Fluid-structure interaction effects for offshore structures     

A. S. Veletsos  A. M. Prasad  G. Hahn 《地震工程与结构动力学》1988,16(5):631-652

Comprehensive analyses are made of the differences in the responses of simple models of offshore structures computed by the standard and extended versions of Morison's equation for the hydrodynamic forces, and of the effects and relative importance of the numerous parameters involved. The responses also are evaluated by the equivalent linearization technique and Penzien's decoupling technique, and the interrelationship and accuracy of these approaches are elucidated. The results are displayed graphically in the form of response spectra for absolute maximum displacement employing dimensionless parameters that are easy to interpret and use. In addition, the decoupling technique is generalized to include consideration of a current of constant velocity, and a simple modification is proposed which improves the accuracy of this approach. A particularly simple approximation is included for the hydrodynamic modal damping values of multi-degree-of-freedom, stick-like systems.  相似文献   

Application of satellite remote sensing to observe and analyse temporal changes of cocoa plantation in Ondo State,Nigeria     

Dada  Emmanuel  Hahn  Michael 《GeoJournal》2022,87(1):231-246

GeoJournal - This study examined the changes in the area of land occupied by cocoa plantation in Ondo state in order to provide useful information for effective agricultural policy to increase...  相似文献   

Social learning towards a more adaptive paradigm? Reducing flood risk in Kristianstad municipality,Sweden     

Åse Johannessen  Thomas Hahn 《Global Environmental Change》2013,23(1):372-381

Social learning is often treated as an intervention, a designed process facilitated or even initiated by a third party. We investigated how a social learning process emerged spontaneously from inside Kristianstad, one of the most flood-prone municipalities in Sweden. Twenty key persons were interviewed over 8 years, many of them several times, to assess the process. A small action oriented group of technical professionals perceived the flood risk and were key drivers providing strategic innovative capacity. We identified the process attributes that fostered the learning, the knowledge generated and other learning outcomes adapting a model by Schusler et al. (2003). Despite some elements of double loop learning, this process was not able to change the prevailing stationary principle/paradigm, feeling safe behind the embankments and continuing building on low lying land. We argue that building resilience and adaptive capacity would require a mind shift to a paradigm of flood proofing/living with floods and preparing for the unexpected, acknowledging that water cannot be controlled at a certain level. We conclude that knowledge development is inhibited by the Swedish decentralisation approach and we call for a multilevel learning strategy including learning from international experience and emphasising more active coordination at the national level.  相似文献   

Messung magnetischer Feldstärken an Bord von Schiffen     

Otto Th. Hahn 《Ocean Dynamics》1955,8(2):49-58

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Cloning and analysis of the CYP1A promoter from the atlantic killifish (Fundulus heteroclitus)     

Powell WH  Morrison HG  Weil EJ  Karchner SI  Sogin ML  Stegeman JJ  Hahn ME 《Marine environmental research》2004,58(2-5):119-124

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The evolution of dark matter halo properties in clusters, filaments, sheets and voids     

Oliver Hahn  C. Marcella Carollo  Cristiano Porciani  Avishai Dekel 《Monthly notices of the Royal Astronomical Society》2007,381(1):41-51

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What is groundwater and what does this mean to fauna? - An opinion     

Susanne I. Schmidt  Hans Jürgen Hahn 《Limnologica》2012,42(1):1-6

Many subsurface waters are considered groundwater but are influenced in shallow depths by hyporheic, parafluvial and/or soil interception water to such a degree that groundwater fauna (stygofauna) communities may be significantly altered. Recharge, even if spatially and temporally distinct, delivers input of dissolved oxygen, organic matter (OM), and nutrients that caters sustainably for ubiquists such as stygophiles and hyporheic fauna, but renders the life of uncompetitive stygobites difficult or impossible. The impact of recharge at shallow groundwater thus needs to be taken into account when determining groundwater fauna reference communities and when evaluating monitoring studies.One of the main characteristics of groundwater is low OM concentration. In contrast, high OM concentrations are typical of hyporheic or parafluvial waters, which are enriched by OM from the river, the riparian soils and from interflow, and which contribute significantly to river OM balance. Consequently, for ecological studies on subsurface waters, both the origin of the water and OM, and the intensity of surface water interactions should be considered. Here, we discuss how groundwater spatial and temporal heterogeneity translates into faunal distribution patterns. In terms of the origin of water and OM, and from an ecological point of view, we need to distinguish between (i) shallow groundwater characterized by infiltrating precipitation and soil recharge, (ii) shallow groundwater interacting with surface water bodies such as continuously flowing and ephemeral streams and rivers, and (iii) “old” groundwater which has no recent connections to the surface and is thus largely secluded from input of nutrients and carbon. Water in the first two groups is characterized by high amounts of OM of varying quality, while water in the third group is characterized by low amounts of low quality OM. Consequently, stygophiles dominate in groups 1 and 2, with hyporheic fauna taking up a considerable proportion in group 2, while stygobites only dominate in group 3. Thus, for studies aiming to assess impacts on groundwater, only sampling sites of the third group should be used for reference sites as these are the most likely sites to have little surface impact and a stygofauna representative of the deeper aquifer.  相似文献   

P/2004 A1 (Loneos) – a comet under transition from Saturn to Jupiter     

G. Hahn  C.‐I. Lagerkvist  O. Karlsson  T. Oja  R. M. Stoss 《Astronomische Nachrichten》2006,327(1):17-20

The newly discovered periodic comet P/2004 A1 (LONEOS) is found to have experienced a recent capture into its present orbit, following a close approach to Saturn in 1992 to within 0.032 AU. This induced orbital change transfered the comet into an orbit tangent to that of Jupiter, which will, after a close passage in 2026, gain control by further decoupling it from the influence of Saturn. A long‐term orbital investigation yields support that the comet is on its first sojourn into the inner solar system. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Influence of microstructure on fracture propagation in rock   总被引：3，自引：1，他引：2  

R. G. Hoagland  G. T. Hahn  A. R. Rosenfield 《Rock Mechanics and Rock Engineering》1973,5(2):77-106

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Book Review     

Gerhard J. Hahn 《Earth, Moon, and Planets》1991,55(1):73-74

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