthly studies of aquatic fauna, artisanal fisheries and tourism characteristics was conducted during wet and dry seasons, over a two year period in the three landscapes along the 6817.7 m length of Agbokum waterfalls by using a close-ended pre-coded survey instrument. Through MANOVA analysis of the 1780 respondents we found strong positive association between peoples visits to the recreational areas and the type of landscape in which the respondents felt happy. People who felt happier in landscape dominated by waterfalls, visit the middle reaches of the river for outdoor recreation more often while people who feel happy in landscapes dominated by slow water current with an extensive wide area and floodplains, visit downstream reaches of the waterfalls more often. Activities performed more often along downstream reaches include fishing, bathing/swimming, boating and hunting while more frequent activities in the middle reaches (waterfalls) include taking photographs, picnics, enjoying nature, outing with family and friends, looking at view, resting and relaxing. A total of 5484 fish representing 22 species belonging to 16 genera from 9 families were sampled with 10 species being restricted to wet season and only 1 in the dry. The number of taxa and individuals present at upstream, midstream and downstream reaches were 16 (2003), 13 (1034), 17 (2447), respectively. Tilapia zillii, Clarias gariepinus and Labeo coubie dominated overall catch constituting 35.5%. Twenty five operational boats counted during the period of study, were only used downstream by 25 full-time fishermen, 87 part-time, 44 shoreline fishermen and 36 assistant fishermen. Common gears were the hook and line constituting 45.8%, cast and dip net (10.1%) bailing (8.7%), gill nets (7.3%), seine net (6.4%) Traps (5.5%), lift net (4.7%) Dip nets (0.9%), poisoning (2.8%), cutlass (3.3%) and spear (1%). Seasonally occurring aquatic fauna include
文摘This paper puts forward a model of Pearl River Delta (PRD) fishery in the South China Sea (SCS) that integrates the ecological, social and economic costs and benefits of fisheries activities in a multidisciplinary framework. In particular, an integrated ECOST model is composed of links between an ecological model constructed by Ecopath with Ecosim (EwE) software and a region Social Accounting Matrix (SAM). Then the costs and benefits of five fishing methods are compared from economic, ecological and social three dimensions base on the ECOST model. The potential effects of fishing effort reduction on fishing communication are explored by a series of dynamic simulations for a 10-year period. Key results from prediction (2005-2015) and policy simulations illustrate that fisheries of PRE are geared toward short-term economic profits at the expense of ecological gains and the whole group of societal benefits associated with fishing. However, the status quo can be improved to better levels by reducing fishing efforts.
文摘鱼骨柔性翼(Fish bone active camber,FishBAC)是一种依靠结构变形实现机翼弯度变化的结构形式,相较于传统的离散式控制面和增升装置,可以在实现机翼弯度变化的同时保持气动表面的连续与光滑。然而,其依靠结构弹性变形实现机翼变弯度的基本特征可能引发潜在气动弹性问题。针对柔性翼潜在的气动弹性问题,本文从结构特性和气动弹性特性两方面进行了研究。在结构特性方面,基于欧拉梁理论和逐段刚化法建立等效结构模型,经有限元验证发现简化模型在计算非均质梁结构保持精度的同时提高了计算效率。在气动弹性特性分析方面,基于等效刚柔耦合翼型模型和非定常气动理论完成了气动弹性特性分析。结果表明,FishBAC建模时需考虑结构柔性,忽略结构柔性会对气动弹性特性的预测存在一定偏差。在驱动力矩低于1.5 N·m时,本文简化的等效结构模型可较好地预测考虑静气动弹性特性的机翼结构形变。使用本文提出的翼型模型考虑结构存在刚柔耦合特性,并预测柔性段所发生的弯度颤振,简化模型与MSC Nastran相比在颤振速度预测上保持了一致性。
