234 research outputs found
Historic maps as a data source for socio-hydrology: a case study of the Lake Balaton wetland system, Hungary
Socio-hydrology is the science of human influence on hydrology and the
influence of the water cycle on human social systems. This newly emerging
discipline inherently involves a historic perspective, often focusing on
timescales of several centuries. While data on human history is typically
available for this time frame, gathering information on the hydrological
situation during such a period can prove difficult: measured hydrological
data for such long periods are rare, while models and secondary data sets
from geomorphology, pedology or archaeology are typically not accurate
enough over such a short time. In the first part of this study, the use of
historic maps in hydrology is reviewed. Major breakthroughs were the
acceptance of historic map content as valid data, the use of preserved
features for investigating situations earlier than the map, and the onset of
digital georeferencing and data integration. Historic maps can be primary
quantitative sources of hydro-geomorphological information, they can provide
a context for point-based measurements over larger areas, and they can
deliver time series for a better understanding of change scenarios.
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In the second part, a case study is presented: water level fluctuations of
Lake Balaton were reconstructed from maps, levelling logs and other
documents. An 18th century map system of the whole 5700 km<sup>2</sup>
catchment was georeferenced, integrated with two 19th century map
systems, and wetlands, forests and open water digitized. Changes in wetland
area were compared with lake water level changes in a 220 yr time series.
Historic maps show that the water level of the lake was closer to
present-day levels than expected, and that wetland loss pre-dates drainage
of the lake.
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The present and future role of historic maps is discussed. Historic
hydrological data has to be treated with caution: while it is possible to
learn form the past, the assumption that future changes will be like past
changes does not always hold. Nevertheless, old maps are relatively
accessible data sets and the knowledge base for using them is rapidly
growing, and it can be expected that long-term time series will be
established by integrating georeferenced map systems over large areas.
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In the Appendix, a step-by-step guide to using historic maps in hydrology is
given, starting from finding a map, through georeferencing and processing
the map to publication of the results
The first scientific description of aurora borealis - the 10 September 1580 event in Transylvania, recorded by Marcello Squarcialupi
New universality class for the fragmentation of plastic materials
We present an experimental and theoretical study of the fragmentation of
polymeric materials by impacting polypropylene particles of spherical shape
against a hard wall. Experiments reveal a power law mass distribution of
fragments with an exponent close to 1.2, which is significantly different from
the known exponents of three-dimensional bulk materials. A 3D discrete element
model is introduced which reproduces both the large permanent deformation of
the polymer during impact, and the novel value of the mass distribution
exponent. We demonstrate that the dominance of shear in the crack formation and
the plastic response of the material are the key features which give rise to
the emergence of the novel universality class of fragmentation phenomena.Comment: 4 pages, 4 figures, appearing in Phys. Rev. Let
Crackling noise in three-point bending of heterogeneous materials
We study the crackling noise emerging during single crack propagation in a
specimen under three-point bending conditions. Computer simulations are carried
out in the framework of a discrete element model where the specimen is
discretized in terms of convex polygons and cohesive elements are represented
by beams. Computer simulations revealed that fracture proceeds in bursts whose
size and waiting time distributions have a power law functional form with an
exponential cutoff. Controlling the degree of brittleness of the sample by the
amount of disorder, we obtain a scaling form for the characteristic quantities
of crackling noise of quasi-brittle materials. Analyzing the spatial structure
of damage we show that ahead of the crack tip a process zone is formed as a
random sequence of broken and intact mesoscopic elements. We characterize the
statistics of the shrinking and expanding steps of the process zone and
determine the damage profile in the vicinity of the crack tip.Comment: 11 pages, 15 figure
Universality class of the fragmentation of plastic materials
We carry out an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene (PP) particles of spherical shape against a hard wall. Our experiments revealed that the mass distribution of fragments has a power law behavior with an exponent close to 1.2, which is significantly different from the known exponents of threedimensional bulk materials. To understand the fragmentation of plastic
materials we developed a threedimensional discrete element model where the sample is represented as a random packing of spherical particles connected by elastic beams. The model reproduces both the large permanent deformation of the polymer during impact, and the novel value of the mass distribution exponent. Computer simulations revealed that the dominance of shear in the crack formation and the healing of compressed crack surfaces are the key features which give rise to the emergence of the novel universality
class of fragmentation phenomena
Universality class of the fragmentation of plastic materials
We carry out an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene (PP) particles of spherical shape against a hard wall. Our experiments revealed that the mass distribution of fragments has a power law behavior with an exponent close to 1.2, which is significantly different from the known exponents of threedimensional bulk materials. To understand the fragmentation of plastic
materials we developed a threedimensional discrete element model where the sample is represented as a random packing of spherical particles connected by elastic beams. The model reproduces both the large permanent deformation of the polymer during impact, and the novel value of the mass distribution exponent. Computer simulations revealed that the dominance of shear in the crack formation and the healing of compressed crack surfaces are the key features which give rise to the emergence of the novel universality
class of fragmentation phenomena
Observation of a local gravity potential isosurface by airborne lidar of Lake Balaton, Hungary
Airborne lidar is a remote sensing method commonly
used for mapping surface topography in high resolution.
A water surface in hydrostatic equilibrium theoretically
represents a gravity potential isosurface. Here we compare
lidar-based ellipsoidal water surface height measurements all
around the shore of a major lake with a local high-resolution
quasi-geoid model. The ellipsoidal heights of the 87 km2 we
sampled all around the shore of the 597 km2 lake surface vary
by 0.8m and strong spatial correlation with the quasi-geoid
undulation was calculated (R2 = 0.91). After subtraction of
the local geoid undulation from the measured ellipsoidal water
surface heights, their variation was considerably reduced.
Based on a network of water gauge measurements, dynamic
water surface heights were also successfully corrected for.
This demonstrates that the water surface heights of the lake
were truly determined by the local gravity potential.We conclude
that both the level of hydrostatic equilibrium of the lake
and the accuracy of airborne lidar were sufficient for identifying
the spatial variations of gravity potential
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