782 research outputs found
Algorithms and Data Structures for Multi-Adaptive Time-Stepping
Multi-adaptive Galerkin methods are extensions of the standard continuous and
discontinuous Galerkin methods for the numerical solution of initial value
problems for ordinary or partial differential equations. In particular, the
multi-adaptive methods allow individual and adaptive time steps to be used for
different components or in different regions of space. We present algorithms
for efficient multi-adaptive time-stepping, including the recursive
construction of time slabs and adaptive time step selection. We also present
data structures for efficient storage and interpolation of the multi-adaptive
solution. The efficiency of the proposed algorithms and data structures is
demonstrated for a series of benchmark problems.Comment: ACM Transactions on Mathematical Software 35(3), 24 pages (2008
Radially resolved simulations of collapsing pebble clouds in protoplanetary discs
We study the collapse of pebble clouds with a statistical model to find the
internal structure of comet-sized planetesimals. Pebble-pebble collisions occur
during the collapse and the outcome of these collisions affect the resulting
structure of the planetesimal. We expand our previous models by allowing the
individual pebble sub-clouds to contract at different rates and by including
the effect of gas drag on the contraction speed and in energy dissipation. Our
results yield comets that are porous pebble-piles with particle sizes varying
with depth. In the surface layers there is a mixture of primordial pebbles and
pebble fragments. The interior, on the other hand, consists only of primordial
pebbles with a narrower size distribution, yielding higher porosity there. Our
results imply that the gas in the protoplanetary disc plays an important role
in determining the radial distribution of pebble sizes and porosity inside
planetesimals.Comment: 10 pages, 6 figures, accepted for publication in MNRAS special issue
'Comets: A new vision after Rosetta and Philae
Henri Temianka Correspondence; (jansson)
This collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/3791/thumbnail.jp
Henri Temianka Correspondence; (jansson)
This collection contains material pertaining to the life, career, and activities of Henri Temianka, violin virtuoso, conductor, music teacher, and author. Materials include correspondence, concert programs and flyers, music scores, photographs, and books.https://digitalcommons.chapman.edu/temianka_correspondence/3790/thumbnail.jp
Ultrasonic benchmarking with UTdefect
UTDefect is a program for simulation of ultrasonic testing with emphasis on applications within the nuclear power industry. The entire testing process, including the ultrasonic transmitter, the receiver, and scattering from various types of defects of simple shape, is modelled. The basic idea behind UTDefect is to use solutions to the elastodynamic wave equation that are esentially exact. For the 2009 benchmark problems the results obtained from UTDefect are in most cases in fairly good agreement with the experimental data from CEA. © 2010 American Institute of Physics
U.S. Humanitarian Demining Research and Development Program (HD R&D)
The anti-tank mine threat on access roads in eastern Angola is the greatest impediment to infrastructural rehabilitation, economic recovery and social development in that area. The authors discuss the method and equipment used by DanChurchAid to verify and clear roads in Moxico and Lunda Sul provinces
Staggered School Hours To Spread Peak Demand For Public Transport – Benefits And Costs
Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne
Staggered School Hours To Spread Peak Demand For Public Transport – Benefits And Costs
Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne
Ultrasonic wave propagation in an anisotropic cladding with a wavy interface
The propagation of ultrasonic waves in a thick plate with a cladding is investigated in the two-dimensional case. The surfaces of the plate are traction-free except where an ultrasonic probe is attached and emits waves into the plate. The plate is made of two different materials, the base material and the cladding, and these are both allowed to be anisotropic. The interface between the base material and the cladding is assumed to be wavy (sinusoidal) and this is common in practice for welded claddings. The null field approach is used to solve the wave propagation problem. Thus the starting point is the (surface) integral representations in the two materials. The Green’s tensors are chosen as the half space Green’s tensors as only the integrals along the interface then remain. The Green’s functions are expanded in Fourier transforms along the interface and the surface fields are likewise expanded. Applying the periodicity of the interface a discretized set of equations remains. For the sinusoidal interface all integrals can be computed analytically which leads to an efficient numerical scheme. Some numerical results show the influence of the anisotropy and the wavy interface
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