Seasonal variation of a molluscan assemblage living in a Caulerpa prolifera meadow within the inner Bay of Cádiz (SW Spain)     

Jose L. Rueda  Carmen Salas 《Estuarine, Coastal and Shelf Science》2003,57(5-6):909-918

The molluscan macrofauna living in shallow muddy bottoms with the green algae Caulerpa prolifera was studied monthly between February 1994 and January 1996 in the inner Bay of Cádiz (SW Spain). The molluscan assemblage followed a similar pattern over the 2 years, displaying seasonal trends in species richness, abundance and structure. During the autumn and winter months, a decrease in abundance, species richness and diversity and an increase in evenness occurred. During the spring and summer months, the molluscan assemblage was characterised by an increase in species richness, abundance and diversity. These seasonal trends were supported statistically by the presence of significantly different groupings of seasonal samples in multivariate analyses.Despite human impacts in the bay (e.g. aquaculture activities, sewage), the presence of repetitive seasonal trends, based on the qualitative and quantitative data, indicates the stability of the molluscan assemblage over 2 years. Benthic characteristics from the inner Bay of Cádiz, such as shallow soft bottoms with the presence of macrophytes and current dynamics, seem to be key factors influencing the composition and seasonality of this molluscan assemblage.  相似文献   

Does Better Spatial Access Lead to Better Use of Prenatal Care? A Population Study in Georgia     

Ping Yin 《The Professional geographer》2018,70(3):363-373

Understanding the effect of spatial accessibility on service utilization is essential to facilitate prenatal care delivery. Previous studies suggest that mothers with better spatial access are more likely to receive adequate prenatal care. Their conclusions, however, are limited by use of small samples and inappropriate spatial accessibility measurements. This article examines the role of spatial accessibility in explaining the variation of prenatal care utilization among 202,377 mothers in Georgia from 2009 to 2011. Specifically, we use geographic information systems and spatial analysis methods to explore the spatial pattern of inadequate prenatal care utilization. A two-transportation-mode, two-step floating catchment area method is used to measure the spatial access to prenatal care by census tract. The effects of spatial accessibility, combined with the influences of demographic, socioeconomic, behavioral, and medical factors, on the adequacy of prenatal care utilization are investigated with statistical models at the individual level. The results show that mothers with better spatial access are less likely to have adequate prenatal care. The inconsistency of this finding with other existing evidence suggests that the effects of spatial accessibility on health service utilization could be complicated and context specific.  相似文献   

Aquaculture of Sarcothalia atropurpurea tetraspores in New Zealand for carrageenan production     

S. E. McNeill 《新西兰海洋与淡水研究杂志》2013,47(4):528-542

The endemic red seaweed Sarcothalia atropurpurea is a potentially valuable source of carrageenan, but no information is available on growing this species as a crop in New Zealand. Tetraspores released from wild-harvested reproductive thalli were settled onto strings and grown initially in tanks under two different day-lengths. Seeded strings were transplanted to open water at 2, 6 and 10 weeks after spore release. Gametophytic biomass was harvested twice by pruning plants approximately six and nine months after spore release. Sporeling length was correlated with day length during tank culture but these differences were not apparent after a period of open-water culture. Spores cultured with medium day-length for 6–10 weeks before transfer to open water grew into harvestable plants that contained similar amounts and types of carrageenan to that from wild material. These results demonstrate for the first time that aquaculture of gametophytic S. atropurpurea from tetraspores is possible.  相似文献   

SEAWEED CULTIVATION: TRADITIONAL WAY AND ITS REFORMATION   总被引：4，自引：0，他引：4  

费修绠  鲍鹰  卢山 《中国海洋湖沼学报》1999,17(3):193-199

INTRODUCTIONSeaweedcultivationisthemosteffectivewayforobtaininglargeamountofseaweedproducts.Thoughseaweedcultivationhasahistoryofonlyafewdecades,itsdevelopmentisfast (Fei,1 996) .Thetotalproductionofcultivatedseaweedatpresentisabout 62 50× 1 0 3tonsfreshweight,ofwhichLaminariaaccountsfor 3 1 0 0× 1 0 3tons,Undaria 2 2 0 0x 1 0 3tons,Porphyra 750× 1 0 3tons,Gracilariasp .1 0 0× 1 0 3tons,EucheumaandKappaphycus 1 0 0× 1 0 3tons,otherkindofseaweeds 1 0 0× 1 0 3tons.Theestimatedtotal…  相似文献   

浮式风机一体化模拟的计算参数设置影响研究     

《海洋技术学报》2024,(1)

随着海上浮式风机的大型化发展，针对漂浮式风机的一体化耦合分析越来越重要。本文利用Simo-Riflex-Aerodyn 仿真工具建立OC4-Deepcwind 漂浮式风机一体化耦合模型，分析计算时间步长、初始截断时间、弹性结构单元离散数等计算参数对模拟结果的影响，包括浮式基础运动、系缆张力、叶片受力等。结果表明：当计算时间步长为0.005 s、0.01 s、0.02 s 时，浮式风机的响应结果差别较小，而计算消耗时间相差较大，0.01 s、0.02 s 的计算时间分别是0.005 s的70%、37%。相同工况下，不同参量响应达到稳定所需时间不同，纵荡需要的时间较长，最长达200 s；不同工况下，同一参量达到稳定所需时间也不相同，切出工况需要的时间最短，较额定工况快约60 s。结构单元离散数对塔柱受力影响较小，对叶片变形影响相对明显，当叶片离散数目减小时，响应值增大12%。实际中应根据具体工况选择合理的计算时间步长、初始截断时间和弹性结构单元离散数量。  相似文献   

浮式风机极限载荷与疲劳载荷对比分析     

张友文  王迎光 《海洋工程》2015,33(3):57-62

根据IEC61400-3设定工况,采用NREL开发的5 MW风机基础模型,应用FAST,以Aero-Hydro-Servo-Elastic耦合仿真技术对风机进行研究。对时域仿真得到的短期载荷,应用分块极大值法联合Gumbel分布外推计算风机极限载荷;以雨流计数法、线性累积损伤理论和S-N曲线为理论基础应用MLife软件,计算风机疲劳载荷。对比分析不同工况下浮式风机、近海单桩风机和陆上风机的极限载荷与疲劳载荷,进而探讨影响浮式风机动态响应的因素。结果表明,对于陆上风机和近海单桩风机,风是其主要载荷来源;而波浪是浮式风机主要载荷来源。对风机进行设计要根据特定海域统计的海洋气候条件,避免风机及其支撑结构的固有频率与波浪频率近似而产生共振;风机制造装配在一定误差范围内,质量不平衡对风机载荷几乎没有影响。  相似文献   

Damage Identification of A TLP Floating Wind Turbine by Meta-Heuristic Algorithms     

M. M. Ettefagh 《海洋工程》2015,29(6):891-902

Damage identification of the offshore floating wind turbine by vibration/dynamic signals is one of the important and new research fields in the Structural Health Monitoring (SHM). In this paper a new damage identification method is proposed based on meta-heuristic algorithms using the dynamic response of the TLP (Tension-Leg Platform) floating wind turbine structure. The Genetic Algorithms (GA), Artificial Immune System (AIS), Particle Swarm Optimization (PSO), and Artificial Bee Colony (ABC) are chosen for minimizing the object function, defined properly for damage identification purpose. In addition to studying the capability of mentioned algorithms in correctly identifying the damage, the effect of the response type on the results of identification is studied. Also, the results of proposed damage identification are investigated with considering possible uncertainties of the structure. Finally, for evaluating the proposed method in real condition, a 1/100 scaled experimental setup of TLP Floating Wind Turbine (TLPFWT) is provided in a laboratory scale and the proposed damage identification method is applied to the scaled turbine.  相似文献   

Experiment Study of Dynamics Response for Wind Turbine System of Floating Foundation   总被引：1，自引：1，他引：0  

唐友刚  宋凯  王宾 《海洋工程》2015,29(6):835-846

The floating foundation is designed to support a 1.5 MW wind turbine in 30 m water depth. With consideration of the viscous damping of foundation and heave plates, the amplitude-frequency response characteristics of the foundation are studied. By taking into account the elastic effect of blades and tower, the classic quasi-steady blade-element/momentum (BEM) theory is used to calculate the aerodynamic elastic loads. A coupled dynamic model of the turbine-foundation- mooring lines is established to calculate the motion response of floating foundation under Kaimal wind spectrum and regular wave by using the FAST codes. The model experiment is carried out to test damping characteristics and natural motion behaviors of the wind turbine system. The dynamics response is tested by considering only waves and the joint action of wind and waves. It is shown that the wind turbine system can avoid resonances under the action of wind and waves. In addition, the heave motion of the floating foundation is induced by waves and the surge motion is induced by wind. The action of wind and waves is of significance for pitch.  相似文献   

浮动车地图匹配算法研究   总被引：3，自引：0，他引：3  

王美玲  程林 《测绘学报》2012,41(1):133-0

针对现有浮动车地图匹配算法应用于城市复杂路网时面临的关键技术难点,本文基于浮动车数据,在 SuperMap GIS 平台下实现了城市交通路网的构建,并研究了一种浮动车地图匹配的新算法：基于网格的候选路段确定,基于距离、航向、可达性权重的定位点匹配及基于最短路径的行驶轨迹选择。算法能够满足浮动车地图匹配准确性与实时性的要求,为获取城市道路的交通拥堵状况信息提供可靠依据。  相似文献   

城市道路交通状态信息服务系统设计与实现     

刘好德 《测绘科学》2012,37(6):169-171

通过对交通信息服务系统的现状分析,本文提出了基于浮动车数据的城市道路交通状态信息服务系统设计方案,阐述了系统的交通工程理论和系统技术基本原理,结合需求分析设计了系统的功能结构,重点研究了一种高效的数据存储管理设计方法,最后结合目前流行的富客户端技术研究了系统实现问题,提出了未来的发展趋势。  相似文献