Jamaica Bay studies III: Abiotic determinants of distribution and abundance of gulls (Larus)     

Joanna Burger 《Estuarine, Coastal and Shelf Science》1983,16(2):191-216

The distribution and abundance of gulls were examined at Jamaica Bay Wildlife Refuge (New York) from 31 May 1978 to 31 May 1979. Gulls were found to be affected by tidal, temporal and weather-related factors. The distribution of gulls was affected primarily by tidal factors on the bay, and by temporal (seasonal, circadian) and weather-related factors on the freshwater ponds. The most important weather-related factors were temperature, wind velocity and wind direction. Herring (L. argentatus), great black-backed (L. fuscus) and ring-billed gulls (L. delawarensis) fed on the bay at low tides, and used the ponds at high tide. Laughing gulls (L. atricilla) fed on the bay at low tide and on rising tides. Herring and great black-backed gulls were present all year, but were most abundant in the winter, ring-billed gulls were abundant in spring and early fall, and laughing gulls were present in the summer following the breeding season but were absent in winter. Gulls used the ponds during high velocity, north winds, when they usually rested or preened. Multiple regression models were used to determine the factors explaining the variability in the numbers of gulls. Temporal variables were important contributors to accounting for the variability in the numbers of great black-backed and herring gulls only; tidal variables were significant for great black-backed and herring gulls on the bay, and for ring-billed and laughing gulls on all areas; and weather variables were significant for all species.  相似文献   

Tidally-induced residual currents in Long Island and Block Island Sounds     

John P. Ianniello 《Estuarine, Coastal and Shelf Science》1981,12(2):177-191

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在FS下观测站特有设备的控制     

薛祝和 《中国科学院上海天文台年刊》2011,(0)

介绍了FS软件的基本特征和ES控制标准硬件的详细工作流程。还具体介绍了在FS软件下控制观测站各种特有硬件的方法、步骤。本文可供中国VLBI网观测站程序员参考。  相似文献   

华北地区大地震的长余震序列     

王辉  刘勉  李振  曹建玲  荆燕 《地震》2013,33(3)

作为活化的古老克拉通,华北地区的地震活动非常频繁。上世纪60年代以来,华北地区曾经发生了1966年邢台M7.2,1975年海城M7.3和1976年唐山M7.8等地震。2012年5月28日,在唐山地震震源区又发生了M4.8地震,引起了国内外地学界的广泛关注和争议。争议的焦点在于此次地震是1976年唐山地震的余震,还是唐山地区乃至整个华北地区新一轮地震活动开始的预兆。本文利用华北地区过去40多年的地震活动资料,研究了邢台、海城和唐山地区的地震活动。研究结果显示,邢台、海城和唐山地区过去30多年的小震活动明显高于这些地区大震前的地震活动及华北地区的背景地震活动,应是余震。同时由GPS资料计算的邢台、海城和唐山地区的地壳水平应变率也明显高于华北地区的背景值。这些小震活动和地壳水平应变率同时表明邢台、海城和唐山强震区的余震数十年后仍在持续。震后粘性松弛可能是华北地区长时间余震持续的主要原因。  相似文献   

Boundary-based analysis for the assessment of coastal dune landscape integrity over time     

《Applied geography (Sevenoaks, England)》2013

Coastal dunes are transitional systems which offer manifold ecosystem services, including material and intangible benefits, whose relevance for human society has been little investigated to date. In order to plan a sustainable use of these threatened ecosystems, proper indicators to quantify ecological services and functions over time should be provided. Since the functionality of coastal dunes is affected by the specific contiguity among different dune habitat patches, in this paper we propose the use of landscape integrity, expressed by the number and length of boundary types among the aforementioned habitats, as an ecosystem functionality indicator. In particular, we aim at properly expressing the trend of coastal dune mosaic integrity in two Italian LTER sites over the last sixty years by applying a generalized diversity function on the number and length of boundary types. Such functions, unlike a traditional diversity index, allow a complete summarization of landscape diversity and structure. The proposed method has proved to be effective in the considered context, because it has adequately underlined the different landscape integrity trend recorded in the two sites. In particular, generalized diversity functions showed to efficiently express both rough and moderate anthropogenic transformations, which affected spatial heterogeneity and functionality of the considered coastal dune mosaic. Further applications at different scales and across different ecosystems are encouraged.  相似文献   

Path Dependency and Patterns of Collective Action: Space,Place, and Agency in Long Beach,California, 1900–1960     

Gary Hytrek 《Urban geography》2013,34(4):496-522

Drawing on the insights of the geography, structural, and social movement literature this study analyzes the interactive effects of structure, space, place, and agency on patterns of collective action in Long Beach, California. Long Beach and Los Angeles occupy the same regional landscape with similar economies, yet the logic of collective action varies considerably. It is argued that preceding 1960, pro-business elites in Long Beach allied with their Los Angeles counterparts to spatially restrict labor organizing and foster patterns of noncontiguous interdependencies within and among labor and community groups. Through violence, cultural references, local and extralocal political policies, and regional coalition building before 1960, the Long Beach ruling elites fragmented the labor and community sector and inhibited the emergence of an organizational infrastructure necessary to foster community-based change after 1960. The legacies of this period are reflected in a fragmented labor and community sector set against a powerful ideologically driven, business-led opposition.  相似文献   

云南中甸香格里拉大酒店项目岩土工程分析     

高伏芳 《云南地质》2012,(1):93-95

经资料整理、数理统计以及参照地区经验,认为场地工程性能一般,应采用桩基础或进行地基处理,提出合理岩土工程参数及地基处理方法、建议。  相似文献   

地下线状长导体对激发极化场的影响——以胶东地区为例     

董寿志 《山东地质》2012,(1):31-33,38

线状长导体,如金属管道、裸金属线、光缆等,其直径相对于埋深虽然很小,但受到激发时,能够产生很大的极化场,生产实践中对极化率的影响很大。该文主要研究了中梯和联剖2种装置下地下线状长导体的异常特征,分析了异常产生的原因,并提出了辨别这种干扰因素的方法。  相似文献   

航磁垂直梯度调整ΔT水平方法研究   总被引：2，自引：1，他引：1       下载免费PDF全文

骆遥  王平  段树岭  程怀德 《地球物理学报》2012,55(11):3854-3861

使用中国自主研发、具有完全自主知识产权的航磁全轴梯度勘查系统首次试飞获得的资料,利用航磁垂直梯度数据进行ΔT水平调整研究,讨论了航磁及航磁梯度资料水平调整的原则,提出梯度资料长波水平的调平方法.对经长波水平调整后的垂直梯度数据进行位场转换,获得不受地磁场随时间变化影响的磁异常,并通过恢复磁异常的长波信息,实现了ΔT的水平调整和增强.实际资料处理表明调平过程具有物理意义、效果明显.  相似文献   

Theory and application of nonlinear river dynamics     

Yu-chuan BAI  Zhao-yin WANG 《国际泥沙研究》2014,29(3):285-303

A theoretical model for river evolution including riverbed formation and meandering pattern formation is presented in this paper.Based on nonlinear mathematic theory,the nonlinear river dynamic theory is set up for river dynamic process.Its core content includes the stability and tropism characteristics of flow motion in river and river selves＇ evolution.The stability of river dynamic process depends on the response of river selves to the external disturbance,if the disturbance and the resulting response will eventually attenuate,and the river dynamics process can be restored to new equilibrium state,the river dynamic process is known as stable;otherwise,the river dynamic process is unstable.The river dynamic process tropism refers to that the evolution tendency of river morphology after the disturbance.As an application of this theory,the dynamical stability of the constant curvature river bend is calculated for its coherent vortex disturbance and response.In addition,this paper discusses the nonlinear evolution of the river peristaltic process under a large-scale disturbance,showing the nonlinear tendency of river dynamic processes,such as river filtering and butterfly effect.  相似文献