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51.
Use of Systematic, Palaeoflood and Historical Data for the Improvement of Flood Risk Estimation. Review of Scientific Methods 总被引:2,自引:0,他引:2
Gerardo Benito Michel Lang Mariano Barriendos M. Carmen Llasat Felix Francés Taha Ouarda Varyl Thorndycraft Yehouda Enzel Andras Bardossy Denis Coeur Bernard Bobée 《Natural Hazards》2004,31(3):623-643
The catastrophic floods recently occurring in Europe warn of the critical need forhydrologic data on floods over long-time scales. Palaeoflood techniques provideinformation on hydrologic variability and extreme floods over long-time intervals(100 to 10,000 yr) and may be used in combination with historical flood data (last1,000 yr) and the gauge record (last 30–50 yr). In this paper, advantages anduncertainties related to the reconstruction of palaeofloods in different geomorphologicalsettings and historical floods using different documentary sources are described.Systematic and non-systematic data can be combined in the flood frequency analysisusing different methods for the adjustment of distribution functions. Technical toolsintegrating multidisciplinary approaches (geologic, historical, hydraulic and statistical)on extreme flood risk assessment are discussed. A discussion on the potential theoreticalbases for solving the problem of dealing with non-systematic and non-stationary data ispresented. This methodology is being developed using new methodological approachesapplied to European countries as a part of a European Commission funded project (SPHERE). 相似文献
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An important claim for the categorisation and study of shrinking cities is that the experience of governance across these cities may offer an alternative to hegemonic discourses of growth. However, there are methodological problems associated with categorizing then researching shrinking cities. Two key problems are: first, the category hides a multiplicity of cause and effect and; second, the danger of fetishizing the city against the reality of broader urban drivers of change. It is argued that the use of governance narratives is a means to addresses this, as narratives focus us on cities as places of practice. We apply the approach to Leipzig, once shrinking but now one of Germany’s fastest growing cities. We conclude that while there was a significant attempt to articulate an alternative to growth, it remained dominant suggesting the need to develop a taxonomy of shrinking cities where not all offer an alternative vision of “development”. 相似文献
55.
TeV Gamma Rays From the Galactic Center Direct and Indirect Links to the Massive Black Hole in Sgr A
The recent detection of TeV gamma-radiation from the direction of the Galactic Center within several arc-minutes around Sgr
A* is the first model-independent evidence of existence of high-energy particle accelerator(s) in the central 10 pc region of
our Galaxy. This is an extraordinary site that harbours many remarkable objects with the compact radio source Sgr A* – a hypothetical super-massive black hole (SMBH) – in the dynamical center of the Galaxy. Here we explore the possible direct and indirect links of the reported TeV emission to the SMBH. We show that at least three γ-ray production scenarios that take place close
to the event horizon of the SMBH can explain the reported TeV fluxes. An alternative (or additional) channel of TeV radiation
is related to the run-away protons accelerated in Sgr A*. Quasi-continuous injection of relativistic protons into the surrounding dense gas environment initiates detectable high-energy
gamma-ray emission. The absolute flux and the energy spectrum of this radiation component strongly depend on the history of
particle injection and the character of diffusion of protons during the last 105 yr. For a reasonable combination of a few model parameters, one can explain the detected gamma-ray flux solely by this diffuse
component. 相似文献
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The classical Poisson equations of rotational motion are used to study the attitude motions of an Earth orbiting, rapidly spinning gyroscope perturbed by the effects of general relativity (Einstein theory). The center of mass of the gyroscope is assumed to move about a rotating oblate Earth in an evolving elliptic orbit which includes all first-order oblateness effects produced by the Earth.A method of averaging is used to obtain a transformation of variables, for the nonresonance case, which significantly simplifies the Poisson differential equations of motion of the gyroscope. Longterm solutions are obtained by an exact analytical integration of the simplified transformed equations. These solutions may be used to predict both the orientation of the gyroscope and the motion of its rotational angular momentum vector as viewed from its center of mass. The results are valid for all eccentricities and all inclinations not near the critical inclination.This paper represents a part of the author's Ph. D. dissertation for the Mathematics Department, Auburn University. 相似文献
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Constructing the Tropics: Introduction 总被引:4,自引:2,他引:2
60.
When using Transient Geo-Electromagnetics (TEM) unusually slow decaying transients are sometimes observed in the absence of well-conductive objects. Many researchers explain this phenomenon by presence of material with magneto-viscous or superparamagnetic (SPM) properties. The analysis of electromagnetic (EM) field equations in conductive SPM medium is suggested in the present paper. It is shown that in a simplest case of small size single-domain magnetic particles with relative higher potential barrier energy, the SPM-medium is characterized by a very slow decaying exponential transient magnetic field, the level of which is much more as compared to that of due to non-magnetic medium of the same conductivity. This situation is traced up to the late transient time like 0.1 s and more. SPM and Induction fields are in the near zone additive. They depend in a different way on the superparamagnetic and electric properties of the SPM-medium. They also depend in different ways on the transient time and on the size of the transmitter–receiver configuration. These characteristics make it possible to recognize the presence of SPM-effect and to separate these fields. 相似文献