219 research outputs found
Numerical evaluation of hypersingular integrals
AbstractBoundary integral equations which employ integrals which exist only if defined in the Cauchy principal value sense or as the Hadamard finite part are currently used with success to solve many two- and three-dimensional problems of applied mechanics. We will recall definitions and main properties of these integrals, examine some numerical approaches for their evaluation and present several new results
Glacial dynamics in pre-Alpine narrow valleys during the Last Glacial Maximum inferred by lowland fluvial records (northeast Italy)
During the Last Glacial Maximum (LGM), most of the major glaciated basins of the European Southern
Alps had piedmont lobes with large outwash plains; only a few glaciers remained within the valley. Piedmont
glaciers have left well-preserved terminal moraines, which allow for investigations to be carried out and inferences
to be made regarding their evolution and chronology. Valley glaciers\u2019 remnants, on the contrary, are often
scantly preserved, and changes can only be detected through correlations with glaciofluvial deposits in downstream
alluvial basins. The Brenta glacial system\u2019s dynamics in the glacier\u2019s terminal tract have been inferred
through a wide range of sediment analysis techniques on an alluvial stratigraphic record of the Brenta megafan
(northeast Italy), and via the mapping of in-valley glacial/glaciofluvial remnants. Glaciers flowing across narrow
gorges could possibly be slowed/blocked by such morphology, and glacial/sediment fluxes may then be diverted
to lateral valleys. Moreover, narrow valleys may induce glaciers to bulge and form icefalls at their front, preventing
the formation of terminal moraines. The Brenta Glacier was probably slowed/blocked by the narrow
Valsugana Gorge downstream of Primolano and was effectively diverted eastwards across a wind gap (Canal La
Menor Valley), joining the Cismon/Piave glaciers near Rocca and ending 2 km downstream. The Cismon and
Piave catchments started to contribute to the Brenta system just after 27 ka cal BP until at least 19:5 ka cal BP.
After the glaciers collapsed, the Piave River once again flowed into its main valley, whilst the Cismon continued
to merge with the Brenta.
This investigation shows that glacial catchments may vary significantly over time during a single glaciation in
rugged Alpine terrains. Sand petrography and the chemical/mineralogical composition of sediments are powerful
proxies for tracing such variations, as they propagate through the glacial and glaciofluvial systems and can be
recognized in the alluvial stratigraphic record far downstream from the glacier front
Properties and numerical solution of an integral equation system to minimize airplane drag for a multiwing system
We consider an open multiwing system, composed of N 2 disjoint openplane curves, not necessarily symmetric, and examine the corresponding (con-strained) induced drag minimization problem. To this end, we first derive theassociated Euler-Lagrange system of equations, which is then reduced to anequivalent system of Cauchy singular integral equations. By generalizing a pre-vious approach of ours for the case of a single open wing, we obtain existenceand uniqueness results for the problem solution in a product of weighted Sobolevtype spaces. This system is then solved by applying to it a collocation-quadraturemethod. For this, we prove stability and derive corresponding error estimates.Finally, to test the efficiency of the proposed numerical method, we apply it tosome multiwing system
A space-time BIE method for nonhomogeneous exterior wave equation problems. the Dirichlet case
Late Quaternary evolution of the sedimentary environment in Modrejce near Most na SoÄi (SoÄa Valley, Julian Alps)
Geomorphological and geological mapping have long been used to study the glacial history of the Slovenian
Alps, but many uncertainties remain regarding the time and extent of Pleistocene glaciations there. Glacial
landforms and undisturbed glacial deposits are rare in the areas of the former glacier terminus, especially in the
SoÄa Valley, where large discrepancies in the interpretation of the extent of the former SoÄa Glacier have been
reported. Early studies proved inconclusive as to whether one or two glaciations extended into the SoÄa Valley as
far as Most na SoÄi. In order to answer this question, the Quaternary sedimentary succession and landforms in
the Modrejce Valley near Most na SoÄi were investigated. New geological and geomorphological field data allow
the interpretation of the sedimentary environment and the stratigraphic relationships between different units.
In response to glacial dynamics, the sedimentation developed from glaciofluvial and glaciolacustrine to fully
glacial environments, followed by slope deposition. At higher altitudes lateral moraines are preserved, while
the staircase-like slope below has been carved into older glacial, glaciofluvial and glaciolacustrine deposits by
glacial and post-glacial processes, including fluvial erosion and slope dynamics. We conclude that the succession
studied here was deposited over the course of two different glacial advances ā LGM and pre-LGM. Our study
thus suggests that the SoÄa Glacier extended as far as the area of Most na SoÄi twice over the course of the late
Quaternary
Two boundary integral equation methods for linear elastodynamics problems on unbounded domains
We consider (transient) 3D elastic wave propagation problems in unbounded isotropic homogeneous media, which can be reduced to corresponding 2D ones. For their solution, we propose and compare two boundary integral equation approaches, both based on the coupling of a discrete time convolution quadrature with a classical space collocation discretization. In the first approach, the PDE problem is preliminary replaced by the equivalent well known (vector) space-time boundary integral equation formulation, while in the second, the same PDE is replaced by a system of two (coupled) wave equations, each one of which is then represented by the associated boundary integral equation. The construction of these two approaches is described and discussed. Some numerical testing are also presented
Abstracts Volume AIQUA Congress 2015 - The Plio-Pleistocene continental record in Italy: highlights on Stratigraphy and Neotectonics
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