939 research outputs found
Prediction of topographic changes of a circular sandy island using BG model
The BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept) was applied to predict the three-dimensional topographic changes of a sandy island due to waves, which were observed in a movable-bed experiment by Uda and Yamamoto (1991). Taketomi island in the Sea of Okhotsk was formed as an island composed of sand by a volcanic eruption, the the island was markedly deformed by wave action, resulting in the formation of a double tombolo behind the island (Zenkovich, 1967). The BG model was also applied to predict these topographic changes of the island. The predicted and measured topographic changes in the two examples were in good agreement
Effects of anthropogenic factors on development of sand spits and cuspate forelands with rythmic shapes
The development of sand spits and cuspate forellands with rhythmic shapes was numerically predicted using the BG model (a 3-D model for predicting beach changes based on Bagnold's concept) under the oblique wave incidence that the angle between the direction normal to the shoreline and the wave direction is +-60 degrees, given an infinitesimal perturbation as the initial condition. Then the effects of the anthropogenic factors such as the construction of a groin and an offshore breakwater on the development of sand spits and cuspate forelands were investigated using the same model. The construction of a groin had a considerable impact on the sandy beach: the alteration from the field with the development of the sand spits to that with the elongation of a single sand spit, as well as the acceleration of offshore sand transport because of the blockage of longshore sand transport. The construction of an offshore breakwater strengthened the wave-seltering effect as well as the blockage of longshore sand transport, resulting in dominant beach changes. The calculated results in case of an offshore breakwater reasonably explained the example of the formation of the sand bars with two lagoons inside observed in a shallow lagoon surrounded by the Black Sea and Azov Sea
Surface-enhanced pair transfer in quadrupole states of neutron-rich Sn isotopes
We investigate the neutron pair transfer modes associated with the low-lying
quadrupole states in neutron-rich Sn isotopes by means of the quasiparticle
random phase approximation based on the Skyrme-Hartree-Fock-Bogoliubov mean
field model. The transition strength of the quadrupole pair-addition mode
feeding the state is enhanced in the Sn isotopes with . The
transition density of the pair-addition mode has a large spatial extension in
the exterior of nucleus, reaching far to fm. The quadrupole
pair-addition mode reflects sensitively a possible increase of the effective
pairing interaction strength in the surface and exterior regions of
neutron-rich nuclei.Comment: 14 page
Change in carbonate beach triggered by construction of a bridge on Irabu island and its simulation using BG model
In constructing the Irabu bridge connecting Miyako to Irabu islands, a causeway was exended as part of the bridge on the reef flat, resulting in the formation of a wave-shelter zone on both sides of the causeway. After the construction, marked beach changes occured on the carbonate surrounded by a coral reef, and the nesting sites of the sea turtles were extensively lost. The BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept) was applied to predict these beach changes. Then, the stabilization method of the beach was considered. A suitable measure was to install groins as well as beach nourishment
Di-neutron correlation and soft dipole excitation in medium mass neutron-rich nuclei near drip-line
The neutron pairing correlation and the soft dipole excitation in medium-mass
nuclei near drip-line are investigated from a viewpoint of the di-neutron
correlation. Numerical analyses by means of the coordinate-space HFB and the
continuum QRPA methods are performed for even-even O, Ca
and Ni. A clear signature of the di-neutron correlation is found in
the HFB ground state; two neutrons are correlated at short relative distances
\lesim 2 fm with large probability . The soft dipole excitation is
influenced strongly by the neutron pairing correlation, and it accompanies a
large transition density for pair motion of neutrons. This behavior originates
from a coherent superposition of two-quasiparticle configurations consisting of continuum states with high orbital angular momenta
reaching an order of . It raises a picture that the soft dipole
excitation under the influence of neutron pairing is characterized by motion of
di-neutron in the nuclear exterior against the remaining subsystem.
Sensitivity to the density dependence of effective pair force is discussed.Comment: 35 pages, 22 figure
Pairing collectivity in medium-mass neutron-rich nuclei near drip-line
We look for collective excitations originating from the strong surface
pairing in unstable nuclei near the neutron drip-line. The soft dipole
excitation is such a pairing mode as it exhibits a character of
core-vs-dineutron motion. Possibility of the hydrodynamic phonon mode (the
Anderson-Bogoliubov mode) is also discussed.Comment: 9 pages, a talk presented at Collective Motion in Nuclei under
Extreme Conditions (COMEX2), June 20-23, 2006, St. Goar, German
Analysis of mechanism of sand deposition inside a fishing port using BG model
A large amount of sand deposited in the wave-shelter zone of Ohtsu fishing port located in northern Ibaraki Prefecture, Japan, resulting in a difficulty in navigation at the pot entrance. The BG model (a three-dimensional model for predicting beach changes based on Bagnold's concept) ws used to solve this problem. Measures against sand deposition inside the port were investigated and the most appropriate measure found for preventing sand deposition was the extension of a jetty by 100 m at the tip of the west breakwater. The applicability of the BG model to such prediction was confirmed
Characterizing Vickrey allocation rule by anonymity
We consider the problem of allocating finitely many units of an indivisible good among a group of agents when each agent receives at most one unit of the good and pays a non-negative price. For example, imagine that a government allocates a fixed number of licenses to private firms, or that it distributes equally divided lands to households. Anonymity in welfare is a condition of impartiality in the sense that it requires allocation rules to treat agents equally in welfare terms from the viewpoint of agents who are ignorant of their own valuations or identities. We show that the Vickrey allocation rule is the unique allocation rule satisfying strategy-proofness, anonymity in welfare, and individual rationality
Topographic changes on Ajigura beach triggered by elongation of offshore breakwater
On Ajigaura Beach in Ibaraki Prefecture, Japan, severe beach erosion has occurred. Despite beach nourishment as a measure against beach erosion, wave run-up damage occurred in the south part of the beach where the foreshore was narrowed. The topographic changes of the beach were investigated on the basis of past aerial photographs and bathymetric survey data, and a numerical simulation using the BG model (a three-dimensional model for predicting beach changes based on Bagnold???s concept) was carried out. The measured and calculated results were in good agreement. It was concluded that the beach changes at Ajigaura Beach were triggered by northward longshore sand transport, which was induced by the wave-sheltering effect of the offshore breakwater
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