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81.
Torsten Bergmark 《Surveys in Geophysics》1984,6(3-4):381-391
A fluxgate magnetometer has been developed at the Geological Survey of Sweden. It measures the field in three orthogonal directions and has sensor elements forming bridges. The instrument can have direct readout in both digital and analogue form with a resolution of 0.1 nT.An instrument of this type has been adopted for stationary recording of geomagnetic elements in digital form. Special attention has been paid to insure good long term stability and high reliability. Experience from routine recording is described. 相似文献
82.
Self-protective behavior by residents of flood-prone urban areas can reduce monetary flood damage by 80%, and reduce the need
for public risk management. But, research on the determinants of private households’ prevention of damage by natural hazards
is rare, especially in Germany. To answer the question of why some people take precautionary action while others do not, a
socio-psychological model based on Protection Motivation Theory (PMT) is developed, explaining private precautionary damage
prevention by residents’ perceptions of previous flood experience, risk of future floods, reliability of public flood protection,
the efficacy and costs of self-protective behavior, their perceived ability to perform these actions, and non-protective responses
like wishful thinking. The validity of the proposed model is explored by means of representative quantitative telephone surveys
and regression analyses, and compared with a socio-economic model (including residents’ age, gender, income, school degree
and being owner or tenant). Participants were 157 residents of flood-prone homes in Cologne, Germany, a city that has traditionally
been subject to minor and major flood events. Results of the study show the explanatory power of the socio-psychological model,
with important implications for public risk communication efforts. To motivate residents in flood-prone areas to take their
share in damage prevention, it is essential to communicate not only the risk of flooding and its potential consequences, but
also the possibility, effectiveness and cost of private precautionary measures. 相似文献
83.
84.
Sebastian Wagner Martin Widmann Julie Jones Torsten Haberzettl Andreas Lücke Christoph Mayr Christian Ohlendorf Frank Schäbitz Bernd Zolitschka 《Climate Dynamics》2007,29(4):333-355
This study investigates the atmospheric circulation in transient climate simulations with a coupled atmosphere–ocean general
circulation model (GCM) for the mid-Holocene (MH) period 7–4.5 ka BP driven with combinations of orbital, solar and greenhouse
gas forcings. The focus is on southern South America. Statistical downscaling models are derived from observational data and
applied to the simulations to estimate precipitation in south-eastern Patagonia during the MH. These estimates are compared
with lake level estimates for Laguna Potrok Aike (LPA) from sediments. Relative to pre-industrial conditions (i.e. 1550–1850),
which show extraordinarily high lake levels, the proxy-based reconstructed lake levels during the MH are lower. The downscaled
simulated circulation differences indicate higher LPA precipitation during the MH from March to August, higher annual means,
and reduced precipitation from September to February. Thus the reconstructed lower LPA lake levels can not be explained solely
by the simulated precipitation changes. Possible reasons for this discrepancy are discussed. Based on proxy data from southern
South America hypotheses have also been proposed on the latitudinal position of the southern hemispheric westerlies (SHWs).
In agreement with some of these hypotheses our simulations show an increased seasonal cycle of the latitudinal position of
the SHWs during the MH, which can be explained by the orbital forcing. The simulations also show stronger SHWs over southern
Patagonia during austral summer and weaker SHWs during winter. The downscaling model associates weaker SHWs with increased
precipitation in the LPA region. However, this relationship is only moderate, and therefore the downscaling model does not
support the assumption of a strong link between mean SHWs and precipitation over south-eastern Patagonia, which is the basis
of many proxy-based hypotheses about the SHWs. 相似文献
85.
Acta Geotechnica - The paper presents an experimental study on the effect of plastic fines content on the undrained behavior and liquefaction susceptibility of sand-fines mixtures under cyclic... 相似文献
86.
Mass media frequently makes use of more than the visual image. With the exception of music, movie scores, and radio news however, media geographers have largely ignored the impact sound in media has on shaping and characterizing our experience of the world. We address this lack by showcasing two types of audio media: audio drama and audio-guided tours. The former will be explored with the help of the world’s most successful audio drama series The Three Investigators to give a historical and theoretical introduction to the realm of sound within mass media. The latter will be illustrated using the example of the Austin Walking Tour as a representative production for city tourism. 相似文献
87.
Stefan Hahmann Jakob Miksch Bernd Resch Johannes Lauer Alexander Zipf 《地球空间信息科学学报》2018,21(3):247-256
AbstractFinding the shortest path through open spaces is a well-known challenge for pedestrian routing engines. A common solution is routing on the open space boundary, which causes in most cases an unnecessarily long route. A possible alternative is to create a subgraph within the open space. This paper assesses this approach and investigates its implications for routing engines. A number of algorithms (Grid, Spider-Grid, Visibility, Delaunay, Voronoi, Skeleton) have been evaluated by four different criteria: (i) Number of additional created graph edges, (ii) additional graph creation time, (iii) route computation time, (iv) routing quality. We show that each algorithm has advantages and disadvantages depending on the use case. We identify the algorithms Visibility with a reduced number of edges in the subgraph and Spider-Grid with a large grid size to be a good compromise in many scenarios. 相似文献
88.
The atmospheric conditions during an observed case of open cellular convection over the North Sea were simulated using the
Weather Research and Forecasting (WRF) numerical model. Wind, temperature and water vapour mixing ratio profiles from the
WRF simulation were used to initialize an idealized version of the model, which excluded the effects of topography, surface
inhomogeneities and large-scale weather forcing. Cells with an average diameter of 17.4 km developed. Simulations both with
and without a capping inversion were made, and the cell-scale kinetic energy budget was calculated for each case. By considering
all sources of explicit diffusion in the model, the budgets were balanced. In comparison with previous work based on observational
studies, the use of three-dimensional, gridded model data afforded the possibility of calculating all terms in the budgets,
which showed that the important terms in the budgets were buoyancy, pressure balance and inter-scale transfer to subgrid scales.
Cells were also composited to calculate the average cell-scale flow and each of the budget terms on two-dimensional cross-sections
through the cells, parallel and perpendicular to the mean wind direction. 相似文献
89.
<正>Terrestrial plants and insects currently account for the majority of the Earth's biodiversity,and approximately half of insect species are herbivores.Thus,insects and plants share ancient associations that date back more than 400 Myr.However,investigations of their past interactions are at the preliminary stages in Western Europe.Herein,we present the first results of our study of various feeding damage based on a dataset of nearly 3500 examined plant specimens from the Lower Miocene of the Lagerstatte Bilina Mine in the Most Basin, Czech Republic.This site provides a unique view of the Neogene freshwater ecosystems.It has long been studied by scientists working in different branches of sedimentology,paleobotany,and paleozoology.The fossils are preserved in three characteristic horizons overlaying the coal seam(Clayey Superseam Horizon,Delta Sandy Horizon,and Lake Clayey Horizon),reflecting paleoenvironmental changes in a short time period of development The trace fossils are classified as functional feeding groups or"guilds",without searching for a direct cause or a recent analog host relation.Approximately 23%of specimens of dicotyledonous plant leaves were found to be damaged and associated with some leaf"morphotypes".Deciduous plant-host taxa,and those with a chartaceous texture typical of riparian habitats,were frequently damaged,such as Populus,recorded with two species Populus zaddachii and Populus populina(57.9%and 31%herbivory levels,respectively),followed by Acer,Alnus,and Carya,averaging almost 30%of damaged leaves/leaflets.There has been evidence of 60 damage types(DT) representing all functional feeding groups recorded at the Bilina Mine,including 12 types of leaf mines and 16 gall- type DT.In total,Lower Miocene of the Lagerstatte Bilina Mine exhibits a high level of external foliage feeding types(23.7%),and a low level of more specialized DT,such as galls(43%)and leaf mines(1%).A broader comparison based on DT of the main sedimentary environments shows significance supporting different biomes by frequency of damage levels and DT diversities. 相似文献
90.
We consider the modeling and simulation of compositional two-phase flow in a porous medium, where one phase is allowed to
vanish or appear. The modeling of Marchand et al. (in review) leads to a nonlinear system of two conservation equations. Each
conservation equation contains several nonlinear diffusion terms, which in general cannot be written as a function of the
gradients of the two principal unknowns. Also the diffusion coefficients are not necessarily explicit local functions of them.
For the generalised mixed finite elements approximation, Lagrange multipliers associated to each principal unknown are introduced,
the sum of the diffusive fluxes of each component is explicitly eliminated and the static condensation leads to a “global”
nonlinear system of equations only in the Lagrange multipliers also including complementarity conditions to cope with vanishing
or appearing phases. After time discretisation, this system can be solved at each time step using a semi-smooth Newton method.
The static condensation involves “local” nonlinear systems of equations associated to each element, solved also by a semismooth
Newton method. The algorithm is successfully applied to 1D and 2D examples of water–hydrogen flow involving gas phase appearance
and disappearance. 相似文献