On the Kashimanada coast, fine sand was selectively transported and deposited in the wave-shelter zone behind the offshore breakwater built on both ends of the coastline, whereas beach was eroded in the central part of the coastline. As a measure, artificial headlands have been constructed on this coast, but beach erosion is still severe. The contour-line-change model considering the effect of changes in grain size was applied to this coast, and the effect of the measure was evaluated. The differences between the total accreted and eroded volumes of sand in the condition with/without headlands became 7.4×106 and 8.1×106 m3. Thus, it was found that the movement of approximately 8.0×106 m3 of sand was controlled by headlands.
The abstraction reactions, T + HD(DH) → HT(DT) + D(H) and T + H2(D2) → HT(DT) + H(D) were studied experimentally in liquid 3He−4He media at 1.3 K and theoretically using the gas-phase reaction model. The experimental reaction system has two characteristics; one is that the tritium atom (T) is produced from one of the constituents, 3He, through 3He(n, p)T nuclear reaction, and the other is that superfluid or normal-fluid reaction medium can be chosen arbitrarily by changing the composition and temperature of the sample. The experimental isotope effect defined by {[HT]/[H2]}/{[DT]/[D2]} for the reactions T + H2(D2) → HT(DT) + H(D) was found to be 158 in superfluid and 146 in normal-fluid solutions. The large isotope effects observed were qualitatively explained via quantum mechanical tunneling on the basis of the theoretical calculations of thermal rate constants for these reactions. In the T + HD(DH) → HT(DT) + D(H) reactions, the experimental isotope effect was <19.8. From the considerations on both the reaction processes based on the experimental results and the theoretical calculations, it has been suggested that the quantum mechanical tunneling abstraction through van der Waals complex plays a predominant role for both the reactions.
Beach changes on the Hazaki coast extending between Kashima Port and Hazaki fishing port were investigated. Numerical simulation of beach changes and grain size changes were carried out, using the contour-line-change model considering the change in grain size (Kumada et al, 2005). In this area, fine sand is transported from outside to inside the wave shelter zone of the breakwater with the construction of Hazaki fishing port. Furthermore, 10.6×104 m3/yr of sand has been supplied from the Tone River and part of fine sand deposited inside the port. The mechanism of deposition of fine sand in the fishing port was well explained by the present model.
Spin-contrast-variation (SCV) small-angle neutron scattering (SANS) is a technique to determine the nanostructure of composite materials from the scattering of polarized neutrons that changes with proton polarization of samples. The SCV-SANS enabled us to determine structure of nanoice crystals that were generated in rapidly frozen sugar solutions by separating the overlapped signals from the nanoice crystals and frozen amorphous solutions. In the frozen glucose solution, we found that the nanoice crystals formed a planar structure with a radius larger than several tens of nanometers and a thickness of 2.5 ± 0.5 nm, which was close to the critical nucleation size of ice crystals in supercooled water. This result suggests that the glucose molecules were preferentially bound to a specific face of nanoice crystals and then blocked the crystal growth perpendicular to that face.
A high-efficiency etalon operated in the THz region has been proposed to generate a THz pulse train. To achieve high-conversion efficiency to the pulse train, an optical shutter is employed in this etalon. A THz pulse train and its comb-shaped spectrum have been realized by the use of the proposed etalon with the optical shutter.
Beach changes of the Akiya coast located in the western part of Miura Peninsula was investigated through field observations, analysis of aerial photographs and numerical simulation using the contour line change model. One of the causes of beach erosion is due to the longshore sand movement associated with the formation ofwave shadow zone of the breakwater of Kuruwa fishing port. The other main cause is the loss of sand due to the northward longshore sand transport, overflowing the foot of Chojagasaki Point located at the north end of the coastlineduring rough wave conditions.
We carried out time-resolved small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) studies of dynamically polarized high-density polyethylene (HDPE) doped with 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) persistent free radicals. We observed a remarkable enhancement of the scattering intensity shortly after a switching of microwave frequency from positive (negative) to negative (positive) dynamic nuclear polarization (DNP). The enhancement was found to be due to spatially heterogeneous proton-spin polarization generated as a result of heterogeneously distributed TEMPO in the HDPE sample. The spatial fluctuation of the polarization ranged up to the length-scale of ≥100 nm. This result strongly suggests that the TEMPO free radicals are localized more in nonfibrils but less in fibrils of HDPE. In this way, we propose that the time-resolved DNP-SANS and DNP-USANS be general techniques to determine mesoscale spatial distribution of electron spins in dielectric materials.
Sorting effect of sand of mixed grain size was investigated by a movable bed experiment under the condition with dominant longshore sand transport. In a plane wave tank of 4m width, a model beach of the slope 1/10 and composed of mixed sand, d50 of which are 0.2mm and 2mm, was made and waves were incident obliquely. Mixed rate of fine and coarse sand is 1:1. Sorting effect by longshore sand transport was confirmed and experimental results were compared with the numerical simulation using the one-line model considering sorting of each grain proposed by Kumada et al. Predicted results agreed with the experimental results.
