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 $2_1^+$ state is enhanced in the Sn isotopes with $A \geq 132$. The transition density of the pair-addition mode has a large spatial extension in the exterior of nucleus, reaching far to $r\sim 12-13$ 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 $^{18-24}$O, $^{50-58}$Ca and $^{80-86}$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 $\sim 50$. 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 $[l\times (l+1)]_{L=1}$ consisting of continuum states with high orbital angular momenta $l$ reaching an order of $l\sim 10$. 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 $A-2$ 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

Evidence for Spin–Orbit Alignment in the TRAPPIST-1 System

In an effort to measure the Rossiter–McLaughlin effect for the TRAPPIST-1 system, we performed high-resolution spectroscopy during transits of planets e, f, and b. The spectra were obtained with the InfraRed Doppler spectrograph on the Subaru 8.2 m telescope, and were supplemented with simultaneous photometry obtained with a 1 m telescope of the Las Cumbres Observatory Global Telescope. By analyzing the anomalous radial velocities, we found the projected stellar obliquity to be λ = 1 ± 28° under the assumption that the three planets have coplanar orbits, although we caution that the radial-velocity data show correlated noise of unknown origin. We also sought evidence for the expected deformations of the stellar absorption lines, and thereby detected the "Doppler shadow" of planet b with a false-alarm probability of 1.7%. The joint analysis of the observed residual cross-correlation map including the three transits gave λ = 19_(-15)^(+13)°. These results indicate that the the TRAPPIST-1 star is not strongly misaligned with the common orbital plane of the planets, although further observations are encouraged to verify this conclusion