Reef status in the Rasfari region (North Malé Atoll,Maldives) five years before the mass mortality event of 1998     

Carla Morri  Stefano Aliani  Carlo Nike Bianchi 《Estuarine, Coastal and Shelf Science》2010

The Maldives was severely hit by massive coral bleaching and subsequent mortality in 1998. The results of reef monitoring in the following years have supported contrasting views about their recovery potential, partly because of the scarcity of information on the situation before 1998. Quantitative data on coral assemblages collected in 1993 in the Rasfari region (North Malé Atoll) may provide a base-line for the evaluation of the present status of the Maldivian reefs. Five years before the 1998 mortality, most coral communities appeared to be similar, in terms of both coral cover and growth-form composition, to those described in 1958 and 1964, notwithstanding increased human pressure and local events such as minor bleaching episodes in 1987 and crown-of-thorns starfish (COTS) attacks in 1989. Three lessons can be learnt from these results to help to understand the present situation, some ten years after the 1998 mass mortality. First, Maldivian reefs proved in the past to be capable of maintaining flourishing coral life despite various disturbances. Second, four years had been sufficient for complete reef recovery after a (minor) bleaching event. Third, recovery after both COTS attack and bleaching follows a predictable path suggesting that the presence of a three-dimensional community structure, which should reduce post settlement mortality of coral recruits, is essential for rapid coral recovery. As coral recruitment remains high and large tabular Acropora colonies are now reappearing, it is expected that Maldivian reefs should return to their original condition within the next few years.  相似文献   

Morphological and sedimentary impacts and recovery on a mixed sandy to pebbly seabed exposed to marine aggregate extraction (Eastern English Channel,France)     

Sophie Le Bot  Robert Lafite  Matthieu Fournier  Agnès Baltzer  Michel Desprez 《Estuarine, Coastal and Shelf Science》2010

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Wave-like aquatic propulsion of mono-hull marine vessels     

V.V. Krylov  E. Porteous 《Ocean Engineering》2010,37(4):378-386

The present paper describes results of the experimental investigation of a small-scale mono-hull model boat propelled by a localised flexural wave propagating along the plate of finite width forming the boat's keel. Forward propulsion of the boat was achieved through flexural wave propagation in the opposite direction, which is similar to the aquatic propulsion used in nature by stingrays. The model boat under consideration underwent a series of tests both in a Perspex water tank and in an experimental pool. In particular, the forward velocity of the boat has been measured for different frequencies and amplitudes of the flexural wave. The highest velocity achieved was 32 cm/s. The thrust and propulsive efficiency have been measured as well. The obtained value of the propulsive efficiency in the optimum regime was 51%. This indicates that the efficiency of this type of aquatic propulsion is comparable to that of dolphins and sharks (around 75%) and to that of a traditional propeller (around 70%). In contrast with a propeller though, the wave-like aquatic propulsion has the following advantages: it does not generate underwater noise and it is safe for people and marine animals.  相似文献   

Improvement of photorefractive properties in Hf:Fe:LiNbO₃ crystals with various [Li]/[Nb] ratios     

孙秀冬  石宏新  骆素华  孟庆鑫  姜永远 《海洋学报(英文版)》2010,29(9)

Photorefractive properties of Hf:Fe:LiNbO₃ crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf:Fe:LiNbO₃ crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf:Fe:LiNbO₃ crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method for Hf:Fe:LiNbO₃ crystal to improve its photorefractive properties.  相似文献   

多元热流体热采技术在海上探井测试中适应性研究     

林涛  孙永涛  马增华  孙玉豹  刘海涛  王少华 《海洋地质译丛》2012,(2):51-53

稠油黏度高,流动性差,常规测试难以正确评价储层的真实产能。随着多元热流体热采技术在海上油田生产平台的成功应用,提出了在探井测试中应用多元热流体热采技术。通过对支撑平台的适应性分析研究,运用数值模拟方法预测多元热流体热采测试的开采效果,并对相应的井口、供给方式等进行了优化研究。通过现场实施,多元热流体热采测试的日产油量可达常规冷采测试产油量的2倍以上,实际效果与数值模拟的结果基本相当。该技术的应用更能准确反映油田的真实产能,为海上稠油油田的探井测试提供了一个新方法。  相似文献   

重庆市工业生产的生态足迹分析     

李伟  杨诗源 《地域研究与开发》2008,27(4)

基于生态足迹理论和计算模型,根据工业生产的特点,计算了1997-2007年重庆市人均工业生态足迹和万元工业产值的生态足迹,并与有关研究数据进行了对比分析.结果显示:重庆市的人均工业生态足迹约相当于全国平均水平,但已超出重庆市总的生态承载力,并呈现出持续上升趋势,工业生产处于生态不可持续状态;万元工业产值的生态足迹略低于全国平均水平,下降趋势明显.表明重庆市通过转变工业发展模式,在不降低生产能力的条件下,减少工业生态足迹大有作为.  相似文献   

鲁甸地震生命线工程震害特点及应急抢修   总被引：2，自引：1，他引：1  

刘爱文  帅向华  吕红山  吴健  徐超 《震灾防御技术》2014,9(3):359-367

在现场调查的基础上,本文总结分析了鲁甸地震交通、通信和电力等三类生命线工程的震害特点及应急抢修情况。鲁甸地震是一次较典型的山区地震,地震地质灾害和强地震动共同作用是造成生命线工程破坏的主要原因。交通系统的主要震害是山体滑坡引起的道路中断,灾区属于高山峡谷地形,道路抢通困难。电力系统的小型水力发电站破坏严重,龙头山变电站的破坏直接导致其下级的2个变电站也断电。通信系统在本次地震中受的影响相对较小,恢复也较快。  相似文献   

Biosorption of Uranium Ions by Marine Macroalga Padina pavonia          下载免费PDF全文

Sule Aytas  Elif Gunduz  Cem Gok 《洁净——土壤、空气、水》2014,42(4):498-506

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Environmental Effect Caused by Over-exploitation of Deep Groundwater in North China     

Xiu-yan WANG  Yu-hong FEI 《地下水科学与工程》2014,2(1):12-20

Based on the formation and development analysis of the environmental geological disaster of land subsidence, earth fissures and other geological disasters in the North China, it showed these disasters caused a very serious problem in some areas of the North China, such as the deep groundwater exploitation cone, which is accumulated with great damage and loss and is hard to be controlled, therefore, great attention should be paid. It is considered that the formation of the deep groundwater cone is the root of various geological environmental problems, and the groundwater cone recovery is the key to solve other environmental problems  相似文献   

摆式波浪发电装置一级转化效率模型试验研究     

田育丰  黄焱  史庆增 《海洋工程》2012,30(3):177-184

一级转换装置是一个波浪能发电装置中的关键技术,而如何提高能量转化效率,是一级转换过程研究的重点问题。为确定一级转换装置的能量转化效率与哪些因素有关,对摆式波浪能发电装置的摆板机构进行了模型试验研究,测试了摆板模型在多种波浪条件下的动力响应参数,确定了摆板的动力输出特性及其控制因素;测试了在极限波浪作用下,摆板模型装置的受力状况。通过试验,为摆式波浪能发电装置的设计提供了必要的参考依据。  相似文献