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1.
H. C. Duthie J-R Yang T. W. D. Edwards B. B. Wolfe B. G. Warner 《Journal of Paleolimnology》1996,15(1):79-97
Limnological changes in Hamilton Harbour, Lake Ontario, over the Holocene were investigated by using proxy evidence from diatoms and other siliceous microfossils in a radiometrically dated sediment core (HH26comp), together with environmental data derived from sediment pollen and oxygen and carbon isotope analyses. The evidence demonstrates that the site of Hamilton Harbour has changed over the past 8300 y from a shallow, separate waterbody, to a deep embayment of Lake Ontario. The earliest evidence, from 8300 BP to 7000 BP, is of a mesotrophic pond of moderate alkalinity, warmer than present, and probably with an extensive marginal wetland. An initial transitory connection with the rising water level of Lake Ontario was established at c. 7000 BP, possibly via a deep outlet channel. This connection is 2000 y earlier then previously estimated. Permanent confluence with Lake Ontario was established at c. 6200 BP, causing a decline in inferred trophic level and water temperatures. Microfossils reach a minimum at 4400 BP coincident with the Nipissing Flood. Decreased mixing of Lake Ontario water from about 4000 BP following the Nipissing Flood highstand is evidenced in isotopic and diatom data. Three isolated shifts in the diatom spectrum at c. 4900 BP, 4500 BP, and 3500 BP may be associated with extreme turbidity or storm deposit events. Between 3200 BP and 280 BP, Hamilton Harbour was evidently a moderately alkaline embayment of Lake Ontario, oligotrophic to mesotrophic, and relatively cooler than present. The final 280 y sedimentary record reveals the magnitude of anthropogenically induced changes to the harbour, including eutrophication and organic pollution. 相似文献
2.
罗德海 《成都信息工程学院学报》1993,(4)
本文通过构造斜压大气运动的原始方程模式和两层模式的Hamilton守恒量及积分不变的Casimir泛函,并使用变分法,得到了斜压大气运动的非线性Lyapunov稳定性判据,这个判据是Arnold-Blumen-Zeng判据的推广。 相似文献
3.
4.
罗德海 《成都信息工程学院学报》1992,(4)
本文首先建立了中尺度对称运动的Hamihon函数,并用变分原理导出了对称运动稳定的充分条件,然后再用Lagrange变分导出了缓变介质中对称运动的波作用量方程,这种波作用量方程与用WKB方法所得到的结果是相同的。同时,本文进一步讨论了中尺度对称扰动渡包的演变规律,并获得了对称运动发展的判据。 相似文献
5.
This paper provides an empirical framework that applies spatial statistics methods to assess the relation between the change
in the geographical clustering of firms and the emergence of urban form. We contend that where firms locate and eventually
cluster give rise to the way commercial and industrial land uses are organized over space, which in turn defines the shape
of urban form. Accordingly, the objectives of our work are twofold: (1) to identify the extent and shape of firm clustering
and co-location at the intra-metropolitan level, and (2) examine how the change in the geographic clustering of different
industries contributes to decentralization and the evolution of urban form. Spatial statistics methods and tools were vital
and helped to fulfill these objectives.
相似文献
6.
Business establishment mobility behavior in urban areas: a microanalytical model for the City of Hamilton in Ontario,Canada 总被引：1，自引：0，他引：1
We present a microanalytical firm mobility model for the City of Hamilton, Canada, developed with data from the Statistics
Canada Business Register. Contributing to the scarce literature on firm migration behavior, we explore and model the determinants
of mobility among small and medium size firms who retained less than 200 employees between 1996 and 1997. Our exploratory
results suggest that short distance moves are more common and tend to occur among smaller firms. Econometric modeling results
support these assertions and indicate that the willingness to move can be explained by a firm’s internal characteristics (e.g.
age, size, growth and industry type) as well as location factors related to the urban environment where the firm is located.
The modeling results will serve as input for the development of an agent-based firmographic decision support system that can
be used to inform the planning process in the study area.
相似文献
7.
面向油气勘探开发提升地震偏移及属性刻划水平 总被引：20，自引：14，他引：6
针对复杂地质条件油气勘探开发的需求,仅就运用地震资料提取地质属性及构建油储模型所可能面临的难点,阐明必需提升地震波传播及成像研究水平的基础理论命题和数值计算的关键环节。文中着重于用形象的数值图像结果,说明开展此类研究的必要性。对我国而言,前新生代海相碳酸盐岩勘探和今后相当时期内对国志经济仍起支撑作用的东部老油田外围及深部油气的勘探开发,这两类研究对象尽管其地质演化年代及过程各异,但对地球物理偏移成像技术进步及油储建模而言,对提升探测的理论所提出的要求,都属于近代的难题,文中还阐明这类研究已是刻不容缓的原因所在。 相似文献
8.
罗德海 《成都信息工程学院学报》1993,(4)
本文通过引入守恒的伪动量(Pseudo-Momentum),并利用Hamilton函数,Casimir泛函,建立了一个新的Lyapunov泛函,在此基础上使用变分原理得到了大气运动所满足的广义稳定性判据。当基本气流仅存在经向切变时,所得到的广义稳定性判据与用经典标准模方法所得到的稳定性判据是一致的。 相似文献
9.
Dynamic response of a flexible cantilever wall retaining elastic soil to harmonic transverse seismic excitations is determined with the aid of a modified Vlasov–Leontiev foundation model and on the assumption of vanishing vertical displacement of the soil medium. The soil–wall interaction is taken into consideration in the presented model. The governing equations and boundary conditions of the two unknown coupled functions in the model are derived in terms of Hamilton׳s principle. Solutions of the two unknown functions are obtained on the basis of an iterative algorithm. The present method is verified by comparing its results with those of the existing analytical solution. Moreover, a mechanical model is proposed to evaluate the presented method physically. A parametric study is performed to investigate the effects of the soil–wall system properties and the excitations on the dynamic response of the wall. 相似文献
10.
LUCIANA MARTINS 《Geographical review》2012,102(2):225-244
In this article I reexamine Alexander Hamilton Rice's seventh expedition to Amazonia (1924–1925) in order to highlight the ways in which the image of the modern explorer was constructed through various technologies of visualization, including maps, still photography, and film. The Rice expedition was equipped with the latest surveying instruments, among them a hydroplane especially adapted for taking aerial photographs, and it was the first to attempt shortwave radio communication in the Tropics. However, the expedition's efforts to reach the headwaters of the Rio Branco ended in failure. I investigate Rice's heavy investment in making a visual record of the expedition in the context of his academic ambitions. Despite his influence in learned societies in the United States and Europe, his questionable reputation within academic circles was difficult to overcome: His reliance on publicity to enhance his academic career had adverse consequences. The retelling of Rice's tale here also sheds light on the role of indigenous local knowledge and agency in the history of exploration. All the modern surveying technology employed notwithstanding, local support remained crucial for Amazonian exploration. 相似文献